Charge control in laterally coupled double quantum dots

We investigate the electronic and optical properties of InAs double quantum dots grown on GaAs (001) and laterally aligned along the [110] crystal direction. The emission spectrum has been investigated as a function of a lateral electric field applied along the quantum dot pair mutual axis. The number of confined electrons can be controlled with the external bias leading to sharp energy shifts which we use to identify the emission from neutral and charged exciton complexes. Quantum tunnelling of these electrons is proposed to explain the reversed ordering of the trion emission lines as compared to that of excitons in our system.Comment: 4 pages, 4 figures submitted to PRB Rapid Com

Earliest Pragian (Early Devonian) corals and stromatoporoids from reefal settings in the Cantabrian Zone (N Spain)

The oldest reefal episode in the Cantabrian Zone (earliest Pragian) consists of small biostromal patch reefs, mainly built by corals and stromatoporoids, and developed on a storm-dominated ramp. Four outcrops provide the stratigraphic framework in which these reef facies developed, and these permitted an interpretation of their depositional setting in terms of a relatively distal or protected shelf. We systematically describe three species of rugose corals, five species of tabulate corals, and six species of stromatoporoids. This fauna is allocated to three Pragian fossil associations. Association 1 is mainly composed of massive tabulate corals and stromatoporoids. Association 2 contains dominant branching rugose and tabulate corals. Finally, association 3 is represented by tiny massive tabulate corals. Each association occurs at a specific location within a framework of high-frequency deepening upward cycles, being related to a specific depositional setting. This mode of occurrence suggests that their development was tuned by relative base-level oscillations, forming during rises that took the sea-bottom to relatively deep or sheltered conditions, with rare reworking by storm-related currents. Finally, a comparison of this reefal fauna with examples of similar age from elsewhere is presented in order to explore their affinities

Point defects on graphene on metals

Understanding the coupling of graphene with its local environment is critical to be able to integrate it in tomorrow's electronic devices. Here we show how the presence of a metallic substrate affects the properties of an atomically tailored graphene layer. We have deliberately introduced single carbon vacancies on a graphene monolayer grown on a Pt(111) surface and investigated its impact in the electronic, structural and magnetic properties of the graphene layer. Our low temperature scanning tunneling microscopy studies, complemented by density functional theory, show the existence of a broad electronic resonance above the Fermi energy associated with the vacancies. Vacancy sites become reactive leading to an increase of the coupling between the graphene layer and the metal substrate at these points; this gives rise to a rapid decay of the localized state and the quenching of the magnetic moment associated with carbon vacancies in free-standing graphene layers

Towards a More Flexible, Sustainable, Efficient and Reliable Induction Cooking: A Power Semiconductor Device Perspective

Esta tesis tiene como objetivo fundamental la mejora de la flexibilidad, sostenibilidad, eficiencia y fiabilidad de las cocinas de inducción por medio de la utilización de dispositivos semiconductores de potencia: Dentro de este marco, existe una funcionalidad que presenta un amplio rango de mejora. Se trata de la función de multiplexación de potencia, la cual pretende resolverse de una manera más eficaz por medio de la sustitución de los comúnmente utilizados relés electromecánicos por dispositivos de estado sólido. De entre todas las posibles implementaciones, se ha identificado entre las más prometedoras a aquellas basadas en dispositivos de alta movilidad de electrones (HEMT) de Nitruro de Galio (GaN) y de aquellas basadas en Carburo de Silicio (SiC), pues presentan unas características muy superiores a los relés a los que se pretende sustituir. Por el contrario, otras soluciones que inicialmente parecían ser muy prometedoras, como los MOSFETs de Súper-Unión, han presentado una serie de comportamientos anómalos, que han sido estudiados minuciosamente por medio de simulaciones físicas a nivel de chip. Además, se analiza en distintas condiciones la capacidad en cortocircuito de dispositivos convencionalmente empleados en cocinas de inducción, como son los IGBTs, tratándose de encontrar el equilibrio entre un comportamiento robusto al tiempo que se mantienen bajas las pérdidas de potencia. Por otra parte, también se estudia la robustez y fiabilidad de varios GaN HEMT de 600- 650 V tanto de forma experimental como por medio de simulaciones físicas. Finalmente se aborda el cálculo de las pérdidas de potencia en convertidores de potencia resonantes empleando técnicas de termografía infrarroja. Por medio de esta técnica no solo es posible medir de forma precisa las diferentes contribuciones de las pérdidas, sino que también es posible apreciar cómo se distribuye la corriente a nivel de chip cuando, por ejemplo, el componente opera en modo de conmutación dura. Como resultado, se obtiene información relevante relacionada con modos de fallo. Además, también ha sido aprovechar las caracterizaciones realizadas para obtener un modelo térmico de simulación.This thesis is focused on addressing a more flexible, sustainable, efficient and reliable induction cooking approach from a power semiconductor device perspective. In this framework, this PhD Thesis has identified the following activities to cover such demands: In view of the growing interest for an effective power multiplexing in Induction Heating (IH) applications, improved and efficient Solid State Relays (SSRs) as an alternative to the electromechanical relays (EMRs) are deeply investigated. In this context, emerging Gallium Nitride (GaN) High‐Electron‐Mobility Transistors (GaN HEMTs) and Silicon Carbide (SiC) based devices are identified as potential candidates for the mentioned application, featuring several improved characteristics over EMRs. On the contrary, other solutions, which seemed to be very promising, resulted to suffer from anomalous behaviors; i.e. SJ MOSFETs are thoroughly analysed by electro‐thermal physical simulations at the device level. Additionally, the Short Circuit (SC) capability of power semiconductor devices employed or with potential to be used in IH appliances is also analysed. On the one hand, conventional IGBTs SC behavior is evaluated under different test conditions so that to obtain the trade‐off between ruggedness and low power losses. Moreover, ruggedness and reliability of several normally‐off 600‐650 V GaN HEMTs are deeply investigated by experimentation and physics‐based simulation. Finally, power losses calculation at die‐level is performed for resonant power converters by means of using Infrared Thermography (IRT). This method assists to determine, at the die‐level, the power losses and current distribution in IGBTs used in resonant soft‐switching power converters when functioning within or outside the Zero Voltage Switching (ZVS) condition. As a result, relevant information is obtained related to decreasing the power losses during commutation in the final application, and a thermal model is extracted for simulation purposes.<br /

Some histopathological and clinical correlations in oral squamous cell carcinoma

Oral squamous cell carcinoma (SCC) is an important health problem that causes high mortality and morbidity. Correlations between some clinical and histopathological parameters were studied in 37 oral SCC. Some interesting aspects in oral SCC arising from precancerous lesions were found such as smaller size and a lower TNM stage at the moment of diagnosis. Histological and clinical differences were also found between tumors invading deep tissues by little groups of dissociated malignant cells and those invading by big masses of malignant cells. The possible significance of the intensity of peritumoral eosinophilic infiltrate was also studied.Le carcinome squameux de la cavité orale constitue un problème important de santé, qui est responsable d’une mortalité et d’une morbidité élevées. Nous avons étudié 37 carcinomes squameux de la cavité orale à travers un suivi clinique et une étude des corrélations entre les variables cliniques et histopathologiques. Nous avons relevé différents aspects intéressants en ce qui concerne les carcinomes squameux de la cavité orale qui procédaient de lésions précancéreuses comme leur petite dimention et le bas stade TNM au moment du diagnostic. Nous avons également trouvé des différences cliniques et histopathologiques entre les tumeurs qui envahissent les tissus adjecents en petits groupes et ceux qui le font en grandes masses de cellules malignes. Finalement, nous avons étudié la signification possible de l’intensité de l’infiltrat à eosinophiles peritumoral

Modelling and simulation of several interacting cellular automata

Cellular Automata are used for modelling and simulation of many systems. In some applications, the system is formed by a set of subsystems that can be modelled separately, but, in such cases, the existence of interactions between these subsystems requires additional modelling and computer programming. In this paper we propose a modelling methodology for the simulation of a set of Cellular Automata models that interact with each other. The modelling methodology is described, together with an insight on implementation details. Also, it is applied to a particular Cellular Automata model, the Sanpile Model, to illustrate its use and to obtain some example simulations

Measuring Oscillations with A Million Atmospheric Neutrinos

We analyze the sensitivity achievable by the current and near-future water(ice)-Cherenkov atmospheric neutrino experiments in the context of standard three-flavor neutrinos oscillations. In this study, we perform an in-depth analysis of the current shared systematic uncertainties arising from the common flux and neutrino-water interactions. We then implement the systematic uncertainties of each experiment and develop the atmospheric neutrino simulations for Super-Kamiokande (SK), with and without neutron-tagging capabilities (SuperK-Gd), IceCube-Upgrade, and ORCA experiments. A careful review of the synergies and features of these experiments is carried out to examine the potential of a joint analysis of these atmospheric neutrino data in resolving the $\theta_{23}$ octant and the neutrino mass ordering. Finally, we assess the capability to constraint $\theta_{13}$ and the CP-violating phase ($\delta_{CP}$ ) in the leptonic sector independently from reactor and accelerator neutrino data.Comment: 39 pages, 33 figure

Interactive Terrain Simulation and Force Distribution Models in Sand Piles

This paper presents an application of Cellular Automata in the field of dry Granular Systems modelling. While the study of granular systems is not a recent field, no efficient models exist, from a computational point of view, in classical methodologies. Some previous works showed that the use of Cellular Automata is suitable for the development of models that can be used in real time applications. This paper extends the existing Cellular Automata models in order to make them interactive. A model for the reaction to external forces and a pressure distribution model are presented and analyzed, with numerical examples and simulations

Global patterns of phosphatase activity in natural soils

imbalance-P paper contact with Olga Margalef: [email protected] phosphatase levels strongly control the biotic pathways of phosphorus (P), an essential element for life, which is often limiting in terrestrial ecosystems. We investigated the influence of climatic and soil traits on phosphatase activity in terrestrial systems using metadata analysis from published studies. This is the first analysis of global measurements of phosphatase in natural soils. Our results suggest that organic P (Porg), rather than available P, is the most important P fraction in predicting phosphatase activity. Structural equation modeling using soil total nitrogen (TN), mean annual precipitation, mean annual temperature, thermal amplitude and total soil carbon as most available predictor variables explained up to 50% of the spatial variance in phosphatase activity. In this analysis, Porg could not be tested and among the rest of available variables, TN was the most important factor explaining the observed spatial gradients in phosphatase activity. On the other hand, phosphatase activity was also found to be associated with climatic conditions and soil type across different biomes worldwide. The close association among different predictors like Porg, TN and precipitation suggest that P recycling is driven by a broad scale pattern of ecosystem productivity capacity