331 research outputs found
The Environmental Impact of a High-Altitude Medical Research Expedition
Get PDFJoyce, Kelsey E., Catherine A. Campbell, Arthur R. Bradwell, Samuel J.E. Lucas, Christopher T. Lewis, Rebekah A.I. Lucas, and Mark Edsell. The environmental impact of a high-altitude medical research expedition. High Alt Med Biol. 00:00-00, 2024. Introduction: Scientists must begin examining the environmental cost(s) of their research. The purpose of this study was to evaluate a component of the environmental impact of a high-altitude medical research expedition by totaling the carbon dioxide (CO2) emissions calculated from as many direct and indirect sources as possible. Methods: Eighteen individuals flew from London to Bagdogra (via Delhi), and then drove onward to Lachung (via Gangtok) where they began their ascent on foot to 4,800 m (Kanchenjunga National Park, Sikkim). Several research experiments were conducted throughout the expedition, which required use of a laboratory centrifuge, solid CO2 (specimen storage), rechargeable laptop computers and battery-powered oximeters. International Civil Aviation Organization calculators estimated aviation CO2 production. Land emissions were calculated for Mahindra vehicles. Solid waste was weighed and CO2 emissions estimated for its incineration. Results: Total CO2 emissions equated to ∼16.7 tonnes from the following sources: air and land transportation of expedition team (87.3%); sublimation and transportation of solid CO2 (7.7%), waste incineration (0.58%), generator transportation and gasoline (12 l) combustion (0.48%), and battery transportation (3.3%). Conclusions: Air travel contributed the most to the overall environmental cost of the research expedition. Further investigation is required to contextualize these findings in relation to lab-based alternative(s).</p
Initial orthostatic hypotension at high altitude
No full textThomas, Kate N., Keith R. Burgess, Rishi Basnyat, Samuel J.E. Lucas, James D. Cotter, Jui-Lin Fan, Karen C. Peebles, Rebekah A.I. Lucas, Philip N. Ainslie. Initial orthostatic hypotension at high altitude. High Alt. Med. Biol. 11:163-167, 2010.-There are several reports on syncope occurring following standing at high altitude (HA), yet description of the detailed physiological responses to standing at HA are lacking. We examined the hypothesis that appropriate physiological adjustments to upright posture would be compromised at HA (5050m). Ten healthy volunteers stood up rapidly from supine rest, for 3min, at sea level and at 5050m. Beat-to-beat mean arterial blood pressure (MAP, Finometer), middle cerebral artery blood velocity (MCAv, Transcranial Doppler), end-tidal PCO2and PO2, and heart rate (ECG) were recorded continuously. After 14 days at HA, baseline MAP and MCAv were not different to sea level, although HR was elevated. Neither the magnitude of initial (0.05). By 3min of standing, MAP was restored to supine values both at sea level (-3±12mmHg) and HA (4±10mmHg), although there was more complete recovery of HR at sea level (+13±10b/min, p=0.02 vs.+23±10b/min, p=0.01). Reduced MCAv at 3min was comparable at sea level and altitude (both-16%). These data indicate that initial cardiovascular and cerebrovascular responses to standing are unaltered when partially acclimatized to HA
Infrared thermographic analysis of surface temperature of the hands during exposure to normobaric hypoxia
Get PDFJones, Daniel, Samuel F. Covins, Gavin E. Miller, Kenneth I. Morrison, Alexander G. Clark, Samuel D. Calcott, Alasdair M. Anderson, Samuel J.E. Lucas, Christopher H.E. Imray, and the Warwick Altitude Research Group. Infrared red thermographic analysis of surface temperature of the hands during exposure to normobaric hypoxia. High Alt Med Biol. 00:000-000, 2018.-Frostbite and other cold-related injuries commonly develop during prolonged exposure to the low environmental temperatures of polar and mountainous regions. Hypoxia is a potent sympathetic stimulus that causes vasoconstriction of the peripheral blood vessels, which may further compound the risk of developing a cold-related injury during high-altitude exposure. To investigate this, we utilized portable infrared thermographic technology to quantitatively measure changes in the surface temperature of the hands during exposure to increasing levels of normobaric hypoxia in a temperature-controlled high-altitude simulation. Surface temperature was assessed at four anatomical locations on both the left and right hands in a cohort of 10 healthy male participants at a series of predetermined levels of hypoxia (0.20 fraction of inspired oxygen [FIO2] [pre- and postexposure], 0.172 FIO2, 0.145 FIO2, 0.128 FIO2). Thermographic analysis revealed an overall decrease in peripheral temperature across the anatomical regions of the hands as the hypoxic stimulus increased, with statistically significant reductions observed at all four anatomical sites during exposure to 0.128 FIO2 (p < 0.05). These findings demonstrate that portable infrared thermography can be used to detect reductions in peripheral surface body temperature during exposure to normobaric hypoxia.</p
Infrared thermographic analysis of surface temperature of the hands during exposure to normobaric hypoxia
Get PDFJones, Daniel, Samuel F. Covins, Gavin E. Miller, Kenneth I. Morrison, Alexander G. Clark, Samuel D. Calcott, Alasdair M. Anderson, Samuel J.E. Lucas, Christopher H.E. Imray, and the Warwick Altitude Research Group. Infrared red thermographic analysis of surface temperature of the hands during exposure to normobaric hypoxia. High Alt Med Biol. 00:000-000, 2018.-Frostbite and other cold-related injuries commonly develop during prolonged exposure to the low environmental temperatures of polar and mountainous regions. Hypoxia is a potent sympathetic stimulus that causes vasoconstriction of the peripheral blood vessels, which may further compound the risk of developing a cold-related injury during high-altitude exposure. To investigate this, we utilized portable infrared thermographic technology to quantitatively measure changes in the surface temperature of the hands during exposure to increasing levels of normobaric hypoxia in a temperature-controlled high-altitude simulation. Surface temperature was assessed at four anatomical locations on both the left and right hands in a cohort of 10 healthy male participants at a series of predetermined levels of hypoxia (0.20 fraction of inspired oxygen [FIO2] [pre- and postexposure], 0.172 FIO2, 0.145 FIO2, 0.128 FIO2). Thermographic analysis revealed an overall decrease in peripheral temperature across the anatomical regions of the hands as the hypoxic stimulus increased, with statistically significant reductions observed at all four anatomical sites during exposure to 0.128 FIO2 (p < 0.05). These findings demonstrate that portable infrared thermography can be used to detect reductions in peripheral surface body temperature during exposure to normobaric hypoxia.</p
Infrared thermographic analysis of surface temperature of the hands during exposure to normobaric hypoxia
Get PDFJones, Daniel, Samuel F. Covins, Gavin E. Miller, Kenneth I. Morrison, Alexander G. Clark, Samuel D. Calcott, Alasdair M. Anderson, Samuel J.E. Lucas, Christopher H.E. Imray, and the Warwick Altitude Research Group. Infrared red thermographic analysis of surface temperature of the hands during exposure to normobaric hypoxia. High Alt Med Biol. 00:000-000, 2018.-Frostbite and other cold-related injuries commonly develop during prolonged exposure to the low environmental temperatures of polar and mountainous regions. Hypoxia is a potent sympathetic stimulus that causes vasoconstriction of the peripheral blood vessels, which may further compound the risk of developing a cold-related injury during high-altitude exposure. To investigate this, we utilized portable infrared thermographic technology to quantitatively measure changes in the surface temperature of the hands during exposure to increasing levels of normobaric hypoxia in a temperature-controlled high-altitude simulation. Surface temperature was assessed at four anatomical locations on both the left and right hands in a cohort of 10 healthy male participants at a series of predetermined levels of hypoxia (0.20 fraction of inspired oxygen [FIO2] [pre- and postexposure], 0.172 FIO2, 0.145 FIO2, 0.128 FIO2). Thermographic analysis revealed an overall decrease in peripheral temperature across the anatomical regions of the hands as the hypoxic stimulus increased, with statistically significant reductions observed at all four anatomical sites during exposure to 0.128 FIO2 (p < 0.05). These findings demonstrate that portable infrared thermography can be used to detect reductions in peripheral surface body temperature during exposure to normobaric hypoxia.</p
Chamulteon: Coordinated Auto-Scaling of Micro-Services
No full textNowadays, in order to keep track of the fast-changing requirements of Internet applications, auto-scaling is used as an essential mechanism for adapting the number of provisioned resources to the resource demand. The straightforward approach is to deploy a set of common and opensource single-service auto-scalers for each service independently. However, this deployment leads to problems such as bottleneckshifting and increased oscillations. Existing auto-scalers that scale applications consisting of multiple services are kept closed-source. To face these challenges, we first survey existing auto-scalers and highlight current challenges. Then, we introduce Chamulteon, a redesign of our previously introduced mechanism, which can scale applications consisting of multiple services in a coordinated manner. We evaluate Chamulteon against four different wellcited auto-scalers in four sets of measurement-based experiments where we use diverse environments (VM vs. Docker), real-world traces, and vary the scale of the demanded resources. Overall, Chamulteon achieves the best auto-scaling performance based on established user-oriented and endorsed elasticity metrics.Data-Intensive System
The cerebrovascular role in cognition during physiological stress
Get PDFCognition may depend in part on cerebral blood flow (CBF) and its regulation. All are affected in similar directions by stress acutely (e.g., mental and exercise-related) and chronically (e.g., fitness and age). For example, cognition, CBF and its major regulator (CO2 pressure in the blood; PETCO2) all show inverted-U responses to exercise intensity. Additionally, cognition, CBF and its reactivity to changes in CO2 improve with fitness and decline with age. However, the relation between changes in cognition and changes in CBF or PETCO2 remains unknown, particularly in an exercise-context. Therefore, the primary aim of this thesis was to manipulate CBF (as indexed by middle cerebral artery blood velocity; MCAv) or PETCO2 upward and downward, and examine their effects on cognition (visuomotor speed, inhibitory control, and mental switching). Secondary aims were to examine possible modulating effects of fitness, training-specificity, swimming (as an accessible but understudied mode of aerobic exercise), and age.
Study 1 was a validation study to characterise the cerebrovascular and haemodynamic responses during acute mental stress, which may occur during cognitive testing. High mental stress increased MCAv by 7% (p<0.01), driven largely by increased blood pressure (17%; p<0.01). High stress also increased the sensitivity of MCAv to increases in PETCO2 (CVRCO2) by 46% (p=0.03). Therefore, acute mental stress can alter the regulation of CBF.
Study 2 demonstrated that the cognitive benefit from acute bouts of exercise is not solely mediated by concomitant changes in PETCO2 and MCAv. Specifically, treadmill walking improved visuomotor performance in active (p=0.046), but not inactive (p=0.15) young adults. However, this improvement was unrelated to exercise-mediated increases in PETCO2 (≥3 mmHg) and MCAv (13%; p<0.01). Hypercapnia increased MCAv (27-39%; p<0.01), but impaired cognition (3-6%; p≤0.04), regardless of session. Overall, increased PETCO2 and MCAv per se were not sole mediators of exercise-related cognitive improvement.
Study 3 revealed that swimming increased MCAv mostly due to postural and PETCO2 effects (p≤0.01), with minimal contributions from water immersion (p=0.76) or motor activity (p=0.32). Swimming at a moderate-intensity for 20 min improved visuomotor speed by 4% (p=0.03), unrelated to increases in MCAv. Upright water immersion increased MCAv by 12% (p<0.01) but without measurable cognitive improvements (p≥0.15). Thus, exercise appears to benefit cognition beyond its effects on MCAv, regardless of exercise modality and environment.
In Study 4 we used indomethacin to acutely decrease MCAv and CVRCO2, by ≥25% and ≥52%, respectively (p<0.01), in young (25±4 y) and older adults (58±6 y). Mental switching was 6% worse after indomethacin (p=0.04), regardless of age, and not measurably associated with changes in MCAv (r=-0.26). Prior to indomethacin, older compared with younger adults had 15% worse cognition overall and 11% lower MCAv (all p<0.05) but not impaired CVRCO2 (p=0.16). The main finding of this study was that cognitive performance may not be influenced by ≥25% reduction in CBF per se in healthy adults.
This thesis experimentally manipulated CBF and PETCO2 while concurrently measuring cognition. Collectively, these studies indicate that: 1) the acute cognitive benefit from exercise is not mediated by increases in CBF per se; 2) In fact, there appears to be no measurable cognitive effect from acute increases or decreases in CBF in healthy adults; 3) age (r≥0.63) and fitness (r≤-0.30) modulate cognitive function, but only age markedly modulates resting MCAv (r=0.35); and 4) CVRCO2 was weakly associated with cognitive performance (r≤-0.14), age (r=-0.23) and fitness (r=-0.16)
Effects of Stroop task duration on subsequent cognitive and physical performance
Get PDFThe strength model of self-control purports to explain why brief cognitive response inhibition tasks impair subsequent isometric handgrip endurance. According to the model, ego depleting tasks requiring self-control resources impair performance on subsequent tasks that also require self-control resources. However, several lines of evidence challenge this model, including evidence of improved exercise performance following longer cognitive tasks. Our study investigated the effects of cognitive task duration on (1) subsequent physical endurance performance, (2) concurrent cognitive task performance, and (3) subsequent novel cognitive task performance. Adopting an experimental design, with Stroop task type (incongruent, congruent) and duration (5, 10, 20 min) as between-participant factors, participants (N = 180) completed a color word Stroop task, an isometric handgrip to exhaustion task, and a novel 5-min incongruent number word Stroop task. In the handgrip task, endurance performance was worse following incongruent word Stroop than congruent word Stroop for 10-min tasks but not 5-min and 20-min tasks. In the word Stroop task, accuracy was lower and speed was slower following incongruent word Stroop than congruent word Stroop. Importantly, reaction times improved with longer task durations. In the novel number Stroop task, accuracy was higher following incongruent word Stroop than congruent word Stroop. In conclusion, the finding that the ego depletion effect was moderated by cognitive task duration is better explained by the expected value of control model than the strength model
Competition in network industries
Get PDFA wave of privatization is sweeping the globe, affecting about 100 countries and adding up to an average of more than $60 billion a year in business in the past decade. The challenge is to ensure that privatization yields clear benefits. Empirical studies suggest that ownership change by itself will often yield results, especially when it reduces government interference. But the regulation required in areas of natural monopoly can become overly intrusive and undermine progress. Real competition is required to generate sizable and lasting welfare improvements. But in infrastructure sectors, the introduction of competition is complicated by the existence of complex transport and communications networks. Debate about whether and how to introduce competition in network industries is sometimes heated. Certain questions recur: Will continuing regulation be needed? Whether and at what terms will private finance be forthcoming? The author argues that policymakers need to understand how competitive forces can be brought to bear in network industries. He explains the following: 1) common principles that are often lost in"technical"debates about specific sectors; 2) various methods for introducing competition in network industries; 3) competition for the market, and bidding for franchises; 4) options for competition for existing networks; 5) options for expanding competitive systems by decentralizing investment in new network capacity; 6) the option of allowing competition among multiple networks; and 7) the implications of these options for the sectors and for financing industry expansion. In case of doubt, he contends, policymakers should not restrict the entry of competitive firms in such networks. If they do, entry restrictions should be subject to an automatic test after a set period, and reviewed for costs and benefits.Economic Theory&Research,Decentralization,Markets and Market Access,Environmental Economics&Policies,Labor Policies,Education for the Knowledge Economy,Economic Theory&Research,Access to Markets,Markets and Market Access,Environmental Economics&Policies
Low-volume intense exercise elicits post-exercise hypotension and subsequent hypervolemia, irrespective of which limbs are exercised
No full textIntroduction: Exercise reduces arterial and central venous blood pressures during recovery, which contributes to its valuable anti-hypertensive effects and to facilitating hypervolemia. Repeated sprint exercise potently improves metabolic function, but its cardiovascular effects (esp. hematological) are less well characterised, as are effects of exercising upper versus lower limbs. The purposes of this study were to identify the acute (<24 h) profiles of arterial blood pressure and blood volume for (i) sprint intervals versus endurance exercise, and (ii) sprint intervals using arms versus legs. Methods: Twelve untrained males completed three cycling exercise trials; 50-min endurance (legs), and 5*30-s intervals using legs or arms, in randomised and counterbalanced sequence, at a standardised time of day with at least eight days between trials. Arterial pressure, hemoglobin concentration and hematocrit were measured before, during and across 22 h after exercise, the first 3 h of which were seated rest. Results: The post-exercise hypotensive response was larger after leg intervals than endurance (AUC: 7540 ± 3853 vs. 3897 ± 2757 mm Hg·min, p=0.049, 95% CI: 20 to 6764), whereas exercising different limbs elicited similar hypotension (arms: 6420 ± 3947 mm Hg·min, p=0.48, CI: -1261 to 3896). In contrast, arterial pressure at 22 h was reduced after endurance but not after leg intervals (-8 ± 8 vs. 0 ± 7 mm Hg, p=0.04, CI: 7 ± 7) or reliably after arm intervals (-4 ± 8 mm Hg, p=0.18 vs leg intervals). Regardless, plasma volume expansion at 22 h was similar between leg intervals and endurance (both +5 ± 5%; CI: -5 to 5%) and between leg and arm intervals (arms: +5 ± 7%, CI: -8 to 5%). Conclusions: These results emphasise the relative importance of central and/or systemic factors in post-exercise hypotension, and indicate that markedly diverse exercise profiles can induce substantive hypotension and subsequent hypervolemia. At least for endurance exercise, this hypervolemia may not depend on the volume of post-exercise hypotension. Finally, endurance exercise led to reduced blood pressure the following day, but sprint interval exercise did not
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