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Bioengineering and Ethics
Published in Howard Winet, Ethics for Bioengineering Scientists, 2021
While Darwin was being reborn, Newton was being redefined. Albert Einstein’s two papers (1905, 1915) replaced a mysterious Newtonian force of gravity with curvature of space in his special and general theories of relativity. In a 1905 paper on photoelectric effect, he provided crucial evidence for light quanta and quantum theory of the atom. In another paper that same year, he provided direct evidence from calculations of Brownian motion for the existence of molecules. Evidence that the atom was not indivisible was provided by J.J. Thompson (1897) and E. Rutherford (1898). The work of these pioneers led to development of the fields of the smallest, nuclear, and the largest, space, physics. We shall spend no more of our history on space physics, although BEs interested in space-related careers will want to pursue the subject. Erwin Schrödinger (1887–1961) developed wave mechanics, the mathematical equations that predict the behavior of subatomic particles using wave equations (Millar et al. 1996).
Fluoroscopic Image Production
Published in Robert J. Parelli, Principles of Fluoroscopic Image Intensification and Television Systems, 2020
The photoelectric effect occurs mainly when low to moderate x-ray energies interact with high atomic absorbers such as bone, barium, and iodine and is a contributing factor to the differential absorption and contrast on the fluoroscopic image. Photoelectric effect will produce a dim image on the fluoroscopic monitor.
Physics of Radiation Biology
Published in Kedar N. Prasad, Handbook of RADIOBIOLOGY, 2020
When an X- or γ-ray photon collides with an atom, it may transfer all its energy to an orbital electron, which is ejected out with a kinetic energy. The process of energy absorption is called the photoelectric effect, and ejected electrons are known as photoelectrons. Kinetic energy of ejected electrons (Ek) equals the energy of the incident photon (hυ) minus the binding energy of the electron (EB). Thus, the photoelectric effect involves bound electrons whose ejection probability is maximum if the photon has just enough energy to knock the electron from its shell. The photoelectric cross-section varies with energy approximately as 1/E3. The photoelectric absorption is dominant up to a photon energy of 50 keV. A diagrammatic representation of the photoelectric effect is shown in Figure 3.10.
Advancements in the use of Auger electrons in science and medicine during the period 2015–2019
Published in International Journal of Radiation Biology, 2023
Atomic vacancies that lead to Auger and ICD processes are created by several mechanisms. One mechanism that creates an inner atomic shell vacancy is the photoelectric effect. The Auger electrons that are emitted following the photoelectric effect were observed by Pierre Auger when he irradiated a cloud chamber with X-rays (Auger 1923). Radionuclides undergoing internal conversion (IC) transitions also create inner atomic shell vacancies, as do radionuclides that decay by electron capture (EC). The shower of low energy electrons that follow was seen by Meitner when she was conducting experiments on radioactive decay (Meitner 1923). The stochastic nature of the atomic and molecular electronic relaxation process results in different yields and energies of electrons for each initial vacancy created. Most of these electrons have very low energies (∼20–500 eV) which have extremely short ranges in water (∼1–10 nm). Biological molecules near the Auger cascade are impacted by the direct effects of electron irradiation as well as indirect effects caused by radical species that are produced during the radiolysis of water by these electrons (Figure 2) (Wright et al. 1990). Other physical mechanisms such as Coulomb explosion, caused by extremely rapid charge neutralization of highly ionized atoms, can cause damage to the molecule in which electronic vacancies are created (Pomplun and Sutmann 2004).
9th international symposium on physical, molecular, cellular, and medical aspects of Auger processes: preface
Published in International Journal of Radiation Biology, 2023
Katherine A Vallis, Roger F. Martin, Nadia Falzone
Removal of an inner orbital electron through the photoelectric effect, electron capture, or internal conversion leads to a vacancy which is then filled by a cascade of electron transitions from the outer shells. These transitions are accompanied by the emission of low energy ‘Auger’ electrons or characteristic X-rays. Auger electrons have low energy (<25 keV), have a short track length and are densely ionizing. As a result, the absorbed radiation dose they deposit in biological material is extremely high but restricted to a nanoscale volume (a few nm3) around the decay site. These qualities mean that Auger electron emitting radionuclides are suited to the ultra-precise delivery of radiation to individual cells, organelles or even to specific molecular targets, and so hold promise as oncologic therapeutic agents.
Comparison and performance evaluation of human bio-field visualization algorithm
Published in Archives of Physiology and Biochemistry, 2022
Gunjan Chhabra, Ajay Prasad, Venkatadri Marriboyina
Further, Max Planck’s study of blackbody radiation, give rise to the quantum mechanics. According to his theory, atoms are tiny oscillators that absorb and emit electromagnetic radiations, with the crucial property that their energies can only take on a series of discrete values. Adding further, Albert Einstein anticipated a validation for the photoelectric effect, that light is composed of individual packets of energy called photons. This implied that the electromagnetic radiation, while being waves in the classical electromagnetic field, also exists in the form of particles (Bhat 2002, Heisenberg and Bond 1959). In addition to this, de Broglie, Werner Heisenberg, Max Born, Erwin Schrödinger, Paul Dirac, and Wolfgang Pauli are some of the researchers who stated various hypothesis, theories, and results on quantisation and wave-particle duality. Nevertheless, all these research was scattered, initially, but latter on these scattered ideas was united under one discipline known as quantum mechanics. In continuation, Einstein published as theory on photoelectric effect based on Maxwell’s electromagnetism as “theory of special relativity.” The Schrödinger equation, illustrated in Equation (i), underlying quantum mechanics could explain the stimulated emission of atoms, where an electron emits a new photon under the action of an external electromagnetic field.