ABSTRACT Pyrite (FeS2) is one of the main tailings derived from coal mining. When processed, pyrite has several applications with high value-added, in contrast, if improperly discarded, it causes major environmental impacts, like the acid mine drainage. For those reasons, the seeking for beneficiation techniques of Pyrite has been the target of numerous studies. One of the most employed techniques is the separation by density using heavy liquids, like bromoform, as a separation medium. In the present work, we propose the use of lithium heteropolytungstate (LST), a non-halogenated and non-toxic solution, as an alternative in the separation by density method. For the experiments, raw pyrite samples were collected from the tailings of coal extraction from a mining company in Santa Catarina, Brazil. After the separation process, the samples before and after the beneficiation were characterized by XRD, FTIR, and XRF techniques. The results revealed that the separation technique used in this work led to a significant increase in the concentration of pyrite, going from less than 10% in the raw sample and reaching almost 80% after processing. This impressive result reveals that LST represents a promising alternative for separating pyrite by density techniques, showing much greater effectiveness than other heavy liquids used in the literature, in addition to being environmentally friendly.

The effect of the incorporation of sweet potato flour, with 30% replacement in 1kg of wheat flour was evaluated to determine the behavior of elastic and mechanical properties during the kneading and baking stage of bread. For the evaluation the following varieties were studied: Morado Brazil, Morado Ecuador, Guayaco Morado, Ina and Toquecita, and the evaluated properties were: texture (hardness, elasticity, firmness, chewiness) measured by a texture meter Bloomfield and volume was measured by INEN standard (NTE INEN 0530: 80). The design employed was completely at random, using analysis of variance at 5% significance level. The results obtained showed that elasticity attribute in texture variable presented significant differences (P <0.05). Analysis concluded that including Toquecita flour in the mixture to form the dough, had the highest elasticity of 13.32mm. However, Morado Ecuador variety flour presented a 6.24 mm elasticity value, ideal for both the malleability of the dough and the freshness of the bread, and concerning volume, the inclusion of Ecuador Morado flour and Ina in the formulation of bread, showed an increase in volume at 93.30 and 93.67cm³ respectively, close to the normed value for wheat flour bread.

Se evaluó el efecto de la incorporación de harina de camote, con sustitución del 30% en 1kg de harina de trigo, para determinar el comportamiento de las propiedades elásticas y mecánicas durante la etapa amasado y horneado del pan. Para la evaluación se estudiaron 5 variedades que fueron: Morado Brasil, Morado Ecuador, Guayaco Morado, Ina y Toquecita, las propiedades evaluadas fueron: textura (dureza, elasticidad, firmeza, masticabilidad), mediante texturómetro Bloomfield y volumen mediante la norma INEN (NTE INEN 0530: 80). Se empleó un diseño completamente al azar, utilizando Análisis de Varianza al 5% de significación. Los resultados alcanzados mostraron que el atributo elasticidad en la variable textura presentó diferencias significativas (p<0,05). Del análisis se llegó a la conclusión de que la inclusión de harina Toquecita en la mezcla para la formación de la masa, presentó la mayor elasticidad de 13,32mm sin embargo la harina de la variedad Morado Ecuador presentó un valor de 6,24 mm de elasticidad, ideal tanto para la maleabilidad de la masa, como para la frescura del pan y en cuanto a volumen la inclusión de Harina Morado Ecuador y de Ina, en la formulación del pan, presentaron un aumento en el volumen con un 93,30 y 93,67cm³ respectivamente, cercanos al valor normado para un pan con harina de trigo.

Evaluate the rheological properties of flour mixes Ipomoea batata and Triticum vulgare for the preparation of bread dough, was the goal of this research for it a completely randomized design, as treatments sweet potato flour was used varieties are used: Toquecita, Guayaco Purple, Purple Ecuador, Brazil and Ina Purple in a 30/70 ratio (sweet potato flour / wheat flour respectively). The rheological variables: water absorption, development time, weakening of the dough stability, water absorption index (C1), mixing rate (C2), gluten strength index (C3), gel viscosity (C4), resistance index amylase (C5) and starch retro gradation index (C6) were evaluated with Mixolab equipment. The results showed that the variety Purple Brazil showed better characteristics of flours recommended premixes for the baking process in response to these indices.

Evaluar las propiedades reológicas de mezclas de harinas de Ipomoea batata y Triticum vulgare para la elaboración de masas panarias, fue el objetivo de esta investigación para ello se empleó un diseño completamente al azar, como tratamientos se emplearon las harinas de camote de las variedades: Toquecita, Guayaco Morado, Morado Ecuador, Morado Brasil e Ina en una relación 30/70 (harina de camote/harina de trigo respectivamente). Las variables reológicas: absorción de agua, tiempo de desarrollo, debilitamiento de la masa, estabilidad, índice de absorción de agua (C1), índice de amasado (C2), índice de fuerza del gluten (C3), índice de viscosidad del gel (C4), índice de resistencia de la amilasa (C5) e índice de retrogradación del almidón (C6) fueron evaluadas con el equipo Mixolab. Los resultados demostraron que la variedad Morado Brasil evidenció mejores características de las mezclas de harinas recomendables para el proceso de panificación atendiendo a estos índices.

Chirality deeply impacts the macroscopic properties on all scales of the universe from elemental particles through biological structures up to astronomic systems. Specifically, chiral liquid crystals give rise to self-organized macrostructures with unparalleled properties. Here we present easy experiments with a special class of chiral liquid crystals that show temperature-induced selective reflection of light (thermochromic effect). Understanding this thermochromic effect allows undergraduate students better realize important properties of super and supramolecular systems.

Synthetic manipulations were carried out with the aim of obtaining an advanced linear fragment for production of thermotropic liquid crystals. The chiral fragment synthesised was introduced in a tolanbenzoate mesogenic core by coupling of Sonogashira. The final chiral tolans showed smectic A and C and nematic liquid crystalline phases. The crystallographic structure of lactone from (-) menthone is presented.