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Open Access Publications from the University of California

Scholarly Works (9 results)

  • Article
  • Peer Reviewed
Proceedings of the Annual Meeting of the Cognitive Science Society, Volume 43 (2021)
Most theoretical accounts of non-instrumental information seeking suggest that the magnitude of rewards has a direct influence on the attractiveness of the information. Specifically, the magnitude of rewards is assumed to be proportional to the strength of information seeking (or avoidant) behaviour. In a series of experiments using numerical and pictorial stimuli, we explore the extent to which observed information seeking behaviour tracks these predictions. Our findings indicate a robust independence of information seeking from outcome magnitude and valence with preferences for information largely remaining constant across different reward valence and magnitudes. We discuss these results in the context of current computational models with suggestions for future theoretical and empirical work.
    Cover page: Invariance of Information Seeking Across Reward MagnitudesCreative Commons 'BY' version 4.0 license
    • Article
    • Peer Reviewed
    Proceedings of the Annual Meeting of the Cognitive Science Society, Volume 41 (2019)
    The categorization literature often considers two types of cat-egories as equivalent: (a) standard categories and (b) negationcategories. For example, category learning studies typicallyconflate learning categories A and B with learning categoriesA and NOT A. This study represents the first attempt at de-lineating these two separate types of generated categories. Wespecifically test for differences in the distributional structure ofgenerated categories, demonstrating that categories identifiedas not what was known are larger and wider-spread comparedto categories that were identified with a specific label. We alsoobserve consistency in distributional structure across multiplegenerated categories, replicating and extending previous find-ings. These results are discussed in the context of providing afoundation for future modeling work.
      Cover page: Novel categories are distinct from “Not”-categories
      • Thesis
      • Peer Reviewed
      UC Berkeley Electronic Theses and Dissertations (2017)

      Stratified combustion, combustion of fuel/air mixtures with temperature and/or mixture-composition stratification, is present in many combustion-related phenomena and applications such as forest wildfires, mining explosions, vessel ruptures, gas turbines, and reciprocating engines to name a few. A new generation of highly efficient internal combustion (IC) engines capable of satisfying stringent emission requirements, including modern direct-injection gasoline engines and gas turbines with lean premixed pre-vaporized (LPP) combustors, requires more comprehensive understanding and control of stratified combustion. Fundamentally, stratification of temperature or mixture composition affects a wide range of combustion characteristics such as flame speed, flammability, mode of combustion, instability, and others.

      This dissertation aims to identify, analyze and evaluate fundamental processes in the combustion of stratified mixtures, using theoretical analysis and advanced numerical simulation tools. ASURF-Parallel, a transient numerical solver of compressible reacting flow, is developed on the basis of the original A-SURF and exploited for stratified combustion simulations. A domain-decomposition parallelization scheme using Message Passing Interface (MPI) is developed and implemented in ASURF-Parallel to speed up the otherwise time-consuming numerical simulations. A significant speedup with the speed-up factor up to 10 is achieved on lab-scale servers.

      Effects of stratification on flame speeds, lean flammability limit, and modes of combustion are numerically investigated and studied. For flame speeds, laminar flame speeds of stratified flames propagating from rich mixtures to lean mixtures are generally faster than those of the corresponding homogeneous flames, primarily due to the preferential diffusion of lighter species and radicals such as H2, H and OH, i.e., the chemical effect. The degree of enhancement in flame speeds can be correlated to the degree of stratification, leading to the development of a transient local stratification level (LSL) model which is able to determine the stratified flame speeds incorporating both chemical effect and memory effect. For lean flammability limits, the extension introduced by stratification is very weak due to reduced overall reactivity and reduced degree of stratification. For modes of combustion, different modes can be realized by specific reactivity gradients, regardless of the sources of such gradients. Pressure waves introduced by ignition in a closed chamber can also lead to different modes of reaction front propagation and end-gas combustion. A transient reactivity gradient method is proposed to identify the onset of detonation.

        Cover page: Fundamental Processes in Combustion of Stratified Mixtures
        • Article
        • Peer Reviewed
        Proceedings of the Annual Meeting of the Cognitive Science Society, Volume 43 (2021)
        People’s desire to seek or avoid information is not only influenced by the possible outcomes of an event, but the probability of those particular outcomes occurring. There are competing explanations however as to how and why people’s desire for non-instrumental information is affected by factors including expected value, probability of outcome, and a unique formulation of outcome uncertainty. Over two experiments, we find that people’s preference for non-instrumental information is positively correlated with probability when the outcome is positive (i.e., winning money) and negatively correlated when the outcome is negative (i.e., losing money). Furthermore, at the aggregate level, we find the probability of an outcome to be a better predictor of information preference than the expected value of the event or its outcome uncertainty.
          Cover page: The effect of uncertainty and reward probability on information seeking behaviourCreative Commons 'BY' version 4.0 license
          • Article
          • Peer Reviewed
          Proceedings of the Annual Meeting of the Cognitive Science Society, Volume 42 (2020)
          People tend to place value on information even when it doesnot affect the outcome of a decision. Two competingaccounts offer explanations for such non-instrumentalinformation seeking. One account foregrounds the role ofanticipation and the other focusses on uncertainty aversion.Both accounts make similar predictions for short cue-outcome delays and when outcomes are positively valenced,but they differ in their explanation of information preferenceat long delays with negative outcomes. We present a seriesof experiments involving both primary and secondaryreinforcers that pit these accounts against each other. Theresults indicate a consistent preference for non-instrumentalinformation even at long cue-outcome delays and noevidence for information avoidance with negative outcomes.This pattern appears to provide more support for theuncertainty-aversion account than one based on anticipation.
            Cover page: Do you want to know a secret? The role of valence and delay in early informationpreferenceCreative Commons 'BY' version 4.0 license
            • Article
            • Peer Reviewed
            UC Berkeley Previously Published Works (2023)
            Understanding nanodiamond structures is of great scientific and practical interest. It has been a long-standing challenge to unravel the complexity underlying nanodiamond structures and to resolve the controversies surrounding their polymorphic forms. Here, we use transmission electron microscopy with high-resolution imaging, electron diffraction, multislice simulations, and other supplementary techniques to study the impacts of small sizes and defects on cubic diamond nanostructures. The experimental results show that common cubic diamond nanoparticles display the (200) forbidden reflections in their electron diffraction patterns, which makes them indistinguishable from new diamond (n-diamond). The multislice simulations demonstrate that cubic nanodiamonds smaller than 5 nm can present the d-spacing at 1.78 Å corresponding to the (200) forbidden reflections, and the relative intensity of these reflections increases as the particle size decreases. Our simulation results also reveal that defects, such as surface distortions, internal dislocations, and grain boundaries can also make the (200) forbidden reflections visible. These findings provide valuable insights into the diamond structural complexity at nanoscale, the impact of defects on nanodiamond structures, and the discovery of novel diamond structures.
              Cover page: Unveiling the complexity of nanodiamond structures
              • Article
              • Peer Reviewed
              UC San Francisco Previously Published Works (2022)
              Ribose-5-phosphate isomerase A (RPIA) regulates tumorigenesis in liver and colorectal cancer. However, the role of RPIA in lung cancer remains obscure. Here we report that the suppression of RPIA diminishes cellular proliferation and activates autophagy, apoptosis, and cellular senescence in lung cancer cells. First, we detected that RPIA protein was increased in the human lung cancer versus adjust normal tissue via tissue array. Next, the knockdown of RPIA in lung cancer cells displayed autophagic vacuoles, enhanced acridine orange staining, GFP-LC3 punctae, accumulated autophagosomes, and showed elevated levels of LC3-II and reduced levels of p62, together suggesting that the suppression of RPIA stimulates autophagy in lung cancer cells. In addition, decreased RPIA expression induced apoptosis by increasing levels of Bax, cleaved PARP and caspase-3 and apoptotic cells. Moreover, RPIA knockdown triggered cellular senescence and increased p53 and p21 levels in lung cancer cells. Importantly, RPIA knockdown elevated reactive oxygen species (ROS) levels. Treatment of ROS scavenger N-acetyl-L-cysteine (NAC) reverts the activation of autophagy, apoptosis and cellular senescence by RPIA knockdown in lung cancer cells. In conclusion, RPIA knockdown induces ROS levels to activate autophagy, apoptosis, and cellular senescence in lung cancer cells. Our study sheds new light on RPIA suppression in lung cancer therapy.
                Cover page: Suppression of Ribose-5-Phosphate Isomerase a Induces ROS to Activate Autophagy, Apoptosis, and Cellular Senescence in Lung Cancer
                • Article
                • Peer Reviewed
                UC Davis Previously Published Works (2018)
                We have previously identified and reported several potent piperidine-derived amide inhibitors of the human soluble epoxide hydrolase (sEH) enzyme. The inhibition of this enzyme leads to elevated levels of epoxyeicosatrienoic acids (EETs), which are known to possess anti-inflammatory, vasodilatory, and anti-fibrotic effects. Herein, we report the synthesis of 9 analogs of the lead sEH inhibitor and the follow-up structure-activity relationship and liver microsome stability studies. Our findings show that isosteric modifications that lead to significant alterations in the steric and electronic properties at a specific position in the molecule can reduce the efficacy by up to 75-fold. On the other hand, substituting hydrogen with deuterium produces a notable increase (∼30%) in the molecules' half-lives in both rat and human microsomes, while maintaining sEH inhibition potency. These data highlight the utility of isosteric replacement for improving bioavailability, and the newly-synthesized inhibitor structures may thus, serve as a starting point for preclinical development. Our docking study reveals that in the catalytic pocket of sEH, these analogs are in proximity of the key amino acids involved in hydrolysis of EETs.
                  Cover page: Novel piperidine-derived amide sEH inhibitors as mediators of lipid metabolism with improved stability
                  • Article
                  • Peer Reviewed
                  UC Irvine Previously Published Works (2017)
                  Phosphoinositide 3-kinase (PI3K) and the proteasome pathway are both involved in activating the mechanistic target of rapamycin (mTOR). Because mTOR signaling is required for initiation of messenger RNA translation, we hypothesized that cotargeting the PI3K and proteasome pathways might synergistically inhibit translation of c-Myc. We found that a novel PI3K δ isoform inhibitor TGR-1202, but not the approved PI3Kδ inhibitor idelalisib, was highly synergistic with the proteasome inhibitor carfilzomib in lymphoma, leukemia, and myeloma cell lines and primary lymphoma and leukemia cells. TGR-1202 and carfilzomib (TC) synergistically inhibited phosphorylation of the eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1), leading to suppression of c-Myc translation and silencing of c-Myc-dependent transcription. The synergistic cytotoxicity of TC was rescued by overexpression of eIF4E or c-Myc. TGR-1202, but not other PI3Kδ inhibitors, inhibited casein kinase-1 ε (CK1ε). Targeting CK1ε using a selective chemical inhibitor or short hairpin RNA complements the effects of idelalisib, as a single agent or in combination with carfilzomib, in repressing phosphorylation of 4E-BP1 and the protein level of c-Myc. These results suggest that TGR-1202 is a dual PI3Kδ/CK1ε inhibitor, which may in part explain the clinical activity of TGR-1202 in aggressive lymphoma not found with idelalisib. Targeting CK1ε should become an integral part of therapeutic strategies targeting translation of oncogenes such as c-Myc.
                    Cover page: Silencing c-Myc translation as a therapeutic strategy through targeting PI3Kδ and CK1ε in hematological malignancies
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