title: Observations of alongshore variability of swash motions on an intermediate beach

authors: Guedes, Rafael Marcondes Carvalho

subjects: Alongshore variability

abstract: Alongshore variability in swash motions - shoreline oscillations about the mean water level on the beach face - were investigated using video images and a high-resolution morphology survey on an intermediate beach. Under mild, swell-dominated offshore wave conditions, alongshore variation of up to 78$ in significant runup height . Rs (defined as 4 times the standard deviation of the swash time series) was observed. This variation was predominantly driven by energy at the incident (>0.05. Hz) frequencies (where most of the swash energy was observed), and, consistent with previous observations, was mainly controlled by changes in the slope of the beach face (measured at the mean swash location). However, alongshore patterning in wave breaking over the sandbar caused variation in the degree of wave dissipation along the beach and also resulted in alongshore changes to swash motions. Although alongshore changes in beach slope and wave breaking patterning over the bar were observed to be typically correlated, both were needed in a regression model to provide the best explaination of alongshore changes in . Rs. At infragravity frequencies (<0.05. Hz), alongshore variability was not well associated either with changes in beach slope or wave breaking patterning. Low-mode edge waves were observed in the swash measurements and their contribution to the total energy spectrum was greatest near the location where a shoal was observed, suggesting this shoal may play a role in forcing. The edge waves may have contributed to the swash variability observed at infragravity frequencies. However, in these reflective conditions, the infragravity band plays a secondary role in controlling alongshore variations to swash motions.

text: Observations of alongshore variability of swash motions on an intermediate beach Alongshore variability in swash motions - shoreline oscillations about the mean water level on the beach face - were investigated using video images and a high-resolution morphology survey on an intermediate beach. Under mild, swell-dominated offshore wave conditions, alongshore variation of up to 78$ in significant runup height . Rs (defined as 4 times the standard deviation of the swash time series) was observed. This variation was predominantly driven by energy at the incident (>0.05. Hz) frequencies (where most of the swash energy was observed), and, consistent with previous observations, was mainly controlled by changes in the slope of the beach face (measured at the mean swash location). However, alongshore patterning in wave breaking over the sandbar caused variation in the degree of wave dissipation along the beach and also resulted in alongshore changes to swash motions. Although alongshore changes in beach slope and wave breaking patterning over the bar were observed to be typically correlated, both were needed in a regression model to provide the best explaination of alongshore changes in . Rs. At infragravity frequencies (<0.05. Hz), alongshore variability was not well associated either with changes in beach slope or wave breaking patterning. Low-mode edge waves were observed in the swash measurements and their contribution to the total energy spectrum was greatest near the location where a shoal was observed, suggesting this shoal may play a role in forcing. The edge waves may have contributed to the swash variability observed at infragravity frequencies. However, in these reflective conditions, the infragravity band plays a secondary role in controlling alongshore variations to swash motions.

year: 2012

title: Cortical patterns and gamma genesis are modulated by reversal potentials and gap-junction diffusion

authors: Steyn-Ross, Moira L.

subjects: gap junctions

abstract: In this chapter we describe a continuum model for the cortex that includes both axon-to-dendrite chemical synapses and direct neuron-to-neuron gap-junction diffusive synapses. The effectiveness of chemical synapses is determined by the voltage of the receiving dendrite V relative to its Nernst reversal potential Vrev. Here we explore two alternative strategies for incorporating dendritic reversal potentials, and uncover surprising differences in their stability properties and model dynamics. In the “slow-soma” variant, the (Vrev - V) weighting is applied after the input flux has been integrated at the dendrite, while for “fast-soma”, the weighting is applied directly to the input flux, prior to dendritic integration. For the slow-soma case, we find that–-provided the inhibitory diffusion (via gap-junctions) is sufficiently strong–-the cortex generates stationary Turing patterns of cortical activity. In contrast, the fast-soma destabilizes in favor of standing-wave spatial structures that oscillate at low-gamma frequency (  30-Hz); these spatial patterns broaden and weaken as diffusive coupling increases, and disappear altogether at moderate levels of diffusion. We speculate that the slow- and fast-soma models might correspond respectively to the idling and active modes of the cortex, with slow-soma patterns providing the default background state, and emergence of gamma oscillations in the fast-soma case signaling the transition into the cognitive state.

text: Cortical patterns and gamma genesis are modulated by reversal potentials and gap-junction diffusion In this chapter we describe a continuum model for the cortex that includes both axon-to-dendrite chemical synapses and direct neuron-to-neuron gap-junction diffusive synapses. The effectiveness of chemical synapses is determined by the voltage of the receiving dendrite V relative to its Nernst reversal potential Vrev. Here we explore two alternative strategies for incorporating dendritic reversal potentials, and uncover surprising differences in their stability properties and model dynamics. In the “slow-soma” variant, the (Vrev - V) weighting is applied after the input flux has been integrated at the dendrite, while for “fast-soma”, the weighting is applied directly to the input flux, prior to dendritic integration. For the slow-soma case, we find that–-provided the inhibitory diffusion (via gap-junctions) is sufficiently strong–-the cortex generates stationary Turing patterns of cortical activity. In contrast, the fast-soma destabilizes in favor of standing-wave spatial structures that oscillate at low-gamma frequency (  30-Hz); these spatial patterns broaden and weaken as diffusive coupling increases, and disappear altogether at moderate levels of diffusion. We speculate that the slow- and fast-soma models might correspond respectively to the idling and active modes of the cortex, with slow-soma patterns providing the default background state, and emergence of gamma oscillations in the fast-soma case signaling the transition into the cognitive state.

year: 2010

title: Whānau aspirations, extracurricular activity  and positive youth development:  The leisure activity patterns and narratives of successful young Māori men and how they might inform  urban whānau raising tamatāne.

authors: Clarke, Gloria Hinemoa

subjects: Leisure

abstract: The purpose of this research is to offer parents and whānau (extended family groups) insight about the kinds of leisure activities that might make a positive contribution to their boys’ development. Focused on the positive developmental benefits of leisure participation in relation to Māori boys, and employing a kaupapa Māori framework and qualitative methods, this study represents a foray into new territory. 
	Conducted ‘by, with, and for’ Māori (the indigenous people of Aotearoa New Zealand), and guided by the question ‘How might the leisure activity patterns and narratives of successful young Māori men inform urban whānau raising tamatāne (Māori boys/sons)?’ the three-phase research design was strengths-based, collaborative, and both retrospective and prospective. In phase one, a group of 11 parents participated in focus group hui (gatherings) in which they established the criteria for ‘successful young Māori men’ (SYMM) based on their aspirations for their primary-school aged boys. In phase two, this whānau of interest then selected six SYMM from a pool of eight volunteers, who, along with one or both of their parents participated in one-off semi-structured interviews. In these interviews, we co-constructed life and leisure maps, and discussed how their childhood leisure activities and experiences contributed to their development and who they are today. In phase three, a selection of raw data from these interviews was prepared for a group analysis, during which the whānau of interest made three key observations: (1) As children and youth, these SYMM had participated in a number and range of organised and informal leisure activities including sport, kapa haka (Māori cultural performance), music, art, and for three of them, faith-based activities; (2) they were “connected” to their parent(s) and whānau; and (3) their leisure activities had brought them into contact with positive male role models. Consequently, the whānau of interest talked about increasing the number and variety of their boys’ leisure activities; how they could further support their boys’ leisure participation; and bringing more male role models into their boys’ lives. 
	The findings of this study support the current literature regarding extracurricular activity participation in relation to positive youth development, but also highlight some methodological issues and cultural and contextual nuances. The research supports international and local studies in which high-performing students participated in a number and combination of extracurricular activities. In contrast, however, the experiences and reflections of the SYMM in this study highlight the limitations of combining all sports and all arts into broad activity categories. The research participants’ leisure activities also point to the relevance and applicability of the Te Whare Tapa Whā model of health and wellbeing. Their involvement in kapa haka contrasts with the (North American) literature in which males are a minority in the performing arts, and while some studies indicate that participation in music making declines in high school, these young men began playing musical instruments in high school. Moreover, the salience and significance of the research participants’ casual leisure activities challenges the tendency to cast informal leisure as the antithesis of extracurricular activity participation. These findings raise questions about the applicability of using international activity categories in Aotearoa New Zealand research, and consequently the need to conduct our own leisure and positive youth development studies. 
Other topics raised in this thesis include rugby and masculinity, spirituality, and the tensions involved in building and honouring our children’s rangatiratanga (independence). The short answer to the research question is that a variety and balance of leisure activities has the potential to make positive contributions to boys’ lives. Implications, limitations, and recommendations for future research are also discussed.

text: Whānau aspirations, extracurricular activity  and positive youth development:  The leisure activity patterns and narratives of successful young Māori men and how they might inform  urban whānau raising tamatāne. The purpose of this research is to offer parents and whānau (extended family groups) insight about the kinds of leisure activities that might make a positive contribution to their boys’ development. Focused on the positive developmental benefits of leisure participation in relation to Māori boys, and employing a kaupapa Māori framework and qualitative methods, this study represents a foray into new territory. 
	Conducted ‘by, with, and for’ Māori (the indigenous people of Aotearoa New Zealand), and guided by the question ‘How might the leisure activity patterns and narratives of successful young Māori men inform urban whānau raising tamatāne (Māori boys/sons)?’ the three-phase research design was strengths-based, collaborative, and both retrospective and prospective. In phase one, a group of 11 parents participated in focus group hui (gatherings) in which they established the criteria for ‘successful young Māori men’ (SYMM) based on their aspirations for their primary-school aged boys. In phase two, this whānau of interest then selected six SYMM from a pool of eight volunteers, who, along with one or both of their parents participated in one-off semi-structured interviews. In these interviews, we co-constructed life and leisure maps, and discussed how their childhood leisure activities and experiences contributed to their development and who they are today. In phase three, a selection of raw data from these interviews was prepared for a group analysis, during which the whānau of interest made three key observations: (1) As children and youth, these SYMM had participated in a number and range of organised and informal leisure activities including sport, kapa haka (Māori cultural performance), music, art, and for three of them, faith-based activities; (2) they were “connected” to their parent(s) and whānau; and (3) their leisure activities had brought them into contact with positive male role models. Consequently, the whānau of interest talked about increasing the number and variety of their boys’ leisure activities; how they could further support their boys’ leisure participation; and bringing more male role models into their boys’ lives. 
	The findings of this study support the current literature regarding extracurricular activity participation in relation to positive youth development, but also highlight some methodological issues and cultural and contextual nuances. The research supports international and local studies in which high-performing students participated in a number and combination of extracurricular activities. In contrast, however, the experiences and reflections of the SYMM in this study highlight the limitations of combining all sports and all arts into broad activity categories. The research participants’ leisure activities also point to the relevance and applicability of the Te Whare Tapa Whā model of health and wellbeing. Their involvement in kapa haka contrasts with the (North American) literature in which males are a minority in the performing arts, and while some studies indicate that participation in music making declines in high school, these young men began playing musical instruments in high school. Moreover, the salience and significance of the research participants’ casual leisure activities challenges the tendency to cast informal leisure as the antithesis of extracurricular activity participation. These findings raise questions about the applicability of using international activity categories in Aotearoa New Zealand research, and consequently the need to conduct our own leisure and positive youth development studies. 
Other topics raised in this thesis include rugby and masculinity, spirituality, and the tensions involved in building and honouring our children’s rangatiratanga (independence). The short answer to the research question is that a variety and balance of leisure activities has the potential to make positive contributions to boys’ lives. Implications, limitations, and recommendations for future research are also discussed.

year: 2020