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Open Access Publications from the University of California

Scholarly Works (7 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2010)
The study on using nanoporous materials for harvesting water from the environment is still in its early stage, involving multiple methodologies, materials, and levels of technology. Insight on several experimentally novel directions shed light on the challenges and prospects associated with atmospheric condensation behavior, pressurized filtration, and ion adsorption on various nanoporous materials. The condensation of water throughout the surface of a porous cylinder was found to be difficult to extract in large quantities. In pressurized filtration, zeolites exhibit ion exclusion effects. It is also found that nanoporous carbon discs have a relatively low capacity of adsorption which is one order of magnitude insufficient to achieve a detectable decrease in solution salinity
    Cover page: Feasibility of using nanoporous materials in water harvesting
    • Thesis
    • Peer Reviewed
    UC San Diego Electronic Theses and Dissertations (2016)

    Sustainable habitat construction on the Moon and Mars focuses on in situ resource utilization (ISRU) to produce infrastructural materials while minimizing recurring supplies from Earth. The current study first explores uniaxial compaction of the soil simulants JSC-1A and JSC Mars-1a with binders. Solvents, monomer polymerization, and melt-compression are investigated for mixing binders with simulants. Results and challenges pertaining to each method are discussed. The second and main part of the current study investigates uniaxial compaction of Mars-1a and montmorillonite without binders. Experimental parameters include initial particle size, compression pressure, lateral boundary condition, and rate of loading. Mechanical strength of compacts is determined via three-point bending flexural strength. The applied compression pressure and lateral boundary condition strongly influence resultant strengths, while initial particle size and rate of loading exhibit more subtle effects. High compression pressures with reduced lateral boundaries generate ~30MPa flexural strength, stronger than a typical steel-reinforced concrete. A smaller initial particle size achieves higher strength. Impact loading of Mars-1a samples achieves marginally higher flexural strength compared to a given peak pressure in the quasi-static case, while montmorillonite shows no such difference. For the former, enhanced particle motion and phase transformation during impact may account for the higher strength. A given impact energy leads to similar flexural strengths regardless of variations in hammer mass or velocity. Characterization using thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, CHNS/O elemental analysis, and evolved gas analysis corroborates the notion that a high specific surface develops secondary bonding responsible for strength. Characterization also rules out possible roles for trace water or organic matter on compaction strengthening. Compaction of analogue materials points toward nanoparticulate iron oxides as the agent of strengthening in Mars-1a. Measured nitrogen permeability suggests the solids are akin to dense rocks. Volumetric energy efficiency is estimated at 0.3-0.4GJ/m3, or about one order of magnitude lower than thermal processes. The compaction process is expected to be scalable and portable to extant or emergent prototyping technologies.

      Cover page: Forming Infrastructural Materials by Mechanical Compaction of Lunar and Martian Regolith Simulants
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2017)
      Martian habitats are ideally constructed using only locally available soils; extant attempts to process structural materials on Mars, however, generally require additives or calcination. In this work we demonstrate that Martian soil simulant Mars-1a can be directly compressed at ambient into a strong solid without additives, highlighting a possible aspect of complete Martian in-situ resource utilization. Flexural strength of the compact is not only determined by the compaction pressure but also significantly influenced by the lateral boundary condition of processing loading. The compression loading can be applied either quasi-statically or through impact. Nanoparticulate iron oxide (npOx), commonly detected in Martian regolith, is identified as the bonding agent. Gas permeability of compacted samples was measured to be on the order of 10-16 m2, close to that of solid rocks. The compaction procedure is adaptive to additive manufacturing.
        Cover page: Direct Formation of Structural Components Using a Martian Soil Simulant
        • Article
        • Peer Reviewed
        UC Santa Barbara Previously Published Works (2014)
        Optogenetic tools enable examination of how specific cell types contribute to brain circuit functions. A long-standing question is whether it is possible to independently activate two distinct neural populations in mammalian brain tissue. Such a capability would enable the study of how different synapses or pathways interact to encode information in the brain. Here we describe two channelrhodopsins, Chronos and Chrimson, discovered through sequencing and physiological characterization of opsins from over 100 species of alga. Chrimson's excitation spectrum is red shifted by 45 nm relative to previous channelrhodopsins and can enable experiments in which red light is preferred. We show minimal visual system-mediated behavioral interference when using Chrimson in neurobehavioral studies in Drosophila melanogaster. Chronos has faster kinetics than previous channelrhodopsins yet is effectively more light sensitive. Together these two reagents enable two-color activation of neural spiking and downstream synaptic transmission in independent neural populations without detectable cross-talk in mouse brain slice.
          Cover page: Independent optical excitation of distinct neural populations
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2023)
          The Infectious Diseases Society of America (IDSA) has set clear priorities in recent years to promote inclusion, diversity, access, and equity (IDA&E) in infectious disease (ID) clinical practice, medical education, and research. The IDSA IDA&E Task Force was launched in 2018 to ensure implementation of these principles. The IDSA Training Program Directors Committee met in 2021 and discussed IDA&E best practices as they pertain to the education of ID fellows. Committee members sought to develop specific goals and strategies related to recruitment, clinical training, didactics, and faculty development. This article represents a presentation of ideas brought forth at the meeting in those spheres and is meant to serve as a reference document for ID training program directors seeking guidance in this area.
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2020)
            Remediation of struggling learners is a challenge faced by all educators. In recognition of this reality, and in light of contemporary challenges facing infectious diseases (ID) fellowship program directors, the Infectious Diseases Society of America Training Program Directors' Committee focused the 2018 National Fellowship Program Directors' Meeting at IDWeek on "Remediation of the Struggling Fellow." Small group discussions addressed 7 core topics, including feedback and evaluations, performance management and remediation, knowledge deficits, fellow well-being, efficiency and time management, teaching skills, and career development. This manuscript synthesizes those discussions around a competency-based framework to provide program directors and other educators with a roadmap for addressing common contemporary remediation challenges.
              Cover page: The Struggling Infectious Diseases Fellow: Remediation Challenges and Opportunities
              • Article
              • Peer Reviewed
              UC San Diego Previously Published Works (2023)

              Background

              While vaccines have established utility against COVID-19, phase 3 efficacy studies have generally not comprehensively evaluated protection provided by previous infection or hybrid immunity (previous infection plus vaccination). Individual patient data from US government-supported harmonized vaccine trials provide an unprecedented sample population to address this issue. We characterized the protective efficacy of previous SARS-CoV-2 infection and hybrid immunity against COVID-19 early in the pandemic over three-to six-month follow-up and compared with vaccine-associated protection.

              Methods

              In this post-hoc cross-protocol analysis of the Moderna, AstraZeneca, Janssen, and Novavax COVID-19 vaccine clinical trials, we allocated participants into four groups based on previous-infection status at enrolment and treatment: no previous infection/placebo; previous infection/placebo; no previous infection/vaccine; and previous infection/vaccine. The main outcome was RT-PCR-confirmed COVID-19 >7-15 days (per original protocols) after final study injection. We calculated crude and adjusted efficacy measures.

              Findings

              Previous infection/placebo participants had a 92% decreased risk of future COVID-19 compared to no previous infection/placebo participants (overall hazard ratio [HR] ratio: 0.08; 95% CI: 0.05-0.13). Among single-dose Janssen participants, hybrid immunity conferred greater protection than vaccine alone (HR: 0.03; 95% CI: 0.01-0.10). Too few infections were observed to draw statistical inferences comparing hybrid immunity to vaccine alone for other trials. Vaccination, previous infection, and hybrid immunity all provided near-complete protection against severe disease.

              Interpretation

              Previous infection, any hybrid immunity, and two-dose vaccination all provided substantial protection against symptomatic and severe COVID-19 through the early Delta period. Thus, as a surrogate for natural infection, vaccination remains the safest approach to protection.

              Funding

              National Institutes of Health.
                Cover page: Risk of COVID-19 after natural infection or vaccination
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