AstraZeneca Covid vaccine clots, and self eating plastic

In recent days, there have been interesting developments in the field of nuclear fusion. American researchers claim they have successfully conducted experiments that could make the process easier. Meanwhile, British scientists have unveiled a special type of reactor - which they say offers new ways of controlling the white hot plasmas generated by nuclear fusion. But are we really any closer to solving one of science’s greatest mysteries? Here’s fusion physicist Brian Appelbe, from Imperial College London…

Brian - Fusion is essentially just a way of making nuclear energy, but it's not like the normal nuclear energy we get from power plants which is fission energy which is based on splitting the heavy atom. Instead, nuclear fusion is when we join light atoms together to release energy. It is very attractive because it essentially gives us much more energy per unit mass than we can get from fission or all other energy resources, and it is also a much cleaner form of nuclear energy than fission. However, it is tremendously difficult to do because in order to make fusion energy, we essentially have to make something that is as hot as the centre of the sun in order to induce the nuclear reactions within it.

Chris - Indeed, because of course we know fusion works, we just look up in the sky to see it at work, it's bathing us in glorious sunlight and warmth. But the sun has the advantage that it's about a million times bigger than the earth and millions of degrees in the middle, isn't it? It has some of the problems solved. How are scientists trying to surmount the fact that we don't have a sun to hand?

Brian - Exactly correct. It's really a question of containment or confinement. So with the sun, we make it very, very hot. When you make something very hot, it wants to explode, it's got a lot of energy, it's under high pressure, it will attempt to explode. The sun stays contained because it is so massive there's a huge gravitational force that keeps it confined whereas, on earth, when we want to generate nuclear fusion energy, we must find alternative manmade ways of confining this very hot material in which the nuclear reactions are happening. Scientists have looked at various ways of trying to confine this very hot (what we refer to as) plasma. When we make the nuclear fuel very hot, it becomes a plasma and scientists have found various ways of confining or containing these hot plasmas, for example, as has been in the news recently, using a magnetic field.

Chris - There's an announcement this week about a wonky or twisted donut. They're dubbing it the 'stellarator.' This is the company or the group Type One Energy. They're enthusiastic about this. Why do they think this will be the game changer or a contributor to becoming a game changer?

Brian - There are many reasons for the excitement, some of which are based on science, more of which are based on economics and money. In particular, the accelerator is a design in which you essentially twist the magnetic field lines to make them into a closed configuration in a manner that very effectively contains this hot plasma. The announcement is Type One Energy, this private fusion company, have got a particular design which they think, on paper, should be able to give them a net energy gain, i.e. get more energy out of the system than you're putting into heat and confine the plasma in the first instance. But much of the excitement about this is because of technological developments that we've had over the last few years. The basic accelerator design itself dates back to I think the 1970s, but what's advanced a lot in the intervening years is technologies like superconducting magnets that actually make it efficient to generate these magnetic field configurations.

Chris - They're saying they want to have a plant to test this active in Tennessee by 2025. That's literally next year.

Brian - Which is very ambitious. You know, I guess it is nice to see such ambition. I've been working in this field for over 10 years and in the last maybe five years there's been a lot of excitement, partly because there's lots of money being invested in the field, there's lots of startup companies that are pursuing different designs, planning to do lots of exciting things, and I think it's very difficult to evaluate all of these in isolation. What we look at is the fact that across the whole field we're seeing a lot of advances both on the scientific and on the economic side of things. It's following a pattern where we've got a lot of companies and laboratories who are making a lot of rapid progress.

Chris - And you talk about the advancements in the science right on cue because there is a paper in the journal 'Nature' this week looking at this. What are they doing and saying?

Brian - This is quite interesting because this is very much a scientific development in fusion. This is a different form of twisty magnetic fields. This is the tokamak, which is essentially a donut shape of magnetic field lines. And there is the DIII-D tokamak in San Diego run by General Atomics, that's a well established device that they've been doing experiments on for a very long time. But they've made a breakthrough in which they've found a way that they can actually keep their hot plasma contained using the magnetic fields, but they've increased the density of the plasma which they're containing quite significantly. That's very exciting because essentially the denser the plasma that we're confining, the more nuclear reactions can happen and the more efficient the whole process can be. So by making lots of the subtle changes to their system at DIII-D, they've been able to increase the density above what was previously thought to be the upper limit on densities that could be contained. From a scientific point of view, this is a very exciting development for tokamaks. The big question with this is how it scales up to larger tokamak devices because the DIII-D device is actually very small by the standards of tokamaks. It's only, I think, of order about two metres in diameter whereas the biggest tokamaks that are currently being planned and built are tens of metres in size; an order of magnitude bigger. What's not clear yet is how the results from DIII-D could actually scale to these larger machines.

Humans produce around 350 million tonnes of plastic waste every year. And, because of its chemical composition, some of that plastic will still be hanging around in our environment for centuries to come. But a team of scientists in the United States believe they have a solution - which involves "self-digesting plastic" that is impregnated with dormant bacteria that can reawaken when the plastic is dumped and break it down. Here’s Han Sol Kim at the University of California, San Diego…

Han Sol - We wanted to mitigate plastic pollution because plastic pollution is one of the pressing environmental problems. And many plastics are escaping our recycling or collection effort and reaching the environment. So we want to make inherently biodegradable plastics that can naturally break down once they are lead to the environment.

Chris - And so what's your solution? How might we be able to achieve that goal?

Han Sol - Inspiration for this study came from the idea of pairing plastics with bacteria because bacteria can program various functions into plastics such as biodegradability.

Chris - Say that again. So you've got bacteria that can change the way plastic behaves.

Han Sol - Yes. Because some bacteria are known to break down plastics. So we envision that if we can incorporate bacteria into plastic, the bacteria will break down the plastic at the end of its lifecycle.

Chris - Will this work for any plastic or are there specific types of plastic? Because plastics come in different formulations and types, don't they?

Han Sol - That's a really good question. But for this work, we only focused on a specific plastic, which is called thermoplastic polyurethane. We screened and engineered bacteria specifically for this plastic. But I believe that if we can screen and engineer bacteria to other plastics, we will be able to expand our work to other plastics beyond thermoplastic polyurethanes.

Chris - So the trick might work more broadly. In essence, how does it work then? Talk us through what you make, what bacteria you use and how that works.

Han Sol - We used Bacillus subtilis. It's a spore forming bacteria, which means that this bacteria will be transformed into a dormant form of life when it's exposed to harsh conditions. So under this spore form, Bacillus subtilis is very stable. So we were able to compound this Bacillus subtilis spore with plastic during the extrusion of plastic.

Chris - I see. So when you are making a plastic item, you're mixing up what makes the plastic with some of these bacteria, they form these inert spores and end up embedded in the plastic product.

Han Sol - Exactly.

Chris - So how do they then know when to come to life and start breaking down the plastic?

Han Sol - So spores can remain dormant for many years until they are exposed to favourable environments that enable them to thrive. For example, nutrients in soil are good triggers for returning spores to life. So spores have several proteins, which are called germinate receptors. And once the nutrients in soil bind into this receptor, they can trigger the germination of spores. This means that spores are likely to remain inactive until they detect these nutrients, which are scars during the useful life of plastic in our daily life. But once they are littered or buried in the soil, the nutrients will wake up spores.

Chris - Wow. And how quickly do the bacteria then degrade the plastic? So if you start with a certain amount of plastic, how quickly does it break down and what does it break down into?

Han Sol - Our study shows that more than 90% of mass was lost within five months, which is twice as fast as the degradation of plastic without spores. And more than 70% of plastic was biomineralised into CO2 within six months.

Chris - So it breaks down into CO2, obviously not ideal, but it's a gas which then just goes off and potentially becomes wood in a tree, I suppose, isn't it? It's critically not a hunk of plastic left in the landfill.

Han Sol - No. We believe this bacteria is environmentally promising because Bacillus subtilis is generally recognised as safe for humans, animals, and plants. Bacillus subtilis is ubiquitous in soil, and sometimes people even eat these Bacillus subtilis spores as probiotic supplements. And Bacillus subtilis can also help the growth of plants by suppressing the growth of other pathogenic microbes. So overall, we believe that this Bacillus subtilis is environmentally promising.