Doctor of Philosophy

dissertationMultiple studies have shown the potential for using implantable microelectrode arrays to record consciously modulated neural signals and to restore volitional control of external devices to patients suffering from various nervous system and motor disorders. However, despite the promising potential of this technology, achieving widespread clinical application requires improving recording consistency and quality over a clinically relevant time frame. There is near consensus in the field that the foreign body response (FBR) that the brain mounts against implanted devices contributes to the observed recording instability. Available evidence suggests that pro-inflammatory and cytotoxic soluble factors secreted by reactive macrophages/microglia at the device-tissue interface mediate the cellular-level changes underlying the FBR. Based on this assumption, we hypothesize that implant designs that passively reduce the activation of these cells and the concentrations of their released soluble factors surrounding the implant will reduce the severity of the FBR. To explore this hypothesis we have studied the FBR to a series of novel test devices based on single-shank, Michigan-style microelectrode arrays. These devices have modified architectures and altered constitutive properties intended to reduce macrophage activation and/or the impact of their secreted factors. To facilitate the design and testing of these devices, we first created a series of three-dimensional (3-D) finite element simulations to predict the distributions of various macrophage-secreted factors around virtual device designs with altered architectures and permeability (Chapter 2). Building on predictions from these models, we have tested the efficacy of reducing the amount of device surface area presented for macrophage interaction/activation in altering the brain FBR (Chapter 3). Furthermore, we also examined the efficacy of increasing device permeability in altering the brain FBR by incorporating coatings that serve as cytokine sinks to passively absorb pro-inflammatory factors into the device and away from adjacent brain tissue (Chapter 4). In the final portion of this dissertation we move from these passive methods of limiting the extent and impact of activated inflammatory cells and describe the creation of extracellular matrix (ECM) based device coatings to bioactively reduce the FBR and drive improved healing and integration into tissue (Chapter 5)

The Challenge of Human Mesenchymal Stromal Cell Expansion: Current and Prospective Answers

In the field of cell therapy, allogenic human mesenchymal stromal cells (hMSCs) are often used in clinical trials, creating a demand for cell mass production using efficient dynamic bioreactor systems. As an advanced therapy medicinal product (ATMP), such cells should meet certain special requirements, including product specifications requiring a production process compatible with good manufacturing practice (GMP). The development of processes in which the cells are the product therefore remains a significant challenge. This chapter describes the requirements at different steps in the upstream and downstream phases of such dynamic processes. Potential solutions are presented and future prospects are discussed, including the selection of media and carriers for the strictly adherent growing cells, allowing efficient cell adhesion and detachment. Strategies for dynamic cultivation in bioreactors are described in detail for fixed‐bed and stirred‐tank reactors based on GMP requirements and the integration of process analytical technology (PAT). Following cell harvest, separation and purification, the formulation and storage of the product are also described. Finally, the chapter covers important cell quality characteristics necessary for the approval of ATMPs

Fisheries development in Nigeria with special reference to Cross River State

The paper appraises fisheries development in Nigeria with specific reference to Cross River State and the problems militating against increased fish production. The potential for developing the industry to supplement the low level of animal protein consumption in Nigeria is discussed as well as the import of a vibrant fishery industry to contribute to the employment and international trade. The need to legislate on fisheries activities while enforcing the existing laws for sustainable exploitation of the fisheries resources is elaborated. Similarly, the need to maximize the proceeds from Nigeria's Exclusive Economic Zone (EEZ) by protecting the operations of this economic sector and other unauthorized fishing practices is elucidated. In view of the present situation where most of the country's water bodies have been over-fished, more attention and emphasis should be placed on aquaculture development. The paper also proffers recommendations to boost fish production in capture and culture fisherie

RURAL-TO-URBAN WATER TRANSFERS: MEASURING DIRECT FOREGONE BENEFITS OF IRRIGATION WATER UNDER UNCERTAIN WATER SUPPLIES

Irrigation water from a southeastern Colorado county has been sold to distant municipalities. The county's junior water right delivered limited and uncertain water supplies which were used on relatively poor soils. The ability of water markets to allocate water to the highest-valued use was addressed by assessing the direct foregone benefits of the transfer using deterministic and discrete stochastic sequential (DSSP) programming models. Crop mix predicted by the DSSP followed observed regional patterns. The DSSP was thus used to derive regional water demand from which foregone value was estimated. Direct regional foregone agricultural benefits were relatively low-due to uncertain water supplies and unproductive soils-indicating the market selected a low-valued supply for transfer.Resource /Energy Economics and Policy,

Contribution of bone marrow-derived cells to in situ engineered tissue capsules in a rat model of chronic kidney disease

Nephrolog

Turning Garlic into a Modern Crop: State of the Art and Perspectives

Garlic is cultivated worldwide for the value of its bulbs, but its cultivation is challenged by the infertility of commercial cultivars and the accumulation of pathogens over time, which occurs as a consequence of vegetative (clonal) propagation. In this review, we summarize the state of the art of garlic genetics and genomics, highlighting recent developments that will lead to its development as a modern crop, including the restoration of sexual reproduction in some garlic strains. The set of tools available to the breeder currently includes a chromosome-scale assembly of the garlic genome and multiple transcriptome assemblies that are furthering our understanding of the molecular processes underlying important traits like the infertility, the induction of flowering and bulbing, the organoleptic properties and resistance to various pathogens

A Nail-Size Piezoelectric Energy Harvesting System Integrating a MEMS Transducer and a CMOS SSHI Circuit

Piezoelectric vibration energy harvesting has drawn much interest to power distributed wireless sensor nodes for Internet of Things (IoT) applications where ambient kinetic energy is available. For certain applications, the harvesting system should be small and able to generate sufficient output power. Standard rectification topologies such as the full-bridge rectifier are typically inefficient when adapted to power conditioning from miniaturized harvesters. Therefore, active rectification circuits have been researched to improve overall power conversion efficiency, and meet both the output power and miniaturization requirements while employing a MEMS harvester. In this paper, a MEMS piezoelectric energy harvester is designed and cointegrated with an active synchronized switch harvesting on inductor (SSHI) rectification circuit designed in a CMOS process to achieve high output power for system miniaturization. The system is fully integrated on a nail-size board, which is ready to provide a stable DC power for low-power mini sensors. A MEMS energy harvester of 0.005 cm3 size, co-integrated with the CMOS conditioning circuit, outputs a peak rectified DC power of 40.6 µW and achieves a record DC power density of 8.12 mW/cm3 when compared to state-of-the-art harvesters

Soil Biogeochemistry and Water Dynamics of Continuous Winter Wheat as Impacted by Cover Crops and Mixed Intercropping

Texas is ranked among the top winter wheat (Triticum aestivum L.) producers in USA. Monoculture wheat production systems are a customary practice in the Southern Great Plains, but have negative effects on ecosystem services and soil functions. The resurgence of cover crops technology in the twenty-first century has been viewed as restoring and sustaining soil ecosystem services and functions. The introduction of cover crops and intercropping during the fallow period may increase diversity, productivity and sustainability. This study was conducted for 3 years at the Smith/Walker Ranch near Vernon, TX, a rainfed leased landholding of Texas A&M AgriLife Research at Vernon. The objectives were to determine the impact of cover crops on nutrient cycling, soil microbial community structure and diversity, soil physical properties and soil moisture dynamics in continuous wheat systems. The study was a randomized complete block design with seven treatments replicated four times. Treatments were: (1) conventional till (CT) wheat without a cover crop; (2) no-till (NT) wheat without a cover crop; (3) NT wheat intercropped with turnip (Brassica rapa subsp. Rapa )/radish (Raphanus sativus) without a summer cover crop; (4) NT wheat with a terminated summer cover crop; (5) NT wheat with a grazed summer cover crop; (6) NT wheat intercropped with turnip/radish with a terminated summer cover crop; and (7) no-till wheat intercropped with turnip/radish with a grazed summer cover crop. Legumes and grasses multi-species mix was used as a warm-season cover crop mix. Introduction of cover crops in continuous wheat systems during the fallow period significantly depleted soil moisture and was reflected in the following wheat period and exacerbated by recurrent drought when study was initiated in 2013. Treatment effects were more pronounced in the top 0-60 cm of the soil profile. Conventional till and NT treatments without cover crops and NT intercropped with radishes and turnips without summer cover crops recorded highest stored soil moisture compared to all NT cover crops treatments during periods of peak cover crops growth. The first two years of investigation showed no differences in soil moisture storage among all no cover crops treatments; however, CT trended lowest during the third year, indicating negative tilling effects. The second and third years of cover crops, which had more normal precipitation, showed improved soil water recharge by all cover crop treatments, with cover crop treatments storing highest soil water compared to no cover crops treatments. Soil nitrate-N was lowest under cover crop treatments compared to no cover crop treatments in the fall and was related to N immobilization and cover crops using N during growth. Generally, no significant soil organic carbon (SOC) sequestration was observed during this investigation. However, water extractable organic C (WEOC) showed a gradual increase under no-till with cover crops. Total living soil microbial biomass, microbial activity and organic C were numerically higher for all NT treatments compared to CT. Conventional till had the least organic N, C, NHv4^+–N and COv2–C emission compared to other treatments, although not always significant. No significant effects due to intercropping or grazing were recorded. Conventional till wheat resulted in the highest soil bulk density compared to all other treatments. Aggregate-size distribution was significantly different in the top 5 cm compared to 5-10 cm depth (p2 mm) were highest under the grazed NT with cover crops plus intercropping treatment. Conventional till resulted in the quickest time to surface runoff initiation compared to all other treatments. Runoff volumes collected were highest under CT compared to NT with cover crops and recorded the highest total P, NHv4^+–N and total solids in runoff (p<0.05). No-till with cover crops improved soil water infiltration, transmission and holding capacity. No significant effects due to turnips and radishes were observed