Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / Chilling injury in banana fruit is caused by prolonged exposure to temperatures less than 13°C. This can occur during bunch development in the field or postharvest handling and storage. Mild symptoms of chilling injury are localised to peel tissue and reduce visual quality of fruit. Light microscopy was used in the present study to analyse symptoms of mild chilling injury in Cavendish cv. Williams banana. Following storage at 5°C for 24hours, symptoms of chilling injury in the form of brown discolouration was observed within laticifers in sub-epidermal peel tissue. Browning was not observed in other vascular tissues as previous research has suggested. Causal mechanisms associated with browning of latex within laticifers were investigated. Polyphenol oxidase (PPO) activity in fractions of banana peel latex was measured and found to be highest in the lutoid fraction. PPO activity also provided indirect evidence that phenolics were present in peel latex. Literature suggests possible compartmentalisation of PPO and phenolics in banana lutoids. In this study it is suggested that PPO and phenolics associated with lutoids in banana peel latex may be involved in browning due to chilling stress. The lipid content of lutoids from banana latex was also investigated using FTIR spectroscopy, but showed no further involvement of lutoids in the browning reaction caused by chilling. Control of field chilling using modified bunch covers was investigated. Bunch covers used in modern banana production are usually polyethylene bags, placed over bunches during development in the field. Experiments in a northern Queensland plantation investigated effects of modified bunch covers on fruit yield and quality characteristics of Cavendish cv. Williams bananas, including the development of mild chilling injury symptoms. A further field trial was conducted using different coloured bunch covers with varied interception of photosynthetically-active radiation (PAR), to determine any negative effects of bunch cover shading on fruit yield and quality. Different coloured and layered polyethylene films (blue, double green, silver yellow and silver black) modified PAR transmission of bunch covers (PAR transmission [%] = 56, 38, 7, 0). During summer 2003, varying PAR transmission of bunch covers significantly affected fruit size. Fruit from blue polyethylene covers, which transmitted most light, were larger than fruit from covers with less light transmission. Between cover treatments of lower light transmission, fruit size remained similar. It is suggested, during summer when cloud cover in northern Queensland limits solar radiation, bunch covers with high PAR transmission facilitate greater bunch photosynthesis, which improves fruit size. Fruit quality was generally unaffected by varying PAR transmission of bunch covers, but cover treatments were found to influence peel colour. Peel colour of fruit from 'silver black' covers was significantly paler. This may have impacted upon green life due to increased de-greening. Results from this experiment suggest that bunch photosynthesis significantly influences fruit size and peel colour during summer growing periods. Modified bunch covers constructed from existing bunch cover films and polyethylene bubble wrap ('blue + silver bubble' and sealed and non-sealed 'silver blue + silver bubble') were used to test control of field chilling during winter 2003 and 2004. Compared to standard blue polyethylene bunch covers, modified covers significantly reduced exposure of bunches to chilling conditions in the field and the development of visible chilling injury symptoms on the peel surface and in underpeel tissue. Greatest control of field chilling was shown using the non-sealed 'silver blue + silver bubble' cover design. Relative to the standard blue cover, in winter 2003 the non-sealed 'silver blue + silver bubble' cover design reduced chilling exposure by 95% at the top and 45% at the bottom of bunches. This totally controlled chilling injury symptoms in the top and middle bunch regions. In winter 2004 chilling conditions were more severe and chilling exposure was reduced by 85% using the non-sealed 'silver blue + silver bubble' cover. This reduced the severity of peel surface chilling symptoms by 67% in the top bunch region relative to fruit from blue covers. Yield characteristics were positively influenced by 'blue + silver bubble' and sealed and non-sealed 'silver blue + silver bubble' covers. Improved fruit size and weight was probably due to enhanced temperature conditions inside the bunch environment, relative to 'control' covers. Fruit quality was generally unaffected by 'blue + silver bubble' and sealed and non-sealed 'silver blue + silver bubble' covers. However peel colour was significantly influenced by these cover treatments, compared to the 'control' covers. Reduced light transmission of covers produced paler fruit. This may have influenced other quality characteristics, such as green life and SSC levels, as it confounded assessment of ripening stage. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1241852 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture and Wine, 2006

In this thesis, the treatments of MEA and the special structures within carbon fiber bunch unipolar plates on the performance of PEMFC are studied. At first, the factors affecting on the water content within MEA will be studied. A passive HFC stack usually exposes in the ambient no matter that it works or not. However, the ambient is far from saturated. The water within MEA will vaporize continuously. Especially, if the stack is shutdown for a long period, there is no water generation in the cathode and then the membrane will be short in water. If it occurs, the conductivity of H+ will decrease greatly, and the electrode of MEA is also possible to separate from its membrane. This separation will make the performance of the stack an unrecovered decay. On the other hand, in order to improve the performance of a air-breathing HFC, the inner structure within cathode carbon fiber bunch unipolar plates is modified. The structure of the unipolar plates is modified in the following three aspects: 1. Increasing soft end height of carbon fiber bunch, 2. Increasing the number of silver-coated wires in carbon fiber bunch, 3. Cutting several serrated slots on the soft end of carbon fiber bunch. In the MEA treatment, firstly, a MEA is boiled in 80oC, 0.5M H2SO4 solution and then boiled in 80oC DI water for an hour, respectively. When the single-cell HFC operates in hydrogen inlet pressure 0.1 bar, air-breathing, and room temperature, experimental results display that the power density of this HFC with the aforementioned treatments and the special structure of unipolar plates can reach a value about 185mW/cm2. This value is about 130% higher than that of the untreated MEA and about 50% higher than that of the treatment of MEA only immersed in DI water. In addition, the comparison of the performance of HFC between with carbon fiber bunch unipolar plates and with graphite unipolar plates are also studied. The experimental result displays that the performance of HFC with the carbon fiber bunch unipolar plates is superior to that with graphite unipolar plates, especially the fuel cell operating under low gas inlet pressure.

In this thesis, a portable PEMFC stack, which can directly power or charge 3C products, will be developed. The stack is developed for portable applications, so the structure of the stack is simplified as possible as we can. The PEMFC stack is made with 32 carbon fiber bunches for current collectors and two 8-cell banded-type MEAs which are made with 8 sets of electrodes on a piece of membrane. The stack can develop a high voltage by serially connecting 8 cell or 16 cell outside of the reaction chamber. The resistance of each carbon bunch assembling with carbon cloth is measured before they are assembled into the stack. Under assembly pressure 3 bar, the total resistance is about 8.7m£[ or 11m£[¡Ecm2. The resistance is about one half of that graphite plate assembling with carbon cloth. Without being compressed greatly in diffusion layer, the fluid can easily flow through the gaps between carbon fiber and within diffusion layers, and then the reactive region will react more uniformly. In addition, the connecting wires are assembled to a wire collecting board, so that the stack is look more neat, and it easier assemble or dissemble. In this thesis, the volume of the developed 16-cell hydrogen fuel cell stack is about 9.6 cm*6.3 cm*2.2 cm. The total electrode area is 50 cm2 (16-cell¡Ñ3.15 cm2 per cell). When the stack is operating at room temperature and air-breathing, an 8-cell stack in series connection can generate 3.7V voltage. Its power at voltage 3.7V is about 3.6W. It can directly power PDAs, mobile phones or digital cameras. A 16-cell stack in series connection can generate 7.2V voltage. Its power at this voltage can offer 7W. The 16-cell stack can directly power digital single-lens reflex cameras. If two or more of this stack are connected in series, it will be able to power a notebook or other more power products.

Für die Reichweiteverifikation in der Protonentherapie mittels Prompt Gamma-Ray Timing (PGT) wird ein Proton-Bunch-Monitor (PBM) benötigt, um Phaseninstabilitäten zwischen den Protonen-Mikropulsen und der Radiofrequenz (RF) des Zyklotrons zu eliminieren. In dieser Arbeit wurde demonstriert, dass ein Diamantdetektor diese anspruchsvolle Aufgabe erfüllen kann. Dazu wurde ein polykristalliner Diamantdetektor in diversen Experimenten umfassend charakterisiert. An ELBE wurde eine Zeitauflösung von 82(6) ps für minimal-ionisierende Elektronen bestimmt. Die Auflösung bei der Detektion von Protonen klinischer Energien wurde am OncoRay ermittelt und betrug im Mittel 314(17) ps. Des Weiteren wurden Experimente durchgeführt, die auf die optimale Position des Detektors in der späteren klinischen Anwendung nahe des Degraders schließen lassen. Bei der Anwendung als PBM konnte der Diamantdetektor Phasenverschiebungen zur RF mit einer zeitlichen Auflösung von weniger als 3 ps bei einem Messintervall von 30 ms detektieren. Diese Phasenverschiebungen konnten auch in weiten Teilen durch das Phasenkontrollsignal U_phi, welches im Rahmen dieser Arbeit erstmalig ausgewertet wurde, bestätigt werden. Mit dem Diamantdetektor und U_phi stehen nun zwei PBM zur Verfügung, mit denen ein zentrales Problem bei der klinischen Anwendung von PGT als Reichweite-Verifikationsmethode gelöst werden kann.:1 Motivation 2 Grundlagen der Reichweiteverifikation in der Protonentherapie 2.1 Wechselwirkung von geladenen Teilchen mit Materie 2.2 Tiefendosiskurven 2.3 Praktische Aspekte der Protonentherapie 2.4 Reichweiteunsicherheiten 2.5 Prompt Gamma-Ray Timing (PGT) 2.6 Proton-Bunch-Monitore (PBM) 3 Entwicklung eines Vorverstärkers für den Diamantdetektor 3.1 Untersuchungen mit Generatorsignalen 3.2 Untersuchungen mit radioaktiven Prüfstrahlern 3.3 Ergebnisse 4 Bestimmung der Zeitauflösung am Elektronenstrahl 4.1 Bestimmung der Zeitauflösung eines Detektors mit einer Flugzeitmessung 4.2 Experimenteller Aufbau 4.3 Datenerfassung 4.4 Ergebnisse 4.5 Zusammenfassung 5 Bestimmung der Zeitauflösung am klinischen Protonenstrahl 5.1 Experimentalraum am OncoRay 5.2 Experimenteller Aufbau 5.3 Bestimmung der Zeitauflösung eines Detektors mit einer Koinzidenzmessung 5.4 Ablauf der Messung 5.5 Datenerfassung 5.6 Ergebnisse 5.7 Diskussion 5.8 Zusammenfassung 6 Optimierung der Position des Diamantdetektors am Degrader 6.1 Vorbetrachtungen 6.2 Experimenteller Aufbau 6.3 Ergebnisse 6.4 Diskussion 6.5 Zusammenfassung 7 Einsatz des Diamantdetektors als PBM 7.1 Experimenteller Aufbau 7.2 Datenerfassung 7.3 Ablauf der Messung 7.4 Ergebnisse 7.5 Diskussion und Ausblick 7.6 Zusammenfassung 8 Zusammenfassende Diskussion A Anhang A.1 Produktzertifikat des Diamantdetektors A.2 Zertifikate der radioaktiven Prüfstrahler A.3 Feinzeit-Korrektur beim U100-Spektrometer A.4 Zeitdifferenz-Histogramme für Variante A1 und A2 des Koinzidenzexperiments A.5 Der Diamantdetektor als PBM bei automatischer Phasenanpassung A.6 Der Diamantdetektor als PBM bei manueller Phasenanpassung Literaturverzeichnis Abbildungsverzeichnis Tabellenverzeichnis Liste der verwendeten Akronyme Danksagung und Eigenständigkeitserklärung

Within the Sceloporus scalaris species group, some species are oviparous while others are viviparous, suggesting the origin of viviparity is relatively recent. This interpopulation comparison focused on Sceloporus scalaris in Arizona because low elevation (1500 m) and high elevation (2500-2900 m) populations exhibit short and long periods of egg retention, respectively, and increased periods of egg retention are presumably an intermediate step in the evolution of viviparity. Low elevation populations had life histories typical of lowland Sceloporus: eggs are laid at embryonic stages 32-33, clutch sizes are relatively large, hatchlings are relatively small, and more than one clutch is produced per season. In contrast, montane populations retain eggs to embryonic stages 36-38, clutch sizes are relatively small, hatchlings are relatively large, and only one clutch is produced per season. In accord with their lengthy retention, eggshells of montane populations were thinner than those of lowland populations. The assumption that prolonged egg retention is mechanistically associated with relatively thin eggshells was tested by comparing the development of embryos in eggs retained in utero with that of control embryos in eggs incubated in Simulated nests where water and gases were presumably not limited. For the low elevation population, growth rates of embryos retained in utero as long as stage 39 were identical to those of control eggs at the same stages. However, water uptake by retained eggs was confined to the embryo whereas water uptake of control eggs was associated with both the embryo and extraembryonic tissues. These results suggest that the length of egg retention by S. scalaris is not constrained by eggshell thickness, and that the capacity to regulate the water balance of eggs may be an important component of the evolution of viviparity. / Master of Science

The problem of the performance decay and the factors affecting on the DMFC performance for long-term operation are studied in this thesis. First, the influence of the initial treatments of MEA and the exposure of MEA in the atmosphere on the water content are measured. In addition, the effects of the pressure of the MEA hot press conditions, the treatments and preservation of MEA, and the operative conditions on the performance are also examined. Eventually, we expect that the best way to increase the DMFC performance and avoid the performance can be found. These can provide for references when a portable DMFC need to be designed and manufactured in future. In order to solve the problem of methanol crossover leading to the cathode poisoned, cells are operated only under the proper methanol concentration and discharged thoroughly before finishing the whole experiment. It is also necessary to maintain MEAs in proper wetness so that the performance of stack will not decay too quickly. In the initial treatment, firstly, a MEA is immersed in 3M MeOH and then boiled with 80oC DI water for an hour, respectively. The experimental conditions of this passive single-cell DMFC are pumpless in anode chamber, air-breathing, and room temperature. The power density of this DMFC with these test conditions can reach a value about 33mW/cm2. This value is about 106% higher than that of the untreated MEA. If MEA boiled with 0.5M H2SO4 for an hour and then boiled with 80oC DI water for an hour, its power density is about 75% higher than that of the untreated MEA.

In this thesis, a long-term operation direct methanol fuel cell (DMFC) stack with no performance decay is developed and improved. In a traditional passive portable DMFC, the Methanol solution is storage at anode Reaction chamber. The performance will drop after a short period due to the concentration of Methanol solution becoming lower (about 1.5M). Although High concentration of Methanol solution could increase the operation time, but it will couse crossover to poison the cathode Pt particle, and it is unable to keep long-term operation stably either. In order to achieve long-term operation stably, to maintain the concentration of methanol solution in the anode chamber will be very important. In our fuel supply stack, there are two chambers in the stack to storage methanol and water, and we could control the supplying rate by adjusting the diffusion area to control the diffusion rate of methanol and water. And the methanol solution deliver to anode reaction chamber by cotton tube. If the anode reaction chamber is filled with 1.3¢W, 2M methanol solution and without any fuel supply, operating on the 185mA constant current (82.2mA/cm2 ). The results shows that the performance begin decay about after 15minutes. If the appropriate amount of methanol and water is supplied, the performance can be steady in a long-term operation. But if supply too much methanol solution, the concentration in the anode reaction chamber will rise up, and the high concentration will cause crossover poised the cathode catalyst, and the performance will decay. If supply rate not enough, the concentration in the anode reaction chamber will become lower, and the performance will decay after long-term operation. In this study, based on operate current and the rate of evaporation of methanol solution, to supply appropriate supplying rate and concentration of methanol solution to anode reaction chamber, could keep the performance in a steady output.

The advantage for new carbon fiber bipolar plate are as follow, low cost, light weight, low contact resistance and good chemical stability. After process automation, to further reduce costs, enhance quality stability, improve production efficiency, bipolar plates can be achieved mass production. Bipolar plate manufacturing process is divided into five parts:(1) the unfolding of carbon fiber (2) automation of gluing (3) hot-compression harden (4) cutting of carbon fiber bunch (5) Injection molding of bipolar plates. Without leakage, tightness test of the carbon fibers must reach a pressure of 0.2 kg/cm2. The contact resistance is lowest when number of carbon fiber has 160 layers, and compressed fiber bunch height of 2mm on the assembly. Anode inlet pressure is 0.1 kg/cm2. Cathode is required to install a fan. And the fan speed has to cooperate with current load. The quality of carbon fiber bunch will affect the performance of the battery, such as the wide of the rubbers, the flat of the section, Tightness, and numbers of fibers. The structure of the bipolar plate must be considered fuel transfer and number of carbon fibers bunch. Fuel supply and the contact resistance value to achieve a good balance.

Abstract The improvement of performance and the maintenance of stability of a portable air-breathing DMFC are studied in this thesis. The effect of the improvement of the internal structural of carbon fiber bunches on the cell performance is studied firstly. The small channels in the soft end of the carbon fiber bunches can be formed by changing the thickness of the copper plates burry within the gluing zone of the fiber bunches. Then one or two transverse grooves are form in proper location by cutting part of the carbon fibers at the soft end to shorten the airflow path to the area of electrode which is covered by the carbon fiber bunches so that the reaction area can obtained enough oxygen or fuel. Experimental results show that the maximum power density is about 20 mW/cm2 with no structure but it raised to about 24 mW/cm2 with the burry a 0.5mm thick copper plate and the two transverse grooves. It improves about 20% power density. The experiments prove that the improvement of the internal structure of the carbon fiber bunches is helpful in stack performance. In order to reduce the unneeded depletion of fuel, the bare nafion membrane pastes another special membrane to block methanol and water leakage. The strategy to block the leakage improved the rate of fuel utilization about 24%. In order to make the direct methanol fuel cell operating stably, a fuel supplying system by gravitation and diffusion forces is delivering the consumed fuel to maintain the concentration of methanol solution in anode reaction, by adjusting a sliding gate to control the diffusion area and utilizing three cotton threads and hoses to distribute the fuel to proper location. The multi-point type of fuel supplementary system allows the methanol solution to be distributed uniformly, so that the stack can maintain stable operation for a long period. In order to make the stack size to a minimization, the volume of the anode reaction chamber will be minimized as possible; however, the reduced chamber is still able to supply sufficient fuel maintaining operating stably in the high-current condition. The transient phenomena of output voltage under the various volume of the reaction chamber are also studied in this research. Finally, we hope to be able to identify the most appropriate space to meet demand. The above optimization results are able to provide a reference in the future design and production of portable DMFCs.

The effects of the structure of new carbon fiber bunch heterogeneous unipolar plates on the performance of PEMFC are studied in this thesis. Internal structure of carbon fiber bunches can be modified by embedding different thickness or number of copper plates in the glue bonding area to increase the air permeability of carbon fiber bunches in its soft end. We can add different thickness or amount of coppers at the middle of bonding area, making the carbon fiber bunches soft side to form parallel to the longitudinal fiber bunch with a small flow channel. We can also make a trench at the appropriate place of the soft side of the carbon fiber bunches to form an extra air passage. In order to make the above flow channel, a new process for making the carbon fiber bunches is developed also. This process will be easier to produce a variety of different structures of carbon fiber bunch. Finally, several different experiments are performed to help us to understand the effect of the carbon fiber bunch structure on the performance and find out the best structure of the carbon fiber bunches. The carbon fiber bunch structures of the test cells on the anode side are all the same, but the carbon fiber bunch structures of on cathode side are all different. Experiments show that there are two structures among all test structures displayed better gas permeability. The first one is two 0.2 mm copper plates embedded within both sides of the glue ends of a cathode carbon fiber bunch, so that a small longitudinal flow channel are formed in soft end of the cathode carbon fiber bunch. When the HFC operates at room temperature and by air-breathing, the highest performance of the HFC can reach a value of 185 mW/cm2. The second one is a 0.2 mm copper plate embedded in the center of the glue end of a carbon fiber bunch, and then three 2 mm wide serrated slots are cut on the soft end of the carbon fiber bunch. The highest performance of the HFC can reach a value of 190 mW/cm2. The highest performance of the HFC with no copper plate and no slot structure can only reach a value 160 mW/cm2. The second design can increase the no structure cell performance 18.8%. Therefore, the internal structures of carbon fiber bunches are significant to affect on the fuel cell performance, and its internal design must be considered.