Dose Calculation
William Y. Song, Kari Tanderup, Bradley R. Pieters in Emerging Technologies in Brachytherapy, 2017
A chemical compound is an entity consisting of two or more different atoms that associate via chemical bonds. For instance, a water molecule consists of two atoms of hydrogen and one atom of oxygen. As the mass of one entity (e.g., a molecule), m(X), is an inconveniently small number, the mass of 1 mol of entities is used in practice. This so-called molar mass, M(X), can be calculated as M(X) = NAm(X), where NA ≅ 6.022 × 1023 mol−1 is the Avogadro’s constant (Mohr et al. 2012). In case of an entity consisting of ai atoms of element Xi, the molar mass is where M(Xi) and Ar(Xi) are the molar mass and relative atomic mass of element Xi, respectively, Mu = 10−3 kg/mol is the molar mass constant and N is the number of elements in the entity. For instance, M(H2O) = 2M(H) + 1M(O) = 2 ⋅ 1.008 + 1 ⋅ 15.995 = 18.011 g/mol. Mass fraction, wi, of element Xi in the compound X is then
Ion Beam Analysis: Analytical Applications
Vlado Valković in Low Energy Particle Accelerator-Based Technologies and Their Applications, 2022
The presence of hydrogen in various materials and the ways in which it affects their properties has been the subject of attention of the scientific community for decades. A major area developed in this context in the second half of the 20th century was hydrogen in metals (Alefeld and Völkl 1978, Fukai 2005). Of special interest is hydrogen in steel. For example, in order to reduce the fuel consumption, it is necessary to reduce the weight of the vehicles. Therefore, the new generation, high-strength steels are largely integrated in the modern car bodies. In recent time, aluminized boron steel, a fully martensitic grade coated with Al-Si alloy, experiences a rapid growth in the anti-intrusion applications of the automotive structures, e.g., bumpers or doors, due to its excellent mechanical properties after hot stamping (Hein and Wilsius 2008). The practice of using aluminized boron steel, in particular the absorption/desorption of diffusible hydrogen in aluminized boron steel is discussed in details by Georges et al. (2013).
The patient with acute renal problems
Peate Ian, Dutton Helen in Acute Nursing Care, 2020
The kidneys and the lungs together control the acid-base balance. In the kidney, the distal convoluted tubule contributes to this process by secreting hydrogen ions. Hydrogen is very important because it maintains the integrity of cellular membranes and it facilitates enzyme action. The body produces about 50 to 100mEq of body acids per day through the metabolism of proteins, fats and carbohydrates, but the concentration of this acid in the body (in the form of hydrogen ions) must be kept within a fairly narrow range with a pH of 7.35–7.45. Even slight changes in the level of body acids can lead to cellular instability and altered biological processes in tissues. In acute and critical illness, a disturbance of the acid-base balance often occurs, and this can lead to organ damage.
Understanding physical mechanism of low-level microwave radiation effect
Published in International Journal of Radiation Biology, 2018
Hiie Hinrikus, Maie Bachmann, Jaanus Lass
Hydrogen bonds are responsible for many of the properties of water and for holding together the DNA double helix. Hydrogen bond can be intermolecular (e.g. bonding between water molecules) as well as intramolecular (e.g. bonding in protein and DNA). Hydrogen bonds are major factors determining the water’s viscosity, boiling temperature and other properties (Petrucci et al. 2007). Hydrogen bonds contribute to the overall stability of the DNA double helix structure and the structure of proteins (Silberberg 2012). The spectrum of hydrogen bonds includes the frequencies up to MW and infrared band (Shiraga et al. 2017). The energies associated with hydrogen bonds are about 2–12 kT (Watson 1965; Van der Spoel et al. 2006). Hydrogen bonds have about a tenth of the strength of an average covalent bond. Although these hydrogen bonding intermolecular attractive forces are rather weak, the consolidated power of the huge amount of hydrogen bonds in DNA provides the stability of a molecule (Silberberg 2012). Hydrogen bonds are being constantly broken and reformed in liquid water as a result of random thermal motion of molecules despite the bonding energy is higher kT (Petrucci et al. 2007).
Hydrogen gas protects against delayed encephalopathy after acute carbon monoxide poisoning in a rat model
Published in Neurological Research, 2020
Meihua Shen, Yijun Zheng, Kaimin Zhu, Zhonghai Cai, Wenwu Liu, Xuejun Sun, Jiankang Liu, Duming Zhu
Hydrogen (H2) is the simplest molecule in nature. It not only exists in nature but also can be generated in the human intestine. Traditionally, H2 is believed to function as an inert gas at body temperature in mammalian cells. In 2007, Ohsawa et al. reported that H2 inhalation protects the brain against I/R injury by selectively neutralizing hydroxyl radicals and peroxynitrite [11]. Since then, the protective effects of H2 have been investigated extensively in multiple organs. Indeed, studies have demonstrated that hydrogen can protect against brain ischemia/reperfusion (I/R) injury [11,12], Parkinson Disease [13], atherosclerosis [14], metabolic syndrome [15] and other diseases, mainly by scavenging hydroxyl radicals, inhibiting inflammation, and suppressing cell apoptosis. Most studies have used 2%-4% hydrogen gas so far [11]. Recently, our group showed high concentration of hydrogen (HCH) gas (67% H2, 33% O2) is also effective in the treatment of several diseases in animal models [16–18]. This mixed gas was produced using an AMS-H-01 hydrogen/oxygen nebulizer (Asclepius, Shanghai, China), which generates H2 and O2 by electrolyzing water. Although several studies have shown that H2 is effective in treating acute CO poisoning in rat models [19–22], hydrogen is mainly administered in the form of hydrogen saturated saline and the effects were limited. Therefore, whether HCH is protective in CO poisoning and its neurological sequelae remains unclear.
Study of FA12 peptide-modified PEGylated liposomal doxorubicin (PLD) as an effective ligand to target Muc1 in mice bearing C26 colon carcinoma: in silico, in vitro, and in vivo study
Published in Expert Opinion on Drug Delivery, 2022
Atefeh Biabangard, Ahmad Asoodeh, Mahmoud Reza Jaafari, Mohammad Mashreghi
To represent the residue movement of the FA12 peptide during 100 ns RMSF (root mean square fluctuation) was calculated (Figure 1c). It was demonstrated that residues 4,8, and 11 (Val, Val, and Arg, respectively) have the most fluctuations. In addition, residues close to N- and C-terminals showed higher RMSF values, especially N-terminal residue. The minimum distance between Muc1 and FA12 peptide during simulation time is shown in Figure 1d. Distance analysis unveiled that the peptide was inbound form at a steady distance (average 0.188 nm), despite the variation during the initial 20 ns. Figure 1e reflects the changes in the hydrogen bond network between FA12 and Muc1. The number of hydrogen bonds gradually increases as the complex structure achieves stable conformation. In all analyses, hydrogen bonds were considered to have a distance of 0.35 Å at a maximum and an angle of 30°. The interaction between Muc1 and FA12 peptide during MD simulations, hydrogen bonding interactions of the complexes, and active residues are depicted in Figure 2.
Related Knowledge Centers
- Atom
- Diatomic Molecule
- Molecular Geometry
- Organic Compound
- Taste
- Standard Temperature & Pressure
- Chemical Formula
- Sense of Smell
- Metallic Hydrogen
- Acid–Base Reaction