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Podcast TranscriptThe Naked Scientists: Science Radio & Science Podcasts |
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Virus to blame for blood pressure
US Scientists have discovered that a common human viral infection may be linked to hypertension, also known as high blood pressure.
Writing in PLoS Pathogens, Beth Israel Deconess Medical Center researcher Clyde Crumpacker and his team infected mice with the rodent equivalent of CMV (cytomegalovirus), which infects 80% of human adults. They found that, compared with uninfected controls, the CMV-exposed animals had significantly higher blood pressure in the weeks after the infection.
They also fed a second group of mice on a high-fat diet and infected half of them with the virus. In the CMV-exposed group the animals again developed hypertension but also showed signs of early atherosclerosis (arterial disease).
To find out why, the team studied the animal's blood vessels and found that the virus was establishing a persistent infection in the vessel wall that led to the production of inflammatory hormones called cytokines including IL-6, TNF-alpha and MCP-1, which have been linked previously to vascular disease. The team also found increases in the activity of two genes that directly control blood pressure - renin and angiotensin.
Next, to find out whether the results also apply to humans the team infected human umbilical cord blood vessels with human CMV with the same results. These findings are important because CMV is part of the herpes virus family, members of which characteristically establish life-long "latent" infections, meaning that CMV is well-placed to provoke long-term injury to blood vessels that could lead to vascular disease. The next step will be to discover whether there is a real association between human onset of hypertension and CMV infection, which increases in prevalence with increasing age, just like blood pressure diagnoses...
17th May 2009
Ultradense deuterium
For a long time researchers have been interested in hydrogen because it is the most common element in the universe and because it fuels the nuclear fusion reactions that power stars. Nuclear fusion involves reacting light atomic such as hydrogen, or its isotopes deuterium or tritium together to form heavier elements. The problem is that in order to get the nuclei to react you have to get them very close together and because they repel one another this is very difficult. To get a decent rate of reaction you need to either have a very high temperature and or a very high density which is difficult because hydrogen is a gas.
For this reason scientists have been interested in finding other forms of hydrogen which are much more dense, one that has been known about for a long time is metallic hydrogen which exists in the centre of planets such a Jupiter and has a density close to that of water.
However researchers in Gothenburg, Sweden have been splitting deuterium molecules up using a catalyst and an electrical field, and studying what is produced by firing a laser into the products which will rip electrons off a pair of atoms. This means that you have two positively charged nuclei very close to each other, which immediately fly apart in what's called a coulomb explosion.
The researchers were measuring the energy of the particles being thrown off and discovered some which appear to have over 60 times as much energy as those from metallic hydrogen. This would relate to a bond length of about 2.3pm or a material with a density of 130,000 times that of water.
This is very interesting because if the nuclei start off this close together they would need far less energy to fuse than conventionally, although of course the lifetimes are measured in nanoseconds and the scientists have only made truly microscopic amounts of this material so far.
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17th May 2009
Natural Velcro helps bees get a grip
Flowers evolved a natural form of Velcro on their petals to help insects get a grip making it easier for them to pay a visit and collect nectar while carrying out that vital job of pollination.
Publishing in the journal Current Biology, Beverly Glover from Cambridge University led a team of botanists who set out to find a solution the long-standing mystery of why the flowers of many insect-pollinated plants are covered in cells shaped like minute cones or pyramids.
Glover and her team made artificial epoxy resin flowers both with and without the microscopic patterns of cone-shaped cells. They put sugar solution in the centre of the flowers and presented them to bumblebees in the laboratory giving them a choice of the smooth or rough petals.
When the petals were laid out horizontally, the bees had no particular preference for the rough or smooth petals, visiting each about half of the time. But when the petals were sloped at a steep angle, up until they were vertical, the bees preferentially visited the rough petals rather than the smooth ones.
High-speed films of the foraging bees revealed why they preferred visiting the rough petals. On the vertical smooth flowers, the bees were unable to get a grip: their feet were constantly slipping and they had to keep beating their wings to stay on the flower. Meanwhile on the rough petals, the bees quickly found a foothold and they could settle down and stop beating their wings, which saves them a lot of energy making their foraging visits far more efficient.
Previous studies have shown that bees can tell the difference between rough and smooth petals, probably by feeling them with tiny sensory hairs on the ends of their antennae. Glover and the team also tested out bees with a range of real snapdragon flowers, some with normal rough petals and a mutant strain with smooth petals. They found that when the flowers were held vertically, the bees visited the rough petals more often, presumably because they could get a better grip.
So it seems that providing insects with a safe landing pad, is one rather elegant and simple way that flowers make sure they pass on their genes to the next generation.
17th May 2009
Droplet Display technology
Most computer and TV displays work by actually emitting light, whether this is produced by making a phosphor screen glow in conventional TVs and plasma screens or from a fluorescent tube behind an liquid crystal panel in a modern LCD displays. This is great in a dark room but if you are outside on a bright day the sunlight completely overwhelms the light from the screen and of course making all that light uses up a significant amount of power so the displays tend to be power hungry.
The solution is to make a display that works like a piece of paper, reflecting light from outside, so no matter how bright it gets you can still see the picture, and you are not producing light so it needs less power. There are several technologies which do this in black and white such as the e-ink on some e-book readers, but they only change very slowly.
However researchers from the University of Cincinnati may have a solution that will give you full colour at video speeds. Their technology works using droplets of ink sandwiched between two hydrophobic surfaces. Normally surface tension pulls an ink drop into a sphere and it sits in a small well in the centre of a pixel. But if you apply a voltage the ink is attracted to the outer surface and it spreads out over the whole of the pixel changing the colour to that of the ink. If you remove the field the droplet shrinks back again, and if you make the pixels small it can switch very quickly. At the moment they have prototypes which can switch in 50ms which is almost fast enough for video applications but they think that they can improve it to about 1ms which is far faster than is needed.
This is still very much a prototype but they have monochrome displays working and they see no reason that they couldn't be made to roll up, so in a few years time you may be carrying one of these displays around in your pocket.
17th May 2009
World Hepatitis Day
Dr Joe Grove, Birmingham UniversityChris Smith - Now it might surprise you to know that around the world about one person in every 12 is actually living with a chronic infection of their liver, usually hepatitis C or hepatitis B, and those numbers totally overwhelm the numbers of people with pandemics that we are well acquainted with, things like HIV and flu. Not many people actually know about the massive disease burden that’s caused by these infectious causes of hepatitis and so to try and remedy this on the 19th May what has been set up is being called World Hepatitis Day and all over the world people will be gathering to try and run events to raise awareness of this. At the University of Birmingham researchers including Dr. Joe Grove will be doing just that and he is with us now to explain a bit about what they are trying to achieve. Hello Joe.
Joe Grove - Hi Chris.
Chris Smith - Welcome to the Naked Scientists. So tell us what you are actually hoping to achieve with the World Hepatitis Day.
Joe Grove - Okay, so like you said World Hepatitis Day would be a lot like World AIDS Day, to raise national awareness of the problem and we are holding an event to highlight the interesting scientific and clinical work that’s done here in Birmingham. The aim of the event is to raise awareness with the public and hopefully reach out to people to get tested. Also to engage with the patient community that’s in the U.K. and to highlight the important work that’s done at the University.
Chris Smith - What will you be doing during the day to tell people a bit about hepatitis B and hepatitis C?
Joe Grove - So we have a couple of MPs, Dr Lynn Jones who is our local constituency MP and Dr Brian Iddon who is a member of All-Party Hepatology Groups. They decide liver policy in parliament. They will be coming down. Also representatives from the local press and the local community and the patient community. We will be giving them a series of talks to outline the scientific research we do here on hepatitis C specifically but also the work that’s done to treat both hepatitis B and C in Birmingham and the clinical research such as clinical trials that are carried out here. And then we will be giving them a tour of the laboratories and also the clinical research facility in the hospital.
Chris Smith - So let’s just look at the actual disease that these agents cause and why you need to raise awareness about them. What are hepatitis B and C and why are they a problem?
Joe Grove - Hepatitis simply means an inflammation of the liver and if you had acute hepatitis, that is a short hepatitis, that’s not necessarily a problem. Viruses like hepatitis A or E cause acute hepatitis that self-resolve. Hepatitis B and C are capable of establishing a persistent infection. So individuals may be infected for the duration of their life. Now this becomes a particular problem because if you have hepatitis over this extended period of time you will start to get other symptoms such as liver cirrhosis and possibly even liver cancer. In the case of hepatitis C there are up to 500,000 people in the U.K. with an infection but 80% of those do not know about it.
Chris Smith - So that makes it a major issue because if they don’t know it they can pass it on because these are of course blood-borne viruses. You spread them by sharing blood, sharing needles, having sex with people. So people, if they don’t know they’ve got it can pass them on. So I guess raising awareness about them in the general population is very important because that encourages people to get tested.
Joe Grove - Yes, of course and also there are actually treatments. It is possible to treat hepatitis C and you have a reasonably good outcome of treatment. We have around 50% of patients resolving. However, people often don’t seek medical attention until the disease has become particularly apparent and by which stage it is harder to treat. So if there is anyone out there who are worried that they may have been exposed, they should get tested and then they got a much better chance of getting a resolution to the illness.
Chris Smith - Thank you very much Joe. That was Dr. Joe Grove who is a researcher at Birmingham University and he is hosting what will be Birmingham’s contribution to World Hepatitis Day on Tuesday - the 19th May 2009. Their events are actually on Monday 18th, so that’s tomorrow. So thank you very much Joe Grove for joining us on this week’s Naked Scientists.
May 2009
Weighing the Atmosphere
Find out how hard a vacuum cleaner can suck, what this has got to do with air pressure and discover how this helps us suck.
What you need
| A Vacuum Cleaner |
| Bathroom scales |
| Large, strong, clear plastic bag |
| A board about the size of your scales, the right sized chopping board would be ideal |
What to Do
Get your bathroom scales and place the board behind them - this should have the corners rounded off.
Put the whole lot inside your plastic bag. Wrap any excess bag around the scales and secure them with some sticky tape.
Put the pipe from the vacuum cleaner into the mouth of the bag and use your hands to wrap all the excess plastic around the tube.
Turn on the vacuum cleaner and see what value the scales read.† Some types of electronic bathroom scales are slightly too clever for these purposes. They will only actually give a reading once the force on them has stabilised. However many of these scales have a mode for calibration in the factory. Inside the box which holds the display there is often a black connector with two pins sticking out of it. This is sometimes behind a hole in the casing so you don't even have to remove any screws. If you connect the two pins together and release them, the scales change mode, and normally the first mode you come to is more conventional.
† Some types of electronic bathroom scales are slightly too clever for these purposes. They will only actually give a reading once the force on them has stabilised. However many of these scales have a mode for calibration in the factory. Inside the box which holds the display there is often a black connector with two pins sticking out of it. This is sometimes behind a hole in the casing so you don't even have to remove any screws. If you connect the two pins together and release them, the scales change mode, and normally the first mode you come to is more conventional calibration mode - beware this often disables the auto power off feature. To get the scales back to normal just pull the batteries out an replace them.
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The connector is sometimes in a hole at the back | It consists of two prongs sticking out of a black block |
What may Happen
Depending on the power of your vacuum cleaner and the surface area of your scales you will find that the scales will read up to and in fact significantly over 150kg.
What is going on?
Although air seems weightless it is actually reasonably heavy - every cubic metre at sea level has a mass of about 1kg. The atmosphere goes up many kilometres which adds up to a really significant weight which must be supported by the air closest to the ground. As air is very compressible this means that all the air around you is compressed by the air above it.
If you compress a spring it pushes back, and if you compress a fluid (something which flows like a gas or liquid), it will push back in all directions - it exerts a pressure. (This is why if you try and squash water between your hands it squirts out at the sides.)
This air pressure pushes on everything in all directions. However the scales can't normally measure this because there is the same pressure and therefore force pushing upwards from underneath the scales as there is pushing downwards, they exactly cancel out, so the scales read zero.
The vacuum cleaner pumps air out of the bag, this lets the air that is left expand, so like a spring it pushes outwards less hard.
Now there is less force pushing outwards than inwards and the scales measure this force.
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Normally there is the same air pressure pushing up as down on the scales so it reads no force. | But if you pump air out from the bag there is more force pushing down than up so the scales take a reading. |
A reading of 150kg seems like a very large force on a set of bathroom scales, but a vacuum cleaner only pumps out a fifth to a quarter of the air in the bag. Air pressure is actually 100,000N/m2 or the equivalent of 10 tonnes per square metre. So if you used a better vacuum pump and pumped out all of the air the force on your bathroom scales (which have an area of about 0.1m2) would be equivalent to nearly a tonne!
What has this got to do with sucking?
Because a gas can keep on expanding forever, it is impossible to pull on it. When we suck on a straw to drink some refreshing lemonade, what actually happens is that we reduce the pressure inside our mouths. This means that the air in our mouths pushes less hard down on the lemonade compared to how hard the air outside is pushing, so the air outside pushes it up the straw.
Written by Dave Ansell
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Why are electric kettles so noisy? |
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Chris Smith - Ah, yes my kettle is no exception and the reason that kettles are noisy, they make that sort of thumping and bashing noise as they boil and then the noise intensifies as they warm up and then it goes silent as they boil. It is because of the way that the heat is being transferred into the water. So you have an electric element inside the kettle, a high current is passing through that element which makes it get hot. The heat from the element is therefore transferred by convection and conduction locally onto the water molecules around the element; they then get excited and get hot. So you have a bubble of hot water around the element which tries to expand and it also floats upwards away from the element because, of course, warm things rise but as it rises of course it loses its heat again to all of the surrounding water. So this bubble of water and water vapour collapses in on itself very quickly and that’s cavitation and you get a shocking, sort of knocking noise. So those thumps that you hear and the sort of ‘shhh’ hissing that you hear, as the water vapour bubbles collapsing on themselves and emitting some sound waves, that’s what the sound is.
Helen Scales - It makes more noise I think when I have less water because I try and have as little as I need for a cup of tea, obviously covering the element but not lots more to save on energy and I think that’s noisier. Chris Smith - It could be there’s a bigger rezonant cavity inside the kettle because the bubble makes a sort of note inside the cattle and if you got lots of free space then the air will help to move around and bounce and sound around inside the kettle like an echo chamber. So that might be why you are hearing more sounds, probably what’s going on. |
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May 2009 |
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jeffaziz asked the Naked Scientists: Chris, Couldn't be a bigger fan of the show; it's gotten me through many a blue morning. My question is as follows: I'm a tea drinker (partial to Darjeeling, but Typhoo will do in a pinch). At the moment, our kitchen is being re-modeled and we lack a gas range. My wife bought us a lovely electric kettle; it boils water about twice as fast as I could do on the stove top. The interesting fact about it is this: it makes a surprising amount of noise, a sort of rushing, crackling sound. Now, the kettle has no moving parts (well, the power switch). It seems clear that it must heat the water by electrical resistance. Where does the noise come from? I mean, it must result from the heating of the water, but what's the physical mechanism behind all the racket? Thanks, Jeff Aziz University of Pittsburgh What do you think? - jeffaziz - 23rd Mar 09
When you heat water on the stove, the layer at the bottom is the first to boil, meaning it turns into a gas. The water vapor collects into bubbles, which rise toward the surface, passing through cooler water en route. The lower temperature causes the vapor to recondense into liquid and the bubbles collapse, making a noise. This gets gradually louder, as bubble production increases, until the water is so uniformly hot that the bubbles make it to the top without popping. At this point the noise diminishes. But it takes a moment before the vapor pressure builds up sufficiently in the top of the kettle to make it start whistling...
See the whole discussion | Make a commentIt's not like electrical imbalance in the kittle Regards Raghu - raghavendra - 23rd Mar 09
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Dave
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Do Fish Sleep? |
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I have got a question for you Helen here. It is from Glenn Colson who says: ‘Do fish sleep?’ Helen Scales - Well I think Diana talked about on Question of the Week a couple of weeks ago about whether fish have eyelids and they don’t. So can they sleep? The answer is yes, they can but it also depends on how you define what sleep is because in humans the transition into sleep involves changes in the patterns of brainwaves in an area of our brain called the neocortex and fish don’t really have the same development in their neocortical region as mammals, really. So it’s kind of difficult to say in the same way what sleep really means for fish but they do. If you count up things like a reduced metabolic rate and slowing down activity then they do seem to sleep and Zebra fish, which are fresh water fish, have been studied in the laboratory. If you watch them, and I think this is rather sweet idea that. You can watch them during the day and they will actually sort of doze and their tails droop down and they stop moving around at certain times of the day and they do seem to sleep. That’s one thing and in Antarctica, actually only last year they discovered the first hibernating fish and apart from mudfish that aestivate and keep themselves alive when things dry out. In Antarctica they actually slow down and stop feeding and their heart rate slows down. They used heart rate monitors on these fish to see what was going on and we think that it was probably because it gets darker in the winter in Antarctica. In fact it gets completely dark because there’s no sun and they find it hard tracking down their prey because this prey is still out there but they are visual hunters and without the light around they find it very difficult to find their food so they sort of stop. Chris Smith - They just sleep. Helen Scales - And they’re a bit like bears. Some bears don’t sleep the entire winter. They will actually kind of wake up every few weeks, have a little wander around, find a bit food, go back and sleep again. That’s what these Antarctic cod seem to be doing as well. Chris Smith - It’s quite interesting because Glenn has written a few things he spotted and this question was provoked by things he actually saw himself. He says: ‘A few years ago I was on a night dive in the sea of Cortez and we actually think we saw a fish sleeping in a number of different ways. There were fish in caves or nooks that were awake but only slightly responsive. There were also fish lying on the sea floor looking like they were dozing soundly and they weren’t at all perturbed by our diving light and there were others that had wrapped themselves in a cocoon of slime that seemed to act almost like a protective blanket.’ He says, ‘I suspect they have nightmares as well because as we watched a large moray eel swam slowly across the bottom of the seafloor stopping to sniff prospective meals as they were snoozing and then choosing his favourites but the moray left the blanketed fish alone.’ A wrass he believes (which he found interesting) because he said that the eels and they normally find it quite tasty. Helen Scales - Yes, they are parrot fish and they produce this kind of sleeping bags and we do think that stops them being able to smell, the predators can’t smell them but there are other fish that come awake at night. In fact if you go night diving you see a completely different eco system really because the ones that were sleep during the day tend to come out. They are often coloured red because they actually, that means they can’t be seen at night because the red colour is absorbed when light is absorbed in the water. So you see kind of a shift change in day and night fish when you go night diving.
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May 2009 |
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Glen Carlson asked the Naked Scientists:
Hi Sci guys.
Last week when I was listening to your podcast you discussed fish sleeping.
A few years ago I was on a night dive in the Sea of Cortez, we saw fish sleeping in a number of ways. Fish in caves or nooks awake but only slightly responsive, fish lying on the sea floor dozing soundly (not at all perturbed by our dive lights) others that wrapped them selves in a cocoon of slime, which seemed to act as a protective blanket.
I suspect they have nightmares too. As we watched, a large moray eel slowly swam across the bottom of the sea floor stopping to sniff prospective meals as they snoozed, and choose his favourites.
The moray left the blanketed fish alone, a wrasse I believe, which I found interesting because usually eels find them quite tasty.
Cheerz,
Glen.
What do you think?
See the whole discussion | Make a comment- Glen Carlson - 7th May 09
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How do re-writable CDs and DVDs work?How do re-writable CDs and DVDs work? We know that when you burn a CD you are burning tiny pits into CDs and DVDs to make digital recordings of sounds and images but how can you then undo that so you can rewrite them hundreds of times? John Campbell |
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Dave - Okay. A normal CD works by just having a sheet of aluminium with lots sort of pits in it. You make the pits by having a glass. You etch a glass thing which you push into the sheet of aluminium, that makes the bumps in the aluminium and then shine a laser on it. Then they get reflected differently from the pits and tops and bottom of the pits and you can read that information and then that information gets turned into sound and you can hear it. The sheet of aluminium is a shiny thing. It’s encased in polycarbonate and so it’s nice and protected. A recordable CD works by having the same polycarbonate disc. They have a layer of dye over the top. This dye is sensitive to light and we have a shiny thing behind it. There’s various different kinds of dye with different - some little better than others and survive a long time that’s why you have different colours of CDs and CD-Rs and so it changes colour. Chris Smith - Oh so when you zap it with a laser rather than burning hole in it what it actually does is changes the dye configuration so that what the reader is looking for is a dark spot rather than a hole. Dave - Yes, and the dye changes colour. Chris Smith - And then when you come along with another laser you can what, reset the dye to it’s original colour which overwrites the… Dave - I think they then hit it with a different pair of laser which heats it up to a different temperature which then re-sets it and then it cools down slowly and so it zeros everything and then you can come along with the second type analyser and we rewrite it. |
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May 2009 |
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Do cold feet mean more colds?Hi guys! My parents have been telling me I should wear socks all the time or I’ll get ill. So my question is does having moderately cold feet really increase your risk of catching a cold or the flu? Emil Sorenson, Denmark |
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Chris Smith - My own take on this is no, because I have chronically cold feet. But they say “cold feet and cold hands - warm heart” so I am all right. But there’s no real evidence connecting going out in the cold with catching a cold. It’s one of those urban legends that gets trotted out, “don’t go out with wet hair because you might catch a cold.”
The only sort of exception to that is if you get very very cold and you get so cold that you get damage to your mucus membranes, your linings of your nose in your mouth, then of course you might make yourself, if you get cracked skin or break down of the mucus membranes more vulnerable to say a bacterial infection coming in on top. So you have to be careful for that but there’s not actually any evidence connecting getting cold or washing your hair and catching more pneumonias or colds or viruses. So you are probably okay Emil. |
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May 2009 |
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The only real evidence in this favour was there was some studies done in Scandinavia in people who were dong very severe exercise and they found that in those individuals, exposed to very cold extremes as well, taking some vitamin C did help to ward off colds, but on the whole getting cold doesn’t increase your risk. It’s actually physically being exposed to the pathogen that increases your risk.
Tech Update - E-Books and E-Readers
Chris Vallance, BBC Technology CorrespondentMeera Senthillingham - Yes, I am at the BBC television centre in White City in London with our tech expert Chris Vallance. How are you Chris?
Chris Vallance - I am fine, although the sun seems to have disappeared today, doesn’t it? After such a lovely week and then we sat outside and it’s actually grey and miserable but there we go, that’s British summers for you…
Meera Senthillingham - Well, other than the horrible weather what have you got lined up for us in terms of technology this month?
Chris Vallance - Well, when the weather closes in there’s nothing better than to curl up with a good book. Of course there has been lot of tech excitement around the launch of the latest version of Amazon’s E-book reader with a bigger screen.
Lot of excitement about whether e-books are one of the ways forward for publishing and it’s not just Amazon that are in there, there are number of other companies vying for this space. We got Sony. We are even expecting a couple of British entrants into the market; two E-book Readers due out maybe later in the year, one from a company called Cool-er and the other one from a company called Plastic Logic which I believe that technology has been featured on the Naked Scientists before, so a lot of excitement in this space.
Publishing and technology have been well developing hand-in-hand for a while now. A lot of publishers are starting to get into social media in a really big way. as a way of marketing books, as a way of engaging with fans, things like YouTube, Twitter, Blogging, all of that publishers are starting to embrace.
I have been speaking to one of the guys, if you like, ‘leading the charge’ into this field in the publishing industry. His name is Jeremy Ettinghausen and he is the digital publisher at Penguin Books.
Jeremy Ettinghausen - For some authors blogging and going on Twitter and making videos on YouTube has given them routes to get closer to their audience and engage readers outside the very specific work of their book.
Chris Vallance - For those authors that do engage in it, what’s in it for them?
Jeremy Etthinghausen - It allows them to tell the readers where they are going to be if they are doing events, tell them news about publishing events, when their new book’s coming out, special offers, that sort of things but it allows the reader to get closer to the author and that in terms of pure kind of commercial things can’t help but sell more books.(34:10).
So ‘We tell stories’ was the project where we paired up authors and game designers. We had six stories running over six weeks, the first one was told on Google Maps and you could follow the character as he explored England and had several adventures.
The last story was by Mohsin Hamid who was short-listed for the Booker Prize last year and he made a very elegant take on a choose-your-own-adventure story and the idea of you know, very literary, prize-winning author creating a kind of detailed schematic for the structure of a choose-your-own-adventure story was absolutely thrilling.
Chris Vallance - And that was Jeremy Ettinghausen talking about how social media is important for publishers.
Meera Senthillingham - Now what about the authors involved in this technology?
Chris Vallance - Well, it’s fair to say not all authors are interested in this at all but I have been speaking to one, he uses Twitter quite a lot to engage with fans and to talk about his work. His name is Nick Harkaway and he is the author of the book ‘Gone away world’.
Nick Harkaway - The wonderful thing about Twitter is not only is it a kind of level playing field where your reader is confined to you and you can talk to them and you don’t have to worry about this concept of the ‘fan’, you can just be people talking about stuff that you like but you can also find authors and you can track down people you admire and say ‘I really like you’, and then feel very embarrassed about it afterwards but it works very well.
I think the really important thing is to be genuine. There are lot of people on social networking sites and Twitter in particular who have that publicist kind of Twitting for them every second and its very obvious and it’s slightly disappointing. You can’t just kind of implant the idea that they must go and buy your book in someone’s head, like an alien egg, you just leave there; it will hatch and you get sort of two pounds nienty nine or whatever your royalty is. You have to be there and engage in the discussion and that’s probably the most important thing.
Chris Vallance - And it’s not limited by genre?
Nick Harkaway - Ben Ocre-twitted a poem line-by-line the other day and P.D. Smith who wrote ‘Doomsday men’ - fantastic book, is constantly Twittering. You find everybody. Susan Hill has a weblog, it’s all sorts.
Chris Vallance - Are there any dangers?
Nick Harkaway - Yes, that you spend too much time and have too much fun, other than that I think it’s no more dangerous than taking a bus.
Chris Vallance - That was author Nick Harkaway. So we got two developments – one, the hardware, the advent of e-books and the other in the way in which you engage with your favourite writers, that you might be able to chat them on Twitter. You don’t have to write a letter to the publisher anymore.
Meera Senthillingham - Now what are your thoughts on this Chris, how popular do you think e-books will become?
Chris Vallance - I don’t know. There’s something about the experience of having a book that’s unique to the physical product, the feel of the book, the way it’s published, the cover and all of that and let’s face it, you don’t want to start reading your e-book in the bath and books are kind of - the fact that they’re slightly disposable and get dog eared, that’s kind of part of the fun of a book, isn’t it?
But on the other hand books do take up a lot of space. I mean in my own home practically every surface is covered with books. It would be a lot nicer if I could just reduce it down into an electronic format. So I guess there are pros and cons.
I think what’s interesting is the way that technology is trying to replicate some of that physical experience of having a book, the screens on these devices are reflective they’re not luminous. They feel more like paper they’re useing this e-ink technology.
I think the really interesting thing would be how these devices effect sales of publications and newspapers. Obviously that’s the magazines and newspapers are having a difficult time of it at the moment. Will reading them on e-books help rejuvenate that industry? I think a lots of interesting questions. I don’t know the answer to your question, very long way of saying that. I don’t know whether they will replace existing books. My guess is probably not.
Helen Scales - So E-books may not replace genuine old-fashioned books but they will certainly save us some space around the house and it’s great the authors can now interact with their readers, gives me something to think about as well because my first book is coming out later this year.
That was Chris Vallance talking to Meera Senthillingham about the latest technology in the field of electronic books or e-books.
Chris Smith - I don’t think that these electronic formats are quite as tangible. They are not as nice as the paper book. I just can’t feel I can bond with them the same way as I can with…
Helen Scales - No, you can’t, and you need them on your shelves and I think, yeah you say, Amazon never got rid of bookstores still. I mean they are obviously going through problems at the moment but economic problems at the moment but we still love to go and browse on bookshops, don’t we? There’s a certain feel and smell about it that we all love.
Chris Smith - Absolutely. This is the Naked Scientist with Chris Smith, with Dave Ansell and with Helen Scales. It’s our science pone-in show. If you have any science questions for us then do drop us a line. It’s 0845 30 50 007 on the phone, our text number 07786 20 1960 – the email address for the program as ever – Chris@thenakedscientists.com.
May 2009
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How does evolution produce new genes? |
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Chris Smith - So in other words you’ve got huge panoply of life on earth, all of it descended from some ancestor that must have got started something like 3.9 billion years ago, that’s when we think life started on earth, how do we have this massive and dramatic genetic diversity we have on earth today?
Now in copying the DNA, a job which is done by enzymes — miniature machines in cells that read a DNA chain and then make an identical (hopefully) copy of it; then you end up with faithful transmission of the genetic message from one cell to another. But occasionally mistakes occur and there are a variety of reasons why mistakes can occur. One of them is that those enzymes that do the copying make a mistake, it’s like me copying a book – I’ve got a book opened in front of me and I’m reading off the book and making a new copy in a second book, I might miss-copy and make some mistakes. Secondly, there are things coming in from the environment that can damage DNA. There are drugs, there are chemicals in the environment; there’s also radiation in the environment that could be ultraviolet radiation, it could be chemicals you take into your body, you could be living in Aberdeen and breathing the radon gas that comes out of the granite there. Anything radioactive that gets into your body can also damage DNA. If that happens to the cells that are making your gametes, your sperms or eggs, that can lead to mutations — changes in DNA. This can cause DNA to rearrange itself, bits of DNA can get copied or duplicated, and this means that there’s the opportunity for new genetic combinations to emerge; and once they emerge they can then get co-opted or changed or manipulated in order to do other jobs; and we know this happens because if you look in human DNA you can find the ghosts of genes long dead hidden in our genetic closet. You can find for example, lots of old genes that used to make our haemoglobin which are now no longer effective, and no longer functioning. They’re called pseudogenes. But this is where we have copied the genes somehow and then its becomes deactivated but it’s still in the genome. Now some other process could come along and reactivate that gene and use it for something else so it’s a way of making genetic diversity. Another way this happens, is something called transposons, you have bits of genetic material that can literally jump and they take themselves out of one bit of your genetic material and put themselves somewhere else carrying bits of DNA with them, and so this is another way of rearranging your genome and producing new forms of genetic sequences which can then become other important genes.
The interesting thing is that the slug has had to steal some genes from the algae in order to power those chloroplasts in its own cells, and the only way researchers think that could happen is if a virus added the genes to the slug in the first place. So the answer is, it’s very complicated but it seems that with nature and evolution, almost anything is possible. |
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May 2009 |
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Destini asked the Naked Scientists:
This is a question posed to me by one of my students who is seeking to find his own understanding of the world: How does macro evolution occur? In other words, how does natural selection ADD new alleles to the genetic sequence?
What do you think?
- Destini - 12th May 09
All evolution will be a result of some kind of genetic error. Most genetic errors are small, like substitution or deletion of a single nucleotide. However, some of these genetic errors can involve duplications, sometimes of small sections of DNA, sometimes of entire chromosomes (think of Down's syndrome, where 3 copies of chromosome 21 are present instead of two as a result of failure of the chromosome to split during meiosis). I would guess that evolution may 'occur' when a duplication occured that didn't impair the hosts ability to reproduce. Even more so if the duplication somehow enhanced it. The wikipedia entry for gene duplication talks about it in more detail that I ever could, so here's the link! http://en.wikipedia.org/wiki/Gene_duplication - fishytails - 12th May 09
Fishytails may have the answer to some genetic change, but I think Destini's student may be looking more to the genetic codes which determine such attributes as the leg ability. For example, say there was once a Forum Goat, which evolved on the plains. With the expansion of the species, some of these goats found themselves living at the foot of a mountainous region. They begin to venture off of the plains, into the mountains, where a nutritious plant will be available only to those adapted to this terrain. The first 'changelings' find these ventures difficult because their hoof is not adapted to this terrain, but as the generations pass, the hoof becomes more and more adapted this type of terrain. The end result, we now have two species of Forum Goat, the Plains Forum Goat and the Mountain Forum Goat, they are identical except for the differently adapted hoof. How are gradual adaptations, such as this, genetically passed down the generations? - Don_1 - 13th May 09
I am assuming that my interpretation of Destini's question is correct. The answer actually lies in the question itself. In the case of our Forum Goat, only those individuals which manage to move around on this new mountainous terrain with relative ease will actually venture into such a habitat, those which are unable to cope, will remain on the plains. Look at it this way, some of us can don a pair of ice skates and manage to stay upright and even move around on the ice rink, while others, me for instance, will venture onto the ice and go arse over tit every time. We are not predisposed to ice skating, so we keep off the ice. The other show off's are, so they stay on the ice. Don't you just hate those clever buggers??? So it is with our Forum Goat. Those which have taken to the mountains will mate among themselves, thus bearing offspring with the same capabilities. These capabilities to deal with this new situation, are in fact already in the genetic code of these particular individuals, but not in the genetic code, or not so well defined in the genetic code, of those goats which have to remain on the plains because of their inability to cope with the new terrain. Because these individuals become separated from the others, they are mating with other individuals with a similar genetic code, therefore, this will become more pronounced in the offspring. Those young which do not receive this predisposition will either perish, or will not be chosen as good mating stock by the others, or will simply lose out in the battle to pass on their genes, to the more capable individuals. In this way, the predisposition will become more and more pronounced over the generations and result in a species separate from those which were unable to cope. This is natural selection at work, survival of the fittest. Not simply the fittest in terms of health and strength, but also the best able or predisposed to adapt to new situations. And not simply a case of the survival of the fittest individual animals, but the survival of the ‘fittest’ genetic code. So this is not a case of the individual animals changing or updating their genetic code, but a predisposition being enhanced by the interbreeding of those with that predisposition. - Don_1 - 14th May 09
Actually, I suppose I need to clarify some more... You are all referring to natural selection, modification of genes that already exist, genetic drift, etc. The question asks how do brand new alleles get added on to what is already there? ie: Your genetic strand is 12 proteins long.... how does it get to 14... - destini - 14th May 09
So sorry, I will write this 100 times. I must read questions thoroughly before answering them. There, done it. I deleted the other 99 to save space! This could be akin to break repair genes either 'repairing' two separate chromosomes, thus fusing them into a single chromosome, or a break repair gene inserting itself into a damaged chromosome, creating two distinct and separate halves. Take a look at this article http://www.pnas.org/content/96/26/14899.full.pdf - Don_1 - 15th May 09
Natural selection is not really responsible for causing mutations, it just acts on them after they have occurred. The mechanisms that maintain and copy DNA and RNA are not perfect. So the nucleotide sequence can be modified by environmental factors (e.g. types of radiation and certain chemicals), and also accidentally during replication. This is how genes change.
See the whole discussion | Make a commentThere are several different types of mutation that you can easily find out more about. Interestingly, natural selection probably does affect mutation by selecting for better replication and repair mechanisms. - _Stefan_ - 15th May 09
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Well the answer is that we use as our genetic material DNA and some organisms use RNA, they are two related molecules and the basis of evolution and inheritance is that that genetic material has to be copied and passed on from one generation to the next in gametes, in other words, sperms and eggs.
A final way is viruses, because viruses — certain kinds of viruses actually physically insert their genetic material into the DNA of their hosts. HIV does that, other viruses could – retro viruses do that and a really elegant example of this is that there is a certain sea slug, it’s called a Sacoglossan sea slug which eats algae and when it eats that algae on the sea floor it actually gets the chlorophyll containing chloroplast — these are tiny bodies inside the algae that contain the green pigment that enables the algae to trap sunlight, and the slug gets hold of those chloroplasts and puts them into its own skin and keeps them alive so the slug can also use the energy of sunlight to get energy.
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How do barnacles mate?How do barnacles mate with each other? Beverley, listening live |
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Helen Scales - You’re talking about sperm and eggs, and barnacles if you’ve ever been down to this shoreline are rooted very solidly to the spot, so how do they move around and find a mate? Well lots of other marine creatures have a similar problem. Things like corals which are animals, they don’t move either but they solve that by sending their sperm and eggs up into the water and hopefully they’ll fertilize and they’ll meet each other and fertilization will take place and larvae will be created, but that’s not what barnacles do.
The male barnacles have very long penises, one of the longest in comparison to the size of the body, that there is in the animal world – animal kingdom, and – Chris Smith - They didn’t include me in the analysis — I’d just like to say that. Helen Scales - No comment – and the barnacle males, will literally poke around next to them and see what they can find, so they don’t have much reach really in actual terms but they can reach out and fertilize female barnacles. Chris Smith - That’s amazing! So if you look at the barnacle crop that you see on rocks, do you see sort of concentric rings of males, females –? Helen Scales - You must see some sort of patterning like that indeed, because you would have to be arranged in space, around on that rock to be able to reach other members of the opposite sex, and they obviously mate with lots of other different barnacles to produce lots of baby barnacles, and but that’s how they do it — and that seems rather wonderful. So take a closer look next time you’re down on the shore. Chris Smith - Thank you very much, Helen! |
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May 2009 |
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Barnacles look a bit like other types of mollusc on the seashore but they are in fact a type of crustacean, like crabs, and lobsters, and things like that, but very much smaller, but they do actually have sex directly and the only way they can do that is by having a very long appendage.
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Could hubble see footprints on the moon?Could the Hubble space telescope see the footprints made by the Apollo astronauts on the moon’s surface? Roger Roerick |
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Dave - Well, Hubble is an incredible telescope but looking up it’s resolution — I reckon it has a resolution of 0.05 arcseconds, that means it can distinguish two objects which are 0.000013 degrees apart, any closer together than that and they sort of merge into one object. Now – Chris - In practical terms what does that mean? Dave - That means if something – the distance of the moon away from us, Hubble is essentially near the earth its very level, but – Chris - So about a quarter of a million miles to the moon? Dave - About 384,000 kilometres—that means you can see something 9 to 10 metres across on the moon, so probably not. Chris - That would be a very big footprint – Bigfoot literally. Okay, thank you Dave! |
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May 2009 |
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Roger Röhrig asked the Naked Scientists: With the mission to repair the Hubble telescope finally under way, I was wondering if this incredible instrument would react to things closer at home. Would it be able to spot the footprints left by the astronauts on the moon or can't it focus that closer or would its optic be scorched by the intense light? What do you think? - Roger Röhrig - 13th May 09
"Hubble's keen vision (0.085 arc seconds.)" This equates to 500 feet at 250,000 miles,quite inadequate for viewing footprints. See http://www.telescope-optics.net/telescope_resolution.htm - syhprum - 13th May 09
The Chandrayaan-1 lunar orbiter is, apparently, able to resolve objects of 5 to 10m. Fine enough to see a landing site but no footprints.
- lyner - 13th May 09
Very interesting information! I was just watching a news report about the space Shuttle repair attempt for Hubble. It is supposed to improve its image resolution a hundred fold. I wonder what will be the new fine field resolution? - Vern - 14th May 09
Very interesting information! I was just watching a news report about the space Shuttle repair attempt for Hubble. It is supposed to improve its image resolution a hundred fold. I wonder what will be the new fine field resolution? Probably one tenth of an olympic sized swimming pool, almost everthing these days seems to be compared to this new? OSSP measurement - I've heard it used twice today on two seperate news items. - Fortran - 14th May 09
But this OSSP unit requires another component to be meaningful. It needs to be OSSP per some distance value.
- Vern - 14th May 09
1 OSSP Per 26 miles 385 yards to keep with the same system
- Fortran - 14th May 09
There is no hope that Hubble's resolution could be increased a hundredfold, assuming everything is made perfectly the resolution is determined by the size of the mirror and the frequency of the light it is operating at, Hubble is already at that limit.
- syhprum - 14th May 09
So that's an Olympic Size Galaxy, quite a long way away? - lyner - 14th May 09
It seems I remember that the CCD's of the early Hubble had a resolution of 800 by 800 pixels. They must do some tricks with those because the images we see are much more detailed. I'm not sure what the news cast was claiming was a hundred times better. What ever tricks they use to capture images have probably improved over the last 20 years or so. - Vern - 14th May 09
It seems I remember that the CCD's of the early Hubble had a resolution of 800 by 800 pixels. They must do some tricks with those because the images we see are much more detailed. I'm not sure what the news cast was claiming was a hundred times better. What ever tricks they use to capture images have probably improved over the last 20 years or so. I'm sure I remember reading that there was some redundancy in the hubble in terms of the 800 x 600 ie 0.48 megapixel - it was known that camera technology would improve thus the resolution was much smaller than a single pixel, by how much I do not know but also remember a lot of the processing is done on board and improvements in software algorhythms will also improve 'effective resolution' I think I read about it in Scientific American at some point. - Fortran - 14th May 09
I am not sure I understand "500 feet at 250,000 miles" and why this is okay for seeing footprints. Does this mean that it can spot something 500 feet across at a distance of 250,000 miles? How far is Hubble from the moon? Chris - chris - 14th May 09
Hubble is about 242,648 miles from the moon which others (being less pedantic than I) have rounded up to 250K Miles. I think the 500 feet is either the smallest object hubble can 'see' at that distance or it is the field width of the image (ie like a picture of an object 500 feet across) in which case the smallest object would be around 12 inches, to resolve a footprint you would probably need a resolution better than 1 pixel per centimetre. Edit: Here's a piece from Nasa on that very subject http://science.nasa.gov/headlines/y2005/11jul_lroc.htm - Fortran - 14th May 09
Once the Lunar reconaissance orbiter is in place the conspiracy theorists will need to step everything up a notch. But will they admit they were wrong? No, it will just involve a further layer of conspiracy. I imagine that there was a team of set builders sent a few years ago to construct fake landing sites. - lyner - 14th May 09
The Mars orbiter,s have been able to identify the rover landing sites.
- syhprum - 15th May 09
So the field of view is 500 feet - will a footprint 1/500th the size of that field be visible? Isn't that asking a lot? Isn't that like looking at a photo of a family holiday on the beach and then being able to see a single grain of sand in one corner of the photo? Sounds like a tall order to me. Chris - chris - 15th May 09
I just read the NASA link posted by Fortran. As I suspected it says: "There are six landing sites scattered across the Moon. They always face Earth, always in plain view. Surely the Hubble Space Telescope could photograph the rovers and other things astronauts left behind. Right? Wrong. Not even Hubble can do it. The Moon is 384,400 km away. At that distance, the smallest things Hubble can distinguish are about 60 meters wide. The biggest piece of left-behind Apollo equipment is only 9 meters across and thus smaller than a single pixel in a Hubble image." So it looks like a footprint is indeed beyond the scope of Hubble's resolving power. Chris - chris - 15th May 09
If it were possible for Hubble to photograph a footprint on the moon I'm not sure conspiracy theorists will take the word of NASA that any picture was genuine, they could suggest the pictures are 'doctored'. The principle conspiricists have a living to make. It is impossible to prove who made a print on the moon and when, it is up to each person to decide for themselves whether or not they believe NASA, I once published an article which rebutted the conspiricists and since none of them could prove me wrong, it is clear the landings happened! - Fortran - 15th May 09
Hello all, great replies so far for the resolution question, especially the NASA link puts things into perspective. But what about the brightness aspect? I'm pretty convinced Hubble's CCD would burn up if the telescope would be pointed directly at the Sun, but what about the Moon (or the Earth)? Would it suffer any damage? Would the CCD be overloaded and produce a completely white picture? Roger - RoRo - 15th May 09
I'd be very surprised if there were no filters, shutters built in, even a system to close the telescope hen being maintained or possibly redirected past the sun. As for the moon no, my understanding is that that there is almost no heat reflected just visible light so although the CCD may be saturated it is unlikely to be damaged. Not sure how much light hits us from the moon but I'll bet it's less than 1 watt/square metre. THats from the whole moon, now consider how much light hits the earth from a a tiny square of that probably only a few nanowatts, (to lazy to do the sums) THe moon only looks bright beacuse of the dark background,during the day it's no brighter than sunlit cloud. EDIT: Moonlight at earth's surface approx 1mW/M2 (1 thousandth of a watt per square meter). THus the total light from the moon entering Hubble would be around 4.5mW (enough power to light a low power LED. (Hubble Mirror 2.4 Metres Radius. Nothing like enough to harm even the most sensitive CCD camera. - Fortran - 15th May 09
ya...We can see the foot steps
- raghavendra - 16th May 09
The danger to the cameras of direct sunlight has precluded Hubble from ever viewing Mercury
- syhprum - 19th May 09
Just stumbled on a gret post on "Bad Astronomy": http://blogs.discovermagazine.com/badastronomy/2009/05/13/ten-things-you-dont-know-about-hubble/ With amazing answers to my - obviously frequently asked - Hubble questions and more surprises. Roger - RoRo - 20th May 09
Taking a photo of the moon (the bright bits) is just the equivalent exposure to an object on Earth, in full Sunlight: 1/125second at f8 or thereabouts. The f number of the Hubble is not particularly low - dunno what it is exactly but it will have a fairly long focal length for its diameter.
- lyner - 20th May 09
So the answer to the original question is "only if it were a lot closer to the moon or if the astronuats had really big feet."
- Bored chemist - 21st May 09
"The FOC (faint object camera)offers three different focal ratios: f/48, f/96, and f/288 on a standard television picture format. The f/48 image measures 22 X 22 arc-seconds and yields resolution (pixel size) of 0.043 arc-seconds. The f/96 mode provides an image of 11 X 11 arc-seconds on each side and a resolution of 0.022 arc-seconds. The f/288 field of view is 3.6 X 3.6 arc- seconds square, with resolution down to 0.0072 arc-seconds"
See the whole discussion | Make a commentThis was an original specification and may have been upgraded now. - syhprum - 21st May 09
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How did the waggle dance evolve?Hello. I was watching a programme on television the other day about bees and how they do a wee dance to tell the other bees where the flowers are. I was talking about this with my friend the other night and about evolution. Neither of us could think of a way that the bee dance could have evolved small steps, if you know what I mean. Could you shed any light on that for us please? Anon, probably somewhere in Scotland |
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We put this first to Andy Barron, Lecturer in the Department of Brain Behaviour and Evolution at Macquarie University.
We also asked Jurgen Tautz head of the Bee Group at the University of Wurzburg in Germany.
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May 2009 |
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The problem is that the bees that dance are the worker bees. They are infertile, so how does the dance evolve? The queen does not dance, and neither do the drones. The queen mates soon after hatching on one mating flight with 5-10 drones, all of which leave their sex organs behind in the mating process, fall from the sky, and die. The queen then returns to the hive, and never mates again.
- Bonnie - 29th Sep 09
Bonnie, it does not matter if queens or drones dance or not, the point is that their genes pass on information about how to do so. The better the workers perform with this information (that includes the waggle dance), the better these genes will propagate.
- arnau - 31st Jan 10
Why do unexplained complexities always get met with 'that's a great question' or 'that's very interesting, but no one knows'. I beg to differ, and scientifically: Maybe someone programmed the genome? I know all the secular humanists start to get ruffled at such 'religious' suggestions, but I am using no lesser reasoning or faith than Lamarckism, Darwinism or Neo-Darwinism. We never see any brand new information added to any genomes, only scrambling of existing information (mutations), which are almost always negative in their effect and represent a loss not a gaining.
I would have to say that there was a transcendent informationer giver to the bees genome, as despite Neo-Darwinist remonstrations, purely naturalistic causes starting from infinite or finite causeless causes(with no intelligence allowed)simply cannot produce information or complexity. My conclusion would be a transcendent intelligent designer gave all bees the information in their genome and the ability to adapt within the limits of their kind.
See the whole discussion | Make a comment- Terrell - 2nd Aug 10
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directional-specific movements and then they head out of the hive and go and find the food. Now what we know is that performing the dance and reading the dance is entirely instinctive. So we have to infer that this whole complex, symbolic communication system is somehow programmed by the honeybee genome. Now how a genome programmes behaviour with this level of complexity I have absolutely no idea, and I don’t think anybody has any idea; but there’s nine honeybee species, and the dances of the dwarf honey bee:, Apis Florea - these are the most primitive honeybees — they have less complex directional information than the European Honeybee; the honeybee that we’re familiar with. Maybe after millions of years this alerting signal was refined to add more space-specific information and over time you get something of a dance and symbolic as the waggle dance. But again, look, as to how the bee genome and how the bee brain have been modified by the evolutionary process to give bees this dance language, really we still have absolutely no idea, but it’s a great question — it is an absolutely fantastic question.
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Do rockets punch holes in the ozone layer? |
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Chris Smith - Well, Fran, we know that the major culprit for making holes in the ozone layer are chemicals called CFCs — chloro-fluoro carbons. These are things that were used in aerosols, even in aspirin inhalers, but also in fridges as refrigerants, and they were used in huge amounts until the Montreal Treaty came in, in the late 80s to try and ban them. What provoked that was that a group of scientists including Brian Gardner (who appeared here on The Naked Scientists a few years back) had actually noticed this massive hole opening up over Antarctica in the mid-to-late 80s and this hole actually grew to be the size of Australia at its peak. It stopped growing; it’s actually beginning to shrink a little bit now and that’s because we have stopped using these chemicals. The reason that they concentrate down in the Antarctic is because the Antarctic is an isolated continent. It’s completely surrounded by ocean and this creates something called a circumpolar current, and this has a sort of whirlpool-like effect in terms of air; and it draws in and concentrates these molecules over the Antarctic over winter when it’s very dark. They then accumulate in high clouds over the Antarctic and when the sun comes out the following spring the sun breaks down the CFCs and they get turned into reactive chemicals that would then react with the ozone and deplete it. They are, by far, in a way the worst culprit. We don’t send enough rockets and spaceships up into space to make a huge difference, I wouldn’t have thought, in grand scheme of things. So I think although we have to be environmentally conscious, I think the benefit of sending rockets into space in terms of what they can do for satellites and furthering research is far greater than the small bit of damage they might make to the ozone layer. So I think on the whole, probably not, it’s probably more a manmade, anthropogenic problem. But great question, thank you for that. |
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May 2009 |
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How does photosynthesis work underwater? |
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Helen Scales - That’s a great question but fundamentally photosynthesis actually began in the oceans — in underwater, because that’s where plants and algae first evolved. They then moved onto land. So light definitely gets into the upper layers of the ocean and that’s where the process of photosynthesis traps that light and converts it into energy — into carbohydrates really, that the rest of the food chain relies on. So it’s really the idea is that you have to maintain plant life, algae has to maintain itself in the upper layers of the ocean because once you get further down into the depths of the ocean, first of all red light gets absorbed which is why the oceans look blue and green-y colours. Light does get down there but it has to maintain itself up in the high levels. So if you look, for example, at coral reefs and they have plants living inside their tissues or algae and those types of coral have to maintain themselves by growing on big reefs, depositing calcium carbonate in great big layers that build up and build up and as sea levels rise, they have to keep up their pace to keep themselves in that lovely, sunny, gorgeous bit of tropical oceans where we all love to go snorkelling and diving. But as you go deeper down, they tend to peter out, and there are some types of corals actually that don’t have photosynthetic algae in their tissues; they actually rely on catching their food like other animals. They catch it from the water, and those are the ones that live deeper down. So you do see this zonation. You see similar things on the beach with different types of seaweed using different types of pigments to harness light both in the open areas where there’s lots of light and then lower down where light start to get absorbed. Dave - Is that why seaweed is a sort of reddish colour, because it doesn’t absorb red if it’s deep under water, blue-light can get all the way down so it absorbs blue but not red? Helen Scales - Some of the seaweeds are red seaweeds, that’s right and that’s a kind of branch of the algae. They have different types of pigment that do—yes, they use up the green and the blue lights and red is reflected back and that’s why they look red. Chris Smith - So the bottom line is that basically, there’s very little difference between the photosynthesis that’s occurring in the oceans and the photosynthesis on land because it’s all the same process. It’s just been tweaked a little bit to make use of the light that’s available and there is slightly more light of different wavelengths available out of the water than in it but the bottom line is it’s pretty much all the same. Helen Scales - It is and it is very important in the oceans. So much photosynthesis goes on and carbon dioxide gets fixed in that process in the oceans and we know that’s really important too. Chris Smith - Of course, because the oceans are the biggest carbon dioxide sink of the whole planet, aren’t they? |
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May 2009 |
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Why store propane but not natural gas? |
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Dave - It’s all about boiling points really. If you look — the bigger the molecule, the higher temperature it will boil at. So butane will boil at sort of -0.1 degrees centigrade, so you don’t need very much pressure to keep that as a liquid at sort of room temperature, so you can have really quite weak-like tanks. Propane boils at about -42 degrees centigrade, which means you have to have 10 or 12 atmospheres of pressure to keep that a liquid at 40 degrees centigrade. But that’s not difficult to make with a small, light steel tank; and it’s quite practical to carry around, that would be sensible. Natural gas is methane which boils at -161 degrees centigrade roughly. To keep that a liquid at all that temperatures you have to have tanks that are strong enough to survive 200 to 220 atmospheres of pressure and from the experiment that we are doing earlier that’s going to involve about 2,000 tonnes of pressure on every square metre of that tank so it’s going to have to be made up incredibly strong steel, it’s going to be very heavy. It just makes it expensive and impractical to carry around — and very dangerous to carry around in vehicles. Chris Smith - So that’s why we have it coming down the pipeline but we don’t store it locally. We use propane, much easier to compress and get lots of it into a small space in a tank. Dave - That’s right. In a pipeline it never has to be at a very high pressure. You never have to liquefy it. |
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May 2009 |
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Nic Browne asked the Naked Scientists:
Hi Gang,
My name is Nic Browne and I live in Victoria, Australia.
I download your podcasts on iTunes every week and I absolutely love your show.
Could you please answer a question for me.
What is the difference between LPG gas used in heaters, and natural gases that do the same thing?
It's been bothering me for a while so an answer would be nice.
Cheers,
Nic
What do you think?
- Nic Browne - 4th Feb 09
The main difference is that LPG (Liquid Petroleum Gas), as its name suggests, can be liquified (by compression) at room temperature and so you don't need extremely big containers to store a useful amount of it.
- lightarrow - 4th Feb 09
People do store natural gas.
See the whole discussion | Make a commenthttp://en.wikipedia.org/wiki/LNG_storage_tank But with propane you need a relatively low pressuure to make it a liquid (at normal temperatures). With natural gas you have to keep it very cold or it boils. - Bored chemist - 4th Feb 09
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