Modeling the Effect of Cooling Vest on Body Thermal Response of People With Paraplegia During Exercise

2019 ◽  
Author(s):  
Farah Mneimneh ◽  
Nesreen Ghaddar ◽  
Kamel Ghali ◽  
Charbel Moussalem ◽  
Ibrahim Omeis
Keyword(s):  
Melting Point ◽  
Latent Heat ◽  
Thermal Response ◽  
Heat Losses ◽  
The Body ◽  
Intensity Level ◽  
Sensible Heat ◽  
Coverage Area ◽  
Thoracic Spinal Cord ◽  
Cord Injury

Abstract Persons with thoracic spinal cord injury (SCI), also named as people with paraplegia (PA), are encouraged to participate in sport activities for sake of improving their quality of life and health. Yet, heat strain is a major consequence of SCI after which the body loses its ability to regulate its temperature. Disruption in body temperature regulation and instability in core temperature (Tcr) endangers the patient health especially when subjected to extreme ambient conditions or high level of physical activity. Since thermophysiology is disrupted after SCI, using conventional personal cooling methods may not be effective on PA in a way similar to that of able-bodied people (AB). Experimental studies evaluated the effect of phase change material (PCM) and ice cooling vests on thermal response of PA during exercise. Results showed no change in Tcr values for both types of vest during exercise. This study aims at studying the effectiveness of PCM cooling vest for PA during exercise at intensity level of 6.5 MET within 21.1–23.9 °C room temperature and 50% relative humidity. A multi-segmented bioheat model of PA coupled with PCM cooling vest model (fabric-PCM-PA model) was deployed to predict Tcr values at different design conditions of the vest. Segmental core and skin temperatures profiles and the sensible and latent heat losses were obtained for torso segments to assess the percentage of enhancement in the cooling vest performance. Results showed that Tcr value of the body and Tcr values of the torso segments didn’t change at different design conditions of the vest; yet sensible heat losses were increased for all torso segments and latent heat losses were reduced. Decreases in latent heat losses affected Tsk values at the torso. Simulations were performed using fabric-PCM model integrated with PA bioheat model applying variation of skin coverage area, melting point of PCM and combination of both designs. An effective design of the vest for PA was found when using PCM packet at 10°C melting point and coverage area about 40% of torso because sensible heat losses were the highest compared to the other design cases of the vest.

Heat and Moisture Transport Through the Micro-Climate Air Annulus of the Clothing-Skin System Under Periodic Motion

2005 ◽  
Author(s):  
N. Ghaddar ◽  
K. Ghali ◽  
E. Jaroudi
Keyword(s):  
Heat Loss ◽  
Latent Heat ◽  
Moisture Transport ◽  
Contact Region ◽  
Heat Losses ◽  
Sensible Heat ◽  
Skin Contact ◽  
Cylinder Model ◽  
Heat And Moisture Transport ◽  
Heat And Moisture

A dynamic thermal model is developed using the 2D cylinder model of Ghaddar et al [1] of ventilated fabric-skin system where a microclimate air annulus separates an outer cylindrical fabric boundary and an inner human body solid boundary for closed and open apertures. The cylinder model solves for the radial, and angular flow rates in the microclimate air annulus domain where the inner cylinder is oscillating within an outer fixed cylinder of porous fabric boundary. The 2-D cylinder model is further developed in the radial and angular directions to incorporate the heat and moisture transport from the inner cylinder when the fabric touches the skin boundary at repetitive finite intervals during the motion cycle. The touch model is based on a lumped fabric transient approach based on the fabric dry and evaporative resistances at the localized touch regions at the top and bottom of points of the cylinder. The film coefficients at the inner cylinder are needed for the model simulation. Experiments are conducted in an environmental chamber under controlled conditions to measure the mass transfer coefficient at the skin to the air annulus separating the wet skin and the fabric in the cylindrical geometry. In addition, experiments have also been conducted at ventilation frequencies of 30, 40, and 60 rpm to measure the sensible heat loss from the inner cylinder to validate the predictions of sensible and latent heat losses of the 2-D ventilation model for the two cases when fabric is in contact with the skin surface and when no contact is present for close aperture. The model prediction of time-averaged steady-periodic sensible heat loss agreed well with the experimentally measured values. A parametric study is performed to predict sensible and latent heat losses from the system by ventilation at different frequencies, fabric skin contact times during the motion cycle measured by a dimensionless amplitude parameter (ζ = amplitude/mean annular spacing). The rate of heat loss increases with increased ventilation frequency at fixed ζ. The latent heat loss in the contact region increases by almost 40% due to increase in fabric temperature during contact. The sensible heat loss decreases between 3% at f = 60 rpm, and 5% at f = 25 rpm in the contact region due to higher air temperature and lack of heat loss by radiation during the contact between fabric and skin.

A Novel Modeling Approach to Estimate Segmental and Intersegmental Ventilation and Heat Transport From a Walking Clothed Human Using Electric Circuit Analogy

2017 ◽  
Author(s):  
Nagham Ismail ◽  
Nesreen Ghaddar ◽  
Kamel Ghali
Keyword(s):  
Heat Transport ◽  
Human Body ◽  
Electric Circuit ◽  
Heat Losses ◽  
The Body ◽  
Effective Model ◽  
Sensible Heat ◽  
Body Experiences ◽  
Circuit Analogy ◽  
Relative Wind

When the clothed human body experiences relative wind due to walking and external wind, heat and vapor transfers from the body to the environment are enhanced by ventilation through clothing. The clothing ventilation is related to the clothing permeability, open and close apertures, relative wind, clothed limbs swinging motion as well as the inter-segmental ventilation that occurs at the interconnection between the clothed human trunk and arms. In this study, a computationally effective model is developed to estimate clothing ventilation based on the analogy between the air flow in the microclimate air layer and an electric circuit composed of resistance and inductance elements. The model takes into account the inter-connection between the segments for the clothed human upper part driven by difference of pressure in the microclimate air of the trunk and the upper arms. The estimation of the segmental ventilation, taking into account the inter-connection, allows the correction of the clothing dry resistances in a bio-heat model that will be used to predict the sensible heat losses of the clothed human.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

scholarly journals Cardiorespiratory Responses to 10 Weeks of Exoskeleton-Assisted Overground Walking Training inChronic Nonambulatory Patients with Spinal Cord Injury

Sensors ◽  
2021 ◽  
Vol 21 (15) ◽  
pp. 5022
Author(s):  
Jae Hyeon Park ◽  
Hyeon Seong Kim ◽  
Seong Ho Jang ◽  
Dong Jin Hyun ◽  
Sang In Park ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Oxygen Consumption ◽  
Exercise Intensity ◽  
Moderate Physical Activity ◽  
Intensity Level ◽  
Cardiorespiratory System ◽  
Cardiorespiratory Responses ◽  
Cord Injury ◽  
Walking Efficiency

Exercise intensity of exoskeleton-assisted walking in patients with spinal cord injury (SCI) has been reported as moderate. However, the cardiorespiratory responses to long-term exoskeleton-assisted walking have not been sufficiently investigated. We investigated the cardiorespiratory responses to 10 weeks of exoskeleton-assisted walking training in patients with SCI. Chronic nonambulatory patients with SCI were recruited from an outpatient clinic. Walking training with an exoskeleton was conducted three times per week for 10 weeks. Oxygen consumption and heart rate (HR) were measured during a 6-min walking test at pre-, mid-, and post-training. Exercise intensity was determined according to the metabolic equivalent of tasks (METs) for SCI and HR relative to the HR reserve (%HRR). Walking efficiency was calculated as oxygen consumption divided by walking speed. The exercise intensity according to the METs (both peak and average) corresponded to moderate physical activity and did not change after training. The %HRR demonstrated a moderate (peak %HRR) and light (average %HRR) exercise intensity level, and the average %HRR significantly decreased at post-training compared with mid-training (31.6 ± 8.9% to 24.3 ± 7.3%, p = 0.013). Walking efficiency progressively improved after training. Walking with an exoskeleton for 10 weeks may affect the cardiorespiratory system in chronic patients with SCI.

scholarly journals Thermal Behaviour of Common Thermoresponsive Polymers in Phosphate Buffer and in Its Salt Solutions

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 90
Author(s):  
Łukasz Otulakowski ◽  
Maciej Kasprów ◽  
Aleksandra Strzelecka ◽  
Andrzej Dworak ◽  
Barbara Trzebicka
Keyword(s):  
Thermal Behaviour ◽  
Phosphate Buffer ◽  
Pure Water ◽  
Thermal Response ◽  
The Body ◽  
Solution Temperature ◽  
Thermoresponsive Polymers ◽  
Aqueous Polymer ◽  
Cloud Point Temperature ◽  
Size Of Particles

Thermoresponsive polymers are a promising material for drug nanocarrier preparation, which makes the study of their aggregation in physiological conditions very important. In this paper, the thermal behaviour of the thermoresponsive polymers poly(N-isopropylacrylamide), poly(2-isopropyl-2-oxazoline-co-2-n-propyl-2-oxazoline) and poly[(2-hydroxyethyl methacrylate)-co-oligo(ethylene glycol) methyl ether methacrylate] were studied in phosphate buffer (PBS) and solutions of its salts in concentration as in PBS. The thermal response of the polymers was measured using UV-Vis and dynamic light scattering (DLS). The salts shifted the cloud point temperature (TCP) of the (co)polymers to higher values compared to the TCP of aqueous polymer solutions. In PBS and NaCl solutions, all polymers exhibited an unexpected and previously unreported transmittance profile. During heating, an additional aggregation of polymers appeared above the TCP accompanied by the formation of a precipitate. In monosodium phosphate solutions and pure water, the studied polymers showed lower critical solution temperature (LCST-type) behaviour. DLS measurements showed that a salt influenced the size of the resulting polymer particles. The sizes and stability of particles depended on the heating rate. In PBS and NaCl solutions, the size of particles in the dispersion decreased above 60 °C, and the precipitate appeared on the bottom of the cuvette. The additional aggregation of polymer and its falling out of solution may hinder the removal of carriers from the body and has to be taken into account when preparing nanocarriers.

scholarly journals The Role of Lipids, Lipid Metabolism and Ectopic Lipid Accumulation in Axon Growth, Regeneration and Repair after CNS Injury and Disease

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1078
Author(s):  
Debasish Roy ◽  
Andrea Tedeschi
Keyword(s):  
Nervous System ◽  
Lipid Metabolism ◽  
Lipid Accumulation ◽  
Axon Regeneration ◽  
Axon Growth ◽  
The Body ◽  
Cns Repair ◽  
Cord Injury ◽  
Cns Trauma

Axons in the adult mammalian nervous system can extend over formidable distances, up to one meter or more in humans. During development, axonal and dendritic growth requires continuous addition of new membrane. Of the three major kinds of membrane lipids, phospholipids are the most abundant in all cell membranes, including neurons. Not only immature axons, but also severed axons in the adult require large amounts of lipids for axon regeneration to occur. Lipids also serve as energy storage, signaling molecules and they contribute to tissue physiology, as demonstrated by a variety of metabolic disorders in which harmful amounts of lipids accumulate in various tissues through the body. Detrimental changes in lipid metabolism and excess accumulation of lipids contribute to a lack of axon regeneration, poor neurological outcome and complications after a variety of central nervous system (CNS) trauma including brain and spinal cord injury. Recent evidence indicates that rewiring lipid metabolism can be manipulated for therapeutic gain, as it favors conditions for axon regeneration and CNS repair. Here, we review the role of lipids, lipid metabolism and ectopic lipid accumulation in axon growth, regeneration and CNS repair. In addition, we outline molecular and pharmacological strategies to fine-tune lipid composition and energy metabolism in neurons and non-neuronal cells that can be exploited to improve neurological recovery after CNS trauma and disease.

scholarly journals Enhanced Performance and Diffusion Robustness of Phase-Change Metasurfaces via a Hybrid Dielectric/Plasmonic Approach

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 525
Author(s):  
Joe Shields ◽  
Carlota Ruiz de Galarreta ◽  
Jacopo Bertolotti ◽  
C. David Wright
Keyword(s):  
Melting Point ◽  
Phase Change ◽  
Noble Metals ◽  
Phase Change Materials ◽  
High Efficiency ◽  
The Body ◽  
Design Stage ◽  
High Melting ◽  
Optical Performance ◽  
Electrical Conductors

Materials of which the refractive indices can be thermally tuned or switched, such as in chalcogenide phase-change alloys, offer a promising path towards the development of active optical metasurfaces for the control of the amplitude, phase, and polarization of light. However, for phase-change metasurfaces to be able to provide viable technology for active light control, in situ electrical switching via resistive heaters integral to or embedded in the metasurface itself is highly desirable. In this context, good electrical conductors (metals) with high melting points (i.e., significantly above the melting point of commonly used phase-change alloys) are required. In addition, such metals should ideally have low plasmonic losses, so as to not degrade metasurface optical performance. This essentially limits the choice to a few noble metals, namely, gold and silver, but these tend to diffuse quite readily into phase-change materials (particularly the archetypal Ge2Sb2Te5 alloy used here), and into dielectric resonators such as Si or Ge. In this work, we introduce a novel hybrid dielectric/plasmonic metasurface architecture, where we incorporated a thin Ge2Sb2Te5 layer into the body of a cubic silicon nanoresonator lying on metallic planes that simultaneously acted as high-efficiency reflectors and resistive heaters. Through systematic studies based on changing the configuration of the bottom metal plane between high-melting-point diffusive and low-melting-point nondiffusive metals (Au and Al, respectively), we explicitly show how thermally activated diffusion can catastrophically and irreversibly degrade the optical performance of chalcogenide phase-change metasurface devices, and how such degradation can be successfully overcome at the design stage via the incorporation of ultrathin Si3N4 barrier layers between the gold plane and the hybrid Si/Ge2Sb2Te5 resonators. Our work clarifies the importance of diffusion of noble metals in thermally tunable metasurfaces and how to overcome it, thus helping phase-change-based metasurface technology move a step closer towards the realization of real-world applications.

scholarly journals The Histopathology of Severe Graded Compression in Lower Thoracic Spinal Cord Segment of Rat, Evaluated at Late Post-injury Phase

2021 ◽  
Author(s):  
Fedorova Jana ◽  
Kellerova Erika ◽  
Bimbova Katarina ◽  
Pavel Jaroslav
Keyword(s):  
Spinal Cord ◽  
Spontaneous Recovery ◽  
Traumatic Injury ◽  
Blue Dye ◽  
Post Injury ◽  
Thoracic Spinal Cord ◽  
Thoracic Spinal ◽  
Severe Traumatic Injury ◽  
Spinal Cord Segment ◽  
Cord Injury

AbstractSpontaneous recovery of lost motor functions is relative fast in rodent models after inducing a very mild/moderate spinal cord injury (SCI), and this may complicate a reliable evaluation of the effectiveness of potential therapy. Therefore, a severe graded (30 g, 40 g and 50 g) weight-compression SCI at the Th9 spinal segment, involving an acute mechanical impact followed by 15 min of persistent compression, was studied in adult female Wistar rats. Functional parameters, such as spontaneous recovery of motor hind limb and bladder emptying function, and the presence of hematuria were evaluated within 28 days of the post-traumatic period. The disruption of the blood-spinal cord barrier, measured by extravasated Evans Blue dye, was examined 24 h after the SCI, when maximum permeability occurs. At the end of the survival period, the degradation of gray and white matter associated with the formation of cystic cavities, and quantitative changes of glial structural proteins, such as GFAP, and integral components of axonal architecture, such as neurofilaments and myelin basic protein, were evaluated in the lesioned area of the spinal cord. Based on these functional and histological parameters, and taking the animal’s welfare into account, the 40 g weight can be considered as an upper limit for severe traumatic injury in this compression model.

Sign in / Sign up

Export Citation Format

Share Document