Possible neurobiological mechanisms of fatigue during prolonged exercise in a warm environment

Capacity to perform prolonged exercise is reduced in high ambient temperatures, but this premature fatigue is not adequately explained by peripheral mechanisms. The aim of this thesis was to examine some possible underlying mechanisms of central fatigue operating during prolonged exercise in a warm environment. The first series of experiments investigated the effect of nutritional manipulation of central serotonergic activity through alterations to the plasma concentration ratio of free-tryptophan to branched-chain amino acids (f-TRP:BCAA). In contrast to previous reports, acute BCAA supplementation failed to alter perceived exertion and delay the onset of fatigue (Chapter 3). This response was similar when exercise was preceded by an exercise and diet regimen designed to reduce glycogen availability (Chapter 4). The ingestion of meals containing added carbohydrate and fat did not alter f-TRP:BCAA at rest (Chapter 5). Acute dopaminergic / noradrenergic reuptake inhibition with bupropion increased exercise perfonnance by 9 % in warm conditions (30C), but this effect was not apparent at 18C (Chapter 6). This response was accompanied by attainment of a higher core temperature and heart rate towards the end of the bupropion trial in the heat despite no detectable difference in perceived exertion and thermal stress. These data suggested that maintenance of catecholaminergic activity may dampen inhibitory signals from the CNS due to the attainment of a high core temperature, allowing power output to be maintained. The blood-brain barrier (BBB) regulates the exchange of substances between the cerebral interstitial fluid and the blood to maintain a stable environment for the CNS. If the BBB is compromised this may adversely influence nonnal brain function. Serum S1OOb, a proposed peripheral marker of BBB penneability, was increased following exercise in a warm environment (Chapter 7). These data indicate that exposure to combined exercise and heat stress may result in a loss of BBB integrity.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Improved techniques to estimate mean sea level, velocity and acceleration from long ocean water level time series to augment sea level (and climate change) research

The prominence of the climate change issue has placed more emphasis on examination of the extensive global repository of mean sea level records, which along with temperature and carbon dioxide, remain the key proxy data sets used to monitor and quantify changes in the global climate system. Over the past decade, the scientific literature is replete with conflicting conclusions regarding the detection (or otherwise) of a measurable acceleration in mean sea level attributable to climate change. The key aim of the research program is to develop improved techniques (and associated tools) for estimating mean sea level and associated velocity and acceleration from long individual ocean water level time series to augment climate change research. This task involved extensive time series analysis which identified Singular Spectrum Analysis (SSA) as an optimal analytic for resolving estimates of mean sea level from long tide gauge records with improved accuracy and temporal resolution. SSA was further tested and optimised, then integrated into an open source analytical software package ( msltrend ), specifically customised for sea level research, providing enhanced estimates of mean sea level and associated velocity and acceleration on a year to year basis. The application of this package to the data rich margins of USA and Europe have provided more insight into the temporal and regional characteristics of mean sea level than previously available. In general, key findings across both margins suggest that not only are more recent accelerations no different to other periods elsewhere in the historical records, but, they are neither sufficiently strong nor sustained enough (yet) to accord with those associated with climate change projection models. Further, until such time as the velocities and accelerations are sufficiently large not to be obscured by complex influences inducing decadal to multi-decadal variability and other background noise, the search for accelerations in ocean water level records require more intuitive, diagnostic considerations which are explored in the research. The techniques espoused in this research form an integral part of the evolutionary process by which to measure kinematic properties of mean sea level with improving robustness and consistency

Dendrochronologic reconstruction of water levels for Pyramid Lake, Nevada, 1745 to 1904 A.D.

Online access for this thesis was created in part with support from the Institute of Museum and Library Services (IMLS) administered by the Nevada State Library, Archives and Public Records through the Library Services and Technology Act (LSTA). To obtain a high quality image or document please contact the DeLaMare Library at https://unr.libanswers.com/ or call: 775-784-6945.The objective of this study is to reconstruct a lake level hydrograph of Pyramid Lake, Nevada over the period of 1745 to 1904 by using tree-ring widths. Validation of the model reproduced the observed elevations of the lake to within five percent using observed inflows, and to within twenty percent using tree-ring generated inflows. Modeling the lake between 1745 and 1904 indicates the fluctuations of the lake were relatively subdued, with the maximum range in elevation being only sixteen feet. It is expected from various limitations within the model that this range of elevation should be twenty-five to fifty percent greater. The mean elevation of the lake in this period is the spill elevation of 3863 feet. This mean elevation would largely be determined by the average long term climatic conditions which the tree-ring data suggest were fairly stable

The Octahedral Hexarot - a novel 6-DOF parallel manipulator

A novel 6-DOF parallel kinematic manipulator named the Octahedral Hexarot is presented and analyzed. It is shown that this manipulator has the important benefits of combining a large positional workspace in relation to its footprint with a sizable range of platform rotations. These features are obtained by combining a rotation-symmetric actuating arm system with links in an octahedral-like configuration. Thus the manipulator consists of a central cylindrical column with six actuated rotating upper arms that can rotate indefinitely around the central column. Each upper arm is connected to a manipulated platform by one 5-DOF lower arm link. The link arrangement of the Octahedral Hexarot is inspired by the original Gough platform. The manipulated platform is an equilateral triangle and the joint positions on the upper arms approximately form an equilateral triangle. A task dependent optimization procedure for the structural parameters is proposed and the workspace of the resulting manipulator is analyzed in depth.<br /

Thirst responses following high intensity intermittent exercise when access to ad libitum water intake was permitted, not permitted or delayed

An increase in subjective feelings of thirst and ad libitum drinking caused by an increase in serum osmolality have been observed following high intensity intermittent exercise (HIIE) compared to continuous exercise. The increase in serum osmolality is closely linked to the rise in blood lactate and serum sodium concentrations. However, during an ensuing recovery period after HIIE when serum osmolality will decrease, the resultant effect on sensations of thirst and subsequent water intake is unclear. Therefore the aim of the study was to assess the sensations of thirst and subsequent effect on ad libitum water consumption when water intake was immediately allowed, delayed or prevented following a period of HIIE.Twelve males (26 ± 4 years, 80.1 ± 9.3 kg, 1.81 ± 0.05 m, V̇O2peak 60.1 ± 8.9 ml.kg(-1).min(-1)) participated in three randomised trials undertaken 7-14 days apart. Participants rested for 30 min then completed a 60 min HIIE exercise period (20 x 1 min at 100% V̇O2peak with 2 min rest) followed by 60 min of recovery, during which ad libitum water intake was provided immediately (W), delayed until the final 30 min (W30) or not permitted (NW). Body mass was measured at the start and end of the trial. Blood lactate and serum sodium concentrations serum osmolality and sensation of thirst were measured at baseline, immediately post-exercise and during the recovery.Body mass loss was different between all trials (W: 0.25 ± 0.45, W30: 0.49 ± 0.37, NW: 1.29 ± 0.37%; p0.05). Serum osmolality (299 ± 6 v 298 ± 5 vs. 298 ± 3 mOsmol.kg(-1)), blood lactate (7.1 ± 1.1 vs. 7.2 ± 1.1 v 7.1 ± 1.2 mmol.l(-1)) and serum sodium concentrations (142 ± 2 vs. 145 ± 2 v 145 ± 2 mmol.l(-1)) peaked post-exercise (W vs. W30 vs. NW; p0.05).Sensations of thirst were increased following HIIE and remained until satiated by water intake. This was despite the likely primary stimulus, serum osmolality, decreasing during the recovery period following a post-exercise peak. A combined effect of reduction in blood lactate and serum sodium concentrations, restoration of plasma volume and water intake contributed to the similar decrease in serum osmolality observed throughout the trials

The role of trauma and partner support in perinatal depression and parenting stress: An Australian pregnancy cohort study

Background: Improving our understanding of the relationship between maternal depression and parenting stress is likely to lie in the range of additional factors that are associated with vulnerability to depression and also to parenting stress. Objectives: To examine the role of trauma and partner support, in understanding the relationship between perinatal depression and parenting stress. Methods: This study utilises data from 246 women in a pregnancy cohort study that followed women from early pregnancy until their infant was 12 months. Included were both women with a diagnosis of depression and those without depression. The measures included Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Edinburgh Postnatal Depression Scale, Childhood Trauma Questionnaire, Social Support Effectiveness Questionnaire and the Parenting Stress Index. Results: We found women with depression were more likely to report a history of childhood trauma. Depressive symptoms were positively associated with parenting stress while partner support was negatively associated with parenting stress. The protective role of partner support for parenting distress was observed in those with no history of childhood abuse and low depressive symptoms, but not in those with a trauma history and high depressive symptoms. Conclusions: These findings highlight the importance of early trauma in understanding the protective role of support on the relationship between parenting and depression. These findings can inform future studies and the refinement of future interventions aimed at both perinatal depression and parenting

Fentanyl related overdose in Indianapolis: Estimating trends using multilevel Bayesian models

Introduction: The opioid epidemic has been largely attributed to changes in prescribing practices over the past 20 years. Although current overdose trends appear driven by the opioid fentanyl, heroin has remained the focus of overdose fatality assessments. We obtained full toxicology screens on lethal overdose cases in a major US city, allowing more accurate assessment of the time-course of fentanyl-related deaths. Methods: We used coroner data from Marion County, Indiana comprising 1583 overdose deaths recorded between January 1, 2010 and April 30, 2017. Bayesian multilevel models were fitted to predict likelihood of lethal fentanyl-related overdose using information about the victim's age, race, sex, zip code, and date of death. Results: Three hundred and seventy-seven (23.8%) overdose deaths contained fentanyl across the seven-year period. Rates rose exponentially over time, beginning well below 15% from 2010 through 2013 before rising to approximately 50% by 2017. At the beginning of the study period, rates of fentanyl overdose were lowest among Black persons but increased more rapidly, eventually surpassing Whites. Currently, White females may be at particularly low risk of fentanyl overdose and Black females at high risk. Rates were highest for younger and middle-aged groups. Over time, fentanyl was more likely detected without the presence of other opioids. Conclusions: Fentanyl has increasingly been detected in fatal overdose deaths in Marion County. Policy and program responses must focus on education for those at highest risk of fentanyl exposure and death. These responses should also be tailored to meet the unique needs of high-risk demographics.This publication was supported by the Grant Number, 5 NU17CE002721-02, funded by the Centers for Disease Control and Prevention. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention or the Department of Health and Human Services

Supplementation with a low-dose of octopamine does not influence endurance cycling performance in recreationally active men

© 2017 Sports Medicine Australia.Objectives: The aim of this study was to examine the influence of octopamine supplementation on endurance performance and exercise metabolism. Design: Double-blind cross-over study. Methods: Ten healthy, recreationally active men (Mean±SD; age: 24±2 years; body mass: 78.4±8.7kg; VO2peak: 50.5±6.8 mLkg-1 min-1) completed one VO2peak test, one familiarisation trial and two experimental trials. After an overnight fast, participants ingested either a placebo or 150mg of octopamine 60min prior to exercise. Trials consisted of 30min of cycle exercise at 55% peak power output, followed by a 30min performance task whereby participants completed as much work (kJ) as possible. Results: Performance was similar between the experimental trials (placebo: 352.8. ±. 39. kJ; octopamine: 350.9. ±. 38.3. kJ; Cohen's d effect size = 0.05; p = 0.380). Substrate oxidation and circulating concentrations of free fatty acids, prolactin and cortisol were similar between trial conditions (all p. >. 0.05). There were also no differences across trials for heart rate or perceived exertion during exercise (both p. >. 0.05). Conclusions: Acute supplementation with a low dose of octopamine did not influence endurance cycle performance, substrate oxidation or circulating hormonal concentrations, which could be due to the low serum octopamine concentrations observed. Future studies should investigate the influence of larger doses of octopamine in recreationally active and well-trained individuals during prolonged exercise in temperate and high ambient conditions

Sorbent Structural Impacts Due to Humidity on Carbon Dioxide Removal Sorbents for Advanced Exploration Systems

The Life Support Systems Project (LSSP) under the Advanced Exploration Systems (AES) program builds upon the work performed under the AES Atmosphere Resource Recovery and Environmental Monitoring (ARREM) project focusing on the numerous technology development areas. The CO2 removal and associated air drying development efforts are focused on improving the current state-of-the-art system on the International Space Station (ISS) utilizing fixed beds of sorbent pellets by seeking more robust pelletized sorbents, evaluating structured sorbents, and examining alternate bed configurations to improve system efficiency and reliability. A component of the CO2 removal effort encompasses structural stability testing of existing and emerging sorbents. Testing will be performed on dry sorbents and sorbents that have been conditioned to three humidity levels. This paper describes the sorbent structural stability screening efforts in support of the LSS Project within the AES Program