Thesis (S.M.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences and the Woods Hole Oceanographic Institution), 2001. / Includes bibliographical references (leaves 44-48).

Subject to a sufficiently large compression, materials may undergo mechanical instabilities of various types. When the material is homogeneous, creases set in. When the material is a bilayer consisting of a stiff thin film on a thick compliant substrate, wrinkles set in. Creases are localized self-contact regions with large strain deviating from the smooth state, while wrinkles are undulations finite in space with infinitesimal strain deviating from the smooth state. After the formation of wrinkles, if the compression further increases, wrinkles double their period and form localized folds. If the substrate is subject to a sufficiently large pre-tension, wrinkles transit to ridges. This thesis explores different types of mechanical instabilities: creases, wrinkles, folds, and ridges. We start with studying creases in different materials. Soft tissues growing under constraint often form creases. We adopt the model of growth that factors the deformation gradient into a growth tensor and an elastic deformation tensor, and show that the critical conditions for the onset of creases take a remarkably simple form. We then perform simulations to explore creases in strain-stiffening materials. For a solid that stiffens steeply at large strains, as the compression increases, the surface is initially smooth, then forms creases, and finally becomes smooth again. For a solid that stiffens steeply at small strains, creases never form for all levels of compression. In order to better control the formation and disappearance of creases, we design a soft elastic bilayer with same moduli of the film and substrate but the substrate pre-compressed, and show that the bilayer can snap between the flat and creased states reproducibly with tunable hysteresis in a large strain range. We also show that an interface between two soft materials can form creases under compression. We then investigate the critical conditions for the onset of wrinkles and creases in bilayers with arbitrary thicknesses and moduli of the two layers, and show several new types of bifurcation behavior when the film and substrate have comparable moduli and thicknesses. We study the effect of substrate pre-stretch on post-wrinkling bifurcations, and show that pre-tension stabilizes wrinkles while pre-compression destabilizes wrinkles. When the pre-compression is sufficiently large, `chaotic' morphologies emerge. When the pre-tension is sufficiently large, we realize ridge localizations and networks under an equi-biaxial compression, and study the mechanics of ridge formation and propagation. / Engineering and Applied Sciences

The Padthaway Ridge is overlain by a thin veneer (< 20 m) of Oligo-Miocene bioclastic carbonates representing the southern most extent of the Mannum Formation, Murray Supergroup, and Murray Basin limestones. The Mannum Formation is composed of warm-temperate carbonates rich in irregular echinoids, coralline algae, benthic foraminifers, and relict particles. The respective lithology are mostly structureless, burrow-mottled, and cross-cut by Thalassinoides burrows. These sediments are interpreted to have resulted from carbonate production along shallow, illuminated seafloors under high mesotrophic conditions. The composition and texture is similar to that of modern temperate seagrass accumulations with the exception of the abundant mobile infauna and bioturbation, which are more akin to associated intercalated and adjacent barren sands. The Mannum Formation is therefore interpreted as an amalgamation of these two environments. The ubiquitous relict grains and Fe-stained cements in the lithologies of the Mannum Formation are thought to be the product of Fe redox pumping within the subsurface of seagrass meadows, whereby consolidated sediments endured prolonged and repeated exposure to juxtaposed destructive and constructive diagenetic conditions at the redox boundary. Fluctuations in the organic carbon and oxygen influx to the subsurface are primarily a function of auto- and allogenic controls on seagrass density (i.e. turbidity, light, depth, hydrodynamics). The overlying Glenforslan Formation is interpreted as a seagrass-influenced deposit that accumulated under warm-temperate, low mesotrophic conditions and more rapid rates of sedimentation. Relict grains, however, are absent from the Glenforslan Formation. The subtle change in trophic resources is thought to have caused a significant shift in primary and secondary production, from organic carbon- to carbonate-dominated. Assessment of previously described temperate seagrass facies together with this research comprise reliable criteria for identification of temperate seagrass depositional settings. The signal of multigenerational accumulation, especially prominent in the Mannum Formation, represents an amalgamation of environments that would be difficult to assess in modern settings. The key attributes of temperate grass facies proposed herein allow for more accurate reevaluation of seagrass influenced, and relict rich lithologies in the rock record. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2009-12-14 17:18:16.853

The Blue Ridge Province of western North Carolina contains a wide variety of metamorphosed igneous and sedimentary rocks that record the tectonic effects of Precambrian and Paleozoic orogenic cycles. Tectonic interpretations of the events that led to the present configuration are varied and often conflicting. This investigation examines metamorphosed mafic rocks that are widely interpreted to have formed during the closure of ocean basins. Metabasites, and specifically eclogites, have a tendency to mark tectonic sutures and frequently preserve pressure (P), temperature (T), and age data (t) that can be gleaned from mineral equilibria and U-Pb isotopic compositions. As such, the examination of the metabasites is considered the key to understanding the orogenic history of the southern Blue Ridge where these metabasites occur. Chapter 2 is an investigation of the retrograde reactions related to the decompression of sodic pyroxenes that react to form diopside-plagioclase-hornblende-quartz symplectites as stability fields are overstepped during isothermal decompression. In Chapter 3 metabasites from the central and eastern Blue Ridge are re-examined and P-T pathways of these lithologies are determined. The argument is made that the Taconic orogeny of the Blue Ridge is the result of a continent-continent collision event that culminated in a mega-mélange that coincides with the Cullowhee terrane and the eastern Blue Ridge mélange of western North Carolina. Chapter 4 contains the results of a geochronological investigation of the Precambrian basement complex of the eastern Great Smoky Mountains. Chapter 5 is a whole rock geochemical study of the same basement complex. In Chapter 6, a potential lithologic correlation between the southern Blue Ridge basement and the Arequipa- Antofalla block of Peru is discussed. The geologic history of western South America from the Mesoproterozoic through Cambrian is summarized, a potential isotope-based lithologic correlation is proposed, and the early tectonic history of the central Blue Ridge is discussed. Chapter 7 contains brief summaries of Chapters 1-6.

Terrane discrimination in polycyclic continental basement rocks is challenging due to high-grade metamorphism and intense deformation. Based on early USGS mapping the Blue Ridge basement in the Dellwood quadrangle of the eastern Great Smoky Mountains was proposed to consist of augen orthogneisses of Laurentian (Grenvillian) affinity interfolded with migmatitic hornblende and biotite paragneisses (“Carolina Gneiss”) and amphibolites of uncertain affinity. However, detailed study reveals that the hornblende gneiss of Hadley and Goldsmith (1963) is a heterogeneous map unit consisting of (1)metaplutonic rocks; (2) variably foliated and folded felsic orthogneisses; (3) strongly migmatitic, folded Hbl+Bt-bearing gneisses; (4) foliated and lineated garnet amphibolites Field relations, petrology, and geochemistry demonstrate that felsic orthogneisses are related to metaplutonic rocks via (post-Taconian) progressive deformation and reconstitution. Whole rock XRF geochemistry reveals likely protoliths of Hbl gneiss and Bt gneiss are geochemically similar and have common sources. U-Pb zircon geochronology and field relationships suggest felsic orthogneisses (1050 Ma,1150-1190 Ma, 1250-1300 Ma) are components of the Mesoproterozoic Grenville basement, and not part of a metamorphosed Neoproterozoic syn-rift Laurentian margin cover sequence. A previously unknown age mode for Mesoproterozoic plutonism in the southern Appalachians was discovered (~1250-1300 Ma) suggesting the presence of a component exotic to pre-Grenvillian Laurentia (Amazonia?).

Iceland is the land-based expression of the Mid-Atlantic Ridge and is one of the most volcanically active regions of the world. Volcanic eruptions on Iceland are a source of geological hazard to humans and the environment due to the release of ash, gases and lava. The composition of the material released is determined by the chemical composition of the surrounding bedrock and the magma upwelling from the Earth’s crust. The effects of historical eruptions on Iceland have been locally devastating and of global impact. The eruption of Lakagígar in 1783-1784 is known to have been the largest eruption in historical time, and is responsible for the death of ~22 % of theIcelandic population. Skeletal fluorosis is a disease that is sometimes observed following large volcanic eruptions. Volcanic ash can travel great distances in the upper atmosphere and spread over vast areas far away from the erupting volcano. Volcanic ash can change incomposition in the atmosphere, and bring about climate-changing effects. Most notably in recent times, violent ash eruptions can also cause problems to the aviation industry, when ash enters and damages airplane engines. Iceland has many active volcanoes and needs to ensure plans for future eruptions are in place. One such measure is an evacuation plan that protects people living close to an active volcano, such as the most lively on Iceland: Hekla, Katla and Eyjafjallajökull.

Mitt arbete handlar om redan från de att jag startade mitt eget band Ridge fram tills dess att vi släppte vår debutskiva Same Ground. Om att våga göra musik från sitt hjärta,att tveka,kämpa,repa,spela in och att släppa skiva på eget bolag. Det handlar också om min uppväxt och hur det påverkat mig. Jag skriver reflekterande om processen. / <p>Bilaga: 1 CD</p>

At fast spreading ridges such as the East Pacific Rise (EPR) volcanic eruptions are predicted to occur on a decadal timescale. Due to the limited ability to observe submarine eruptions, little is known about the magmatic processes occurring in the underlying magma chamber leading up to a volcanic event, including differentiation and magma mixing. The recent 2005-06 eruption at 9˚46’N-9˚56’N along the EPR provides a unique opportunity to gain a better understanding of rates of magma transport and magma replenishment associated with a typical eruption. This study examines the geochemistry of phenocrysts from the 2005-06 eruption in order to determine if they are in equilibrium with their host melt, or if magma mixing occurred prior to eruption. A diffusion model is used to model those crystals which are out of equilibrium with their erupted host to determine timescales of magma mixing. The major and trace element contents of plagioclase and olivine phenocrysts provides evidence for melts both more evolved (> 3.5 wt % MgO) and more primitive (< 8.8 wt % MgO) than those found within the host lava (7.7-8.3 wt % MgO; Goss et al., 2010). Glomerocrysts and resorbed crystals in equilibrium with evolved melts (3.5-6.5 wt % MgO) suggests an origin in a roof mush zone, and were disrupted and entrained into their host melt within days of eruption. Modelling of the zoning profiles of phenocrysts suggest the 2005-06 eruption was likely triggered by an influx of hotter, more primitive melt (~ 9.0 wt % MgO) which was injected into the melt lens a few weeks to months prior to the eruption. With decreasing time before eruption, there is an overall increase in the number of crystals with modelled timescales representing mixing events in the magma chamber. This increase in modelled timescales appears to correlate with the increase in seismic activity recorded prior to the eruption (Tolstoy et al., 2006). This suggests magma mixing events within the underlying magma chamber may be linked to seismic activity at fast spreading ridges. / Graduate / 0372 / 0996

Graduation date: 1997 / Best scan available for figures. Original figures are black and white photocopies.

Abstract Biotechnological strategies aimed at producing male-only offspring have the potential to improve the yield of the Australian beef industry. As a proof-of-concept project, I aimed to target the primary male sex-determining gene Sry to the X chromosome in mice, to produce a transgenic XY male that would transmit Sry – and hence maleness – to both XX and XY offspring. In this project I aimed to target a 14.5 kb DNA fragment containing Sry to an X-chromosome locus that escapes X-inactivation. After considering many potential loci, a targeting strategy and construct were designed for the SMCX locus, which is well conserved between mouse, human and bovine. A targeting vector with 5kb and 3kb arms of homology was also constructed without Sry, to target the locus. Attempts to introduce the 14.5 kb Sry fragment into the construct were unsuccessful, and a smaller construct, containing only the coding sequence of the Sry gene driven by a strong promoter, is currently being made. In order to translate this transgenic approach into cattle, other facets of bovine sex determination required investigation. First, it was important to identify the necessary regulatory regions upstream of bovine SRY needed for the gene to be functional, and secondly to investigate the timing of testis development in male bovine embryos. To enable sequence comparison, I sequenced upstream of the bovine and goat SRY gene and through bioinformatic analysis identified regulatory regions common to several mammals. I identified four regions of high homology upstream of bovine SRY conserved between human, goat, and pig, but not mouse. These regions are likely to be important for the regulation of the gene in these species, as they share unique transcription factor binding sites. From this research I concluded that 9 kb upstream of bovine SRY were likely to be useful in transgenic strategies to produce sex-reversed cattle. Although I attempted to use a 15 kb bovine genomic fragment containing SRY to sex reverse XX mice, this project was unsuccessful. I also investigated the expression pattern of genes known to have a role in sex determination, including SRY, in early bovine embryos. I identified the major time points important for male sex determination, including the first appearance of the gonadal ridge from the mesonephros at day 31, the onset of SRY expression and its peak at day 39, and the appearance of testis cords at day 42, along with the pattern of expression of many other genes downstream of SRY. This information will allow future researchers to check that transgenic SRY expression is occurring at the correct time and place for it to be able to cause XX sex reversal in cattle. I also identified some of the major time points important for female sex determination, including that ovigerous cords form between CRL 37-91 in female bovine embryos. In addition I show the cellular differentiation of the cortex and medulla at this time. I have also predicted the female germ cell entry into meiosis around CRL 40 in bovine embryos through the use of qRT-PCR for STRA8 and SYCP3. This is the first detailed account of gene expression profiles in early female bovine embryos, unfortunately the data is incomplete due to an uneven distribution of embryo ages due to the difficulty of obtaining embryos from timed matings. Hopefully in the future obtaining more female embryos of the missing stages can complete the female data. This project has provided additional basic knowledge about bovine sex-determination events to ensure the possibility of making single-sex livestock a real possibility in the future. The similarity between human and bovine developmental time frames also points to cattle being a good alternative model for human development, and emphasises the need for further research in species other than mouse, with the aim of ultimately understanding our own biology.