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Open Access Publications from the University of California

Scholarly Works (43 results)

  • Thesis
  • Peer Reviewed
UC Irvine Electronic Theses and Dissertations (2021)

One of the most exciting tools that has entered our life in recent years is machine learning. The family of cognitive learning algorithms has already proved to bring convenience in many aspects considerably in our daily life. However, it is still unclear how machine learning can be utilized and create incremental value over existing information technologies and algorithms. This dissertation examines value creation with machine learning and compares its value to other competing systems. In the first two essays, we begin with an examination of the forecasting accuracy of machine learning algorithms compared to other traditional econometric models in predicting daily demand cases at a theme park. In the first essay (Chapter 2), we find improvements in machine learning algorithms' prediction accuracy in nonlinear and non-stationary daily demand forecasting. In the second essay (Chapter 3), we create a deep-learning neural network using a Human-in-the-Loop (HITL) approach. This chapter shows that the HITL approach outperforms prior approaches in prediction accuracy & consistency and in (in)direct economic benefits over other benchmarks. These results indicate that human expertise complements, rather than substitutes, machine learning. Also, the HITL approach performs better in demand prediction with sudden changes, bringing considerable advantages to business practices. In Chapter 4, we show the existence of price dispersion online. We leverage a machine learning application to measure information asymmetry in this research context. The analysis finds robust evidence of value creation with machine learning. The last chapter discusses implications and limitations for academia and practice for future machine learning applications, investments, and value creation research.

    • Article
    • Peer Reviewed
    ICTS Publications (2011)

    Application of pulsed radiofrequency (PRF) currents to the dorsal root ganglia (DRG) has been reported to produce relief from certain pain states without causing thermal ablation. In this study, we examined the direct correlation between PRF application to DRG associated with spinal nerve injury and reversal of injury-induced behavioral hypersensitivity in a rat neuropathic pain model.

    Neuropathic lesioning was performed via left L5 spinal nerve ligation on male adult Sprague-Dawley rats. Once the injured rats had developed tactile allodynia, one group was then assigned to PRF treatment of the L5 DRG and another group was assigned to the sham treatment to the DRG. Behavioral testing was performed on both the control and treated paws using the von Frey filament test before the surgery and at indicated days. The resulting data were analyzed using a linear mixed model to assess the overall difference between the treatment groups and the overall difference among the study days. Cohen's d statistic was computed from paired difference-from-baseline scores for each of the 14 study days after treatment and these measures of effect size were then used to descriptively compare the recovery patterns over time for each study group.

    Spinal nerve injury resulted in the development of behavioral hypersensitivity to von Frey filament stimulation (allodynia) in the hindpaw of the left (injury) side. Mixed linear modeling showed a significant difference between the treatment groups (P = 0.0079) and a significant change of paw withdrawal threshold means over time (P = 0.0006) for all 12 animals. Evaluation of Cohen's d (effect size) revealed that the PRF-treated animals exhibited better recovery and recorded larger effect sizes than the sham-treated animals on 10 of the 14 post-PRF treatment days and exhibited moderate-to-strong effects posttreatment at days 8 to 10 and at and beyond day 32.

    Findings from this study support that PRF of the DRG causes reversal of nerve injury (spinal nerve ligation)-induced tactile allodynia in rats. This allodynia reversal indicates that nonablative PRF acting via modulation of the DRG can speed recovery in nerve injury-induced pain.

      Cover page: Application of pulsed radiofrequency currents to rat dorsal root ganglia modulates nerve injury-induced tactile allodynia.
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2009)
      Nerve injury-induced expression of the spinal calcium channel alpha-2-delta-1 subunit (Ca(v)alpha(2)delta(1)) has been shown to mediate behavioral hypersensitivity through a yet identified mechanism. We examined if this neuroplasticity modulates behavioral hypersensitivity by regulating spinal glutamatergic neurotransmission in injury-free transgenic mice overexpressing the Ca(v)alpha(2)delta(1) proteins in neuronal tissues. The transgenic mice exhibited hypersensitivity to mechanical stimulation (allodynia) similar to the spinal nerve ligation injury model. Intrathecally delivered antagonists for N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxyl-5-methylisoxazole-4-propionic acid (AMPA)/kainate receptors, but not for the metabotropic glutamate receptors, caused a dose-dependent allodynia reversal in the transgenic mice without changing the behavioral sensitivity in wild-type mice. This suggests that elevated spinal Ca(v)alpha(2)delta(1) mediates allodynia through a pathway involving activation of selective glutamate receptors. To determine if this is mediated by enhanced spinal neuronal excitability or pre-synaptic glutamate release in deep-dorsal horn, we examined wide-dynamic-range (WDR) neuron excitability with extracellular recording and glutamate-mediated excitatory postsynaptic currents with whole-cell patch recording in deep-dorsal horn of the Ca(v)alpha(2)delta(1) transgenic mice. Our data indicated that overexpression of Ca(v)alpha(2)delta(1) in neuronal tissues led to increased frequency, but not amplitude, of miniature excitatory post synaptic currents mediated mainly by AMPA/kainate receptors at physiological membrane potentials, and also by NMDA receptors upon depolarization, without changing the excitability of WDR neurons to high intensity stimulation. Together, these findings support a mechanism of Ca(v)alpha(2)delta(1)-mediated spinal sensitization in which elevated Ca(v)alpha(2)delta(1) causes increased pre-synaptic glutamate release that leads to reduced excitation thresholds of post-synaptic dorsal horn neurons to innocuous stimuli. This spinal sensitization mechanism may mediate at least partially the neuropathic pain states derived from increased pre-synaptic Ca(v)alpha(2)delta(1) expression.
        Cover page: Enhanced pre-synaptic glutamate release in deep-dorsal horn contributes to calcium channel alpha-2-delta-1 protein-mediated spinal sensitization and behavioral hypersensitivityCreative Commons 'BY' version 4.0 license
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2023)
        In mammals, photic information delivered to the suprachiasmatic nucleus (SCN) via the retinohypothalamic tract (RHT) plays a crucial role in synchronizing the master circadian clock located in the SCN to the solar cycle. It is well known that glutamate released from the RHT terminals initiates the synchronizing process by activating ionotropic glutamate receptors (iGluRs) on retinorecipient SCN neurons. The potential role of metabotropic glutamate receptors (mGluRs) in modulating this signaling pathway has received less attention. In this study, using extracellular single-unit recordings in mouse SCN slices, we investigated the possible roles of the Gq/11 protein-coupled mGluRs, mGluR1 and mGluR5, in photic resetting. We found that mGluR1 activation in the early night produced phase advances in neural activity rhythms in the SCN, while activation in the late night produced phase delays. In contrast, mGluR5 activation had no significant effect on the phase of these rhythms. Interestingly, mGluR1 activation antagonized phase shifts induced by glutamate through a mechanism that was dependent upon CaV1.3 L-type voltage-gated Ca2+ channels (VGCCs). While both mGluR1-evoked phase delays and advances were inhibited by knockout (KO) of CaV1.3 L-type VGCCs, different signaling pathways appeared to be involved in mediating these effects, with mGluR1 working via protein kinase G in the early night and via protein kinase A signaling in the late night. We conclude that, in the mouse SCN, mGluR1s function to negatively modulate glutamate-evoked phase shifts.
          Cover page: Activation of mGluR1 negatively modulates glutamate-induced phase shifts of the circadian pacemaker in the mouse suprachiasmatic nucleus
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2015)

          Aims

          Type 2 diabetes mellitus (T2DM) and visceral obesity are associated with each other and with cardiovascular diseases. We determined whether increased visceral adiposity without weight gain was associated with sex-specific accelerated carotid atherosclerosis in South Koreans with T2DM.

          Methods

          From 2003 to 2012, we recruited 280 participants with T2DM for the Seoul Metabolic Syndrome cohort who had body weight, visceral fat thickness (VFT), and carotid intima-media thickness (CIMT) measured at intervals of 2years. According to VFT change, sex-specific quartiles of clinical characteristics and changes of CIMT were determined. Logistic regression models predicted the odds of the progression of CIMTs in each quartile.

          Results

          During 2years of observation, VFTs fell by 5.2±13.5mm in men (P<0.001) and 3.4±10.5mm in women (P<0.001). Progression of CIMT was only significant for women's maximal CIMT (0.031±0.145mm, P=0.012), while significant improvements in HbA1c were found (0.9%; P<0.001 in both sexes). There were no significant differences in clinical characteristics, or in progression of CIMT in men or women according to 2-year quartiles of VFT change.

          Conclusions

          Our results do not suggest that increased visceral adiposity without body weight changes impacts the CIMT progression in South Korean men or women with T2DM.
            Cover page: Can increased visceral adiposity without body weight changes accelerate carotid atherosclerosis in South Korean participants with type 2 diabetes?
            • Article
            • Peer Reviewed
            UC Irvine Previously Published Works (2014)
            To investigate a potential mechanism underlying trigeminal nerve injury-induced orofacial hypersensitivity, we used a rat model of chronic constriction injury to the infraorbital nerve (CCI-ION) to study whether CCI-ION caused calcium channel α2δ1 (Cavα2δ1) protein dysregulation in trigeminal ganglia and associated spinal subnucleus caudalis and C1/C2 cervical dorsal spinal cord (Vc/C2). Furthermore, we studied whether this neuroplasticity contributed to spinal neuron sensitization and neuropathic pain states. CCI-ION caused orofacial hypersensitivity that correlated with Cavα2δ1 up-regulation in trigeminal ganglion neurons and Vc/C2. Blocking Cavα2δ1 with gabapentin, a ligand for the Cavα2δ1 proteins, or Cavα2δ1 antisense oligodeoxynucleotides led to a reversal of orofacial hypersensitivity, supporting an important role of Cavα2δ1 in orofacial pain processing. Importantly, increased Cavα2δ1 in Vc/C2 superficial dorsal horn was associated with increased excitatory synaptogenesis and increased frequency, but not the amplitude, of miniature excitatory postsynaptic currents in dorsal horn neurons that could be blocked by gabapentin. Thus, CCI-ION-induced Cavα2δ1 up-regulation may contribute to orofacial neuropathic pain states through abnormal excitatory synapse formation and enhanced presynaptic excitatory neurotransmitter release in Vc/C2.
              Cover page: Calcium channel α2δ1 proteins mediate trigeminal neuropathic pain states associated with aberrant excitatory synaptogenesis.
              • Article
              • Peer Reviewed
              UC Irvine Previously Published Works (2014)
              To investigate a potential mechanism underlying trigeminal nerve injury-induced orofacial hypersensitivity, we used a rat model of chronic constriction injury to the infraorbital nerve (CCI-ION) to study whether CCI-ION caused calcium channel α2δ1 (Cavα2δ1) protein dysregulation in trigeminal ganglia and associated spinal subnucleus caudalis and C1/C2 cervical dorsal spinal cord (Vc/C2). Furthermore, we studied whether this neuroplasticity contributed to spinal neuron sensitization and neuropathic pain states. CCI-ION caused orofacial hypersensitivity that correlated with Cavα2δ1 up-regulation in trigeminal ganglion neurons and Vc/C2. Blocking Cavα2δ1 with gabapentin, a ligand for the Cavα2δ1 proteins, or Cavα2δ1 antisense oligodeoxynucleotides led to a reversal of orofacial hypersensitivity, supporting an important role of Cavα2δ1 in orofacial pain processing. Importantly, increased Cavα2δ1 in Vc/C2 superficial dorsal horn was associated with increased excitatory synaptogenesis and increased frequency, but not the amplitude, of miniature excitatory postsynaptic currents in dorsal horn neurons that could be blocked by gabapentin. Thus, CCI-ION-induced Cavα2δ1 up-regulation may contribute to orofacial neuropathic pain states through abnormal excitatory synapse formation and enhanced presynaptic excitatory neurotransmitter release in Vc/C2.
                Cover page: Calcium Channel α2δ1 Proteins Mediate Trigeminal Neuropathic Pain States Associated with Aberrant Excitatory Synaptogenesis*
                • Article
                • Peer Reviewed
                UC Irvine Previously Published Works (2009)
                Nerve injury-induced expression of the spinal calcium channel alpha-2-delta-1 subunit (Cavalpha2delta1) has been shown to mediate behavioral hypersensitivity through a yet identified mechanism. We examined if this neuroplasticity modulates behavioral hypersensitivity by regulating spinal glutamatergic neurotransmission in injury-free transgenic mice overexpressing the Cavalpha2delta1 proteins in neuronal tissues. The transgenic mice exhibited hypersensitivity to mechanical stimulation (allodynia) similar to the spinal nerve ligation injury model. Intrathecally delivered antagonists for N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxyl-5-methylisoxazole-4-propionic acid (AMPA)/kainate receptors, but not for the metabotropic glutamate receptors, caused a dose-dependent allodynia reversal in the transgenic mice without changing the behavioral sensitivity in wild-type mice. This suggests that elevated spinal Cavalpha2delta1 mediates allodynia through a pathway involving activation of selective glutamate receptors. To determine if this is mediated by enhanced spinal neuronal excitability or pre-synaptic glutamate release in deep-dorsal horn, we examined wide-dynamic-range (WDR) neuron excitability with extracellular recording and glutamate-mediated excitatory postsynaptic currents with whole-cell patch recording in deep-dorsal horn of the Cavalpha2delta1 transgenic mice. Our data indicated that overexpression of Cavalpha2delta1 in neuronal tissues led to increased frequency, but not amplitude, of miniature excitatory post synaptic currents mediated mainly by AMPA/kainate receptors at physiological membrane potentials, and also by NMDA receptors upon depolarization, without changing the excitability of WDR neurons to high intensity stimulation. Together, these findings support a mechanism of Cavalpha2delta1-mediated spinal sensitization in which elevated Cavalpha2delta1 causes increased pre-synaptic glutamate release that leads to reduced excitation thresholds of post-synaptic dorsal horn neurons to innocuous stimuli. This spinal sensitization mechanism may mediate at least partially the neuropathic pain states derived from increased pre-synaptic Cavalpha2delta1 expression.
                  Cover page: Enhanced Pre-Synaptic Glutamate Release in Deep-Dorsal Horn Contributes to Calcium Channel Alpha-2-Delta-1 Protein-Mediated Spinal Sensitization and Behavioral HypersensitivityCreative Commons 'BY' version 4.0 license
                  • Article
                  • Peer Reviewed
                  Biological Systems & Engineering (2018)

                  Background

                  Cancer-associated fibroblasts (CAFs) are one of the most important components of tumor stroma and play a key role in modulating tumor growth. However, a mechanistic understanding of how CAFs communicate with tumor cells to promote their proliferation and invasion is far from complete. A major reason for this is that most current techniques and model systems do not capture the complexity of signal transduction that occurs between CAFs and tumor cells.

                  Methods

                  In this study, we employed a stable isotope labeling with amino acids in cell culture (SILAC) strategy to label invasive breast cancer cells, MDA-MB-231, and breast cancer patient-derived CAF this has already been defined above cells. We used an antibody-based phosphotyrosine peptide enrichment method coupled to LC-MS/MS to catalog and quantify tyrosine phosphorylation-mediated signal transduction events induced by the bidirectional communication between patient-derived CAFs and tumor cells.

                  Results

                  We discovered that distinct signaling events were activated in CAFs and in tumor epithelial cells during the crosstalk between these two cell types. We identified reciprocal activation of a number of receptor tyrosine kinases including EGFR, FGFR1 and EPHA2 induced by this bidirectional communication.

                  Conclusions

                  Our study not only provides insights into the mechanisms of the interaction between CAFs and tumor cells, but the model system described here could be used as a prototype for analysis of intercellular communication in many different tumor microenvironments.
                    Cover page: Quantitative phosphoproteomic analysis reveals reciprocal activation of receptor tyrosine kinases between cancer epithelial cells and stromal fibroblasts
                    • Article
                    • Peer Reviewed
                    LBL Publications (2019)
                    We measured the near-field infrared response of MnPS3 in bulk, few-, and single-layer form and compared our findings with traditional far-field vibrational spectroscopies, a symmetry analysis, and first-principles lattice dynamics calculations. Trends in the Bu mode near 450cm-1 are striking, with the disappearance of this structure in the thinnest sheets. Combined with the amplified response of the activated Ag mode and analysis of the Au+Bu features, we find that symmetry is unexpectedly increased in few- and single-sheet MnPS3 due to a restoration of the threefold axes of rotation. Monoclinicity in this system is therefore a consequence of the long-range stacking pattern and temperature rather than local structure.
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