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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2023)

Robots that operate in natural environments encounter diverse terrains, ranging from solid ground to granular materials like sand and even full liquids. Various types of robots, including wheeled and legged robots, have been designed to excel in specific domains. Screw-based locomotion is a promising approach for multi-domain mobility, and has been leveraged for amphibious vehicle and robotic designs. Additionally, a snake-like architecture has led to extremely versatile exploratory robots. However, there is limited understanding of the models, parameter effects, and efficiency for multi-terrain Archimedes screw locomotion, and many snake-like robot still face certain limitations.

In this work, we present the design of a mobile test bed, a method to quantitatively study screw-based locomotion across a wide variety of real-world environments. Our mobile test bed enables indoor and outdoor experimentation, including water tests, to collect data on screw performance. We present experimental results and performance analysis across different media, and analyze the performance of different screw designs to inform optimal design choices.Furthermore, we construct an amphibious screw-propelled snake robot to demonstrate the mobility of screw-based locomotion. The robot is capable of traversing different terrains while maintaining stability and maneuverability. Our experimental results show that screw-based locomotion is effective in multi-domain mobility and can be optimized with specific screw designs. Our findings provide valuable insights into the performance and design of screw-based locomotion for future researchers and engineers. We envision that our results can inform the development of effective screw-based locomotion systems for a range of applications.

    Cover page: Amphibious Locomotion with a Screw-propelled Snake-like Robot
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2015)
    Bacterial pathogens stimulate periodontitis, the most common osteolytic disease in humans and the most common cause of tooth loss in adults. Previous studies identified leukocytes and their products as key factors in this process. We demonstrate for the first time that osteoblast lineage cells play a critical role in periodontal disease. Oral infection stimulated nuclear localization of NF-κB in osteoblasts and osteocytes in the periodontium of wild type but not transgenic mice that expressed a lineage specific dominant negative mutant of IKK (IKK-DN) in osteoblast lineage cells. Wild-type mice were also susceptible to bacteria induced periodontal bone loss but transgenic mice were not. The lack of bone loss in the experimental group was linked to reduced RANKL expression by osteoblast lineage cells that led to diminished osteoclast mediated bone resorption and greater coupled new bone formation. The results demonstrate that osteoblast lineage cells are key contributors to periodontal bone loss through an NF-κB mediated mechanism.
      Cover page: Osteoblast Lineage Cells Play an Essential Role in Periodontal Bone Loss Through Activation of Nuclear Factor-Kappa B
      • Article
      • Peer Reviewed
      UC San Francisco Previously Published Works (2015)

      Objective

      To examine whether the presence of sleep-disordered breathing (SDB) is associated with an earlier age at mild cognitive impairment (MCI) or Alzheimer disease (AD)-dementia onset in participants from the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort. We also examined whether continuous positive airway pressure (CPAP) use is associated with delayed onset of cognitive decline.

      Methods

      From the ADNI cohort, 3 subsets with progressively stringent criteria were created in a step-wise manner. Age at MCI or AD-dementia onset was the main outcome variable. Analyses were performed separately for each subset in untreated SDB+ vs SDB- and untreated SDB+ vs CPAP+ groups. Chi-square and t tests were performed to examine between-group differences. Survival analyses were performed using the Kaplan-Meier method, compared by the log-rank test, and assessed by multivariate Cox regression adjusting for potential confounders.

      Results

      SDB+ patients had a younger age at MCI onset in all subsets (MC1: 72.63 vs 83.67; MC2: 72.15 vs 83.45; MC3: 77.40 vs 89.89; p < 0.01). SDB+ patients had a younger age at AD-dementia onset only in our most conservative subset (AC3: 83.46 vs 88.13; p < 0.05). In a combined outcome analysis, SDB+ patients had a younger age at onset to MCI or AD-dementia in all subsets. In subsets 1 and 2, CPAP use delayed the age at MCI onset (CMC1: 72.63 vs 82.10; CMC2: 72.11 vs 82.10; p < 0.01).

      Conclusions

      Consistent with our hypothesis, the presence of SDB was associated with an earlier age at cognitive decline. Our findings in CPAP+ participants suggest that CPAP treatment of SDB may delay progression of cognitive impairment.
        Cover page: Sleep-disordered breathing advances cognitive decline in the elderly
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