Thèses sur le sujet « SEP events »

Gradual SEP events is one of the greatest hazards in space environment, particularly for the launch and operation of spacecraft and for manned exploration. Predictions of their occurrence and intensity are essential to ensure the proper operation of technical and scientific instruments. However, nowadays there is a large gap between observations and models these events that can lead to predictions. This work focuses on the modelling of SEP events, particularly, on the influence of the observer's relative position and of the shock strength, on the simulated SEP flux profiles. Part I of the thesis, deals with 3D MHD simulations of interplanetary shocks. We have studied the potential relevance of the latitude of the observer on the evolution of the strength of the shock and its influence on the injection rate of shock-accelerated particles; thus, on the resulting flux profiles. It is the first time that such dependence on the latitude is quantified from the modelling of SEP events, because most of the codes used so far to simulate interplanetary shocks are not 3D codes or they have been applied to near-ecliptic events. To study the influence of the latitude of the observer and the strength of the shock in the SEP flux profiles, we have simulated the propagation of two shocks (slow and fast) up to several observers placed at different positions with respect to the nose of the shock. We have calculated the evolution of the plasma and magnetic field variables at the cobpoint, and we have derived the injection rate of shock-accelerated particles and the resulting proton flux profiles to be measured by each observer. We have discussed how observers located at different positions in space measure different SEP profiles, showing that variations on the latitude may result in intensity changes of up to one order of magnitude. In Part II, we have used a new shock-and-particle model to simulate the 1 March 1979 SEP event that was observed by three different spacecraft. These spacecraft were positioned at similar radial distances but at significantly different angular positions, with respect to the associated solar source location. This particular scenario allows us to test the capability of the model to study the relevance of longitudinal variations in the shape of the intensity flux profiles, and to derive the injection rate of shock-accelerated particles. Despite the interest of multi-spacecraft events and due to the restrictions that they impose, this is just the second multi-spacecraft scenario for which their shock-particle characteristics have been modelled. For the first time, a simulation of a propagation of an interplanetary shock has simultaneously reproduced the time shock arrival and the relevant plasma jumps across the shock at three spacecraft. We have fitted the proton intensities at the three spacecraft for different energy channels, and we have derived the particle transport conditions in space. We have quantified the efficiency of the shock at injecting particles in its way toward each observer, and we have discussed the influence of the observer's relative position on the injection rate of shock-accelerated particles. We have concluded that in this specific event the evolution of the injection rate can not be completely explained in terms of the normalized velocity jump. The work performed during this thesis shows that the injection rate of shock-accelerated particles and their resulting flux profiles depend both on the latitude and on the longitude of the observer. This implies that more SEP events have to be modelled in order to quantify this conclusion on firm ground.<br>Els esdeveniments graduals de partícules solars energètiques (SEP) són un risc important per als astronautes i l’ instrumentació espacial. És per això que són necessàries eines de predicció de la intensitat i l'ocurrència de les tempestes de partícules solars per a garantitzar l'operativitat del material tècnic i científic embarcat. Existeix un gran buit, però, entre les prediccions del models actuals (per a ús en meteorologia espacial), i les observacions d'esdeveniments SEP. El treball realitzat durant aquesta tesi doctoral es centra en diversos aspectes de la simulació d'esdeveniments SEP. En particular, analitzem la influència de la posició relativa de l'observador i de la força del xoc en els perfils de flux derivats del nostre model combinat xoc-i-partícula. A partir de simulacions 3D, obtenim que el ritme d'injecció de partícules accelerades pel xoc depèn de la longitud de l'observador i demostrem, per primera vegada, que també depèn de la seva latitud. I es mostra que, conseqüentment, els perfils de flux detectats poden variar en un ordre de magnitud depenent de la connexió magnètica de l'observador amb el front del xoc. A més a més, presentem una simulació 2D d'un esdeveniment solar vist per tres sondes interplanetàries, pel qual s'ha ajustat, per primera vegada, l'arribada del xoc i els perfils de intensitat dels protons de diferents canals d'energia observats per cadascuna de les sondes. Així mateix, hem ajustat els salts en velocitat i camp magnètic a l'arribada del xoc, hem derivat les condicions de transport de les partícules i hem quantificat l'eficiència del xoc com a injector de partícules. La conclusió final del treball és que els futurs models de predicció d'esdeveniments SEP per a meteorologia espacial han de tenir en compte la geometria global de l'escenari solar-interplanetari.

Galactic-cosmic-rays (GCR) exist in space from unknown origins. A cosmic ray is a very high energy electron, proton, or heavy ion. As a GCR transverses a power semiconductor device, electron-hole-pairs (ehps) are generated along the ion track. Effects from this are referred to as single-event-effects (SEEs). A subset of a SEE is single-event burnout (SEB) which occurs when the parasitic bipolar junction transistor is triggered leading to thermal runaway. The failure mechanism is a complicated mix of photo-generated current, avalanche generated current, and activation of the inherent parasitic bipolar transistor. Current space-borne power systems lack the utility and advantages of terrestrial power systems. Vertical-double-diffused MOSFETs (VDMOS) is by far the most common power semiconductor device and are very susceptible to SEEs by their vertical structure. Modern space power switches typically require system designers to de-rate the power semiconductor switching device to account for this. Consequently, the power system suffers from increased size, cost, and decreased performance. Their switching speed is limited due to their vertical structure and cannot be used for MHz frequency applications limiting the use of modern digital electronics for space missions. Thus, the Power Semiconductor Research Laboratory at the University of Central Florida in conjunction with Sandia National Laboratories is developing a rad-hard by design lateral-double-diffused MOSFET (LDMOS). The study provides a novel in-depth physical analysis of the mechanisms that cause the LDMOS to burnout during an SEE and provides guidelines for making the LDMOS rad-hard to SEB. Total dose radiation, another important radiation effect, can cause threshold voltage shifts but is beyond the scope of this study. The devices presented have been fabricated with a known total dose radiation hard CMOS process. Single-event burnout data from simulations and experiments are presented in the study to prove the viability of using the LDMOS to replace the VDMOS for space power systems. The LDMOS is capable of higher switching speeds due to a reduced drain-gate feedback capacitance (Miller Capacitor). Since the device is lateral it is compatible with complimentary-metal-oxide-semiconductor (CMOS) processes, lowering developing time and fabrication costs. High switching frequencies permit the use of high density point-of-load conversion and provide a fast dynamic response.<br>M.S.E.E.<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering MSEE

The representation of deep convection in ocean models is a fundamental challenge for climate science. Here a regional simulation of the Labrador Sea circulation and convective activity obtained with the Regional Oceanic Modeling System (ROMS) over the period 1980-2009 is used to characterize the response of convection to atmospheric forcing and the variability in its seasonal cycle. This integration compares well with the sparse in time and space hydrographic surveys and ARGO data (Luo et al. 2012). It is found that convection in the convective region of the Labrador Sea has experienced variability in three key aspects over the 30 years considered. First, the magnitude of convection varies greatly at decadal scales. This aspect is supported by the in-situ observations. Second, the initiation and peak of convection (i.e. initiation and maximum) shift by two to three weeks between strong and weak convective years. Third, the duration of convection varies by approximately one month between strong and weak years. The last two changes are associated to the variability of winter and spring time heat fluxes in the Labrador Sea, while the first results from changes in both atmospheric heat fluxes and oceanic conditions through the inflow of warm Irminger Water from the boundary current system to the basin interior. Changes in heat fluxes over the Labrador Sea convective region are strongly linked to large scale modes of variability, the North Atlantic Oscillation and Arctic Oscillation. Correlations between the mode indices and the local heat fluxes in the convective area are largest in winter during strong, deep events and in spring whenever convection is shallow.

Turbulence is important since it affects the exchange of momentum, heat, and trace gases between the atmosphere and the ocean. However, measuring oceanic turbulence is not straightforward and that is why parameterizations that describe turbulence events are important. In this thesis turbulence data from the Baltic Sea is investigated and compared to already existing parameterizations.  The thesis considers turbulence in the ocean surface boundary layer (OSBL) and how atmospheric parameters act as driving mechanisms. Turbulence creates mixing that enables the dispersion of various particles and a more efficient gas transfer at the air-sea interface. This thesis aimed to investigate the connection between the drivers of oceanic turbulence, wind, waves, and buoyancy fluxes and how they contribute to the formation of enhanced turbulence events. To investigate this, turbulence data from the Baltic Sea from June to August 2020, collected by an ADCP (Acoustic Doppler Current Profiler), was used to find connections to meteorological data during the same time period. Since turbulence is difficult to measure, three already existing parameterizations were compared to the observed turbulence to investigate their performance. The results showed that conditions with higher wind speeds with corresponding waves gave a better correlation between surface turbulence and wind and waves. The parameterization that included wind and waves gave results closest to the observed turbulence at the surfaces, compared to when only wind shear was included. It was also detected that the parameterized turbulence was in almost all cases under-predicted in comparison to the observed turbulence. To clarify why this is the case, a more detailed analysis would be needed to find what parameters are missing for better predictions of the surface turbulence.

Le interazioni oceano-atmosfera sono di primaria importanza sia in ambito climatico che meteorologico. Sono importanti sia su scale temporali orarie, come nell'intensificazione di cicloni tropicali, che su scale interannuali o interdecadali, come nel modo di variabilità climatica ENSO. Questa tesi si focalizza sui transferimenti di energia e quantità di moto all'interfaccia aria-mare in processi su scale temporali brevi caratterizzati da condizioni estreme. Sono presi in considerazione sia la risposta dinamica dell'oceano ad una forzante atmosferica estrema che l'effetto dello stato del mare sullo sviluppo di un evento meteorologico estremo. I sistemi studiati sono il campo di onde interne oceaniche nella scia di un ciclone tropicale e il ruolo dello stato termico dell'oceano superficiale nello sviluppo di piogge intense. In particolare, gli scambi di energia tra onde interne oceaniche nella scia di un ciclone tropicale idealizzato sono studiati con un approccio teorico supportato da appropriate simulazioni numeriche alle equazioni primitive. Si vuole capire come i cicloni tropicali possano contribuire al mescolamento oceanico interno in luoghi lontani dalla loro scia. Infatti, nonostante siano intermittenti nel tempo e nello spazio, sono caratterizzati da venti molto intensi, che eccitano onde interne oceaniche. Esse contribuiscono al mescolamento lontano dal luogo in cui sono state generate, attraverso la loro rottura. Dato che la propagazione di energia è legata alle loro caratteristiche spettrali, una descrizione dettagliata di come l'energia è divisa tra modi verticali e frequenze aiuta a quantificare l'estensione e la velocità di tale propagazione. Una nuova descrizione analitica degli scambi energetici che portano alla formazione del picco doppio-inerziale viene introdotta sulla base della teoria sviluppata. Rispetto a lavori precedenti, si considera una stratificazione oceanica realistica e viene sottolineata una possibile cascata energetica dalla larga scala della forzante atmosferica alla piccola scala del mescolamento. L'altra categoria di eventi estremi considerata è quella del sistemi convettivi a mesoscala (MCS). Essi sono fenomeni comuni lungo le coste del Mediterraneo e rilasciano abbondanti volumi di pioggia in poche ore e su aree dell'ordine di 100 km2. Si sa che un mare mediamente più caldo in prossimità di un MCS produce più pioggia, ma prima di questa tesi non c'erano informazioni circa l'influenza che un pattern spaziale di temperatura marina superficiale (SST) a scala chilometrica potesse avere sull'evento precipitativo. Opportune simulazioni atmosferiche, eseguite con un modello numerico non-idrostatico alle equazioni primitive, fanno luce sui meccanismi attraverso cui le strutture alla sotto-mesoscala di SST possono influenzare la struttura del vento superficiale e, di conseguenza, possono influenzare l'evoluzione della pioggia intensa. Si trova che, attraverso un maggiore mescolamento verticale di quantità di moto su aree di SST più calda, la presenza di fronti di temperatura nel mare può significativamente influenzare la convergenza superficiale, che è spesso l'elemento scatenante della convezione nei MCS, su scale temporali orarie. Questo potrebbe anche far spostare le linee di pioggia. Viene introdotta, poi, la possibilità di un fenomeno di retroazione oceanico legato al profilo verticale di temperatura. Con simulazioni accoppiate oceano-atmosfera, si trova che, in condizioni particolari, i venti intensi in cui il MCS è inglobato possono mischiare l'oceano superficiale a tal punto che la stabilità atmosferica è aumentata e la convezione è soppressa. Tali condizioni, tipiche della tarda estate, sono caratterizzate da uno strato mescolato sottile e una forte stratificazione. Questo potrebbe essere il motivo per cui i MCS sono generalmente osservati più avanti nell'anno, quando lo strato mescolato è più profondo e tale effetto oceanico di mitigazione è assente.<br>Ocean-atmosphere interactions are of paramount importance in both climatic and meteorological contexts. They are known to play important roles from hourly time scales, such as in the intensification of tropical cyclones, to interannual and even longer time scales, such as in El Niño Southern Oscillation mode of variability of the climate system. The focus of this thesis has been on the energy and momentum transfers at the air-sea interface in short time scales processes characterized by extreme conditions. Both the oceanic dynamical response to an extreme atmospheric forcing and the effects of the sea state on the development of a meteorological extreme event are considered. The systems under study are the ocean internal wave field in the wake of a tropical cyclone and the role of the upper ocean thermal state on the development of heavy rainfalls. In particular, the energy exchanges among oceanic internal waves in the wake of an idealized tropical cyclone are studied with a theoretical approach supported by relevant primitve equation numerical simulations. The goal of this analysis is to understand how tropical cyclones might contribute to the internal ocean mixing in locations far from their track. In fact, despite their intermittency in space and time, they are characterized by very intense winds, which are known to excite oceanic internal waves. These are thought to contribute to ocean mixing far from their generation site through their breaking. Since the energy propagation is linked to the spectral features of the waves, a detailed description of the energy partitioning in different vertical modes and frequencies helps to better constrain the extent and the velocity of such energy propagation. A new detailed analytical description of the exchanges leading to the formation of the first superinertial peak is introduced on the basis of the theory developed. Compared to previous works, a realistic oceanic stratification is included and a path for the energy cascade from the large scales of the atmospheric forcing to the small scales of the mixing is highlighted. The second category of extreme events considered are the heavy-rain-producing mesoscale convective systems (MCSs). They are common phenomena along the coasts of the Mediterranean sea and they release large amounts of rain in few hours and over relatively small areas, O(100 km2). It is known that an average warmer sea in the vicinity of their location produces a larger volume of rain, but before this thesis work no information was available on the influence that a spatial pattern of sea surface temperature (SST), with structures on the kilometric scale, might have on the precipitation event. Appropriate atmospheric numerical simulations, run with a non-hydrostatic primitive equation model, shed light on the mechanisms through which submesoscale SST oceanic features can influence the surface wind structure and, in turns, can affect the evolution of the heavy rainfall. It is found that through enhanced vertical momentum mixing in the atmosphere over warmer SST areas, the presence of temperature fronts in the sea can significantly affect the surface wind convergence, which is often the trigger for deep convection in MCSs, over hourly time scales. This might also lead to significant displacement of the rain bands. The possibility of an ocean dynamical feedback related to the vertical temperature profile is then introduced. By means of atmosphere-ocean coupled numerical simulations, it is found that in particular conditions the intense winds in which the MCS is embedded can mix the upper ocean strongly enough to enhance the stability of the atmospheric boundary layer and suppress deep convection. Such conditions, characterized by a shallow mixed layer and strong stratification, are typical of the late summer. This could be the reason why MCSs are generally observed later during the year, when the mixed layer is deeper and this oceanic mitigating effect is absent.

During an upwelling event the cold bottom-water is brought to the sea surface. This cools the atmosphere from below and the stratification becomes more stable. When the atmosphere is more stable the turbulence is reduced and, as a consequence, so are the turbulent fluxes. This study is investigating four periods of upwelling from the Östergarnsholm-site, in the Baltic Sea east of Gotland, during the summer of 2005. The air measurements are taken at a tower at the southernmost tip of Östergarnsholm while the measurements in the water are from a buoy moored 1 km south-southeast of the tower. During all the upwelling events the wind is south-westerly, along the coast of Gotland. This means that the buoy is not within the flux footprint area and is perhaps not always representative of what happens there. All the periods show a stabilization of the atmosphere as the SST (Sea Surface Temperature) decreases. The heat fluxes, especially the latent heat flux, decreases as the SST decreases. The amount of CO2 in the atmosphere, in the summer, is usually higher than the amount in the surface water of the seas because the oceans are a net sink of CO2. The air-sea flux of CO2 is to a large extent controlled by this difference. Therefore the flux of CO2 is usually directed to the sea. The deep-water contains more CO2 than the surface water because the phytoplankton near the surface removes CO2 through photosynthesis. The deep-water is also colder and can solve more CO2. During an upwelling event this CO2-rich water is brought to the surface. As an upwelling event progresses the difference in CO2-concentration between the air and the sea is reduced, sometimes reversed, and the flux decreases. This is what happens in three of the investigated periods in this study. During the fourth period a counter gradient flux is observed.<br>När en uppvällning inträffar förs kallt djupvatten upp till havsytan. Det kalla vattnet kyler atmosfären nedifrån, något som leder till mer stabil skiktning. När atmosfären blir mer stabilt skiktad dämpas turbulensen och det medför att de turbulenta flödena också avtar. I den här studien analyseras fyra perioder med uppvällning. Mätningarna kommer från Östergarnsholm, öster om Gotland, under sommaren 2005. Mätningarna i luften är tagna från en mast vid Östergarnsholms södra udde. Mätningarna i vattnet kommer från en boj som är förankrad 1 km sydsydöst om masten. Vid samtliga uppvällnings-perioder i den här studien är vinden sydvästlig (längs Gotlandskusten). Det betyder att bojen inte befinner sig inom flödenas footprint-area och dess mätningar är kanske inte hela tiden representativa för vad som händer i footprint-arean. Samtliga undersökta perioder visar på en stabilisering av atmosfären då havsytans temperatur avtar. Värmeflödena, i synnerhet det latenta värmeflödet, avtar i samband med att temperaturen i havsytan sjunker. Halten av CO2 i atmosfären är vanligtvis högre än halten i havens ytvatten (under sommaren) eftersom de är en nettosänka för CO2 globalt sett. CO2-flödet mellan havsytan och atmosfären styr till en stor del av denna skillnaden i CO2-halt. Det innebär att CO2-flödet är riktat neråt, mot havet. Havens djupvatten innehåller mer CO2 därför att växtplankton nära ytan reducerar CO2-halten genom fotosyntesen. Djupvattnet är också kallare och kan därför lösa mer CO2. Under en uppvällning förs detta CO2-rika vatten upp till ytan. När en uppvällning fortskrider minskar skillnaden i CO2-halt mellan hav och atmosfär (ibland kan CO2-halten i ytvattnet även komma att överstiga atmosfärens halt) och flödet avtar. Tre av perioderna i den här studien visar på ett avtagande flöde. Den fjärde perioden uppvisar ett flöde motriktat CO2-gradienten.

Condizioni ambientali estreme del mare possono avere un forte impatto sulla navigazione e/o sul successo di operazioni di salvataggio. Le tecniche statistiche sono cruciali per quantificare la presenza di eventi estremi e monitorarne variazioni di frequenza e intensità. Gli eventi estremi "vivono" nella coda di una funzione distribuzione di probabilità (PDF), per questo è importante studiare la PDF in punti lontani diverse deviazioni standard dalla media. L’altezza significativa dell’onda (SWH) è il parametro solitamente usato per valutare l’intensità degli stati del mare. L’analisi degli estremi nella coda di una distribuzione richiede lunghe serie temporali per stime ragionevoli della loro intesità e e frequenza. Dati osservativi (i.e. dati storici da boe), sono spesso assenti e vengono invece utilizzate ricostruzioni numeriche delle onde, con il vantaggio che l’analisi di eventi estremi diventa possibile su una vasta area. Questa tesi vuole condurre un’analisi preliminare delle variazioni spaziali dei valori estremi della SWH nel Mediterraneo. Vengono usati dati orari dal modello del Med-MFC (dal portale del CMEMS), una ricostruzione numerica di onde per il Mediterraneo, che sfrutta il modello "WAM Cycle 4.5.4", coprendo il periodo 2006-2018, con risoluzione spaziale 0.042° (~ 4km). In particolare, consideriamo dati di 11 anni (dal 2007 al 2017), concentrandoci sulle regioni del Mar Ionio e del Mar Iberico. La PDF della SWH è seguita piuttosto bene dall’andamento di una curva Weibull a 2 parametri sia durante l’inverno (Gennaio) che durante l’estate (Luglio), con difetti per quanto riguarda il picco e la coda della distribuzione. A confronto, la curva a 3 parametri Weibull Esponenziata sembra essere più appropriata, anche se non è stato trovato un metodo per dimostrare che sia un fit migliore. Alla fine, viene proposto un metodo di stima del rischio basato sul periodo giornaliero di ritorno delle onde più alte di un certo valore di soglia, ritenute pericolose.

Questa tesi studia l’applicazione di simulazioni numeriche relative ad eventi estremi, sia atmosferici che oceanici, che si verificano nel bacino del Mediterraneo e che sono fortemente influenzati dall'interazione aerea-mare. Nella prima fase di questo lavoro viene proposta la caratterizzazione fisica degli eventi studiati. I fenomeni studiati sono: i) un evento di Cold Air Outbreak (CAO) avvenuto nell'inverno del 2012 nell'area del Mediterraneo centrale, e in particolare nel nord dell'Italia; ii) un evento di Dense Waters Formation (DWF) prodotta da questo evento CAO; e iii) un evento di "Tropical-Like Cyclone" (TLC) (chiamato "ROLF") che si è sviluppato sulle isole Baleari tra il 6 e il 9 novembre 2011. Inoltre vengono proposti i risultati preliminari di uno studio su un Flood Flash formato sulla Laguna di Venezia. Discuteremo le caratteristiche fisiche che governano questi fenomeni, in particolare l'interazione oceano-atmosfera. Dopo aver descritto questi fenomeni, proponiamo alcune considerazioni sulle applicazioni numeriche necessarie per una corretta simulazione di questi fenomeni, basandoci principalmente su tre approcci numerici. Il primo approccio numerico utilizzato è del tipo "Uncoupled", che consiste nell'uso di modelli atmosferici non accoppiati con modelli oceanici ricavano i dati di SST da datasets satellitari. Il secondo approccio utilizzato si riferisce all'uso di modelli accoppiati di atmosfera-oceano, mentre il terzo presenta l'accoppiamento completo tra atmosfera-oceano ed onde. Lo scopo di queste tecniche di modellizzazione è cercare di descrivere con maggiore precisione i flussi di momento e di calore che si esplicano all’interfaccia aria-mare e che caratterizzano e guidano l’evoluzione di alcuni fenomeni estremi, atmosferici ed oceanici. I risultati mostrano che l'uso di modelli accoppiati fornisce risultati migliori se comparato ad applicazioni non accoppiate, suggerendo spunti significativi per lavori futuri anche nel campo climatologico.<br>This thesis is the result of the work carried out in the three years of course, dealing with the issue of the application of numerical simulations related to extreme events, both atmospheric and oceanic, that appear over the Mediterranean basin and that are strongly influenced by the air-sea interaction. In the first phase of this work the physical characterization of the studied events is proposed. The phenomena studied are i) a case of Cold Air Outbreak (CAO) formed in the winter of 2012 on the central Mediterranean area, and in particular in the north of Italy; ii) a Dense Waters Formation (DWF) produced by this CAO event; and iii) one event of "Tropical-Like Cyclone" (TLC) (called “ROLF”) that developed on the Balearic Islands between the 6th and the 9th of November 2011. Moreover, preliminary results about a Flash Flood formed over the Venice Lagoon are showed in the end of this manuscript. We will discuss the physical characteristics that govern these phenomena, in particular the interaction between sea and atmosphere. After describing and studying the above mentioned phenomena, we propose some considerations regarding the numerical applications that are needed in order to obtain better results. The modeling techniques used for this thesis are mainly three. The first approach used is a classical "Uncoupled", which consists in the use of atmospheric models uncoupled to ocean models and wave models that exploit SST satellite data. The second approach used refers to the use of "Coupled" ocean-atmosphere models, and the third presents the ocean-wave atmosphere coupling. The purpose of these modeling techniques is to try to describe accurately the momentum and heat fluxes that appear at the air-sea interface, and that characterize, very often, some atmospheric and oceanic phenomena. Results show that the use of coupled models provide improved results, having this approach a direct impact mostly on some heat and momentum fluxes and the SST evolution, fundamental in some applications. Moreover, other indirect implications brought along by the use of coupled models, that are often important at the basin scale and regarding also the case of deep marine ventilation, are presented and discussed (Benetazzo et al., 2013, Carniel et al., 2016, Ricchi et al., 2016, Ricchi et al., 2017, Bonaldo et al., 2017).

Made available in DSpace on 2013-08-07T19:03:00Z (GMT). No. of bitstreams: 1 000422739-Texto+Completo-0.pdf: 1435459 bytes, checksum: f6319ddd22b6cda20d948b2f14cd31d3 (MD5) Previous issue date: 2010<br>The objective of this dissertation is two-fold. The general objective is to contribute to the understanding of a method of investigation that emphasizes interdisciplinary and intradisciplinary relations in guiding foundational, theoretical and empirical analyses. The specific objective is to apply this method to the topic of temporal-aspectual phenomena in natural languages. To achieve a better understanding of the meaning associated to the present perfect structure in Brazilian Portuguese, known as the “pretérito perfeito composto” (PPC), this dissertation takes an approach that involves constructing interfaces at every level of analysis. The unique problem the PPC presents is its often obligatory meaning of repetition, even in the absence of adverbial modification and despite its morphological structure, ter+past participle, mirroring those of other Romance and Germanic languages. The approach taken in this study involves four stages: i) an investigation of the philosophical foundations of plurals and events; ii) an investigation of the linguistic foundations of plurals and events; iii) an examination of how the first two stages influence the conception of theories of lexical aspect and grammatical aspect; iv) a compositional analysis of the PPC, taking into consideration the previous three stages.<br>A presente tese visa um duplo objetivo. O objetivo geral é contribuir para o entendimento de um método de investigação que enfatiza as relações interdisciplinares e intradisciplinares nas análises de fundamentos, teóricas e empíricas. O objetivo específico é aplicar este método ao tópico de fenômenos tempo-aspectuais nas línguas naturais. Para obter um entendimento melhor do significado associado à estrutura do pretérito perfeito composto (PPC) no português brasileiro, esta tese assume uma abordagem que envolve a construção de interfaces em todos os níveis de análise. O problema excepcional que o PPC apresenta é o seu significado muitas vezes obrigatório de repetição, mesmo que sem modificação adverbial, e apesar da sua estrutura morfológica, ter+particípio passado, que se espelha nas de outras línguas românicas e germânicas. A abordagem assumida neste estudo envolve quatro etapas: i) uma investigação de fundamentos filosóficos de plurais e eventos; ii) uma investigação dos fundamentos lingüísticos de plurais e eventos; iii) uma análise de como as primeiras duas etapas modelam a concepção de teorias de aspecto lexical e aspecto gramatical; iv) uma análise composicional do PPC, levando em consideração as primeiras três etapas.

Thesis (Nav.E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (M.Eng.)--Joint Program in Marine Environmental Systems, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1998.<br>Includes bibliographical references (p. 85-86).<br>by Kurtis Wayne Crake.<br>Nav.E.

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores<br>Sailboat navigation started as a way to explore the world. Even though performance is significantly lower than that of a motorboat, in terms of resources, these vessels still are the best low-cost solutions. On the past, navigation depended greatly on estimates or on the stars. Nowadays it depends on precise data provided by a variety of electronic devices, independent from the user’s location. Autonomous sailboats are vessels that use only the wind for propulsion and have the capacity to control its sails and rudders without human intervention. These particularities give them almost unlimited autonomy and a very valuable ability to fulfill long term missions on the sea, such as collecting oceanographic data, search and rescue or surveillance. This dissertation presents a fuzzy logic controller for autonomous sailboats based on a proposed set of sensors, namely a GPS receiver, a weather meter and an electronic compass. Following a basic navigation approach, the proposed set of sensorswas studied in order to obtain an effective group of variables for the controller’s fuzzy sets, and rules for its rule base. In the end, four fuzzy logic controllers were designed, one for the sail(to maximize speed) and three for the rudder (in order to comply with all navigation situations). The result is a sailboat control system capable of operation in a low cost platform such as an Arduino prototyping board. Simulated results obtained from a data set of approximately 100 tests to each controller back up the theory presented for the controller’s operation, since physical experimentation was not possible.

The performance of a modern computing system is improving with technology scaling due to advancements in the modern semiconductor industry. However, the power efficiency along with reliability does not scale linearly with performance efficiency. High leakage and standby power in sub 100 nm technology are critical challenges faced by circuit designers. Recent developments in device physics have shown that emerging non-volatile memories are very effective in reducing power dissipation because they eliminate stand by power and exhibit almost zero leakage powerThis dissertation studies the use of emerging non-volatile memory devices in designing circuit architecture for improving power dissipation and the performance of the computing system. More specically, it proposes a novel spintronic Ternary Content AddressableMemory (TCAM), a novel memristive TCAM with improved power and performance efficiency. Our experimental evaluation on 45 nm technology for a 256-bit word-size spintronic TCAM at a supply voltage of 1 V with a sense margin of 50 mV show that the delay is lessthan 200 ps and the per-bit search energy is approximately 3 fJ. The proposed spintronic TCAM consumes at least 30% less energy when compared to state-of-the-art TCAM designs. The search delay on a 144-bit proposed memristive TCAM at a supply voltage of 1 V and a sense margin of 140 mV is 175 ps with per bit search energy of 1.2 fJ on a 45 nm technology. It is 1.12 x times faster and dissipates 67% less search energy per bit than the fastest existing 144-bit MTCAM design.Emerging non-volatile memories are well known for their ability to perform fast analog multiplication and addition when they are arranged in crossbar fashion and are especially suited for neural network applications. However, such systems require the on-chip implementation of the backpropagation algorithm to accommodate process variations. This dissertation studies the impact of process variation in training memristive neural network architecture. It proposes a low hardware overhead on-chip implementation of the backpropagation algorithm that utilizes effectively the very dense memristive cross-bar arrayand is resilient to process variations.Another important issue that needs a careful study due to shrinking technology node is the impact of space or terrestrial radiation in Integrated Circuits (ICs) because the probability of a high energy particle causing an error increases with a decrease in thethreshold voltage and the noise margin. Moreover, single-event effects (SEEs) sensitivity depends on the set of input vectors used at the time of testing due to logical masking. This dissertation analyzes the impact of input test set on the cross section of the microprocessorand proposes a mechanism to derive a high-quality input test set using an automatic test pattern generation (ATPG) for radiation testing of microprocessors arithmetic and logical units..

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (M.S.)--Joint Program in Marine Environmental Systems, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1998.<br>Includes bibliographic references (p. 79).<br>by Charles E. Rawson.<br>M.S.

Los efectos de la radiación en circuitos electrónicos se conocen desde los comienzos de la carrera espacial en los años 60, pues fuera de la atmósfera terrestre se está expuesto a niveles más altos de radiación que en la superficie. Sin embargo, el escalado de la tecnología electrónica ha conllevado un aumento de su susceptibilidad a la radiación, que puede desembocar en errores de funcionamiento incluso a nivel de tierra. Esta tesis estudia un efecto de la radiación, en memorias SRAM (Static Random Access Memory), denominado evento transitorio, que se caracteriza por corromper los datos almacenados en la memoria sin dañarla permanentemente. Se estudian por simulación diversas técnicas para diseñar memorias más robustas frente a eventos transitorios. Además, se ha diseñado y fabricado un prototipo de SRAM que incorpora algunas de estas técnicas. Finalmente, se ha validado experimentalmente su eficacia mediante la irradiación controlada del circuito<br>Radiation effects in electronic circuits are known since the beginning of the space race in the 1960s, because out of the terrestrial atmosphere, radiation exposure level is higher than on the surface. However, electronic technology scaling has led to an increase in radiation susceptibility that can result in operation errors even at ground level. This thesis deals with a radiation effect, in SRAMs (Static Random Access Memory), named transient event, which is characterized by corrupting data stored in the memory without causing any permanent damage to it. Several techniques to design more robust memories against radiation effects are studied by simulation. In addition, an SRAM prototype, including some of these techniques, has been designed and manufactured. Finally, the effectiveness of these techniques has been experimentally validated through controlled irradiation of the circuit.<br>Els efectes de la radiació en circuits electrònics es coneixen des dels inicis de la carrera espacial als anys 60, ja que fora de l’atmosfera terrestre s’està exposat a nivells més alts de radiació que a la superfície. No obstant això, l’escalat de la tecnologia electrònica ha comportat un augment de la susceptibilitat a la radiació, que pot desembocar en errors de funcionament fins i tot a nivell de terra. Aquesta tesi estudia un efecte de la radiació, en memòries SRAM (Static Random Access Memory), anomenat event transitori, que es caracteritza per corrompre les dades emmagatzemades a la memòria sense danyar-la permanentment. S’estudien per simulació diverses tècniques per dissenyar memòries més robustes en front a events transitoris. A més, s’ha dissenyat i fabricat un prototipus d’SRAM que incorpora alguna d’aquestes tècniques. Finalment, s’ha validat experimentalment la seva eficàcia mitjançant la irradiació controlada del circuit.

Made available in DSpace on 2013-08-07T19:04:29Z (GMT). No. of bitstreams: 1 000430255-Texto+Completo-0.pdf: 1176318 bytes, checksum: 4850238e491d62ada84dedd411f149d1 (MD5) Previous issue date: 2011<br>The relationship between anticardiolipin antibodies (ACA), markers of the antiphospholipid syndrome, and vascular complications of diabetes is a matter of debate. This cross-sectional study assessed the frequency of IgG, IgM, and IgA-ACA in type 2 diabetics with or without history of vascular events in the last 5 years and in healthy controls. Antibodies were detected by enzyme immunoassay. A total of 73 type 2 diabetics (33 with history of vascular events) and 54 healthy controls were tested. Most diabetics were female (p = 0. 003), and older than controls (p < 0. 001). Mean duration of disease was 10 years. The prevalence of a positive ACA test was 7. 4% in controls and 9. 5% in diabetics (p = 0. 910). Comparison of healthy controls and diabetics with or without history of macrovasculopathy, after adjusting for gender and age, showed no significant differences in ACA positivity (p > 0. 09). ACA positivity rates were also similar when diabetics with or without recent history of vascular events were compared (p > 0. 47). After adjusting for gender, age, hypertension, and smoking status, a weak but statistically nonsignificant association was found between IgM-ACA and vasculopathy in diabetics (adjusted OR 2. 7; 95%CI 0. 2 – 34. 2; p = 0. 441). Overall, levels of IgG (r = 0. 25; p = 0. 005) and IgM (r = 0. 23; p = 0. 010) ACA were associated with advancing age. In short, the frequency of positive ACA test in type 2 diabetics (with or without previous vascular events) was not significant as compared to healthy controls. There was no association between ACA and vascular events in patients with type 2 diabetes.<br>A relação entre anticorpos anticardiolipina (aCL), marcadores da síndrome antifosfolípide, e vasculopatia em diabéticos é matéria de debate. Este estudo, transversal controlado, avaliou a freqüência de IgG, IgM e IgA aCL em diabéticos do tipo 2 com ou sem eventos vasculares nos últimos 5 anos e em controles sadios. Os anticorpos foram detectados por ensaio imunoenzimático. Setenta e três diabéticos (33 com eventos vasculares prévios) e 54 controles foram estudados. Diabéticos foram predominantemente mulheres (p=0,003), e de idade mais avançada (p<0,001) em relação aos controles. A duração média da doença foi de 10 anos. A prevalência de teste positivo para anticorpos aCL foi de 7,4% em controles e de 9,5% em diabéticos (p=0,910). Após ajuste para sexo e idade, a freqüência de anticorpos aCL não diferiu significativamente quando se comparou controles e diabéticos com ou sem macrovasculopatia (p>0,09). A freqüência de anticorpos aCL também não diferiu quando se comparou os dois grupos de diabéticos entre si (p>0. 47). Após ajuste para sexo, idade, hipertensão e tabagismo, uma associação fraca, mas estatisticamente insignificante, foi 28 observada entre IgM aCL e diabéticos com vasculopatia (OR ajustado 2,7; IC95% 0,2-34,2; p=0,441). Globalmente, níveis de IgG (r=0,25; p=0,005) e IgM (r=0,23; p=0,010) aCL se correlacionaram com idade progressiva. Em resumo, a freqüência de teste positivo para anticorpos aCL em diabéticos tipo 2 (com ou sem histórico vascular) não foi significativa em relação a controles sadios. Não houve associação entre presença de anticorpos aCL e eventos vasculares em diabéticos tipo 2.

Rapidly shrinking technology node and aggressive scaling of voltage have increased the probability of soft errors. In the current deep sub-micron technology, a small inaccuracy in computing the probability of occurrence of a soft error results in an unacceptably large chip failure rate. We propose a method that considers timing information to determine accurately the probability of SET propagation resulting into an error. Disjoint covers of appropriately formulated functions are used for the probability computations in order to consider re-convergent paths in the circuit. The probabilities are calculated at the output gate at different time instants that SET can propagate within a latching window considering electrical attenuation. Bayes' theorem is used to model the SET injection. The method is extended to consider multiple SETs. A novel method is proposed to enhance SET propagation probability and is shown how it can assist the hardening process. A method to determine a set of patterns is also proposed that must be applied at the inputs to determine propagation characteristics of the SET that are meaningful for hardening purposes. A heuristic based on the probabilistic framework for SET propagation is proposed to diagnose (on-line or off-line) the location and time of strike based on errors observed at multiple points. The proposed diagnostic framework requires a new approach to calculate the probability for SET propagation to multiple non-independent variables. It is shown experimentally that the error appearances at multiple observable points help in SET diagnosis. The time performance of the proposed diagnostic framework is compared against an alternative implementation. This is particularly important in on-line diagnosis. The proposed methods are experimentally verified on ISCAS and ITC benchmarks considering both fixed gate delays and probability distribution function gate delays .

Les composants mémoires sont omniprésents en électronique : ils sont utilisés pour stocker des données, et sont présents dans tous les champs d’application - industriel, automobile, aérospatial, grand public et télécommunications, entre autres. Les technologies mémoires ont connu une évolution constante depuis la création de la première mémoire vive statique (Static Random-Access Memory, SRAM) à la fin des années 60. Les besoins toujours plus importants en termes de performance, de capacité et d’économie d’énergie poussent à une miniaturisation constante de ces composants : les mémoires modernes contiennent des circuits dont certaines dimensions sont de l’ordre du nanomètre.L’un des inconvénients de cette miniaturisation fut un accroissement de la sensibilité de ces composants aux radiations. Depuis la détection des premiers effets singuliers (Single-Event Effects, SEE) dans un satellite à la fin des années 70, et la reproduction du phénomène en laboratoire, les fabricants de composants mémoires et les ingénieurs en électronique se sont intéressés au durcissement aux radiations. Au début, les besoins en stockage pour des applications civiles et militaires – comme le développement d’accélérateurs de particules, de réacteurs nucléaires et d’engins spatiaux – créa un marché pour les composants durcis aux radiations. Ce marché s’est considérablement réduit avec la fin de la Guerre Froide et la perte d’intérêt des gouvernements, et après quelques années, les ingénieurs durent se tourner vers des composants commerciaux (Commercial Off-The-Shelf Components, COTS).Les composants COTS n’étant pas conçus pour résister aux radiations, chaque composant doit être évalué avant d’être utilisé dans des systèmes dont la fiabilité est critique. Ce processus d’évaluation est appelé Radiation Hardness Assurance (RHA). Les tests aux radiations des composants commerciaux sont devenus une pratique standardisée (en particulier dans l’industrie aérospatiale). Ces composants sont irradiés à l’aide d’accélérateurs de particules et de sources radioactives, afin d’évaluer leur sensibilité, de prédire leur taux d’erreur dans un environnement radiatif donné, et ainsi de déterminer leur adéquation pour une mission donnée.Cette étude porte sur le test de composants mémoires aux effets singuliers. Les objectifs, difficultés et limitations des tests aux radiations sont présentés, et des méthodes d’analyse de données sont proposées ; l’identification et l’étude des modes de défaillance sont utilisées pour approfondir les connaissances sur les composants testés. Cette étude est basée sur de nombreuses campagnes de test aux radiations, étalées sur une période de quatre ans, pendant lesquelles des mémoires de différentes technologies – mémoires vives statique (SRAM), ferroélectrique (FRAM), magnétorésistive (MRAM) et mémoire flash – furent irradiées avec des faisceaux de muons, neutrons, protons et ions lourds. Les données générées ont également servi au développement d’un CubeSat développé conjointement par le LIRMM et le Centre Spatial Universitaire de Montpellier, MTCube, dont la mission est l’irradiation de ces mêmes composants en milieu spatial. Les concepts sous-jacents liés aux radiations, aux environnements radiatifs, à l’architecture des composants mémoires et aux tests aux radiations sont introduits dans les premiers chapitres, et les avancées scientifiques de cette étude sont présentées dans le dernier chapitre<br>Electronic memories are ubiquitous components in electronic systems: they are used to store data, and can be found in all manner of industrial, automotive, aerospace, telecommunication and entertainment systems. Memory technology has seen a constant evolution since the first practical dynamic Random-Access Memories (dynamic RAMs) were created in the late 60's. The demand for ever-increasing performance and capacity and decrease in power consumption was met thanks to a steady miniaturization of the component features: modern memory devices include elements barely a few tens of atomic layers thick and a few hundred of atomic layers wide.The side effect of this constant device miniaturization was an increase in the sensitivity of devices to radiation. Since the first radiation-induced single-event effects (SEEs) were identified in satellites in the late 70’s and particle-induced memory upsets were replicated in laboratory tests, radiation hardness has been a concern for computer memory manufacturers and for systems designers as well. In the early days, the need for data storage in radiation-rich environments, e.g. nuclear facilities, particle accelerators and space, primarily for military use, created a market for radiation-hardened memory components, capable of withstanding the effects of radiation. This market dwindled with the end of the Cold War and the loss of government interest, and in a matter of years, the shortage of available radiation-hard components led system designers to turn to so-called Commercial Off-The-Shelf (COTS) components.Since COTS devices are not designed with radiation hardness in mind, each COTS component must be assessed before it can be included in a system where reliability is important – a process known as Radiation Hardness Assurance (RHA). This has led to the emergence of radiation testing as a standard practice in the industry (and in the space industry in particular). Irradiation tests with particle accelerators and radioactive sources are performed to estimate a component’s radiation-induced failure rate in a given radiation environment, and thus its suitability for a given mission.The present work focuses on SEE testing of memory components. It presents the requirements, difficulties and shortcomings of radiation testing, and proposes methods for radiation test data processing; the detection and study of failure modes is used to gain insight on the tested components. This study is based on data obtained over four years on several irradiation campaigns, where memory devices of different technologies (static RAMs, ferroelectric RAM, magnetoresistive RAM, and flash) were irradiated with proton, heavy-ion, neutron and muon beams. The yielded data also supported the development of MTCube, a CubeSat picosatellite developed jointly by the Centre Spatial Universitaire (CSU) and LIRMM in Montpellier, whose mission is to carry out in-flight testing on the same memory devices. The underlying concepts regarding radiation, radiation environments, radiation-matter interactions, memory component architecture and radiation testing will be introduced in the first chapters, while the academic advances which were made during this study are presented in the final chapter

Field Programmable Gate Arrays, FPGAs, since their introduction on the market presented a very innovative way of implementing hardware designs. The fundamental property of these integrated circuits is the capability of a user's customization after manufacturing. An FPGA’s general architecture is composed of configurable elements that can be programmed to implement basic combinatorial and/or sequential logic. Configurable connection architecture can wire the configurable elements to implement complex circuits. Furthermore, input/output blocks manage interfacing with the external world, giving an option to configure various voltage and communication standards. These devices offer an extreme flexibility because they can be re-programmed in the field, hence they allow to comply with new needs or to improve an existing design (or even to post-correct design errors). Circuits can be described using high-level languages without a need for a long and expensive design process to be implemented as required for ASICs. Designers can use the same development environments and description languages through different devices (of the same vendor) and for different projects, providing very short time to market. Flexibility is obtained storing the device configuration to implement a desired circuit in a configuration memory, and based on used memory technology we can identify SRAM-based FPGAs and Flash-based FPGAs. All these facts have spread FPGA use into various sectors, including harsh radiation environments and safety-critical applications. For example, in space application, their use is constantly increasing, because FPGAs can comply with increasing computational needs – image processing, telecommunication – and their re-configurability can extend an application’s lifespan. Unfortunately, a great disadvantage of these devices is their sensitivity to radiation effects. As well, technology scaling along with the introduction of new material and new embedded structures is exacerbating radiation reliability issues. A citation of Robert Baumann, fellow IEEE, clearly expresses the reliability problem related to radiation: “Soft errors induce the highest failure rate of all other reliability mechanisms combined.” Any radiation-induced effects these devices suffer depend on various factors. In particular, configuration memory technology and the technological process node. In this scenario, it is very important to understand failure modes of FPGAs to provide a more suitable mitigation technique to preserve their correct circuit functionalities. This Thesis is a studying of radiation-induced effects on FPGAs. Testing radiation sensitivity of such devices is a complex process. First, specific platforms have to be developed to monitor a device’s behavior and its implemented circuit under a radiation source. Further, data analysis is complicated by a lack of detailed physical information from manufacturers. In this work, we present complete experimental methodologies to study radiation effects on FPGAs, analyzing any induced errors and decoding affected resources. Detailed analysis of these failure modes has been carried out; in particular, this work has targeted two different FPGA technologies: • SRAM-based FPGAs, such as Xilinx Spartan-3 devices; and • Flash-based FPGAs, such as Actel ProASIC3 devices. As their names suggest, these devices use different kinds of memory to store device configuration, and hence, different phenomena affect these two FPGA families. After a review of radiation-induced events, we present an analysis of mitigation techniques at design level. In particular, we focused on Triple Modular Redundancy, TMR, and Redundant Residue Number System, RRNS, implementations in SRAM-based FPGAs. Both techniques intend to increment a design’s reliability using additional information to detect and mask faults to the external world. This presented work has been made possible thanks to collaboration with Politecnico di Torino and Università Tor Vergata, Rome. The Thesis is organized as follows: • Chapter 1 is a brief overview of radiation and its effects on electronics; • Chapter 2 describes radiation-induced effects on SRAM-based FPGAs. In particular, irradiation experiments to understand and analyze the induced failure modes are presented. These tests have focused on Xilinx Spartan-3 devices; we have irradiated this FPGA with neutrons, heavy ions and alpha particles; • Chapter 3 presents studies on hardening-by-design techniques implemented in SRAM-based FPGAs. The impact of error accumulation in their configuration memory is analyzed on different implementations of the TMR scheme. Furthermore, a hardening technique based on modular arithmetic, RRNS, to implement a totally fault-tolerant FIR filter is presented, proving its effectiveness. Finally, a methodology to study the impact of multiple bit upsets on TMR circuits is proposed; • Chapter 4 focuses on Single Event Effects on Flash-based FPGAs. The studied event in this kind of FPGA is the Single Event Transient phenomenon. Irradiation tests to measure induced transient pulse width are presented. Further experiments to assess SET impact in real-like circuits are reported; and • Chapter 5 discusses the results gathered in this work.<br>Le Field Programmable Gate Array (FPGA) sin dalla loro introduzione nel mercato presentarono un modo davvero innovativo nell’implementazione di circuiti hardware. La proprietà fondamentale di questi circuiti integrati è la possibilità di personalizzazione delle funzionalità dopo il processo produttivo da parte dell’utente finale. L’architettura generale di una FPGA è composta di elementi configurabili che possono essere programmati per implementare funzionalità base di logica combinatoria e/o sequenziale. Una struttura configurabile d’interconnessioni permette di connettere questi elementi per l’implementazione di circuiti complessi. Inoltre, blocchi di input/output gestiscono l’interfacciamento con il mondo esterno, permettendo la possibilità di configurare vari livelli di tensione e standard di comunicazione. Questa tipologia di dispositivi offre una flessibilità estrema e possono essere riprogrammati anche nel sistema finale, quindi permettendo di rendere un design esistente conforme a nuovi requisiti, migliorarlo o addirittura correggere errori progettuali. I circuiti possono essere descritti utilizzando linguaggi ad alto livello e la loro implementazione, non richiede il lungo e costoso processo di design come per la tecnologia ASIC. Gli sviluppatori possono usare il medesimo ambiente di sviluppo e linguaggio di descrizione per diversi progetti e differenti dispositivi (dello stesso produttore) fornendo rapidi tempi d’ingegnerizzazione per collocare il prodotto sul mercato. La flessibilità è ottenuta memorizzando le informazioni della configurazione del dispositivo per implementare il circuito desiderato in una memoria dedicata, detta di configurazione. In base alla tecnologia utilizzata per la memoria, si possono distinguere FPGA basate su memoria RAM statica e quelle basate su memoria flash non volatile. Tutte queste proprietà hanno diffuso l’utilizzo delle FPGA in vari settori anche per applicazioni operanti in ambienti soggetti a livelli di radiazione e per applicazioni safety-critical. A esempio, in ambito spaziale, l’utilizzo delle FPGA è in costante incremento in quanto questi dispositivi possono adempiere la costante crescita di richiesta di calcolo computazionale (come nelle applicazioni di elaborazione digitale delle immagini e di telecomunicazione) e le proprietà di ri-configurabilità possono estendere la vita di un’applicazione. Sfortunatamente, un grosso svantaggio di questi dispositivi è la loro sensibilità agli effetti della radiazione. Inoltre, l’evoluzione della tecnologia e allo stesso tempo l’introduzione di nuovi materiali e nuove strutture stanno esacerbando problemi di affidabilità riguardanti la radiazione. Una citazione di Rober Baumann, fellow IEEE, chiaramente esprime i problemi di affidabilità riguardanti la radiazione: “Gli errori indotti dalla radiazione inducono un tasso di errore più alto di tutti gli altri meccanismi relativi affidabilità messi assieme” Gli effetti indotti dalla radiazione in questi dispositivi dipendono da vari fattori: in particolare dalla tecnologia usata per la memoria di configurazione e il nodo tecnologico utilizzato per la produzione. In questo scenario è davvero importante capire le modalità di fallimento delle FPGA, in modo tale da fornire la più appropriata tecnica di irrobustimento ai fini di preservare la corretta funzionalità del circuito implementato. Scopo di questa tesi è lo studio degli effetti indotti dalla radiazione su FPGA. Testare la sensibilità della radiazione per questi dispositivi è un processo complesso. Prima di tutto, specifiche piattaforme devono essere sviluppate per monitorare i funzionamenti del dispositivo e del circuito implementato sotto irraggiamento. Inoltre, l’analisi dei dati non è immediata a causa di mancanza di dettagliate informazioni sul layout fisico da parte dei produttori. In questo lavoro sono presentate delle complete metodologie per lo studio degli effetti di radiazione, analizzando gli errori indotti e codificando le risorse interne affette. Dettagliate analisi delle modalità di guasto sono state svolte: in particolare questo lavoro focalizza su due differenti tecnologie di FPGA: • FPGA basate su RAM statica come i dispositivi Spartan-3 prodotti da Xilinx; • FPGA basate su memoria Flash come i dispositivi ProAsic3 prodotti da Actel. Questi dispositivi utilizzano differenti tipologie di memoria per mantenere la configurazione interna e quindi, differenti fenomeni affliggono le due famiglie di FPGA. In seguito allo studio degli eventi indotti dalla radiazione, sono presentate analisi di alcune tecniche di mitigazione a livello di design. In particolare, ci siamo focalizzati nella ridondanza tripla modulare (TMR) e sistemi numerici ridondanti basati sui residui (RRNS) implementati in FPGA basate su RAM statica. L’intento di entrambe le tecniche è incrementare l’affidabilità dell’applicazione utilizzando informazioni addizionali per rivelare e mascherare i guasti al mondo esterno. I lavori presentati sono stati resi possibili grazie alla collaborazione con il Politecnico di Torino e l’università di Roma Tor Vergata. La tesi è organizzata come segue: • Il Capitolo 1 presenta una breve panoramica della radiazione e i suoi effetti nell’elettronica; • Il Capitolo 2 presenta gli effetti della radiazione su FPGA basate su memoria RAM statica. In particolare sono presentati esperimenti per capire e analizzare le modalità di guasto indotte dalla radiazione. I test eseguiti hanno utilizzato dispositivi Xilinx Spartan-3 che sono stati irraggiati con neutroni, ioni pesanti e particelle alfa; • Nel Capitolo 3 sono presentati studi riguardanti tecniche di irrobustimento a livello di design per circuiti implementati in FPGA basate su RAM statica. L’impatto dell’accumulo di errori nella memoria di configurazione è stato analizzato in funzione a differenti schemi d’implementazione della ridondanza tripla modulare. Inoltre, una tecnica di irrobustimento basata sull’aritmetica modulare (RRNS) è presentata per implementare un filtro totalmente tollerante ai guasti. Il capitolo conclude proponendo una metodologia per lo studio dell’impatto di eventi multipli in circuiti TMR; • Il Capitolo 4 verte sullo studio degli effetti da evento singolo per FPGA basate su memoria di tipo flash. Il particolare evento studiato su questi dispositivi è il fenomeno dei transienti. Sono presentati test d’irraggiamento per la misura della durata dei transienti indotti dalla radiazione. Nell’ultima parte del capitolo sono riportati ulteriori esperimenti per stimare l’impatto dei transienti indotti su circuiti simili a quelli realmente utilizzati (ossia, diversi da specifiche strutture di test). • Il Capito 5 conclude la tesi discutendo in modo generale i risultati raccolti in questo lavoro.

Made available in DSpace on 2015-04-22T22:11:22Z (GMT). No. of bitstreams: 1 Alberjan.pdf: 1648406 bytes, checksum: e7cc01faadea0adae547a7958b75ccce (MD5) Previous issue date: 2011-07-15<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>This work was aimed at applying the tools of the PRS System (Lean Production), whose primary tool was crafted VSM (Value Stream Mapping), a process known as SMT (Surface Mount Technology). Principles for lean production, eliminating waste and creating value stream in a real situation through kaizen events, were used to obtain results of this application, showing a lean transformation, with significant reductions in waste generated in the process. The study period was eight months into a private company located in PIM, where through the use of tools of this system and methodology of action research, it was possible to identify the critical process - setup - where focused improvement actions. With the change in the system setup, the standard work and creating a setup program using visual aid, favoring the continuous flow in this process. During the research, trainings were conducted in the factory with the operators, leaders, supervisors and engineers responsible, who participated actively in the improvement actions. Therefore, through value stream mapping, we propose to draw the current state of the stream, offering a future state, identifying and eliminating everything does not add value. To quantify the increase in productivity on the factory floor and total earnings of areas in the factory.<br>Este trabalho teve como objetivo a aplicação das ferramentas do Sistema de Produção Enxuta (SPE), cuja principal ferramenta trabalhada foi o Mapeamento da cadeia de valor (VSM), num processo denominado Tecnologia em Montagem de Superfície (SMT). Princípios que regem a produção enxuta, eliminação de desperdícios e a criação do fluxo de valor em uma situação real, através de eventos kaizen, foram utilizados para a obtenção de resultados dessa aplicação, evidenciando uma transformação enxuta, com expressivas reduções dos desperdícios gerados no processo. O período da pesquisa foi de oito meses em uma empresa privada situada no PIM, onde por meio da utilização de ferramentas desse sistema e a metodologia da pesquisa-ação, foi possível identificar o processo crítico setup para onde se concentraram as ações de melhorias. Com a mudança na sistemática de setup, no trabalho padronizado e criação de um setup programado, utilizando indicações visuais, favorecendo o fluxo contínuo nesta cadeia produtiva. No desenvolvimento da pesquisa, foram realizados treinamentos in loco com os operadores, líderes, supervisores e os engenheiros responsáveis, os quais participavam ativamente nas ações de melhoria. Portanto, através do mapeamento da cadeia de valor, propõem-se desenhar o estado atual da cadeia, propondo um estado futuro, identificando e eliminando aquilo que não agrega valor. Com isso, quantificar o aumento na produtividade no chão de fábrica e ganhos totais de áreas na fábrica.

Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2006.<br>Includes bibliographical references (p. 81-86).<br>The impact of the Greenland tip jet on the wintertime mixed-layer of the southwest Irminger Sea is investigated using in-situ moored profiler data and a variety of atmospheric data sets. The mixed-layer was observed to reach 400 m in the spring of 2003, and 300 m in the spring of 2004. Both of these winters were mild and characterized by a low North Atlantic Oscillation (NAO) index. All of the storms that were advected through the region were tracked, and the tip jet events that occurred throughout the two winters were identified. Composite images of the tip jets elucidated the conditions during which tip jets were likely to take place, which led to an objective method of determining tip jet occurrences by taking into account the large-scale pressure gradients. Output from a trajectory model indicates that the air parcels entering a tip jet accelerate and descend as they are deflected around southern Greenland. A heat flux timeseries for the mooring site was constructed that includes the enhancing influence of the tip jet events. This was used to drive a one-dimensional mixed-layer model, which was able to reproduce the observed mixed-layer deepening in both winters. All of the highest heat flux events took place during tip jets, and removal of the tip jets from the heat flux timeseries demonstrated their importance in driving convection east of Greenland.<br>(cont.) The deeper mixed-layer of the first winter was in large part due to a higher number of robust tip jet events, which in turn was caused by a greater number of storms passing northeast of southern Greenland. This interannual change in storm tracks was attributable to a difference in upper level steering currents. Application of the mixed-layer model to the winter of 1994-1995, during a period characterized by a high NAO index, resulted in convection reaching 1600 m. This prediction is consistent with concurrent hydrographic data, supporting the notion that deep convection can occur in the Irminger Sea during strong winters.<br>by Kjetil Våge.<br>S.M.

Negli ultimi decenni si sono raccolte prove a dimostrazione del fatto che gli ambienti marini profondi non siano stabili come creduto in precedenza. Ad oggi studi quantitativi di ecologia degli ambienti profondi sono stati condotti in tutti i maggiori bacini oceanici e sono stati descritti i principali pattern ecologici e biogeografici degli oceani profondi. Nonostante ciò, la maggior parte di questi studi si sono focalizzati su gradienti batimetrici basati o su un singolo sito di campionamento. Le indagini a lungo termine sono vitali per comprendere la varietà e la complessità dei processi che avvengono negli ambienti profondi. In particolare, non sono state finora analizzate le variazioni stagionali e annuali delle comunità profonde e se tali cambiamenti possano dipendere da un gradiente batimetrico o dalla tipologia di habitat. Le conoscenze sulla relazione fra abbondanza, biomassa, diversità delle comunità profonde e disponibilità delle risorse trofiche e condizioni ambientali è determinata dalla mancanza di informazioni sufficienti sull’effetto della variabilità spaziale e temporale. Nella presente tesi di dottorato ho provato a far fronte alla necessità di integrare le informazioni relative agli effetti della variabilità temporale degli ambienti marini profondi e la loro biodiversità. Ho utilizzato la meiofauna come modello di studio per investigare gli effetti dei cambiamenti temporali su variabili biotiche quali la struttura di comunità, la diversità (livello tassonomico superiore e diversità di specie dei nematodi) e il loro legame con le variabili ambientali (e.g., input stagionali di materia organica provenienti dalla zona fotica). Ho analizzato con cadenza regolare (biennale quando possibile) la variabilità temporale (intra- e inter- annuale) delle variabili ambientali, delle condizioni trofiche (contenuto in materia organica e composizione biochimica dei sedimenti) e della comunità della meiofauna (abbondanza, biomassa, numero di taxa e diversità dei nematodi). I campioni di sedimento sono stati raccolti lungo il margine continentale Catalano, nel Mar Mediterraneo nord-occidentale, a profondità comprese tra 1000 e 2400m nel canyon Cap de Creus e nella scarpata adiacente durante 6 campagne oceanografiche da Aprile 2005 a Ottobre 2009. La regione studiata è frequentemente sottoposta a eventi episodici di sprofondamento di acque dense superificiali, che si sono formate a seguito del raffreddamento e/o evaporazione delle acque costiere. Questi eventi, generando forti correnti di fondo con trasporto di sedimento, possono causare un’abrasione del substrato e determinare un potenziale disturbo sulle comunità bentoniche presenti lungo le scarpate e i canyon nell’area interessata da tale fenomeno. Analisi oceanografiche e sedimentologiche hanno rivelato come nell’inverno 2004-2005 questo evento è stato particolarmente drammatico. I risultati della presente tesi dimostrano che questo evento ha causato, a partire da 1000m fino alla porzione più profonda del bacino (2400m) un trasporto elevato di sostanza organica e una evidente diminuzione di abbondanza, biomassa e diversità della meiofauna. I risultati mettono inoltre in evidenza che la comunità bentonica ha mostrato una rapida resilienza a seguito del fenomeno di disturbo, nonostante i più alti livelli di biodiversità si raggiungano soltanto dopo 4-5 anni dall’evento di cascata di acque dense. I risultati di questa tesi evidenziano che la principale variabilità temporale in termini di quantità e qualità della sostanza organica, abbondanza, biomassa e biodiversità della meiofauna si verifica su scala inter-annuale con andamenti diversi al variare della diversa tipologia di habitat considerata. L’effetto della profondità del campionamento è apparentemente più forte della scala temporale intra-annuale nel determinare il cambiamento delle variabili investigate. Allo stesso tempo, la variabilità della comunità di meiofauna e della diversità dei nematodi è più forte nella porzione superficiale della scarpata continentale e si riduce nella piana abissale. I risultati di questa tesi pongono le basi per una migliore comprensione dell’importanza della variabilità temporale nell’analizzare il benthos profondo e dei limiti associati alle analisi basate su singoli tempi di campionamento.<br>In last two decades, a strong evidence is accumulating that the deep-sea environments are not as stable as previously thought. Quantitative studies of deep-sea ecology have been now conducted in all major oceanic basins and the main deep-sea biogeographic and ecological patterns are being disclosed. However, most of these investigations have been focused on the analysis of bathymetric gradients based on a single sampling. Long-term studies are vital to understand the diverse range of processes which occur in the deep sea. In particular, is still unknown whether deep-sea assemblages display significant seasonal or inter-annual variations, if these changes occur at all depths or are dependent on bathymetric gradients and whether they are more variable in different habitat types. The picture we have on the abundance, biomass and diversity of deep-sea assemblages and of their relationships with food availability and other environmental factors is therefore constrained by the lack of sufficient information on the effect of spatial and temporal variability. In the present PhD thesis I tried to partly cope with the need of integrating the information of the effects of temporal variability of deep-sea ecosystems and their biodiversity. I used deep-sea meiofauna as a model for investigating the effects of temporal changes on assemblage structure, higher taxa, species diversity and on several attributes as well as their links with environmental variables (e.g., the seasonal pulses of organic matter from the photic zone). I investigated on a regular basis (biannual when possible) the temporal (intra- and inter- annual) variability of environmental variables, trophic condition (organic matter content and biochemical composition of sediments) and meiofaunal assemblage (abundance, biomass, number of taxa of meiofaunal assemblage and nematode biodiversity). Sediments samples were collected along a continental margin (Catalan margin in the North-Western Mediterranean) at depth from 1000 to 2400m in Cap de Creus Canyon and in the adjacent slopes during 6 oceanographic cruises from April 2005 to October 2009. The investigated region is frequently subjected to episodic events of dense shelf water cascading, because of the formation of dense water due to cooling and/or evaporation of coastal shallow waters. These events by generating strong bottom currents and associated sediment transport can cause the physical abrasion of the deep-sea floor and determine a potential disturbance on the benthic assemblages inhabiting the open slopes and canyons of this margin. Oceanographic and sedimentological analyses revealed that in the winter 2004-2005 this event was particularly dramatic. I show here that this event caused, from 1000 down to the deepest part of the basin (2400 m depth), a major transport of organic matter and the collapse of meiofaunal abundance, biomass and diversity. I also demonstrated that the benthic assemblages displayed a rapid resilience after the cessation of the disturbance event, but the highest levels of biodiversity were reached only 4-5 years after. The analysis of the temporal changes revealed the presence of the highest variability in terms of quantity and quality of organic matter, total meiofaunal abundance, biomass and diversity over the inter-annual scale. The second source of variability was provided by the differential response of the different habitat types (e.g., canyons vs slopes) to changes in the environmental conditions. Interestingly, the effect of sampling depth was apparently stronger than that of intra-annual temporal scale in determining the variability of the investigated variables. At the same time the variability in meiofaunal and nematode biodiversity was stronger in the upper part of the slope and much reduced in the bathyal plain. Our results pose the basis for a better understanding of the importance of temporal variability in the analysis of deep-sea benthos and on the comprehension of the limits associated to the analyses based on single sampling times.

Thesis (M.S.)--Joint Program in Oceanography/ Applied Ocean Science and Engineering, Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, 2006.<br>"September 2006." Bibliography: p. 74-79.

With the different threats sea turtles are currently facing, such as habitat reduction and pollution, increase of fishing and harvesting of aquatic resources by Humans, or invasive species, it is important to learn as much as possible about their biology and behaviour in order to ensure the success of conservation programs. In this study, loggerhead sea turtles (Caretta caretta) feeding behaviour duration as well as energy expenditure approximation during a feeding event were tested and compared using two different types of food: green shore crabs (Carcinus maenas) or Japanese clam (Ruditapes phillipinarum) or Venus clams (Chamelea gallina). The data show that the turtles took longer to approach the crabs but took more time to eat the clams. However, comparison of energy expenditure values for the feeding phase showed no significant differences. The turtles were observed to eat the clams’ shell as well as their meat. These shells are rich in calcium, which is one possible explanation for this behaviour. This study shows that data loggers represent a viable tool for studying the behaviours of marine animals.

Blacks in the United States have the highest rates of hypertension in the world, and their cardiovascular disease mortality rates are higher than for any other population group as a result of traditional risk factors such as obesity and stronger family history. However, additional underlying factors, such as social determinants of health (e.g., socioeconomic status [SES]) and macrosocial factors (e.g., racism), also correlate with adverse health outcomes. This study investigated whether the interaction between SES mobility over the lifecourse and lifetime racial discrimination influenced the extent to which hypertension contributed to the cardiovascular disease health disparities observed among Blacks in the Jackson Heart Study (JHS). Using a socioecological framework, cross-sectional data collected from the baseline period on a cohort of 5,302 JHS participants were analyzed with multiple regression techniques. The study findings indicated that SES mobility, as measured by education, predicted both the racial discrimination exposure and the burden that individuals experience. However, neither SES mobility nor racial discrimination had any effect in moderating the relationship between hypertension and cardiovascular disease when examined individually or collectively. This study examined a new approach for measuring the influence of racial discrimination on health outcomes. Multidisciplinary public health and research partners should continue to advance understanding of the complex health impact of such experiences on individuals and the dynamics that create racial factors in order to effect social change.

More than 1.2 million Americans are hospitalized annually with an acute coronary syndrome (ACS); many impaired quality of life after discharge with an ACS. This dissertation focuses on two novel aspects of patient health status (PHS) after ACS: how it can be predicted based on the socioeconomic status (SES) of the patient, and how it evolves over time. We used data from TRACE-CORE, a longitudinal prospective cohort of patients hospitalized with ACS. We measured PHS using both the SF-36 mental and physical component subscales (MCS and PCS) and the Seattle Angina Questionnaire (SAQ) health-related quality of life (HRQoL) and physical limitations subscales at the index hospitalization and at 1, 3, and 6-months post-discharge. Firstly, after adjusting for individual-level SES, we found that individuals living in the neighborhoods with the lowest neighborhood SES had significantly worse PHS. Secondly, we found that each of the components of PHS had subgroups with distinct patterns of evolution over time (trajectories). Both the PCS and the SAQ physical limitations subscale had two trajectories; one with average and one with impaired health status over time. For the HRQoL subscale of SAQ, we found three trajectories: Low, Average, and High scores. For MCS, we found four trajectories: High (consistently high scores), Low (consistently low scores), and two with average scores at baseline that either improved or worsened over time, referred to as Improving and Worsening, respectively. All PHS trajectories, except for MCS, predicted readmission and mortality during the 6 months to 1 year post-ACS discharge.

Reactive halogen species (RHS) are responsible for ozone depletion and oxidation of gaseous elemental mercury and dimethyl sulphide in the polar boundary layer, but the sources and mechanisms controlling their catalytic reaction cycles are still not completely understood. To further investigate these processes, ground– based Multi–Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of boundary layer BrO and IO were made from a portable instrument platform in McMurdo Sound during the Antarctic spring of 2006 and 2007. Measurements of surface ozone, temperature, pressure, humidity, and wind speed and direction were also made, along with fourteen tethersonde soundings and the collection of snow samples for mercury analysis. A spherical multiple scattering Monte Carlo radiative transfer model (RTM) was developed for the simulation of box-air-mass-factors (box-AMFs), which are used to determine the weighting functions and forward model differential slant column densities (DSCDs) required for optimal estimation. The RTM employed the backward adjoint simulation technique for the fast calculation of box-AMFs for specific solar zenith angles (SZA) and MAX-DOAS measurement geometries. Rayleigh and Henyey-Greenstein scattering, ground topography and reflection, refraction, and molecular absorption by multiple species were included. Radiance and box-AMF simulations for MAX-DOAS measurements were compared with nine other RTMs and showed good agreement. A maximum a posteriori (MAP) optimal estimation algorithm was developed to retrieve trace gas concentration profiles from the DSCDs derived from the DOAS analysis of the measured absorption spectra. The retrieval algorithm was validated by performing an inversion of artificial DSCDs, simulated from known NO2 profiles. Profiles with a maximum concentration near the ground were generally well reproduced, but the retrieval of elevated layers was less accurate. Retrieved partial vertical column densities (VCDs) were similar to the known values, and investigation of the averaging kernels indicated that these were the most reliable retrieval product. NO₂ profiles were also retrieved from measurements made at an NO₂ measurement and profiling intercomparison campaign in Cabauw, Netherlands in July 2009. Boundary layer BrO was observed on several days throughout both measurement periods in McMurdo Sound, with a maximum retrieved surface mixing ratio of 14.4±0.3 ppt. The median partial VCDs up to 3km were 9.7±0.07 x 10¹² molec cm ⁻ in 2007, with a maximum of 2.3±0.07 x 10¹³ molec cm⁻², and 7.4±0.06 x 10¹² molec cm⁻² in 2006, with a maximum of 1.05 ± 0.07 x 1013 molec cm⁻². The median mixing ratio of 7.5±0.5 ppt for 2007 was significantly higher than the median of 5.2±0.5 ppt observed in 2006, which may be related to the more extensive first year sea ice in 2007. These values are consistent with, though lower than estimated boundary layer BrO concentrations at other polar coastal sites. Four out of five observed partial ozone depletion events (ODEs) occurred during strong winds and blowing snow, while BrO was present in the boundary layer in both stormy and calm conditions, consistent with the activation of RHS in these two weather extremes. Air mass back trajectories, modelled using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, indicated that the events were locally produced rather than transported from other sea ice zones. Boundary layer IO mixing ratios of 0.5–2.5±0.2 ppt were observed on several days. These values are low compared to measurements at Halley and Neumayer Stations, as well as mid-latitudes. Significantly higher total mercury concentrations observed in 2007 may be related to the higher boundary layer BrO concentrations, but further measurements are required to verify this.

The nature and assessment of executive function are areas of active research. Many current assessments of executive function are complex, have limited reliability and validity, and suffer from task impurity, meaning other cognitive processes may indirectly influence task performance. Additionally, measures may be culture, language, or education bound limiting their use in certain populations (Miyake, Emerson, & Friedman, 2000; Miyake, Friedman, et al., 2000; Strauss, Sherman, & Spreen, 2006; Stuss, 2007). The purpose of this project was to develop a novel set of executive function measures to address issues with current clinical measures. The new measures 1) can be used in an ERP environment, 2) use the same stimulus set to address task impurity and 3) use simpler cognitive operations of inhibition, set-shifting, and updating, identified in previous research by Miyake et al., (2000). Twenty-nine undergraduate participants at the University of South Florida were administered currently used clinical measures of executive function theorized to engage in inhibition, set-shifting, and updating and the set of the novel tasks. ERP data was collected during the administration of the novel tasks. Behaviorally, conditions theorized to engage executive function resulted in slower response reaction time than control conditions. Additionally, behavioral results indicated that performance on novel tasks were differentially related to different clinical EF tasks. ERP differences were observed between both Go/No-Go conditions (inhibition) and among N-back conditions (updating). Results suggest the novel executive function tasks are tapping into different cognitive processes and may be a viable tool for studying executive function in the future.

L’environnement radiatif spatial est particulièrement critique pour la fiabilité des circuits intégrés et systèmes électroniques embarqués. Cet environnement chargé en particules énergétiques (proton, électron, ions lourds, etc) peut conduire à des pannes transitoires (SET), ou permanentes (SEU) et dans certains cas destructives (type Latchup, SEL) dans les dispositifs embarqués. L'effet d'une seule particule est identifié comme un événement singulier (SEE). Les contraintes imposées par l'intégration technologique poussent les fabricants micro-électroniques à prendre en considération la vulnérabilité de leurs composants vis-à-vis du Latchup tout en considérant les phénomènes non destructifs tels que la corruption de données (SEU/MBU). Cette thèse est le fruit d'une collaboration entre l'ONERA et Sofradir, fabriquant électronique d'imageurs infrarouge. L'objectif de cette thèse est d'étudier les effets singuliers (SET/SEU/SEL) de la technologie CMOS utilisée par Sofradir dans des conditions de températures cryogéniques, et plus particulièrement l'effet Latchup<br>The spatial radiative environment is particularly critical for the reliability of integrated circuits and embedded electronic systems. This environment loaded with energetic particles (proton, electron, heavy ions, etc.) can lead to transient (SET), or permanent (SEU) and insome cases destructive failures (Latchup, SEL) in embedded devices. The effect of a single particle is identified as a single event effect(SEE). The constraints imposed by technological integration push microelectronics manufacturers to consider the vulnerability of their components to Latchup while consideringnon-destructive phenomena such as data corruption (SEU/MBU). This thesis is the result ofcollaboration between ONERA and Sofradir, an electronic manufacturer of infrared imagers. The aim of this thesis is to study the singular effects (SET / SEU / SEL) of the CMOS technology used by Sofradir under cryogenic temperature conditions, and more particularly the Latchup effect

The aim of this thesis has been to reconstruct paleoenvironment, paleohydrology and paleoclimate in coastal southern Mozambique, with emphasis on tracing past flooding events on the lower Limpopo River floodplain. In order to extend flood chronologies beyond periods covered by instrumental data, sediments from lakes on the floodplain were studied (Lake Lungué, Coassane Oxbow, Lake Magandane and Lake Soane). Past sea-level variations and climate changes were deduced by analyzing sediments from coastal sites north of the floodplain area (Lake Chilau, Lake Nhauhache and Macassa Bay). To achieve the established objectives, a multi-proxy approach was applied on most of the retrieved sediment cores, involving analysis of mineral magnetic parameters, grain-size and organic carbon in combination with analysis of microfossils such as diatoms and/or phytoliths. Chronologies for the constructed time-series analysis were obtained by radiocarbon dating and age-depth modelling. The synthesized data from the sampled sites on the Limpopo River floodplain suggest that the area was affected by at least 16 flooding events of variable magnitudes during the studied period. These are dated to c. AD 940, 980, 1040, 1100, 1250, 1300, 1370, 1580, 1665, 1730, 1755, 1855, 1920, 1945, 1970 and 2000. In calibrated years BP these ages correspond to 1010, 970, 910, 850, 700, 650, 580, 370, 285, 220, 195, 95, 30, and 5 cal yrs BP. The two youngest are dated to 20 and 50 years AP (After Present being 1950). Proxy data further suggest that southern Africa was subject to two periods of sea-level highstands, at c. 5000–4200 BC (6950–6150 cal yrs BP) and AD 300–950 (1650–1000 cal yrs BP). The former represents the middle part of the postglacial climatic optimum. The wettest period in the Limpopo River floodplain was reported between AD 1360 and 1560 (590 and 390 cal yrs BP) in the Lake Lungué record, while Lake Chilau experienced wet conditions between AD 1200 and 1400 (750 and 550 cal yrs BP), then returning to drier conditions that prevailed until c. AD 1600. In Lake Nhauhache, however, drier conditions prevailed from c. AD 1200–1700 (750–250 cal yrs BP), shifting towards wetter at c. AD 1900 (50 cal yrs BP). The deviating signals between records can partly be explained by Lake Lungué basin being located on the Limpopo River floodplain, responding to flooding events associated with precipitation upstream the drainage area. Therefore, wet and dry periods in floodplain lakes (e.g. Lake Lungué) are not expected to correlate with precipitation changes on a local scale, as indicated by e.g. Lake Nhauhache. This is supported by a relatively weak agreement between Lake Lungué record and other nearby records (outside the floodplain), but a better correlation with records from the upper catchment, where a more regional climate signal is provided of the southern African summer rainfall region.<br>Denna avhandling behandlar studier av paleomiljöer i södra Mozambique med fokus på översvämningshistorik i Limpopo-flodens nedre lopp. Tidsspannet är mitt- och sen-holocen och inkluderar även klimat och havsnivåvariationer. Följande analysmetoder har applicerats på ett flertal sedimentkärnor för att belysa ovanstående frågeställningar: mineralmagnetiska parameterar, kornstorlek, organiskt kol samt kiselmikrofossil (diatoméeter och fytoliter). Åldrar har bestämts med 14C-metoden.  Analyserna visar att mineralmagnetiska parametrar är lämpliga för att identifiera översvämningar, speciellt magnetisk susceptibilitet och SIRM. Dessa parametrar visar på ett sediments magnetiska kornstorlerkar och koncentrationen av finkorniga magnetiska mineral. Även kornstorleksanalyser fungerade som ett bra komplement till dessa metoder. Sammantaget har ett minimum av 16 översvämningar registrerats i Limpopo/flodens nedre lopp under de senaste 1100 åren. Särskilt stora översvämningar har daterats till AD 1250 (700 kal år BP), AD 1370 (580 kal år BP), AD 1580 (370 kal år BP), AD 1855 (95 kal år BP), AD 1920 (30 kal år BP), AD 1970 (20 kal år AP) och AD 2000 (50 kal år AP), där AP betyder ”after present”, vilket är 1950. Mindre kraftiga översvämningar har daterats till AD 940 (1010 kal år BP), AD 980 (970 kal år BP), AD 1040 (910 kal år BP), AD 1100 (850 kal år BP), AD 1300 (650 kal år BP), AD 1665 (285 kal år BP), AD 1730 (220 kal år BP), AD 1755 (195 kal år BP) och AD 1945 (5 kal år BP). Skriftliga källor visar på att åtminstone åtta översvämningar har ägt rum under de senaste 62 åren. Under samma period har denna undersökning registrerat två händelser, vilket indikerar att endast ett fåtal har registrerats med ovan nämnda metoder. Det är sannolikt att sedimentationsmönstret under en översvämning är komplicerat och inte heller likartad från gång till gång. Detta innebär att ett flertal sedimentkärnor behöver analyseras och dateras väl. Ytterligare en försvårande faktor är flodens mycket aktiva meandringsaktivitet. Analys av diatoméer har visats vara värdefulla när det gäller översvämningshistorik, klimatförändringar och havsytevariationer. Sedimenten i den något till flodslättens nedre lopp perifert belägna sjön Lungué indikerar fuktiga förhållanden mellan AD 1360 och 1560 (590 till 390 kal år BP). Kombinerade fytolit- och diatoméanalyser av sedimenten i sjön Chilau indikerar fuktiga förhållanden från AD 1200 till 1400 (750 till 550 kal år BP), varefter torrare förhållanden rådde till ca AD 1600 (350 kal år BP). Diatoméanalys av sedimenten i sjön Nhauhache indikerar generellt sett torrare förhållanden mellan AD 1200 och AD 1700 (750 till 250 kal år BP) då klimatet blev fuktigare. De fuktiga och torra förhållanden som dokumenterats i sjön Lungué och översvämningshistoriken korrelerar inte helt med lokala nederbördsförhållanden. Däremot stämmer erhållna data bättre med förhållanden i den övre delen av Limpopoflodens dräneringsområde. Även sjöar och fyllda meanderbågar på själva flodslätten verkar reagera tydligare på översvämningar orsakade av nederbörd i den övre delen av flodloppet. Undersökningen indikerar två faser av en förhöjd havsyta längs kusten i södra Mozambique. En äldre fas är daterad till ca 5000–4200 f.Kr. (6950–6150 kal år BP), vilken representerar den mellersta delen av det postglaciala värmeoptimet. Denna tolkning stöds även av andra undersökningar. En yngre fas har daterats till AD 300–950 (1650–1000 kal år BP), vilken korresponderar till en period med något förhöjda temperaturer i ett globalt perspektiv.<br>O presente projecto teve como objectivo a reconstrução do paleoambiente, paleohidrologia e paleoclima da costa Sul de Moçambique, com ênfase na identificação de vestígios de eventos de cheias que tenham, no passado, afectado a planície de inundação do Rio Limpopo, com vista a fazer a extensão das datações de cheias para o período anterior aos instrumentos de medição. Deste modo, foram estudados sedimentos recuperados através de testemunhos de sondagem em lagos dentro da planície de inundação (Lago Magandane, Lago Lungué, Lago Soane e o canal abandonado Coassane). As variações do nível do mar e mudanças climáticas do passado foram deduzidas a partir da análise de sedimentos de áreas costeiras a norte da planície de inundação (Lago Chilau, Lago Nhauhache e a Baía de Macassa). Para o alcance destes objectivos, os sedimentos dos testemunhos de sondagem recuperados foram submetidos a várias análises laboratoriais que incluem propriedades de minerais magnéticos, granulometria, teor de matéria orgânica e de microfósseis (diatomáceas e fitólitos). Para o estabelecimento do modelo cronológico foram usadas datações pelo método 14C feitas em matéria orgânica, assim como conchas de gastrópodes e bivalves. A combinação dos resultados obtidos para os pontos de amostragem localizados dentro da planície de inundação do Rio Limpopo, sugerem que esta área foi afectada por um mínimo de 16 eventos de cheias de variada magnitude nos últimos 1100 anos. As cheias de alta magnitude tiveram lugar nos anos 1250, 1370, 1580, 1855, 1920, 1970 e 2000. Por seu turno, as cheias de magnitude moderada ocorrerram nos anos 940, 980, 1040, 1100, 1300, 1665, 1730, 1755 e 1945.. Os anos a negrito são indicativos de eventos de cheias de alta magnitude. O número total de eventos identificados no presente estudo é um mínimo que poderá ter afectado a planície de inundação, tendo em consideração que fontes escritas reportam a ocorrência de pelo menos oito eventos nos últimos 62 anos, tendo o presente estudo revelado somente dois. Isto indica que apenas eventos de cheias intensos podem ser revelados pelos métodos aplicados nesta investigação. Adicionalmente, este estudo mostra a necessidade de aumentar o número de pontos de amostragem para permitir a identificação de mais eventos de cheias ocorridos no passado, devido à diferenciada resposta sedimentológica e geomagnética às cheias, a qual se encontra directamente relacionada à distância do rio meandrante. As análises de microfósseis de diatomáceas permitiram reconstruir o paleoclima e as influências do nível do mar nas áreas de estudo deste projecto. Os registros de diatomáceas do Lago Lungué indicam um período húmido entre AD 1360 e 1560. No Lago Chilau, dados de diatomáceas e fitólitos sugerem condições de humidade entre AD 1200 e 1400. Por seu turno, no Lago Nhauhache, condições de seca dominam entre AD 1200 e 1700. As condições de seca e humidade documentadas no Lago Lungué e os eventos de cheias revelados pelos sedimentos analisados da planície de inundação do Rio Limpopo não mostram total correlação com períodos de baixa e alta precipitação a nível local, mas apresentam boa correlação com evidências a montante na área de drenagem do Rio Limpopo. Em geral, lagos activos ou preenchidos por sedimentos mostrarão ser mais susceptíveis a cheias com origem a montante do que a nível local. As investigações conduzidas permitiram identificar dois períodos de alto nível do mar na região sul de Moçambique. A fase mais antiga teve lugar há cerca de 5000–4200 BC (6950–6150 anos do calendário BP), representando a fase mais recente do pós-glaciar climático óptimo (postglacial climatic optimum, PCA). A fase recente é datada de AD 300–950 (1650–1000 anos do calendário BP), correspondendo a um período de temperaturas relativamente altas a nível global.<br>Climate and Environmental Research

The investigation of extreme precipitation events over the western coast of Saudi Arabia is necessary to estimate their potential impact on both socioeconomic activities and the regional environment. The current study aims at understanding the atmospheric dynamics leading to extreme precipitation, to improve weather forecasting in the target region and the development of long-term adaptation policies. Preliminary results reveal that extreme precipitation events in this region occur during the wet season (Nov–Jan). The synoptic mechanisms of these events are a function of the complex interaction between tropical, subtropical and middle-latitude dynamics. The synoptic dynamic processes were identified by a subjective study of the highest 30 extreme events. In addition, the weather circulation patterns (WCPs) of all extreme events were classified objectively by means of an empirical orthogonal function (EOF) analysis based on the mean sea level pressure. WCPs were linked with synoptic dynamic processes and teleconnected with large-scale climate variability modes. Furthermore, WCPs, precipitation and data regarding other atmospheric variables from different regional climate models were used to investigate future changes in extreme precipitation events under climate change. The most important weather circulation patterns, which are associated with extreme precipitation events, were identified. The possibility of extreme precipitation events increases with great uncertainty.

Thesis: Ph. D., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 129-143).<br>In winter, Greenland's coastline adjacent to the subpolar North Atlantic and Nordic Seas is characterized by a large land-sea temperature contrast. Therefore, winds across the coast advect air across a horizontal temperature gradient and can result in significant surface heat fluxes both over the ice sheet (during onshore winds) and over the ocean (during offshore winds). Despite their importance, these winds have not been investigated in detail, and this thesis includes the first comprehensive study of their characteristics, dynamics and impacts. Using an atmospheric reanalysis, observations from local weather stations, and remote sensing data, it is suggested that high-speed wind events across the coast are triggered by the superposition of an upper level potential vorticity anomaly on a stationary topographic Rossby wave over Greenland, and that they intensify through baroclinic instability. Onshore winds across Greenland's coast can result in increased melting, and offshore winds drive large heat losses over major ocean convection sites. Strong offshore winds across the southeast coast are unique over Greenland, because the flow is funneled from the vast ice sheet inland into the narrow valley of Ammassalik at the coast, where it can reach hurricane intensity. In this region, the cold air, which formed over the northern ice sheet, is suddenly released during intense downslope wind events and spills over the Irminger Sea where the cold and strong winds can drive heat fluxes of up to 1000 W m-2, with potential implications for deep water formation. Moreover, the winds advect sea ice away from the coast and out of a major glacial fjord. Simulations of these wind events in Ammassalik with the atmospheric Weather Research and Forecast Model show that mountain wave dynamics contribute to the acceleration of the downslope flow. In order to capture these dynamics, a high model resolution with a detailed topography is needed. The effects of using a different resolution locally in the valley extend far downstream over the Irminger Sea, which has implications for the evolution and distribution of the heat fluxes.<br>by Marilena Oltmanns.<br>Ph. D.

Relative to the rest of the Southern Ocean, the Ross Sea continental shelf experiences very high productivity and phytoplankton biomass, which supports an extensive food web including high concentrations of upper trophic level biomass. Conventional observational methods, including ship-based sampling, instrumented moorings, satellite imagery, and computer-based modelling, have illustrated the seasonal progression of the phytoplankton bloom over the past four decades. While we have been sampling phytoplankton variability in the Ross Sea on a variety of relatively large scales, with observations at specific locations or times, over spans of time, or at specific depths, our understanding of smaller scales of variability (on the order of a few hours or several kilometers) is still poor. Utilizing two seasons (2010-2011 and 2012-2013) of high-resolution autonomous glider deployments in the southwestern Ross Sea, I examined the mechanisms driving both the transitions between stages of the phytoplankton bloom and the short-term perturbations in average 0-50 m chlorophyll. By including the available raw fluorescence data from both glider seasons and three mooring seasons, I determined that the 2012-2013 season had greater than average variability, with greater levels of variability observed in only two other seasons. Differences in the timing of bloom transitions were relatively constrained; the transition from bloom to post-bloom levels occurred within a temporal span of 6 d. These findings were likely the result of the location of the 2012-2013 glider adjacent to Ross Island and the Ross Ice Shelf, where complex bathymetry, turbulent flows, and the presence of an ice field contributed to the greater observed variability. To investigate the mechanisms driving the short-term perturbations in chlorophyll, I examined the relationships between average chlorophyll, average temperature, and mixed layer depth measured by the gliders and wind speed measured by two automatic weather stations atop the Ross Ice Shelf. Over the course of the 2012-2013 season, perturbations or responses in chlorophyll were heavily influenced by the degree of temporal coupling between wind events and the depth of mixing. Longer delays of 12-24 h observed prior to the biomass maximum shortened following the transition to biomass dissipation to 2-12 h. Furthermore, by causing aggregate formation and rapid vertical flux, physical forcing factors contributed to the observed short-term perturbations through reductions in biomass in surface layers and the appearance of chlorophyll in deeper layers. These results suggest that the small-scale observing capabilities of autonomous gliders allow for an improved understanding of the mechanisms that drive variability and short-term perturbations in shallow chlorophyll in the southwestern Ross Sea.

L’augmentation de la densité et la réduction de la tension d’alimentation des circuits intégrés rend la contribution des effets singuliers induits par les radiations majoritaire dans la diminution de la fiabilité des composants électroniques aussi bien dans l’environnement radiatif spatial que terrestre. Cette étude porte sur la modélisation des mécanismes physiques qui conduisent à ces aléas logiques (en anglais "Soft Errors"). Ces modèles sont utilisés dans une plateforme de simulation,appelée TIARA (Tool suIte for rAdiation Reliability Assessment), qui a été développée dans le cadre de cette thèse. Cet outil est capable de prédire la sensibilité de nombreuses architectures de circuits (SRAM,Flip-Flop, etc.) dans différents environnements radiatifs et sous différentes conditions de test (alimentation, altitude, etc.) Cette plateforme a été amplement validée grâce à la comparaison avec des mesures expérimentales effectuées sur différents circuits de test fabriqués par STMicroelectronics. La plateforme TIARA a ensuite été utilisée pour la conception de circuits durcis aux radiations et a permis de participer à la compréhension des mécanismes des aléas logiques jusqu’au noeud technologique 20nm<br>Aggressive integrated circuit density increase and power supply scaling have propelled Single Event Effects to the forefront of reliability concerns in ground-based and space-bound electronic systems. This study focuses on modeling of Single Event physical phenomena. To enable performing reliability assessment, a complete simulation platform named Tool suIte for rAdiation Reliability Assessment (TIARA) has been developed that allows performing sensitivity prediction of different digital circuits (SRAM, Flip-Flops, etc.) in different radiation environments and at different operating conditions (power supply voltage,altitude, etc.) TIARA has been extensively validated with experimental data for space and terrestrial radiation environments using different test vehicles manufactured by STMicroelectronics. Finally, the platform has been used during rad-hard digital circuits design and to provide insights into radiation-induced upset mechanisms down to CMOS 20nm technological node

Les composants électroniques utilisés pour des applications spatiales sont soumis à des rayonnements susceptibles de les rendre inopérants. Pour se prémunir de tels effets, leur sensibilité est testée au sol dans des accélérateurs de particules, onéreux et complexes à mettre en œuvre. Ce travail de thèse porte sur l’utilisation d’impulsions laser pour reproduire sous certaines conditions les effets des ions lourds. Le déclenchement de phénomènes parfois destructifs sur plusieurs types de composants de niveaux d’intégration différents a été obtenu sur le banc laser développé pendant cette thèse. Cela ouvre la voix à l’utilisation du laser comme outil de diagnostic en tirant partie de ses avantages en termes d’accessibilité, de coûts et de compréhension fine des effets<br>Electronic components used for space applications may exhibit failures under radiation. To prevent uch effects, the radiation sensitivity is evaluated using particle accelerators. Since those facilities are nly few around the world and expensive, complementary tests are needed to analyse radiation ensitivity. This work contributes to the use of laser pulses to reproduce under given conditions the ffects of heavy ions. Using the laser set-up developed during this thesis, single events which may be estructive were triggered on several types of electronic components. This paves the way to the use of aser as a diagnostic tool, given its advantages in terms of accessibility, costs and detailed analysis

Philosophiae Doctor - PhD<br>Apple (Malus x domestica) production in the Western Cape, South Africa, is one of the major contributors to the gross domestic product (GDP) of the region. The production of apples is affected by a number of diseases. One of the economically important diseases is apple scab that is caused by the pathogenic fungus, Venturia inaequalis. Research to introduce disease resistance ranges from traditional plant breeding through to genetic manipulation. Parallel disease management regimes are also implemented to combat the disease, however, such strategies are increasingly becoming more ineffective since some fungal strains have become resistant to fungicides. The recently sequenced apple genome has opened the door to study the plant pathogen interaction at a molecular level. This study reports on proteomic and transcriptomic analyses of apple seedlings infected with Venturia inaequalis. In the proteomic analysis, two-dimensional gel electrophoresis (2-DE) in combination with mass spectrometry (MS) was used to separate, visualise and identify apple leaf proteins extracted from infected and uninfected apple seedlings. Using MelanieTM 2-DE Gel Analysis Software version 7.0 (Genebio, Geneva, Switzerland), a comparative analysis of leaf proteome expression patterns between the uninfected and infected apple leaves were conducted. The results indicated proteins with similar expression profiles as well as qualitative and quantitative differences between the two leaf proteomes. Thirty proteins from the apple leaf proteome were identified as differentially expressed. These were selected for analysis using a combination of MALDI-TOF and MALDI-TOF-TOF MS, followed by database searching. Of these spots, 28 were positively identified with known functions in photosynthesis and carbon metabolism (61%), protein destination and storage (11%), as well as those involved in redox/response to stress, followed by proteins involved in protein synthesis and disease/defence (7%), nucleotide and transport (3%). RNA-Seq was used to identify differentially expressed genes in response to the fungal infection over five time points namely Day 0, 2, 4, 8 and 12. cDNA libraries were constructed, sequenced using Illumina HiScan SQTM and MiSeqTM instruments. Nucleotide reads were analysed by aligning it to the apple genome using TopHat spliceaware aligner software, followed by analysis with limma/voom and edgeR, R statistical packages for finding differentially expressed genes. These results showed that 398 genes were differentially expressed in response to fungal infection over the five time points. These mapped to 1164 transcripts in the apple transcripts database, which were submitted to BLAST2GO. Eighty-six percent of the genes obtained a BLAST hit to which 77% of the BLAST hits were assigned GO terms. These were classed into three ontology categories i.e. biological processes, molecular function and cellular components. By focussing on the host responsive genes, modulation of genes involved in signal perception, transcription, stress/detoxification, defence related proteins, transport and secondary metabolites have been observed. A comparative analysis was performed between the Day 4 proteomic and Day 4 transcriptomic data. In the infected and uninfected apple leaf proteome of Day 4, we found 9 proteins responsive to fungal infection were up-regulated. From the transcriptome data of Day 4, 162 genes were extracted, which mapped to 395 transcripts in the apple transcripts. These were submitted to BLAST2GO for functional annotation. Proteins encoded by the up-regulated transcripts were functionally categorised. Pathways affected by the up-regulated genes are carbon metabolism, protein synthesis, defence, redox/response to stress. Up-regulated genes were involved in signal perception, transcription factors, stress/detoxification, defence related proteins, disease resistance proteins, transport and secondary metabolites. We found that the same pathways including energy, disease/defence and redox/response to stress were affected for the comparative analysis. The results of this study can be used as a starting point for targeting host responsive genes in genetic manipulation of apple cultivars.

Il SEPA (SPARQL Event Processing Architecture) si pone come middleware tra un endpoint SPARQL e i suoi clienti, offrendo vari servizi, in particolare la possibilità di registrarsi a delle sottoscrizioni. Il SEPA dunque implementa il design pattern publish-subscribe o anche chiamato Pub-Sub, che permette ai clienti di sottoscriversi designando il loro interesse a un certo sottoinsieme di conoscenza. In questo caso, il meccanismo di Pub-Sub si basa su richieste SPARQL dove ogni sottoscrizione indica l'interesse a quella parte della conoscenza che viene delimitata da una query SPARQL (query di sottoscrizione). Ogni pubblicazione degli aggiornamenti dei dati è rappresentata da una update SPARQL. Fornire questo servizio di sottoscrizioni, nel contesto semantico in cui il SEPA si pone, risulta molto costoso in termini prestazionali. L'obiettivo di questa tesi è quello di analizzare l'attuale meccanismo Pub-Sub, ricercare e implementare una prima parte di una possibile ottimizzazione per poi condurre ulteriori analisi, con lo scopo di realizzare un algoritmo che possa essere utilizzato per ottimizzare i tempi di gestione delle sottoscrizioni del SEPA, fornendo anche delle metriche sull'algoritmo stesso. Lo svolgimento dell'attività di tesi si può suddividere in quattro fasi. La prima fase è stata di studio sul SEPA e di approfondimento delle tecnologie coinvolte. Nella seconda fase è stato implementato un programma per eseguire dei benchmark in grado di valutare le attuali prestazioni del SEPA ed ottenere così i primi dati significativi sull'algoritmo nativo che gestisce le sottoscrizioni. La terza fase è stata un alternarsi tra studio, progettazione, implementazione e test sul nuovo algoritmo. La quarta e ultima fase si è occupata di riordinare i dati e consolidare il nuovo algoritmo. Al termine della tesi, i dati raccolti hanno confermato la validità dell'algoritmo, dimostrando come questo possa ridurre i tempi necessari alla gestione del meccanismo publish-subscribe.

In this thesis, we address the problem of identifying and quantifying variants (alternative splicing and genomic polymorphism) in RNA-seq data when no reference genome is available, without assembling the full transcripts. Based on the idea that each variant corresponds to a recognizable pattern, a bubble, in a de Bruijn graph constructed from the RNA-seq reads, we propose a general model for all variants in such graphs. We then introduce an exact method, called KisSplice, to extract alternative splicing events and show that it outperforms general purpose transcriptome assemblers. We put an extra effort to make KisSplice as scalable as possible. In order to improve the running time, we propose a new polynomial delay algorithm to enumerate bubbles. We show that it is several orders of magnitude faster than previous approaches. In order to reduce its memory consumption, we propose a new compact way to build and represent a de Bruijn graph. We show that our approach uses 30% to 40% less memory than the state of the art, with an insignificant impact on the construction time. Additionally, we apply the techniques developed to list bubbles in two classical problems: cycle enumeration and the K-shortest paths problem. We give the first optimal algorithm to list cycles in undirected graphs, improving over Johnson's algorithm. This is the first improvement to this problem in almost 40 years. We then consider a different parameterization of the K-shortest (simple) paths problem: instead of bounding the number of st-paths, we bound the weight of the st-paths. We present new algorithms using exponentially less memory than previous approaches

Made available in DSpace on 2015-04-14T13:35:09Z (GMT). No. of bitstreams: 1 430255.pdf: 1176318 bytes, checksum: 4850238e491d62ada84dedd411f149d1 (MD5) Previous issue date: 2011-03-22<br>A rela??o entre anticorpos anticardiolipina (aCL), marcadores da s?ndrome antifosfol?pide, e vasculopatia em diab?ticos ? mat?ria de debate. Este estudo, transversal controlado, avaliou a freq??ncia de IgG, IgM e IgA aCL em diab?ticos do tipo 2 com ou sem eventos vasculares nos ?ltimos 5 anos e em controles sadios. Os anticorpos foram detectados por ensaio imunoenzim?tico. Setenta e tr?s diab?ticos (33 com eventos vasculares pr?vios) e 54 controles foram estudados. Diab?ticos foram predominantemente mulheres (p=0,003), e de idade mais avan?ada (p<0,001) em rela??o aos controles. A dura??o m?dia da doen?a foi de 10 anos. A preval?ncia de teste positivo para anticorpos aCL foi de 7,4% em controles e de 9,5% em diab?ticos (p=0,910). Ap?s ajuste para sexo e idade, a freq??ncia de anticorpos aCL n?o diferiu significativamente quando se comparou controles e diab?ticos com ou sem macrovasculopatia (p>0,09). A freq??ncia de anticorpos aCL tamb?m n?o diferiu quando se comparou os dois grupos de diab?ticos entre si (p>0.47). Ap?s ajuste para sexo, idade, hipertens?o e tabagismo, uma associa??o fraca, mas estatisticamente insignificante, foi 28 observada entre IgM aCL e diab?ticos com vasculopatia (OR ajustado 2,7; IC95% 0,2-34,2; p=0,441). Globalmente, n?veis de IgG (r=0,25; p=0,005) e IgM (r=0,23; p=0,010) aCL se correlacionaram com idade progressiva. Em resumo, a freq??ncia de teste positivo para anticorpos aCL em diab?ticos tipo 2 (com ou sem hist?rico vascular) n?o foi significativa em rela??o a controles sadios. N?o houve associa??o entre presen?a de anticorpos aCL e eventos vasculares em diab?ticos tipo 2.

Cette thèse propose une méthode pour construire des réseaux de régulation causales réalistes, qui a une taux de faux positifs inférieur aux méthodes traditionnelles. Cette approche consiste à intégrer des informa- tions hétérogènes à partir de deux types de prédictions de réseau pour déterminer une explication causale du gène observé co-expression. Ce processus d'intégration se modélise comme un problème d'optimisation combinatoire, de complexité NP-difficile. Nous introduisons une approche heuristique pour déterminer une solution approchée en un temps d'exécution pratique. Notre évaluation montre que, pour l'espèce modèle E. coli, le réseau de régulation résultant de l'application de cette méthode a une précision supérieure à celle construite avec des outils traditionnels. La bactérie Acidithiobacillus ferrooxidans présente des défis particu- liers pour la détermination expérimentale de son réseau de régulation. En utilisant les outils que nous avons développés, nous proposons un réseau de régulation putatif et analysons la pertinence de ces régulateurs centraux. Il s'agit de la quatrième contribution de cette thèse. Dans une deuxième partie de cette thèse, nous explorons la façon dont ces relations réglementaires se manifestent, en développant une méthode pour compléter un réseau de signalisation lié à la maladie d'Alzheimer. Enfin, nous abordons le problème ma- thématique de la conception de la sonde de puces à ADN. Nous concluons que, pour prévoir pleinement les dynamiques d'hybridation, nous avons besoin d' une fonction de l'énergie modifiée pour les structures secondaires des molécules d'ADN attaché surface et proposons un schéma pour la détermination de cette fonction.