No description available.

No description available.

In this thesis we investigate a sequence of important inverse problems associated with the bio-heat transient flow equation which models the heat transfer within the human body. Given the physical importance of the blood perfusion coefficient that appears in the bio-heat equation, attention is focused on the inverse problems concerning the accurate recovery of this information when exact and noisy measurements are considered in terms of the mass, flux, or temperature, which we sampled over the specific regions of the media under investigation. Five different cases are considered for the retrieval of the perfusion coefficient, namely when this parameter is assumed to be either constant, or dependent on time, space, temperature, or on both space and time. Theanalytica:l and numerical techniques that arc used to investigate the existence and uniqueness of the solution for this inverse coefficient identification are embedded in an extensiveú computational approach for the retrieval of the perfusion coefficient. Boundary integral methods, for the constant and the time-dependent cases, or Crank-Nicolson-type global schemes or local methods based on solutions of the first-kind integral equations, in the space, temperature, or space and time cases, are used in conjunction either with Gaussian mollification or with Tikhonov regularization methods, which arc coupled with optimization techniques. Analytically, a number of uniqueness and existence criteria and structural results are formulated and proved.

No description available.

Thermoregulation system and human body responses, both physiological (i.e. skin and core temperature) and psychological (thermal sensation and thermal comfort), have been of considerable interest to researchers. However, while reactions to extreme conditions are well understood and explained, there is a considerable knowledge gap for mild temperature range adaptation. Previous research focused on the whole body response, while local analysis is more appropriate for a new generation of intelligent thermal control systems such as needed in planes. Furthermore majority of previous studies were carried out predominantly on mannequins or with subjects placed in highly controlled lab chambers, hence adaptations in normal shared spaces is not investigated in sufficient depth. In addition, no study investigated infants’ temperature adaptation. This thesis describes the comprehensive study of the human temperature distribution in selected areas, both for adults and infants under the age of 2. Furthermore, variation of core and local skin temperature, thermal sensation and level of comfort due to long periods of inactivity were also investigated in adults. These studies have set the basis for the development of temperature monitoring systems. The first monitoring system specific to children under 2 provides fever detection based on skin temperature measurement. It was developed for a Spanish textile company (AITEX), and it is a patent under consideration. The second system monitors level of comfort and thermal sensation of adults in indoor environments. The system is based on pre-existing statistical studies and Fanger’s steady-state model. It adapts to the individual while analysing real time skin temperature distribution, and identifies.

When exercise is undertaken in warm, humid conditions, the thermal gradient between the skin and environment, and the capacity for evaporative heat loss, are reduced. These factors, along with an increase in metabolic heat production, lower work capacity and exercise performance. Thermoreceptors located within the skin and deep in the body convey information on this accumulation of thermal energy to higher brain structures and, if mean body temperature rises uncontrollably, the cumulative neuronal input is thought to produce inhibitory signals that lower work capacity, such that metabolic heat production decreases to protect the organism from heat injury. Lessening these inhibitory signals may enhance or help to maintain exercise performance in the heat. The inhibitory signals might be lessened by cooling the skin and deep body temperature prior to or during exercise, or perhaps by applying menthol on the skin, or some combination of these. Menthol is a chemical compound that activates cold receptors (TRPM8) in the skin to elicit cool sensations. These receptors are not otherwise activated unless cooled below 27 °C. Hence, menthol, when applied to the skin of heat stressed humans, may provide a “cool’’ neuronal input to higher brain structures in addition to the neuronal signals arising from warm thermoreceptors located within the body. But menthol may also induce a heat storage (cold defense) response that would then heighten the activity of warm receptors deep in the body. Therefore, it is not clear whether menthol might reduce, enhance or help to maintain exercise performance in heat stressed humans. Moreover, no studies have assessed the perceptual and thermoregulatory response to menthol during rest or exercise, or the consequence of its repeated use. Before it is recommended as a possible ergogenic aid, these studies should be undertaken. The early work presented in this thesis tested the hypotheses that a water-based spray, containing ethanol and/or menthol, would enhance evaporative cooling when sprayed on the skin, thereby lowering heat storage and improving thermal perception compared to an unsprayed Control condition; but menthol would also improve thermal perception independent of temperature by directly stimulating cold receptors, during rest and exercise in warm, humid conditions. The hypothesis that menthol-mediated cool sensations would not undergo any habituation after repeated exposures was also tested. The general approach to testing these hypotheses involved presenting human participants with a thermal challenge that would induce warm sensations and increase thermal discomfort, whilst encouraging a level of heat storage that could be compensated for by increasing heat loss through v sodilation and sweating. This was achieved by manipulating metabolic heat production through a combination of rest and fixed intensity exercise in warm (30 °C) and humid (70 %) conditions. The influence of a menthol solution spray was tested against the backdrop of this thermal challenge. The results supported the general hypothesis that a water-based upper-body spray containing menthol can increase sensations of coolth compared to no spraying or wateronly spraying during rest and exercise in warm, humid conditions, but menthol also influences body temperature regulation. The effect that menthol exerts over perception and thermoregulation differs by dose and fades with time. Specifically, 0.2 % menthol spraying encourages heat storage by enhancing vasoconstriction, and there is no habituation in these responses. 0.05 % menthol spraying did not encourage any additional heat storage compared to a Control spray. Menthol also influenced perception, with a 0.2 % menthol spray promoting cooler sensations and greater irritation than 0.05 % menthol and Control spraying. Compared to a Control spray, 0.2 % menthol reduced thermal comfort during rest and improved it during exercise, while 0.05 % menthol did not alter thermal comfort during rest, and may have improved it during exercise. Neither menthol spray influenced perceived exertion during exercise. Menthol-mediated cool sensations lasted 15 to 30 minutes. Both 0.2 % and 0.05 % menthol sprays underwent an habituation compared to the Control spray, with cool sensations diminishing after repeated daily exposures. It is concluded that a 0.05 % menthol spray, which induces cool sensations without a significant heat storage response, could be considered as a perceptual cooling intervention with some capacity to enhance evaporative heat loss when sprayed on the skin during rest and moderate fixed-intensity exercise in the heat. A 0.2 % menthol spray might be deployed later in exercise, but may increase heat storage and irritation. Further testing is required to identify whether menthol spraying improves maximal exercise performance.