4,593 research outputs found

    Towards comprehensive characterisation and modelling of the forming and wrinkling mechanics of engineering fabrics

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    Through a combination of direct measurement and inverse modelling, a route to characterising the main mechanical forming properties of engineering fabric is demonstrated. The process involves just two experimental tests, a cantilever bending test and a modified version of the uniaxial bias extension test. The mechanical forming properties of a twill weave carbon fabric have been determined, including estimates of the in-plane bending stiffness and the torsional stiffness of a sheared fabric. As a result of measuring and incorporating all the main mechanical properties of the fabric in forming simulations (tensile, shear, out-of-plane bending, in-plane bending & torsion), the specimen size-dependent shear kinematics and wrinkling response measured in experiments, is faithfully reproduced in simulations of the uniaxial bias extension (UBE) test

    Application of Pyridazinediones in the Construction of Self-Immolative Scaffolds for Potential Use in Small Molecule–Drug Conjugates

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    Cancer constitutes one of the leading causes of death worldwide and research in this field is constantly aiming to discover and develop ever more efficient ways in which to treat and manage this disease. For much of the 20th century the leading strategy has been that of chemotherapy: a treatment invariably accompanied by undesirable side effects due to its lack of specificity. The field has therefore moved towards targeted-drug delivery, with antibody–drug conjugates (ADCs) having established themselves in this area with great success. Less work however has been undertaken on small molecule–drug conjugates (SMDCs) and this thesis describes the design of SMDC precursors based on the pyridazinedione (PD) molecule, as well as the development of a novel, sulfur-based self-immolative linker which could enable the attachment of drugs and fluorophores to such a construct. The first primary focus of this work centres around the PD core’s thiol reactive centres, with the exploration of whether thioaryl- or thioalkyl-PDs fare better when subjected to human serum- and tumour cell-mimicking conditions. It was found that a bis-thioaryl PD performed best, and its aromatic thiol substituents were subsequently derivatised for the purpose of attaching a fluorophore via a novel, sulfur-based self-immolative linker. The release of the fluorophore seen by LC-MS and the turn-on fluorescence observed by fluorescence spectroscopy both confirmed the self-degradative mechanism of this linker. The second primary objective of this work was to then install groups that are relevant to an SMDC precursor onto the N-handles of the PD core, culminating in the successful isolation of di-bromo PEG azide and PEG alkyne PDs. The latters’ bromine positions were then substituted with a derivatisable thiol to demonstrate that incorporating three distinct groups onto the same PD platform is possible, thus vindicating its versatility and modularity. Consequently, novel SMDC precursors have been synthesised whose functional groups have potential for future attachment of fluorophores, drugs and tumour-targeting ligands

    On the impact of early marriage on schooling outcomes in sub-Saharan Africa and South West Asia

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    This paper examines the effect of age of marriage on women's schooling outcomes for 36 countries from Sub-Saharan Africa and South West Asia. We employ an instrumental variable approach to account for the endogeneity of early marriage driven by socio-economic and cultural factors. Our results show that delaying early marriage by one year is associated with an increase of half a year of education in Sub-Saharan Africa and nearly one third of a year of education in South West Asia as well as a lower likelihood of dropping out from secondary school of 5.5% in South West Asia

    An Exploratory Analysis Of A Time Synchronization Protocol For UAS

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    This dissertation provides a numerical analysis of a Receiver Only Synchronization (ROS) protocol which is proposed for use by Unmanned Aircraft Systems (UAS) in Beyond Visual Line of Sight (BVLOS) operations. The use of ROS protocols could reinforce current technologies that enable transmission over 5G cell networks, decreasing latency issues and enabling the incorporation of an increased number of UAS to the network, without loss of accuracy. A minimum squared error (MSE)-based accuracy of clock offset and clock skew estimations was obtained using the number of iterations and number of observations as independent parameters. Although the model converged after only four iterations, the number of observations needed was considerably large, of no less than about 250. The noise, introduced in the system through the first residual, the correlation parameter and the disturbance terms, was assumed to be autocorrelated. Previous studies suggested that correlated noise might be typical in multipath scenarios, or in case of damaged antennas. Four noise distributions: gaussian, exponential, gamma and Weibull were considered. Each of them is adapted to different noise sources in the OSI model. Dispersion of results in the first case, the only case with zero mean, was checked against the Cramér-Rao Bound (CRB) limit. Results confirmed that the scheme proposed was fully efficient. Moreover, results with the other three cases were less promising, thus demonstrating that only zero mean distributions could deliver good results. This fact would limit the proposed scheme application in multipath scenarios, where echoes of previous signals may reach the receiver at delayed times. In the second part, a wake/sleep scheme was imposed on the model, concluding that for wake/sleep ratios below 92/08 results were not accurate at p=.05 level. The study also evaluated the impact of noise levels in the time domain and showed that above -2dB in time a substantial contribution of error terms disturbed the initial estimations significantly. The tests were performed in Matlab®. Based on the results, three venues confirming the assumptions made were proposed for future work. Some final reflections on the use of 5G in aviation brought the present dissertation to a close

    The role of B [Beta]-hydroxybutyrate in the regulation of ketogenesis in sheep

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    Eleven ewes weighing between 55 and 65 kg were randomly placed in one of three experimental categories: normal (n=5); diabetic insulin-treated, DIT (.n=3); and diabetic 72-hour-untreated, DUT (.n=3). Animals were rendered diabetic pharmacologically via intravenous doses of alloxan (50 mg/kg). The femoral artery and vein, along with the portal, hepatic, and mesenteric veins were cannulated immediately prior to each experiment. Experiments were therefore conducted in anesthetized (sodium pentobarbital) animals following surgery. Mesenteric infusion of para-aminohippuric acid (PAH) was used to determine whole blood flow rates across the splanchnic tissues. Three sets of preinfusion or control samples were obtained at 15-minute intervals immediately followed by continuous infusion of β-hydroxybutyrate into the caudal vena cava with four subsequent serial whole blood samples obtained from the femoral artery, and portal and hepatic veins at 30-minute intervals. The whole blood samples were analyzed for β-hydroxybutyrate, acetoacetate, and PAH, and plasma analyzed for free fatty acids and insulin. As expected, free fatty acid levels were depressed by β-hydroxy-butyrate infusion in the normal, DIT, and DUT animals. Since there was a concomitant decrease in net hepatic and total splanchnic uptake of free fatty acids, the concentration changes must have been due to decreased peripheral tissue lipolysis. Infusion of β-hydroxybutyrate increased pancreatic insulin release, but there was a corresponding hepatic uptake of the hormone, and thus, no net change in total splanchnic insulin flux was observed. In the normal and DIT, but not the DUT sheep, a net increase in total splanchnic acetoacetate uptake and a concomitant decrease in net total splanchnic β-hydroxybutyrate release during infusion of the ketone body was observed. From these results it was concluded that the effects of β-hydroxybutyrate infusion on ketone body and free fatty acid concentrations and fluxes may be mediated at the insulin receptor site and not by increased pancreatic insulin production

    Monte Carlo model of the uncertainty of SEA loss factors

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    Finite Element Methods are widely used to model vibro-acoustic systems, but as the modal density becomes higher this type of model becomes inaccurate and impractical. This is why in the high modal density region the use of Statistical Energy Analysis (SEA) models has become increasingly popular. SEA has some obvious advantages such as its simple formal expression, being based on linear equation systems or the reduced number of variables involved. But SEA has drawbacks as well, such as the absence of local information or the necessity of frequency averaging. A key quantity in SEA models is the loss factor. This takes into account the energy dissipated within a given subsystem or when power flows from one subsystem to another. Even though analytical expressions exist for a number of subsystems of differing nature, the measurement of the loss factor is still advisable and a necessity for a large number of cases. The most commonly used method of measuring loss factors is the Power Injection Method. This method is based on the injection of power into every single subsystem in sequence while the energy in each subsystem is measured. In spite of its simplicity, there remain a number of problems where the accuracy of the results is influenced by various practical issues. In this paper, a Monte Carlo model is used to describe the uncertainty of a two subsystemproblem consisting of two planar elements connected along one side. The influence of the input variables is studied and the conditioning of the coefficient matrix that model the system is also taken into accoun

    Selection of materials for a nuclear rocket engine

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    Selection of materials which will be used in the construct of a nuclear reactor for a space rocket

    Qubit authentication

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    Secure communication requires message authentication. In this paper we address the problem of how to authenticate quantum information sent through a quantum channel between two communicating parties with the minimum amount of resources. Specifically, our objective is to determine whether one elementary quantum message (a qubit) can be authenticated with a key of minimum length. We show that, unlike the case of classical-message quantum authentication, this is not possible.Comment: LaTeX, 8 page

    Assessing Cultural Drivers of Safety Resilience in a Collegiate Aviation Program

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    Organizational safety resilience is a key factor in sustaining an effective safety management system (SMS) in high-reliability organizations (HROs) such as aviation. Extant research advocates for monitoring, assessing and continuously improving safety in an organization that has a fully-functional SMS. Safety resilience provides a buffer against vulnerabilities. Extant research also suggests a paucity in terms of a measurement framework for organizational safety resilience in collegiate aviation operations. A quantitative approach using Reason’s safety resilience concept (Reason, 2011) is used to assess organizational safety resilience in a collegiate aviation program with an active conformance SMS accepted by the FAA. A sample of 516research participants responded to an online survey instrument derived from Reason (2011). Structural Equation Model (SEM)/Path Analysis (PA) techniques are used to assess models that measure the strength of relationships between three cultural drivers (Commitment, Cognizance, Competence)of safety and safety resilience. There were strong significant relationships between these cultural drivers and safety resilience. Path analysis suggests that Commitment significantly mediates the path between Cognizance and Competence and highlights its important role in sustaining safety competencies. There were significant differences in the perceptions of safety resilience among top-level leadership, flight operations and ground operations. Flight operations and ground operations had higher mean scores on safety resilience than top-level leadership. Study provides a validated model of safety resilience that is essential for SMS improvements in collegiate aviation programs. Future studies will utilize this safety resilience model to assess other collegiate aviation programs in various phases of SMS implementation, airlines, and air traffic control operations
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