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Podcast TranscriptThe Naked Scientists: Science Radio & Science Podcasts |
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Plants hide too!
The animal kingdom is full of species that do their best to hide from predators by adopting all sorts of clever camouflage to help them blend with their surroundings and not get spotted. And now it seems that some plants might do something similar.
Many plants are brightly coloured to attract pollinators or they take on the colour of the chlorophyll pigments they use to generate energy by the process of photosynthesis.
Matthew Klooster from Harvard University in US and colleagues have been studying an unusual plant called *Monotropsis odorata*, which doesn't have any chlorophyll because it gets all the food it needs from mycorrhizal fungus that live in close association with their roots.
Freed from the constraints of photosynthesis, this plant has the option of adopting different colouration to suit its needs.
As Klooster and the team discovered, it seems Monotropsis odorata does its best to hide from plant-munching herbivores by covering vulnerable purple flowers and stems in brown bracts that resemble dead, brown leaf litter.
By analysing the colour of light reflected by these bracts, the researchers found that they closely match the colour of dead leaf litter.
They also found that in the wild, plants with more intact brown bracts suffered around 20% less damage from herbivores compared to plants in which bracts had been experimentally removed. Plants with more intact bracts also produced between 7 and 20% more mature fruit over the two-year study than plants with no bracts, demonstrating the major advantage that this camouflage can have on individual plants.
The odd thing is that these plants don't want to disappear altogether, because they still rely on animals paying them a visit to disperse their pollen and seeds. Klooster and the team saw bumble bees successfully finding the flowers of these plants and think perhaps the bees are lured in by a sweet scent that doesn't attract herbivores - an idea for another study to work on.
So it seems that cunning camouflage is no-longer a unique characteristic of animals, but plants can do it too.
30th Nov 2009
Osmotic power plant
Osmosis is a process that is vital to the whole of life. It is based on a partially permeable membrane which will allow water through but not allow salts or other dissolved substances. If you put salty water on one side and fresh water on the other water will move through the membrane from the fresh water side to the salty one. This drives lots of processes in living cells and is the reason that soaking lettuce in water will make it swell and become more crisp.
Now a Norwegian energy company, called Statkraft, have made use of this effect in the world's first osmosis-driven power station.
The principle is to put seawater on one side of a membrane and fresh water from a lake on the other. Water flows passively through the polymer membrane from the fresh to the salty side, increasing the pressure of the seawater. This pressure increase is then used to drive a turbine to generate electricity.
The current installation uses a 2000 square metre membrane capable of generating energy at the rate of 2-4 kW. This is a promising start but there are many challenges ahead including optimising the membranes so that they are not compromised by impurities in the water and in cutting costs, but Statkraft thinks that there is the potential to generate 10% of Norway's energy by osmosis, and potentially more across the rest of the world.
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| - http://www.statkraft.com/energy-sources/osmotic-power/ | |||||
| - Power Production based on Osmotic Pressure. Article; Waterpower XVI, July 2009 | |||||
30th Nov 2009
New gene-screen "knocks-out" pathogen targets
Scientists have discovered a quick way to flush out how pathogens like bacteria and viruses target our cells. The system could show researchers where to target their efforts in developing the next generation of antimicrobials.
The research is presented in Science by Whitehead Institute-based scientist Jan Carette and his colleagues. The team use a human cell line called KBM7 which, unusually, contains just one copy of each chromosome (except for chromosome 8 which is present in the normal two copies). First the researchers infect these cells with viruses which insert themselves into the cells' genetic material in random places, adding a genetic marker and simultaneously inactivating the gene into which the insertion takes place.
Next the team expose the cells to a pathogen, such as influenza. Cells that are still vulnerable to infection will succumb, leaving behind just those cells in which genes that are essential for the pathogen to gain entry or to kill the cell have been deactivated. These genes can then be tracked down by looking for the genetic marker inserted into them previously. The team show that the method can be used effectively to identify genes essential for influenza infectivity as well as the cellular targets of a range of bacterial toxins.
At the moment, comprehensive identifications of molecular targets are excrutiatingly difficult because scientists have to painstakingly unpick the biochemical pathways involved. With this tool, however, researchers will be able to deploy the molecular equivalent of a drag-net to find everything at once, helping them to spot new targets for rational drug design.
30th Nov 2009
Why the strange head?
The peculiar shape of hammerhead sharks is a biological conundrum that has long puzzled scientists.
Now American scientists have uncovered some of the secrets of these odd hammer-shaped heads, showing that having eyes spaced far apart on their wide heads lets hammerhead sharks see better than more conventionally-shaped sharks. In particular hammerheads may have enhanced depth perception, a crucial skill for predators to judge how far away prey is before swooping in for the kill.
Various ideas have been put forward over the years to explain the hammerhead sharks' extraordinary compressed and laterally expanded head, known as a cephalofoil. Possibilities include greater sensitivity to smells or the weak electric signals given off by prey animals, greater lift and manoeuvrability in the water or maybe it helps in catching and manipulating prey. But until now, few studies have tested out any of these ideas.
The research team led by Michelle McComb from Atlantic Florida University set out to test another idea which has sparked a lot of controversy among shark biologists, namely, do hammerhead sharks see better than normal sharks.
To do this the researchers mapped out the 3D visual fields of various shark species, including three hammerheads (the bonnethead, scalloped and winghead hammerhead sharks), by anaesthetising each one and using an electrode they worked out if an electrical signal is generated in the retina when a narrow beam of light is shone into the eye from a range of angles.
Of all the sharks, the hammerheads had the most overlap of vision from their two eyes in front of them - and sharks with wider heads had even more visual overlap. The team also discovered that all the shark species tested had extraordinary 3600 vision in the vertical plane - they can see all the way above and below them.
One thing hammerheads seem to be bad at is seeing what's going on behind them. There are reports of prey fish hanging behind hammerheads, perhaps hoping not to be spied.
McComb and colleagues analysed videos of sharks swimming and found that to make up for having compromised vision behind them, hammerhead sharks swing their heads from side to side to see what's going all around them.
Of course, having better vision might not be the only thing that having a hammer-shaped head might be good for. But this study unveils one of the secrets behind the evolution of these amazing animals.
30th Nov 2009
Moved by the Power of Speech
Dr Bryan Gick, University of British ColumbiaChris - We often hear that people can move you by their words that they use. Well, it turns out that that’s actually physically true as well. Bryan Gick is a researcher of the University of British Columbia and he’s published a paper this week showing that actually we respond to the sensation of the breath of a speaker on our skin which helps to reinforce meaning. He’s with us now. Hello, Bryan.
Bryan - Hi.
Chris - Welcome to the Naked Scientists. Do tell us what have you been doing?
Bryan - Well, we’ve just been aiming puffs of air at people basically and seeing how that affects their speech perception.
Chris - So talk us through the experiment, what did you actually do?
Bryan - Well, initially, we thought that there are certain things that we can pick up in our environment that help us to perceive speech. And we haven’t had so much insight into how the tactile sense works into this.
Chris - So, in another words, we know that we’re comfortable with the fact that people lip read, for example, and so they help their comprehension of what someone is saying by following the movements of someone’s lips. But there’s an additional dimension to this which is the air coming out of their mouth.
Bryan - Exactly. And we aren’t particularly fond of the air approach, it just happens that the air approach is the best way to get at what kind of information could somebody be conveying, that you can just sort of passively pick up from your environment.
Chris - So how did you do this?
Bryan - So we thought about these little puffs of air that people produce when you say a sound like “pah”. If you put your hand in front of your face, if you’re an English speaker, you can feel a little puff of air in your hand. And if you say “bah” you don’t really feel a puff of air. So we took little tiny puffs of air and put them on different places on people’s bodies, and at the same time we played sounds that they could hear through headphones.
We found that if you if you play the sound “bah” to someone and at the same time, somewhere on the body, they feel a little gentle puff of air that’s inaudible to them, they’ll experience the sense of having heard “pah”.
Chris - Alright. So you can completely throw them off the scent and you can make them think they’re hearing a different sound because you’re pairing a puff of air which they would normally associate with hearing the “pah” sound and in fact you played them a “buh”sound.
Bryan - You’re right. So, a B will sound like a P, a D will sound like a T and so on. And this is interesting to us, not just because it draws up your perception, but it suggests something, I think, bigger which is that we really seem to take all the information around us from whatever sense modality is available and we incorporate it into percepts of the world.
Chris - Does it matter where on the person’s body you give the puff of air when doing this experiment?
Bryan - It doesn’t seem to matter. In the Nature paper, we looked at puffs of air on the neck and the hand and in other studies that we haven’t published yet, we looked at the ankle, for example, and we get the same effect anywhere.
Chris - So in other words, the brain is pretty clever in that it’s integrating information coming in from all over the place to reinforce the information that would be coming in just from the spoken language?
Bryan - Exactly. And it sort of challenges this traditional idea that you see with your eyes and that gets processed by a particular part of your brain and you hear with your ears and that gets processed by another part of your brain. It looks like our brains just perceive things and take everything in.
Chris - And obviously, people who talk on the radio or listen to a podcast, TV programmes, they have no problem interpreting what people are saying. So when would the body want to use this additional dimension of comprehension?
Bryan - Well, the way I view it, we’re biological parts of our environment and we, like everything, like the plants without chlorophyll, we use whatever we’ve got to get by. And in our particular case, if we happen to only have one sense modality available to us, we’ll get by. If however we’ve got all of our senses and they can pick up information from our environment, we’ll use it all and we’ll do it seamlessly.
Chris - So I guess that puts a whole new spin on the meaning “breathing down in someone’s neck,” doesn’t it?
Bryan - Yes, it does.
Chris - Bryan, thank you very much. That’s Dr. Bryan Gick, who’s a researcher at the University of British Columbia, paper in Nature this week, explaining how puffs of air can actually distort our perception of what people are saying.
December 2009
Swindon goes Wireless!
Chris VallanceHelen - And now it’s time to find out the latest from the world of technology. And this week Meera has been finding out how the Internet is transforming the town of Swindon.
Meera - Yes, it’s time to find out what’s been happening in the world of technology. So once again, I’ve come down to the BBC Television Centre in London to meet our resident techie Chris Vallance. Hello, Chris.
Chris - Hi, Meera.
Meera - Now Chris, what is this I hear about Swindon, the entire town of Swindon, becoming WiFi?
Chris - Well, there have been a lot of efforts to create municipal WiFi and Swindon certainly isn’t the first place to do that. What I think is interesting about Swindon is they’ve got a very ambitious project, a partnership with the local council and private enterprise. The aim is that the whole of Swindon Borough Council, 186 thousand citizens will have access to free WiFi by April of next year.
Now, they’re going to be offering a range of services, so the free service is going to be very limited, very basic and then there will be options to pay for services that are more like the regular kind of broadband service you might have at the moment at home.
Meera - So it’s not as straightforward as the case if you just live in Swindon you are going to have great free WiFi then?
Chris - No. I think you’re not going to have the same kind of experience you’d have with a paid package. The people behind this scheme, the council and Digital City UK limited their aim is that everybody in Swindon, whether in the borough of Swindon, where they live in a small village out lying in the town or in the town itself, will be able to get online.
What’s interesting is the way they‘re doing this as well, I mean, they’re starting in one village and then they’re rolling it out. So it’s not going to start like most schemes in the city centre where most users are. It’s also going to be WiFi-based which again is interesting. It’s not going to be a lot of digging up the roads. It’s mostly going to be around from WiFi boxes that operate in a mesh that connect with each other. So again that’s a different approach from approaches that have been tried before.
To get a little more information about this, I paid a visit to Swindon, and I spoke with Ricky Hunt who is the entrepreneur behind the scheme.
Ricky - This is a great opportunity to talk to people sending them information about its simple level when schools are going to be closed because of bad weather, updates on swine flu or traffic or whatever. So yes, we have a landing portal which will provide local information.
Chris - There is a problem acknowledged in the Digital Britain report, with access in outlying villages and rural communities. The main reason those places don’t have a WiFi at the moment, this is not economically viable. Why does it make sense for you to supply WiFi to these places?
Ricky - If you look at them individually, it doesn’t. But when you look at the whole, if we can put it together where we’ve got enough commercial services and fill in the some of the outline areas later, so it’s quicker and a lot cheaper than cable and that’s part of the key as well.
Chris - In fact we’re standing under one of the key bits of infrastructure of your project a lamp post, what was their role in the whole scheme?
Ricky - Our transmitters will sit on lampposts. It gives us access to power and of course, lamp posts are where people are. So we’ll use the lamp post as the power and it will create a mesh over the whole of the town.
Chris - One of the big costs with installing broadband is the simple infrastructure, digging up streets, laying cables, how does your system get around that problem?
Ricky - The boxes all connect to each other and at some point they’ll be linked to an exchange, maybe in two or three units, a Wi-Max backbone and then they will just all talk to each other.
Chris - An important part of your business plan is once you’ve built the wireless network here in Swindon, the extra services you can sell. Tell me about some of your plans there.
Ricky - Well, we have a range of products. We have energy monitoring, for example, and we all know, these products have been around for a while but nobody has been able to utilize them properly because they haven’t got connectivity. We’ll be able to monitor electricity at the beginning, but actually remotely intervene so if I left the lights on at home I can actually see it on my phone and switch it off.
And that’s quite unique. We will by, certainly in February, we’ll have gas and water as well, being able to be monitored and intervened with. We’ll have Medicare systems, where we can monitor people at home so, you know, when we talk about the hospitals trying to keep people in their home rather than in hospital, we have products that will facilitate that. CCTV, you know, we can monitor CCTV. You can have a look at it on your computer when you’re away, or we can have it live monitored for you by local company.
Chris - The idea of people having individual numbers or a growth of sort of domestic CCTV, and some people would be listening to that and thinking great. Others will be listening to it and starting to think about George Orwell, obviously, data and data securities are very important.
Ricky - It’s very secure. It uses the latest technology. It’s very, very secure, secure as anything that exists, probably a little bit more because technology’s moved on at the point becoming to the market. So, we’re very comfortable with the security, that’s not an issue, and there always people who don’t want to access this sort of technology. And that’s fine, they don’t have to.
Chris - So that was Ricky Hunt, talking about Swindon’s plans.
Meera - Now, of all of the towns in the UK, why Swindon? I mean nothing against Swindon, but why Swindon above everything else?
Chris - Ricky Hunt has very strong connections with the town. He’s really been the driving force behind it. So it’s purely the fact that he’s primarily based there. I think what’s interesting is that for them, it’s more than about just having the infrastructure in places. It’s about the extra services they can offer to people as well. So it’s very much a commercial model. It’s also a service that Ricky told me he feels could work in more places that just Swindon. And he’s quite keen, if Swindon is a success, to take the idea out to other towns and cities across the UK. So, we’ll see if that happens.
November 2009
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What makes steak tough? |
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Helen - That’s a great question and I don’t actually indulge in steak myself. But I know many people who like them and specially a nice tender steak. So I had a bit of a look around to understand more about the meat-eating habits of you lot. And it seems it’s quite an involved answer and there are various factors involved. These includes things like the breed of the animal, how old it was, and what I found really quite interesting was how you treat an animal just up to the point at which it’s slaughtered has an awful lot to do with how tender its meat is. Now that was really quite surprising. I was also having a read around and it seems that how animals are transported, if they’re herded with things like dogs that scare them and things like that can also really affect how good the meat turns out. And even if the breed of the meat is meant to be very good and very tender, if it’s treated badly just before slaughter, this can really harm great meat; so that’s something to bear in mind. In terms of toughness, a lot of it also comes down to the collagen because that’s the main tough part of the meat; it's the connective tissue, and as an animal gets older it produces more collagen, which also becomes more interconnected (cross-linked) which makes it tougher; so, in general, older creatures are tougher to eat! Also, weight-bearing muscles tend to have more collagen in them as well, so they tend to be less tender. There is a measure of tenderness, which sounds nice! It’s the "Warner-Bratzler Shear Force Test"... Chris - Bit of a mouthful, excuse the pun... Helen - It’s the scientific (objective) way of measuring meat tenderness - it’s the number of kilograms needed to shear, cut or pull apart a cubic centimetre of muscle. This measure varies from a tenderloin, really nice steak at about 2.6 through to a really tough cut of steak, which is more like five, five and a half. |
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November 2009 |
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Why does cutting hair make it stronger? |
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Chris - Actually, this is a myth. There is no evidence that cutting hair, shaving, doing anything like that actually makes hair grow more or adjust its strength or its length. Hair goes through three phases and its lifetime. The hair follicle has an anagen phase, when actually grows and makes hair and depending upon what sort of hair, where on the body surface you’re looking, that phase last different lengths of time. On the head, for example, it lasts for several years, whereas on the face, it might last for weeks and an eyelash, for example, only grows for about three weeks before it goes into the next phase which is called the catagen phase when the hair falls out. And that’s when the hair follicle stops for a while. Obviously, you can imagine if your eyelashes grew for three years that would be a bit disadvantageous because you’ll be looking out through under these curtains, won’t you? So, it’s good that doesn’t happen. Then the third phase is something called the telogen phase, when the follicle rests before it re-starts itself again. People often say when a person dies, their hair carries on growing after they die. Or, when you cut the hair it comes back far bushier. Both of those things are down to, in the case of someone dying, the skin dries and shrinks a bit around the hair coming out through the skin surface and this makes the hair look artificially a lot longer; and, when you cut hair, instead of having this tapered thin end, it’s got a very abrupt, cut off, sharp end, so the hair looks thicker when it comes back. So, it’s just sort of illusion; it’s not really any fatter. |
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November 2009 |
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How do solar panels turn sunlight into electricity? |
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A solar panel is a semi-conductor device which will produce an electrical voltage and current if light falls on it. It is actually a giant diode - a one way valve for electricity, and when light falls on it this gives some electrons enough energy to jump through the valve, and the only way they can get back is to flow around the circuit doing useful work. What is going on in more detail?Normally each atom in the semi-conductor has 4 electrons and there are none free, but if you add a few atoms with 5 electrons there are some extra electrons which can move easily and carry a current (an N-type semi-conductor). Similarly if you add some atoms with only 3 electrons and then you get some gaps which other electrons can move into (a P-type semi-conductor). The electrons can now move a bit like the tiles in a sliding tile puzzle, but it is easier to think of a positively charged hole moving through the semiconductor.
A diode is made if you join a lump of P-type semi-conductor to a lump of N-type. When you do this there are lots of extra electrons in the n-type region which will tend to diffuse into the p-type region and holes from the p-type region will diffuse into the N-type. So you end up wit the p-type region being negatively charged and the n-type region being positively charged.
If you connect the diode to a circuit, this charge will flow around the circuit evening out the voltage on the two sides, and you will be left with a region in the centre with no charge carriers.
Light can hit this non-conducting region in the middle with no free electrons , and knock an electron off an atom. This creates a free electron and a hole. These can then flow through the circuit as electricity and do useful work. The more light which hits it the more current and therefore power it will produce. |
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November 2009 |
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Does a spoon in the neck prevent Champagne going flat?We had some friends around on Friday for dinner. They brought with them a bottle of pink Cava. We didn’t finish it because they were driving home and we said, “Oh, well, we better stuff a bit of paper down to stop it going flat.” “No,” they said “Why don’t you try putting a teaspoon down the neck?” So we did. On Saturday, the day after, we thought we’d try it with some lunch; we took the teaspoon out, poured a glass and it fizzed up like nothing on Earth! “Goodness me, how did that happen? Why didn’t the bubbles escape with all the space around the teaspoon?” Gerry |
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Chris - There’s no evidence, unfortunately, Gerry, that this actually works. The bottom line is - the reason there is fizz in the champagne is because the champagne was turned into wine, in other words, had alcohol in it because there was yeast, which converted sugars in the original grape juice into alcohol. When you ferment something, you grow yeast in the absence of air, the yeast produces alcohol as a by-product of survival and it also produces CO2 as the other by-product. And if you put a cork in the bottle and pressurise the liquid, the CO2 can’t escape and therefore it dissolves in the liquid and you get a fizzy beverage. And to increase the "fizziness" of champagne what they will sometimes do is to add additional sugar after the primary fermentation and that encourages it to make even more fizz. If you take the cork off of a bottle of champagne or a fizzy drink, what you’re now doing is exposing the gas which is dissolved in the liquid to atmospheric pressure; this means that there’s now no pressure to hold the gas in solution and it would gently and progressively come out. And when you pour a glass of fizzy drink, you’ll see the bubbles arising from one point to a number of points on the glass and they stream upwards. That’s because there are irregularities or rough points on the surface of the glass. But there’s no reason why a spoon in the neck of the bottle should make any difference because the bottle is open to the air and, therefore, the air above the liquid is at atmospheric pressure and, therefore, the gas will move from an area of high concentration in the liquid to the lower concentration, lower pressure in the air. Therefore, I think this is a myth and you’d have to do a proper experiment and take several bottles of champagne and open them and put no spoon in them and simultaneously do the same thing with bottles of champagne with spoons in the neck and then have some objective measure of how much “fizziness” was in there and I think you’d find it wouldn’t make a difference. Would you agree, Dave? Dave - Yeah, I found actually on the internet, someone has done this experiment and the spoon makes no difference at all. The important thing is putting the drink in the fridge, which makes the liquid a lot colder. And the colder liquid is the more gas it can hold. So I think it will just lose its fizz a lot slower that you’d expect when it’s in the fridge especially if it’s in a very clean bottle. Chris - There you go, myth busted. Sorry about that, Gerry. Gerry - That’s a disappointment. Chris - Never mind. But drink the champagne up. I mean that’s the key thing, isn’t it? Gerry - Oh, sure, we will next time. Oh, thanks very much for that! |
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November 2009 |
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Gerry Myer asked the Naked Scientists:
Why does a teaspoon put in the top of a half filled bottle of Cava (or champagne) keep the drink fresh, with its bubbles until the next day at least (I've tried this - it does work)
What do you think?
- gerry myer - 29th Nov 09
Although I've drunk a fair amount of champagne and cava in my time, I don't ever remember hearing that one. But then the belief that it would go off if not drunk was always a good enough reason to finish the bottle (and have a new bottle the next day <wistful_sigh>I was getting 1976 vintage M&C for £11/bottle at the time</wistful_sigh>).
- LeeE - 29th Nov 09
We have done the experiment and it shows little difference. Let me repost the results here: Terry's Great Champagne Experiment! Day 1. 3.30 pm. Opened both bottles, and poured a glass from each. Drank said glasses. Both quite nice, despite being from $5 bottles and being consumed in the middle of the afternoon. Both quite bubbly. Placed both bottles in the door of my fridge. Placed a teaspoon in the neck of one! Stay tuned for further reports! ---- Day 2. 4 am (PT + 0/12:30:00) Drank two more half glasses, one from each bottle. No noticable reduction in bubbliness, no noticable variation between the glasses. ------ Day 3. 12.30 am (PT + 1/09:00:00) Distinctly less bubbly now than when first opened. No readily identifyanble difference in the bubblyness between the bottles. Swiss female research assistant concurs (at lest she did before she fell asleep). Day 3. 9.30 am (PT + 1/18:00:00) Little change from previous report. ----- Day 4. 3 pm (PT + 2/23:30:00) Wine is still in relatively good condition. Remarkably little degradation of bubblyness over the last 48 hours (at least my perception of it, as this aspect is not controlled). No readily identifying difference in the bubblyness between the bottles. ---- Day 6. 7.30 pm (PT + 5/04:00:00) What do you know. Still bubbly. Both bottles. ----- Day 9. 9.30 am (PT + 7/18:00:00) Remarkably, both bottles still have some fizz, at least on pouring. Both rather flat to drink, and it's starting to taste funny. ----- Day 14. 2 am (PT + 12/10:30:00) Poured two more glasses. Nearly flat, but still enough fizzyness to form a high density of small (diameter < 1 mm) bubbles on the glass. Tastes much better than last time. No observable difference between the bottles. In the interests of my reputation, I hereby declare Terry's Great Champagne Experiment completed. ----- The theory that a teaspoon placed in the neck of an opened bottle of champagne improves the longevity of the wine was tested by storing two bottles of Australian sparkling wine in a fridge with a teaspoon in the neck of one. The wine was sampled over a period of two weeks. The bubblyness of the wine from each bottle was tested by the investigator drinking a half glass from each bottle. Some of the observations were confirmed by Swiss female research assistant. The apparent persistence of effervescence---though not a controlled aspect of the experiment---was quite remarkable. At no stage was there a detectable difference between the wine from each bottle. The conclusion must be made that the "teaspoon in the neck of the bottle" theory be classed as an "urban myth". This experiment was conducted November 1999. Feel free to start a 21st century one. - JnA - 30th Nov 09
Absolutely brilliant! Thanks JnA ! Chris - chris - 5th Jan 10
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What would a substance at absolute zero look like? |
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Dave - I see no particular reason why it would look any different to how it would appear at any other temperature (below melting point). If its staying at absolute zero, especially if you can look at it and you’re shining light on it, then it’s not absorbing very much energy, because as soon as you shine some light on it, and if any of the light was absorbed, then its going to get hotter than absolute zero. But I’ve seen very, very cold substances down to sort of minus 270-odd and they look pretty much like other substances. Chris - Wouldn’t the pure act of looking at them, visualizing them, wouldn’t that put some energy and so it couldn’t be at absolute zero anyway? Dave - Yes. Essentially, if you’re shining light on them, you’re going to give them energy and you’re going to heat them up. And that said, it could be transparent, so the only one thing you could look at and keep at absolute zero will be transparent but it’s not to say that all things at absolute zero are transparent. Not that you can ever get there! |
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November 2009 |
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Davy Stump asked the Naked Scientists:
While watching a show on space, I had a question.
What would an object taken to Absolute Zero (0° K) look like? Would it be black, shiny, white, or what?
Thank you,
David Stump
What do you think?
- Davy Stump - 27th Aug 09
it depends on if light gives things it hits energy. i think it must. but that means it's no longer at absolute zero. so we couldn't actually observe things at absolute zero. i am not sure about this, though. what if dark matter is mass that can't be heated? is that a possibility? wouldn't that fit the criteria of being unable to be interacted with? - glovesforfoxes - 27th Aug 09
I don't think you can talk in terms of 0K but, at a very low temperature, there doesn't seem any reason why the surface charges couldn't be moved. That would produce reflection, if the energy gap was appropriate..
- lyner - 27th Aug 09
It's impossible to tell. We cannot even observe a zero-temperature. It seems to not even exist. - Mr. Scientist - 1st Dec 09
At a zero temperature all emanations will stop. As we only can define subatomic particles by probability and those are what makes what we call matter we better look at a subatomic particle first. And as that is a matter :) of probability only, unable to be defined as anything else? Well, I think it wouldn't be 'there' any more. - yor_on - 2nd Dec 09
You can't get to 0K but you can get arbitrarilly close. There's no reason why something shpould look different near 0K than at some higher temperature. Obviously, for example, if it's water it will look like ice rather than water, but that transition happens at about 273K. It won't seem to change much as you cool it further. - Bored chemist - 2nd Dec 09
It is a interesting question BC. Let us assume that you are right and that we take a particle to 0K and that it still is there. Well, to my eyes we then seem to have split times arrow from matter :) We would have us a chunk of primordial 'time' That as I think that matter just might be what creates time(s arrow) , and if we take it to 0K there will be no uncertainties any longer to it (HUP) which then should contradict all physics we have today. Crazy? - yor_on - 2nd Dec 09
Which part of "You can't get to 0K" didn't you understand? - Bored chemist - 3rd Dec 09
Shouldn't that be: "We can't observe 0K" ? - Nizzle - 3rd Dec 09
You cannot observe it because it cannot exist, and if it did the light needed to see it's colour would give it energy so it wouldn't be 0K anymore. But if it came up in a Star Trek episode my bet is it would be black. - ...lets split up... - 3rd Dec 09
Shouldn't that be: "We can't observe 0K" ? No. It's true that we cant observe it but since it doesn't exist that doesn't tell you a lot. It's like asking you for a description of my sister. I don't have a sister so it isn't just that you have not observed her, but that she doesn't exist. - Bored chemist - 3rd Dec 09
Shouldn't that be: "We can't observe 0K" ? No. It's true that we cant observe it but since it doesn't exist that doesn't tell you a lot. It's like asking you for a description of my sister. I don't have a sister so it isn't just that you have not observed her, but that she doesn't exist. I tend to agree with you Bored - it's pretty straight forward. Since no one has ever been able to observe or attain to such a temperature,is surely a proof alone that the temperature itself does not exist. There is always going to be half that heat of single quantum oscillator, where there is no absence of temperature in any square box of spacetime. - Mr. Scientist - 3rd Dec 09
I'm betting 0K would turn the universe to scrambled eggs, which might explain why the closer we get to absolute zero the harder it is to get there.
- ...lets split up... - 4th Dec 09
There is no state for the universe at OKelvin, because it doesn't exist. There would be no scramblin of eggs, because it doesn't exist. - Mr. Scientist - 4th Dec 09
I prefer my scrambled eggs hot anyway !!
- neilep - 4th Dec 09
Sorry BC got the impression you wanted to discuss it? thanks. - yor_on - 4th Dec 09
What is there to discuss? One of the laws of thermodynmics says you can't get to absolute zero. - Bored chemist - 5th Dec 09
Without observational evidence however, the arguement of what it may or could look like is redundant, especially in a vacuum were OK ceases to even have an existence. - Mr. Scientist - 5th Dec 09
Quite right BC, why even bother to say something? It would have been sufficient in that case to say.. It can't. Voila. the rest is just verbal subterfuge :) Don't know why I react at your answer, probably the tone of it? Uncivil? - yor_on - 12th Dec 09
if your talking about getting to "absolute zero" then, no, its not possible. we have attained -273 Celsius or -459.4 Fahrenheit. which is pretty close to -273.15 Celsius/-459.67 Fahrenheit (the supposed number of absolute zero). but it is impossible to remove all the heat from an object. something colder must exist to transfer the heat to, but since absolute zero is as cold as it gets it is unattainable.
See the whole discussion | Make a comment- ... - 10th Feb 10
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How does lead absorb radiation like x-rays and gamma rays? |
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Chris - Well, the reason that lead is a good choice is because it’s a very dense substance, because dense substances can get in the way of the radiation and soak it up. And the denser something is the more atoms, and in the case of things like x-rays and gamma rays the more electrons, there are to potentially interact with that ray as it goes through and stop it. So, if you look at the density of lead; lead weighs something like 11 grams per centimetre cubed. Iron, on the other hand, is only seven. So in other words, you can get lots and lots of shielding with lead for much less space than if you use, say iron or concrete, which doesn’t have the same density, although both could soak up x-rays in the same way. What happens is that the x-ray, which is effectively a light wave, when it goes through the material it’s interacting with the cloud of electrons around each of the atoms. And what could happen is the x-ray, when it does have this opportunity to interact with the electrons, can add some energy to an electron, and this can make the electron depart from the nucleus that it was originally orbiting. This can make an ion, for example, and the electron can then move away or be captured elsewhere. So what that does is basically turn the energy in the x-ray or the gamma ray into other forms of energy inside the material, so it’s basically a safe form of energy and a way of neutralizing the effects of the radiation. Lead is a good choice because it’s very, very dense, so you can pack in more protection into a smaller area than you would otherwise. But lead is very, very heavy to wear for personal protection! I’ve worn lead aprons when doing x-rays medically in hospital, and it really is very, very heavy. So I wouldn’t recommend it if you can avoid it! Dave - The other effect is because lead has got a very, very positively-charged nucleus. The electrons around the middle of it can absorb a huge amount of energy before they get kicked off the atom. So an electron which is very near to the centre of the nucleus, can absorb a much more energetic gamma ray or x-ray, than say a hydrogen atom, because in a hydrogen atom, the electron can take just a small kick to remove it, and so it can't absorb any more energy. |
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November 2009 |
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Andrew Wike asked the Naked Scientists:
How does Lead absorb radiation? and why is it used over other metals in x-rays?
What do you think?
- Andrew James Wike - 29th Nov 09
I'm not too sure if it absorbs it, more like blocks it..I think !! More klevur peeps will answer this I am sure. - neilep - 29th Nov 09
Lead is very dense and is a good electrical conductor. I suspect that lead does absorb the radiation so that the radiation becomes part of the lead. I haven't studied the dynamics of the absorption but it probably contributes to the energy of electrons in the lead. Some types of radiation could affect the nucleons causing the lead to become radioactive.
- Vern - 29th Nov 09
One of the odd things about lead is that it's not very dense. It's about as dense as silver but each atom is (about) twice as heavy so they must be packed quite loosely in lead. Anyway there are two ways that radiation gets blocked. Neutrons get stopped by absorbtion onto the nuclei of atoms but that's an unusual form of radiation. The other thing that happens is that X and gamma rays get scattered by the electrons in materials. Lead has a high atomic number and, to maintain neutrallity, the nucleus is surrounded by a lot of electrons. That's essentially what makes it a goos radiation sheild. Each time an Xray is scattered it loses some energy and once it's lost that energy it's no longer there. The conductivity of lead dosn't enter into it for most radiation screening (it would for blocking radio waves or visible light but they are not in the original question). Lead glass is used for blocking Xrays and it's a very good insulator. Lead isn't the only thing that gets used as shielding but it has the advantage of being fairly cheap. For some purposes concrete is more ecconomical and sometimes tungsten is used- it's not as good on an atom-for-atom basis but it's nearly twice as dense so there are a lot more atoms of it in a given volume. - Bored chemist - 29th Nov 09
If lead does absorb radiation, does it then become full ?...what happens to the radiation it absorbs ?
- neilep - 30th Nov 09
In the case of gamma and X rays it just warms the lead up a bit. For alpha and beta it might knock some of the atoms out of their nice orderly place in the crystal latice (yes, lead is crystaline). In the case of neutrons it might get "full" eventually, but the neutron flux to do that would need to be big- rather more than you get from a nuclear bomb.
- Bored chemist - 30th Nov 09
From what i remember in my general science studies is that lead can deflect most gamma energy. - Mr. Scientist - 30th Nov 09
Thank you all it makes sense now.
- Andrew James Wike - 1st Dec 09
If a material "blocks" some form of radiation, it either absorbs or reflects it. (Or a mix of both, I suppose). X-rays and gamma-rays are just very high-frequency (extremely short wavelength) electromagnetic radiation, like light. When these are absorbed, the energy is turned to heat. Materials don't become 'full' of light or electromagnetic radiation, so that's a non-issue. Because lead is a big atom it has a lot of electrons. This high density of electrons will tend to make it more opaque (absorbing) to high-energy EM radiation than other materials. For 'nuclear' radiation (alpha particles (i.e. protons), neutrons) these will get absorbed into the lead nuclei (which are much bigger, and more stable, than other common elements), where they will accumulate. Does lead have several stable isotopes? If so, then it can absorb a limited amount of radiation "permanently". Otherwise, some of the lead atoms will become transmuted into something else (possibly radioactive)... although these will still be distributed among all the other sheilding lead atoms, so it can probably take a very high dose of nuclear radiation before it becomes substantially radioactive itself? - techmind - 4th Dec 09
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Why do whales beach themselves? |
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Helen - That’s a great question, but unfortunately part of the answer is, we actually don’t know. In only around half of the whales stranded around the world is a cause found. And there are usually all sorts of things we know can cause whales to beach themselves, often fatally. These include things like diseases, trauma if they’ve been hit by a boat or something like that, or an anomaly in magnetic fields. We know a little about how whales use magnetic fields to navigate. If there’s an anomaly that doesn’t seem to make sense to them, or perhaps a change to a coastline, they might get confused, and that may lead them into an area that can’t escape from and eventually end up on a beach. Also, things like underwater noise has been implicated including military sonar though there’s very little evidence that is what’s going on. We need a lot more studies to really understand if that is a problem because whales can be very sensitive to underwater noise. We know that they can hear each other so if humans are being very noisy, that can certainly is likely to confuse them and end up having these big problems. You also have to remember that these mass strandings, when lots and lots of whales and dolphins end up on a beach, has been going on for an awfully long time. Since Aristotle's time people have been seeing these mass strandings, so clearly a long time before we were making really big impact on the oceans. This means that there must be a natural element to it as well. There are reports of increased mass strandings at the moment, but there are also more people looking for them and more of us at the coast. So that might be one reason, and we should really be taking all these things into account when we’re considering what’s causing it, and whether we should be trying to do something to stop it. |
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November 2009 |
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This is a real puzzle. It may be due to distortions in the Earths magnetic field, although it is questionable whether whales use this field for navigation. It may be due to shipping. In 2002, 14 beaked whales came ashore in the Canary Islands. Navy ships in the area were using active sonar. Some may come ashore due to illness making them too weak to swim. Or it could be that they come into shallow water for support during this time to avoid drowning and get washed further inshore than they intended by waves or left in too shallow water by receding tides. Only a couple of days ago 55 False Killer Whales beached near Cape Town. Volunteers helped them back into the water, but they turned back and beached themselves again. It has also been suggested that it could be due to pollution, but this strange phenomenon is known to have been going on for hundreds of years, so man cannot be blamed for this. The fact is, we just don't know the answer to this question. Read this interview with DARLENE KETTEN http://www.myhero.com/myhero/hero.asp?hero=Darlene_Ketten_06 - Don_1 - 5th Jun 09
I have studied seismic activity and Earthquakes around the world for over 26 years. I have found to prove that with most whales or Dolphins beaching is caused by underwater sounds from seismic activity is very excruciating on these animals and they beach to get out of the water. Even trying to put them back into the ocean they will simply turn around and beach again. I have noticed in my finding that a few days after the beaching earthquakes above 6.0 usually occur in the surrounding regions. An example late last month whales beaches in New Zealand near Wellington, a few days after Christchurch was hit be a 7.1 earthquake. I have much more evidence and information available on this. Sonar from naval submarines etc also upsets them. Its like a dog whistles, we can not hear it, but it drives dogs crazy.
Regards
Gary Matthews
Adelaide Australia
- Gary Matthews - 13th Sep 10
Diving pods of offshore toothed whales and dolphins (odontoceti) feed on squid above mid-oceanic ridges where they are often exposed to oscillations in ambient water pressure when shallow-focused earthquakes suddenly erupt in the seafloor below them. On rare occasion these changes in pressure are too excessive and/or too rapid to be counterbalanced by the whales' pressure regulating anatomy resulting in barotrauma in the sinuses and air sacs of each animal's head. Since echo-navigation and echo-location are not possible without intact and functional sinuses and air sacs, a pressure related injury in this system renders the victims unable to use their acoustic navigation system to determine their position and find food. Nor are they able to dive without suffering intense pain. The injured pod huddles together for protection against sharks and swims slowly away from the epicenter, but not in a random direction. Rather, increased resistance (drag) to swimming against or perpendicular to the surface flow will turn the whales headfirst and point them in the path of the least drag, which is always downstream with the flow of the surface currents.
Many barotraumatized pods recover after an unknown period of rest on the surface. Those that do not recover are eventually: (a) guided to a stranding beach by the surface current, (b) harvested by sharks and killer whales, or (c) die and sink to the bottom. Decomposing gases will form in the carcasses that sink in water less than 100 meters deep. After about a week underwater, the gases formed will re-float these carcasses and they will be carried by the surface currents to a beach.
Non-navigating whales, carcasses, and flotsam are deposited on beaches because the current that carried each grain of sand to build the beach in the first place, is the same energy determining the path of everything floating on the surface. Where currents wash shoreward, there are beaches, flotsam, and beached whales; where current does not wash toward the shore, there are no beaches, no flotsam, and no beached whales.
http://deafwhale.com/seaquake_solution/
See the whole discussion | Make a comment- D. Williams - 7th Aug 11
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What would happen if the moon was destroyed?I would like to know what would happen to the Earth if a meteor hit the moon and destroyed it - the weather and the tides and gravity, and stuff like that. How would that be affected if the moon was destroyed? Dave, London |
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Dave - Okay. There are two questions there. If a meteor hit the moon and blew it in to thousands and thousands of pieces, what would happen to the Earth? The short answer is that we would have a nuclear winter. You would put huge amounts of rock into the atmosphere. It would block out the sun. Chris - It will actually reach us, would it? Dave - If it hit hard enough to blast the moon into millions of pieces, then there would be enough energy that a significant portion of the moon would land on our atmosphere. You’ll get huge amounts of dusts in the atmosphere. All the plants would die. Chris - Because some people suggested that one way to mitigate against global warming is in fact to create a cloud of dust by mining the moon and ejecting material into orbit in the same orbit as the moon, therefore, creating a sort of buffer against solar influx, and this would cool down the Earth a bit. Dave - Yes. If you completely destroy the moon, it would be like that... Chris - In fact it would cool down a lot! Dave - A billion times over! And the Earth would be a pretty nasty place. The other question is if you just got the moon and took it away, and disappeared it somehow, what would happen? You’d immediately lose the tides because those are due to the moon’s gravity. And also, on a longer term, there would be some subtle effects; the axis of the Earth is actually stabilised by the moon orbiting it. The moon’s got huge amounts of angular momentum, so perturbations don’t tend to have a very large effect on it and it tends to stabilise the direction of the Earth’s axis over millions of years. So, if you then waited millions of years, the Earth’s axis would rotate and that could have all sorts of complex effects on the weather and life in general and also not having tides could have all sorts of strange effects on weather because you’re not mixing the oceans and the oceans move far more energy around the Earth than the atmosphere does. |
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November 2009 |
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Why are some hard boiled eggs hard to peel?Why is it that sometimes when you hard boil an egg, the shell membrane will peel off easily, whereas at other times, it’s really hard to peel the egg? You can’t actually separate the shell away from the inside of the egg. James in Cambridge |
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Chris - Well, I have one theory on this which is that, when you hard boil the egg, what you do is to create a potential vacuum because the proteins in the egg white denature and they form a solid in close apposition to the inside of the shell, squeezing out any air that was in there. And so what you basically get is the egg-equivalent of the thing that holds your tax disc to your car windscreen. - You’ve got a potential space there which if you have the egg shell's not separated, is being held squeezed on to the egg on both sides by atmosphere. And so you've basically got to create a bit of a vacuum before you can separate the two, and I think that’s probably why it’s so hard, in some cases, to peel it. Dave - It’s also possible that, especially if you’ve got an older egg, the white tends to shrink a bit. So you get a nice big air sac at the top when you put that into hot water, and that air is going to expand, and it might squeeze its way around in between the membrane and the shell and that might be making it easier to peel the two apart. |
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November 2009 |
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Why isn’t beetroot dye broken down by digestion? |
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Chris - Well, in some people it is, but in some people it isn’t. The chemical that’s in beetroot that makes them red and makes some people wee red and also pass red faeces, which is what can happen if you eat a lot of beetroot, is a chemical called betacyanin. It’s actually an anti-oxidant that the beetroot makes and it can be used a colour change indicator too, but it doesn’t necessarily breakdown in the intestines of all people. The things that seem to make it breakdown more are acidity, so if you have very strong stomach acid then it breaks down more. If you have weaker stomach acid, then more can get through into the small intestine, and there, pancreatic juice is alkaline. So that can encourage it to pass through into the colon which is actually where it’s absorbed. People have done experiments on patients who have had things called ileostomies, which is where you take the ileum, the terminal bowel, and you bring it to the surface of the skin. And you take the contents away into a bag, for example. If you feed these patients with the betacyanins in beetroot they don’t ever get beeturia, in other words, the red dye getting into their urine. That shows that the absorption must take place in the large intestine. The other things that seem to affect the absorption is a chemical called oxalate, oxalic acid, which you get from rhubarb and rhubarb leaves. That actually gets broken down by bacteria in the small intestine and in the large bowel. So it’s possible that there’s a combined effect whereby some people have a certain genetic makeup that makes them break this stuff down more than others because they have more acidity. It’s also possible that they have certain bacteria living in the intestine that breaks this stuff down more than others, and so that affects whether or not you see it appearing in the bloodstream. But in people who do get beeturia, what seems to happen is that the pigment comes through the wall of the bowel, doesn’t get broken down, goes around in the bloodstream, and then it gets filtered out by the kidneys and goes into urine, and makes urine go red. But what’s really interesting is that on its way to the kidneys, of course, it has to go through the blood. And I was rooting around on the Internet, and I found this wonderful paper. It was published in the Christmas BMJ 2005 by two doctors, Julia Handysides and Stuart Handysides, who work in Essex... What they did was to - well, they’ve written this paper. I’ll read you this because it’s hilarious. “One Sunday evening in 2004, our 11-year old son went to bed after various delaying tactics, arguments about friends staying up later, forgetting to brush his teeth, forgetting to come down for a drink of water, and so on. But shortly afterwards, the dining door room opens, and in he comes, cupping a bleeding nose in one hand and gripping the bridge of his nose with the other. We led him to the kitchen sink and helped him to clean up and stem the bleeding, but oddly, the blood on his hands would not wash off. And it also looked brighter than usual. The poor child was interrogated. Is this some kind of ruse or lark to stay up later? The bleeding stopped, his hands, although stained pink, were now clean and dry. Upstairs, we found crimson stains on the bathroom carpet which proved impossible to shift and remain there over one year later. Our garden’s harvest of beetroot was very good in 2004, and we had eaten some the day before the nosebleed. It dawned on us that on its way to staining urine, the pigment in beetroot might also stain blood as well.” So that means potentially, all of your internal organs are getting stained bright red by beetroot, and if you bleed, the stuff can come out and stain your skin. I mean, that’s just amazing! |
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November 2009 |
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Byran Spease asked the Naked Scientists:
Love your show!
I have a question for you.
What is different about colour in a red beetroot that allows it to pass through your digestive system without being absorbed?
Could it, or is it used for anything beneficial or practical?
Thanks,
Byran from Pennsylvania USA
What do you think?
- Byran Spease - 29th Nov 09
This was the answer given on the podcast to "Why isn't beetroot pigment broken down by digestion?":
See the whole discussion | Make a comment"Well, in some people it is, but in some people it isn’t. The chemical that’s in beetroot that makes them red and makes some people wee red and also pass red faeces, which is what can happen if you eat a lot of beetroot, is a chemical called betacyanin. It’s actually an anti-oxidant that the beetroot makes and it can be used a colour change indicator too, but it doesn’t necessarily breakdown in the intestines of all people. The things that seem to make it breakdown more are acidity, so if you have very strong stomach acid then it breaks down more. If you have weaker stomach acid, then more can get through into the small intestine, and there, pancreatic juice is alkaline. So that can encourage it to pass through into the colon which is actually where it’s absorbed. People have done experiments on patients who have had things called ileostomies, which is where you take the ileum, the terminal bowel, and you bring it to the surface of the skin. And you take the contents away into a bag, for example. If you feed these patients with the betacyanins in beetroot they don’t ever get beeturia, in other words, the red dye getting into their urine. That shows that the absorption must take place in the large intestine. The other things that seem to affect the absorption is a chemical called oxalate, oxalic acid, which you get from rhubarb and rhubarb leaves. That actually gets broken down by bacteria in the small intestine and in the large bowel. So it’s possible that there’s a combined effect whereby some people have a certain genetic makeup that makes them break this stuff down more than others because they have more acidity. It’s also possible that they have certain bacteria living in the intestine that breaks this stuff down more than others, and so that affects whether or not you see it appearing in the bloodstream. But in people who do get beeturia, what seems to happen is that the pigment comes through the wall of the bowel, doesn’t get broken down, goes around in the bloodstream, and then it gets filtered out by the kidneys and goes into urine, and makes urine go red. But what’s really interesting is that on its way to the kidneys, of course, it has to go through the blood. And I was rooting around on the Internet, and I found this wonderful paper. It was published in the Christmas BMJ 2005 by two doctors, Julia Handysides and Stuart Handysides, who work in Essex... What they did was to - well, they’ve written this paper. I’ll read you this because it’s hilarious. “One Sunday evening in 2004, our 11-year old son went to bed after various delaying tactics, arguments about friends staying up later, forgetting to brush his teeth, forgetting to come down for a drink of water, and so on. But shortly afterwards, the dining door room opens, and in he comes, cupping a bleeding nose in one hand and gripping the bridge of his nose with the other. We led him to the kitchen sink and helped him to clean up and stem the bleeding, but oddly, the blood on his hands would not wash off. And it also looked brighter than usual. The poor child was interrogated. Is this some kind of ruse or lark to stay up later? The bleeding stopped, his hands, although stained pink, were now clean and dry. Upstairs, we found crimson stains on the bathroom carpet which proved impossible to shift and remain there over one year later. Our garden’s harvest of beetroot was very good in 2004, and we had eaten some the day before the nosebleed. It dawned on us that on its way to staining urine, the pigment in beetroot might also stain blood as well.” So that means potentially, all of your internal organs are getting stained bright red by beetroot, and if you bleed, the stuff can come out and stain your skin. I mean, that’s just amazing! November 2009" - chris - 6th Dec 09
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How does temperature determine sex in some species? |
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Helen - That’s a great question. It’s a wonderful phenomenon that happens in lots of reptiles, and it also happens in some fish as well. Instead of having genes or chromosomes, that determine whether or not an embryo turns into a male or female, it depends on temperature. So for example, alligators: they will lay their eggs in a nest, and if it’s incubated at around 30 degrees, they will all turn into females. If they’re incubated at 33 degrees, they will all turn into males. And if you get temperatures in between those two, you get a varying mixture of males and females in a different ratio. So, clearly, the environment is telling the animal whether to turn into a male or a female. And it’s a wonderful question to think about how this happens, and also why this happens. Why should an animal benefit from letting the environment determine whether or not its offspring turns into male or female? Some of these questions were answered by a study in Nature last year by Daniel Warner and Rick Shine from the University of Sydney. They were working with these wonderful creatures called Jacky Dragon Lizards from Australia and they look wonderful, and they sound wonderful. And they have this temperature-based sex determination. But another good thing about them is that they've got quite short life spans, because the big problem with studying this type of sex determination in things like crocodiles and turtles, which also do this, is that they live an awfully long time. So to really to get the grips of what’s going on they’re not an ideal subject. But these little lizards only live for about three or four years and what they’ve shown is that a key event in the sex determination of these lizards is the conversion of testosterone into oestradiol, a form of oestrogen. This is brought about by an enzyme called aromatase, happens at very low temperatures and tells the developing dragon to become a female. What they did in the paper was to override the enzyme, and by blocking it they could artificially turn males into females even if they were being incubated at a female temperature. What that showed was that over a number of breeding seasons males actually have more babies if they were hatched at a normal temperature than if they were hatched at a female temperature. So really what they’re showing, and they’ve done this the other way around as well, is that if you’re forced to be the wrong sex, you’re not as good at having babies. So that reveals a bit about why this has evolved in the first place, and it gives us an idea of how it happens as well. But it doesn’t really explain in nature why it should occur. There has to be a benefit. It has evolved. We see it in many different species. So there have to be reasons why, at different temperatures, males do better than females because that’s what we see in all these different animals. This also leads us to think about maybe an ongoing problem we might have to face with climate change: that if in these animals their sex is being determined by a temperature and if that temperature is going up, especially of things like fish and the oceans, which we know may increase in temperature, it could start causing all sorts of trouble. So we will see. But it’s all rather wonderful and fascinating. |
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November 2009 |
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Joel Hillman asked the Naked Scientists:
Naked Scientists,
I had been taught that some animals genders can be decided by the temperatures and some other factors, for example, a warmer temperature will induce a male.
But now with my further studies (good old medicine!), in humans at least, gender is decided at conception, by combinations of X and Y chromosomes.
I would have assumed that these these would have been the same with humans and animals. Could you explain this please?
Joel
Johnny was a chemist, Johnny is no more,
What Johnny thought was H2O was H2SO4
What do you think?
- Joel Hillman - 27th May 09
It is advantageous for male crocodiles to become as big as possible, this can only happen when conditions are warm producing the maximum vegetation and consequently the maximum amount of prey. Also warm conditions enable the cold-blooded croc to be most active and able to catch more prey and become big as possible. - RD - 27th May 09
But how does it actually affect it? the advantages you stated are clear, but what is the physiological effect?
See the whole discussion | Make a commentThanks - Shadec - 12th Jun 09
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What distance separates two gamma ray bursts that are 13 billion light years from Earth each but in opposite directions?Recently, a gamma burst was detected in the sky from a star about 13 billion light years away. Would it be possible for a detection of a gamma burst from a star 13 billion light years away in the exact opposite direction with respect to our galaxy? If yes, how far would the two stars be away from each other? I don't think it could be 26 billion light years? Sean Thompson |
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Dave - The concept of distance gets quite difficult when you start thinking on the scale of the universe above anything else, because Einstein's relativity work says that depending on how fast you’re moving, distances can get compressed. The first thing is, because the (13 billion light year) distant gamma ray burst is moving at a very different speed to us, the space in between is going to get distorted due to relativity. And if we’re both moving at the same speed, then the burst would be about 30 light years away. The universe is expanding all the time in every direction, and as far as we can tell this expansion looks the same wherever you are. If you can see an object which is 13 billion light years away you are looking at it 13 billion years ago, in that time it is going to have moved away a lot, it should now be about 46 billion light years away. So in some senses, the two gamma ray bursts are now over 90 billion light years apart. However if the two gamma ray bursters could see one another then they wouldn't appear more than 13.7 billion light years away, as the only way one could see the other is right at the beginning of the universe when they were much much closer together. Chris - So why would you end up with the potential light wave that had or looked like it was 90 billion light years away? Dave - Well, the light hasn’t travelled 90 billion light years, the light has travelled 13 billion light years, but the object that emitted it has moved another 70-80 billion light years off in the other direction, so where it is now isn’t where it was when it emitted the light. |
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November 2009 |
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Why not mount a telescope on the International Space Station?I was wondering with all the maintenance that the Hubble telescope has shown to require why there isn't simply a telescope similar to it as part of the International Space Station? Wouldn't it be easier to maintain and operate? Joe DeLuco |
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Dave - The simple answer is that there are people on the Space Station, and they are doing things! For instance, if you pushed off the inside of the space station to move yourself down, the Space Station is going to move up a bit. Tiny movements like this, even though people are very small compared to the weight of the space station, are more than enough to ruin your pictures. So, if you want to make a good telescope, you want it to be as far away from anything else as possible. We don’t actually really want it in low Earth orbit at all, although the Hubble space telescope is, because heat from the nearby Earth can affect things. But you definitely don’t want any vibrations, so you want it away from any people, especially if they’re moving around. That's why they built their own satellite for the Hubble, independent of the space station. |
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November 2009 |
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Can the medieval warm period and little Ice Age be used to explain or be explained in terms of current climate models? |
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Chris - We think that it was something called the Maunder minimum and it produced the mini ice age in the Middle Ages, probably about 300 or 400 years ago. Italy was amongst the countries affected and it may be one of the reasons why some of the most wonderful violins ever made came out of that period - because the trees grew more slowly and the wood was denser during the cold period, which may explain Stradivarius’s success. But, we think that these weather conditions were down to, in that instance, a difference in solar activity; so people explain the Maunder minimum and the subsequent warming as an effect of differential solar activity, rather than the present climate change situation which is, we think, rising levels of CO2. |
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November 2009 |
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How many medical x-rays are safe?How much radiation are you exposed to during a medical x-ray? How does that compare to the dosage levels radiation workers are allowed to receive? Steve, Little Walden |
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We put this to Phil Clarke and Stuart Yates: Phil - Hi, I’m Phil Clark from the Particle Physics group in Edinburgh University. And first of all, when you’re discussing radiation dosage, it often gets quite complex due to the different ways to measure radiation and there’s often an abundance of different units like, rems, grays, sieverts, Röntgens, Becquerels, Curies and so on so that can confuse things so much. But the important unit of measurement is what known as the Gray (Gy) and that’s the unit of absorbed dose.
And one sievert is actually quite a large value so you typically measure in millisieverts, so thousands of sieverts. Now a typical standard chest x-ray produces about 0.1 millisievert and the dosage that are recommended for people working at CERN or the maximum dose is about 6 millisieverts. And if you’re a radiation worker it goes up to about 20, or if you’re an airline staff member, the usual measurement is 5 millisieverts. So the amount of radiation you get from an x-ray is actually quite small. Diana - That’s the physics of x-ray doses but what about the different types of x-ray scans? Stuart - My name’s Stuart Yates and I’m a radiation protection advisor working at Addenbrookes Hospital. Well, you get a very wide range of different x-rays giving different amounts of radiation dose, but taking a typical example chest x-ray, its’ very common lots of people might be referred to by the GP or hospital doctor. And a typical x-ray gives you about the same amount of radiation dosage you’d get in three or four days from natural sources of radiation in the environment and also natural radioactivity in food that we eat, for example, Brazil nuts contain radium and so they’re slightly radioactive. And so typically, a chest x-ray is about the same as eating three or four bags of Brazil nuts in terms of radiation dose. The CT scans I think can give you more radiation dose or your equivalent perhaps to a few years of natural radiation but then the benefit is also that much greater because the doctors will get that much more information and so one of the key things in all x-rays is that, you will only get that x-ray if the benefit outweighs the risk. Because radiation comes naturally from cosmic rays from outer space we’re actually quite well-protected at ground level from that radiation because of absorption in the atmosphere. But when we fly, we’re less protected because we’re higher up in the atmosphere and so typically you’d get the same amount of radiation dose from a chest x-ray as you would from say, a return flight to Southern Europe. Diana - So, a simple chest x-ray will give you 0.1 millisieverts. That’s the 60th of the dose limit for someone at CERN. However, a CT scan can give you up to 20 millisieverts of radiation which is four years worth of background radiation and that’s unless you live in some parts of Cornwall where it’s only two years worth because the rocks there emit lots of lovely radioactive radon. |
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November 2009 |
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I think a chest x ray (CXR) is the equivalent radiation dose to 4.5 days of environmental solar exposure...an abdominal CT, on the other hand, is the equivalent of about 4.5 years, so a significant exposure. Chris - chris - 26th Nov 09
I guess you also need to take into account the reason why the person is having the X-ray - if life is that dangerous to you then the risk from an x-ray is probably minor in comparison! Chris - chris - 27th Nov 09
Every doctor,chemist and biologist and all owe Physics a lot. physics and math helping all of fields. - ScientificBoyZClub - 27th Nov 09
I'm sure the dosage-level and risks for a medical X-ray varies considerably depending on the type of X-ray, and in general a CT-scan (computed tomography) scan will be much higher than for a conventional 'shadow' X-ray. It's a different situation really though, comparing occupational exposure for health workers against patients, as the patient hopefully only receives a few dozen X-rays in their life - whereas the health worker or other scientific staff who get occupational exposure probably see a much smaller exposure, but on a day-in day-out basis. A professor from my University who used to work with radioactivity and was continually monitored with a film-badge dosimeter says the only time it came back black (recorded significant dosage) was after he'd been on an international flight. I never quite ascertained whether it had gone through the hand-baggage X-ray scanner, or whether it was indeed blackened by in-flight cosmic-rays... Here's a pic of a film-badge dosimeter: http://www.nanobox.endoftheinternet.org/Download/files/Dosimeter/dosimeter.html Here's another pic showing the insides: http://www.malaysianbiomed.org/images/FilmBadge.JPG (the white tab is a lightproof wrapping for the photographic film contained inside) The organisation the person works for will usually send the films off to a lab for processing and assessment every few weeks. And another pic: http://www.bartsandthelondon.nhs.uk/ilibrary/filmbadge2.jpg I wore a film-badge just like this when doing my final-year undergrad project and as a PhD student where I did various experiments involving radioactivity. - techmind - 28th Nov 09
X-ray usage has not always been so tightly controlled ... http://en.wikipedia.org/wiki/Shoe-fitting_fluoroscope ]. - RD - 29th Nov 09
This is a relevant news story to your thread I feel http://news.bbc.co.uk/1/hi/8339877.stm It seems that, almost universally amongst people that I meet, the impact of physics on medicine is greatly appreciated. - Shibs - 29th Nov 09
Quote from the reference provided by Shibs above: "The public has voted the X-ray machine as the best invention, ahead of the Apollo 10 space capsule and Stephenson's Rocket. Out of nearly 50,000 votes cast, one in five people named it for having made the greatest impact on the past, present and future. Ten of the most significant objects in science, engineering, technology and medicine were selected for the vote." I was actually very surprised by this result because, despite the obvious benefits to modern health provision that x-rays have brought, the actual number of lives saved, relative to other interventions like antimicrobials - or even just plain old hand-washing, is tiny. I think people are swayed by the very visual nature of the x-ray and the fact that because you can see inside someone that must be good. But the reality is that most people die of things that are far too small to see with an x-ray - bacterial and viral infections and arterial obstructions. Cancers, I grant you, you can see on x-ray, but by the time they are sufficiently big to be visible they are usually incurable. So sorry radiologists, my vote therefore was for penicillin... - chris - 30th Nov 09
Ok, so your vote was for penicillum, hum?
Fine, when you get abdominal pain and think you have appendicitis, I think you should skip the cat scan and ask for penicillen and go home.
See what happens. When you need a CT, it is the BEST inventin of the world, we do not miss appendicitis anymore and the lawyers are mad. They are hoping to scare the docs with radiation worries, WHO CARES about radiaition if yo need to know about appendicitis?
Just skip your flight to hawaii for the next three years and turn off your TV for 500 hours.
Yes, so remember, you get penicillin, and no cat scan.
Fine.
Put that in your last will and testament.
- Real guy - 7th Jan 10
I have always wondered why the radiation goes up as you fly.
Could it be that there is an accumulation of radiation in the atmosphere because of atomic testing in Nevada , Muroara , and all those other places ? Also I always wondered why there is a slightly higher radiation count in the Rockies ? Could it be that there was open air boxcars with yellow cake going to a nuclear processing plant ?
See the whole discussion | Make a comment- lumos - 18th Nov 10
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It corresponds to one joule of energy absorbed by a kilogram of material. Now the different types of radiation like alpha, beta and gamma decays, result in different biological effects. So what you do is you have to take the grey number and multiply it by what’s often called the Q factor and an example would be for x-rays and electrons, the Q value would be one. So, if you multiply those two together, you get what’s known as the dose equivalent and the scientific measurement for that is a sievert.
Build your own airbrush - Applying Bernoulli
Find out how to build an airbrush to produce beautifully smooth paint finishes, and what this has to do with a car engine.
What you need
| A straw |
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| Scissors |
What to Do
Cut the straw into two halves.
Hold one of half-straw in your mouth.
Put the other half into the water, and hold, or tape it so that it sits vertically, with about 1-2cm emerging from the surface.
Use the straw in your mouth to blow quite hard, across the top of the other straw.
If nothing happens, try lowering the straw in the water.
What may Happen
You should find that when you blow hard enough, you produce a spray of tiny water droplets, just like an airbrush.
If you put some colour or paint into the waterm you can use it to paint with (though this could get very messy, very quickly, so make sure you do it outside).
What is going on?
Rapidly moving air will be at a lower pressure than when it is stopped. This is called Bernoulli's principle. So when you blow across the top of the straw, the rapidly moving air is at a lower pressure than the air above the water in your glass.
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One straw is set up to blow over the top of the other one. | The fast moving air is at a lower pressure than the air above the water, so the water is pushed up the straw. |
If you blow hard enough, the air above the glass will push the water all the way up the straw, and out of the top, where the rapidly moving air breaks the water up into tiny droplets, which are good for painting with.
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Eventually the water gets to the top of the tube, and is broken up into small drops by the fast moving air. |
Commercial airbrushes work exactly the same way, they just use higher pressures and better designed nozzles and produce smaller droplets.
This is also how fuel is mixed with air in an engine's carburettor: Air moves across a nozzle, and fuel is sucked up, and forms a fine, flammable mist, which is then burnt in the engine.
Why is fast moving air at a lower pressure?
Air, being a gas, can only be accelerated by a change in pressure. If the air is slowing down, then it must be going from an area of low pressure to a higher pressure, so the rapidly moving air must be at a lower pressure than the slower moving air.
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