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Open Access Publications from the University of California

Scholarly Works (5 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2022)

Binaries play an important role in the overall dynamic and evolution of nuclear star clusters. In this dissertation, I explore, using semi-analytic methods, the dynamical evolution of binaries in galactic nuclei after the end of their luminous lives --- starting from supernovae and continuing to the compact object phase --- and their interactions with other cluster objects, in particular the supermassive black hole (SMBH). This stage of evolution can result in many observable phenomena, the abundance and properties of which are highly dependent on the properties of the underlying stellar binary population. Thus, an understanding of the dynamics of stellar remnants is crucial to understanding of the underlying stellar population.

I have shown that natal kicks in stellar binaries during supernovae can trigger a very wide variety of observable phenomena. These include but are not limited to: X-ray binaries, extreme mass ratio inspirals (EMRIs), and hypervelocity objects (including hypervelocity X-ray binaries). The population of X-ray binaries created by supernova kicks is a diagnostic for the black hole (BH) natal kick distribution, which remains highly debated. In particular, we found that no X-ray binaries with a BH primary is created if we assume no BH natal kicks. Subsequent to the natal kicks, most single and binary compact objects (COs) created remain bound to the SMBH. These COs can form gravitational wave (GW) mergers detectable the by Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo, the Laser Interferometer Space Antenna (LISA), and other future GW observatories.

In galactic nuclei, gravitational perturbations by the SMBH can induce eccentricity oscillations in binary COs, resulting in an elevated GW merger rate. I have shown that these eccentricity oscillations can be detected with LISA, out to a few Mpcs. This will allow us distinguish a variety of binary GW sources in galactic nuclei, from sources in other astrophysical environments. As for the single COs, although by themselves they do not emit GWs, in a dense stellar environment like nuclear clusters, they undergo frequent close encounters and emit energy in the form of GWs. If enough energy is emitted, they will form very close very eccentric binaries and merge. I have studied this mechanism as a formation channel for NSBH mergers and found that it is not likely to a major contributor to the overall NSBH rate detectable by LIGO. However, since the rate of merger from this mechanism is highly contingent on the characteristics of the single CO population, especially the density profile, we can use the future observations of NSBH mergers to confirm or revise our current understanding of the nuclear cluster environment.

    Cover page: Binary Dynamics in Galactic Nuclei: Gravitational Waves and Electromagnetic Signatures
    • Multimedia
    • Peer Reviewed
    UCLA Previously Published Works (2015)
    Multiple myeloma (MM), a plasma cell malignancy, is the second most prevalent hematologic malignancy in the US. Although much effort has been made trying to understand the etiology and the complexities of this disease with the hope of developing effective therapies, MM remains incurable at this time. Because of their antiproliferative and proapoptotic activities, interferons (IFNs) have been used to treat various malignancies, including MM. Although some success has been observed, the inherent toxicities of IFNs limit their efficacy. To address this problem, we produced anti-CD138 antibody fusion proteins containing either IFNα2 or a mutant IFNα2 (IFNα2(YNS)) with the goal of targeting IFN to CD138-expressing cells, thereby achieving effective IFN concentrations at the site of the tumor in the absence of toxicity. The fusion proteins inhibited the proliferation and induced apoptosis of U266, ANBL-6, NCI-H929, and MM1-144 MM cell lines. The fusion proteins decreased the expression of IFN regulatory factor 4 (IRF4) in U266. In addition, the fusion proteins were effective against primary cells from MM patients, and treatment with fusion proteins prolonged survival in the U266 murine model of MM. These studies show that IFNα antibody fusion proteins can be effective novel therapeutics for the treatment of MM.
    • 1 supplemental PDF
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2022)
    All-solid-state batteries have recently gained considerable attention due to their potential improvements in safety, energy density, and cycle-life compared to conventional liquid electrolyte batteries. Sodium all-solid-state batteries also offer the potential to eliminate costly materials containing lithium, nickel, and cobalt, making them ideal for emerging grid energy storage applications. However, significant work is required to understand the persisting limitations and long-term cyclability of Na all-solid-state-based batteries. In this work, we demonstrate the importance of careful solid electrolyte selection for use against an alloy anode in Na all-solid-state batteries. Three emerging solid electrolyte material classes were chosen for this study: the chloride Na2.25Y0.25Zr0.75Cl6, sulfide Na3PS4, and borohydride Na2(B10H10)0.5(B12H12)0.5. Focused ion beam scanning electron microscopy (FIB-SEM) imaging, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) were utilized to characterize the evolution of the anode-electrolyte interface upon electrochemical cycling. The obtained results revealed that the interface stability is determined by both the intrinsic electrochemical stability of the solid electrolyte and the passivating properties of the formed interfacial products. With appropriate material selection for stability at the respective anode and cathode interfaces, stable cycling performance can be achieved for Na all-solid-state batteries.
      Cover page: Evaluating Electrolyte–Anode Interface Stability in Sodium All-Solid-State Batteries
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2023)
      A preregistered meta-analysis, including 244 effect sizes from 85 field audits and 361,645 individual job applications, tested for gender bias in hiring practices in female-stereotypical and gender-balanced as well as male-stereotypical jobs from 1976 to 2020. A “red team” of independent experts was recruited to increase the rigor and robustness of our meta-analytic approach. A forecasting survey further examined whether laypeople (n = 499 nationally representative adults) and scientists (n = 312) could predict the results. Forecasters correctly anticipated reductions in discrimination against female candidates over time. However, both scientists and laypeople overestimated the continuation of bias against female candidates. Instead, selection bias in favor of male over female candidates was eliminated and, if anything, slightly reversed in sign starting in 2009 for mixed-gender and male-stereotypical jobs in our sample. Forecasters further failed to anticipate that discrimination against male candidates for stereotypically female jobs would remain stable across the decades.
        Cover page: On the trajectory of discrimination: A meta-analysis and forecasting survey capturing 44 years of field experiments on gender and hiring decisions
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2024)
        Anode-free batteries possess the optimal cell architecture due to their reduced weight, volume and cost. However, their implementation has been limited by unstable anode morphological changes and anode–liquid electrolyte interface reactions. Here we show that an electrochemically stable solid electrolyte and the application of stack pressure can solve these issues by enabling the deposition of dense sodium metal. Furthermore, an aluminium current collector is found to achieve intimate solid–solid contact with the solid electrolyte, which allows highly reversible sodium plating and stripping at both high areal capacities and current densities, previously unobtainable with conventional aluminium foil. A sodium anode-free all-solid-state battery full cell is demonstrated with stable cycling for several hundred cycles. This cell architecture serves as a future direction for other battery chemistries to enable low-cost, high-energy-density and fast-charging batteries.
          Cover page: Design principles for enabling an anode-free sodium all-solid-state batteryCreative Commons 'BY-NC-ND' version 4.0 license
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