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We report on characterization of bio-additive from Jatropha curcas L. oil (JBA) in mineral-based oil (MBO) at different viscosities with 10 % and 20 % ratios blends of JBA. Measurements of kinematic viscosity and mass density were carried out to know the physical changes of MBOs when JBA is added. Also, a thermal characterization of the samples was performed. The thermal conductivity, k, and specific heat, c, were obtained using their relationship with thermal effusivity, e, and thermal diffusivity, α, which were determined by the front and back photopyroelectric techniques, respectively. We show that a correlation between kinematic viscosity and thermal conductivity exists with the percentage of JBA in the blend. The obtained thermal conductivities values were compared with those retrieved using the hot-wire technique showing a good agreement. JBA demonstrated special features to improve the thermal properties and to be able to be used as a viscosity modifier of the MBOs, which could be reflected in a better performance in machinery that uses engine oil. [ABSTRACT FROM AUTHOR]

Biological pigments are chemical compounds that absorb light in the wavelength range of the visible region. They are present in all living organisms, vegetables being among their main producers. In this work, the photoacoustic spectroscopy technique was used to investigate some qualitative features related to pigments of ground and roasted coffee. The samples were collected at several Colombian commercial markets from different regions. Colombian coffee is known worldwide for its quality and flavor, being the main agricultural export product of the country. Therefore, it is important to study the composition and color of ground and roasted coffee in order to show quality and special characteristics of local varieties. Studying the content of pigments after roasting and grinding the coffee can allow a better understanding of the coloring process, which can lead to the definition of new criteria for evaluating the quality and other characteristics of the final product by comparing the optical spectra. In this work, the optical absorption spectra obtained by photoacoustic spectroscopy show absorption bands that match those of the pigments capsanthin, lutein and chlorophyll. In addition, an absorption peak in the near-infrared region was revealed, which also provides information regarding the composition of roasted and ground coffee. [ABSTRACT FROM AUTHOR]

The effect of titanium dioxide photocatalysis against bacteria that are dangerous for human health has been investigated in the past, suggesting the possibility of using a specific behavior for each microorganism during this process for its discrimination. In this study, the behavior of some plants' growth promoting bacteria ( Burkholderia unamae (Strain MTI 641), Acetobacter diazotrophicus (Strain PAl 5), A. diazotrophicus (Strain CFN-Cf 52), and B. unamae (Strain TATl-371)) interacting with light and bactericidal titanium dioxide films have been analyzed using the photoacoustic technique. The monitoring of these interactions shows particular characteristics that could serve for identifying these species. [ABSTRACT FROM AUTHOR]