The application of composite action ushered a new era in the use of double-layer spaceframes as efficient floor systems in addition to their competitiveness as roof coveringstructural systems. Earlier research on space frames demonstrated large improvementsin their static behaviour caused by the introduction of composite action. Theseimprovements included an increase in ductility to avoid progressive collapse, a largeincrease in load-carrying capacity and a considerable reduction in materialconsumption.In this work, the effect of introducing composite action in changing the dynamiccharacteristics of space frames, in particular the natural frequencies and damping ratioswas presented. The study was expanded to determine the effect of composite action inchanging the response to dynamic excitations. The measured responses included thelateral displacements and changes in the internal member force distribution undershaking table vibrations.Three aluminium space frame models of the square on square (SOS) configuration weremanufactured. The first model was non-composite, while composite action was appliedto the other two models with a top aluminium deck and a timber deck, respectively.Two common cases of support conditions were used in connecting the models to theloading frame, which was the platform of the shaking table.Initial displacement method (snap test) was used to determine the frequency of vibrationand the damping ratio of test models in the vertical and horizontal directions usinglogarithmic decrement method. All models were then exposed to shaking tablevibrations to determine the changes in dynamic responses between different models.These tests were repeated for the three models after the successive removal of panelsfrom one direction to identify the changes to their characteristics and behaviour withdifferent aspect ratios.The second part of the study was carried out numerically by using the finite elementpackage ABAQUS. It started by selecting a valid finite element model from nineproposed models using experimental test results on physical structures. A parametricstudy was conducted using the validated finite element model to expand the study toinclude two common space frame configurations; the square on large square (SOLS)and square on diagonal (SOD), and two other cases of support configurations, namely,fully edge-supported and supports at corners and middle edges of models.Based on the work done in this study, it can be concluded that composite actionchanged the dynamic characteristics of space frames, which was clear in the increase oftheir vibration frequencies in all directions as a result of the increase in stiffness.Furthermore, the increase in stiffness resulted in a general reduction in the dampingratio of space frames covered with aluminium deck, while the high friction with topjoints and the nature of timber as a good energy absorbent material resulted in a variableeffect on the damping ratio associated with the increase in aspect ratio.The effect of composite action was clear in reducing the lateral displacement ofcomposite models by more than 50% compared to the non-composite case. Moreover,composite action resulted in changing the distribution of internal forces in diagonal andlower chord members such that forces became more concentrated at corners and edgesparallel to the direction of vibrations in both cases of corner and edge-supportedmodels.

No description available.

The electrochemical double layer (EDL) at the solid–liquid interface is the near surface region where important electrochemical processes (e.g., electrodeposition, corrosion, and heterogeneous catalysis) take place. Subtle changes in the electrode surface material/topography and the nature of the fluid medium can drastically alter interactions between liquid molecules and the solid surface. A better understanding of this interfacial region can help advance numerous applied fields, such as battery technologies, solar cells, double layer capacitors, and carbon dioxide capture/conversion. Ionic liquids (IL) are an emerging class of solvents that could replace traditional aqueous/non-aqueous solvents due to their advantageous physiochemical properties (e.g., wide solvent window, high thermal stability, and excellent solvating power). However, our understanding of the near-surface structure of ILs in the EDL is still being developed. This thesis focuses on the fundamental electrochemical behavior of ILs to help understand its interfacial behavior in three main areas: 1) the nature of capacitance-potential relationships in neat ILs, 2) the role of ‘user-defined’ experimental variables on capacitive electrochemical measurements, and 3) the impact of IL + water mixtures on experimental data. The general shape of capacitance-potential curves can suggest at the broad architecture of the EDL region. Fundamental capacitive studies of the IL EDL show a wide range of results, even for similar electrochemical systems. Theoretical predictions suggest the capacitance-potential curve should exhibit bell- or camel-shaped curvature depending on the nature of the IL. Experimental observations have demonstrated several functional shapes such as U-shaped, bell-shaped, camel-shaped, and relatively featureless responses. Much of the work in this thesis starkly contrasts theoretical expectations by demonstrating capacitive behavior that is analogous to high temperature molten salts and dilute aqueous electrolytes with metallic and non-metallic electrode materials. However, our systematic studies of a model IL electrochemical system reveal that there are several ‘user-defined’ experimental variables (i.e. potential scan direction, data acquisition protocol, experimental technique, and potential range probed) which in some instances can significantly impact the resulting capacitance curvature. Some of these variables are often overlooked in the literature and our efforts are aimed at uniting the scientific community in this area to help better compare and understand results. An additional experimental variable of importance is the sorption of water into ILs, which is nearly impossible to prevent due to their hygroscopic nature. The presence of water is known to have a significant effect on the resulting mixtures’ bulk and interfacial properties. While the interaction between ILs and water can significantly vary depending on the nature of the IL, this thesis demonstrates that within small quantities (e.g., < 5000 ppm) of sorbed water there are only minor changes in spectroscopic and electrochemical responses. Collectively, the work outlined in this thesis helps the scientific community better understand electrochemical measurements in IL solvents by examining key analytical variables associated with capacitive measurements. The fundamental electrochemical studies described in this thesis demonstrate that the solid-liquid interface for IL solvents is response to even subtle changes in surface chemistries. These governing interfacial properties have ramifications in myriad applications from energy storage to lubrication.

No description available.

DNA double strand break (DSB) repair is critical to maintain genomic integrity and cell viability. DSBs can occur during the course of cell cycle during replication or transcription, or by exogenous agents such as chemicals or ionizing radiation. For my thesis, I studied homologous recombination (HR), which has two sub-pathways: Homology Directed Repair (HDR) and Single Strand Annealing (SSA). HDR involves strand invasion of a homologous template to prime DNA synthesis; SSA involves annealing of homologous segments flanking a DSB. Background data showed that depletion of XAB2 protein by RNA interference reduced both HDR and SSA events. XAB2 protein contains 15 tetratricopeptide repeat (TPR) motifs, which likely enable protein-protein interactions. While XAB2 is speculated to have a role in transcription coupled repair and pre-mRNA splicing, its role in HR pathway is uncertain. The overall hypothesis for my thesis is that XAB2 mediates a specific step of HR (5’-3’ end resection), and the TPR motifs present in XAB2 enable the protein to function in a complex during HR. By using an end resection assay and cell biology analysis, I found that XAB2 is essential for 5’ – 3’ end resection, an intermediate step common to both HDR and SSA pathways. With a functional complementation assay I developed, I have shown that specific TPR regions are critical for XAB2 functions in HR. Overall, my research demonstrates that XAB2 protein has a key role in the 5’-3’ end resection step of HR, and its function in HR requires specific sets of its TPR regions.

We will explore progenitors extensively throughout this project. The progenitor, developed by Robert T Curtis, is a special type of infinite group formed by a semi-direct product of a free group m*n and a transitive permutation group of degree n. Since progenitors are infinite, we add necessary relations to produce finite homomorphic images. Curtis found that any non-abelian simple group is a homomorphic image of a progenitor of the form 2*n: N. In particular, we will investigate progenitors that generate two of the Mathieu sporadic groups, M11 and M11, as well as some classical groups. We will prove their existences a variety of different ways, including the process of double coset enumeration, Iwasawa's Lemma, and linear fractional mappings. We will also investigate the various techniques of finding finite images and their corresponding isomorphism types.

The main objective of this project is to find the original symmetric presentations of some very important finite groups and to give our constructions of some of these groups. We have found the Mathieu sporadic group M11, HS × D5, where HS is the sporadic group Higman-Sim group, the projective special unitary group U(3; 5) and the projective special linear group L2(149) as homomorphic images of the monomial progenitors 11*4 :m (5 :4), 5*6 :m S5 and 149*2 :m D37. We have also discovered 24 : S3 × C2, 24 : A5, (25 : S4), 25 : S3 × S3, 33 : S4 × C2, S6, 29: PGL(2,7), 22 • (S6 : S6), PGL(2,19), ((A5 : A5 × A5) : D6), 6 • (U4(3): 2), 2 • PGL(2,13), S7, PGL (2,8), PSL(2,19), 2 × PGL(2,81), 25 : (S6 × A5), 26 : S4 × D3, U(4,3), 34 : S4, 32 :D6, 2 • (PGL(2,7) :PSL(2,7), 22 : (S5 : S5) and 23 : (PSL3(4) : 2) as homomorphic images of the permutation progenitors 2*8 : (2 × 4 : 2), 2*16: (2 × 4 :C2 × C2), 2*9: (S3 × S3), 2*9: (S3 × A3), 2*9: (32 × 23) and 2*9: (33 × A3). We have also constructed 24: S3 × C2, 24 : A5, (25: S4), 25 : S3 × S3,: 33: S4 × C2, S6, M11 and U (3,5) by using the technique of double coset enumeration. We have determined the isomorphism types of the most of the images mentioned in this thesis. We demonstrate our work for the following examples: 34 : (32 * 23) × 2, 29 : PGL(2,7), 2•S6, (54 : (D4 × S3)), and 3: •PSL(2,19) ×2.

Catalytic hydrophosphination has enormous potential in the selective preparation of value-added organophosphines, despite the challenge of the reaction. This dissertation aims to address the hurdles in catalytic hydrophosphination with respect to substrate scope, selectivity, and reaction conditions using [қ5 –N,N,N,N,C– (Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2]Zr (1). Compound 1 readily engages with a suite of primary phosphines. These are challenging substrates for this reaction, but 1 readily provides high conversions with these substrates. Increasingly large primary phosphines, including chiral phosphines, undergo catalysis with 1. Furthermore, a variety of underreported unsaturated substrates can be functionalized in catalytic hydrophosphination with 1. Alkynes are underreported substrates, but 1 showed not only catalytic reactivity with internal alkynes, but also the first example of a double hydrophosphination with these substrates. Almost entirely absent from catalytic hydrophosphination are unactivated alkenes, yet 1 catalyzes them with TON and TOF that now rival those of styrenes. Additionally, a new tandem inter- and intramolecular diene hydrophosphination was reported to give cyclic phosphine products. The selectivity in catalytic hydrophosphination 1 in all processes is novel in many regards. In alkyne hydrophosphination, vinyl phosphines or double hydrophosphination products could be isolated as secondary phosphines, depending on reaction conditions. For alkenes, secondary or tertiary phosphines can be formed by modification of the reaction stoichiometry. Isolated secondary phosphines were further elaborated into chiral tertiary phosphines. Catalytic hydrophosphination with a chiral, air-stable primary phosphine gave chiral secondary phosphine products. Efforts to synthesize a chiral ligand to close the gap on catalysts (and therefore substrates) for asymmetric hydrophosphination are discussed. Catalysis with 1 proceeds under photolysis. Direct irradiation of 1 by ultraviolet or visible light during alkene hydrophosphination substantially enhanced catalytic activity. For example, previous reports of styrene hydrophosphination with 1 showed TON = 18 and TOF = 1.5 h-1. Under irradiation, the process is substantially more efficient (TON = 20 and TOF = 60 h-1) and the substrate scope is expanded. Computational and spectroscopic data indicate that photoexcitation results in a charge transfer in the active catalyst, which appears to accelerate catalysis by promoting substrate insertion based on a linear freeenergy relationship. The impressive substrate scope, mild conditions, and increased catalytic activity from photoexcitation, rather than heat, are among the best reported for the reaction. Identification of a photoexcitation event that promotes substrate insertion may enable enhanced reactivity from other metal catalysts for this transformation.

Cette thèse est consacrée à une enquête sur la structure et la dynamique, avec des modèles théoriques et essais de laboratoire, sur deux types communs de défauts arrivant dans la molécule d’ADN, après des dégâts de radiation ou le produit chimique: mésappariements des base(MB) et casseurs de brin.Tels défauts pourraient arriver naturellement, d’imperfections dans le processus cellulaire, induit par l’environnement et ou induit artificiellement, comme pour la radiothérapie de cancer. Nous avons utilisé la spectroscopie de force moléculaire exécutée par des pinces optiques accompagnées par des simulations all-atom en Dynamique Moléculaire (MD), pour caractériser des MB dans des hairpin d’ADN. Ensuite nous avons construit des modèles structurels pour les casseurs de brin d’ADN, dans les deux indexent les éléments constitutifs de la chromatine: le ADN linker et le nucléosome. Grâce à l'application de diffèrent techniques (Essential Dynamics, Steered MD, …) on a caractérisé les stades précoces de l’évolution de cette lésion d’ADN dans les deux éléments. / This thesis is dedicated to a combined theoretical and experimental investigation of the structure and dynamics of two common types of defects occurring in the DNA molecule, after chemical or radiation damage: basemismatches and strand breaks. We used single-molecule force spectroscopy performed by optical tweezers accompanied by Molecular Dynamics (MD) all-atom simulations, to characterize mismatches in short DNA hairpins. We demonstrate that it is possible to use SMFS. Subsequently, we designed structural models for the DNA strand-break defects, in the two key constitutive elements of the chromatin: the DNA linker and the nucleosome. Using different techniques (Essential Dynamics, steered MD, covariant mechanical stress, …) we characterized the early stages of the evolution of this DNA lesion in the two elements.

Chamber music is a major area of neglect in the study of the double bass, and the instrument has also suffered from a scarcity of chamber music literature written by major composers. As bassists focus predominantly on solo and orchestral repertoire, the purpose of this study is to enrich the double bass literature and increase awareness of chamber music as a tool for bassists to develop as artists by providing a transcription of Johannes Brahms’s Trio in A minor, Op.114 for double bass, clarinet, and piano. The transcription adds to the literature for double bass from the Romantic era, giving players the chance to work on their technical and musical skills in a chamber music setting. In addition, performance of this transcription will enhance double bassists’ understanding of the style of one of the most important nineteenth-century composers.