The challenge of modelling nitrogen management at the field scale : simulation and sensitivity analysis of N2O fluxes across nine experimental sites using DailyDayCent

Peer reviewedPublisher PD

Modelling spatial and inter-annual variations of nitrous oxide emissions from UK cropland and grasslands using DailyDayCent

This work contributes to the Defra funded projects AC0116: ‘Improving the nitrous oxide inventory’, and AC0114: ‘Data Synthesis, Management and Modelling’. Funding for this work was provided by the UK Department for Environment, Food and Rural Affairs (Defra) AC0116 and AC0114, the Department of Agriculture, Environment and Rural Affairs for Northern Ireland, the Scottish Government and the Welsh Government. Rothamsted Research receives strategic funding from the Biotechnology and Biological Sciences Research Council. This study also contributes to the projects: N-Circle (BB/N013484/1), U-GRASS (NE/M016900/1) and GREENHOUSE (NE/K002589/1).Peer reviewedPublisher PD

Many-body localization and thermalization in the full probability distribution function of observables

We investigate the relation between thermalization following a quantum quench and many-body localization in quasiparticle space in terms of the long-time full distribution function of physical observables. In particular, expanding on our recent work [E. Canovi {\em et al.}, Phys. Rev. B {\bf 83}, 094431 (2011)], we focus on the long-time behavior of an integrable XXZ chain subject to an integrability-breaking perturbation. After a characterization of the breaking of integrability and the associated localization/delocalization transition using the level spacing statistics and the properties of the eigenstates, we study the effect of integrability-breaking on the asymptotic state after a quantum quench of the anisotropy parameter, looking at the behavior of the full probability distribution of the transverse and longitudinal magnetization of a subsystem. We compare the resulting distributions with those obtained in equilibrium at an effective temperature set by the initial energy. We find that, while the long time distribution functions appear to always agree {\it qualitatively} with the equilibrium ones, {\it quantitative} agreement is obtained only when integrability is fully broken and the relevant eigenstates are diffusive in quasi-particle space.Comment: 18 pages, 11 figure

Incorporação de resíduos cerâmicos vidrados em argamassas bastardas: estudo de propriedades físicas e mecânicas

Dissertação de Natureza Científica para obtenção do grau de Mestre em Engenharia Civil Perfil de EdificaçõesA conservação do património edificado constitui no presente, a memória de uma civilização. O conhecimento da composição e comportamento dos revestimentos antigos é importante para garantir a conservação do património edificado através das intervenções de conservação e reabilitação. A presente dissertação tem como objetivo o estudo do desempenho de argamassas bastardas de cal aérea e cimento com substituição de cal aérea por resíduo cerâmico vidrado. As argamassas formuladas foram sujeitas a cura laboratorial. Realizou-se a caracterização física, e mecânica de modo a avaliar o seu desempenho ao longo do tempo. O sector da construção pauta a sua atividade por elevados impactos ambientais ao nível da extração de elevadas quantidades de matérias-primas não renováveis, de elevados consumos energéticos e das consequentes e elevadas emissões de gases responsáveis por efeito de estufa. Além dos enormes excedentes que provem da indústria que normalmente seguem para aterro. De forma a aproveitar esses excedentes de algumas indústrias, nomeadamente da cerâmica procedeu-se à transformação de produtos excedentes em resíduo, de forma a ser possível a sua incorporação argamassas, uma vez que na antiguidade, no império romano já se efetuava esta incorporação. A produção de cimento tem elevados impactos ambientais, deste modo a redução da sua utilização através da incorporação de outros ligantes de natureza natural (cal aérea) e a possível substituição desses recursos naturais por excedentes irá aumentar a sustentabilidade do sector.In the present, the conservation of the built heritage constitutes the memory of a civilization. The knowledge of composition and performance of the old coverings is crucial to ensure the preservation of the built heritage through intervention of conservation and rehabilitation. This thesis aims to study the performance of aerial lime based mortars and cement with replacement of the aerial lime with glazed ceramic waste. The bastard mortars have characteristics well-suited for these functions, once incorporates the best features of air lime and cement. The construction sector bases its activity by high environmental impacts, because of the extraction of non-renewable raw material, high energy consumption and high emission of gases responsible for the greenhouse effect. In addition to huge surpluses that comes from the industry and that usually goes to landfill. In order to take advantage of the surpluses in some industries, including ceramics, it was proceeded the transformation of surpluses in residue. In this way was possible to incorporate the residues in mortars, as the Roman Empire in ancient time proceeded. The production of cement has high environmental impacts, thereby reducing their use by incorporating other ligands with natural source (air lime) and the possible replacement of these natural resources by surpluses will increase the sustainability of the sector. The incorporation of residues leads to the study of new mortars formulations. The formulated mortars were subject to a process of laboratory cure. It was reported over time, the performance, the physical and mechanical characterization of the mortars. In the properties studied was recorded a good performance of the mortars, due to the placement of the ceramic powder

Manipulation and removal of defects in spontaneous optical patterns

Defects play an important role in a number of fields dealing with ordered structures. They are often described in terms of their topology, mutual interaction and their statistical characteristics. We demonstrate theoretically and experimentally the possibility of an active manipulation and removal of defects. We focus on the spontaneous formation of two-dimensional spatial structures in a nonlinear optical system, a liquid crystal light valve under single optical feedback. With increasing distance from threshold, the spontaneously formed hexagonal pattern becomes disordered and contains several defects. A scheme based on Fourier filtering allows us to remove defects and to restore spatial order. Starting without control, the controlled area is progressively expanded, such that defects are swept out of the active area.Comment: 4 pages, 4 figure

"LUDO" - Kids playing Distributed Denial of Service

Distributed denial of service attacks pose a serious threat to the availability of the network infrastructures and services. GE̿ANT, the pan-European network with terabit capacities witnesses close to hundreds of DDoS attacks on a daily basis. The reason is that DDoS attacks are getting larger, more sophisticated and frequent. At the same time, it has never been easier to execute DDoS attacks, e.g., Booter services offer paying customers without any technical knowledge the possibility to perform DDoS attacks as a service. Given the increasing size, frequency and complexity of DDoS attacks, there is a need to perform a collaborative mitigation. Therefore, we developed (i) a DDoSDB to share real attack data and allow collaborators to query, compare, and download attacks, (ii) the Security attack experimentation framework to test mitigation and response capabilities and (iii) a collaborative mitigation and response process among trusted partners to disseminate security event information. In addition to these developments, we present and would like to discuss our latest research results with experienced networking operators and bridging the gap between academic research and operational business

Quantum Quench in the Transverse Field Ising chain I: Time evolution of order parameter correlators

We consider the time evolution of order parameter correlation functions after a sudden quantum quench of the magnetic field in the transverse field Ising chain. Using two novel methods based on determinants and form factor sums respectively, we derive analytic expressions for the asymptotic behaviour of one and two point correlators. We discuss quenches within the ordered and disordered phases as well as quenches between the phases and to the quantum critical point. We give detailed account of both methods.Comment: 65 pages, 21 figures, some typos correcte

Future climate variability impacts on potential erosion and soil organic carbon in European croplands

We investigate the impact of future climate variability on the potential vulnerability of soils to erosion and the consequences for soil organic carbon (SOC) in European croplands. Soil erosion is an important carbon flux not characterized in Earth System Models. We use a European implementation of EPIC, driven by reference climate data (CNTRL), and climate data with reduced variability (REDVAR). Whether erosion regimes will change across European cropland depends on the spatial conjunction of expected changes in climate variability and physiographic conditions conducive to erosion. We isolated the effect of erosion by performing simulations with and without erosion. Median CNTRL and REDVAR erosion rates equaled 14.4 and 9.1 ton/ha, and 19.1 and 9.7, for 1981-2010 and 2071-2100, respectively. The total amount of carbon lost from European cropland due to erosion was estimated at 769 Tg C for 1981-2010 (from a total storage of 6197 Tg C without erosion) under CNTRL climate. Climate trend impacts reduce the European cropland SOC stock by 578 Tg C without - and by 683 Tg C with - erosion, from 1981 to 2100. Climate variability compounds these impacts and decreases the stock by an estimated 170 Tg C without erosion and by 314 Tg C with erosion, by the end of the century. Future climate variability and erosion will thus compound impacts on SOC stocks arising from gradual change alone