Although sterol-phospholipid interactions have been of interest for many years now, a complete thermodynamic profile of these systems is still missing. To contribute to a better understanding of the thermodynamic functions of these systems, we determined isothermal compressibility coefficient data for dipalmitoylphosphocholine (DPPC) and DPPC-containing cholesterol and ergosterol vesicles by means of molecular acoustics (ultrasound velocimetry and densimetry) and differential scanning and pressure perturbation calorimetric techniques. A particular focus was on the influence of the differential structural properties of the two sterols on the thermodynamic properties of lipid bilayers, and on the nature of the critical point region of phospholipid-sterol systems by determining thermodynamic fluctuation parameters. Contrary to significant changes in conformational and dynamical properties of the DPPC-sterol membranes, no marked differences were found in the various thermodynamic properties studied, including the adiabatic (beta(S)(lipid)) and isothermal (beta(T)(lipid)) compressibility, as well as the volume fluctuations. Differences in beta(T)(lipid) and beta(S)(lipid) become dramatic in the gel-fluid transition region only, due to a significant degree of slow relaxational processes in the microsecond time range in the transition region. Our data show no evidence for the existence of a typical critical point phenomenon in the concentration and temperature range where a critical point in the DPPC-sterol phase diagram is expected to appear. Hence, on a macroscopic level, it seems more appropriate to describe the sterol-phospholipid binary mixtures in the liquid-ordered/liquid-disordered coexistence region as a phase region consisting essentially of small nanodomains only. Such small-domain dimensions, with a series of particular properties such as increased line energy, spontaneous curvature, and limited lifetime, seem also to be typical of raftlike domains in cell membranes.

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The effects of increasing gramicidin D (gD) concentration on the partial specific volume, v o , and the adiabatic compressibility coefficient of the lipid, β S lipid of the bilayer reveals a continual decrease in  o and β S lipid (within the range of concentration studied) with concentration, except between 5 and 7.5 %, where a very slight decrease was observed. At gD concentrations higher than 5 mol%, the isothermal compressibility coefficient, β T lipid is greater than β S lipid at the gel-fluid region by  10 -20 % in the entire temperature range covered. The maximum value of the relative volume fluctuation of 12 % is reached for DPPC at the main transition, and is strongly dampened upon addition of gD. A gradual decrease in the calculated relative volume fluctuations with gD concentration at T m is observed between concentrations 1 and 10 mol%.

This research was undertaken to examine the corrosion behavior of some metals in different acid solutions using weight loss technique. The magnitude of corrosion of these metals in 0.5 -3.0 M of solutions of HCl, H2SO4, and HNO3 was studied for an exposure period of 100 minutes (at 20 minutes interval). Rate of corrosion in metals followed this order: zinc > galvanized iron > copper >, while rate of corrosion in aqueous media followed this order: HNO3 > H2SO4 > HCl. It has been obtained that concentration increase leads to increase in rate of corrosion. Further study on the corrosion kinetics has revealed that the rate of reaction of the metals increases with increase in solution concentration, while the half life decreases with increase in solution concentration.

Tamarindus indica leaves extract was used as a green corrosion inhibitor for mild steel in 1 M hydrochloric acid (HCl) under varied conditions using weight loss technique. The inhibition efficiency, thermodynamics, kinetics and mechanism of inhibition by Tamarindus indica leaves extract on the mild steel were determined. The inhibitor’s concentrations used for the study were 0.0g/15ml (blank), 0.2g/15ml, 0.4g/15ml, and 0.6g/15ml, at the temperatures of 28°C (301K), 40°C (313K), 50°C (323K), and 60°C (333K). The results obtained showed that the inhibition efficiency of the inhibitor was inversely proportional to the temperature, but directly proportional to the concentration of inhibitor in the acid. The maximum efficiency of 79.68%, was observed at 28°C (301K) and at a concentration of 0.6g/15ml. The heat of adsorption and free energy (ΔGads) calculations yielded negative values. This indicates that the reaction between the inhibitor molecules and the metal surface was favorable since all the calculated values were negative. As the concentration of the inhibitor increased, the negativity of the ΔGads increased; suggesting physical adsorption. The data obtained fitted in the Langmuir and Temkin adsorption isotherms at lower temperatures. The results from the phytochemical analysis showed that saponins, were absent, but the extract has tannins, phenolic compounds, alkaloids, cardiac glycosides and flavonoids.