Transport studies of water and aqueous—dioxane through a pyrex sintered disc impregnated with cellulose acetate

Experimental results for the measurements of hydrodynamic permeability, electroosmotic velocity and streaming potential of water and dioxane—water (DH₂O) mixtures (10, 20, 30 and 40% by mass of dioxane) using a pyrex sintered disc (G₂) impregnated with cellulose acetate at 30°C and at voltages up to 40 V are reported. The data have been analysed in the light of non-equilibrium thermodynamics. Onsager's reciprocity relation for all compositions of aqueous—dioxane has been found to hold true. It has been found that the concentration dependence of the phenomenological coefficients conform to the Spiegler's frictional model. Efficiencies of electrokinetic energy conversion, i.e. electroosmosis and streaming potential, have been determined and the results are in accordance with the theory of non-equilibrium thermodynamics. The maximum value of the efficiency of energy conversion for both the modes has been found to be independent of the input force. Membrane characteristics such as pore radius and number of pores have been determined, whereas the membrane—permeant interface is characterised in term of the zeta potential.     

Ab initio and anion photoelectron studies of Rhn (n = 1 − 9) clusters

We present an analysis of Na-He collisional profiles at high density and very low temperature in a unified line shape semi-classical theory which contains the impact as well the quasistatic limits. Clearly understanding the variation of shape of the two fine-structure components of the 3s?3p line with increasing helium density allows us to understand experimental spectra of a Na atom attached to He nanodroplets. We compare our collisional approach to path integral Monte Carlo calculations using the same ab initio Na-He molecular potentials.     

Photocured characteristics of fast photocurable acrylic formulations and investigations by differential photo calorimeter

Nanofluids are obtained by suspending metallic or non-metallic nanoparticles in conventional base liquids and can be employed to increase heat transfer rate in various applications. In this study, the effects of adding three types of nanofluids on turbulent convective heat transfer at the entrance region of a constant wall heat flux tube were experimentally studied. The nanofluids were mixtures of aluminium oxide, copper oxide, and silicon carbide at various nanoparticle volume fractions ranging from 0.0002 to 0.002 in water. The convective heat transfer coefficient was measured at different Reynolds numbers of 10,000–50,000. At these concentrations and Reynolds numbers, a maximum of 11–18% of convection heat transfer coefficient was observed as compared to the base fluid, showing a 6–9% increase on average. In this study, it was observed that changes in the nanoparticle type had no considerable effect on heat transfer coefficient increase. According to the model proposed here, the dimensionless thickness of laminar sub-layer is specified as a functional equation of the volume fraction of nanoparticles for each material.

     

Independent measurement of the total active 8B solar neutrino flux using an array of 3He proportional counters at the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nu_x) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54_-0.31;+0.33(stat)-0.34+0.36(syst)x10(6) cm(-2) s(-1), in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields Deltam2=7.59_-0.21;+0.19x10(-5) eV2 and theta=34.4_-1.2;+1.3 degrees. The uncertainty on the mixing angle has been reduced from SNO's previous results.     

tert-Butyl nitrite induced radical dimerization of primary thioamides and selenoamides at room temperature

A simple and efficient method for the dimerization of primary thioamides into 1,2,4-thiadiazoles using tert-butyl nitrite is described. The optimized condition was also found to be suitable for the dimerization of benzoselenoamides into 1,2,4-selenadiazoles. All the reactions proceed smoothly at room temperature and gave the desired products in excellent yields in a short span of time.     

Effect of lattice oxygen on optical absorption, radiation hardness and thermally stimulated luminescence of BaF2 crystal

The influence of the presence of BaO impurity on the optical absorption, radiation hardness and thermally stimulated luminescence of BaF₂ has been investigated. The presence of oxygen impurity gives rise to three absorption bands in the UV region, peaking around 220, 280 and 335 nm. Further, the impurity is found to be detrimental to crystal hardness against ionizing radiations. The thermally stimulated luminescence (TSL) has been studied from gamma-irradiated crystals containing different fractions of BaO impurity. Four prominent glow peaks around 100°C (peak I), 150°C (peak II), 220°C (peak III) and 290°C (peak IV) are observed for crystals containing BaO impurity concentrations lower than 0.5% (by wt). For crystals containing higher impurity concentrations, two additional peaks around 75°C and 260°C are also observed. The kinetics of TSL emission is observed to be of first order, implying that the absorption and the emission centers responsible for TSL are the same. The normalized TSL output for peak I is found to vary linearly with the concentration of oxide impurity. This fact can be utilized to detect the presence of minute amounts of oxygen in BaF₂ lattice, which is crucial to the growth of crystals exhibiting high radiation hardness.     

Drug and surfactant transport in Cyclosporine A and Brij 98 laden p-HEMA hydrogels

Surfactants are commonly incorporated into hydrogels to increase solute loading and attenuate the release rates. In this paper we focus on understanding and modeling the mechanisms of both surfactant and drug transport in hydrogels. Specifically, we focus on Brij 98 as the surfactant, Cyclosporine A (CyA) as the hydrophobic drug, and poly-hydroxy ethyl methacrylate (p-HEMA) as the polymer. The models developed here are validated by experiments conducted with gels of different thicknesses and surfactant loadings. Also the model is compared with prior experimental studies in literature. The model predicts that the percentage surfactant as well as drug release scales as 1/(surfactant loading)(0.5), and thus a four fold increase in surfactant loading leads to a two fold reduction in percentage release for both drug and surfactant at a given time. The models for the surfactant and drug release are fitted to the experimental data to obtain values of 1.44 x 10(-14) m(2)/s for CyA diffusivity and 414.4 for the partition coefficient between drug concentration inside the micelle and that in the gel. These models can be very helpful in tuning the drug release rates from hydrogels by controlling the surfactant concentration. The results also show that Brij 98 loaded p-HEMA exhibit an extended release of CyA and so contact lenses made with this material can be used for extended ocular delivery of CyA, which is an immunosuppressant drug commonly used for treatment of various ocular ailments.     

Coupling Effects of Electrostatic Interactions and Salt Concentration Gradient in Polymer Translocation through a Nanopore: A Coarse-Grained Molecular Dynamics Simulations Study

We study the influence of polymer pore interactions and focus on the role played by the concentration gradient of salt in the translocation of polyelectrolytes (PE) through nanopores explicitly using coarse-grained Langevin dynamics simulations. The mean translocation time is calculated by varying the applied voltage, the pH, and the salt concentration gradient. Changing the pH can alter the electrostatic interaction between the protein pore and the polyelectrolyte chain. The polymer pore interaction is weakened by the increase in the strength of the externally applied electric field that drives translocation. Additionally, the screening effect of the salt can reduce the strong charge-charge repulsion between the PE beads which can make translocation faster. The simulation results show there can be antagonistic or synergistic coupling between the salt concentration-induced screening effect and the drift force originating from the salt concentration gradient thereby affecting the translocation time. Our simulation results are explained qualitatively with free energy calculations.