Noncommutative spacetime symmetries from covariant quantum mechanics

In the last decades, noncommutative spacetimes and their deformed relativistic symmetries have usually been studied in the context of field theory, replacing the ordinary Minkowski background with an algebra of noncommutative coordinates. However, spacetime noncommutativity can also be introduced into single-particle covariant quantum mechanics, replacing the commuting operators representing the particle's spacetime coordinates with noncommuting ones. In this paper we provide a full characterization of a wide class of physically sensible single-particle noncommutative spacetime models and the associated deformed relativistic symmetries. In particular, we prove that they can all be obtained from the standard Minkowski model and the usual Poincar\'e transformations via a suitable change of variables. Contrary to previous studies, we find that spacetime noncommutativity does not affect the dispersion relation of a relativistic quantum particle, but only the transformation properties of its spacetime coordinates under translations and Lorentz transformations.Comment: 14 pages; v2: minor changes to match published versio

In vitro toxicological assessment of amorphous silica particles in relation to their characteristics and mode of action in human skin cells

Background: Silica is the common name for silicon dioxide (SiO2) materials and exists in both crystalline and amorphous forms. While crystalline silica is known for its severe health effects, amorphous silica has been considered safe and applied in many areas. However, some recent studies have showed evidence of their toxicity, raising concerns about its use as nanomaterial for biomedical applications. When nanomaterials enter the body, they are enveloped in biological fluids rich in biomolecules, which compete for binding to the nanomaterial. Such effect could alter their surface chemistry and therefore affect their bio-distribution and interaction with cells. Aim and objectives: As part of the EU-funded NANODRUG network programme, the aim of this project was the in vitro toxicity assessment of commercially-sourced fumed and colloidal amorphous silica particles in relation to their physico-chemical properties and potential application as carriers for drug delivery. The objectives were 1) characterization of silica particles hydrodynamic (Hd) size and dispersity in different cell culture media; 2) in vitro toxicological assessment of silica particles in human skin cells; 3) delineation of toxicity mechanisms in relation to their size; 4) assessment of the influence of Foetal Bovine Serum (FBS) on particle Hd size and toxicity; and 5) contributing to the overall objective of the NANODRUG programme - development of safe nanodrugs for skin application - through collaborations with different partners. ...[cont.

Intermolecular charge transport in dye monolayers

This thesis reports the experimental investigation of intermolecular charge transport in dye monolayers anchored to the surface of nanocrystalline oxides. I use electrochemistry and transient spectroscopy to measure diffusion of holes within dye monolayers and interpret my observations on the basis of the non-adiabatic Marcus theory of charge transfer. I observe thermally activated hole diffusion for dyes used in dye sensitized solar cells (DSSCs) anchored to TiO2 and immersed in an inert acetonitrile based electrolyte. The corresponding values of reorganization energy of charge transfer between the dyes range between 700 and 1500 meV. Assuming negligible contribution from energetic disorder, this shows agreement with previously reported calculations of reorganization energy. Low outer sphere and low inner sphere reorganization energies correlate with delocalization of the HOMO and with rigid molecular structures showing extended conjugation. I show that hole diffusion in the monolayer can be controlled both at the μm and at the nm scale by varying the fraction of TiO2 surface covered with dyes. I present the effect of decreasing the dye surface coverage and consequently stopping hole diffusion on photo-electrochemical device structures. First, I observe a slowdown of the photo-induced recombination reaction of holes in the dye monolayer to electrons in the TiO2 when decreasing the dye loading. This result is consistent with the hypothesis that hole diffusion in the dye monolayer contributes to faster recombination. Second, I show that hole transport in the dye monolayer is responsible for increased dye regeneration efficiency in solid state DSSCs. I quantify improved regeneration yield by between 50% and 5% depending on the degree of the pore filling by the hole transporting material spiro OMeTAD. Finally I demonstrate that effective photo-conversion can occur in solar cell structures where dye monolayers function as the only hole transport phase.Open Acces

Cerebrovascular reactivity mapping and its impact on BOLD fMRI of task induced activity and rest.

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Covariant quantum mechanics as a tool for quantum-gravity phenomenology

Covariant quantum mechanics (CQM) is a background-indipendent reformulation of quantum mechanics in which the time coordinate is treated as a dynamical degree of freedom, rather than an external evolution parameter. CQM was originally conceived and developed as a basic relational quantum formalism for discussing some conceptual issues associated with quantum gravity in a simplified setting. However, in recent times, a few papers have fruitfully employed it to incorporate quantum-gravity effects such as spacetime noncommutativity into simple phenomenological models. In this Ph.D thesis, I explore in more detail this possibility, providing a first systematic investigation of CQM as a tool for quantum-gravity phenomenology, rather than a toy model of full quantum gravity. In particular, starting from the ordinary CQM of a single relativistic particle, I build generalized models for the description of free quantum particles propagating on noncommutative or curved spacetimes. The present work is theoretical in character. I mainly focus on the development and characterization of a CQM-based framework suitable for dealing with generic spacetime noncommutativity or metric, and study simple examples

Analysis of thermal performance of multilayer systems for fire doors

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do ParanáResidential fires are responsible for over 5000 deaths a year in Europe. One way to increase fire safety in homes is to use fire doors. Wood is more sustainable compared to other materials used in construction. The present research focused on developing and analysing the reaction to fire of cork panels for a future application as the core of a fire door made of a multilayer wooden sandwich panel. In total, ten different cork agglomerates were produced. The thickness (12 or 19 mm), the resin (MDI or TDI) and the amount of expandable, flame-retardant graphite used (0%, 5%, 10% or 20%) were varied. The samples were tested in the calorimetric cone following the EN ISO 13927 standard. Triplicate mass loss tests were performed at constant heat fluxes of 50 and 75 kW/m². First, the influence of the thickness of the agglomerate on its fire performance was studied. The thicker panels (19 mm) showed lower HRR peak values than the thinner panels for both resins evaluated. The results allowed us to analyse that, although they present a similar behaviour, the samples made with TDI released more heat in total than the MDI samples for the same thickness and amount of graphite. It was also possible to notice that the thinner samples presented the second peak of the HRR before the thicker ones. Therefore, it was chosen to carry out the analysis of the influence of expandable graphite on 19 mm thick cork agglomerates. Expandable graphite (EG) showed good results. Its addition reduced HRR and THR values of the specimens. The mass loss of the samples with EG was more gradual than the samples without the additive. MDI resin was shown to react better with the flame retardant.Incêndios residenciais são responsáveis por mais de 5000 mortes por ano na Europa. Uma maneira de aumentar a segurança contra incêndio em residências é usar portas corta-fogo. A madeira é mais sustentável em comparação com outros materiais utilizados na construção. A presente investigação centrou-se no desenvolvimento e análise da reação ao fogo de painéis de cortiça para uma futura aplicação como núcleo de uma porta corta-fogo constituída por um painel sanduíche de madeira. No total, foram produzidos dez aglomerados de cortiça diferentes. A espessura (12 ou 19 mm), a resina (MDI ou TDI) e a quantidade de grafite expansível retardador de chama utilizada (0%, 5%, 10% ou 20%) foram variados. As amostras foram testadas no cone calorimétrico seguindo a norma EN ISO 13927. Testes de tripla perda de massa foram realizados em fluxos de calor constantes de 50 e 75 kW/m². Em primeiro lugar, estudou-se a influência da espessura do aglomerado no seu comportamento ao fogo. Os painéis mais espessos (19 mm) apresentaram valores de pico de HRR menores do que os painéis mais finos para ambas as resinas avaliadas. Os resultados permitiram analisar que, apesar de apresentarem um comportamento semelhante, as amostras feitas com TDI liberaram mais calor no total do que as amostras de MDI para a mesma espessura e quantidade de grafite. Também foi possível notar que as amostras mais finas apresentaram o segundo pico da HRR antes das mais grossas. Assim, optou-se por realizar a análise da influência do grafite expansível em aglomerados de cortiça com 19 mm de espessura. O grafite expansível (EG) apresentou bons resultados. Sua adição reduziu os valores de HRR e THR dos espécimes. A perda de massa das amostras com EG foi mais gradativa do que as amostras sem o aditivo. A resina MDI mostrou reagir melhor com o retardador de chama

Correction to: Reversal agents for oral anticoagulant-associated major or life-threatening bleeding

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Um estudo sobre a segurança e privacidade no armazenamento de dados em nuvens

Orientador: Marco Aurélio Amaral HenriquesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Armazenamento de dados na nuvem é um serviço que traz diversas vantagens aos seus usuários. Contudo, em sistemas de nuvens públicas, os riscos envolvidos na terceirização do armazenamento de dados pode ser uma barreira para a adoção deste serviço por aqueles preocupados com sua privacidade. Vários provedores de serviços em nuvem que afirmam proteger os dados do usuário não atendem alguns requisitos considerados essenciais em um serviço seguro, confiável e de fácil utilização, levantando questionamentos sobre a segurança efetivamente obtida. Apresentamos neste trabalho um estudo relacionado aos requisitos de privacidade dos usuários e de segurança de seus dados em nuvens públicas. O estudo apresenta algumas técnicas normalmente usadas para atender tais requisitos, juntamente com uma análise de seus benefícios e custos relativos. Além disso, ele faz uma avaliação destes requisitos em vários sistemas de nuvens públicas. Depois de comparar estes sistemas, propomos um conjunto de requisitos e apresentamos, como prova de conceito, uma aplicação baseada nos mesmos, a qual melhora a segurança dos dados e a privacidade dos usuários. Nós mostramos que é possível proteger os dados armazenados nas nuvens contra o acesso por terceiros (incluindo os administradores das nuvens) sem sobrecarregar o usuário com protocolos ou procedimentos complexos de segurança, tornando o serviço de armazenamento em nuvens uma escolha mais confiável para usuários preocupados com sua privacidadeAbstract: Cloud data storage is a service that brings several advantages for its users. However, in public cloud systems, the risks involved in the outsourcing of data storage can be a barrier to the adoption of this service by those concerned with privacy. Several cloud service providers that claim to protect user's data do not fulfill some requirements considered essential in a secure, reliable and easy to use service, raising questions about the effective security obtained. We present here a study related to user's privacy and data security requirements on public clouds. The study presents some techniques normally used to fulfill those requirements, along with an analysis of their relative costs and benefits. Moreover, it makes an evaluation of them in several public cloud systems. After comparing those systems, we propose a set of requirements and present a proof of concept application based on them, which improves data security and user privacy in public clouds. We show that it is possible to protect cloud stored data against third party (including cloud administrators) access without burdening the user with complex security protocols or procedures, making the public cloud storage service a more reliable choice to privacy concerned usersMestradoEngenharia de ComputaçãoMestre em Engenharia Elétrica153392/2014-2CNP