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Basic Thermal Physics: Heat Exchange and Infrared Radiation
Published in Kurt Ammer, Francis Ring, The Thermal Human Body, 2019
Radiant flux, dφ/dA, is the radiant flow per unit area (unit:W m−2). The radiant flux emitted by a surface is the thermal radiant exitance. The radiant flux incident on or passing through an area is the irradiance.
Photoirritation (Phototoxicity) Testing in Humans
Published in Francis N. Marzulli, Howard I. Maibach, Dermatotoxicology Methods: The Laboratory Worker’s Vade Mecum, 2019
Francis N. Marzulli, Howard I. Maibach
The basic unit of radiant work energy emitted by a source is the joule (J). One J delivered over 1 sec is 1 watt (W) of radiant power. Radiant power, or irradiance, is reported in watts/square meter (often mW/square meter), and radiant exposure is reported in J/square meter (often J/cm2 skin). Optical radiation is measured with a radiometer. Other details about spectral measurements are in chapter 18 and in the chapter on spectral equipment for photobiology (Sliney, 1996).
Healing with Light
Published in Aruna Bakhru, Nutrition and Integrative Medicine, 2018
Anadi Martel, Wesley Burwell, Magda Havas
Response to light energy is biphasic, which means that stimulation occurs above a certain low-level energy threshold and increases to a maximum. Further increases in irradiance decrease beneficial effects and, above an upper energy threshold, may damage cells.
ALSUntangled #60: light therapy
Published in Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2022
Richard Bedlack, Paul Barkhaus, Ben Barnes, Michael Bereman, Tulio Bertorini, Gregory Carter, Jesse Crayle, Sky Kihuwa-Mani, Robert Bowser, Pamela Kittrell, Christopher McDermott, Gary Pattee, Kristiana Salmon, Paul Wicks
Light is a type of electromagnetic radiation, which comes in discrete quantized packages known as photons (5). It can be characterized according to its wavelength (measured in nanometers, nm). Visible light has wavelengths between 400 and 700 nm. Light with wavelengths below this range is referred to as “ultraviolet”, and light with wavelengths above this range is referred to as “infrared” (5). Light can be generated by different sources (ex. lamps, LEDs, lasers). In addition to having different wavelengths, these different sources can deliver different amounts of energy (measured in joules, J) and power (measured in watts, W). When describing power or energy, it is important to state the area the energy is delivered over. This is called “power density” or “irradiance” (measured in milliwatts per square centimeter; mW/cm2) and/or “energy density” or “fluence” (measured in joules per square centimeter; J/cm2, 5,6).
Ocular toxicology: synergism of UV radiation and benzalkonium chloride
Published in Cutaneous and Ocular Toxicology, 2020
Manlong Xu, Jacob G. Sivak, David J. McCanna
UV exposure was conducted in a custom-designed UV irradiation unit at 37 °C with 5% CO2. The light source used in this study was two UV fluorescence tubes (Lifespan at the time of experiment: 100–200 h, Microlites Scientific, Toronto, Canada) that emit broadband UVA and UVB (280–400 nm). Before irradiation, the irradiance of the UV source was measured with a USB 2000+ fibre optic spectrometer (Ocean Optics, Inc. Dunedin, FL). The calculated irradiance was 5.73 W/m2. Samples were exposed to UV radiation at a distance of 30 cm from the light source for 5 min. The corresponding dose was 0.17 J/cm2. This dose was selected for 3 reasons. Firstly, it is a relevant human exposure level. It equals to ∼10-min exposure to a very intense natural sunlight on a sunny day at noon in the summer in Waterloo, ON, Canada (measured irradiance: 2.76 W/m2); it also equals to about 1-h exposure to the sunlight in a slightly cloudy evening in the fall at the same location (measured irradiance: 0.43 W/m2). Secondly, this dose showed mild toxicity to HCEC that allowed the detection of additive and synergistic effects when combined with BAK. Finally, it requires only 5 min of exposure to the UV lamps, which is easily applicable in our experiments without overheating or over-drying the cultured cells.
Light-triggered nanoparticles for pain management
Published in Expert Opinion on Drug Delivery, 2020
Gracia Mendoza, Manuel Arruebo
Later, these authors showed the combination of both approaches in only one system [30]. DDS based on liposomes loading the photosensitizer described above together with TTX as anesthetic were tethered with gold nanorods to enhance the DDS absorbance at 730 nm in order to accomplish superior photosensitivity and repeatability. The synthesized DDS showed in vitro that the phototriggered release of TTX could be achieved at least five times. The in vivo efficiency of the fabricated DDS was evaluated in a rat model similar to those reported above though at a different irradiance (200 mW/cm2, 3 min) and the effects were tested by means of a nociceptive behavioral test based again on the Touch Test sensory evaluator [29]. The anesthetic effects of the administered DDS were recorded up to two irradiations (1.5 ± 0.3 h after the first irradiation, 0.8 ± 0.6 h after the second irradiation) whereas a third irradiation did not involve neurobehavioral effects. Histological analysis did not reveal significant myotoxicity though mild to moderate inflammation, which was attributed to the reaction to particles administration. In this work, it is very significant the use of a reduced irradiance since it is less likely to involve thermal injury and suggests the possibility to trigger in deeper tissues.