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Electrospun Scaffolds for Spinal Cord Explant Cultures
No full textSpinal cord injury (SCI) affects thousands of patients worldwide every year, and leads to numerous lifelong medical difficulties for these patients. Ex vivo research into strategies for improving neural interfaces is a key area of development for neural prosthetics, a method for restoring function after SCI. Such improved neural interfaces are also important for the ex vivo study of neuronal biology, for example the formation of neuromuscular junction synapses, neuronal survival and axonal outgrowth. This is especially true as in vivo studies are challenging due to technical limitations and a high level of complexity, and in vitro studies do not adequately model native cell populations and architecture. Electrospun fibers are an excellent interface material, as they can not only serve as a topographically tunable culture substrate, but can also be used for controlled delivery of neuroprotective molecules ex vivo. In this thesis, the formulation of electrospun nanofibers for enhanced ex vivo neuronal outgrowth is explored. Firstly, the incorporation of cationic polymer polyethylenimine (PEI) into electrospun gelatin was achieved, using both linear and branched PEI of various molecular weights (Chapter 3). The resulting branched PEI/gelatin scaffolds were demonstrated to increase the outgrowth of neurites from spinal cord explants. Secondly, polyacrylonitrile (PAN) was electrospun with PEI to determine if the addition of PEI could make non-biocompatible hydrophobic PAN into a biocompatible material (Chapter 4). The mats containing 600 MW branched PEI allowed for increased numbers of dissociated spinal cord explant to attach. The mats containing 600 and 10,000 MW branched PEI also demonstrated increased hydrophilicity. This indicates that other electrospun polymers may be made permissible for spinal cord explant growth with the addition of PEI. Thirdly, uric acid (UA) was incorporated into electrospun gelatin nanofibers and released under physiological conditions (Chapter 7). UA is a powerful neuroprotective biomolecule that acts as an antioxidant in vivo, however excess systemic UA can lead to gout and/or kidney stones. This indicates that UA is an ideal candidate for controlled localized release. The UA release achieved was ~ 80 μg, more than the ~21 μg needed for beneficial effect in neuronal cultures with induced peroxynitrite- or glutamate-induced toxicityPh.D., Biomedical Engineering -- Drexel University, 201
Effect of spent hop extract on haze stability, total polyphenols and antioxidant activity of Pale Ale beer
No full textChilled haze formation resulting from protein-polyphenol interaction in beer is a serious problem in the brewing industry limiting consumer acceptability and storage life of the product. Commercial polyphenols such as tannic acid are often used as fining agents to clarify and stabilize beer haze. Spent hops, discarded as waste in landfills, contain some significant amounts of polyphenols and spent hop extract has potential as a fining agent. The goal of this study was to recover polyphenol rich extract from spent hops and study the influence of spent hop extract in stabilization of haze, total polyphenols and antioxidant activity of pale ale beer when added post fermentation. Total polyphenol content (TPC) contributing towards the haze formation was analyzed at each brewing stage throughout the commercial brewing of pale ale. Haze stability tests were performed on laboratory brewed pale ale. Polyphenol rich extract was recovered from spent hops using ethanol (80%). TPC and antioxidant activity(AOA) were measured using Folin Ciocelteu method and 1,1Diphenyl 2, picrylhydrazyl (DPPH), respectively. Results from this study demonstrated that TPC and antioxidant activity values in the pale ale brewing process vary with the brewing stage, significantly higher values at the end of boiling and significantly lower in the last wort. The spent hop extract has high DPPH clearance ratio (~53%), showing potential to scavenge free radicals. Addition of spent hop extract (0.3-0.5% v/v) in the beer post fermentation led to reduction in chilled haze in beer brewed with hopback wort, indicated by the decrease in NTU, TPC, and DPPH. In beer brewed from non-hopback wort, addition of spent hop extract (0.3% v/v) showed the potential to reduce NTU, TPC, and DPPH clearance ratio values during initial chilling. Extracts did not have any impact on the permanent haze after accelerated aging. Furthermore, addition of 0.2% of spent hop extract showed high TPC and DPPH clearance ratio of beer with no significant increase in turbidity values. In conclusion, addition of spent hop extracts in pale ale will reduce chilled haze formation and have no negative effect on haze stability during beer's storage life. HPLC analysis revealed the presence of haze active procyanidin B2, epicatechin and sinapic acid that are potential antioxidants found in fruits and vegetables. These polyphenols play an important role in forming protein-polyphenol complexes. Considering drawbacks of current fining agents and residual bitterness of spent hops preventing them from use in animal feed, extracting polyphenols from a plethora of natural hop waste in beer industry is a sustainable, cost effective, and effective approach to reduce waste, produce natural fining agents and increase antioxidant activity of beer product.M.S., Food Science -- Drexel University, 201
Determining Nutritional and Delivery Conditions for an Urban In-Home Unit for Growing Fruits and Vegetables
No full textObesity is a complex issue with multiple impacts on individual and public health. It carries increased risk for a variety of serious conditions, such as type 2 diabetes mellitus, hypertension, cardiovascular disease, and certain cancers. Higher rates of obesity and associated conditions are often seen in urban food deserts where residents lack food sovereignty and resources. These communities are underserved by grocery stores and lack access to affordable healthy food. Additionally, these areas typically lack suitable land for agriculture. Increasing access to fresh produce is one possible strategy for addressing obesity and its related conditions in the context of urban health. The intent of this work was to test conditions for an in-home device for growing fruits and vegetables. The experiments described here represent a proof of concept for an indoor hydroponic device that uses cyanobacteria as fertilizer, examining the media composition and nutrient delivery to this hydroponic unit. Due to the use of this fertilizer and the hydroponic setup, the device requires minimal space and maintenance. The device aims to increase the user's control over and understanding of their food sources, while enabling dietary changes through the production of fresh herbs and produce. This work is one arm of a larger project encompassing the development and optimization of the hydroponic unit. Combining biology and human-centered design, this research focuses on a) optimizing cyanobacteria and plant growth, b) increasing the efficacy of cyanobacteria as fertilizer, and c) evaluating and enhancing the user's experience with the hydroponic unit. Through this transdisciplinary, multi-pronged approach, we intend to add another tool to the toolbox of strategies to remedy obesity and improve health for underserved communities.M.S., Biological Sciences -- Drexel University, 201
The Effect of Side Chain Functionalization and Formulation of Cashew Nutshell Liquid (CNSL) on the Properties of Thermoset Networks
No full textCardanol which is the main component of the thermally treated cashew nutshell liquid (CNSL) is a versatile molecule with a C15 aliphatic side chain connected to a phenyl ring at the -meta position. The dual structure of cardanol which combines a rigid aromatic ring with a flexible and hydrophobic side chain with different degrees of unsaturation makes this molecule a suitable and sustainable candidate to utilize in top coat and primer formulations to improve corrosion performance. However, cardanol lacks reactive polymerizable functional groups on its structure and cardanol-derived networks possesses long dangling chains on their backbone which decrease the network performance regardless of their benefits. Thus, in this dissertation, the effect of cardanol's side chain functionalization on network properties and corrosion performance was explored. The unsaturation sites of the side chain of the mono-epoxy cardanol molecule, cardanol glycidyl ether (CGE), were epoxidized via peroxyacids to achieve secondary epoxies on the side chain and to connect the C15 chain of the cardanol into the polymer network. This side chain epoxidized CGE (SCECGE) epoxy resin was cross-linked with a range of amine curing agents. The lower reactivity of the secondary epoxies towards amines was demonstrated via a number of direct and indirect curing studies and a systematic methodology was developed to assess the extent of cure of secondary epoxies by using cardanol-derived model secondary epoxy. Structural characterization of SCECGE monomer also revealed the reduced reactivity of the terminal double bonds of the aliphatic chain towards epoxidation with respect to inner ones because of their reduced electronegativity. Thus, a useful methodology was developed to effectively epoxide the terminal double bonds of the SCECGE and to make a correlation between the degree of side chain functionalization and the network performance. SCECGE monomer was mixed with a bis-phenol A derived di-epoxy monomer (DGEBA, EPON 828) with changing weight rations and thermally cross-linked with a cycloaliphatic amine (PACM) to demonstrate the effect of side chain cross-linking on the water barrier and corrosion performance. Network properties and the coating performance of the DGEBA/SCECGE blends were evaluated and the results showed that; upon proper functionalization and careful formulation with DGEBA, cardanol based building blocks can meet significant requirements ofthermoset coatings while keeping satisfactory thermal and mechanical resistance for corrosion coating applications. The reactivity issue of the secondary epoxies was addressed via further reacting the epoxy moieties with methacrylic acid to fully react the side chain into the polymer network thus to improve the polymer performance and network properties. Due to the stearic limitations of the secondary epoxies; they are not able to fully react with amine hardeners. Replacing these secondary epoxies with methacrylate units and using the free radical polymerization mechanizm resulted in almost full cross-linking of the side chain in vinyl ester formulations. Finally, a useful hybrid molecule synthesized via the combination of cardanol and fatty acid based building blocks was incorporated with DGEBA-PACM system. This hybrid molecule demonstrated similar toughening effect to epoxidized soybean oil based tougheners while keeping the modulus significantly higher owing to its aromatic content.Ph.D., Chemical Engineering -- Drexel University, 201
Managing Personal Health Information from Activity Trackers: The Healthy Users’ Perspective
No full textToday's consumer-facing activity trackers, such as fitness wristbands and smartwatches, often hold the promise of improving users' health, yet problems in user interaction with activity tracking technology, such as low user adoption, short-lived use, and limited user engagement, undermine the potential health benefits. In this dissertation, I tackle these problems by developing a comprehensive understanding of non-patient healthy activity tracker users' personal health information management (PHIM) with the data generated by their devices, an essential component of long-term user interaction with activity tracking technology. Building on personal information management (PIM) theories and activity tracker user research, I present results from a web survey study and an in-depth interview study that jointly examined healthy activity tracker users' PHIM behaviors with data generated by their devices. Major findings include: the identification of healthy activity tracker users' health/fitness-related needs and information needs; an in-depth portrayal of their PHIM, covering the spectrum of PHIM tools they used, the six types of PHIM activities they performed, as well as the concurrent and subsequent PHIM practices they engaged in; and the depiction of the ways their needs were met, partially met, or unmet by their activity tracking technology use and relevant PHIM. This dissertation contributes to existing research in information science, human-computer interaction, ubiquitous computing, and health informatics at empirical, theoretical, and methodological levels. First, I contribute empirical updates to both activity tracker user research and PIM research by examining healthy activity tracker users' PHIM. Second, I generate practical design implications for future activity tracking technology to better support PHIM based on my empirical findings. Finally, I reflect on my enhanced participant-driven photo elicitation techniques and provide methodological recommendations for future qualitative research to adopt the method.Ph.D., Information Studies -- Drexel University, 201
Effect of Cold Plasma Treatment on Microbial Load and Quality of Baby Carrots
No full textIn the United States, about 80 percent of all food shipments and 91 percent of all temperature controlled freight shipments, including about 28.5 million tons of refrigerated fruit and vegetables, are transported by truck. In the complex food transportation system, microbial contamination is a problem, which may be introduced at earlier stages in the supply chain and can spread out to many distributors, retailers, and consumers. Baby carrots are consumed worldwide because of their nutritional benefits. However, in the past two decades, there has been an increase in foodborne diseases outbreaks caused by microorganisms associated with fresh produce. Cold plasma treatment of fresh produce, an emerging food preservation technology, is a fast and environmentally friendly method that disinfects the product at a low temperature (30-40ºC). Cold plasma uses an ionized gas comprised of charged ions and free electrons for the treatment of the product and kills microorganisms by altering their metabolic pathways. Till date, very little research has been focused on the effect of cold plasma mist (micro meter size water droplets) on the quality and shelf life of fresh produce, and its efficacy in transportation. Therefore, the purpose of this study was to evaluate the efficacy of dielectric barrier discharge (DBD) cold plasma mist on the microbial load and quality of baby carrots in a refrigerated plasma chamber simulating a transportation truck. Conditions in transportation truck were simulated by installing cold plasma mist system in a 100 L volume refrigerator termed as plasma chamber. Baby carrots were inoculated with E. coli O157:H7 and treated with cold plasma mist for different treatment times. The effect of cold plasma on microbial load and quality (color values, texture, moisture content, total polyphenol content, [beta]-carotene) was evaluated at each treatment time. Carrots treated with tap water mist (no plasma) were used as controls. Complete inactivation of E. coli O157:H7 was achieved when baby carrots were treated with plasma mist for 30 min. At each treatment time, lower microbial load was observed for plasma mist treated carrots compared to tap water mist treated carrots. While no significant changes in color values (L*, a*, b*, chroma, hue, and browning index) were observed when baby carrots were treated with plasma mist for 30 minutes, browning index values decreased with an increase in treatment time but was not significantly different. Further, there was no significant difference between firmness values and moisture content (wet basis) of baby carrots treated with tap water mist or plasma mist. The change in total polyphenol content (TPC) of carrots was almost negligible in both tap water and plasma mist treatments. However, plasma mist treatment resulted in no significant difference in [beta]-carotene of baby carrots. This research demonstrated the potential of cold plasma system as an efficient disinfection system that may achieve complete inactivation of microorganisms with no noticeable negative effect on the quality.M.S., Food Science -- Drexel University, 201
Reconstruction of the Musculotendinous System of the Necks of Sauropods and the Dodo Based on Anatomical Comparison with Modern Birds and Implications for Biomechanical Function and Ecological Roles
No full textHerein I redescribe the giant titanosaurian sauropod Daxiatitan binglingi, which has previously only received a preliminary description. The skeleton was incompletely preserved. The articulation of the vertebral column of Daxiatitan suggests that strong connective tissue prevented disarticulation, but parallel dorsal ribs and disarticulated limb bones indicate that these elements were disarticulated by paleo-disturbance prior to burial. Examination of the vertebral column and appendicular skeleton of Daxiatitan brings several anatomical insights to the reconstruction of the soft-tissue attachments. The complicated “N” & “M”-pattern laminae on the neural arches, plus multiple curved ridges on the lateral surfaces of the dorsal vertebrae likely indicate tendons and soft tissue attachment sites. Huge pneumatic fossae on the lateral surfaces of the centra indicate the presence of pneumatic diverticula from cervical air sacs. A system of three air sacs is suggested to have filled the pneumatic space. A reconstruction of the ventral musculotendinous system of the neck of the sauropod Daxiatitan is based on comparisons with the distinctly different osteological and myological patterns in the great blue heron (Ardea herodias) and the tundra swan (Cygnus columbianus): the neck of the heron possesses long, light muscles (LL configuration), whereas the swan possesses short, strong muscles (SS configuration). The LL overlapping-tendon pattern of the great blue heron represents a long tendon–light muscle system supported osteologically by deep pulley-grooves on the carotid processes of the cervical vertebrae. Trunk-shifted cervical muscles, nerves, and blood vessels operate biomechanically as a “remote command center” to control the whole neck. The dominant long tendon, trunk-centered muscle belly and kinked, S-shaped neck are controlled by one muscle group, the m. Longus colli ventralis and three key vertebrae. In contrast, the SS chevron pattern of the short cervical tendons of the swan, and the absence of grooves on the carotid processes, indicate cervical flexibility to control individual cervical vertebra rather than the neck as a whole unit. The uniformly muscled swan maintains more of its body mass in the neck. In the SS, chevron pattern, the musculotendinous, vascular, and nervous systems act in concert as an integrated network, which controls the positions of individual cervical vertebrae for flexibility. The contrast of the two patterns suggests that the hyperelongate cervical ribs of Daxiatitan and other sauropods had a feeding or self-defense function. Long-necked sauropods, including Daxiatian and Mamenchisaurus, better fit the LL tendon-overlapping pattern in locomotion and body mass balance, while short-ribbed sauropods, including Diplodocus and Apatosaurus, better fit the SS pattern. A reconstruction of the cervical myology of the dodo, Raphus cucullatus, is based on anatomical comparison with the Nicobar pigeon (Caloenas nicobarica) and reveals robust cranio-cervical osteological features that supported robust neck muscles. Bifurcate cervical spinous processes in the dodo and its kin—the extinct Rodrigues solitaire (Pezophaps solitaria) as well as the gigantic birds such as Dinornis robustus (South Island giant moa)—provide large surface area for the attachment of the elastic interspinal ligament, which functioned for dorsal flexion of the neck. The elongation of the cervical vertebrae, the bifurcation of their spinous processes, and the orientation of their zygapophyses in the dodo suggest it, as well as the Rodrigues solitaire, maintained an elevated, elongate, laterally flexible, S-shaped neck pose. This novel, vertical neck pose epitomized the success of the giant flightless pigeons both in their cranio-cervical biomechanical functions and ecological roles. The adaptation contributed to the acquisition of suitable higher, wider bush-fruit-browsing ecological niches for the flightless dodo and its kin in lowland and highland ecosystems. These adapted traits helped the dodo expand its ecological niche to survive on Mauritius before humans arrived.Ph.D., Environmental Science -- Drexel University, 201
D3 Receptor Agonism Attenuates Deficits Observed in Rodents with 6-OHDA-Induced Medial Forebrain Bundle Lesions
No full textParkinson’s Disease (PD) is a neurodegenerative disorder associated with the progressive loss of dopaminergic neurons in the substantia nigra. This pathology impairs the dopaminergic nigrostriatal pathway, thereby reducing dopamine (DA) input to the striatum and eliciting motor deficits. In addition to these motor deficits, PD patients are often afflicted by non-motor symptoms such as mild cognitive impairment (PD-MCI). PD-MCI patients display deficits in executive function and pathological alterations within the prefrontal cortex (PFC). Specifically, decreases in DA D3 receptor (D3R) expression in the PFC correlate with decreases in cognitive performance. The role of D3Rs in PD are well-established in motor impairments, but their effect on cognitive tasks is yet to be investigated. Additionally, pharmacological agents that target the D3R concurrently demonstrate affinity for other DA receptors. Our lab has developed a selective D3R agonist called SK609 to specifically examine D3R agonism in a hemiparkinson rodent model. We utilized behavioral assays that assess sustained attention and cognitive flexibility, two PFC-mediated tasks compromised in PD-MCI. We found that SK609 dose dependently ameliorated cognitive deficits in lesioned rodents. Taken together, we demonstrated that the prefrontal loss of D3Rs observed in patients may contribute to cognitive impairment by promoting adverse effects in DA signaling. Therefore, D3R agonism, and the consequential normalizing of prefrontal function, may be a therapeutic target for PD-MCI patients.Ph.D., Neuroscience -- Drexel University, 201
Dysregulation of the Wnt signaling pathway in the development of colorectal cancer in HIV-infected patients
No full textWith the advent of antiretroviral therapy (ART), patients with human immunodeficiency virus-1 (HIV-1) have experienced an improvement in morbidity and life expectancy. As this patient population ages, there has been evidence of an elevated risk and earlier onset of colonic neoplasia. The average age of developing colon cancer in HIV-1-infected patients is 48 compared to 60 in the general population. Moreover, the stage of colorectal cancer diagnosed in HIV-1-infected patients is more advanced compared to uninfected individuals. During primary HIV-1 infection, an observed loss of CD4+ T cells is seen in the gastrointestinal (GI) tract along with subsequent systemic immune hyperactivation. Additionally, increased expression of proinflammatory cytokines in the GI tract during HIV-1 infection results in chronic mucosal inflammation. While HIV-induced immunodeficiency and immune activation certainly play a role, there are other possible avenues through which HIV-1 promotes the pathogenicity of oncogenesis. Many of the proteins produced upon viral genomic integration have been demonstrated to interact with components of various cellular pathways. In an effort to elucidate how viral and cellular interaction might aid in colorectal oncogenesis, this study investigates the HIV-1-encoded protein Negative Regulatory Factor (Nef) and its interaction within the Wnt signaling pathway. This pathway is critical within the gastrointestinal stem cell niche for its role in repopulating the intestinal tract lining. Upon dysregulation of the Wnt signaling pathway, [beta]-catenin begins to accumulate in the cytosol and translocates into the nucleus where is binds with transcription factors TCF/LEF leading to an increase in transcription/translation of several key target genes known to upregulate cellular proliferation. The Nef protein has been shown to directly bind to [beta]-catenin in HEK293T cells. What has not been demonstrated is which gene products of the Wnt signaling pathway are dysregulated in the presence of Nef. Understanding the molecular mechanisms behind how HIV may modulate the Wnt signaling pathway will be crucial to better understand the link between HIV and cancer. Therefore, these studies will proceed to examine how HIV-1-encoded Nef modulates the Wnt signaling pathway by interacting with the [beta]-catenin complex in colorectal carcinoma cells leading to accelerated colon tumor outgrowth.M.S., Molecular and Cell Biology and Genetics -- Drexel University, 201
Corporate Political Activism Crises Response and Attachment Styles
No full textThis dissertation investigates how consumers' attachment styles affect their responses to corporate political activism stands. Traditionally, businesses have shied away from politics, except when lobbying for more favorable business policies. But in the past few years, many companies have moved beyond lobbying and have gotten involved in or have been pulled into controversial social and political issues, which often pit different segments of society against each other. Examples of corporate political activism (CPA) include the stands taken by Apple on gay marriage, Starbucks on Immigration, and NCAA on LGBT rights. Given the contentious nature of such issues, these companies have faced a backlash from consumers that hold contrary views. Such crises, related to a company's political activities, are becoming common and can lead to severe deterioration of customer relationships with a company. Handling CPA crises in a manner that minimizes damage to these relationships is of critical importance. Given that a company has no option but to upset some customers when responding to CPA crises, knowing which customers are more likely to excuse its actions is of great value as it enables the company to minimize crises damage by accommodating customers that are less forgiving. In this dissertation, I employ attachment theory to develop response strategies that can be used in case of CPA crises. Attachment theory is particularly useful in predicting consumer response to CPA crises as it can (a) help identify consumers who are more likely to continue their relationship with the company despite CPA related transgressions (e.g. taking an opposing stand), and (b) guide the development post-crisis communication strategies that improve the chances of appeasing disgruntled consumers (e.g. message frames). Study 1 investigates the impact of consumers' attachment styles on their response to a company's decision to reverse its original stand on the issue of gun control. As predicted, results show that avoidant consumers have greater purchase intention than anxious consumers when the company changes its stand even when the change aligns with their own stand on gun-control. Study 2 shows that the effect of a company's decision to reverse its original stand or stand by it on consumers' purchase intent is mediated by the perceived responsiveness of the company. Avoidant consumers are more likely to perceive a company to be responsive when it doubles down on its original stand even when it is opposite to their own views on the issue. Study 3 explores the use of dependent versus independent message frames to communicate a company's decision to reverse its stand to minimize the negative impact on perceived responsiveness for avoidant consumers.Ph.D., Business Administration -- Drexel University, 201