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The main purpose of the present study was to characterize the juice and rind of the Persian lime (Citrus latifolia) with different quality of samples, by means of the Photoacoustic Spectroscopy (PAS) technique. In agreement to the Mexican quality standards, the samples under study were classified into four degrees of quality i.e. Extra, Second, Third and Waste classes. We have used PAS to characterize the optical properties of each one of the samples. Thus, we have obtained the absorption spectra of the juice as well as in that part of the rind called flavedo. After that, using another different photoacoustic configuration, we have measured the water vapor permeability of the albedo; i.e. the innermost, white and spongy layer of the rind. Our results show that PAS is a reliable technique to get the grading quality of samples in situ of fresh fruits such as Persian limes by means of the study of some of their physical properties.

Thermal conductivity of two types of nanobiodiesels (NBs) was investigated theoretically and experimentally. The first type of NBs (C4-Au) was composed of C4 biodiesel (purchased from Biofuels of Mexico) filled with Au nanoparticles (Au-NPs) and the second type (SB-Ag) was composed of soybean biodiesel (SB) filled with Ag nanoparticles (Ag-NPs). It has been demonstrated in the literature that the addition of Au-NPs or Ag-NPs to biodiesel can lead to a significant increase in thermal properties. The photothermal techniques were used to determine the thermal diffusivity (D), thermal effusivity (e), and thermal conductivity (k) of biodiesel filled with Au-NPs or Ag-NPs for different concentrations. For about two decades, researchers have made the effort to predict the enhancement of the thermal conductivity of nanofluids based on experiments and several theoretical models have been proposed. One of these analytical models, which have allowed researchers to calculate the thermal conductivity of the nanofluids, is the Hamilton–Crosser Model. This model is based on the classical theory of compounds and mixtures containing particles in the order of millimeters or micrometers and fails dramatically in predicting the thermal conductivity of nanofluids. In that sense, the Hamilton–Crosser model (H–C) cannot represent adequately the enhancement in k as a function of NP’s concentration. Then, the artificial neural network (ANN) modeling method was used to predict the thermal conductivity of the two NBs studied in this work.

Photoacoustic spectroscopy (PAS) has been widely used to analyze biological samples. For example, PAS has been applied to the study of blood which could be related to some diseases. In the present research, the optical absorption spectra of Fisher rat blood, with hepatic damage, were obtained by PAS. Also, the daily intake of turmeric (Curcuma longa), as a protection of liver damage, was evaluated through the characteristic optical absorption peaks of blood, α(585 nm), β(550 nm), and γ(420 nm), where it is possible to associate them with differences in hemoglobin concentrations of the studied samples, by means of the peak ratios γ/β and γ/α, for each analyzed group.

In recent years, has been reported an increasing interest to study vegetables and fruits in order to know their benefits to prevent different types of health problems. Curcuma longa has a great potential to prevent diseases as different types of cancer. In the present study, C. longa samples, of different trademarks, were optically and thermally characterized by using photoacoustic spectroscopy and photopyroelectric techniques, obtaining their optical absorption spectra, optical absorption length spectra, the thermal diffusivity, effusivity, conductivity and heat capacity per unit volume, observing optical absorptions corresponding to antioxidant elements, reported such as beneficial for health. These properties also could be important in the food industry for the commercialization of functional foods.

In this work, the optical absorption spectrum of peppers was monitored by phase-resolved photoacoustic spectroscopy during a dehydration process based on hot-air drying, yielding simultaneous information about changes in the exocarp and mesocarp. Our results show that between all of the dehydration processes of green Capsicum annuum L. variety pasilla peppers, only very small changes occur in the different phase angles, which has been correlated with the small changes in the exocarp thickness. The phase-resolved spectra of mesocarp show more clearly the evolution of the carotenoid compounds with respect to the optical absorption spectrum without phase resolving, due to the last spectrum having a band broadening in that region with more signals convolved. We have shown that not only do the ripened chili peppers produce new carotenoid compounds, but also we are probing that the dehydration process, beginning with the green stage, preserves the nutrimental content, similar to changes that occur in the natural ripening process.

Photoacoustic spectroscopy (PAS) is singled out by its capability to resolve the optical absorption spectra of each element, of a multicomponent system, by the named phase resolved method. The possibility of the use of this method is due to the fact that the Photoacoustic signal is not only sensitive to the optical absorption of the sample as well as the non-radiative relaxation times of its elements. In the present study we compare and analyze, by phase resolved method, Fisher rat blood in four groups: healthy rat blood, liver cancer rat blood, healthy rat blood given by a daily dose of Curcuma longa, and liver cancer rat blood given by a daily dose of Curcuma longa (turmeric), where the optical absorption spectra of the analyzed blood samples was obtained by PAS, in a wavelength range from 350 nm to 650 nm. Three repetitions of 60 μl of blood for each group was done. By using the phase resolved method a new optical absorption band suggestive of methemoglobin was found, observing the benefits of the intake of turmeric due to the fact that the optical absorption spectrum of the Cancer + turmeric group diminish 14% with respect to the Cancer group, anticipating a lower concentration of methemoglobin in blood.

400 million people suffer diabetes around the world. It is the second cause of death in Mexico. The problem is that glucose control is difficult (mainly because of the poor treatment adherence) and the current biomarkers are not efficient enough for the early detection of diabetic complications (before symptoms are present). The goal of the present study was to use the technique called photoacoustic spectroscopy on blood samples obtained from diabetic male Wistar rats, to detect the optical absorption spectra related to haemoglobin. We assume that such spectra modifications are related to toxic heme, a product of haemoglobin, that could be associated with hyperglycaemia as well as the presence of diabetic complications. We postulate that changes on spectra of blood samples taken after 1 to 10 weeks of diabetes are related to the evolution of diabetes. It is necessary to analyse samples from diabetic animals at longer times, diabetes longer than 10 weeks, to find out if those changes have any relation with complications. We conclude that photoacoustic spectroscopy of haemoglobin could be used to assess the evolution of diabetes.

Four experiences in health education in communities located in the state of Lara in Venezuela were analyzed from a sociopsychological perspective. Under a qualitative approach, the information was obtained from three sources: documentary analysis of didactic material; participant observation in workshops, and interviews to leaders and participants.