Matching Items (103)
Description
Mounting evidence suggests that gender biases favoring men and racial biases favoring whites and Asians contribute to the underrepresentation of women and underrepresented minorities (URM) in science, technology, engineering, and mathematics (STEM). Systemic issues caused by gender and racial biases create barriers that prevent women and URM from entering STEM from the structure of education to admission or promotions to higher-level positions. One of these barriers is unconscious biases that impact the quality of letters of recommendation for women and URM and their success in application processes to higher education. Though letters of recommendation provide a qualitative aspect to an application and can reveal the typical performance of the applicant, research has found that the unstructured nature of the traditional recommendation letter allows for gender and racial bias to impact the quality of letters of recommendation. Standardized letters of recommendation have been implemented in various fields and have been found to reduce the presence of bias in recommendation letters. This paper reviews the trends seen across the literature regarding equity in the use of letters of recommendation for undergraduates.
ContributorsKolath, Nina (Author) / Brownell, Sara (Thesis director) / Goodwin, Emma (Committee member) / Barrett, The Honors College (Contributor) / School of Criminology and Criminal Justice (Contributor) / School of Life Sciences (Contributor)
Created2022-05
Description
This work focuses on a novel approach to combine electrical current with cyanobacterial technology, called microbial electrophotosynthesis (MEPS). It involves using genetically modified PSII-less Synechocystis PCC 6803 cells to avoid photoinhibition, a problem that hinders green energy. In the work, a cathodic electron delivery system is employed for growth and synthesis. Photoinhibition leads to the dissipation energy and lower yield, and is a major obstacle to preventing green energy from competing with fossil fuels. However, the urgent need for alternative energy sources is driven by soaring energy consumption and rising atmospheric carbon dioxide levels. When developed, MEPS can contribute to a carbon capture technology while helping with energy demands. It is thought that if PSII electron flux can be replaced with an alternative source photosynthesis could be enhanced for more effective production. MEPS has the potential to address these challenges by serving as a carbon capture technology while meeting energy demands. The idea is to replace PSII electron flux with an alternative source, which can be enhanced for higher yields in light intensities not tolerated with PSII. This research specifically focuses on creating the initiation of electron flux between the cathode and the MEPS cells while controlling and measuring the system in real time.
The successful proof-of-concept work shows that MEPS can indeed generate high-light-dependent current at intensities up to 2050 µmol photons m^‒2 s^‒1, delivering 113 µmol electrons h^‒1 mg-chl^‒1. The results were further developed to characterize redox tuning for electron delivery of flux to the photosynthetic electron transport chain and redox-based kinetic analysis to model the limitations of the MEPS system.
ContributorsLewis, Christine Michelle (Author) / Torres, César I (Thesis advisor) / Fromme, Petra (Thesis advisor) / Woodbury, Neal (Committee member) / Hayes, Mark (Committee member) / Arizona State University (Publisher)
Created2023
Description
Mental health conditions can impact college students’ social and academic achievements. As such, students may disclose mental illnesses on medical school applications. Yet, no study has investigated to what extent disclosure of a mental health condition impacts medical school acceptance. We designed an audit study to address this gap. We surveyed 99 potential admissions committee members from at least 43 unique M.D.-granting schools in the U.S. Participants rated a fictitious portion of a medical school application on acceptability, competence, and likeability. They were randomly assigned to a condition: an application that explained a low semester GPA due to a mental health condition, an application that explained a low semester GPA due to a physical health condition, or an application that had a low semester GPA but did not describe any health condition. Using ANOVAs, multinomial regression, and open-coding, we found that committee members do not rate applications lower when a mental health condition is revealed. When asked about their concerns regarding the application, 27.0% of participants who received an application that revealed a mental health condition mentioned it as a concern; 14.7% of participants who received an application that revealed a physical health condition mentioned it as a concern. Committee members were also asked about when revealing a mental health condition would be beneficial and when it would be detrimental. This work indicates that medical school admissions committee members do not exhibit a bias towards mental health conditions and provides recommendations on how to discuss mental illness on medical school applications.
ContributorsAbraham, Anna (Author) / Brownell, Sara (Thesis director) / Cooper, Katelyn (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor) / Department of Psychology (Contributor) / School of Human Evolution & Social Change (Contributor)
Created2022-05
Description
Similar-identity role models, including instructors, can benefit science undergraduates by enhancing their self-efficacy and sense of belonging. However, for students to have similar-identity role models based on identities that can be hidden, instructors need to disclose their identities. For concealable stigmatized identities (CSIs) – identities that can be hidden and carry negative stereotypes – the impersonal and apolitical culture cultivated in many science disciplines likely makes instructor CSI disclosure unlikely. This dissertation comprises five studies I conducted to assess the presence of instructor role models with CSIs in undergraduate science classrooms and evaluate the impact on undergraduates of instructor CSI disclosure. I find that science instructors report CSIs at lower rates than undergraduates and typically keep these identities concealed. Additionally, I find that women instructors are more likely to disclose their CSIs to students compared to men. To assess the impact of instructor CSI disclosure on undergraduates, I report on findings from a descriptive exploratory study and a controlled field experiment in which an instructor reveals an LGBTQ+ identity. Undergraduates, especially those who also identify as LGBTQ+, benefit from instructor LGBTQ+ disclosure. Additionally, the majority of undergraduate participants agree that an instructor revealing an LGBTQ+ identity during class is appropriate. Together, the results presented in this dissertation highlight the current lack of instructor role models with CSIs and provide evidence of student benefits that may encourage instructors to reveal CSIs to undergraduates and subsequently provide much-needed role models. I hope this work can spark self-reflection among instructors to consider revealing CSIs to students and challenge the assumption that science environments should be devoid of personal identities.
ContributorsBusch, Carly Anne (Author) / Cooper, Katelyn (Thesis advisor) / Brownell, Sara (Thesis advisor) / Collins, James (Committee member) / Zheng, Yi (Committee member) / Arizona State University (Publisher)
Created2024
Description
Understanding the diversity, evolutionary relationships, and geographic distribution of species is foundational knowledge in biology. However, this knowledge is lacking for many diverse lineages of the tree of life. This is the case for the desert stink beetles in the tribe Amphidorini LeConte, 1862 (Coleoptera: Tenebrionidae) – a lineage of arid-adapted flightless beetles found throughout western North America. Four interconnected studies that jointly increase our knowledge of this group are presented. First, the darkling beetle fauna of the Algodones sand dunes in southern California is examined as a case study to explore the scientific practice of checklist creation. An updated list of the species known from this region is presented, with a critical focus on material now made available through digitization and global aggregation. This part concludes with recommendations for future biodiversity checklist authors. Second, the psammophilic genus Trogloderus LeConte, 1879 is revised. Six new species are described, and the first, multi-gene phylogeny for the genus is inferred. In addition, historical biogeographic reconstructions along with novel hypotheses of speciation patterns within the Intermountain Region are given. In particular, the Kaibab Plateau and Kaiparowitz Formation are found to have promoted speciation on the Colorado Plateau. The Owens Valley and prehistoric Bouse Embayment are similarly hypothesized to drive species diversification in southern California. Third, a novel phylogenomic analysis for the tribe Amphidorini is presented, based on 29 de novo partial transcriptomes. Three putative ortholog sets were discovered and analyzed to infer the relationships between species groups and genera. The existing classification of the tribe is found to be highly inadequate, though the earliest-diverging relationships within the tribe are still in question. Finally, the new phylogenetic framework is used to provide a genus-level revision for the Amphidorini, which previously contained six valid genera and 253 valid species. This updated classification includes more than 100 taxonomic changes and results in the revised tribe consisting of 16 genera, with three being described as new to science.
ContributorsJohnston, Murray Andrew (Author) / Franz, Nico M (Thesis advisor) / Cartwright, Reed (Committee member) / Taylor, Jesse (Committee member) / Pigg, Kathleen (Committee member) / Arizona State University (Publisher)
Created2018
Description
Education through field exploration is fundamental in geoscience. But not all students enjoy equal access to field-based learning because of time, cost, distance, ability, and safety constraints. At the same time, technological advances afford ever more immersive, rich, and student-centered virtual field experiences. Virtual field trips may be the only practical options for most students to explore pedagogically rich but inaccessible places. A mixed-methods research project was conducted on an introductory and an advanced geology class to explore the implications of learning outcomes of in-person and virtual field-based instruction at Grand Canyon National Park. The study incorporated the Great Unconformity in the Grand Canyon, a 1.2 billion year break in the rock record; the Trail of Time, an interpretive walking timeline; and two immersive, interactive virtual field trips (iVFTs). The in-person field trip (ipFT) groups collectively explored the canyon and took an instructor-guided inquiry hike along the interpretive Trail of Time from rim level, while iVFT students individually explored the canyon and took a guided-inquiry virtual tour of Grand Canyon geology from river level. High-resolution 360° spherical images anchor the iVFTs and serve as a framework for programmed overlays that enable interactivity and allow the iVFT to provide feedback in response to student actions. Students in both modalities received pre- and post-trip Positive and Negative Affect Schedules (PANAS). The iVFT students recorded pre- to post-trip increases in positive affect (PA) scores and decreases in negative (NA) affect scores, representing an affective state conducive to learning. Pre- to post-trip mean scores on concept sketches used to assess visualization and geological knowledge increased for both classes and modalities. However, the iVFT pre- to post-trip increases were three times greater (statistically significant) than the ipFT gains. Both iVFT and ipFT students scored 92-98% on guided-inquiry worksheets completed during the trips, signifying both met learning outcomes. Virtual field trips do not trump traditional in-person field work, but they can meet and/or exceed similar learning objectives and may replace an inaccessible or impractical in-person field trip.
ContributorsRuberto, Thomas (Author) / Semken, Steve (Thesis advisor) / Anbar, Ariel (Committee member) / Brownell, Sara (Committee member) / Arizona State University (Publisher)
Created2018
Description
The fundamental photophysics of fluorescent probes must be understood when the probes are used in biological applications. The photophysics of BODIPY dyes inside polymeric micelles and rhodamine dyes covalently linked to proteins were studied. Hydrophobic boron-dipyrromethene (BODIPY) dyes were noncovalently encapsulated inside polymeric micelles. Absorbance and fluorescence measurements were employed to study the photophysics of these BODIPY dyes in the micellar environments. Amphiphilic polymers with a hydrophobic character and low Critical Micelle Concentration (CMC) protected BODIPYS from the aqueous environment. Moderate dye loading conditions did not result in ground-state dimerization, and only fluorescence lifetimes and brightnesses were affected. However, amphiphilic polymers with a hydrophilic character and high CMC did not protect the BODIPYS from the aqueous environment with concomitant ground-state dimerization and quenching of the fluorescence intensity, lifetime, and brightnesses even at low dye loading conditions. At the doubly-labeled interfaces of Escherichia coli (E. coli) DNA processivity β clamps, the interchromophric interactions of four rhodamine dyes were studied: tetramethylrhodamine (TMR), TMR C6, Alexa Fluor 488, and Alexa Fluor 546. Absorbance and fluorescence measurements were performed on doubly-labeled β clamps with singly-labeled β clamps and free dyes as controls. The absorbance measurements revealed that both TMR and TMR C6 readily formed H-dimers (static quenching) at the doubly-labeled interfaces of the β clamps. However, the TMR with a longer linker (TMR C6) also displayed a degree of dynamic quenching. For Alexa Fluor 546 and Alexa Fluor 488, there were no clear signs of dimerization in the absorbance scans. However, the fluorescence properties (fluorescence intensity, lifetime, and anisotropy) of the Alexa Fluor dyes significantly changed when three methodologies were employed to disrupt the doubly-labeled interfaces: 1) the addition of sodium dodecyl sulfate (SDS) detergent to denature the proteins, 2) the addition of clamp loader (γ complex) to open one of the two interfaces, and 3) the use of subunit exchange to decrease the number of dyes per interface. These fluorescence measurements indicated that for the Alexa Fluor dyes, other interchromophoric interactions were present such as dynamic quenching and homo-Förster Resonance Energy Transfer (homo-FRET).
ContributorsDonaphon, Bryan Matthew (Author) / Levitus, Marcia (Thesis advisor) / Van Horn, Wade (Committee member) / Woodbury, Neal (Committee member) / Arizona State University (Publisher)
Created2018
Description
The highly predictable structural and thermodynamic behavior of deoxynucleic acid (DNA) and ribonucleic acid (RNA) have made them versatile tools for creating artificial nanostructures over broad range. Moreover, DNA and RNA are able to interact with biological ligand as either synthetic aptamers or natural components, conferring direct biological functions to the nucleic acid devices. The applications of nucleic acids greatly relies on the bio-reactivity and specificity when applied to highly complexed biological systems.
This dissertation aims to 1) develop new strategy to identify high affinity nucleic acid aptamers against biological ligand; and 2) explore highly orthogonal RNA riboregulators in vivo for constructing multi-input gene circuits with NOT logic. With the aid of a DNA nanoscaffold, pairs of hetero-bivalent aptamers for human alpha thrombin were identified with ultra-high binding affinity in femtomolar range with displaying potent biological modulations for the enzyme activity. The newly identified bivalent aptamers enriched the aptamer tool box for future therapeutic applications in hemostasis, and also the strategy can be potentially developed for other target molecules. Secondly, by employing a three-way junction structure in the riboregulator structure through de-novo design, we identified a family of high-performance RNA-sensing translational repressors that down-regulates gene translation in response to cognate RNAs with remarkable dynamic range and orthogonality. Harnessing the 3WJ repressors as modular parts, we integrate them into biological circuits that execute universal NAND and NOR logic with up to four independent RNA inputs in Escherichia coli.
This dissertation aims to 1) develop new strategy to identify high affinity nucleic acid aptamers against biological ligand; and 2) explore highly orthogonal RNA riboregulators in vivo for constructing multi-input gene circuits with NOT logic. With the aid of a DNA nanoscaffold, pairs of hetero-bivalent aptamers for human alpha thrombin were identified with ultra-high binding affinity in femtomolar range with displaying potent biological modulations for the enzyme activity. The newly identified bivalent aptamers enriched the aptamer tool box for future therapeutic applications in hemostasis, and also the strategy can be potentially developed for other target molecules. Secondly, by employing a three-way junction structure in the riboregulator structure through de-novo design, we identified a family of high-performance RNA-sensing translational repressors that down-regulates gene translation in response to cognate RNAs with remarkable dynamic range and orthogonality. Harnessing the 3WJ repressors as modular parts, we integrate them into biological circuits that execute universal NAND and NOR logic with up to four independent RNA inputs in Escherichia coli.
ContributorsZhou, Yu (Ph.D.) (Author) / Yan, Hao (Thesis advisor) / Green, Alexander (Thesis advisor) / Woodbury, Neal (Committee member) / Ros, Alexandra (Committee member) / Arizona State University (Publisher)
Created2019
Description
The complex life cycle and widespread range of infection of Plasmodium parasites, the causal agent of malaria in humans, makes them the perfect organism for the study of various evolutionary mechanisms. In particular, multigene families are considered one of the main sources for genome adaptability and innovation. Within Plasmodium, numerous species- and clade-specific multigene families have major functions in the development and maintenance of infection. Nonetheless, while the evolutionary mechanisms predominant on many species- and clade-specific multigene families have been previously studied, there are far less studies dedicated to analyzing genus common multigene families (GCMFs). I studied the patterns of natural selection and recombination in 90 GCMFs with diverse numbers of gene gain/loss events. I found that the majority of GCMFs are formed by duplications events that predate speciation of mammal Plasmodium species, with many paralogs being neutrally maintained thereafter. In general, multigene families involved in immune evasion and host cell invasion commonly showed signs of positive selection and species-specific gain/loss events; particularly, on Plasmodium species is the simian and rodent clades. A particular multigene family: the merozoite surface protein-7 (msp7) family, is found in all Plasmodium species and has functions related to the erythrocyte invasion. Within Plasmodium vivax, differences in the number of paralogs in this multigene family has been previously explained, at least in part, as potential adaptations to the human host. To investigate this I studied msp7 orthologs in closely related non-human primate parasites where homology was evident. I also estimated paralogs’ evolutionary history and genetic polymorphism. The emerging patterns where compared with those of Plasmodium falciparum. I found that the evolution of the msp7 multigene family is consistent with a Birth-and-Death model where duplications, pseudogenization and gene lost events are common. In order to study additional aspects in the evolution of Plasmodium, I evaluated the trends of long term and short term evolution and the putative effects of vertebrate- host’s immune pressure of gametocytes across various Plasmodium species. Gametocytes, represent the only sexual stage within the Plasmodium life cycle, and are also the transition stages from the vertebrate to the mosquito vector. I found that, while male and female gametocytes showed different levels of immunogenicity, signs of positive selection were not entirely related to the location and presence of immune epitope regions. Overall, these studies further highlight the complex evolutionary patterns observed in Plasmodium.
ContributorsCastillo Siri, Andreina I (Author) / Rosenberg, Michael (Thesis advisor) / Escalante, Ananias (Committee member) / Taylor, Jesse (Committee member) / Collins, James (Committee member) / Arizona State University (Publisher)
Created2016
Description
Humanity’s demand for energy is increasing exponentially and the dependence on fossil fuels is both unsustainable and detrimental to the environment. To provide a solution to the impending energy crisis, it is reasonable to look toward utilizing solar energy, which is abundant and renewable. One approach to harvesting solar irradiation for fuel purposes is through mimicking the processes of natural photosynthesis in an artificial design to use sunlight and water to store energy in chemical bonds for later use. Thus, in order to design an efficient energy conversion device, the underlying processes of the natural system must be understood. An artificial photosynthetic device has many components and each can be optimized separately. This work deals with the design, construction and study of some of those components. The first chapter provides an introduction to this work. The second chapter shows a proof of concept for a water splitting dye sensitized photoelectrochemical cell followed by the presentation of a new p-type semiconductor, the design of a modular cluster binding protein that can be used for incorporating catalysts, and a new anchoring group for semiconducting oxides with high electron injection efficiency. The third chapter investigates the role of electronic coupling and thermodynamics for photoprotection in artificial systems by triplet-triplet energy transfer from tetrapyrroles to carotenoids. The fourth chapter describes a mimic of the proton-coupled electron transfer in photosystem II and confirms that in the artificial system a concerted mechanism operates. In the fifth chapter, a microbial system is designed to work in tandem with a photovoltaic device to produce high energy fuels. A variety of quinone redox mediators have been synthesized to shuttle electrons from an electron donor to the microbial system. Lastly, the synthesis of a variety of photosensitizers is detailed for possible future use in artificial systems. The results of this work helps with the understanding of the processes of natural photosynthesis and suggests ways to design artificial photosynthetic devices that can contribute to solving the renewable energy challenge.
ContributorsBrown, Chelsea L (Author) / Moore, Ana L (Thesis advisor) / Gust, Devens (Committee member) / Woodbury, Neal (Committee member) / Arizona State University (Publisher)
Created2015