Structure and dynamics of chain-grafted polymer nanocomposites

Polymer nanocomposites are of considerable interest in academia and industry, due to the enhanced properties arising from the addition of nanoparticles to a polymer matrix. Recent developments in controlled radical polymerisations have led to the synthesis of well-defined chain-grafted polymer nanocomposites. Research into the changes in chain conformation and dynamics in these systems is crucial for understanding the effect on macroscopic properties. Therefore, this thesis focuses on an extensive study of the structure and dynamics of these chain-grafted polymer nanocomposites. Two types of nanocomposites were investigated: polymer-silica nanocomposites and polystyrene-fullerene stars. The samples were studied primarily by neutron scattering techniques, along with complementary techniques such as dynamic light scattering (DLS) and rheological measurements. Small-angle neutron scattering (SANS) data on 6 arm PS-fullerene samples were analysed using the standard star and core-star models. The model fits have shown that the PS-fullerene stars have slightly extended chains around the fullerene core, leading to the stars being larger than expected compared to pure polymer stars. Differential scanning calorimetry (DSC), quasi-elastic neutron scattering (QENS) and rheological measurements showed that PS-fullerene stars have unusual dynamics compared to typical polymer stars, exhibiting total rather than arm molecular weight dependence. SANS measurements on polymer-silica nanocomposites in solution established that samples prepared with colloidal silica exhibit no change in chain conformation. However, fumed silica nanocomposites show a significant change in the large structure region that could not currently be modelled. QENS measurements on these samples showed that the dynamics of the polymer chains are significantly slowed down by the presence of fumed silica nanoparticles. Using the Time-Temperature Superposition principle (TTS) on the QENS and rheological data on these samples revealed a significant loss of free volume, which is therefore suggested to be the main cause of the decreased chain dynamics. Rheological measurements also confirmed a large increase in viscosity and modulus of dispersed poly(butyl acrylate)-silica nanocomposites. The presence of fumed silica has a greater effect on these properties than colloidal silica. Finally, a preliminary SANS and microscopy study on two polymer blends containing silica nanoparticles was carried out, establishing that the addition of silica can significantly decrease the miscibility of the blend. The effect of silica on the phase separation temperature is complex, and depends on the concentration of nanoparticles

Patient Advocates or Patient Adversaries? Using Fiduciary Law to Compel Disclosure of Managed Care Financial Incentives

This Article advocates disclosure as a compromise between wholeheartedly embracing financial incentives and flatly prohibiting them, and suggests using fiduciary law to compel such disclosure. This Article also argues that courts should recognize a cause of action for breach of fiduciary duty when a physician fails to disclose managed care financial incentives to her patients. Part I gives a brief overview of fiduciary law and fiduciary duties. Part II examines the fiduciary nature of the physician-patient relationship and looks at court cases that have characterized the physician-patient relationship as a fiduciary relationship. Part Ill discusses the only two published opinions that have addressed the issue of whether a patient can bring a breach of fiduciary claim against a physician. Building on these two cases, Part IV recommends that courts recognize a cause of action for breach of fiduciary duty for failure to disclose managed care financial incentives and discusses the remedies for breach. Finally, Part V examines the benefits and limits of disclosure as a way of dealing with financial incentives

Middle School Tutoring Practices in Illinois

Districts must provide successful cost-effective programs for students who are failing. One method that has proven both cost effective and successful is tutoring by staff, community volunteers, and students. The study investigated the tutoring practices in 45 schools and large unit districts in Illinois. As implemented, neither peer nor cross-age tutoring followed a predictable pattern. Results indicated that the most comon type of tutoring was after-school with remedial activities focusing on math and reading and taught by certified staff. The study described some of the design and administrative features that shape the programs, discussed possible implications for minority constituencies, and listed schools with programs that others may find helpful

Middle School Tutoring Practices in Illinois

Districts must provide successful cost-effective programs for students who are failing. One method that has proven both cost effective and successful is tutoring by staff, community volunteers, and students. The study investigated the tutoring practices in 45 schools and large unit districts in Illinois. As implemented, neither peer nor cross-age tutoring followed a predictable pattern. Results indicated that the most comon type of tutoring was after-school with remedial activities focusing on math and reading and taught by certified staff. The study described some of the design and administrative features that shape the programs, discussed possible implications for minority constituencies, and listed schools with programs that others may find helpful

Superconductivity and Physical Properties of CaPd2Ge2 Single Crystals

We present the superconducting and normal state properties of CaPd2Ge2 single crystal investigated by magnetic susceptibility \chi, isothermal magnetization M, heat capacity C_p, in-plane electrical resistivity \rho and London penetration depth \lambda versus temperature T and magnetic field H measurements. Bulk superconductivity is inferred from the \rho(T) and C_p(T) data. The \rho(T) data exhibit metallic behavior and undergoes a superconducting transition with T_c onset = 1.98 K and zero resistivity state at T_c 0 = 1.67 K. The \chi(T) reveal the onset of superconductivity at 2.0 K. For T>2.0 K, the \chi(T) and M(H) are weakly anisotropic paramagnetic with \chi_ab > \chi_c. The C_p(T) confirm the bulk superconductivity below T_c = 1.69(3) K. The superconducting state electronic heat capacity is analyzed within the framework of a single-band \alpha-model of BCS superconductivity and various normal and superconducting state parameters are estimated. Within the \alpha-model, the C_p(T) data and the ab plane \lambda(T) data consistently indicate a moderately anisotropic s-wave gap with \Delta(0)/k_B T_c ~ 1.6, somewhat smaller than the BCS value of 1.764. The relationship of the heat capacity jump at T_c and the penetration depth measurement to the anisotropy in the s-wave gap is discussed.Comment: 12 pages, 9 figures, 2 Tables; Submitted to PR

Synthesis, Crystal Structure and Magnetic Properties of the Linear-Chain Cobalt Oxide Sr5Pb3CoO12

The novel spin-chain cobalt oxide Sr5Pb3CoO12 [P-62m, a = 10.1093(2) A and c = 3.562 51(9) A at 295 K] is reported. Polycrystalline sample of the compound was studied by neutron diffraction (at 6 and 295 K) and magnetic susceptibility measurements (5 to 390 K). The cobalt oxide was found to be analogous to the copper oxide Sr5Pb3CoO12, which is comprised of magnetic-linear chains at inter-chain distance of 10 A. Although the cobalt oxide chains (mu_eff of 3.64 mu_B per Co) are substantially antiferromagnetic (theta_W = -38.8 K), neither low-dimensional magnetism nor long-range ordering has been found; a local-structure disorder in the chains might impact on the magnetism. This compound is highly electrically insulating.Comment: To be published in J. Solid State Che

Stopovers as valued-based experience: A conceptual model

This study on stopovers, defined as consisting of a one to three-night transition to a destination featuring value-based experiences, uses a multi-site data collection approach of focus groups in six cities to examine stopovers during long-haul air travel in Dubai and Abu Dhabi, Singapore and Hong Kong. It contributes to the literature on stopovers by defining and conceptualizing the term and identifying the key influences of stopover choice and value experiences of travelers from distant geographic areas, namely, the United Kingdom, France, Australia, and New Zealand. The proposal of the conceptual model on stopovers offers a basis for destination marketers a greater understanding of stopover travelers and facilitates the destination\u27s promotion from a practical perspective

Puppy love in the time of Corona: dog ownership protects against loneliness for those living alone during the COVID-19 lockdown

Background: The COVID-19 pandemic has resulted in many countries enforcing a ‘lockdown’, whereby people are instructed to stay at home. Aim: The aim of this study was to capture the experience of such a lockdown in Australians living alone, with and without a dog or a cat. Method: Three hundred and eighty-four participants completed an online survey evaluating their levels of loneliness, mindfulness and mood. For participants who owned a dog or a cat, a measure of dog/cat interactions was also administered as well as two open-ended questions about how being a pet owner affected their experience of COVID-19 and how COVID-19 affected their pet. Results: Contrary to expectations, cat owners were found to be less mindful than non-owners and pet interactions did not account for levels of loneliness or levels of mindfulness. In line with our expectations, however, stress and depression positively predicted loneliness, while mindfulness and being a dog owner were protective against it. Insights from qualitative responses suggest that this might be due to the fact that dogs encourage a routine which involves getting out of the house and walking, which itself offers opportunities to socialise with other people doing the same thing. Conclusion: These findings add to the emerging literature on mental well-being during a lockdown and the unique role that pets play in their owners’ experiences

Fit, Simplicity and Risk: Multiple Paths to Strategic IT Change

The dominant rational approach to IT-centered strategic change derives from the positioning literature in business strategy. It assumes a single best path to successful organizational transformation. Three cases are used to show that,inpractice,therearemultiplealternativepaths. ThestrategicITandbusinessstrategyliteraturesarecritiqued in terms of the process of fit so as to explain why these alternative paths are successful. Two distinctive characteristics of the fit process -- the search for simplicity and differential risk management profiles -- are identified. Their roles in successful paths are discussed