Trace Elemental Distributions Within Organophosphatic Brachiopod Shells: Implications for Growth, Preservation and Paleoenvironment

The initial incorporation of elements into the accretionary hardparts of marine invertebrates is controlled by prevailing seawater chemistry and vital effects. While trace-element signatures of invertebrates accreting carbonate hardparts have been examined extensively, the shells of phosphatic organisms have largely been ignored. In this study, major and trace elements of fossil organophosphatic brachiopod shells are investigated to determine the fidelity with which their shell chemistry may be preserved, and to evaluate their potential as paleoenvironmental archives. Trace elements within the shells of lingulid brachiopods from the Kanguk Formation of Devon Island, Arctic Canada and the Blufftown Formation of Stewart County, Georgia, USA were analyzed via electron microprobe. Elemental maps revealed spatial distributions, and element concentrations were measured within dorso-ventral transects proceeding toward the shell interior. The distributions of Mg, Na and Sr are similar among all lingulids, and absolute values of Mg and Na were similar between all fossil specimens. Concentrations of Mg and Sr are similar between fossil lingulids and modern calcitic brachiopods, suggesting that their signatures may be preserved. Ca, Fl and P are zoned within fossil shells from Stewart County and a modern lingulid, but are heterogeneously distributed in Devon Island specimens. While Mn and Fe concentrations are orders of magnitude greater in fossil lingulids than in modern calcitic brachiopods, they exhibit opposite distributional trends between fossil sites. Among fossil assemblages, elemental concentrations along dorso-ventral transects exhibit pronounced correlations between element pairs. Fossil specimens show a positive correlation between Na--Mg (80% of shells) and Fe--Mn (60% of shells). These trends suggest that elements observed to occur in the same zones in element maps and those that commonly substitute for one another are most likely to exhibit positive correlations. Ratios of mean concentrations of Mg/Ca and Sr/Ca decline sharply with shell length, suggesting that rates of biofractionation decreased with age. The chemical signatures analyzed in this study indicate that all of the fossil lingulids are diagenetically altered, but that the Devon Island specimens are more altered than those from Stewart County. Ultimately, reliable paleoenvironmental information was not extracted from these samples

An Anomalous Type IV Secretion System in Rickettsia Is Evolutionarily Conserved

Bacterial type IV secretion systems (T4SSs) comprise a diverse transporter family functioning in conjugation, competence, and effector molecule (DNA and/or protein) translocation. Thirteen genome sequences from Rickettsia, obligate intracellular symbionts/pathogens of a wide range of eukaryotes, have revealed a reduced T4SS relative to the Agrobacterium tumefaciens archetype (vir). However, the Rickettsia T4SS has not been functionally characterized for its role in symbiosis/virulence, and none of its substrates are known.Superimposition of T4SS structural/functional information over previously identified Rickettsia components implicate a functional Rickettsia T4SS. virB4, virB8 and virB9 are duplicated, yet only one copy of each has the conserved features of similar genes in other T4SSs. An extraordinarily duplicated VirB6 gene encodes five hydrophobic proteins conserved only in a short region known to be involved in DNA transfer in A. tumefaciens. virB1, virB2 and virB7 are newly identified, revealing a Rickettsia T4SS lacking only virB5 relative to the vir archetype. Phylogeny estimation suggests vertical inheritance of all components, despite gene rearrangements into an archipelago of five islets. Similarities of Rickettsia VirB7/VirB9 to ComB7/ComB9 proteins of epsilon-proteobacteria, as well as phylogenetic affinities to the Legionella lvh T4SS, imply the Rickettsiales ancestor acquired a vir-like locus from distantly related bacteria, perhaps while residing in a protozoan host. Modern modifications of these systems likely reflect diversification with various eukaryotic host cells.We present the rvh (Rickettsiales vir homolog) T4SS, an evolutionary conserved transporter with an unknown role in rickettsial biology. This work lays the foundation for future laboratory characterization of this system, and also identifies the Legionella lvh T4SS as a suitable genetic model

The use of numerical models for exploring the effects of nonuniform illumination in solar cells

To model solar cells accurately one must solve coupled second order, partial, linear differential equations derived from Boltzmann's equation, continuity equations and electrostatics. Analytical solutions prove to be insufficient for modeling complex applications such as concentrating systems. A network model and computer programs which use a sophisticated one-dimensional solar cell model were developed to simulate nonuniformly illuminated cells in concentrating systems.This project's task was to make these programs more efficient and to simulate nonuniform illumination cases with higher intensity levels and with spectral variations previously untried. To this end, modifications were effected resulting in a factor of one hundred reduction in the error of gvalue, an important model parameter, a reduction in running time by a factor of ten for the best cases and no less than two for the worst, and an overall simplification of the modeling process.Presented herein are the results of the simulations performed by the model. Eleven cases of nonuniformity previously untested were modeled at different levels of metalization and degrees of nonuniformity. A comparison of the results obtained was also made to previous work done in this field. In addition to the results of the simulations, the actual computer programs of the network model are included.Thesis (M.S.)Department of Physics and Astronom

Creating a System to Remotely Monitor the Impedance Change of Cement

As the number of concrete structures continues to grow, the need for smart and effective sensing and monitoring technology comes with it. This goal of this project is to create a system that can sense changes in the integrity of concrete and can be monitored remotely. To accomplish this, an AD5933 chip was used with a microcontroller to measure the impedance between two probes. The AD5933 chip must be calibrated every time measurements are taken, so a MUX chip was used to accomplish this process automatically. The device was powered using a solar panel and a lithium-ion battery to allow it to be used remotely. A Raspberry Pi was used to host an SQL database that the microcontroller sent data to, which was then displayed using an html webpage. Currently, the device successfully sends data to the database and can be monitored remotely, but the project is ongoing and there are a number of improvements to be made. The impedance measurement system currently has a bug which causes incorrect values to be made, the solar panel cannot supply enough power to the device while it is taking rapid measurements, and the MUX chip used to calibrate the system may have some leakage current causing the impedance measurements to be inaccurate.Electrical and Computer Engineering, Department ofHonors Colleg

A closer look at The Woman's Right To Know Act : the sociology and politics of women's reproductive health care in Texas

This project reviews the literature, language and primary arguments surrounding a Texas policy commonly known as The Woman’s Right to Know Act of 2003. In addition to analyzing the details of this law and the repercussion it has for women’s reproductive healthcare in Texas, this thesis also takes a closer look at the social and political aspects that influence legislative policy and its implementation. In this thesis, I identify the limitations of this law to provide accurate, unbiased and comprehensive information to women seeking an abortion.Women's and Gender Studie

Critical studies of soil and vegetation relations

Soil studies were made on two soils supporting two different dominant woody perennials, mesquite and pine, the vegetation contact, across which invasion is not occurring, marking the line of two geological formations. Smilax was found to be the only woody perennial found equally abundant in the two areasPlant Biolog