As abelhas são consideradas os polinizadores mais importantes das culturas agrícolas ao redor do mundo e os mais efetivos. As necessidades nutricionais desses animais são atendidas através da coleta de néctar (transportado à colônia e armazenado nos favos) e pólen (consumido após a realização de processos fermentativos de microrganismos, denominando-se beebread ou pão de abelha). O beebread possui uma atratividade natural a essas abelhas. Com o desaparecimento das abelhas, pela falta de alimento disponível, entre outras causas, a alimentação suplementar auxilia apicultores na manutenção dessas colônias em períodos críticos, porém esses suplementos muitas vezes não possuem valor nutritivo adequado e fraca atratividade. Verificar assim quais os compostos voláteis presentes no beebread de diferentes regiões do Brasil e uma dieta fermentada a base desse pólen, faz-se hoje uma importante ferramenta para tentar elucidar o problema da atratividade. Foram feitas análises de atratividade, através de testes em túnel Y com duas dietas artificiais: uma dieta não fermentada e outra fermentada com o próprio beebread, durante quatro dias; análises cromatográficas, com beebread coletado de colônias de abelhas A. mellifera em: Ribeirão Preto/São Paulo; Mossoró/Rio Grande do Norte; Muzambinho/Minas Gerais; Porto Alegre/Rio Grande do Sul; análise polínica das amostras de beebread de todas as localidades. Os testes em túnel Y confirmaram que as abelhas são atraídas pelo cheiro da dieta fermentada, sendo que quanto mais tempo permanecem sem alimentação proteica, mais rapidamente é a escolha do local onde se encontra a dieta fermentada. Já as análises químicas apontaram que tanto a dieta fermentada quanto o beebread coletado nas diferentes localidades possuem alguns compostos voláteis em comum, oriundos principalmente de fermentação: Acetoína, Ácido Acético e 2,3-Butanodiol. Sendo que a classe química que esteve mais presente foi a de terpenoides. A análise polínica das amostras de beebread confirmou os dados obtidos pela análise química. Nossos dados indicam a grande importância da gama de compostos encontrados no beebread e a presença daqueles que indicam a fermentação. Assim, saber qual desses compostos voláteis são atrativos às abelhas será fundamental para a liofilização dos mesmos e adicioná-los às rações proteicas artificiais, tornando-as mais palatáveis e atrativas para esses insetos. / Honey bees are considered to be the most important and most effective pollinators of agricultural crops throughout the world. The nutritional necessities of these insects are met by collecting nectar (transported to the colony and stored in the comb) and pollen (consumed after it has been fermented by microorganisms, becoming bee bread). Bee bread contains substances that are attractive to the bees. As the increasing need for bees has become hard to meet because of a lack of natural food sources to sustain their colonies, it has become increasingly common for beekeepers to provide pollen substitutes. However, nutritional quality and palatability are often inferior to those of bee bread. In a search for key compounds that could help stimulate the bees to consume artificial diets, we examined the volatile compounds present in bee bread and in artificial protein diets that had been fermented with microorganisms present in bee bread. Attractiveness of fermented versus unfermented artificial protein diets for honey bees was compared using a Y odor choice test, for four days. Additionally, chromatographic analyses were made of bee bread collected from apiaries located in Ribeirão Preto, São Paulo, Mossoró, Rio Grande do Norte, Muzambinho, Minas Gerais, and Porto Alegre, Rio Grande do Sul. Pollen analyses were made of all bee bread samples to determine plant origin. The bees preferred the odors from fermented compared to unfermented diet. The rapidity with which they made this choice was positively correlated with the time that they remained without protein food. Several of the volatiles from bee bread from the different regions of the country were similar, despite considerably different contributing pollen species. These volatiles were also found in the fermented pollen substitute diet, indicating that they were products of fermentation; these included acetoin, ascetic acid and 2,3-butanediol. The most common class of volatiles in these materials was terpenoids. There was a large variety of volatile compounds in the bee bread samples and in the fermented bee diet; these included substances that are a result of fermentation. A next step would be to determine which of these substances are most attractive to bees that require protein, so that they can be added to artificial bee diets in order to make them more palatable and useful.

Com o objetivo de obter informações básicas sobre a bioecologia e o comportamento de Sphenophorus levis Vaurie, foram realizados diferentes bioensaios para conhecer seu comportamento sexual e reprodutivo; obter e testar a atividade biológica de seu feromônio natural em condições de laboratório e campo; verificar a eficiência de captura do feromônio sintético de agregação em condições de campo; determinar o tipo de armadilha mais eficiente para a captura e manejo de adultos; e avaliar o raio de ação das atuais armadilhas. Os resultados mostraram que S. levis, acasala-se em qualquer hora do dia, tem múltiplas cópulas, e os casais entre 14 e 35 dias de idade apresentaram as maiores frequências de cópulas, com 76 a 88%, respectivamente. A duração média da primeira cópula foi de 5,75 ± 4,22 h, e o tempo total de cópula variou entre 1 a 17 h. O período de pré-oviposição em fêmeas entre 14 e 35 dias, foi de 5,52 ± 4,53 a 10,90 ± 5,37 dias. O número de ovos/fêmea foi de 0,25 a 7,80, com viabilidade entre 33 e 63%. Fêmeas de S. levis com idade avançada entre 85 e 210 foram receptivas ao acasalamento (66%), ovipositaram entre 4,50 a 7,09 ovos, com viabilidade entre 49 e 79%. Machos e fêmeas de S. levis aptos ao acasalamento, apresentaram uma sequência típica de comportamentos para efetivar a cópula. A duração da pré-cópula variou de 2 a 5 horas. A cópula foi longa, com uma duração entre 7 a 13 horas. A pós-cópula durou entre 1,31 a 1,41 horas. O comportamento sexual associado à cópula foi influenciado pelo contato visual entre os casais e físico com outros indivíduos da espécie. Bioensaios em olfatômetro Y demonstraram que os machos foram estimulados por voláteis de cana; cana + machos; e cana + fêmeas; enquanto as fêmeas apenas por cana + machos. Os machos responderam ao extrato natural de macho + cana; as fêmeas ao extrato de machos + cana, extrato de fêmeas e extrato de fêmeas + cana. O isômero (S)-2-metil-4-octanol gerou atividade comportamental de ambos os sexos de S. levis. No campo, a avaliação da atratividade dos extratos naturais e os compostos sintéticos (isômeros S; R e mistura racêmica S-R), mostraram diferença na captura de fêmeas e totais de adultos de S. levis entre o isômero R e o controle; no entanto, não diferiram dos demais tratamentos. A captura de adultos selvagens de S. levis nas diferentes armadilhas testadas, diferiu entre o controle (isca CTC) e as armadilhas testadas (modelos galão, funil, e moleque da bananeira). A recaptura de adultos marcados de S. levis foi baixa e correspondeu a apenas 2% dos insetos liberados, sendo maior a distância de 5 m (10 adultos). De forma geral, estes resultados contribuem para o conhecimento do comportamento sexual e reprodutivo de S. levis e são úteis para futuros programas de manejo integrado desta praga. / With the aim of obtaining basic information on bioecology and behavior of Sphenophorus levis Vaurie, different bioassays were realized in order to understand its sexual and reproductive behavior; obtain and test the biological activity of its natural pheromone under laboratory and field conditions; verify the capture efficiency of the synthetic aggregation pheromone under field conditions; determine the most efficient type of traps for capture and management of the adults; and evaluate the radius of action of the current traps. The results showed that S. levis mates any time of the day, has multiple mating and the mates between the ages of 14 and 35 days presented the highest mating frequencies of 76 to 88%, respectively. The mean duration for the first mating was 5.75 ± 4.22 h, and the total mating time varied between 1 to 17 h. The pre-oviposition period for females between 14 and 35 days, was 5.52 ± 4.53 to 10.90 ± 5.37 days. The number of eggs/female was 0.25 to 7.80, with viability of between 33 and 63%. Females of S. levis with advanced age between 85 and 210 days were receptive to mating (66%), oviposited between 4.50 to 7.09 eggs with viability between 49 and 79%. Males and females of S. levis with capacity to mate presented typical frequency behavior to effect mating. The pre-mating duration varied from 2 to 5 hours. Mating was long with duration of 7 to 13 hours. The post-mating duration lasted between 1.31 to 1.41 hours. Sexual behavior associated with mating was influenced by visual contact between the couples and the physical among coespecifics. Bioassays in a Y tube olfatometer demonstrated that the males were responsive to sugarcane volatiles; sugarcane + males; and sugarcane + females; while the females were stimulated at least by sugarcane + males. The males responded to the natural extract of male + sugarcane; while the females to the extract of males + sugarcane, extract of females and extract of females + sugarcane. The isomer (S)-2- methil-4-octanol generated behavioral activity of both sexes of S. levis. In the field, the evaluation of attractivity of natural extracts and the synthetic compounds (isomer S; R and racemic mixture of S-R), showed differences in the capture of females and totals of adults of S. levis between the isomer R and the control; however, it was not different in other treatments. The capture of wild S. levis adults in the different tested traps differed between the control (bait CTC) and the tested baits/traps (models galão, funil, and moleque da bananeira). The recapture of marked adults of S. levis was low and corresponded to 2% of the liberated insects within the longest distance of 5 m (10 adults). In general, these results add to the knowledgment of S. levis sexual and reproductive behavior and are useful to future programs of integrated management of this pest.

The Cape Verde archipelago is located 2000 km east of the Atlantic oceanic ridge and 500 km west of the western part of Africa. The plateau of the archipelago rises on average 2 km above the seafloor, which makes it one of the highest oceanic plateaus on Earth. Cape Verde originates from hotspot formation, a geological phenomenon which takes place beyond the tectonic plate boundaries where magma rises to the surface. In this thesis, volcanic material taken from the Charles Darwin volcanic field at a depth of more than 3000 meter and made up by four basaltic rocks and one agglomerate will be investigated. The agglomerate and vesicles in the rock shows that explosive volcanism occurs in high water depths, which is generally not common. Therefore, the material will be investigated to find out how explosive volcanism can occur at high water depths. The investigation will be based on quantifying the number of vesicles to able to calculate their area and analyze the magmatic water content in clinopyroxene crystals taken from the agglomerate by FTIR spectroscopy. Water is a volatile substance in the composition of magma and has a huge effect on its behavior at eruption. The results of quantification show that the area taken by vesicles varies from 7- 54 % which shows that magmatic products with high number of vesicles are common. The FTIR analysis shows that the magmatic water content can be high enough to cause an oversaturated magma system, which creates explosive eruptions. This statement is based on only one clinopyroxene crystal that had a magmatic water content of 3,87 ± 0,77 %. Other possible reasons for explosive eruptions at high water depth are the CO2 content in the magma and the size of volcanic vent. / Kap Verde är en arkipelag, situerad cirka 2000 km öster om den mittatlantiska spridningsryggen och 500 km väster om det afrikanska fastlandet. Arkipelagens platå har en genomsnittlig höjd på 2 km, vilket gör den till en av världens högsta oceaniska platåer. Arkipelagen har uppkommit av hetfläcksbildning, ett geologiskt fenomen baserad på att magma erupteras till ytan där jordskorpan är förtunnad och inte har någon anknytning till de tektoniska plattgränserna. Det som undersöks i detta kandidatarbete är vulkaniskt material, taget från den vulkaniska undervattensön Charles Darwin vulkanfält som ligger i den västra del Kap Verdes norra ö-grupp på över 3000 meterdjup. Materialet består av ett agglomerat och fyra stenstuffer av basaltisk komposition. Agglomeratet tyder på att explosiva vulkanutbrott förekommer, vilket även bekräftas av stenstufferna som har rikligt förekomst av luftbubblor. Explosiva vulkanutbrott är generellt inte förekomliga vid höga vattendjup, därav undersöks materialet för att kunna reda ut orsakerna som ger upphov till förekomsten av explosiva vulkanutbrott. Undersökningen baseras på att kvantifiera luftbubblor hos stenstufferna för att kunna räkna ut arean som upptas och analysera vattenhalten i klinopyroxenkristaller i agglomeratet med hjälp av FTIR spektroskopi. Vatten tillhör de flyktiga beståndsdelar i magmas sammansättning som kallas för volatiler och utgör en viktig parameter för magmans uppträdande vid eruption. Resultatet kvantifiering av luftbubblor visar att arean som upptas av luftbubblor varierar mellan 7–54 % av stenstufferna total area, vilket understryker att magmatiska produkter med hög andel luftbubblor är förkomliga. FTIR analysen visar att det finns tillräckliga höga vattenhalter för ett övermättat magmasystem som ger upphov till vulkanutbrott med explosiva förlopp, baserat på vattenhalten 3,87 ± 0,77 % av en klinopyroxenkristall. Andra möjliga orsaker till uppkomsten av magmatiska produkter med hög andel luftbubblor är koldioxidhalten i magman och storleken på vulkanrören.

Parmi les desserts à base d’ovoproduits, l’île flottante est reconnue comme particulièrement sensible d’un point de vue microbiologique car sa commercialisation souffre de la survenue intempestive d’altérations que les industriels souhaitent maîtriser. Les travaux réalisés au cours de cette thèse avaient pour objectif de mieux appréhender ces phénomènes afin de mieux les contrôler. Nous avons montré que l’altération de l’île flottante concernait principalement la crème anglaise et qu’elle s’accompagnait d’un développement bactérien conséquent, d’une fréquente diminution du pH et de modifications sensorielles liées à l’aspect et à l’odeur. Les principales bactéries détectées ont été identifiées comme appartenant au groupe Bacillus cereus et aux genres Staphylococcus et Enterococcus. Le blanc d’œuf pasteurisé, utilisé pour la fabrication des œufs en neige, s’est avéré être une source de contamination possible.Cependant, l’implication de bactéries installées sous forme de biofilms dans l’environnement de production ou véhiculées par d’autres ingrédients a aussi été fortement envisagée. La ré-inoculation, en culture pure, d’une collection bactérienne représentative dans de la crème anglaise stérile a montré que différents types de modifications sensorielles et physico-chimiques s’exprimaient d’un genre bactérien à l’autre et qu’ils étaient notamment corrélés à la capacité des bactéries à consommer les sucres et les protéines de la crème anglaise et à produire des métabolites dont des composés volatils odorants. Ces résultats à l’appui, différents tests ont pu être proposés, p / Among the chilled egg products-based desserts, the French dessert “île flottante” is recognized as particularly sensitive from a microbiological point of view, because marketing is suffering from untimely spoilage occurrence that manufacturers wish to control. The work done in this thesis aimed to better understand these phenomena in order to better control them. We have shown that the dessert spoilage mainly concerned the custard cream and it was characterized by high bacterial count, frequent pH decreasing and sensory changes of appearance and smell. The main bacteria detected were identified as belonging to the Bacillus cereus group and Staphylococcus and Enterococcus genera. The possible involvement of bacteria from the pasteurized egg white, used for the egg white foaming, in the dessert spoilage issue was established.However, the involvement of bacteria from biofilms installed in the production environment or provided by other ingredients was also strongly suspected. The spoilage potential assessment of pure culture of a representative bacterial collection in sterile custard cream has shown that different types of sensory and physicochemical changes were expressed according to bacterial genus and that these changes were particularly correlated with the ability of bacteria to consume sugars and proteins of custard and to produce various volatile compounds with specific odorous. With these results, various tests have been proposed for a better control of the white egg batches orientation according to their microbiological quality and so to guarantee their safety with

Les plantes médicinales Diplotaxis harra et Diplotaxis simplex occupent une place importante dans la pharmacopée traditionnelle grâce à leurs compositions variées en métabolites secondaires tels que les flavonoïdes. Ces derniers jouent un rôle important dans plusieurs activités biologiques, notamment anti-inflammatoires et anti-cancéreuses. Dans ce contexte, et à la recherche de molécules bioactives dans D. harra et D. simplex, nous avons mis au point un nouveau modèle d'étude in vitro des cellules souches à l'origine des pathologies inflammatoires et cancéreuses coliques où leur survie dépend de l'activation de la Glycogène Synthase Kinase 3beta (GSK3beta) en aval du récepteur de protéases inflammatoires PAR2. Ce modèle a permis la purification bioguidée de glucoflavonoïdes à partir d'un extrait méthanolique des fleurs de D. harra capables d'inhiber GSK3beta via la voie PKC. Ainsi, l'Isorhamnétine-3,7-di-O-glucoside s'est révélé cytotoxique vis à vis des cellules inflammatoires ou cancéreuses coliques tout en épargnant les cellules normales. D'autre part, en raison de l'intérêt grandissant porté aux fractions volatiles en thérapeutique, nous avons étudié les compositions chimiques et les activités antioxydantes des fractions volatiles des feuilles et des fleurs de D. simplex. En se basant sur la technique chromatographique en phase gazeuse couplée à la spectrométrie de masse (GC-MS), nous avons montré que les deux fractions volatiles contiennent des quantités importantes de composés soufrés/azotés, parmi lesquels le 5-methylthiopentanenitrile et le 1-isothiocyanatobutane pourraient être impliqués dans l'effet antioxydant des fleurs de D. simplex. En conclusion, nos travaux ont permis de révéler l'axe PAR2/GSK3beta comme une nouvelle voie de survie des cellules souches coliques et l'intérêt thérapeutique des glucoflavonoïdes et des fractions volatiles de l'espèce Diplotaxis. / The medicinal plants Diplotaxis harra and Diplotaxis simplex occupy an important place in traditional medicine due to their varied compositions in secondary metabolites such as flavonoids. Flavonoids play an important role in many biological activities, including inflammation and cancer. In this context and in search of bioactive molecules in D. harra and D. simplex, we have developed a new study model, in vitro, where colonic stem cells causing inflammatory diseases and colorectal cancer survive through the activation of Glycogen Synthase Kinase 3beta (GSK3beta) downstream of inflammatory proteases PAR2 receptor. This model allowed the bio-guided purification of glucoflavonoids from a methanol extract of D. harra flowers able to inhibit GSK3beta via a PKC-dependent pathway. Thus, isorhamnetin-3,7-di-O-glucoside was found to be cytotoxic against inflammatory or colon cancer cells while sparing normal cells. On the other hand, due to the growing interest in therapeutic volatile fractions, we studied the chemical composition and antioxidant activity of volatile fractions of leaves and flowers of D. simplex. Based on the gas chromatography mass spectrometry technique (GC-MS), we have shown that both volatile fractions contain significant amounts of sulfur/nitrogen compounds, including 5-methylthiopentanenitrile and 1-isothiocyanatobutane, which might be involved in the antioxidant effect of flowers from D. simplex. In conclusion, our work revealed the axis PAR2/GSK3beta as a new survival pathway for colon stem cells and the therapeutic value of glucoflavonoids and volatile fractions of Diplotaxis species.

La mémoire Flash est actuellement extrêmement utilisée en tant que mémoire non volatile pour le stockage des données numériques dans presque tout type d'appareil électronique nomade (ordinateur portable, téléphone mobile, tablette, …). Pour dépasser ses limites actuelles (densité d'informations, endurance, rapidité), un grand nombre de recherches se développent notamment autour du concept de mémoires résistives qui repose sur la commutation entre différents niveaux de résistance, via l'application d'une tension.Les mémoires dont la variation de résistance dépend de réactions électrochimiques (ReRAM) sont potentiellement de bonnes candidates pour les mémoires non volatiles de prochaine génération; les mécanismes d'oxydo-réduction impliqués sont cependant souvent de type filamentaire, mettant notamment en jeu des migrations de cations d’éléments métalliques (provenant des électrodes), ou de lacunes d’oxygène. Ce caractère filamentaire rend difficilement atteignable la miniaturisation extrême, à l’échelle nanométrique.Dans cette thèse, une classe de matériaux particulière -utilisée dans le domaine du stockage d'énergie- est étudiée. L’objectif est d’approfondir l’origine des processus de commutation de résistance observés sur des films de LixCoO2. Nous caractérisons d'abord les propriétés structurales et électriques de tels films, ainsi que le comportement électrique des dispositifs élaborés à partir de ces films. Nous étudions ensuite les mécanismes électrochimiques qui sont à l’origine des commutations résistives, dans la configuration d’un contact micrométrique électrode/film/électrode. Nous cherchons à déterminer la validité d’un mécanisme qui avait été proposé auparavant, mais non démontré. Nous étudions également la cinétique de commutation des dispositifs, et proposons un modèle numérique permettant d’expliquer les résultats expérimentaux observés. Enfin, nous étudions l’applicabilité potentielle des dispositifs (intégrant les films de LixCoO2) aux mémoires Re-RAM au travers de leurs performances en termes d’endurance (nombre maximum de cycles d’écriture/effaçage), et de stabilité. En particulier, nous étudions l’influence de plusieurs paramètres (impulsions de tension, nature des électrodes, température et c…) sur ces performances. / Flash memory is now extensively used as non-volatile memory for digital data storage in most mobile electronic devices (laptop, mobile phone, tablet...). To overcome its current limits (e.g. low information density, low endurance and slow speed), many researches recently developed around the concept of resistive memories based on the switching between different resistance levels by applying appropriate bias voltages.Memories whose resistance variations depend on electrochemical reactions (ReRAM) are potentially good candidates towards next-generation non-volatile memories. The underlying redox mechanisms observed are however often of the filamentary type, involving in particular migration of cations of metal elements (coming from the electrodes), or oxygen vacancies. This filamentary character makes it challenging to attain extreme downscaling towards the nanometric scale.In this thesis, a particular class of materials - used in the field of energy storage - is studied. The aim is to investigate the origin of the resistance switching processes observed in LixCoO2 films. We first characterize the structural and electrical properties of such films, as well as the electrical behaviors of the devices elaborated therefrom. We then investigate the electrochemical mechanisms which are at the origin of resistive switching, in the micrometric electrode/film/electrode configuration. We try to determine the validity of a formerly proposed mechanism which was however not yet demonstrated. Furthermore, we study the experimental switching kinetics of devices, and propose a numerical model to explain the results observed. Finally, we examine the potential applicability of LixCoO2-based devices to Re-RAM memories through the study of their performances in terms of endurance (i.e. maximum number of write/erase cycles) and retention. Specifically, the influence of several parameters (such as voltage pulses, chemical nature of the electrodes, temperature etc.) on these performances is investigated.

.La jonction magnétique à effet tunnel, noyau de la mémoire MRAM (magnetic random access memory), a suscité beaucoup d'intérêt pour les technologies de stockage et de traitement de l'information de faible puissance. Cette thèse se concentre sur l'influence de l'effet de bord pour les propriétés magnétiques des nanodispositifs. Deux nanostructures magnétiques typiques sont concernés: nanopiliers MTJ sous un processus spécial d'encapsulation, et nanodots magnétiques avec la même structure que la couche libre de pilier MTJ.Tout d'abord, nous développons le processus de fabrication complet pour nanopiliers MTJ et nanodots magnétiques, qui est compatible avec la technologie standard du CMOS.Ensuite, un nouveau dispositif memristive hétérogène composé de nanopiliers MTJ entourés de commutateurs résistifs en silicium est étudié par la mesure de transport et la caractérisation structurale. Son application potentielle en tant que dispositif de mémoire à logique avec fonction de cryptage de la mémoire est discutée.Enfin, les nanodots magnétiques avec anisotropie magnétique perpendiculaire (Perpendicular Magnetic Anistopy, PMA) est étudiés par le microscope Kerr. Un modèle physique de la pression de Laplace appliqué sur un mouvement de DW aux bords des nanodots est chargé d'expliquer le décalage inattendu de la distribution du champ de commutation (switching field distribution, SFD) pour des nanodots de tailles variées / Magnetic tunnel junction (MTJ), the core of the magnetic random access memory (MRAM), have attracted intensive interest for low-power storage and information processing technologies. This thesis focuses on the discussion of the influence of edge effect for the magnetic proprieties of nanodevices. Two typical magnetic nanostructures are involved: MTJ nanopillar under a special encapsulation process, and magnetic nanodots with the same structure as the free layer of MTJ stack.First, we develop the full fabrication process for both MTJ nanopillar and magnetic nanodots, which is compatible with standard CMOS technology.Then, a novel heterogeneous memristive device composed of an MTJ nanopillars surrounded by resistive silicon switches is investigated by transport measurement and structural characterization. The potential application as a logic-in-memory device with memory encryption function is discussed.Finally, the magnetic nanodots with perpendicular magnetic anisotropy (PMA) is investigated using Kerr microscope. A physical model of Laplace pressure applied on a DW motion at the edges of nanodots is responsible for explaining the unexpected shifting of switching field distribution (SFD) for nanodots with varied sizes.

<div>To compensate for their sessile existence, plants synthesize and emit a wide diversity of volatile organic compounds (VOCs) that serve important biological functions pertaining to defense, reproduction, and plant-plant signaling. In addition to their importance in plant secondary metabolism, VOCs are used as fragrances, flavoring agents, and therapeutics. Plant metabolic engineering has successfully been implemented towards the design of value-added plants with enhanced defense, improved aroma and flavor, and increased production of specialty chemicals. However, rational design requires rigorous characterization of the mechanisms controlling metabolic fluxes in a network. Thus, the major aims of this dissertation are to study biological and physical mechanisms controlling the synthesis and emission of plant VOCs. This dissertation focuses on (i) modeling 2-phenylethanol biosynthesis in Arabidopsis and (ii) characterization of the biophysical properties of flower cuticles with respect to the emission of VOCs.</div><div><br></div><div>2-Phenylethanol (2-PE) is a naturally-occurring aromatic volatile with properties that make it a candidate oxygenate for petroleum-derived gasoline. In plants, 2-PE biosynthesis competes with the phenylpropanoid pathway for the common precursor L-phenylalanine (Phe). The phenylpropanoid pathway directs up to 30% of fixed carbon towards the production of lignin, a major constituent of plant cell walls that renders biomass recalcitrant to pretreatment techniques impeding the economical production of biofuels. An initial genetic engineering approach was proposed, whereby a portion of the carbon flux towards lignin production is diverted towards the biosynthesis 2-PE. Transgenic Arabidopsis thaliana expressing enzymes catalyzing the biosynthetic steps from Phe to 2-PE were generated. Excised stems from transgenic Arabidopsis were supplied 13C6-ring labeled Phe, and isotopic enrichment of downstream metabolites were quantified to calculate fluxes. By combining flux measurements with predictions from a kinetic model of the Phe metabolic network, we hypothesized that 2-PE biosynthesis in transgenic Arabidopsis was limited by endogenous pools of cytosolic Phe. Multiple independent genetic strategies were proposed based on model-guided predictions, such as inducing Phe hyper-accumulation, reduction of the activity of the competing phenylpropanoid pathway, and sequestering the 2-PE biosynthesis pathway in plastids. Combining kinetic modeling with time-course in vivo metabolomics led to successful rational engineering of 2-PE accumulating plants.</div><div><br></div><div>The plant cuticle is the physical interface between the flower and its surrounding environment. Passage of VOCs through the cuticle is driven solely by diffusion and is thus dependent on the cuticle physicochemical properties. Wax compounds in the cuticular matrix self-assemble into a multiphase system of crystalline and amorphous regions, where their relative amounts and arrangements govern VOC diffusion. To investigate the effect of wax composition on the crystallinity and permeability of the cuticle, we characterized the cuticular waxes of Petunia hybrida petals using GC-MS, FTIR, DSC, and XRD. Petal waxes were found to be enriched with long-chain hydrocarbons forming semi-crystalline waxes localized on petal surfaces. A ternary system of wax compounds was proposed as a model for petal cuticles to investigate the effect of wax composition on cuticle crystallinity and permeability. Atomistic simulations of VOC displacement in waxes of varying chemical composition were performed at 298 K and 1 bar under NPT conditions to estimate diffusivities. Wax anisotropy was found to be highly dependent on the elongation of methylene chains, restricting the molecular diffusion path. Changes in crystalline symmetry were found to have measurable effects on VOC diffusion. Simulations of compositional variants of the model cuticle shows that changes in relative crystallinity exert differential control on the dynamics of VOC emissions.</div><div><br></div><div>To directly determine the effect of the cuticle on VOC emissions in petunia flowers, the wax exporter PhABCG12 was silenced using RNA interference, resulting in flowers with thinner cuticles. However, VOC emissions were found to have significantly decreased in transgenic flowers relative to the wild-type control. Dewaxing wild-type and transgenic petunia revealed that the cuticle serves as a site of VOC build-up during emission, and deficient coverage limits the extent to which compounds can accumulate. In addition, the cuticle was found to impart differing levels of mass transfer resistance for certain VOCs, suggesting that the cuticle controls the dynamics of VOC emissions. Taken together, petal cuticles provide an additional layer of regulation in emission of VOCs from plants.</div><div><br></div>

Males of South American fruit fly Anastrepha fraterculus form leks and release sex pheromone to attract females during the reproductive behavior. The aim of my diploma thesis was to collect samples of volatiles released by variously old males, subsequently to analyze and to determine the changes in the quantitative composition of the sex pheromone depending on age. The volatiles were trapped on adsorbent, eluted with hexane containing internal standard and analyzed by gas chromatography with mass detection. Males release twenty volatiles, including fourteen terpenes: α-pinene, camphene, -pinene, myrcene, Δ3-carene, limonene, (Z)--ocimene, (E)--ocimene, aromadendrene, trans-α-bergamotene, (Z)-β-farnesene, (Z,E)-α-farnesene, germacrene D, (E,E)-α-farnesene; one aldehyde: nonanal; two alcohols: (3Z)-non-3-en-1-ol, (3Z,6Z)-nona-3,6-dien-1-ol and three lactones: suspensolide, anastrephin a epianastrephin. From the list of named compounds there were proved antenal activity of six compounds in previous work, namely trans-α-bergamotene, (Z,E)-α-farnesene, (E,E)-α-farnesene, (3Z)-non-3-en-1-ol, (3Z,6Z)-nona-3,6-dien-1-ol and epianastrephin.

Aujourd’hui, les applications de stockage de données utilisent principalement deux types de matériaux : les chalcogénures pour le stockage optique (e.g. Blu-Ray) et le silicium pour le stockage électronique (e.g. mémoires Flash). Malgré le fait qu’ils se soient avérés les plus efficaces pour des applications répandues, ces matériaux ont des limitations. Récemment, avec la montée en puissance du graphene, les allotropes du carbone ont été étudiés à la fois pour leurs propriétés intrinsèques et pour des applications ; ils ont des propriétés électroniques, thermiques et mécaniques très intéressantes qui peuvent rendre ces matériaux plus efficaces que les chalcogénures ou le silicium pour certaines applications. Dans cette thèse, nous étudions la faisabilité et le potentiel du carbone comme matériau pour le stockage de données.Nous nous concentrons d’abord sur le développement de stockage optique. Nous découvrons que les lasers continus et pulsés peuvent être utilisés pour induire des changements de phase réversibles dans des couches minces de carbone, confirmant la possibilité d’utiliser le carbone comme un matériau pour le stockage optique. De plus, nous découvrons plusieurs nouveaux phénomènes, que nous expliquons en utilisant des techniques de caractérisation avancées et de la modélisation par ordinateur de la propagation thermique dans le carbone.Ensuite, nous nous concentrons sur le stockage de données électronique en développant des mémoires à base de graphene qui peuvent être dans deux états de résistance bien séparés pour un grand nombre de cycles. Pour évaluer le potentiel de cette technologie, on caractérise le mécanisme de changement de résistance et on développe un modèle électromécanique qui permet de prédire les meilleures performances atteignables : ces mémoires ont le potentiel de commuter bien plus rapidement que les mémoires Flash tout en étant non-volatiles. / Today, data storage applications rely mainly on two types of materials: chalcogenides for optical storage (e.g. Blu-Ray) and silicon for electronic storage (e.g. Flash memory). While these materials have proven to be the most efficient for widespread applications, both have limitations. Recently, with the rise of graphene, carbon allotropes have been studied both for their intrinsic properties and for applications; graphene and other carbon allotropes have very interesting electronic, thermal and mechanical properties that can make these materials more efficient than either chalcogenides or silicon for certain applications. In this thesis, we study the feasibility and potential of the usage of carbon as a data storage material.Firstly, we focus on developing optical data storage. It is found that both continuous-wave and pulsed lasers can be used to induce reversible phase changes in carbon thin films, thus opening the way toward carbon-based data storage. Along the way, several phenomena are discovered, shown and explained by using advanced characterization techniques and thermal modelling.Secondly, we focus on electronic data storage by developing graphene-based memories that are found to switch reliably between two well-separated resistance states for a large number of cycles. To assess the potential of this new technology, we characterize the switching mechanism and develop an electro-mechanical model enabling to predict the best performances attainable: these memories would potentially be much faster than Flash memories while playing the same role (non-volatile storage).