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Legumes form a symbiotic relationship with a group of bacteria, collectively known as rhizobia. The bacterial symbiont fixes atmospheric nitrogen within root nodules, thus providing the host with an assimilative nitrogen source. Nodule formation involves a complex signalling pathway within the legume host. The plant hormone auxin is involved in nodule organogenesis, but how auxin regulates nodulation is still poorly described. Several studies have found increased auxin signalling in nodule primordia, but so far auxin metabolites have never been quantified during the early stages of nodulation. Therefore, the first aim of this thesis was to establish methods for auxin quantification in legume roots. The presumed build-up of auxin in nodule primordia has been predicted to be due to inhibition of auxin export from cells at the nodule initiation site, but the regulation of auxin transport has not been tested systematically in different legumes. Therefore, the second aim was to compare auxin concentrations and auxin transport changes during nodulation in different legumes. Third, the regulation of auxin transport and auxin accumulation was placed into the known signalling pathway of nodulation in the model legume, Medicago truncatula. Auxins are naturally present in low quantities in the root. We developed an LC-MS/MS method for the accurate and sensitive quantification of auxins in root tissues. The method was validated and produced sensitive limits of detection / quantification and correlation coefficients. To compare the role of auxin between indeterminate and determinate nodule types, we measured auxin transport and auxin content in M. truncatula (forming indeterminate nodules) and Lotus japonicus (forming determinate nodules). In addition to acropetal auxin transport, basipetal auxin transport was regulated in response to rhizobia inoculation in both legumes. Different auxins with distinct levels of abundance were detected in separate legumes, with some unique to the nodule tissues. Auxin concentrations increased at the early stages of nodule formation in M. truncatula, but not Lotus japonicus. The inhibition of acropetal polar auxin transport by rhizobia occurred only in indeterminate nodule-forming legumes and correlated with the ability of synthetic auxin transport inhibitors to induce pseudonodules in those legumes. Finally, we investigated the role of the cytokinin receptor CRE1 in modulating auxin transport during nodulation in M. truncatula. We found that cytokinin signalling through CRE1 is necessary for inhibition of acropetal auxin transport, increased auxin concentration and auxin signalling in response to rhizobia. The CRE1 receptor was also required for the correct induction of several flavonoids, which could act as endogenous auxin transport inhibitors. External application of those flavonoids rescued nodulation in the cre1 nodulation-deficient mutant. In conclusion, we demonstrated that the auxin transport machinery is a crucial component in the host legume that is regulated in response to rhizobia. Auxin transport changes could explain measured changes in auxin concentrations during nodule initiation of M. truncatula, but not L. japonicus. Auxin transport control is mediated by endogenous flavonoids, and both flavonoid induction and auxin transport control are regulated by cytokinin signalling in M. truncatula.

Fluid ingestion has been reported to influence cardiovascular and thermoregulatory function, thereby affecting exercise performance. It remains unclear whether ice slurry ingestion during exercise results in similar effects. Three experiments examined thermal-, cardiovascular-, and exercise-related responses to ice slurry ingestion. In the first study, participants in firefighter protective clothing walked at ~7 METs in 35 °C while ingesting carbohydrate-electrolyte beverages as a tepid fluid, cold fluid, and ice slurry in a counterbalanced repeated measures study design. When ingested in large quantities and during uncompensable heat stress, ice slurry ingestion mitigated physiological strain by attenuating the rise in heart rate and rectal temperature. In a second study, cardiovascular drift (CV drift) was measured during 45 min of cycling at 60% maximal oxygen uptake (V̇O2max) in 35 °C, immediately followed by measurement of V̇O2max. Participants ingested fluid and ice slurry during two counterbalanced trials of exercise. CV drift was attenuated with ice slurry ingestion but V̇O2max was unaffected. In a third study, participants ingested ice slurry or cold fluid ad libitum while cycling at 50% maximal workload in 35 °C, immediately followed by a 15-min time trial during which participants completed as much work as possible. Compared to the fluid treatment, participants consumed half as much ice slurry, but total work completed during the time trial was not different. In conclusion, ice slurry ingestion blunts physiological strain during conditions in which evaporative heat loss is impaired, such as when wearing occlusive coverings. Furthermore, ice slurry ingestion attenuates the magnitude of CV drift during exercise in the heat, but this does not blunt the decrease in V̇O2max associated with exercise in hot conditions. Lastly, a smaller quantity of ice slurry is voluntarily ingested compared to cold fluid during prolonged submaximal exercise in the heat, but this does not differentially affect exercise performance.

This study examines the growth in total factor productivity (TFP) of 12 Asia-Pacific telecommunications carriers for the period 1987 through 1990. Carriers are chosen to represent the stages of telecommunications liberalisation identified by the International Telecommunication Union (1995a). A model relating TFP growth to output growth, changes in output mix, technology change and market competition and private ownership is estimated on a unique data set obtained from telecommunications carrier annual reports. Empirical results show competition, private ownership, technology change and scale economies improve carrier TFP growth.

The clinical implication of this work is that an improved understanding of atrial arrhythmias and the surface ECG can aid in directing specific treatment.

Space-time array communications have gained a great deal of interest in recent years. Its superior performance in practical multipath propagation environments has established it as a core aspect in next generation mobile networks, as well as several portable wireless communication systems. In fact the employment of the sensor array component has already been provided for in the current UMTS standard, and there is presently a major thrust to make space-time processing an important part of 3G/4G networks. This book hence attempts to bridge the knowledge gap, looking at the integration of two emerging technologies from an array manifold perspective ? space-time array processing and spread spectrum multiple access communications. It covers a range of novel multiuser channel estimation and reception techniques, which is designed to provide mitigations of the various associated channel impairments in accordance to its environmental context. For convenience of the readers, the book is written in a self-contained modular format with its mathematical frameworks and tools readily extendable to other research domains.