Physical insights, characteristics and diagnosis of structural freeplay nonlinearity in transonic aeroelastic systems: a system identification based approach

The Next Generation of aircraft sustainment is based on an emerging paradigm known as Prognostics and Health Management. PHM encompasses numerous innovative concepts which shape the future of air asset sustainment according to pre-emptive condition-based maintenance, intelligence-based individual aircraft tracking, and damage/fault prognosis. Smart Diagnostics is an integral component of the SPHM paradigm, and refers to the detection, localisation and tracking of nonlinear structural anomalies that occur in various forms across the airframe structure or within mechanical interfaces. Control surface damage/ failure scenarios, such as, nonlinear hinge stiffness, backlash, and structural freeplay, are a class of structural anomaly which plague modern aircraft and introduce a range of dangerous nonlinear dynamic behaviours, such as, chaotic response and limit cycle oscillation. As a result, the freeplay structural anomaly can reduce fatigue life and is problematic for the stakeholder on many levels, including the management of structural health, maintenance practices, asset availability, mission capability, and sustainment provisions. The traditional approach to handling freeplay-type nonlinear events is based on avoidance and pre-emptive repetitive maintenance practices which, despite being over-conservative, inefficient and expensive, have remained unchanged for more than half a century. As the aerospace sector begins to adopt modern aircraft design and sustainment practices, including the realisation of SPHM-based technologies, there is an urgent requirement for contemporary solutions towards the diagnosis and tracking of structural freeplay anomalies. The research presented in this thesis is pursued with the global objective of contributing towards contemporary structural health monitoring technology through a nonlinear system identification framework for rapid control surface freeplay diagnostics. The proposed framework is driven by the fundamental assumption that all information pertaining to the freeplay event is contained within the time-histories extracted from an aircraft¿s sensory network. It is shown that through careful adaptation of well-established nonlinear system identification methods, namely the Higher-Order Spectra (HOS) and Hilbert-Huang Transform (HHT), rapid detection, localisation and magnitude tracking of the freeplay event is realisable, through a truly data-driven framework, with no inherent dependency of knowledge of the airframe structure, the flight parameters, the aerodynamic condition, or uncertainties. A novel and systematic approach is used to characterise the freeplay event, where nonlinear aeroelastic predictions (numerical aeroelastic models of increasing complexity) are considered to study the isolated physical freeplay mechanism in a nonlinear system identification setting, to understand how its physical action on an aeroelastic system can be exploited for diagnostics purposes. The findings are adapted to formulate temporal and spectral characteristic signatures, then implemented as a basis for the data-driven diagnostics strategy. A flight test case study is used to show that the signature-based diagnostics framework which is formulated using numerical cases with well-defined parameters, remains valid when diagnosing freeplay in a real-world aircraft system. The freeplay is detected and isolated, then a single tuned algorithm is shown to efficiently track the freeplay magnitude over the course of three years with several maintenance/ repair cycles, using a sensor with significant spatial discrepancy to the freeplay source. It is shown that rapid actionable diagnostics information can be extracted with a high level of robustness, demonstrated and verified by making consistent predictions despite: i) a large deviation in Mach number and angle-of-attack (with high angle manoeuvres), ii) highly nonlinear aerodynamic conditions, iii) no knowledge of uncertainty bounds, iv) mixture between stationary nonstationary response, and iv) little information available pertaining to the aircraft structural properties or geometry (a single geometric vector is used). In developing the diagnostics framework, numerous freeplay induced nonlinear phenomena are revisited, providing a new understanding of the structural freeplay physical mechanism. Several freeplay-induced nonlinear phenomena are defined, quantified and related according to a consolidated underlying nonlinear mechanism, founded upon empirically derived correlations. In showing that data-driven signature-based diagnostics is feasible for freeplay, this research makes a significant contribution towards the fields of nonlinear system identification, applied nonlinear dynamics and aircraft structural health monitoring. This provides a clear pathway to extend this signature-based system identification diagnostics strategy to capture other discrete nonlinear mechanisms in aircraft systems, or any relevant mechanical systems across the engineering disciplines. Requirements and limiting aspects of the data-driven approach are thoroughly discussed, predominantly related to sensory network requirements, and recommendations on how to address the limitations and progress with this research are clearly outlined

Declining Medicaid Fees and Primary Care Availability for New Medicaid Patients

Primary care appointment availability for new Medicaid patients declined when Medicaid fees for providers decreased after the ACA-mandated “fee bump” expired

Patients’ experiences: Healthwatch Nottingham and Nottinghamshire. Stage 1 report

Patient and public involvement in their health and social care became prominent following the Francis inquiry report into the Mid Staffordshire NHS Foundation Trust in 2013 (Francis 2013, Department of Health 2014). The government’s response was a pledge to ensure that the leadership and management of the system would view the health and care system from patients’ perspectives and to consider their views. Since the Francis report, patient and public involvement has been assumed as an inherent design feature of the NHS policy and delivery and is ‘sewn-in’ to achieving the triple aims of the NHS, the development of Integrated Care Systems and the achievement of the NHS Long-Term Plan. This report reviews the current situation in Nottingham and Nottinghamshire

Do carer tasks predict carer employment? Evidence from the Survey of Adult Carers in England

Due to the large number of unpaid carers in England, there is an extensive body of research which examines the determinants of carers' employment. Despite this, little is known about the relationship between the specific tasks that carers perform and their labour supply. Using data from the Survey of Adult Carers in England, we examine the relationship between carer tasks and carer employment outcomes. We find that carers who perform tasks that are time-bound have a lower probability of working compared to carers who do not perform these tasks. Similarly, carers who perform shiftable tasks have a higher probability of working compared to carers who do not perform these tasks. If future social policy is to be designed to allow carers to also maintain their employment, then targeting services at the carer tasks which have the largest impact on employment needs to be taken into account

Securing Information Technology in Healthcare

Information technology (IT) has great potential to improve healthcare quality while also improving efficiency, and thus has been a major focus of recent healthcare reform efforts. However, developing, deploying and using IT that is both secure and genuinely effective in the complex clinical, organizational and economic environment of healthcare is a significant challenge. Further, it is imperative that we better understand the privacy concerns of patients and providers, as well as the ability of current technologies, policies, and laws to adequately protect privacy. The Securing Information Technology in Healthcare (SITH) workshops were created to provide a forum to discuss security and privacy for experts from a broad range of perspectives, from officers at large healthcare companies, startups and nonprofits, to physicians, researchers and policy makers

Long Term Immune Responses to Pandemic Influenza A/H1N1 Infection in Solid Organ Transplant Recipients

In solid organ transplant (SOT) recipients it is unknown if natural infection with influenza confers protection from re-infection with the same strain during the next influenza season. The purpose of this study was to determine if infection with pandemic influenza A/H1N1 (pH1N1) resulted in a long-term immunologic response. Transplant recipients with microbiologically proven pH1N1 infection in 2009/2010 underwent humoral and cell-mediated immunity (CMI) testing for pH1N1 just prior to the next influenza season. Concurrent testing for A/Brisbane/59/2007 was done to rule-out cross-reacting antibody. We enrolled 22 adult transplant patients after pH1N1 infection. Follow up testing was done at a median of 7.4 months (range 5.8–15.4) after infection. After excluding those with cross-reactive antibody, 7/19 (36.8%) patients were seroprotected. Detectable pH1N1-specific CD4+ and CD8+ interferon-γ producing T-cells were found in 11/22 (50%) and 8/22 (36.4%) patients respectively. Humoral immunity had a significant correlation with a CD4 response. This is the first study in transplant patients to evaluate long-term humoral and cellular response after natural influenza infection. We show that a substantial proportion of SOT recipients with previous pH1N1 infection lack long-term humoral and cellular immune responses to pH1N1. These patients most likely are at risk for re-infection

Contribution of TAT System Translocated PhoX to Campylobacter jejuni Phosphate Metabolism and Resilience to Environmental Stresses

Campylobacter jejuni is a common gastrointestinal pathogen that colonizes food animals; it is transmitted via fecal contamination of food, and infections in immune-compromised people are more likely to result in serious long-term illness. Environmental phosphate is likely an important sensor of environmental fitness and the ability to obtain extracellular phosphate is central to the bacteria's core metabolic responses. PhoX is the sole alkaline phosphatase in C. jejuni, a substrate of the TAT transport system. Alkaline phosphatases mediate the hydrolytic removal of inorganic phosphate (Pi) from phospho-organic compounds and thereby contribute significantly to the polyphosphate kinase 1 (ppk1) mediated formation of poly P, a molecule that regulates bacterial response to stresses and virulence. Similarly, deletion of the tatC gene, a key component of the TAT system, results in diverse phenotypes in C. jejuni including reduced stress tolerance and in vivo colonization. Therefore, here we investigated the contribution of phoX in poly P synthesis and in TAT-system mediated responses. The phoX deletion mutant showed significant decrease (P<0.05) in poly P accumulation in stationary phase compared to the wild-type, suggesting that PhoX is a major contributor to the inorganic phosphate pool in the cell which is essential for poly P synthesis. The phoX deletion is sufficient for a nutrient stress defect similar to the defect previously described for the ΔtatC mutant. Additionally, the phoX deletion mutant has increased resistance to certain antimicrobials. The ΔphoX mutant was also moderately defective in invasion and intracellular survival within human intestinal epithelial cells as well as in chicken colonization. Further, the ΔphoX mutant produced increased biofilm that can be rescued with 1 mM inorganic phosphate. The qRT-PCR of the ΔphoX mutant revealed transcriptional changes that suggest potential mechanisms for the increased biofilm phenotype

Campylobacter jejuni transcriptome changes during loss of culturability in water

Background: Water serves as a potential reservoir for Campylobacter, the leading cause of bacterial gastroenteritis in humans. However, little is understood about the mechanisms underlying variations in survival characteristics between different strains of C. jejuni in natural environments, including water. Results: We identified three Campylobacter jejuni strains that exhibited variability in their ability to retain culturability after suspension in tap water at two different temperatures (4°C and 25°C). Of the three strains C. jejuni M1 exhibited the most rapid loss of culturability whilst retaining viability. Using RNAseq transcriptomics, we characterised C. jejuni M1 gene expression in response to suspension in water by analyzing bacterial suspensions recovered immediately after introduction into water (Time 0), and from two sampling time/temperature combinations where considerable loss of culturability was evident, namely (i) after 24 h at 25°C, and (ii) after 72 h at 4°C. Transcript data were compared with a culture-grown control. Some gene expression characteristics were shared amongst the three populations recovered from water, with more genes being up-regulated than down. Many of the up-regulated genes were identified in the Time 0 sample, whereas the majority of down-regulated genes occurred in the 25°C (24 h) sample. Conclusions: Variations in expression were found amongst genes associated with oxygen tolerance, starvation and osmotic stress. However, we also found upregulation of flagellar assembly genes, accompanied by down-regulation of genes involved in chemotaxis. Our data also suggested a switch from secretion via the sec system to via the tat system, and that the quorum sensing gene luxS may be implicated in the survival of strain M1 in water. Variations in gene expression also occurred in accessory genome regions. Our data suggest that despite the loss of culturability, C. jejuni M1 remains viable and adapts via specific changes in gene expression

Influenza vaccination for immunocompromised patients: systematic review and meta-analysis from a public health policy perspective.

Immunocompromised patients are vulnerable to severe or complicated influenza infection. Vaccination is widely recommended for this group. This systematic review and meta-analysis assesses influenza vaccination for immunocompromised patients in terms of preventing influenza-like illness and laboratory confirmed influenza, serological response and adverse events