Prosocial behavior during adolescence is consistently associated with a myriad of positive outcomes including fewer risk-taking behaviors and greater positive affect. Although limited, there is some literature that suggests prosocial behavior is an important protective factor in attenuating the effects of stressful life events such as exposure to community violence. Unfortunately work examining prosocial behaviors in African American adolescents is very sparse. The present study examined the moderating role of altruism, a specific form of prosocial behavior, on relationships between exposure to violence and negative mental health outcomes in a sample of 207 African American adolescents (136 females, 71 males). Participant’s age ranged from 13 to 18 (M = 15.78, SD = 1.19). Results indicated that boys and girls engaged in similar levels of altruistic behaviors, but these behaviors were especially important in moderating the impact of community violence on antisocial behaviors for boys. The findings suggest that encouraging altruistic behaviors in boys may be critical in improving outcomes for adolescent males developing in violent ecologies. / acase@tulane.edu

Density functional theory (DFT) is a widely used quantum mechanical method for the simulation of the electronic structure of atoms, molecules, and solids. The only part that needs to be approximated is the exchange-correlation energy as a functional of the electron density. After many-year development, there is a huge variety of exchange-correlation functionals. According to the ingredients, an exchange-correlation functional can be classified as a semi-local functional or beyond. A semi-local functional can be nonempirical or empirical and only uses locality information, such as electron density, gradient of the density, Laplacian of the density, and kinetic energy density. Unlike a non-local functional that uses non-locality information, a semi-local functional is computationally efficient and can be applied to large systems. The meta-generalized gradient approximation (meta-GGA), which is the highest-level semi-local functional, has the potential to give a good description for condensed matter physics and quantum chemistry. We built the self-consistent revised Tao-Perdew-Staroverov-Scuseria (revTPSS) meta-GGA into the band-structure program BAND to test the performances of some self-consistent semi-local functionals on lattice constant with a 58-solid test set. The self-consistent effect of revTPSS was also discussed. The vibration of a crystal has a contribution to the ground state energy of a system, which is the zero-point energy at zero temperature. It has anharmonicity at the equilibrium geometry. The standard DFT doesn’t consider the zero-point energy of a crystal. We used density functional perturbation theory (DFPT), which is a powerful and flexible theoretical technique within the density functional framework, to study the zero-point energy and make a correction to the lattice constant. The method was compared to a traditional zero-point anharmonic expansion method that is based on the Debye and Dugdale-MacDonald approximations. We also tested some new meta-GGA functionals (revTPSS, regularized revTPSS, and meta-GGA made simple) on a big molecular test set - GMTKN30 - that is composed of 30 smaller test sets and covers a large cross section of chemically relevant properties. The performances of these new meta-GGAs were compared with some other popular functionals or meta-GGAs. / acase@tulane.edu

The breath figure method is a versatile and facile approach of generating ordered micro and nanoporous structures in polymeric materials. When a polymer solution (dissolved in a high vapor pressure organic solvent) is evaporated out in the presence of a moist air stream, the evaporative cooling effect causes the condensation and nucleation of water droplets onto the polymer solution surface. This leads to the formation of an imprinted porous structure upon removal of the residual solvent and water. The facile removal of the water droplet template leaving its structural imprint is a specifically appealing aspect of the breath figure film technology. The first part of the dissertation work involves the fabrication of drug loaded breath figure thin films and its utilization as a controlled drug release carrier and biomaterial scaffold. In a single fabrication step, single layer/multilayer porous thin films were designed and developed by combining the breath figure process and a modified spin or dip coating technique. Using biodegradable polymers such as poly (lactic-co-glycolic acid) (PLGA) and poly (ethylene glycol) (PEG), drug loaded films were fabricated onto FDA approved medical devices (the Glaucoma drainage device and the Surgical hernia mesh). The porosity of the films is in the range of 2-4 µm as characterized by scanning electron microscope. The drug coated medical implants were characterized for their surface and bulk morphology, the degradation rate of the film, drug release rate and cell cytotoxicity. The results suggest that the use of breath figure morphologies in biodegradable polymer films adds an additional level of control to drug release. In comparison to non-porous films, the breath figure films showed an increased degradation and enhanced drug release. Furthermore, the porous nature of the film was investigated as a biomaterial scaffold to construct three dimensional in vitro tissue model systems. The breath figure film with interconnected pores facilitates cell infiltration and tissue remodelling in vitro, suggesting its high potential in regenerative medicine and tissue engineering applications. In the second part of the dissertation, the versatility of breath figure polymers was explored as a reverse template to create micropatterned soft materials. Unlike traditional lithographic masters, the breath figure assembly is a simple and cost-effective approach to create micro/nano sized “bead†like uniform patterns on the surface of hydrogels and biopolymers. By incorporating iron nanoparticles into the pores, this technique was extended to form hydrogels decorated with nanoparticles specifically in the pattern. The morphology features and the functional characteristics were demonstrated through scanning electron microscopy. The potential applications of these micro-fabricated materials in biosensors and cell culture substrates are outlined. / acase@tulane.edu

In 2005, 1.6 million Americans lived with a debilitating amputation and this figure is predicted to double by 2050. But the ability of a mammal to recapitulate a complex limb structure is not impossible. Evidence of children and mice re-growing digit tips following amputation midway through the terminal phalanx (P3) exists. The hallmark of this phenomenon is development of a blastema housing undifferentiated cells capable of being re-programmed to replicate the missing part. Our central goal is to understand specific components of this process for application into pro-scarring injuries. The mouse digit anatomy is prominently outlined by microfilaments containing ER-TR7, and antigen derived from fibroblast reticular cells (FRCs) of the thymus shown to facilitate intercellular communication to promote lymphoid organogenesis. A unique blastema characteristic is the upregulation of an ER-TR7+ scaffold stemming from half of the blastema population which reverts to its pre-existing pattern after regenerate differentiation concludes. We measured a correlation between ER-TR7 and type III collagen (COL3) at the transcriptional and protein levels both in vitro during induction of ER-TR7 in primary P3 cells and throughout digit regeneration. Co-expression with COL3 sheds light on ER-TR7 identity and allows testing various approaches to manipulation of the scaffold through the better understood mechanism of COL3 regulation. Furthermore, we aimed at determining the origin of ER-TR7+ blastema FRCs. Using bone marrow (BM) transplantation, we generated eGFP+ BM chimeras to study the fate of BM-derived cells (BMDCs) after amputation based on the hypothesis that in the regenerate, multipotent BMDCs contribute to various cellular phenotypes including FRCs. So we tested co-immunolocalization of eGFP with antigens particular to fibroblastic, hematopoietic, endothelial, osteoblastic, and mural cells. Many BMDCs homed to the injury throughout regeneration. But hematopoietic BMDCs were limited to inflammation whereas mesenchymal BMDCs expanded and were primed as ER-TR7+ FRCs in the P3 BM niche prior to homing to the blastema site, where they amounted to nearly 50% of cells. Moreover, BMDCs differentiated into endothelial, osteoblastic, and smooth muscle subpopulations and although diluted by pre-existing progenitors by the endpoint of regeneration, BMDCs persisted as part of various structures thus contributing to long-term function. / acase@tulane.edu

Knowledge about how body parts are configured is crucial in determining appropriate strategies for achieving desired goals. Prior work suggests that this knowledge is evident in later infancy (Brownell et al., 2010; Slaughter et al., 2004), however, the methods used to assess canonical body knowledge arguably require a conceptual form of knowledge. In contrast, we propose that a functional knowledge about the configuration of the body can be detected in younger infants. We used a tactile localization procedure in which the child's task was to retrieve a target that emitted proprioceptive information via a slight vibration. Children aged 7 - 22 months received targets placed on various locations on the head and body one at a time. The results suggest that even the youngest children in the current study were able to map their actions to get to target locations. Notably, this was also the case for locations that require a form of canonical body knowledge to reach successfully. When the area could be reached with either the ipsilateral or the contralateral hand (i.e., head locations), there was a tendency for ipsilateral hand use, though contralateral hand use increased with increasing age. Visual-proprioception integration (i.e., both seeing and feeling the target on the body) did facilitate manual target localization, however, visual localization became less important for successful manual localization as age increased. In sum, the current study demonstrates the perceptuo-motor competencies that manifest prior to children's ability to succeed on mirror recognition and discrimination tasks. / acase@tulane.edu

acase@tulane.edu

It is well recognized that rivers are the primary pathway that delivers sediment to the ocean. However, the fate of these sediments is poorly understood, and is complicated by relative sea level rise and meteorological forcings. One coastal system to examine these issues is the Atchafalaya River-Chenier Plain (ARCP) of southwest Louisiana, which relies on Mississippi River sediment supply and is vulnerable to coastal erosion and land loss. Despite regional coastal degradation, some land gain and marsh growth have been observed here. Land gain in south Louisiana is generally observed at the mouths of the rivers – the Bird’s Foot, and the Atchafalaya and Wax Lake deltas. However, satellite imagery and sedimentological analyses indicate that coastal lakes in southwest Louisiana have also filled in and converted into salt marshes in the last 40 years. To understand sediment delivery in these marshes, multiple short cores were collected in a central Chenier Plain tidal creek system, and analyzed for 210Pb, 137Cs, 7Be, δ13C, and grain size distribution. We propose that Chenier Plain reactivation processes are triggered by the increase in Atchafalaya River flow that began in the early 1900s. Fluvial sediments delivered through westward longshore transport and resuspended during energetic events become available to the sediment-starved Chenier coast, leading to deposition, infilling, mudflat progradation, and marsh growth. / acase@tulane.edu

Humans and mice lack the broad regenerative capacity of Urodele amphibians, capable only of partial regeneration of the terminal phalanx (P3), i.e., amputation mid-way through P3 results in essentially complete regeneration of the digit tip mediated via blastema formation and subsequent direct bone formation, culminating in distal bone growth, patterning, and function. Conversely, amputation injuries occurring proximal to the mid-point of P3 result in scar formation. Here, in part, we studied the endochondral bone healing response following amputation of the middle phalanx (P2). We showed the endochondral ossification healing response post amputation of P2 is analogous to the fracture healing response of P2 and other long bones of the body, ultimately proving useful in yielding insight into effectively inducing regeneration of the amputated digit. We showed the periosteal-derived chondrocytes of P2 play an integral role in the bone healing process in that they provide a template for subsequent bone formation following amputation injury. We also showed the periosteal-derived cells can be targeted through the temporal application of BMP2 to accumulate and proliferate at the distal digit tip and thus induce regeneration of the amputated bone. Our studies indicated that P2 amputation injuries of various time points, i.e. previously healed injuries, can be induced to regenerate via re-wounding of the periosteal tissue and subsequent BMP2 application, and thus is immeasurably promising from a translational therapeutic perspective. Lastly, we studied the fracture healing response in conjunction with the intramembranous regeneration response of P3. Following fracture of the digit, we showed the relative lack of periosteal callus formation, the lack of periosteal chondrogenesis, and a novel endosteal/marrow chondrogenic response. Unlike P2, the periosteal tissue of the fractured P3 bone does not respond to BMP2-treatment via endochondral bone growth, instead the bone heals via intramembranous ossification, possibly via intrinsic differentiation limitations and extrinsic factors. Notably, we showed that in the absence of the periosteal tissue of the amputated P3 bone, the regeneration response was greatly attenuated. Taken together, our work blending regeneration and fracture repair may prove useful in enhancing regeneration studies with methods and ideas not previously considered. / acase@tulane.edu

The goal of this research is to investigate computational and experimental techniques to effectively analyze microscale fluid dynamics, transport, and mixing of an analyte-antibody system. This work is applicable to the development of an in-plane, passive mixer component of a miniature antibody-based sensor suitable for environmental monitoring, food testing, and medical diagnostics. The computational methods allow the efficient evaluation of microchannel designs to enhance analyte-antibody binding, which may reduce the time and cost required for experimental trials. We describe a computational algorithm to solve the governing equations for microscale fluid flow and transport in complex 2-D domains created through a graphical user interface. We implement the particle strength exchange method to solve the convection-diffusion-reaction equations, coupled to the boundary element method to compute the velocity field from the steady state Stokes equations. We validate the numerical methods by comparison to analytical and finite element method solutions. Because the chosen methods require no internal mesh, our algorithm provides an efficient alternative to grid-based methods when solving transport in complex geometries with internal obstacles. We characterize two fluorescein-antibody clones through competitive ELISA experiments and demonstrate the quenching effect of the antibodies with a fluorescence spectrophotometer. We describe a microchannel flow system to image the quenching of fluorescence by the antibody when fluorescein and fluorescein-antibody solutions are injected into separate inlets of the microchannel. We correlate the fluorescence intensity of microscope images of fluorescein flowing through the microchannel to concentrations of fluorescein to establish a calibration curve. This system provides a method to visualize and quantitatively analyze the mixing and reaction in a microfluidic device. We test the numerical methods by comparing the experimentally determined fluorescein concentration to the outlet amount numerically predicted by the computational model under identical conditions and find good agreement between the two fluorescein concentration profiles. We complete the transport-reaction computation in a set of microchannels with cylindrical obstructions. We find that decreasing the channel width and increasing the fluid path length by placing the obstruction on the walls is more effective than placing free-standing obstructions within the channel to enhance the fluorescein and fluorescein-antibody reaction. / acase@tulane.edu

This dissertation is a detailed scientific study concerning a proton exchange membrane fuel cell, which is coupled to a DC-to-DC converter as the power processor, serving as a power source. The novel aspect of the dissertation is the use of a new controller or nonlinear observer to predict parameter estimation of the fuel cell and the DC-to-DC converter as the load potential changes for the automated control system. Nonlinear control algorithms, which include nonlinear observers, were developed for such systems. / acase@tulane.edu