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Structure, Formation, And Mechanics Of Nanofibrillar Spider Silk
No full textSpider silk rivals the best synthetic materials in terms of strength and toughness. It is widely accepted that these properties arise from its internal structure. Despite extensive research, comprehensive experimental evidence of formation, morphology, mechanics, and the protein makeup of its internal structures are still limited, controversially discussed, or not studied at all. First, we report the complete mechanical decomposition of natural silk fibers from golden silk orb-weaver into ≈10 nm-diameter nanofibrils, the material’s apparent fundamental building blocks. Also, we produced nanofibrils of virtually identical morphology by triggering an intrinsic self-assembly mechanism of silk proteins. By analyzing protein self-assembly, we revealed independent physico-chemical fibrillation triggers which assemble proteins from stored precursors “at-will”. We also presented the first evidence-based structural model for spider silk fibers. According to our experimental work determining the nanofibrillar structure of spider silk, nanofibrils tend to align parallel to the fiber (axial) direction. The axially oriented nanofibrillar structure of spider silk gives rise to a significant mechanical anisotropy. This mechanical anisotropy is extremely difficult to quantify, especially for microscopically small materials such as spider silk, but has the potential to reveal important knowledge about the material’s structure-property relationships. We developed a novel method utilizing atomic force microscope (AFM) nanoindentations and finite element analysis (FEA) to characterize the mechanical anisotropy of such systems. We successfully used this method to measure the mechanics of nonfibrillar silk ribbons of the Chilean recluse spider, revealing the tensile and transverse elastic moduli as 9 GPa and 1 GPa, respectively, and the binding strength between silk nanofibrils as 159 ± 13 MPa. Furthermore, based on this binding strength, we derived the nanofibrils’ surface energy, as 37 mJ/m2, and also, found van der Waals forces play a decisive role in inter-fibrillar binding. Due to its versatility, our novel nanoindentation technique has many potential applications including early disease diagnostics, based on the mechanical properties of soft tissues. The impressive mechanical properties of spider silk nanofibrils can be further understood by studying their secondary protein structure, especially in the presence of fiber strain. We conducted strain-dependent Raman spectroscopy on nanofibrillar recluse silk and observed strain-dependent red shift in amide III protein band and strain-induced relative peak height changes in amide I/II/II bands. A wealth of knowledge about the behavior of protein secondary structures in the presence of fiber strain can be extracted by decomposing the amide bands into their subpeaks which correspond to each of the secondary protein structures. This extensive investigation of the structure, formation, and mechanics of nanofibrillar spider silk furthers our understanding of this exceptional material, and ultimately, leads us toward the realization of high-performance silk-based materials.Applied ScienceDoctor of Philosophy (Ph.D.
“Deforesting the ‘Princely Trunk:’ Deforestation and Invasion in Shakespeare’s Plays”
No full textCaliban spends Shakespeare’s Tempest “fetch[ing] in [Prospero’s] wood” (Shakespeare, 1.2.311-312) from a place where there’s “neither bush nor scrub” (2.2.18) to a place surrounded by a “grove” (5.1.10) while Ferdinand suffers under “wooden slavery” (3.1.63) as a “patient log-man” (3.1.67) who enters “bearing” (3.1.1sd) one of “thousands of…logs” (3.1.10) to be burned green (3.1.19) in order to heat but a “poor cell” (1.2.20). But what are the implications of this deforestation? This thesis argues that Shakespeare employs arboreal image patterns to situate colonial power dynamics in The Tempest and that Shakespeare’s treatment of logs in The Tempestis the culmination of his treatment of moving trees in Caliban spends Shakespeare’s Tempest “fetch[ing] in [Prospero’s] wood” (Shakespeare, 1.2.311-312) from a place where there’s “neither bush nor scrub” (2.2.18) to a place surrounded by a “grove” (5.1.10) while Ferdinand suffers under “wooden slavery” (3.1.63) as a “patient log-man” (3.1.67) who enters “bearing” (3.1.1sd) one of “thousands of…logs” (3.1.10) to be burned green (3.1.19) in order to heat but a “poor cell” (1.2.20). But what are the implications of this deforestation? This thesis argues that Shakespeare employs arboreal image patterns to situate colonial power dynamics in The Tempest and that Shakespeare’s treatment of logs in The Tempest is the culmination of his treatment of moving trees in Macbeth and that of the rooted forest in As You Like It. I ultimately argue that Shakespeare offers a critique of deforestation used to reinforce political power. The thesis traces the progression between these plays in their own early modern ecological contexts and extends that progression forward into the 21st century, both on stage in a production of The Tempest and off stage in the context of postcolonial power dynamics and deforestation.EnglishBachelors of Arts (BA
Upending student expectations: Enhancing classroom learning and engagement with levity, dialogue, and storytelling
No full textThe Faces Of Substance Use: A Reverse Correlation Analysis Of Perceptions Of Alcohol And Cannabis Use
Get PDFAlcohol and cannabis are some of the most ubiquitous substances on college campuses. While the reason for use varies between each individual, from social lubricant to sleeping aid, nearly half of higher-education students endorse alcohol and/or cannabis use in the last month. Despite this popularity, there is still a deeply ingrained level of stigma around substance use and substance use disorders and people who use substances or struggle with substance use disorders are subject to a litany of damaging perceptions, such as being deemed violent, unpredictable, weak, and untrustworthy.. Most research on the stereotypic thinking surrounding substance use focuses on explicit judgements about the moral character of users. However, to the best of our knowledge, there is little information about the implicit judgements and perceptions of people who use substances. Humans glean vast amounts of information just from looking at another person’s face and the fluency of that processing often leads to fallible judgments. Do you know what a person with substance use disorder looks like? Are there characteristics in a person’s appearance that may lend themselves to being identified as a user or nonuser of substances? The purpose of this study is to determine the implicit visual characteristics that are part of the implicit perceptual biases regarding substance use — the primary aims being (1) create proxies of the mental representations of alcohol and cannabis users in a reverse correlation paradigm and (2) determine if there are common properties within the images generated that can be used to discriminate between substance type and use status. The results revealed that implicit perceptual biases regarding substance were rooted in gender differences with masculinity being strongly associated with substance use. Interestingly, the implicit perceptual biases related to the type of drug used (alcohol or cannabis) was less rooted in gender biases but defined more by dimensions of race and personality. These findings confirm that there are implicit biases related to substance use and demonstrate that these biases may be unique to different substance types.PsychologyMaster of Science (M.Sc.
Spatial and spatio-temporal epidemiological approaches to inform COVID-19 surveillance and control: a systematic review of statistical and modelling methods in Africa
No full textObjective Various studies have been published to better understand the underlying spatial and temporal dynamics of COVID-19. This review sought to identify different spatial and spatio-temporal modelling methods that have been applied to COVID-19 and examine influential covariates that have been reportedly associated with its risk in Africa. Design Systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Data sources Thematically mined keywords were used to identify refereed studies conducted between January 2020 and February 2022 from the following databases: PubMed, Scopus, MEDLINE via Proquest, CINHAL via EBSCOhost and Coronavirus Research Database via ProQuest. A manual search through the reference list of studies was also conducted. Eligibility criteria for selecting studies Peer-reviewed studies that demonstrated the application of spatial and temporal approaches to COVID-19 outcomes. Data extraction and synthesis A standardised extraction form based on critical appraisal and data extraction for systematic reviews of prediction modelling studies checklist was used to extract the meta-data of the included studies. A validated scoring criterion was used to assess studies based on their methodological relevance and quality. Results Among 2065 hits in five databases, title and abstract screening yielded 827 studies of which 22 were synthesised and qualitatively analysed. The most common socioeconomic variable was population density. HIV prevalence was the most common epidemiological indicator, while temperature was the most common environmental indicator. Thirteen studies (59%) implemented diverse formulations of spatial and spatio-temporal models incorporating unmeasured factors of COVID-19 and the subtle influence of time and space. Cluster analyses were used across seven studies (32%) to explore COVID-19 variation and determine whether observed patterns were random. Conclusion COVID-19 modelling in Africa is still in its infancy, and a range of spatial and spatio-temporal methods have been employed across diverse settings.Kinesiology & Health Science
Captain Sinclair's Recreational Area Living Shoreline and Oyster Restoration
No full textPresentation report on Captain Sinclair's Recreational Area Living Shoreline and Oyster Restoration project. Project awarded 2023 ASBPA Best Restored Shore awardVirginia Institute of Marine Scienc
Mapping a Terrapin Town
No full textGrade Level: 7th Grade Life Science and Environmental Science In small groups, students will explore diamondback terrapin habitat requirements, conservation, and how land use planning can affect their population
Sleep and Early Childhood Stressors in College Students: Examining Alcohol Use as a Moderator
No full textEarly childhood stressors (ECS) consist of certain emotional, physical, or sexual experiences that may have long term consequences including sleep problems. Previous research has also found that alcohol use can negatively affect sleep; however, few studies have investigated alcohol use as a moderator of the relationship between sleep and other variables. In the current study, we examined whether the relationship between a general measure of ECS and sleep in college students may be moderated by alcohol use, a common psychoactive substance among this age group. Additionally, we examined this model with emotional abuse and neglect as a measure of ECS. Seventy-three undergraduate students wore an Actiwatch for approximately one week to measure sleep quality (i.e., sleep latency and wake after sleep onset). Throughout this time, participants also completed daily diaries to assess sleep duration. Participants also responded to the Childhood Trauma Questionnaire (CTQ) and the Alcohol Use Disorder Identification Test (AUDIT). In contrast to our predictions, alcohol use did not moderate the relationship between general ECS and sleep, or the relationship between the combined emotional abuse and neglect scales and sleep. Future research on the moderating effect of alcohol use within the relationship between ECS and sleep should be done with a larger and more diverse sample. Additionally, future research should consider measuring use of alcohol as a coping strategy for ECS, and sleep outcomes that may be associated with this specific form of alcohol use.PsychologyBachelors of Arts (BA