Abstract In this paper we introduce the notion of orbit equivalence for semi-group actions and the concept of generalized linear control system on smooth manifold. We prove that, under certain conditions, the semi-group system of a generalized linear control system on a smooth manifold is orbit equivalent to the semigroup system of a linear control system on a homogeneous space.

Resumo O interesse por espécies vegetais com ação antiviral tem crescido exponencialmente e algumas tem sido relatadas como possuídoras de propriedades anti-HIV. Essa pesquisa tem como objetivo realizar o fracionamento fitoquímico biodirecionado pela atividade antirretroviral das cascas do caule da espécie Lafoensia pacari. Trata-se de um estudo experimental in vitro e a metodologia envolve preparo do material vegetal, obtenção do extrato etanólico, fracionamento, purificação, identificação e quantificação das frações, extração ácido-base, ressonância magnética nuclear, teste de inibição da TR do HIV-1 e estudos de docking molecular. A partir do fracionamento biodirecionado pela atividade antirretroviral verificou-se uma maior atividade nas subfrações acetanólica. Com destaque para a subfração acetanólica neutros com 60,98% de inibição de TR e o ácido elágico com 88,61% de inibição de TR e ausência de citotoxicidade. Verificou-se com o teste de citotoxicidade em linhagem de macrófagos que a fração clorofórmica foi mais tóxica que a fração acetanólica. A análise do espectro J-resolvido na região aromática apresentou um simpleto em 7.48 e 6.93 ppm que foram identificados como ácido elágico e ácido gálico respectivamente. A enzima 5TIQ obteve melhor parâmetro de afinidade com o ligante ácido elágico que foi confirmado pelos espectros HSQC-1H-13C. O ácido gálico mostrou-se também favorável a formar interação com a enzima 5TIQ, sendo confirmado através do espectro HSQC-1H-13C. Através da avaliação do PreADMET verificou-se que o ácido elágico é uma molécula promissora pela sua atividade de inibição da TR e parâmetros farmacocinéticos e de toxicidade.

Abstract Interest in antiviral plant species has grown exponentially and some have been reported to have anti-HIV properties. This research aims to perform the bio-guided phytochemical fractionation by antiretroviral activity of Lafoensia pacari stem barks. This in vitro experimental study involved the preparation of plant material, obtention of ethanolic extract, fractionation, purification, identification and quantification of fractions, acid-base extraction, nuclear magnetic resonance, HIV-1 RT inhibition test and molecular docking studies. From the bio-guided fractionation by the antiretroviral activity there was a higher activity in the acetanolic subfractions, highlighting the acetate subfraction – neutrals with 60.98% of RT inhibition and ellagic acid with 88.61% of RT inhibition and absence of cytotoxicity. The macrophage lineage cytotoxicity assay showed that the chloroform fraction was more toxic than the acetate fraction. The analysis of the J-resolved spectrum in the aromatic region showed a singlet at 7.48 and 6.93 ppm which was identified as ellagic acid and gallic acid, respectively. The 5TIQ enzyme obtained better affinity parameter with the ellagic acid ligand, which was confirmed by the HSQC-1H-13C spectra. Gallic acid was also favorable to form interaction with the 5TIQ enzyme, being confirmed through the HSQC-1H-13C spectrum. From the PreADMET evaluation it was found that ellagic acid is a promising molecule for its RT inhibition activity and pharmacokinetic and toxicity parameters.

RESUMO O objetivo deste estudo foi testar a viabilidade de uma nova ferramenta de software informático para avaliação da lassitude articular passiva da articulação coxofemoral. A lassitude articular da articulação coxofemoral foi estimada usando-se um programa informático especial, desenvolvido para o efeito, por dois avaliadores, um com treino prévio e outro não treinado, na medição do índice de distração, em duas sessões independentes, utilizando-se 230 articulações coxofemorais de 115 cães, as quais efetuaram o rastreio de displasia coxofemoral realizando a projeção de distração da articulação coxofemoral. Previamente, todas as radiografias foram enviadas para o PennHIP Analysis Center, para se obter uma medida oficial do índice de distração. A repetibilidade das medições das duas sessões foi adequada para ambos os avaliadores. A reprodutibilidade do índice de distração oficial, média±desvio-padrão 0,44±0,15, foi adequada (P>0,05) para o avaliador treinado, 0,44±0,15, e não adequada (P>0,05) para o avaliador não treinado, 0,47±0,17. A ferramenta de medição do índice de distração proposta pode ser usada com segurança na medição do índice de distração por avaliadores treinados, uma vez que mostra uma adequada repetibilidade e reprodutibilidade das medições oficiais do índice de distração. A simplicidade do processo apresentado torna-o menos demorado e mais econômico.

ABSTRACT The aim of this study was to test the accuracy of a new automated computer software tool for the assessment of passive hip laxity. The hip laxity was estimated using the dedicated computer software by two blinded evaluators, one previously trained and one without specific training for distraction index measurement, in two independent sessions using 230 hip joints from 115 dogs that underwent screening for passive hip laxity using the distraction view. Previously, all of these radiographs were sent to PennHIP Analysis Center for an official distraction index record. The measurement repeatability of the two sessions was adequate for both evaluators. The reproducibility of the official distraction index measurement, mean distraction index±standard deviation 0.44±0.15, was adequate (P>0.05) for the trained evaluator, 0.44±0.15, and non-adequate (P<0.05), for the non-trained evaluator 0.47±0.17. The distraction index measurement tool proposed can be used with confidence for hip laxity evaluation by trained evaluators, as it provided good repeatability and reproducibility of official reports. The simplicity of the process described leads to a less time-consuming and more affordable procedure.

Abstract Synthetic biology (SynBio) it is considered a very recent discipline. View as a tool serves to design or re-design biological systems, giving them improved qualities or new qualities. In the SynBio, the design of new biological systems requires very precise molecular tools, such as: a) bioinformatics, b) sequencing NGS (Next Generation Sequencing), assembly and synthesis of DNA c) and CRISPR- Cas9 genome editing. Within the SynBio there are other social profile disciplines which concerned to ethical, legal, philosophical, and economic, and for that reason it is considered a multidiscipline. The SynBio is promoting the development of new (emerging) technologies based on an engineering perspective. In SynBio, DNA is understood in a practical and abstract way as a series of parts that can be assembled in a certain order to obtain the desired products once the functionality of each part is known. The SynBio has given rise to a new conception of the economy worldwide and consequently the term Bioeconomy is already taken very seriously as a new discipline that will transform societies.

Resumen La biología sintética (SynBio) es una disciplina de reciente aparición que sirve para diseñar o re-diseñar sistemas biológicos y otorgarles cualidades mejoradas o nuevas cualidades. En la SynBio el diseño de nuevos sistemas biológicos requiere de herramientas moleculares muy precisas, tales como: a) la bioinformática, b) la secuenciación NGS (Next Generation Sequencing), el ensamble y/o síntesis de ADN c) y la edición de genomas a través de CRISPR-Cas9. En la SynBio encontramos además otras disciplinas con un perfil más hacia el ámbito social, las cuales tocan aspectos éticos, legales, filosóficos y económicos, considerándose así una multidisciplina. La SynBio está propiciando el desarrollo de nuevas tecnologías (emergentes) partiendo de una óptica ingenieril. En la SynBio, al ADN se le entiende de forma práctica y abstracta como una serie de partes que se pueden ensamblar en cierto orden para obtener los productos deseados una vez que se conoce la funcionalidad de cada parte. La SynBio ha dado pie a una nueva concepción de la economía a nivel mundial y por consecuencia se ha tomado muy seriamente el termino Bioeconomía como una nueva disciplina que transformará a las sociedades.

Abstract In order to determine the effect of regrowth age on the components of yield, chemical composition and polyphenolic profile of Tithonia diversifolia, an experiment was carried out using a randomized block design with four replications in brown soil with carbonate. The treatments consisted of three regrowth ages (60, 120 and 180 days). To establish the functional relationship between the different evaluated indicators and age, linear, quadratic, cubic and Gompertz equations were analyzed, selecting the best fit according to high value of R2, high significance of the terms and of the equation, low standard error of estimation and of terms, and significant contribution of terms and of the equation. The equations of the best fit for the functional relationship between the different evaluated indicators and age, in each seasonal period, were quadratic. There was an increase in yield of dry matter, NDF, ADF, ADL with age, with maximum values at 180 days (23.92t/ha, 47.63, 31.38 and 21.01%, respectively); edible biomass, CP, cellular content, in vitro degradability of dry matter decreased with age and the best values were obtained at 60 days (26.16 t/ha, 27.49 %, 59.56 % and 75.78 %, respectively) and the contents of total phenols, total tannins, total condensed tannins, free condensed tannins and condensed tannins bound to the fiber showed their highest values during the rainy period (12.36, 5.36, 14.55, 4.07 and 11.16 g/kgDM, respectively). The regression equations that explain the close relationship of age with yield, chemical composition and degradability were established, as well as response patterns were established for each seasonal period. It is recommended to endorse these results in other climatic and management conditions of the species.

Resumen Con el objetivo de determinar el efecto de la edad de rebrote en los componentes del rendimiento, la composición química y perfil polifenólico de la Tithonia diversifolia, se realizó un experimento mediante un diseño de bloques al azar con cuatro réplicas en suelo pardo con carbonato. Los tratamientos consistieron en tres edades de rebrote (60, 120 y 180 días). Para establecer la relación funcional entre los diferentes indicadores evaluados y la edad, se analizaron las ecuaciones lineales, cuadráticas, cúbicas y Gompertz seleccionando la de mejor ajuste según: alto valor de R2, alta significación de los términos y de la ecuación, bajo error estándar de estimación y de los términos, y aporte significativo de los términos y de la ecuación. Las ecuaciones de mejor ajuste para la relación funcional entre los diferentes indicadores evaluados y la edad, en cada período estacional, fueron las cuadráticas. Hubo incremento del rendimiento en materia seca, FDN, FDA, LAD con la edad con valores máximos a los 180 días (23.92t/ha; 47.63; 31.38 y 21.01 %, respectivamente); la biomasa comestible, PB, contenido celular, degradabilidad in vitro de la materia seca disminuyeron con la edad y los mejores valores se obtuvieron a los 60 días (26.16 t/ha; 27.49 %; 59.56 % y 75.78 %, respectivamente) y los contenidos de fenoles totales, taninos totales, taninos condensados totales, taninos condensados libres y taninos condensados ligados a la fibra mostraron sus mayores valores durante el período lluvioso, (12.36; 5.36; 14.55; 4.07 y 11.16 g/kgMS, respectivamente). Se establecieron las ecuaciones de regresión que explican la estrecha relación de la edad con el rendimiento, composición química y la degradabilidad, así como se establecieron los patrones de respuesta para cada período estacional. Se recomienda avalar estos resultados en otras condiciones climáticas y de manejo de la especie.

Resumo O Papilomavírus Humano (HPV) é uma infecção de transmissão sexual com um alto índice de contágio na população jovem e adulta, e principal fator de Câncer do Colo Uterino ligado ao inicio precoce das relações sexuais. Objetivo: Determinar o nível de conhecimentos de adolescentes de uma escola preparatória sobre o HPV. Métodos: Estudo transversal descritivo realizado em 242 alunos de ambos os sexos. Aplicou-se um instrumento com 46 itens agrupados em quatro seções: dados sociodemográficos, conhecimentos sobre o vírus, aspectos da saúde sexual e fontes de informação, nível de confiabilidade de 0.7. Resultados: 53.7% mulheres, 40.5% com 17 anos e 97.1% solteiro. 64.6% não identificou o que é o HPV, 68.6% não soube que afecções pode gerar o vírus, e 88% não identifica que fumar pode predispor nas mulheres risco para a aquisição do vírus; 78.5% identificou o fator principal de risco e 82.6% a melhor via de proteção contra a infecção. O nível de conhecimentos gerais foi baixo, em 80% dos participantes. Conclusões: O desconhecimento perante o fenômeno pode contribuir à imperícia em saúde ou a ter atividades de risco como ter múltiplos casais sexuais ou não usar o preservativo ante um contato sexual.

Abstract The human papilloma virus, a sexually transmitted infection with a high likelihood of contagion among young and adult populations, is the main cervical- uterine cancer causing factor linked to early initiation of sexual intercourse. Objective: To determine the level of knowledge on the topic among adolescents in one high school. Methods: This is a transversal and descriptive study with a sample of 242 students of both sexes. An instrument with 42 items grouped in four sections: social-demographic data, knowledge on the human papilloma virus, issues on sexual health, and sources of information was applied. The reliability level was estimated at 0.7. Results: From the sample, 53.7% were women, 40.5% were 17 years old, and 91.1% were single. Sixty four point six percent did not identify the virus, 68.6% did not know about the illnesses the virus can provoke, and 88% did not know that smoking can predispose women towards a greater risk of acquiring the virus. From the sample, 78.5% identified the principal risk factor, and 82.6% were aware of the best protection against infection. The general level of knowledge was low in 80% of the participants. Conclusions: The lack of knowledge on the issue can lead to risky lifestyles such as having multiple sexual partners or nor using the condoms accordingly.

Resumen El virus del papiloma humano es una infección de transmisión sexual con un alto índice de contagio en población joven y adulta y principal factor del cáncer cérvico-uterino ligado al inicio precoz de las relaciones sexuales. Objetivo: Determinar el nivel de conocimientos de adolescentes de una escuela preparatoria, sobre el virus del papiloma humano. Métodos: Estudio transversal, descriptivo realizado en 242 alumnos de ambos sexos. Se aplicó instrumento con 46 ítems agrupados en cuatro secciones: datos sociodemográficos, conocimientos sobre el virus, aspectos de salud sexual y fuentes de información; nivel de confiabilidad de 0,7. Resultados: Un 53.7% mujeres, 40.5% con 17 años y un 97.1% soltero. El 64.6% no identificó qué es el virus del papiloma humano, El 68.6% no supo qué afecciones puede generar el virus, y el 88% no identifica que el fumar puede predisponer, en las mujeres, riesgo para la adquisición del virus; el 78.5% identificó el factor principal de riesgo y el 82.6% la mejor vía de protección contra la infección. El nivel de conocimientos general fue bajo en el 80% de los participantes. Conclusiones: El desconocimiento frente al fenómeno puede contribuir a la mala praxis en salud o a tener actividades riesgosas como el tener múltiples parejas sexuales o no usar el preservativo ante un contacto sexual.

The productive performance of growing females of the Cuban Charolais breed under a silvopastoral system with Leucaena leucocephala cv. Peru, in a 3 x 5 sowing frame, associated with an improved grass (Cynodon nlemfuensis) was studied compared to a monoculture. The experiment was conducted at the Empresa de Genética y Cría “Manuel Fajardo”, Granma province, Cuba. Thirty animals per cycle were used and the experiment lasted three years. Data were processed through a multivariate analysis and measurement of the impact index. The best live weights gains with 0.55 kg.animal.d-1 and age at incorporation to reproduction of the females of 19 months of age were obtained in the leucaena silvopastoral system. The best gain and the lowest cost per animals were recorded in the silvopastoral system. It is recommended using this leucaena sowing density for maintaining favorable total pasture productions, live weight gains and adequate weight for age relationship at the incorporation in rearing systems of replacement Cuban Charolais growing females

Se estudió el comportamiento productivo de hembras en crecimiento de la raza Charolais de Cuba en silvopastoreo con Leucaena leucocephala vc. Perú, en marco de siembra 3 x 5, asociada a gramínea mejorada (Cynodon nlemfuensis), con respecto a un monocultivo. La investigación se realizó en la Empresa de Genética y Cría “Manuel Fajardo”, Granma, Cuba. Se utilizaron 30 animales por ciclo y el experimento duró tres años. La información se procesó mediante análisis multivariado y medición del índice de impacto. Las mejores ganancias de peso vivo, con 0.55 kg.animal.d-1 y edad de incorporación a la reproducción de las hembras de 19 meses se obtuvieron en el silvopastoreo con leucaena. La mayor ganancia y el menor costo por animal se registraron en el silvopastoreo. Se recomienda utilizar esta densidad de siembra de leucaena para sostener favorables producciones totales de pasto, ganancias de peso vivo y adecuada relación de peso por edad a la incorporación en sistemas de crianza de hembras bovinas en crecimiento Charolais de Cuba, destinadas al reemplazo

Abstract: Introduction: Radio-humeral dislocation is rare, as it generally occurs with ulnar fracture. It is unusual in children and chronic lesions are even more unusual. Objective: Report of a case, its treatment and two-year follow-up. Material and method: Treatment consisted of open reduction and annular ligamentoplasty with fascia lata allograft, maintaining the reduction with a Kirschner nail for 6 weeks. The latter was then removed and rehabilitation was started. Result: The two-year follow-up report stated that the child has resumed his activities at school and his physical activity. Discussion: The authors report that the techniques used to approach inveterate lesions should include shortening the ulna to be able to reduce the radius and maintain it. The standard technique was modified and good results were obtained.

Resumen: Introducción: La luxación radio-humeral es rara, ya que generalmente se acompaña de fractura de cúbito. En los niños es poco común, y las lesiones crónicas son casos aún más infrecuentes. Objetivo: Presentación de un caso, su tratamiento y su seguimiento a dos años. Material y métodos: Se le realizó reducción abierta y plastía del ligamento anular con aloinjerto de fascia lata, manteniendo la reducción con clavo de Kirschner por seis semanas; se retiró e inició su rehabilitación. Resultado: A los dos años de seguimiento, el paciente se ha reincorporado a sus actividades en la escuela y físicas. Discusión: En cuanto a las técnicas para resolver las luxaciones inveteradas, refieren los autores que se debe acortar el cúbito para que se pueda reducir el radio y mantener. Se realizó una modificación a la técnica descrita convencionalmente, con buenos resultados.

We propose and analyze a high resolution capacitive sensor appropriate for monitoring physical or chemical processes in liquid films. The proposed sensor is based on a planar interdigitated capacitor with planar electrodes of dimensions in the milimeter scale. The electric field between electrodes extend above the plane of the electrodes up to a few milimeters and thus permits placing a dielectric container with a liquid film on top and still be sensitive to changes in the liquid film. First, we present numerical calculations of the capacitance of an interdigitated sensor as a function of the thickness and dielectric constant of a film placed on top of it using a finite element method. Then, we describe a suitable electronic system to sense with very high-resolution capacitance variations of the sensor by measuring the phase lag and amplitude change of a sinusoidal current signal passing through it. This is accomplished by subtracting a stable sinusoidal current of the same frequency going through a reference device. Initially the system is balanced by adjusting the reference current to cancel out the net output current. In this way, we compensate parasitic capacitances due to electronics, wiring and system hardware as well. When the capacitance of the sensor element varies the system gets unbalanced and a net current appears. The resulting current is measured with a locking-amplifier. To illustrate the sensitivity and resolution achieved by the sensing system, we present results of monitoring the capacitance of the sensor during the evaporation of liquid solvent films and discuss the time-evolution of the registered signals. The floor noise throughout the measurements was in the order of 50 atto-Farads while the signal varied in the range of several femto-Farads.

The influence of different polyols as plasticizers of alginate films on their physical attributes like moisture content, soluble mass in water, water uptake, water vapor permeability, opacity and mechanical properties were determined and the results discussed based on scanning electron microscopy observations and glass transition temperature. The alginate films were obtained by casting, using three different gramatures. Calcium crosslinked and non-reticulated films were considered. The films plasticized with glycerol and xylitol were more hygroscopic than the films with mannitol. The lowest water vapor permeability values were found for films plasticized with mannitol, at all studied thicknesses. The films plasticized with glycerol and xylitol showed very similar functional attributes regarding their application as food wrappings. The Ca2+ crosslinked mannitol films showed the highest tensile strength at rupture (>140 MPa).

Abstract: Today, existing power plants based on coal present in the world emit about 2 billion tons of CO2 per year. Because of its fundamental engineering and economic advantages in competing separation technologies, membrane operations are being explored for the separation of CO2 and other exhaust emissions of power plants based on fossil fuels. [1] The zeolite imidazolate framework (ZIFs) are novel microporous materials with different structures and pore sizes and large surface areas. Membranes of these materials have great potential for the separation of gas mixtures energy and environmental interest. [2-4] This paper reports the synthesis and characterization of two potentially useful membrane separation of CO2 from the compound known as ZIF-8 and an amendment thereto using a mixture of metals (Zn and Co). This modification is expected to modulate the interaction enthalpy and thereby turn the selectivity of the membrane as a result of the involvement of two types of metals in the molecular lattice.

Resumen: Hoy en día, las plantas existentes de energía a base de carbón presentes en el mundo emiten cerca de 2 billones de toneladas de CO2 al año. Debido a su ingeniería fundamental y las ventajas económicas que compiten en tecnologías de separación, las operaciones de membrana están siendo exploradas para la separación de CO2 y otros gases de combustión de las emisiones de centrales eléctricas basados en combustibles fósiles. [1] Los enrejados imidazolato tipo zeolita (ZIFs) son nuevos materiales microporosos con diversidad de estructuras y tamaños de poros, así como grandes áreas superficiales. Las membranas de estos materiales poseen un gran potencial para la separación de mezclas de gases de interés energético y ambiental. [2-4] En este trabajo se presenta la síntesis y caracterización de dos membranas potencialmente útiles para separación de CO2, a partir del compuesto conocido como ZIF-8 y una modificación del mismo usando una mezcla de metales (Zn y Co). Con esta modificación se espera modular la entalpía de interacción y con ello a su vez, la selectividad de la membrana como resultado de la participación de dos tipos de metales en el enrejado molecular.

The Humboldt-09 cruise covered a narrow meridional band along the Chilean continental slope (44-23° S). Here we use physical and biochemical data from a long meridional section (4000 km) and three short zonal sections (100 km) to describe the distribution of the different water masses found in this region. Six water masses were identified: Subantarctic Water (SAAW), Summer Subantarctic Water (SSAW), Subtropical Water (STW), Equatorial Subsurface Water (ESSW), Antarctic Intermediate Water (AAIW), and Pacific Deep Water (PDW). For the first time, a novel set of source water mass properties (or water types) is introduced for SSAW, and nutrient and dissolved oxygen water types are proposed for all the water masses. Optimum multiparameter (OMP) analysis was used through an iterative process to obtain a sound definition of the water types that minimizes the residuals of the method. Both the classic OMP and the quasi-extended OMP models reproduced the data rather well. Finally, the spatial distribution of the different water masses was calculated with the quasi-extended OMP, which is not influenced by the respiration of organic matter. The distribution of the different water masses is presented over the meridional and zonal transects and in property-property diagrams. A smooth meridional transition from subantarctic to tropical and equatorial water masses is observed in this area. This transition takes place in surface, central, and intermediate waters over distances of the order of 1000 km. The meridional transition contrasts with the abrupt zonal changes found in the cross-slope direction, which are of comparable magnitude but over distances of the order of 100 km. Both AAIW and SAAW (fresh and well oxygenated) partially mix with the hypoxic ESSW and, therefore, play an important role in the ventilation of the southern part of the oxygen minimum zone.

La campaña Humboldt-09 abarcó una estrecha franja latitudinal a lo largo del talud continental chileno, de 44 a 23°S. En este trabajo se utilizan los datos físicos y bioquímicos obtenidos a lo largo de una sección latitudinal (4000 km) y de tres secciones zonales cortas (100 km) para describir la distribución de las diferentes masas de agua presentes en la región. Se identificaron seis masas de agua: Agua Subantártica (SAAW, por sus siglas en inglés), Agua Subantártica de Verano (SSAW), Agua Subtropical (STW), Agua Ecuatorial Subsuperficial (ESSW), Agua Antártica Intermedia (AAIW) y Agua Profunda del Pacífico (PDW). Se propone, por primera vez, un conjunto completo de propiedades de la masa de agua en origen (o valores tipo) para caracterizar SSAW, así como valores tipo de oxígeno disuelto y nutrientes para todas las masas de agua. Para su correcta definición se empleó el análisis óptimo multiparamétrico (OMP) de manera iterativa, seleccionando el conjunto de valores tipo que generó menores residuos. Tanto el modelo OMP clásico como el cuasi-extendido reproducen de manera fiel las observaciones. Finalmente, se determinó la distribución espacial de las diferentes masas de agua con el OMP cuasi-extendido, que no se encuentra influenciado por la respiración de la materia orgánica. La distribución de las distintas masas de agua se representa en las diferentes secciones y en los diagramas propiedad-propiedad. En esta región se aprecia una progresiva transición latitudinal de masas de agua de origen subantártico a masas de agua de origen tropical y ecuatorial. Esta transición tiene lugar en los 1000 m superiores, en distancias del orden de 1000 km. Esto contrasta con los rápidos cambios observados en las secciones zonales, de magnitud comparable pero en distancias del orden de 100 km. Tanto el AAIW como el SAAW (relativamente menos salinas y bien oxigenadas) se mezclan parcialmente con la hipóxica ESSW y, en consecuencia, juegan un papel importante en la ventilación de la parte austral de la zona de mínimo oxígeno.

We discuss and analyze a practical methodology for the determination of the dielectric constant of a macroscopic solid sample in a nondestructive way. The technique consists in measuring the capacitance between a pointer electrode and the dielectric surface as a function of the separation distance in a scale comparable to the radius of curvature of the tip's apex. The changes in capacitance that must be measured will commonly be in the atto-farad scale and require specialized instrumentation which we also describe here. The technique requires two calibration standards and the sample needs to have a portion of its surface flat and some minimum dimensions, but otherwise it can have an arbitrary shape. We used a simple model based on the method of images to explain the methodology and present experimental results with the proposed methodology.

Se describe una metodología práctica para determinar la constante dieléctrica de una muestra sólida de una manera no destructiva. La técnica consiste en la medición de la capacitancia entre un apuntador y la superficie dieléctrica como función de la distancia de separación en una escala comparable al radio de curvatura de la punta. Los cambios en la capacitancia que se deben medir estarán normalmente en la escala de los ato-faradios y requieren de instrumentación especializada la cual también se describe aquí. La técnica requiere de dos patrones de calibración y la muestra necesita tener una porción plana en su superficie y con algunas dimensiones mínimas, pero fuera de eso puede tener una forma arbitraria. Utilizamos un modelo sencillo basado en el método de las imágenes para explicar la metodología y presentamos resultados experimentales con la metodología propuesta.

O objetivo do trabalho foi analisar a viabilidade econômica dos sistemas de cultivo com Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby e Ananas comosus var. erectifolius (L. B. Smith) Coppus & Leal, considerando-se três sistemas distintos: I) Monocultivo de Paricá; II) Monocultivo de Curauá; e III) Sistema Paricá e Curauá. Os sistemas foram implantados no Campo Experimental da Empresa Tramontina Belém, localizado no município de Aurora do Pará (PA). A partir dos registros das contas de despesa e receita do orçamento unitário, elaborados para cada sistema, foi construído o fluxo de caixa. A viabilidade econômica foi determinada por meio do valor presente líquido (VPL), razão benefício/custo (B/C) e taxa interna de retorno (TIR). Utilizou-se como custo de oportunidade uma taxa de juros de longo prazo de 12% ao ano. Os custos e as receitas foram mensurados em R$/ha. Os resultados mostraram que o monocultivo de Curauá apresentou o maior VPL (R$ 19.853,44), seguido do sistema agroflorestal de Paricá e Curauá (R$ 9.507,795). O sistema Paricá e Curauá apresentou a maior relação benefício/custo (1,29) enquanto a menor ficou com o monocultivo de Paricá. Das atividades analisadas, o monocultivo de Curauá apresentou maior TIR (44%), seguido do sistema Paricá e Curauá (33%), valores superiores ao custo de oportunidade. A associação Paricá e Curauá mostrou-se economicamente viável, tanto para agricultores que desejam implantar um povoamento florestal, quanto para as empresas madeireiras interessadas na redução dos custos da implantação de povoamentos florestais.

The main purpose of this work was to analyze the economic viability of crop systems with Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby and Ananas comosus var. erectifolius (L. B. Smith) Coppus & Leal, considering three distinct systems: I) parica Monoculture; II) Curauá monoculture; and III) Paricá + Curauá system. The experiment was carried out in the Tramontina's Belém experimental field in Aurora do Pará, PA. From the registers of the accounts of expenditure and prescription of the unitary budget, elaborated for system each, a box flow was elaborated. The economic viability was determined through calculations of: Net Present Value (NPV), Benefit/cost ratio (B/C.R), Break-even point (BEP) and Internal Rate of Return (IRR) in three distinct activities. For tax calculations of a 12% of discounting was chosen. The costs and the prescriptions had been esteem in R$/ha. Results showed that Curauá monoculture had a greater VPL (R$ 19,853.44), followed by the plantation of parica and curaua (R$ 9,507.795). The Paricá and Curauá system showed a high benefit/cost relation (1.29), while parica monoculture the B/C.R was less than 1. Among the analyzed activities, the Curauá monoculture showed a greater TIR (44%) followed by the Paricá and Curauá system (33%). The association between Paricá and Curauá showed to be economically recommendable, as for agriculturists, whom they desire to implant a forest stand, as for companies interested in the reduction of the forest costs.