Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (39 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2019)

An innovative idea that ferromagnetic resonance (FMR) can be utilized to improve the radiation efficiency and input impedance matching for electrically small antennas (ESAs) simultaneously is proposed. This idea is inspired by the recent discovery that using magnetic materials with extremely large imaginary permeability can still achieve high radiation efficiency in designs of ESAs. The equation of radiation efficiency for ESAs as a function of ferrites’ complex permeability is re-derived based on the field modeling and analysis of an ideal thin-film ferrite radiator to verify the discovery. Furthermore, taking FMR into consideration, a conclusion is made that the gilbert damping factor of the resonance determines radiation efficiency more essentially than of ferrites. The first practical design for the proposed FMR enhanced ESAs has been realized through a modified, small single loop antenna loaded with a thin-film yttrium-iron-garnet (YIG) core. A real physical prototype has been fabricated and evaluated through both full-wave simulations and experiments. The simulation results match to the experimental results, demonstrating the efficacy and significance of the idea. Novel frequency-independent, equivalent circuit models for small loops and FMR enhanced ESAs have been developed in this paper to guide the design of highly efficient ESAs in the future. The circuit models prove to be trustworthy in predicting input impedance and radiation efficiency by comparing with full-wave simulations and agreed.

    Cover page: Ferromagnetic Resonance Enhanced Electrically Small Antennas
    • Thesis
    • Peer Reviewed
    UCLA Electronic Theses and Dissertations (2016)

    A broadband dynamic method for characterizing thin film magnetic material is presented. The method is designed to extract the permeability and linewidth of thin magnetic films from measuring the reflection coefficient (S11) of a house-made and short-circuited strip line testing fixture with or without samples loaded. An adaptive de-embedding method is applied to remove the parasitic noise of the housing. The measurements were carried out with frequency up to 10GHz and biasing magnetic fields up to 600 Gauss. Particular measurement setup and 3-step experimental procedures are described in detail. The complex permeability of a 330nm thick continuous FeGaB, 435nm thick laminated FeGaB film and a 100nm thick NiFe film will be induced dynamically in frequency-biasing magnetic field spectra and compared with a theoretical model based on Landau-Lifshitz-Gilbert (LLG) equations and eddy current theories. The ferromagnetic resonance (FMR) phenomenon can be observed among these three magnetic materials investigated in this thesis.

      Cover page: Dynamic Characterization of Thin Film Magnetic Materials
      • Article
      • Peer Reviewed
      UC San Francisco Previously Published Works (2019)
      Nearly all infectious agents contain DNA or RNA genomes, making sequencing an attractive approach for pathogen detection. The cost of high-throughput or next-generation sequencing has been reduced by several orders of magnitude since its advent in 2004, and it has emerged as an enabling technological platform for the detection and taxonomic characterization of microorganisms in clinical samples from patients. This review focuses on the application of untargeted metagenomic next-generation sequencing to the clinical diagnosis of infectious diseases, particularly in areas in which conventional diagnostic approaches have limitations. The review covers ( a) next-generation sequencing technologies and common platforms, ( b) next-generation sequencing assay workflows in the clinical microbiology laboratory, ( c) bioinformatics analysis of metagenomic next-generation sequencing data, ( d) validation and use of metagenomic next-generation sequencing for diagnosing infectious diseases, and ( e) significant case reports and studies in this area. Next-generation sequencing is a new technology that has the promise to enhance our ability to diagnose, interrogate, and track infectious diseases.
        Cover page: Clinical Metagenomic Next-Generation Sequencing for Pathogen Detection
        • Article
        • Peer Reviewed
          Cover page: Hashimoto’s Thyroiditis in children and adolescents: at presentation and during long-term follow up
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2022)
            Creative Commons 'BY' version 4.0 license
            • Article
            • Peer Reviewed
            UC San Francisco Previously Published Works (2013)
            It is widely accepted that different forms of stress activate a common target, p53, yet different outcomes are triggered in a stress-specific manner. For example, activation of p53 by genotoxic agents, such as camptothecin (CPT), triggers apoptosis, while non-genotoxic activation of p53 by Nutlin-3 (Nut3) leads to cell-cycle arrest without significant apoptosis. Such stimulus-specific responses are attributed to differential transcriptional activation of various promoters by p53. In this study, we demonstrate that CPT, but not Nut3, induces miR-203, which downregulates anti-apoptotic bcl-w and promotes cell death in a p53-dependent manner. We find that acetylation of K120 in the DNA-binding domain of p53 augments its association with the Drosha microprocessor and promotes nuclear primary miRNA processing. Knockdown of human orthologue of Males absent On the First (hMOF), the acetyltransferase that targets K120 in p53, abolishes induction of miR-203 and cell death mediated by CPT. Thus, this study reveals that p53 acetylation at K120 plays a critical role in the regulation of the Drosha microprocessor and that post-transcriptional regulation of gene expression by p53 via miRNAs plays a role in determining stress-specific cellular outcomes.
              Cover page: Acetylation of p53 stimulates miRNA processing and determines cell survival following genotoxic stress
              • Article
              • Peer Reviewed
              UC San Francisco Previously Published Works (2020)
              In early-to-mid March 2020, 20 of 46 (43%) COVID-19 cases at a tertiary care hospital in San Francisco, California were travel related. Cases were significantly associated with travel to either Europe (odds ratio, 6.1) or New York (odds ratio, 32.9). Viral genomes recovered from 9 of 12 (75%) cases co-clustered with lineages circulating in Europe.
                Cover page: Associations of Early COVID-19 Cases in San Francisco with Domestic and International Travel
                • Article
                • Peer Reviewed
                UC Merced Previously Published Works (2013)
                Here we present the draft genome sequence of Janthinobacterium sp. strain CG3, a psychrotolerant non-violacein-producing bacterium that was isolated from the Cotton Glacier supraglacial stream. The genome sequence of this organism will provide insight as to the mechanisms necessary for bacteria to survive in UV-stressed icy environments.
                  Cover page: Draft Genome Sequence and Description of Janthinobacterium sp. Strain CG3, a Psychrotolerant Antarctic Supraglacial Stream Bacterium.
                  • Article
                  • Peer Reviewed
                  UCLA Previously Published Works (2024)
                  Plasticity among cell lineages is a fundamental, but poorly understood, property of regenerative tissues. In the gut tube, the small intestine absorbs nutrients, whereas the colon absorbs electrolytes. In a striking display of inherent plasticity, adult colonic mucosa lacking the chromatin factor SATB2 is converted to small intestine. Using proteomics and CRISPR-Cas9 screening, we identify MTA2 as a crucial component of the molecular machinery that, together with SATB2, restrains colonic plasticity. MTA2 loss in the adult mouse colon activated lipid absorptive genes and functional lipid uptake. Mechanistically, MTA2 co-occupies DNA with HNF4A, an activating pan-intestinal transcription factor (TF), on colonic chromatin. MTA2 loss leads to HNF4A release from colonic chromatin, and accumulation on small intestinal chromatin. SATB2 similarly restrains colonic plasticity through an HNF4A-dependent mechanism. Our study provides a generalizable model of lineage plasticity in which broadly-expressed TFs are retained on tissue-specific enhancers to maintain cell identity and prevent activation of alternative lineages, and their release unleashes plasticity.
                    Cover page: A MTA2-SATB2 chromatin complex restrains colonic plasticity toward small intestine by retaining HNF4A at colonic chromatin.Creative Commons 'BY' version 4.0 license
                    • Article
                    • Peer Reviewed
                    UC San Francisco Previously Published Works (2021)

                    Background

                    Metagenomic next-generation sequencing (mNGS) of body fluids is an emerging approach to identify occult pathogens in undiagnosed patients. We hypothesized that metagenomic testing can be simultaneously used to detect malignant neoplasms in addition to infectious pathogens.

                    Methods

                    From two independent studies (n = 205), we used human data generated from a metagenomic sequencing pipeline to simultaneously screen for malignancies by copy number variation (CNV) detection. In the first case-control study, we analyzed body fluid samples (n = 124) from patients with a clinical diagnosis of either malignancy (positive cases, n = 65) or infection (negative controls, n = 59). In a second verification cohort, we analyzed a series of consecutive cases (n = 81) sent to cytology for malignancy workup that included malignant positives (n = 32), negatives (n = 18), or cases with an unclear gold standard (n = 31).

                    Results

                    The overall CNV test sensitivity across all studies was 87% (55 of 63) in patients with malignancies confirmed by conventional cytology and/or flow cytometry testing and 68% (23 of 34) in patients who were ultimately diagnosed with cancer but negative by conventional testing. Specificity was 100% (95% CI 95-100%) with no false positives detected in 77 negative controls. In one example, a patient hospitalized with an unknown pulmonary illness had non-diagnostic lung biopsies, while CNVs implicating a malignancy were detectable from bronchoalveolar fluid.

                    Conclusions

                    Metagenomic sequencing of body fluids can be used to identify undetected malignant neoplasms through copy number variation detection. This study illustrates the potential clinical utility of a single metagenomic test to uncover the cause of undiagnosed acute illnesses due to cancer or infection using the same specimen.
                      Cover page: Detection of cryptogenic malignancies from metagenomic whole genome sequencing of body fluids
                      Top