Anisotropic hybrid excitation modes in monolayer and double-layer phosphorene on polar substrates

We investigate the anisotropic hybrid plasmon-SO phonon dispersion relations in monolayer and double-layer phosphorene systems located on the polar substrates, such as SiO2, h-BN and Al2O3. We calculate these hybrid modes with using the dynamical dielectric function in the RPA by considering the electron-electron interaction and long-range electric field generated by the substrate SO phonons via Frohlich interaction. In the long-wavelength limit, we obtain some analytical expressions for the hybrid plasmon-SO phonon dispersion relations which represent the behavior of these modes akin to the modes obtaining from the loss function. Our results indicate a strong anisotropy in plasmon-SO phonon modes, whereas they are stronger along the light-mass direction in our heterostructures. Furthermore, we find that the type of substrate has a significant effect on the dispersion relations of the coupled modes. Also, by tuning the misalignment and separation between layers in double-layer phosphorene on polar substrates, we can engineer the hybrid modes.Comment: 10 pages, 7 figure

The Role of Corporate Controls, Size, and Corporate Headquarters in the Effect of Corporate-Level Strategy on Business-Level Strategy and Business-Level Performance

The aim of this thesis is to re-examine the relationship between corporate strategy and business unit strategy. Past research has often failed to deconstruct the notion of corporate effects to properly assess the role of corporate strategy in the behaviour and performance of business units. As a result, conflicting findings have led to researchers disagreeing on the significance of corporate effects and corporate strategy. Through this thesis, I have taken steps to clarify the misunderstood significance of corporate strategy to business-unit-level strategy and performance. This dissertation has drawn on the literature from agency theory, information processing theory, and upper echelons theory, as well as the economic logic that underlies value creation in corporations. Through this dissertation, I deconstruct the notion of corporate effects to theoretically redefine the role of controls as the mediator between corporate strategy and business unit strategy to respond to the research question, “How does corporate strategy influence business unit performance?” In addition, I deconstruct business unit effects to examine the impact of business strategy on business unit performance. Finally, I consider business unit strategy to be an exogenous factor. To explore the effect of corporate strategy on business-unit-level strategy and performance, I conducted a quantitative analysis of data corresponding to over 2,500 business units from 193 corporations. Building on a proprietary dataset made accessible for this research, I tested the theoretical model for this thesis using previously collected data from each of the studied business units and the corporate headquarters of their corporate parents. The dataset comprises objective measures of business unit financial performance, objective characteristics of corporate headquarters and structure, and more subjective and behavioural data based on surveys that focus on control mechanisms to which business units are subject and the strategic orientation they pursue. The quantitative analysis was undertaken after performing steps for validation of the measures used and in compliance with measures and techniques used in past research. I find support in my analysis for a partial mediating role of controls in the relationship between corporate strategy and business-unit-level strategy. The results from the analysis demonstrate that the strategic orientations of business units are endogenous to the corporate strategy through the mechanism of controls to which each business unit is subject. I also find support for the moderating effect of certain factors at the corporate level, such as size of corporate headquarters, number of business units managed by the corporation, and the corporate CEO’s background in the relationship between corporate strategy and controls. The findings of this thesis re-establish the role of corporate strategy in our understanding of business-unit-level strategy and performance. Contrary to past research, I have theorized business-unit-level strategy to be endogenous to corporate strategy. I have also developed the controls construct and have measured it for each business unit studied in order to test my theoretical model. My findings in this thesis take a step towards enhancing our understanding of how corporate strategy influences strategy and performance at the business unit level. To explore the effect of Corporate Strategy on Subsidiary level strategy and performance, I have conducted a quantitative analysis of data corresponding to over 2500 subsidiaries from 193 corporations. Building on a proprietary dataset made accessible for this research, I tested the theoretical model for this thesis using previously collected data from each of the studied subsidiaries and the corporate headquarters of their corporate parents. The dataset comprises of objective measures of subsidiary and corporate financial performance, objective characteristics of corporate headquarters characteristics and structure, as well as more subjective and behavioural data based on surveys which focus on control mechanisms to which subsidiaries are subject and the strategic orientation they pursue. The quantitative analysis was undertaken after performing steps for validation of the measures used and in compliance with measures and techniques used in past research. I find support in my analysis for the mediating role of Controls in the relationship between Corporate Strategy and subsidiary level strategy. The results from the analysis demonstrate that the strategic orientations of subsidiaries are endogenous to the corporate strategy through the mechanism of Controls each subsidiary is subject to. I also find support for the moderating effect of certain aspects and characteristics at corporate level such as size of corporate headquarters, number of subsidiaries managed by the corporation, and corporate CEO’s background in the relationship between Corporate Strategy and Controls. The findings of this thesis re-establish the role of Corporate Strategy in our understanding of subsidiary level strategy and performance. Contrary to past research, I have theorized subsidiary level strategy to be endogenous to corporate strategy. I have also developed the Controls construct and have measured it for each subsidiary studied in order to test my theoretical model. My findings in this thesis take a step towards enhancing our understanding of how Corporate Strategy influences strategy and performance at corporate and subsidiary levels

Toward an artificial Mott insulator: Correlations in confined, high-density electron liquids in SrTiO3

We investigate correlation physics in high-density, two-dimensional electron liquids that reside in narrow SrTiO3 quantum wells. The quantum wells are remotely doped via an interfacial polar discontinuity and the three-dimensional (3D) carrier density is modulated by changing the width of the quantum well. It is shown that even at 3D densities well below one electron per site, short-range Coulomb interactions become apparent in transport, and an insulating state emerges at a critical density. We also discuss the role of disorder in the insulating state.Comment: Accepted for publication in Physical Review B (Rapid Communication

Carrier-controlled ferromagnetism in SrTiO3

Magnetotransport and superconducting properties are investigated for uniformly La-doped SrTiO3 films and GdTiO3/SrTiO3 heterostructures, respectively. GdTiO3/SrTiO3 interfaces exhibit a high-density two-dimensional electron gas on the SrTiO3-side of the interface, while for the SrTiO3 films carriers are provided by the dopant atoms. Both types of samples exhibit ferromagnetism at low temperatures, as evidenced by a hysteresis in the magnetoresistance. For the uniformly doped SrTiO3 films, the Curie temperature is found to increase with doping and to coexist with superconductivity for carrier concentrations on the high-density side of the superconducting dome. The Curie temperature of the GdTiO3/SrTiO3 heterostructures scales with the thickness of the SrTiO3 quantum well. The results are used to construct a stability diagram for the ferromagnetic and superconducting phases of SrTiO3.Comment: Revised version that is closer to the published version; Fig. 2 correcte

How Human Resource and Information Systems Practices Amplify the Returns on Information Technology Investments

This study examines the important roles that human resources (HR) for information technology (IT) professionals and information systems (IS) practices for all workers in an organization play in shaping returns on firms’ IT investments. In particular, we consider how incentives, autonomy, and training for IT professionals can enable a firm to better leverage the value of its IT investments. We argue that well-trained, motivated, and empowered IT professionals can help firms make better strategic choices in allocating IT investments and implementing IT projects. We also demonstrate how this moderating relationship depends upon collaborative IS and autonomy-enhancing IS practices that affect other knowledge workers in the firm. We leverage archival data for 228 firms with 736 firm-year observations and document two key findings. We find (1) that empowering HR practices for IT professionals positively moderate the effect of IT investments on firm performance, and (2) that the alignment between empowering HR practices for IT professionals and firm-wide collaborative IS practices enhances the value that firms derive from IT investments. Our results suggest that the business value of IT investments is linked to the rewards and opportunities offered to IT professionals, who have a pivotal role in the effective deployment of IT in organizations

The Use of Growth Factors and Mesenchymal Stem Cells in Orthopaedics: In particular, their use in Fractures and Non-Unions: A Systematic Review.

AIM: The aim was to look at current evidence for treating non-unions or delayed fracture healing in regard to novel methods applying mesenchymal stem cells (MSCs) and growth factors (GF). METHODS: Pre-clinical and clinical trials focusing on the use of Mesenchymal Stem Cells and Growth Factors for fracture healing were included in this review. Published articles were identified using specific search terms in Medline, Cochrane Library, PubMed, Scopus and Web of Science. RESULTS: Of the 580 articles found, 82 met my selection criteria and were included, with 39 papers involving trials on the effects of GFs and MSCs on non-unions or bone repair. These included 11 articles on MSCs, 10 on Bone Morphogenetic Proteins, 2 on Vascular-Endothelial GF, 5 on Insulin like-GF, 4 on Transforming-GF-β, 4 on Platelet-Rich Plasma, 1 on Platelet Derived-GF and 2 on Fibroblast-GF, with the other articles included qualitatively. Overall results were positive with the addition of MSCs, Bone Morphogenetic Proteins, VEGF, IGF and TGF-β in aiding fracture healing compared to controls, with mixed results for other factors. CONCLUSION: Overall this review shows promising results regarding the use of MSCs and various Growth factors in the treatment of fractures and non-unions, as well as synergistic effects observed when combined together. However more research is indicated as these methods are still in the early stages of development