A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. As the catalyst itself takes part in the reaction it may undergo a physical change. Metal complexes are typically regarded as catalysts that convert organic substrates into more valuable compounds; however, to date, catalytic transformations […]
Spallation is a type of nuclear reaction in which the interacting nuclei disintegrate into a large number of protons, neutrons and other light particles, rather than exchanging nucleons between them. It is thought that most of the nuclei of light elements, such as boron, are made in this way. Spallation reactions of this type are […]
There are chemical compounds, called isomers, that have the same molecular formulae but different molecular structures or different arrangements of atoms in space. In constitutional isomerism the molecules have different molecular structures: i.e., they may be different types of compound, or they may simply differ in the position of the functional group in the molecule […]
Condensed matter • Materials • Physics • Theoretical physics
The interactions between moving charges and magnetic fields can be quite complicated; more if we consider the quantum effects. One example is the collection of Hall effects. Imagine that we have a conductor or a semiconductor through which a current is flowing. Then we apply a strong transverse magnetic field. As a result, we can […]
Proteins can perform a huge number of biological functions with amazing efficiency. In order to achieve these different functions, proteins rely on the precise 3D arrangement of functional groups which are referred to as the protein fold. Some of these functions include acting as a catalyst in biochemical reactions; in these cases proteins are called […]
Achieving room temperature superconductivity is among the most pursued but elusive goals of scientists. I n December 2014 researchers claimed to have observed superconductivity as high as 200 K in hydrogen sulfide at high pressure, breaking all the records thus far. This meant that cuprates could be knocked from their position as the highest temperature […]
Condensed matter • Materials • Nanotechnology • Quantum physics • Theoretical physics
Plasmonic nanostructures confine light to dimensions far smaller than the free-space wavelength, as they mix optical fields with electronic excitations. It was not until the 1990s, with the appearance of accurate and reliable nanofabrication techniques, that plasmonics blossomed. It was found then that local fields around nanostructures could be directly measured by near-field scanning optical […]
Terahertz (THz) radiation is all around us. For example, this page emits blackbody radiation mainly in the THz region (defined here from 0.3 THz to 30 THz). Because terahertz radiation begins at a wavelength of around one millimeter and proceeds into shorter wavelengths, it is sometimes known as the submillimeter band, and its radiation as […]
Symmetry is a unifying principle that governs all aspects of physics. The physical properties of crystalline solids are no different. But, as symmetry is progressively lowered through the 32 crystallographic point groups, novel transport effects emerge. Crystal symmetry dictates also the geometry of a phenomenon that has attracted a lot of attention in recent years […]
Topological insulators are materials with special universal properties, which are protected against perturbations. Such properties are theoretically described by topology, a branch of mathematics concerned with the properties of geometrical objects that are unchanged by continuous deformations. Topological insulators are electronic materials that have a bulk band gap like an ordinary insulator but have conducting […]