Análisis exergético de escenarios integrados de producción de etanol y otros productos a partir de la caña de azúcar

Se realiza el análisis exergético de seis escenarios parala producción conjunta de alcohol y otros productos derivados de la caña de azúcar, con el objetivo de identificar y localizar las principales fuentes generadoras de irreversibilidades en estos esquemas. En los esquemas integrados se considera la caña de azúcar como materia prima principal para la generación de productos y coproductos. Los seis escenarios de integración evaluados incluyen la producción de azúcar, alcohol de primera y segunda generación y coproductos tales como: furfural y lignina, la obtención de levadura torula y la recuperacióndel CO2. Se realizaron los balances de masa y energía para cada proceso, determinando los flujos de las corrientes que intervienen en el análisis exergético. Para el análisis exergético el esquema integrado fue dividido en diez subsistemas. Los subsistemas extracción de jugo, cristalización y cocción, fermentación y destilación resultaron los mayores generadores de pérdidas exergéticas. Para los primeros cinco escenarios la eficiencia exergética total se encuentra entre 71-80% y para el escenario de tiempo de no zafra en un 59%

Phase mapping of aging process in InN nanostructures: oxygen incorporation and the role of the zincblende phase

Uncapped InN nanostructures undergo a deleterious natural aging process at ambient conditions by oxygen incorporation. The phases involved in this process and their localization is mapped by Transmission Electron Microscopy (TEM) related techniques. The parent wurtzite InN (InN-w) phase disappears from the surface and gradually forms a highly textured cubic layer that completely wraps up a InN-w nucleus which still remains from original single-crystalline quantum dots. The good reticular relationships between the different crystals generate low misfit strains and explain the apparent easiness for phase transformations at room temperature and pressure conditions, but also disable the classical methods to identify phases and grains from TEM images. The application of the geometrical phase algorithm in order to form numerical moire mappings, and RGB multilayered image reconstructions allows to discern among the different phases and grains formed inside these nanostructures. Samples aged for shorter times reveal the presence of metastable InN:O zincblende (zb) volumes, which acts as the intermediate phase between the initial InN-w and the most stable cubic In2O3 end phase. These cubic phases are highly twinned with a proportion of 50:50 between both orientations. We suggest that the existence of the intermediate InN:O-zb phase should be seriously considered to understand the reason of the widely scattered reported fundamental properties of thought to be InN-w, as its bandgap or superconductivity.Comment: 18 pages 7 figure

Respuesta del flóculo en el crecimiento de camarones blancos juveniles litopenaeus vannamei en condiciones experimentales: dieta comercial con flóculo vs dieta comercial sin flóculo en sistema de producción semi-intensivo

Target. To determine the effect of floc on the growth of juvenile white shrimp Litopenaeus vannamei under experimental conditions: commercial diet with floc vs. commercial diet without floc in a semi-intensive production system. Materials and methods. To determine which treatment presented the greatest growth, physical-chemical factors (dissolved oxygen, temperature, salinity and pH) and population parameters (Accumulated Growth, Growth Rate, Growth Rate, Feed Conversion Factor, Survival and Productive Yield) were taken. ). These data were collected in 27 days where the juvenile Litopenaeus vannamei shrimp had an initial weight of 1.5 g in both treatments. Results. According to the results, the following is presented: the treatment with floc acquired a final growth of 5.3 gr, obtaining an average of 3.8 gr, while the treatment without floc reached a final growth of 4.6 gr, obtaining an average of 3.1 gr. . Conclution. The treatment with floc gained more biomass due to the protein complement of the floc in the commercial diet, while the treatment without floc gained little biomass since they only had the protein from the commercial feed; When using statistical analysis, it was found that p>0.05 supported that growth is greater when floc is added to the feed.  Objetivo. Determinar el efecto  del  flóculo en el crecimiento de camarones blancos  juveniles Litopenaeus vannamei   en condiciones experimentales: dieta comercial con flóculo  vs dieta comercial sin flóculo en sistema de producción semi-intensivo. Materiales y Métodos. Para determinar cuál tratamiento presentó un mayor crecimiento se realizaron toma de factores físico-químicos (oxígeno disuelto, temperatura, salinidad y pH) y parámetros poblacionales (Crecimiento Acumulado, Ritmo de Crecimiento, Tasa de Crecimiento, Factor de Conversión Alimenticio, Sobrevivencia y Rendimiento Productivo). Estos datos se recolectaron  en 27 días donde los camarones juveniles Litopenaeus vannamei poseían un peso inicial de 1,5 gr en ambos tratamientos. Resultados. Según los resultados se presenta lo siguiente: el tratamiento con flóculo adquirió un crecimiento final de 5,3 gr obteniendo como promedio 3,8 gr en cambio el tratamiento sin flóculo alcanzó un crecimiento final de 4,6 gr obteniendo como promedio 3,1 gr. Conclusión. El tratamiento con flóculo ganó mayor  biomasa por el complemento de proteína del flóculo en  la dieta comercial, en cambio el tratamiento sin flóculo ganó poca biomasa ya que estos solo contaban con la proteína del alimento comercial; al emplear  los análisis estadísticos se encontró que p>0.05 fundamentó que el crecimiento es mayor cuando se adiciona flóculo en la alimentación

Vivências e envolvimento acadêmico de estudantes universitários : adaptação e validação de escalas para a sua avaliação

Este artículo describe los procesos preliminares de adaptación y validación de dos instrumentos diseñados para describir Vivencias Académicas (centradas en la satisfacción) y la Implicación Académica (centrada en el compromiso) en estudiantes universitarios. De acuerdo con la literatura científica en el área, las vivencias y la implicación académica se encuentran asociadas con las dificultades relacionadas al abandono de los alumnos. Para este estudio se aplicaron dos cuestionarios a 261 estudiantes pertenecientes a la Universidad de Concepción, Campus Los Ángeles, Chile. Ambos instrumentos mostraron niveles adecuados de homogeneidad o consistencia interna en los ítems repartidos para las subescalas de cada cuestionario. Paralelamente, se calcularon las correlaciones entre las dimensiones de ambos cuestionarios, siendo los coeficientes obtenidos adecuados para los constructos evaluados. Estos antecedentes permiten el comienzo de la validación de los cuestionarios en estudio.This paper presents preliminary findings regarding the adaptation and validation of two instruments designed to measure Academic Experiences (centred on satisfaction) and Academic Involvement in university students. Previous research has shown that academic experience and involvement are strongly correlated with student drop-out rates. For the present study, the two surveys were administered to 261 students at the University of Concepción, Chile, on the Los Ángeles campus. Both instruments showed suitable levels of reliability and internal consistency on the subscales. Furthermore, the correlation coefficients obtained when comparing dimensions on each survey were acceptable for the constructs being evaluated. These findings allow for a preliminary validation of the two questionnaires included in the study.Descrevem-se os processos preliminares de adaptação e validação de dois instrumentos voltados para a avaliação das Vivências Acadêmicas (centradas na satisfação) e da Implicação Acadêmica (centrada no compromisso) de estudantes universitários. Conforme a literatura científica na área, vivências e implicação acadêmica encontram-se associadas às dificuldades relacionadas ao abandono dos alunos. Este estudo envolveu a aplicação dos dois questionários a 261 estudantes da Universidade de Concepción, campos Los Angeles, Chile. Ambos os instrumentos mostram níveis adequados de homogeneidade ou consistência interna dos itens divididos em subescalas, em cada questionário. Paralelamente, calculam-se as correlações entre as dimensões dos questionários, sendo os coeficientes obtidos adequados aos constructos avaliados. Estes antecedentes permitem o início da validação dos questionários em estudo.Red de Revistas Científicas de América Latina, el Caribe, España y Portugal Sistema de Información CientíficaUniversidad Austral de Chile Valdivia, Chil

Growth of Low-Density Vertical Quantum Dot Molecules with Control in Energy Emission

In this work, we present results on the formation of vertical molecule structures formed by two vertically aligned InAs quantum dots (QD) in which a deliberate control of energy emission is achieved. The emission energy of the first layer of QD forming the molecule can be tuned by the deposition of controlled amounts of InAs at a nanohole template formed by GaAs droplet epitaxy. The QD of the second layer are formed directly on top of the buried ones by a strain-driven process. In this way, either symmetric or asymmetric vertically coupled structures can be obtained. As a characteristic when using a droplet epitaxy patterning process, the density of quantum dot molecules finally obtained is low enough (2 × 108 cm−2) to permit their integration as active elements in advanced photonic devices where spectroscopic studies at the single nanostructure level are required

Toxicity of four Cuban botanical derivatives against two stored-products coleopteran pests: Poster

Plants are a source of substances for protection of stored products. The Cuban flora has not yet been fully studied as a source of pesticides for postharvest protection, partly due to its great diversity. The toxicity of four Cuban plant derivatives against Lasioderma serricorne (F.) and Sitophilus zeamais Motschulsky was investigated. The anti-insect activity of the powders and the essential oil from plants belonging to Asteraceae, Fabaceae and Piperaceae was tested. Mortality and emergence of adult insects and the repellent effect of products were evaluated. Two products derived from Piper aduncum subsp. ossanum, caused high mortality (81,6 and 100%), reduced emergence (27,9 and 0,4%) and exhibited strong repellent activity on L. serricorne. Against S. zeamais, treatments with the highest mortality values were stems of Lonchocarpus punctatus (72,4%), seeds and stems of Canavalia ensiformis (64,9 and 69,9%), and leaves of Tithonia diversifolia (67,2%). The progeny production of S. zeamais was inhibited by powders of L. punctatus stems (31,8%), C. ensiformis seeds (40,5%), leaves (43,7%) and stems (30,6%), and T. diversifolia leaves (38,7%). The stems of C. ensiformis, leaves of T. diversifolia and L. punctatus had the highest repellent effect. These products have potential for small-scale treatments of grains for protection against both insects, and P. aduncum subsp. ossanum-based products to control L. serricorne infestation in tobacco. Identification of local candidates to develop effective and safe pesticides offers new alternatives to the Cuban agriculture in the control of storage pests.Plants are a source of substances for protection of stored products. The Cuban flora has not yet been fully studied as a source of pesticides for postharvest protection, partly due to its great diversity. The toxicity of four Cuban plant derivatives against Lasioderma serricorne (F.) and Sitophilus zeamais Motschulsky was investigated. The anti-insect activity of the powders and the essential oil from plants belonging to Asteraceae, Fabaceae and Piperaceae was tested. Mortality and emergence of adult insects and the repellent effect of products were evaluated. Two products derived from Piper aduncum subsp. ossanum, caused high mortality (81,6 and 100%), reduced emergence (27,9 and 0,4%) and exhibited strong repellent activity on L. serricorne. Against S. zeamais, treatments with the highest mortality values were stems of Lonchocarpus punctatus (72,4%), seeds and stems of Canavalia ensiformis (64,9 and 69,9%), and leaves of Tithonia diversifolia (67,2%). The progeny production of S. zeamais was inhibited by powders of L. punctatus stems (31,8%), C. ensiformis seeds (40,5%), leaves (43,7%) and stems (30,6%), and T. diversifolia leaves (38,7%). The stems of C. ensiformis, leaves of T. diversifolia and L. punctatus had the highest repellent effect. These products have potential for small-scale treatments of grains for protection against both insects, and P. aduncum subsp. ossanum-based products to control L. serricorne infestation in tobacco. Identification of local candidates to develop effective and safe pesticides offers new alternatives to the Cuban agriculture in the control of storage pests

Frame dragging, vorticity and electromagnetic fields in axially symmetric stationary spacetimes

We present a general study about the relation between the vorticity tensor and the Poynting vector of the electromagnetic field for axially symmetric stationary electrovacuum metrics. The obtained expressions allow to understand the role of the Poynting vector in the dragging of inertial frames. The particular case of the rotating massive charged magnetic dipole is analyzed in detail. In addition, the electric and magnetic parts of the Weyl tensor are calculated and the link between the later and the vorticity is established. Then we show that, in the vacuum case, the necessary and sufficient condition for the vanishing of the magnetic part is that the spacetime be static.Comment: 16 pages Latex. Some minor changes in the text and typos correcte

Understanding and exploiting plant beneficial microbes

After a century of incremental research, technological advances, coupled with a need for sustainable crop yield increases, have reinvigorated the study of beneficial plant–microbe interactions with attention focused on how microbiomes alter plant phenotypes. We review recent advances in plant microbiome research, and describe potential applications for increasing crop productivity. The phylogenetic diversity of plant microbiomes is increasingly well characterized, and their functional diversity is becoming more accessible. Large culture collections are available for controlled experimentation, with more to come. Genetic resources are being brought to bear on questions of microbiome function. We expect that microbial amendments of varying complexities will expose rules governing beneficial plant–microbe interactions contributing to plant growth promotion and disease resistance, enabling more sustainable agriculture