Etheostoma flabellare has a long history of taxonomic confusion due to complex patterns of morphological variation. Four or five subspecies are currently recognized. Alternative hypotheses suggest species-level descriptions are warranted. No studies have tested the morphology-based taxonomy and phylogenetic relationships have not been proposed. Relationships within the E. flabellare species group of Catonotus are also problematic Genetic markers are used to generate phylogenies to test alternate taxonomic hypotheses for E. flabellare by examining patterns of lineage diversification and the monophyly of subspecies. Phylogenies are also used to examine relationships within the species group and test hypotheses associated with Central Highlands Vicariance Biogeography. Mitochondrial haplotypes are used to examine population genetic structure and test the predicted limited dispersal ability of E. flabellare. Associations between phylogeny and geography of haplotypes are examined with nested clade analysis (NCA) to infer historic and ongoing population-level processes that have been important in the evolutionary history of the species and in shaping genetic structure. NCA fragmentation events are re-examined in a phylogenetic context and to identify evolutionary lineages that warrant species-level recognition Phylogenies recover each subspecies as paraphyletic, providing no support for the current taxonomy. High genetic divergence among geographically-concordant monophyletic clades suggests that species-level designations more accurately describe diversity and highlight the need for taxonomic revision. Relationships recovered for E. flabellare species group members suggest species group designations within Catonotus require revision. Phylogeographic patterns illustrate that current clade distributions and diversity in E. flabellare require vicariant and dispersal explanations. Population-level genetic structure shows that E. flabellare is subdivided at broad and fine spatial scales, supporting limited dispersal ability as predicted by intrinsic and extrinsic features of the species. NCA revealed significant non-random associations between the phylogeny and geographic distribution of haplotypes, rejecting the hypothesis of panmixia in E. flabellare populations. NCA recovered several population processes, including historic fragmentation, restricted gene flow, and range expansions, highlighting the complexity of events associated with the history of the species and its genetic diversity. Most inferred fragmentation events corresponded to populations that also formed exclusive phylogenetic clades, further supporting unrecognized species-level diversity in E. flabellare / acase@tulane.edu

The efficiency of aircraft engines can be improved significantly by increasing the temperature in the combustion chambers and the gas path in the high-pressure turbine sections. The temperatures in these areas of today's high thrust engines exceed the temperature capability of typical turbine alloys. Thermal Barrier Coating (TBCs) has played an important role in last three decades in increasing the temperature capability of gas turbine engines. The development of ceramic TBCs for high heat flux environments requires a fundamental understanding of fracture mechanisms in order to prevent the spalling of the coating from the substrate In the present work, a specific computational procedure for the problem is developed. The method we have employed is based on the singular integral equations - boundary collocation technique. The advantage of this method is its effectiveness and accuracy in evaluation of the principle fracture mechanics parameters. The developed integral equations are formed using basic singular solutions for dislocations interacting with the biomaterial interface. The principle singular solutions for periodic dislocations are derived in the form of complex valued analytic potentials Analyses of the thin TBC systems show that the thermal stresses provide sufficient driving force for cracks to propagate through the coating from the free surface toward the interface. The cracks branching above the interface tend to be deflected toward the interface due to the material combination of TBC systems and thermal expansion of the substrate. Cracks branching and growth along the interface appears to be a preferable stable path under these conditions Based on the numerical method and developed scheme, fracture mechanics characteristics of the thin and thick TBC system are investigated. Computations of the transient temperature fields of a two-layer system with cracks branching above or along the interface are carried out using finite difference method. The results show that the insulation effect of the branching cracks leads to complex temperature distributions around the cracks tips, and the insulation effect increases the stress intensity factors of the branching cracks. The investigation of the thick TBC systems shows that thicker thermal barrier coatings provide better protections / acase@tulane.edu

Object oriented design (OOD) technology has become a standard in the industry today, due to the fact that it models the real world more precisely and accurately as compared to the traditional structured techniques. This makes object oriented technology easier to understand and in turn easier to maintain. The most constant attribute of software is change. OOD technology uses the same modeling concepts throughout the software life-cycle, thereby handling changes to the software more gracefully. The Unified Modeling Language (UML) is largely used as a design and documenting tool for object oriented designs. It is important to evaluate and verify the design at an earlier stage of software development so as to detect errors, which if not detected soon enough can turn out to be expensive at a later stage. This requires rigorous analysis to be performed on the design. To perform rigorous analysis more formality is required. It is also important that the user be able to specify analysis goals for the design as (s)he sees fit. The goal of this research is to provide a formal framework for specification and analysis of object oriented designs. The framework will support rigorous analysis of the design by providing a formal notation and a formal language to specify the analysis goals. The formal notation maps to the UML design and thus incorporates the advantages of both formal and informal specification techniques, without requiring the user to learn the details of the formal specification notation. The formal language developed is simple and close to natural language, once again requiring minimal learning effort from the user. To test the implementation of the language processor, we used design principles as specified by Object Management Group (OMG) on a UML and CSP-based system design. The language was then further extended to support specification of dynamic analysis goals / acase@tulane.edu

Heterochromatin is nucleated at a specific site and spreads into adjacent sequences through interaction between modified histories and non-histone proteins. In the yeast Saccharomyces cerevisiae, these non-histone proteins are Sir2, Sir3, and Sir4. We have previously used a tethered silencing assay to isolate the C-terminal domain 144 amino acids of Sir3 (CTD) that, when tethered adjacent to telomere, is able to restore the silencing defect conferred by the rap1-17 allele that encodes a C-terminal truncation of Rap1. Here, we explore the function and structure of CTD involving in the nucleation of silent chromatin. We demonstrate that CTD is the minimum Sir3 dimerization domain that is conserved in divergent yeasts. The CTD is able to recruit Sir2, Sir3, and Sir4 at tethering sites and to spread Sir proteins into adjacent sequences. However, the CTD-Sir3 interaction is not sufficient to restore tethered silencing because a specific CTD mutation is severely defective in tethered silencing despite its ability to recruit Sir3. In addition, CTD is able to facilitate deacetylated H4-K16. Our data suggest that cooperative interactions between CTD, Sir3p, and deacetylated H4-K16 are essential to nucleate silent chromatin. Furthermore, the sequence alignment predicts that the CTD has a Cdc6 domain III winged-helix structure found in many transcription and replication, proteins, including Orc1. Consistent with the prediction, insertion mutations in the junction of CTD abrogate silencing, suggesting that the projection of CTD toward its interaction partners is critical for Sir3 function. Interestingly, tethering of the corresponding C-terminus of Orc1 confers significant, albeit low levels, of silencing. Our results suggest that Sir3 and Orc1p may derive from the same ancestral gene Additionally, we have isolated histone H2A alleles, hta1tpe, which are defective in telomeric position effect (TPE) and the nonhomologous end joing (NHEJ) repair pathway, and confer Spt- phenotype, suggesting that hta1tpe alleles may change subtelomeric chromatin structure, resulting in impairment to recruit silencing or repair factors / acase@tulane.edu

Synaptic inhibition in the DMV is mainly mediated through GABAergic connections within the vagal complex. The dorsal motor nucleus of the vagus (DMV) mainly contains well-described preganglionic motor neurons that control the majority of the subdiaphragmatic viscera, especially the gastrointestinal tract, but may also have a few putative interneurons. Experiments were aimed at clarifying and obtaining novel information about the morphological and electrophysiological properties of pre-gastric and GABAergic neurons in the DMV. Our results suggested that most of DMV neurons are preganglionic motor neurons, with a few small and/or GABAergic neurons interspersed, which may be misplaced NTS interneurons GABAA receptors are expressed in the DMV and critically regulate the activity of vagal motor neurons and, by inference, the gastrointestinal tract. In some brain areas, two types of GABAA receptor-mediated inhibition have been identified, represented by phasic and tonic inhibitory currents. I tested the hypothesis that the tonic current was present in DMV, and phasic and tonic GABA currents were differently regulated by pharmacological agents. The data presented here support the hypothesis that the tonic current is evident in DMV, and it shows pharmacological properties distinct from those of the phasic current. The tonic current did not depend on the degree of synaptic conductance, and it contributed to DMV neuron membrane potential and activity. Using gabazine, two components of the tonic current were revealed. GABA transporters, THIP and zolpidem differently modulated the GABA currents in DMV, and these drugs all have significant effects on the DMV motor neuron activity. These substances would be expected to have profound effects on the gastrointestinal tract through their significant effects on inhibition of DMV neurons / acase@tulane.edu

The geometrical and electronic surface properties of In2O 3 and Sn-doped In2O3 (ITO) have been investigated. Sn-doped In2O3 is widely used as a transparent conducting oxide in flat panel displays, organic-light-emitting-diodes, solar cells, and electrochromic windows. Despite the fact that surface and interfaces are important in all these applications, a fundamental understanding of the surface properties of this material is lacking. Meaningful surface investigations are best conducted on single-crystalline samples, thus epitaxial thin films of In2O3 and ITO were grown and used as samples for the surface investigations This work focuses on two low-index surfaces of ITO, the non-polar (111) orientation and the (100) orientation, which, in its bulk-terminated form, is polar. The epitaxial films were grown with oxygen-plasma assisted molecular beam epitaxy (MBE) on yttria-stabilized zirconia, which exhibits a cube-on-cube epitaxy as well as a small lattice mismatch with respect to In2O 3 The YSZ(111) substrate was characterized with Re ection-high-electron-energy-diffraction (RHEED) and Low-energy-electron-diffraction (LEED) and its surface was found to be (1x1) terminated. RHEED and LEED measurements on the substrate were possible if the substrate was kept at 300°C in order to avoid charging effects of this insulating material. RHEED exhibited 2-dimensional growth mode for the Sn-doped In2O3 thin films. Using LEED it was found that the surface of In2O3 and Sn-doped In 2O3 poses a (1x1) terminated surface. A de-convolution of X-ray core level photoemission (XPS) of In 3d peaks; into one component that is due to regular photoemission and one that is due to interaction of core holes with electronic plasmons, provided the plasmon energy, E p; From Ep the electron density n of the doped films was obtained. For an ITO film with 6.2 at% of Sn, it was found that 1/3 of the Sn atoms contribute one electron to the conduction band. Scanning-tunneling-microscopy (STM) was measured and atomic resolution was achieved. Bright and dark atomic features were assigned to a surface with bulk (1x1) termination. Density-functional-theory (DFT) calculations performed by collaborators confirmed that indium atoms are being imaged bright and dark in empty-states STM, depending on the configuration of their oxygen neighbors; bright when neighboring three-fold and dark when neighboring four-fold oxygen atoms Epitaxial (100)-oriented thin films of In2O3 and Sn-doped In2O3 were also grown. The YSZ substrate was characterized using RHEED and LEED and was found to have a (2x2) reconstructed surface. RHEED showed that the Sn-doped In2O3 grows in a 3-dimensional growth mode. Using LEED it was found that the surface of Sn-doped In2O3 exposes a surface with a c(1x1) termination. Considering symmetry arguments and the systematic absence of LEED spots, it was concluded that the surface can have only an oxygen termination. Due to the polarity of this orientation, it was found that unusually high concentrations of tin, ca. 15.6 at%, are needed to render the surface flat. Comparing STM measurements with DFT calculations published in the literature, it was concluded that surface oxygen atoms are dimerized, with all O dimers present for a high Sn concentration in ITO. At low Sn-concentrations the observed STM images are consistent with a model where only 2/3 of the oxygen atoms are present, again consistent with published DFT predictions. It is thus concluded that both, the Sn concentration and oxygen dimerization, are instrumental in stabilizing the polar ITO (001) surface / acase@tulane.edu

As development proceeds in spinal motor neurons, there is a period of increased dendrite proliferation followed by a period during which arbor is lost. While the exact molecular mechanisms underlying these changes are unknown, activity-dependent processes have been implicated. Since both the AMPA and NMDA subtypes of glutamate receptors are developmentally regulated in spinal motor neurons, we investigated the role played by changes in AMPA and NMDA receptor subunit expression levels in the establishment of mature motor neuron dendrite architecture. We found that over-expression of the GluR1 AMPA receptor subunit caused a significant increase in the total amount and complexity of dendrite arbor with an increase in filopodial numbers. GluR1 over-expression also caused an increase in the number of GFP-labeled PSD95 puncta, suggesting an increase in the number of excitatory synapses in transfected cells. On the contrary, over-expression of the GluR2 AMPA receptor subunit was associated with a modest increase in total dendrite arbor, decreased filopodial numbers and no changes in dendrite complexity or number of PSD95 puncta. These results suggest that GluR1 may facilitate motor neuron dendrite outgrowth and branching by promoting excitatory synaptogenesis and the outgrowth of filopodia while GluR2, present at high levels in adult motor neurons, may act to stabilize existing motor neuron dendrite branching by inhibiting filopodial extension. Analysis of local protein translation in motor neuron dendrites by CPEB showed that while the GluR1 mediated effects on dendrite branching may be independent of CPEB, local synthesis of GluR2 or an associated protein may be involved Over-expression of the NR3B NMDA receptor subunit, which acts as a dominant-negative subunit and is up-regulated in adult motor neurons, resulted in increased amount and complexity of dendrite arbor with higher numbers of filopodia. Administration of AP5, an NMDA receptor antagonist, caused a re-organization of dendrite arbor without any changes in numbers of filopodia or amount and complexity of dendrite arbor. Thus, our results indicate that NR3B plays a role in the activity-dependent regulation of dendrite branching, but in a manner that is inconsistent with loss of NMDA receptor activity / acase@tulane.edu

Integral bridges are single or multiple span bridges that are built in the form of an integral or a semi-integral configuration. Integral bridges have their superstructures cast monolithically with the abutments. This type construction eliminates costly joints and sealers as well as reduces maintenance costs associated with their use. This generally results in a more economical and low maintenance structure and better overall rideability. A slight modification of the integral abutment bridge is the semi-integral design, which eliminates joints, but still uses conventional bearings. However, unlike conventional bridges, the jointless slab protects these moveable bearings. Semi-integral bridges have end diaphragms (headwalls) integral with the superstructure, but non-integral with the foundations. Semi-integral bridges require a horizontal joint separating the superstructure and the abutment In this research, the behavior of semi-integral bridges was investigated through field monitoring and laboratory testing. For a period of 18 months, the field investigation included the monitoring and testing of all six semi-integral bridges constructed in Louisiana. One of theses six bridge, bridge 39-04-31 was selected for extensive monitoring and testing. In view of the review of existing records and field inspections and monitoring, the overall performance of these bridges was found to be satisfactory. It was concluded that the present design of semi-integral bridges used in Louisiana is structurally sound A small-scale semi-integral abutment bridge model was constructed in the materials lab of Tulane University. Several tests were then performed using this model to study the impact of several variables on the overall performance of the bridge. Displacement of the headwall and the lateral earth pressure are some of the parameters monitored during theses tests. Several sensors were attached to the model to collect the necessary data used in the analysis Results of the tests performed indicated that placing a geofoam between the abutment headwall and the embankment would significantly reduce the earth pressure on the abutment headwall. The use of uncompacted sand would also help in minimizing the magnitude of pressure / acase@tulane.edu

Several studies have investigated the extent to which implicit theories predict stereotyping, namely perceived outgroup homogeneity (Levy & Dweck, 1999: Levy. Stroessner, & Dweck, 1998). Entity theorists believe that traits are fixed and immutable, while incremental theorists contend that traits are malleable and can be incrementally gained or lost. At the group level, entity theorists (relative to incremental theorists) perceive outgroups in terms of relevant stereotypes, and in particular, perceive outgroups as highly homogenous (Levy et al., 1998). The current project suggests that the extent to which entity theorists perceive outgroup homogeneity may depend on the stereotype content associated with a salient outgroup exemplar. The Stereotype Content Model (SCM: Fiske. Xu, Cuddy, & Glick, 1999) suggests that two dimensions, competence and warmth, inform outgroup stereotypes. For entity theorists in particular, exposure to a prototypical Black exemplar (i.e., neither competent nor warm) should accentuate perceived outgroup homogeneity, while exposure to an atypical Black exemplar (i.e., competent and/or warm) should attenuate perceived outgroup homogeneity about the larger outgroup. Results lend support for these hypotheses on perceived homogeneity with respect to warmth (but not competence). These findings are discussed in terms of the necessity of intergroup contact and the subsequent implications for improving outgroup attitudes toward typically disparaged groups / acase@tulane.edu

The addition of a 21-bp triplication in the long terminal repeat (LTR) of feline leukemia virus (FeLV) affected disease outcome. The lymphoma from which the triplication-containing provirus, FeLV-945, was isolated was anatomically classified as multicentric. Subsequent studies showed that experimental FeLV-945 infection of cats resulted in multicentric lymphoma of B-cell origin. In this dissertation we wanted to explore the mechanism by which the FeLV-945 21-bp triplication affected disease outcome. The FeLV-945 21-bp triplication was demonstrated to contain 2 binding sites for the transcription factor, c-Myb. These binding sites span the junctions of the repeat indicating a selective pressure for the precise retention of the repeat. The 21-bp triplication renders the virus responsive to c-Myb in a dose-dependent manner. By direct interaction with c-Myb, the transcriptional co-factor CBP is recruited the LTR and increases transcriptional activity. Next the impact of the FeLV-945 LTR on bone marrow hematopoiesis was examined. A recombinant murine retrovirus, MoFe2-MuLV, was used which contains the U3 region of FeLV-945 in the backbone of Moloney murine leukemia virus (M-MuLV). MoFe2-MuLV and M-MuLV infection of laboratory mice resulted in decreased CFU-pre-B clonogenic potential during the preleukemic stage of disease. This is the first observation that M-MuLV affects B-lymphopoiesis. To explore the mechanism of decreased CFU-pre-B potential we used the murine multi-potential hematopoietic progenitor cell line, EML. This cell line gave us the opportunity to examine a possible block in B-lymphopoiesis following infection in vitro. A potential block in B-cell differentiation at the pro-B stage was observed in infected cells. A density-dependent reduction of proliferation during B-cell differentiation in infected cells was detected. Acute infection of EML cells with MoFe2-MuLV or M-MuLV resulted in a p53-mediated apoptotic crisis. Crisis lasted approximately 4-6 days, after which a chronically infected population arose. YB-1, a multifunctional protein which suppresses p53-mediated apoptosis, is upregulated in chronically infected EML cells. In vivo, a p53-dependent apoptotic crisis of hematopoietic progenitor cells, followed by increased YB-1 activity, represents a mechanism of rapid selection of a population of cells that are predisposed to malignant transformation / acase@tulane.edu