title: Strategies for determining the cascade rate in MHD Turbulence: isotropy, anisotropy, and spacecraft sampling

authors: Wang, Yanwen

abstract: Exact laws for evaluating cascade rates, tracing back to the Kolmogorov "4/5"law, have been extended to many systems of interest including magnetohydrodynamics (MHD), and compressible flows of the magnetofluid and ordinary fluid types. It is understood that implementations may be limited by the quantity of available data and by the lack of turbulence symmetry. Assessment of the accuracy and feasibility of such third-order (or Yaglom) relations is most effectively accomplished by examining the von Kármán-Howarth equation in increment form, a framework from which the third-order laws are derived as asymptotic approximations. Using this approach, we examine the context of third-order laws for incompressible MHD in some detail. The simplest versions rely on the assumption of isotropy and the presence of a well-defined inertial range, while related procedures generalize the same idea to arbitrary rotational symmetries. Conditions for obtaining correct and accurate values of the dissipation rate from these laws based on several sampling and fitting strategies are investigated using results from simulations. The questions we address are of particular relevance to sampling of solar wind turbulence by one or more spacecraft.

text: Strategies for determining the cascade rate in MHD Turbulence: isotropy, anisotropy, and spacecraft sampling Exact laws for evaluating cascade rates, tracing back to the Kolmogorov "4/5"law, have been extended to many systems of interest including magnetohydrodynamics (MHD), and compressible flows of the magnetofluid and ordinary fluid types. It is understood that implementations may be limited by the quantity of available data and by the lack of turbulence symmetry. Assessment of the accuracy and feasibility of such third-order (or Yaglom) relations is most effectively accomplished by examining the von Kármán-Howarth equation in increment form, a framework from which the third-order laws are derived as asymptotic approximations. Using this approach, we examine the context of third-order laws for incompressible MHD in some detail. The simplest versions rely on the assumption of isotropy and the presence of a well-defined inertial range, while related procedures generalize the same idea to arbitrary rotational symmetries. Conditions for obtaining correct and accurate values of the dissipation rate from these laws based on several sampling and fitting strategies are investigated using results from simulations. The questions we address are of particular relevance to sampling of solar wind turbulence by one or more spacecraft.

year: 2022-10-01

title: Investigation of glucose and energy metabolism in eumenorrheic female ultra-runners across the menstrual cycle

authors: Dole, Andrew

subjects: blood glucose

abstract: Female athletes, ultra-running, and the utilization of continuous glucose sensors in endurance sports are each individually underrepresented in current literature. When these areas are examined collectively, a substantial gap in knowledge becomes evident. Therefore, the purpose of this PhD study was to collect glucose and energy metabolism data in regularly menstruating female athletes within the complex sporting environment of ultra-running. Initially, a narrative review of the current study methodologies in female performance research was completed. The narrative review aided in the identification of gaps in study design and validation methodologies within female performance research, put forth a suggestive framework for standardizing terminology, and provides a comprehensive list of options for a combined methods approach to menstrual tracking. Subsequently, a randomized, cross-over experimental design was performed with twelve experienced female ultra-runners (age 39 ± 6 y) acting as their own control across menstrual cycle phases during an ultra-marathon simulation. Participants completed a 3-hour fasted outdoor run (FASTED) followed by a one-hour treadmill run (TREAD) where three standardized oral glucose doses were provided, in the mid-follicular (FOL) and mid-luteal phases (LUT). Using a mixed linear model, the menstrual phase was identified as being statistically significant for differences in glucose measurements between CGM and capillary glucose during TREAD (p = 0.02) but not FASTED. Also, the CGM reported glucose levels an average of -0.43 mmol·L-1 (95% CI -0.86, -0.005) and -1.02 mmol·L-1 (95% CI -1.63, -0.42) lower in fasted and fed scenarios respectively when compared to capillary glucose. Median glucose was higher in the LUT (Capillary 0.25-0.29 mmol·L-1, CGM 0.38-0.4 mmol·L-1) both when fasted or supplemented with carbohydrate. Of note, this is the first study to show that glucose is on average higher in the mid-luteal phase as well as observe the avoidance of clinically significant non-diabetic hypoglycemia (< 3.0 mmol·L-1) during 3-hours of fasted running following an 8-hour fast among female ultra-runners. Additionally, higher individual responses of low blood sugar were observed in the follicular phase. Further, there were no significant differences in the respiratory exchange ratio (RER) between the FOL (0.805 ± 0.028) and LUT phases (0.809 ± .035); t (10) -0.401, p = 0.697 during comparable submaximal running intensity (57% ± 7.3% and 57.3% ±7.9% VO2MAX respectively). Post-hoc analysis revealed no significant main effect of RER on glucose levels.

text: Investigation of glucose and energy metabolism in eumenorrheic female ultra-runners across the menstrual cycle Female athletes, ultra-running, and the utilization of continuous glucose sensors in endurance sports are each individually underrepresented in current literature. When these areas are examined collectively, a substantial gap in knowledge becomes evident. Therefore, the purpose of this PhD study was to collect glucose and energy metabolism data in regularly menstruating female athletes within the complex sporting environment of ultra-running. Initially, a narrative review of the current study methodologies in female performance research was completed. The narrative review aided in the identification of gaps in study design and validation methodologies within female performance research, put forth a suggestive framework for standardizing terminology, and provides a comprehensive list of options for a combined methods approach to menstrual tracking. Subsequently, a randomized, cross-over experimental design was performed with twelve experienced female ultra-runners (age 39 ± 6 y) acting as their own control across menstrual cycle phases during an ultra-marathon simulation. Participants completed a 3-hour fasted outdoor run (FASTED) followed by a one-hour treadmill run (TREAD) where three standardized oral glucose doses were provided, in the mid-follicular (FOL) and mid-luteal phases (LUT). Using a mixed linear model, the menstrual phase was identified as being statistically significant for differences in glucose measurements between CGM and capillary glucose during TREAD (p = 0.02) but not FASTED. Also, the CGM reported glucose levels an average of -0.43 mmol·L-1 (95% CI -0.86, -0.005) and -1.02 mmol·L-1 (95% CI -1.63, -0.42) lower in fasted and fed scenarios respectively when compared to capillary glucose. Median glucose was higher in the LUT (Capillary 0.25-0.29 mmol·L-1, CGM 0.38-0.4 mmol·L-1) both when fasted or supplemented with carbohydrate. Of note, this is the first study to show that glucose is on average higher in the mid-luteal phase as well as observe the avoidance of clinically significant non-diabetic hypoglycemia (< 3.0 mmol·L-1) during 3-hours of fasted running following an 8-hour fast among female ultra-runners. Additionally, higher individual responses of low blood sugar were observed in the follicular phase. Further, there were no significant differences in the respiratory exchange ratio (RER) between the FOL (0.805 ± 0.028) and LUT phases (0.809 ± .035); t (10) -0.401, p = 0.697 during comparable submaximal running intensity (57% ± 7.3% and 57.3% ±7.9% VO2MAX respectively). Post-hoc analysis revealed no significant main effect of RER on glucose levels.

year: 2024-12-20

title: COVID-19 and blind spaces: Responding to digital (in)accessibility and social isolation during lockdown for blind, deafblind, low vision, and vision impaired persons in Aotearoa New Zealand

authors: Graham, Rebekah Sarah

abstract: In this chapter we, as Indigenous (Māori) and non-Indigenous (Pākehā) academics, practitioners, and disability advocates critically examine the experiences of people who are blind, deafblind, low vision and vision impaired (BLV) during the COVID-19 lockdown of Aotearoa New Zealand. We pay particular attention to the ways in which access (or lack thereof) to digital spaces facilitated experiences of social inclusion (and exclusion). Digital connectivity was heavily relied upon during lockdown in Aotearoa New Zealand to disseminate health information and to connect people socially. The use of digital technologies during lockdown extended the interpersonal space of the home beyond the physicality of the urban home people were confined to, drawing people together across the country and creating a sense of shared experience. However, these experiences were not shared equally across the citizenry. Conversations during lockdown with disability advocates and practitioners working with BLV persons identified that. For example, the government website on COVID19 was initially inaccessible for BLV persons and there were assumptions of digital accessibility and literacy within the domestic space of the home. Taken together, these exacerbated existing inequities for BLV persons, some of whom experience multiple domains of exclusion (for example, Indigenous BLV persons with reduced access to services and for whom English is their second language). Drawing on Lefebvre’s (1991) work on the dialectics of space and Lewin’s (1936/2013) construction of the life-space, we consider the interplay of space and experience with regards to the digital and physical space(s) available and inhabited during the shared social experience of lockdown. We discuss possibilities for co-creating socially inclusive (digital) spaces of belonging that reflect and refract life-space relational connections across social groups. Our reflections on the lockdown experience include opportunities post-pandemic for policy makers and practitioners to address digital accessibility inequities.

text: COVID-19 and blind spaces: Responding to digital (in)accessibility and social isolation during lockdown for blind, deafblind, low vision, and vision impaired persons in Aotearoa New Zealand In this chapter we, as Indigenous (Māori) and non-Indigenous (Pākehā) academics, practitioners, and disability advocates critically examine the experiences of people who are blind, deafblind, low vision and vision impaired (BLV) during the COVID-19 lockdown of Aotearoa New Zealand. We pay particular attention to the ways in which access (or lack thereof) to digital spaces facilitated experiences of social inclusion (and exclusion). Digital connectivity was heavily relied upon during lockdown in Aotearoa New Zealand to disseminate health information and to connect people socially. The use of digital technologies during lockdown extended the interpersonal space of the home beyond the physicality of the urban home people were confined to, drawing people together across the country and creating a sense of shared experience. However, these experiences were not shared equally across the citizenry. Conversations during lockdown with disability advocates and practitioners working with BLV persons identified that. For example, the government website on COVID19 was initially inaccessible for BLV persons and there were assumptions of digital accessibility and literacy within the domestic space of the home. Taken together, these exacerbated existing inequities for BLV persons, some of whom experience multiple domains of exclusion (for example, Indigenous BLV persons with reduced access to services and for whom English is their second language). Drawing on Lefebvre’s (1991) work on the dialectics of space and Lewin’s (1936/2013) construction of the life-space, we consider the interplay of space and experience with regards to the digital and physical space(s) available and inhabited during the shared social experience of lockdown. We discuss possibilities for co-creating socially inclusive (digital) spaces of belonging that reflect and refract life-space relational connections across social groups. Our reflections on the lockdown experience include opportunities post-pandemic for policy makers and practitioners to address digital accessibility inequities.

year: 2021