Probing past and future materials with neutrons
Glossary
alloys. Metal mixtures with greater strength, hardness or malleability than their component metals. The ratio of each component determines the properties of the alloy. Modern alloys may be created by adding just a few per cent of another metal.
atom. The fundamental unit of all matter consisting of a nucleus of protons and neutrons surrounded by orbiting electrons (or in the case of hydrogen, just one electron). For more information see Back to Basics: Atoms and molecules (Australian Academy of Science).
ceramics. Are inorganic, non-metallic solids processed or used at high temperatures. A ceramic is made by combining metallic and non-metallic elements. Traditional ceramic products such as clay pots and chinaware are hard, porous and brittle. Modern ceramics are used to create bones and teeth, cutting tools or to conduct electricity. For more information see Advanced ceramics (A to Z of Materials) and About ceramics (The American Ceramic Society).
colloids. Particles dispersed in a different phase, so that they do not easily filter or settle. The simplest case of particles dispersed in water is known as a colloidal dispersion. Examples of colloids include smoke (fine liquid droplets or solid particles in a gas), homogenised milk (fine droplets of fat in an aqueous phase) and paint (fine solid particles in a liquid).
composites. Composite materials are formed by combining two or more materials that have quite different properties. The different materials work together to give the composite unique properties, but within the composite you can easily tell the different materials apart – they do not dissolve or blend into each other. One material (the matrix or binder) surrounds and binds together a cluster of fibres or fragments of a much stronger material (the reinforcement). For more information see our Nova topic Putting it together – the science and technology of composite materials.
DNA (deoxyribonucleic acid). The nucleic acid forming the genetic material of all organisms with the exception of some viruses which have RNA. DNA is present in the nucleus and other organelles such as mitochondria and chloroplasts.
electromagnetic radiation. Electromagnetic radiation is simply energy which travels through space at about 300,000 kilometres per second – the speed of light. We imagine radiation moving like a wave. The distance between two adjacent wave crests is called a wavelength. The shorter the wavelength, the more energetic the radiation is said to be. Also, the shorter the wavelength, the greater the frequency of the radiation. Other than wavelength, frequency and energy there is no difference between a radio wave, an X-ray and the colour green. They all possess the same physical nature. For more information see Back to Basics: Electromagnetic radiation (Australian Academy of Science) and Electromagnetic Spectrum (NASA Goddard Space Flight Center, USA).
electron. A negatively charged particle that is a constituent of an atom. Electrons can move from atom to atom. When they do, they produce an electric current.
emulsions. Small droplets of oil dispersed in water or small droplets of water dispersed in oil. Since oil and water don't mix, emulsifiers are added to produce the small droplets and to prevent the oil and water phases from separating. Emulsifiers work by changing the surface tension between the water and the oil, thus producing a homogeneous product with an even texture. Examples of emulsions include butter and mayonnaise.
membrane. A thin, pliable sheet or layer. Biological membranes consist of a double layer of lipids – organic molecules that are not soluble in water – and associated proteins. Biological membranes are selectively permeable – not all molecules can pass through the membrane. For more information see Structure of plasma membranes (British Broadcasting Corporation, UK) and Cell membranes (Kimball's Biology Pages, USA).
neutron. A particle having no charge that is a constituent of an atom. It has a mass similar to a proton.
nuclear fission. Also referred to as atomic fission. The process by which large nuclei are split into two parts, by bombarding them with neutrons, in order to release large amounts of energy.
polymer. Polymers are large molecules that are made up of many units (monomers) linked together in a chain. There are naturally occurring polymers (eg, starch and DNA) and synthetic polymers (eg, nylon and silicone). More information can be found at The basics – polymer definition and properties (Plastic Resource, USA), Introduction to polymers (Case Western Reserve University, USA) and History of polymers and plastics for teachers (Hands On Plastics, American Plastics Council).
protease inhibitors. Molecules that block the function of enzymes that degrade proteins. They are classified either by the type of protease they inhibit or by their mechanism of action. Protease inhibitors are used in the treatment of HIV, where they prevent the activity of a protease that makes the active form of an enzyme used to make more viral particles. For more information see Disarming a deadly virus: Proteases and their inhibitors (National Academy of Sciences, USA).
protein. A large molecule composed of a linear sequence of amino acids. This linear sequence is a protein's primary structure. Short sequences within the protein molecule can interact to form regular folds (eg, alpha helix and beta pleated sheet) called the secondary structure. Further folding from interaction between sites in the secondary structure forms the tertiary structure of the protein.
Proteins are essential to the structure and function of cells. They account for more than 50 per cent of the dry weight of most cells, and are involved in most cell processes. Examples of proteins include enzymes, collagen in tendons and ligaments, and some hormones. More information can be found at Protein structure and diversity (Molecular Biology Notebook, Rothamsted Research, UK).
Relenza. The commercial name for an anti-influenza drug (zanamivir) that binds to and inactivates an enzyme, preventing the formation of new viral particles. For more information see CSIRO research leads to effective treatment against the flu virus (CSIRO, Australia).
superconductor. A substance that has no resistance to the flow of an electric current. Superconductors currently require very low temperatures to function. They can be used for energy storage, storing and retrieving digital information, medical imaging machines and friction free transport. For more information see What is superconductivity? (How Stuff Works, USA) and Superconductor information for the beginner (Superconductors.org).
uranium. A radioactive heavy metal. The natural element is a mixture of different isotopes or atomic forms. The isotope uranium-235 is used in nuclear non-breeder reactors.
virus. A submicroscopic infectious agent consisting of a nucleic acid (DNA or RNA) molecule surrounded by a protein coat. Viruses cannot replicate outside a living cell. More information can be found at How viruses work (How Stuff Works, USA).
X-ray. A high energy form of electromagnetic radiation with very short wavelengths (less than 1 x 10-8 metres). For more information see How X-rays work (How Stuff Works, USA) and From X-rays to synchrotron light (ELETTRA Synchrotron Light Laboratory, Italy).
X-ray crystallography. X-ray crystallography involves firing X-rays through the crystal of a molecule to produce a diffraction pattern. This pattern provides information on the structure of that crystal. For example, X-ray crystallography helped scientists discover that the DNA molecule exists as a double helix. For more information see Introduction to crystallography (Matter, UK).
Posted March 2007.