Phase-resolved photoacoustic spectroscopy: Application to metallic-ion-doped glasses

Vitis vinifera Red Globe grape: In natura investigations on skin pigmentation using phase-resolved photoacoustic and TDDFT methods

In this work we aimed to investigate the source of the Red Globe grape skin pigmentation. To achieve this goal, we used the phase-resolved photoacoustic technique to investigate the sample in natura and to access the phase-dependent absorbing entities. In addition, we used the time-dependent density functional theory (TDDFT) to contrast with our experimental spectroscopic results. We measured the absorption spectrum of the Red Globe grape in natura using the photoacoustic technique and recovered the main source pigmentation spectrum using the phase-resolved technique. Finally, using the TDDFT, we qualitatively analyzed the physical sources of the grape pigmentation and we found significant evidence that the main biomolecules responsible for the coloration of the grape are the cyanidin-3-O-glucoside and the peonidin-3-O-glucoside.

Photoacoustic Spectroscopy and Hyperglycemia in Experimental Type 1 Diabetes

According to the World Health Organization, diabetes was the seventh leading cause of death in 2016. Long-term diabetes complications are associated with hyperglycemia. It is difficult to predict the beginning and evolution of those complications. The goal of the study was to evaluate the relationship between glycemia and blood spectroscopic variables in an experimental model of type 1 diabetes (streptozotocin model). Blood samples were taken weekly (10 weeks) from the tail of male Wistar rats with or without diabetes. Blood optical absorption spectra were obtained by means of photoacoustic spectroscopy. It was possible to estimate the time-course of blood characteristic peak ratios. The area under the curve of those peaks correlated with hyperglycemia. The evolution of the optical absorption at 450 nm, related to cytochrome p450, was obtained by using the phase-resolved method. The area under the curve of p450 correlated also with hyperglycemia. It is concluded that photoacoustic spectroscopy is a reliable technology to detect the effects of hyperglycemia on blood with possible applications in the study of long-term diabetes complications.

The phase-resolved photoacoustic method to indicate chemical assignments of paracetamol

In this work, the phase-resolved photoacoustic method was applied to provide specific information on the chemical assignments of paracetamol in the near-infrared region. Two broad bands, centered at 1370 and 1130 nm, were well-resolved using this method, making it possible to assign the peaks centered at 1398, 1355 and 1295 nm to a C-H combination from a CH3 structure and the peak at 1305 nm to a C-H combination from the aromatic ring. This information represents a new finding in chemical studies regarding this medicament.

Statistical design of experiments: study of cross-linking process through the phase-resolved photoacoustic method as a multivariable response

This work presents an add-on result of cross-linking using photoacoustic spectroscopy (PAS) phases in a multivariable process using the phase-resolved photoacoustic (PRPA) method. The method is tested to separate contributions from groupings -OH, -CH(2)-, -CH(3), and Si-OH overtones in the range from 700 to 2600 nm. Samples of the copolymers ethylene vinyltrimethoxysilane (EVS) and grafted vinyltrimethoxysilane (VTS) on low-density polyethylene (LDPE) were prepared having concentrations (C) of 3, 5, and 7% of catalyst and temperatures (T) of 70, 80, and 90 degrees C. By considering the condensation reaction, the reduction of -OH groups is monitored. The PRPA analysis was carried out using the surface response methodology and results indicated the optimum point for both answers (signal and phase-resolved) and for both factors of interest (C, T). For the copolymers, it was found that C approximately (5.00 +/- 1.14)% and T approximately (82.4 +/- 4.3) degrees C, while for grafted LDPE PE(g) it was found that C approximately (4.92 +/- 0.85)% and T approximately (80.8 +/- 2.5) degrees C. These results agreed with the chemical analysis for gel content, which showed as the optimum point 5% of catalyst and temperature of 80 degrees C. Further, it is an advantage that the photoacoustic method allows one to per- form a nondestructive analysis.