"The development and clinical adoption of more effective fixation devices for re-approximating and immobilizing the sternum after open-heart surgery to enable bony healing has been limited, in part, by the lack of in vitro test methods used to evaluate these devices which precisely emulate in vivo loading of the sternum. The present study is an initial effort to determine the loading parameters necessary to improve current in vitro and numerical test methods by characterizing the direction, magnitude, and distribution of loading along the sternotomy midline in vivo using a porcine model. Changes in forces incurred by death and embalming were also investigated to estimate the applicability of cadavers as chest models for sternal fixation. Two instrumented plating systems were used to measure the magnitude, direction, and distribution of forces across the bisected sternum in four pigs during spontaneous breathing, ventilated breathing, and coughing for four treatments; live, dead, embalmed, and refrigerated. Forces were highest in the lateral direction and highest at the xiphoid. An important finding was that the magnitude of the respiratory forces in all directions was smaller than anticipated from previous estimations, ranging from 0.37 N to 43.8 N. No significant differences in force were found between the four treatments, most likely due to the very small magnitude of the forces and high variability between animals. These results provide a first approximation of in vivo sternal forces and indicate that small cyclic fatigue loads should be applied for long periods of time, rather than large quasistatic loads, to best evaluate the next generation of sternal fixation devices. "

Sternal malunion is a complication resulting in displacement of the sternal halves following open heart surgery. Currently, little is known about the effectiveness of alternative fixation systems under physiologically relevant loading scenarios. The goal of this study was to mechanically test several currently marketed sternal fixation devices and compare them to a prototype device in different loading conditions to simulate sitting up or breathing. Each system showed unique differences in cost, failure mode and efficiency; however, no statistical difference in failure load or displacement was observed between the testing groups.

MMed (Orthopaedic Surgery), Faculty of Health Sciences, University of the Witwatersrand / Intramedullary nail insertion into a fractured bone allows stabilisation of the fracture with minimal intervention through the zone of injured tissue. This study aimed to assess whether intramedullary nailing of the forearm bones (radius and/or ulna) is a safe and effective form of management of these often complex fractures. A prospective case series was followed from presentation to fracture union. Between April 2006 and February 2008, 21 patients were enrolled in the study. The fracture union rate was high and complication rate was low. There was no increased risk of sepsis. The use of intramedullary nailing for diaphyseal fractures was successful but metaphyseal fractures, particularly with shortening, may be problematic. The use of intramedullary nailing for radius/ulna fractures is safe and effective, however the widespread use of this technique may be limited by the cost of the implant.

This thesis consists of three manuscripts describing ecophysiological research on the cyanolichen Lobaria oregana. The first manuscript includes a re-evaluation of the assumptions underlying past estimates of N fixation by this species and provides an estimate of annual N fixation at the Wind River Canopy Crane (WRCC). Based upon litterfall data, canopy biomass data, N content of lichen tissue, and published growth rates, L. oregana fixes 0.4-1.6 kg N₂ ha⁻¹ yr⁻¹. The second manuscript presents a series of physiological response curves and a model of N fixation by L. oregana. Temperature is the most important parameter controlling nitrogenase activity in hydrated thalli. The model is used to predict annual N fixation at the WRCC and at the H.J. Andrews (HJA) Experimental Forest. Lobaria oregana fixes 1.4-1.8 kg N₂ ha⁻¹ yr⁻¹ at the WRCC, and low winter temperatures often inhibit nitrogenase activity. Temperatures at the HJA are slightly warmer during the winter, and L. oregana fixes 2.6-16.5 kg N₂ ha⁻¹ yr⁻¹ depending on its stand-level biomass. The third manuscript investigates the effects of thallus water content, light, and temperature on CO₂ exchange in L. oregana. This species shows a typical photosynthetic response upon rehydration, and like other lichens it becomes light-saturated at low PAR levels. Positive net photosynthesis in L. oregana occurs only between 1-12°C. High respiration rates prevent carbon gain at warmer temperatures. The temperature constraints on carbon gain and nitrogen fixation may explain some of the landscape distribution patterns of L. oregana. / Graduation date: 2002

Abstract This research investigated the spatial and temporal distributions of Trichodesmium spp. and Richelia intracellularis in the South China Sea. The surveys covered the period from July 2000 to July 2002. A total of eight cruises, including spring, summer and fall were conducted. The sampling stations located between 18~22o N and 115~122 o E , over the continental shelf, the slope, and the basin of the northern South China Sea. Trichodesmium biomass was higher in summer and fall than spring. There was no significant difference in biomass among shelf , slope and basin. The averaged biomass was 69

Abstract: Dimeric dimethylAluminum complexes, [Me2Al(m-R)]2 (R= Me, NiPr2, NiBu2, NPh2, NHnBu, OMe) and Al(NiPr2)3 react with carbon dioxide, yielding a series of carbamato aluminum complexes: [Me2Al(m-OCMe3)]2 (1); [Me2Al(m-O2CNiPr2)]2 (2); [Me2Al(m-O2CNiBu2)]2 (3); [Me2Al(m-O2CNPh2)]2 (4); [Me2Al(m-O2CNHnBu)]2 (5); Al4Li2(m4-O)2(m-O2CNiPr2)10 (6). X-ray crystallographic determinations were performed on compounds (2), (3), (4) and (6). The general trends identitide in these structures suggest that depending upon the bonding energy of aluminum with bridge ligand and electron density on bridge ligand. One novel crystal structure (6), Al4Li2(m4-O)2(m-O2CNiPr2)10 , was found from the previous reaction in the presence of lithium chloride. These compounds were characterized with 1H, 13C NMR, IR spectroscopy, mass spectrometer, and elemental analyses.

The reaction of Mg(NPh2)2 with LiNR2 (R= SiMe3, NiPr, NiBu) generated the same product, [Mg(NPh2)3(THF)][Li(THF)4] which was identified by 1H-NMR and X-ray crystallography. The magnesium-lithium mixed metal complex reacted with excess carbon dioxide in the ice bath to generate the tetralithium complex, Li4(O2CNPh2)4(THF)4 which was identified by 1H-NMR, 13C-NMR, IR, and X-ray crystallography.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references.

published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

The responses of two cowpea (Vigna unguiculata (L.) Walp.) cultivars inoculated with granular inoculum (a mixture of rhizobia) at different levels of applied nitrogen were evaluated. California Blackeye 5 (Ca5) and Knuckle Purple Hull (KPH) cowpeas were examined under field conditions for percent nodulation, nodule number, and nodule mass per plant, and nitrogenase activity at various times during the 1983 and 1984 growing seasons. Data were also obtained for shoot and root dry weights, seed yield, and protein content. Significant differences between inoculated and uninoculated plots were found at all nitrogen treatments for both cultivars with respect to nodulation percentage, nodule number, nodule mass, and nitrogenase activity. An inverse trend linear and quadratic was noted between nitrogen increments and nodulation (nodule number and nodule mass) of Ca5 and KPH cowpeas. High N (168 kg N ha('-1)) was more inhibitory to nodulation than low (28 kg N ha('-1)) N applied. Nitrogenase activity of both cultivars was significantly stimulated with low and inhibited by high levels of ammonium nitrate. Effects of nitrogen treatments on nodulation and nitrogenase activity were influenced by the stage of growth and cowpea cultivar. At the pod-fill stage, higher nodule numbers and nitrogenase activity were recorded for Ca5 as compared to KPH cowpeas. Morphological differences, with Ca5 plants being erect with few vines, whereas KPH plants were semi-erect and bushy, were observed between inoculated and uninoculated plants of Ca5 and KPH cowpeas at all levels of applied nitrogen. Dry weights of vegetative components of both cultivars were significantly improved when low (28 kg N ha('-1)) rather than high (168 kg N ha('-1)) nitrogen was added. Inoculation significantly increased seed yield of Ca5 cowpeas. When conditions were favorable seed yield of inoculated Ca5 exceeded that of inoculated KPH in all comparisons within the same increments of applied N. Seed yield of both cultivars was adversely affected when high levels of nitrogen were applied. Seed, leaf, petiole, and stem protein content were significantly higher with respect to inoculated than uninoculated plots. However, nitrogen fertilizers tended to decrease protein content of the measured parameters for Ca5 and KPH cowpeas.