Ionomers are polymers that contain ionic groups in relatively low concentrations along the polymer backbone. These ionic groups, in the presence of oppositely charged ions, form aggregates that lead to novel physical properties of the polymer. React-A-Seal® and Surlyn® are poly(ethylene-co-methacrylic acid) (EMAA) ionomer-based materials and Nucrel® is the EMAA acid copolymer neutralized to produce Surlyn®. React-A-Seal® , Surlyn® , and Nucrel® recover into their original shapes following a high impact puncture at velocities ranging from 300 to 1200 ft/s ("self-healing"). This self-healing process may be of great benefit in space applications where structures are exposed to matter impacts. A thermal IR camera indicated a temperature increase to 98°C for Nucrel® 925, Surlyn® 8940, React-A-Seal® , and Surlyn® 8920 after initial penetration. To understand and generalize the observed phenomena, questions concerning the mechanism of the puncture resealing must be answered. One suggestion is that the elastic character of the melt created by the puncture drives the self-healing. This inference is based on the observed temperature rise of ~3°C above the melting temperature of the samples (~95°C) during the impact. With the expectation of gaining additional insight into the self-healing phenomenon, a thermodynamic and viscoelastic investigation was conducted using primarily DSC and DMA. Surlyn® and React-A-Seal® showed the characteristic order-disorder transition at ~52°C that has been reported in literature. Master curves were constructed from the creep isotherms for the four EMAA samples. An aging study was performed to investigate the irreproducibility and ®tailing effect” observed in the creep data. The aging study indicated that, with increased aging time and temperature, changes in the polyethylene matrix lead to complexities in morphology resulting in changes in the magnitude and shape of the creep curves. As a result of the thermodynamic, viscoelastic, and high-speed impact experiments it has been theorized that self-healing can occur in Nucrel® 925, Surlyn® 8940, React-A-Seal® , and Surlyn® 8920 because of two features, ionic aggregation and complex flow behavior. / Master of Science

Cette étude est une contribution à la valorisation du grignon d’olives (GO), sous produits oléicoles à caractère lignocellulosique. La voie proposée consiste à utiliser le GO comme charge dans des polymères de grande diffusion à savoir le poly (éthylène/propylène) [CEP] d’origine fossile et le poly (acide lactique) [PLA], issu des ressources renouvelables. Les différentes formulations, CEP/GO et PLA/GO, élaborées à l’état fondu dans une extrudeuse bivis ont été étudiés du point de vue des propriétés rhéologiques, thermique, mécanique et de la morphologie. Différents tiers-corps copolymères de structures diverses ont été utilisés dans le but de promouvoir l’adhésion à l’interface des composants et/ou de réduire la dégradation du polymère matrice et améliorer les performances des systèmes composites ainsi conçus. Les observations morphologiques ont corroboré parfaitement l’ensemble des propriétés étudiées. / This study is a contribution to the valorization of Olive Solid Waste (OSW) which displays a Lignocellulosic nature. The proposed approach consists in using the OSW as a filler in commodity polymers namely the poly (ethylene/propylene) [CEP] of fossil origin and the poly (lactic acid), derived from renewable resources. The different formulations, CEP/GO and PLA/GO, processed in the molten state in a twin screw extruder were studied from the side of rheological, thermal, mechanical properties and morphology. Different copolymers of various structures were used in order to promote the adhesion in the interface of the components and/or to reduce the polymer matrix degradation and to improve the composite systems performances. Morphological observations corroborated perfectly the studied properties.

Indiana University-Purdue University Indianapolis (IUPUI) / Stiffening and softening of extracellular matrix (ECM) are critical processes governing many aspects of biological processes. The most common practice used to investigate these processes is seeding cells on two-dimensional (2D) surfaces of varying stiffness. In recent years, cell-laden three-dimensional (3D) scaffolds with controllable properties are also increasingly used. However, current 2D and 3D culture platforms do not permit spatiotemporal controls over material properties that could influence tissue processes. To address this issue, four-dimensional (4D) hydrogels (i.e., 3D materials permitting time-dependent control of matrix properties) are proposed to recapitulate dynamic changes of ECM properties. The goal of this thesis was to exploit orthogonal enzymatic reactions for on-demand stiffening and/or softening of cell-laden hydrogels. The first objective was to establish cytocompatible hydrogels permitting enzymatic crosslinking and stiffening using enzymes with orthogonal reactivity. Sortase A (SrtA) and mushroom tyrosinase (MT) were used sequentially to achieve initial gelation and on-demand stiffening. In addition, hydrogels permitting reversible stiffening through SrtA-mediated peptide ligation were established. Specifically, poly(ethylene glycol) (PEG)-peptide hydrogels were fabricated with peptide linkers containing pendent SrtA substrates. The hydrogels were stiffened through incubation with SrtA, whereas gel softening was achieved subsequently via addition of SrtA and soluble glycine substrate. The second objective was to investigate the role of dynamic matrix stiffening on pancreatic cancer cell survival, spheroid formation, and drug responsiveness. The crosslinking of PEG-peptide hydrogels was dynamically tuned to evaluate the effect of matrix stiffness on cell viability and function. Specifically, dynamic matrix stiffening inhibited cell proliferation and spheroid formation, while softening the cell-laden hydrogels led to significant increase in spheroid sizes. Matrix stiffness also altered the expression of chemoresistance markers and responsiveness of cancer cells to gemcitabine treatment. markers and responsiveness of cancer cells to gemcitabine treatment.

京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第13241号 / 論工博第4179号 / 新制||工||1720(附属図書館) / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 吉崎 武尚, 教授 中村 洋, 教授 古賀 毅 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Poly Pipe Tubing is widely used in the Mississippi Delta for supplemental irrigation of crops during the growing season. Computerized Hole Selection (CHS) is a tool used to create a prescriptive hole punching map to manage flow and minimize tail-water runoff. Some producers have documented that CHS does not work on their farm. The common thought of failure in poly pipe tubing is the rupturing or splitting of the tubing. This research was based on the thought that failure occurs before the tubing is ruptured and is caused by over pressurization during an irrigation event. Static testing revealed that there are tensile material property differences between different thicknesses of tubing. Dynamic testing revealed on small single hole sections of tubing that hole flow increases once yield tensile strength has been surpassed for all thicknesses of tubing. Therefore, this shows that over pressurization could be the cause for CHS not working on some producers’ field.

Electrochemical biosensors have been used to detect biomarkers sensitively at low limits of detection. The organic electrochemical transistor (OECT) is a special class of electrochemical biosensors characteristically known for its intrinsic amplification abilities. Nevertheless, if the biosensor is to be used with real clinical samples a strategy aiming to increase the specificity of the device other than the dependance on the respective biorecognition unit is necessary to minimize, if not eliminate, interference from foulants in complex biological media. In this work we test the antifouling performance of several Poly(ethylene glycol) based SAMs using Electrochemical impedance spectroscopy (EIS). We also evaluate the overall performance of the device and its ability to detect total α-synuclein, its aggregate and phosphorylated forms spiked in heat-inactivated human serum. Limits of detection in the fM and aM ranges were achieved.

Background: Patients with pre-existing vascular disease are known to have worse outcomes after acute myocardial infarction (AMI). However, there is limited data for outcomes stratified by type and number of vascular territories involved. Methods: Using the Nationwide Inpatient Sample (2015–2017), we examined outcomes of AMI in patients with pre-existent vascular disease stratified by number as well as types of diseased beds including all five major vascular sites: cardiac, cerebrovascular, renal, aortic and peripheral vascular disease (PVD). Multivariable logistic regression was used to determine the adjusted odds ratios (aOR) of adverse outcomes and invasive procedure utilization. Results: Out of 2,184,614 AMI admissions, 49.7% had pre-existent vascular disease. The odds of major adverse cardiovascular and cerebrovascular events (MACCE), mortality, ischemic stroke and major bleeding incrementally increased and was highest in those with ≥3 vascular sites involved (aOR for MACCE 1.16, CI 1.13–1.19; mortality 1.3, CI 1.26–1.34; stroke 1.15, CI 1.1–1.2; major bleeding 1.21, CI 1.16–1.25). Amongst those with a single pre-existent diseased vascular bed, the adjusted odds of MACCE appeared to be higher in those with PVD (1.28, CI 1.26–1.31), aortic disease (1.24, CI 1.19–1.29), and cerebrovascular disease (1.22, CI 1.2–1.25). Patients with pre-existent vascular disease had a lower overall likelihood of undergoing invasive revascularization procedures. Conclusions: Approximately half of the population presenting with AMI have pre-existent vascular disease. There is an incremental increase in adverse outcomes with increasing number of diseased vascular beds, with further differences in outcomes and utilization of invasive procedures based on sub-types of sites involved.

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No description available.