Perceptual Variations in Thermoregulation During Exercise in a Hot Environment

ABSTRACT Professionals are seeking to find ways to prevent exertional heat illness (EHI) in populations working in hot environments as well as populations that are physically active. The purpose of the present study was to evaluate individuals’ ability to accurately perceive core temperature ranges associated with homeothermic and EHI temperatures during exercise. Ten physically active males exercised on a treadmill at a self-selected rate until core temperature reached 39°C. Participants rated perceived core and skin temperature on 100 mm scales each time core temperature increased 0.25˚ C (37.5-39.0˚ C), along with thermal comfort and sweating sensation. During exercise core temperature was overestimated by 0.46 ±0.11˚ C. Following exercise, participants consistently underestimated core temperature by a mean perceived rating of 0.71±0.05˚ C. Skin temperature was overestimated by 1.45 ±1.21˚ C. Correlations were found between core temperature and perceived core temperature (r =0.54), perceived skin temperature (r =0.55), thermal comfort (r =0.41), and sweating sensation (r =0.42). No correlation was found between core and skin temperature(r =0.02). These data suggest that although people are able to recognize increases in core temperature to the point of overestimation during exercise, they may return to exercise or work too quickly following breaks to cool themselves

N-Acetyl and Glutamatergic Neurometabolites in Perisylvian Brain Regions of Methamphetamine Users.

Background:Methamphetamine induces neuronal N-acetyl-aspartate synthesis in preclinical studies. In a preliminary human proton magnetic resonance spectroscopic imaging investigation, we also observed that N-acetyl-aspartate+N-acetyl-aspartyl-glutamate in right inferior frontal cortex correlated with years of heavy methamphetamine abuse. In the same brain region, glutamate+glutamine is lower in methamphetamine users than in controls and is negatively correlated with depression. N-acetyl and glutamatergic neurochemistries therefore merit further investigation in methamphetamine abuse and the associated mood symptoms. Methods:Magnetic resonance spectroscopic imaging was used to measure N-acetyl-aspartate+N-acetyl-aspartyl-glutamate and glutamate+glutamine in bilateral inferior frontal cortex and insula, a neighboring perisylvian region affected by methamphetamine, of 45 abstinent methamphetamine-dependent and 45 healthy control participants. Regional neurometabolite levels were tested for group differences and associations with duration of heavy methamphetamine use, depressive symptoms, and state anxiety. Results:In right inferior frontal cortex, N-acetyl-aspartate+N-acetyl-aspartyl-glutamate correlated with years of heavy methamphetamine use (r = +0.45); glutamate+glutamine was lower in methamphetamine users than in controls (9.3%) and correlated negatively with depressive symptoms (r = -0.44). In left insula, N-acetyl-aspartate+N-acetyl-aspartyl-glutamate was 9.1% higher in methamphetamine users than controls. In right insula, glutamate+glutamine was 12.3% lower in methamphetamine users than controls and correlated negatively with depressive symptoms (r = -0.51) and state anxiety (r = -0.47). Conclusions:The inferior frontal cortex and insula show methamphetamine-related abnormalities, consistent with prior observations of increased cortical N-acetyl-aspartate in methamphetamine-exposed animal models and associations between cortical glutamate and mood in human methamphetamine users

Results of the MRI substudy of the intravenous magnesium efficacy in stroke trial

<p><b>Background and Purpose:</b>Although magnesium is neuroprotective in animal stroke models, no clinical benefit was confirmed in the Intravenous Magnesium Efficacy in Stroke (IMAGES) trial of acute stroke patients. The Magnetic Resonance in IMAGES (MR IMAGES) substudy investigated the effects of magnesium on the imaging surrogate outcome of infarct growth.</p> <p><b>Methods:</b> IMAGES trial patients in participating centers were randomized to receive either intravenous magnesium or placebo within 12 hours of stroke onset. Infarct growth was defined as volume difference between baseline diffusion-weighted imaging and day 90 fluid-attenuated inversion recovery image lesions. Patients who died were imputed the largest infarct growth observed.</p> <p><b>Results:</b> Among the 90 patients included in the primary analysis, there was no difference in infarct growth (median absolute growth, P=0.639; median percentage growth, P=0.616; proportion with any growth, P=0.212) between the 46 treated with magnesium and 44 with placebo. Infarct growth correlated with NIHSS score change from baseline to day 90. There was a trend showing baseline serum glucose correlated with infarct growth with magnesium treatment, but not in the placebo group. The mismatch frequency was reduced from 73% to 47% by increasing the mismatch threshold from >20% to >100% of core volume.</p> <p><b>Conclusions:</b> Infarct growth, confirmed here as a surrogate for clinical progression, was similar between magnesium and placebo treatment, paralleling the main IMAGES trial clinical outcomes. Glucose was a covariate for infarct growth with magnesium treatment. A more stringent mismatch threshold to define penumbra more appropriately would have excluded half of the patients in this 12-hour time window stroke study.</p&gt

Frontal Asymmetry Changes Following Passive Hypo-Hydration

INTRODUCTION: Universal fluid consumption prescriptions among both athletic and non-athletic populations continue to elicit both hypo- and hyper-hydration (hypo-natremia). Thus, the need to find novel, identifiable traits within individuals who may be at higher risk to experience hypo-hydration, as well as hypo-natremia, is warranted. Of interest here, behavior is encapsulated by two motivational systems, referred to as approach/reward (R) or avoidance/non-reward (NR), respectively, in response to a behavioral stimulus. Past literature has revealed individual differences in consumptive traits of various types of foods between these motivational systems. Therefore, the purpose of this study was to evaluate changes in R/NR via frontal asymmetry (FA) in response to water exposure during eu-hydrated and hypo-hydrated conditions. METHODS: Participants included 11 active college-aged males. Electroencephalogram (EEG) assessed motivational orientations to water exposure in both eu-hydrated and hypo-hydrated states. A 5-minute nature video was used to stabilize mood, followed by 2 minutes of resting EEG recordings. Then, FA was assessed with the presentation of a glass of ice water, with instructions to observe, but not consume for 3 minutes. FA was re-assessed in the same manner following a dehydration trial (~90 minutes). Dehydration trials were performed in a controlled hot water bath at a mean of 39°C. Participants remained in the bath until 2% body mass loss, with no fluids consumed during the trials. Urine voids were collected before and after trials to assess specific gravity and color. Body core temperature was monitored throughout the protocol, with \u3e38.7°C set as criteria for removal of the subject. Participants reported perceptual affective measures using Feeling Scale (FS) and Felt Arousal Scale (FAS) throughout the session to account for any unusual affective states. RESULTS: EEG recordings were applied to the Frontal Asymmetry Index (FAI) (log right alpha power minus log left alpha power). Higher scores on the FAI indicate higher relative left frontal lobe activity, corresponding with an affinity to the water (R). Where as a lower score indicates higher relative right frontal activity, thus less reward motivation (NR). Data revealed that FAI decreased by a mean of 0.055 ±0.193 from eu-hydrated to hypo-hydrated states, with eu-hydration and hypo-hydration FAI of 0.06 and 0.004 respectively. In total, 37.4% of participants showed an increased affinity(R) for water from eu-hydrated to hypo-hydrated states. Pre and post FS were 2.91 ±1.51 and .45 ±2.88, respectively. Pre and post FAS were 2.73 ±.91 and 2.73 ±1.49. DISCUSSION: Reward/non-reward motivational orientations (affinity to water) changes were less than anticipated following hypo-hydration trials. However, data revealed that 37.4% of participants exhibited an increased affinity for water according to the FAI scale, supporting the hypothesis. It is possible that 2% body mass loss is insufficient to create distinct motivational orientation changes within the present sample. Due to the small sample size of the current study, little can be concluded thus far. Additional research addressing the aforementioned methods, as well as larger sample sizes is warranted. If motivational orientation state variability can be established during eu-hydrated and hypo-hydrated states, it may be possible to identify the consumptive tendencies of fluids among individuals

Electron Magnetic Resonance: The Modified Bloch Equation

We find a modified Bloch equation for the electronic magnetic moment when the magnetic moment explicitly contains a diamagnetic contribution (a magnetic field induced magnetic moment arising from the electronic orbital angular momentum) in addition to the intrinsic magnetic moment of the electron. The modified Bloch is coupled to equations of motion for the position and momentum operators. In the presence of static and time varying magnetic field components, the magnetic moment oscillates out of phase with the magnetic field and power is absorbed by virtue of the magnetic field induced magnetic moment, even in the absence of coupling to the environment. We explicitly work out the spectrum and absorption for the case of a $p$ state electron

Advanced information processing system: The Army fault tolerant architecture conceptual study. Volume 1: Army fault tolerant architecture overview

Digital computing systems needed for Army programs such as the Computer-Aided Low Altitude Helicopter Flight Program and the Armored Systems Modernization (ASM) vehicles may be characterized by high computational throughput and input/output bandwidth, hard real-time response, high reliability and availability, and maintainability, testability, and producibility requirements. In addition, such a system should be affordable to produce, procure, maintain, and upgrade. To address these needs, the Army Fault Tolerant Architecture (AFTA) is being designed and constructed under a three-year program comprised of a conceptual study, detailed design and fabrication, and demonstration and validation phases. Described here are the results of the conceptual study phase of the AFTA development. Given here is an introduction to the AFTA program, its objectives, and key elements of its technical approach. A format is designed for representing mission requirements in a manner suitable for first order AFTA sizing and analysis, followed by a discussion of the current state of mission requirements acquisition for the targeted Army missions. An overview is given of AFTA's architectural theory of operation

Advanced information processing system: The Army fault tolerant architecture conceptual study. Volume 2: Army fault tolerant architecture design and analysis

Described here is the Army Fault Tolerant Architecture (AFTA) hardware architecture and components and the operating system. The architectural and operational theory of the AFTA Fault Tolerant Data Bus is discussed. The test and maintenance strategy developed for use in fielded AFTA installations is presented. An approach to be used in reducing the probability of AFTA failure due to common mode faults is described. Analytical models for AFTA performance, reliability, availability, life cycle cost, weight, power, and volume are developed. An approach is presented for using VHSIC Hardware Description Language (VHDL) to describe and design AFTA's developmental hardware. A plan is described for verifying and validating key AFTA concepts during the Dem/Val phase. Analytical models and partial mission requirements are used to generate AFTA configurations for the TF/TA/NOE and Ground Vehicle missions