RESUMO

Experimental studies of TiO2 nanotubes have been conducted for nearly three decades and have revealed the remarkable advantages of this material. Research based on computer simulations is much rarer, with research using density functional theory (DFT) being the most significant in this field. It should be noted, however, that this approach has significant limitations when studying the macroscopic properties of nanostructures such as nanosheets and nanotubes. An alternative with great potential has emerged: classical molecular dynamics simulations (MD). MD Simulations offer the possibility to study macroscopic properties such as the density of phonon states (PDOS), power spectra, infrared spectrum, water absorption and others. From this point of view, the present study focuses on the distinction between the phases of anatase and rutile TiO2. The LAMMPS package is used to study both the structural properties by applying the radial distribution function (RDF) and the electromagnetic properties of these phases. Our efforts are focused on exploring the effect of temperature on the vibrational properties of TiO2 anatase nanotubes and an in-depth analysis of how the phononic softening phenomenon affects TiO2 nanostructures to improve the fundamental understanding in different dimensions and morphological configurations. A careful evaluation of the stability of TiO2 nanolamines and nanotubes at different temperatures is performed, as well as the adsorption of water on the nanosurface of TiO2, using three different water models.

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The quality control for fruit maturity inspection is a key issue in fruit packaging and international trade. The quantification of Soluble Solids (SS) in fruits gives a good approximation of the total sugar concentration at the ripe stage, and on the other hand, SS alone or in combination with acidity is highly related to the acceptability of the fruit by consumers. The non-destructive analysis based on Visible (VIS) and Near-Infrared (NIR) spectroscopy has become a popular technique for the assessment of fruit quality. To improve the accuracy of fruit maturity inspection, VIS−NIR spectra models based on machine learning techniques are proposed for the non-destructive evaluation of soluble solids in considering a range of variations associated with varieties of stones fruit species (peach, nectarine, and plum). In this work, we propose a novel approach based on a Convolutional Neural Network (CNN) for the classification of the fruits into species and then a Feedforward Neural Network (FNN) to extract the information of VIS−NIR spectra to estimate the SS content of the fruit associated to several varieties. A classification accuracy of 98.9% was obtained for the CNN classification model and a correlation coefficient of Rc>0.7109 for the SS estimation of the FNN models was obtained. The results reported show the potential of this method for a fast and on-line classification of fruits and estimation of SS concentration.

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RESUMO

In this research, changes in several characteristics of partially reduced titania were studied. The reduction process used made it possible to gradually observe changes in the material depending on the amount of reducing agent used. We used NaBH4 to impregnate commercial TiO2 with isopropyl alcohol. Impregnated TiO2 nanoparticles were dried and thermally treated in a nitrogen flow to obtain blue titania samples. Thorough spectroscopic characterization showed that oxygen atoms from hydroxyl groups, as well as from the surface, and the lattice of TiO2 was consumed. This caused changes in the surface and even in the bulk of TiO2 when the amount of reducing agent used was increased. Structural, optical, superficial, and textural characteristics were studied using XRD, Raman, DRS UV-Vis-NIR, Mid-DRIFT, XPS, and nitrogen adsorption/desorption isotherms. A photocatalytic test of the degradation of methylene blue dye was performed. Among different effects on the mentioned characteristics, we found evidence of changes in the surface properties of the blue titania samples and their probable effect on the photocatalytic properties. The reduction process implied a preponderant decrease in the surface hydrophilicity of the reduced samples, an effect shown for the first time in this type of material.

RESUMO

Balamtetik is the receiving body of the Rio Grande de Comitán and is located just at the outskirts of the Montebello National Park, Chiapas, México. Multi-elemental, infrared spectra, 137Cs, 210Pb, and diatom analyses in a 75-cm sediment core were used to reconstruct the recent disturbance history of the lake. The sequence chronology, based mostly on 137Cs profiles, allowed to infer high sedimentation rates in Balamtetik (~ 7 mm/year) and a nearly cyclic series of disturbance events that can be related to anthropogenic causes such as deforestation and increased development of agriculture and urban areas at local and regional scale. These disturbance events show high local and regional erosion (high Ca, TIC, and Ti), soil organic matter (IR spectra), eutrophication (high P and diatoms), and anoxic bottom water conditions (low Mn) and can be dated to the early 1950s, the late 1950s, and from the 1980s until the 2000s. The entrance of wastewaters is related with an increase in salinity inferred by the diatom record and the organic matter type. The first two disturbance events are related to changes in land use during the agrarian reform that started during the 1940s; the last event is related with the increase in local population and the introduction of intensive agriculture. This last phase of disturbance corresponds with the reports of fish mortality events around 2003; however, high lake turbidity and anoxic bottom waters seem to have been established since the 1980s. The record from Lake Balamtetik also shows that during the intermediate periods, there was a recovery of the lake and its catchment; however, the future trends might be different, as the increase in the speed of organic matter and nutrients arrival to the lake reduces its resilience.

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RESUMO

The infrared and Raman spectra of the two hydrates of strontium oxalate, SrC2O4⋅H2O and SrC2O4⋅2H2O, were recorded and discussed on the basis of their structural peculiarities and in comparison with the spectra of the related calcium oxalates and other previously investigated metallic oxalates.

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RESUMO

O objetivo do presente estudo foi estudar a caracterização do amido extraído das raízes da Cissus simsiana Roem. & Schult. A extração do amido foi por via úmida e por decantação, calculando-se seu rendimento. Do amido isolado foram estudados sua composição química, morfologia e distribuição de tamanho dos grânulos, difração de raios-X, espectros no infravermelho médio, poder de inchamento e solubilidade, propriedades de pasta e térmicas, claridade e sinerese. O rendimento de amido, com base na presença de amido na raiz, que pode ser isolado, foi de 13,68% com 3,12 10-3 mg/g de carotenóides. Os grânulos de amido são predominantemente elipsoidais com 50-60 mm de comprimento e 20-30 mm de largura. Exibiram padrão de difração de raios-X tipo B, com 41,2% de cristalinidade, teor de amilose aparente de 26,2% e espectros de infravermelho médio semelhante de outros amidos de raízes. As temperaturas de pico de gelatinização inicial e final foram 64,2 e 68,56C, respectivamente, e a entalpia de gelatinização foi de 19,2 J/g. O perfil de viscosidade aparente foi semelhante àquele do amido de mandioca, porém, com maior pico de viscosidade (6500 cP), menor tendência à retrogradação (600 cP) e com géis menos claros mostrando sinerese. Cissus simsiana raízes tem uso potencial para a produção de amido e há espaço para aumentar o seu rendimento. Cissus simsiana amidos tem um grânulo de tamanho médio de fécula de batata com clara tipo B padrão de difração de raios-X, típico de tubérculos com arranjo de cadeias moleculares diferentes de amidos de cereais. Cissus simsiana amidos tinham temperaturas e entalpias de gelatinização semelhantes a mandioca e outros amidos isolados a partir de fontes não-convencionais, que podem ser interessantes para a possível utilização como uma alternativa tecnológica em algumas aplicações industriais.(AU)

The aim of this study was to investigate the characterization of starch from Cissus simsiana Roem. & Schult. roots. The starch was extracted by steeping, wet grinding and sedimentation processes and its yield was calculated. Isolated starch was then characterized for chemical composition, morphology and granules size distribution, X-ray diffraction, mid-infrared spectra, swelling powder and solubility, pasting and thermal properties and clarity and syneresis behavior. The starch yield, based on starch presence in the root that can be isolated, were between 13.68% with 3.12 10-3 mg/g of carotenoids. C. simsiana granules were predominantly ellipsoids with 50-60 mm length and 20-30 mm wide. They exhibited B-type X-ray diffraction pattern with 41.2% of crystallinity, apparent amylose content of 26.2% and presented similar mid-infrared spectra to other starches. Onset and peak gelatinization temperatures were 64.2 and 68.56C, respectively, and gelatinization enthalpy was 19.2 J/g. The apparent viscosity profile was comparable to cassava starch, but with higher peak viscosity (6500 cP), lower set back viscosity (600 cP) and less clear gel showing syneresis.(AU)

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Paracoccidioides brasiliensis (P. brasiliensis) is a thermo-dimorphic fungus that causes paracoccidioidomycosis. Brazil epidemiological data shows that endemic areas are the subtropical regions, especially where agricultural activities predominate such as the Southeast, South, and Midwest. There are several tests to diagnose paracoccidioidomycosis, but they have many limitations such as low sensitivity, high cost, and a cross-reacting problem. In this work, gold nanoprobes were used to identify P. brasiliensis as an alternative diagnostic technique, which is easier to apply, costs less, and has great potential for application. The specific Ribosomal sequence of P. brasiliensis DNA was amplified and used to design the nanoprobes using a thiol-modified oligonucleotide. The results of positive and negative tests were done by UV-visible and Fourier Transform Infrared (FT-IR) measurements. The deconvolution of FT-IR sample spectra showed differences in the vibrational modes from the hydrogen bridge NHN and NHO bands that form the double helix DNA for samples matching the DNA sequence of nanoprobes that could be used to classify the samples.

Assuntos

RESUMO

O objetivo do presente estudo foi estudar a caracterização do amido extraído das raízes da Cissus simsiana Roem. & Schult. A extração do amido foi por via úmida e por decantação, calculando-se seu rendimento. Do amido isolado foram estudados sua composição química, morfologia e distribuição de tamanho dos grânulos, difração de raios-X, espectros no infravermelho médio, poder de inchamento e solubilidade, propriedades de pasta e térmicas, claridade e sinerese. O rendimento de amido, com base na presença de amido na raiz, que pode ser isolado, foi de 13,68% com 3,12 10-3 mg/g de carotenóides. Os grânulos de amido são predominantemente elipsoidais com 50-60 mm de comprimento e 20-30 mm de largura. Exibiram padrão de difração de raios-X tipo B, com 41,2% de cristalinidade, teor de amilose aparente de 26,2% e espectros de infravermelho médio semelhante de outros amidos de raízes. As temperaturas de pico de gelatinização inicial e final foram 64,2 e 68,56C, respectivamente, e a entalpia de gelatinização foi de 19,2 J/g. O perfil de viscosidade aparente foi semelhante àquele do amido de mandioca, porém, com maior pico de viscosidade (6500 cP), menor tendência à retrogradação (600 cP) e com géis menos claros mostrando sinerese. Cissus simsiana raízes tem uso potencial para a produção de amido e há espaço para aumentar o seu rendimento. Cissus simsiana amidos tem um grânulo de tamanho médio de fécula de batata com clara tipo B padrão de difração de raios-X, típico de tubérculos com arranjo de cadeias moleculares diferentes de amidos de cereais. Cissus simsiana amidos tinham temperaturas e entalpias de gelatinização semelhantes a mandioca e outros amidos isolados a partir de fontes não-convencionais, que podem ser interessantes para a possível utilização como uma alternativa tecnológica em algumas aplicações industriais.

The aim of this study was to investigate the characterization of starch from Cissus simsiana Roem. & Schult. roots. The starch was extracted by steeping, wet grinding and sedimentation processes and its yield was calculated. Isolated starch was then characterized for chemical composition, morphology and granules size distribution, X-ray diffraction, mid-infrared spectra, swelling powder and solubility, pasting and thermal properties and clarity and syneresis behavior. The starch yield, based on starch presence in the root that can be isolated, were between 13.68% with 3.12 10-3 mg/g of carotenoids. C. simsiana granules were predominantly ellipsoids with 50-60 mm length and 20-30 mm wide. They exhibited B-type X-ray diffraction pattern with 41.2% of crystallinity, apparent amylose content of 26.2% and presented similar mid-infrared spectra to other starches. Onset and peak gelatinization temperatures were 64.2 and 68.56C, respectively, and gelatinization enthalpy was 19.2 J/g. The apparent viscosity profile was comparable to cassava starch, but with higher peak viscosity (6500 cP), lower set back viscosity (600 cP) and less clear gel showing syneresis.

Assuntos