Volume changes are one of the priority characteristics of concrete that plays an important role place mainly in the durability of structures as such. These low volume changes are required especially for structures as: industrial concrete floors, massive structures and waterproof structures. One of the possibilities in reducing these changes is the use of mineral admixtures with suitable grain curve of aggregate. Another possibility is the use of shrinkage reducing admixtures. There can occur problem with efficiency (long term age) with other components of the mixture. Therefore, the effort of this work is to use the avaible processes for maximum reduction of shrinkage and hydration temperatures.

In the construction industry, concrete is the most common material, because of its good properties such as compressive strength and endurance. Concrete is a composition of several different materials where one of the main components is cement. When the hydration process starts, large amount of heat is generated. This leads to temperature rise within the structure. The heat development that takes place can become critical for massive structures such as dams and power plants, where natural cooling is not sufficient. This in combination with internal and external restraint resulting in tensions causing cracks in the structure. By controlling the temperature development, one can reduce the risk of cracking in massive structures. The controlling is divided into pre-cooling and post-cooling. Reduction of the risk for thermal cracking can be done in different ways. Parts of the cement in the concrete can be replaced by a pozzolan material such as silica fume, blast furnace slag or fly ash. Another method is to increase the size of the aggregates which makes it possible to reduce the cement content with remained strength. Cooling the aggregates or use of ice can also be used as a pre-cooling methods. The most common post-cooling method is the installation of cooling pipes. Pipes are installed between the reinforcement bars, in which one then pump through with cold water. This thesis aims at practicing the methods examined by Lagundžija & Thiam (2017). Focusing on those results that proved to be most effective, i.e. the combination of fly ash, ice and large aggregates. The results retrieved during the tests shows a significant increase in the compressive strength when using a combination of fly ash, ice and large aggregates. This gives us the opportunity to reduce the initial cement content. Reducing the cement content is the most effective factor regarding the heat development. When replacing amounts of the water with ice, it can be seen that the initial casting temperature was reduced. Further studies can be done to find the right amount of reduction of the cement that can be done while maintaining the required compressive strength. / Inom byggbranschen är betong det mest förekommande materialet, detta tack vare dess goda egenskaper, som till exempel tryckhållfasthet och uthållighet. Betongen utgörs av flera olika beståndsdelar där den centrala komponenten är cement. När cementets hydratationsprocess startar utvecklas en markant värmeutveckling. Detta leder till temperaturhöjningar inuti den nygjutna konstruktionen. Värmeutvecklingen kan bli kritisk för grövre konstruktioner, som till exempel dammar och kraftverk, där naturlig avkylning inte är tillräcklig. Detta i kombination med att inre och yttre tvång resulterar i dragspänningar som orsakar sprickor i konstruktionen. Genom att styra temperaturutvecklingen kan man minska risken för sprickbildning i massiva konstruktioner. Styrningen delas in i förberedande kylning och efterkylning. Reduktion av risken för termisk sprickbildning kan ske på olika sätt. Delar av cementen i betongen kan ersättas med ett puzzolant material som till exempel silikatstoft, masugnsslagg eller flygaska. En annan metod är att öka ballaststorleken vilket gör det möjligt att minska cementhalten med kvarvarande hållfasthet. Man kan även kyla ballasten alternativt blanda in is i mixen för att sänka den initiala temperaturen. Den mest förekommande efterkylningsmetoden är installation av kylrör. Det monteras in rör mellan armeringsjärnen, vilket man sedan pumpar kallt vatten igenom. Denna uppsats syftar på att praktiskt tillämpa de metoder som undersöktes av Lagundžija & Thiam (2017). Fokus på de resultat som visade sig vara mest effektiva, dvs kombinationen av flygaska, is och grov ballast. Resultaten som uppnåddes under de tester som utfördes visar en markant ökning i tryckhållfastheten vid användning av kombinationen med flygaska, is och grov ballast. Detta ger oss utrymmet att reducera den initiala cementhalten som används. Att minska cementinnehållet är den faktor som ger störst effekt gällande värmeutvecklingen. Fortsatta studier kan göras för att hitta rätt mängd reduktion av cementet som kan göras samtidigt som anvisad tryckhållfasthet bibehålls.

Cement hydration is the result of a series of simultaneous chemical reactions occurring during the production of concrete. An excessive amount of heat is generated, which consequently may give rise to thermal stresses and cause early age cracks in concrete that may affect its structural integrity, and load bearing capacity. Incorporating fly ash into the concrete mixture has shown to be an efficient method to reduce the temperatures developed during early age hydration, especially for massive concrete structures. Fly ash does additionally affect the concrete's development of compressive strength, tensile strength and Young's modulus. The MahanaKhon tower's mat foundation is divided into 14 layers, with fly ash incorporated in the concrete mix. A finite element model was developed of the mat foundation with COMSOL Multiphysics to simulate the developed temperatures and thermal stresses during curing. The simulations were carried out as parametric studies with different strain reference temperatures. The simulated temperatures were compared with existing temperature measurements that were conducted in three different elevations in each concrete layer. The result of the temperature analyses showed that the measured temperatures were generally larger than the simulated ones, which may have been the result of the numerical model's heat conductivity and convective heat transfer coeffcient not reflecting the actual case. Furthermore, the numerical model did not take into account the effects of solar radiation, which would most likely have increased the temperature of the concrete. The maximum simulated temperatures were mostly found in the center level of the concrete, followed by the lower level, and the lowest at the top. It was also observed that the maximum temperatures in some of the mat foundation layers could exceed 70 °C, which is generally considered high since the risk of delayed ettringite formation may arise. The large temperature is partially a result of not using cooling methods, such as cooling pipes, but also due to the high initial and ambient temperatures. The result of the thermal stress analyses showed that no tensile stresses arose when the strain reference temperature, Tref, was specified to 30 °C, corresponding to the mean ambient temperature. This is due to the concrete temperature not falling below Tref, and the concrete will therefore be in expansion and only be subject to compressive stresses. Increasing Tref to 50 °C, which was considered a reasonable estimation, resulted in developed tensile stresses in all mat foundation layers, where the majority of the mat foundation layers showed a risk of superficial surface cracks. The maximum tensile stresses were found at the final time of the simulations, which was expected, since the temperatures were at their lowest as a result of removing the curing insulation. Finally, setting Tref to 70 °C, corresponding to the maximum temperature during hardening, increased the induced tensile stresses considerably, due to the large temperature gradient between Tref and the concrete temperature. The maximum stresses were, as expected, located at the top level and caused by internal restraint. The second largest tensile stresses were found in the center level, also subject to internal restraint. The lowest tensile stresses were located in the lower level, subject to external restraint. / Cementhydratation är resultatet av en serie kemiska reaktioner som sker under tillverkningen av betong. Stora mängder värme genereras, vilket följaktligen kan ge upphov till termiska spänningar och orsaka tidig sprickbildning som påverkar betongens hållfasthet, och bärförmåga. Inkludering av flygaska i betongblandningen har visat sig vara en effektiv metod avsedd att minska temperaturerna som utvecklas under hydratationen i ung betong, särskilt i massiva betongkonstruktioner. Flygaska påverkar också betongens utveckling av tryckhållfasthet, draghållfasthet och elasticitetsmodul. MahanaKhon towers bottenplatta är uppdelad i 14 lager, där flygaska inkluderades i bottenplattans betong. En finit elementmodell av bottenplattan skapades i COMSOL Multiphysics, där de utvecklade temperaturerna och termiska spänningarna i den unga betongen simulerades under bottenplattans härdningsfas. Simuleringarna genomfördes som parameterstudier med olika referenstemperaturer. De simulerade temperaturerna jämfördes vidare med befintliga temperaturmätningar som utfördes i tre olika elevationer i varje gjutetapp. Resultaten av temperaturerna visade att de uppmätta temperaturerna var generellt högre än de simulerade, vilket bland annat kan bero på att betongens värmeledningsförmåga, samt konvektiva värmeöverföringskoefficient inte återspeglade det aktuella fallet. Den numeriska modellen tog inte heller hänsyn till effekten av solinstrålning, som sannolikt skulle ökat betongens temperatur. De maximala temperaturerna hittades mestadels i betongens mittnivå, följt av den lägre nivån och slutligen lägsta nivåerna vid toppen. Det observerades även att de maximala temperaturerna i bottenplattan kunde överstiga 70 °C, vilket generellt anses vara högt då risken för fördröjd ettringitbildning kan uppstå. De höga temperaturerna beror delvis på avsaknad av kylmetoder, såsom kylrör, men även på den höga initialtemperaturen och omgivningstemperaturen. Resultaten av spänningsanalysen påvisade att inga dragspänningar uppstod när referenstemperaturen Tref denierades till 30 °C, som motsvarar den genomsnittliga omgivningstemperaturen. Detta förklaras av att betongen kommer att vara i expansion och följaktligen endast utsättas för tryckspänningar. Efter att Tref ökats till 50 °C, vilken ansågs vara en rimlig estimering i denna studie, uppstod dragspänningar i alla lager i bottenplattan, där vissa utsattes för risk för ytsprickor. De maximala dragspänningarna uppstod vid simuleringarnas slut, vilket var förväntat då temperaturerna var som lägst vid den tidpunkten till följd av att isoleringen avlägsnades. Slutligen höjdes Tref till 70 °C, vilket motsvarar den maximala temperaturen i bottenplattan under härdning. De inducerade dragspänningarna ökade avsevärt på grund av den stora temperaturgradienten mellan Tref och betongtemperaturen. Samtliga lager utsattes i detta fall för risk för genomgående sprickor. De maximala dragspänningarna påträffades på toppnivån och orsakades av inre tvång. De näst största dragspänningarna fanns i mitten av plattan och var också resultatet av inre tvång. De lägsta dragspänningarna påträffades vid plattans lägre nivå, som utsattes för yttre tvång.

The heat development that occurs due to the hydration of cement is important to consider during casting of massive concrete structures. By using computer programs that are based on finite element methods (FEM), simulations can be performed on the heat- and strength development. In this project, a FE program called ConTeSt has been used in order to predict the temperature- and strain development in a massive concrete wall. If the potential risks in a concrete structure are evaluated before casting, economical savings, including a better casting plan could be obtained. The structure under investigation was a concrete wall behind one of the spillways in the hydro power dam of Storfinnforsen. Due to a re-construction of the wall, an opportunity occurred to develop a measurement plan of the casting and perform simulations on the wall. A sensitivity analysis was performed in order to investigate the effects on the temperature- and strain development, by varying the cement content, ambient temperature, wind speed and degree of restraint in translation. The results showed, that a higher cement content increased the rate of hydration and hence the temperature in the concrete. Higher wind speeds contributed to more cooling of the concrete which, in some cases, resulted in cracking due to contraction of the material. Cracking due to contraction also occurred when the ambient temperature was decreased. The ambient temperature did not have a significant impact on the rate of hydration, but instead the impact was larger from the initial temperature of the fresh concrete. A higher initial temperature of the fresh concrete increased the rate of hydration, which increased the temperature in the material. The degree of restraint could only be varied in translation in ConTeSt and hence the effect on the strain development was not that significant. A crack risk analysis was performed where the developed tensile stresses were compared with the tensile strength of the concrete. The same factors were varied as in the sensitivity analysis. The results showed that the tensile strength was exceeded for most of the cases and thus that the crack risk was high. The required equipment, in order to perform the measurements on site, consisted of 7 strain gauges of the module KM-100B from TML Tokyo Sokki Kenkyujo, 2 data loggers of the module Spider-8 from HBM, at least a 25 m ø9 mm 5-core shielded cable and a computer with the software Catman Easy. / Värmeutvecklingen som uppstår på grund av hydratationen av cement är viktig att beakta vid gjutning av massiva betongkonstruktioner. Detta brukar göras genom simuleringar av värmeutvecklingen och hållfasthetstillväxten med hjälp av olika finita element (FE) program. I detta projekt har programmet ConTeSt använts för att på förhand kunna förutse temperatur - och töjningsutvecklingen i en massiv betongvägg. I och med detta kan bl.a. gjutningen planeras bättre samtidigt som ekonomiska besparingar kan åstadkommas om eventuella risker kan kartläggas innan gjutningen påbörjas. En ledmur bakom ett av utskoven i Storfinnforsens kraftverk undersöktes närmare i samband med en ombyggnad. Möjligheten uppstod att planera en mätning av gjutningen av ledmuren samt att utföra simuleringar av väggen i ConTeSt. En känslighetsanalys utfördes för att undersöka effekterna på temperatur- och töjningsutvecklingen genom att variera cementhalten, omgivningstemperaturen, vindhastigheten och graden av tvång i förskjutningen i längdriktningen av väggen. Resultaten visade att högre cementhalter ökade graden av hydratation vilket ökade temperaturen i betongen. Högre vindhastigheter bidrog till snabbare kylning av betongen vilket i vissa fall lett till sprickor på grund av kontraktion av materialet. Sprickor till följd av kontraktion uppstod även då omgivningstemperaturen sänktes. Omgivningstemperaturen hade ingen större påverkan på hydratationen, utan istället var det temperaturen av den färska betongmassan som visade större påverkan. Högre temperatur av den färska betongmassan ökade graden av hydratation vilket ökade temperaturen i betongen. Graden av tvång kunde i ConTeSt endast varieras i förskjutningen i längdriktningen av väggen vilket inte hade någon större effekt på töjningsutvecklingen. En sprickrisk analys utfördes där den utvecklade dragspänningen jämfördes med draghållfastheten. Analysen utfördes genom att variera samma faktorer som varierades i känslighetsanalysen. Resultaten visade att draghållfastheten överskreds i de flesta fall och att därmed sprickrisken var hög. För att genomföra mätningen blev slutsatsen att det behövs 7 st töjningsgivare av modell KM-100B från TML Tokyo Sokki Kenkyujo, 2 st data logger av typ Spider8 från HBM samt minst en 25 m ø9 mm skärmad 5-kärnkabel, inklusive en dator med programvaran Catman Easy.

[pt] O presente estudo busca definir uma relação de mistura estável utilizando aditivos poliméricos à base de álcool polivinílico (PVOH) para controlar a perda de filtrado, antiespumante e dispersante, caracterizando a influência de cada adição na cinética de hidratação, propriedades mecânicas, físicas e reologia da mistura. Além disso, foi caracterizado o comportamento das pastas de cimento em condições de cura que simulam a situação do poço até 6100 m de profundidade, seguindo as recomendações da API, e o comportamento do material nos estados in situ, utilizando pressões confinantes para realizar os ensaios de compressão. Por fim, propôs-se a inclusão de microfibras de álcool polivinílico (PVA) para melhorar o desempenho mecânico das pastas cimentícias, avaliando diferentes tipos de carregamento e definindo os impactos da adição de fibras na viscosidade e tixotropia das misturas. Verificou-se que o uso de PVOH como aditivo de perda de filtrado não influencia na cinética de hidratação para concentrações de até 0,4% em peso de cimento, mas à medida que a quantidade de PVOH é aumentada na mistura, o processo de hidratação da pasta de cimento pode ser modificado por causa do mecanismo de absorção do PVOH. Além disso, novas fases de produtos de hidratação aparecem com o aumento da temperatura e pressão de cura: dellaite, hydroxyellestadite e alpha-C2SH. A última fase (alpha-C2SH) está relacionada à perda de capacidade de resistência das amostras curadas a 149°C, simulando o caso do poço de petróleo de 6100 m de profundidade. Para os ensaios triaxiais, a pressão de confinamento conferiu às amostras um comportamento diferente do caso uniaxial, implicando em uma considerável melhora da plasticidade no comportamento tensão-deformação. Embora se observe algum reforço por atrito devido a tensões de cisalhamento no plano das fissuras, o efeito mais importante do confinamento é suportar a deformação dúctil, mesmo para o caso da pasta de cimento reforçada com fibra de PVA. Finalmente, o estudo mostrou que as fibras de PVA conferem um leve aumento da viscosidade da pasta de cimento, uma fase plástica prolongada aparentemente sem perda de capacidade de carga em testes triaxiais e uma capacidade aprimorada de absorver energia ao avaliar cargas de tração e cisalhamento. / [en] The present study seeks to define a stable mixing ratio using powder Polyvinyl Alcohol (PVOH) based polymeric additives to control the loss of filtrate, defoamer, and dispersant, characterizing the influence of each addition on hydration kinetics, mechanical and physical properties, and rheology of the mix. The behavior of cement pastes under curing conditions that simulate the wellbore situation up to 6100 m depth was also evaluated, following API recommendations. Moreover, the behavior of the material under in situ states, using confining pressures to perform the compression tests, was characterized. Finally, the inclusion of Polyvinyl Alcohol (PVA) microfibers is proposed to improve the mechanical performance of cement pastes, evaluating different types of loading and defining the impacts of the fiber addition on the viscosity and thixotropy of the mixtures. It was found that the use of PVOH as a fluid loss additive does not influence hydration kinetics for concentrations up to 0.4% by weight of cement, but as the amount of PVOH is increased in the mixture, the hydration process of the cement paste may be modified because of the PVOH absorptive mechanism. Moreover, new hydration products phases appear with increasing curing temperature and pressure: dellaite, hydroxyellestadite, and alpha-C2SH. The last phase (alpha-C2SH) is related to the loss of strength capacity of the samples cured at 149°C, simulating a 6100 m depth wellbore. For the triaxial tests, the confining pressure gave the samples a behavior markedly different from the uniaxial case, implying a considerable improvement in the plasticity of the stress-strain behavior. Although some frictional reinforcement is observed due to shear stresses in the cracks surface, the most important effect of confinement is to withstand ductile deformation, even in the case of PVA fiber-reinforced cement paste. Finally, the study has shown that PVA fibers impart a slight viscosifying effect on the cement slurry, a prolonged plastic phase with apparently no loss of load-carrying capacity in triaxial tests, and an improved ability to absorb energy when evaluating tensile and shear loads.

Anhand von theoretischen Untersuchungen wird eine umfassende Beschreibung von kleinen Metalloxidclustern gegeben. Bei den untersuchten Systemen handelt es sich um Aluminium- und Eisenoxid-Ionen sowie entsprechende Oxid-Cluster, die beide Metalle enthalten. Neben der Bestimmung der geometrischen Struktur der Cluster werden auch die allgemeinen elektronischen Eigenschaften der eisenhaltigen Verbindungen untersucht. Alle Vorhersagen werden durch Vergleich mit verfügbaren experimentellen Ergebnissen -- hauptsächlich aus der Infrarot-Photodissoziations- und der Photoelektronenspektroskopie -- überprüft und bewertet. Soweit möglich werden die Bewegungen von Atomen oder kleinen Gruppen innerhalb der Cluster einzelnen experimentellen Signalen zugeordnet. Besondere Aufmerksamkeit wird dem Eisendioxidmolekül und seinem Anion gewidmet. Es wird mit spezialisierten Wellenfunktionsmethoden untersucht, mit denen ab initio Franck-Condon-Simulationen einschließlich nicht-adiabatischer und Spin-Orbit-Kopplungen für die Photoionisation des Anions erstellt werden. Sie liefern Erklärungen für die komplizierte Schwingungsstruktur des experimentellen hochauflösenden Photoelektronenspektrums. / By means of theoretical investigations, a comprehensive description of small metal oxide clusters is given. The studied systems are aluminum and iron oxide ions as well as respective bi-metallic oxide clusters. Besides the determination of the geometrical structure of the clusters, the general electronic properties of the iron-containing compounds are investigated. All predictions are checked and assessed by comparison with available experimental results, mainly infrared photodissociation and photoelectron spectroscopy measurements. As far as possible, motions of atoms or small groups within the clusters are assigned to distinct experimental vibrational features. Particular attention is paid to the iron dioxide molecule and its anion. It is studied with sophisticated wave function methods based on which ab initio Franck-Condon simulations for the photodetachment from the anion, including non-adiabatic and spin-orbit couplings, are generated. They provide explanations for the complicated vibrational structure of the experimental high-resolution photoelectron spectrum.

Das Verhalten von durch Graphen oder Graphenoxid (GO) begrenzten Molekülen hat sich, bedingt durch die bemerkenswerten strukturellen und optischen Eigenschaften dieser quasi-zweidimensionalen Materialien, als vielversprechendes Forschungsfeld erwiesen. Die vorliegende Arbeit konzentriert sich auf das Hydrationsverhalten von GO und das Verhalten kleiner, von Graphen begrenzter Moleküle. In dieser Arbeit wurde auf Rasterkraftmikroskopie (SFM) zurückgegriffen, um die GO-Hydration zu untersuchen. Die Ergebnisse zeigen ein graduelles bzw. stufenweises Ansteigen des durchschnittlichen Schichtabstands für relative Luftfeuchtigkeiten (RH) unter halb von 80%, beziehungsweise in flüssigem Wasser. Diese experimentellen Beobachtungen stimmen mit den XRD an vielschichtigem GO in der Literatur überein. Die hier gezeigten Ergebnisse lassen jedoch den angenommenen Einlagerungseffekt, bei der Hydrierung von GO bei geringer RH, außen vor. Stattdessen wird die allmähliche Ausdehnung der kontinuierlichen Einlagerung von Wassermolekülen in den einzelnen GO-Schichten zugeschrieben, während die stufenweise Ausdehnung im komplett in Wasser getauchten Zustand auf das Eindringen einer ganzen Wassermonolage zurückgeführt wird. Andererseits könnte die Grenzfläche zwischen Graphen und dem Substrat ein begrenztes elektrisches Feld aufweisen, das ein weit verbreitetes, auf Ladungstransfer an Grenzflächen zurückzuführendes Phänomen darstellt. Die vorliegende Arbeit behandelt dieses Thema unter Nutzung von Rhodamin 6G (R6G) als Molekül zwischen Graphen und Glimmer, die es begrenzen. Eine Rot-Verschiebung der R6G-Maxima bei geringer RH wird sowohl auf elektrische Felder, die sich auf die Moleküle auswirken, als auch auf mechanische Deformationen der R6G-Struktur an der Grenzschicht zurückgeführt. Die Stärke des elektrischen Feldes wird anhand des Graphen-Raman-Spektrums auf etwa 1 V/nm abgeschätzt. / The behavior of molecules confined by graphene or graphene oxide (GO) has proven to be a promising area of research owing to the remarkable structural and optical properties of these quasi two-dimensional materials. This thesis focuses on the hydration behavior of GO and the behavior of small molecules confined by graphene. In this work, scanning force microscopy (SFM) has been employed to investigate the hydration of GO. The results show a gradual and a step-like increase of the average interlayer distance for relative humidities (RH) below 80% and in liquid water, respectively. These experimental observations are consistent with XRD results on multilayered graphite oxide as reported in the literature. However, the results presented here exclude the postulated interstratification effect, for hydration of GO at low RH. Instead, the gradual expansion is attributed to the continuous incorporation of water molecules into single GO layers, while the step-like expansion when completely immersed in water, is attributed to the insertion of a full monolayer of water. On the other hand, the interface between graphene and its substrate may exhibit a confined electric field, a common phenomenon due to charge transfer at interfaces. In this work, this subject is addressed using Rhodamine 6G (R6G) as a probe molecule confined between graphene and mica. A red shift of the RG6 peaks at low RH is argued to be due to both, electric fields acting on the molecules and mechanical deformation of the R6G structure at the interface. The strength of the field is estimated from the graphene Raman spectra to be on the order of 1 V/nm.

The need for energy efficient, clean and quiet, energy conversion devices for mobile and stationary applications has presented proton exchange membrane (PEM) fuel cells as a potential energy source. The use of PEM fuel cells for automotive and other transient applications, where there are rapid changes in load, presents a need for better understanding of transient behavior. In particular at low humidity operations; one of the factors critical to the performance and durability of fuel cell systems is water transport in various fuel cell layers, including water absorption in membrane. An essential aspect to optimization of transient behavior of fuel cells is a fundamental understanding of response of fuel cell system to dynamic changes in load and operating parameters. This forms the first objective of the dissertation. An insight in to the time scales associated with various transport phenomena will be discussed in detail. In the second component on the study, the effects of membrane properties on the dynamic behavior of the fuel cells are analyzed with focus on membrane dry-out for low humidity operations. The mechanical behavior of the membrane is directly related to the changes in humidity levels in membrane and is explored as a part third objective of the dissertation. Numerical studies addressing this objective will be presented. Finally, porous media undergoing physical deposition (or erosion) are common in many applications, including electrochemical systems such as fuel cells (for example, electrodes, catalyst layer s, etc.) and batteries. The transport properties of these porous media are a function of the deposition and the change in the porous structures with time. A dynamic fractal model is introduced to describe such structures undergoing deposition and, in turn, to evaluate the changes in their physical properties as a function of the deposition. / Ph. D.

Die Energierelaxationsdynamik und strukturelle Dynamik der DNA spielen eine entscheidende Rolle für das Verständnis der photochemischen Eigenschaften und biologischen Funktion von DNA. Die schnellsten Prozesse geschehen dabei auf Zeitskalen im Femto- bis Pikosekundenbereich und können durch zeitaufgelöste (ultraschnelle) Messungen an molekularen Schwingungsanregungen in Echtzeit beobachtet werden. In dieser Arbeit werden NH-Streck Schwingungsmoden der Nukleobasen sowie OH-Streckmoden der Hydrathülle mittels linearer infrarot (IR) Spektroskopie sowie ultraschneller Pump-Probe und zweidimensionaler IR Spektroskopie untersucht. Messungen an monomerartigen Nukleobasen, wasserstoffverbrückten Nukleobasenpaaren und kurzen DNA Fragmenten in Doppelhelixstruktur ermöglichen es, die Effekte der verschiedenen Wasserstoffbrücken und Schwingungskopplungen separat voneinander zu untersuchen. Im Zusammenspiel mit exzitonischen und quantenchemischen Rechnungen werden so weitreichende Einsichten in die spektroskopischen Eigenschaften und die Relaxationsdynamik von Schwingungsanregungen in DNA gewonnen. Es wird u.a. gezeigt, dass Wasserstoffbrücken zwischen Nukleobasen eine Lebensdauer größer 1 ps besitzen und eine beschleunigte Energierelaxation durch Fermiresonanzen mit niederfrequenten Schwingungsmoden des Fingerprintbereichs bewirken. Die DNA-Hydrathülle zeigt eine ultraschnelle strukturelle Dynamik unabhängig von der Basenpaarzusammensetzung und fungiert als effiziente Wärmesenke für hochfrequente Schwingungsanregungen. / Energy relaxation and structural dynamics in DNA play a crucial role for the understanding of the photochemical properties and biological function of DNA. The fastest of such processes occur on the femto- to picosecond time scale and can be followed in real time through time-resolved (ultrafast) measurements on molecular vibrations. In this work, NH stretching excitations of nucleobases and OH stretching modes of the hydration shell are analyzed through linear infrared (IR) spectroscopy as well as ultrafast pump-probe and two-dimensional IR spectroscopy. Measurements on monomeric nucleobases, hydrogen-bonded nucleobase pairs, and short DNA fragments in double helix structure allow one to examine the effects of the different hydrogen bonds and vibrational couplings separately from each other. The combination with excitonic and quantum chemical calculations provides profound new insights into the spectroscopic properties and relaxation dynamics of vibrational excitations in DNA. This work shows that hydrogen bonds between nucleobases have a lifetime greater than 1 ps and lead to an accelerated dissipation of energy due to Fermi resonances with vibrational modes in the fingerprint range. The hydration shell of DNA exhibits ultrafast structural dynamics independent of the base pair composition and serves as an efficient heat sink for high-energy vibrational excitations.

La peau est l’organe le plus étendu du corps humain. Doté d’une membrane biologique fine appelée la couche cornée, celle-ci le protège du desséchement et des agressions extérieures chimiques ou mécaniques auxquelles le corps humain doit faire face. Ce travail de thèse a consisté, dans un premier temps, à décrire via la littérature existante les effets de l’âge,dûs au vieillissement intrinsèque et extrinsèque,sur la physiologie cutanée du Stratum Corneum (SC).La partie expérimentale basée sur la microscopie vibrationnelle traitera des variations de la fonction barrière et de l’hydratation du SC lors du vieillissement chronologique et photo-vieillissement. D’autres méthodes ont également été utilisées comme la chromatographie liquide en phase normale couplée à la spectrométrie de masse haute résolution dotée d’une source APCI et d’un détecteur Orbitrap pour l’étude de la composition détaillée des lipides du SC ainsi que des méthodes plus globales comme la PIE ou la cornéométrie. Le caractère non invasif de toutes ces méthodes a permis de réaliser ces études in vivo. L’évolution de la fonction barrière a été étudiée aux niveaux tissulaire, moléculaire et supramoléculaire par micro-spectroscopie confocale Raman et spectroscopie Infrarouge. Puis le lien moléculaire a été fait entre le vieillissement intrinsèque et les céramides de la matrice lipidique intercornéocytaires par chromatographie en phase liquide couplée à la spectrométrie de masse. Les molécules discriminantes entre population jeune et âgée ont été déterminées par analyse chimiométrique. L’évolution de l’hydratation cutanée aux niveaux tissulaire, moléculaire et supramoléculaire a également été l’objet d’une investigation approfondie. Les variations de la composition des NMF et la teneur en eau dans le SC lors du vieillissement cutané ont été mises en lumière en utilisant des descripteurs spectraux Raman. Les variations structurelles des molécules d’eau impactant l’organisation supramoléculaire des édifices lipidiques ont également été évaluées. Au cours du vieillissement, la fonction barrière cutanée et hydratation sont conservées. / Skin is the external surface defining the human body in space. Its outer-most layer is a thin biological membrane, called Stratum Corneum(SC), that protects the internal organs from desiccation as well as chemical or mechanical external aggressions. The present thesis aimsin a first step, to summarize the current knowledge regarding the effects of intrinsic and extrinsic aging on SCphysiology,based on available literature. The experimental part addresses the gaps in our understanding of the effects of chronological aging and photoaging on the SC barrier function and hydration, using traditional methods (such as trans epidermal water loss and skin conductance) as well as more advanced ones (vibrational spectroscopies, liquid chromatography in normal phase tandem mass spectrometry high resolution with an APCI source and an Orbitrap detector. As these methods are non-invasive, all studies have been carried out in vivo. The evolution of the barrier function has been studied at the tissular, molecular and supramolecular levels using confocal Raman micro-spectroscopy and infrared spectroscopy. Then the link between the intrinsic aging and the ceramides of the intercorneocytary lipid matrix has been studied by liquid chromatography tandem mass spectrometry. The discriminant molecules between young and old population have been identified by a chemometric analysis. The evolution of cutaneous hydration at the tissular, molecular and supramolecular level has also been investigated. The variations in the NMF composition and the SC water content have been studied by Raman spectral descriptors. Moreover, the structural variations of water molecules impacting the supramolecular organization of the lipid structures have been evaluated. Chronological aging and chronic exposure to environmental factors mildly affect SC barrier function and hydration levels. However, the processes controlling these properties are affected by aging in a site-dependent fashion.