Henselian Discrete Valued Fields Admitting One-Dimensional Local Class Field Theory

2000 Mathematics Subject Classification: 11S31 12E15 12F10 12J20.

Stripe domains formation and their affect on three-dimensional and perpendicular magnetic recording

In this study, the formation of stripe domains in permalloy (NisoFe20) thin films was investigated mainly utilizing magnetic force microscopy. Stripe domains are a known phenomenon, which reduces the "softness" of magnetic material and introduces a significant source of noise when used in perpendicular magnetic media. For the particular setup mentioned in this report, a critical thickness for stripe domains initiation depended on the sputtering rate, the substrate temperature, and the film thickness. Beyond the stripe domain formation, an increase in the periodicity of highly ordered stripe domains was evident with increasing film thickness. Above a particular thickness, stripe domains periodicity decreased along with magnetic domain randomization. The results led to the inference that the perpendicular anisotropy responsible for the formation of stripe domains originated mainly from magnetostriction.

Three-dimensional tomographic reconstruction of an exceptionally well preserved ichnological assemblage from the Stainmore Foundation, Carboniferous, UK

This Ph.D. thesis addresses current issues with ichnotaxonomic practice, and characterizes an exceptionally well preserved ichnological assemblage from the Carboniferous Stainmore Formation, Northumberland, United Kingdom. Samples were collected from closely localized float representative of various units throughout the succession, which was deposited in a storm-dominated marine shoreface. Three dominant ichnotaxa were selected for three-dimensional morphological analysis due to their complicated morphology and/or unclear taxonomic status: 1) Dactyloidites jordii isp. nov.; 2) Beaconites capronus, and; 3) Neoeione moniliformis comb. nov. Using serial grinding and photography, these ichnotaxa were ground and modelled in true colour. High-resolution models of three taxa produced in this study are the basis of the first complete three-dimensional consideration of the traces, and forms the basis for refined palaeobiological and ethological analysis of these taxa. Dactyloidites jordii isp. nov. is a stellate to palmate burrow composed of numerous long, narrow rays that exhibit three orders of branching arranged into tiered galleries radiating from a central shaft. It is considered to be the feeding structure produced by a vermiform organism. Beaconites capronus is a winding trace with distinctly chevron-shaped, meniscate backfill demonstrated herein to backfill the vertical shafts associated with its burrows in a comparable fashion to the horizontal portion of the burrow. This lack of a surface connection would result in the trace making organism being exposed to low-oxygen porewater. Coping with this porewater dysoxia could be approached by burrowing organisms in a number of ways: 1) revisiting the sediment-water interface; 2) creating periodic shafts; or 3) employing anaerobic metabolism. Neoeione moniliformis was originally introduced as Eione moniliformis, however, the genus Eione Tate, 1859 is a junior homonym of Eione Rafinesque, 1814. This led to the transfer of Eione moniliformis to Parataenidium. Through careful examination and three-dimensional characterization of topotypes, the transfer to Parataenidium moniliformis is demonstrated herein to be problematic, as Parataenidium refers to primarily horizontal burrows with two distinct layers and Eione moniliformis is composed of one distinct level. As such, the new ichnogenus Neoeione is created to accommodate Neoeione moniliformis.

Benthic and substrate cover data derived from photo-transect surveys in Lizard Island, Great Barrier Reef conducted on October 3-7, 2012

Underwater georeferenced photo-transect surveys were conducted on October 3-7, 2012 at various sections of the reef and lagoon at Lizard Island, Great Barrier Reef. For this survey a snorkeler swam while taking photos of the benthos at a set distance from the benthos using a standard digital camera and towing a GPS in a surface float which logged the track every five seconds. A Canon G12 digital camera was placed in a Canon underwater housing and photos were taken at 1 m height above the benthos. Horizontal distance between photos was estimated by three fin kicks of the survey snorkeler, which corresponded to a surface distance of approximately 2.0 - 4.0 m. The GPS was placed in a dry bag and logged the position at the surface while being towed by the photographer (Roelfsema, 2009). A total of 1,265 benthic photos were taken. Approximation of coordinates of each benthic photo was conducted based on the photo timestamp and GPS coordinate time stamp, using GPS Photo Link Software (www.geospatialexperts.com). Coordinates of each photo were interpolated by finding the GPS coordinates that were logged at a set time before and after the photo was captured. Benthic or substrate cover data was derived from each photo by randomly placing 24 points over each image using the Coral Point Count for Microsoft Excel program (Kohler and Gill, 2006). Each point was then assigned to 1 of 79 cover types, which represented the benthic feature beneath it. Benthic cover composition summary of each photo scores was generated automatically using CPCE program. The resulting benthic cover data of each photo was linked to GPS coordinates, saved as an ArcMap point shapefile, and projected to Universal Transverse Mercator WGS84 Zone 55 South.

(Table I-II) Station details and isopoda abundance of samples taken during POLARSTERN cruise ANT-XV/3 to the eastern Weddell Sea and King George Island

Abundance, diversity, and distribution of suprabenthic Isopoda caught from a water layer between 0.27 to 0.60 m above the seafloor were analysed. The samples were taken during the ANT XV/3 cruise on RV Polarstern by means of an epibenthic sledge along two transects in the southern Weddell Sea (Vestkapp and Halley Bay) and another one east of King George Island. At each of these three bathymetric transects, five to six stations were sampled between 200 and 2000 m. In total, 4258 specimens of isopods were sampled at 14 stations standardized to 1000 m2 hauls. 114 species were identified from 49 genera and 23 higher taxa (families and suborders) of Isopoda. Most of them belonged to the suborder Asellota. Dominant families are Munnopsididae (Eurycopinae, Ilyarachninae), Joeropsidae, Munnidae, Paramunnidae, Ischnomesidae and Desmosomatidae. No striking differences were found between areas (Vestkapp, Halley Bay, Kapp Norvegia, and Bransfield Strait). Overall isopod abundances were highest at the shallowest station; species richness was slightly higher above 1000 m depth.

Star formation in a stellar mass-selected sample of galaxies to z=3 from the GOODS-NICMOS Survey

We present a study of the star-forming properties of a stellar mass-selected sample of galaxies in the GOODS (Great Observatories Origins Deep Survey) NICMOS Survey (GNS), based on deep Hubble Space Telescope (HST) imaging of the GOODS North and South fields. Using a stellar mass-selected sample, combined with HST/ACS and Spitzer data to measure both ultraviolet (UV) and infrared-derived star formation rates (SFRs), we investigate the star forming properties of a complete sample of ∼1300 galaxies down to log M_*= 9.5 at redshifts 1.5 < z < 3. Eight per cent of the sample is made up of massive galaxies with M_*≥ 10^11 M_⊙. We derive optical colours, dust extinctions and UV and infrared SFR to determine how the SFR changes as a function of both stellar mass and time. Our results show that SFR increases at higher stellar mass such that massive galaxies nearly double their stellar mass from star formation alone over the redshift range studied, but the average value of SFR for a given stellar mass remains constant over this ∼2 Gyr period. Furthermore, we find no strong evolution in the SFR for our sample as a function of mass over our redshift range of interest; in particular we do not find a decline in the SFR among massive galaxies, as is seen at z < 1. The most massive galaxies in our sample (log M_*≥ 11) have high average SFRs with values SFR_UV, corr= 103 ± 75 M_⊙ yr^−1, and yet exhibit red rest-frame (U−B) colours at all redshifts. We conclude that the majority of these red high-redshift massive galaxies are red due to dust extinction. We find that A_2800 increases with stellar mass, and show that between 45 and 85 per cent of massive galaxies harbour dusty star formation. These results show that even just a few Gyr after the first galaxies appear, there are strong relations between the global physical properties of galaxies, driven by stellar mass or another underlying feature of galaxies strongly related to the stellar mass.

Isotopic ratios and ion composition of massive ground ice on Herschel Island

Herschel Island in the southern Beaufort Sea is a push moraine at the northwestern-most limit of the Laurentide Ice Sheet. Stable water isotope (d18O, dD) and hydrochemical studies were applied to two tabular massive ground ice bodies to unravel their genetic origin. Buried glacier ice or basal regelation ice was encountered beneath an ice-rich diamicton with strong glaciotectonic deformation structures. The massive ice isotopic composition was highly depleted in heavy isotopes (mean d18O: -33 per mil; mean dD: -258 per mil), suggesting full-glacial conditions during ice formation. Other massive ice of unknown origin with a very large d18O range (from -39 to -21 per mil) was found adjacent to large, striated boulders. A clear freezing slope was present with progressive depletion in heavy isotopes towards the centre of the ice body. Fractionation must have taken place during closed-system freezing, possibly of a glacial meltwater pond. Both massive ground ice bodies exhibited a mixed ion composition suggestive of terrestrial waters with a marine influence. Hydrochemical signatures resemble the Herschel Island sediments that are derived from nearshore marine deposits upthrust by the Laurentide ice. A prolonged contact between water feeding the ice bodies and the surrounding sediment is therefore inferred.

Physical oceanography and processed 2 minutes-averaged continuous VM-ADCP profiles during POLARSTERN cruise ANT-XXVIII/3

The physical and biological carbon pumps in the different hydrographic and biogeochemical regimes of the Atlantic Sector of the Southern Ocean are controlled by a series of coupled physical, chemical and biological processes and a project named Eddy-Pump was designed to study them. The Eddy Pump field campaign was carried out during RV Polarstern Cruise ANT-XXVIII/3 between January and March 2012. Particular emphasis was laid on the differences which occur along the axis of the Antarctic Circumpolar Current (ACC) with its associated mesoscale eddy field. The study sites were selected in order to represent (1) the central ACC with its regular separation in different frontal jets, investigated by a meridional transect along 10°E; (2) a large-scale bloom west of the Mid-Atlantic Ridge which lasted several months with conspicuous chlorophyll-poor waters to its immediate east studied by a three-dimensional mesoscale survey centred at 12°40'W; and (3) the Georgia Basin north of the island of South Georgia, which regularly features an extended and dense phytoplankton bloom, was investigated by a mesoscale survey centred at 38°12'W. While Eddy-Pump represents an interdisciplinary project by design, we here focus on describing the variable physical environment within which the different biogeochemical regimes developed. For describing the physical environment we use measurements of temperature, salinity and density, of mixed-layer turbulence parameters, of dynamic heights and horizontal current vectors, and of flow trajectories obtained from surface drifters and submerged floats. This serves as background information for the analyses of biological and chemical processes and of biogeochemical fluxes addressed by other papers in this issue. The section along 10°E between 44°S and 53°S showed a classical ACC structure with well-known hydrographic fronts, the Subantarctic Front (SAF) at 46.5°S, the Antarctic Polar Front (APF) split in two, at 49.25°S and 50.5°S, and the Southern Polar Front (SPF) at 52.5°S. Each front was associated with strong eastward flows. The West Mid-Atlantic Ridge Survey showed a weak and poorly resolved meander structure between the APF and the SPF. During the first eight days of the survey the oceanographic conditions at the Central Station at 12°40'W remained reasonably constant. However after that, conditions became more variable in the thermocline with conspicuous temperature inversions and interleavings and also a decrease in temperature in the surface layer. At the very end of the period of observation the conditions in the thermocline returned to being similar to those observed during the early part of the period with however the mixed layer temperature raised. The period of enhanced thermohaline variability was accompanied by increased currents. The Georgia Basin Survey showed a very strong zonal jet at its northern edge which connects to a large cyclonic meander that itself joins an anticyclonic eddy in the southeastern quadrant. The water mass contrasts in this survey were stronger than in the West Mid-Atlantic Ridge Survey, but similar to those met along 10°E with the exception that the warm and saline surface water typical of the northern side of the SAF was not covered by the Georgia Basin Survey. Mixed layers found during Eddy-Pump were typically deep, but varied between the three survey areas; the mean depths and standard variations of the mixed layer along the 10°E were 77.2±24.7 m, at the West Mid-Atlantic Ridge 66.7±17.7 m, and in the Georgia Basin 36.8±10.7 m.

Travel, back and forth, to the myth. Cinema´s contribution to the formation of the tourist iconography of Mallorca

Mallorca, the largest of the Balearic Islands, is a well-known summer holidays destination; an ideal place to relax and enjoy the sun and the sea. That tourist gaze reflected on postcards results from advertising campaigns, where cinema played an important role with documentaries and fiction films. The origins of that iconography started in the decades of the 1920’s and 1930’s, reflecting the so-called myth of the “island of calm”. On the other hand, the films of the 1950’s and 1960’s created new stereotypes related to the mass tourism boom. Busy beaches and the white bodies of tourists replaced white sandy beaches, mountains and landscapes shown up in the movies of the early decades of the 20th century. Besides, hotels and nightclubs also replaced monuments, rural landscapes and folk exhibitions. These tourist images mirror the social and spatial transformations of Mallorca, under standardization processes like other seaside mass tourist destinations. The identity was rebuilt on the foundations of "modernity". Although "balearization" has not ceased, nowadays filmmaking about Mallorca is advertising again a stereotype close to that one of the 1920s and 1930s, glorifying the myth of the "island of calm". This singular identity makes the island more profitable for capital that searches socio-spatial differentiation in post-fordist times.

Geochemistry of crustal formation and evolution

Terrestrial planets produce crusts as they differentiate. The Earth’s bi-modal crust, with a high-standing granitic continental crust and a low-standing basaltic oceanic crust, is unique in our solar system and links the evolution of the interior and exterior of this planet. Here I present geochemical observations to constrain processes accompanying crustal formation and evolution. My approach includes geochemical analyses, quantitative modeling, and experimental studies. The Archean crustal evolution project represents my perspective on when Earth’s continental crust began forming. In this project, I utilized critical element ratios in sedimentary records to track the evolution of the MgO content in the upper continental crust as a function time. The early Archean subaerial crust had >11 wt. % MgO, whereas by the end of Archean its composition had evolved to about 4 wt. % MgO, suggesting a transition of the upper crust from a basalt-like to a more granite-like bulk composition. Driving this fundamental change of the upper crustal composition is the widespread operation of subduction processes, suggesting the onset of global plate tectonics at ~ 3 Ga (Abstract figure). Three of the chapters in this dissertation leverage the use of Eu anomalies to track the recycling of crustal materials back into the mantle, where Eu anomaly is a sensitive measure of the element’s behavior relative to neighboring lanthanoids (Sm and Gd) during crustal differentiation. My compilation of Sm-Eu-Gd data for the continental crust shows that the average crust has a net negative Eu anomaly. This result requires recycling of Eu-enriched lower continental crust to the mantle. Mass balance calculations require that about three times the mass of the modern continental crust was returned into the mantle over Earth history, possibly via density-driven recycling. High precision measurements of Eu/Eu* in selected primitive glasses of mid-ocean ridge basalt (MORB) from global MORs, combined with numerical modeling, suggests that the recycled lower crustal materials are not found within the MORB source and may have at least partially sank into the lower mantle where they can be sampled by hot spot volcanoes. The Lesser Antilles Li isotope project provides insights into the Li systematics of this young island arc, a representative section of proto-continental crust. Martinique Island lavas, to my knowledge, represent the only clear case in which crustal Li is recycled back into their mantle source, as documented by the isotopically light Li isotopes in Lesser Antilles sediments that feed into the fore arc subduction trench. By corollary, the mantle-like Li signal in global arc lavas is likely the result of broadly similar Li isotopic compositions between the upper mantle and bulk subducting sediments in most arcs. My PhD project on Li diffusion mechanism in zircon is being carried out in extensive collaboration with multiple institutes and employs analytical, experimental and modeling studies. This ongoing project, finds that REE and Y play an important role in controlling Li diffusion in natural zircons, with Li partially coupling to REE and Y to maintain charge balance. Access to state-of-art instrumentation presented critical opportunities to identify the mechanisms that cause elemental fractionation during laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. My work here elucidates the elemental fractionation associated with plasma plume condensation during laser ablation and particle-ion conversion in the ICP.

Three-dimensional kinetic simulations of active suspensions: effect of chemotaxis and steric interaction

In this work, the effects of chemotaxis and steric interactions in active suspensions are analyzed by extending the kinetic model proposed by Saintillan and Shelley [1, 2]. In this model, a conservation equation for the active particle configuration is coupled to the Stokes equation for the flow arising from the force dipole exerted by the particles on the fluid. The fluid flow equations are solved spectrally and the conservation equation is solved by second-order finite differencing in space and second-order Adams-Bashforth time marching. First, the dynamics in suspensions of oxytactic run-and-tumble bacteria confined in thin liquid films surrounded by air is investigated. These bacteria modify their tumbling behavior by making temporal comparisons of the oxygen concentration, and, on average, swim towards high concentrations of oxygen. The kinetic model proposed by Saintillan and Shelley [1, 2] is modified to include run-and-tumble effects and oxygentaxis. The spatio-temporal dynamics of the oxygen and bacterial concentration are analyzed. For small film thicknesses, there is a weak migration of bacteria to the boundaries, and the oxygen concentration is high inside the film as a result of diffusion; both bacterial and oxygen concentrations quickly reach steady states. Above a critical film thickness (approximately 200 micron), a transition to chaotic dynamics is observed and is characterized by turbulent-like 3D motion, the formation of bacterial plumes, enhanced oxygen mixing and transport into the film, and hydrodynamic velocities of magnitudes up to 7 times the single bacterial swimming speed. The simulations demonstrate that the combined effects of hydrodynamic interactions and oxygentaxis create collective three-dimensional instabilities which enhances oxygen availability for the bacteria. Our simulation results are consistent with the experimental findings of Sokolov et al. [3], who also observed a similar transition with increasing film thickness. Next, the dynamics in concentrated suspensions of active self-propelled particles in a 3D periodic domain are analyzed. We modify the kinetic model of Saintillan and Shelley [1, 2] by including an additional nematic alignment torque proportional to the local concentration in the equation for the rotational velocity of the particles, causing them to align locally with their neighbors (Doi and Edwards [4]). Large-scale three- dimensional simulations show that, in the presence of such a torque both pusher and puller suspensions are unstable to random fluctuations and are characterized by highly nematic structures. Detailed measures are defined to quantify the degree and direction of alignment, and the effects of steric interactions on pattern formation will be presented. Our analysis shows that steric interactions have a destabilizing effect in active suspensions.

DnaG interacts with a linker region that joins the N- and C-domains of DnaB and induces the formation of 3-fold symmetric rings

Loading of the replicative ring helicase onto the origin of replication (oriC) is the final outcome of a well coordinated series of events that collectively constitute a primosomal cascade. Once the ring helicase is loaded, it recruits the primase and signals the switch to the polymerization mode. The transient nature of the helicase-primase (DnaB-DnaG) interaction in the Escherichia coli system has hindered our efforts to elucidate its structure and function. Taking advantage of the stable DnaB-DnaG complex in Bacillus stearothermophilus, we have reviewed conflicting mutagenic data from other bacterial systems and shown that DnaG interacts with the flexible linker that connects the N- and C-terminal domains of DnaB. Furthermore, atomic force microscopy (AFM) imaging experiments show that binding of the primase to the helicase induces predominantly a 3-fold symmetric morphology to the hexameric ring. Overall, three DnaG molecules appear to interact with the hexameric ring helicase but a small number of complexes with two and even one DnaG molecule bound to DnaB were also detected. The structural/functional significance of these data is discussed and a speculative structural model for this complex is suggested.