Precision thermometry of the skin can, together with other measurements, provide clinically relevant information about cardiovascular health, cognitive state, malignancy and many other important aspects of human physiology. Here, we introduce an ultrathin, compliant skin-like sensor/actuator technology that can pliably laminate onto the epidermis to provide continuous, accurate thermal characterizations that are unavailable with other methods. Examples include non-invasive spatial mapping of skin temperature with millikelvin precision, and simultaneous quantitative assessment of tissue thermal conductivity. Such devices can also be implemented in ways that reveal the time-dynamic influence of blood flow and perfusion on these properties. Experimental and theoretical studies establish the underlying principles of operation, and define engineering guidelines for device design. Evaluation of subtle variations in skin temperature associated with mental activity, physical stimulation and vasoconstriction/dilation along with accurate determination of skin hydration through measurements of thermal conductivity represent some important operational examples.

Ultrathin conformal devices for precise and continuous thermal characterization of human skin.

This paper is one of several in this Special Issue of the International Journal of Hyperthermia that discusses the current state of knowledge about the human health risks of hyperthermia This special issue emanated from a workshop sponsored by the World Health Organization in the Spring of 2002 on this topic It is anticipated that these papers will help to establish guidelines for human exposure to conditions leading to hyperthermia This comprehensive review of the literature makes it clear that much more work needs to be done to clarify what the thresholds for thermal damage are in humans This review summarizes the basic principles that govern the relationships between thermal exposure (temperature and time of exposure) and thermal damage, with an emphasis on normal tissue effects Methods for converting one time-temperature combination to a time at a standardized temperature are provided as well as a detailed discussion about the underlying assumptions that go into these calculations There are few in vivo papers examining the type and extent of damage that occurs in the lower temperature range for hyperthermic exposures (eg 39-42 degrees C) Therefore, it is clear that estimation of thermal dose to effect at these thermal exposures is less precise in that temperature range In addition, there are virtually no data that directly relate to the thermal sensitivity of human tissues Thus, establishment of guidelines for human exposure based on the data provided must be done with significant caution There is detailed review and presentation of thermal thresholds for tissue damage (based on what is detectable in vivo) The data are normalized using thermal dosimetric concepts Tables are included in an Appendix Database which compile published data for thresholds of thermal damage in a variety of tissues and species This database is available by request (contact MWD or PJH), but not included in this manuscript for brevity All of the studies reported are for single acute thermal exposures Except for brain function and physiology (as detailed in this issue by Sharma et al) one notes the critical lack of publications examining effects of chronic thermal exposures as might be encountered in occupational hazards This review also does not include information on the embryo, which is covered in detail elsewhere in this volume (see article by Edwards et al) as well as in a recent review on this subject, which focuses on thermal dose

Basic principles of thermal dosimetry and thermal thresholds for tissue damage from hyperthermia

A dynamic model predicting human thermal responses in cold, cool, neutral, warm, and hot environments is presented in a two-part study. This, the first paper, is concerned with aspects of the passi...

https://www.physiology.org/doi/pdf/10.1152/jappl.1999.87.5.1957

A computer model of human thermoregulation for a wide range of environmental conditions: the passive system.

The UTCI-Fiala mathematical model of human temperature regulation forms the basis of the new Universal Thermal Climate Index (UTC). Following extensive validation tests, adaptations and extensions, such as the inclusion of an adaptive clothing model, the model was used to predict human temperature and regulatory responses for combinations of the prevailing outdoor climate conditions. This paper provides an overview of the underlying algorithms and methods that constitute the multi-node dynamic UTCI-Fiala model of human thermal physiology and comfort. Treated topics include modelling heat and mass transfer within the body, numerical techniques, modelling environmental heat exchanges, thermoregulatory reactions of the central nervous system, and perceptual responses. Other contributions of this special issue describe the validation of the UTCI-Fiala model against measured data and the development of the adaptive clothing model for outdoor climates.

/pdf/utci-fiala-multi-node-model-of-human-heat-transfer-and-5cmgs9n595.pdf

UTCI-Fiala multi-node model of human heat transfer and temperature regulation.

Ultrasonic biophysics is the study of mechanisms responsible for how ultrasound and biological materials interact. Ultrasound-induced bioeffect or risk studies focus on issues related to the effects of ultrasound on biological materials. On the other hand, when biological materials affect the ultrasonic wave, this can be viewed as the basis for diagnostic ultrasound. Thus, an understanding of the interaction of ultrasound with tissue provides the scientific basis for image production and risk assessment. Relative to the bioeffect or risk studies, that is, the biophysical mechanisms by which ultrasound affects biological materials, ultrasound-induced bioeffects are generally separated into thermal and non-thermal mechanisms. Ultrasonic dosimetry is concerned with the quantitative determination of ultrasonic energy interaction with biological materials. Whenever ultrasonic energy is propagated into an attenuating material such as tissue, the amplitude of the wave decreases with distance. This attenuation is due to either absorption or scattering. Absorption is a mechanism that represents that portion of ultrasonic wave that is converted into heat, and scattering can be thought of as that portion of the wave, which changes direction. Because the medium can absorb energy to produce heat, a temperature rise may occur as long as the rate of heat production is greater than the rate of heat removal. Current interest with thermally mediated ultrasound-induced bioeffects has focused on the thermal isoeffect concept. The non-thermal mechanism that has received the most attention is acoustically generated cavitation wherein ultrasonic energy by cavitation bubbles is concentrated. Acoustic cavitation, in a broad sense, refers to ultrasonically induced bubble activity occurring in a biological material that contains pre-existing gaseous inclusions. Cavitation-related mechanisms include radiation force, microstreaming, shock waves, free radicals, microjets and strain. It is more challenging to deduce the causes of mechanical effects in tissues that do not contain gas bodies. These ultrasonic biophysics mechanisms will be discussed in the context of diagnostic ultrasound exposure risk concerns.

Ultrasound—biophysics mechanisms

A nonlinear singular perturbation theory for non-similar melting or freezing problems

Etude de jets turbulents tridimensionnels desaxes se dechargeant de canaux rectangulaires parallelement a une surface plane

Experimental study of surface pressure in three-dimensional turbulent jet/boundary interaction

Transient heat transfer in fins undergoing phase transformation

This paper presents a quasi-steady state approximation solution for the three dimensional melting or freezing around a fluid carrying pipe which is buried in a semi-infinite phase change medium (PCM). The two-dimensional quasi-steady approximation solution method previously developed by the authors, the virtual free surface technique, has been extended to three dimensions where axial thermal interaction between the moving fluid and PCM is considered. Of particular interest herein is the motion of the phase change interface and the time variation of the axial temperature distribution in the fluid. Due to the singularities of the differential equations along the pipe surface, an axisymmetric analytic solution is provided for the region near the pipe wall. Solutions are presented for several representative dimensionless burial depths of the pipe and initial conditions. The computational time to predict the three dimensional interface location up to 10 years is of the order of several minutes on an IBM 4341 computer.

An Approximate Three-Dimensional Solution for Melting or Freezing Around a Buried Pipe Beneath a Free Surface

Power Plant Spray Cooling: Design and Performance Studies

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