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Ceria-based compounds with trivalent dopant ions are currently being investigated as electrolytes for solid oxide fuel cells operating at low to intermediate temperatures. In these materials, the dependence of the ionic conductivity on the dopant content, the relative cation size and the dopant/vacancy or vacancy/vacancy interactions are the subject of intense research, but there is scarce information about a possible correlation between these properties and microstructural ones, such as texture. Here, we address this question in the heavily doped fluorite-like La2Ce2O7 oxide, using a combination of X-ray diffraction, electron microscopy, optical absorption, Raman scattering and impedance spectroscopy. In all cases, materials with varying degree of 〈1 1 1〉 texture are compared with untextured samples. In this context, the most relevant Raman signatures are the fluorite-like mode at ∼448 cm−1 and a vacancy-related band at ∼578 cm−1. Although remarkable changes were observed upon varying the sintering temperature or the excitation wavelength, both textured and untextured materials displayed similar evolution. A selective enhancement of the vacancy-related band was observed upon decreasing the excitation wavelength from 647 to 488 nm, which is attributed to a resonance phenomenon involving vacancy-related electronic transitions. An indication of incipient vacancy ordering was given by the observation of an intense band at ∼346 cm−1, denoting C-R2O3-like short-range order; its enhancement with the annealing temperature is attributed to the growth of the C-like regions. Conductivity was measured in textured and untextured, fully dense pellets, in the former along and across the texture direction. Impedance plots suggest that the conductivity is dominated by oxide ions and do not allow to separate a grain boundary contribution in these materials with grain size around 1–2 μm. The conductivity amounts to around 10−5 S/cm at 650 K, with activation energy of 1.08–1.16 eV in the temperature range from around 470 to 870 K. Results were similar in textured and untextured materials. We conclude that there is no significant correlation between texture and vacancy concentration or vacancy ordering. A similar conclusion – no influence of texture – is reached concerning the electrical properties. Resumen: Los compuestos a base de ceria dopada con iones trivalentes se están investigando como electrolitos para pilas de combustible de óxido sólido que funcionen a temperaturas bajas o intermedias. En estos materiales se ha estudiado profusamente la dependencia de la conductividad iónica con el contenido de dopante, el tamaño relativo de los cationes y las interacciones dopante/vacante o vacante/vacante, pero hay escasa información sobre la posible correlación entre estos factores y propiedades microestructurales como la textura. En este trabajo abordamos esta cuestión en la fluorita defectiva La2Ce2O7, utilizando para su caracterización difracción de rayos X, microscopía electrónica, absorción óptica, dispersión Raman y espectroscopia de impedancia. En cada caso se comparan materiales con distinto grado de textura a lo largo de las direcciones y muestras sin textura. En este contexto, los indicadores más relevantes del espectro Raman son el modo de tipo fluorita en ∼448 cm-1 y una banda relacionada con las vacantes en ∼578 cm-1. Aunque se observaron cambios notables al variar la longitud de onda de excitación o la temperatura de sinterización, la evolución fue similar en materiales texturados y no texturados. La banda relacionada con las vacantes se intensifica al disminuir la longitud de onda de excitación de 647 a 488 nm, lo que se atribuye a un fenómeno de resonancia entre la energía de excitación y transiciones electrónicas asociadas a las vacantes. Por otra parte, la presencia de una banda en torno a 346 cm-1, típica de fases C-R2O3, sugiere que existe un cierto grado de ordenamiento de vacantes a corto alcance. El aumento de la banda con la temperatura de sinterización se atribuye al crecimiento de las regiones de tipo C. Se midió la conductividad eléctrica en cerámicas densas texturadas y no texturadas, en el primer caso paralela y perpendicularmente a la dirección de la textura. Los gráficos de impedancia sugieren que la conductividad se debe principalmente a iones de oxígeno y no permiten separar una contribución de las fronteras de grano en estos materiales con un tamaño de grano de alrededor de 1 a 2 μm. La conductividad es ∼10-5 S/cm a 650 K, con una energía de activación de 1,08 a 1,16 eV en el intervalo de temperaturas de ∼470 a 870 K. Se obtuvieron resultados similares en materiales texturados y no texturados. Se concluye que no existe una correlación significativa entre la textura y la concentración de vacantes o el ordenamiento de las mismas. Se llega a una conclusión similar en lo que se refiere a las propiedades eléctricas.

In this letter, unique extra-long chemically derived pyramidal graphitic ribbons (PGR) were individualized and deposited onto a SiO2 substrate via simple spin-coating. The length of the individualized PGRs was found to exceed the average length of graphene nanoribbons (GNRs) by hundreds of microns. The physicochemical individualization method resulted in the creation of a novel "graphene nanoribbon intercalation compound" (GNRIC), following a strict stoichiometric relation between the GNR powder and alkali metals. Our experiments were conducted with the use of Na and K as intercalants at NaC8, KC8, and KC24 concentrations. Furthermore, we exposed them to THF and discovered that the nanoribbon bundles obtained from CVD bottom-up bulk synthesis of GNRs can be exfoliated. The exfoliated nanoribbons (ex-GNRs) were analyzed using SEM, Raman spectroscopy, optical microscopy, and AFM, revealing the existence of ribbon-like pyramidal nanostructures that are larger than 100 µm. The morphology of these graphitic ribbons, brings a new starting point and immense potential to the development of graphene-based devices for optoelectronics and solar cells. [ABSTRACT FROM AUTHOR]

Ginebra's gold mineralization is hosted by the Ginebra Ophiolitic Massif and the Buga Batholith, in the western flank of the Central Cordillera of Colombia. Gold occurs as disseminations, quartz-carbonate stockwork veinlets and quartz lodes with a strong structural control and are composed by small amounts of sulfides, mostly pyrite, with galena, sphalerite and chalcopyrite in at least two different deposition events and related to strong sericite-chlorite-epidote haloes, indicative of near-neutral and reduced fluids. Petrography and Raman spectroscopy allowed to identify two main fluid inclusions assemblages primary to pseudo-secondary in origin, both of them aqueous and CO2-rich, with variable N2. Microthermometric analysis indicates the hydrothermal fluids associated with the gold were low saline (0.75-6.22 wt% NaCl equiv.) and presented a minimum trapping temperature ranging from 237.4 to 301.6°C. Petrography and microthermometric results suggest an isothermal fluid mixing and/or H2S loss as the main mechanisms related to gold bi-sulfide/thio-sulfide complexes destabilization and precipitation. Sulfur isotopes indicates a close to zero range (-8.2-+4.8?), suggesting a restricted fluid circulation through the magmatic rocks of the Buga Batholith and the Ginebra Ophiolitic Massif. Besides, the oxygen and deuterium isotopes from hydrothermal sericite and chlorite accompanying to gold events, indicates a metamorphic origin for the hydrothermal fluids. 40Ar-39Ar dating of the hydrothermal alteration haloes, from El Retiro and La Esperanza, indicates a late Cretaceous-Paleocene age, between 67 and 65 Ma, contemporaneous with a regional strong dextral transpressive deformation related to subduction to obduction and exotic terrane accretion against the north-western part of the South American Plate. Although the hydrothermal fluid characteristics of the Ginebra Gold Disctrict are compatible with both the Intrusion-Related and Orogenic Gold deposit types, the metamorphic nature of the hydrothermal fluids and the tectonic regime at the time of mineralization event, allow us to propose they are compatible with an Orogenic Gold deposit. [ABSTRACT FROM AUTHOR]

The effects of lipid peroxidation on rice bran protein (RBP) structure was examined through Raman Spectroscopy. 2,2’-azobis (2-amidinopropane) dihydrochloride (AAPH), acrolein, and malondialdehyde (MDA) are chosen for lipid peroxidation. Incubation of RBP with the increasing concentration of three oxidants resulted in a gradual generation of protein carbonyl derivatives. It can be deduced from the Raman spectra that a low concentration of AAPH and acrolein both decreased the percentage of α-helix and β-sheet, which increased with MDA concentration. The Raman intensities of tryptophan residues of oxidized RBP by AAPH and acrolein, both initially increased and then decreased with oxidation concentration. After MDA treatment, the Raman intensities corresponding to Trp residues and Tyr doublet ratio of RBP were increased and then decreased, and decreased and then increased with oxidation concentration, respectively. The structural change induced by RBP oxidation with the Raman Spectroscopy can aid in refining the function of RBP characteristics and control the adjustment of the storage condition.

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Los alótropos de carbono han ganado interés en las últimas décadas debido a sus propiedades y a la gran variedad de posibles aplicaciones tecnológicas que han demostrado. Por dichas razones, la obtención de estos alótropos con diferentes propiedades y coberturas es ampliamente investigado. La Deposición Química en Fase de Vapor (CVD, por sus siglas en inglés) es una de las técnicas más utilizadas para obtener este tipo de materiales con una alta calidad y cobertura en una forma controlada. En CVD, se utilizan metales de transición como catalizadores, fuentes de carbono gaseosas y altas temperaturas. En este reporte, se presentan estructuras de carbono sintetizadas sobre substratos de cobre utilizando Deposición Química en Fase de Vapor a Baja Presión (LPCVD, por sus siglas en inglés) con acetileno como fuente de carbono. Los sustratos de cobre se trataron térmicamente bajo una atmósfera reductora de hidrógeno-argón y luego se expusieron a acetileno, variando el flujo de acetileno y el tiempo de deposición. Los materiales resultantes se caracterizaron mediante Microscopía Óptica y Espectroscopia Raman. El enfoque seguido permitió determinar las mejores condiciones de síntesis de grafeno monocapa, de crecimiento irregular.

Esta investigación tuvo como objetivo establecer un modelo matemático, haciendo uso de información espectral Raman y el algoritmo regresión de mínimos cuadrados parciales (PLS), para pronosticar el porcentaje de adulteración de la miel de abeja por jarabe de azúcar. El modelo de regresión obtenido puede ser usado para identificar muestras que presenten jarabe de azúcar en miel de abeja en concentraciones en el rango del 10% al 50% (v/v). Se utilizó el método de la validación cruzada con la estrategia de dejar una muestra fuera. El intervalo que resultó optimo es el rango de numero de onda de 643 - 770 cm-1. El modelo de regresión lineal obtenido presenta coeficiente de correlación múltiple de 99,87%, valor mínimo de suma de cuadrados del error residual pronosticado (PRESS) de 551,26 y el valor del estadístico F, 43,65 nos permite establecer que si existe una relación lineal significativa entre las intensidades Raman y los valores de las concentraciones de jarabe de azúcar en la mezcla. El valor del nivel crítico p= 0,022 indica que, si existe una relación lineal significativa, y, por tanto, que el hiperplano definido por la ecuación de regresión ofrece un buen ajuste. Esta investigación reporta un nuevo método analítico para la determinación cuantitativa del porcentaje de pureza de la miel de abeja adulterado por jarabe de azúcar.

El biodiésel es una alternativa biodegradable que permite reemplazar parte del consumo del petrodiésel. Este artículo analiza el efecto corrosivo del biodiésel en materiales metálicos en motores mediante técnicas de caracterización, incluyendo espectroscopia infrarroja por transformada de Fourier (FTIR), espectroscopia de Raman, microscopía de barrido electrónico (SEM) y difracción de rayos X (XRD). Mediante un estudio del estado del arte de dichas técnicas se reúnen recomendaciones para evaluar el desempeño de metales en motores que funcionan a base de biodiésel. Además, se abarcan los mecanismos de corrosión a los que los componentes de los motores están sujetos para mejorar sus procesos de diseño. El estudio finalmente se enfoca en la corrosión por picadura para identificar estrategias viables para mitigar su efecto en este tipo de motores y mejorar sus características de desempeño, para lo cual la ciencia de materiales se demuestra como una herramienta fundamental. El principal resultado de esta revisión fue la identificación de la corrosión por picadura y los compuestos formados como principal mecanismo de falla en motores de biodiesel.

Los minerales translúcidos fueron apreciados por las sociedades prehistóricas por su rareza, y fueron utilizados como elementos altamente simbólicos. Este trabajo aborda el uso y la caracterización de las cuentas translúcidas de la península ibérica, mediante análisis químico (espectroscopía Raman, espectrómetro de fluorescencia de rayos X portátil, difracción de rayos X y espectroscopia en región visible y en infrarrojo cercano) y contextual, junto a una revisión de la bibliografía arqueológica sobre la producción y uso de adornos y elementos translúcidos durante la Prehistoria Reciente ibérica. Un total de 54 cuentas de 47 yacimientos, mayoritariamente funerarios, han sido analizadas; 33 fueron trabajadas en fluorita, mientras que las restantes 21 fueron realizadas en distintos minerales translúcidos (calcita, cuarzo y varios silicatos). La escasez de adornos translúcidos en el registro arqueológico, su escala regional y suprarregional de intercambio, y su asociación recurrente a otros elementos de prestigio en contextos singulares refuerzan la hipótesis del alto estatus de sus poseedores/portadores.

Actualmente, los nanomateriales son de gran interés para la ciencia y la tecnología, debido a que sus propiedades físicas, químicas y mecánicas pueden ajustarse de acuerdo con su dimensionalidad, lo que se ve reflejado en la mejora de su rendimiento si se compara con los materiales en bulto o de mayor escala. Otra ventaja de los nanomateriales es que pueden adoptar diversas morfologías, dependiendo del método de fabricación utilizado. Hoy en día existen diferentes técnicas de fabricación de nanomateriales. En este trabajo se utilizó la técnica de anodización para obtener nanovarillas de CuOH, debido a que, comparado con otras técnicas, la anodización no requiere de equipos costosos o sistemas de alta complejidad. Para la obtención de nanovarillas de CuOH se construyó una celda electrolítica formada por láminas de cobre al 99.9 % de pureza, calibre de 0.3 mm y un área de 3 cm2 como ánodo; se empleó además una barra cilíndrica de grafito de 6 mm de diámetro como cátodo y una solución de hidróxido de potasio (KOH) con una concentración 3 M como electrolito. Se fabricó un total de 21 muestras utilizando tiempos de 2 a 8 minutos. Un par de muestras representativas se estudiaron por microscopia electrónica de barrido (MEB) para identificar la morfología presente en las láminas anodizadas y 7 muestras se estudiaron por espectroscopía Raman. Por MEB se corroboró la presencia de nanovarillas; se identificó que el largo y el espesor de las nanoestructuras es de aproximadamente 10 µm y 200 nm respectivamente. Además, se logró apreciar que las nanovarillas están compuestas de nanohilos que tienen un espesor de 50 nm aproximadamente. Por microscopia Raman se determinó que las nanovarillas están compuestas de CuOH y se encontró una tendencia clara en el incremento de la intensidad de las señales Raman asociadas al CuOH, conforme incrementa el tiempo de anodización.

The effects of lipid peroxidation on rice bran protein (RBP) structure was examined through Raman Spectroscopy. 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH), acrolein, and malondialdehyde (MDA) are chosen for lipid peroxidation. Incubation of RBP with the increasing concentration of three oxidants resulted in a gradual generation of protein carbonyl derivatives. It can be deduced from the Raman spectra that a low concentration of AAPH and acrolein both decreased the percentage of α-helix and β-sheet, which increased with MDA concentration. The Raman intensities of tryptophan residues of oxidized RBP by AAPH and acrolein, both initially increased and then decreased with oxidation concentration. After MDA treatment, the Raman intensities corresponding to Trp residues and Tyr doublet ratio of RBP were increased and then decreased, and decreased and then increased with oxidation concentration, respectively. The structural change induced by RBP oxidation with the Raman Spectroscopy can aid in refining the function of RBP characteristics and control the adjustment of the storage condition. [ABSTRACT FROM AUTHOR]

Nanomaterials are currently of great interest to science and technology due to their physical, chemical, and mechanical properties can be adjusted according to their dimensionality, which is reflected in an improvement in their performance when compared to bulk or larger scale materials. Another advantage of nanomaterials is that can adopt different morphologies depending on the manufacturing method used. Nowadays there are different techniques for manufacturing nanomaterials. In this work, the anodization technique was used to obtain CuOH nanorods, because, compared to other techniques, anodization does not require expensive equipment or highly complex systems. To obtain CuOH nanorods, an electrolytic cell was used, formed by copper foils at 99.9 % purity, 0.3 mm caliber, and 3 cm2 of surface as anode. A 6 mm diameter cylindrical graphite rod as cathode and a solution of potassium hydroxide (KOH) with a concentration of 1.5 M as electrolyte also was used. A total of 21 samples were fabricated using times of 2 to 8 minutes, by 1-minute increments. Only a couple of samples were studied by scanning electron microscopy (SEM) to identify the morphology in anodized sheets and 7 samples were studied by Raman spectroscopy. The presence of nanorods composed of nanowires was corroborated by SEM, it was identified that nanorods have around 10 µm length and that the thicknesses are 200 nm and 50 nm respectively. By Raman microscopy was determined that nanorods are composed of CuOH, and a clear trend was found at the increase in the intensity of the Raman signals associated with CuOH as the anodization time increases. The reliability of use anodization technique for the manufacture of CuOH nanorods was demonstrated by means of the analysis carried out by Raman spectroscopy, since intensities in Raman signals associated with CuOH increase as the anodization time increases, strongly binding the thickness of the anodized layer with the anodizing time even though relatively short anodizing times (2-8 minutes) were used. [ABSTRACT FROM AUTHOR]

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Este trabalho aborda sobre a espectroscopia Raman de baixa frequência, nomeada usualmente de terahertz Raman. Aqui são mostrados os benefícios associados a esta versátil técnica de análise estrutural, uma vez que seu emprego, na análise da estrutura química dos materiais, vem ganhando espaço em ritmo acelerado. Também apresentamos alguns recentes e didáticos resultados, bem como as limitações desta técnica.

El meteorito de Dalgety Downs, hallado en el Desierto de Australia Occidental, es una condrita ordinaria muy poco estudiada, que sin embargo contiene una valiosa información acerca de la evolución de la materia primitiva del Sistema Solar y los procesos que le afectan. Este ejemplar presenta unas características texturales, mineralógicas y geoquímicas en la matriz y cóndrulos que revelan procesos metamórficos de temperaturas intermedias y eventos de impacto moderados, además de una intensa alteración desarrollada durante su entrada en la atmósfera terrestre y su posterior exposición al clima, en lo que se define como la costra de fusión. Entre los métodos empleados en este estudio destaca la espectroscopía Raman como herramienta de identificación mineralógica, técnica que ha demostrado una gran precisión en materiales geológicos y que será empleada en próximas misiones espaciales.

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Se fabricaron películas delgadas de óxido de vanadio por la técnica de Sputtering RF, usando un blanco de dióxido de vanadio, sobre sustratos de vidrio Corning. Las películas fueron fabricadas con diferentes valores de potencia: 40, 60, 80 y 100 W. Posteriormente, las películas fueron sometidas a tres series de tratamientos térmicos en una atmósfera de aire, usando una temperatura de 350 °C y variando el tiempo del tratamiento en una, dos y tres horas. La formación de las diferentes fases de los óxidos de vanadio fue estudiada usando microscopía Raman en función de la potencia de fabricación y de los tratamientos térmicos pos-depósito. Los resultados obtenidos mostraron que espectroscopía Raman es una técnica altamente sensible para determinar la presencia de las diferentes fases de dióxido de vanadio en películas amorfas. Se encontró que sin tratamiento térmico se puede obtener películas de pentóxido de vanadio fabricadas a 100 W.

La resistencia a la degradación, alta demanda y deficiente gestión de residuos sólidos favorecen la acumulación de plástico en el medio ambiente. Un componente importante de este problema se le atribuye a los microplásticos (MP). Estos son residuos plásticos que, por su reducido tamaño, son difíciles de remover, funcionan como vectores de contaminantes, interfieren con el metabolismo de especies marinas y se incorporan a la cadena alimenticia con mayor facilidad que sus congéneres de mayor tamaño. Dado el interés de muchos investigadores por determinar la magnitud de la contaminación por MP, en este artículo se presenta una muy breve revisión de la definición, composición, distribución en el ambiente, impacto ambiental y caracterización mediante espectroscopía vibracional de los MP.

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This work explains about the low-frequency Raman spectroscopy, called Raman terahertz, displaying the benefits of this versatile technique of structural analysis, since the use this technique for chemistry structural analysis have been increasingly used. Also, here is some recent and didactic data as well as the technique limitations. [ABSTRACT FROM AUTHOR]

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The chemical and mineralogical characterization of rock paintings of the Agreste and Geometric traditions of the Descoberta and Saco do Cipó archaeological sites, Piauí, Brazil was performed by the archaeometrical techniques: (i) benchtop and portable X-ray fluorescence (FRX) by energy dispersion, and (ii) Raman spectroscopy. The results show large amounts of silicon, aluminum, phosphorus, sulfur, potassium, calcium and iron. Rock paintings of different shades of color were prepared with hematite-rich materials (a-Fe2O3). Raman spectroscopy allowed the identification of hematite iron oxide and anatase titanium oxide (TiO2), as well as many quartz crystals (SiO2). The similarities in the chemicalmineralogical composition of the rock paintings on both traditions indicate that they have the same elemental composition and that raw materials from the same source area were probably used in their processing. [ABSTRACT FROM AUTHOR]

The intensities of the Raman lines of the ceramic complex (lead titanate) have been investigated as a function of the relation of the areas of the low Raman frequency modes E(1TO) and silent. A change of tetragonal phase into cubic material was observed by Raman spectrjky. The samples were subjected to the same conditions at the time of making the Raman measurements. The UV-vis spectra of absorption suggested a change in energy levels with increasing concentration of lanthanum element (La). This study’s intention is to observe structural changes in the material by means of Raman intensities without using the traditional central position of the peak width in the bands.

Se sintetizaron compósitos formados entre polióxido de etileno (PEO) y trifluoroacetato de sodio (PEO10CF3COONa) con diferentes concentraciones de óxido de aluminio (Al2O3). Los compósitos fueron caracterizados por espectroscopía infrarroja (IR), espectroscopía Raman, difracción de rayos X (XRD) y microscopía de fuerza atómica (AFM). Las combinaciones del electrolito sólido PEO10CF3COONa con diferentes concentraciones de Al2O3, mostraron cambios en la intensidad de los picos de XRD, así como cambios en la intensidad y posición de algunos picos de IR y Raman. El decrecimiento de los picos del PEO en XRD, cuando este fue combinado con la sal, reveló que la cristalinidad del polímero se redujo, siendo más baja cuando se le adicionó alúmina. Se observó un incremento en la raíz cuadrática media de la rugosidad (RRMS) obtenida por microscopia de fuerza atómica cuando se adicionó Al2O3. Este incremento está en concordancia con la reducción de la cristalinidad observada con estudios de XRD. Los cambios en la estructura del PEO mostrados en las líneas de absorción de IR y Raman, debidos a la adición de CF3COONa y Al2O3, fueron atribuidos a interacciones entre el electrolito y el relleno Al2O3.

El avance tecnológico de las últimas décadas ha propiciado el desarrollo de nuevas metodologías para la caracterización de materiales de origen biológico. La espectroscopía Raman es utilizada principalmente en la caracterización de sustancias orgánicas e inorgánicas puras, sin embargo, recientemente se está utilizando para el estudio de organismos y estructuras moleculares de interés biológico. La principal dificultad en el análisis de estos materiales mediante la espectroscopía Raman es la fluorescencia que presentan las muestras al ser iluminadas con el haz de luz láser, pero mediante la técnica SERS (Surface Enhanced Raman Spectroscopy), es posible aumentar la señal Raman y reducir la interferencia de la fluorescencia. Para la aplicación de las técnicas SERS se pueden utilizar nanopartículas metálicas, principalmente oro y plata, de una adecuada distribución de tamaños. En este trabajo se presentan los resultados de la aplicación de técnica SERS a la caracterización espectroscópica del ADN de dos organismos diferentes, de un ser humano y de una bacteria del género Rickettsia, utilizando nanopartículas de oro y plata para la aplicación de la metodología.

Carbon nanostructures, obtained by underwater arc discharge of graphite electrodes, were studied by X-Ray Photoelectron Spectroscopy (XPS). It was observed that the spectra of the samples taken from the floating part of the synthesis products, composed basically by Carbon nano-onions (CNO), present differences with those obtained from the precipitate, which contains a mixture of CNOs and multi-walled Carbon Nanotubes (MWCNT). These differences are related with the presence of atoms of carbon located in orbitals with different degree of hybridization (sp2-sp3), which in turn is related to the diverse grade of curvature of the planes of carbon in the nanostructures present in the samples. The obtained results indicate that XPS can be an important element in the characterization of the products obtained by the above-mentioned method of synthesis.

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NiO has a variety of applications, mainly in the production of electrochemical sensors and of metallic nickel. In addition, it is widely used as catalysts to produce hydrogen from natural gas. In this work, hydrotalcites based on nickel-aluminum and nickel-zinc-aluminum were synthesized, calcined at 500 °C and studied by different techniques. It was observed that nickel-aluminum hydrotalcites are thermally more stable, collapsing at higher temperatures than hydrotalcites containing zinc. During calcination, aluminum is incorporated into NiO lattice, leading to a decrease in crystallographic parameters. However, zinc decreases this effect, favoring the formation of NiO with lattice parameters close to pure nickel oxide. Zinc also contributes to the formation of smaller NiO particles, which is very useful for its use as a catalyst. In addition, aluminum led to a distortion in NiO lattice, an effect that is minimized by zinc, showing that it hinders the incorporation of Al3+ in the NiO lattice. [ABSTRACT FROM AUTHOR]

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In this paper we discuss the use of mineral pigments recovered in stratigraphic position from three excavated archaeological sites (Traful Lake area, Argentina) with the aim of providing information on selection and frequency of use of these raw materials. In this region, human occupation has been recorded since 4000 BP. In order to identify the chromophoric minerals, we applied wavelength dispersive X-ray fluorescence spectrometry, Raman spectroscopy, and X-ray diffraction techniques. Green, red, yellow ochre, and white pigments dated between 3490 and 590 BP were analyzed. The results show that different analytical techniques provide complementary information in order to identify the pigments. Green, red, and yellow samples are related to iron-based compounds. The green pigments can be associated with celadonite and the others with hematite. White samples revealed the presence of hydroxyapatite. Black dots, identified as carbon, were observed in several samples. Red pigments are always predominant, and their relative abundance increases in recent strata. Results are discussed in light of the context and previous reports of chroniclers. [ABSTRACT FROM AUTHOR]

Amino acids containing L-Arginine (Arg), L-Lysine (Lys) and L-Histidine (His) are recognized to increase the solubility of myosin at low ionic strength, but there is a difference in the researchers' views on their effects on the secondary structure of myosin. To elucidate which method is relatively appropriate for the determination of secondary structures of myosin added with Arg, Lys or His, Circular dichroism (CD) spectra and Raman spectroscopy were carried out respectively. Raman spectroscopy was more suitable than CD method for determination of the secondary structures of myosin added with His, while CD spectra was more accurate for the myosin samples added with Lys and the adequate concentration of Lys should be under 10 mM. Both CD and Raman methods could be applied to myosin added with Arg, however, the latter was recommended and the adequate additive content of Arg in CD method should be less than 10 mM. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effects of growth hormone (GH) and muscle strength training (ST) on the composition of bone tissue of Wistar rats through Raman spectroscopy. In total, 40 male rats were randomly distributed into four groups: (N = 10) control (C), control with the application of GH (GHC), strength training (T), and strength training with the application of GH (GHT). The training consisted of four series of 10 water jumps, performed three times a week, with an overload corresponding to 50 % of body weight and duration of four weeks. GH was applied at a dose of 0.2 IU / kg in each animal three times a week and every other day. After four weeks, the animals were euthanized and the right femurs collected for analysis of the bone structure. Raman spectroscopy (ER) was used to observe the following compounds from their respective bands: Calcium Carbonate-Triglycerides (fatty acids) 1073 cm-1, Collagen type I 509 cm-1, Bone-DNA Phosphate (Protein) 589 cm-1, Phosphate Phospholipids 1078 cm-1. For the statistical analysis, the Shapiro-Wilk and ANOVA One-Way variance analysis normality tests were performed, followed by the Tukey post-test. The results showed an increase in the concentrations of calcium carbonate-triglycerides (fatty acids), type I collagen, bone phosphate-DNA (protein), and phosphate phospholipids in all experimental groups, with or without ST and/or GH , But only the isolated training group differed significantly from the control group (P <0.05). It was concluded that all treatments could promote bone tissue gain, however, only the T group demonstrated a significant difference in the mineral compounds analyzed. [ABSTRACT FROM AUTHOR]

Graphite thin films on silicon substrate were synthesized by the fundamental and second harmonics of a Nd: YAG pulsed laser, varying the substrate temperature from 200°C to 500°C. The oxygen gas pressure was of 2x10-5 Torr for all thin films grown. The samples were characterized by Raman and UVVis spectroscopy. With Raman spectroscopy the vibrational modes D, G and 2D, were identified. The absorbance dependence of substrate temperature was discussed using Uv-vis spectroscopy. The nanostructure of sample grown at 500°C corresponding to graphene oxide, while for the other temperatures, the samples have a graphitic structure. The average thick of thin films was of 65 nm and 40 nm for fundamental and second harmonics respectively. [ABSTRACT FROM AUTHOR]