1,624,394 research outputs found

    Bio-sensing textile based patch with integrated optical detection system for sweat monitoring

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    Sensors, which can be integrated into clothing and used to measure biochemical changes in body fluids, such as sweat, constitute a major advancement in the area of wearable sensors. Initial applications for such technology exist in personal health and sports performance monitoring. However, sample collection is a complicated matter as analysis must be done in real-time in order to obtain a useful examination of its composition. This work outlines the development of a textile-based fluid handling platform which uses a passive pump to gather sweat and move it through a pre-defined channel for analysis. The system is tested both in vitro and in vivo. In addition, a pH sensor, which depends on the use of a pH sensitive dye and paired emitter-detector LEDs to measure colour changes, has been developed. In vitro and on-body trials have shown that the sensor has the potential to record real-time variations in sweat during exercise

    An evaluation of personal cooling systems for reducing thermal strain whilst working in chemical/biological protective clothing

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    © 2019 The Authors. Published by Frontiers Media. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3389/fphys.2019.00424© 2019 Bach, Maley, Minett, Zietek, Stewart and Stewart. Objective: The use of personal cooling systems to mitigate heat strain on first-responders achieves two potential performance benefits relative to the absence of such cooling: (1) the completion of a workload with less effort; and/or (2) the completion of a greater workload for the same effort. Currently, claims made by manufacturers regarding the capability of their products for use in conjunction with chemical/biological protective clothing remain largely unsubstantiated. The purpose of this investigation was to evaluate the means by which heat strain can be alleviated during uncompensable heat stress in chemical/biological clothing, using the ASTM F2300-10 methodology. Methods: Eight healthy males completed five trials of continuous walking (4.5 km h-1; 35°C; 49% RH) for up to 120 min while wearing one of four cooling systems and/or a National Fire and Protection Association 1994 Class-3 chemical/biological ensemble. The four cooling methods (ice vest [IV], phase-change vest [PCM], water-perfused suit [WS], and combination ice slurry/ice vest [SLIV]) and no cooling (CON). Results: We observed significant improvements in trial times for IV (18 ± 10 min), PCM (20 ± 10 min) and SLIV (22 ± 10 min), but no differences for WS (4 ± 7 min). Heart rate, rectal, mean skin, and body temperatures were significantly lower in all cooling conditions relative to control at various matched time points in the first 60 min of exercise. Thermal sensation, comfort and perceived exertion all had significant main effects for condition, and time, there were no differences in their respective interactions. Conclusion: The IV, PCM, and SLIV produced lower heart rate, mean skin, rectal and mean body temperatures in addition to improved work times compared to control. The WS did not improve work times possibly as a result of the cooling capacity of the suit abating, and magnifying thermal insulation. Considering the added time and resources required to implement combination cooling in the form of ice slurry and ice vest (SLIV), there was no significant additive effect for perception, cardiovascular strain, rectal temperature and total trial time relative to the phase change vest or ice vest alone. This may be a product of a "ceiling" effect for work limit set to 120 min as part of ASTM F2300-10.This project is financially supported by the United States Government through the United States Department of Defense (DOD).Published versio

    Short-term heat acclimation is effective and may be enhanced rather than impaired by dehydration

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    Most heat acclimation data are from regimes longer than 1 week, and acclimation advice is to prevent dehydration. Objectives: We hypothesized that (i) short-term (5-day) heat acclimation would substantially improve physiological strain and exercise tolerance under heat stress, and (ii) dehydration would provide a thermally independent stimulus for adaptation. Methods: Nine aerobically fit males heat acclimated using controlled-hyperthermia (rectal temperature 38.5°C) for 90 min on 5 days; once euhydrated (EUH) and once dehydrated (DEH) during acclimation bouts. Exercising heat stress tests (HSTs) were completed before and after acclimations (90-min cycling in T a 35°C, 60% RH). Results: During acclimation bouts, [aldosterone] plasma rose more across DEH than EUH (95%CI for difference between regimes: 40-411 pg ml -1 ; P=0.03; n=5) and was positively related to plasma volume expansion (r=0.65; P=0.05), which tended to be larger in DEH (CI: -1 to 10%; P=0.06; n=9). In HSTs, resting forearm perfusion increased more in DEH (by 5.9 ml 100 tissue ml -1 min -1 : -11.5 to -1.0; P=0.04) and end-exercise cardiac frequency fell to a greater extent (by 11 b min -1 : -1 to 22; P=0.05). Hydration-related effects on other endocrine, cardiovascular, and psychophysical responses to HSTs were unclear. Rectal temperature was unchanged at rest but was 0.3°C lower at end exercise (P < 0.01; interaction: P=0.52). Conclusions: Short-term (5-day) heat acclimation induced effective adaptations, some of which were more pronounced after fluid-regulatory strain from permissive dehydration, and not attributable to dehydration effects on body temperature. Am. J. Hum. Biol. 26:311-320, 2014. © 2014 Wiley Periodicals, Inc

    Colossal Magnetoresistant Materials: The Key Role of Phase Separation

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    The study of the manganese oxides, widely known as manganites, that exhibit the ``Colossal'' Magnetoresistance (CMR) effect is among the main areas of research within the area of Strongly Correlated Electrons. After considerable theoretical effort in recent years, mainly guided by computational and mean-field studies of realistic models, considerable progress has been achieved in understanding the curious properties of these compounds. These recent studies suggest that the ground states of manganite models tend to be intrinsically inhomogeneous due to the presence of strong tendencies toward phase separation, typically involving ferromagnetic metallic and antiferromagnetic charge and orbital ordered insulating domains. Calculations of the resistivity versus temperature using mixed states lead to a good agreement with experiments. The mixed-phase tendencies have two origins: (i) electronic phase separation between phases with different densities that lead to nanometer scale coexisting clusters, and (ii) disorder-induced phase separation with percolative characteristics between equal-density phases, driven by disorder near first-order metal-insulator transitions. The coexisting clusters in the latter can be as large as a micrometer in size. It is argued that a large variety of experiments reviewed in detail here contain results compatible with the theoretical predictions. It is concluded that manganites reveal such a wide variety of interesting physical phenomena that their detailed study is quite important for progress in the field of Correlated Electrons.Comment: 76 pages, 21 PNG files with figures. To appear in Physics Report

    Gauged R-symmetry, Fermion and Higgs Mass Problem

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    We consider the simplest model of SU(3)×SU(2)×U(1)Y×U(1)RSU(3) \times SU(2) \times U(1)_Y \times U(1)_R gauge symmetry with one extra singlet field whose vacuum expectation value breaks the horizontal RR-symmetry U(1)RU(1)_R and gives rise to Yukawa textures. The U(1)RU(1)_R symmetry is able to provide both acceptable fermion mass hierarchies and a natural solution to the μ\mu problem only if its mixed anomalies are cancelled by the Green-Schwarz mechanism. When the canonical normalization g32=g22=53g12g_3^2=g_2^2={5\over3}g_1^2 of the gauge coupling constants is assumed, the Higgs mass parameter μm3/2\mu \sim m_{3/2} can arise taking into acount the uncertainty in the ultraviolet relation memμmτ/mdmsmbλqm_e m_\mu m_\tau/m_d m_s m_b \simeq \lambda^q with q0q \neq 0. When q=0q=0 is taken only a suppressed value of μλm3/2\mu \sim \lambda m_{3/2} can be obtained.Comment: 6 pages, Latex, no figure

    Real-time sweat pH monitoring based on a wearable chemical barcode micro-fluidic platform incorporating ionic liquids

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    This work presents the fabrication, characterisation and the performance of a wearable, robust, flexible and disposable chemical barcode device based on a micro-fluidic platform that incorporates ionic liquid polymer gels (ionogels). The device has been applied to the monitoring of the pH of sweat in real time during an exercise period. The device is an ideal wearable sensor for measuring the pH of sweat since it does not contents any electronic part for fluidic handle or pH detection and because it can be directly incorporated into clothing, head- or wristbands, which are in continuous contact with the skin. In addition, due to the micro-fluidic structure, fresh sweat is continuously passing through the sensing area providing the capability to perform continuous real time analysis. The approach presented here ensures immediate feedback regarding sweat composition. Sweat analysis is attractive for monitoring purposes as it can provide physiological information directly relevant to the health and performance of the wearer without the need for an invasive sampling approac