In 1839 the first ever hydrogen fuel cell was created. It was already well known that when enough energy was put into water it could be broken into the hydrogen and oxygen that form it. One William Robert Grove had the idea that if hydrogen and oxygen could be recombined with an electrolyte present to reproduce the water but also gain a flow of charge. Now vehicles can be fuelled with hydrogen but there is a catch. How is the least dense element going to be contained in a reasonable volume. It could be cooled into a liquid but this doesn’t seem practical for a car or perhaps out under high pressure but there are quite a lot of safety concerns about putting high pressure tanks in road vehicles. One of the suggestions that is being looked into is that of using metal hydrides as a way of chemically storing hydrogen by reacting it with a metal from which it can be extracted when used in the car.
An optical resonator can be described as just a box made of mirrors. If strong enough laser light is shone on the outside it will transmit through one of the mirrors and the photons will start bouncing back and forth inside the box, known as a cavity. As all lasers must have some divergence eventually this bouncing light is destined to spread out and fade away. It is however possible to form lasting stable reflections within the cavity and when this happens the set up is known as an optical resonator. This can be imagined as a standing wave of light in a fixed shape. If a gain medium is present then this design can be turned into a laser with the present photons generating more through stimulated emission. When an active medium is present the resonator is called active and unsurprisingly passive is the name given to when there is no contributing medium.
The free electron model is a simple model for electrons in a metal crystal where it is assumed that the electrons become completely separate from their metal ions. This means they can be seen as behaving like an ideal gas with all the qualities that come with it. This means the electrons electrostatic repulsion is assumed to be negligible (hopefully reduced by the positive ions), the crystal lattice is generally ignored except for the boundary. The mass of the electrons is replaced with an effective mass to assist in this analysis with even negative effective mass being possible if it is a hole moving instead of an electron.
The simplest of all antiatoms to fabricate is antihydrogen, composed of only a single positron and antiproton. This makes it the easiest complex system to study when it comes to symmetry between matter and antimatter. The Antiproton Decelerator at CERN is used to produce antiprotons and antiatoms. It works by firing high energy protons into a block of high density metal which then produces a range of secondary particles with high energy antiprotons among them. Strong electric fields are used to slow down these antiprotons (hence why its called a decelerator) so that they can be used in experiments. All aspects of antihydrogen are put under scrutiny such as band structure, band splitting, overall neutrality as well as the charge to mass ratio and magnetic moment of the antiproton. If even a small discrepancy could be found, despite how unlikely it seems at the moment, it would be the most revolutionary discovery in the last 50 years.
Occasionally I struggle when it comes to finding papers to write about over the course of a week. Sometimes there is a shortage of papers published, sometimes the papers are there but I can’t understand them well enough to be confident in writing about them. Luckily most of the time it’s the opposite problem and I end the week with at least a few papers that I didn’t have room include because there were just six others papers slightly more interesting. Today I’ll be writing a quick blurb on each of these papers over the last week and perhaps I’ll continue this into the future.
There was a paper that described the recent evolution in the longwave radiation output of the Earth. The Earth’s main method of radiating the heat it absorbs is through longwave radiation which can then affect global precipitation. A Hadley cell is a specific air circulation where warm air rises at the equator, moves poleward and then descends in the subtropics. This paper examined the results of the shrinking accession current of this cell and the reduced numbers of high clouds (cirrus and its brethren) on outgoing radiation. Paper link: Tightening of tropical ascent and high clouds key to precipitation change in a warmer climate
Another paper described the application and adaptation of neuroimaging techniques, that have hereto only been used on rodents, onto non human primates such as marmosets. Using a double excitation technique on calcium ions (Ca2+) which work to form dendric (tree like) formations for neurones in the brain. It may be possible to study the entire primates brain under both sick and healthy conditions using this technique. Paper links: Targeted Patching and Dendritic Ca2+Imaging in Nonhuman Primate Brain in vivo
The final paper that didn’t quite make the cut was describing the development of new magnetic nanostructures. Traditionally such structures, which have applications in memory storage, imaging methods, magnetic fluids, magneto-optics and so on, are flat and two dimensional. New synthesis techniques presented aim to grow these structures into three dimensions which is a completely unexplored area of science. Paper links: Three-dimensional nanomagnetism
There you go, three papers (technically the last one is a review article but its still very interesting) which could easily have been made into posts and there are three more beyond these that I could also try writing a paragraph on. But sometimes you need to smile and be happy with the work you’ve done and move on to something else. Until tomorrow, goodnight.
If you were to ask any child for a method of cleaning water then filtering is probably the answer they would give. A step up from a piece of filter paper is a membrane which only allows water or water sized particles through while resisting others. Separation by membrane is a very useful process as it is nontoxic, requires little energy input and can be easily up sized for different water quantities. Unfortunately, like with all filters, the impurities and contaminants will remain on the membrane if not treated and severely limits the practical applications of such membranes. What is required is a membrane that has some way of cleaning itself, hopefully during the process.
Animals in nature have an uncanny ability to operate as a single unit with collective movement when they group together. Flocks of birds have been found to fit statistical models, people walking together naturally match each others step, bacteria can form groups that then move as one, with each individual responding to the same chemical stimuli.