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• 7891. [Article] Seasonal and Sex Differences in the Effects of Melatonin on Brain Arginine Vasotocin in Green Treefrogs (Hyla cinerea): Relationship to Melatonin Receptor 1a

  Critical life history events such as breeding, migration and hibernation must take place in the correct environmental context to minimize deleterious consequences on survival and reproductive fitness. ...

  Citation × Citation Citation Abstract Copy Title: Seasonal and Sex Differences in the Effects of Melatonin on Brain Arginine Vasotocin in Green Treefrogs (Hyla cinerea): Relationship to Melatonin Receptor 1a Author: Howard, Christina Marie Year: 2014 Critical life history events such as breeding, migration and hibernation must take place in the correct environmental context to minimize deleterious consequences on survival and reproductive fitness. Neuroendocrine mechanisms synchronizing internal physiological states with extrinsic environmental cues are vital to timing life history events appropriately. Secretion of the pineal hormone melatonin is sensitive to light and temperature cues, which provides a physiological indicator of time of day and time of year for organisms. Melatonin influences seasonal reproduction in a variety of vertebrates, likely by altering the synthesis and/or release of reproductive neuropeptides in the brain. The neuropeptides arginine vasotocin and its mammalian homologue, arginine vasopressin, are well-known modulators of reproductive and sociosexual behavior across vertebrate taxa, and are likely targets of melatonin in the context of seasonal reproduction. There is extensive evidence that vasotocin/vasopressin innervation in the brain is subject to seasonal variation, and that this variation is frequently sexually dimorphic. However, evidence that melatonin directly modulates this important neuropeptide system is lacking. Melatonin receptor 1a (MT1 in mammals) may be responsible for mediating melatonin's influence on brain vasotocin, as it is known to regulate seasonal reproduction in a variety of vertebrates. In the present study, I asked whether melatonin influences brain vasotocin in male green treefrogs (Hyla cinerea), and compared the distribution of melatonin receptor 1a in the brain of green treefrogs between sexes and seasons. Adult male and female green treefrogs were collected from field sites in Louisiana during the summer breeding season. Summer animals were acclimated to lab conditions for 3 weeks, then euthanized and their brains collected. Winter animals were maintained in the lab for four months under incrementally changing photo-, thermo-, and hygroperiod regimes that mimicked the transition to winter in their natural habitat, followed by euthanasia and brain collection. A subset of winter males (Experiment 1) were implanted with melatonin-filled or blank silastic capsules for a period of one month prior to euthanasia and brain collection. Brains of these males were processed for vasotocin immunohistochemistry. I quantified AVT-ir cell number in Experiment 1 males in the nucleus accumbens (NAcc), amygdala and caudal striatum (AMG), preoptic area (POA), suprachaismatic nucleus (SCN), and ventral hypothalamus (VH). Melatonin did not influence brain vasotocin-ir cell number in any brain region. Brains from untreated summer and winter males and females were collected and processed for MT1 immunohistochemistry. MT1-ir cells were quantified in the NAcc, striatum (STR), AMG, POA, SCN, and VH. In all regions quantified, reproductively active males had significantly more MT1-ir cells than nonreproductive males. Within the summer breeding season, males had significantly more MT1-ir cells in the NAcc than did reproductively active females. In all other regions there was no significant difference in MT1-ir cell number between reproductively active males and females. Collectively, these data suggest that melatonin modulates vasotocin via MT1. These findings assist in elucidating the neuroendocrine mechanisms by which vertebrates integrate seasonal cues with physiology to correctly time critical life history events. Title: Seasonal and Sex Differences in the Effects of Melatonin on Brain Arginine Vasotocin in Green Treefrogs (Hyla cinerea): Relationship to Melatonin Receptor 1a Author: Howard, Christina Marie Year: 2014 Critical life history events such as breeding, migration and hibernation must take place in the correct environmental context to minimize deleterious consequences on survival and reproductive fitness. Neuroendocrine mechanisms synchronizing internal physiological states with extrinsic environmental cues are vital to timing life history events appropriately. Secretion of the pineal hormone melatonin is sensitive to light and temperature cues, which provides a physiological indicator of time of day and time of year for organisms. Melatonin influences seasonal reproduction in a variety of vertebrates, likely by altering the synthesis and/or release of reproductive neuropeptides in the brain. The neuropeptides arginine vasotocin and its mammalian homologue, arginine vasopressin, are well-known modulators of reproductive and sociosexual behavior across vertebrate taxa, and are likely targets of melatonin in the context of seasonal reproduction. There is extensive evidence that vasotocin/vasopressin innervation in the brain is subject to seasonal variation, and that this variation is frequently sexually dimorphic. However, evidence that melatonin directly modulates this important neuropeptide system is lacking. Melatonin receptor 1a (MT1 in mammals) may be responsible for mediating melatonin's influence on brain vasotocin, as it is known to regulate seasonal reproduction in a variety of vertebrates. In the present study, I asked whether melatonin influences brain vasotocin in male green treefrogs (Hyla cinerea), and compared the distribution of melatonin receptor 1a in the brain of green treefrogs between sexes and seasons. Adult male and female green treefrogs were collected from field sites in Louisiana during the summer breeding season. Summer animals were acclimated to lab conditions for 3 weeks, then euthanized and their brains collected. Winter animals were maintained in the lab for four months under incrementally changing photo-, thermo-, and hygroperiod regimes that mimicked the transition to winter in their natural habitat, followed by euthanasia and brain collection. A subset of winter males (Experiment 1) were implanted with melatonin-filled or blank silastic capsules for a period of one month prior to euthanasia and brain collection. Brains of these males were processed for vasotocin immunohistochemistry. I quantified AVT-ir cell number in Experiment 1 males in the nucleus accumbens (NAcc), amygdala and caudal striatum (AMG), preoptic area (POA), suprachaismatic nucleus (SCN), and ventral hypothalamus (VH). Melatonin did not influence brain vasotocin-ir cell number in any brain region. Brains from untreated summer and winter males and females were collected and processed for MT1 immunohistochemistry. MT1-ir cells were quantified in the NAcc, striatum (STR), AMG, POA, SCN, and VH. In all regions quantified, reproductively active males had significantly more MT1-ir cells than nonreproductive males. Within the summer breeding season, males had significantly more MT1-ir cells in the NAcc than did reproductively active females. In all other regions there was no significant difference in MT1-ir cell number between reproductively active males and females. Collectively, these data suggest that melatonin modulates vasotocin via MT1. These findings assist in elucidating the neuroendocrine mechanisms by which vertebrates integrate seasonal cues with physiology to correctly time critical life history events. Close

• 7892. [Article] Where Is Portland Made? The Complex Relationship between Social Media and Place in the Artisan Economy of Portland, Oregon (USA)

  Portland, Oregon (USA) has become known for an artisanal or ‘maker’ economy that relies on a resurgence of place specificity (Heying), primarily expressed and exported to a global audience in the notion ...

  Citation × Citation Citation Abstract Copy Title: Where Is Portland Made? The Complex Relationship between Social Media and Place in the Artisan Economy of Portland, Oregon (USA) Author: Marotta, Stephen, Cummings, Austin, Heying, Charles H. Year: 2016 Portland, Oregon (USA) has become known for an artisanal or ‘maker’ economy that relies on a resurgence of place specificity (Heying), primarily expressed and exported to a global audience in the notion of ‘Portland Made’ (Roy). Portland Made reveals a tension immanent in the notion of ‘place’: place is both here and not here, both real and imaginary. What emerges is a complicated picture of how place conceptually captures various intersections of materiality and mythology, aesthetics and economics. On the one hand, Portland Made represents the collective brand-identity used by Portland’s makers to signify a products’ material existence as handcrafted, place-embedded, and authentic. These characteristics lead to certain assumptions about the concept of ‘local’ (Marotta and Heying): what meaning does Portland Made convey, and how is such meaning distributed? On the other hand, the seemingly intentional embedding of place-specificity in objects meant for distribution far outside of Portland begs another type of question: how does Portland come to be discursively representative of these characteristics, and how are such representations distributed to global audiences? How does this global distribution and consumption of immaterial Portland feed back into the production of material Portland? To answer these questions we look to the realm of social media, specifically the popular image-based service Instagram. For the uninitiated, Instagram is a web-based social media service that allows pictures to be shared and seen by anyone that follows a person or business’ Instagram account. Actions include posting original photos (often taken and posted with a cell phone), ‘liking’ pictures, and ‘hash-tagging’ posts with trending terms that increase visibility. Instagram presents us with a complex view of place as both material and virtual, sometimes reifying and sometimes abstracting often-contradictory understandings of place specificity. Many makers use Instagram to promote their products to a broad audience and, in doing so, makers participate in the construction of Portland’s mythology. In this paper, we use empirical insights to theorise makers’ role in shaping and cultivating the virtual and material aspects of place. Additionally, we discuss how makers navigate the complex relationships tied to the importance of place in their specific cultural productions. In the first section, we develop the notion of a curated maker subjectivity. In the second section, we consider the relationship between subjectivity and place. Both sections emphasize how Instagram mediates the relationship between place and subjectivity. Through spotlighting particular literatures in each section, we attempt to fill a gap in the literature that addresses the relationship between subjectivity, place, and social media. Through this line of analysis, we attempt to better understand how and where Portland is made, along with the implications for Portland’s makers. Title: Where Is Portland Made? The Complex Relationship between Social Media and Place in the Artisan Economy of Portland, Oregon (USA) Author: Marotta, Stephen, Cummings, Austin, Heying, Charles H. Year: 2016 Portland, Oregon (USA) has become known for an artisanal or ‘maker’ economy that relies on a resurgence of place specificity (Heying), primarily expressed and exported to a global audience in the notion of ‘Portland Made’ (Roy). Portland Made reveals a tension immanent in the notion of ‘place’: place is both here and not here, both real and imaginary. What emerges is a complicated picture of how place conceptually captures various intersections of materiality and mythology, aesthetics and economics. On the one hand, Portland Made represents the collective brand-identity used by Portland’s makers to signify a products’ material existence as handcrafted, place-embedded, and authentic. These characteristics lead to certain assumptions about the concept of ‘local’ (Marotta and Heying): what meaning does Portland Made convey, and how is such meaning distributed? On the other hand, the seemingly intentional embedding of place-specificity in objects meant for distribution far outside of Portland begs another type of question: how does Portland come to be discursively representative of these characteristics, and how are such representations distributed to global audiences? How does this global distribution and consumption of immaterial Portland feed back into the production of material Portland? To answer these questions we look to the realm of social media, specifically the popular image-based service Instagram. For the uninitiated, Instagram is a web-based social media service that allows pictures to be shared and seen by anyone that follows a person or business’ Instagram account. Actions include posting original photos (often taken and posted with a cell phone), ‘liking’ pictures, and ‘hash-tagging’ posts with trending terms that increase visibility. Instagram presents us with a complex view of place as both material and virtual, sometimes reifying and sometimes abstracting often-contradictory understandings of place specificity. Many makers use Instagram to promote their products to a broad audience and, in doing so, makers participate in the construction of Portland’s mythology. In this paper, we use empirical insights to theorise makers’ role in shaping and cultivating the virtual and material aspects of place. Additionally, we discuss how makers navigate the complex relationships tied to the importance of place in their specific cultural productions. In the first section, we develop the notion of a curated maker subjectivity. In the second section, we consider the relationship between subjectivity and place. Both sections emphasize how Instagram mediates the relationship between place and subjectivity. Through spotlighting particular literatures in each section, we attempt to fill a gap in the literature that addresses the relationship between subjectivity, place, and social media. Through this line of analysis, we attempt to better understand how and where Portland is made, along with the implications for Portland’s makers. Close

• 7893. [Article] Investigation into Effects of Instability and Reactivity of Hydride-Passivated Silicon Nanoparticles on Interband Photoluminescence

  While silicon has long been utilized for its electronic properties, its use as an optical material has largely been limited due to the poor efficiency of interband transitions. However, discovery of visible ...

  Citation × Citation Citation Abstract Copy Title: Investigation into Effects of Instability and Reactivity of Hydride-Passivated Silicon Nanoparticles on Interband Photoluminescence Author: Radlinger, Christine Marie Year: 2017 While silicon has long been utilized for its electronic properties, its use as an optical material has largely been limited due to the poor efficiency of interband transitions. However, discovery of visible photoluminescence (PL) from nanocrystalline silicon in 1990 triggered many ensuing research efforts to optimize PL from nanocrystalline silicon for optical applications. Currently, use of photoluminescent silicon nanoparticles (Si NPs) is commercially limited by: 1) the instability of the energy and intensity of the PL, and 2) the low quantum yield of interband PL from Si NPs. Herein, red-emitting, hydrogen-passivated silicon nanoparticles (H-Si NPs) were synthesized by thermally-induced disproportionation of a HSiCl3-derived (HSiO1.5)n polymer. The H-Si NPs produced by this method were then subjected to various chemical and physical environments to assess the long-term stability of the optical properties as a function of changing surface composition. This dissertation is intended to elucidate correlations between the reported PL instability and the observed changes in the Si NP surface chemistry over time and as a function of environment. First, the stability of the H-Si NP surface at slightly elevated temperatures towards reactivity with a simple alkane was probed. The H-Si NPs were observed by FT-IR spectroscopy to undergo partial hydrosilylation upon heating in refluxing hexane, in addition to varying degrees of surface oxidation. The unexpected reactivity of the Si surface in n-hexane supports the unstable nature of the H-Si NP surface, and furthermore implicates the presence of highly-reactive Si radicals on the surfaces of the Si NPs. We propose that reaction of alkene impurities with the Si surface radicals is largely responsible for the observed surface alkylation. However, we also present an alternate mechanism by which Si surface radicals could react with alkanes to result in alkylation of the surface. Next, the energy and intensity stability of the interband PL from H-Si NPs in the presence of a radical trap was probed. Upon addition of (2,2,6,6,-tetramethyl-piperidin-1-yl)oxyl (TEMPO), the energy and intensity of the interband transition was observed to change over time, dependent on the reaction conditions. First, when the reaction occurred at 4ºC with minimal light exposure, the interband transition exhibited a gradual hypsochromic shift to between 595 nm and 655 nm, versus the λmax of the original low energy emission peak at 700 nm, depending on the amount of TEMPO in the sample. Second, when the reaction proceeded at room temperature with frequent exposure to 360 nm irradiation, the original interband transition at 660 nm was quenched while a new peak at 575 nm developed. Based on all the data collected and analyzed, we assign the 595 -- 655 nm transition as due to interband exciton recombination from Si NPs with reduced diameters relative to the original Si NPs. We furthermore assign the 575 nm transition as due to an oxide-related defect state resulting from rapid oxidation of photo-excited Si NPs. Title: Investigation into Effects of Instability and Reactivity of Hydride-Passivated Silicon Nanoparticles on Interband Photoluminescence Author: Radlinger, Christine Marie Year: 2017 While silicon has long been utilized for its electronic properties, its use as an optical material has largely been limited due to the poor efficiency of interband transitions. However, discovery of visible photoluminescence (PL) from nanocrystalline silicon in 1990 triggered many ensuing research efforts to optimize PL from nanocrystalline silicon for optical applications. Currently, use of photoluminescent silicon nanoparticles (Si NPs) is commercially limited by: 1) the instability of the energy and intensity of the PL, and 2) the low quantum yield of interband PL from Si NPs. Herein, red-emitting, hydrogen-passivated silicon nanoparticles (H-Si NPs) were synthesized by thermally-induced disproportionation of a HSiCl3-derived (HSiO1.5)n polymer. The H-Si NPs produced by this method were then subjected to various chemical and physical environments to assess the long-term stability of the optical properties as a function of changing surface composition. This dissertation is intended to elucidate correlations between the reported PL instability and the observed changes in the Si NP surface chemistry over time and as a function of environment. First, the stability of the H-Si NP surface at slightly elevated temperatures towards reactivity with a simple alkane was probed. The H-Si NPs were observed by FT-IR spectroscopy to undergo partial hydrosilylation upon heating in refluxing hexane, in addition to varying degrees of surface oxidation. The unexpected reactivity of the Si surface in n-hexane supports the unstable nature of the H-Si NP surface, and furthermore implicates the presence of highly-reactive Si radicals on the surfaces of the Si NPs. We propose that reaction of alkene impurities with the Si surface radicals is largely responsible for the observed surface alkylation. However, we also present an alternate mechanism by which Si surface radicals could react with alkanes to result in alkylation of the surface. Next, the energy and intensity stability of the interband PL from H-Si NPs in the presence of a radical trap was probed. Upon addition of (2,2,6,6,-tetramethyl-piperidin-1-yl)oxyl (TEMPO), the energy and intensity of the interband transition was observed to change over time, dependent on the reaction conditions. First, when the reaction occurred at 4ºC with minimal light exposure, the interband transition exhibited a gradual hypsochromic shift to between 595 nm and 655 nm, versus the λmax of the original low energy emission peak at 700 nm, depending on the amount of TEMPO in the sample. Second, when the reaction proceeded at room temperature with frequent exposure to 360 nm irradiation, the original interband transition at 660 nm was quenched while a new peak at 575 nm developed. Based on all the data collected and analyzed, we assign the 595 -- 655 nm transition as due to interband exciton recombination from Si NPs with reduced diameters relative to the original Si NPs. We furthermore assign the 575 nm transition as due to an oxide-related defect state resulting from rapid oxidation of photo-excited Si NPs. Close

• 7894. [Article] Shifting Advertising Agency Structure and Evolving Technology

  As a senior at Portland State University I have been exposed to many real-life advertising situations. This immersion in the advertising world has been an invaluable experience that has given me significant ...

  Citation × Citation Citation Abstract Copy Title: Shifting Advertising Agency Structure and Evolving Technology Author: Norris, Sarah A. Year: 2017 As a senior at Portland State University I have been exposed to many real-life advertising situations. This immersion in the advertising world has been an invaluable experience that has given me significant insight into advertising agencies and their operations from multiple different positions throughout the typical firm. This experience has helped me shape my thesis into a question that is relevant not only for the advertising community as a whole but also as someone hoping to enter the field within the next few years. My goal for this thesis is not to simply gain total knowledge in one specific area of advertising, but to create an accurate perspective of the advertising ecosystem and all the businesses and people that interact with or depend on it, as it exists today. I will go in depth on all the aspects of the “advertising ecosystem” later in this paper,) I am using this terminology as an overarching term for all businesses that rely or drive any form of work related to advertising). These businesses can range from the advertising firm itself to the catering business that supplies sandwiches for a Nike photo-shoot. As a soon-to-be college graduate, it’s important to know exactly what the climate is for any potential field of work. I came to my topic by researching trends in the advertising ecosystem that have come about with the increased use of the Internet and technology in business. Almost everyone can not only advertise for themselves, but can also have access to a multitude of analytic tools that would previously have only been available to advertising and marketing professionals. There are a growing number of firms who use social media and low-cost creative departments, and whose success now threatens the larger advertising agencies. Because only a relatively few brands and companies have the funds to access larger more traditional firms, more small and micro businesses are turning to the only alternatives most of them can afford. For clarification, the traditional advertising firm is an all in-house firm that deals with every aspect of the advertising process from the PR to coupon development and media buying. These traditional firms are priced in one of three ways that I will explain further in my thesis. These firms tend to be more costly than most brands can afford. As I will discuss in my thesis the growing importance of small advertising firms has had reverberating effects on not only the industry but also the employees of the firms in question. Technology and the evolving tools of the Internet have allowed many brands and companies to reconsider the need for the traditional advertising agency, and has allowed for the growth of more non-traditional advertising shops. Title: Shifting Advertising Agency Structure and Evolving Technology Author: Norris, Sarah A. Year: 2017 As a senior at Portland State University I have been exposed to many real-life advertising situations. This immersion in the advertising world has been an invaluable experience that has given me significant insight into advertising agencies and their operations from multiple different positions throughout the typical firm. This experience has helped me shape my thesis into a question that is relevant not only for the advertising community as a whole but also as someone hoping to enter the field within the next few years. My goal for this thesis is not to simply gain total knowledge in one specific area of advertising, but to create an accurate perspective of the advertising ecosystem and all the businesses and people that interact with or depend on it, as it exists today. I will go in depth on all the aspects of the “advertising ecosystem” later in this paper,) I am using this terminology as an overarching term for all businesses that rely or drive any form of work related to advertising). These businesses can range from the advertising firm itself to the catering business that supplies sandwiches for a Nike photo-shoot. As a soon-to-be college graduate, it’s important to know exactly what the climate is for any potential field of work. I came to my topic by researching trends in the advertising ecosystem that have come about with the increased use of the Internet and technology in business. Almost everyone can not only advertise for themselves, but can also have access to a multitude of analytic tools that would previously have only been available to advertising and marketing professionals. There are a growing number of firms who use social media and low-cost creative departments, and whose success now threatens the larger advertising agencies. Because only a relatively few brands and companies have the funds to access larger more traditional firms, more small and micro businesses are turning to the only alternatives most of them can afford. For clarification, the traditional advertising firm is an all in-house firm that deals with every aspect of the advertising process from the PR to coupon development and media buying. These traditional firms are priced in one of three ways that I will explain further in my thesis. These firms tend to be more costly than most brands can afford. As I will discuss in my thesis the growing importance of small advertising firms has had reverberating effects on not only the industry but also the employees of the firms in question. Technology and the evolving tools of the Internet have allowed many brands and companies to reconsider the need for the traditional advertising agency, and has allowed for the growth of more non-traditional advertising shops. Close

• 7895. [Article] Using Cultural Relevancy to Promote African American Brain Health

  African Americans are disproportionately more likely than older whites to develop Alzheimer’s disease and other dementias (ADOD). Despite these disparities, there is difficulty in motivating African Americans ...

  Citation × Citation Citation Abstract Copy Title: Using Cultural Relevancy to Promote African American Brain Health Author: Walker, Miya Year: 2017 African Americans are disproportionately more likely than older whites to develop Alzheimer’s disease and other dementias (ADOD). Despite these disparities, there is difficulty in motivating African Americans to engage in activities suitable to maintaining cognitive health (walking, social engagement, physical activity). The Sharing History through Active Reminiscence and Photo-imagery (SHARP) walking program (Croff, PI) combines these proactive activities in a culturally relevant way to create a motivational force to preserve cognitive health. SHARP engaged 19 African Americans aged 55 and older on 72 themed, 1-mile walks over 6 months in Portland, Oregon’s historically Black neighborhoods. This study examines participant responses to the SHARP walk “Afrocentrism” to illustrate how culture can be used to motivate walking and social engagement among older African Americans. The “Afrocentrism” walk presents three questions with historic neighborhood images, each approximately 10 minutes apart along the route: What are your memories of Afrocentric art? What did it mean to you and your community? Did you, your friends or family show your Afrocentrism in the 1960's, 70's and 80's? How? What did it mean to you? Do you have any memories about this [African clothing] shop? How were expressions of Afrocentrism accepted in the 1960's and 70's in Portland? Participant narratives were audio recorded. Narratives were then coded for common themes that gave insight to the importance of culture in health programming. Specific conversations amongst walking groups varied around the “Afrocentrism” prompts, however, walking groups reminisced over the same prominent people and places in the community. The commonality of participants shared neighborhood experiences creates a collective historical narrative and allows for connection to one another in ways that support connection to the neighborhood and to African American culture. This collective narrative informs researchers and allows for a deeper understanding of the Black experience, thus further facilitating the incorporation of culturally relevant prompts into the program. This is an essential way SHARP motivates participants to exercise and engage socially. Incorporating culture into health programs, as SHARP does, can be transferable to other health promotion programs to sustain retention and engagement. Title: Using Cultural Relevancy to Promote African American Brain Health Author: Walker, Miya Year: 2017 African Americans are disproportionately more likely than older whites to develop Alzheimer’s disease and other dementias (ADOD). Despite these disparities, there is difficulty in motivating African Americans to engage in activities suitable to maintaining cognitive health (walking, social engagement, physical activity). The Sharing History through Active Reminiscence and Photo-imagery (SHARP) walking program (Croff, PI) combines these proactive activities in a culturally relevant way to create a motivational force to preserve cognitive health. SHARP engaged 19 African Americans aged 55 and older on 72 themed, 1-mile walks over 6 months in Portland, Oregon’s historically Black neighborhoods. This study examines participant responses to the SHARP walk “Afrocentrism” to illustrate how culture can be used to motivate walking and social engagement among older African Americans. The “Afrocentrism” walk presents three questions with historic neighborhood images, each approximately 10 minutes apart along the route: What are your memories of Afrocentric art? What did it mean to you and your community? Did you, your friends or family show your Afrocentrism in the 1960's, 70's and 80's? How? What did it mean to you? Do you have any memories about this [African clothing] shop? How were expressions of Afrocentrism accepted in the 1960's and 70's in Portland? Participant narratives were audio recorded. Narratives were then coded for common themes that gave insight to the importance of culture in health programming. Specific conversations amongst walking groups varied around the “Afrocentrism” prompts, however, walking groups reminisced over the same prominent people and places in the community. The commonality of participants shared neighborhood experiences creates a collective historical narrative and allows for connection to one another in ways that support connection to the neighborhood and to African American culture. This collective narrative informs researchers and allows for a deeper understanding of the Black experience, thus further facilitating the incorporation of culturally relevant prompts into the program. This is an essential way SHARP motivates participants to exercise and engage socially. Incorporating culture into health programs, as SHARP does, can be transferable to other health promotion programs to sustain retention and engagement. Close

• 7896. [Article] Beyond the Angle of Repose: A Review and Synthesis of Landslide Processes in Response to Rapid Uplift, Eel River, Northern Eel River, Northern California

  In mountainous settings, increases in rock uplift are often followed by a commensurate uptick in denudation as rivers incise and steepen hillslopes, making them increasingly prone to landsliding as slope ...

  Citation × Citation Citation Abstract Copy Title: Beyond the Angle of Repose: A Review and Synthesis of Landslide Processes in Response to Rapid Uplift, Eel River, Northern Eel River, Northern California Author: Roering, Joshua J., Mackey, Benjamin H., Handwerger, Alexander L., Booth, Adam M., Schmidt, David A., Bennett, Georgina L., Cerovski-Darriau, Corina Year: 2015 In mountainous settings, increases in rock uplift are often followed by a commensurate uptick in denudation as rivers incise and steepen hillslopes, making them increasingly prone to landsliding as slope angles approach a limiting value. For decades, the threshold slope model has been invoked to account for landslide-driven increases in sediment flux that limit topographic relief, but the manner by which slope failures organize themselves spatially and temporally in order for erosion to keep pace with rock uplift has not been well documented. Here, we review past work and present new findings from remote sensing, cosmogenic adionuclides, suspended sediment records, and airborne lidar data, to decipher patterns of landslide activity and geomorphic processes related to rapid uplift along the northward-migrating Mendocino Triple Junction in Northern California. From historical air photos and airborne lidar, we estimated the velocity and sediment flux associated with active, slow-moving landslides (or earthflows) in the mélange- and argillite-dominated Eel River watershed using the downslope displacement of surface markers such as trees and shrubs. Although active landslides that directly convey sediment into the channel network account for only 7% of the landscape surface, their sediment flux amounts to more than 50% of the suspended load recorded at downstream sediment gauging stations. These active slides tend to exhibit seasonal variations in velocity as satellite-based interferometry has demonstrated that rapid acceleration commences within 1 to 2 months of the onset of autumn rainfall events before slower deceleration ensues in the spring and summer months. Curiously, this seasonal velocity pattern does not appear to vary with landslide size, suggesting that complex hydrologic-mechanical feedbacks (rather than 1-D pore pressure diffusion) may govern slide dynamics. A new analysis of 14 years of discharge and sediment concentration data for the Eel River indicates that the characteristic mid-winter timing of earthflow acceleration corresponds with increased suspended concentration values, suggesting that the seasonal onset of landslide motion each year may be reflected in the export of sediments to the continental margin. The vast majority of active slides exhibit gullied surfaces and the gully networks, which are also seasonally active, may facilitate sediment export although the proportion of material produced by this pathway is poorly known. Along Kekawaka Creek, a prominent tributary to the Eel River, new analyses of catchment-averaged erosion rates derived from cosmogenic radionuclides reveal rapid erosion (0.76 mm/yr) below a prominent knickpoint and slower erosion (0.29 mm/yr) upstream. Such knickpoints are frequently observed in Eel tributaries and are usually comprised of massive (>10m) interlocking resistant boulders that likely persist in the landscape for long time periods (>105yr). Upstream of these knickpoints, active landslides tend to be less frequent and average slope angles are slightly gentler than in downstream areas, which indicates that landslide density and average slope angle appear to increase with erosion rate. Lastly, we synthesize evidence for the role of large, catastrophic landslides in regulating sediment flux and landscape form. The emergence of resistant blocks within the mélange bedrock has promoted large catastrophic slides that have dammed the Eel River and perhaps generated outburst events in the past. The frequency and impact of these landslide dams likely depend on the spatial and size distributions of resistant blocks relative to the width and drainage area of adjacent valley networks. Overall, our findings demonstrate that landslides within the Eel River catchment do not occur randomly, but instead exhibit spatial and temporal patterns related to baselevel lowering, climate forcing, and lithologic variations. Combined with recent landscape evolution models that incorporate landslides, these results provide predictive capability for estimating erosion rates and managing hazards in mountainous regions. Title: Beyond the Angle of Repose: A Review and Synthesis of Landslide Processes in Response to Rapid Uplift, Eel River, Northern Eel River, Northern California Author: Roering, Joshua J., Mackey, Benjamin H., Handwerger, Alexander L., Booth, Adam M., Schmidt, David A., Bennett, Georgina L., Cerovski-Darriau, Corina Year: 2015 In mountainous settings, increases in rock uplift are often followed by a commensurate uptick in denudation as rivers incise and steepen hillslopes, making them increasingly prone to landsliding as slope angles approach a limiting value. For decades, the threshold slope model has been invoked to account for landslide-driven increases in sediment flux that limit topographic relief, but the manner by which slope failures organize themselves spatially and temporally in order for erosion to keep pace with rock uplift has not been well documented. Here, we review past work and present new findings from remote sensing, cosmogenic adionuclides, suspended sediment records, and airborne lidar data, to decipher patterns of landslide activity and geomorphic processes related to rapid uplift along the northward-migrating Mendocino Triple Junction in Northern California. From historical air photos and airborne lidar, we estimated the velocity and sediment flux associated with active, slow-moving landslides (or earthflows) in the mélange- and argillite-dominated Eel River watershed using the downslope displacement of surface markers such as trees and shrubs. Although active landslides that directly convey sediment into the channel network account for only 7% of the landscape surface, their sediment flux amounts to more than 50% of the suspended load recorded at downstream sediment gauging stations. These active slides tend to exhibit seasonal variations in velocity as satellite-based interferometry has demonstrated that rapid acceleration commences within 1 to 2 months of the onset of autumn rainfall events before slower deceleration ensues in the spring and summer months. Curiously, this seasonal velocity pattern does not appear to vary with landslide size, suggesting that complex hydrologic-mechanical feedbacks (rather than 1-D pore pressure diffusion) may govern slide dynamics. A new analysis of 14 years of discharge and sediment concentration data for the Eel River indicates that the characteristic mid-winter timing of earthflow acceleration corresponds with increased suspended concentration values, suggesting that the seasonal onset of landslide motion each year may be reflected in the export of sediments to the continental margin. The vast majority of active slides exhibit gullied surfaces and the gully networks, which are also seasonally active, may facilitate sediment export although the proportion of material produced by this pathway is poorly known. Along Kekawaka Creek, a prominent tributary to the Eel River, new analyses of catchment-averaged erosion rates derived from cosmogenic radionuclides reveal rapid erosion (0.76 mm/yr) below a prominent knickpoint and slower erosion (0.29 mm/yr) upstream. Such knickpoints are frequently observed in Eel tributaries and are usually comprised of massive (>10m) interlocking resistant boulders that likely persist in the landscape for long time periods (>105yr). Upstream of these knickpoints, active landslides tend to be less frequent and average slope angles are slightly gentler than in downstream areas, which indicates that landslide density and average slope angle appear to increase with erosion rate. Lastly, we synthesize evidence for the role of large, catastrophic landslides in regulating sediment flux and landscape form. The emergence of resistant blocks within the mélange bedrock has promoted large catastrophic slides that have dammed the Eel River and perhaps generated outburst events in the past. The frequency and impact of these landslide dams likely depend on the spatial and size distributions of resistant blocks relative to the width and drainage area of adjacent valley networks. Overall, our findings demonstrate that landslides within the Eel River catchment do not occur randomly, but instead exhibit spatial and temporal patterns related to baselevel lowering, climate forcing, and lithologic variations. Combined with recent landscape evolution models that incorporate landslides, these results provide predictive capability for estimating erosion rates and managing hazards in mountainous regions. Close