Where do lost socks go?

There are many processes in physics chemistry and biology which are very interesting but happen very quickly so they are hard to study. There are many forms of high speed imaging but they work by making conventional cameras faster, which normally involves expensive mechanical systems and they often have a limited light sensitivity because their exposure time is so short. So if you are not careful you have to illuminate the sample so brightly that the light levels will damage it, and they are useless if you are looking at light emitted by a process.

The Megaframe project had just built a camera capable of 1 million frames per second by approaching the problem from a different direction. They have taken sensors called Single Photon Avalanche Diodes, which, as the name suggests, can detect individual photons, making the camera far more sensitive than a converntional camera. These detectors are then connected to timers which can tell you when the photon arrived to within 100ps and be ready to receive another photon 32ns afterwards. They have then made arrays of these detectors up to 128 square, which is a long way from HD video, but immensely better than the alternative of using individual detectors.

The precise measurement of when each photon gets to the detector makes this camera particularly means that it can be used for a variety of forms of imaging which need to know very precisely when the photons arrive at your detector.

This makes the camera useful in a variety of ways, not least, because the rate that some dyes (Oregon Green Bapta-1 ) emit light after they have been given energy by a laser is dependent on the concentration of calcium around them. Calcium is used in the firing of a nerve cell so this means that they have been able to make a video of an indivdual nerve cell firing and as they get more pixels on their detectors, they should be able to video groups of cells interacting.

If you have travelled by aeroplane recently you will probably have been annoyed by the rules limiting the liquids you can take onto the plane. The problem is that there are various liquids that can be used to make explosives or just a fire, which are hard to detect quickly and easily in the security check.

A group for Julich in Germany think they may have a solution. They are looking at the frequencies reflected in the GHz to 10 THz region of the spectrum, which is the frequency of your mobile phone and upwards. Different liquids have different spectra so you can detect which one is in a bottle, however these frequencies are difficult to deal with and conventional spectrometers are very slow, or they only use a single frequency.

Their solution is to use a Josephson junction, which is a small gap between two pieces of superconductor. The relationship between the voltage across the junction and the current flowing through it changes when you apply GHz  and THz frequencies. So they have been able to shine a variety of different frequencies onto a suspicious liquid and the focus the reflections onto the Josephson junction and work out what frequencies were reflected.

At the moment they have only distinguished 5-6 liquids including water and a variety of alcohols, ketones and water but there is no reason it shouldn't work for more, and they can take a spectrum in a second or so which getting towards a practical speed for testing baggage.

Chris - Now also in the news this week, two international teams of astronomers have described what we can only describe as the most distant object ever discovered.  What they've seen is the gamma ray burst of the star that died when the universe was just 640 million years old.  That's less than 5% of its present age.  The universe would've been only about 9% of its present size and that means the light from that star has been going across space, coming towards us for over 13 billion years.  And one of the people who manage to see was Professor Nial Tanvir who's at the University of Leicester and is with us now.  Hello, Nial.

Nial -   Yes, good evening.

Chris -   Welcome to the Naked Scientists.  So, tell us first of all, how did you make this observation?

Nial -   So, these gamma ray bursts are actually quite tricky to observe because their main characteristic is a short flash of gamma rays and of course, the gamma rays don't penetrate the earth's atmosphere.  So, we have to observe them initially with satellites and the current sort of work-horse satellite doing this stuff is one called Swift and that's the satellite that the UK is partially - built part of the satellite so has an interest in.  So, Swift finds about, on average, two gamma ray bursts every week and it reports the positions on the sky of these events down to the ground within a matter of seconds or minutes so that observers on the ground like myself can make follow up observations using a variety of different large ground-based telescopes.  And it's by analyzing the information that we get from those ground-based telescopes that we ascertain things like the distance and in this case of course found that it was a record breaker.

Chris -   What actually causes the gamma ray bursts in the first place?

Nial -   That's a good question.  It's something that is still enshrouded in a certain amount of mystery, but we think actually, there are a number of different kinds of objects in the universe that can give rise to these sorts of flashes gamma rays.  But in particular, the one that seems to be most frequently are seen are related to the collapse of a very massive star.  So, we have a star that's maybe 20, 30, 40 times the mass of the sun.  At the end of its life, ceases to create energy in its core and no longer supports  nuclear reactions.  And so, the star just collapses on the under gravity there's no pressure, radiation pressure to keep it up.  Now, that's a reasonably common and fairly well understood process but it seems that in certain rate situations, instead of just producing a normal supernova which is what we would expect normally to happen, such a star can also produce an extremely energetic and highly relativistic jet of material that pierces its way after the star.  And if you happen to be sort of lying and looking along the line of site, down the barrel of this jet as it were then you see this phenomenon of the gamma ray burst.

Chris -   Why is it that we've not seen one that's this old before?  Because presumably, the universe has had stars forming and ploughing themselves to pieces and producing gamma ray burst like these for a long time.

Nial -   Yeah.  The problem really boils down to just rarity.  It seems that it's only very exceptional stars that explode in this way.  And therefore, even in the whole universe, as I say, Swift sees a good chunk of the universe in a sense as it scan off the sky every day, and yet, it still only detects in the whole universe a couple a week.  So really, it just boils down to the fact that we needed to wait a long time until we were lucky enough to spot one at this sort of distance.  If we carry on observing, we may getting more sensitive satellites and scan even more of the sky then the hope is in the future that we'll find more at this sort of age.

Chris -   What can you learn from the fact or what can you infer from the fact that there was a star burning 600 million years after the Big Bang when the universe was created?  What's written into that gamma ray burst in terms of the signature and the chemistry that can inform you of the structure of the early universe around that time?

Nial -   Right, okay.  Well, I should say that in this particular instance, gamma ray burst and what - the initial flashes is very bright in the gamma rays, but then the object will then sort of track through the ground-based telescopes is a sort of fading ember.  It's what we called the afterglow of the burst.  And in principle, the afterglow can give you a great deal of information about the local chemistry and the conditions at the time and in the vicinity of the burst.  And so, that's very important for example if we find that there is a lot or a certain amount of elements heavier than hydrogen and helium.  So for instance, oxygen, carbon, iron, all the things that we're familiar with.  If we find that those are present at this time, we know those could've only been cooked in the senses of stars.  And so, it gives a very important clue, not just to what's happening there and then, but what must have happened at even earlier times to produce those heavier elements.

Chris -   Are they there?

Nial -   So that's the principle.  But on the other hand, the problem is that with the GRB afterglows, they come in a sort of great range of different brightness.  And really, if we're going to find that sort of information from a gamma ray burst afterglow, it needs to be a particularly bright afterglow and unfortunately, this one wasn't a particularly bright one.  I mean, it was fairly bright, but it wasn't bright enough.  I mean, we didn't really - at the end of the day, manage.  If we had been very lucky with the kind of data that we'd got, then it's possible we would've done it.  But with these things that they go from random times and so, you have to live with whatever telescopes can make the observations at that time and we've made the first observations in fact, using telescopes in Hawaii which we sort of triggered from the UK.  But conditions weren't great in Hawaii that night, so you see the problem.  We obtained enough data to prove that we got this record breaker, but we unfortunately didn't manage to get good enough data to sort of take it to the next step to do those sort of, you know, refined pieces of analysis.

Chris -   I see.  And just to finish off, Nial.  Can you tell us?  What does this tell us about the structure of the universe at that time, the fact that there was this big star burning at that time?  How does this inform our understanding of the early universe?

Nial -   Well, it tells us that there's at least one star and of course, one who seems that there were more and we hope in the future, by building up statistics of these things, we'll be able to really sort of measure the rates of star formation in the universe, even at those very early times.  The other thing it does is it pinpoints the position on the sky presumably, it's galaxy that hosted this stars.  So, stars forming galaxies and we'd like to know, not only about the properties of stars at this time, but also the properties of galaxies.  And so, the galaxy is going to be far, far fainter than the gamma ray burst because gamma ray bursts is stupendously bright and galaxies only have, you know, a few hundred million stars in them or something like that.  So they're much fainter.  But we can now know the position and knowing the distance, we can go away with all the other facilities that we have without disposal like the Hubble Space telescope, and look really hard for the host galaxy.  And so, that's certainly something that we haven't yet achieved, but we hope to do next year is to really search very hard and see if we can find this host galaxy and therefore, for the first time, learn something about the properties of the galaxies which existed at this really early era.

Dan - I'm just wondering why car wheels sometimes appear to be going backwards when you view them under streetlights sometimes? Chris - I think I've seen it. As you're driving along, the car next to you is accelerating away and it looks like their wheels are going backwards in the streetlights, illuminating the wheels of the car. Dan - Yeah, that's right. Chris - Yeah. It's actually a stroboscopic effect. If you've been a fan of Westerns, if you were a big John Wayne fan and you used to watch those early Westerns where the cart would pull away from the scene and the wheels would initially go forwards and then appear to start going backwards. Did you see those? Dan - Yeah. I've seen that before. Chris - Yeah. It's the same phenomenon. In the case of the cart, it's because the camera is taking X number of frames. In other words, pictures every second. In the case of the car driving down the road to where next to you, it's the streetlight flashing on and off about 120 times a second because mains electricity is 60 hertz. So the light goes on and off 60 times a second. So as a result, you're seeing 60 flashes or illuminations of the car wheel per second. Now if the car is accelerating, if you imagine the - say you drew a line on the car wheel, a chalk mark and you watched that go around, it would go around in a circle. But you only see it in the dark when it's illuminated by the street light. Now say, the street light flashes on, you see the chalk mark pointing straight upwards, the light goes off and the wheel turns around a bit, agree? Dan - Yes. Chris - Light comes back on, the chalk mark is now in the new position, agree? Dan - Okay. Chris - Now as the car wheel speeds up the distance of the chalk mark makes it around the wheel will change according to how fast the car is going, yeah? Dan - Yup. Chris - There will therefore be a speed at which the wheel will go when it doesn't look like it's moving at all because the chalk mark is starting going all the way around and finishing before the light comes back on again. Dan - Okay. Chris - Once it speeds up a bit more, the chalk mark will go right the way around and then a bit further. So it will look like that it was going faster, faster and faster. Eventually, you'll get to a speed where it's actually going right around and back on itself again. So it looks like it's actually going backwards a bit because it's doing more than one complete revolution a bit more. So it looks like it's going backwards and it's because of acceleration. Once it reaches the constant speed, that effect would stop. But it's stroboscope, that you're seeing flashes of light, illuminating the wheel and your eyes sees it, doesn't see it for a fraction of a second and then sees it in the new position. And when the speed is right, it looks like it's going backwards.

Well the answer is that some bacteria don't harm you only by infecting you: they can actually put things into the food that are called toxins, and the toxins are not broken down by heat.

So, bacteria multiplying in the food can lead to the accumulation of toxins in the food, which will then make you ill even though the bacteria themselves that made the toxins may have been destroyed by reheating the food.

And if you repeatedly cool and re-warm food, the food might spend enough time at a sufficient temperature to encourage the bacteria to grow and put toxins into the food whilst not themselves actually really posing much of a threat. That's one way.

Another reasons is that, if you keep on warming up and cooling down food, some bacteria will just end up flourishing and they'll go from being at very low levels in the food, where they're not growing very fast because the temperature is low, to reaching a very high population in the food that might be an infectious dose.

To catch Salmonella, for example, you actually need to eat about a million organisms, 10⁶ particles, of Salmonella. That's an infectious dose of Salmonella. Other bacteria infect you at much lower doses. So it really depends on what the pathogen is and the mechanism through which it makes you sick.

The bottom line is, if food spends more time at higher temperatures, there's a higher chance that bacteria will grow and therefore, make you sick. So, the best advice is to either cook it and eat it, or cool it and eat it, but don't keep reheating it, because that could be bad...

Dr Chris Smith answered this question...

Chris - The answer is both yes and no!

When you give vaccines to people, what you're aiming to do is get the immune system to respond so that it can recognise that pathogen in the future and protect you, either with antibodies or cells that kill viruses in cells.

Now, one way of vaccinating people is what's called Live Attenuated Vaccine. This is where you grow viruses in culture for many generations, and, through the effects of mutation, they lose the ability to make you ill, but they nonetheless remain infectious. So, with the MMR - Measles, Mumps and Rubella - for example, you put the virus into the person. It doesn't cause severe disease, but what it does do is to display to the immune system the entire repertoire of viral genes, viral proteins. And what that does is it makes a very broad immune response, involving making both antibodies and cells that can attack virally infected cells. That way, your body is very powerfully primed to recognise and prevent you from getting that virus in the future.

The problem is that, when you go into that state of infection, what it does is to release large amounts of a signalling hormone called interferon - Alpha interferon, in fact. And what that does is put all the cells in the body into this anti-viral state where the cells are undergoing surveillance. They increase the surface markers they display to the immune system so that they're more likely to get killed if they've got a virus in them; they degrade genetic material that they think might be viral; and they become much harder to infect for viruses.

Now, that means if you've had one virus, that's attenuated vaccine, about a week or two before, your body makes loads of this interferon. If you then come along and then try and infect yourself with another attenuated virus, for instance another vaccine, it won't work very well because it doesn't get into the cells, and the body kills it really quick before it has a chance to prime your immune system.

So, live vaccines, if you don't have them at the same time is a bad thing to do. Having them all together is fine because the immune system works by discriminating very powerfully between different epitopes that different viruses display anyway. So that's not a problem.

For the present situation we're in now though, people are asking me, "What about flu vaccines?" Because lots of people had a seasonal flu vaccine but then they're also saying, "Well now, we need to have a swine flu vaccine. Will the fact that I had the seasonal vaccine about two weeks ago make a difference for me having the swine flu vaccine now?" And the answer is not in that circumstance, no, because the flu vaccine is a killed vaccine. You're just putting in bits of dead virus - shrapnel if you like - which the immune system then learns to recognise.

This doesn't trigger the same interferon response, so it doesn't make you feel ghastly in the same way. It doesn't actually prevent you getting infected with other viruses in the same way.

Dave - Is this interferon response the reason why I still feel really quite shattered now, two weeks after I had the flu?

Chris - Yeah and the reason that flu makes you feel so rotten, despite the fact that the virus is only confined to your respiratory tract, nose and throat, and sometimes lungs if you get a very severe infection, you probably had symptoms that were nonetheless across your whole body. Muscle aches and pains, tiredness, very bad headache, temperatures, just feeling ghastly. That's because of these hormones, the interferons, that the body produces in response to the infection, which then turn all of your cells into this very antiviral prime state. So, exactly right, yeah and that's why after some vaccines that do provoke lots of interferons to be released, you have a day of feeling a bit rotten. It's not because you're infected, although you might be. It's actually the interferons - it's your body's own hormones that are making you feel like that.

I think that very much depends on the chemistry of your batteries. A battery is essentially a chemical reaction which is split into two halves and the only way - and let's say you got part half A and half B, the whole lot's got to happen to be driven in any way that can happen is quite passing electron through your circuit. And eventually, the battery runs out because you run out of all the chemicals you need for the chemical reaction. Now, basically you're saying, if we apply a large voltage and carry on pushing electrons through the battery, what's going to happen? That would depend on what other the chemical reactions go on to move charge through the electrolyte in the battery. Normally, that's often quite inefficient. If you've got have something like a lead acid battery which is symmetrical, it will just start up in the wrong direction. Certainly a very simple that acid battery will - and so, it will turn into battery but pointing the wrong direction. If you have other chemistries of batteries, it could cause all sorts of havoc and it will depend on the exact chemistry. It will certainly become a very high resistance. It will work for a bit but eventually, it's going to run out of - it will either stop or it could do all sorts of strange things to your battery, it's certainly going to damage a rechargeable battery.

Kat - Now this week, there are events running all over the country as part of National Pathology Week.  This is giving people a chance to look into the work and the lives of pathologists.  And on the line now, we have Suzy Lishman from the Royal College of Pathologists to tell us more about this.  So hello Suzy. 

Suzy - Good evening.

Kat -   Thanks for coming on the show.  Now, do tell us to start with, what on earth do pathologists do?  I have this vision that they're all in the lab wearing coats, cutting up dead people.  What do pathologists do?

Suzy -   Well, you're quite right there.  Research has shown that most people get their information about pathology from the television, watching things like CSI and Silent Witness.  And I'm afraid it's just not really like that.  There are over 6,000 pathologists and 20,000 scientists working in 18 different pathology specialities.  And less that 1% of those people actually work in forensics, the bit you tend to see on TV.  So, there's no typical day for a pathologist because they all do completely different things.  For example, I'm a histopathologist, a member of the largest specialty and I study disease by examining tissue with the naked eye and under the microscope, and that might be a biopsy, a small piece of tissue that's removed during an operation, anything up to a whole organ like a breast or a kidney or a limb.  So, I'm then involved in a team, deciding the best treatment to offer the patient according to what I can see when I have a look at that tissue.  But then, other big specialties include haematology, the study of diseases of the blood and the bone marrow, medical microbiology, looking at the diagnosis, management and control of all sorts of infections, clinical biochemistry, the diagnosis and treatment of disease through analysis of body fluids like blood and urine.

Kat -   So, you're pretty much covering the whole gamut of biology and medicine there with pathology?

Suzy -   That's right.  In fact, over 70% of all diagnoses in the NHS involve pathology in some way and over 700 million tests are done every year in the U.K.  That's an average of over 14 for every man, woman and child in the country.

Kat -   Impressive stuff.  So, tell us about National Pathology Week.  What sort of stuff are you focusing on this year?  It's the second year, isn't it?

Suzy -   Yes.  Last year we just had a general year when we said, "Pathologists and scientists, get out there and promote what you're doing."  We thought to give it a slightly different angle this year.  We've chosen the theme of the heart and out strapline is Pathology, the heart of modern health care.  So we're focusing on the diagnosis and treatment of all different types of heart disease by members of all the different pathology specialities. 

Kat -   So what sort of things do pathologists find out about heart disease?  What sort of things would you be looking at if someone comes to you with heart problems?

Suzy -   Well, pathologists are involved in even preventing heart disease developing in the first place which is a very important role so, for example, diagnosing and treating diseases like diabetes, keeping the blood sugar under control, checking people's cholesterol level to making sure that that doesn't build up because cholesterol is a risk factor for developing heart disease.  And also, genetics, geneticists are also pathologists and they can look at inherited diseases and enable people to be treated for heart disease before they even know they've got it.

Kat -   Fantastic stuff - so tell us about some of the heart-based events that you've got going on.

Suzy -   We've got an Awareness Day at the Royal College on Monday.  It's called Think Heart: Save the Baby's Life.  And what we're trying to do is raise awareness of some of the heart pathology that can present in the first week of a baby's life so that parents, midwives, and GPs can be aware of what to look out for because a lot of these disorders, although very serious, can be cured if they're picked up quickly enough.  There are also events around risk factors.  People have the opportunity to learn about some of the risk factors for heart disease like, high cholesterol, which I've mentioned, high blood pressure, poor diet, and do some interactive events to try and find out what various factors are. 

Kat -   And I understand you're also having a heart - the anatomy of a heart attack.  Looking at heart attacks.

Suzy -   I'm particularly looking forward to this one.  It's at the Royal Institution and I grew up watching their Christmas lectures so it's going to be real treat to organize an event in there.  Yes, we're going to have a virtual autopsy, with a model who's going to play the body and we have a pathologist Ali Winstanley who's going to come in and talk us through on autopsy and what we would do to look - what we would look for in somebody who has died of a suspected heart attack.  Ali's then going to dissect a pig's heart, for obvious reasons we can't dissect a human one, just to show a bit of the anatomy on what it is pathologists would look for at an autopsy.  And then we've got illustrations of what the diseased heart would look like so you can see the damage that is done.

Kat -   That sounds absolutely fascinating.  How can people find out about all these events and where to go?

Suzy -   We have a website
www.nationalpathologyweek.org and that has a full program.  We have now over 420 events taking place around the country, in schools, hospitals, shopping centres, libraries--absolutely everywhere.  So, do have a look.  They're arranged by regions so there should be something near you.

Okay. There's a secondary effect. The world is far more complicated than you'd like to think. That tends to be because cold air falls. So, the valleys at low places on average are warmer. But if you got somewhere which is high up and the air can cool down on the tops of mountains, it's then denser around it and it falls downwards and if it's not falling very far it doesn't compress very much, doesn't get very much hotter so you get, locally very cold air is in bottoms of valleys but globally it's warmer low down and colder higher.

The answer is they don't. It's basically good old-fashioned quackery as far as we know. There's this idea that if you wear copper bracelets or magnetic bracelets in some way, it can help with things like arthritis. Research has shown that this is absolute bunkem There isn't really any truth in there. There's some recent results published in October where they did a rigorously controlled trial looking at magnetic or copper bracelets compared to plastic bracelets so people didn't know what it had, and really they found that it was just a placebo effect if you tell someone they've got a magnetic bracelet they think it's doing them some good but there's actually there's no science supporting it. But it's a multimillion-pound industry so, you know, maybe worth it, if you're making them.

You won't see the same photons of light, the individual particles of light but the properties on either side of the earth are going to be very, very similar.

Kat - I think you have to give up some socks as a sacrifice to the "God of Washing". I don't know. Maybe they didn't end up as pairs in the washing machine when you put them in. Chris - I've got a theory of this actually. I think what happens is that socks, very often, glue themselves to the inside of the machine so you remove the washing but you might leave one glued to the top so it gets separated from its counterpart. You then go to the washing, hang washing up, process it, put it all back in your bedroom all ironed and stuff and now you got an oddsock. You find the other one and that gets processed separately but by then you've got this odd sock in the bedroom and you think "Oh I must have forgotten to wash this one" so I put back in the wash. Its counterpart is probably - or in the wash then the other one comes back from the wash having been found later but by then its counterpart is now in the wash and the two remain separate forever. I think that's what it is. Kat - (Laughing) Yeah that's the same circulating odd socks. Chris - Actually I just got an email from Drew Merchant and he says 'I had to take apart my wasjing machine recently and I found 3 socks stuck in the drain tube, so this is where I think they end up'.