Lasers in Medicine: Healing with Light
Suzanne Amador Kane, Boris A. Gelman in Introduction to Physics in Modern Medicine, 2020
The light employed in laser surgery does damage because it transfers energy by absorption or scattering to human tissues. Each photon carries energy that can be converted into other forms of energy, such as chemical bond energy. Although energy can be transformed between different types (kinetic energy – energy of motion – chemical bond energy, light energy, etc.), energy cannot be destroyed or created from nothing, a fundamental principle referred to as the conservation of energy. The most common energy transformation in laser surgery involves heating tissue through the absorption of photon energy. Atoms are in constant random motion in gaseous and liquid materials, and they are vibrating around their equilibrium positions in solids. The temperature of the material characterizes the average energy of this motion, and the total energy due to this motion is called the material's thermal energy. The energy carried by light is most often converted into thermal energy of the molecules of the tissue being illuminated; this energy input thus raises the material's temperature. Energy transfers that change the thermal energy of a material are called heat. Thus, the transfer of energy from photons of light can also result in the heating of tissue. For example, heat lamps work by providing infrared radiation that is efficiently absorbed by our tissue as heat. On a clear day this effect is quite evident in the heat we feel from sunlight.
Concepts of Potential Energy, Enthalpy, and Bond Energy Calculations
Patrick E. McMahon, Rosemary F. McMahon, Bohdan B. Khomtchouk in Survival Guide to General Chemistry, 2019
Kinetic energy (abbreviated as kE) is the energy of motion of matter. Kinetic energy includes both the motion of bulk matter and the production of heat. Heat is thermal energy and is a measure of the kinetic energy of motion of individual atoms, molecules, or ions in bulk matter. Kinetic energy ( kE) of matter is proportional to mass and the velocity: kE = ½mv2The metric units of the equation are (kg) × (m/sec)2 = (kg-m2/sec2) = one JouleJoule ( J) is the metric unit of energy; one kiloJoule ( kJ) = 1000 J; 4.184 Joules = 1 calorie.Temperature (in °K) is a measure of the average kinetic energy of atoms and molecules.
Entropy
Nicholas Stergiou in Nonlinear Analysis for Human Movement Variability, 2018
Before discussing the application of entropy concepts to biological time series, a historical perspective on entropy is presented to develop an understanding of what it is intended to measure. The concept of entropy was first developed in classical thermodynamics, where it grew out of the work by Carnot (1824) on steam engines, to develop an understanding of the limits of mechanical work that could be produced by such engines. The term “entropy” was introduced to the vocabulary of classical thermodynamics by Clausius (1867). In classical thermodynamics, entropy is a state function that quantifies the energy in a system that cannot be used to perform work. The study of statistical thermodynamics, first published by Boltzmann (1896), gave further insight into the concept of entropy, by using probability concepts to describe entropy on a molecular scale. Thermal energy is associated with the movement of atoms and molecules, which results in an increased variability in position and velocity of those atoms and molecules. Statistical thermodynamics views entropy as the amount of microscopic variability that a system has for a given macroscopically observable state and is based on the distribution of microscopic configurations that can give rise to the macroscopic state. Boltzmann quantified the concept of entropy as follows:
Fractional radiofrequency in the treatment of skin aging: an evidence-based treatment protocol
Published in Journal of Cosmetic and Laser Therapy, 2020
Ileana Afroditi Kleidona, Dimitrios Karypidis, Nicholas Lowe, Simon Myers, Ali Ghanem
Radiofrequency (RF) devices use electromagnetic radiation to conduct alternating electric current to biologic tissues, causing motion of charged particles against the tissue’s resistance (impedance). This kinetic energy is converted to thermal energy (12). The heat causes initial collagen contraction and subsequent new collagen synthesis through long-term repair processes, resulting in dermal remodeling and skin tightening. It is hypothesized that since RF is not selectively absorbed by chromophores is safe in darker skin (13). More recently, fractional radiofrequency (FRF) has gained traction as the last generation stratagem combining efficacy and safety in skin rejuvenation. This technique uses minimally invasive microneedles or electrode pins to achieve targeted dermal injury with minimal superficial involvement. The thermal injury results in denaturated fibrils of collagen and initiates a wound healing response (14).
Temperature measurement and control system for transtibial prostheses: Functional evaluation
Published in Assistive Technology, 2018
Kamiar Ghoseiri, Yong Ping Zheng, Aaron K. L. Leung, Mehdi Rahgozar, Gholamreza Aminian, Tat Hing Lee, Mohammad Reza Safari
In both heating and cooling activities, during 1,192 seconds (~20 minutes), the temperature change of all thermistors was recorded. Moreover, the temperature of the poured water inside the phantom model was 24°C and its fluctuations during both heating and cooling activities was recorded using a thermocouple. A thermal shield was used on top of the phantom model during evaluations to prevent conductive cooling by air. Thermal energy and power of the TM&C system were calculated separately for heating and cooling activities using the mean value of temperature change during the three evaluation trials. Thermal energy and power formulas are Q is the thermal energy, m is the mass, c is the specific thermal capacity, and ∆θ is the temperature change), and P = Q/∆t (where P is the thermal power, Q is the thermal energy, and ∆t is the elapsed time of temperature change), respectively.
Main radiation pathways in the landscape of Armenia
Published in International Journal of Radiation Biology, 2023
V. B. Arakelyan, G. E. Khachatryan, A. G. Nalbandyan-Schwarz, C. E. Mothersill, C. B. Seymour, V. L. Korogodina
Yerevan – The capital of Armenia – is a densely populated city (over 1 mln) with heavy traffic. There are many industrial enterprises in Yerevan itself, and a thermal power plant is located 6.2 km from it, in which the thermal energy of the fuel is converted into electrical energy. Figure 2(a,b) shows the mosaic distribution of gross β-radiation in soils of Yerevan city in 1990 and 2002 (Nalbandyan and Karapetyan 2003). A trend toward a decrease in gross β-radiation and contents of Sr-90 and Cs-137 throughout the city was revealed for system atmospheric precipitation–soil–plant for period 1969–2003 (Nalbandyan 2005) (Figure 3(a,b)). Atmospheric precipitation was represented by radionuclides K-40, U-238, Th-232, Pb-210, Cs-137 and Sr-90 (Ananyan et al. 2004). Subsequent studies of the radioactivity of herbaceous plants in Yerevan showed a high level of β-radiation caused by contamination with natural isotopes of the U-238 and Th-232 families (47%). The background content of chemical elements in Yerevan was determined (Tepanosyan et al. 2017).
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