Basic Radiological Science
Thomas A. Carder in Handling of Radiation Accident Patients, 1993
As shown in Section A of Figure 1.9, the water molecule, H20, is composed of two hydrogen atoms and one oxygen atom. The electron of each hydrogen atom is shared with the oxygen atom to make one unit (equation 1-3). Nuclear radiation (ionizing radiation) can ionize the valence electrons of a water molecule and thus create unwanted ion pairs and chemical changes in the irradiated water. Chemical changes in the water due to irradiation by ionizing radiation is called radiolysis of water. Ionizing radiation can also cause the creation of free radicals from the water molecule. The combinations of ion pairs and free radicals created by ionizing radiation can create a chemically poisonous environment for the cell or tissue that originally used the normal water molecule. Radiolysis of water and free radicals are explained below.
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
Holistic view of health and illness
Mabel Aghadiuno, Christopher Dowrick in Soul Matters – The Spiritual Dimension within Healthcare, 2017
Two particular atoms illustrate the idea of holism nicely. A water molecule is much more than the sum of its parts – two hydrogen atoms and one oxygen atom. The oxygen and hydrogen atoms are the components of invisible gases. Oxygen is colourless, tasteless and odourless but we could not live without it. Hydrogen is also imperceptible. Together the two gases combine to form water: a vital, visible liquid, something more much more than the individual constituents. Water quenches thirst, is the gardener’s dream when its advent is timely and brings joy and laughter in the swimming pool. Culturally and mythologically over the ages it has been and still is the symbol to many of expiation and purification. Water is also therapeutic and Napoleon Bonaparte once said, ‘Water, air, and cleanness are the chief articles in my pharmacy.’
Cheminformatics and virtual screening studies of COMT inhibitors as potential Parkinson’s disease therapeutics
Published in Expert Opinion on Drug Discovery, 2020
Kalliopi Moschovou, Georgia Melagraki, Thomas Mavromoustakos, Lefteris C. Zacharia, Antreas Afantitis
Tsuji et al. crystallized the complex of 4-phenyl-7,8-hydroxy-coumarin (4PCM), a coumarin derivative and non-nitrocatechol COMT inhibitor (Figure 2(d)), with COMT [47]. The crystallized complex of 4PCM with COMT reveals the mode of the inhibitor recognition by the protein (Figure 3(e), Table 1). More specifically, the carbonyl oxygen of 4PCM faced the side chain of Trp143 while the phenyl ring substitute at 4-position was exposed to solvent. Mg2+, which is an essential co-factor for methylation reaction, is octahedrally coordinated in the active site by: (i) the side chains of Asp141, Asp169, Asn170, (ii) the two phenolic hydroxyl groups of the catechol substrate, and (iii) a water molecule. The phenyl ring of 4PCM was conformationally restricted by the side chains of Trp38 and Pro174, making it unable to exert relevant contacts with the protein. The authors concluded that a substitution of hydrophobic functional group with a phenyl ring constitutes a promising way to increase the inhibitory activity. In addition, they found that on the protein surface Trp38, is available for hydrophobic interactions.
From laboratory- to pilot-scale: moisture monitoring in fluidized bed granulation by a novel microwave sensor using multivariate calibration approaches
Published in Drug Development and Industrial Pharmacy, 2018
Johanna Peters, Wolfgang Taute, Claas Döscher, Robin Meier, Michael Höft, Reinhard Knöchel, Jörg Breitkreutz
The measurement principle of the used MRT sensor system is based on the interaction of water molecules with an alternating electromagnetic field induced by microwaves in the stray field of the resonator. Due to their dipole properties, water molecules align according to the field’s polarity. The alignment process is dissipative. This result in a decrease of resonance frequency (Δf) and an increase of resonance bandwidth (ΔB) of the resonator’s microwave response. The MRT sensor measures resonance frequency and bandwidth in air as a reference (f0 and B0). When the sensor is loaded with material, both are determined again (f1 and B1) and compared to the references. The resulting differences Δf and ΔB depend multiplicatively on functions of the moisture content and the density of the tested material. Calculation of the ratio of both (Equation (1)) eliminates the influence of the bulk density and results in a density-independent microwave moisture value M(Ψ) [29–31].
Permeation enhancer nanovesicles mediated topical delivery of curcumin for the treatment of hyperpigmentation
Published in Journal of Liposome Research, 2022
Raziya Khatoon Farooqui, Monika Kaurav, Manoj Kumar, M. S. Sudheesh, Ravi Shankar Pandey
DSC of pure SPC exhibited endothermic peaks at 58.2, 80.1, 160, and 208.9 °C, respectively. In the thermogram, the first endothermic peak at 58.2 °C of SPC expresses a more ordered firmly packed lamellar gel phase and at this transition temperature (Tm) gel phase converted to a crystalline state and above it, thickness and density of SPC decrease thus fluidity increases (El-Maghraby et al.2000, Rolland et al.1991). The peak observed at 208.9 °C may be related to the liquid phase of PC. An exothermic peak at 342 °C is probably related to the release of the SPC-bound water molecules (Fang et al.2001). The blank NVs and PE-NVs thermograms showed reduced Tm peaks at 55.3 °C due to the presence of DMSO, which is a lipid fluidizing agent thus decreases phase transition temperature. The DSC thermograms of the drug loaded NVs also showed sharp peaks at 55.3 °C indicating that homogenous mixture of all ingredients and absence of detectable drug peak in this thermogram revealed that CUR molecularly dispersed and encapsulated within lipid vesicles. It was observed previously that the amorphous or disordered crystalline drug diffuses through the polymeric matrix and provides sustained release of the encapsulated drug (Mohanty and Sahoo 2010).
Related Knowledge Centers
- Acid
- Carbon Monoxide
- Molecule
- Chemical Polarity
- Hydrogen
- Ion
- Amphoterism
- Self-Ionization of Water
- Thermodynamic Activity
- Chemical Formula