Distributed Tree Kernels

In this paper, we propose the distributed tree kernels (DTK) as a novel method to reduce time and space complexity of tree kernels. Using a linear complexity algorithm to compute vectors for trees, we embed feature spaces of tree fragments in low-dimensional spaces where the kernel computation is directly done with dot product. We show that DTKs are faster, correlate with tree kernels, and obtain a statistically similar performance in two natural language processing tasks.Comment: ICML201

Good gradings of simple Lie algebras

This thesis aims to study the good gradings of simple finite-dimensional Lie algebras. The Dynkin grading is given as an example of good Z-grading of a semisimple Lie algebra. The main properties of a good Z-grading of a semisimple Lie algebra are proved and all good Z-gradings of gl(n), the Lie algebra of all matrices of order n, are classified. Finally, we extend the definition of good gradings to Lie superalgebras and start studying the good gradings of the Cartan superalgebra W(n). The case of W(2) and W(3) are analyzed

Progettazione assistita (CAD) di un sistema meccanico di terra (MGSE) a supporto dei montaggi di uno strumento per la Stazione Spaziale

In questa tesi si parte dallo sviluppo di un metodo di progettazione teorico basato sulla letteratura che riguarda il design e l'esperienza dell'azienda con cui progetto è stato portato avanti, per poi applicarlo a un caso di progettazione aerospaziale. Il tutto in un’ottica di efficientamento delle soluzioni così da evitare l’utilizzo di parti inutili, lo spreco di materiali e ridurre il numero di oggetti da trasportare. L'obbiettivo di questo progetto è di ottenere i modelli CAD degli assiemi progettati, i fogli d'ordine delle parti commerciali e le tavole di produzione delle parti non commerciali che devono essere prodotte in azienda così da poter arrivare al montaggio completo del prodotto. Il progetto sviluppato riguarda un sistema meccanico di terra (MGSE) a supporto dei montaggi della struttura che deve contenere gli esperimenti a gravità zero tenuti sulla Stazione Spaziale Internazionale e quelli di confronto con la gravità terrestre che saranno portati avanti sulla terra nello Space Center di Toulouse

Physics of bacterial microcolonies

The growth of bacterial colonies is a very ubiquitous phenomenon occurring in nature and observed in the laboratories. However, there is a limited knowledge on how at the microscopic level these colonies develop and the individual cells spatially organize. In this thesis, we experimentally investigate the physics of growing microcolonies at the level of the individual Escherichia coli (E. coli ) cells, focussing on the order-disorder evolution and the understanding of it in the context of active matter. Bacterial cells are indeed constantly transducing energy from the environment to move and grow, therefore they behave as active microscopic units, defining an inherently far from equilibrium system. In Part I, we present a brief summary of passive liquid crystals that provide us with some basic concepts and tools for investigating the bacterial microcolony evolution. Then an overview of the biology of E. coli cell is given, both as part of multicellular structures (biofilm) and as individuals. Active matter is then discussed along with some examples of active nematics. This first part ends with the materials and methods used in the experiments and analysis. In Part II, we provide our experimental results on the study of growing bacterial microcolonies as active nematics. We describe the way a bacterial microcolony evolves from the first mother cell into a layer of hundreds of cells, and we study the global and local orientational order. We find that a transition from an anisotropic to an isotropic phase occurs as the colony increases and that instabilities and topological defects develop, in analogy to the case of an active nematic. We also compare the real system with simulated ones by investigating (i ) the case of equilibrated configurations with respect to experimental nonequilibrium ones, and (ii ) long-time behaviour of nonequilibrium analogues. In Part III, we discuss the buckling of bacterial microcolonies, that is, the transition from a 2D layer of cells to a 3D structure. We investigate the link between the buckling event and the presence of topological defects in the nematic map of the bacterial microcolony, finding that the buckling sites tend to be closer to topological defects with a negative charge. Later, we present some results of buckling in microcolonies composed of mutants lacking some appendages that play a role in the motion in and attachment to the surrounding environment, finding that buckling occurs at earlier times in the case of these mutants than the wild type. The aim of this work is to show that a growing bacterial microcolony is an interesting model of active matter to experiment on, and that the investigation tools developed for the study of liquid crystals can be useful for describing the evolution of these living systems in mechanistic terms, and for improving the current understanding of nonequilibrium phenomena

Teorema fondamentale dei politopi convessi

In questa tesi si presenta il concetto di politopo convesso e se ne forniscono alcuni esempi, poi si introducono alcuni metodi di base e risultati significativi della teoria dei politopi. In particolare si dimostra l'equivalenza tra le due definizioni di H-politopo e di V-politopo, sfruttando il metodo di eliminazione di Fourier-Motzkin per coni. Tutto ciò ha permesso di descrivere, grazie al lemma di Farkas, alcune importanti costruzioni come il cono di recessione e l'omogeneizzazione di un insieme convesso

Mecanismos, cinética y toxicidad de insecticidas cloronicotinoides y sus productos de degradación con especies reactivas oxidantes de interés ambiental

Objetivo de la tesis: - Estudiar la reactividad química en medio acuoso de los insecticidas cloronicotinoides con radicales inorgánicos y estados excitados, denominados en conjunto especies reactivas de importancia ambiental, para evaluar la capacidad de los métodos abióticos en detoxificar las aguas contaminadas con estos insecticidas. Para alcanzar este objetivo se plantearon los siguientes objetivos específicos, para cada una de las especies reactivas estudiadas: - Investigar la naturaleza de los intermediarios de corta vida generados durante el ataque de las especies reactivas a los insecticidas a fin de establecer los sitios de mayor reactividad de las moléculas. - Identificar los productos de degradación primaria de los insecticidas. - Postular los mecanismos de reacción involucrados. - Evaluar la toxicidad de los insecticidas y de las mezclas de insecticidas con sus productos de degradación.Facultad de Ciencias Exacta

Physalis pruinosa var. argentina J. M. Toledo & Barboza

Colonia Muñiz, a 8 km de Las LomitasFil: Ariza Espinar, L. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal; Argentin

Caracterización bioclimatológica, fenológica y productiva de dos híbridos de tomate (<i>Solanum lycopersicum</i>)

El objetivo del trabajo fue caracterizar fenológica, biometeorológica y productivamente a dos híbridos de tomate (Solanum lycopersicum), Eterei y SVTH 2900 (Seminis®), buscando generar información para predecir su desempeño productivo en el cinturón hortícola platense. Se trasplantaron el 22/01/2020 en un invernadero de la Estación Experimental Julio Hirschhorn (FCAyF, UNLP). Mediante una estación meteorológica automática ubicada dentro del invernadero se computó la temperatura del aire, humedad relativa y radiación global, siendo las adecuadas para el cultivo. Se registró las fechas de floración y fructificación hasta el quinto racimo, primera y última cosecha y se calcularon los días y grados-día necesarios para alcanzar cada etapa y entre las mismas. Se midió el diámetro del tallo, altura de planta y contenido de clorofila al trasplante y primera floración. Se calculó la PAR interceptada. Se evaluó el rendimiento total y el peso medio de los frutos. Se empleó un diseño en bloques completos al azar con 4 repeticiones, utilizando 5 plantas por parcela. Los datos se sometieron a análisis de la varianza (p<0,05), utilizando el software estadístico Infostat. Eterei presentó un Índice de Esbeltez ligeramente mayor. Las características de los plantines al momento del trasplante fueron similares y no se encontraron diferencias significativas en el incremento relativo en diámetro de tallo e incremento relativo en altura de la planta hacia la primera floración, que ocurrió luego del mismo número de días con igual requerimiento energético para ambos materiales. La primera fructificación y cosecha ocurrieron antes en SVTH 2900, evidenciando una menor exigencia térmica y cantidad de días para alcanzarlas. No hubo diferencias significativas en la radiación interceptada. El rendimiento fue semejante, con un número reducido de frutos de tercera categoría y una mayor proporción de frutos de segunda en SVTH 2900. El peso medio de los frutos de Eterei fue superior. Los híbridos mostraron buenas condiciones de adaptabilidad, pudiendo esperarse respuestas equivalentes a las de otros híbridos de uso generalizado en la zona.Facultad de Ciencias Agrarias y Forestale

Helical and oscillatory microswimmer motility statistics from differential dynamic microscopy

The experimental characterisation of the swimming statistics of populations of microorganisms or artificially propelled particles is essential for understanding the physics of active systems and their exploitation. Here, we construct a theoretical framework to extract information on the three-dimensional motion of micro-swimmers from the Intermediate Scattering Function (ISF) obtained from Differential Dynamic Microscopy (DDM). We derive theoretical expressions for the ISF of helical and oscillatory breaststroke swimmers, and test the theoretical framework by applying it to video sequences generated from simulated swimmers with precisely-controlled dynamics. We then discuss how our theory can be applied to the experimental study of helical swimmers, such as active Janus colloids or suspensions of motile microalgae. In particular, we show how fitting DDM data to a simple, non-helical ISF model can be used to derive three-dimensional helical motility parameters, which can therefore be obtained without specialised 3D microscopy equipment. Finally, we discus how our results aid the study of active matter and describe applications of biological and ecological importance

A transition to stable one-dimensional swimming enhances E. coli motility through narrow channels

Living organisms often display adaptive strategies that allow them to move efficiently even in strong confinement. With one single degree of freedom, the angle of a rotating bundle of flagella, bacteria provide one of the simplest examples of locomotion in the living world. Here we show that a purely physical mechanism, depending on a hydrodynamic stability condition, is responsible for a confinement induced transition between two swimming states in E. coli. While in large channels bacteria always crash onto confining walls, when the cross section falls below a threshold, they leave the walls to move swiftly on a stable swimming trajectory along the channel axis. We investigate this phenomenon for individual cells that are guided through a sequence of micro-fabricated tunnels of decreasing cross section. Our results challenge current theoretical predictions and suggest effective design principles for microrobots by showing that motility based on helical propellers provides a robust swimming strategy for exploring narrow spaces