Viscoelastic characterization of thin-film polymers exposed to low Earth orbit

The materials made available through the Long Duration Exposure Facility (LDEF) satellite provide a set of specimens that can be well characterized and have a known exposure history with reference to atomic oxygen and ultraviolet radiation exposure. Mechanical characteristics measured from control samples and exposed samples provide a data base for predicting the behavior of polymers in low earth orbit. Samples of 1.0 mil thick low density polyethylene were exposed to the low earth orbit environment for a period of six years. These materials were not directly exposed to ram atomic oxygen and offer a unique opportunity for measuring the effect of atomic oxygen and UV radiation on mechanical properties with little concern to the effect of erosion. The viscoelastic characteristics of these materials were measured and compared to the viscoelastic characteristics of control samples. To aid in differentiating the effects of changes in crystallinity resulting from thermal cycling, from the effects of changes in chemical structure resulting from atomic oxygen/UV attack to the polymer, a second set of control specimens, annealed to increase crystallinity, were measured as well. The resulting characterization of these materials will offer insight into the impact of atomic oxygen/UV on the mechanical properties of polymeric materials. The viscoelastic properties measured for the control, annealed, and exposed specimens were the storage and loss modulus as a function of frequency and temperature. From these datum is calculated the viscoelastic master curve derived using the principle of time/temperature superposition. Using the master curve, the relaxation modulus is calculated using the method of Ninomiya and Ferry. The viscoelastic master curve and the stress relaxation modulus provide a direct measure of the changes in the chemical or morphological structure. In addition, the effect of these changes on long-term and short-term mechanical properties is known directly. It should be noted that the dependence on directionality for the polymer films was considered since these films were manufactured by a blown-film process

Classical ballet training for apparently healthy older adults : evaluation of biomechanical and functional outcomes

Ageing is associated with a progressive decline in muscular strength, balance ability, and joint range of motion. Exercise interventions mitigate age-related decline in physical function but are seldom maintained long-term. A key barrier is lack of enjoyment. Dance-based interventions offer an enjoyable form of physical activity which may promote long-term engagement. This thesis investigates the effectiveness of a classical ballet intervention for adults aged 50 years and older on biomechanical and functional outcomes. An alternative method for quantitative biomechanical analysis of joint angles for classical ballet movements is investigated. A systematic review of the literature (Chapter 2) investigated the physical and psychological benefits of classical ballet training across all age groups. Results indicated that novice dancers were seldom reported (included in 6 groups), compared to experienced dancers (19 groups). Balance was the most frequently reported outcome in novice dancers and improved in 75% of studies. Included populations were diverse, thus the most efficacious training prescription could not be determined. More ballet training interventions for novice populations are required. The first experimental study (Chapter 3) aimed to evaluate the effectiveness of classical ballet training for adults aged 50 years and older. Twenty-two female participants completed a 10-week intervention, consisting of a one-hour class, once per week (mean age = 56.2 years). Results indicated strong adherence rates, with improvements in aspects of lower limb strength and joint range of motion, and limited improvements in balance. The second study (Chapter 4) aimed to determine the validity of Inertial Measurement Units (IMU), compared to optical motion capture (gold standard) for lower limb 3D kinematic analysis of classical ballet movements. Optical motion capture requires expensive equipment and is time consuming. Conversely, IMU are small, portable devices which may provide a viable alternative. Results indicated that overall, the IMU did not show strong agreement with optical motion capture data for quantitative analysis of lower limb joint angles for classical ballet movements. The Discussion (Chapter 5) presents a summary of the findings, general conclusions, and recommendations for future work

The Hybridization of a Graphene and Silicon Carbide Schottky Optoelectronic Device by the Incorporation of a Lead Sulfide Quantum Dot Film

The work that follows examines the impact of lead sulfide quantum dots on a native epitaxial graphene (EG) SiC Schottky device, resulting in a hybrid optoelectronic device which presents a possible avenue towards a novel hybrid carbide-based Schottky solar cell. The active (n-type SiC) and contact (graphene) layers for the Schottky junction of the device were grown epitaxially using a novel technique incorporating tetrafluorosilane (TFS) as a precursor gas. The bare EG/SiC device was characterized based on its I-V behavior in dark and under illumination for both forward and reverse bias conditions. The initial characterization demonstrated the expected Schottky diode rectifying behavior and an action spectra consistent with absorption at and above the bandgap of 4h-SiC (3.23 eV, 380 nm). After initial characterization, PbS QDs synthesized as described by Zhang et al.[63] and treated with an ethanedithiol (EDT) ligand exchange[29] were incorporated with the Schottky device. The hybrid device demonstrated significant changes in I-V behavior and the observed action spectra. There was an increase in photocurrent and responsivity at wavelengths above ≈380 nm, corresponding to a device response below the bandgap of 4h-SiC. We confirmed quantitatively an enhanced hybrid device behavior due to the application of QDs, laying the foundation for a novel approach at creating a QD sensitized solar cell

Studying time and disease using two different cell line models

The scientific approach of modelling uses manipulation of simpler systems in order to understand aspects of more complex ones. This method is extensively used to understand the biology of complex organisms through studying representative cells artificially cultured in vitro. The work presented here uses in vitro cell line model systems to investigate two aspects of cell biology: the coupling between the circadian clock and cell cycle, and the role BEST1 protein localisation in Autosomal Dominant Vitreoretinochoroidopathy (ADVIRC) disease. 1. The circadian clock is an internal time-keeping mechanism that allows organisms to anticipate daily environmental changes. This mechanism operates at an organismal level as well as being intrinsic to each cell through oscillating genetic negative feedback loops. One of the many cellular functions that has been found to be regulated by the circadian clock is cell cycle progression. However, it is still an outstanding question as to whether the circadian clock drives cell cycle progression actively or whether it passively gates particular cell cycle transitions to certain times of day. In the first experimental chapter zebrafish (Danio rerio) cell lines are used to investigate the relationship between the circadian clock mechanism and cell cycle behaviour. This relationship is examined at a population and single cell level to address the question as to the effect of varying the circadian clock period on the timing and average length of the cell cycle output. It is demonstrated that altering the period length of the circadian oscillation affects the timing of cell cycle progression, but not the length of the cell cycle or its phases. This provides strong evidence in support of the gating theory of circadian regulation of the cell cycle. In the second experimental chapter the effects of cell density on this coupling between the circadian clock and cell cycle are considered. It is shown that this coupling is not observed in cell populations that are at low density and that are highly proliferative, providing insight into how the assay conditions used in previously published work on this coupling could be contributing to conflicting results. 2. Bestrophinopathies are a group of retinal dystrophic diseases that share a common cause: mutations in the Bestrophin-1 (BEST1) gene, expressed in the retinal pigmented epithelium (RPE). Epithelial cell models, particularly derived from the kidney, have been used as models to study the function and dysfunction of the BEST1 protein in RPE cells through overexpression of the BEST1 gene. The results of these studies have suggested that in ADVIRC disease mutant BEST1 shows mis-splicing defects. However, this has not been supported by work using induced 5 pluripotent stem cell-derived RPE (iPS-RPE) cell models, raising the question as to whether the model cells used are providing accurate insights into the actual properties of native RPE. In this section human epithelial cell lines are used to investigate the relationship between specific point mutations in the gene Bestrophin1 and the localisation within the cell of the resulting protein product. It is shown that the localisation of an ADVIRC mutant BEST1 protein depends partially on the cell line used to express it, as well as the cell culture conditions used. This suggests that the use of non-RPE model cell lines for investigating Bestrophin-1 may be leading to conclusions that do not apply in vivo

Hazardous fuel mapping and thematic accuracy assessment in the wildland urban interface

Escalating costs related to fighting wildfire in the wildland urban interface and throughout the United States have raised concerns regarding risks and complexities associated with fire management. Assessment of conditions associated with fire risk, hazardous fuels, and fire behavior are enhanced using geographic information systems (GIS). However, many geospatial datasets are not sufficiently accurate for project level planning (20,000 ha). I compared the thematic accuracy of two surface fuel data sets derived from publicly available federal and state standard vegetation data with surface fuel data generated by rural community members for an area in the wildland urban interface. The one-sided 95% (P 0.05) confidence level for overall thematic accuracy of the surface fuel maps generated by public participants (75.9%) was higher than that of USFS 2004 CALVEG (38.6%) and 2005 California Department of Forestry and Fire Protection's Fire Resource Assessment Program (50.5%) datasets. Minimum mapping requirements adherent to United States Geological Survey and National Park Service standards (80%) were not met. However, results suggest that participatory GIS based fuel maps generated by rural community members can be more accurate for project level planning and management than federal and state surface fuel data sets.application/pdfThesis (M.S.)--Humboldt State University, Natural Resources: Natural Resource Planning & Interpretation, 200

Peripheral Neuropathy Phenotyping in Rat Models of Type 2 Diabetes Mellitus: Evaluating Uptake of the Neurodiab Guidelines and Identifying Future Directions

Diabetic peripheral neuropathy (DPN) affects over half of type 2 diabetes mellitus (T2DM) patients, with an urgent need for effective pharmacotherapies. While many rat and mouse models of T2DM exist, the phenotyping of DPN has been challenging with inconsistencies across laboratories. To better characterize DPN in rodents, a consensus guideline was published in 2014 to accelerate the translation of preclinical findings. Here we review DPN phenotyping in rat models of T2DM against the ‘Neurodiab’ criteria to identify uptake of the guidelines and discuss how DPN phenotypes differ between models and according to diabetes duration and sex. A search of PubMed, Scopus and Web of Science databases identified 125 studies, categorised as either diet and/or chemically induced models or transgenic/spontaneous models of T2DM. The use of diet and chemically induced T2DM models has exceeded that of transgenic models in recent years, and the introduction of the Neurodiab guidelines has not appreciably increased the number of studies assessing all key DPN endpoints. Combined high-fat diet and low dose streptozotocin rat models are the most frequently used and well characterised. Overall, we recommend adherence to Neurodiab guidelines for creating better animal models of DPN to accelerate translation and drug development

Nonlinear viscoelastic characterization of polymer materials using a dynamic-mechanical methodology

Polymer materials retrieved from LDEF exhibit nonlinear constitutive behavior; thus the authors present a method to characterize nonlinear viscoelastic behavior using measurements from dynamic (oscillatory) mechanical tests. Frequency-derived measurements are transformed into time-domain properties providing the capability to predict long term material performance without a lengthy experimentation program. Results are presented for thin-film high-performance polymer materials used in the fabrication of high-altitude scientific balloons. Predictions based upon a linear test and analysis approach are shown to deteriorate for moderate to high stress levels expected for extended applications. Tests verify that nonlinear viscoelastic response is induced by large stresses. Hence, an approach is developed in which the stress-dependent behavior is examined in a manner analogous to modeling temperature-dependent behavior with time-temperature correspondence and superposition principles. The development leads to time-stress correspondence and superposition of measurements obtained through dynamic mechanical tests. Predictions of material behavior using measurements based upon linear and nonlinear approaches are compared with experimental results obtained from traditional creep tests. Excellent agreement is shown for the nonlinear model

The effects of integrated care: a systematic review of UK and international evidence

BACKGROUND: Healthcare systems around the world have been responding to the demand for better integrated models of service delivery. However, there is a need for further clarity regarding the effects of these new models of integration, and exploration regarding whether models introduced in other care systems may achieve similar outcomes in a UK national health service context. METHODS: The study aimed to carry out a systematic review of the effects of integration or co-ordination between healthcare services, or between health and social care on service delivery outcomes including effectiveness, efficiency and quality of care. Electronic databases including MEDLINE; Embase; PsycINFO; CINAHL; Science and Social Science Citation Indices; and the Cochrane Library were searched for relevant literature published between 2006 to March 2017. Online sources were searched for UK grey literature, and citation searching, and manual reference list screening were also carried out. Quantitative primary studies and systematic reviews, reporting actual or perceived effects on service delivery following the introduction of models of integration or co-ordination, in healthcare or health and social care settings in developed countries were eligible for inclusion. Strength of evidence for each outcome reported was analysed and synthesised using a four point comparative rating system of stronger, weaker, inconsistent or limited evidence. RESULTS: One hundred sixty seven studies were eligible for inclusion. Analysis indicated evidence of perceived improved quality of care, evidence of increased patient satisfaction, and evidence of improved access to care. Evidence was rated as either inconsistent or limited regarding all other outcomes reported, including system-wide impacts on primary care, secondary care, and health care costs. There were limited differences between outcomes reported by UK and international studies, and overall the literature had a limited consideration of effects on service users. CONCLUSIONS: Models of integrated care may enhance patient satisfaction, increase perceived quality of care, and enable access to services, although the evidence for other outcomes including service costs remains unclear. Indications of improved access may have important implications for services struggling to cope with increasing demand. TRIAL REGISTRATION: Prospero registration number: 42016037725

Circadian Clock Synchronization of the Cell Cycle in Zebrafish Occurs through a Gating Mechanism Rather Than a Period-phase Locking Process

Studies from a number of model systems have shown that the circadian clock controls expression of key cell cycle checkpoints, thus providing permissive or inhibitory windows in which specific cell cycle events can occur. However, a major question remains: Is the clock actually regulating the cell cycle through such a gating mechanism or, alternatively, is there a coupling process that controls the speed of cell cycle progression? Using our light-responsive zebrafish cell lines, we address this issue directly by synchronizing the cell cycle in culture simply by changing the entraining light-dark (LD) cycle in the incubator without the need for pharmacological intervention. Our results show that the cell cycle rapidly reentrains to a shifted LD cycle within 36 h, with changes in p21 expression and subsequent S phase timing occurring within the first few hours of resetting. Reentrainment of mitosis appears to lag S phase resetting by 1 circadian cycle. The range of entrainment of the zebrafish clock to differing LD cycles is large, from 16 to 32 hour periods. We exploited this feature to explore cell cycle entrainment at both the population and single cell levels. At the population level, cell cycle length is shortened or lengthened under corresponding T-cycles, suggesting that a 1:1 coupling mechanism is capable of either speeding up or slowing down the cell cycle. However, analysis at the single cell level reveals that this, in fact, is not true and that a gating mechanism is the fundamental method of timed cell cycle regulation in zebrafish. Cell cycle length at the single cell level is virtually unaltered with varying T-cycles