Synovial joints are among the most important structures that give us complex motor abilities as humans. Degenerative joint diseases, such as arthritis, cause loss of normal joint functioning and affect over 40 million people in the USA and approximately 350 million people worldwide. Therapies based on regenerative medicine hold the promise of effectively repairing or replacing damaged joints permanently. Here, we introduce a model for synovial joint regeneration utilizing the chick embryo. In this model, a block of tissue that contains the prospective elbow is excised, leaving a window with strips of anterior and posterior tissue intact (window excision, WE). In addition, we also slice out the same area containing the elbow and the distal piece of the limb is pinned back onto the stump (Slice Excision, SE). For making excisions precisely we first carried out a cell fate analysis for elbow forming tissue in the developing limb and carefully determined the tissue to be removed. Interestingly, when the elbow is removed via WE, regeneration of the joint takes place, whereas the elbow joint does not regenerate following SE. In order to investigate whether the regeneration response recapitulates the developmental program of forming joints, first we made a gene expression analysis for the elbow joint because a specific gene expression analysis for the elbow joint was not available in the literature. Among the genes analyzed, we used GDF-5 and Autotaxin (Atx) as joint tissue specific markers and Sox-9 and Col-9 as cartilage markers for in situ hybridization on sections at different time points after WE and SE surgeries. Re-expression of GDF-5 and Atx is observed in the WE samples by 60 hours after the surgery. In contrast, the majority of the samples that underwent SE surgery did not express GDF-5 and Atx. Also, in SE fusion of cartilage elements takes place and the joint interzone does not form. This is indicated by continuous Col-9 expression in SE, whereas Col-9 is down-regulated at the joint interzone in the regenerating WE samples. This order and pattern of gene expression observed in regenerates is similar to the development of a joint suggesting that regeneration recapitulates development at the molecular level. Various growth factors have been shown to trigger or enhance the regenerative response in different models and organs. The regeneration response we observe in WE is present in 50% of the embryos. In order to test the effect of growth factors on this response, we implanted window excised limbs with BMP-2, Noggin, or BSA beads as control. BMP-2 inhibits the joint regeneration, while Noggin does not improve regeneration of the joint tissue. On the other hand, Noggin treatment resulted in elongation of the cartilage elements from the amputated surface This model defines some of the conditions required for inducing joint regeneration in an otherwise nonregenerating environment. This knowledge can be useful for designing new therapeutic approaches for joint loss or for conditions affecting joint integrity in humans / acase@tulane.edu

This dissertation is mostly devoted to the study of concordance classes of S¹ x R Pn. For the goal of our research, we first obtain the topological structure of S¹ x R Pn x I and the structure of the first concordance group of Aut( S¹ x R Pn) which help reveal the structure of the concordance classes of the block automorphism group Top&d15; (S¹ x R Pn). The last result allows us to obtain the structure of pi1( Top&d15; ( S¹ x R Pn)). We continue by examining the concordance classes of S¹ x Sn and studying the correspondence between the concordance classes of S¹ x Sn and S¹ x R Pn / acase@tulane.edu

Schizophrenia is a debilitating neurological disorder affecting 1% of people. While the causes remain unknown, evidence demonstrates both developmental and anatomical origins of the disorder. Reduced volume and neuropil in the prefrontal cortex (PFC) and mediodorsal (MD) the thalamus is found in schizophrenics, possibly through loss of dendrite complexity and volume. Many symptoms of schizophrenia are linked to the function of these structures. Reduced dendritic arborization may result in abnormal neurotransmission, as dendritic complexity determines information processing capabilities of a neuron. The studies presented here explore the role of dendrite plasticity in the PFC and MD thalamus. Antipsychotic treatment may restore volume in affected brain regions. Our data show that chronic treatment with the atypical antipsychotic, clozapine, which treats more symptoms of schizophrenia, increases dendritic complexity and length in the MD thalamus, whereas haloperidol, a typical antipsychotic, had no effect. Both drugs had affected dendrite morphology in the PFC, although in different patterns. This suggests that symptom improvement and volume restoration may be due to changes in dendritic architecture. Protein levels of factors related to synaptic plasticity and dendrite morphology were examined in these areas following treatment. This study found that clozapine may increase surface expression of glutamate receptors in the PFC and increases dendritic spines in the thalamus, implying increased synaptic connectivity. However, a putative mechanism was not revealed. The direct actions of these drugs on cortical and thalamic neurons were tested in vitro to further elucidate their actions. The changes in dendrite morphology found in this model differed from what was found in vivo, suggesting antipsychotic drugs act at a circuit level. A developmental glutamate hypofunction model of schizophrenia, based on evidence of glutamate disruption in schizophrenia, was examined and compared to known abnormalities in schizophrenia. This study revealed evidence of impaired synaptic pruning in the thalamus following glutamate hypofunction. However, the changes were not representative of known changes in schizophrenia, suggesting this treatment protocol does not generate a representative model of schizophrenia. The findings presented here better define the role of dendrite morphology in the corticothalamic circuit with regards to the treatment and pathology of schizophrenia / acase@tulane.edu

A two-dimensional laboratory simulator was designed and assembled to investigate removal of dense non-aqueous phase liquid (DNAPL) contaminants from ground water by water flooding and neutral buoyant co-solvent flooding. Preliminary experiments indicated that optimum DNAPL removal was achieved during water flooding for viscous-to-capillary scaling ratios between 0.00075 and 0.001. The simulator was used to investigate effects of the direction of gradient flow on DNAPL removal efficiency by neutral buoyant co-solvent flooding. Results indicated that approximately 90 percent DNAPL was removed when injection was performed either in the direction of gradient flow or against it. However, injection in the direction of gradient flow was more efficient in terms of time and total co-solvent needed. Nevertheless, during injection in the direction of the flow more contamination occurred downstream due to dispersion. Results also indicated that size of the plume does not play an important role in the recovery efficiency of this system / acase@tulane.edu

Spray deposition is an approach to manufacture net or near-net shape metallic materials. It is achieved by atomizing a liquid metal sheet with an inert gas to form molten droplets, which are then subsequently deposited onto a moving cold substrate. Significant technical progress over the past three decades has helped spray forming to mature into a manufacturing technique. However, the fundamentals of spray deposition remain to be established During spray deposition processes, the developing pre-form loses thermal energy through a combination of heat transfer processes. To investigate such issues, the growth of the deposit layer was mathematically formulated employing a continuous flow assumption, and a heat transfer model was developed to simulate the pre-form growth, both for pure metal and binary alloys. First it was assumed there was no relative motion in the deposited materials, and the heat transfer characterization in the solidification process resulting from the spray deposition process was fully investigated. Then by taking into account the convection phenomenon in the melt, together with the heat conduction in the substrate and deposit, a thorough model of the process was developed, and the relevant thermal, momentum, fluid and solidification phenomena were established An interface-tracking method was used to solve the governing equations, and a grid subdivision technique was adopted on the moving interface. The numerical results demonstrated that the thermal profile in the deposit is affected in a complex way by process parameters, such as substrate temperature, velocity, mass deposition rate, thermal state of the impinging droplets and the environment conditions in the spraying chamber etc. We believe that by optimizing the processing parameters, solidification conditions during deposition can be achieved to manufacture a desired deposit of uniform microstructure and minimum porosity A grid-independence check was also made to assure the accuracy of numerical schemes / acase@tulane.edu

This work was motivated by the distributed information processing needs in tactical environments such as disaster relief and military operations. Tactical network environments are characterized by mobile ad hoc networks under resource and policy constraints, tasked for critical missions Mission success directly depends on the effective use of computation resources in the field for distributed data processing and information propagation. However, the dynamic nature of the network and the lack of centralized coordination components make it very difficult to globally allocate and maintain resources for distributed tasks in a manner that is itself distributed, efficient and adaptive to the volatile nature of the environment Current approaches to the problem can be broadly classified in three main categories, centralized decision making (applicable only to small scale networks), local greedy decision making and arbitrage models also known as agent-based negotiation In this work, we introduce a new solution to the problem which utilizes online learning strategies at the local node level, to quickly evolve the global resource allocation solution that asymptotically converges to a global optimum The resource allocation problem in mobile ad hoc networks is first formulated as a k-arm bandit problem at the local level. As data flows through the network, each node locally learns the best policies to the used under different data flows, different constraints and local network topology Two learning strategies (epsilon -greedy and SoftMax) are adapted to the problem domain and used for tests and comparisons. A proof-of-concept implementation of the proposed resource allocation algorithm is introduced, discussed and tested in simulated networks The preliminary experimental results and the theoretical guarantees provided for the algorithm indicate that the approach is applicable to the resource allocation problem in mobile ad hoc networks for tactical environments / acase@tulane.edu

Most studies of species diversity in habitat fragments are conducted either implicitly or explicitly within the context of the island model of population dynamics, or of species-specific metapopulation models. Whether such equilibrium models are generally applicable to tropical forest understory birds in recently fragmented landscapes remains unknown. In this dissertation, I investigated whether local populations of an understory rainforest bird (Myrmeciza exsul, Chestnut-backed Antbird) are connected via dispersal. Local populations tend to be temporally stable: Mean annual apparent survival of M. exsul was approximately 0.80 in both sexes within a large tract of forest in northern Costa Rica, and breeding dispersal was minimal. Thus, natal dispersal is the main mechanism of gene flow. I used population genetic methods to investigate dispersal and population genetic structure of five populations of M. exsul in relation to forest fragmentation. Mean natal dispersal distance was approximately 1 km, with no evidence of direct dispersal between any of the five populations sampled. Population genetic structure was significant, especially considering the small geographic scale (10-30 km), short time since putative isolation (40-60 years), and generally large populations (often > 100 pairs), all of which generally prevent genetic drift- and population differentiation. The smallest (80 ha), most isolated forest fragment population provided the strongest genetic evidence for complete isolation of populations in forest fragments. Individuals in this population exhibited significantly elevated pairwise relatedness compared to other sites, indicating a reluctance to disperse out of the site. I found no evidence of sex-biased dispersal in any of my genetic or field-based analyses. The patterns of dispersal documented here are consistent with expectations of both prevalent hypotheses for the evolution of dispersal (i.e., inbreeding avoidance and kin competition avoidance), and a null model of natal dispersal -- wherein birds settle on the first available territory they encounter -- cannot be rejected. The presence of significant population structure even between populations separated by intact forest suggests naturally short dispersal distances of M. exsul, even within continuously forested landscapes. Evidence from my studies, as well as published observations of M. exsul in Panama, suggest that this species exhibits non-equilibrium metapopulation structure in highly fragmented landscapes. These results challenge the assumption that species persisting in fragmented landscapes must have better dispersal capabilities than those that disappear from fragmented landscapes, and strongly supports hypotheses of weak dispersal capacity in some tropical forest understory birds / acase@tulane.edu

In this thesis, we continue the study of domain theoretic structures in quantum information theory initiated by Keye Martin and Bob Coecke in 2002 The first part of the thesis is focused on exploring the domain theoretic properties of qubit channels. We discover that the Scott continuous qubit channels are exactly those that are unital or constant. We then prove that the unital qubit channels form a continuous dcpo, and identify various measurements on them. We show that Holevo capacity is a measurement on unital qubit channels, and discover the natural measurement in this setting. We find that qubit channels also form a continuous dcpo, but capacity fails to be a measurement In the second part we focus on the study of exact dcpos, a domain theoretic structure, closely related to continuous dcpos, possessed by quantum states. Exact dcpos admit a topology, called the exact topology, and we show that the exact topology has an order theoretic characterization similar to the characterization of the Scott topology on continuous dcpos. We then explore the connection between exact and continuous dcpos; first, by identifying an important set of points, called the split points, that distinguishes between exact and continuous structures; second, by exploring a continuous completion of exact dcpos, and showing that we can recover the exact topology from the Scott topology of the completion / acase@tulane.edu

Polymeric composites are extensively used in aerospace and light weight civil engineering structures. The behavior of structural members and sub-assemblies made of these materials depend on the stiffness of the individual components and the connectors utilized for composite action Finite element method of analysis is utilized to investigate the effects of material and connector stiffness variability on load response of polymeric composite structural members and sub-assemblies. The shear connectors in the composite members and sub-assemblies are modeled by connector elements to simulate the slip behavior of the system. The study deals with polymeric composite T-beams and deck systems. In the development of the finite element model, the mechanical and physical properties of the components -- modulus of elasticity, coefficient of thermal expansion, Poisson's ratio -- were properly accounted for in order to simulate the behavior of the real system. The applicability of the finite element model for analyzing T-beams and deck systems is verified by comparing the predicted responses with well established analytical solutions The influence of discontinuities (gaps) in the decking layer of polymeric composite deck system is also investigated. These discontinuities (gaps) are accounted for in the finite element model by introducing elements of low stiffness at the location of the gaps. A method of estimating the response of polymeric composite members and sub assemblies at different service temperature was also developed / acase@tulane.edu

Piezoelectric materials have long been recognized for their ability to transform energy from the mechanical domain to the electrical domain and vice-versa. As a result there has been continuing research and development efforts to develop new materials with enhanced properties. However, inherent limitations in single phase piezoelectric materials have stunted their growth potential. Hence, the composites approach has been proposed as a desirable alternative to extend the functionalities of present piezoelectric systems beyond those available to the single phase materials. In the present study, analytical and finite element based numerical formulations are proposed to model the behavior of piezoelectric composites. These composites are further sub-divided in to several groups, based on the inhomogeneity; (i) geometry (zero-, one-, two-, or three-dimensional); (ii) spatial distribution; (iii) shape; and (iv) poling orientation. Complete set of design maps are proposed to tailor the composite according to industry approved figures of merit. Strategies for designing novel piezoelectric composites with enhanced sensitivities in multiple directions are also identified / acase@tulane.edu