Activated carbon is just the fancy way of talking about carbon which has been designed for purification. Carbon is quite good at adsorbing various chemicals onto it and so in order to optimise this feature we want the carbon to have the greatest surface area possible to let more material stick to it. Normally produced by thermal decomposition under controlled conditions the result is a piece of carbon riddled with pores and networks which maximise the surface area to the point that one gram of activated carbon could easily have 4,000 m2 of surface area. This optimises it for activities such as cleaning drinking water.
Topology is the mathematical study of distorting objects through stretching them (this also includes some aspects of networks as distorting the links between nodes does not change the inherent pattern of the network). A system that can be studied under topology and that exists in nature would be flexible circular chains. Their ability to stretch and contort matches many of the prerequisites of topology. The example important for today is plasmids.
Transition metals are defined as any metal with an incomplete d-subshell. In other words one particular electron layer isn’t quite complete which opens a wide range of properties granted by variable electron configurations mostly focused on in chemistry through the three Cs of catalyst, colour and complex. For physics we love looking at the properties of transition metal oxides due to an increased stability which makes working with them easier. The cuprates, all the metal oxides containing copper, are particularly interesting as they have shown superconductivity and other electronic properties. Of course when we want to study what gives cuprates their properties it is best to study something very similar in many ways but with one clear distinct difference.
Although radioactive dating is often talked about, another no less important type of dating, luminescence dating, is not. Luminescence dating is used to study the last time a piece of rock was in the sunlight. It can only be used on materials seen as semiconductors, mainly quartz and feldspar as these both contain silicon, but if the date these rocks were buried is known then the date of the surroundings is also known. The dating works by looking at the number of trapped electrons present in the rock. You see crystal lattices can develop defects which in this case are called electron traps. As various radioactive decays occur in the rocks around them the ionising radiation produces electron-hole pairs within the lattice. The holes exist in the valence band and electrons exist in the conduction band and these electrons also can get trapped in the interband region caused by the defect. These electrons can then be released when light is shone upon the rock and so we can learn how long it has been in the ground based on the amount of charge stored within it.
Antihydrogen, made from a single antiproton and single positron, is the simplest antiatom that can be created. As tests are constantly going on to try and find some asymmetry between matter and antimatter there is always a demand for antihydrogen to be experimented with. Of course the production is hard enough as it involves trying to create and then bind two significantly different particles but afterwards containment is also an issue as the antihydrogen threatens to annihilate any matter it touches.
The easiest response to the question “why do we need to sleep?” is simply that “we get tired.” In truth this is the best explanation we have. Obviously people perform better in a variety of mental and physical tasks when they are not tired and sleep has definite benefits relating to the physiological effects it has on us (lower body temperature, faster healing of wounds etc). It has been shown that rats forced to not sleep eventually died; but exactly what killed them? Whether it was the breakdown of cells or an infection or perhaps their rapid drop in body temperature is still unknown, meaning that we don’t know what exactly about sleep keeps us alive.