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Open Access Publications from the University of California

Scholarly Works (30 results)

  • Thesis
  • Peer Reviewed
UC Merced Electronic Theses and Dissertations (2009)

This research examined the in-stream sediment sources for four 1 km2 headwater catchments in the central Sierra Nevada, California. Erosion of material from two major sediment sources within headwater channels was estimated: headcut erosion and bank erosion. Repeat surveys of channel headcuts were conducted; measurements of channel geometry were used in conjunction with bank erosion measurements in a bank migration model to estimate bank erosion for the length of the channel. High amounts of variability were found in the measured stream parameters and eroded volumes both within each catchment and across the four catchments, but values were within one order of magnitude for all four study watersheds. Results also showed that though migration rates were similar in headcuts and bank bends, bank erosion totals were much higher than headcut erosion totals for three of the four catchments and roughly equal in the remaining catchment. Values ranged from 0.89 m3 to 4.24 m3 per year for total headcut erosion and 1.43 m3 to 23.61m3 per year for total bank erosion in the four study catchments. Finally, a scaled down version of a linear meander migration model based on the sediment continuity equation, shows potential as a tool for managers to estimate bank erosion, as it appears to give reasonable values using a few relatively simple to measure model inputs.

    • Thesis
    • Peer Reviewed
    UC Merced Electronic Theses and Dissertations (2017)

    The work presented herein examines how and to what extent turbidity, channel bed movement and stream source water ratios change over different temporal scales in four forested mountain headwater catchments in the Sierra Nevada, California. This work focuses on the water quality topics of sediment and source waters as part of a larger study on the effects of forest fuels treatments. No effects on water quality were expected because treatments were set far back from the stream channel and relatively light (8.0% and 7.5% decrease in mean Leaf Area Index (LAI) for the northern and southern site respectively). Therefore, this work was designed to characterize sediment and source waters rather than explore treatment impacts. In doing so important insights were gained around sediment and stream water sources.

    Sediment movement was found to be highly episodic and tied to low-frequency, short-duration discharge events with pronounced seasonality. Turbidity hysteresis patterns indicated localized (bed and banks) sediment sources that were mobilized quickly but became progressively depleted. Continuous measurement of channel bed elevations in the thalweg pointed to seasonal mobilization (connectedness) of sediment during winter, a gradual depletion through spring and early summer, and disconnectedness in low flow season when material builds up again at the base of banks mirroring patterns seen in the turbidity hysteresis loops. Stream water chemistry data showed higher concentrations during base flow, which was exacerbated by consecutive years of drought. The high base flow ion concentrations were tied to high ratios of groundwater. End-member mixing analysis showed that wet and dry years had similar source water ratios during high flow (winter and spring) but during the low flow season (late summer), a shift toward higher ratios of groundwater was seen for drought years. Recent tree mortality observed across the Sierra Nevada after four consecutive years of drought underscores the critical role of groundwater in maintaining baseflow and sustaining forest ecosystems. Better understanding of sediment processes, source water contributions, and drought effects in small, forested, mountain, headwater catchments provides an important foundation for sustainable land use management, more effective channel restoration design, and improved mitigation of downstream water quality.

      Cover page: WATER QUALITY IN FORESTED MOUNTAIN STREAMS: AN INVESTIGATION INTO SEDIMENT PRODUCTION, SEDIMENT TRANSPORT, AND SOURCE WATERS IN HEADWATER CATCHMENTS OF THE SIERRA NEVADA, CALIFORNIACreative Commons 'BY' version 4.0 license
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2022)
      Pediatric patients with invisible symptomology, such as chronic pain syndromes, are more likely to experience pain-related stigma and associated discrimination by others, including medical providers, peers, school personnel, and family members. The degree of this pain-related stigma may depend on several social dimensions, including observer (e.g., attentional and implicit biases) and patient characteristics (e.g., racial identity, socioeconomic stressors). In this mini-review, we introduce the concept of pain-related stigma, and the intersectionality of stigma, within the context of social determinants of health in pediatric pain populations. Stigma theory, observer attentional biases, healthcare provider implicit/explicit biases, adverse childhood experience, and psychophysiology of socio-environmental stressors are integrated. Several ethical, clinical, and research implications are also discussed. Because the study of pain-related stigma in pediatric pain is in its infancy, the purpose of this conceptual review is to raise awareness of the nuances surrounding this social construct, propose avenues through which stigma may contribute to health inequities, present frameworks to advance the study of this topic, and identify areas for further investigation.
        Cover page: Pain-related stigma as a social determinant of health in diverse pediatric pain populations.
        • Article
        • Peer Reviewed
        UC Merced Previously Published Works (2014)
        Seasonal turbidity patterns and event-level hysteresis analysis of turbidity verses discharge in four 1 km2 headwater catchments in California's Sierra Nevada indicate localized in-channel sediment sources and seasonal accumulation-depletion patterns of stream sediments. Turbidity signals were analyzed for three years in order to look at the relationships between seasonal turbidity trends, event turbidity patterns, and precipitation type to stream sediment production and transport. Seasonal patterns showed more turbidity events associated with fall and early to mid- winter events than with peak snow-melt. No significant turbidity patterns emerged for periods of snow melt vs. rain. Single event hysteresis loops showed clockwise patterns were dominant suggesting local sediment sources. In successive discharge events, the largest turbidity spike was often associated with the first but not necessarily the largest discharge event-indicating seasonal depletion of local sediment stores. In multi-peaked discharge events, hysteresis loops shifted from clockwise to linear or random patterns suggesting that localized sediment stores are being used up and sufficient flow energy must be reached to start entraining the more consolidated bank/bed sediment or that dominant sediment sources may be shifting to less localized areas such as hill slopes. A conceptual model with phases of accumulation and transport is proposed.
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2020)
          OBJECTIVE: Pediatric chronic pain evaluation includes self-reports and/or caregiver proxy-reports across biopsychosocial domains. Limited data exist on the effects of caregiver-child discrepancies in pediatric pain assessment. In children with chronic pain, we examined associations among discrepancies in caregiver-child reports of child anxiety and depressive symptoms and child functional impairment. METHODS: Participants were 202 children (Mage=14.49 ± 2.38 years; 68.8% female) with chronic pain and their caregivers (95.5% female). Children and caregivers completed the Revised Child Anxiety and Depression Scale (RCADS) and RCADS-Parent, respectively. Children also completed the Functional Disability Inventory. Mean difference tests examined caregiver-child discrepancies. Moderation analyses examined whether associations between child self-reported anxiety and depressive symptoms and functional impairment varied as a function of caregiver proxy-report. RESULTS: Children reported more anxiety and depressive symptoms compared with their caregivers proxy-reports (Z = -4.83, p < .001). Both informants reports of child anxiety and depressive symptoms were associated with child functional impairment (rs = .44, rs = .30, p < .001). Caregiver proxy-report moderated associations between child-reported anxiety and depressive symptoms and functional impairment (B = -0.007, p = .003). When caregiver proxy-report was low, child self-reported anxiety and depressive symptoms were positively related to functional impairment (B = 0.28, SE = 0.07, 95% CI [0.15, 0.41], p < .001). CONCLUSIONS: Discrepant caregiver-child perceptions of child anxiety and depressive symptoms may be associated with functioning in children with chronic pain, especially when caregivers report less child internalizing symptoms. These findings highlight the need for further examination of the effects of caregiver-child discrepancies on pediatric chronic pain outcomes and may indicate targets for intervention.
            Cover page: Caregiver-Child Discrepancies in Reports of Child Emotional Symptoms in Pediatric Chronic Pain.
            • Article
            • Peer Reviewed
            UC Irvine Previously Published Works (2024)
            BACKGROUND: Paediatric laceration repair procedures are common in the ED; however, post-discharge recovery remains understudied. Perioperative research demonstrates that children exhibit maladaptive behavioural changes following stressful and painful medical procedures. This study examined post-discharge recovery following paediatric laceration repair in the ED. METHODS: This prospective observational study included a convenience sample of 173 children 2-12 years old undergoing laceration repair in a paediatric ED in Orange, California, USA between April 2022 and August 2023. Demographics, laceration and treatment data (eg, anxiolytic medication), and caregiver-reported child pre-procedural and procedural pain (Numerical Rating Scale (NRS)) were collected. On days 1, 3, 7 and 14 post-discharge, caregivers reported childrens pain and new-onset maladaptive behavioural changes (eg, separation anxiety) via the Post Hospitalization Behavior Questionnaire for Ambulatory Surgery. Univariate and logistic regression analyses were conducted to identify variables associated with the incidence of post-discharge maladaptive behavioural change. RESULTS: Post-discharge maladaptive behavioural changes were reported in 43.9% (n=69) of children. At 1 week post-discharge, approximately 20% (n=27) of children exhibited maladaptive behavioural changes and 10% (n=13) displayed behavioural changes 2 weeks post-discharge. Mild levels of pain (NRS ≥2) were reported in 46.7% (n=70) of children on post-discharge day 1, 10.3% (n=14) on day 7 and 3.1% (n=4) on day 14. An extremity laceration (p=0.029), pre-procedural midazolam (p=0.020), longer length of stay (p=0.043) and post-discharge pain on day 1 (p<0.001) were associated with incidence of maladaptive behavioural changes. Higher pain on post-discharge day 1 was the only variable independently associated with an increased likelihood of maladaptive behavioural change (OR=1.32 (95% CI 1.08 to 1.61), p=0.001). CONCLUSION: Over 40% of children exhibited maladaptive behavioural changes after ED discharge. Although the incidence declined over time, 10% of children continued to exhibit behavioural changes 2 weeks post-discharge. Pain on the day following discharge emerged as a key predictor, highlighting the potential critical role of proactive post-procedural pain management in mitigating adverse behavioural changes.
              Cover page: Paediatric laceration repair in the emergency department: post-discharge pain and maladaptive behavioural changes.
              • Article
              • Peer Reviewed
              UC Irvine Previously Published Works (2017)
              BACKGROUND: Vaso-occlusive pain crises (VOCs) are the hallmark of sickle-cell disease (SCD) and can lead to sympathetic nervous system dysfunction. Increased sympathetic nervous system activation during VOCs and/or pain can result in vasoconstriction, which may increase the risk for subsequent VOCs and pain. Hypnosis is a neuromodulatory intervention that may attenuate vascular and pain responsiveness. Due to the lack of laboratory-controlled pain studies in patients with SCD and healthy controls, the specific effects of hypnosis on acute pain-associated vascular responses are unknown. The current study assessed the effects of hypnosis on peripheral blood flow, pain threshold, tolerance, and intensity in adults with and without SCD. SUBJECTS AND METHODS: Fourteen patients with SCD and 14 healthy controls were included. Participants underwent three laboratory pain tasks before and during a 30-minute hypnosis session. Peripheral blood flow, pain threshold, tolerance, and intensity before and during hypnosis were examined. RESULTS: A single 30-minute hypnosis session decreased pain intensity by a moderate amount in patients with SCD. Pain threshold and tolerance increased following hypnosis in the control group, but not in patients with SCD. Patients with SCD exhibited lower baseline peripheral blood flow and a greater increase in blood flow following hypnosis than controls. CONCLUSION: Given that peripheral vasoconstriction plays a role in the development of VOC, current findings provide support for further laboratory and clinical investigations of the effects of cognitive-behavioral neuromodulatory interventions on pain responses and peripheral vascular flow in patients with SCD. Current results suggest that hypnosis may increase peripheral vasodilation during both the anticipation and experience of pain in patients with SCD. These findings indicate a need for further examination of the effects of hypnosis on pain and vascular responses utilizing a randomized controlled trial design. Further evidence may help determine unique effects of hypnosis and potential benefits of integrating cognitive-behavioral neuromodulatory interventions into SCD treatment.
                Cover page: The effect of hypnosis on pain and peripheral blood flow in sickle-cell disease: a pilot study.
                • Article
                • Peer Reviewed
                UC Irvine Previously Published Works (2020)
                Pain and vaso-occlusive crises (VOC) are hallmark complications of sickle cell disease (SCD) and result in significant physical and psychosocial impairment. The variability in SCD pain frequency and triggers for the transition from steady state to VOC are not well understood. This paper summarizes the harmful physiological effects of pain and emotional stressors on autonomically-mediated vascular function in individuals with SCD and the effects of a cognitive, neuromodulatory intervention (i.e. hypnosis) on microvascular blood flow. We reviewed recent studies from the authors vascular physiology laboratory that assessed microvascular responses to laboratory stressors in individuals with SCD. Results indicate that participants with SCD exhibit marked neurally mediated vascular reactivity in response to pain, pain-related fear, and mental stress. Further, pilot study results show that engagement in hypnosis may attenuate harmful microvascular responses to pain. The collective results demonstrate that autonomically-mediated vascular responses to pain and mental stress represent an important SCD intervention target. This ongoing work provides physiological justification for the inclusion of cognitive, neuromodulatory and complementary treatments in SCD disease management and may inform the development of targeted, integrative interventions that prevent the enhancement of autonomic vascular dysfunction in SCD.
                  Cover page: Autonomically-mediated decrease in microvascular blood flow due to mental stress and pain in sickle cell disease: A target for neuromodulatory interventions.
                  • Article
                  • Peer Reviewed
                  UC Irvine Previously Published Works (2021)

                  Background and objective

                  The goal of the present study was to determine the incidence of new onset maladaptive behaviours in paediatric emergency department (PED) patients during the COVID-19 pandemic and to examine whether child and parent anxiety and parental health status were predictors for the new-onset of maladaptive behaviours.

                  Methods

                  Participants included child-parent dyads seen in a PED following the state's issuance of mandatory stay-at-home orders on 19 March 2020. A total of 351 children age 0-25 years and 335 parents enrolled in the study. Parents provided baseline demographic data and completed standardised surveys that assessed aspects of parental and child anxiety and parental health, as well as child new-onset maladaptive behaviours. Children ≥8 years of age completed surveys that assessed child anxiety.

                  Findings

                  Parents reported the new onset of maladaptive behaviours in children during the pandemic with frequencies up to 43%. Bivariate analysis identified predictors such as child anxiety (t(96) = -2.04, P = 0.044) as well as parental variables such as state anxiety (t(190) = -4.91, P < 0.001) and parental sensitivity to anxiety (t(243) = -3.19, P = 0.002). A logistic regression model identified parent mental health and COVID-19 anxiety as predictors of new onset maladaptive behaviours in children (X2 (6) = 42.514, P < 0.001). Specifically, every unit change in parental anxiety of COVID-19 was associated with a unit increase in maladaptive behaviours in children.

                  Conclusions

                  We identified distinct parent and child-related factors that predicted new onset child maladaptive behaviours during the COVID-19 pandemic. The identification of such predictors may help clinicians to prevent maladaptive responses to the pandemic quarantine.
                    Cover page: Predictors for COVID‐19‐related new‐onset maladaptive behaviours in children presenting to a paediatric emergency department
                    • Article
                    • Peer Reviewed
                    UC Irvine Previously Published Works (2022)
                    Recurrent or chronic pain affects 11-38% of children and adolescents. Pediatric pain research typically focuses on risk factors, such as anxiety and parent functional disability, but resilience-building, protective factors also play an important role in the pain experience. New methods to incorporate resilience-enhancing factors into pain research are needed. Photovoice is a highly participatory research method, where participants take photos to address a common question, caption their photos, and discuss the meaning of the photos in a group. The main objective of this study was to determine whether photovoice is an acceptable method to young people living with chronic pain for identifying and sharing sources of joy. Another objective was to explore sources of joy. Sixteen adolescents and young adults participated, which involved meeting in a group to discuss the goal of the study, taking photographs of self-identified sources of joy over a two-week period, and meeting as a group again to discuss the photographs and participate in a focus group about the experience. Results suggest that photovoice is an acceptable method, as all participants took photographs and attended both meetings, and three themes from the focus group data suggested the participants considered photovoice to be appropriate: 1.) Relief associated with meeting peers, 2.) Potential to benefit young people living with pain, and 3.) Potential to raise awareness. Three themes emerged from the discussion of the photographs to describe sources of joy: 1.) Gratitude for everyday pleasures and accomplishments, 2.) Support from pets, and 3.) Journey of acceptance. Results add to the strengths-based literature on pediatric pain by identifying an acceptable method that could be further explored for use as an intervention to enhance protective factors such as positive affect, gratitude, and social support and to compare the experiences of different populations of youth living with pain.
                      Cover page: The acceptability of photovoice as a method for incorporating resilience-enhancing factors into pediatric pain research.
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