Coating of polylactide films by chitosan: Comparison of methods

Control over biomaterials surface characteristics through surface modification or deposition of coatings is one of the key aspects of tissue engineering. This work was aimed to evaluate an effectiveness of various methods of chitosan-coating formations onto polylactide films using a number of techniques, such as vacuum deposition by electron-beam sputtering, chemical entrapment method, and electrospray procedure. Differently coated films were studied in terms of surface morphology (scanning electron and atomic-force microscopy), chemical structure (FTIR and X-ray photoelectron spectroscopy), and hydrophilic/hydrophobic balance (goniometry). The effect of coating technique on homogeneity of chitosan distribution over the substrate surface was evaluated using genipin and fluorescein isothiocyanate labeling as well as FTIR-microscopy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48287.     

Transient changes of volatile organic compounds (VOCs) during dulce de leche preparation by a direct injection mass spectrometer based on proton transfer reaction (PTR-MS)

The capacity of a direct injection mass spectrometer based on proton transfer reaction (PTR-MS) to monitor the transient changes of the volatile organic compounds (VOCs) during dulce de leche production was investigated. We found a correlation between the mass fingerprint and some physio-chemical properties of the dulce de leche samples. The intensity of the selected mass fragments related to VOCs was positively correlated with the changes of solids content but negatively with that of water activity. Rheological and textural changes were also highly correlated with the intensity observed for several mass fragments. Hence, this relationship could be useful to predict the textural and rheological changes during heating a complex fluid. Although not all the correlations between physical changes and VOCs formation reflected a direct cause–effect relationship, but those results demonstrated the suitability of the PTR-MS technique to monitor the quality changes even in complex food mixture during thermal processing.     

Kinetics of desorption of organic compounds from dissolved organic matter

This study presents a new experimental technique for measuring rates of desorption of organic compounds from dissolved organic matter (DOM) such as humic substances. The method is based on a fast solid-phase extraction of the freely dissolved fraction of a solute when the solution is flushed through a polymer-coated capillary. The extraction interferes with the solute-DOM sorption equilibrium and drives the desorption process. Solutes which remain sorbed to DOM pass through the extraction capillary and can be analyzed afterward. This technique allows a time resolution for the desorption kinetics from subseconds up to minutes. It is applicable to the study of interaction kinetics between a wide variety of hydrophobic solutes and polyelectrolytes. Due to its simplicity it is accessible for many environmental laboratories. The time-resolved in-tube solid-phase microextraction (TR-IT-SPME) was applied to two humic acids and a surfactant as sorbents together with pyrene, phenanthrene and 1,2-dimethylcyclohexane as solutes. The results give evidence for a two-phase desorption kinetics: a fast desorption step with a half-life of less than 1 s and a slow desorption step with a half-life of more than 1 min. For aliphatic solutes, the fast-desorbing fraction largely dominates, whereas for polycyclic aromatic hydrocarbons such as pyrene, the slowly desorbing, stronger-bound fraction is also important.     

Development of a vision based deflection measurement system and its accuracy assessment

A vision-based method for measuring civil engineering constructions’ in-plane deflection is presented in this paper. Displacements of points are computed by means of digital image correlation. The application of homography mapping enables the deflection field to be computed from two images of the structure acquired from two different points in space. The verification of the developed system is performed using the coordinate measuring technique. Results of the beam deflection obtained from the developed vision system and Laser Tracker device are compared. Moreover, the uncertainty of the system is evaluated and possibilities for its improvement discussed.     

Intensity and Efficiency of Luminescence in U(IV) Oxidation with Xenon Difluoride,as Influenced by the Solution Acidity

Unusually strong influence of the solution acidity on the chemiluminescence intensity (I_cl) in U(IV) oxidation with xenon difluoride was found. Although the intensity of uranyl photoluminescence (I_fl) increases by a factor of 3 with increasing HClO₄ concentration from 0.5 to 2 M, under these conditions the maximal I_cl in U(IV) oxidation with XeF₂ decreases by a factor of 8 and the quantum yield of CL (η_cl) decreases by a factor of 4.6. This strong influence of pH of the solution on I_cl and η_cl is likely due to deceleration of hydrolysis of U(V) intermediate to form uranyl(V) ion.