Search

We present an experimental method whereby ‘Pink Beam’ synchrotron radiation is used in X-ray microtomography to investigate pore structure changes during supercritical CO2 injection in very heterogeneous carbonates at high temperatures and pressures.The raw images were binarized and the magnitude of dissolution was identified on a voxel-by-voxel basis. This information was used to extract pore-by-pore dissolution data.

Defective chromatin remodeling proteins are associated with both germline and acquired human disease. PHF6 is encoded by an X-linked gene that is predominantly expressed in the brain and thymus. Structurally, PHF6 contains nuclear and nucleolar localization sequences as well as two ZaP domains, which bind dsDNA. Germline mutations in PHF6 are the cause of BFLS, an XLID, while somatic PHF6 mutations have been identified in T-ALL, AML, and CML. Indeed, screening of a pediatric cohort of nine T-ALL patients revealed a novel H329Q mutation. In a further clinical analysis, T-ALL onset occurred in a 9-year old male BFLS patient with an R342X mutation, suggesting that BFLS might be a cancer predisposition syndrome. To better understand its protein function, recombinant PHF6 was co-immunoprecipitated for a mass spectrometry based proteomic screen. Notably, PHF6 co-purified with multiple constituents of the NuRD complex, an important transcriptional regulator during embryogenesis and lineage commitment with particularly well characterized responsibilities during lymphogenesis. PHF6-NuRD localization was restricted to the nucleoplasm, however PHF6 also co-purified with several ribosomal and splicing proteins. When examined further, PHF6 was found to be recruited to the nucleolus by an RNA-mediated interaction and co-localized within the subnucleolar FC and DFC compartments. ChIP-qPCR revealed that PHF6 binds to transcribed regions of rDNA, resulting in the repression of rRNA. These data thus present a model of PHF6 acting as a tumour suppressor by mediating both nucleoplasmic and nucleolar transcriptional events.

X-ray microtomography was used to image, at a resolution of 6.6 µm, the pore-scale arrangement of residual carbon dioxide ganglia in the pore-space of a carbonate rock at pressures and temperatures representative of typical formations used for CO2 storage. Chemical equilibrium between the CO2, brine and rock phases was maintained using a high pressure high temperature reactor, replicating conditions far away from the injection site. Fluid flow was controlled using high pressure high temperature syringe pumps. To maintain representative in-situ conditions within the micro-CT scanner a carbon fiber high pressure micro-CT coreholder was used. Diffusive CO2 exchange across the confining sleeve from the pore-space of the rock to the confining fluid was prevented by surrounding the core with a triple wrap of aluminum foil. Reconstructed brine contrast was modeled using a polychromatic x-ray source, and brine composition was chosen to maximize the three phase contrast between the two fluids and the rock. Flexible flow lines were used to reduce forces on the sample during image acquisition, potentially causing unwanted sample motion, a major shortcoming in previous techniques. An internal thermocouple, placed directly adjacent to the rock core, coupled with an external flexible heating wrap and a PID controller was used to maintain a constant temperature within the flow cell. Substantial amounts of CO2 were trapped, with a residual saturation of 0.203 ± 0.013, and the sizes of larger volume ganglia obey power law distributions, consistent with percolation theory.

"With the increasing professionalisation of the Australian Football League (AFL), greater demands are being placed upon AFL players with respect to their technical, tactical, and physiological training, in addition to increased requirements to promote their club’s brand via community appearances. Modern AFL players have an additional challenge as their careers will be typically limited to, at best, a decade or slightly more at the elite level. This means that they are also encouraged to develop an alternative career for when their playing days are over. Thus, given these demands, there is substantial challenge for the modern footballer in achieving a sense of balance between work and non-work life whilst also preparing for their next career. Although there is a strong ethical argument to support professional athletes’ off-field activities and development away from the field, there is also a growing argument from some coaches and athletes that participating in these activities actually carries some benefit for the way athletes perform in their sport. Such an argument is consistent with contemporary human resource and management literature where in demanding professions, the support of employee work-life balance and holistic development has been shown to be associated with employee engagement and productivity. Within the AFL however there has been mixed views concerning the value of supporting player off-field activities and preparations for life after football. This is understandable given that there is often an underlying assumption in elite sport that to be successful you must ‘out work’ those you are competing with. The present thesis sought to investigate the potential value that participation in off-field activities associated with their lives away from football (i.e., their social, recreational, and career development activities) may have with respect to AFL players’ experience of engagement in their roles as footballers."

X-ray microtomography was used to image the shape and size of residual ganglia of supercritical CO2 at resolutions of 3.5 and 2 μm and at representative subsurface conditions of temperature and pressure. The capillary pressure for each ganglion was found by measuring the curvature of the CO2-brine interface, while the pore structure was parameterized using distance maps of the pore space. The formation of the residual clusters by snap-off was examined by comparing the ganglion capillary pressure to local pore topography. The capillary pressure was found to be inversely proportional to the radius of the largest restriction (throat) surrounding the ganglion, which validates the imbibition mechanisms used in pore-network modeling. The potential mobilization of residual ganglia was assessed using a reformulation of both the capillary (Ncmacro) and Bond numbers (Nbmacro), rigorously based on a balance of pore-scale forces, with the majority of ganglia remobilized at Ncmacro around 1. Buoyancy forces were found to be small in this system (Nbmacro << 1), meaning the gravitational remobilization of CO2 after residual trapping would be extremely difficult.

Firstly capillary trapping is examined in a range of five different rock types, including both carbonates and sandstones. Rocks are imaged both after drainage and imbibition, and in all cases between 65-70% of the CO2 in place after drainage was trapped. Trapped cluster size distributions are compared to rock connectivity as determined using pore network modelling. Better connected pore-spaces tend to have more large clusters relative to small clusters, and visa-versa. This is important as small clusters are more difficult to remobilise by viscous and gravitational forces. They also present a relatively larger surface area for reaction and mineralization. Secondarily wettability is analysed by measuring contact angle manually. In order to do this the contact line was found in 3D and the data set resampled onto planes perpendicular to the contact line at a particular point. Contact angles ranging from 35-55o were found, indicating that the super-critical CO2-brine-carbonate system is weakly water wet. The range in contact angles is interpreted as the result of contact angle hysteresis associated with surface heterogeneity. Finally the first images of CO2 drainage at reservoir conditions are also presented, imaged at Diamond Light Source, represented an unprecented depth of information about pore-scale flow processes.

[1] While geological carbon dioxide (CO2) storage could contribute to reducing global emissions, it must be designed such that the CO2 cannot escape from the porous rock into which it is injected. An important mechanism to immobilize the CO2, preventing escape, is capillary trapping, where CO2 is stranded as disconnected pore-scale droplets (ganglia) in the rock, surrounded by water. We used X-Ray microtomography to image, at a resolution of 6.4 µm, the pore-scale arrangement and distribution of trapped CO2 clusters in a limestone. We applied high pressures and temperatures typical of a storage formation, while maintaining chemical equilibrium between the CO2, brine, and rock. Substantial amounts of CO2 were trapped, with an average saturation of 0.18. The cluster sizes obeyed a power law distribution, with an exponent of approximately −2.1, consistent with predictions from percolation theory. This work confirms that residual trapping could aid storage security in carbonate aquifers.

We have used high-pressure high-temperature equipment to image trapped (residual) super-critical CO2 in carbonate and sandstone systems with a voxel size of around 6.5µm. A residual saturation and trapping capacity (Sor) was obtained for each rock type, showing that, in all cases, a significant proportion of the scCO2 was trapped. A size analysis is performed on the residual phase clusters, finding results broadly consistent with percolation theory. This analysis is compared to the volumetric connectivity of networks extracted from dry scans rock types examined. We show techniques which allow for the extraction of larger scale parameters, such as contact angle, capillary pressure and specific interfacial area from higher resolution (2µm voxel size) pore-scale images of fluid distribution. We also demonstrate the usage of extremely bright synchrotron sources to obtain results from dynamic displacements with a time resolution of around 30 seconds. This allows for the first time to analyse fundamental dynamic processes of drainage and imbibition at the pore scale at conditions representative of subsurface flow.

Searches for radio signatures of ultra-high energy neutrinos and cosmic rays could benefit from improved detection efficiency by using real-time beamforming or correlation triggering. For missions with power limitations, such as the ANITA-3 Antarctic balloon experiment, full speed high resolution digitization of incoming signals is not practical at the trigger level. To this end, the University of Hawaii has developed the Realtime Independent Three-bit Converter (RITC), a 3-channel, 3-bit, streaming analog-to-digital converter implemented in the IBM 0.13 µm CMOS process. RITC is primarily designed to digitize broadband radio signals produced by the Askaryan effect, and thus targets an analog bandwidth of >1 GHz, with a sample-and-hold architecture capable of storing up to 2.6 gigasamples-per-second. An array of flash analog-to-digital converters perform 3-bit conversion of sets of stored samples while acquisition continues elsewhere in the sampling array. A serial interface is provided to access an array of on-chip digital-to-analog converters that control the digitization thresholds for each channel as well as the overall sampling rate. Demultiplexed conversion outputs are read out simultaneously for each channel via a set of 36 LVDS links, each running at 650 Mb/s. We briefly describe the design architecture of RITC, and report preliminary results of performance characterization, including prospects for the use of this architecture as the analog half of a novel triggering system for the ANITA-3 ultra-high energy neutrino experiment.

In recent years inexpensive, multi-Giga sample per second CMOS waveform samplers have become available, enabling a new generation of low-power, high channel count experiments in particle and astroparticle physics. Power savings over other architectures is realized by having nothing operating at the direct sampling rate of interest. Instead, the Switched Capacitor Array sampling is driven by timing generators based upon voltage-controlled delay lines. Stabilization of the timebase and the significant calibration effort required, due to the non-uniform time-steps introduced by CMOS process variations in these delay lines, have limited their more wide-spread adoption in the community. In most of the CMOS processes used, the sample-to-sample time step difference is of order 10–20%, and cannot be neglected in many applications. Especially for applications involving real-time processing of the waveform samples from these devices, splining and resampling the smoothed waveforms on a uniform time grid is computationally very expensive. To address this issue, in the 4th generation LABRADOR ASIC, individual time sample trim DACs have been implemented to tune out this time step variance. Available results of this hardware-level calibration are reported.

Extremely fast timing from Microchannel Plate PhotoMultiplier Tubes (MCP-PMTs) and multi-gigasample per second (GSa/s) waveform sampling ASICs will allow precision timing to play a pivotal role in the next-generation of Ring Imaging CHerenkov (RICH) detectors. The Instrumentation Development Laboratory at the University of Hawai'i has developed a prototype of the electronics to instrument the Imaging Time of Propagation (iTOP) counter for the Belle II detector at KEK in Tsukuba, Japan. The front-end electronics modules consist of an array of waveform sampling / digitizing ASICs controlled by an FPGA. The ASICs digitize signals from an array of multi-anode MCP-PMTs coupled to a quartz radiator bar. Readout and control are done via multi-gigabit-per-second fiber optic links to a custom back-end, where Digital Signal Processors (DSPs) correct for unwanted artifacts in the data before performing feature extraction. Variants of the modules will be used in other applications in addition to Belle II, including a tabletop neutrino detector, beam size monitoring at SuperKEKB, readout of wavelength shifting fibers for the Belle II K L /μ system, and a Focusing Detection of Internally Reflected Cherenkov (fDIRC) prototype. Important aspects of the system include thermal management problems in a very compact module, as well as the expected lifetime of the module in the intended high radiation environment(s). Our experiences running these modules as standalone entities with a pulser/laser on the bench have fed into the design of the next version of each component in the system. Cosmic ray tests and running a full system at a Fermilab beam test in late 2011 have contributed to our understanding of needed improvements for the system as a whole.

We examined the suggestion that some of the processes subserving learning through action-observation and motor-execution are different because sensory motor reafference is not available while the limb is at rest in the former condition. We confirmed the action-observation and motor-execution groups learned equally the absolute time and relative time constraints associated with a movement sequence timing task. However, data from mirror (same motor commands as those in practice) and non-mirror (same visual spatial coordinates as those in practice) intermanual transfer tests showed a clear dissociation in performance following these forms of practice. While positive transfer was exhibited by both groups in the non-mirror condition, there was a significant decrement in relative time performance in the mirror condition only after action-observation. These findings confirm that some of the processes underpinning these forms of motor learning are not somatotopic. Indeed, while motor and visual representations are developed during motor-execution, the absence of sensorimotor reafference during action-observation enables relative time to be represented in visual spatial coordinates only. These behavioural effects for intermanual transfer are discussed with reference to activity in supplementary motor area.

Regular physical activity (PA) leads to an increased quality of life by means of certain physiological adaptations. Regular PA is beneficial to the human body and its functionality, including the physiological, biochemical and even psychological modalities. During PA an increased burden is placed on all physiological mechanisms due to the increased energy demand, resulting in an adaptation of the physiological systems. Currently the biochemical mechanisms by which these adaptations occur are not well understood or defined. During the flow of electrons through the electron transport chain in the mitochondria free radicals and reactive oxygen species (ROS) are produced. PA results in increased ROS production. The relationship of different exercise intensities and ROS production with resulting DNA damage is unclear. These free radicals and ROS disturb the pro-oxidant anti-oxidant balance resulting in oxidative stress. When this balance is disturbed oxidative stress could lead to potential oxidative damage, Oxidative damage occurs in lipid, protein and nucleic acid macromolecules. ROS can attack DNA bases or deoxyribose residues to produce damaged bases and/or single and double strand breaks. When the DNA is regarded and the damages are replicated it could cause mutations or apoptosis, affecting the cell function and physiology. The purpose of this study was to investigate the influence of different aerobic intensities on oxidative DNA damage and repair in middle aged men by means of the Comet assay. Five PA males and five physically inactive males were assigned to an experimental and control group respectively. The subjects did not differ significantly at baseline. The VO2-max of each subject was determined at baseline. Subjects were then randomly assigned to 60, 70, 80 and 90% of individual baseline VO2-max intensities for an acute exercise intervention of 30 minutes on a bicycle ergometer. Blood sampling was done at baseline, post-exercise and 24 hours post-exercise for oxygen radical absorbance capacity (ORAC) and hydroperoxide analysis (dROM). Peripheral blood was obtained for DNA damage testing by means of Comet analysis at baseline, post-exercise, 5, 15, 30 minutes, and also 6, 12, 24, 48 and 72 hours after exercise. The results obtained indicated that subjects who regularly participate in PA had an increased baseline reading of ORAC and dROM values. ORAC levels after each acute exercise session increased, with the highest increase in the control group, with a decrease in the direction of baseline readings 24 hours post exercise. A biphasic damage-repair cycle over the 72 hour period was observed with the Comet analysis. The most damaged cells occur directly after acute exercise. The highest incidence of DNA damage over a 72 hour period was observed at 70% VO2-max, with the least amount of damage after 90% VO2-max. In conclusion the study indicates stress proteins or other kinds of physiological reaction to minimize the damaging effect of oxidative stress, is in place to restore the cell's homeostasis. Thus PA results in the development of oxidative DNA damage. To minimize DNA damage the optimal intensity for acute physical exercise is between 70-80% VO2-max. At higher intensities the release of stress proteins are initiated to buffer the damaging effect of oxidative stress and to restore homeostasis. Thesis (M.Sc. (Human Movement Science))--North-West University, Potchefstroom Campus, 2007.

With ever increasing numbers of Hybrid Electric Vehicles (HEV’s) being developed, come new challenges in the field of automotive engineering. Whilst there has been considerable work conducted on HEV’s from a powertrain, efficiency, and control systems perspective, very little work has been instigated in the field of how the introduction of such hybrid systems effect passive vehicle dynamics. One of the possible obstacles in the way of such studies is the multitude of powertrain architectures that are present or possible in HEV’s. This obstacle can make investigations very application specific, and leads to inefficiencies in the modelling process. This paper discusses the development of a model constructed in Dymola in order to investigate the effects of hybrid powertrains on ride and handling. The modelling methodology is presented, along with model based testing and validation of component and the full vehicle models. Whilst the development of the model is introduced for a specific study, it is shown that the way in which the model has been developed lends itself easily to use in other fields. It is shown that the modular construction of the model, and the physical, object orientated modelling approach facilitated by Dymola, allow varying numbers and complexities of component models to be utilised within the same basic model. Such an approach means that one base model can be utilised for differing hybrid architectures for ride, handling and drivability studies thus reducing modelling time and complexity.