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Recycling and re-use of water is essential for achieving United Nations' sustainable development goal - 6 : "Ensure availability and sustainable management of water and sanitation for all". Photocatalytic degradation can help provide clean water by destroying pollutants or converting them to less toxic form. To achieve this aim, we need to develop efficient photocatalysts, which in its turn requires thorough understanding of the properties of photocatalysts and their interactions with pollutants. This thesis reports our studies of TiO2 photocatalysts and TiO2-based interfaces, their optical properties and interactions with model pollutants and with surface modifiers, using dispersion-corrected density functional theory (DFT) calculations. Firstly, this thesis investigated interactions of the TiO2 anatase (101) surface with model pollutants: benzoic, nicotinic, salicylic and anthranilic acid. Different adsorption modes were investigated. Monodentate adsorbed configurations were found to be more stable than the bidentate structures for all the molecules studied. Thermodynamic probabilities of different adsorption configurations were analysed using the Boltzmann distribution, which showed dispersionstabilised tilted structures to be by far the most abundant. Dispersion was found to have a significant contribution to the adsorption energies, in addition to hydrogen bonding, in the most stable structures. Different methods of describing dispersion within DFT were compared, and the relative stabilities of TiO2/acid systems were found to be independent of the method of describing dispersion. Secondly, the effect of organic adsorbates as photosensitisers on TiO2 was investigated by modelling the optical properties of the TiO2/carboxylic acids interfaces. Aromatic carboxylic acids with additional functional groups, such as anthranilic and salicylic acids, were found to enhance the optical absorption of TiO2 in the visible region. Thus, adsorption of aromatic acids sensitises TiO2 photocatalysts to the visible region of the solar spectrum and enhances their light harvesting.

We attempt to draw a straight line connecting financial shocks, portfolio reallocation by firms, and drop in aggregate productivity using a dynamic general equilibrium model. Our objective is to study whether the presence of financial frictions can produce business cycle-like response of variables to a financial shocks, as well as lower aggregate productivity. We propose a model that shows how an adverse shock to credit access for firms causes them to change the balance sheet portfolio composition of productive assets, which in turn causes loss of efficiency, and manifests as an efficiency wedge. We find some evidence for these dynamics in the data in the form of loss of measured TFP in countries after a financial shock, and a change in portfolio composition of assets for the U.S. data. Specifically, we find that post the 2008 crisis firms changed their allocation between assets of varying depreciation rates. We calibrate the model such that the impulse response functions are qualitatively similar to data facts. We take the canonical real business cycle model as base and modify it to incorporate our hypothesis stated above. We develop the simple model without frictions first and discuss its unique features, then add the friction and discuss how the full model responds to shocks and how the response of variables is very close to a business cycle. Then we address some technical issues in the model to make it comparable to a standard model with financial frictions. We also conduct welfare analysis and compute welfare costs by comparing a model of constrained firms with one of unconstrained firms.

The million degree temperature of the solar corona has been a continuing puzzle to scientists. A detailed study of energetic events such as solar flares, coronal mass ejection and solar jets may provide important clues about how changes in the magnetic activity lead to explosive eruptions in the corona and contribute to coronal heating. In this thesis, the author has studied solar jets, ubiquitous energetic transients observed in the solar atmosphere. They have been observed to originate from the edge of active regions and show signatures in different layers of the solar atmosphere. A systematic investigation has been carried out by the author to understand the temperature structure of active region jets (AR jets) by combining imaging and spectroscopic observations using the differential emission measure (DEM) technique. The study gives a new perspective to our understanding of the dynamics involved in AR jets. Multiwavelength high-resolution imaging observations from space-based telescopes such as the Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamic Observatory (SDO), the X-ray Telescope (XRT) on board the Hinode satellite, and spectroscopic observations from the Extreme UV Imaging Spectrometer (EIS) on board the Hinode and the Interface Region Imaging Spectrometer (IRIS) were used to study the physical parameters of jets such as plasma flows, electron number densities, emission measure, peak temperature, velocities (plane-of-sky, Doppler, nonthermal) and filling factors. In addition, the relationship between AR jets and other phenomena such as photospheric magnetic activity, nonthermal type-III radio bursts and soft/hard X-ray emission has been studied using the Helioseismic and Magnetic Imager (HMI) on board SDO, the WAVES instrument on board the Wind satellite and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) respectively. The observations and results obtained in this study compare well with numerical simulations and theoretical models available in the literature.

Otitis Media (OM) is the most common paediatric disease and a leading cause of conductive hearing impairment. This multifactorial disease shows significant involvement of innate immunity genes and epithelial abnormalities are also commonly implicated. BPIFA1, a member of BPI fold containing family of putative innate defence proteins, is one of the most abundant secretory proteins in the upper airways and SNPs in BPIFA1 have been associated with OM susceptibility. Recent studies suggest that BPIFA1 plays a pleiotropic host defense role. This thesis describes experiments aimed at investigating the role of BPIFA1 in protection of the middle ear and in the development of OM. Bpifa1-/- mice do not spontaneously develop OM and do not demonstrate increased nasopharyngeal carriage of the human otopathogen, NTHi. However, deletion of Bpifa1 in Junbo (Evi1Jbo/+) mice, an established model of chronic OM, leads to significant exacerbation of OM severity and ME mucosal thickness. This thesis also describes the development of a novel in vitro model of the murine middle ear epithelium. Using a combination of transcriptional and proteomic approaches, I demonstrate that the model closely mimics the native middle ear epithelium and differentiates into ciliated cells, goblet cells and secretory cells and also supports infection by NTHi. Attempts were made to recapitulate the OM phenotype in vitro using this culture system. Overall, the data from this thesis indicate that BPIFA1 is involved in maintaining homeostasis within the middle ear under steady state conditions through nonspecific defence of the middle ear mucosa. Loss of BPIFA1 in presence of infection or inflammation increases the sensitivity of the epithelium and leads to an exacerbated host defence response and excessive epithelial remodelling. Furthermore, the novel in vitro culture system can be applied as an effective tool to study the interaction between the middle ear epithelium and various otopathogens.

Breast Cancer is the most common cancer among women and nearly 1 in every 8 American women suffer from it. Triple negative breast cancer, a type of breast cancer that can be only treated using chemotherapy, affects nearly 20% of the breast cancer diagnosed women. Early detection of breast cancer increases survival rates among patients. This dissertation discusses the development of a new two-functional folate-targeted poly(ethylene glycol)-based fluorescein-labeled conjugate (FA-FL-PEG-FL-FA) for potential applications in selective diagnosis of triple negative breast cancer.Since folate, or vitamin B9, receptors (FRs) are overexpressed in breast cancer cells, the diagnosis of these cells is targeted by using a γ-thiolated folic acid (FA-γ-SH) as the targeting precursor. α-carboxyl group present on folate is necessary for binding with the FRs, therefore, exclusive γ-thiolation was achieved by using n-butyllithium that selectively forms the lithium salt (FA-γ-Li) at the γ-carboxyl position due to its higher pKa. The subsequent thiolation was achieved by reducing FA-γ-S-S-γ-FA, which was prepared by reacting a dibrominated disulphide compound (Br-S-S-Br, synthesized via enzyme-catalyzed transesterification) with FA-γ-Li. To increase the retention time in the body and improve the solubility of the agent in water, functionalized PEGs were used as the hydrophilic linkers. Diamine, dithiol, and dibromide functionalization of PEGs were achieved using novel enzyme (Candida antartica Lipase B)-catalyzed esterifications and transesterifications. Specifically, three strategies to synthesize FA-FL-PEG-FL-FA were investigated for their synthetic convenience and feasibility. Strategy 1 used diamine-functionalized PEG (H2N-PEG-NH2), Strategy 2 used dithiol-functionalized PEG (HS-PEG-SH), and Strategy 3 used dibromide-functionalized PEG (Br-PEG-Br) as the precursors. The first strategy and the third strategy were not successful owing to not quantitatively yielding the intermediate products. Two-functional folate-targeted PEG-based fluorescein-labeled conjugates (FA-FL-PEG-FL-FA) with tetraethylene glycol, PEG with Mn = 1000 g/mol and 2050 g/mol, and discreet PEG (MW = 898 g/mol, Ð = 1) as the hydrophilic linkers were successfully synthesized using the second strategy.The enzyme-catalyzed Michael addition of thiol-functionalized PEGs to Sefose and the synthesis of cyclic polydisulfide polymers made using Reversible Redox Ring Polymerization (R3P) was also investigated and is discussed in this dissertation. In addition, my NSF-sponsored internship report is also presented in the appendices.

Al 2024 T-3 is a commonly used alloy in the aircraft industry which is highly susceptible to localized corrosion when subjected to corrosive environments. Of the many corrosion protection systems, applying a coating is one of the most cost effective methods. The classical physical barrier properties offered by the coatings in combination with a galvanic sacrificial anode offers to extend the life of the alloy against corroding environments. Since, aluminium is already at a lower position in the galvanic series; it must be protected by a more active material. Hence, a magnesium enriched coating is suggested for protection of such alloys. The present research aims at characterizing a magnesium rich primer (MgRP) applied over Al 2024 T-3 substrate. The Al 2024 T-3 substrate was pre-treated with PreKote to enhance the electrical contact between the magnesium particles and the substrate to activate the galvanic cathodic protection. Electrochemical Impedance Spectroscopy is used to characterize the interfacial mechanisms existing at the substrate/electrolyte interface. The MgRP/Al 2024 T-3 system is subjected to 0.6M NaCl solution to emulate the sea water conditions; and 0.6M sodium sulphate solution to emulate the acid rain conditions. The coating characteristics were varied on Al 2024 T-3 substrates in order to compare the response of the interface, and to study the existing transport mechanism of the coating layer. The interfacial reactions are being studied to determine the corrosion mechanism within the formed layer based on the damage evolution concept. Electrochemical characterization of the system was carried out by monitoring the coating/substrate/electrolyte interface in real time. The multi-scale theoretical tools which comprise of electrochemical testing techniques, high surface resolution techniques and characterization methods, analyse the performance of the substrate/coating interface with respect to the physical characteristics (thickness and environment) of the primer layer.

The use of communication networks has increased over the years. Due to many advantages like modularity, system flexibility and ease of maintenance, these networks have made their way into control systems. Today, in majority of applications, real-time networks like CAN (Controller-Area Network), Ethernet, FlexRay, ARINC, etc are used to close the control loop. However, the use of networks leads to communication constraints like transmission delays and packet dropouts. In the thesis, we consider the case of a networked control model wherein the presence of a communication protocol introduces delays in the control input. Additionally, in most of the applications, the plant is in continuous-time domain, whereas the controller is in discrete-time domain. Thus, the choice of sampling rate and the amount of network induced delay play a crucial role in the system stability. Perturbation or modeling errors arise in the nominal system due to parameter variations, un-modeled dynamics, neglected non-linearities or neglected external disturbances. In the thesis, we tackle the perturbations and time delays simultaneously and formulate bounds for stability of uncertain sampled data time delayed systems.The formulation is novel since till now obtaining robust bounds taking uncertainties and time delays simultaneously into consideration has rarely been tackled in the literature. The formulation takes into account the exponential structure of the perturbations due to sampling, the sampling period and time delays arising from the presence of a network in the control loop. Discrete-time Lyapunov stability criterion is used to obtain reasonably sufficient stability margins. Finally, the significance of the problem definition and its effectiveness is illustrated using the distributed turbine engine control case.

Strategic planning within complex service organizations (universities, cities, and other large service – oriented organizations) is extremely challenging due to 1) tensions between top-down versus bottom-up needs, 2) number of different stakeholders and goals at each level of the organization, 3) current and future goals, and4) continuously evolving environments and changing goals. Also keeping track of and modeling the interactions between different units within the organization is another hard task. While most of the industry uses top-down strategic planning, the disadvantage is that many details often fail as they are too farfetched and unrealistic. Most of the plans are developed for long term and these timelines don’t demand immediate actions from the middle and lower level employees. Top-down approach is good to communicate the management’s objectives and aims explicitly to lower levels. But it lacks a feedback loop to get inputs from ground level workers. Whereas in case of bottom-up approach, endless iterations to consolidate the final plan and resolve the negotiations between business owners and management delays & kills stakeholders interest in coming up with solid strategic plan. In this thesis, we study software features and benefits of developing a ‘Participatory Strategic Planning System’ (P2S2), based on a hybrid approach combining top-down control and bottom-up creativity. We identify how P2S2 helps in knowledge mining, decision making processes and improves the resource and people collaboration. The system (P2S2) we designed and modeled has bi-directional flow of information coming from top level executives and bottom level front line workers. It sets standards to collect and convey the information and it is also a single point of information related to any strategic planning efforts in the organization. P2S2 is a two phased, multi iteration system based on the enterprise domain model that we developed for The Ohio State University strategic planning. We illustrate the flexibility of this model through its application in another business enterprise.