Several pyrene-labeled polymers and polypeptides were synthesized and their chain dynamics were characterized using steady-state and time-resolved fluorescence techniques. Firstly, four series of pyrene-labeled polystyrenes (Py-PS) were synthesized to determine the effect that the method used for pyrene attachment, the linker connecting pyrene to the backbone, and the distribution of pyrene along the backbone all have on excimer formation. It was found that the amount of excimer formed was different in each case. The differences were described by utilizing the fluorescence blob model (FBM) analysis of the time-resolved monomer and excimer fluorescence decays. Secondly, two Py-PS series were studied in several different solvents with viscosities ranging from 0.36 to 1.19 mPa.s to demonstrate the effect of viscosity on the FBM parameters. The rate constant for excimer formation within a blob, kblob, was found to remain constant with viscosity while the number of monomer units per blob, Nblob, increased with decreasing viscosity. Thirdly, in a technical note, the inherent analogy existing between the aggregation number of surfactant micelles, Nagg, and Nblob, is taken advantage of to establish a “model-free” procedure to determine Nblob. This procedure was validated through the analysis of the time-resolved fluorescence decays of five different pyrene-labeled polymers in seven different solvents. Fourthly, the side-chain dynamics of alpha-helical pyrene-labeled poly(glutamic acid) were investigated. A longer linker connecting pyrene to the backbone resulted in an increase in Nblob which agreed quantitatively with predictions made by molecular modeling. Decreasing the lifetime of the excited pyrene from 215 ns to 50 ns with a quencher increased kblob significantly, while Nblob decreased slightly. Finally, the backbone dynamics of pyrene-labeled poly(aspartic acid) (Py-PAA) were investigated and quantified using the FBM. It was determined that excimer formation was controlled by the very rigid polypeptide backbone and not by the solvent viscosity, contrary to previous results obtained with other pyrene-labeled vinyl polymers.

Several pyrene-labeled polymers and polypeptides were synthesized and their chain dynamics were characterized using steady-state and time-resolved fluorescence techniques. Firstly, four series of pyrene-labeled polystyrenes (Py-PS) were synthesized to determine the effect that the method used for pyrene attachment, the linker connecting pyrene to the backbone, and the distribution of pyrene along the backbone all have on excimer formation. It was found that the amount of excimer formed was different in each case. The differences were described by utilizing the fluorescence blob model (FBM) analysis of the time-resolved monomer and excimer fluorescence decays. Secondly, two Py-PS series were studied in several different solvents with viscosities ranging from 0.36 to 1.19 mPa.s to demonstrate the effect of viscosity on the FBM parameters. The rate constant for excimer formation within a blob, kblob, was found to remain constant with viscosity while the number of monomer units per blob, Nblob, increased with decreasing viscosity. Thirdly, in a technical note, the inherent analogy existing between the aggregation number of surfactant micelles, Nagg, and Nblob, is taken advantage of to establish a “model-free” procedure to determine Nblob. This procedure was validated through the analysis of the time-resolved fluorescence decays of five different pyrene-labeled polymers in seven different solvents. Fourthly, the side-chain dynamics of alpha-helical pyrene-labeled poly(glutamic acid) were investigated. A longer linker connecting pyrene to the backbone resulted in an increase in Nblob which agreed quantitatively with predictions made by molecular modeling. Decreasing the lifetime of the excited pyrene from 215 ns to 50 ns with a quencher increased kblob significantly, while Nblob decreased slightly. Finally, the backbone dynamics of pyrene-labeled poly(aspartic acid) (Py-PAA) were investigated and quantified using the FBM. It was determined that excimer formation was controlled by the very rigid polypeptide backbone and not by the solvent viscosity, contrary to previous results obtained with other pyrene-labeled vinyl polymers.

No description available.

No description available.

No description available.

The photosensitive unit triggering the negative phototaxis in the haloarchaeum Natronomonas pharaonis consists of the receptor sensory rhodopsin II (NpSRII) and its cognate transducer (NpHtrII) in a 2:2 stoichiometry. Upon light excitation, a structural rearrangement in the receptor initiates a displacement/rotation of the transducer helix TM2, which can be considered as starting event for the signal transduction. This signal is further transmitted to the cytoplasmic signaling domain through the signal transduction unit comprising two HAMP domains.Structural information already exists for the transmembrane region of this complex (crystal structure) as well as for the rod shaped cytoplasmic part of NpHtrII due to its high homologies with chemoreceptors. Moreover, the solution NMR structure of the isolated HAMP domain from A. fulgidus recently obtained shows a homodimeric, four-helical, parallel coiled-coil with an unusual interhelical packing, that is thought to propagate a signal by virtue of concerted helix rotations. Here, an electron paramagnetic resonance (EPR) investigation of site-directed spin labeled transducers in the NpSRII/NpHtrII complex has been carried out for structural and functional elucidation of the N. pharaonis HAMP. For this purpose, cw as well as pulse EPR techniques have been used in terms of mobility, accessibility and intra-transducer dimer distance analyses. Conformational changes induced by environmental inputs, namely salt, temperature and pH, give insight into the two-state equilibrium existing between a highly dynamic (dHAMP) and a more compact (cHAMP) conformation of this linker region.

Hot-melt extruded solid dispersion technique is increasingly employed to improve the solubility of poorly water-soluble drugs. The technique relies on the enhanced solubility of the amorphous form of the drug compared to its crystalline counterpart. These systems however are thermodynamically unstable. This means that the drug crystallises with time. Therefore, efforts to measure the stability of these systems over the life span of the product are crucial. This study focused on investigating the use of Hansen Solubility Parameters to quantify polymer-drug interaction and to predict the stability of solid dispersions. This was achieved through a systematic review of hot-melt extruded solid dispersion literature. The study also investigated the use of a combined mechanical and rheological model to characterise the physicochemical and release behaviour of three solid dispersion immediately after preparation and after storage for one month at 40oC or three months at room temperature. Results revealed that the total solubility parameter |ΔбT| was able to predict the stability of the systems for more than 4 months using a cut-off point of 3 MPa-1 with a negative predictive value of 0.9. This was followed by ΔбD with a cut-off point of 1.5 MPa- 1. Moreover, Dynamic Mechanical Analyser and shear rheometry data were shown to be more sensitive than Differential Scanning Calorimetry, Powder X-Ray Diffraction, Scanning Electron Microscope and Fourier Transform Infrared in detecting crystallisation and the interaction between the drug and the polymer. The Dynamic Mechanical Analyser data were consistent with the dissolution behaviour of the samples when comparing the freshly prepared samples with those after storage. The results highlight the need for a unified characterisation approach and the necessity of verifying the homogeneity of mixing during the extrusion process.

The purpose of this thesis is to model the effects of anti-price gouging (APG) legislation on the costs to businesses during the recovery period of a disaster. A system dynamics model of a business’s replenishment procedures is used to simulate the effects of APG legislation on business performance. Economists have published expansive research on the effects of price ceilings on supply and demand, but there is little research evidence on the operational consequences of price ceiling legislation on business costs. APG legislation increases consumer’s forward buying and shortage gaming after a disaster by removing price incentives to be frugal. Forward buying and shortage gaming are two key drivers of the demand variation and the bullwhip effect, which leads to increased inventory costs, misguided capacity expansion and reduced service levels. These costs have a negative impact on local businesses that are critical to a community’s economic health and recovery from a disaster. The simulation results from this thesis show that APG legislation is not an effective regulatory response to decrease the impact of disasters on affected communities.

Segmental chain dynamics in polymer blends is a very important topic, not only from a fundamental point of view but also from technological applications. Because of the difficulties in the commercialization of new polymers, industries have turned increasingly towards blending of polymers to optimise their end use (mechanical, rheological) properties. The design of tailor-made materials would be enormously facilitated by the understanding of the blending phenomena at a molecular level. The key question to address is to understand the dynamics of each component of the blend modified by blending? The thesis has systematically studied the effect of multiwalled carbon nanotubes on the chain dynamics, demixing temperature, structural properties and evolution of morphology in a classical miscible polymer blend system (PVDF/PMMA). The thesis comprises of six chapters, Chapter 1 is an introductory chapter that outlines the fundamentals of polymer blends, crystallisation in polymer blends and the basics of dielectric spectroscopy. As one of the rationales of this work is to systematic study whether phase separated in these blends can be used as a tool to develop membrane for water purification. This chapter also gives an overview of the reported studies of ultrafiltration membrane fabrication, factors affecting membrane morphology and flux. In Chapter 2, the materials and methodology used to carry out experiments and the experimental procedures are discussed. Chapter 3 discusses the effect of concentration of PMMA and amine functionalized multiwalled carbon nanotubes (MWNTs) on the crystallisation induced phase separation using FTIR, XRD, POM and shear rheology. Electron microscopy and selective etching confirmed the localisation of MWNTs in the PVDF phase of the blends. Blends with MWNTs facilitated in heterogeneous nucleation manifesting in an increase in crystallisation temperature. The crystallisation induced phase separation in PVDF/PMMA blends was observed to influence the interconnected network of MWNTs in the blends. Chapter 4 discuss the effect of concentration of PMMA and MWNTs on the miscibility and the segmental relaxations was probed in situ by DSC and dielectric relaxation spectroscopy (DRS). The dynamic heterogeneity in the blends as manifested by the presence of an extra relaxation at a higher frequency at or below the crystallisation induced phase separation temperature was also discussed. We found that PVDF/PMMA blend (PVDF ≥ 80 wt%) exhibits three distinct relaxations; αc corresponding to crystalline PVDF, αβ segmental relaxation of PMMA and αm of amorphous miscibility whereas all relaxations overlap and constitute a single broad relaxation in PVDF/PMMA blend (PVDF ≤ 70 wt%). This confirms that there is a certain composition width in this blend wherein three distinct relaxations can be traced. This could due to many reasons like the width of crystal-amorphous interphase in the crystal lamellae, crystal size and morphology is strongly contingent on the concentration of PMMA. Relaxations are not very distinct in presence of MWNTs due to defective spherulites that shift the relaxations towards a higher frequency. Chapter 5 has attempted to tune the microporous morphology of PVDF membranes using crystallisation induced phase separation in PVDF/PMMA blends. As PVDF/PMMA is a melt-miscible blend, the samples were allowed to crystallise and the amorphous PMMA phase, which isolates in the interlamellar or inter-spherulitic regions in the blends, was etched out to generate microporous structures. The pore sizes can be tuned by varying the PMMA concentration in the blends. We observed that 60/40 PVDF/PMMA blends showed larger pores as compared to 90/10 PVDF/PMMA blends. We further modified PVDF membranes by sputtering silver on the surface. The bacterial cell viability was distinctly suppressed (99 %) in silver sputtered membranes. The ICP analysis suggests that slow Ag+ ions release from the sputtered membrane surface assisted in developing antibacterial surface. Our findings open new avenues in designing water filtration membranes and also help in understanding the crystallisation kinetics for tuning pore size in membranes. Chapter 6 summarises the important results of this work. MWNTs act as hetero nucleating agent and specifically interact with PVDF thereby influences the dynamics of PVDF chains. MWNTs can also restrict the amorphous segmental mobility and can influence the intermolecular cooperativity and coupling. The crystallisation induced phase separation in various blends can result in various crystalline morphologies depending on the PVDF concentration. By selectively etching PMMA from the phase-separated blends, microporous morphology can be generated

Globalization and the surge of competition across industries forced companies to improve their supply chain capabilities to serve their customers efficiently and effectively. Due to this fact, businesses are no longer capable of handling all supply chain operations without collaboration and coordination with other firms. One of the key obstacles to coordination is the lack of information sharing and trust between firms since they view information as a sensitive asset. Digital technologies like blockchain, with its inherited features, have the capability to facilitate real-time information sharing, solve trust issues, and improve end-to-end visibility across the supply chain. This licentiate thesis highlights the impact of multiple aspects of information sharing on the bullwhip effect mitigation and explores the potential of blockchain technology as a new coordination mechanism for reducing information distortions, enhancing trust, and orchestrating decision making. Three research papers have been produced within this context and are appended to the thesis. Paper A presents an information sharing-based blockchain architecture to mitigate the bullwhip effect in service supply chains. Paper B aims to explores the literature in terms of using multiple aspects of information sharing to lessen the bullwhip effect. Finally, Paper C introduces an agent-based modeling and simulation approach for two aspects of information sharing: “what to share” and “how to share.” The results show that blockchain technology does provide a significant solution to trust-based issues and information sharing visibility considering the bullwhip effect mitigation. The results also provide a guide for supply chain managers to achieve better coordination and serve as a roadmap for supply chain researchers.