Materials have always had a large impact on society over the different ages. Piezoelectric materials are the often ‘invisible’ materials which find widespread use, unknown to the general public by large. Mobile electronics, automotive systems, medical and industrial systems are few of the key areas where ‘piezoelectricity’ is indispensable. The parking sensor of our car uses the effect and even the echo to image an unborn baby in a womb requires the exploitation of the piezoelectric effect. The work presented in this thesis investigates the piezoelectric effect in semiconductors, namely in III V, III N and II VI materials to have a better understanding and design potential applications in light emitting diodes (LEDs) and other electronic devices. The current work focuses on the non-linear behaviour in the strain of the piezo effect, which is manifested by the generation of electric field under crystal deformation. Previous works have already confirmed the reports of the existence of non-linear piezoelectric effects in zincblende III V semiconductors. Here, the same semiempirical approach using Density Functional Theory has been utilized to investigate the strain dependent elastic and dielectric properties of wurtzite III N materials. While we report the strong non-linear strain induced piezoelectric behaviour with second order coefficients, all spontaneous polarization terms are substantially smaller than the previously proposed values. We show that, unlike existing models, our calculated piezoelectric coefficients and nonlinear model provide a close match to the internal piezoelectric fields of quantum well and superlattice structures. Also, pressure dependence of the piezoelectric field in InGaN based LEDs predicts a significant improvement of the spontaneous emission rate can be achieved as a result of a reduction of the internal field. The LED devices using the proposed structures including a metamorphic layer under the active region of the device are expected to increase their light output power by up to 10%. We also explored the impact of the non-linear piezo effect in nanowires and present a further theoretical computational study of single photon sources optimization in InGaN based wurtzite single quantum dots. We observed the light emission can be made by those single photon sources covering the entire visible spectrum through suitable change in the alloy composition.

Ces travaux présentent une nouvelle méthode de conception dont l’objectif est de maximiser la durée de vie d’une structure en béton armé soumise à la carbonatation et de minimiser ses impacts environnementaux sur son cycle de vie. Cette approche est basée sur le développement d’un nouveau métamodèle de carbonatation couplé à une approche d’Analyse de Cycle de Vie (ACV). Une recherche de leviers d’actions sur la durabilité et les impacts environnementaux est réalisée via une combinaison de deux méthodes d’analyse de sensibilité. Nous définissons les leviers d’action comme étant des paramètres technologiques influents sur la durée de vie et/ou les impacts environnementaux de la structure en béton armé étudiée. Notre approche est appliquée au cas d’étude d’une structure en béton armé soumise à la carbonatation pour une durée de vie prévue de 100 ans située à Madrid, dans une classe d’exposition XC4 selon la norme EN 206-1. Pour ce cas d’application nous trouvons que la solution la plus durable et la plus respectueuse de l’environnent est celle utilisant du ciment CEM III/C, en minimisant le rapport eau sur ciment, l’épaisseur du béton d’enrobage, et la distance de la centrale fournissant le béton au site de construction. / This thesis presents a new design approach of which objective is to maximize service life of reinforced concrete structure and minimize its environmental impacts. This approach is based on the development of a new carbonation meta-model coupled with Life Cycle Assessment (LCA). A search for action levers on both durability and environmental impacts is conducted using a combination of two sensitivity analysis methods. We define action levers as technological parameters that are found influential on service life and/or environmental impacts for the studied reinforced concrete structure. Our approach is applied to a case study of a reinforced concrete structure design for a 100-year service life and located in Madrid within a XC4 exposure class according to the EN 206-1 standard. In that case study, we find that the most favorable solution for the RC structure is designed with the lowest cement content, water-to-cement ratio, concrete cover depth and distance from the concrete factory to the site, in association with the CEM III/C cement type.

Due to their initially metal-free composition, the fi rst stars in the Universe, which are termed Population III (Pop III) stars, were fundamentally different than later generations of stars. As of now, we have yet to observe a truly metal-free star although much effort has been placed on this task and that of nding the second generation of stars. Given they were the first stars, Pop III stars are expected to have made the fi rst contributions to elements heavier than those produced during the Big Bang. For decades signi cant mixing between H and He burning layers has been reported in simulations of massive Pop III stars. In this thesis I investigate this poorly understood phenomenon and I posit that interactions between hydrogen and helium-burning layers in Pop III stars may have had a profound impact on their nucleosynthetic contribution to the early universe, and second generation of stars. First, I examined a single massive Pop III star. This was done using a combination of stellar evolution and single-zone nucleosynthesis calculations. For this project I investigated whether the abundances in the most iron-poor stars observed at the time of publication, were reproducible by an interaction between H and He-burning layers. Here it was found that the i process may operate under such conditions. The neutrons are able to ll in odd elements such as Na, creating what is sometimes called the `light-element abundance signature' in observed CEMP stars. I also present the finding that it is possible to produce elements heavier than iron as a result of the i process operating in massive Pop III stars. A parameter study I conducted on H-He interactions in a grid of 22/26 MESA stellar evolution simulations is then described. I grouped these interactions into four categories based on the core-contraction phase they occur in and the convective stability of the helium-burning layer involved. I also examine in detail the hydrogen burning conditions within massive Pop III stars and the behaviour of the CN cycle during H-He interactions. The latter is compared to observed CN ratios in CEMP stars. Finally, I describe the first ever 4pi 3D hydrodynamic simulations of H-He shells in Pop III stars. I also examine the challenges in modelling such con gurations and demonstrate the contributions I have made in modelling Pop III H and He shell systems in the PPMStar hydrodynamics code. My contributions apply to other stellar modelling applications as well. / Graduate

III-nitride direct bandgap semiconductors have attracted significant research interest due to their outstanding potential for modern optoelectronic and electronic applications. However, the high cost of III-nitride devices, along with low performance due to dislocation defects, remains an obstacle to their further improvement. In this dissertation, I present a significant enhancement of III-nitride devices based on emerging materials. A promising substrate, (-201)-oriented β-Ga2O3 with unique properties that combine high transparency and conductivity, is used for the first time in the development of high-quality vertical III-nitride devices, which can be cost-effective for large-scale production. In addition, hybridizing GaN with emerging materials, mainly perovskite, is shown to extend the functionality of III-nitride applications. As a part of this investigation, high-performance and high-responsivity fast perovskite/GaN-based UV-visible broadband photodetectors were developed. State-of-the-art GaN epilayers grown on (-201)-oriented β-Ga2O3 using AlN and GaN buffer layers are discussed, and their high optical quality without using growth enhancement techniques is demonstrated. In particular, a low lattice mismatch (⁓4.7%) between GaN and the substrate results in a low density of dislocations ~4.8Å~107 cm−2. To demonstrates the effect of (-201)-oriented β-Ga2O3 substrate on the quality of III-nitride alloys, high-quality ternary alloy InxGa1−xN film is studied, followed by the growth of high quality InxGa1−xN/GaN single and multiple quantum wells (QWs). The optical characterization and carrier dynamics by photoluminescence (PL) and time-resolved PL measurements were subsequently performed. Lastly, to investigate the performance of a vertical emitting device based on InGaN/GaN multiple QWs grown on (-201)-oriented β-Ga2O3 substrate, high-efficiency vertical-injection emitting device is developed and extensively investigated. The conductive nature of the substrate developed as a part of this study yields better current and heat characteristics, while its transparency ensures high light extraction. The straightforward and direct growth process employed does not require a high-cost complex fabrication process. Finally, a broadband photodetector composed of the emerging CH3NH3PbI3 perovskite with the p-GaN, is developed. The findings reported in this dissertation demonstrate the superior performance of CH3NH3PbI3/GaN photodetectors produced by simple and cost-effective solution processed spray-coating method. In particular, it is demonstrated that perovskite/GaN device can work as a self-powered photodetector.

ABSTRACT This thesis focuses on the Basketmaker III period of the Ancestral Puebloan culture commonly known as the Anasazi, which means ‘ancient stranger’ or ‘ancient enemy’ in the Navajo language, or as preferred by the Hopi; "Hisatsinom" for "The Ones Who Came Before." I use the terms Anasazi and Ancestral Puebloan interchangeably in this study. My particular focus concentrates on a Basketmaker III settlement (42Sa2112 – Hidden Village) in Montezuma Canyon in southeastern Utah. My thesis presents data and an interpretive hypothesis that village formation and complex social organization emerged earlier than most standard texts (Plog 1997) assume. Analysis of the data I use shows that the Basketmaker III peoples lived in larger, more complex, and more permanent social groups in southeastern Utah than generally thought. Data from other researchers are presented for the existence of substantial Basketmaker III villages in the Four Corners region that consisted of multi-component habitation structures, storage facilities, farming terraces, and great pit houses. By focusing on Basketmaker III village descriptions and Geographical Information Systems (GIS) Locational data I show how these settlement patterns support a cultural-ecological framework for settled village life. Furthermore I use the (GIS) site data developed for Hidden Village (42Sa2112), Montezuma Canyon, Utah to illustrate a site plan that may reflect village planning particular to Basketmaker III social organization, which may be the antecedent to later Puebloan social structure. Spatial analysis provides insight to problems dealing with site distributions (Hodder and Orton 1976). GIS and spatial analysis presentopportunities for large-scale regional analyses and predictive modeling of settlement patterns and land use. Previous research and a GIS applications program (ESRI ArcView) are used to show the development of settlement patterns for the Ancestral Puebloan peoples across the Four Corners region of the Southwest. The potential of GIS as a tool for the organization and analysis of spatial data presents research opportunities for the development of new models and methods. GIS applications allow archaeologists to deal with large amounts of spatial data and develop models and methods for analysis. Using the software applications, I created a GIS map of Hidden Village to demonstrate a method for site mapping that examines the clustering of structures and features within a site. This method can also be used to map sites within a geographic region (Montezuma Canyon) and provides applied methods to test for the organization of villages and communities within a given geography.

Diploma thesis deals with preparation of peripherally functionalized polydentate Schiff ligands, suitable for metal coordination, such as Fe(III) or Co(III). The compounds, formed by this functionalization using organic molecule or stable organic radical, provide coordination site for another central atom. The compounds were synthesized for their potential biological activity. The organic ligands series was prepared, and these ligands were submitted to coordination reactions with selected transition metals. The prepared compounds were characterized by nuclear magnetic resonance, mass spectrometry, electron paramagnetic resonance and X-ray structure analysis.

Les ARN polymérases sont des acteurs indispensables de la transcription. Chez les eucaryotes il existe trois ARN polymérases (I, II et III). La ARN polymérase III (Pol III) possède 17 sous-unités, dont une qui existe sous deux formes: RPC32α et RPC32β. Seulement une des deux formes peut être intégrée dans la Pol III, créant ainsi deux polymérases différentes Pol IIIα et Pol IIIβ. Alors que RPC32β est présent dans les cellules somatiques, RPC32α est exprimé surtout dans des cellules souches et des cellules tumorales. Aujourd’hui rien n’est connu sur leurs rôles respectifs. Le cancer du sein est un problème majeur de santé publique car c’est le cancer féminin le plus fréquent. Plusieurs types de cancer du sein sont identifiés selon la présence ou absence de certains récepteurs hormonaux. Des cancers qui testent négative pour le récepteur d’oestrogène et de progestérone et qui ne surexpriment pas le récepteur pour les facteurs de croissance épidermiques humains 2 (HER2) sont appelés triple-négative. Ils ont un pronostique peu favorable, due à l’agressivité de ce type de cancer et un manque de thérapie cibles. Pour étudier le rôle de RPC32α il fallait identifier un model tumorale. En collaboration avec Jean-Paul Feugeas (INSERM UMR 1098) une étude transcriptomique a été fait sur 2627 échantillons cliniques de tissus de sein. L’étude montre que RPC32α est surexprimé dans les cancers triple-négative, alors que son homologue RPC32β est surexprimé dans les tissues normaux. Une analyse sur six lignées de cancer du sein et une ligné non-tumorale ont pu confirmer les résultats de l’analyse transcriptomique. Le modèle de cancer du sein a donc été validé. Une caractérisation des différentes lignées de cancer du sein a démontré que d’autres sousunités de la Pol III n’étaient pas surexprimées dans les cancers triple-négative. La surexpression de RPC32α n’était donc pas une conséquence d’une hyperactivité de la Pol III. Une analyse des transcrits synthétisé par la Pol III a montré que en générale les transcrits de la Pol III étaient plus fortement exprimé dans les cancers triple-négative que dans d’autres cancers. Afin d’étudier l’implication de RPC32α dans les phénomènes de tumorisation, plusieurs lignées cellulaires dépourvues de RPC32alpha ont été créé utilisant la technique CRISPRCAS9. L’absence de RPC32α n’a pas induit une augmentation de transcription ni de l’ARN de 4 RPC32α, ni de celle de RPC32β. Il n’existe donc pas de boucle de rétroaction pour RPC32α et les deux homologues ne sont pas co-régulés. Plusieurs, mais pas tous les transcrits synthétisé par la Pol III ont une expression fortement baissé dans les lignées mutants. Le fait que pas tous les transcrits ne soit affectés par la perte de RPC32α, indique qu’il existe une spécificité de transcription pour Pol IIIα et Pol IIIβ. Les cellules des linges mutants ne présentaient pas de phénotype différent des cellules mères et la croissance était la même dans toutes les lignées. Par contre les tests de croissance en agar-mou ont révélé que les lignées mutants formaient 85% de moins de colonies, indiquant que RPC32α est nécessaire pour la croissance tumorigénique in vitro. Pour tester l’effet de la perte de RPC32α sur la croissance tumorigénique in vivo, des cellules mutants et des cellules mères ont été injecté dans des souris. Les souris greffées avec des cellules mutantes montrent un départ de tumorisation retardé. Au bout de six semaines elles avaient de tumeurs deux fois plus petit que les souris avec des cellules mères. Après ablation de la tumeur primaire, les souris ont été surveillées pour l’apparition de métastases. Quatre semaines plus tard les souris greffées avec des cellules mutantes avaient 100 fois moins de métastases que les souris contrôles. Ces résultats montrent que RPC32α est nécessaire pour la tumorisation in vitro et in vivo. La protéine semble surtout jouer un rôle dans la formation des métastases, qui sont un des problèmes majeurs dans le traitement des cancers. / The RNA polymerases are key players of transcription. Eukaryotes have three RNA polymerases (I, II and III). The RNA polymerase III (Pol III) has 17 subunits, one of which exists in two alternative forms: RPC32α and RPC32β. Only one of the two forms can be integrated into the enzymes, thus generating either Pol IIIα or Pol IIIβ. While RPC32β is found in all somatic cells, RPC32α is expressed in stem cells and tumor cells. To date nothing is known of their respective roles. Breast cancer is one of the major public health problems, as it is the most common cancer in women. Several types of breast cancers are distinguished, according to the presence or absence of hormonal receptors. Cancers that test negative for estrogen receptors, progesterone receptors and that do not overexpress the human epidermal growth factor receptor 2, are called triple-negative breast cancers. They tend to have a poor prognosis, due to the aggressive nature of the cancer and the lack of targeted therapies. To study the role of RPC32α, a tumor model needed to be identified. In collaboration with Jean-Paul Feugeas (INSERM UMR 1098) a transcriptomic study was performed on 2627 clinical breast tissue samples. The study showed that RPC32α was overexpressed in triplenegative breast cancer, whereas RPC32β was overexpressed in normal tissue. A study on six breast cancer cell lines and one non-tumorigenic line confirmed the results of the transcriptomic study. The breast cancer model was thus validated. A characterization of different breast cancer cell lines showed that other Pol III subunits were not overexpressed in triple-negative breast cancer. The overexpression of RPC32α was therefore not a mere consequence of a Pol III hyperactivity. An analysis of the transcripts synthesized by Pol III showed that overall the Pol III transcript levels were elevated in triplenegative breast cancer compared to other breast cancer subtypes. In order to study the role of RPC32α in tumorigenesis, several RPC32α knock-out cell lines were created using CRISPR-Cas9. The loss of RPC32α did not induce an increase in transcription of the RNAs of RPC32α or RPC32β. This shows that no feed-back loop exists for RPC32α and that the two homologues are not co-regulated. Various Pol III transcripts showed decreased expression levels in the knock-out cell lines. Yet not all transcripts were reduced in the absence of RPC32α. This indicates that some sort of transcription specificity must exist for Pol IIIα and Pol IIIβ. The knock-out cell lines did not show any alterations in their phenotype or growth rates. However, in soft agar assays the knock-out cell lines produced 85% less colonies than the mother cell line. This proves that RPC32α is necessary for tumorigenic growth in vitro. To find out if RPC32α was also necessary for tumorigenic growth in vivo, knock-out and wild type cells were injected into mice. The mice grafted with knock-out cells showed a slowed onset of tumor growth. After six weeks, the mice injected with knock-out cells had tumors half the size of the mice injected with wild type cells. The primary tumor was ablated and mice were tracked for metastasis. Four weeks later, mice injected with RPC32α knock-out cells had 100 times less metastasis than the control group. These results show that RPC32α is necessary for tumorigenic growth in vitro and in vivo. The protein seems also to be implicated in the formation of metastasis, which are one of the greatest problems in cancer treatment today.

<p>Tetraazamacrocycles, such as cyclam (1,4,8,11-tetraazacyclotetradecane), are useful ancillary ligands in the formation of organometallic complexes. Coordination of a 3d metal can lead to the formation of square planar complexes, such as with Ni^II and Cu^II, or octahedral complexes upon coordination of additional ligands, such as with Co^II/III and Cr^II/III. Notably with Cr, a mixture of <i>cis-</i> and <i>trans-</i>octahedral complexes are formed, and the isomerism can be influenced through <i>C</i>-substitution of the cyclam macrocycle. Herein, Cr^III complexes featuring <i>C</i>-substituted cyclam derivatives and either redox-active ligands or alkynyl ligands are reported.</p> <p>Chapter 1 features an introduction to the photophysical processes of Cr(III), an overview of cyclam and its derivatives, and a brief review of Cr^III(cyclam/cyclam’) bis-alkynyl complexes for various applications. Chapter 2 discusses the structural, optical, electronic, and magnetic characterizations of <i>cis</i>-[Cr(HMC)catecholate]⁺ and <i>cis</i>-[Cr(HMC)semiquinonate]²⁺ complexes, which feature redox-active catecholate and semiquinonate ligands. Chapter 3 highlights a series of <i>trans</i>-[Cr(HMC)(C₂Ar)Cl]⁺ complexes, which expands upon prior research on bis-alkynyl complexes. Chapter 4 discusses how a different <i>C</i>-substituted cyclam derivative, MPC, is used to produce <i>trans</i>-[Cr(MPC)Cl₂]⁺ starting material in higher quantity than the HMC derivative. This allows for higher amounts of <i>trans</i>-[Cr(MPC)(C₂Ar)₂]⁺ complexes to be synthesized, making it a more practical macrocycle for the future pursuit of dissymmetric bis-alkynyl complexes.</p>

Group-III-nitrides have been intensively investigated for optoelectronics and power electronics and are uniquely suitable for energy-related applications, such as solar hydrogen generation and nanogenerators. Compared to planar group-III-nitrides, their nanostructures offer a high surface-to-volume ratio, increased light absorption cross-section, and improved carrier transportation behavior. This thesis focuses on molecular-beam-epitaxy-grown group-III-nitrides, specifically nanowires and membranes, and applications in renewable energy harvesting and conversion. A Mo2C-decorated (In,Ga)N nanowire-based photocathode was demonstrated for nitrogen fixation. The conventional Haber-Bosch method demands high reaction pressure and temperature while releasing a considerable amount of greenhouse gas. The proposed photoelectrocatalytic method can utilize solar energy to generate ammonia without carbon emissions. The proposed photocathodes can achieve maximum faradaic efficiency of 12 %, ammonia yield of 8.9 µg/h/cm2, and excellent stability for over 12 hrs. Moreover, group-III-nitrides were fabricated into a freestanding membrane through a novel method combining electrochemical porosification and controlled spalling. The novel method is reproducible and scalable, which can significantly reduce the consumption of sacrificial substrates compared to existing nitride membrane exfoliation techniques, thus promising a scalable platform. The as-fabricated GaN membranes were demonstrated for photoelectrocatalytic methylene blue degradation. Through laboratory tests and rooftop field tests, we proved the feasibility of our wafer-scale GaN membranes in achieving a dye degradation efficiency of 92%, a total organic carbon removal rate of 50.2%, and extraordinary stability for ~ 50 hours under solar illumination. The membrane can also degrade ~87% of MB under visible-light illumination. Furthermore, the (Al,Ga)N membranes were fabricated into flexible transparent piezoelectric devices. The devices can sense compression pressure and bending strain while giving a comparable compression sensitivity to other thin film piezotronics devices of ~ 2.41 mV/kPa and 42.36 pA/kPa, a maximum bending gauge factor of ~ 1271, and an output power density of ~ 5.38 nW/cm2. The sensors can withstand over 35000 cycles of operation and can be utilized for sensing and harvesting mechanical energies from human motions and environmental signals. This research utilized nanowires and membrane-based group-III-nitrides for different photoelectrocatalytic reactions and piezotronics devices, from material preparation and characterizations, and demonstrated practical devices for clean energy-related applications.

<p>Nitride semiconductors are promising for applications in opto-electronic devices due to their wide band gap that is adjustable by appropriate choice of alloy composition. To date, many III-nitride devices have been demonstrated, such as light-emitting diodes, lasers, etc. Most opto-electronic devices make use of the optical transition from conduction band to valence band. Moreover, the large conduction band offset achieved by III-nitrides makes it possible to take advantage of transitions inside the conduction band or valence band, which provide much more freedom for band engineering. Although many III-nitrides based opto-electronic devices have been invented and implemented in commercial use, there is still a need for more compact, rugged, higher efficiency devices with lower cost. Many challenges of III-nitride semiconductors are related to material defects, lattice mismatch and internal polarization fields. Photoluminescence is a convenient technique to characterize sample quality and optical properties. It does not destroy the samples or need any electrical contacts. Therefore, it is commonly used in qualitative analysis of III-nitrides. This thesis focuses on non-polar m-plane III-nitrides structures, because this crystal orientation eliminates internal polarization fields in heterostructures. We first performed a photoluminescence study of a series of m-plane InGaN thin films with In compositions up to 24.5%. Evidence of large In composition fluctuations was observed. This inhomogeneity of In composition contributes to the non-monotonic temperature dependence of photoluminescence peak energy and linewidth. A large drop of internal quantum efficiency when temperature increases to room temperature was observed, which indicates the presence of a large number of non-radiative recombination centers. This is due to low temperature growth of InGaN by plasma assisted molecular beam epitaxy. The InGaN film with 11% has a linewidth close to theoretical calculations for InGaN with random In distribution, and much smaller than many reported polar c-plane InGaN films with comparable In compositions, which suggests improved material quality. This In composition was selected for the design of InGaN/AlGaN superlattices.</p> <p>In order to avoid the disadvantage of strain buildup, we designed nearly strain-balanced non-polar m-plane InGaN/AlGaN structures with In composition of about 9%. Steady-state photoluminescence and time-resolved photoluminescence were performed on these structures. A significant discrepancy between measured and calculated PL peak positions was observed. This is likely due to the In composition fluctuations and quantum confinement in quantum wells. The broadening mechanism of the PL in the superlattices was investigated. The low-temperature linewidth of undoped superlattices is comparable to many previously reported values for m-plane InGaN/GaN quantum wells. Similar to InGaN films, the internal quantum efficiency drops dramatically when temperature reaches room temperature. Regions with high In compositions act as localization centers for excitons. An average localization potential depth of 21 meV was estimated for undoped superlattices. This small potential depth does not reduce the degree of polarization of emitted light, and contributes to the narrow linewidth. A fast decay time of 0.3 ns at 2 K was observed for both doped and undoped superlattices. This value is much smaller than that for polar c-plane InGaN/GaN superlattices. The localization of excitons was found to be strong and not affected by magnetic field at low temperatures. Compared with undoped superlattices, the doping sheets reduce decay pathways of excitons in doped superlattices.</p> <p> </p>