An investigation was carried out to study the process of rotating stall inception in a low hub-tip ratio fan. Such fans are expected, based on an elementary analysis, to stall from the root. However, experimental evidence had led to the belief that the fans stalled from the tip. The effects of streamtube contraction were first studied and this was followed by an experimental investigation on an isolated rotor, with successive build modifications to increase the likelihood of rotating stall inception occurring at the root. A computer based streamline curvature method was used to study the effects of streamtube contraction and streamtube diffusion that commonly occur when a fan is operated at flows below its' design flow rate. The results indicated a reduced expectation for the root to stall first when compared to a simple 2-D flow analysis. Experimental measurements were then carried out to determine how the experimental local characteristics differed from the predicted characteristics. It was apparent that real fluid effects tended to steepen the root characteristic, thus enhancing the stability of the root. The tip characteristics tended to droop and become less stable. The enhancement of the root stability was also seen in the profiles of deviation angle. The axial Velocity contours at the rotor exit supported the conclusion that the root stability enhancement was caused by "centrifuging". To determine the actual radial location of rotating stall inception, an array of hot wires was used to record events during the inception transient. Inception was first detectable at the tip. This tip stalling behaviour persisted for all the build modifications. Measurements of unsteady pressure were also made to study the movement of the overall operating point since it was felt that this could continuously alternate between a pair of closely spaced characteristics. The results indicated that the fan operated along a unique characteristic. The overall conclusion was that a low hub-tip ratio fan shows a strong reluctance to stall at the root due to "centrifuging" of the blade boundary layer. The inception process appears to be dominated by events in the tip region.

Developmental nicotine exposure (DNE) exerts negative consequences on the CNS via the activation of nAChRs that are available early and widely throughout development (refs). In this work, we examined how DNE changed excitatory and inhibitory neurotransmission in brainstem regions involved in central breathing control. Previous work using the brainstem-spinal cord preparation had shown that DNE augmented the respiratory-related response to AMPA, muscimol (a GABAA agonist), and glycine (Luo et al., 2004; Luo et al., 2007; Pilarski and Fregosi, 2009a). These studies used a split-bath preparation in which a drug (AMPA, muscimol, or glycine) was applied to medulla, and the frequency of the respiratory response (in the form of spontaneous, rhythmic bursting activity) was recorded from cervical nerve 4 (C4), which provides output to the diaphragm. Although these studies showed that DNE AMPA, GABA(A), and glycine neurotransmission in the medulla, the regions mediating the effect and the mechanism of DNE's action remained unclear. In this study we tested the hypothesis that the observed changes in respiratory burst frequency were mediated through the preBötzinger complex (preBötC), and the mechanism of enhanced activity involved an upregulation of neurotransmitter receptors. Additionally, we were interested in studying the effect of DNE on breathing-related motor pools, and therefore studied DNE's effect on excitatory and inhibitory neurotransmission in the XIIMN. We approached these questions and aims using a combination of techniques, including extracellular recordings from whole nerve output in rhythmic brainstem slices, immunohistochemistry, and Western blotting. We found enhanced AMPA, GABA(A), and glycine neurotransmission in the XIIMN and preBötC, and varying changes in neurotransmitter receptor expression in both groups. Additionally, we found a decrease in motoneuron soma size in XII motoneurons that stained positively for the glycine receptor. Overall, this study shows that DNE alters inhibitory and excitatory neurotransmission in both the preBötC and XIIMN, and that these changes may be mediated through a combination of change in cell size and receptor expression.

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Thesis (MApSc(Physiotherapy)-Research)--University of South Australia, 2003.

Thesis (MAppSc, in Physiotherapy) -- University of South Australia, 1994

Thesis (MAppSc, in Physiotherapy) -- University of South Australia, 1994

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 174-179). Also available via the Internet.