Rise In Core Temperature Research Articles

First access to ELM-free negative triangularity at low aspect ratio

Abstract A plasma scenario with negative triangularity (NT) shaping is achieved on MAST-U for the first time. While edge localized modes (ELMs) are eventually suppressed as the triangularity is decreased below δ ≲ − 0.06 , an extended period of H-mode operation with Type-III ELMs is sustained at less negative δ even through access to the second stability region for ideal ballooning modes is closed. This documents a qualitative difference from the ELM-free access conditions documented in NT scenarios on conventional aspect ratio machines. The electron temperature at the pedestal top drops across the transition to ELM-free operation, but a steady rise in core temperature as δ is decreased allows for similar normalized β in the ELM-free NT and H-mode positive triangularity shapes.

Research on the Impact and Parameters of Liquid-Cooling Garment on Thermal Comfort

Liquid-cooling garment (LCG) can alleviate heat stress and improve thermal comfort in high-temperature environments. This study conducted human experiments to assess the impact of the LCG on physiological parameters and subjective evaluations during heat stress. Then, a numerical parametric study was performed to examine the effect of environmental temperature, inlet temperature, and flow rate on LCG performance. The results demonstrate a significant inhibition of physiological parameter escalation compared to the absence of protective measures. Specifically, skin temperature exhibited a reduction ranging from 1.6% to 4.9%, whereas heart and core temperature rise rates experienced respective decreases of 27.5% and 24.2%. Additionally, there was a notable reduction of 20.76% in sweat production. Elevated skin temperature was associated with heightened thermal sensation and diminished thermal comfort. Moreover, applying the LCG resulted in a noteworthy decrease of 28.5% and 14% in the physiological and perceived stress indexes, respectively. Adjusting inlet temperature better reduces skin temperature than flow rate when environmental temperature and labor intensity increase. Lowering inlet water temperature improved LCG performance. An inlet temperature of 20 °C and a flow rate of 500 mL/min were optimal for moderate labor.

Influence of ground motion characteristics on the heating effect of lead‐rubber bearings in base‐isolated structures

AbstractUnder earthquake excitations, the lead core inside the lead‐rubber bearing (LRB) generates heat, causing the mechanical degradation of LRBs. However, the heating effect is not commonly considered in the seismic analysis and design of base‐isolated structures with LRBs, which may underestimate the seismic response of structures, especially under ground motions with certain specific characteristics. This paper aims to reveal the influence of ground motion characteristics on the heating effect and provide useful references for the seismic analysis and design. In this study, the validated LRB model considering heating effect was employed in a base‐isolated building calibrated by testing data. Ground motion characteristics including amplitude, duration, and frequency content were separated by spectrally equivalent and different records. The results indicate that the rate and peak of the lead core temperature rise are strongly correlated to ground motion characteristics. Seismic responses ignoring the heating effect are underestimated, and this underestimate varies as the amplitude, duration, and frequency content change and reaches up to 60% in the studied case. Note that seismic responses of the isolation system are more affected by heating effects than the superstructure, and the duration shows a more significant influence on the stiffness degradation of LRBs than the frequency content. It is strongly recommended that the required duration of ground motions should be raised and the low stories of the superstructure should be reinforced for isolated structures with LRBs. The significant duration indicator DS5–95 is more reasonable than DS5–75 in the analysis of the heating effect.

Age-Related Differences in the Onset of Cardiovascular Drift during Progressive Heat Stress (PSU HEAT Project)

As a result of the increasing duration, frequency, and severity of heat waves, older men and women are at greater risk for heat-related morbidity and mortality, with the majority of excess heat-related deaths attributed to increased cardiovascular strain associated with heat stress. PURPOSE: To (1) identify the environmental conditions (ambient temperature (Tdb) and humidity (rh)) at which heart rate (HR) begins to increase from equilibrium (i.e., the onset of cardiovascular drift), and (2) compare the environments in which cardiovascular drift begins relative to those at which a continuous rise in core temperature (Tc) is observed in young (Y), middle (MA), and older (O) adults. Methods: 26 Y (10 F; 19-29 yrs), 27 MA (21F; 40-64 yrs), and 19 O (7 F; 65-76 yrs) subjects were exposed to progressive heat stress in an environmental chamber at a low metabolic rate reflecting activities of daily living (159 ± 34 W) in a warm-humid (WH, 34-36°C, 50-80% rh) and a hot-dry (HD, 38°C-52°C, <30% rh) environment. The environmental thresholds above which HR and Tc equilibrium could no longer be maintained were identified. Results: In WH environments, sustained increases in HR preceded the Tc inflection point in Y (73±5% rh vs. 81±5% rh; p<0.001), MA (67±11% rh vs. 73±12% rh; p<0.001), and O adults (53±11% rh vs. 57±12% rh; p=0.041). Similarly, in HD (15-20% rh) environments, the onset of cardiovascular drift preceded the Tc inflection point in Y (47±3°C vs. 49±3°C; p=0.004), MA (44±4°C vs. 46±4°C; p<0.001), and O adults (42±5°C vs. 44±4°C; p=0.007). Additionally, in WH environments, cardiovascular drift began at lower combinations of Tdb and rh in O vs. Y subjects (34°C, 53±11% rh vs. 34°C, 73±5% rh; p<0.001) and O vs. MA adults (34°C, 53±11% rh vs. 34°C, 67±11% rh; p=0.008). In HD environments, cardiovascular drift began at lower environments in MA vs. Y (44±4°C, 18% rh vs. 47±3°C, 15% rh; p=0.044) and O vs. Y (42±5°C, 20% rh vs. 47±3°C, 15% rh; p=0.006) CONCLUSION: These data suggest that cardiovascular drift, indicating increases in cardiovascular strain, occurs during compensable heat stress at metabolic rates reflecting activities of daily living in Y, MA, and O adults. Further, there is an age-associated shift in the onset of cardiovascular drift toward lower combinations of Tdb and rh. SIGNIFICANCE/NOVELTY: These results are the first to identify the specific environmental conditions at which increases in cardiovascular strain occur across the adult age spectrum. These findings provide concrete data for the development of safety guidelines and policy decisions to mitigate cardiovascular-related morbidity and mortality during impending heat events. Supported by NIA Grant T32 AG049676 (to R.M.C.) and NIH Grant R01 AG067471 (to W.L.K.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Safety Assessment of Electromagnetic Environmental Exposure for GPS Antenna of Electric Vehicle

The present GPS (global positioning system) is widely used in electric vehicle navigation; it is usually installed in the middle-to-rear position on the car’s roof, near the rear windshield. Since the GPS antenna operating frequency is 1.575 GHz, the health risk of the passengers in the car in this high-frequency electromagnetic exposure is a matter of concern. In this paper, we construct models for a GPS antenna, an electric vehicle, and a human body. Through the multiphysics field coupling calculation in COMSOL Multiphysics, a finite element simulation software, in both frequency domain and transient analysis, we obtain the electric field strength distribution, specific absorption rate, and temperature distribution of the human body at three positions inside the electric vehicle after being exposed to the GPS antenna radiation for 30 minutes. The peak human-induced electric field is 18.4 V/m, and the peak specific absorption rate is 0.193 W/kg. The 30 minute average maximum human-induced electric field is 1.6906 V/m, which is 3.1% of the ICNIRP limit, the 30 minute average whole-body SAR is 0.0036 W/kg, which is 4.5% of the ICNIRP limit, and the 30 minute average human core temperature rise is 0.06°C, which is 6% of the ICNIRP limit. In addition, we simulate the impact of three different vehicle shell materials on the level of electromagnetic exposure to the human body, which can provide reference for electromagnetic shielding design in automobiles. The results indicate that the induced electric field strength, specific absorption rate (SAR), and temperature rise in various parts of the human body did not exceed the standard limits in the latest version of ICNIRP. This suggests that the electromagnetic exposure from the GPS antenna in a typical automotive environment does not pose a threat to human health.

Sex differences in thermophysiological responses of elderly to low-intensity exercise during uncompensable heat strain

PurposeThe rising frequency of extreme heat events poses an escalating threat of heat-related illnesses and fatalities, placing an additional strain on global healthcare systems. Whether the risk of heat-related issues is sex specific, particularly among the elderly, remains uncertain.Methods16 men and 15 women of similar age (69 ± 5 years) were exposed to an air temperature of 39.1 ± 0.3 °C and a relative humidity (RH) of 25.1 ± 1.9%, during 20 min of seated rest and at least 40 min of low-intensity (10 W) cycling exercise. RH was gradually increased by 2% every 5 min starting at minute 30. We measured sweat rate, heart rate, thermal sensation, and the rise in gastrointestinal temperature (Tgi) and skin temperature (Tsk).ResultsTgi consistently increased from minute 30 to 60, with no significant difference between females and males (0.012 ± 0.004 °C/min vs. 0.011 ± 0.005 °C/min; p = 0.64). Similarly, Tsk increase did not differ between females and males (0.044 ± 0.007 °C/min vs. 0.038 ± 0.011 °C/min; p = 0.07). Females exhibited lower sweat rates than males (0.29 ± 0.06 vs. 0.45 ± 0.14 mg/m2/min; p < 0.001) in particular at relative humidities exceeding 30%. No sex differences in heart rate and thermal sensation were observed.ConclusionElderly females exhibit significantly lower sweat rates than their male counterparts during low-intensity exercise at ambient temperatures of 39 °C when humidity exceeds 30%. However, both elderly males and females demonstrate a comparable rise in core temperature, skin temperature, and mean body temperature, indicating similar health-related risks associated with heat exposure.

Impact of strong magnetization in cylindrical plasma implosions with applied B-field measured via x-ray emission spectroscopy

Magnetization is a key strategy for enhancing inertial fusion performance, though accurate characterization of magnetized dense plasmas is needed for a better comprehension of the underlying physics. Measured spectra from imploding Ar-doped D2-filled cylinders at the OMEGA laser show distinctive features with and without an imposed magnetic field. A multizone spectroscopic diagnosis leads to quantitative estimates of the plasma conditions, namely revealing a 50% core temperature rise at half mass density when a 30-T seed field is applied. Concurrently, experimental spectra align well with predictions from extended-magnetohydrodynamics simulations, providing strong evidence that the attained core conditions at peak compression are consistent with the impact of a 10-kT compressed field. These results pave the way for the validation of magnetized transport models in dense plasmas and for future magnetized laser implosion experiments at a larger scale. Published by the American Physical Society 2024

A new perspective on cardiovascular function and dysfunction during endurance exercise: identifying the primary cause of cardiovascular risk.

Exercise mechanical efficiency typically falls within the range of approximately 20 to 25%. This means that a great part of the metabolic energy converted to generate movement is released as heat. Therefore, the rise in core temperature during endurance exercise in humans is proportional to generated work. Cutaneous vasodilation occurs when the core temperature threshold is reached. The rise in heart rate in response to thermal stress is a cardiovascular response that increases cardiac output and skin blood flow. The cardiovascular response during endurance exercise is a complex phenomenon potentially influenced by the involvement of nitric oxide in active thermoregulatory vasodilation. Excessive exercise can create high oxidative stress by disrupting the balance between free radicals' production and scavenging, resulting in impaired cardiovascular function. The above considerations are related to the severity and duration of endurance exercise. The first focus of this narrative review is to provide an updated understanding of cardiovascular function during endurance exercise. We aim to explore the potential role of oxidative stress in causing cardiovascular dysfunction during endurance exercise from a fresh perspective. Additionally, we aim to identify the primary factors contributing to cardiovascular risk during strenuous prolonged exercise by highlighting recent progress in this area, which may shed light on previously unexplained physiological responses. To ascertain the effect of endurance exercise on cardiovascular function and dysfunction, a narrative review of the literature was undertaken using PubMed, ScienceDirect, Medline, Google Scholar, and Scopus. The review highlighted that high oxidative stress (due to high levels of catecholamines, shear stress, immune system activation, and renal dysfunction) leads to a rise in platelet aggregation during endurance exercise. Importantly, we clearly revealed for the first time that endothelial damage, vasoconstriction, and blood coagulation (inducing thrombosis) are potentially the primary factors of cardiovascular dysfunction and myocardial infarction during and/or following endurance exercise.

Quantifying Exercise Heat Acclimatisation in Athletes and Military Personnel: A Systematic Review and Meta-analysis.

Athletes and military personnel are often expected to compete and work in hot and/or humid environments, where decrements in performance and an increased risk of exertional heat illness are prevalent. A physiological strategy for reducing the adverse effects of heat stress is to acclimatise to the heat. The aim of this systematic review was to quantify the effects of relocating to a hotter climate to undergo heat acclimatisation in athletes and military personnel. Studies investigating the effects of heat acclimatisation in non-acclimatised athletes and military personnel via relocation to a hot climate for < 6weeks were included. MEDLINE, SPORTDiscus, CINAHL Plus with Full Text and Scopus were searched from inception to June 2022. A modified version of the McMaster critical review form was utilised independently by two authors to assess the risk of bias. A Bayesian multi-level meta-analysis was conducted on five outcome measures, including resting core temperature and heart rate, the change in core temperature and heart rate during a heat response test and sweat rate. Wet-bulb globe temperature (WBGT), daily training duration and protocol length were used as predictor variables. Along with posterior means and 90% credible intervals (CrI), the probability of direction (Pd) was calculated. Eighteen articles from twelve independent studies were included. Fourteen articles (nine studies) provided data for the meta-analyses. Whilst accounting for WBGT, daily training duration and protocol length, population estimates indicated a reduction in resting core temperature and heart rate of - 0.19°C [90% CrI: - 0.41 to 0.05, Pd = 91%] and - 6beats·min-1 [90% CrI: - 16 to 5, Pd = 83%], respectively. Furthermore, the rise in core temperature and heart rate during a heat response test were attenuated by - 0.24°C [90% CrI: - 0.67 to 0.20, Pd = 85%] and - 7beats·min-1 [90% CrI: - 18 to 4, Pd = 87%]. Changes in sweat rate were conflicting (0.01L·h-1 [90% CrI: - 0.38 to 0.40, Pd = 53%]), primarily due to two studies demonstrating a reduction in sweat rate following heat acclimatisation. Data from athletes and military personnel relocating to a hotter climate were consistent with a reduction in resting core temperature and heart rate, in addition to an attenuated rise in core temperature and heart rate during an exercise-based heat response test. An increase in sweat rate is also attainable, with the extent of these adaptations dependent on WBGT, daily training duration and protocol length. CRD42022337761.

Intensity analysis of frictional heat source during core tube sampling and drilling

AbstractCurrently, the heat generated during coal core tube sampling causes rapid gas desorption, leading to substantial measurement errors in laboratory gas content assessments. Reducing these errors requires studying frictional heat from core tube friction against the hole wall and coal core temperature rise. Combining the independently developed device to simulate the thermal effect of coring and the COMSOL finite element analysis software, the intensity of the frictional heat source during the core tube sampling and drilling process was analyzed under different coring depth and rotational speed conditions. The research results show that: At constant speed, frictional heat intensifies as the core depth increases. However, the rate of temperature rise decreases with increasing core depth; when the coring depth is constant, the frictional heat is proportional to the rotational speed. For example, at a depth of 140 m and a rotational speed of 120 r/min, the intensity of frictional heat generated by drilling is 2.21 ∗ 10E6J. Similarly, at 180 r/min, the strength is 2.28 ∗ 10E6J, and at 240 r/min, the strength reaches 3.65 ∗ 10E6J; Under certain conditions, core tube wall temperature will not rise indefinitely but will stabilize to a certain value.

Influence of topical menthol gel on thermoregulation and perception while walking in the heat.

Menthol is known to elicit opposing thermoregulatory and perceptual alterations during intense exercise. The current purpose was to determine the thermoregulatory and perceptual effects of topical menthol application prior to walking in the heat. Twelve participants walked (1.6m s-1, 5% grade) for 30min in the heat (38°C, 60% relative humidity) with either a 4% menthol or control gel on the upper (shoulder to wrist) and lower (mid-thigh to ankle) limbs. Skin blood flow (SkBF), sweat (rate, composition), skin conductivity, heart rate, temperature (skin, core), and thermal perception were measured prior to and during exercise. Skin conductivity expressed as time to 10, 20, 30, and 40 µS was delayed due to menthol (559 ± 251, 770 ± 292, 1109 ± 301, 1299 ± 335s, respectively) compared to the control (515 ± 260, 735 ± 256, 935 ± 300, 1148 ± 298s, respectively, p = 0.048). Sweat rate relative to body surface area was lower due to menthol (0.55 ± 0.16 L h-1 m(2)-1) than the control (0.64 ± 0.16 L h-1 m(2)-1, p = 0.049). Core temperature did not differ at baseline between the menthol (37.4 ± 0.3°C) and control (37.3 ± 0.4°C, p = 0.298) but was higher at 10, 20, and 30 min due to menthol (37.5 ± 0.3, 37.7 ± 0.2, 38.1 ± 0.3°C, respectively) compared to the control (37.3 ± 0.4, 37.4 ± 0.3, 37.7 ± 0.3°C, respectively, p < 0.05). The largest rise in core temperature from baseline was at 30min during menthol (0.7 ± 0.3°C) compared to the control (0.4 ± 0.2°C, p = 0.004). Overall, the menthol treatment was perceived cooler, reaching "slightly warm" whereas the control treatment reached "warm" (p < 0.001). Menthol application to the limbs impairs whole-body thermoregulation while walking in the heat despite perceiving the environment as cooler.

Distribution of upper limit of the prescriptive zone values for acclimatized and unacclimatized individuals.

Heat stress has an adverse impact on worker health and well-being, and the effects will increase with more frequent and severe heat events associated with global warming. Acclimatization to heat stress is widely considered to be a critical mitigation strategy and wet bulb globe temperature- (WBGT-) based occupational standards and guidelines contain adjustments for acclimatization. The purpose here was to 1) compare the mean values for the upper limit of the prescriptive zone (ULPZ, below which the rise in core temperature is minimal) between unacclimatized and acclimatized men and women; 2) demonstrate that the change in the occupational exposure limit (ΔOEL) due to acclimatization is independent of metabolic rate; 3) examine the relation between ΔOEL and body surface area (BSA); and 4) compare the exposure-response curves between unacclimatized and acclimatized populations. Empirically derived ULPZ data for unacclimatized participants from Pennsylvania State University (PSU) and acclimatized participants from University of South Florida (USF) were used to explore the difference between unacclimatized and acclimatized heat exposure limits. The findings provide support for a constant 3°C WBGT OEL decrease to account for unacclimatized workers. Body surface area explained part of the difference in ULPZ values between men and women. In addition, the pooled PSU and USF data provide insight into the distribution of individual values for the ULPZ among young, healthy unacclimatized and acclimatized populations in support of occupational heat stress guidelines.NEW & NOTEWORTHY Occupational exposure limit guidelines using wet bulb globe temperature (WBGT) distinguish between acclimatized and unacclimatized workers with about a 3°C difference between them. For the first time, empirical data from two laboratories provide support for acclimatization state adjustments. Using a constant difference rather than increasing differences with metabolic rate better describes the limit for unacclimatized participants. Furthermore, the lower upper limit of the prescriptive zone (ULPZ) values set forth for women do not relate to fitness level but are partly explained by their smaller body surface area (BSA). An examination of individual ULPZ values suggests that many unacclimatized individuals should be able to sustain safe work at the exposure limit for acclimatized workers.

Efficacy of high-volume fly ash and slag on the physicomechanical, durability, and analytical characteristics of high-strength mass concrete

In the last decade, the use of high-strength mass concrete has increased for the building of various high-impact infrastructure projects. Due to the larger size of sections and greater volume of Portland cement, the reduction of core strength and durability is often witnessed in these concrete sections. In this study, an attempt has been made to minimize the above issues by substituting ordinary Portland cement (OPC) with high-volume fly ash (FA) and ground granulated blast furnace slag (GGBFS). For this purpose, six types of samples viz. S1 (100% OPC), S2 (20% FA + 80% OPC), S3 (35% FA + 65% OPC), S4 (50% GGBFS + 50% OPC), S5 (70% GGBFS + 30% OPC), and S6 (33% FA + 33% GGBFS + 34% OPC) were prepared. The performances on the actual core concrete were evaluated by analyzing the peak temperature, compressive strength of cylindrical cores, rapid chloride migration test (RCMT), X-ray diffraction (XRD), thermogravimetry (TG), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM). Additionally, the bulk densities (wet and dry), water absorption, apparent porosity, and compressive strength of cube samples are also reported. Analyzing the results critically, it was observed that the use of high-volume FA and GGBFS (S5 and S6 samples) lowered the peak core temperature by 11–13 °C, increased the compressive strength of cores by 8–10 MPa, and lowered the RCMT values of cores by 12 × 10−12 - 13 × 10−12 m2/s as compared to the S1 (control) sample. Additionally, the increase in the ratio of the core-to-cube strength for the S5 and S6 samples is noted to be 24% and 29%, respectively, more than the control sample at 56 days of curing. The enhanced performance of the high-volume FA and GGBFS-based samples is due to the less core temperature rise due to less hydration reaction at the early ages and more secondary hydration reaction at the later ages, which has been justified by the XRD, FTIR, TG, and FESEM analyses. Finally, the sustainability and cost analysis revealed that the use of high-volume FA and GGBFS can significantly reduce embodied energy by 39–42%, embodied carbon by 53–58%, and production costs by 16–17%. The approach proposed in the article regarding the use of high-volume FA and GGBFS results in more green, durable, sustainable, and cost-effective high-strength mass concrete.

A Systematic Review of Post-Work Core Temperature Cooling Rates Conferred by Passive Rest.

Physical work increases energy expenditure, requiring a considerable elevation of metabolic rate, which causes body heat production that can cause heat stress, heat strain, and hyperthermia in the absence of adequate cooling. Given that passive rest is often used for cooling, a systematic search of literature databases was conducted to identify studies that reported post-work core temperature cooling rates conferred by passive rest, across a range of environmental conditions. Data regarding cooling rates and environmental conditions were extracted, and the validity of key measures was assessed for each study. Forty-four eligible studies were included, providing 50 datasets. Eight datasets indicated a stable or rising core temperature in participants (range 0.000 to +0.028 °C min-1), and forty-two datasets reported reducing core temperature (-0.002 to -0.070 °C min-1) during passive rest, across a range of Wet-Bulb Globe Temperatures (WBGT). For 13 datasets where occupational or similarly insulative clothing was worn, passive rest resulted in a mean core temperature decrease of -0.004 °C min-1 (-0.032 to +0.013 °C min-1). These findings indicate passive rest does not reverse the elevated core temperatures of heat-exposed workers in a timely manner. Climate projections of higher WBGT are anticipated to further marginalise the passive rest cooling rates of heat-exposed workers, particularly when undertaken in occupational attire.

Voluntary torque production is unaffected by changes in local thermal sensation during normothermia and hyperthermia.

What is the central question of this study? Hyperthermia reduces the human capacity to produce muscular force, which is associated with decreased neural drive: does mitigating a reduction in neural drive by altering localised thermal sensation help to preserve voluntary force output? What is the main finding and its importance? Altering thermal sensation by cooling and heating the head independent of core temperature did not change neural drive or benefit voluntary force production. Head cooling did slow the rate of rise in core temperature during heating, which may have practical applications in passive settings. This study investigated altered local head and neck thermal sensation on maximal and rapid torque production during voluntary contractions. Nine participants completed four visits in two environmental conditions: at rectal temperatures ∼39.5°C in hot (HOT; ∼50°C, ∼39% relative humidity) and ∼37°C in thermoneutral (NEU; ∼22°C, ∼46% relative humidity) conditions. Local thermal sensation was manipulated by heating in thermoneutral conditions and cooling in hot conditions. Evoked twitches and octets were delivered at rest. Maximum voluntary torque (MVT), normalised surface electromyography (EMG) and voluntary activation (VA) were assessed during brief maximal isometric voluntary contractions of the knee extensors. Rate of torque development (RTD) and EMG were measured during rapid voluntary contractions. MVT (P=0.463) and RTD (P=0.061) were similar between environmental conditions despite reduced VA (-6%; P=0.047) and EMG at MVT (-31%; P=0.019). EMG in the rapid voluntary contractions was also lower in HOT versus NEU during the initial 100ms (-24%; P=0.035) and 150ms (-26%; P=0.035). Evoked twitch (+70%; P<0.001) and octet (+27%; P<0.001) RTD during the initial 50ms were greater in the HOT compared to NEU conditions, in addition to a faster relaxation rate of the muscle (-33%; P<0.001). In conclusion, hyperthermia reduced neural drive without affecting voluntary torque, likely due to the compensatory effects of improved intrinsic contractile function and faster contraction and relaxation rates of the knee extensors. Changes in local thermal perception of the head and neck whilst hyperthermic or normothermic did not affect voluntary torque.

Daily Brief Heat Therapy Reduces Seizures in A350V IQSEC2 Mice and Is Associated with Correction of AMPA Receptor-Mediated Synaptic Dysfunction.

Purposeful induction of fever for healing, including the treatment of epilepsy, was used over 2000 years ago by Hippocrates. More recently, fever has been demonstrated to rescue behavioral abnormalities in children with autism. However, the mechanism of fever benefit has remained elusive due in large part to the lack of appropriate human disease models recapitulating the fever effect. Pathological mutations in the IQSEC2 gene are frequently seen in children presenting with intellectual disability, autism and epilepsy. We recently described a murine A350V IQSEC2 disease model, which recapitulates important aspects of the human A350V IQSEC2 disease phenotype and the favorable response to a prolonged and sustained rise in body core temperature in a child with the mutation. Our goal has been to use this system to understand the mechanism of fever benefit and then develop drugs that can mimic this effect and reduce IQSEC2-associated morbidity. In this study, we first demonstrate a reduction in seizures in the mouse model following brief periods of heat therapy, similar to what was observed in a child with the mutation. We then show that brief heat therapy is associated with the correction of synaptic dysfunction in neuronal cultures of A350V mice, likely mediated by Arf6-GTP.

The effects of cooling vests on thermoregulatory responses and exercise performance in individuals with spinal cord injury: A systematic review

BACKGROUND: Individuals with spinal cord injury (SCI) present thermoregulatory impairments that prejudice thermal compensation and heat dissipation during exercise practice. Thus, cooling vests (CV) seems to be a promising strategy to attenuate it. OBJECTIVE: Our aim was to evaluate the efficacy of CV in controlling the rise in body temperature and in enhancing exercise performance in individuals with SCI. METHODS: The searches were performed in PubMed, Web of Science, Scopus, PEDro, and SciELO databases. We selected randomized controlled trials, quasi-randomized trials, or cross-over trials that evaluated the efficacy of CV before or during exercise practice in thermoregulatory responses and exercise performance of individuals with SCI. RESULTS: A total of 400 reports were identified through databases searches and another article was found through citation searching. Seven cross-over trials were included in this review after the screening processes. CONCLUSION: CV may not be effective in attenuating the rise in core temperature in persons with SCI, but it seems to be effective in controlling skin temperature and in improving thermal comfort/sensation. It is unclear whether the CV is more effective when applied before or during exercise practice. Individuals with tetraplegia may benefit more and the CV may be more effective in strenuous exercises.

The impact of castration on physiological responses to exertional heat stroke in mice.

The capability of male mice to exercise in hot environments without succumbing to exertional heat stroke (EHS) is markedly blunted compared to females. Epidemiological evidence in humans and other mammals also suggests some degree of greater vulnerability to heat stroke in males compared to females. The origins of these differences are unknown, but testosterone has previously been shown to induce faster elevations in core temperature during acute, passive heat exposure. In this study, we tested the hypothesis that loss of testosterone and related sex hormones through castration would improve the performance and heat tolerance of male mice during EHS exposure. Twenty-four male mice were randomly divided into 3 groups, untreated EHS mice (SHAM-EHS), castrated EHS mice (CAS+EHS) and naïve exercise controls (NAIVE). Exercise performance and physiological responses in the heat were monitored during EHS and early recovery. Two weeks later, blood and tissues were collected and analyzed for biomarkers of cardiac damage and testosterone. Core temperature in CAS+EHS rose faster to 39.5°C in the early stages of the EHS trial (P<0.0001). However, both EHS groups ran similar distances, exhibited similar peak core temperatures and achieved similar exercise times in the heat, prior to symptom limitation (unconsciousness). CAS+EHS mice had ~10.5% lower body mass at the time of EHS, but this provided no apparent advantage in performance. There was no evidence of myocardial damage in any group, and testosterone levels were undetectable in CAS+EHS after gonadectomy. The results of these experiments exclude the hypothesis that reduced performance of male mice during EHS trials is due to the effects of male sex hormones or intact gonads. However, the results are consistent with a role of male sex hormones or intact gonads in suppressing the early and rapid rise in core temperature during the early stages of exercise in the heat.

A modified Kalman filter-based model for core temperature estimation during exercise and recovery with/without personal cooling interventions

One of the most important parameters to consider while analysing heat related illness is the human body core temperature. It is therefore required to monitor real-time core temperature in an ambulatory situation for industrial workers, athletes, military personnel, and a variety of other people. As conventional methods of monitoring core temperature are unsuitable for ambulatory use or prohibitively expensive, it is necessary to develop a reliable, inexpensive and non-invasive method for real-time measurement of core temperature. Kalman filter based models for core temperature estimation are found promising to meet these requirements. In this work, we have highlighted one of the major shortcomings of the existing extended Kalman filter model and proposed a modification. The modified extended Kalman filter based model has better performance compared to the existing model in estimating the core temperature as it considers two separate measurement models for exercise and recovery periods. The proposed modified model is validated using human trials data which includes participants wearing regular clothing and different types of personal cooling clothing. It is found that the proposed modified model can predict core temperature more accurately (bias= −0.03 to −0.06°C, LoA=±0.14 – ±0.32°C, and RMSE=0.09–0.16°C) as compared to the existing model (bias=−0.03 – 0.08°C, LoA=±0.26 – ±0.33°C, and RMSE=0.14°C–0.18°C). Personal cooling intervention minimises core temperature rise significantly and thus helps in heat stress mitigation. It is observed that the proposed modified model can estimate core temperature more accurately for cooling intervention cases and intermittent working cases as compared to the existing model. It can be used effectively in an ambulatory setting, but for situations where higher accuracy is required and invasiveness of the method is not a concern, direct contact method of core temperature is always preferred as the proposed model has varying accuracy levels between individuals.

Development of a fast thermal-hydraulic model to simulate heat and fluid flow in MNSR

Extending a reliable and fast thermal–hydraulic model is the first stage in developing a micro-simulator for a miniature neutron research reactor (MNSR) with training and educational objectives. The framework of the TH model, which comprises an explicit finite difference formulation for solving coupled hydraulic and thermal equations with variable water properties, is explored in this study. The hydraulic section uses the integral form of the momentum equation to relate the mass flow rate variation to buoyancy and friction forces. The thermal part of the model relies on the integral form of the energy equation for different elements of the reactor including fuel, core, reflector, tank, chimney, and pool. The model's results are compared to reactor operation data and available correlations for various reactor powers. According to the comparison, the model's output matches the trend of experimental data for all power in both short and long time periods and predicts the eventual temperature rise of the core with an error of less than 5%. The performance of the model in other operational conditions is also evaluated. The model's performance in different operational circumstances is also assessed, and the results suggest that reducing the reactor's initial temperature would enhance the core's temperature rise.