In situ photoacoustic spectroscopy of phycobiliproteins in Gracilaria chilensis

peer reviewedPhycobiliproteins, the main polypeptidic components of the phycobilisomes (PBS), are biolog- ical macromolecules arranged in complex interaction systems to perform light harvesting and conduction. The optical properties of these systems can hardly be studied by conventional spectroscopic techniques. Furthermore this techniques also involve laborious chemical extraction methods. Photoacoustic (PA) spec- troscopy was successfully applied to an in situ study of the phycobiliproteins expression in the eukaryotic red algae: Gracilaria chilensis

Planeamiento territorial sostenible: un reto para el futuro de nuestras sociedades; criterios aplicados

In a large part of the 17 sustainable development objectives set as goals for humanity by the UN, sustainability can be glimpsed. As a result of the dominant socio-productive model, the only way to head towards more sustainable territories that allow achieving and maintaining the well-being of the world's population is to bear in mind the need to properly plan territorial development. This work reflects on this need and takes a step forward in the definition of the main criteria to achieve territorial sustainability at regional and local scales

Determination of recombination parameters in CdTe films on glass substrates by using open photoacoustic cell

In the present work we used open photoacoustic cell (OPC) technique to study the thermal properties and the surface recombination velocity of CdTe/glass samples. Experimental photoacoustic (PA) signal as a function of modulation frequency, in OPC configuration, was fitted to the theoretical expression for PA signal amplitude, in appropriate frequency range, to obtain the sample thermal diffusivities; after this it was obtained the surface recombination velocity by fitting the experimental PA signal to the theoretical PA signal phase, which takes into account the heat sources resulting from the absorption light in semiconductors. The samples under study were polycrystalline CdTe film deposited on glass slides. CdTe layers were deposited by gradient recrystallization and growth (GREG) technique. By varying the deposition times three different CdTe films thicknesses were obtained. A small increment in the thermal diffusivity is observed as the thickness of the CdTe layer increase while the recombination surface velocity have a clear increment

In vitro determination of the non radiative relaxation time of triplet state in protoporphyrin IX

In this work we used Photoacoustic Spectroscopy (PAS) to determine in vitro the non radiative relaxation time (NRRT) of protoporphyrin IX (PpIX) triplet state. In order to obtain this characteristic time, we have used PpIX disodium salt (DS) solutions of 25 % HCl. From each solution it was obtained its optical absorption spectrum, by using PAS, ranging from 300 to 800 nm. In the maximum absorption peak, at 410nm, we obtain the photoacoustic (PA) signal, amplitude and phase, as a function of the light modulation frequency, from 17 to 80 Hz. From the PA signal phase it was possible to determine, for each solution, the NRRT by using the Rosencwaig-Gesho theory, modified to include the effect of a finite nonradiative deexitation time. A NRRT average value, obtained from these solutions, is reported and compared with some NRRT of triplet states reported in the literature for molecules with the same tetrapyrrolic structure

Determinación de difusividad térmica en muestras degradadas de aceite de uva

En este trabajo se reportan mediciones de difusividad térmica en muestras líquidas degradadas de aceite de uva. En el arreglo experimental es usado un detector de LiTaO3 para obtener la señal piroeléctrica en función del espesor de la muestra. Ajustando la expresión teórica de la señal fotopiroeléctrica a los datos experimentales es posible obtener la difusividad térmica de las muestras

Determinación de difusividad térmica de muestras líquidas de infusiones de café soluble

En este trabajo se reportan mediciones de difusividad térmica en muestras líquidas de infusiones de café mediante la técnica de fotopiroeléctrica en configuración directa. En el arreglo experimental es usado un detector de LiTaO3 para obtener la señal piroeléctrica en función del espesor de la muestra. Ajustando la expresión teórica de la señal fotopiroeléctrica a los datos experimentales es posible obtener la difusividad térmica para dichas infusiones

Photoacoustic study of the effect of Mn ion concentration on the thermal diffusivity of Zn1 - xMnxIn2Se4 mono-crystals

Thermal diffusivities of Zn1 - xMnxIn2Se4 series are reported in this article. Manganese nominal concentration ranging from x = 0.05 to x = 1. Measurements were performed at room temperature by using the open photoacoustic cell technique. Thermal diffusivity varies from $1.2 \cdot 10^{-2} \frac{cm^2}{s} \ (x=0.05)$ to $0.30 \cdot 10^{-2} \frac{cm^2}{s} \ (x=1)$, follows a close pattern to the crystal parameter variations

Photoacoustic evaluation of molecular weight and crosslinking effects on thermal diffusivity in Poly(N-vinyl-2-pirrolidone)

The thermal diffusivity of Poly(N-vinyl-2-pirrolidone) (PVP) samples was investigated using open photoacoustic cell technique (OPC) as function of molecular weight and crosslinking. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and X~ray diffraction (XRD) techniques were also used to the PVP characterization

Estudio de la composición química de pericarpio de maíz con las técnicas XPS y EDAX

XPS and EDAX surface techniques were used to determine the chemical composition of pericarp of crude maize and maize submissive a process of traditional nixtamalization varying the content of Ca(OH)2. Also maize with 1 and 2 % of NaOH and 1 % of KOH was used. With XPS it is observed that, pericarp crude and cooked are compound mainly of C and O. In addition, pericarp crude has a small amount of N; whereas pericarp cooked has small amounts of Ca and N. For pericarp crude and cooked with 0, 2 and 3 % of Ca(OH)2, the amount of C is greater in the outer part compared with the inner. However, pericarp cooked with 4 % of Ca(OH)2 has greater amount of C in the inner part. All the samples of pericarp have amounts of Si and Al near ones it limits of detection of XPS spectroscopy. In pericarp cooked with Ca(OH)2, the Ca forms the compound CaCO3. Whereas in pericarp cooked with 1 and 2 % of NaOH and 1 % of KOH, sodium and potassium they form the compounds Na2CO3 and KNO3, respectively. On the other hand, results EDAX also show, besides of signals intense of K, for pericap crude, and Ca, for the cooked, the existence of small peaks of Si, P, and S