Ecological non-linear state space model selection via adaptive particle Markov chain Monte Carlo (AdPMCMC)

We develop a novel advanced Particle Markov chain Monte Carlo algorithm that is capable of sampling from the posterior distribution of non-linear state space models for both the unobserved latent states and the unknown model parameters. We apply this novel methodology to five population growth models, including models with strong and weak Allee effects, and test if it can efficiently sample from the complex likelihood surface that is often associated with these models. Utilising real and also synthetically generated data sets we examine the extent to which observation noise and process error may frustrate efforts to choose between these models. Our novel algorithm involves an Adaptive Metropolis proposal combined with an SIR Particle MCMC algorithm (AdPMCMC). We show that the AdPMCMC algorithm samples complex, high-dimensional spaces efficiently, and is therefore superior to standard Gibbs or Metropolis Hastings algorithms that are known to converge very slowly when applied to the non-linear state space ecological models considered in this paper. Additionally, we show how the AdPMCMC algorithm can be used to recursively estimate the Bayesian Cram\'er-Rao Lower Bound of Tichavsk\'y (1998). We derive expressions for these Cram\'er-Rao Bounds and estimate them for the models considered. Our results demonstrate a number of important features of common population growth models, most notably their multi-modal posterior surfaces and dependence between the static and dynamic parameters. We conclude by sampling from the posterior distribution of each of the models, and use Bayes factors to highlight how observation noise significantly diminishes our ability to select among some of the models, particularly those that are designed to reproduce an Allee effect

A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high speed flow fields

Regulation of TP thromboxane receptor expression and activity by selective P2Y12 receptor antagonists:consequences for dual antiplatelet therapy?

Platelets are small anucleate cells which play a fundamental role in haemostasis restricting blood loss following vessel injury. They also play a critical role in arterial thrombus formation in acute coronary syndromes (ACS). Platelets can respond to small molecule agonists leading to an aggregation response forming a clot or thrombus. Two particularly relevant small molecule agonists are thromboxane (TxA2) and ADP which act on different G protein coupled receptors (GPCRs), present on the platelet plasma membrane. ADP acts through P2Y1 and P2Y12 receptors while TxA2 acts through thromboxane (TP) receptors. Current clinical practice to reduce the risk of thrombus formation in ACS patients employs a dual antiplatelet therapy (DAPT) approach. DAPT consists of a P2Y12 receptor antagonist to block the effects of ADP at P2Y12, and aspirin to ablate the synthesis of TxA2. Notably DAPT, although clinically efficacious, can have the significant side-effect of patient bleeding. However, emerging in vivo and in vitro evidence suggests certain P2Y12 receptor antagonists can reduce the activity of TP receptors and modulate their expression. If specific P2Y12 receptor antagonists can reduce thromboxane receptor activity, the use of aspirin in DAPT may be unnecessary with its removal potentially reducing major bleeding risk. In this thesis, the thromboxane and P2Y12 receptors expression is shown to be deeply connected where co-expression of both receptors bilaterally increases surface receptor expression which is increased further by P2Y12 receptor antagonist Ticagrelor. Further, thromboxane receptor reactivity to agonists is reduced by Ticagrelor pre-treatment in human platelets and cells co-expressing P2Y12R. Lastly, through co-immunoprecipitation, this thesis reports a novel physical interaction between the thromboxane receptor and the P2Y12 receptor which appeared to be further stabilised by Ticagrelor. These findings aim to improve our mechanistic understanding of the interplay between P2Y12 receptor antagonists and the thromboxane receptor in order to inform clinical practice and supplement past and ongoing P2Y12 receptor antagonist monotherapy trials, that challenge the paradigm of DAPT. <br/

Measurements at low energies of the polarization-transfer coefficient Kyy' for the reaction 3H(p,n)3He at 0 degrees

Measurements of the transverse polarization coefficient Kyy' for the reaction 3H(p,n)3He are reported for outgoing neutron energies of 1.94, 5.21, and 5.81 MeV. This reaction is important both as a source of polarized neutrons for nuclear physics experiments, and as a test of theoretical descriptions of the nuclear four-body system. Comparison is made to previous measurements, confirming the 3H(p,n)3He reaction can be used as a polarized neutron source with the polarization known to an accuracy of approximately 5%. Comparison to R-matrix theory suggests that the sign of the 3F3 phase-shift parameter is incorrect. Changing the sign of this parameter dramatically improves the agreement between theory and experiment.Comment: 12 pages, RevTeX, 5 eps figures, submitted to Phys. Rev.

Cellulases from extremely thermophilic bacteria

Cellulose is the most abundant biopolymer on earth, and is the major component of urban waste. Thus cellulose must be seen as a very significant renewable source of chemical foodstocks when fossil fuels become restricted

An LDA (Laser-Doppler Anemometry) investigation of three-dimensional normal shock wave boundary-layer interactions

Nonintrusive measurements were made of a normal shock wave/boundary layer interaction. Two dimensional measurements were made throughout the interaction region while 3-D measurements were made in the vicinity of the shock wave. The measurements were made in the corner of the test section of a continuous supersonic wind tunnel in which a normal shock wave had been stabilized. Laser Doppler Anemometry, surface pressure measurement and flow visualization techniques were employed for two freestream Mach number test cases: 1.6 and 1.3. The former contained separated flow regions and a system of shock waves. The latter was found to be far less complicated. The results define the flow field structure in detail for each case