Conjugated polymers are organic macromolecules whose carbon chain is formed of alternating single and double bonds. The reason the image to the left gives the title “π Conjugated polymers” is because a double bond between atoms is formed from the overlap of the electrons in the p-orbital as well as the s-orbital. This second bond is called a π bond and the electrons within it π electrons. Now because of the polymers structure the p-orbitals form a long overlap along the chain resulting in a large system of delocalised π electrons. As the image shows, some of these polymers have found their use in electronic and optical systems due to the behaviour of these electrons.
The Kerr effect is the change of refractive index of a material when an electric field is applied to it. All materials demonstrate the Kerr effect to some degree but it most cases the change is so small as to be unnoticeable. In liquids the Kerr effect allows for existence of filament propagation. This is where a laser beam is able to travel through a medium without diffraction as the Kerr effect changes the refraction index along the laser beam as to constantly refocus it. Multiple filamentation can occur when a laser beam has an uneven beam pattern, an avoidable defect, which results in each hot zone across the beam individually focussing into their own mini filament.
Nitrogen (N) is a very useful element and is required by almost every living creature in order to create the proteins essential for life. The most abundant source of nitrogen in nature is in the atmosphere which is about 70% nitrogen. Unfortunately this nitrogen is in the form of N2 (N≡N) whose strong triple bond is a nightmare for most organisms to break. Instead, fixed nitrogen (the term given to useful nitrogen) is normally gained from ammonia (NH3) as the nitrogen-hydrogen bond is much easier to sever. However there is a group of bacteria, called the diazotrophs, who go about fixing atmospheric nitrogen into its more useful forms. As can be imagined, bacteria of this type grow to dominate oceans areas where and when fixed nitrogen concentrations are low.
Clean water is an incredibly important resource. If Antarctica ever falls back into territorial dispute it may not be for oil or some mineral resource but it may be caused simply because countries wish to claim the colossal volume of fresh water held there. As the world’s population grows and the number of non polluted rivers falls, a scarcity of fresh water is certainly a plausible event. Current water filtration takes time and a lot of energy and also lacks the potential to be used on a truly massive scale as to service the majority of the population.
When it comes to greenhouse gasses it is undeniable that the most famous has to be carbon dioxide (CO2). It is clear why this is the case, 80% of the greenhouse gas we emit is carbon dioxide with the other 20% being made up of methane (CH4), water vapour (H2O) and nitrous oxide (N2O). It’s this nitrous oxide that we’ll be looking at today as despite making up 5% of the total produced greenhouse gas it is estimated to be a few hundred times more effective at trapping heat than CO2 and quite annoyingly it has an atmospheric lifetime of 121 years while CO2 has a lifetime of about 30 to 95 years which means the N2O produced now will be blighting us far into the next century. To make matters worse the removal pathway of nitrous oxide also removes ozone so it acts to destroy the ozone layer while it’s stifling the planet.
As circuits become more and more integrated the components of the circuits are going to become more and more exposed to different conditions. Now dielectric breakdown is a well known effect where as you begin upping the charge on a capacitor, eventually dielectric you’re using between will simply not be able to handle the strength of the electric field and it breaks down into becoming a conductor. A spark will then leap between the capacitor plates and that’s the stored charge gone. The main theory behind this is called the percolation theory. According to this theory a dielectric within an electric field develops tiny point defects which can connect to other defects in proximity. As the defect concentration increases with growing electric field sooner or later both sides of the dielectric will be connected by a network of defects, dielectric breakdown will occur, and the dielectric’s electrical properties will be significantly changed to become conducting.
In 2010 two dimensional molybdenum disulphide (MoS2), just a few layers thick, was being isolated and examined. It was discovered that in this state the electron movement fell under the theory of ballistic conduction, this is where the electrons have a mean free path great enough that the majority of their interactions are rebounding off a materials edges rather than the defects that normally cause restive scattering. Since then, 2D transition metal dichalcogenides have been the focus of intense research for various other esoteric electronic transport properties with ranging successes.