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Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
The Fermi level is the energy at which there is a 50% probability of it being occupied by an electron. In an intrinsic semiconductor, the Fermi level is located approximately midway between the conduction and valence bands. When a semiconductor is doped with a donor impurity, this probability increases and therefore the Fermi level shifts upward. On doping with an acceptor impurity, the situation reverses and Fermi level shifts downward.
Craniofacial Regeneration—Bone
Published in Vincenzo Guarino, Marco Antonio Alvarez-Pérez, Current Advances in Oral and Craniofacial Tissue Engineering, 2020
Laura Guadalupe Hernandez, Lucia Pérez Sánchez, Rafael Hernández González, Janeth Serrano-Bello
PET scans also use radiopharmaceuticals to create three-dimensional images. The main difference between SPECT and PET scans is the type of radiotracers used. While SPECT scans measure gamma rays, the decomposition of radiotracers used with PET scans produces small particles called positrons. A positron is a particle with approximately the same mass as an electron, but with an opposite charge. These react with the electrons in the body and when these two particles combine they annihilate each other. This annihilation produces a small amount of energy in the form of two photons that fire in opposite directions. The PET scanner detectors measure these photons and use this information to create images of the internal organs. With this non-invasive technique, quantitative information on biological processes at the molecular level is obtained through tomographic images that reflect the concentration of activity of a radiopharmaceutical administered to a patient. The information obtained depends on the metabolic pathway, the targeted target receptor, the biodistribution and the rates of accumulation and elimination of the radiopharmaceutical. This makes it possible to perform an early detection of pathological processes with PET (Phelps 2000).
Finite-Element Electrostatic Solutions
Published in Stanley Humphries, Field Solutions on Computers, 2020
Electrostatics describes the forces between charged bodies at given positions. We denote the charge on an object, a positive or negative quantity, by the symbol q. Throughout this book, we shall use the International System of Units where the charge is given in units of coulombs. The charge of an electron is –1.60219 × 10-19 coulombs. The empirical relationship for the forces between stationary charges was discovered by Coulomb in 1771. Suppose there are two small objects with charges q1 and q2. As shown in Figure 2.1, the unit vector n^21 points from object 2 to object 1 and the distance between the charges is r21. The electric force on object 1 from object 2 is () F1=n^21q1q24πεo r212.
The Hall current effect of magnetic-optical-elastic-thermal-diffusive semiconductor model during electrons-holes excitation processes
Published in Waves in Random and Complex Media, 2022
Shreen El-Sapa, Kh. Lotfy, Alaa A. El-Bary
In modern physical studies, moving charge carriers are free of particles, yet they carry electric charges and this is clearly shown during the study of semiconductors. There are many charge carriers such as electrons, ions, and holes. In semiconductor material electrons and holes are charge carriers. At absolute temperatures, the free electrons in the atoms of the semiconductors are present in the lower levels (the valence energy band). In this case, the electrons cannot move or move from one place to another, and the electric current cannot flow. Since the internal resistance of semiconductors decreases with increasing temperature, and with the gradual temperature rise, some electrons can jump from the valence band to the conduction band. In this case, with the movement of electrons, a flow of electric current is created. With each transition of an electron into the conduction band, there will be a hole in the valence band. Therefore, electrons and holes are adjacent in semiconductors. In any case, the electric current created in a semiconductor is caused by the free electrons. In some special cases where the material is exposed to gradient temperatures, the holes also transmit electric current.
Analysis of the current–voltage curves and saturation currents in burner-stabilised premixed flames with detailed ion chemistry and transport models
Published in Combustion Theory and Modelling, 2018
Memdouh Belhi, Jie Han, Tiernan A. Casey, Jyh-Yuan Chen, Hong G. Im, S. Mani Sarathy, Fabrizio Bisetti
Analysis of non-thermal electron transport properties in methane–air flames suggests a breakdown threshold of 140 Td [39]. Since the reduced electric field strength does not exceed this threshold in the configurations considered in our work, electrons are assumed to be thermal. The electron mobility was computed as a function of temperature and mixture composition by [40]: where m = 9.109 × 10−31 kg is the mass of the electron. The effective cross-sections of electron-neutral pairs (σj) were collected from the LXcat repository [41]. The electron diffusivity was estimated from the electron mobility using Einstein's relation: Sensitivity of the electric currents to the transport properties of ions and electrons is discussed in Section 5.2.2.
Use of activated carbon and camphor carbon as cathode and clay cup as proton exchange membrane in a microbial fuel cell for the bioenergy production from crude glycerol biodegradation
Published in Journal of Environmental Science and Health, Part A, 2022
Verónica Ávila Vázquez, Eduardo Arturo Enciso Hernández, Sathish Kumar Kamaraj, Miguel Mauricio Aguilera Flores, José Roberto Espinosa Lumbreras, Sergio Miguel Durón Torres, Gladis Judith Labrada Delgado
The exoelectrogenic microorganisms oxidize the organic matter in the anode chamber under anaerobic conditions to produce protons and electrons while degrading the substrate.[2,4] The produced protons migrate through a proton exchange membrane (PEM) to a second aerobic chamber called a cathodic one. An oxygen reduction reaction (ORR) is performed in this chamber, and the protons combine with the electrons and oxygen to form water. The electrons generate a current through an external circuit.[2,5,6]