Crosslinking-Dependent Drug Kinetics in Hydrogels for Ophthalmic Delivery

Drug-diffusion kinetics in 2-hydroxyethyl methacrylate hydrogels were studied as a function of the crosslinking density and porosity. By varying the concentration of the crosslinker, tetraethylene glycol dimethacrylate, we demonstrated how the release of Timolol maleate could be optimized to allow for efficient drug delivery. FTIR and spectrophotometry supplied optical inferences into the functional groups present. By studying the swelling and degradation of hydrogels, supplemented with drug-release kinetics studies, the relationship between these two tenets could be formulated.

Influence of Halide Substitution and External Stimuli on Ion Transport in Inverted MAPb(I1-xBrx)3 Perovskite Solar Cells

The coupled electronic-ionic response in various MAPb(I1-xBrx)3-based inverted perovskite solar cells (PSCs) is studied in-operando by impedance spectroscopy (IS) under varied AM1.5G light intensities and electrical biases. We show that the concentration of Br- in the composition significantly alters the capacitance and resistive response of the PSC under external stimuli. For example, we observed that the low frequency capacitance does not increase proportionally with light intensity, instead it is highly dependent on the amount of Br- in the composition. We found that the recombination resistance (Rrec) has a linear inverse relationship with light intensity in MAPbI3 and MAPbBr3 whereas, the mixed compositions show deviation. Interestingly, the deviation of Rrec from linearity also scales with the increase in Br- concentration. Upon applying an electrical bias, a large deviation of Rrec from linearity was observed all mixed halide compositions exhibited a non-linear inverse trend. We further report the diffusion coefficient (D) for each MAPb(I1-xBrx)3 composition under different light intensity. Notably, the D values decreased on changing the composition from MAPbI3 (10-7 cm2 s-1) to MAPb(I0.8Br0.2)3 and MAPbBr3 (10-8 cm2 s-1). On the other hand, mixed compositions containing more than 20% Br- concentration show faster diffusion kinetics. Overall, our results emphasize on the complex and intertwined nature of electronic and ionic response in PSC that is tunable by changing the halide composition.

Computer 3D-simulation of the temperature and diffusion kinetics of SHS in the closest packing of Ni@Al “core-shell” mesocells for modes with variable values of the key ignition parameters

The paper presents the results of computer 3D-simulation of the temperature and diffusion kinetics of SHS in a test model cluster of Ni-Al particles for modes with variable values of the key parameters of the SHS combustion wave ignition. The key parameters for the SHS combustion wave ignition were chosen as follows: the initial temperature for preliminary heating of the Ni-Al particles mixture, the ignition temperature of the combustion wave in the mixture of Ni-Al particles, the duration of the action of the heat pulse until the combustion wave ignition, and the thickness of the ignited layer in the mixture of particles. A program has been created to generate a test model cluster in the form of the closest ball packing of the Ni@Al “core-shell” mesocells (CBP-structure cluster of the Ni@Al “core-shell” mesocells). Using such a CBP-structure cluster, was continued a testing of created software package intended for 3D-simulation of SHS macrokinetics in a heterogeneous particle mixture, taking into account parallel MPI-calculations. In addition, the value ranges of the key parameters of the SHS combustion wave ignition for which the simulation results are in adequate agreement with the experimental data are determined as the parameters of the program model for SHS-simulation. The results of computational experiments have shown that diffusion kinetics is interrelated with temperature kinetics, and in mesocells with different locations within the CBP-structure cluster, the formation of intermetallic phases occurs inhomogeneously.

Study of the supramolecularly ordered layered structure of chitosan gel films

Structural and morphological features of chitosan gel films with a radially periodic structure, obtained by neutralizing the salt form of the polymer with sodium hydroxide or triethanolamine, were visualized by scanning electron microscopy. The formation of such supramolecularly ordered layered structures was found to obey diffusion kinetics and the regularities of Liesegang periodic precipitation. The revealed dependence of the morphostructure of our chitosan gel films on the neutralizing reagent used is due to differences in the diffusion rate of inorganic and organic substance, as well as some spatio-temporal features of the mass transfer process.