Scary Split Brain Situations

As it is Halloween I thought I would write a bit about a spooky part of science. Now epileptic fits and seizures in a vast simplification can be described as when all the neurones in someones brain activate simulatanously. Sometimes it is necessary for very extreme cases of epilepsy to damp these rogue firings by severing the connections between the left and right hemispheres of the brain. The corpus collosum is the main connection and this process is called callosotomy although the commissures which are smaller connections are severed as well. Never letting a good opportunity go to waste scientists study the people who have undergone this treatment to see what effects it has on their life.

Since previously each half of the brain had some specialities but now they fail to communicate some interesting actions occur. If a person sits so there is a screen right down the centre of their face what there left and right can see are now partitioned from each other. Generally the left eye feeds information to the right side of the brain but language is the majority of the population is controlled with the left side of the brain. So when an image is presented in the left hand section, the person can not say what they are seeing, but in the  right hand section they can. Even stranger is when both sides are presented with two distinct images, lets say a car and a mountain, and the person is asked to pick two words from a long list that relate to these images. The person will often choose correctly such as picking a tyre and some snow but when asked the reason for there pick they will only respond talking about one image. The car is driving in the snow or the tyre is rolling down a mountain. Even more unnerving again is when the left hand side is asked to pick up an object shown on a screen. Once they have hold of it the person is asked what they are holding. Due to the lack of communication the person will either respond saying they don’t know or that they aren’t holding anything. Finally  although this is rare, the two sides of the brain can disagree on a course of action. This was most prominently displayed when a man, attempting to assault his wife with his left hand, was stopped by his intervening right hand.

The question about which brain actually represents the person is very difficult and should be considered thoroughly. Since only the left brain can talk it is certainly the one you communicate with, but emotional memories are stored in the right brain and without them would you really be who you are?

Weekly Roundup 43

There has been some big news this week regarding theoretical and particle physics. A new idea has been presented called the SMASH model that claims to solve reportedly  five (but technically four) of the biggest standing problems in modern physics. In increases the standard model show below, to include three new neutrinos and two new particles called the axion (predicted at ten billion times lighter than the electron) and the inflaton that are both contained in one field.

File:Standard Model of Elementary Particles.svg
Thank you to Dave Fehling and Johns Hopkins University

The three neutrinos explain how neutrino oscillations occur and also assist with explaining baryogenesis, the excess of real baryons over anti baryons. The axion is the particle responsible for the missing mass often known as dark matter and the inflaton is behind accelerating expansion also known as dark energy. On a complete divergence there is also talk from a paper that in fact the universe may not be undergoing accelerating expansion and this idea could have been wrong since the start. If any more on this idea comes up I will be certain to talk about it but back to the particles. The field explains what is called the charge parity problem where particles and their antiparticles can behave slightly differently (demonstrated with kaons alternating between particle and antiparticle but with a probability bias for one direction). This is inherently linked with baryogenesis and so I would choose to see them as one problem personally. This theory should hopefully be tested in the next ten years but until then these ideas will just have to be sent to the realm of string theory and alternate universes.

Until tomorrow, goodnight.

Electromagnetic Production Of Electron Pulses

When a small metallic tip in the nanometre range is excited by incident laser pulses of very short interval electrons are given off as would be expected. Due to the slightly strange nature of the excitation this method produces slightly different results than the photoelectric effect. As the electromagnetic field magnitude increases on the surface of the metal electrons begin to tunnel right out of the metal rather than just be excited to the surface. This can lead to the emitted electrons forming coherent waves that can demonstrate various quantum phenomenon. As the laser intensity is ramped up and up the effective current produced by these moving electrons also increases. At high currents, many electrons are released per pulse of laser light. Just before the energy given is enough that the electrons can begin to escape by tunnelling; some electrons that would be emitted get forced back into the metal and then get released after a few moments with a loss of energy, some do not even make it back out and it can be assumed they were scattered so much as to lose the energy required to escape. It is believed this effect is caused by the oscillating nature of the electromagnetic field although there is a clear point where the laser goes from producing weak to strong electric field. The weak never causes the effect and the strong rarely doesn’t. The ability to produce pulsed emission of electrons is important for various experimental and imaging techniques, understanding when and why strange anomalies occur makes these applications more viable and reliable.

Looking At Chromosome Locations In Cells

The genome is the set of paired chromosomes that exists in every cell of your body. It contains the complete information for every cell in a humans body but of course only some of the genome is required to mould the cell its in. The exact layout and structure of the genome inside the cell has been explored in recent years through methods such as fluorescent dying and a bit of X-ray crystallography. A very effective method that was only produced a few decades ago was conformation capture techniques. To do this two cells (more specifically the DNA from them) is cross linked using formaldehyde. Then the DNA molecules are split, cut up and separated using enzymes known as restriction endonucleases. Then another enzyme is introduced that produces ligation and bonds these DNA fragments into rings. Then the cross linking is reversed and the DNA straightens our. Chemical analysis of this mix and match DNA will reveal which area the ligand bonds wished to from in and the more bonds the more reactive the area. If the pairs of chromosomes propensity to react is known then thing about their nature can be deduced, such as their domains and compactness. In order to gain some more information researchers have recently presented a modelling and experimental approach to analysing the genome from within cells. To do this the model imagined chromosomes like rough grains of sand only 30 nanometres across. Colloidal models combined with Hi-C, a program that can generate a general map of where the chromosomes are most likely to be, demonstrated the ability to predict results demonstrated in living cells. An example is the shuffling a location with low gene density to the edges of a region while compacting as many activated genes as possible in the centre. The fact that previous models have never predicted this observed event but this new one does is very promising for the research’s future.

Extremely Elliptical Eclipsing Binaries

Variable stars are, as their name suggests, stars whose brightness varies over time in a periodic way. There are only three options:

  • The star is a Cepheid variable (type 1 of type 2), stars that due to a cycle of ionising and doubly ionising helium vary in brightness.
  • The star is an RR Lyrae variable, the same as a Cepheid variable but in the infra red spectrum.
  • Or the star is part of a binary system, called binary eclipsing stars.

This last one is very interesting. When the two suns are orbiting each other so long as their movement is in a plane with the Earth there will come a time when they block the line of sight to each other. It is unlikely that both stars will be of equal size and so when the small star obscures only part of the bigger twin we see a dip in light and when their rolls are reversed the completely eclipsed smaller star results in a bigger dip. Of course there are many variations and unique situations when it comes to eclipsing binary systems.

The Kepler missions have recently brought back information of eclipsing binary stars with incredibly eclipsed orbits. The stars get only a few solar radii away from each other at perihelion (closest point) to nearly fifteen times this at aphelion (farthest point). Their proximity results in both stars distorting out of their normally spherical shape.  This has resulted in luminosity time graphs resembling saw tooth wave rather than a classic sinusoid:

Image result for sawtooth wave
Thank you to Erik Cheever from swarthmore.edu for this image.

The real mystery is how these stars have managed to maintain this cycle for so long. Distorting the shape of a sun isn’t easy and it should have damped the system into having a circular orbit in less than a hundred cycles. There are ideas being investigated that perhaps a third sun is lending a hand to maintaining the distorted orbit. Observations are being made to try and locate this “third man” of these systems but none have managed to locate the hidden sun yet.

Wet Nanowires With Magnified Work Output

Terahertz radiation is a very specific part of the electromagnetic spectrum, just slightly below the far infrared and slightly above microwaves. It is still a section where analysis needs to be completed and there are many regions of medical physics where it is  hypothesised that terahertz radiation could be applied. Burn imaging, skin cancer detection and analysis of skins hydration. Based on its wavelength any analysis of the skin or a couple of millimetres below it could theoretically be performed with terahertz radiation.

Currently the detectors are based on semiconductors but it is the production method that is of interest today. Indium Arsenic (InAs) is the alloy that is most often used and it has been known for some time that nanowires (exactly what they sound like) are more effective at radiation production then epilayers (layers of the material forming a composite). A study has found that besides changing the length, thickness and general dimensions of these nanowires; there is a easier way to improve their output. By dipping these minuscule strands in water (tap water to be specific) improved their terahertz output by almost three times. This means that nanowires may operate even better then expected in a liquid phase and so placing them in the bloodstream could provide an opportunity for detailed mapping of the circulatory system. Sometimes research does not have to be incredibly complicated and sometimes breakthroughs can come from the simplest things.

Fabricating Quantum Thermometers

In classical mechanics heat and energy are removed from a system either by conduction, convection or radiation. This is because when the system is big enough and there are many particles the models are relatively easy because the actions of any one particle can be ignored. A standard example would be an electron in a wire with a current flowing through it. Although the current can be seen as going from point A to point B each electron is actually moving in a much more erratic way. Scattered by the metal lattice the electrons move randomly with only a trend of travelling towards the positive terminal. This is why drift velocity is surprisingly low for an electron in most wires.

In quantum systems heat becomes even more important. The idea of information and how it can not be destroyed along with various scatterings and thermal breakdowns means that knowing exactly where energy is being dissipated becomes very important. Nanoscale thermometry is the study of this specific section of condensed matter physics. Unfortunately it has remained almost entirely theoretical as the ability to measure temperature on these scales has been extremely limited. Recently however there has been a new thermal probe developed, consisting of a device less than 50 nanometers wide at the end of a sharp pipette. It is, in essence, a quantum thermometer. It can operate all the way down to 4 Kelvin and can record even single electrons gaining or losing energy. This non contact method is many times better than previously designed devices and will no doubt be useful in the future analysis of quantum matter.