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Open Access Publications from the University of California

Scholarly Works (14 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2012)

A device that has the potential to provide electrical power to wireless sensors is investigated in this thesis. The device uses a ferromagnetic material to exploit the temperature difference between a heat source and a heat sink to produce oscillating motions and temperature polarizations, which can then be converted into electrical energy by piezoelectric materials and pyroelectric materials, respectively. One advantage of the proposed device is that it can exploit the characteristics of both piezoelectric materials and pyroelectric materials to harvest waste heat energy; therefore, it is expected to have potential high power output and conversion efficiency. Furthermore, the advantages of the reversible liquid interface can be exploited in this device to improve its performance.

The work presented in this thesis uses a coupled thermal and mechanical mathematical model to optimize the design of the proposed device. Three important parameters used in the mathematical model, the spring constant, the capillary force and the magnetic force, are calculated and then validated with experimental results to ensure that the modeling predictions match the actual behaviors of the device.

The mathematical model is then solved, and the modeling results are validated with experimental results to confirm that the model is able to correctly predict the behaviors of the device with reasonable levels of accuracy. The oscillation frequency is an important parameter for the device operation because a higher oscillation frequency means that more electrical energy can be collected in a given amount of time. Thus, the oscillation frequency is used as an index to evaluate the performance of the device. A parametric study is conducted for some design parameters, including the liquid volume of the reversible liquid interface, the total gap distance and the cold surface temperature, to attempt to increase the oscillation frequency.

The mathematical model predicts that the device can achieve a relatively high oscillation frequency when the optimized design parameters are used.

A thermal energy harvester using a ferromagnetic material with a reversible liquid interface is then physically built. Experiments are performed to study the effect of the reversible liquid interface on the performance of the device, and the results indicate that the reversible liquid interface can effectively increase the oscillation frequency in the low hot surface temperature region. Finally, when the optimized design parameters predicted by the mathematical model are applied, the device achieves a maximum oscillation frequency of 8.3Hz at a hot surface temperature of 41.8oC.

    Cover page: A Magnetomechanical Thermal Energy Harvester With A Reversible Liquid Interface
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2003)
    In this talk we discuss the phenomenology of models with replicated electroweak gauge symmetries, based on a framework with the gauge structure [SU(2) or U(1)] x U(1) x SU(2) x SU(2).
      Cover page: PRECISION ELECTROWEAK CONSTRAINTS ON HIDDEN LOCAL SYMMETRIES
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2004)
      In this talk, using deconstruction, we analyze the form of the corrections to the electroweak interactions in a large class of ``Higgsless'' models of electroweak symmetry breaking, allowing for arbitrary 5-D geometry, position-dependent gauge coupling, and brane kinetic energy terms. Many models considered in the literature, including those most likely to be phenomenologically viable, are in this class. By analyzing the asymptotic behavior of the correlation function of gauge currents at high momentum, we extract the exact form of the relevant correlation functions at tree-level and compute the corrections to precision electroweak observables in terms of the spectrum of heavy vector bosons. We determine when nonoblique corrections due to the interactions of fermions with the heavy vector bosons become important, and specify the form such interactions can take. In particular we find that in this class of models, so long as the theory remains unitary, S - 4 c^2_W T > O(1), where S and T are the usual oblique parameters.
        Cover page: Oblique Corrections in Deconstructed Higgsless Models
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2004)
        This paper studies models with extended electroweak gauge sectors of the form [Formula Presented] We establish the general behavior of corrections to precision electroweak observables in this class of theories and connect our results to previous work on specific models whose electroweak sectors are special cases of our extended group. © 2004 The American Physical Society.
          Cover page: Structure of electroweak corrections due to extended gauge symmetries
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2016)

          Background

          Pancreatic ductal adenocarcinoma remains one of the most lethal of all solid tumours. Treatment options are limited and gemcitabine-based chemotherapy remains the standard of care. Although growing evidence shows that p21-activated kinase 1 (PAK1) plays a crucial role in pancreatic cancer, its role has not been fully elucidated. This study aimed to characterise the expression and functional relevance of PAK1 in pancreatic cancer.

          Methods

          PAK1 expression was measured in pancreatic cancer specimens by immunohistochemistry and in pancreatic cancer cell lines by western blotting. The effect of inhibition of PAK1 by either shRNA knock-down (KD), or by a selective inhibitor, FRAX597, alone or in combination with gemcitabine, on cell proliferation and migration/invasion was measured by thymidine uptake and Boyden chamber assays, respectively. The effect on tumour growth and survival was assessed in orthotopic murine models.

          Results

          PAK1 was expressed in all human pancreatic cancer samples tested, an7d was upregulated in all pancreatic cancer cell lines tested. PAK1 KD inhibited pancreatic cancer cell growth and survival, and increased sensitivity to gemcitabine treatment. AKT activity and HIF1α expression were also inhibited. FRAX597 inhibited pancreatic cancer cell proliferation, survival, and migration/invasion. When combined with gemcitabine, FRAX597 synergistically inhibited pancreatic cancer proliferation in vitro and inhibited tumour growth in vivo.

          Conclusions

          These results implicate PAK1 as a regulator of pancreatic cancer cell growth and survival. Combination of a PAK1 inhibitor such as FRAX597 with cytotoxic chemotherapy deserves further study as a novel therapeutic approach to pancreatic cancer treatment.
            Cover page: FRAX597, a PAK1 inhibitor, synergistically reduces pancreatic cancer growth when combined with gemcitabine
            • Article
            • Peer Reviewed
            LBL Publications (2018)
            Searching for new Higgs particle beyond the observed light Higgs boson h0(125 GeV) will unambiguously point to new physics beyond the standard model. We study the resonant production of a CP-even heavy Higgs state H0 in the di-Higgs channel, gg → H0 → h0h0 → WW*WW*, at the LHC Run-2 and the high luminosity LHC (HL-LHC). We analyze two types of the 4W decay modes, one with the same-sign di-leptons (4W → ℓ±νℓ±ν4q) and the other with tri-leptons (4W → ℓ±νℓ∓νℓ±ν2q). We perform a full simulation for the signals and backgrounds, and estimate the discovery potential of the heavy Higgs state at the LHC Run-2 and the HL-LHC, in the context of generic two-Higgs-doublet models (2HDM). We determine the viable parameter space of the 2HDM as allowed by the theoretical constraints and the current experimental limits. We systematically analyze the allowed parameter space of the 2HDM which can be effectively probed by the heavy Higgs searches of the LHC, and further compare this with the viable parameter region under the current theoretical and experimental bounds.
              Cover page: LHC search of new Higgs boson via resonant di-Higgs production with decays into 4W
              • Article
              • Peer Reviewed
              UC Riverside Previously Published Works (2022)
              Commercial Cu-exchanged small-pore SSZ-13 (Cu-SSZ-13) zeolite catalysts are highly active for the standard selective catalytic reduction (SCR) of NO with NH3. However, their activity is unexpectedly inhibited in the presence of NO2 at low temperatures. This is strikingly distinct from the NO2-accelerated NOx conversion over other typical SCR catalyst systems. Here, we combine kinetic experiments, in situ X-ray absorption spectroscopy, and density functional theory (DFT) calculations to obtain direct evidence that under reaction conditions, strong oxidation by NO2 forces Cu ions to exist mainly as CuII species (fw-Cu2+ and NH3-solvated CuII with high CNs), which impedes the mobility of Cu species. The SCR reaction occurring at these CuII sites with weak mobility shows a higher energy barrier than that of the standard SCR reaction on dynamic binuclear sites. Moreover, the NO2-involved SCR reaction tends to occur at the Brønsted acid sites (BASs) rather than the CuII sites. This work clearly explains the strikingly distinctive selective catalytic behavior in this zeolite system.
                Cover page: Strikingly distinctive NH3-SCR behavior over Cu-SSZ-13 in the presence of NO2.
                • Article
                • Peer Reviewed
                UC San Diego Previously Published Works (2010)
                The three site Higgsless model has been offered as a benchmark for studying the collider phenomenology of Higgsless models. In this talk, we present how well the three site Higgsless model performs as a general representative of Higgsless models in describing W_L W_L scattering, and which modifications can make it more representative. We employ general sum rules relating the masses and couplings of the Kaluza-Klein (KK) modes of the gauge fields in continuum and deconstructed Higgsless models as a way to compare the different theories. After comparing the three site Higgsless model to flat and warped continuum Higgsless models, we analyze an extensions of the three site Higgsless model, namely, the Hidden Local Symmetry (HLS) Higgsless model. We demonstrate that W_LW_L scattering in the HLS Higgsless model can very closely approximate scattering in the continuum models, provided that the parameter `a' is chosen to mimic rho-meson dominance of pi-pi scattering in QCD.
                  Cover page: Identifying Better Effective Higgsless Theories via W_L W_L Scattering
                  • Article
                  • Peer Reviewed
                  UC San Diego Previously Published Works (2014)
                  We study the physics potential of the 8 TeV LHC to discover signals of extended gauge models or extra dimensional models whose low energy behavior is well represented by an SU(2) x SU(2) x U(1) electroweak gauge structure. We find that with a combined integrated luminosity of 40 fb^(-1), the first new Kaluza-Klein mode of the W gauge boson can be discovered up to a mass of about 400 GeV, when produced in association with a Z boson.
                    Cover page: Vector Bosons Signals of Electroweak Symmetry Breaking
                    • Article
                    • Peer Reviewed
                    UC Riverside Previously Published Works (2024)
                    Efficient heterogeneous catalyst design primarily focuses on engineering the active sites or supports, often neglecting the impact of trace impurities on catalytic performance. Herein, we demonstrate that even trace amounts of sulfate (SO42-) residuals on Ru/TiO2 can totally change the CO2 reduction from methanation to reverse-water gas shift (RWGS) reaction under atmospheric pressure. We reveal that air annealing causes the trace amount of SO42- to migrate from TiO2 to Ru/TiO2 interface, leading to the significant changes in product selectivity from CH4 to CO. Detailed characterizations and DFT calculations show that the sulfate at Ru/TiO2 interface notably enhances the H transfer from Ru particles to the TiO2 support, weakening the CO intermediate activation on Ru particles and inhibiting the further hydrogenation of CO to CH4. This discovery highlights the vital role of trace impurities in CO2 hydrogenation reaction, and also provides broad implications for the design and development of more efficient and selective heterogeneous catalysts.
                      Cover page: Sulfate residuals on Ru catalysts switch CO2 reduction from methanation to reverse water-gas shift reaction.
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