Fundamentals of Infrared Thermal Imaging
U. Snekhalatha, K. Palani Thanaraj, Kurt Ammer in Artificial Intelligence-Based Infrared Thermal Image Processing and Its Applications, 2023
“Heat capacity” c is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. The SI unit of heat capacity is joule per kelvin (J/K). Thus, heat capacity describes the ability of matter to store thermal energy. Specific heat capacity cp is found by dividing the heat capacity of an object by its mass. The subscript p in c points to the condition of constant pressure, in which heat supplied to the system would contribute to both the work done and the change in internal energy. Density ρ is defined by the mass of a substance per unit volume. The product of density ρ and specific heat capacity cp is called volumetric heat capacity ρ cp. Finally, thermal diffusivity α combines thermal conductivity with density ρ and specific heat cp: . At interfaces of contact, the product k ρ c represents an important feature of the capacities for heat transfer in transient state. The square root of the product of the material’s thermal conductivity and volumetric heat capacity is called thermal inertia. The greater the thermal inertia, the higher the heat transfer. Thermal inertia explains why the sensation of the temperature of a given object depends not only on its actual temperature, but even more on its k ρ c values (Houdas and Ring, 1982).
Basic Thermal Physics: Heat Exchange and Infrared Radiation
Kurt Ammer, Francis Ring in The Thermal Human Body, 2019
The inverse of the ratio ρc/k is generally termed thermal diffusion or in other words thermal diffusivityα = k/ρcp (m2 · s−1) is the thermal conductivity of a substance divided by its density ρ and specific heat at constant pressure cp, [4]. Thermal diffusivity is a measure of how quickly a material can carry heat away from a hot source. Since material does not just transmit heat but must be warmed by it as well, α involves both the conductivity, k, and the volumetric heat capacity, ρc [12].
Nondegradable Intraocular Sustained-Release Drug Delivery Devices
Glenn J. Jaffe, Paul Ashton, P. Andrew Pearson in Intraocular Drug Delivery, 2006
Reservoir systems consist of a central drug core surrounded by a layer of semipermeable nondegradable material. The release rate of the reservoir devices is based on Fick's law of diffusion and is determined by the area of release, the thickness of the semipermeable coatings, the shape of the implant, and the ease with which the drug diffuses through the semipermeable coating, which is also termed the diffusivity. The release profile follows zero-order kinetics and is characterized by a minimal initial burst of drug release followed by constant drug release over time.
Long-term cognitive disability after traumatic brain injury: Contribution of the DEX relative questionnaires
Published in Neuropsychological Rehabilitation, 2020
Blandine Lesimple, Elsa Caron, Muriel Lefort, Clara Debarle, Mélanie Pélégrini-Issac, Didier Cassereau, Sébastien Delphine, Grégory Torkomian, Valentine Battisti, Pierrette Bossale, Damien Galanaud, Louis Puybasset, Pascale Pradat-Diehl, Vincent Perlbarg
As far as anosognosia is concerned, results are heterogeneous from one study to another in the literature concerning the brain network involved in self-awareness. For example, according to Morton and Barker (2010), this complex process may imply prefrontal, inferior parietal and anterior temporal lobes, angular gyrus and supramarginal gyrus and, more generally, involve the anterior cingulate cortex, the anterior insula and fronto-parietal areas (Craig, 2009), which could be affected by a diffuse brain injury rather than a focal lesion (Morton & Barker, 2010). Anosognosia could be a dysfunctional result of a more extensive and distinct cerebral network (Morton & Barker, 2010). In this context, mean diffusivity is a measure that allows one to evaluate microstructural white matter integrity. After a mild TBI, Kinnunen et al. (2011) and Messé et al. (2011) have shown that an increased MD value could discriminate patients with poor outcome from those with a good outcome and from controls, three months after injury. Haberg et al. (2015) reported a correlation between the mean of MD measures and GOSE in TBI patients. Our results showed a link between global white matter alteration (in terms of MD value) and anosognosia, suggesting that anosognosia, even at long term after TBI, could be a consequence of brain damages.
Thermal diffusivity and perfusion constants from in vivo MR-guided focussed ultrasound treatments: a feasibility study
Published in International Journal of Hyperthermia, 2018
Christopher R. Dillon, Viola Rieke, Pejman Ghanouni, Allison Payne
Immediately following the MRgFUS experiment, the rabbits were euthanised and, in two of the three animals, invasive measurements of thermal diffusivity in the back muscle were made with a commercial thermal property analyser (KD2 Pro, Decagon Devices, Pullman, WA). The property analyser induces a 1–3 °C temperature rise in the tissue over 2 min via a thin-needle that applies uniform power along its 30 mm length. A second needle spaced 6 mm away measures transient temperature changes in the tissue. Fitting the transient temperature data with the analytical temperature solution for an infinite line source with constant power per unit length [35] yields the thermal diffusivity of the tissue. The manufacturer reported accuracy of this device is ±10% for thermal diffusivity between 0.1 and 1.0 mm2 s−1. In total, nine measurements were made at unique locations within the back muscle.
The effects of aerobic exercise on corpus callosum integrity: systematic review
Published in The Physician and Sportsmedicine, 2020
Paul D. Loprinzi, Jacob Harper, Toshikazu Ikuta
Integrity of the human CC is often measured via diffusion tensor imaging. Including metrics of fractional anisotropy (FA), higher values indicate greater white matter integrity. Also, calculated from axial diffusivity (AD) and radial diffusivity (RD), as well as mean diffusivity (MD), higher values indicate lesser white matter integrity. Integrity of animal (mice) CC often consists of anesthetizing the specimen to prepare brain tissue under investigation. Analysis is conducted through dissection followed by microscopic evaluation or custom-made MRI devices. Dissection of the CC has been known to result in ‘split-brain’ where two cerebral hemispheres minimally interact and exhibit independence from each other [2]. Interhemispheric connectivity provided by the CC is associated with cortical functions. For example, in the context of motor function, the CC influences bi-manual motor performance and may be involved in transferring inhibitory signals to the opposing hemisphere before and during motor execution [5,6]. Association between motor functions and interhemispheric motor fibers via the CC has been shown in adults and children [7,8]. With this in mind, maintaining the corpus callosum integrity is essential.
Related Knowledge Centers
- Diffusion
- Fick'S Laws of Diffusion
- Physical Chemistry
- Pairwise Comparison
- Arrhenius Equation
- Activation Energy
- Atomic Diffusion
- Effective Diffusion Coefficient
- Lattice Diffusion Coefficient
- Knudsen Diffusion