In this thesis, the features of electric field signatures of narrow bipolar pulses (NBPs) generated by cloud flashes are investigated and their effects on wireless communication systems are studied. A handful amount of NBPs (14.5%) have been observed to occur as part of cloud-to-ground flashes in South Malaysia. Occurrence of NBPs in Sweden has been reported for the first time in this thesis. The electric field waveform characteristics of NBPs as part of cloud-to-ground flashes were similar to isolated NBPs found in Sweden and South Malaysia and also to those isolated NBPs reported by previous studies from various geographical areas. This is a strong indication that their breakdown mechanisms are similar at any latitudes regardless of geographical areas. A comparative study on the occurrence of NBPs and other forms of lightning flashes across various geographical areas ranging from northern regions to the tropics is presented. As the latitude decreased from Uppsala, Sweden (59.8°N) to South Malaysia (1.5°N), the percentage of NBP emissions relative to the total number of lightning flashes increased significantly from 0.13% to 12%. Occurrences of positive NBPs were more common than negative NBPs at all observed latitudes. However, as latitudes decreased, the negative NBP emissions increased significantly from 20% (Sweden) to 45% (South Malaysia). Factors involving mixed-phase region elevations and vertical extents of thundercloud tops are invoked to explain the observed results. These factors are fundamentally latitude dependent. In this thesis, the interaction between microwave radiations emitted by cloud-to-ground and cloud flashes events and bits transmission in wireless communication networks are also presented. To the best of our knowledge, this is the first time such effects are investigated in the literature. Narrow bipolar pulses were found to be the strongest source of interference that interfered with the bits transmission.

No description available.

Chromatography is a widely used separation technique including many different modes, for example supercritical fluid chromatography (SFC) which uses a supercritical fluid as mobile phase. A supercritical fluid is achieved when a substance is subjected to a temperature and pressure above the critical point and the boundary between the liquid phase and gas phase is erased. The interest for SFC has increased in recent years, mainly for separation of chiral molecules in the pharmaceutical industry. What makes SFC interesting is that it is a quick, cost-efficient and green method. This is in part due to less organic solvent used in the mobile phase in SFC compared with liquid chromatography and that the carbon dioxide that represents the major part of the mobile phase is a by-product from other processes. In SFC modifiers, often small alcohols, are added to carbon dioxide based mobile phase in order to increase the solubility of polar compounds. In this study the adsorption of methanol to two different stationary phases; Kromasil-Diol and chiral Lux Cellulose-4 were studied. Adsorption is a phenomenon where surface interactions crate a higher density of molecules at the surface than in the bulk. The aim of this work has been to study the adsorption of modifier (methanol) to the stationary phase both to determine the extent of adsorption and the kinetics for system equilibration. These findings were then put into perspective of normal use of SFC for separation of molecules. There are a number of techniques for measuring adsorption; in this study the tracer pulse method is used. This is a pulse method where a concentration plateau is created and an isotope labelled molecule is injected. This was performed in the mobile phase composition from pure carbon dioxide to pure methanol. In addition to the tracer pulse experiments the isotope effect, the eluent flow, equilibration times for the column and retention times for a set of analytes were measured. For the Diol column no large isotope effect was observed, the method was also proved to be highly reproducible since several runs gave consistent results. Calculations based on the experimental data showed that a 6.3 Å thick layer was built up at a methanol fraction of 13% (v/v), corresponding to a monolayer. Changes of the methanol fraction below the saturation level has has greater effect on the retention factor for the analytes than at higher methanol fractions, when the monolayer was saturated. The conclusion of this is that SFC is more stable in the area where the layer has been built up. A preliminary study has been made for the chiral Lux Cellulose-4 column which was not as conclusive as for the Kromasil-Diol column. This type of column needs further studies to confirm the deviating observations and to investigate the cause for these.

No description available.

Delayed control of haemorrhage or blood loss has been recognised as a major contributor to preventable trauma deaths, but early detection of internal bleeding is difficult due to unreliability of heart rate (HR) and blood pressure (BP) as markers of volume status. This thesis explores a novel method of early blood loss detection using a noninvasive finger photoplethysmographic (PPG) pulse oximetry waveform that is normally utilised in pulse oximeters for estimating arterial oxygen saturation. Graded head-up tilt (n = 13) and blood donation (n = 43) in human volunteers were selected as experimental models of mild to moderate blood loss. From the tilt study, a novel method for automatically detecting left ventricular ejection time (LVET) from the finger PPG waveform has been developed and verified by comparison with the LVET measured from aortic flow velocity. PPG waveform derived LVET (LVETp) and pulse transit time (PTT) were strongly correlated with aortic LVET and pre-ejection period respectively (median r = 0.954 and 0.964) and with the decrease in central blood volume indicated by the sine of the tilt angle (median r = -0.985 and 0.938), outperforming R-R interval (RRI) and BP in detecting mild central hypovolaemia. In the blood donation study, progressive blood loss was characterised by falling LVETp and rising PTT (p < 0.01). A new way of identifying haemorrhagic phases by monitoring changes and trends in LVETp, PTT and RRI has been proposed based on the results from the two studies. The utility of frequency spectrum analysis of PPG waveform variability (PPGV) in characterising blood loss has also been examined. A new technique of PPGV analysis by computing the coherence-weighted cross-spectrum has been proposed. It has been shown that the spectral measures of finger PPGV exhibited significant changes (p < 0.01) with blood donation and were mildly correlated with systemic vascular resistance in intensive care unit patients (r from 0.53 to 0.59, p < 0.0001), therefore may be useful for identification of different haemorrhagic phases. In conclusion, this thesis has established finger PPG waveform as a potentially useful noninvasive tool for early detection of blood loss.

1 v. (various paging) : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1972) from the Dept. of Electrical Engineering, University of Adelaide

Thesis (M.S.)--University of Toledo, 2007. / Typescript. "Submitted as partial fulfillment of the requirements for The Master of Science in Bioengineering." Bibliography: leaves 152-154.

Thesis (Ph.D.)--University of Texas at Dallas, 2007. / Includes vita. Includes bibliographical references (leaves 91-93)

Thesis (Ph.D. 1972) from the Dept. of Electrical Engineering, University of Adelaide.

Thesis (M.S.)--Rochester Institute of Technology, 1991. / Includes bibliographical references (leaves 132-138).