Producción de la enzima lignina peroxidasa H8 en la levadura metilotrófica Pichia pastoris

La producción de enzimas del complejo degradador de la madera es importante para un amplio rango de actividades industriales, tal es el caso de la lignina peroxidasa que es usada en el pretratamiento del material lignocelulósico en procesos de biorefinado y la degradación de compuestos tóxicos como colorantes, hidrocarburos aromáticos policíclicos (HAPs), nanomateriales y antibióticos mediante estrategias de biorremediación. Adicionalmente se le han atribuido funciones de producto con alto valor agregado como agente despigmentante, biosensor o en la generación de aditivos alimenticios (ácido ferúlico y vainillina) y biocombustibles basados en la conversión de lignina. Lo anterior hace que su producción recombinante sea de interés biotecnológico. Los esfuerzos previos de clonación han generado resultados desalentadores siendo los más comunes: bajo rendimiento, baja actividad y la necesidad de procesos adicionales para favorecer el correcto plegamiento. En el presente trabajo se exploró una alternativa para solventar estos inconvenientes mediante la producción heteróloga de la enzima lignina peroxidasa H8 en la levadura metilotrófica Pichia pastoris, además se implementó una estrategia de optimización de codones basada en emular el perfil de uso de codones presente en el organismo nativo en la secuencia de interés a insertar en el organismo hospedero. Objetivo: Expresar y caracterizar la isoforma H8 de la enzima lignina peroxidasa en la cepa GS115 de Pichia pastoris. Metodología. Se diseñó una secuencia con armonización de codones de la isoforma del gen LiPH8 de la lignina peroxidasa de Phanerochaete chrysosoporium y se envió a sintetizar artificialmente en el vector de expresión para levaduras pPIC9K

Generalizing segregation and chemical ordering in bimetallic nanoclusters through atomistic view points

"We predict general trends for surface segregation in binary metal clusters based on the difference between the atomic properties of the constituent elements. The energetically most favorable site for a guest atom on a pure metal cluster is determined considering the attractive and repulsive contributions of the cohesive energy of an atom in the cluster. It is predicted that for adjacent elements in a period of the periodic table, the bimetallic system would be more stable if the component with smallest valence electron density is placed on the surface. On the other hand, in bimetallic clusters built with elements of only one group, the trend to be in the volume (of the atomic component with smaller core density) will be higher for that cluster with atomic components most separated in the group. Such chemical ordering trends in the lowest energy configurations of Pt-Au, Pt-Pd, and Pt-Ni binary alloy clusters are verified for their 561 atom systems through a simulated annealing process. Some of our atomistic predictions are verified through quantum mechanical calculations.

Robust and fast sliding-mode control for a DC-DC current-source parallel-resonant converter

Modern DC-DC resonant converters are normally built around a voltage-source series-resonant converter. This study aims to facilitate the practical use of current-source parallel-resonant converters due to their outstanding properties. To this end, this study presents a sliding-mode control scheme, which provides the following features to the closed-loop system: (i) high robustness to external disturbances and parameter variations and (ii) fast transient response during large and abrupt load changes. In addition, a design procedure for determining the values of the control parameters is presented. The theoretical contributions of this study are experimentally validated by selected tests on a laboratory prototype.Peer ReviewedPreprin

PI-based controller for low-power distributed inverters to maximise reactive current injection while avoiding over voltage during voltage sags

This paper is a postprint of a paper submitted to and accepted for publication in IET Power Electronics and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library.In the recently deregulated power system scenario, the growing number of distributed generation sources should be considered as an opportunity to improve stability and power quality along the grid. To make progress in this direction, this work proposes a reactive current injection control scheme for distributed inverters under voltage sags. During the sag, the inverter injects, at least, the minimum amount of reactive current required by the grid code. The flexible reactive power injection ensures that one phase current is maintained at its maximum rated value, providing maximum support to the most faulted phase voltage. In addition, active power curtailment occurs only to satisfy the grid code reactive current requirements. As well as, a voltage control loop is implemented to avoid overvoltage in non-faulty phases, which otherwise would probably occur due to the injection of reactive current into an inductive grid. The controller is proposed for low-power rating distributed inverters where conventional voltage support provided by large power plants is not available. The implementation of the controller provides a low computational burden because conventional PI-based control loops may apply. Selected experimental results are reported in order to validate the effectiveness of the proposed control scheme.Peer ReviewedPostprint (updated version

Performance evaluation of secondary control policies with respect to digital communications properties in inverter-based islanded microgrids

A key challenge for inverted-based microgrids working in islanded mode is to maintain their own frequency and voltage to a certain reference values while regulating the active and reactive power among distributed generators and loads. The implementation of frequency and voltage restoration control policies often requires the use of a digital communication network for real-time data exchange (tertiary control covers the coordi- nated operation of the microgrid and the host grid). Whenever a digital network is placed within the loop, the operation of the secondary control may be affected by the inherent properties of the communication technology. This paper analyses the effect that properties like transmission intervals and message dropouts have for four existing representative approaches to secondary control in a scalable islanded microgrid. The simulated results reveals pros and cons for each approach, and identifies threats that properly avoided or handled in advance can prevent failures that otherwise would occur. Selected experimental results on a low- scale laboratory microgrid corroborate the conclusions extracted from the simulation study.Peer ReviewedPostprint (author's final draft

Pollen collection and honey bee forager distribution in cantaloupe

Honey bee (Apis mellifera, L.) pollen collection and forager distribution were examined during the 2002 summer in a cantaloupe (Cucumis melo, L., Cruiser cv ) field with plastic mulch and drip irrigated. The experimental site was located near the INIFAP Campo Experimental La Laguna, Matamoros, Coahuila within La Laguna region, Mexico. Two trials were conducted in the same location, but were separated by a 800 m wide pecan orchard. Both cantaloupe trials were planted the same date. Trial 1. Nine honey-bee hives were placed in a three hectare field at the start of bloom. Each hive was fitted with a modified-Ontario pollen trap. The pollen was collected one day a week from each colony every hour beginning from 8:30 hr to 14:30 hr during the first four blooming weeks of the crop. Trial 2. Three weeks after the start of bloom, in a ten-ha field 30 honey bee colonies were located. In four randomlyselected rows of 105 m long, 10 m transects at 25, 50, 75 and 100 m distances from the apiary were marked. The foraging bees were counted simultaneously at the transects every half hour from 7:30 hr until 20:30 hr at the same pollen collection-day during the third week of cantaloupe bloom. Pollen collection was higher early in the morning (22.6 g per colony), dropping to medium amount from 9:30 hr (13.7 g), 10:30 hr (12.5 g) to 11:30 hr (9.5 g) and remaining low from 12:30 through the afternoon (less than 2.6 g per colony; p< 0.05). The distribution pattern showed that bees were in the cantaloupe after 8:00 hr, reaching a maximum between 10:30 hr and 14:30 hr when the bees began to decrease, until foraging flights ceased completely at about 20:30 hr. No statistical differences were found in the number of foraging bees among the evaluated distances from the apiary.Durante el verano del 2002 la colecta de polen y la distribución de las abejas (Apis mellifera L.) pecoreadoras fueron estudiadas en el cultivo de melón (Cucumis melo L., cv Cruiser ) bajo condiciones de riego por goteo y acolchado plástico. El lote experimental estuvo localizado cerca del Campo Experimental La Laguna del INIFAP, en el municipio de Matamoros, Coahuila, México. Dos experimentos se realizaron en el mismo predio, en lotes separados 800 m por una huerta de nogal. Ambas superficies de melón fueron sembradas en la misma fecha. Experimento N° 1. Al inicio de la floración se colocaron nueve colmenas en tres hectáreas de cultivo. Cada colmena contó con una trampa de polen tipo Ontario modificada. El polen se colectó cada hora de cada colmena un día por semana de las 8:30 hr a las 14:30 hr durante las cuatro primeras semanas de floración del cultivo. Experimento N° 2. Tres semanas después del inicio de la floración se colocaron 30 colmenas en un campo de melón de diez hectáreas. En cuatro surcos de 105 m de longitud se marcaron transectos de diez metros a 25, 50, 75 y 100 metros de distancia del apiario. Las abejas pecoreadoras fueron contadas simultáneamente en cada transecto cada media hora de las 7:30 hr hasta las 20:30 horas, el mismo día en que fue colectado el polen de la tercera semana de floración. La colecta de polen fue mayor temprano por la mañana (22.6 g por colmena), disminuyendo a una cantidad media de las 9:30 hr (13.7 g), 10:30 hr (12.5 g) a las 11:30 hr (9.5 g) y permaneciendo baja desde las 12:30 hasta el mediodía (menos de 2.6 g por colmena; p<0.05). El patrón de distribución mostró que las abejas se presentaron en el cultivo de melón después de las 8:00 hr y alcanzaron su máximo entre las 10:30 hr y las 14:30 hr cuando las abejas iniciaron su disminución hasta el cese de los vuelos a las 20:30 hr. No se encontraron diferencias significativas en el número de abejas pecoreadoras a las diferentes distancias del apiario que fueron evaluadas

Especies de plantas visitadas por abejas pecoreadoras durante la inducción de polinización en melón.

The purpose of the research was to determine, by identifying pollen in corbicular pellets, the different plant species visited by honeybees (Apis mellifera L.) during cantaloupe (Cucumis melo L.) induced pollination. This work was carried out in La Laguna region, located in the states of Coahuila and Durango, Mexico in the spring of 2003. During the first 31 days of cantaloupe bloom, 18 honey bee colonies were placed in a six ha field, nine of which had a bottom pollen trap. Trapped pollen was collected twice per a week weighed and frozen. Through the year, anthers of wild and cultivated flowering plant species around the cantaloupe field and in La Laguna were collected, acetolyzed and preserved for pollen identified. Corbicular pollen from the 5th, 9th, 12th, 20th, 24th and 31st sample dates after start of staminate bloom was processed, identified and counted by microscopy. Pollen size was calculated with the formula: volume V=?a2b where a is the major axe and b the minor axis and multiplied by the number of pollen grains to get the total volume. Cantaloupe pollen made up 8.7 %, 9.8%, 17.6 %, 9.3 %, 28.1% and 83.5% of that collected (number of pollen grains) on respectively for the sample dates. The percentage of volume basis pollen for cantaloupe was: 51.6%, 85.0%, 66.6 %, 84.4 %, 68.9% and 95.0% respectively. It is concluded that the cantaloupe was the main species visited as a plant pollen source for pollinating honeybees and that the plants present in the sample like mesquite (Prosopis juliflora (Swartz) DC.), alfalfa (Medicago sativa L.), creosote bush (Larrea tridentata (DC) Cov.), cucumber (Cucumis sativus L.), London rocket (Sysimbrium irio L.) and sorghum (Sorghum vulgare L.) were species visited as supplementary pollen sources.El objetivo de la investigación fue determinar, a través de la identificación del polen corbicular, las diferentes especies de plantas que son visitadas por las abejas (Apis mellifera L.) durante la polinización inducida del melón (Cucumis melo L.). El trabajo se llevó a cabo en La Laguna ocalizada en los estados de Coahuila y Durango, México en la primavera del 2003. Durante los primeros 31 días de la floración del melón, un campo de seis hectáreas fue polinizada por 18 colmenas, nueve de las cuales tenía una trampa para captura de polen. El polen fue colectado dos veces por semana, pesado y congelado. Durante el año se colectaron anteras de plantas silvestres y cultivadas en floración alrededor del cultivo y en la región para preservarlas e identificar su polen usando la técnica de acetolisis. El polen corbicular, muestreado los días 5°, 9°, 12°, 20°, 24° y 31° contados a partir del inicio de la aparición de las flores estaminadas, fue procesado y contado en el microscopio óptico. El tamaño del polen fue calculado mediante la fórmula: volumen V=?a2b donde a es el eje mayor y b el eje menor y multiplicado por el número de granos de polen se obtuvo el volumen total. El polen de melón fue el 8.7 %, 9.8%, 17.6 %, 9.3 %, 28.1% y 83.5% del colectado (en base al número de granos) respectivamente en las fechas de muestreo. El porcentaje del polen de melón en base al volumen fue: 51.6%, 85.0%, 66.6 %, 84.4 %, 68.9% y 95.0% respectivamente. Se concluye que el melón fue la principal planta visitada por las abejas como fuente de polen y que las especies de plantas con mayor número de granos de polen presentes en las muestras como mezquite (Prosopis juliflora (Swartz) DC.), alfalfa (Medicago sativa L.), gobernadora (Larrea tridentata (DC) Cov.), pepino (Cucumis sativus L.), mostacilla (Sysimbrium irio L.) y sorgo (Sorghum vulgare L.) fueron especies visitadas como fuentes suplementarias de polen

Sugerencias para el laboratorio de electrónica

1 archivo PDF (51 páginas)Documento que tiene como objetivo cubrir ciertos temas que no son contemplados como conocimiento previo en diversas UEA's y que, en muchas ocasiones, son causa de que un alumno no pueda "ligar" un tema con otro

Reduction of Current Harmonic Distortion in Three-Phase Grid-Connected Photovoltaic Inverters via Resonant Current Control

The resonant current control has been extensively employed to reduce the current harmonic distortion in a wide range of grid-connected distributed generation applications, including photovoltaic (PV) inverters, wind and water turbines, and fuel-cell inverters. However, the performance of these systems is deteriorated when the utility grid voltage experiences abnormal conditions such as voltage harmonics and imbalances. Several advanced control solutions have been recently introduced to cope with this problem but at the cost of a significant increase in the control computational load. This paper first analyzes the limitations of the standard resonant current control operating under abnormal grid conditions and then introduces a control scheme that improves the current harmonic distortion in such adverse conditions without increasing the computational load of the standard current control. This theoretical contribution is validated by means of selected experimental results from a three-phase PV inverterPostprint (published version