The technique of transcranial Doppler ultrasound (TCD) was used to assess cerebral blood flow (CBF) in humans. Studies were performed at rest and during dynamic submaximal exercise. In the resting experiments, TCD was combined with the technique of dynamic end-tidal forcing to study the dynamics of the CBF response to step changes in end-tidal (i.e. arterial) PC02 and PO2 In the resting and exercise experiments, the degree of consistency was examined between three indices of CBF that can be extracted from the TCD spectrum. Finally, the ventilatory and the CBF responses to acute isocapnic hypoxia were examined to try to quantify the possible reduction in ventilation that could be attributed to changes in CBF with hypoxia. In the studies performed at rest, during either hypoxia and/or hypercapnia (Chapter 2), the three indices of CBF extracted from the TCD spectrum were all consistent. However, during submaximal exercise (Chapter 5), the indices were less consistent and results suggest that the increase in CBF with exercise that has been reported with TCD needs to be treated with caution. The dynamic studies of the CBF response to step changes in end-tidal PC02 and PO2 in humans revealed that the CBF response to hypercapnia (Chapter 3) is characterised by a significant asymmetry, with a slower on-transient than off-transient, and also by a degree of undershoot following the relief of hypercapnia. The CBF response to hypocapnia (Chapter 4) is also characterised by a significant asymmetry, with a faster on-transient than off-transient. Furthermore, there is a slow progressive adaptation throughout the hypocapnic period. These studies show that the CBF responses to hypercapnia and hypocapnia are much faster than previously been thought. Finally, the work described in Chapter 6 attempts to quantify the possible reduction in ventilation that could be attributed to changes in CBF with hypoxia to determine whether it could be of sufficient magnitude to underlie hypoxic ventilatory decline (HVD). The results suggest that, in awake humans, changes in CBF during acute isocapnic hypoxia are quantitatively insufficient to underlie HVD.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 114-119). Also available on the World Wide Web.

Thesis (M.D.)--University of Hong Kong, 1995. / Includes bibliographical references (leaf 208-230).

Thesis (M.D.)--University of Hong Kong, 1995. / Includes bibliographical references (leaf 208-230). Also available in print.

Thesis--Lund Institute of Technology, 1994. / Added t.p. with thesis statement inserted.

Thesis--Lund Institute of Technology, 1994. / Added t.p. with thesis statement inserted.

Electrophoresis is the technique used to characterize proteins, oligonucleotides, and DNA. Methods employed to date include gel and capillary electrophoresis. Most samples can be characterized by these methods. However, large DNA molecules do not separate well with either method. A newer electrophoresis method involves the use of the Doppler effect to determine a particle’s characteristics. This thesis is concerned with the design and development of an open geometry Doppler electrophoresis instrument for macromolecular characterization in solution where gel characteristics and electroosmotic flow need not be considered. / Master of Science

published_or_final_version / Medicine / Master / Doctor of Medicine

published_or_final_version / Obstetrics and Gynaecology / Master / Master of Philosophy

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