This research is focused on engineering submicron spherical carbon particles as effective carriers/supports for nanoscale zerovalent iron (NZVI) particles to address the in situ remediation of soil and groundwater chlorinated contaminants. Chlorinated hydrocarbons such as trichloroethylene (TCE) and tetrachloroethylene (PCE) form a class of dense non-aqueous phase liquid (DNAPL) toxic contaminants in soil and groundwater. The in situ injection of NZVI particles to reduce DNAPLs is a potentially simple, cost-effective, and environmentally benign technology that has become a preferred method in the remediation of these compounds. However, unsupported NZVI particles exhibit ferromagnetism leading to particle aggregation and loss in mobility through the subsurface. This work demonstrates two approaches to prepare carbon supported NZVI (iron-carbon composites) particles. The objective is to establish these iron-carbon composites as extremely useful materials for the environmental remediation of chlorinated hydrocarbons and suitable materials for the in situ injection technology. This research also demonstrates that it is possible to vary the placement of iron nanoparticles either on the external surface or within the interior of carbon microspheres using a one-step aerosol-based process. The simple process of modifying iron placement has significant potential applications in heterogeneous catalysis as both the iron and carbon are widely used catalysts and catalyst supports. Furthermore, the aerosol-based process is applied to prepare new class of supported catalytic materials such as carbon-supported palladium nanoparticles for ex situ remediation of contaminated water. The iron-carbon composites developed in this research have multiple functionalities (a) they are reactive and function effectively in reductive dehalogenation (b) they are highly adsorptive thereby bringing the chlorinated compound to the proximity of the reactive sites and also serving as adsorption materials for decontamination (c) they are of the optimal size for transport through sediments (d) they have amphiphilic chemical functionalities that help stabilize them when they reach the DNAPL target zones. Finally, the iron-carbon composite microspheres prepared through aerosol-based process can used for in situ injection technology as the process is conductive to scale-up and the materials are environmentally benign. / acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

Focal chondral defects of the knee develop in hyaline cartilage when subjected to repetitive overloading or impact trauma. The degeneration of the articular surface results in joint pain and stiffness during daily activities such as walking. In most cases palliative non-invasive treatments can be used to alleviate pain; however, more severe lesions require restorative or replacement surgical interventions to repair the damaged cartilage. The use of a novel pyrolytic carbon knee trochlear implant aims to eliminate the aforementioned orthopedic pain by providing a focal replacement of lesions in the patellar sulcus. Pyrolytic carbon was the selected material due to its superior wear properties, mechanical strength, and biocompatibility. The purpose of this study was to develop a verified computational simulation in Abaqus to evaluate the experienced tensile stress of six different pyrolytic carbon trochlear implants undergoing two different physiologically relevant load conditions. This data was compared to an experimental conjugate study to provide insight into the implants strength. Regions of peak maximum principal stress were observed to be at the medial fillet and sulcus groove when undergoing a single- or two-point loading condition, respectively. The magnitude of tensile stress in the medial fillet was 2-3 times of that experienced at the sulcus groove. These findings reflected experimental data in which trochlear implants failed at either the medial fillet or sulcus groove during their respective loading conditions. Verified simulations allowed for computational testing of a modified implant and calculations of expected critical fracture loads. / acase@tulane.edu

Silicon nanoparticles (SiNPs) are regarded as a promising alternative of traditional II-VI quantum dots in the field of bio-applications due to their photoluminescence and bio-compatibility. <br>Chapter 1 reviews various synthetic routes and applications of SiNPs. <br>Chapter 2 describes the mechanochemical synthesis of photoluminescent SiNPs with an organic ligand shell through reactive high energy ball milling (RHEBM). The morphology and size distribution of as-prepared SiNPs were determined by TEM. The bonding modes of the ligand shell including their mole fractions were investigated based on NMR and FTIR spectra of the as-prepared SiNPs.<br>Chapter 3 introduces the removal of the iron impurities, which were introduced into the SiNPs product from the milling media, stainless steel, by a physical method (GPC) and a chemical method (washing by HCl aqueous solution). The effect of the iron impurities to the optical properties of SiNPs is discussed.<br>Chapter 4 exhibits the surface functionalization of SiNPs with various functional groups through thiol-ene click reactions of vinyl-terminated SiNPs with various thiols. In addition, SiNP nanoclusters and DNA-conjugated SiNPs were prepared through thiol-ene click reactions of vinyl-terminated SiNPs with a tetrathiol-terminated crosslinker and a thiol-functionalized DNA, respectively<br>Chapter 5 is a miscellaneous chapter which includes the preparation of SiNPs through RHEBM of silicon wafers with 2,3-dimethyl-1,3-butadiene, and the effect of UV irradiation at 254 nm to the chemical structures and optical properties of SiNPs. / acase@tulane.edu

Acute Respiratory Distress Syndrome (ARDS) is a lung condition with a mortality rate of 40 % that affects about 225,000 individuals in the U.S. In these patients, epithelial injury can contribute to alveolar flooding and injury to type II cells by disrupting normal epithelial fluid transport, impacting the removal of edema fluid from alveolar space. Mechanical stresses associated with opening occluded airways damages the epithelial lining of the lungs. Prior studies explore the nature of the stresses and damage in straight tube models of airways. Our model presented in this work accounts for the branching in the pulmonary airways. We have developed a scalable microfluidic model of pulmonary airway bifurcations for investigation of reopening near the bifurcation as well as the macroscopic reopening pattern. We utilize a μ-PIV/Shadowgraph system to visualize the flow fields near the interface as a semi-infinite finger of air propagates through the bifurcation model. Further, we utilize μ-PIV for downstream flow-rate monitoring to examine the symmetry of reopening through bifurcating networks. In the absence of surfactant, propagation preferentially opens the low-resistance path, and leads to asymmetric reopening. However, with SDS and albumin inactivated surfactant, interfacial propagation preferentially reopens the pathway with the higher hydraulic resistance. The propagation pattern with pulmonary surfactant stabilizes the system so that the daughter branches of a nearly symmetric bifurcation open simultaneously. Our multiple generation network serves to validate the stability of the single generation. However, the second generation does not mirror the behavior of the first generation. We explore the reasons for this, and also present preliminary studies for the investigation of restoring surfactant function after deactivation by serum proteins. / acase@tulane.edu

acase@tulane.edu

Polyethylene oxide polymers are intrinsic to oil spill dispersants used in Macondo well blowout of 2010. We believe that effective thermo-physical modeling of these materials should assist the application of lab-scale results into ocean-scales. Fully defensible molecular scale theory of such materials will be challenging. This thesis is the first step towards that challenge. Molecular dynamics simulations are useful in generating structural and phase behavior data for these versatile polymers. Microstructures of PEO polymers, hydrophobic interactions, direct numerical test of controversial Pratt-Chandler theory, concentration dependence of Flory-Huggins interaction parameter and neutron scattering experiments will be discussed. / acase@tulane.edu

With recent advancements in the synthesis and characterization of polymeric materials, scientists are able to create multi-scale novel polymers with various cases of chemical functionalities, diversified topologies, as well as cross-linking networks. Due to those remarkable achievements, there are a broad range of possible applications of smart polymers in catalysis, in environmental remediation, and especially in drug-delivery. Because of rising interest in developing therapeutic drug binding to specific treating target, polymer chemists are in particular interests in design and engineering the drug delivery materials to be not only bio-compatible, but also to be capable of self-assembly at various in-vivo physiological stimulus. Both experimental and theoretical work indicate that the thermodynamic properties relating to the hydrophobic effect play an important role in determining self-assembly process. At the same time, computational simulation and modeling are powerful instruments to contribute to microscopic thermodynamics' understanding toward self-assembly phenomenon. Along with statistical approaches, constructing empirical model based on simulation results would also help predict for further development of tailored nano-structured materials. My Research mainly focused on investigating physical and chemical characteristics of polymer materials through molecular dynamics simulation and probing the fundamental thermodynamic driving force of self-assembly behavior. We tried to surmount technological obstacles in computational chemistry and build an efficient scheme to identify the physical and chemical Feature of molecules, to reproduce underlying properties, to understand the origin of thermodynamic signatures, and to speed up current trial and error process in screening new materials. / acase@tulane.edu