HANS ARP: SCULPTOR AND POET

HANS ARP: SCULPTOR AND POE

Dynamic performance of high frequency floors

This thesis presents an investigation into the dynamic performance of high frequency floors (HFFs) due to walking excitation. The rationale behind the research is the lack of knowledge of the dynamic characteristics of the HFFs and the poor guidance available in estimating the vibration response due to walking excitation. The most recent design guides published for the evaluation of HFF are by the Concrete Centre and the Steel Construction Institute. The design of HFF is based on similar principles used in the design of low frequency floors (LFFs). However, the dynamic characteristics of each floor type are very different, which leads to inaccurate response estimations. The thesis is split into three main sections: the classic source, path, receiver layout. The source, within the scope of this work, is excitation due to walking. HFFs are defined at which resonance will not occur from walking, and are designed for environments that require low levels of vibration. Traditionally, a floor's response to walking was analysed using the harmonic amplitudes of the footfall force. As resonance does not occur, this approach is no longer valid, and a number of different methods were developed, namely the 'kf method', Arup's 'effective impulse', and a polynomial method presented in a European Commission (EC) report. It was shown that each method has a number of flaws and characteristics for a new, improved, footfall model are defined. A new footfall model is created based on a cubic spline fit of 'key points' of the footfall force. The new model included intra-subject variability (i.e. natural variation between each pace rate). The new model was shown to be more accurate than current models recommended in the relevant guidance. Due to the inclusion of variation in the model, the spline force was also valid for LFFs and is therefore the first accurate universal force model. Assessment of the path consisted evaluating current deign methods for HFFs. It was found that for a transient response of floor (i.e. not resonant) a large number of modes contribute to the response. As such, the only simplified guidance suitable for analysis was the guide published by the Concrete Centre. The Concrete Centre guide was then compared with finite element analysis (FEA) and was found to give inaccurate response estimates due to poor estimates of modal mass and mode shapes. HFFs are often large structures containing many floor bays. These multi-bay structures have interesting characteristics, unique to this style of floor. A large parametric study considering the effects of the number of bays within the structure, the size of the floor bay and the stiffness of columns had on the characteristics of the floor. It was found that mode groupings of closely spaced modes exist due to the large number of bays. It was also found the column stiffness affects the modal mass of the floor. Due to the complexities of the large multi-bay floors, a number of methods were investigated to make the analysis process more efficient. A method of modal participation was developed to assess the importance of the large number of modes. The degree of modelling detail that was required in the model was investigated, and it was found that away from areas of interest the structure could be modelled very crudely. Wave propagation analysis was conducted on the floors using the spectral element method (SEM) applied to a grillage model of the floor. It was shown that the SEM had advantages over conventional FEA, including more efficient analysis and the use of semi-infinite elements. Assessment of the receiver consisted of an evaluation of the current generic vibration criteria for sensitive occupancies. The vibration criteria were assessed under a number of different types of responses. It was shown that if a criteria for a sensitive machine was developed using one type of excitation (e.g. pure-tone sine) it could not be compared with the response of another type of excitation (e.g. broadband random). Overall, it was shown that all aspects regarding response estimation of HFFs require further research. The work presented in this thesis adds to the current knowledge surrounding HFFs

On AIMD Congestion Control in Multiple Bottleneck Networks.

We consider a linear algebraic model of the Additive-Increase Multiplicative-Decrease congestion control algorithm and present results on average fairness and convergence for multiple bottleneck networks. Results are presented for networks of both long-lived and short-lived flows

Mixed-methods pilot study exploring the influence of the novel Paediatric Anaesthetic Drug Solution tool on clinician cognitive load during simulated paediatric rapid sequence intubation in the emergency department

Aim: Rapid sequence intubation (RSI) in children is a low-incidence, high-risk event associated with cognitive overload and potential errors producing unfavourable outcomes. Cognitive aids, such as charts, algorithms and flow diagrams, are prompts that externalise and structure mental processes to reduce cognitive load, thereby reducing errors. The Paediatric Anaesthetic Emergency Drug Solution (PAEDS) approach combines a colour-coded chart and medication box with a simplified mathematical system of volume-based dosing; the effect of which on cognitive load during a simulated RSI has not previously been described.Methods: A randomised, cross-over trial was conducted with 26 multi-disciplinary emergency medicine clinicians (doctors and nurses) allocated to four groups, performing four high-fidelity RSI simulations, two mandating the use of the PAEDS approach. This mixed methods study followed the pragmatic ontology using grounded theory methodology. Qualitative data were collected from nine individual interviews by a process of thematic analysis via an inductive approach, to allow for appropriate open and axial coding to occur. Quantitative data collected included cognitive loading using the raw NASA-Task Load Index as well as time to intubation and drug dosage details to assess for safety.Results: Qualitative results showed that the PAEDS approach reduced cognitive loading through the use of both the labelled medication box and colour-coded medication charts. The PAEDS approach also showed improved perceived time pressure without feeling rushed, and with no recorded drug errors. Differences in the quantitative data for total cognitive load, error and time were not statistically significant, likely due to sample size.Conclusion: The PAEDS approach is a multifaceted system which is not inferior to current practice, with some components described as an improvement. Further research on a larger sample size needs to be conducted to assess the aspects of the PAEDS approach both collectively and independently.</p

In vivo visual screen for dopaminergic Rab ⇿ LRRK2-G2019S interactions in Drosophila discriminates Rab10 from Rab3

LRRK2 mutations cause Parkinson’s, but the molecular link from increased kinase activity to pathological neurodegeneration remains undetermined. Previous in vitro assays indicate that LRRK2 substrates include at least 8 Rab GTPases. We have now examined this hypothesis in vivo in a functional, electroretinogram screen, expressing each Rab with/without LRRK2-G2019S in selected Drosophila dopaminergic neurons. Our screen discriminated Rab10 from Rab3. The strongest Rab/LRRK2-G2019S interaction is with Rab10; the weakest with Rab3. Rab10 is expressed in a different set of dopaminergic neurons from Rab3. Thus, anatomical and physiological patterns of Rab10 are related. We conclude that Rab10 is a valid substrate of LRRK2 in dopaminergic neurons in vivo. We propose that variations in Rab expression contribute to differences in the rate of neurodegeneration recorded in different dopaminergic nuclei in Parkinson’s

Chemokine receptors in the rheumatoid synovium: upregulation of CXCR5

In patients with rheumatoid arthritis (RA), chemokine and chemokine receptor interactions play a central role in the recruitment of leukocytes into inflamed joints. This study was undertaken to characterize the expression of chemokine receptors in the synovial tissue of RA and non-RA patients. RA synovia (n = 8) were obtained from knee joint replacement operations and control non-RA synovia (n = 9) were obtained from arthroscopic knee biopsies sampled from patients with recent meniscal or articular cartilage damage or degeneration. The mRNA expression of chemokine receptors and their ligands was determined using gene microarrays and PCR. The protein expression of these genes was demonstrated by single-label and double-label immunohistochemistry. Microarray analysis showed the mRNA for CXCR5 to be more abundant in RA than non-RA synovial tissue, and of the chemokine receptors studied CXCR5 showed the greatest upregulation. PCR experiments confirmed the differential expression of CXCR5. By immunohistochemistry we were able to detect CXCR5 in all RA and non-RA samples. In the RA samples the presence of CXCR5 was observed on B cells and T cells in the infiltrates but also on macrophages and endothelial cells. In the non-RA samples the presence of CXCR5 was limited to macrophages and endothelial cells. CXCR5 expression in synovial fluid macrophages and peripheral blood monocytes from RA patients was confirmed by PCR. The present study shows that CXCR5 is upregulated in RA synovial tissue and is expressed in a variety of cell types. This receptor may be involved in the recruitment and positioning of B cells, T cells and monocytes/macrophages in the RA synovium. More importantly, the increased level of CXCR5, a homeostatic chemokine receptor, in the RA synovium suggests that non-inflammatory receptor–ligand pairs might play an important role in the pathogenesis of RA