A Geophysical Investigation Of The Northeastern Rim Of The St. Martin Impact Structure, Manitoba, Canada.

The St. Martin impact structure is a 40 Km diameter structure located in Manitoba, Canada lies in featureless, glaciated terrain lacking any surface expression of an impact structure. The age of the structure has been re-determined to range between 224.3 Ma to 241.4 Ma which nullified a previous hypothesis suggesting this impact was part of a multiple impact event. Within the proposed structural boundary two outcrops of Archean granite are present. The first outcrop is located in what has been identified as the central peak of the impact structure. The second outcrop lies along the northeastern boundary and is known locally as Big Rock. The purpose of this investigation was to determine the relationship of Big Rock, if any, to the impact event and to constrain a more accurate diameter of the structure. To accomplish this I conducted two geophysical surveys and used selected data from a previous survey. The two methods I conducted were: a magnetic survey and seismic reflection profiling. Selected data from a previous gravity survey was used to supplement survey results. The magnetic survey was conducted using the total field G-856 Memory-Mag proton precession magnetometer which measures local or regional field strength. The seismic reflection survey was conducted using three Geometrics Geode exploration seismographs. Due to the complexity of seismic data processing I retained an outside seismic data processing company. Previous gravity anomaly data were acquired using a LaCoste and Romberg Model G gravimeter. The results of this geophysical investigation reveal a shallowing of granitic basement rock with exposure near Big Rock. However, a suggested listric fault near Big Rock was not identified via seismic reflection profiling, but was suggested by both the gravity and magnetic surveys. Listric faults that are genetically related to impact structures are also indicative of the structure\u27s outer boundary and therefore can confirm that the St. Martin impact structure is indeed 40 Km in diameter

A Geophysical Investigation of the Northeastern Rim of the St. Martin Impact Structure, Manitoba, Canada

The St. Martin impact structure is a 40 Km diameter structure located in Manitoba, Canada lies in featureless, glaciated terrain lacking any surface expression of an impact structure. The age of the structure has been re-determined to range between 224.3 Ma to 241.4 Ma which nullified a previous hypothesis suggesting this impact was part of a multiple impact event. Within the proposed structural boundary two outcrops of Archean granite are present. The first outcrop is located in what has been identified as the central peak of the impact structure. The second outcrop lies along the northeastern boundary and is known locally as Big Rock. The purpose of this investigation was to determine the relationship of Big Rock, if any, to the impact event and to constrain a more accurate diameter of the structure. To accomplish this I conducted two geophysical surveys and used selected data from a previous survey. The two methods I conducted were: a magnetic survey and seismic reflection profiling. Selected data from a previous gravity survey was used to supplement survey results. The magnetic survey was conducted using the total field G- 856 Memory-Mag proton precession magnetometer which measures local or regional field strength. The seismic reflection survey was conducted using three Geometrics Geode exploration seismographs. Due to the complexity of seismic data processing I retained an outside seismic data processing company. Previous gravity anomaly data were acquired using a LaCoste and Romberg Model G gravimeter. The results of this geophysical investigation reveal a shallowing of granitic basement rock with exposure near Big Rock. However, a suggested listric fault near Big Rock was not identified via seismic reflection profiling, but was suggested by both the gravity and magnetic surveys. Listric faults that are genetically related to impact structures are also indicative of the structure’s outer boundary and therefore can confirm that the St. Martin impact structure is indeed 40 Km in diameter

Study of granular temperature in dense fluidized beds by diffusing wave spectroscopy

Diffusing wave spectroscopy (DWS), a non-intrusive multiple scattering technique, can be used to study the fundamentals of particle motion in dynamic dense granular media and measure the mean of the square of the particle velocity fluctuations about their mean, which is related directly to the so-called ‘granular temperature’ that underpins many theories for dynamic granular processes. An overview of DWS in the context of other techniques for studying the granular temperature and dynamics of particles in granular systems, and its application to a range of fluidized bed configurations is reported in this thesis. The thesis reports how the granular temperature and particle dynamics varies with the level of forcing for a liquid fluidized bed, and both dry and water-immersed vibro-fluidized beds. This data reveals that the granular temperature scales with, and is of the same order as, the forcing velocity (i.e. superficial velocity or peak vibrational velocity) for all except the water-immersed vibro-fluidized bed where it scales with the peak acceleration. The former appear to be in accord with theory, while no theory as yet has predicted the latter. The experimental data was also deconvoluted to reveal how the solid fraction affects the granular temperature in a liquid fluidized bed, which represents the most detailed experimental study in this regard. For the first time is revealed that vertical profiles of the granular temperature are a consequence of observed concentration stratification in a liquid fluidized bed. By way of example of the results that can be obtained using DWS, we have shown how it has provided a basis for us to hypothesise that particles in vibro-fluidized beds (both dry and water-immersed) rattle around in cages formed by their neighbours until their collective re-arrangement occurs at long time scales

Flow regime map of a liquid-solid micro-circulating fluidized bed

Solid-liquid micro-fluidised beds (FBs), which are essentially fluidisation of micro-particles in sub-centimetre beds, hold promise of applications in the microfluidics and micro-process technology context. This is mainly due to fluidised particles providing enhancement of mixing, mass and heat transfer under the low Reynolds number flows that dominate in micro-devices. Sometimes particle circulations is required or desirable (e.g. continuous regeneration of a catalyst) for which circulating fluidised beds are ideal, not to mention advantages of better interfacial contacting and reduced backmixing compared to a classical fluidised bed (1). Albeit there are quite a few studies of solid-liquid micro-fluidised beds, we are presenting the first study of micro-circulating fluidised bed. A transparent micro-circulating fluidised bed was made by micro-machining channels of 1 mm2 square cross section in Perspex as shown in Fig. 1. We used soda-lime glass microparticles and tap water as fluidising medium to study flow regime transition for this micro-circulating fluidised bed. The flow regime map as proposed by Liang et al. (2) was produced for a micro-circulating fluidised bed and is given in Fig. 2. Essentially results are almost the same as for the macroscopic counterparts with the transition to the circulating fluidised regime occurring at velocities, Ucr, slightly above the particle terminal velocities, Ut (1,2). The reported critical transition velocity is for high enough solid inventories (above 10% of the system volume) where this transition velocity is constant, while for lower solid inventories it is bigger as in previous experiments (1,2). While the minimum fluidization velocity, Umf, is influenced by adhesion forces and wall effects (3), there is a weak increase in the normalized critical transition velocity for circulating regime, Ucr/Ut, with an increase of particle diameter (not shown here). This may be due to the wall effects but more studies are needed to elucidate this further. Please click Additional Files below to see the full abstract

The Prevalence of Spine Deformities and Flat Feet Among 10-12 Year Old Children Who Train Basketball – Cross-Sectional Study

The aim of this study is to estimate the prevalence of spine and feet deformities among children who are regularly involved in basketball trainings, as well as finding differences in the prevalence of those deformities between children of different gender and age. The study included a total of 64 children, of which 43 were boys and 21 were girls, ages 10-12. All subjects have been regularly participating in basketball trainings for at least one year. Postural disorder is defined as an irregularity in posture of the spine and feet, and it is assessed by visual methods from the front, side and rear side of the body. The prevalence of spinal deformities in our group was 53.13%. The boys had a significantly higher prevalence than girls, 65.1% compared to 28.57% (p=0.006). There was no significant difference in prevalence of spine deformities between children of different ages. The prevalence of feet deformities was 64.06%. There was a statistically significant difference between the sexes, where boys had a significantly greater prevalence of the feet deformities than girls, 83.7% compared to 23.81% (p=0.001). Flat feet were the most common in 10 year old children (85.71%). In conclusion, it can be said that despite regular participation in basketball training, subjects in this study have high prevalence of deformities; especially boys who stand out with the high prevalence of flat feet

Experimental study of efficient mixing in a micro-fluidized bed

Micro-fluidized beds represent a novel means of significantly enhancing mixing and mass and heat transfer under the low Reynolds number flows that dominate in microfluidic devices. This study experimentally evaluates the mixing performance of a micro-fluidized bed and the improvements it affords over the equivalent particle-free system. The dye dilution technique coupled with standard top-view image analysis was used to characterize the mixing in a 400×175μm 2 polydimethylsiloxane (PDMS) Y-microchannel. Overall, the micro-fluidized bed provided a mixing effectiveness and energetic efficiency of mixing that were up to three times greater than those of a particle-free channel of the same dimensions. The mixing performance is strongly affected by specific power input and bed voidage. The optimal operating voidage, which corresponds to the energetic efficiency of mixing being maximal, is around 0.77 for the smallest particle-to-channel size ratio considered here 0.121, and appears to increase beyond this with size ratio