Analysis of night-time climate in plastic-covered grenhouses

Este trabajo analiza el clima nocturno del invernadero. EL objeto del estudio es el invernadero de plástico sin calefacción, cuyo clima se estudia utilizando modelos CFD, modelos basados en los balance de energía (ES) y s datos experimentales. El fin es doble, por un lado se trata de analizar y comprender el clima nocturno del invernadero, y proponer soluciones a los problemas relacionados con las altas tasas de humedad. Por otro lado se investigan nuevos métodos de simulación del clima del invernadero, métodos basados en el uso conjunto o acoplamiento de modelos CFD y ES , y también basados en la técnica de optimización. El Capitulo 1 introduce el contexto general y los objetivos que plantea el trabajo. El Capitulo 2 estudia el clima nocturno en un invernadero de capa sencilla. Para ello desarrolla un modelo CFD que incluye una UDF (User Define Function) para calcular la tasa de condensación. Una vez validado el modelo se analiza el comportamiento del invernadero bajo distintas condiciones de contorno.. El Capitulo 3 analiza una solución para combatir las bajas temperaturas nocturnas, la pantalla térmica. Los efectos de la pantalla se analizan mediante el uso del CFD. Se lleva a cabo una comparación completa entre el invernadero de capa sencilla y el invernadero con pantalla. El capitulo proporciona información detallada sobre el clima del invernadero y presenta un estudio paramétrico del efecto de la temperatura equivalente del cielo y la cesión de calor desde el suelo en el clima del invernadero con pantalla térmica. EL Capitulo 4 presenta un nuevo método para optimizar el diseño del invernadero. El método se basa en el acoplamiento de dos algoritmos de optimización que operan con el modelo ES. A su vez el modelo ES está conectado con el modelo CFD. El objetivo es doble, por un lado introducir una nueva manera de optimizar el diseño del invernadero, y por el otro lado tratar de resolver uno de los problemas evidenciados en el capítulo 2. El resultado muestra que un material de cubierta de alto poder de reflexión del infrarrojo lejano aportaría mejorías relevantes al clima del invernadero. El Capitulo 5 presenta un modelo acoplado para el estudio del clima del invernadero. EL CFD se utiliza para proporcionar las tasas de ventilación y los coeficientes convectivos al modelo ES. Esta técnica se utiliza para estudiar los efectos de diferentes estrategias de ventilación sobre el régimen de humedad con diferentes condiciones externas. Finalmente, el Capitulo 6 resume las conclusiones y propone algunos temas para futuras investigacionesThis work studied night-time greenhouse climate. The focus was on unheated plastic greenhouses and analyses were carried out using CFD models, Energy balance (ES) models and experimental data. The aims were twofold: on the one hand, it was intended to analyse and understand night-time greenhouse climate and propose solutions to the high-humidity issue. On the other hand, the aim was to investigate novel simulation approaches based on the coupling of CFD and ES models as well as the use of optimisation algorithms to study greenhouse climate. Chapter 1 is an introductory chapter which includes the general context and overall research objectives. Chapter 2 studies night-time climate in single-layer greenhouses by means of CFD. The model is validated and condensation User Defined Function (UDF) is introduced which accounted for the condensation rate found on the inner face of the greenhouse cover. Chapter 3 studies a commonly used solution to the issue of low night-time temperature. A thermal screen was analysed by means of CFD simulations. A thorough comparison was made between single-layer and screened greenhouses and detailed information was provided in order to build a framework for taking decisions as to whether to use a screen or not. Chapter 4 introduces a novel approach to optimizing greenhouse design; the approach relies on two optimization algorithms linked to an ES model which was coupled to a CFD model. The aim of the study was twofold: on the one hand to introduce a method offering a general approach for optimizing greenhouse design and on the other, to attempt to solve one of the issues highlighted in Chapter 2. It was shown that using a highly reflective covering material would have a theoretically significant impact on greenhouse performance. Chapter 5 introduces a coupled model for studying greenhouse climate. The CFD was used to provide the ventilation rate and convective coefficients for the ES model. This approach was applied to study the effects of different ventilation strategies on humidity under different outside air conditions. Finally Chapter 6 summarizes the conclusions and proposes themes for future research

Indagini sull\u27evoluzione del popolamento zooplanctonico: confronto con i dati pregressi anche alla luce delle mutate condizioni meteo-climatiche

Not availableRicerche sull\u27evoluzione del Lago Maggiore. Aspetti limnologici. Programma triennale 2013-2015. Campagna 2013. Indagini sull\u27evoluzione del popolamento zooplanctonico: confronto con i dati pregressi anche alla luce delle mutate condizioni meteo-climatich

Not only Cladocera: what we can learn from RRE analysis in deep lake sediment cores

Since early palaeolimnological studies, Cladocera have been largely investigated in lakes of different typologies and from a large variety of sites. Analyses of their subfossil remains provide evidence for changes in trophodynamics, habitat and water level fluctuations and of impact of drivers such as climate change on lake ecosystem functioning. Rotifers are an important component of lacustrine food webs. They are responsible for the largest part of zooplankton diversity. Because of short developmental times and intrinsic rate of increase, they promptly respond to different impacts, such as changes in trophy, pollution and recovery as well as climatedriven changes. Rotifers have been overlooked in palaeolimnological studies because they do not leave subfossil remains. They do produce, however, resting eggs of a variety of morphotypes (MTs), which preserve well in sediments. We report here results of a study in which we applied RRE MTs (Rotifer Resting Eggs MorphoTypes) analyses to a sediment core of Lake Orta on which cladocera and diatoms were analysed along with lake chronic, heavy metal pollution and acidification as well as recovery. We found that RRE abundance increased during pollution. RRE MTs differed substantially before vs. during pollution and along with the different recovery phases. The restored RRE community differed substantially from the pre-pollution one. Unexpectedly, RREs persisted over the full pollution phase, when copper concentration in the water column was as high as 108 ?g/L (in the late fifties) and when lake pH (value at the winter mixing) was of 3.8 (in the middle eighties). The presence of open egg cases also proves attempts of e.g. Brachionus calyciflorus to establish also during pollution phase. Extending RREMTs analyse to other deep subalpine lakes (i.e. Leman, Annecy and Bourget) encourage to further develop this approach to contribute to understanding impact of local vs. global drivers affecting lake ecosystem functioning

Invasione di specie aliene: comparsa di Polyphemus pediculus (Linnaeus, 1761; Crustacea Cladocera) nel Lago Maggiore

Polyphemus pediculus (Linnaeus, 1761) is a holoarctic cladoceran species typically inhabiting the littoral zone of lakes. It is a voracious predator, hunting its prey by visual predation, able to deplete the zooplankton population. Its detection for the first time in Lake Maggiore, at a sampling station close to the littoral, in which zooplankton was monitored for 20 years is worth of being discussed. First, because it represents a further increase in predatory Cladocera, after Bythotrephes longimanus (Leydig, 1860) have successfully re-emerged in the open water. Second, because it may be regarded as an increasing invasion trend in a lake traditionally considered as a stable, mature environment, in which invasions should be hardly successful.Polyphemus pediculus (Linnaeus, 1761) ? un cladocero oloartico che tipicamente colonizza la zona litorale dei laghi. ? un predatore vorace, che attua una strategia di predazione visiva, in grado di decimare il popolamento zooplanctonico. La presenza di questo organismo, rilevata per la prima volta in campioni provenienti da una stazione del Lago Maggiore, posta vicino alla zona litorale nella quale lo zooplancton viene monitorato da 20 anni, ? meritevole di discussione. Primo, perch? rappresenta un ulteriore aumento della frazione di Cladoceri predatori, dopo l\u27accresciuta presenza numerica di Bythotrephes longimanus (Leydig, 1860) nelle acque pelagiche. Secondo, perch? pu? essere considerato un aumento della tendenza alle invasioni, in un lago tradizionalmente considerato come un ambiente stabile e maturo, nel quale pertanto la probabilit? di successo delle invasioni dovrebbe essere bassa

Mechanisms underlying recovery of zooplankton in Lake Orta after liming

The goal of this study was to improve the understanding of the large-scale mechanisms underlying the recovery of the zooplankton of Lake Orta from historical contamination, following reduced input of ammonia and metals and the subsequent 1989/90 liming intervention. The industrial pollution had been severe and long-lasting (1929-1990). Zooplankton biodiversity has improved, but most of the new taxa appearing in our counts are rotifers, while many calanoids and the large cladoceran predators (Bythotrephes and Leptodora) that are common in the nearby Lake Maggiore, were still absent from Lake Orta 17 years after liming. To aid understanding of the large-scale mechanisms controlling changes in annual richness, we assessed the annual persistence (P) of Crustacea and Rotifera taxa as an estimator of whether propagules that survived introduction, as result of the natural recolonization process, also thrived. We found that the rate of introduction of zooplankton colonists and their persistence in the water column of Lake Orta changed from 1971 to 2007. New rotifer taxa appeared in the lake after the mid-1980s, when discharge of toxic substances decreased, but their annual persistence was low (P<0.5) until the turn of the century. The numerical values of rotifer and crustacean persistence in Lake Orta were unexpectedly high in 2001 and 2007 (0.55 and 0.72 for rotifers, 0.85 and 0.86 for crustacean, respectively), much higher than in limed lakes in Sudbury, Canada, and in adjacent Lake Maggiore. We hypothesize this could be related to the lack of Cladoceran predators and zooplanktivorous fish in the pelagic waters of Lake Orta

Demographic cost and mechanisms of adaptation to environmental stress in resurrected Daphnia

A characteristic feature of the Daphnia (Crustacea: Cladocera) life cycle are the so-called ephippia, which are fertilised eggs that need to undergo diapause. When they are shed by the female, they sink to the lake bottom, where they may become embedded in the sediment and may remain viable for decades. Extracting and hatching ephippia in the laboratory and subjecting resurrected lineages to conditions representative of historic lake environments allows retrospective investigation of life-history responses to environmental change. Here we reanalyse data from such a resurrection experiment (Piscia et al., 2015: Bull. Environ. Contam. Toxicol. 94:46-51). Contemporary and past lineages of Daphnia galeata Sars 1863 were obtained from Lake Orta (Italy), a deep, subalpine lake with a well-documented history of industrial copper pollution. Experimental Daphnia were subjected to three copper treatments representative of two levels of historic as well as to current (i.e., unpolluted) lake conditions, and life-table data were collected. With these data at hand, we first estimated vital rates (survival, maturation, and reproduction) and used these rates to project the asymptotic population growth rates (?) for each population-by-treatment combination. Next, we performed life-table response experiments (LTRE) to estimate the contributions of the vital rates to observed differences in ?. Finally, we used elasticity analysis to explore the functional relationship between ? and each of the vital rates. We found that survival rates were only compromised at elevated copper levels. Moreover, past, resurrected Daphnia had a higher ? at low copper concentrations compared to unpolluted conditions, but a lower ? when exposed to high copper levels. Contemporary Daphnia, on the other hand, only reproduced successfully in unpolluted water. Under these conditions, however, they had a higher population growth rate than the past Daphnia, suggesting a cost of copper tolerance in the latter. This cost was mainly due to a lower probability of reproduction and reduced fecundity, whereas survival remained largely unaffected. Finally, we found higher elasticity values of ? to survival than to reproductive rates. This suggests that any change in the environment that will affect survival rather than reproductive parameters will have a much larger impact on Lake Orta\u27s current Daphnia population

Evaluation of the Egg Bank of Two Small Himalayan Lakes

High mountain lakes are biodiversity treasures. They host endemic taxa, adapted to live in extreme environments. Among adaptations, production of diapausing eggs allows for overcoming the cold season. These diapausing eggs can rest in the sediments, providing a biotic reservoir known as an egg bank. Here, we estimated changes in abundance of the egg bank in two lakes in the Khumbu Region of the Himalayas, during the last ca. 1100 and 500 years, respectively, by analyzing two sediment cores. We tested viability of the diapausing eggs extracted from different layers of the sediment cores under laboratory conditions. We found that only diapausing eggs of the Monogont rotifer Hexarthra bulgarica nepalensis were able to hatch, thus suggesting that a permanent egg bank is lacking for the other taxa of the lakes, not least for the two Daphnia species described from these sites. Our results confirm previous studies suggesting that in high mountain lakes, the production of diapausing is mainly devoted to seasonal recruitment, therefore leading to a nonpermanent egg bank. The different ability of different taxa to leave viable diapausing eggs in the sediments of high mountain lakes therefore poses serious constraints to capability of buffering risk of biodiversity loss in these extremely fragile environments

Contaminanti nello zooplancton

Not availableIndagini su DDT e sostanze pericolose nell\u27ecosistema del Lago Maggiore. Programma 2013-2015. Rapporto annuale 2014 - Contaminanti nello zooplancto

Contaminanti nello zooplancton

Not availableContaminanti nello zooplancton nell\u27ambito del progetto di ricerca "Indagini su DDT e sostanze pericolose nell\u27ecosistema del Lago Maggiore"

Paralelización a algoritmos de compresión fractal de imágenes

Se analiza la paralelización de un algoritmo clásico de compresión fractal de imagenes, utilizando procesadores heterogéneos conectados en red con un soporte de procesamiento distribuido basado en PVM y XPVM. En particular se discuten dos métricas de interés: el speed-up obtenible (separando los tiempos propios del overhead de comunicaciones) al incrementar el número de procesadores y la pérdida resultante del índice de compresión alcanzado. Si bien se trata de una clase de algoritmo muy particular, resulta de interés tecnológico sobre todo en aplicaciones donde la información es comprimida una vez y almacenada para su recuperación en consulta muchas veces (por ejemplo en servidores de información InterNet) ya que los índices de compresión alcanzables con una pérdida aceptable son muy altos y al mismo tiempo el algortimo de descompresión es muy rápido. Por último se discute el efecto de variar el particionamiento de la imagen sobre los tiempos de procesamiento y la posibilidad de realizar un particionamiento adaptivo con el fin de optimizar la relación índice de compresión/pérdida aceptable sin deterioro del speed-up.Eje: Procesamiento distribuido y paralelo. Tratamiento de señalesRed de Universidades con Carreras en Informática (RedUNCI