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The Spinnaker Limited A Freshman\u27s Guide to Everything UNF
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Investigating the role of tesserae in energy absorption in shark cartilage
Get PDFUnlike mammals, shark endoskeletons are composed of cartilage, which is less stiff compared to bone. Despite this structural disadvantage, sharks have risen to become apex predators, with reported maximum posterior bite force estimates approximating 5914 N in bull sharks. Shark jaws are estimated to undergo high cycle loading within the organism’s lifecycle without evidence of failure. Fatigue resistance may relate to mineral distribution within a component of the endoskeletal system – tesserae. Tesserae are thin, roughly hexagonal tiles composed of calcium phosphate hydroxyapatite (HA) crystals and grow by accretion to eventually surround the hyaline cartilage core. Though tesserae dimensions are variable, they are reported to be on average 500 µm across and 250 µm thick. Ultrastructure characterization using backscatter electron imaging and micro-computed tomography (µ-CT) have revealed regions consist of oscillating layers of high and low calcium concentrations, referred to as spoke regions. Though mechanical behavior of the bulk material has been examined, an investigation into the mechanics of spoke regions has been limited due to the microscale of these structures. The objective of this research was to design and manufacture tesserae models mimicking material gradients in the spoke regions that could be optically resolved during mechanical testing to investigate regional variation in strain. Finite element analysis (FEA) of the models was utilized to further examine stress evolution within regions. It was hypothesized that the spoke structures may reduce long-range stress in the skeletal element, and under compressive loading would exhibit variable strain related to regional material composition. Mechanical testing and simulation indicated that the addition of neighboring tiles resulted in stress flow between adjacent tiles regardless of orientation to loading direction. Results further indicated that an ideal proportion of high- and low-modulus material exists in the spoke-like structures such that stress concentrations are mitigated, and strain in spoke-structures is minimized
Transformer-enabled deep reinforcement learning for coverage path planning
Get PDFCoverage path planning (CPP) is the problem of covering all points in an environment and is a well-researched topic in robotics due to its sheer practical relevance. This paper investigates such an offline CPP problem where the primary objective is to minimize the path length to achieve complete coverage. Furthermore, the literature suggests that taking turns leads to a higher energy use than going straight. To this end, we design a novel objective function that aims to minimize the number of turns as well. We have proposed a deep reinforcement learning (DRL)-based framework that uses a Transformer model. Unlike state-of-the-art reinforcement learning-based CPP solutions that primarily use convolutional neural networks, Transformers need a minimal number of inductive biases for their design. We tested our proposed Transformer-based DRL framework on seven 8x8 environments with varying numbers and shapes of obstacles under fully and partially observable settings. Experimental results show that our proposed solution outperforms Breadth-first search coverage solutions in terms of the number of steps and turns needed to yield 100% coverage. Furthermore, when compared to a comparable deep Q-network-based CPP technique that uses a convolutional neural network, our proposed approach always converges to higher coverage percentages and lower turn counts
Functional investigation of shaggy, an inhibitor of canonical Wnt signaling, in the tardigrade Hypsibius exemplaris
Get PDFTardigrades have a highly simplified anteroposterior (AP) axis. The mechanisms that regulate the development of this secondarily simplified AP axis are not known. In many animals, the canonical Wnt (cWnt) signaling pathway regulates primary axis establishment through antagonistic interactions with inhibitors of cWnt signaling. This study investigated the roles of shaggy, an inhibitor of cWnt signaling, in regulating development in the tardigrade Hypsibius exemplaris. Gene expression patterns of shaggy and other components of the cWnt signaling pathway were analyzed alongside markers of anterior and posterior identity using Hybridization Chain Reaction in situ in H. exemplaris. RNA interference targeting shaggy resulted in tardigrades with a variety of defects, including anterior defects, elongation defects, AP axis duplications, and everted hindguts. Most of these specimens experienced stalled development at the elongation stage, a stage during which the AP axis normally forms. Additionally, six3, a marker of anterior fate was either lost or reduced while caudal, a marker of posterior identity, was expressed ectopically in some shaggy RNAi specimens. These data may reflect a role of shaggy in regulating AP axis development by regulating anterior fate, a function that is conserved in most other bilaterians investigated. Shaggy RNAi also produced segmentation defects that ranged from minor fusions between segments to the loss of several segments. Shaggy regulates segmentation in insects. Therefore, the segmentation defects recovered in H. exemplaris could represent a conserved segmentation role of shaggy. In summary, shaggy regulates the development of key features of the highly derived tardigrade body plan
Examining potential causal associations of sedentary time and physical activity with heart failure using subjective and objective measures: A mendelian randomization analysis
Get PDFPurpose: The objective of this study was to assess the causal relationship between both subjectively and objectively measured sedentary time (ST) and physical activity (PA) with heart failure (HF) risk, utilizing Mendelian Randomization (MR) approach.
Methods: The present MR used genetic instruments identified for self-reported ST and PA extracted from 51 genome wide association studies (GWAS), encompassing data from 703,901 individuals. The GWAS identified 89 independent single nucleotide polymorphisms (SNPs) associated with leisure screen time. Eleven loci were reported to be associated with moderate to vigorous physical activity (MVPA). From another GWAS examining accelerometer-based activities, three loci were found to be associated with PA and four with ST. Outcome HF data were extracted from a GWAS HF including cases and controls. Univariable MR estimates were obtained using various methods including MR-Egger, inverse variance weighted (IVW), weighted median, simple mode, and weighted mode.
Results: The results from univariable MR analysis showed a significant association of genetically-predicted ST with an increased risk of HF. However, this association was not supported across all sensitivity analyses (P \u3e0.05 for all). Results also showed a significant association of genetically-predicted PA with increased risk of HF. This association was not supported when utilizing different sensitivity analyses (P \u3e0.05 for all). Results demonstrate a potential positive association between objectively measured ST and HF risk across all methods. A potential negative association between objectively measured PA and HF risk was also discovered. Conclusions: The findings suggest a significant causal relationship between self-reported ST and increased HF risk, supported by univariate MR analysis using the IVW method. However, the association was attenuated under different sensitivity analyses, and when utilizing objectively measured ST. Similarly, while there is indication of a potential protective effect of physical activity against HF, inconsistencies among sensitivity analyses warrant cautious interpretation
Navigating unknown complexities: School superintendent perspectives of leading during COVID
Get PDFThe COVID-19 pandemic has presented unprecedented challenges for educational leaders, particularly superintendents, who have been tasked with navigating the complexities of leading during a global crisis. In this study I explored the perspectives of superintendents on leading during COVID-19 and examined the application of Complexity Leadership Theory in educational settings. Through semi-structured interviews with superintendents from diverse districts, I investigated the strategies and approaches employed by educational leaders to address the multifaceted challenges posed by the pandemic. I also examined the impact of Complexity Leadership Theory on educational practices and outcomes during the pandemic. The findings suggest that superintendents have adopted adaptive, collaborative, and innovative leadership practices informed by Complexity Leadership Theory to address the dynamic and unpredictable nature of the pandemic. The study contributes to the understanding of effective educational leadership and highlights the importance of Complexity Leadership Theory in action
Potentiating effects of interim tests and metacognitive judgments on future learning
No full textInterpolated tests benefit retention of both tested material and material learned afterward. One proposed mechanism for the potentiating effect of testing involves the learner gleaning metacognitive information from tests regarding how well the material is being learned, curbing overconfidence and influencing future encoding strategies. The current study investigated whether making judgments of learning (JOLs) may similarly induce metacognitive introspection and benefit learning. An online sample of 464 adults from the United States was randomly assigned to one of three interim task conditions and one of three JOL conditions that determined how they would interact with each of the four text passage sections they read. Participants either made no JOLs, one JOL, or four JOLs, and either restudied, completed a test, or completed a brief filler task after each section. All participants were tested on the final section. Analyses revealed that participants who were tested on previous sections performed better on a test of the final section than those who were not tested. Though there was no significant interaction between interim task and JOL conditions, exploratory analyses found that eliciting JOLs eliminated the potentiating effects of testing under certain conditions. Eliciting JOLs may influence future memory and may not be a neutral event in retrieval practice contexts. Future studies are recommended to determine the boundary conditions of JOL reactivity in testing paradigms
Paper, Diet Suggestions for the Growing Child Paper
Get PDFDocument: Typed paper listing diet suggestions for a growing child. Handwritten note on back. Undated
Membership Drive Form, Colored Branch Young Woman Christian Association
Get PDFForm: Blank membership form and membership fee pledge for Y.W.C.A., Jacksonville, Florida. Undated
Zadar
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