Mountain Scholar

Mountain Scholar is an open access repository service that collects, preserves, and provides access to digitized library collections and other scholarly and creative works from Colorado State University and the University Press of Colorado. It also serves as a dark archive for the Open Textbook Library.

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Colorado State University, Fort Collins 29051
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Open Textbook Library Archive 1846
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University Press of Colorado 1106
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Access status: Open Access ,
Fetal liver-derived CD34+, KDR+ hematopoietic stem cells: gene transduction with an HIV-based lentiviral vector
(2001) Nasuti, Jacki M., author; Pearson, Leonard D., advisor; Akkina, Ramesh, advisor; Chang, Jeffery, committee member
Gene therapy is a potentially attractive option for treatment of HIV infection as well as for many hematopoietic disorders. To realize this goal, it is critical that hematopoietic stem cells with the highest self-renewal capacity and long-term engraftment capabilities be utilized as cell targets for therapeutic gene transfer. Previous studies have sought to identify the most primitive hematopoietic cells from sources such as umbilical cord blood (UCB), bone marrow (BM), peripheral blood (PB), and mobilized peripheral blood (MPB). As the fetal liver is the major site of hematopoiesis during embryogenesis, it is likely that a significant number of primitive hematopoietic cells exist in this site. Present studies have sought to identify primitive KOR-expressing CD34 stem cells in human fetal liver using direct mAb staining and to isolate these cells by FACS. Results have shown that approximately 1% of CD34+ cells isolated from 16-23 gestational-week old human fetal livers were positive for the KDR marker. This represents a significantly higher proportion compared to the level of 0.1-0.5% CD34, KDR double positive cells that has been found in other sources (UCB, PB, MPB, BM). It was previously shown that stem cells retain long-term hematopoiesis when cultured in the presence of mesenchymal stem cell (MSC) stromal cell layers. Accordingly, the fetal liver derived CD34+/KDR+ stem cells were cultured in the presence of MSC. This has allowed maintenance of a very small numbers ofCD34+/KDR+ cells (1000 cells) in culture and subsequently expand them to 100-fold. These findings provide a means of maintaining low numbers ofCD34+/KDR+ cells and expanding them to a working population for future experimentation. In vitro maintained CD34+/KDR+ cells were subjected to gene transduction with an HIV-1 based lentiviral vector. Although MSC did not serve to significantly increase transduction efficiencies of CD34+/KDR- progenitors, the progenitors cultured in the presence of MSC were relatively more refractory to the apparent toxicity effects of high-titer lentiviral vector exposure. In comparative studies, it was found that the transducibility of CD34+/KDR+ primitive hematopoietic cells is equivalent to that of CD34+/KDR- progenitors (approximately 86% EGFP expression as analyzed by FACS). Results presented here demonstrate the existence of CD34+, KDR+ cells in fetal liver at significantly higher levels than other sources. These cells could possibly serve as key cell targets for achieving sustained gene transduction with lentiviral vectors for current AIDS gene therapy strategies.
Access status: Open Access ,
Amazonian conservation across archipelagos of Indigenous territories
(2024-10-22) Esbach, Michael S., author; Correia, Joel E., author; Valdivia, Gabriela, author; Lu, Flora, author; Wiley Periodicals LLC, publisher
Indigenous stewardship is essential to the conservation of biocultural diversity, yet conventional conservation models often treat Indigenous territories (ITs) as homogeneous or isolated units. We propose that archipelagos of Indigenous territories (AITs), clusters of ITs that span geographies but are connected through shared cultural or political ties maintained by Indigenous nations, are crucial for understanding and enhancing conservation strategies that recognize the complexity of Indigenous stewardship. We classified 3572 ITs in the Amazon into 4 categories—single or multiple nations with either singular IT or AIT—to assess their spatial heterogeneity, governance, and conservation potential. We then assessed species richness, carbon stocks, and pressures across these different categories. To examine how AITs can enhance biocultural conservation efforts, we conducted a case study of the Cofán Nation in Ecuador. AITs covered 45% of the Amazonian land area and had higher species richness and carbon stocks than single IT configurations. However, AITs faced greater pressures from development and extractive activities. In the case study, the Cofán AIT was shaped by colonization and land titling challenges, but their community-driven governance, cross-territorial collaboration, and adaptive responses—such as comanagement agreements and resisting extractive activities—enhanced their ecological and cultural resilience amid growing development pressures. Our findings suggest that AITs facilitate the exchange of resources, knowledge, and cultural practices, which strengthens social connectivity, reinforces governance structures, and enables adaptive management across ITs, thereby enhancing biocultural resilience across discontinuous spaces. This work advocates for a paradigm shift in conservation planning and practice that recognizes the vital role of AITs in sustaining Amazonian ecosystems and Indigenous lifeways, particularly in the face of increasing pressures.
Access status: Open Access ,
Haze, heat, and human bonds: a mixed methods study of attachment's influence on risk information behavior among outdoor workers facing air quality and extreme heat hazards
(2026) Bice, Channing, author; Long, Marilee, advisor; Abrams, Katie, committee member; Anderson, Ashley, committee member; MacPhee, David, committee member; Most, David, committee member
Outdoor workers face disproportionate exposure to compound environmental hazards on the job, yet little is known about the factors that shape how they seek and process relevant risk information. This dissertation investigates these factors by integrating attachment theory into the risk information seeking and processing (RISP) model to examine how attachment anxiety and attachment avoidance influence outdoor workers' risk information seeking behaviors related to extreme heat and poor air quality. Using an explanatory sequential mixed-methods design, the study first employed a national online survey (N = 220) of outdoor workers across the United States, followed by focus groups (N = 29) with municipal outdoor workers in Fort Collins, Colorado. Quantitative results from a series of hierarchical regressions and mediation analyses indicated that attachment orientations shaped key RISP model variables, though the strength and significance of these relationships varied by hazard. Specifically, attachment avoidance predicted reduced risk perception, negative affective response, and informational subjective norms in the extreme heat context, while attachment anxiety predicted increased negative affective response and informational subjective norms for extreme heat. Neither attachment anxiety nor attachment avoidance predicted information insufficiency, attitudes toward information seeking, or perceived information seeking control across either hazard. Core RISP model pathways were broadly supported across both hazard contexts. Qualitative findings yielded five key themes that expanded on and contextualized the quantitative results. First, workers perceived extreme heat as a more urgent and physically threatening hazard than air quality, which they often normalized or noticed only when symptoms became intolerable. Second, information seeking was shaped by peer behavior, supervisor guidance, and workplace norms; workers higher in attachment anxiety exhibited heightened sensitivity to social cues, while those higher in attachment avoidance tended to minimize risk and emphasize self-sufficiency. Third, workers expressed uncertainty about translating hazard indices, particularly the air quality index, into task-relevant decisions. Fourth, workers preferred task-specific information well in advance of hazard events to better plan protective actions into work schedules. Finally, workers expressed strong support for integrating air quality and heat information into a unified communication system to streamline workplace decision-making. Integration of the two phases confirmed that extreme heat functions as a more powerful motivational driver than poor air quality across emotional, social, and behavioral pathways, and expands our understanding of how differences in workers' motivational responses to each hazard can be put to work through integrated communication systems that use heat engagement as an entry point for air quality awareness. Overall, these findings make theoretical contributions by demonstrating that attachment orientation functions as a meaningful individual difference variable within the RISP model by influencing risk perception, affective response, and informational subjective norms, particularly for risks perceived as immediate and salient. These findings also challenge traditional distinctions between active and passive information seeking. Practically, the findings call for risk communication strategies that are emotionally and socially attuned, task-relevant, and reconsider vulnerable population message framing. Future research should continue to examine attachment effects on risk information seeking and avoidance across additional hazard contexts and among more diverse populations.
Access status: Embargo ,
Advancing approaches to resource recovery from waste materials
(2026) Muabuay, Ficky Frischard Fendy, author; Sharvelle, Sybil, advisor; De Long, Susan, committee member; Carlson, Kenneth, committee member; Stackhouse-Lawson, Kim, committee member
The rising volume and complexity of municipal, agricultural, and industrial waste streams place considerable pressure on conventional waste management systems and create an opportunity to reframe these streams as feedstock sources for water, energy, and chemical recovery. Dairy facilities generate large volumes of flushed manure that drive on-site water demand and contribute to greenhouse gas emissions when stored or treated in lagoons, while the organic fraction of municipal solid waste (MSW), including food waste, paper and paperboard, and agricultural residues such as grass, together with agricultural residues such as feedlot manure, represents a large and diverse feedstock supply for biological conversion. This dissertation addresses barriers to resource recovery from these waste streams through studies that evaluate (1) a pilot-scale integrated vibrating screen (V-SC) and vibrating reverse osmosis (V-RO) membrane system for treating flushed dairy manure and (2) a laboratory-scale upflow leach bed reactor (ULBR) platform for converting diverse organic feedstocks into carboxylic acids for generation of high value volatile fatty acids (VFAs). Dairy facilities have a high demand for water, and treatment of on-site flushed dairy manure is challenging due to high organic and solids content. Pressure-driven membrane systems for dairy manure face severe fouling at high solids and high organic loading, requiring extensive pretreatment to maintain stable flux and recovery. To address barriers to the wide-scale implementation of water and energy recovery from flushed dairy manure, the performance of an integrated V-SC and V-RO membrane system was evaluated at pilot scale. Flushed dairy manure with influent concentrations of 46.2 ± 5.4 g/L total suspended solids (TSS), 47.9 ± 6.4 g/L chemical oxygen demand (COD), 2.4 ± 0.6 g/L total nitrogen (TN), and 0.8 ± 0.2 g/L total phosphorus (TP) was first pre-screened using V-SC at 125 µm, then treated by V-RO at 400 PSI and 25 °C. The V-RO unit achieved removals of 98.7 ± 0.6% of COD, 92.1 ± 1.7% of TN, and 84.1 ± 3.9% of ammonia, with complete elimination of TSS and TP, while maintaining an average flux of 6 GFD at approximately 70% recovery. Physical cleaning every 30 minutes and alkaline chemical cleaning approximately every 24 hours of operation were sufficient to sustain stable performance. The V-RO permeate generally met irrigation and livestock drinking water standards, although TN and 5-day biochemical oxygen demand occasionally exceeded surface water discharge limits in selected states. The combined V-SC and V-RO solids supported a biochemical methane potential of 227.8 ± 10.8 mL CH4/g VS, exceeding values typically reported for flushed dairy manure. These results showed that a vibration-assisted membrane configuration can recover reusable water and concentrated solids from high-strength dairy waste without extensive pretreatment. Conventional anaerobic digestion of organic waste streams generates methane, but converting organic matter in these wastes into VFAs, particularly medium-chain carboxylic acids (MCCAs), through arrested anaerobic digestion (AAD) offers a route to higher-value chemical precursors for bioplastics, biofuels, and animal feed additives. AAD systems require reliable methanogenesis suppression, which is typically achieved through extreme operating conditions or chemical inhibitors that add cost and operational complexity. The influence of feedstock composition, hydraulic retention time (HRT), and reactor configuration on AAD performance in upflow leach bed reactors (ULBRs) is not well understood, and strategies that eliminate the need for external chemical addition while maintaining stable methanogenesis suppression remain underdeveloped. To address the methanogenesis suppression barrier in AAD, methanogenesis inhibition via lactic acid addition, which can be generated on-site as a byproduct, was evaluated in 10 L laboratory-scale ULBRs across three feedstocks representative of common U.S. organic waste streams: food waste, food waste co-digested with feedlot manure (FM), and alfalfa hay. All three feedstocks were tested at pH control setpoints of 5.25, 5.50, and 5.75 over 26-day batch runs. Food waste reactors maintained leachate pH below the lowest setpoint without intervention and fractional methane yield (%YCH4,theor) indistinguishable from zero throughout the experiment. On the other hand, both FM and alfalfa hay required lactic acid addition to maintain AAD condition. Among the three setpoints tested, pH 5.75 provided equivalent methanogenesis suppression with the lowest lactic acid demand in FM system. A %YCH4,theor threshold of 5% was introduced as a dosing criterion that more appropriately reflects methanogenic threat than gas-phase methane concentration alone, particularly in slow-degrading feedstocks. These results provided the first systematic evaluation of pH-controlled AAD in a ULBR system. To examine HRT as an operational parameter for controlling carboxylic acid (CA) production in ULBRs, the effect of HRT on VFA titers, cumulative CA yields, acid chain-length distribution, and methanogenic stability was evaluated across food waste (HRTs of 5, 8, and 11 days), grass (HRTs of 8, 31, and 78 days), and paper and paperboard mixed with feedlot manure (PPB + manure; HRTs of 14, 28, and 71 days). For food waste, total carboxylic acid (TCA) yield was largely insensitive to HRT (0.39 to 0.43 g COD/g VS), but longer HRTs provided increased C4-C7 fractions, with C6-C7 acids accounting for up to 21% of late-phase TCA at HRT 11 days. For grass, cumulative TVFA yield fell with increasing HRT (0.27 to 0.10 g COD/g VS across 8 to 78 days), while caproic and heptanoic acids remained observable across all conditions. For PPB + manure, lactic acid addition was required at HRTs of 14 and 28 days to restore methanogenesis suppression, while HRT 71 days needed none. Dosing at HRT 14 days resulted in desirable C4-C7 acid products, while HRT 71 days, though self-sufficient, produced very low overall CA yields. Correlation analysis confirmed that feedstock biodegradability, protein, and fat content drove total acid yield, while leachate pH and lignocellulosic content governed chain-length distribution. These findings showed that HRT is an important parameter for controlling the CA spectrum but does not override the dominant role of feedstock composition. To eliminate the need for external chemical addition in AAD, a series-fed leachate ULBR configuration was evaluated in which food waste and PPB + manure were physically layered with physical separation within a single reactor to mimic a two-reactor in-series configuration. Previous research conducted by our research group conducted in batch reactors indicated feeding products generated from food waste AAD to manure feedstocks can control methanogenesis and increase carbon chain length of products. Leachate was recirculated upward between the two feedstocks to assess the benefits observed at batch scale in an operational ULBR. The series-fed configuration produced a TCA yield of 0.323 g COD/g VS over 35 days at a 7-day HRT, exceeding the volatile solids-weighted theoretical baseline calculated from standalone food waste and standalone PPB + manure operation by 33.3% (p = 0.007), and supported a strong selectivity shift toward longer-chain CAs in the C4-C7 range without any lactic acid addition. %YCH4,theor in the series-fed configuration reached 1.4 ± 0.8%, a 69.3% reduction relative to PPB + manure standalone operation (4.6 ± 1.2%) despite the standalone receiving 203 g VS of external lactic acid. The ULBR in series therefore outperformed standalone operation of either feedstock for AAD targeting longer-chain CAs (C4-C7), delivering higher TCA yields and stronger methanogenesis suppression without lactic acid addition. These findings established the ULBR in series configuration as a more effective and operationally simpler approach than standalone ULBRs for converting mixed food waste and lignocellulosic-rich feedstocks into C4-C7 CAs.
Access status: Open Access ,
Representation conversations: how Indigenous video game players and others experience "Never alone"
(2026) Clotfelter, Susan C., author; Long, Marilee, advisor; Plaisance, Patrick L., advisor; Arthur, Tori O., committee member; Browne, Kate, committee member; Moore, Emily L., committee member
"Never Alone" is a video game co-created by an Alaska Native tribal council and an educational video game company. This dissertation asks the question: How do Indigenous players who are not Alaska Natives experience and discuss the game? Existing video game research into whether, and how, under-represented audiences value representation in video games, and research specifically on Indigenous video game players is rare. In addition, "Never Alone" has many unusual aspects, including commercial success, critical acclaim and its production process. There is also some published anecdotal evidence that Indigenous players experienced a boost in well-being from playing the game. I conducted in-depth interviews with Indigenous players of "Never Alone" who discussed playing this particular game as well as Indigenous representation in other games, movies, television, and other pop-culture genres. I combined this interview data with transcripts of three publicly available panel discussions of Indigenous representation in stand-up comedy, comic books, and the Star Wars science fiction universe. I also analyzed comments about the game on Reddit and interviewed three members of the game's production team. Using a theoretical perspective that included self-determination theory (SDT), visual sovereignty scholarship, communitarian media ethics, and an Indigenous self-determination perspective, I identified themes that build a picture of what these Indigenous media consumers and creators believe are important elements of their identities as well as how they classify examples including "Never Alone" into negative, positive, and best representation. I also identified two processes – Representation via Adoption and Representation via Adaptation -- by which Indigenous media consumers imaginatively "fix" representation when it is absent or poorly done. In addition, I found that while media consumers were not necessarily aware of the detailed, collaborative, intercultural production process that the creators of "Never Alone" developed, they were aware that many elders and artists from Alaska's Inupiaq community were involved in key decisions. This study contributes to the literature on representation in video games, and that on "Never Alone" specifically, by showing how players discuss a representative game in the context of their overall consumption of entertainment media. It also offers a window on how Indigenous consumers of entertainment media value, assess, and imaginatively create representation. It also shows that some Indigenous players value cultural production and want Indigenous people involved in key media-making decisions. For media producers and researchers, this study gives detailed insight into the goals of the video game company, tribal council leaders, and the decision-making process that helped ensure the game would be seen as "good representation."