Succinct and Self-Indexed Data Structures for the Exploitation and Representation of Moving Objects

Programa Oficial de Doutoramento en Computación . 5009V01[Abstract] This thesis deals with the efficient representation and exploitation of trajectories of objects that move in space without any type of restriction (airplanes, birds, boats, etc.). Currently, this is a very relevant problem due to the proliferation of GPS devices, which makes it possible to collect a large number of trajectories. However, until now there is no efficient way to properly store and exploit them. In this thesis, we propose eight structures that meet two fundamental objectives. First, they are capable of storing space-time data, describing the trajectories, in a reduced space, so that their exploitation takes advantage of the memory hierarchy. Second, those structures allow exploiting the information by object queries, given an object, they retrieve the position or trajectory of that object along that time; or space-time range queries, given a region of space and a time interval, the objects that are within the region at that time are obtained. It should be noted that state-of-the-art solutions are only capable of efficiently answering one of the two types of queries. All of these data structures have a common nexus, they all use two elements: snapshots and logs. Each snapshot works as a spatial index that periodically indexes the absolute position of each object or the Minimum Bounding Rectangle (MBR) of its trajectory. They serve to speed up the spatio-temporal range queries. We have implemented two types of snapshots: based on k2-trees or R-trees. With respect to the log, it represents the trajectory (sequence of movements) of each object. It is the main element of the structures, and facilitates the resolution of object and spatio-temporal range queries. Four strategies have been implemented to represent the log in a compressed form: ScdcCT, GraCT, ContaCT and RCT. With the combination of these two elements we build eight different structures for the representation of trajectories. All of them have been implemented and evaluated experimentally, showing that they reduce the space required by traditional methods by up to two orders of magnitude. Furthermore, they are all competitive in solving object queries as well as spatial-temporal ones.[Resumen] Esta tesis aborda la representación y explotación eficiente de trayectorias de objetos que se mueven en el espacio sin ningún tipo de restricción (aviones, pájaros, barcos, etc.). En la actualidad, este es un problema muy relevante debido a la proliferación de dispositivos GPS, lo que permite coleccionar una gran cantidad de trayectorias. Sin embargo, hasta ahora no existe un modo eficiente para almacenarlas y explotarlas adecuadamente. Esta tesis propone ocho estructuras que cumplen con dos objetivos fundamentales. En primer lugar, son capaces de almacenar en espacio reducido los datos espaciotemporales, que describen las trayectorias, de modo que su explotación saque partido a la jerarquía de memoria. En segundo lugar, las estructuras permiten explotar la información realizando consultas sobre objetos, dado el objeto se calcula su posición o trayectoria durante un intervalo de tiempo; o consultas de rango espacio-temporal, dada una región del espacio y un intervalo de tiempo se obtienen los objetos que estaban dentro de la región en ese tiempo. Hay que destacar que las soluciones del estado del arte solo son capaces de responder eficientemente uno de los dos tipos de consultas. Todas estas estructuras de datos tienen un nexo común, todas ellas usan dos elementos: snapshots y logs. Cada snapshot funciona como un índice espacial que periódicamente indexa la posición absoluta de cada objeto o el Minimum Bounding Rectangle (MBR) de su trayectoria. Sirven para agilizar las consultas de rango espacio-temporal. Hemos implementado dos tipos de snapshot: basadas en k2-trees o en R-trees. Con respecto al log, éste representa la trayectoria (secuencia de movimientos) de cada objeto. Es el principal elemento de nuestras estructuras, y facilita la resolución de consultas de objeto y de rango espacio-temporal. Se han implementado cuatro estrategias para representar el log de forma comprimida: ScdcCT, GraCT, ContaCT y RCT. Con la combinación de estos dos elementos construimos ocho estructuras diferentes para la representación de trayectorias. Todas ellas han sido implementadas y evaluadas experimentalmente, donde reducen hasta dos órdenes de magnitud el espacio que requieren los métodos tradicionales. Además, todas ellas son competitivas resolviendo tanto consultas de objeto como de rango espacio-temporal.[Resumo] Esta tese trata sobre a representación e explotación eficiente de traxectorias de obxectos que se moven no espazo sen ningún tipo de restrición (avións, paxaros, buques, etc.). Na actualidade, este é un problema moi relevante debido á proliferación de dispositivos GPS, o que fai posible a recollida dun gran número de traxectorias. Non obstante, ata o de agora non existe un xeito eficiente de almacenalos e explotalos. Esta tese propón oito estruturas que cumpren dous obxectivos fundamentais. En primeiro lugar, son capaces de almacenar datos espazo-temporais, que describen as traxectorias, nun espazo reducido, de xeito que a súa explotación aproveita a xerarquía da memoria. En segundo lugar, as estruturas permiten explotar a información realizando consultas de obxectos, dado o obxecto calcúlase a súa posición ou traxectoria nun período de tempo; ou consultas de rango espazo-temporal, dada unha rexión de espazo e un intervalo de tempo, obtéñense os obxectos que estaban dentro da rexión nese momento. Cómpre salientar que as solucións do estado do arte só son capaces de responder eficientemente a un dos dous tipos de consultas. Todas estas estruturas de datos teñen unha ligazón común, empregan dous elementos: snapshots e logs. Cada snapshot funciona como un índice espacial que indexa periodicamente a posición absoluta de cada obxecto ou o Minimum Bounding Rectangle (MBR) da súa traxectoria. Serven para acelerar as consultas de rango espazo-temporal. Implementamos dous tipos de snapshot: baseadas en k2-trees ou en R-trees. Con respecto ao log, este representa a traxectoria (secuencia de movementos) de cada obxecto. É o principal elemento das nosas estruturas, e facilita a resolución de consultas sobre obxectos e de rango espacio-temporal. Implementáronse catro estratexias para representar o log nunha forma comprimida: ScdcCT, GraCT, ContaCT e RCT. Coa combinación destes dous elementos construímos oito estruturas diferentes para a representación de traxectorias. Todas elas foron implementadas e avaliadas experimentalmente, onde reducen ata dúas ordes de magnitude o espazo requirido polos métodos tradicionais. Ademais, todas elas son competitivas para resolver tanto consultas de obxectos como espazo-temporais

Species-specific effects of epigeic earthworms on microbial community structure during first stages of decomposition of organic matter

Background: Epigeic earthworms are key organisms in organic matter decomposition because of the interactions they establish with microorganisms. The earthworm species and the quality and/or substrate availability are expected to be major factors influencing the outcome of these interactions. Here we tested whether and to what extent the epigeic earthworms Eisenia andrei, Eisenia fetida and Perionyx excavatus, widely used in vermicomposting, are capable of altering the microbiological properties of fresh organic matter in the short-term. We also questioned if the earthworm-induced modifications to the microbial communities are dependent on the type of substrate ingested. Methodology/Principal Findings: To address these questions we determined the microbial community structure (phospholipid fatty acid profiles) and microbial activity (basal respiration and microbial growth rates) of three types of animal manure (cow, horse and rabbit) that differed in microbial composition, after being processed by each species of earthworm for one month. No differences were found between earthworm-worked samples with regards to microbial community structure, irrespective of type of manure, which suggests the existence of a bottleneck effect of worm digestion on microbial populations of the original material consumed. Moreover, in mesocosms containing cow manure the presence of E. andrei resulted not only in a decrease in bacterial and fungal biomass, but also in a reduced bacterial growth rate and total microbial activity, while no such reduction was found with E. fetida and P. excavatus. Conclusions/Significance: Our results point to the species of earthworm with its associated gut microbiota as a strong determinant of the process shaping the structure of microbial communities in the short-term. This must nonetheless be weighed against the fact that further knowledge is necessary to evaluate whether the changes in the composition of microbiota in response to the earthworm species is accompanied by a change in the microbial community diversity and/or function.Ministerio de Ciencia e Innovación | Ref. CTM2009-0847

Adaptation of soil microbial communities to temperature: comparison of fungi and bacteria in a laboratory experiment

Temperature not only has direct effects on microbial activity, but can also affect activity indirectly by changing the temperature dependency of the community. This would result in communities performing better over time in response to increased temperatures. We have for the first time studied the effect of soil temperature (5–50 °C) on the community adaptation of both bacterial (leucine incorporation) and fungal growth (acetate‐in‐ergosterol incorporation). Growth at different temperatures was estimated after about a month using a short‐term assay to avoid confounding the effects of temperature on substrate availability. Before the experiment started, fungal and bacterial growth was optimal around 30 °C. Increasing soil temperature above this resulted in an increase in the optimum for bacterial growth, correlated to soil temperature, with parallel shifts in the total response curve. Below the optimum, soil temperature had only minor effects, although lower temperatures selected for communities growing better at the lowest temperature. Fungi were affected in the same way as bacteria, with large shifts in temperature tolerance at soil temperatures above that of optimum for growth. A simplified technique, only comparing growth at two contrasting temperatures, gave similar results as using a complete temperature curve, allowing for large scale measurements also in field situations with small differences in temperature

Recycling and valorization of distilled grape marc through vermicomposting: a pilot-scale study

The present study sought to evaluate the effectiveness of vermicomposting for the valorization of distilled grape marc, one of the main solid by-products of the winery sector during a 56-day pilot-scale trial. The increase in the density and biomass of earthworms ( Eisenia andrei ) during the earlier stages of the process reflected the suitability of the distilled marc ( Vitis vinifera L. cv. Mencía) as feedstock in order to sustain large earthworm populations on a pilot-scale level. Supporting this, from 14 days onwards the pH of Mencía distilled marc fell within weak-alkaline levels and the electrical conductivity was between 0.21 and 0.11 mS cm −2 providing optimum conditions for earthworm growth. A rapid decrease in microbial activity as well as in the content of total polyphenols, both indicative of stabilized materials was also recorded after 14 days of vermicomposting. Moreover, the content of macro- and micronutrients in the end product matched with those considered to have the quality criteria of a good vermicompost with respect to plant health and safe agricultural use. Altogether, it underlines the feasibility of vermicomposting as an environment-friendly approach for the biological stabilization of distilled grape marc fulfilling both environmental protection and fertilizer production.Agencia Estatal de Investigación | Ref. PID2021-124265OB-I00Xunta de Galicia | Ref. ED431C 2022/07Agencia Estatal de Investigación | Ref. RYC-2016-21231Universidade de Vigo/CISU

Changes in chemical and microbiological properties of rabbit manure in a continuous-feeding vermicomposting system

In the present study the potential of the earthworm Eisenia fetida to process large amounts of waste was evaluated through continuous feeding reactors in which new layers of rabbit manure were added sequentially to form an age gradient inside the reactors. An optimal moisture level, ranging from 66% to 76%, was maintained throughout the process using an automatic watering system. The pH was close to 8.3, but decreased to 7.6 after 200 d of vermicomposting. No changes in electrical conductivity through the prole of layers were detected. Based on comparisons of phospholipid fatty acid (PLFA) proles and microbial activity measurements (basal respiration), a decrease in the levels of bacteria and fungi in layers corresponding to vermicomposting times of more than 200 d occurred. This points to a higher degree of stabilisation in the nal product, which is of utmost importance for its safe use as an organic amendment.Ministerio de Ciencia e Innovación | Ref. CTM2009-0847