Transport Through a Clay Barrier with the Contaminant Concentration Dependent Permeability

Transport of contaminants through clays is characterized by a very low dispersivity, but depends on the sensitivity of its intrinsic permeability to the contaminant's concentration. An additional constitutive relationship for a variable intrinsic permeability is thus adopted leading to a coupled system of equations for diffusive–advective transport in multicomponent liquid. A one-dimensional transport problem is solved using finite difference and Newton–Raphson procedure for nonlinear algebraic equations. The results indicate that although diffusion contributes to an increase of transport with respect to pure advection, the flux ultimately depends on end boundary conditions for concentration which, if low, may actually slow down the evolution of concentration and thus of permeability. Indeed, the advective component of flux may still remain secondary if the end portion of the layer remains unaffected by high concentrations. With no constraints on concentration at the bottom (zero concentration gradient boundary condition) and high concentration applied at the top, a significant shortening of the breakthrough time occurs.     

Effect of phosphate on sorption of Eu(III) by montmorillonite

Eu(III) sorption by Na-montmorillonite, the principal component of bentonite, has been studied in absence and presence of phosphate under varying experimental conditions of pH, metal ion, phosphate and sorbent concentration. The sorption edge was found to shift to high pH with decreasing sorbent concentration indicating site heterogeneity on the clay. Eu(III) sorption by Na-montmorillonite was found to increase in presence of phosphate at lower sorbent concentration of 0.5 g/L while at higher sorbent loading no effect of phosphate was observed. ATR–FTIR spectroscopy has been used to understand transition from surface complexation to surface precipitation with decreasing sorbent concentration.     

Investigation of gamma radiation induced changes in local structure of borosilicate glass by TDPAC and EXAFS

Gamma radiation induced changes in local structure around the probe atom (Hafnium) were investigated in sodium barium borosilicate (NBS) glass, used for immobilization of high level liquid waste generated from the reprocessing plant at Trombay, Mumbai. The (NBS) glass was doped with ¹⁸¹Hf as a probe for time differential perturbed angular correlation (TDPAC) spectroscopy studies, while for studies using extended X-ray absorption fine structure (EXAFS) spectroscopy, the same was doped with 0.5 and 2 % (mole %) hafnium oxide. The irradiated as well as un-irradiated glass samples were studied by TDPAC and EXAFS techniques to obtain information about the changes (if any) around the probe atom due to gamma irradiation. TDPAC spectra of unirradiated and irradiated glasses were similar and reminescent of amorphous materials, indicating negligible effect of gamma radiation on the microstructure around Hafnium probe atom, though the quaqdrupole interaction frequency (ω _Q) and asymmetry parameter (η) did show a marginal decrease in the irradiated glass compared to that in the unirradiated glass. EXAFS measurements showed a slight decrease in the Hf-O bond distance upon gamma irradiation of Hf doped NBS glass indicating densification of the glass matrix, while the cordination number around hafnium remains unchanged.     

Distributionally robust chance-constrained games: existence and characterization of Nash equilibrium

We consider an n-player finite strategic game. The payoff vector of each player is a random vector whose distribution is not completely known. We assume that the distribution of a random payoff vector of each player belongs to a distributional uncertainty set. We define a distributionally robust chance-constrained game using worst-case chance constraint. We consider two types of distributional uncertainty sets. We show the existence of a mixed strategy Nash equilibrium of a distributionally robust chance-constrained game corresponding to both types of distributional uncertainty sets. For each case, we show a one-to-one correspondence between a Nash equilibrium of a game and a global maximum of a certain mathematical program.     

Synthesis,characterization, and applications with the manifestation of antifungal activity and seed germination properties of nickel doped zinc oxide nano platform by biochemical contrivance

In the recent era, nanotechnology, a rapidly emerging field, has been explored as the most studied field worldwide. The goal of this study is to use neem leaves extract as an effective ‘reducing agent’ and ‘stabilizing agent’ in the green synthesis of bio-medically important Zn_1-XNi_XO (X = 0.00, 0.04, 0.08, 0.12) nanoparticles. The molar concentrations of nickel nitrate and zinc nitrate are varied to produce nickel-doped ZnO nanoparticles. Color change is the first indicator of nanoparticle formation during this biosynthesis. The hexagonal wurtzite structure with good crystallinity is confirmed by X-ray diffraction. FTIR analysis reveals the fact that the Zn–O stretching vibration shifts with the introduction of impurities into the ZnO matrix. UV–Vis spectra show the typical surface plasma resonance around 370 nm and the hydrodynamic diameter is larger than the size calculated from the XRD value, according to DLS. The main finding of this study is that Ni_0.12Zn_0.88O has a strong antifungal activity against and a significant growth rate after treating wheat seeds with biologically synthesized Ni_0.12Zn_0.88O nanoparticles.     

Improvement in hygroscopic property of macro-defect free cement modified with hypromellose/potassium methyl siliconate copolymer and pulverized fly ash

Journal of Thermal Analysis and Calorimetry - Macro-defect-free (MDF) cement composites are high-strength materials produced by applying high shear to cement-polymer pastes, using twin roller mill...     

Refractive index and molar refractivity of benzonitrile, chlorobenzene, benzyl chloride and benzyl alcohol with benzene at T = 298.15, 303.15, 308.15 and 313.15 K

Densities and refractive indices were measured for the binary liquid mixtures formed by benzonitrile, chlorobenzene, benzyl chloride, and benzyl alcohol with benzene at (T = 298.15, 303.15, 308.15 and 313.15 K) and atmospheric pressure over the whole concentration range. The Lorentz–Lorentz mixing rule, the Ramaswami and Anbananthan model, and the model devised by Glinski were used to study the refractive index and molar refractivity. These results have been discussed to study the type of mixing behavior between the mixing molecules. The measured data were fitted to the Redlich–Kister polynomial relation to estimate the binary coefficients and standard errors. Furthermore, the McAllister multibody interaction model is used to correlate the binary refractive index with the experimental findings. It is observed that molar refractivity, molecular interaction, and association constant can be better understood from these models.     

PE-CPE blends and their graphene oxide nanocomposites with reduced low temperature brittleness

The low-temperature flexibility of polyethylene (PE)–chlorinated polyethylene (CPE) blends and their composites with a small amount of graphene oxide filler was studied. Quantitative height variation in the AFM images, rheological as well as fracture analyses were employed to gain insights into the generation of flexibility in the matrix phase. The semi-crystalline CPE (CPE25) polymer did not induce viscoelastic behavior at temperatures lower than the glass transition temperature of PE, whereas the amorphous CPE (CPE35) had completely different behavior. The samples with CPE35 could not be sufficiently hardened even at ?180 °C and remained too soft for cryosectioning. Therefore, compression, which results in a 30–60 % reduction in length along the cutting direction with no change in the dimension perpendicular to it, was very prominent for both thin section and block face of the sample. The composites had even higher degree of compression due to additional effect of weak filler matrix interactions and as a consequence, the topographical variations led to filler pull out during sectioning. It was also confirmed using the rheological analysis that composites (and blends with 10 % CPE35 content) had phase immiscibility as CPE phase was suspected to concentrate near the graphene oxide phase leading to generation of chlorine-rich phases. The addition of graphene oxide did not lead to reduced flexibility and the composites also retained the modulus similar to pure polymer. The mechanical fracture of the samples also confirmed the flexibility of the CPE containing blends and composites as these samples were still flexible at ?195 °C.