Tuesday, 28 March 2017

Talk - Gravitational Waves and Black Holes

Dr Thomas Sotiriou from the University of Nottingham recently gave a Café Sci (or Café Scientifique et Cultural to give it its full name) talk on Gravitational Waves and Black Holes - Einstein's Amazing Legacy. @Gav Squires was there and has kindly written this guest post summarising the event, with some linkage added by NSB.

Dr Sotiriou began by describing how scientific theories are replaced with better ones, starting with Newton's law of universal gravitation, which describes the gravitational forces between two bodies in terms of their masses and the distance between them - multiplied by a factor called the Gravitational Constant.

Newton's law of universal gravitation

Gravity doesn't just attract things, it determines how objects move in space. In Newton's time his theory unified how we understood gravity both on the scale of the solar system and also how it works on Earth. It was a theory that proved useful for 200 years. Then, in the 19th century, it was observed that the planet Mercury didn't really obey this theory. Its orbit was very slightly different to what was predicted but this didn't really concern anybody. At this time the outermost planet that had been discovered was Uranus and its orbit didn't match Newton's theory either. The observed orbit hinted that there was another planet that was affecting it - this is how Neptune was discovered. It was then thought that something similar must be happening to Mercury and so an innermost planet called Vulcan was predicted. In reality, it was Newton's theory that was incorrect.

Dr Thomas Sotiriou, with visual aid

Einstein was very interested in light (his Nobel prize was for the discovery of the photoelectric effect). At the start of the 20th century it was known that observers moving at different speeds who are measuring the speed of light get the same value. This is counter-intuitive - if you're running straight at the light then surely you'd get a different speed. Einstein knew that the only way to explain this was that people moving at different speeds must have a different view of time and distance. This was the basis for his theory of special relativity. Einstein realised that space and time were independent, this is where his idea of spacetime came from. To pin down an event you need to know where and when it happened. This revolutionised the way that people thought about physics. The theory of electromagnetism worked really well with special relativity but Newton's theory of gravity did not.

Special relativity only relates to observes moving at constant speed. Einstein knew that to say something about observers that were accelerating, he would have to say something about gravity. For 10 years, he tried to formulate a theory that included both accelerating observers and gravity. The result was his theory of general relativity and it explains how matter curves spacetime. If we know what the matter distribution is then we know how spacetime will curve and this curvature tells matter how to move. This theory accounted for the deviations in Mercury's orbit.

This didn't impress scientists, they wanted a prediction for some unknown thing that existed only in the theory. Einstein predicted the bending of light rays and a year after the theory was published Eddington proved it during an eclipse. This was not the only ground-breaking prediction. Special relativity told us that nothing could travel faster than light and general relativity showed that light is affected by gravity. If light feels this pull and has finite speed then if there was something of huge mass in a very small space not even light could escape its pull. This is what we call a black hole and was predicted by general relativity. People didn't believe it for a long time.

The day light was shown to be affected by gravity

What happens when objects move around in space time? When a boat moves in water in causes ripples - the same thing happens in spacetime and this is where we get gravitational waves. This emits energy and this loss of energy causes objects to get closer together. This is happening with the Earth and the sun but it would take billions of years for the Earth to plunge into the sun. These emissions of energy are very small but when you come to black holes, the gravitational waves are much larger. It took four decades to develop the technology required to detect gravitational waves. The LIGO detector discovered the gravitational waves caused by the collision of two black holes. The energy emitted from the collision was more than the energy from all of the stars in the universe at that moment. Even so, the movement that LIGO detected was the size of an atom over 4km.

The LIGO Black Hole collision

Unlike with Newton's theory, general relativity has nothing to do with mass or forces - this is why it works with photons. While we know that energy and mass are related (E=MC2) but we don't need mass to have energy - photons have kinetic energy. It is actually energy that causes the curvature of spacetime. The famous equation E=MC2 actually only relates to mass at rest.

General relativity is better than Newton's theory but could we eventually have an even better one? Are dark energy and dark matter the equivalent of the procession of Mercury for general relativity? General relativity isn't a quantum theory so it's possible that at some point we will get a new theory of gravity or maybe even a new theory of matter.

Café Sci returns to The Vat & Fiddle on the 13th of March at 8pm where Graham Harrison from the University of Nottingham will talk on Photobiology - Effects Of UV Radiation On Normal Skin. For more information check out the MeetUp site: https://www.meetup.com/nottingham-culture-cafe-sci/

Sunday, 12 March 2017

Talk : Things That Go Bang In The Night (Sky)

The University of Nottingham Science Public Lecture Series had their February talk presented by Julian Onions on the subject of Things That Go Bang In The Night (Sky). @Gav Squires was there and has kindly written this guest post summarising the event, with a few additions from NSB who was also at the event.

Julian Onions

Of everything in the universe what would go off with the biggest bang? At that size, scales are in the region of billions of years - astronomy is a slow science. And it's big, we talk about things in terms of solar masses. A solar mass is approximately 2x10^30kg.

First a bit of solar theory. A big ball of gas collapses down and the pressure makes it get hotter and hotter and in the centre nuclear fusion happens. So there is gravity pushing inwards and energy pushing out and at some point these two forces reach equilibrium. The sun is around 15million degrees Kelvin at the centre. A red dwarf is around half a solar mass and it like a boiling pot. It last for a long time and it very efficient. The sun is a boiling mass at the edge but from around a third of the way out from the centre it is being held up by radiative pressure (light). Giant stars, from around five solar masses, are being held up by just light.

When the sun runs out of fuel, the outward pressure will stop and gravity will win. It will contract down to around the size of the Earth and will become a white dwarf. Then it will glow for hundreds of billions of years. In fact, no white dwarf formed since the beginning of the universe has gone out yet.

Nova are new stars - they are things that suddenly brighten in the night sky. White dwarfs start to steal material from a fellow binary star, building up a hydrogen shell. This warms the star up and can cause the nuclear reactions to start again. It burns very fiercely and this is almost instantaneous and we get a burst of light. It happens for between 25 and 80 days and then it dims. This can happen several times.

A white dwarf is around the size of the Earth and is less than 1.5 solar masses. A neutron star is between 1.5 and 5 solar masses and is around 20km wide. A black hole is larger than 5 solar mases and has an even horizon that is around 30km across. Is there anything between a neutron star and a black hole? In a white dwarf matter goes into a fiery, squashed state called degenerate matter, which is very odd stuff. If you add more matter, it gets smaller. In a regular start matter is around 0.1kg/cm3. Degenerate matter is 10,000kg/cm3 while neutron star matter is 1014kg/cm3.
Masses of different star types compared

At this point it's time to introduce a new unit of measure, the foe. It's a unit of super nova power. One foe is equivalent to 10^44 Joules or around the same amount of energy in 186 Earths. To give that a little context in terms of "bang", the biggest hydrogen bomb we've ever developed is 10^17 Joules.

A kilonova is around 10 foe. It happen when 2 neutron stars are orbiting each other, losing energy through gravitational waves. There is a huge explosion when the two stars become one and this is one of the major ways that heaver elements in the universe are created. This creates short gamma ray bursts but because neutron stars are difficult to see these kilonovas are hard to track down.

There are several types of supernova - 1a/1ax/1b/1c, 2a/2p/2c/2b. Zwicky originally had other types but these have since been subsumed into one of these. Type 1a supernova detonate while 1b, 1c and all type 2 suffer from core collapse.

Comparing supernova types 

Type 1a is around 1 foe in energy and is very similar to the nova. However, the white dwarf is a bit more advanced. It still steals material from a companion but rather than just the outer layers burning off it all lights up. The temperature gets to around 100,000,000 degrres Kelvin and then it explodes. This happens at the same point in every white dwarf - when it reaches around 1.5 solar masses. These are a favourite of astronomers as they almost always give off the same amount of light so it is easy to measure distance. They are almost like a "standard candle" for measuring the universe.

SN1987a - a recent Supernova

Type 1ax was only discovered in 2013. It's where a white dwarf that has lost nearly all of its outer layer of hydrogen and helium goes supernova. Energy wise it's at maximum half a foe and probably around a third of supernova are of this type.

In types 1b, 1c and 2 the hydrogen in the centre of the star is burnt off. Then the star starts burning the less efficient helium. To give some context, the sun will burn for 10 billion years using its hydrogen but only for an extra billion by burning its helium. By the time it reaches silicon, the star is getting desperate and when it reaches iron, it is using more energy to burn it than is being given off. With the power off, there is nothing to counteract the force of gravity. The star contracts at a third of the speed of light. The whole thing then stops, shudders and explodes but no-one knows why. One theory is that the gravity creates neutrinos - most of the energy comes out in neutrinos rather than light. The centre that is left is now a white dwarf or a neutron star.

"Onion Burning"

In a type 1b, the star loses its outer layer of hydrogen so its surface is just helium. Type 1c loses its hydrogen and its helium so it has carbon and oxygen at its outer layers. Type 2l are between 5 and 100 foe but you don't see the actual explosion as it doesn't give out light. Then there is a Peak of luminosity, which slowly fades. Type 2p has a Peak of luminosity and then a plateau before the fade. Type 2n and 2b are all pretty much the same.

A hypernova is a much bigger star that explodes and these generate long gamma ray bursts. Again, they are caused by core collapse. For stats between 8 and 10 solar masses, electron capture takes away the power that was being used to support the star. The temperature gets up around 10^10 degrees Kelvin and then the whole thing catches fire. Between 10 and 140 solar masses, the star suffers from iron core collapse. Between 140 and 250 solar masses, the star suffers from pair instability. Very high energy gamma rays are produced and the energy coming out goes into creating matter rather than supporting the star. These are very rare. Over 250 solar masses and you get photodisintegration. The star turns in on itself and the iron is turned into helium. This then turns into a black hole. The size and the amount of heavy metal in a star determines its fate.

What of other "bangs" in the night sky? The recent detection of gravitation waves was caused by two black holes colliding. Three solar masses worth of energy were given off, around 5300 foe. So, what if two super massive black holes collided? These are 1,000,000 solar masses each and could happen when two galaxies collide. This is a very rare occurrence and it would also be quite a drawn out affair - the two super massive black holes would orbit each other for a billion years. Super massive black holes give off 10^9 foe of energy anyway, this is emitted constantly over millions of years.

Then of course there is the big one, literally. The big bang gave off 10^25 foe of energy. It took around 20 minutes and then the universe went into a decline for the next 300,000 years. That's a one off though and the likelihood of a local black hole collision is very low. So, the supernova is the winner. If a supernova goes off in our galaxy it will probably be visible during the day and Betelgeuse is a candidate to go off in the not too distant future.

So, which big bang are we most likely to see....

The Public Lecture series returns on the 16th of March where Dr Mandy Roshier and Dr Steve North will be talking about Bits & Bytes - When Horses Meet Computers. For more information visit the UoN website: https://www.nottingham.ac.uk/physics/outreach/science-public-lectures.aspx

Image sources
All courtesy of Gav Squires from the talk

Talk : Thinking outside the (pill) box): alternative drug delivery strategies

The University of Nottingham Science Public Lecture Seriesstarted 2017 with a talk by Claire Sycamore entitled "Thinking Outside the (Pill) Box - Alternative Drug Delivery Strategies". Claire is a PhD student in Prof Neil Thomas's research group in the UoN Faculty of Science. @Gav Squires was there and has kindly written this guest post summarising the event, with a few additions from NSB who was also at the event.

Claire Sycamore

Local vs Systemic delivery
Pharmacology is the superhero of our time, different from other treatments such as surgery or radiology. It first came to prominence in the 1930s following the discovery of penicillin in 1928. These days a person will take on average 14,000 prescription pills and 40,000 non-prescription pills. The three most popular non-prescription drugs are all non-targeted and you can actually take quite large maximum doses in a day:

Paracetamol - 4.0g
Ibuprofen - 1.2g
Asprin - 3.6g

Drug delivery systems are all about the interaction at the point that the drug is taken. By working on these systems you can improve the efficacy and the safety of the drugs and control the rate and location of the drug being released. A drug delivery system is something that is given at the same time as the drug.

Ibuprofen has a ph of 4.4, is not very well absorbed and can lead to stomach ulcers. It acts on a fatty hormone called prostaglandin H2 and has two forms "R" & "S". It is only the "S" form that actually works as a painkiller (although the but R can be converted into S in your body over time).

Ideally, we would have something that works locally, not just systematically. For example, the anti-fungal drug Terbinafine can be applied as a cream to the affected area or taken as a tablet. When you take a tablet, the whole body is flooded with the drug. This can lead to strong side effects such as problems with the kidney and the liver.

Common painkillers and their max allowed dosages

Microneedles
So, we need to look at routes of delivery - how the drug gets into the body, for example orally, inhalation, injection. One of the latest inventions is the microneedle (see also here). Needles in general are a great way of getting a drug into a body quickly. They are easy to use and cheap to produce. However, not everyone likes needles and there can be issues with training people to use them properly, for example with diabetes patients. Microneedles avoid all pain, you don't actually feel them piercing the skin. There's less to be fearful of, it requires no training and it give precise localisation. They can even be used to deliver drugs straight into the eye. The only real issue with microneedles is that they can only be used for drugs that you inject.

For drugs that can't easily be delivered by microneedles, a key area of research is delivery vehicles - getting the drugs get to the places that they need to go. Nanotechnology and nanoparticles are the big thing here, allowing controlled targeting and greatly reducing side effects.

But why nanoparticles?

Due to their size nanoparticles have a greater mass to surface ratio. They also have some quantum properties, in that they act more like a wave in some respects. They also have the ability to absorb and carry other compounds. Can we assume that something that works at the "bulk" scale will be just as effective at the nano level?

Microneedles (Copyright: Ryan Donnelly, Queen''s University Belfast)

Prodrugs
Getting drugs to the target areas is particularly important in cancer treatment, where the drugs are designed to kill cells and have harsh side effects. These side effects are one reason that an estimated 50% of cancer patients do not comply with their medication pathways. If we can target just the tumour then we can reduce these side effects and make treatment better for patients.

This can be done by using something called a pro-drug. These are drugs which are inactive when administered and are converted within the body, often by an enzyme, into a therapeutic drug.

Prodrugs have been tested on mice where the enzyme is added to a clostridia bacteria and then spores(dormant forms of the bacteria) are taken. These spores are injected into a mouse and then allowed to grow for a couple of weeks. Critically, clostridia bacteria (and the enzymes they carry) will only grow in a low oxygen environment - like a tumour. Then, when the pro-drug is injected it will only activate in the tumour because that is the only place where the bacteria (and hence enzymes) are. You can read more on this research here and here.

Polymer delivery systems
Another problem is the rise in antibiotic resistance. For example, an American woman died in January despite being given all 26 available antibiotics.

According to the World Health Organisation, "Without effective antimicrobials for prevention and treatment of infections, medical procedures such as organ transplantation, cancer chemotherapy, diabetes management and major surgery (for example, caesarean sections or hip replacements) become very high risk."

A potential answer to the threat of antibiotic resistance is to use plastics for drug delivery. Plastics are a type of polymer (incidentally so is DNA) and polymers have a number of advantages in the body:

Timeable
Versatile
Easy to prepare
Reduces dosing frequency
Maintain therapeutic concentration with one dose
Reduced side effects
Improved stability
Prolonged release

However, we need to consider what happens with this plastic long term. How long is acceptable to leave in the body? So, we need to find a biodegradable polymer. This isn't as straightforward as it could be as you need the right enzymes and bacteria to degrade the polymer. For example, a biodegradable polymer wouldn't actually degrade in a landfill because it is too dry and there is too little oxygen so the enzymes and bacteria can't survive there.

There are some very specific requirements for this plastic. It has to be bio-compatible, non-toxic, permeable, biodegradable, pure and with a high tensile strength. There are three plastics that are being looked at, PLA, PGA and PTMC. The later seems to be the best choice as it is resistant to hydrolysis, which means that it sticks around longer and it isn't brittle.

Polymers for drug delivery

How can we alter the properties of PTMC to make it into the delivery system that we want? Through using technical processes such as cross-linking, copolymerization and functionalization to incorporate functional side chains. The idea is to attach antibiotics into the basic structure of the PTMC. The antibiotics Gentamicin and Clindamycin are both being looked at with regard to this process as they cause severe side effects (Gentamicin can cause permanent deafness). You can read more about this research here.

Different delivery vehicles to get drugs into the eye are also being looked at. 95% of dose placed in the eye using a dropper is washed away. Is there a better way? Work has started on a contact lens that would include an antibiotic imprinted into it. That way the drug is trapped between the contact lens and the cornea - See UoN's research here and also some work by Harvard here.

Another big area of research is on the cargo - the drug itself. Does it have to be a small molecule? For example, even though there is no human-human transmission at the moment, there are huge fears about H5N1 influenza, also known as bird flu. It has a 60% mortality rate and would be a massive issue if it became pandemic. So a nanovaccine has been created, which is preventative rather than curative (some background can be found in this UoN pdf presentation and this research from the US).

Flu Virus 

Virus Like Particles
The final area of research is targeting strategies. The exterior of a virus is often a protein polymer cage known as a capsid. So called "virus like particles" mimic these capsids and tripper an antibody resonse that protects the vaccine recipient from later infection. An example of this technology is the Gardasil HPV vaccine.

You can also make these biological cages from things such as Ferritin, a storage protein for iron. The cage can opened and closed by varying the pH of the environment - while the cage is open, the iron can replaced by other things such as cancer drugs.

Ferritin

Final Comments
Of course there are crossovers between lots of these areas of research. It may take a while for some to reach the public but these are exciting times in the field of drug delivery strategies.

Overall, it is clear that the direction of travel is for new drugs to be highly targetted so that only milligram dosages are required - aspirin certainly would not be licensed today!

The Public Lecture Series returns to the University of Nottingham on the 16th of February at 6:00pm where Julian Onions will talk about Things That Go Bang In The Night (Sky) For more information, please visit the Public Lecture Series site: https://www.nottingham.ac.uk/physics/outreach/science-public-lectures.aspx

Image Sources
Ferritin
Microneedles - Copyright: Ryan Donnelly, Queen''s University Belfast
Images from Talk - Copyright : Gav Squires
Flu Virus

Monday, 6 March 2017

Truss Me

A buddy I shall call Dr K tipped NSB about an iOS and Android app called "Truss Me" in which you are challenged to build support structures for increasingly difficult combinations of weights and base fixing points. It's a great combination of game and educational experience, and really provides a feel for what kind of structures work....and which ones don't!

The game award a rating of 1-3 "bolts" to your design, depending on how lightweight it is. The app also helpfully shows which beams are in tension and which are in compression, which is helpful to know as beams in compression tend to buckle if made too thin. - NSB is working through the game with the aim of getting 3 bolts at each stage! [Update 25th March - now completed all 24 levels, 3 bolts all the way!]

You can read more about Truss Me on the developers page at http://www.scientificmonkey.com/software.html.

BFTF's scores are shown below - can you beat them by designing a lighter structure?

3-Bolt-Tastic! 

Challenge 1 : 799 points, 3.1kg
Challenge 2 : 249 points, 10.0kg

Challenge 3 : 283 points, 8.8kg

Challenge 4 : 268 points, 9.3kg
Challenge 5 : 94 points, 26.6kg

Challenge 6 : 87 points, 28.7kg

Challenge 7 : 278 points, 27.0kg
Challenge 8 : 98 points, 25.4kg

Challenge 9 : 211 points, 35.6kg

Challenge 10 : 74 points, 33.9kg
Challenge 11 : 214 points, 23.4kg


Challenge 12 : 54 points, 46.2kg


Challenge 13 : 230 points, 43.5kg
Challenge 14 : 88 points, 28.3kg
Challenge 15 : 63 points, 79.4kg
Challenge 16 : 177 points, 42.4kg
Challenge 17 : 111 points, 22.6kg
Challenge 18 : 98 points, 76.6kg
Challenge 19 : 349 points, 28.7kg
Challenge 20 : 245 points, 61.2kg
Challenge 21 : 874 points, 11.4kg
Challenge 22 : 320 points, 46.8kg
Challenge 23 : 201 points, 87.3kg

Challenge 24 : 306points, 24.5kg