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One of the main uses of energy is the heating of fluids, mainly water and air. In the residential and industrial sectors, energy applications are diverse, mainly; Prepared food, washing clothes and personal hygiene, as well as the generation of steam and heat to process. The solar collectors represented an excellent sustainable alternative to cover the needs of these sectors. In Mexico there is a diverse market of brands and solar equipment, mostly of foreign origin. But those manufactured in our country. With selective coatings, such as titanium oxide, they are imported, and the substances and processes used are highly toxic and harmful to the environment. Given this, selective organic coatings represent an excellent alternative. It is important to increase the thermal efficiency of the solar collectors, as well as to improve the heat transfer in a thermal tank. For all the above, this research proposes a solar collector for 15 liters of water with organic selective coating and the support of a heat exchanger with nano fluid. So far, the best results are: thermal efficiency of 0.58 with a 0.1% concentration of ZnO nano fluid, thermal efficiency of 0.6 with a concentration of 0.1% ZnCuO nano fluid and thermal efficiency of 0.63 with a concentration of 0.1% CuO nano fluid. Uma das principais utilizações da energia é o aquecimento de fluidos, principalmente água e ar. Nos sectores residencial e industrial, as aplicações energéticas são diversas, principalmente; alimentos preparados, lavagem de roupa e higiene pessoal, bem como a geração de vapor e calor para processar. Os colectores solares representaram uma excelente alternativa sustentável para cobrir as necessidades destes sectores. No México existe um mercado diversificado de marcas e equipamentos solares, na sua maioria de origem estrangeira. Mas aqueles fabricados no nosso país. Com revestimentos selectivos, tais como óxido de titânio, são importados, e as substâncias e processos utilizados são altamente tóxicos e prejudiciais para o ambiente. Por isso, os revestimentos orgânicos selectivos representam uma excelente alternativa. É importante aumentar a eficiência térmica dos colectores solares, bem como melhorar a transferência de calor num tanque térmico. Por tudo isto, esta investigação propõe um colector solar para 15 litros de água com revestimento orgânico selectivo e o apoio de um permutador de calor com nanofluido. Até agora, os melhores resultados são: eficiência térmica de 0,58 com uma concentração de 0,1% de ZnO nano fluido, eficiência térmica de 0,6 com uma concentração de 0,1% de ZnCuO nano fluido e eficiência térmica de 0,63 com uma concentração de 0,1% de CuO nano fluido.

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.

Due to the confinement at home that is lived in various countries by the pandemic of the new coronavirus COVID-19 in Wuhan, China and its spread worldwide. Changes have been brought about in the daily life of the population, for example the way of carrying out academic and professional work. Work hours increased and with it the use of various visual devices to carry out activities. Therefore, the objective of this research was to evaluate the state of visual health and ergonomics by the population during the health contingency. An evaluation instrument generated in the "Microsoft Forms" software was applied to evaluate ergophthalmology and visual health. An absolute positive correlation was found in the symptoms of blurred vision and muscle pain in the male gender, while for the female gender an absolute correlation was reported in the glare symptom and a positive correlation in dry eye, red eye, burning, tearing and muscle pain. Therefore, it is of utmost importance to disseminate ergophthalmic measures to reduce the visual symptoms of the population.

Magnetite (Fe3O4) nanoparticles (MNPs) below 30 nm are considered addressable magnetic cores which can be stimulated by an external AC magnetic field. In this study, MNPs were covered directly with Curcuma longa extract from a modified coprecipitation route as an organic base. The particle size distribution ranging from 9 to 18 nm according to transmission electron microscopy (TEM) and dynamic light scattering (DLS). Two main particle size populations were found associated with particle aggregation in the samples. In addition, their thermal features were determined using photothermal techniques to obtain their thermal diffusivity, effusivity, conductivity, and heat capacity per unit volume. The thermal diffusivity and effusivity values of the MNPs were obtained using a thermal wave resonator cavity (TWRC) and inverse photopyroelectric (IPPE) photothermal techniques, respectively. The obtained thermal parameters were similar to the water thermal values because the MNPs were measured in aqueous solutions. The main goal of this study was to define the thermal response, by obtaining the thermal characterization, of MNPs in suspensions related to superparamagnetic cores and Curcuma longa coatings.

En esta investigación se planteó como objetivo caracterizar color, textura y calidad sanitaria de pan adicionado con maíz criollo y cúrcuma. Se realizaron 14 diferentes panes empleando seis tipos de maíces (M1, M2, M3, M4, M5 y M6). Los principales hallazgos fueron a) El color de los maíces, harinas nixtamalizada y masas tuvieron diferencia significativa (p < 0.05) al comparar valores medios de parámetros de Luminosidad, a* y b*. Los maíces azules y rojizo M2 (37.01), M3 (44.06) y M6 (41.07) y, amarillos y amarillo-naranja M1 (21.26), M4 (15.92) y M5 (26.01) presentaron los valores inferiores en L* y superiores en b*, respectivamente. La menor diferencia en color ?E encontrada en el proceso de transformación de maíz a harina y masa, fue para maíces amarillos. b) En el pan de maíz se encontraron diferencias significativas en variable a* al compararse el mismo tipo de pan durante tres días consecutivos, en los panes BM1, BM5 y BM6, con una disminución de 7.5, 2.6 y 16.9%, con respecto al primer día. c) La calidad sanitaria del pan de trigo mejora con la adición de maíz nixtamalizado y cúrcuma. En los panes adicionados de maíz los que presentaron menor cantidad de colonias de hongos fueron los maíces azules y rojo (M2, M3 y M6). d) La dureza del pan de maíz criollo y cúrcuma no presentó diferencias durante tres días consecutivos beneficiando su conservación. El pan de maíz amarillo y cúrcuma BM1-C mostró incrementos en la dureza en los días 2 y 3.

The trachea serves a variety of functions during breathing and swallowing. In cases requiring a partial resection, the treatment may involve anastomosis of the healthy ends of the trachea. The tension in the anastomosis should not exceed 1,000 g. Traditional methods for estimating tension in the trachea are very invasive. The aim of this work is to develop a noninvasive optical system devoted to estimate the tension of the trachea in vivo. An optical system was designed using a light source and a photosensor. To determine the most suitable wavelength for the light source, a photoacoustic spectroscopy study was performed. To test the system, a cadaveric pig trachea was mounted on a universal testing machine, and it was subjected to three tensile tests of up to 30 mm elongation. The optical response was measured at 0, 10, 20, and 30 mm elongation. An exponential response was observed so that the optical voltage-response curves were adjusted, and three exponential equations were derived to correlate the voltage with the optical response. We can conclude that the proposed optical system is able to noninvasively estimate the tension of a cadaveric porcine trachea.

International audience; The pro-health action of germinated lentils could be useful to be added with wheat flour in the production of box bread. In this work, we spectroscopically evaluate the germinated and non-germinated lentils, and use them at the concentrations of 5 and 10% for the production of box bread. The chemical and physical tests of the bread and its determination of phenolic acids and flavonoids (by HPLC) were also performed. As well as the evaluation of the quality of flour and dough used to produce the bread and the acceptance of the germinated lentil bread with a population of 20 people with diabetes or with diabetic relatives It is shown that: (1) The amplitude of photoacoustic signal obtained by photoacoustic spectroscopy is modified as a function of the percentage of germinated lentil (GL) flour (0, 5 or 10%) add to the bread; being higher the photoacoustic amplitude to higher concentration of GL in the absorption band of 300–425 nm, which is related to higher content of phenols and flavonoids. (2) The contents of phenolic acids (Sinapinic, β- resorcylic, Chlorogenic and Ferulic) and flavonoids (Quercetin and Isorhamnetin) tended to increase in the germinated lentil bread with 10% concentration of germinated lentil flour with respect to the control bread (0% GL). (3) The addition of germinated lentils flour to 5 and 10% into wheat flour to produce bread with higher hardness and less cohesiveness than bread based on wheat flour only. The Falling number indicate that there is no significant difference between the control sample and the 5% GL flour, while in the 10% GL flour there was a reduction of 21 s, with respect to the control. The effect of the germinated lentil flour percentage on the pasting properties of the flours was significant between the control and 10% GL flour. In general, the quality of the dough and flour are modified due to the addition of germinates lentils, and this affectation increases with the increase in the concentration of GL. (4) The bread added with germinated lentil has sensory acceptance with a group of people with diabetes and/or diabetic relatives in their attributes in general. The obtained results thus support the production of wheat bread with mixed germinated lentils flour, as a nutraceutical option for human consumption.

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.

X-ray Photoelectron Spectroscopy (XPS) and Photoacoustic (PA) techniques are useful to identify the structure and optical properties of chemical compounds used in archaeology, among others. In the present study XPS and PA techniques were used to analyze seven samples obtained from the Talavera House, during the conservation and restoration works carried out in the 2012-2013 period. Talavera House is located between the República del Salvador, Talavera and Roldán streets, in the historic center of Mexico City. The objective of this study was to identify the chemical compounds added to the lime when burned in the furnace and its use in the tanneries during the 18th century, both elements located in the second yard, as well as in the construction of the corridor in the 20th century located in the first courtyard. The samples were collected at these points and analyzed by XPS and Photoacoustic (PA) techniques, comparing these results with other excavated sites.

International audience; Photoacoustic spectroscopy is applied to evaluate the impact of Moringa at different concentrations (0, 1.25, 2.5, 5 and 10%) on the elaboration, sanity, texture, and color of wheat bread. It was found that: i) Photoacoustic signal amplitude values of bread significantly increase from 37 to 90% when moringa powder concentration raises from 1.25% to 10%, at 300 nm wavelength. ii) Comparing the photoacoustic signal values at 300, 330, and 370 nm wavelengths, produced by the different bread types, there were statistically significant differences. iii) The sanitary quality of bread mixed with a 2.5% of moringa is relatively higher than the ones obtained for other concentrations, such that the number of fungal colonies were reduced by 99% in comparison with the control bread without moringa, after six days of storage. Moringa at 2.5% of concentration could thus improve the sanitary quality of wheat bread. iv) The addition of moringa for making bread slows down its textural changes (hardness, elasticity, cohesiveness, resilience, and chewiness) during storage. v) Finally, the highest correlation between the photoacoustic amplitude and the moringa concentration occurs at the wavelengths of 300 and 330 nm, which could be related to significant changes in the content of flavonoids and phenolic acids.

The thermal properties of graphene oxide (GO) nanoparticles’ colloidal suspensions prepared using the microwave-assisted hydrothermal method were determined. The mode-mismatched dual-beam thermal lens technique was employed to measure the thermal diffusivity of GO nanoparticles for different concentrations in the base fluid. By fitting the experimental data to the theoretical expression, the characteristic time constant was determined. The thermal diffusivity of the fluids seemed to be strongly dependent on the presence of the nanoparticles, increasing from 15.02 ± 0.16 × 10−4 cm2·s−1 to 27.59 ± 0.51 × 10−4 cm2·s−1 for concentrations ranging from 0.82 %V to 4.00 %V of GO/H2O. As nanofluids concentration increased, a higher value of thermal diffusivity was obtained. The optical properties, morphology and chemical structure and functional groups of the nanoparticles were characterized by UV–Vis spectroscopy, transmission electron microscopy (TEM) and Fourier Transform infrared spectroscopy (FTIR). Two main absorption peaks at 230 nm and at 303 nm in the UV–Vis spectra were observed. TEM images revealed a uniform size distribution and spherical in shape NPs with mean diameter of 7.4 nm. This novel type of nanofluids have potential applications for heat transfer fluids like solar collectors and heat exchange systems.

New nanofluids containing Ag nanowires with different concentrations were prepared by chemical reduction method. The metallic nanowires were monodispersed and soluble in distilled water. Thermal properties of nanofluids containing Ag nanowires were obtained using photothermal techniques. The thermal-wave resonator cavity (TWRC) technique was used to obtain the samples’ thermal diffusivity. Open Photoacoustic Cell (OPC) technique was used to obtain the thermal effusivity of Ag nanowires. The thermal diffusivity and effusivity were obtained by fitting the theoretical expressions for each configuration as a function of the sample thickness and frequency to the experimental data. The thermal properties of the nanofluids seems to be strongly dependent of Ag nanowire concentration. It was observed an increase of thermal parameters when concentration of nanowires increased. Thermal conductivity behavior of the nanofluids is explained. UV–vis spectroscopy, Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques were used to characterize the nanofluids.

International audience; We quantitatively evaluate the effects of UV-C radiation on bean seeds Oti (Phaseolus vulgaris), their germination and phenolic compounds of seedlings, by means of photoacoustic spectroscopy and scanning electron microscopy. It is shown that (i) The photoacoustic signal produced by the bean seeds exposed to UV-C radiation during 15 min, reduces from 0.24 to 0.10 mV for the wavelengths of 295 and 340 nm, as a result of their degradation. This significant reduction of 58.3% decreases, but keeps over 50% for other spectral UV wavelengths within the interval (270-400 nm). (ii) As the UV-C radiation time increases from 2 to 15 min, the morphological changes at the surface of the bean seeds exhibit micro-holes and detachment of the cotyledon sclereids. (iii) There are no significant statistical differences in the variables of germination, dry weight, and seedling length, for exposure times up to 15 min. (iv). The phenolic acids and flavonoids of the bean seedlings of seeds treated by UV-C for different exposure times (0, 2, 5, 10, and 15 min) display significant statistical differences (P ≤ 0.05) in both roots and foliage. For both the roots and foliage, the highest concentration of phenolic acids is observed at 10 and 15 min, while for root flavonoids, it appears at 5 and 15 min.

During the last decades, digital image processing algorithms have been developed to measure external characteristics of agricultural products due to the great potential that these methods offer. So, in this research, the thermal images obtained from a thermographic camera were analysed considering two genotypes of maize seeds: crystalline and floury in their natural state, previously irradiated with a laser light source of 650 nm for exposure times of 15 s and 35 s. The methods applied in the analysis were: a) histogram to obtain the distribution of gray levels of images, b) mean value that indicates the brightness of images, c) variance which means the contrast of images, d) entropy applying both Shannon and Tsallis definitions, which provide the average self-information of images, e) estimation of the probability density of temperature variations on seeds to quantitatively characterize them from thermal images. Higher mean and variance were obtained from crystalline seeds indicating higher brightness and contrast. Furthermore, thermal images of floury seeds had higher entropy of Shannon indicating that images had greater disorder with respect to images of crystalline seeds. In the case of the entropy of Tsallis, the entropic index q could be used for characterization of seeds. Thermal images obtained from seeds with a floury structure provided a higher redundancy value for a shorter exposure time to laser light. Thus, the viability of the statistical methods of digital image processing applied to thermal imaging for the characterization of seeds is shown.

Currently evaluation of agricultural product quality is of great importance, in order to guarantee a consumption free of contaminants. In different research areas several techniques are used to evaluate food attributes, related to its quality. Among the techniques used to characterize food stuffs, photothermal techniques have shown versatility to obtain different physical parameters of foods. In the present investigation, the temperature variation effects of different varieties of corn kernels, when excited by laser light during 60 s, were obtained from digital and thermal images, which were analyzed by using artificial vision for characteristic color patterns and geometric measurements to observe the thermal effects, respectively. From these images it was possible to observe variations in temperature, through differences in digital and thermal images of corn samples. Also photoacoustic (PA) spectra were obtained in a wavelength range from 300 to 750 nm, for each variety of corn kernels. Different behaviors of both, image analysis and the PA spectra, showing that one variety of corn kernels present a greater response in both techniques compared to the other varieties. The information obtained could be used in food production areas to identify, classify and determine attributes of grains and seeds of different types of crops.

In this documentary investigation, we review literature about the transdisciplinary perspective (TD) to generate knowledge, locating its origin, evolution and characteristic features. It is found that: i) This origin is located in France and the United States, although some characteristic features related to self-knowledge, participatory research and the unity of knowledge, were proposed before the creation of this TD term introduced in 1970. ii) The concept of transdisciplinarity has evolved over time involving a transition of vision towards the application of perspective to investigate. Switzerland was the first country to apply the transdisciplinarity in research in the 1990s. iii) The key world events that gave impetus to the transdisciplinarity are the world (1994) and Zurich (2000) congresses, as well as the special edition entitled “the foundation of Academy of Transdisciplinary Learning of Advanced Studies (ATLAS)” of the Journal "Futures" (2004) and the 10th anniversary edition of the Transdisciplinarity Journal of Engineering & Science (TJES) in 2010. iv) the main features of transdisciplinary research are: a) research for society and with society, i.e. participatory research, b) scientific research under systemic thinking, c) communication of results to the scientific community and disseminated to non-scientific population. v). The number of transdisciplinary research publications have increased over time, along with the quantity of authors per publication and citations thereof. Some contributions from the 90s were the most impactful due to the number of cites today. The transdisciplinary approach could be the best pathway to develop research in Latin American countries and the world, for solving the diverse problems of society.

Photoacoustic spectroscopy (PAS) has been widely used as a nondestructive and sensitive analytical technique used to determine the thermal diffusivity, effusivity and heat capacity of different materials. In this work, the open cell photoacoustic technique (OPC) technique was used for the kinematic study of heat transfer processes as a function of time for curing nanoresin composites. An exponential growth of the signal during the process of curing was observed. The nanoresin was based on silver nanoparticles (AgNPs) that were synthesized using a green method from an aqueous extract of Capsicum annuum var annuum as an Ag reducer and an acrylic resin. It was cured using a violet laser beam with a wavelength of 405 nm with an average power of 120 mW. The characteristic curing time was measured as a function AgNPs concentration of 0.0, 5.16, 7.27, 11.85, 14.50, 16.86 and 20.96 × 10−4 vol%. The results showed an increase in the curing time of composite resin containing the AgNPs compared to the pure resin. This study has applications in printing parts using laser stereolithography.

High pollution rates in large cities have had a negative impact on human, animal and plant health. In the case of plants, several techniques have been used to analyze the physical and physiological parameters of their seedlings and seed germination process, under different environmental conditions. This study proposed the evaluation of seedlings from corn, lentils and bean seeds, exposed to polluting gases (CO, CO2) through a container system of a vehicle engine, during different times (0, 20, 40, 60 and 80 min). The seeds, after the exposition to the pollutant gases, were planted, and the optical absorption spectra of each seedling were obtained by photoacoustic spectroscopy. The absorption spectra were obtained in a wavelength range from 250 to 750 nm. The obtained spectra demonstrated significant statistical differences in the wavelength range from 290 to 300 nm (corresponding to optical absorption mainly by flavonoids) and also from 650 to 680 nm (corresponding to optical absorption of chlorophylls). In addition, changes in physiological parameters, during the seed germination process, were evaluated.

Ancient documents are of historical interest because they contain valuable information for future generations. One of the most common causes of documents damage and degradation is due to the presence of fungi. Therefore, it is very important to protect them from these microorganisms. In this work, TiO2 nanoparticles (TiO2NPs) were synthesized and used along with UV treatment for application as a potential antifungal against paper damage. Transmission electron microscopy (TEM) showed an average size of 70 nm for the nanoparticles. From scanning electron microscopy (SEM) micrographs, different structures of fungi in damaged cellulose fibers were observed. Energy dispersive X-ray spectrometry (EDS) detected the presence of elements related to organic and inorganic materials. Photoacoustic spectroscopy (PAS) as a non-invasive and versatile technique was used to study ancient documents deterioration presented in this manuscript. Through this technique, pigments produced by fungi in the wavelength between 277 nm and 700 nm were detected, being PAS an important characterization tool to study biodeterioration caused by fungi.

International audience; In this research, we to apply photoacoustic spectroscopy and evaluate bread added with turmeric (Curcuma longa Linnaeus) at different concentrations in relation to wheat flour weight (0, 1.25, 2.5, 5 and 10%). The amplitude of the photoacoustic signal was related to measures of antioxidant activity and evaluate the sanitary quality and also, the texture, color and sensory acceptability of the breads. It is shown that: i) The photoacoustic signal produced by bread significantly increases with the turmeric concentration, such that it raises more than 100% for a concentration of 10% at the wavelengths of 428 and 515nm. ii) The Bread antioxidant activity is directly proportional to the level of photoacoustic signal at 515 nm and its value increases from 73.21% to 91.73%, when the concentration increases from 0 to 10%. iii) The sanitary quality of bread added with 2.5 % of turmeric is relatively higher than the ones obtained for other lower concentrations. No fungal colonies were observed in bread mixed with 2.5%, 5% and 10%, after six days of storage. iv) The addition of turmeric powder for bread making can slow down their textural changes (hardness, elasticity, cohesiveness, resilience and chewiness) during storage. v) Bread at 2.5 and 5% of turmeric concentration showed the yellowest color, while the one with a 10% concentration exhibited the most reddish color. Finally, through Principal component analysis it was possible to demonstrate that a concentration of either 5 or 10% of turmeric added to wheat flour could be used to improve its sanitary quality and antioxidant activity.

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.

Scientific reports around the world indicate that solar radiation has increased its intensity and consequently its UV radiation, making it necessary to improve protective materials against this radiation. Textiles can be used as a protective material against the UV radiation, and one way to increase their UV protection capacity could be by adding biomaterials with optical absorption in the UV region. In the present study, flavonoids, natural pigments absorbing UV radiation, were extracted from corn seeds by using two methods (maceration and microwave oven assisted). The extracted flavonoids as well as a commercial protector of UV-B radiation were added to a cotton textile and then exposed to different UV-B radiation times (0 min, 30 min and 60 min). The optical absorption spectra of flavonoids and textile materials were obtained by photoacoustic spectroscopy. These spectra showed differences, observing that the textile added with commercial protector was degraded with the exposition of UV radiation; meanwhile in the case of the textile added with flavonoids increased its UV protection.

Over the last years extensively research has been carried out on full or partial substitution of supplies resources coming from renewable resources on traditionally non-renewable, in the case of the automobile sector there are progresses in bio-combustibles (biofuel) and synthetic oils coming from vegetable sources. There are strong efforts to find oil additives which can improve oils features in automobile industry, by adding vegetables oils to commercial lubricant oils, is expected to improve oil thermal stability. In the present research, different ratios of castor oil (ricinus comunis)-motor oil blends were obtained and their thermal properties were characterized by using the so-called Back and Front Photopyroelectric (BPPE/FPPE) techniques. Several oil-additives concentrations were measured and thermal diffusivities and effusivities as well as densities are reported, getting full thermal characterization for every concentration.

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.

In this work, thermal characterization of centrifuged aromatic citrus oils was studied using thermal lens (TL) and open photoacoustic cell (OPC). The thermal diffusivity ( D ) was obtained by TL, fitting the critical time parameter of the experimental curves to the theoretical values. An experimental arrangement of non-matched mode lasers with a probe and an excitation lasers was used. On the other hand, the thermal effusivity ( e ) of the samples was obtained by using OPC. The thermal conductivity ( k ) was calculated from the relationship between D and e . The thermal parameters obtained were compared with theoretical values ​​in the literature. UV–vis spectroscopy, Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) and 1 H Nuclear Magnetic Resonance (NMR) were used to determine the absorption coefficients and chemical structure of the citrus oils. The importance of this research work was the determination of the thermal parameters of essential oils as an alternative technique for quality control application.

We describe the preparation of clay with the incorporation of sawdust with different sieving (0.425, 0.84, and 1.41 mm) using a furnace at 890 °C by 9 h. After burned, some samples were immersed in a solution of Ag nanoparticles. The samples were analyzed to obtain their physical, structural, and morphological properties. The densities for each sample were obtained in the range of 3.44 and 2.673 (g/ml) and the volumetric absorption between 16.06 and 45.11%. The XRD pattern shows the four main characteristic phases of the clay as quartz (SiO2), Al2O3, Fe2O3, and TiO2. The morphology of the samples was analyzed by scanning electron microscopy (SEM) observing various pore sizes depending on the sieves used for sawdust.

The evolution of the optical absorption spectra, thermal properties and structure of Pb1-xLax(ZryTi1-y)1-x/4O3 ferroelectric ceramics, which are widely known due to extended use in electronics, are studied when ceramics are submitted to different poling voltages. Structure analysis was done using XRD, Scanning Electronic Microscopy, and Rietveld Refinement. XRD and Rietveld Refinement attest phase transition upon poling. Thermal properties are investigated using Inverse photothermal technique. Thermal diffusivity results show an increment as poling voltage increase. Photoacoustic Spectroscopy is used to determine optical absorption spectra, revealing higher optical transmission through material when higher voltages are applied.

Septic shock is the main cause of death in patients in the intensive care unit. Nowadays, few methods exist in the clinical area that provide an early diagnosis of this condition, and these methods even deliver imprecise values on the concentration of hemoglobin. Photoacoustic spectroscopy (PAS) has been previously used to determine the concentration of hemoglobin in blood, based on the identification of the γ, β, and α peaks in the optical absorption spectrum, located at approximately 412 nm, 550 nm, and 580 nm, respectively. The absorption peak γ/β and γ/α ratios have been reported to be inversely proportional to the concentration of hemoglobin, which could be related to the severity of septic shock. The main goal of this work was to analyze the evolution of the γ/β and γ/α ratios, obtained by PAS, in blood samples of rats with septic shock induced through the intravenous administration of lipopolysaccharide (LPS, 6 mg·Kg−1). Ratios of γ/β and γ/α increased as a function of time, implying a decrease in the hemoglobin concentration. Hemoglobin identified by PAS seems to be a prognostic biomarker in shock.

In the present study, the thermal effusivities of human fluids, such as human blood serum, urine, saliva and tears, were obtained by the photopyroelectric (PPE) technique in inverse configuration (IPPE). Human blood serum and urine were obtained from studies carried out in a government hospital for public servants in Mexico City, whereas saliva and tears were artificial. Making use of both, the amplitude and phase of the PPE signal, the thermal effusivities of each one of the mentioned human fluids were obtained. In order to obtain them, the experimental PPE data were normalized to the PPE signal with air as sample and the theoretical PPE equation was fitted to the normalized experimental data.

The study of structures in different materials is increasingly important. In many cases, these materials have different layers that compose them, and it is not easy to observe or detect some internal structures or damages without destroying the samples. Photothermal (PT) techniques, such as photoacoustic spectroscopy, photoacoustic (PAM) and photopyroelectric microscopies, are valuable nondestructive techniques. PT microscopies allow to make scans of samples in order to obtain their thermal images. In this study, thermal images of two different samples were obtained, by using PAM at different excitation wavelengths.

Recently, conductive polymers have attracted attention in the field of advanced materials. Conducting polymers include polypyrrole (PPy), which is a material with commercial applications due to its stability and electrical conductivity. As technology demands increasingly flexible devices, PPy was mixed with a biodegradable and flexible polymer, polylactic acid, in order to create a composite possessing of newer properties. As it is a new material, thermal properties of this composite such as thermal diffusivity, thermal effusivity, specific heat capacity, and thermal conductivity have been investigated through the application of photoacoustic calorimetry and photopyroelectric techniques.

Photothermal techniques are useful experimental methodologies for characterization of the optical and thermal parameters of different materials like maize seeds due to its advantages such as non-invasive and non-destructive nature. Among these techniques, the photopyroelectric microscopy was applied in the present research to obtain thermal images where each of their coordinates represents amplitude values of the photopyroelectric signal, indicating differences in the structural components of both genotypes of maize seeds. The random variations of the amplitude of the photopyroelectric signal caused by the heterogeneous nature of the thermal properties of the samples, were represented by histograms to identify the probability density function underlying the data sample, observing that in the case of the maize seed with floury structure, the amplitude variations could be described statistically by the transformed Moyal distribution when a linear transformation with censored data was applied to the data set obtained from the thermal image with a significance level of 0.001, according to the Kolmogorov–Smirnov statistical test for goodness-of-fit. In the case of the photopyroelectric signal obtained from a maize seed with crystalline structure, it was not possible to describe statistically the amplitude variations of the signal by means of the transformed Moyal distribution because it did not pass the Kolmogorov–Smirnov test, so the same statistical test for goodness of fit was applied to both genotypes of maize seeds for analyzing the populations of the data sample, in order to find the distributions that best fit each population with a significance level of at least 0.05 increasing in this way the power of the test. The distributions with the best fit were logistic, log-logistic, uniform, least extreme value and normal.

Antimonide-based family holds the potential for developing a new generation of mid-infrared applications. Here, we report on the growth of InSbxAs1-x alloys on n − and p − type GaSb(100) substrates varying the Sb mole fraction ( x ) , using the liquid phase epitaxy (LPE) technique. We show that the ternary alloy grown on the n − type GaSb substrate presents higher crystalline quality, thermal diffusivity and interfacial thermal conductivity, as compared to the one grown on pin equation type GaSb substrates which decrease as the Sb mole fraction (x) in the layer increases. Our results demonstrate that the InSb x As 1 - x / n − GaSb heterostructure reaches the thermal equilibrium faster than the InSb x As 1 - x / p − GaSb structure, with lower roughness, strain, as well as a better chemical abruptness at substrate-layer interface. We also find that the growth mechanism of the InSbxAs1-x alloy is constituted by In − As and In − Sb bonds. Furthermore, the Raman scattering spectra measured at different layer depths evidence that the crystalline quality improves with depth and allow the identification of an intrinsic depletion region. Since the InSbxAs1-x alloy presents a long-range atomic order grown on both n − and p − type GaSb substrates, the phonon-plasmon coupled L − and L + modes are observed, and from the L + coupled mode, we obtain the intrinsic carrier concentration and its variation with the Sb mole fraction. Therefore, this work provides important guidance on the structural, thermal, and chemical properties of the surface, bulk and interface of InSbxAs1-x alloys, that should be considered to improve the performance of future devices, such as better heat dissipation.$

Improving heat transfer on superhydrophobic surfaces is one of the most important wettability challenges due to its wide application. In this study a superhydrophobic coating, with enhanced thermal properties and excellent water drops impact resistance, was performed by the sol-gel process and spray coating technique with different alumina (Al2O3) solution concentrations, heat-treatment temperatures, and heat treatment temperature times. The results of variance analysis (ANOVA) showed that the heat-treatment temperature was the factor that significantly affected the superhydrophobic properties of samples. Furthermore, in this research, the best formulation for superhydrophobicity was obtained with an alumina solution concentration of 0.20 M, heat-treatment temperature of 475 °C and heat-treatment time at 20 min, under these conditions, films with 1.29 ± 0.05 μm roughness and 159.80 ± 0.50° static contact angle were obtained. Thus, superhydrophobic coatings displayed good thermal stability up to 475 °C. The results showed differences in thermal properties of films, indicating a good enhancement in thermal insulation. SEM and AFM micrographs studies have shown a binary surface topography composed of micro/nano scale granules. This method is simple and low cost and can be applied to different kinds of building materials as concrete, steel, and glass.

Vegetable oils can undergo changes in their physical and chemical properties when they are subjected to processes such as extraction, purification, cooking, frying, or chemical modifications that are required depending on their application in the food industry. In the present research, different methods were used to determine physical, chemical, and thermal properties of avocado, sesame, extra virgin flaxseed, extra virgin olive, and grape seed oils, in order to evaluate and compare the compositional effects of each vegetable oil. By using an adiabatic scanning calorimeter, an alternative calorimetric method, the specific heat of five vegetable oils was obtained as a function of the temperature, in the range of 25–90 °C. The fatty acid profile was determined via gas chromatography. Monounsaturated acids present in avocado and extra virgin olive oil cause higher specific heat values in these oils, and the presence of polyunsaturated acids, contained mainly in extra virgin flaxseed oil, reduces the specific heat values. We found an almost linear behavior of vegetable oil specific heats, as a function of the temperature, and the slopes of these linear fits depend on the contained percentage of polyunsaturated fatty acids in the vegetable oil. The unsaturated acids are an important factor to analyze the behavior of specific heat of vegetable oils. The obtained specific heat values were compared with the estimation from the Rowlinson–Bondi equation, for specific heat of vegetable oils, giving a very good adjustment, mainly in a temperature range near to the room temperature.

Diversos laseres han demostrado ser potencialmente utiles a determinados parametros de irradiacion y podrian beneficiar el establecimiento de siembra en condiciones adversas por radiacion UV-B, sequia, frio, salinidad, contaminacion por cadmio, etc. Esta revision de literatura cientifica exhibe las aplicaciones posibles de los laseres en los ultimos anos, como tratamiento de semillas y plantas, destacando el uso de los laseres de He-Ne, Ar, Neodimio-YAG, CO y los diodos laser. Es evidente que las aplicaciones de laseres a parametros de irradiacion especificos en semillas y plantas han adquirido cada vez mayor importancia debido a la necesidad de incrementar la produccion de alimentos a nivel global mediante metodos que protejan el medio ambiente y contribuyan a combatir los efectos del cambio climatico y a la conservacion de la biodiversidad, mejorando la calidad de vida humana y animal. De esta manera, en este Ano Internacional de "la Luz y las tecnologias basadas en la luz", fue importante tomar conciencia del posible uso potencial de la luz laser en la agricultura, ya que podria coadyuvar a un desarrollo sostenible y ofrecer soluciones a problematicas diversas. Los avances encontrados por diversos cientificos lo evidencian y en los proximos anos podria tener un auge en su aplicacion en la agricultura como un elemento "bioestimulador" de semillas, plantulas y plantas.

Cubic GaN/GaAs (001) heterostructures were grown by RF-plasma assisted molecular beam epitaxy with different GaN nucleation temperatures. The heterostructures were studied by an open cell configuration of a photoacoustic experiment to obtain the effective thermal diffusivity ( α) of the composite, which presented values varying from 14 to 28 mm 2/s. Also, a two-layer model was used in order to obtain the interfacial thermal conductivity ( η), revealing values from 5 to 35 W / cm 2 K. Both α and η presented higher values for cubic GaN films grown with higher nucleation temperatures. The crystalline quality of the samples, studied with high resolution x-ray diffraction and photoluminescence measurements, showed that the increase in the nucleation temperature produced films with fewer defects, implying a dependence between the interfacial thermal properties and the bulk crystalline quality. This variation of η can be associated with phonon scattering due to disorder at the interface region. The results provide an important understanding of how the growth temperature of the nucleation layer can affect the quality and the properties of the cubic GaN.

Graphical abstract, Highlights • InP-In2O3 QDs are synthesized by a single-step chemical method without injection of hot precursors. • HR-TEM images show the synthesis of InP and In2O3 QDs. • The InP and In2O3 QDs size increases with the P(TMS)3 concentration. • PL spectra reveal emission bands attributed to InP and In2O3 QDs. • XPS confirms the formation of InP, In2O3 and amorphous InPOx., InP-In2O3 colloidal quantum dots (QDs) synthesized by a single-step chemical method without injection of hot precursors (one-pot) were investigated. Specifically, the effect of the tris(trimethylsilyl)phosphine, P(TMS)3, precursor concentration on the QDs properties was studied to effectively control the size and shape of the samples with a minimum size dispersion. The effect of the P(TMS)3 precursor concentration on the optical, structural, chemical surface, and electronic properties of InP-In2O3 QDs is discussed. The absorption spectra of InP-In2O3 colloids, obtained by both UV–Vis spectrophotometry and photoacoustic spectroscopy, showed a red-shift in the high-energy regime as the concentration of the P(TMS)3 increased. In addition, these results were used to determine the band-gap energy of the InP-In2O3 nanoparticles, which changed between 2.0 and 2.9 eV. This was confirmed by Photoluminescence spectroscopy, where a broad-band emission displayed from 2.0 to 2.9 eV is associated with the excitonic transition of the InP and In2O3 QDs. In2O3 and InP QDs with diameters ranging approximately from 8 to 10 nm and 6 to 9 nm were respectively found by HR-TEM. The formation of the InP and In2O3 phases was confirmed by X-ray Photoelectron Spectroscopy.

The mechanochemical synthesis of PbTe nanostructures via the high-energy milling (HEM) process is proposed, as a synergistic approach, to minimize the thermal conductivity of this semiconductor material at room temperature. In this study, the effect of process control agent (PCA) addition on the microstructure and thermal properties of the as-milled PbTe nanostructures was also investigated. The synthesis design is based on a solid-state technique which allows enhancing the grain boundary scattering and consequently, decreases the thermal conductivity in the PbTe nanostructures. Moreover, the challenging part is the formation of coarse particles with embedded quantum dots and nanoparticles, which are expected to scatter long- and mid-wavelength phonons. In this sense, via the HEM-process, it is feasible to activate other phonon scattering modes by introducing rough-surfaced grains and nanoroughness to the particle surfaces. Overall, the thermal conductivity is decreased in the PbTe nanostructures by two means; namely, adding scattering processes and phonon group velocity, which were heightened due to the PCA added during milling. To elucidate the role of these components of the phonon thermal conductivity, atomic force microscopy and high-resolution transmission electron microscopy were used. On the other hand, photoacoustic (PA) and photopyroelectric (PP) techniques were applied to study the thermal properties of the PbTe nanostructures obtained by the HEM-process. The total thermal conductivity values of the PbTe nanostructures obtained by the PA and PP techniques were at least a half lower (1.06 W m−1 K−1) than that of bulk PbTe value counterpart (∼2.13 W m−1 K−1) and lower than those from PbTe nanomaterials (ranging from 1.5 to 2.2 W m−1 K−1) obtained via other means. The thermal conductivity values of the as-milled PbTe nanostructures were closely related to the carrier concentration experimental findings. We inferred that this strategy can be widely applicable to enhance existing thermoelectric compounds into their nanoforms by a scalable and a simple low-cost route.

In the present research, nanospheres of chitosan (CS), maltodextrin, and sodium tripolyphosphate (STPP), loaded with urea, were synthesized by using an ionic gelation technique. In the nanosphere synthesis was used a central composite experimental design, obtaining nanospheres with an average size of 275 ± 32 nm and 27.5 mV zeta potential. The nanospheres were characterized by their hydrodynamic diameter, polydispersity index, nitrogen content, and thermal properties such as thermal diffusivity (α), effusivity (e), and conductivity (k); also melting temperature was obtained by differential scanning calorimetry. The thermal properties of nanospheres show that the sample with the smallest size has a thermal diffusivity value of (14.4 ± 0.4) × 10−8 m2·s−1 and a thermal conductivity value of (6.4 ± 0.1) × 10−1 W·m−1·K−1, and the obtained melting temperature was 157 °C. Higher concentrations of CS increase the values of these thermal properties, probably because chitosan interacts ionically with STPP forming a reticular network due to the opposite charges of both molecules.

In this study, photothermal techniques were used to investigate the thermal diffusivity, effusivity, and conductivity of samples based on polyvinylidene difluoride (PVDF) polymeric nanofibers incorporated with silver nanoparticles (Ag-NPs). Different amounts were investigated to analyze the thermal effect of Ag-NPs on the polymeric matrix. The Ag-NPs were synthesized by sol–gel and microwave-assisted methods, which have advantages over conventional synthesis methods. The composite of PVDF nanofibers and Ag-NPs was obtained by electrospinning technique while varying the processing parameters. The UV–Vis characteristic spectrum of the nanoparticles was obtained. The hydrodynamic radius of the Ag-NPs was about 16 nm, which was determined by a nanozetasizer. A ζ potential of about 0.03 mV was also measured in this system. This parameter is a measure of the magnitude of the repulsion or electrical attraction between particles and is one of the main measurements to determine the stability of nanoparticles. The morphologies were observed by scanning electron microscopy and showed cylindrical fibers with diameters ranging from 159 nm to 658 nm. Transmission electron microscopy was used to observe the incorporation and distribution of Ag-NPs in the PVDF nanofibers. The thermal effects of Ag-NPs on the polymeric matrix were determined from the thermal properties. The thermal conductivity increased from 0.12 W·m−1·K−1 to 0.34 W·m−1·K−1 when the Ag-NP amount was increased from 4 % to 12 % in the polymeric matrix.

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.