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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Thesis
  • Peer Reviewed
UC Santa Barbara Electronic Theses and Dissertations (2014)

Cellular materials are ubiquitous in our world being found in natural and engineered systems as structural materials, sound and energy absorbers, heat insulators and more. Stochastic foams made of polymers, metals and even ceramics find wide use due to their novel properties when compared to monolithic materials. Properties of these so called hybrid materials, those that combine materials or materials and space, are derived from the localization of thermomechanical stresses and strains on the mesoscale as a function of cell topology. The effects of localization can only be generalized in stochastic materials arising from their inherent potential complexity, possessing variations in local chemistry, microstructural inhomogeneity and topological variations. Ordered cellular materials on the other hand, such as lattices and honeycombs, make for much easier study, often requiring analysis of only a single unit-cell. Theoretical bounds predict that hybrid materials have the potential to push design envelopes offering lighter stiffer and stronger materials. Hybrid materials can achieve very low and even negative coefficients of thermal expansion (CTE) while retaining a relatively high stiffness - properties completely unmatched by monolithic materials. In the first chapter of this thesis a two-dimensional lattice is detailed that possess near maximum stiffness, relative to the tightest theoretical bound, and low, zero and even appreciably negative thermal expansion. Its CTE and stiffness are given in closed form as a function of geometric parameters and the material properties. This result is confirmed with finite elements (FE) and experiment. In the second chapter the compressive stiffness of three-dimensional ordered foams, both closed and open cell, are predicted with FE and the results placed in property space in terms of stiffness and density. A novel structure is identified that effectively achieves theoretical bounds for Young's, shear and bulk modulus simultaneously, over a wide range of relative densities, greatly expanding the property space of available materials with a pragmatic manufacturable structure. A variety of other novel and previously studied ordered foam topologies are also presented that are largely representative of the spectrum of performance of such materials, shedding insight into the behavior of all cellular materials.

    Cover page: The Design and Modeling of Periodic Materials with Novel Properties
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2023)
    Purpose: To evaluate whether computer program-estimated urolith stone volume (SV) was a better predictor of spontaneous passage (SP) compared with program-estimated stone diameter (PD) or manually measured stone diameter (MD), and whether utilizing SV and MD together provided additional value in SP prediction compared with MD alone. Materials and Methods: Retrospective analysis of patients with acute renal colic and single renal/ureteral stone on CT from July 2017 to April 2020. Diameter obtained from radiology reports or manually measured when report not available. Semiautomated stone analysis software (qSAS) was used to estimate SV and PD. ROC analysis was performed to compare accuracy of SV vs MD vs PD in predicting SP by 2, 4, and 6 weeks. Subgroup analysis was performed by stone size (
      Cover page: Software-Estimated Stone Volume Is Better Predictor of Spontaneous Passage for Acute Nephrolithiasis.
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2023)
      INTRODUCTION: Despite its minimally invasive nature, percutaneous nephrolithotomy (PCNL ) may be associated with significant pain. Challenges in pain control may prevent timely discharge (and expose patients to adverse effects of opioid use). We sought to evaluate whether our patients who underwent erector spinae plane (ESP) regional blocks experienced improved postoperative pain control and decreased opioid use after PCNL (compared with those who did not receive blocks). METHODS: We retrospectively reviewed consecutive PCNL cases on patients admitted for greater than 24 hours without pre-existing opioid regimens for chronic pain. Cases were completed by a single high-volume surgeon. Patients who accepted an ESP block were compared to those who did not receive a block. Patients received either a single injection or a disposable pump delivering intermittent boluses of ropivacaine 0.2%. Demographic and perioperative data were analyzed. The primary outcomes were opioid use measured in morphine milligram equivalent (MME ) and patient-reported pain scores during the first 24 hours of hospitalization. RESULTS: From March 2019 to August 2021, 44 patients were identified who met criteria - 28 of whom received an ESP block (including 14 continuous blocks). The patients who received blocks had significantly decreased opioid use (18.3 vs. 81.3 MME, p=0.004) and a longer mean time to first non-zero pain score (p=0.004). Continuous blocks had similar opioid use to single shot blocks (21.0 vs. 15.6 MME, p=0.952). CONCLUSIONS: ESP regional blocks appear to offer an effective adjunct method for pain control after PCNL and may reduce post-PCNL opioid use while maintaining adequate patient analgesia.
        Cover page: Erector spinae plane blocks for analgesia after percutaneous nephrolithotomy A pathway to reduce opioids.
        • Article
        • Peer Reviewed
        UC Davis Previously Published Works (2016)

        Background and purpose

        The impact of audiovisual (AV) biofeedback on four dimensional (4D) positron emission tomography (PET) and 4D computed tomography (CT) image quality was investigated in a prospective clinical trial (NCT01172041).

        Material and methods

        4D-PET and 4D-CT images of ten lung cancer patients were acquired with AV biofeedback (AV) and free breathing (FB). The 4D-PET images were analyzed for motion artifacts by comparing 4D to 3D PET for gross tumor volumes (GTVPET) and maximum standardized uptake values (SUVmax). The 4D-CT images were analyzed for artifacts by comparing normalized cross correlation-based scores (NCCS) and quantifying a visual assessment score (VAS). A Wilcoxon signed-ranks test was used for statistical testing.

        Results

        The impact of AV biofeedback varied widely. Overall, the 3D to 4D decrease of GTVPET was 1.2±1.3cm(3) with AV and 0.6±1.8cm(3) for FB. The 4D-PET increase of SUVmax was 1.3±0.9 with AV and 1.3±0.8 for FB. The 4D-CT NCCS were 0.65±0.27 with AV and 0.60±0.32 for FB (p=0.08). The 4D-CT VAS was 0.0±2.7.

        Conclusion

        This study demonstrated a high patient dependence on the use of AV biofeedback to reduce motion artifacts in 4D imaging. None of the hypotheses tested were statistically significant. Future development of AV biofeedback will focus on optimizing the human-computer interface and including patient training sessions for improved comprehension and compliance.
          Cover page: The impact of audiovisual biofeedback on 4D functional and anatomic imaging: Results of a lung cancer pilot study
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2023)
          In 2018, the Endourology Disease Group for Excellence (EDGE) published a prospective trial comparing dusting versus basketing during ureteroscopy. One hundred fifty-nine patients were included in the original analysis, which found no difference in stone-free rate at 3 months. We report the intermediate and long-term outcomes of patients included in the original trial. Two analyses were performed. At 1-year, a retrospective chart review was performed, and data collected on stone episodes, Emergency Department (ED) visits, hospital admissions and surgical interventions. To obtain long-term outcomes, the four sites with the largest initial accrual were included in a second phase of data collection with updated analyses. The patients from those sites were contacted, re-consented, and data were collected on stone surgical interventions, stone episodes, stone recurrences on imaging, emergency department (ED) visits, and hospital admissions for stone-related care since their original procedure. One-year follow-up data were collected in 111 of the original 159 (69.8%) patients from the nine sites. There were no statistically significant differences in the number of painful episodes, ED visits, hospital admissions, or surgical interventions. 94 patients from four sites were included in the long-term analysis. There were no statistically significant differences in surgical interventions, painful stone episodes, stone recurrence on imaging, ED visits or hospitalizations for stone-related events between the two groups. Long-term outcomes of dusting versus basketing during ureteroscopy indicate that there are no significant differences in clinical outcomes between the two surgical modalities.
            Cover page: Long-term follow-up on dusting versus basketing during ureteroscopy: a prospective multicenter trial from the EDGE Research Consortium
            • Article
            • Peer Reviewed
            UC San Francisco Previously Published Works (2017)

            Purpose

            We evaluated the relative risk of biochemical recurrence, metastasis and death from prostate cancer contributed by biopsy Gleason pattern 5 among men at high risk with Gleason 8-10 disease in the SEARCH (Shared Equal Access Regional Cancer Hospital) cohort.

            Materials and methods

            Men with biopsy Gleason sum 8-10 prostate cancer treated with radical prostatectomy were evaluated. The cohort was divided into men with Gleason 4 + 4 vs those with any pattern 5 (ie Gleason 3 + 5, 5 + 3, 4 + 5, 5 + 4 or 5 + 5). Predictors of biochemical recurrence, metastases, and prostate cancer specific and overall survival were analyzed using Kaplan-Meier, log rank test and Cox proportional hazards models.

            Results

            We identified 634 men at high risk in the SEARCH database, of whom 394 (62%) had Gleason 4 + 4 and 240 (38%) had Gleason pattern 5 on biopsy. Baseline characteristics did not significantly differ between the groups. On multivariable analysis relative to Gleason 4 + 4 men at high risk with Gleason pattern 5 showed no difference in the risk of biochemical recurrence (HR 1.26, 95% CI 0.99-1.61, p = 0.065). However, they were at significantly greater risk for metastasis (HR 2.55, 95% CI 1.50-4.35, p = 0.001), prostate cancer specific mortality (HR 2.67, 95% CI 0.1.26-5.66, p = 0.010) and overall mortality (HR 1.60, 95% CI 1.09-2.34, p = 0.016).

            Conclusions

            Preoperative subclassification of high risk prostate cancer by biopsy Gleason grade (4 + 4 vs any Gleason pattern 5) identified men at highest risk for progression. Any Gleason 5 on biopsy is associated with a greater risk of metastasis, and prostate cancer specific and overall mortality. Grouping all Gleason 8-10 tumors together as high risk lesions may fail to fully stratify men at highest risk for poor outcomes.
              Cover page: Biopsy Detected Gleason Pattern 5 is Associated with Recurrence, Metastasis and Mortality in a Cohort of Men with High Risk Prostate Cancer
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