This dissertation combines laboratory experiments and analysis of field samples to examine tungsten (W) geochemistry. Data from low ionic strength experimental solutions at room temperature containing between 0.01 M to 0.0002 M total sulfide and 0.0027 M - 0.0001 M tungstate were analyzed using UV/VIS spectrophotometry. Stability constants have been determined for the formation of mono-thiotungstate log K01= 3.43 ± 0.61, di-thiotungstate log K12 = 3.02 ± 0.61, tri-thiotungstate log K23 = 2.82 ± 0.02, and we estimated the tetra-thiotungstate log K34 ~ 2.34. Analysis of W, Mo, Mn, and Fe concentrations in estuarine surface and pore waters and sediments captured environmental samples from oxic and sulfidic conditions. Both surface waters and sediments demonstrated a positive correlation between W and Fe. Unlike Mo, which was depleted in sulfidic salt marsh pore waters, W was enriched in all pore waters in comparison to overlying waters. Thermodynamic modeling of W and Mo thioanion species in sulfidic pore water samples predicts ≤ 50% of tungstate (WO42-) forms thiotungstate species and complete conversion of molybdate (MoO42-) to tetrathiomolybdate (MoS42-). Unlike tetrathiomolydate that is known to be more particle reactive than molybdate, increases in dissolved W coincide with increases in dissolved sulfide in pore waters, suggesting thiotungstates are less particle reactive than thiomolybdates at circum-neutral pH. Finally, sediment analysis suggests sequestration of W is dependent on surface water salinity in the intermediate marsh sediments, and long-term W entrapment occurs in sulfidic salt marsh sediments. / acase@tulane.edu

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The present study examined the relationships between anxiety, cognitive functioning, weak central coherence, and social skills in a group of 102 children diagnosed with an Autism Spectrum Disorder (ASD; Autistic disorder, Asperger's disorder, and PDD-NOS). The results indicated that children diagnosed with Asperger's disorder had significantly higher cognitive functioning and Block Design scores (i.e., weaker central coherence) compared to those diagnosed with autism or PDD-NOS. Regression analyses results showed that anxiety and cognitive functioning moderated the association between weak central coherence and social skills. For children with low cognitive functioning and high anxiety, weak central coherence was associated with poorer social skills than those with low cognitive functioning, high anxiety, and strong central coherence. For children with high cognitive functioning and high anxiety, weak central coherence was associated with better social skills than those with high cognitive functioning and strong central coherence. Implications of these findings are discussed. / acase@tulane.edu

This research is aimed at studying the ionic liquid/n-pentanol interface via video-microscopy and molecular dynamic simulations. Understanding the interfacial phenomena and interfacial transport between ionic liquids and other liquids is of interest to the development and application of ionic liquids in a number of areas. One such area is the biphasic hydroformylation of alkenes to obtain alcohol and aldehyde, in which case ionic liquid is the reaction medium where a catalyst resides. The dissolution of an ionic liquid into an alcohol was studied by microscopically observing and measuring the shrinking of a micropipette-produced droplet in real time. Although microscopic investigation of droplet dissolution has been studied before, no attempt had been made to measure the di↵usion coefficient D of the droplet species in the surrounding medium. A key finding of this work is that the Epstein-Plesset mathematical model, which describes the dissolution of a droplet/bubble in another fluid medium, can be used to measure D. Other experimental studies of the ionic liquid/alcohol system include electrical conductivity and UV-visible spectroscopy measurements of solutions of 1-hexyl-3-methylimidazolium tetrafluoroborate in n-pentanol. Those experiments were done in order to understand the molecular state of the particular ionic liquid in n-pentanol, as well as obtaining the dissociation constant K of such weak electrolyte solution. The experimental results provide an entry to the assessment of ionic liquid interaction with n-pentanol at molecular scale. Subsequently, molecular dynamics simulation was implemented for the investigation of such interaction. The computation started with simulation of the bulk phase of 1-butyl-3-methylimidazolium tetrafluoroborate, an affine ionic liquid on which molecular simulations had already been reported. A generalized probability based on Fuoss approximation for the closest ion to a distinguished countercharge ion was developed. In addition to 1-butyl-3- methylimidazolium tetrafluoroborate, the generalization was tested also on tetraethyl ammonium tetrafluoroborate in propylene carbonate from low to high concentrations, and on the corresponding primitive model. Such generalization helps us understand paring of ions in electrolyte solution, especially for elevated concentrations. Two cases of 1-hexyl-3-methylimidazolium tetrafluoroborate ionic liquid/npentanol system were studied, which are (i) liquid-liquid interface; and (ii) solution of the former in the latter. Computation of biphasic interface revealed interaction at the liquid-liquid junction, e.g., the transport of molecules from one phase to another, and lead to evaluation of di↵usion coefficient that has good agreement with experimental measurement. The simulation of dilute electrolyte solution, i.e., an ionic liquid pair in n-pentanol, gives free energy change as a function of ion separation distance. The dissociation constant K was evaluated and found to be closed to experimental value that was obtained from solution conductivity measurement. The investigation of ion dynamics, especially the memory function transformed from velocity autocorrelation function, lead to the finding of dielectric friction in the system. Furthermore, precise evaluation of D gives satisfied agreement with experimental measurement from micropipette technique. / acase@tulane.edu

Flux gradient terms and source terms are two fundamental components of hyperbolic systems of balance law. Though having distinct mathematical natures, they form and maintain an exact balance in a special class of solutions, which are called steady-state solutions. In this dissertation, we are interested in the construction of well-balanced schemes, which are the numerical methods for hyperbolic systems of balance laws that are capable of exactly preserving steady-state solutions on the discrete level. We first introduce a well-balanced scheme for the Euler equations of gas dynamics with gravitation. The well-balanced property of the designed scheme hinges on a reconstruction process applied to equilibrium variables---the quantities that stay constant at steady states. In addition, the amount of numerical viscosity is reduced in the areas where the flow is in (near) steady-state regime, so that the numerical solutions under consideration can be evolved in a well-balanced manner. We then consider the shallow water equations with friction terms, which become very stiff when the water height is close to zero. The stiffness in the friction terms introduces additional difficulty for designing an efficient well-balanced scheme. If treated explicitly, the stiff friction terms impose a severe restriction on the time step. On the other hand, a straightforward (semi-) implicit treatment of the stiff friction terms can greatly enhance the efficiency, but will break the well-balanced property of the resulting scheme. To this end, we develop a new semi-implicit Runge-Kutta time integration method that is capable of maintaining the well-balanced property under the time step restriction determined exclusively by non-stiff components in the underlying equations. The well-balanced property of our schemes are tested and verified by extensive numerical simulations, and notably, the obtained numerical results clearly indicate that the well-balanced property plays an important role in achieving high resolutions when a coarse grid is used. / acase@tulane.edu

The objective of this project is to develop novel treatments, using expression-targeted gene therapy and minicell technology, to replace current methodologies used in the clinic for the treatment of carcinomas, especially transitional cell carcinoma of the bladder. The expression-targeted gene therapy procedure involves cancer-specific DNA elements (promoters) to drive the expression of engineered suicide genes to induce apoptosis in cancer cells. Minicells, a kind of bacterial derivative , prevent tumor recurrence and growth through targeted toxicity and an induced immune response that is similar to that induced by Bacille Calmette-Guerin (BCG), but without the risk of infection due to lack of chromosomes. The osteopontin promoter (popn) was selected via currently accepted methods by comparing endogenous gene expression between normal and cancerous cells. The opn gene is expressed in far greater amounts in cancer cells, so it was reasoned that the opn promoter would be more active in cancer cells as well. Reporter constructs using popn were transfected into both cancerous and normal cell types, with maximum Popn-driven reporter intensity in the cancer cells showing up as strong (102.7%) compared to Pcmv-driven positive controls. Popn-driven reporter intensity was reduced by ~90% in the non-cancer cells. Further enhancements to targeting and expression were obtained through the incorporation of single-nucleotide polymorphisms (SNPs) in the promoter sequence. Further investigations to confirm a correlation between endogenous opn mRNA levels and Popn-driven reporter expression produced a surprising lack of correlation (R2=0.24). However, taking into account opn mRNA splicing variants, a strong negative correlation was determined between mRNA levels of the variant opn-a and Popn-driven transgene activity (R2=0.95). Three novel cancer-specific promoter pran, pbrms1 and pmcm5 were identified through a new screening logic. The activities of those promoters were verified to be much higher in the tested cancer cell lines than the current gold standard used to target gene expression to cancer cells: the promoter of human telomerase reverse transcriptase (phTERT). A constitutively active, apoptosis-inducing analog of caspase 3, referred to as Reverse Caspase3 (RevCasp3), was engineered via gene recombination and cloned into expression-targeted plasmid constructs. These constructs showed excellent activity in inducing apoptosis within the cancer cells tested. Moreover, Pran-RevCasp3 constructs were shown to have significant, cancer-specific killing action within both human and murine cell in vitro. The therapeutic effects of minicell constructs known as VAX-IP were tested within our orthotopic, murine model of transitional cell carcinoma of the bladder. In trials focused on the prevention of tumor growth and tumor implantation, bell-shaped curves were produced by data reflecting the relation between drug dose and tumor burden. The median and average bladder weights, used as a surrogate for tumor burden, decreased with increasing doses of VAX-IP minicells administered via intravesical, transurethral delivery. Activity was lost at high doses of VAX-IP minicells. Compared with the sham-treated group, 1x108 VAX-IP minicells, delivered at 24 hours post-surgery with repeated administrations every 7 days for a total of four treatments, yielded a significant survival advantage to the treated animals (P=0.03). / acase@tulane.edu

Although women have made great strides in society working to close the gender gap, sexism still exists that may impact women’s psychological wellness. The current research examines the relationship between sexist attitudes toward women, stigma consciousness, and psychological well-being among 235 female participants from a medium sized Southern city. Participants took part in the research by completing a cross-sectional survey about the health and well-being of women in exchange for class credit or cash. The primary hypothesis was that stigma consciousness would serve as a mediator of the relationship between sexist attitudes toward women and psychological well-being. Results indicated a positive relationship between hostile sexism and psychological well-being and a negative relationship between hostile sexism and stigma consciousness. However, the relationship between stigma consciousness and psychological well-being was not significant. Therefore, stigma consciousness did not serve as a mediator between sexism and psychological well-being. This not significant relationship is explained in accord with past research. Possible reasons for the positive relationship between holding more sexist views toward women and having greater psychological well-being are discussed. / acase@tulane.edu

During the critical period of CNS development, dendritic architecture is shaped, in part, by activity-dependent stabilization and elimination of branches. This restructuring is partly dependent on the subunit composition of glutamate receptors in a manner that is both regionally specific and temporally regulated. We used primary cultures of rodent hippocampal neurons to investigate the consequences for hippocampal dendrite development when the glutamate ?-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid receptor (AMPAR) subunit composition was altered. Overexpression of the AMPAR subunits GluR1 or GluR2 differentially modified hippocampal dendrite architecture. We investigated signaling pathways known to be involved in activity-dependent circuit development as possible downstream effectors of AMPA-mediated morphogenesis. We identified extracellular signal regulated kinase (ERK) 1/2 as a potential candidate of GluR1-mediated dendrite outgrowth. We found that levels of docosahexaenoic acid (DHA) and a DHA-derived bioactive metabolite, neuroprotectin D1 (NPD1) are differentially regulated by GluR1 and GluR2. DHA, but not NPD1, induced extensive dendritic branching and outgrowth. Overexpression of 15 lipoxygenase 1 (15LOX1), the enzyme responsible for conversion of DHA to NPD1, interrupted outgrowth mediated by GluR1 overexpression. In order to investigate molecular mechanisms that regulated neural circuitry outside of the critical period of CNS development, we examined dendrite morphology across the CNS in response to chronic variable stress (CVS). We found wide-spread changes in circuits implicated in neurocognitive dysfunctions associated with chronic stress, and observed substantial dendritic plasticity in the adult brain. / acase@tulane.edu

In the reopening of fluid occluded airways, the pressure gradient due to the propagation of an air bubble causes extensive epithelial cell damage. The mechanism of cell necrosis and biotransport may be further understood by characterizing the flow fields near the tip of a semi-infinite bubble propagating through a fluid-filled bifurcation. A symmetric microfluidic pulmonary bifurcation model was fabricated for optical diagnostics with an instantaneous μ-PIV/ shadowgraphy microscopy system. Data handling and processing techniques were developed to calculate interfacial characteristics of multiphase flow from the microscopy system and accuracy was quantified through varying the apparatus set up. Differences in the interfacial geometric characteristics were quantified for changes in static and dynamic surface tension in comparisons of water, SDS, and Infasurf that may reflect changes in the mechanical stress that stimulate, and potentially damage, epithelial cells that line the airways. From these results, the asymmetrical tendencies of opening a symmetric pulmonary bifurcation model were quantified. It was found that pulmonary surfactant stabilized symmetric bifurcations that opened asymmetrically without the aid of surfactant. / acase@tulane.edu

Schizophrenia is a prevalent neurological disorder characterized by disrupted neuronal circuitry. Antipsychotic drugs (APDs) are capable of ameliorating the symptoms of schizophrenia with varying efficacy. Clozapine, the "gold-standard" for antipsychotic drug treatment, has been shown by this lab to induce the outgrowth of mediodorsal thalamic (MDT) dendritic arbor in rodents, a brain region which has altered function and decreased regional volume in schizophrenic patients. These studies further explored the ability of APD treatment to restructure dendrite arbor and the mechanisms of clozapine's ability to elaborate MDT arbor. Additionally, glutamate hypofunction is thought to contribute to the schizophrenic disease state. Using a novel model of perinatal glutamate hypofunction, we examined the long-term effects on dendritic architecture of developmental glutamate signaling disruption. MDT dysfunction is hypothesized to contribute to cognitive symptoms of schizophrenia. Clozapine has increased efficacy in ameliorating these symptoms. To further understand clozapine’s actions to remodel MDT dendritic architecture, we examined whether clozapine-induced morphological alterations are limited to the thalamus or if they also occur in additional regions associated with cognitive schizophrenic pathology, the hippocampus and striatum. We found that clozapine can induce dendritic remodeling in the hippocampus, but the not to the amplitude of remodeling seen in the thalamus, indicating that the MDT is uniquely altered by clozapine treatment and may be an important locus of clozapine's action. The mechanisms of clozapine's remodeling of MDT arbor, we examined changes to mRNA and miRNA expression and calcium dynamics in the MDT in response to APD treatment. Clozapine-treatment altered the expression of genes involved in cytoskeletal remodeling, external membrane receptors, and calcium dynamics, as well as increased the rate of calcium influx into thalamic neurons. Disruption to glutamate signaling has been hypothesized to contribute to schizophrenic pathology. Disruption to perinatal vesicular glutamate packaging along the corticolimbic axis has long term effects for neuronal morphology and function. Interestingly, we find that disruption along the corticolimbic axis also has downstream effects on MDT dendritic architecture. These studies show that the MDT is an important locus of action for clozapine and is capable of remodeling dendritic architecture in response to afferent circuitry dysfunction. / acase@tulane.edu