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- Genre: Doctoral Dissertation
Description
Engineered nanoparticles (NP; 10-9 m) have found use in a variety of consumer goods and medical devices because of the unique changes in material properties that occur when synthesized on the nanoscale. Although many definitions for nanoparticle exist, from the perspective of size, nanoparticle is defined as particles with diameters less than 100 nm in any external dimension. Examples of their use include titanium dioxide added as a pigment in products intended to be ingested by humans, silicon dioxide NPs are used in foods as an anticaking agent, and gold or iron oxide NPs can be used as vectors for drug delivery or contrast agents for specialized medical imaging. Although the intended use of these NPs is often to improve human health, it has come to the attention of investigators that NPs can have unintended or even detrimental effects on the organism. This work describes one such unintended effect of NP exposure from the perspective of exposure via the oral route. First, this Dissertation will explain an event referred to as brush border disruption that occurred after nanoparticles interacted with an in vitro model of the human intestinal epithelium. Second, this Dissertation will identify and characterize several consumer goods that were shown to contain titanium dioxide that are intended to be ingested. Third, this Dissertation shows that sedimentation due to gravity does not artifactually result in disruption of brush borders as a consequence of exposure to food grade titanium dioxide in vitro. Finally, this Dissertation will demonstrate that iron oxide nanoparticles elicited similar effects after exposure to an in vitro brush border expressing model of the human placenta. Together, these data suggest that brush border disruption is not an artifact of the material/cell culture model, but instead represents a bona fide biological response as a result of exposure to nanomaterial.
ContributorsFaust, James J (Author) / Capco, David G. (Thesis advisor) / Ugarova, Tatiana (Committee member) / Chandler, Douglas (Committee member) / Baluch, Page (Committee member) / Herman, Richard (Committee member) / Arizona State University (Publisher)
Created2014
Description
This dissertation focuses on the structure-function relationships of nanomaterials (NMs) and some of their applications in environmental engineering. The aim is to investigate NMs of different surface chemistries and assess their interactions with biological models, evaluate the weathering impact and degradation parameters to improve polymer coatings, test their efficiency for contaminant removal and provide further understanding in the safe design of nanomaterials. Nanoecotoxicological risk assessment currently suffers from a lack of testing procedures adapted to nanomaterials. Graphene oxide (GO) is a carbon nanomaterial (CNM) that consists of a single layer of carbon atoms arranged in a hexagonal network. It is decorated with a high density of oxygen functional groups including epoxide and hydroxyl moieties on the basal planes and carboxylic and carbonyl groups at the edges. The changes in surface chemistry give GO unique properties that can be tailored for a function. Additionally, because of its simple synthesis and flexible chemistry, GO has been a popular building block of many composite CNMs. In environmental engineering, specifically, water treatment, GO has been studied by itself or as a composite for pollutant removal, biofouling reduction, and as an antimicrobial agent, just to name a few. Like GO, silver (Ag) is another NM widely used in water treatment for its biocidal properties. Despite the recent growth in this field, a fundamental understanding of the function-structure relationships in NMs is still progressing. Through a systematic set of experiments, the structure-properties-function and structure-properties-hazard relationships were investigated. These relationships can be used to establish guidelines to engineer “safe-by-design” functional nanomaterials, where materials are tailored to enhance their function while minimizing their inherent biological or environmental hazard.
ContributorsBarrios, Ana Cecilia (Author) / Perreault, Francois (Thesis advisor) / Abbaszadegan, Morteza (Committee member) / Conroy-Ben, Otakuye (Committee member) / Hua-Wang, Qing (Committee member) / Arizona State University (Publisher)
Created2021
Description
The livestreaming platform Twitch allows users to engage with one another and with content creators, known as streamers, in real-time, creating a cyclical pattern in which viewers and streamers simultaneously influence one another and co-construct the livestreams. While this active engagement has resulted in numerous benefits, it has also led to a surge in toxic behavior – actions meant to disrupt the flow of the livestream and harm the streamer and viewers involved. Toxic behavior is often directed at individuals who do not conform to the norms of a space or community. Because Twitch evolved out of an interest in video game spectatorship, and video game culture is burdened by the gamer stereotype, which typecasts gamers as young, white, male, and cishet, Twitch users who do not fit this identity category (e.g., women; black, Indigenous and people of color [BIPOC]; queer people; etc.) are labeled as threats to the perceived homogeneity of video game (and Twitch) culture. This project examines toxic discourses surrounding three women Twitch streamers, considering how the streamers’ performances, community-building efforts, and methods of regulation impact the levels and types of toxicity in their livestreams. A critical technocultural discourse analysis of 30 hours of livestreaming data reveals diverse approaches to managing toxicity. While all three streamers expressed that they neither liked nor approved of toxic behavior, their methods of addressing it varied greatly, from active channel moderators and explicit rules to public acts of moderation. Furthermore, the manifestation of toxicity differed across the three streamers’ communities, signaling that the streamers’ strategies impact not only users’ willingness to engage in this behavior but also other viewers’ responses to this issue. Twitch’s positioning as a service provider, which places most of burden of regulating user behavior on streamers, further complicates this problem, as streamers are largely responsible for enforcing Twitch’s rules as well as their own, leading to disparate and conflicting social norms and enforcement patterns. This project underscores the need for Twitch and its streamers to create standardized methods of behavior regulation that are inclusive and hold users accountable for their behavior.
ContributorsRines, Olivia (Author) / Adams, Karen (Thesis advisor) / SturtzSreetharan, Cindi (Committee member) / Florini, Sarah (Committee member) / Arizona State University (Publisher)
Created2021