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Open Access Publications from the University of California

Scholarly Works (9 results)

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

Early detection of high-grade malignancy, such as glioblastoma (GBM), using new contrast mechanism and enhanced magnetic resonance imaging (MRI) techniques increases the treatment options available, and therefore may expand survival in GBM beyond the natural history of the disease and possibly increase the patients’ survival rate. To achieve early detection, it is important to evaluate commonly used MRI techniques, as well as to develop a theoretical model of GBM growth to predict the consequential changes in MR parameters and to evaluate the performance of newly developed MRI techniques. For this purpose, popular MRI methods such as the spin-echo, the Carr-Purcell-Meiboom-Gill (CPMG), and the spin-locking radio-frequency (RF) pulse sequences were used to acquire in vivo T2-weighted and T1-weighted MR images of orthotopic GBM mouse/rat models from U87MG and C6 cell lines. Statistical results (N = 18) showed that, while the spin-echo T2-weighted MR imaging may not provide the required contrast to detect early GBM, the CPMG T2-weighted MR imaging and the spin-locking T1-weighted MR imaging did slightly improve the early GBM contrast, but at the cost of significantly elevated specific absorption rate (SAR) and increased potential risk, if applied to human patients. To facilitate the development of innovative MRI RF pulse sequences to enhance early GBM contrast with low SAR, a simple, computationally efficient theoretical model on early GBM was proposed based on the experimental observation that vessel density decreases together with the increase of vessel size during the early stage of the GBM growth. Based on this model, Monte Carlo spin dynamics simulations were carried out by solving the Bloch equations for the water magnetizations diffusing in the magnetic-field gradients induced by paramagnetic deoxyhemoglobin in the vessels. The interplay among the spin dynamics, early GBM contrast, RF pulse sequences, vessel distributions, and GBM staging can be numerically evaluated. The simulated early GBM contrast and the relaxation time constants, T2 and T1, from the spin-echo, the CPMG, and the spin-locking RF pulse sequences were compared with those from the in vivo MR imaging of orthotopic early GBM mouse models to study the relaxation mechanisms. It may also serve as a computationally efficient alternative for laboratory use of animals following the 3R (reduction, refinement and replacement) strategy in evaluating the performance of commonly use or newly developed MR methods for early GBM detection.

    Cover page: Towards Early Glioblastoma Detection: In Vivo MR Imaging and Spin Dynamics Simulations
    • Article
    • Peer Reviewed
    UC Riverside Previously Published Works (2012)
    The performances of nine biosorbents derived from dead fungal biomass were investigated for their ability to remove Reactive Black 5 from aqueous solution. The biosorption data for removal of Reactive Black 5 were readily modeled using the Langmuir adsorption isotherm. Kinetic analysis based on both pseudo-second-order and Weber-Morris models indicated intraparticle diffusion was the rate limiting step for biosorption of Reactive Black 5 on to the biosorbents. Sorption capacities of the biosorbents were not correlated with the initial biosorption rates. Sensitivity analysis of the factors affecting biosorption examined by an artificial neural network model showed that pH was the most important parameter, explaining 22%, followed by nitrogen content of biosorbents (16%), initial dye concentration (15%) and carbon content of biosorbents (10%). The biosorption capacities were not proportional to surface areas of the sorbents, but were instead influenced by their chemical element composition. The main functional groups contributing to dye sorption were amine, carboxylic, and alcohol moieties. The data further suggest that differences in carbon and nitrogen contents of biosorbents may be used as a selection index for identifying effective biosorbents from dead fungal biomass.
      Cover page: Computational Identification and Analysis of the Key Biosorbent Characteristics for the Biosorption Process of Reactive Black 5 onto Fungal Biomass
      • Article
      • Peer Reviewed
      UC Berkeley Previously Published Works (2021)
      Mosquito-borne diseases, such as dengue and malaria, pose significant global health burdens. Unfortunately, current control methods based on insecticides and environmental maintenance have fallen short of eliminating the disease burden. Scalable, deployable, genetic-based solutions are sought to reduce the transmission risk of these diseases. Pathogen-blocking Wolbachia bacteria, or genome engineering-based mosquito control strategies including gene drives have been developed to address these problems, both requiring the release of modified mosquitoes into the environment. Here, we review the latest developments, notable similarities, and critical distinctions between these promising technologies and discuss their future applications for mosquito-borne disease control.
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2019)

        Objectives

        This study sought to determine whether T2 cardiac magnetic resonance (CMR) can stage both hemorrhagic and nonhemorrhagic myocardial infarctions (MIs).

        Background

        CMR-based staging of MI with or without contrast agents relies on the resolution of T2 elevations in the chronic phase, but whether this approach can be used to stage both hemorrhagic and nonhemorrhagic MIs is unclear.

        Methods

        Hemorrhagic (n = 15) and nonhemorrhagic (n = 9) MIs were created in dogs. Multiparametric noncontrast mapping (T1, T2, and T2*) and late gadolinium enhancement (LGE) were performed at 1.5- and 3.0-T at 5 days (acute) and 8 weeks (chronic) post-MI. CMR relaxation values and LGE intensities of hemorrhagic, peri-hemorrhagic, nonhemorrhagic, and remote territories were measured. Histopathology was performed to elucidate CMR findings.

        Results

        T2 of nonhemorrhagic MIs was significantly elevated in the acute phase relative to remote territories (1.5-T: 39.8 ± 12.8%; 3.0-T: 27.9 ± 16.5%; p < 0.0001 for both) but resolved to remote values by week 8 (1.5-T: -0.0 ± 3.2%; p = 0.678; 3.0-T: -0.5 ± 5.9%; p = 0.601). In hemorrhagic MI, T2 of hemorrhage core was significantly elevated in the acute phase (1.5-T: 17.7 ± 10.0%; 3.0-T: 8.6 ± 8.2%; p < 0.0001 for both) but decreased below remote values by week 8 (1.5-T: -8.2 ± 3.9%; 3.0-T: -5.6 ± 6.0%; p < 0.0001 for both). In contrast, T2 of the periphery of hemorrhage within the MI zone was significantly elevated in the acute phase relative to remote territories (1.5-T: 35.0 ± 16.1%; 3.0-T: 24.2 ± 10.4%; p < 0.0001 for both) and remained elevated at 8 weeks post-MI (1.5-T: 8.6 ± 5.1%; 3.0-T: 6.0 ± 3.3%; p < 0.0001 for both). The observed elevation of T2 in the peri-hemorrhagic zone of MIs and the absence of T2 elevation in nonhemorrhagic MIs were consistent with ongoing or absence of histological evidence of inflammation, respectively.

        Conclusions

        Hemorrhagic MIs are associated with persisting myocardial inflammation and edema, which can confound staging of hemorrhagic MIs when T2 elevations alone are used to discriminate between acute and chronic MI. Moreover, given the poor prognosis in patients with hemorrhagic MI, CMR evidence for myocardial hemorrhage with persistent edema may evolve as a risk marker in patients after acute MI.
          Cover page: Influence of Myocardial Hemorrhage on Staging of Reperfused Myocardial Infarctions With T2 Cardiac Magnetic&nbsp;Resonance Imaging Insights Into the Dependence on Infarction Type With Ex&nbsp;Vivo&nbsp;Validation
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2019)

          Methods:

          Nine patients (seven pancreas, one liver, and one lung) were recruited. 4D-MRI was performed using two prototype k-space sorted techniques, stack-of-stars (SOS) and koosh-ball (KB) acquisitions. Post-processing using MoCoAve was implemented for both methods. Image quality score, apparent SNR (aSNR), sharpness, motion trajectory and standard deviation (σ_GTV) of the gross tumor volumes were compared between original and MoCoAve image sets.

          Results:

          All subjects successfully underwent 4D-MRI scans and MoCoAve was performed on all data sets. Significantly higher image quality scores (2.64 ± 0.39 vs 1.18 ± 0.34, p = 0.001) and aSNR (37.6 ± 15.3 vs 18.1 ± 5.7, p = 0.001) was observed in the MoCoAve images when compared to the original images. High correlation in tumor motion trajectories in the superoinferior direction (SI: 0.91 ± 0.08) and weaker in the anteroposterior (AP: 0.51 ± 0.44) and mediolateral (ML: 0.37 ± 0.23) directions, similar image sharpness (0.367 ± 0.068 vs 0.369 ± 0.072, p = 0.805), and minimal average absolute difference (0.47 ± 0.34  mm) of the motion trajectory profiles was found between the two image sets. The σ_GTV in pancreas patients was significantly (p = 0.039) lower in MoCoAve images (1.48 ± 1.35  cm3) than in the original images (2.17 ± 1.31  cm3).

          Conclusion:

          MoCoAve using interphase motion correction and averaging has shown promise as a post-processing method for improving k-space sorted (SOS and KB) 4D-MRI image quality in thoracic and abdominal cancer patients.

          Advances in knowledge:

          The proposed method is an image based post-processing method that could be applied to many k-space sorted 4D-MRI methods for improved image quality and signal-to-noise ratio while preserving image sharpness and respiratory motion fidelity. It is a useful technique for the radiotherapy planning community who are interested in using 4D-MRI but aren't satisfied with their current MR image quality.
            Cover page: A post-processing method based on interphase motion correction and averaging to improve image quality of 4D magnetic resonance imaging: a clinical feasibility study
            • Article
            • Peer Reviewed
            LBL Publications (2022)
            Nanoparticle surfactant (NPS) offers a powerful strategy to generate all-liquid constructs that integrate the inherent properties of the NPs into 3D architectures. Here, using the co-assembly of fluorescent polymeric nanoparticles and amine-functionalized polyhedral oligomeric silsesquioxane, the assembly and jamming behavior of a new type of NPS at the oil-water interface is uncovered. Unlike "solid" inorganic nanoparticles, "soft" polymeric nanoparticles can reorganize when jammed, leading to a relaxation and deformation of the interfacial assemblies, for example, the 3D printed sugar-coated haw stick-like liquid tubules. With NPS serving as emulsifiers, stable Pickering emulsions are prepared that can be converted into robust colloidosomes with pH responsiveness, showing numerous potential applications for encapsulation and controlled release.
              Cover page: Interfacial Assembly and Jamming of Soft Nanoparticle Surfactants into Colloidosomes and Structured LiquidsCreative Commons 'BY' version 4.0 license
              • Article
              • Peer Reviewed
              LBL Publications (2022)
              The orbital occupancy, as the origin of Hund's rule coupling, provides critical information in understanding the multiorbital iron-based superconductors. The one-unit-cell (1UC) FeSe thin film on a SrTiO3 substrate with superconductive Tc above 60 K has been reported with unique electronic structures as well as orbital occupancy. In this paper, we present the x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) study of the FeSe/STO thin films of different thicknesses. Together with the atomic multiplet simulation analysis, the FeSe/STO thin films (from 1UC to 10UC) are shown with the pure 3d6 electronic configuration which is identical to the bulk FeSe. Moreover, 1UC FeSe/STO is found to be distinctively more persistent in hosting the 3d6 configuration other than the thicker films under the oxidization process. The robustness of the 3d6 in 1UC FeSe/STO is discussed as a result of charge transfer from the substrate, as well as a mechanism to maintain the high-Tc superconductivity. Finally, our research calls for a further high-resolution RIXS study of the pristine superconductive 1UC FeSe/STO thin film.
                Cover page: Robust Fe divalent state in one-unit-cell FeSe/SrTiO3 thin filmsCreative Commons 'BY' version 4.0 license
                • Article
                • Peer Reviewed
                LBL Publications (2021)
                Kagome superconductors with TC up to 7 K have been discovered for over 40 y. Recently, unconventional chiral charge order has been reported in kagome superconductor KV3Sb5, with an ordering temperature of one order of magnitude higher than the TC. However, the chirality of the charge order has not been reported in the cousin kagome superconductor CsV3Sb5, and the electronic nature of the chirality remains elusive. In this paper, we report the observation of electronic chiral charge order in CsV3Sb5 via scanning tunneling microscopy (STM). We observe a 2 × 2 charge modulation and a 1 × 4 superlattice in both topographic data and tunneling spectroscopy. 2 × 2 charge modulation is highly anticipated as a charge order by fundamental kagome lattice models at van Hove filling, and is shown to exhibit intrinsic chirality. We find that the 1 × 4 superlattices form various small domain walls, and can be a surface effect as supported by our first-principles calculations. Crucially, we find that the amplitude of the energy gap opened by the charge order exhibits real-space modulations, and features 2 × 2 wave vectors with chirality, highlighting the electronic nature of the chiral charge order. STM study at 0.4 K reveals a superconducting energy gap with a gap size 2Δ=0.85meV, which estimates a moderate superconductivity coupling strength with 2Δ/kBTC=3.9. When further applying a c-axis magnetic field, vortex core bound states are observed within this gap, indicative of clean-limit superconductivity.
                  Cover page: Electronic nature of chiral charge order in the kagome superconductor CsV3Sb5
                  • Article
                  • Peer Reviewed
                  UC San Diego Previously Published Works (2017)
                  Hand grip strength is a widely used proxy of muscular fitness, a marker of frailty, and predictor of a range of morbidities and all-cause mortality. To investigate the genetic determinants of variation in grip strength, we perform a large-scale genetic discovery analysis in a combined sample of 195,180 individuals and identify 16 loci associated with grip strength (P<5 × 10-8) in combined analyses. A number of these loci contain genes implicated in structure and function of skeletal muscle fibres (ACTG1), neuronal maintenance and signal transduction (PEX14, TGFA, SYT1), or monogenic syndromes with involvement of psychomotor impairment (PEX14, LRPPRC and KANSL1). Mendelian randomization analyses are consistent with a causal effect of higher genetically predicted grip strength on lower fracture risk. In conclusion, our findings provide new biological insight into the mechanistic underpinnings of grip strength and the causal role of muscular strength in age-related morbidities and mortality.
                    Cover page: Large-scale GWAS identifies multiple loci for hand grip strength providing biological insights into muscular fitness.
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