Structural Characterisation of Bioactive Glasses

Melt-quenched glasses containing SiO2, CaO, Na2O and P2O5, and sol-gel derived glasses containing SiO2 and CaO are known to have bioactive properties. Foaming of binary sol-gel derived bioactive glasses containing SiO2 and CaO can be used to produce 3D porous scaffolds which mimic the structure of trabecular bone, increasing the potential for these glasses to be used as bioactive bone-regenerative materials. A range of experimental techniques have been used to investigate the atomic scale structure of these materials, and also to observe the reaction mechanisms which occur when these materials are immersed in a simulated physiological solution (simulated body fluid, SBF) and a standard cell culture medium (tris buffer solution, TBS). A robust structural model of the most bioactive of the melt-quenched glasses, namely Bioglass®, has been produced by combining high energy X-ray and neutron diffraction data, magic angle spinning nuclear magnetic resonance (MAS NMR) and reverse Monte Carlo (RMC) modelling. It has been shown that Ca clustering occurs in the glass, which is of direct relevance to the understanding of the facile nature of calcium within such glasses giving rise to its relatively rapid diffusion from the solid into solution. Hydroxyapatite has been confirmed as the calcium phosphate phase which grows on the surface of Bioglass® when immersed in the standard cell culture medium, TBS. A new method which can be used for in-situ time resolved high-energy X-ray diffraction studies of reaction mechanisms, such as those involved when a bioactive glass is immersed in a simulated physiological solution, is decribed in this thesis. Small-angle X-ray scattering has enabled the growth of mesopores to be observed during the foamed sol-gel stabilisation process. In-situ simultaneous small and wide angle X-ray scattering measurements of a foam in SBF have shown that the mesoporous network facilitates the rapid growth of relatively high-density HCA, which will therefore eventually replace the initial silicate glass as the material bounding the macropores. The data presented herein reveal the structure of highly important materials in the field of biomaterials and enable a link to be made between the atomic scale structure of the materials and their bioactive properties

Does The Application of Kinesiology Tape Aid in Increasing Venous Flow

Kinesiology tape has become extremely popular among athletes of all ages. It’s bright colors and the unique patterns created by the tape have gained an astonishing amount of attention. KT tape is a highly elastic tape that is advertised to increase muscle proprioception, reduce pain, and increase the space between fascial layers for higher venous flow. There has been a large amount of controversy surrounding KT tape and the placebo effects its usage may have. The purpose of this study is to determine if kinesiology tape actually increases venous flow which will result in a reduction of edema and ecchymosis after injury

Structural characterisation of bioactive glasses

Melt-quenched glasses containing SiO2, CaO, Na2O and P2O5, and sol-gel derived glasses containing SiO2 and CaO are known to have bioactive properties. Foaming of binary sol-gel derived bioactive glasses containing SiO2 and CaO can be used to produce 3D porous scaffolds which mimic the structure of trabecular bone, increasing the potential for these glasses to be used as bioactive bone-regenerative materials. A range of experimental techniques have been used to investigate the atomic scale structure of these materials, and also to observe the reaction mechanisms which occur when these materials are immersed in a simulated physiological solution (simulated body fluid, SBF) and a standard cell culture medium (tris buffer solution, TBS). A robust structural model of the most bioactive of the melt-quenched glasses, namely Bioglass®, has been produced by combining high energy X-ray and neutron diffraction data, magic angle spinning nuclear magnetic resonance (MAS NMR) and reverse Monte Carlo (RMC) modelling. It has been shown that Ca clustering occurs in the glass, which is of direct relevance to the understanding of the facile nature of calcium within such glasses giving rise to its relatively rapid diffusion from the solid into solution. Hydroxyapatite has been confirmed as the calcium phosphate phase which grows on the surface of Bioglass® when immersed in the standard cell culture medium, TBS. A new method which can be used for in-situ time resolved high-energy X-ray diffraction studies of reaction mechanisms, such as those involved when a bioactive glass is immersed in a simulated physiological solution, is decribed in this thesis. Small-angle X-ray scattering has enabled the growth of mesopores to be observed during the foamed sol-gel stabilisation process. In-situ simultaneous small and wide angle X-ray scattering measurements of a foam in SBF have shown that the mesoporous network facilitates the rapid growth of relatively high-density HCA, which will therefore eventually replace the initial silicate glass as the material bounding the macropores. The data presented herein reveal the structure of highly important materials in the field of biomaterials and enable a link to be made between the atomic scale structure of the materials and their bioactive properties.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Preparation, characterisation and secondary crystallisation of PHB based copolymers and carbohydrate blends

Poly(hydroxybutyrate) copolymers are sustainable and biodegradable, but they are known to exhibit secondary crystallisation, which severely reduces the ductility of these materials, thus hindering their current commercial use. Therefore, the main focus of this research was to explore a number of strategies to control the secondary crystallisation behaviour of two Poly(hydroxybutyrate) based copolymers. Blends of P(HB-co-HV)(3 wt % HV) with carbohydrate molecules of varying chain lengths were prepared by melt blending, characterised, and monitored over time to assess their capability to reduce secondary crystallisation. Additives were found to hinder the secondary crystallisation process, demonstrated by a reduction in the percentage change of mechanical properties as the concentration and chain length increased. The effect of storage temperature on the secondary crystallisation behaviour of P(HB-co-HHx)(33 % HHx) was also reported. Samples were stored at a range of storage temperatures and the effects on thermal, chemical and mechanical properties discussed. Increasing storage temperature caused the secondary process to occur to a greater extent, with greater increases in the melting temperature recorded in samples stored at 100 $^∘$C (128 $^∘$C - 135 $^∘$C) compared to samples stored at 7 $^∘$C (128 $^∘$C – 128 $^∘$C). Sub-melting point degradation of the material was also noted

Preparation, characterisation and secondary crystallisation of PHB based copolymers and carbohydrate blends

Poly(hydroxybutyrate) copolymers are sustainable and biodegradable, but they are known to exhibit secondary crystallisation, which severely reduces the ductility of these materials, thus hindering their current commercial use. Therefore, the main focus of this research was to explore a number of strategies to control the secondary crystallisation behaviour of two Poly(hydroxybutyrate) based copolymers. Blends of P(HB-co-HV)(3 wt % HV) with carbohydrate molecules of varying chain lengths were prepared by melt blending, characterised, and monitored over time to assess their capability to reduce secondary crystallisation. Additives were found to hinder the secondary crystallisation process, demonstrated by a reduction in the percentage change of mechanical properties as the concentration and chain length increased. The effect of storage temperature on the secondary crystallisation behaviour of P(HB-co-HHx)(33 % HHx) was also reported. Samples were stored at a range of storage temperatures and the effects on thermal, chemical and mechanical properties discussed. Increasing storage temperature caused the secondary process to occur to a greater extent, with greater increases in the melting temperature recorded in samples stored at 100 $^∘$C (128 $^∘$C - 135 $^∘$C) compared to samples stored at 7 $^∘$C (128 $^∘$C – 128 $^∘$C). Sub-melting point degradation of the material was also noted

Chronology of gypsum dunes at Knolls, Utah: refining OSL techniques and timing of Holocene eolian processes

Master of ScienceDepartment of GeologyJoel SpencerThis study examines eolian samples from post-Lake Bonneville gypsum dunes in Knolls, UT, primarily to determine suitability of optically stimulated luminescence (OSL) dating protocols for gypsum geochronology. Sedimentologists often rely on proxies to understand geologic timescales, OSL may eliminate that need in environments with gypsum. Using OSL we aimed to identify the ages of punctuated climatic events that are linked to deposition of the gypsum rich dunes found in the study area. To accomplish this pursuit, systematic research of gypsum preparation protocols were required. Multiple experiments were undertaken to assess the effectiveness of mineral isolation and etching. Knowledge of gypsum behavior is of particular interest, as it is found in both lacustrine and marine environments and is typically less soluble than other evaporites found in both settings, such as sodium chloride. Gypsum has also been observed at several hundred meters water depth in the alkaline environment of the Arctic Ocean. Additionally, gypsum sand grains are accessible to researchers in geomorphic features like unconsolidated to semi-consolidated dunes, making them easier to sample for OSL analyses than gypsum or quartz found in an outcrop. Sampling strategy can be quickly determined for dunes that are exposed on all sides. The focus of this study seeks to resolve discrepancies observed in the small body of literature on gypsum as an OSL chronometer. Relatively homogenous eolian gypsum sand grain samples with grain sizes ranging from 250 μm from two adjacent paleodunes (KNP-A and KNP-B) and one coppice dune (CD-5) were used to determine best preparation practices and identify if punctuated climatic events during the Holocene could be detected using gypsum. The sample site was selected for a case study on OSL dating techniques because previous work has constrained the maximum age of post-Lake Bonneville dune formation (~12 ka BP). Preparation protocols, independently checked using various methods, were selected with minimal mineralogical impact and OSL sensitivity considerations in mind. Bulk composition and mineralogy of the sediment at various steps in sample preparation have been analyzed using X-Ray Diffraction, bulk elemental extraction, particle size analysis, Scanning Electron Microscopy and binocular microscopy. Etching experiments indicate that an air-dried, dry-sieved, and gypsum-rich fraction (90-125 μm) can be effectively isolated and etched in ~36 wt % HCl for 40 minutes. Of the various OSL measurement protocols attempted, we confirmed a modified single-aliquot regenerative-dose protocol produces detectable luminescence signals and equivalent doses (Dₑ) that are usable in age calculations. Age results are likely to be underestimated by approximately 0.5-0.8 ka, based on comparison to a single quartz OSL sample (KNP-A1) with an age of 2.2 ka and it’s equivalent gypsum sample of 1.4 ka. This is the oldest age sampled from the stratigraphically lowest section of either KNP-A or KNP-B. Samples from KNP-B identify this smaller dune was deposited after KNP-A began developing. Age results from the stratigraphically lowest sample collected, KNP-B1, indicate deposition occurred at 0.88 ka. The active coppice dune (CD-5) gypsum OSL age is 0.09 ka. This study recommends further investigation into why the apparent discrepancy between gypsum and quartz OSL chronology exists

A rhlI 5′ UTR-Derived sRNA Regulates RhlR-Dependent Quorum Sensing in Pseudomonas aeruginosa

N-Acyl homoserine lactone (AHL) quorum sensing (QS) controls expression of over 200 genes in Pseudomonas aeruginosa. There are two AHL regulatory systems: the LasR-LasI circuit and the RhlR-RhlI system. We mapped transcription termination sites affected by AHL QS in P. aeruginosa, and in doing so we identified AHL-regulated small RNAs (sRNAs). Of interest, we noted that one particular sRNA was located within the rhlI locus. We found that rhlI, which encodes the enzyme that produces the AHL N-butanoyl-homoserine lactone (C4-HSL), is controlled by a 5′ untranslated region (UTR)-derived sRNA we name RhlS. We also identified an antisense RNA encoded opposite the beginning of the rhlI open reading frame, which we name asRhlS. RhlS accumulates as wild-type cells enter stationary phase and is required for the production of normal levels of C4-HSL through activation of rhlI translation. RhlS also directly posttranscriptionally regulates at least one other unlinked gene, fpvA. The asRhlS appears to be expressed at maximal levels during logarithmic growth, and we suggest RhlS may act antagonistically to the asRhlS to regulate rhlI translation. The rhlI-encoded sRNAs represent a novel aspect of RNA-mediated tuning of P. aeruginosa QS

Education for a Future in Crisis: Developing a Humanities-Informed STEM Curriculum

In the popular imagination, science and technology are often seen as fields of knowledge production critical to social progress and a cooperative future. This optimistic portrayal of technological advancement also features prominently in internal discourses amongst scientists, industry leaders, and STEM students alike. Yet, an overwhelming body of research, investigation, and first-person accounts highlight the varying ways modern science, technology, and engineering industries contribute to the degradation of our changing environments and exploit and harm global low-income and marginalized populations. By and large, siloed higher-education STEM curricula provide inadequate opportunities for undergraduate and graduate students to critically analyze the historical and epistemological foundations of scientific knowledge production and even fewer tools to engage with and respond to modern community-based cases. Here, we describe the development of a humanities- and social sciences-informed curriculum designed to address the theory, content, and skill-based needs of traditional STEM students considering technoscientific careers. In essence, this course is designed to foster behavior change, de-center dominant ways of knowing in the sciences, and bolster self-reflection and critical-thinking skills to equip the developing STEM workforce with a more nuanced and accurate understanding of the social, political, and economic role of science and technology. This curriculum has the potential to empower STEM-educated professionals to contribute to a more promising, inclusive future. Our framework foregrounds key insights from science and technology studies, Black and Native feminisms, queer theory, and disability studies, alongside real-world case studies using critical pedagogies.Comment: 25 pages, 1 figure, 4 table

Myo/Nog Cells Are Present in the Ciliary Processes, on the Zonule of Zinn and Posterior Capsule of the Lens Following Cataract Surgery

Myo/Nog cells, named for their expression of MyoD and noggin, enter the eye during early stages of embryonic development. Their release of noggin is critical for normal morphogenesis of the lens and retina. Myo/Nog cells are also present in adult eyes. Single nucleated skeletal muscle cells designated as myofibroblasts arise from Myo/Nog cells in cultures of lens tissue. In this report we document the presence of Myo/Nog cells in the lens, ciliary body and on the zonule of Zinn in mice, rabbits and humans. Myo/Nog cells were rare in all three structures. Their prevalence increased in the lens and ciliary body of rabbits 24 h following cataract surgery. Rabbits developed posterior capsule opacification (PCO) within one month of surgery. The number of Myo/Nog cells continued to be elevated in the lens and ciliary body. Myo/Nog cells containing alpha smooth muscle actin and striated muscle myosin were present on the posterior capsule and overlaid deformations in the capsule. Myo/Nog cells also were present on the zonule fibers and external surface of the posterior capsule. These findings suggest that Myo/Nog contribute to PCO and may use the zonule fibers to migrate between the ciliary processes and lens