Groundbed is a buried item, such as junk steel or graphite rods, that serves as the anode for the cathodic protection of pipelines or other buried structures.
Cellulose, (C6H10O5)n, is a polysaccharide that consists of a long unbranched chain of glucose units linked by (1→4)-β-glycoside bonds. Nature uses cellulose primarily as a structural material to impart strength and rigidity to plants. Leaves, grasses, and cotton are primarily cellulose. The fibrous nature of extracted cellulose has led to its use in textile industry for the production of cotton, artificial silk, etc. Cellulose also serves as raw material for the manufacture of cellulose acetate, known commercially as acetate rayon, and cellulose nitrate, known as guncotton. Gunncotton is the major ingredient in smokeless powder, the explosive propellant used in artillery shells and in ammunition for firearms.
Conformation is one of the very large numbers of possible spatial arrangements of atoms that can be interconverted by rotation about a single bond in a molecule. The conformation of a molecule is not fixed, though one or another shape may be more likely to occur. There are two extreme cases:
Staggered conformation (antiperiplanar) is a conformation about a carbon-carbon single bond in which the atoms on one carbon are as far apart as possible from the atoms on an adjacent carbon.
Eclipsed conformation (syn-periplanar) is a conformation about a carbon-carbon single bond in which the atoms on one carbon are as close as possible to the atoms on an adjacent carbon.
Henry (H) is the SI derived unit of inductance equal to the inductance of a closed circuit in which an e.m.f. of one volt is produced when the electric current in the circuit varies uniformly at a rate of one ampere per second (H = V·s/A). The unit was named after the American physicst Joseph Henry (1797-1878).
Crystal system is a method of classifying crystalline substances on the basis of their unit cell. There are seven unique crystal systems. The simplest and most symmetric, the cubic (or isometric) system, has the symmetry of a cube. The other six systems, in order of decreasing symmetry, are hexagonal, tetragonal, rhombohedral (also known as trigonal), orthorhombic, monoclinic and triclinic.
Crystal system
|
Unit-cell
|
Conditions on unit-cell edges and angles |
cubic |
a=b=c α=β=γ=90° |
|
hexagonal |
a≠c α=γ=90° β=120° |
|
tetragonal |
a=b≠c α=β=γ=90° |
|
rhombohedral |
a=b=c α=β=γ≠90° |
|
orthorhombic |
a≠b≠c α=β=γ=90° |
|
monoclinic |
a≠b≠c α=γ=90°≠β |
|
triclinic |
a≠b≠c α≠β≠γ≠90° |
Infrared (IR) spectroscopy is a technique used for determining the structure (and sometimes concentration) of molecules by observing how infrared radiation is absorbed by a sample.
Isomorphism is the existence of two or more substances that have the same crystal structure, so that they form solid solutions.
Deoxyribonucleic acid (DNA) is a nucleic acid with 2-deoxy-D-ribose as the sugar in its nucleotides. DNA contains encoded genetic information, specifically templates for the synthesis of all of an organism’s proteins and enzymes.
DNA was first identified in the 1869 by Swiss chemist Friedrich Miescher (1844-1895). In 1953, American biologist James Dewey Watson (1928-) and English physicist Francis Harry Compton Crick (1916–2004) had discovered that DNA occurs in the cell as a double helix, with two long strands of the molecule wound around each other, and further that the chemical structure of the molecule dictates that adenine (A) always aligns or pairs with thymine (T), and cytosine (C) always pairs with guanine (G). It is this base pairing that allows DNA in a cell to copy itself, and transfer its information to a new cell. The diameter of the helix is 2.0 nm and there is a residue on each chain every 0.34 nm in the z direction. The angle between each residue on the same strand is 36°, so that the structure repeats after 10 residues (3.4 nm) on each strand.
Ligand field theory is a description of the structure of crystals containing a transition metal ion surrounded by nonmetallic ions (ligands). It is based on the construction of molecular orbitals involving the d-orbitals of the central metal ion and combinations of atomic orbitals of the ligands.
Generalic, Eni. "Hexagonal close-packed structure." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
Glossary
Periodic Table