Application of laser-induced breakdown spectroscopy for total carbon quantification in soil samples

The increase of greenhouse gas (i.e., CO(2)) levels in the atmosphere has caused noticeable climate change. Many nations are currently looking into methods of permanent underground storage for CO(2) in an attempt to mitigate this problem. The goal of this work is to develop a process for studying the total carbon content in soils before, during, and after CO(2) injection to ensure that no leakage is occurring or to determine how much is leaking if it is occurring and what effect it will have on the ecosystem between the injection formation and the atmosphere. In this study, we quantitatively determine the total carbon concentration in soil using laser-induced breakdown spectroscopy (LIBS). A soil sample from Starkville, Mississippi, USA was mixed with different amounts of carbon powder, which was used as a calibration for additional carbon in soil. Test samples were prepared by adding different but known amounts of carbon powder to a soil sample and then mixing with polyvinyl alcohol binder before being pressed into pellets. LIBS spectra of the test samples were collected and analyzed to obtain optimized conditions for the measurement of total carbon in soil with LIBS. The total carbon content in the samples was also measured by a carbon analyzer, and the data (average of triplicates) were used as a reference in developing calibration curves for a modified version of the single linear regression model and the multiple linear regression model. The calibration data were then used to determine the total carbon concentration of an unknown sample. This work is intended to be used in the initial development of a miniaturized, field-portable LIBS analyzer for CO(2) leak detection.     

Effect of dietary fats on some membrane-bound enzyme activities,membrane lipid composition and fatty acid profiles of rat heart sarcolemma

The effect of various dietary fats on membrane lipid composition, fatty acid profiles and membrane-bound enzyme activities of rat cardiac sarcolemma was assessed. Four groups of male weanling Charles Foster Young rats were fed diets containing 20% of groundnut, coconut, safflower or mustard oil for 16 weeks. Cardiac sarcolemma was prepared from each group and the activities of Na⁺,K⁺-ATPase, 5′-nucleotidase, Ca²⁺-ATPase and acetylcholinesterase were examined. ATPase activities were similar in all groups except the one fed coconut oil, which had the highest activities. Acetylcholinesterase activity was also similar in all the groups, however, it was significantly higher in the group fed mustard oil. No significant changes were observed among the groups in 5′-nucleotidase activity, in the cholesterol-to-phospholipid molar ratio and in sialic acid content. The coconut, safflower and mustard oil diets significantly increased cholesterol and phospholipid contents and the lipid-to-protein ratio of cardiac sarcolemma as compared to feeding the groundnut oil diet. The fatty acid composition of membrane lipids was quite different among the various groups, reflecting the type of dietary fat given. The total unsaturated-to-saturated fatty acid ratio was not different among the various groups; however, the levels of some major fatty acids such as palmitic (16∶0), oleic (18∶1) and linoleic (18∶2) acids were significantly different. Cardiac sarcolemma of the group fed safflower oil had the highest polyunsaturated fatty acid content. The results suggest that dietary fats induce changes not only in the fatty acid composition of the component lipids but also in the activities of sarcolemmal enzymes involved in the regulation of cardiac function.     

Activity of myocardial lipase using natural edible oils as substrates

Rat heart homogenates were tested for their lipolytic activity toward synthetic and natural substrates such as edible oils. Triolein was hydrolyzed very efficiently by myocardial lipase whereas trierucin was not cleaved by the enzyme. Among the natural substrates, safflower oil, which has the highest degree of unsaturation, was hydrolyzed to a greater extent than the other oils. Mustard oil rich in erucic acid formed a poor substrate for the myocardial lipase.     

A simulation-based heuristic solution procedure for analyzing human postural balance

Human postural movements can be simulated by a biomechanical model. Biomechanical models, however, involve differential equations and do not admit conventional optimization techniques for solution. Introducing the notion of dynamic grid-sizing, this paper presents an easy-to-implement simulation-based heuristic procedure for solving biomechanical models. We adopt the four-segment sagittal model for human postural analysis from [Iqbal K, Pai YC (2000) Predicted region of stability for balance recovery: motion at the knee joint can improve termination of forward movement. J Biomech 33:1,619–1,627] for illustration and solve it to predict a region of stability for the model. The size and the feasibility of the stability region predicted by the proposed scheme in comparison with results reported in (Iqbal K, Pai YC (2000) Predicted region of stability for balance recovery: motion at the knee joint can improve termination of forward movement. J Biomech 33:1,619–1,627) demonstrate that the proposed scheme is fairly efficient and effective and further suggest its practical usage in analyzing human postural balance.     

Determination of elemental impurities in plastic calibration standards using laser-induced breakdown spectroscopy

Dual-energy computed tomography (CT) scanning is a rapidly emerging imaging technique employed in nondestructive evaluation of various materials. CT has been used for characterizing rocks and visualizing multiphase flow through rocks for over 25 years. The most common technique for dual-energy CT scanning relies on homogeneous calibration standards to produce the most accurate decoupled data. However, the use of calibration standards with impurities increases the probability of error in the reconstructed data and results in poor rock characterization. Laser-induced breakdown spectroscopy was used to determine impurity concentration in a set of commercially purchased calibration standards used in dual-energy scanning for material identification with coal samples. Two calibration models were developed by using univariate calibration with the internal ratio method and multiple linear regression. Seven elements (Al, Fe, Mg, Na, Ni, Sr, and Ti) were examined in five different samples containing varying amounts of each ion to compare calibration from univariate data analysis and from multivariate data analysis. The contaminant concentrations were also measured by a commercially available inductively coupled plasma optical emission spectroscopy instrument, and the data were used as a reference in developing calibration curves for a modified version of the single linear regression model and the multiple linear regression model.