Wikipedia:Reference desk/Archives/Science/2010 June 24

= June 24 =

Thrust vectoring
Does thrust vectoring have any disadvantages? Since it makes an airplane much more maneuverable, one would think it would be used on more fighters.
 * There's a relatively small amount of extra weight for the equipment, plus the additional complexity.
 * Additionally allowing a jet engine to provide it's thrust in a direction other than in the direction of flight means that the 'airframe' must be able to support/resist that thrust - ie the vectored thrust must be able to be transmitted to the plain without the plane snapping into bits.. This could mean addition weight due to extra trusses etc needed - especially since the torque is different to that due to the mass of the engine in manouvers - ie the trust vectoring force is not coaxial with the centre of the mass of the engine (I've assumed that the thrust vectoring force is transmitted though the engine assembly - this might not be the case) - in short additional reinforcement may be needed.77.86.123.157 (talk) 01:23, 24 June 2010 (UTC)
 * You also need the power available to redirect the thrust, which is power that isn't available for other purposes (such as speed). Physchim62 (talk) 01:42, 24 June 2010 (UTC)
 * Personally, I think that the reason why we don't see it on fighters is because it's still a pretty new concept, plus the fact that on fighter planes (crammed as they are with fuel tanks, weapons and electronics) it's often not clear where one could stick the extra ducting and equipment. That said, the F-22 and F-35 both incorporate a form of thrust vectoring where the rear-mounted jet nozzles pivot up/down to give a super-fast response in the pitch plane. As for Physchim's point, it's completely irrelevant because the power to redirect the thrust is the power supplied to the actuators, not the power taken from the jet exhaust, and in any case it's only a small fraction of the power generated by the engine.  Clear skies to you 67.170.215.166 (talk) 01:52, 24 June 2010 (UTC)
 * How is it a new concept? It's a completely obvious one as soon as you have jet engines. What's new is the ability to actually put it into action efficiently and effectively. The OP's question is what was stopping this being done sooner, and what is stopping being done more widely? --Tango (talk) 02:07, 24 June 2010 (UTC)
 * Well it might not be a new concept, but the way it is applied to fighter aircraft is fairly new. The article even states at first thrust vectoring was only envisioned for VTOL and STOL capability. I imagine just the fact that it is substantially more complex and therefore expensive and more difficult to maintain is probably the main reason you don't see it on more aircraft as yet. Vespine (talk) 02:32, 24 June 2010 (UTC)
 * There's at least two more reasons why it's not as good an idea as it might appear:
 * 1. The ability to suddenly change direction eg pitch of an aircraft means that the wings will experience massive forces - ie the wind force at mach 1+ on a couple of square meters will probably just rip the wings off.. If the wings are strong enough the pilot has to survive the acceleration too. There's a limit to how fast you can turn at high speeds for both these reasons.
 * 2. Aerial combat is quite missile based - the missile doesn't need a direct hit, and are very maneouverable - even with thrust vectoring the mass of the plane is likely going to prevent it from being able to evade a missile even if 1. can be avoided.
 * On the other hand thrust vectoring does raise the possibility of a plane with fewer control surfaces, and thus a simplified wing (numerous advantages). You can yaw, roll and pitch with suitable thrust vectoring. landing control might be a problem.77.86.123.157 (talk) 03:09, 24 June 2010 (UTC)
 * The Sukhoi PAK FA has thrust vectoring too. I think modern fighters do in fact have thrust vectoring; but soon there might not be any modern fighters, because the sixth generation might all be UAVs... at least some of which will have thrust vectoring . 213.122.59.238 (talk) 15:24, 24 June 2010 (UTC)
 * Every additional moving part you add to a propulsion system (in fact, any change at all to an existing design) brings an additional risk of failure. The people who design propulsion systems for aircraft tend to be very paranoid about that sort of thing.  Nimur (talk) 03:25, 24 June 2010 (UTC)
 * The first practical jet engines weren't really around until the 1940's - and the first practical vectored-thrust jet was the British Hawker Siddeley P.1127, which started development in 1957 and first flew in 1960. So given the problems with pushing out new technology during WWII - there really wasn't much of a lag between the time when people were able to start seriously considering jet engines and the time when thrust vectoring was first used. SteveBaker (talk) 14:51, 24 June 2010 (UTC)
 * I disagree with the above, thrust vectoring in the Hawker and later the harrier were developed specifically for VTOL, It's a very different thing. The concept of thrust vectoring to improve combat maneuverability is a completely different paradigm and a relatively new one. Vespine (talk) 00:05, 25 June 2010 (UTC)
 * And thrust vectoring would work with prop aircraft as well. I think the older airships (USS Akron (ZRS-4) perhaps?) were able to use some degree of thrust vectoring with their engines back in the 30s, but I do not know if we mention such capabilities in our article.  Googlemeister (talk) 15:00, 24 June 2010 (UTC)

Difference of animals
What is the difference between cheetah and leopard? --Extra 999 (Contact me +  contribs) 01:15, 24 June 2010 (UTC)
 * If you mean on how to recognize the difference, then look at the size. Cheetahs (Acinonyx jubatus) are much smaller and slimmer, whereas leopards (Panthera pardus) are more robust and heavyset. Also, the spots on a leopard are rings, called rosettes, whereas on a cheetah they are spots. Cheetahs can also run much faster - up to 65 mph. If you mean what makes them separate species, I suppose it's the fact that they can't interbreed. --The High Fin Sperm Whale 01:23, 24 June 2010 (UTC)


 * One has evolved itself into a specialized and therefore vulnerable evolutionary niche while the other has retained more general abilities that will allow it to survive future bottlenecks. TheGoodLocust (talk) 02:05, 24 June 2010 (UTC)

Grebe
I am fairly sure that this is a grebe, but does anyone know what species it is? It could possibly be a Red-necked Grebe (Podiceps grisegena), but I don't think Red-necked Grebes have a red head, only a red neck. Thanks, --The High Fin Sperm Whale 03:34, 24 June 2010 (UTC)
 * looks more like a merganser to me. Particularly note the hooked bill and the spiked crest (not features of grebes) -- Ludwigs 2  04:14, 24 June 2010 (UTC)
 * I concur. Look up 'merganser' on Google images and there is plenty of evidence. Richard Avery (talk) 07:10, 24 June 2010 (UTC)
 * A female Common Merganser (Mergus merganser), known in Britain as Goosander. Ghmyrtle (talk) 07:22, 24 June 2010 (UTC)

Piezoelectric body armor?
The idea would be similar (and perhaps incorporate) body armors made from non-Newtonian fluids, but I'm basically wondering if you could make a body armor with a bunch of microscopic crystals (similar to how some warriors use to soak their armor in brine), which, upon impact, would generate an electric charge to power an electromagnetic reaction to harden a magnetorheological fluid? I'm not sure how much of a charge could be generated in this manner or if it would require specially designed materials rather than something common like quartz. Properly designed I'd think armor like this would protect from tasers/stun guns too. TheGoodLocust (talk) 04:29, 24 June 2010 (UTC)
 * No. You're writing fantasy - a piezoelectric material that stops bullets without breaking doesn't exist. Have you don e any research on this at all - or are we expected to comment on every scheme you dream up? 77.86.123.157 (talk) 13:19, 24 June 2010 (UTC)


 * I thought it was pretty clear I was wondering about microscopic crystals that are either incorporated into the fluid itself or which use a conductive fabric as a substrate - not giant sheets of the substance. The actual stopping of the bullets would be done by the magnetorheological fluid. Also, such crystals would be harder than anything coming out of a gun (not that it really matters that much). TheGoodLocust (talk) 16:34, 24 June 2010 (UTC)


 * And a cool defense would be emitting an EM field so that your supercommandos will be frozen solid in their armor for easy capture. Googlemeister (talk) 14:52, 24 June 2010 (UTC)


 * Yes, I suppose that could be a problem even with current concepts for magnetorheological armor, but current power/range limits would, i suspect, limit the practicality of such a device.TheGoodLocust (talk) 16:34, 24 June 2010 (UTC)
 * A related idea is dilatant based body armours such as Liquid Armor or d3o which exist. The set-up you describe seems to require nano-engineering and would be years away if ever practicable, also see Magnetorheological_fluid. You also might want to consider using a material that thickens with an electric field eg Electrorheological fluid.
 * Also http://www.memagazine.org/backissues/membersonly/sept06/features/narmour/narmor.html
 * And especially this patent (UK patent 2460493):"An impact protection device comprises a web of piezoelectric fibres and an electrorheological fluid suspended by said web. In response to an impact event, the piezoelectric fibes generate an electrical signal, This is used either directly or indirectly to apply a second electrical signal to one or more electrodes, in response to which an electric field is applied to the rheologolical fluid. This causes the fluid to stiffen, providing protection against the impact event."
 * it's possible that similar patents exist similar to your idea too. 77.86.123.157 (talk) 18:44, 24 June 2010 (UTC)


 * Yes, I referred to such substances in my initial post as non-Newtonian fluids. I was unaware that electrorheological fluids exist (makes sense though) and that would be a better method of implementation. Nanotech might be a requirement, but I suspect in this application it wouldn't be terribly difficult to grow large amounts of small crystals. The big question is whether it would be cost effective and superior to current body armor technologies. The article on ER fluids states that under compressive stress they become solid or nearly solid, which seems to indicate some potential in this application. Cheers. TheGoodLocust (talk) 19:00, 24 June 2010 (UTC)


 * Ah yes, it looks like people are already looking into this. This isn't surprising since it is a pretty basic concept. TheGoodLocust (talk) 19:00, 24 June 2010 (UTC)

TO220 heat sinking
While designing a circuit, I had a bit of a fleeting thought: suppose you had a board with plenty of space parallel to the plane of the board (i.e. horizontally), but little space perpendicular to it (i.e. vertically), and you need to use a TO220 package under conditions requiring a heat sink (such as an LM7805 pulling 800mA with VCC=12V). If, then, you were to use solder paste to solder the heat sink tab directly to a large, exposed copper plane on the PCB (bending the pins at the vias so it lies flat on the board, of course), would that be a viable alternative to a tall, bulky heat sink? (I'd imagine so considering D²PAK packages often have similar specs to TO220s, but don't usually have a vertical heat sink - but I'm still not certain.) Also, if you were to do that, would that have a (much) more significant parasitic thermal effect on nearby semiconductors than a vertical heat sink? And one more: if you used Arctic Silver 5 instead of solder paste and then bolted the tab to the board instead of soldering it, how would that compare (in terms of heat dissipation) to the previously described way of soldering it (assuming an otherwise identical board)? Thanks! (And forgive me for the amount of parentheses I used. (I'm rather addicted to them, you see.)) -- Link (t&bull;c&bull;m) 06:39, 24 June 2010 (UTC)


 * Your LM7805 dissipates (.8A x (12-5)) = 5.6W. Here are some TO220 heatsinks. For example the twisted vane type has thermal resistance 9.9 degC/W so the LM7805 temperature would increase 5.6 x 9.9 = 55 deg C. The PCB copper plating being so thin and insulated on one side would have much higher thermal resistance. A rule of thumb I remember is that a semiconductor device's lifetime is halved for every 10 degC rise. Tip: you can pass the minimum output current through a resistor in parallel with the regulator thereby sharing the 5.6W dissipation between two devices. Cuddlyable3 (talk) 12:16, 24 June 2010 (UTC)
 * I agree that the thickness of copper in a standard pcb would not make a suitable sink. If vertical space is limited why not use a horizontal copper or Al plate above the surface of the PCB (ie bend te package the opposite way so that the thermal contact area is pointing up) - you could if necessary cut holes in the plate to both allow air circulation to/from other components, as well as allowing large vertical components (eg big caps and inductions etc) to poke through?? (No idea above comparison between artic silver and solder paste ) 77.86.123.157 (talk) 14:36, 24 June 2010 (UTC)
 * Interesting. It was a purely hypothetical question so it won't matter either way, but thanks for the replies! A custom-cut heat sink with TO220s attached face-down is a very interesting idea. It might even double as a form of casing or mounting bracket. Would make for a funny-looking board, that's for sure. -- Link (t&bull;c&bull;m) 16:47, 24 June 2010 (UTC)
 * Here is a project I did recently that has horizontal mounted to220 with heatsinks. The pictures aren't great but you can see it to the right of the bottom board and also see it in the assembled picture from the side. HTSSOP package relies on using the board as a heatsink and a trick I saw recently was to have a patch of closely packed vias which the bottom of the package is soldered to. The vias carry away more heat then just a patch of copper, but these were just LED drivers, not voltage regulators. Vespine (talk) 00:28, 25 June 2010 (UTC)


 * If you can get your hands on them you can also use one of the 5V switch mode regulators, which gets rid of the issue completely. --antilivedT 05:29, 25 June 2010 (UTC)

astrophotography with the webcam
i have bought a webcam to use it in the astrophotography, i dismounted its lens and then i assembled a small plastic cylinder in its place. after that, i tried to picture the Moon by the webcam through a binocular, but i pictured just a scattered white light. is this method in the astrophotography don`t work with the binoculars? or i did a something wrong? --Abbad Dira (talk) 09:28, 24 June 2010 (UTC).


 * Maybe the position is out of focus? Have you tried at different depths? 77.86.123.157 (talk) 14:38, 24 June 2010 (UTC)

thank you all for the answers.


 * i looked through the binocular before taking the picture and everything was right --Abbad Dira (talk) 19:56, 24 June 2010 (UTC).


 * You have to make sure that the image plane of the camera (the little silicon chip that picks up the light) lies at the focal point of the binoculars. You'll need to vary the distance between the camera and the binocular eyepiece to get it in focus.  Remember also that the binoculars are designed to focus light THROUGH the lens of your eye to form a sharp image onto your retina - in the case of your lens-less camera, the distance will be different than from the eyepiece to your eye.  I think you need to experiment with different lengths of the plastic cylinder, fine tuning it with the focussing controls of the binoculars to get the most accurate focus. SteveBaker (talk) 14:40, 24 June 2010 (UTC)


 * i tried now, but i couldn`t find a good thing to set the binocular on it and in the same time i can observe a bright and enough distant object from its place. however, i tried with a faint and non-celestial object, and i could see just a white light with a scattered black-points on it. i will try to experiment a different lengths --Abbad Dira (talk) 19:56, 24 June 2010 (UTC).


 * I don't think the setup you're trying is going to work. The page you linked to discusses removing the lens from a webcam and using it in place of the eyepiece of a telescope.  A binocular is like a telescope with a permanently attached eyepiece.  With a binocular, I think you need to do afocal photography, which would mean the webcam's lens should remain attached.  (Basically, if your "telescope" is something you can look through with your eye (that is, one that produces a virtual image), you need a camera with a lens.  If your "telescope" is something that can project a real image onto a piece of paper or film, you need a sensor without a lens.)  -- Coneslayer (talk) 14:50, 24 June 2010 (UTC)


 * so why i don`t use a digital camera?! what i should to do with the lens of the camera?! --Abbad Dira (talk) 19:56, 24 June 2010 (UTC).
 * Astrophotography is a very challenging and potentially expensive hobby! I think you'd be much better off finding a forum specifically on the subject, rather then trying to work it out on the ref desk. My fav forum is iceinspace.com.au, don't let the fact that it's Australian put you off, it's one of the best astro photography forums I've ever found. Lots of beginners and amateurs, and several people so good they get their pictures on NASA APOD. Vespine (talk) 00:19, 25 June 2010 (UTC)

Strange parrot behaviour
Can anyone suggest what the parrot in this: http://www.youtube.com/watch?v=DWYv-R5x9Cw video is actually doing and why? My guess would be that he's, for some reason, trying to seduce the dishwasher, but that's just a guess. --95.148.107.169 (talk) 10:11, 24 June 2010 (UTC)


 * Perhaps it has fleas or an itch from some other source? Either that or drugs and/or calisthenics. TheGoodLocust (talk) 16:39, 24 June 2010 (UTC)


 * Is the dishwasher perhaps blowing some air out through the lower vent, e.g. from heating cycle perhaps? I know my cat loves to sprawl in front of the kitchen heat register because the heat is blowing towards him rather than up into the room.
 * On the other hand, there's a reason someone coined the term "birdbrain", too! DaHorsesMouth (talk) 00:00, 25 June 2010 (UTC)


 * It may be Anting (bird activity) or having a Dust bath, without any ants or dust. 92.28.242.52 (talk) 16:37, 25 June 2010 (UTC)

finite element
where commercially used this process —Preceding unsigned comment added by Dhirajsharma89 (talk • contribs) 10:46, 24 June 2010 (UTC)
 * Are you referring to the Finite element method? --Ouro (blah blah) 11:50, 24 June 2010 (UTC)

Spacetime and diverging timelines - not really a question, just a request for more information
Okay, so the speed of light seems to be the upper limit for speed in the universe, which means that nothing can accelerate above this velocity.

This means that:


 * nothing which happens in the Moon will affect us before 1.28 seconds.
 * nothing which happens in the Sun will affect us before 499 seconds.
 * nothing which happens in Córdoba, Argentina, will affect Wuhan, China before 0.066 seconds.

Since no phenomena can propagate above the speed of light, for all intents and purposes, these locations are not only in different points of space but also in different points in time. In effect, the Moon is 1.28 seconds out of synch with the Earth, the Sun is 499 seconds out of synch, and antipodal points in the world are 0.066 seconds out of synch with each other.

Therefore, when I take an airplane to see my girlfriend, I am not only covering 1,400 km in space, but I'm actually synchronising her timeline and my timeline by 0.005 seconds.

Please, could you direct me to articles, either here or off-Wikipedia, which deal with the subject of travelling in time by travelling in space?--83.38.102.61 (talk) 13:33, 24 June 2010 (UTC)


 * I think you have slightly the wrong idea. The problem is that you are still clinging to the idea of 'absolute time'.  The moon isn't 1.28 seconds "behind" the Earth - because if you were standing on the moon, you'd see events from Earth delayed in exactly the same way - so it's just as easy to say that the earth is 1.28 seconds "behind" the moon.  Ignoring the teeny-tiny effects of relativity, the timeline of someone on the Earth is the same as that for someone on the moon - the speed of light only limits how information gets from one place to another.  Relativity adds a much larger and harder concept - which is that the idea of two events being "simultaneous" at all is a fairly meaningless concept.  However, the lack of the concept of "simultaneity" is really only an issue when things are moving very fast relative to each other.  Here on Earth, you can say that two events happened "simultaneously" in Cordoba and Wuhan - but that the person in Cordoba can only possibly find out about a simultaneous event in Wuhan 66 milliseconds later...but that delay doesn't represent a 'time shift' as you seem to be implying because an event that happens in Cordoba isn't somehow magically known to have happened 66 milliseconds EARLIER in Wuhan...they still only know about it 66ms AFTER it happened in Cordoba.  So in 'normal' situations where relativity is a negligable effect, you don't have to "synchronise timelines" at all...all you are doing is reducing the communications delay by getting closer. SteveBaker (talk) 14:35, 24 June 2010 (UTC)


 * The article you want is Relativity of simultaneity but be aware than it's not an easy concept, and you'll probably need other sources besides wikipedia to help you understand it. Ariel. (talk) 14:37, 24 June 2010 (UTC)

This is also interesting to think about Count Iblis (talk) 14:44, 24 June 2010 (UTC)
 * Also technically, no two points on earth can be more the 0.043 light seconds away. You have to consider going straight through the earth, not traveling on the surface for the correct distance.  Googlemeister (talk) 14:51, 24 June 2010 (UTC)


 * As are light cones. 86.164.66.4 (talk) 18:55, 24 June 2010 (UTC)


 * The Rietdijk–Putnam argument is complete nonsense; please ignore it. It confuses an arbitrary way that special relativity is taught (and probably shouldn't be) with the actual physical content of the theory. -- BenRG (talk) 09:58, 27 June 2010 (UTC)
 * Hmm? From the WP article on it, the argument doesn't appear to be about the physical content, but the metaphysical content &mdash; questions about whether the future and the past really exist.  If you want to criticize it, fine, but you have to do so in its own context. --Trovatore (talk) 10:10, 27 June 2010 (UTC)

how many g's can a gourmet salad be subjected to without being ruined?
How many g's of acceleration can a gourmet salad be subjected to without being ruined? (e.g. cherry tomatoes in it popping and so on). I don't mean for a very long time, just long enough to get to the other side of the earth in a vacuum tunnel. 2) at that, most-crushing-but-without-being-ruinous g of acceleration and deceleration, how long would it take to get from the one side of the earth to the diametrical opposite side of the earth along a great circle (e.g. along the equator) in a vacuum tube at sea level? Thank you. 85.181.145.173 (talk) 19:54, 24 June 2010 (UTC)
 * The answer, my friend, is blowin' in the wind.... --Trovatore (talk) 19:55, 24 June 2010 (UTC)
 * (The more serious answer is I don't know; maybe someone else will. But you know, it's always a good time for Dylan.) --Trovatore (talk) 19:59, 24 June 2010 (UTC)
 * Maybe it depends on the salad's GI index. :) --   Jack of Oz    ... speak! ...   20:02, 24 June 2010 (UTC)
 * I'll take a stab at a serious attempt to find a lower bound. Salad can survive being in a salad spinner. Salad spinners go at, perhaps, 10 revolutions per second and are, perhaps, 30cm in diameter. The centripetal acceleration required to make something go in a circle is $$a=r\omega^2$$ where r=15cm and $$\omega=20\pi \mathrm{s^-1}$$, so a=9.4 m/s or just under 1g. Since it is also under 1g from gravity, the resultant acceleration is $$\sqrt 2$$ g or about 1.4g. So that's the best lower bound I can offer you. --Tango (talk) 20:17, 24 June 2010 (UTC)

tangent

 * judging from the responses so far, perhaps I've hit on an "inherently funny" concept (like a salami sandwich). I know there are clown colleges, perhaps someone could refer me to a researcher at one with whom I could apply for a grant to study and refine the material along these lines.  This is basic research, so it might never lead to comedy or a joke, but pure research has a calling of its own for me. 85.181.145.173 (talk)  —Preceding undated comment added 20:08, 24 June 2010 (UTC).
 * Try here http://www.clownsforhire.com/clownschools.html : "Most "clown schools" hold clown classes when there are enough students to fill or justify having a class" 77.86.123.157 (talk) 21:39, 24 June 2010 (UTC)
 * I don't know about funding for this kind of research, but the Ig Nobel Prizes are awarded for it. --Tango (talk) 20:11, 24 June 2010 (UTC)
 * Well if you want it to be somewhat fresh when it arrives, it would probably have to average 6,000 km/hr on its trip. It will be 2 hours old by then, but if refrigerated, might not be a disaster when it arrives.  Granted, a gourmet chef would probably prefer it to be fresher then that.  Googlemeister (talk) 20:21, 24 June 2010 (UTC)
 * I'd like it to arrive within 7 minutes, as parts are hot/freshly roasted. Looking at it from that end, how many g's of acceleration must it endure to go through a vacuum tunnel clear around the Earth (to the other side) along the equator at sea level in 7 minutes?  85.181.145.173 (talk) 20:26, 24 June 2010 (UTC)
 * I did a rough calc and got 22g, but that did not allow time to slow down at the end, so I hope you like your salad served at mach 12. Googlemeister (talk) 21:08, 24 June 2010 (UTC)
 * I'm getting mach 120 ?77.86.123.157 (talk) 21:20, 24 June 2010 (UTC)
 * I did not actually calculate arrival speed, I just stated a big number. Technically there is no speed of sound in a vacuum in any case.  Googlemeister (talk) 13:04, 25 June 2010 (UTC)
 * (edit conflict) ok so the equations. v=ra/t where v= velocity, r=radius of earth, a=angle you want to travel through (use radians ie 180 degrees = pi radians), and t is the time.
 * and the acceleration is v2/r
 * so the acceleration is a2r/t2 undefined
 * 77.86.123.157 (talk) 21:09, 24 June 2010 (UTC)

um, it should be at the destination at rest at the end of the journey, not flying through it at mach 120 or whatever.

Now, what do these answers, e.g. 36g mean?
Does it mean that a cherry tomato will feel like it just has 36 cherry tomatoes sitting on top of it? 85.181.145.173 (talk) 21:46, 24 June 2010 (UTC)
 * yes. 77.86.123.157 (talk) 22:13, 24 June 2010 (UTC)
 * No. 35 other cherry tomatoes, not sitting on top but connected at the midriff. That's if tomatoes have midriffs and can feel. Which they don't. Instead you will get this. Cuddlyable3 (talk) 23:06, 24 June 2010 (UTC)


 * Have a look at g-force Dolphin  ( t ) 11:10, 25 June 2010 (UTC)

breakup/thinning of plant calluses into solution via ultrasound/high-frequency sonication
I'm trying to image strips of plant cells connected by plasmodesmata by Differential interference contrast microscopy. Of course my hand isn't that precise, so I've used ultrasound sonication as a strategy.

I've been a little unrigourous in my methodology (just trying to figure out what seems to work), but I've been using a combination of surfactants, vortexing, centrifugation slicing and grinding. Ideally I want majority intact cells and a slight minority of injured/broken cells (for nanoparticles to enter through). What combination should I use?

I was thinking of flattening the callus and then slicing into tiny strips/squares, dissolving it a little in water (should I add osmolarity/pH buffer?) and sonicating it. Should I go for low-amplitude, long term sonication (5-15 mins maybe?) or short, powerful bursts? What about adding a little bit of surfactant, alcohol or detergent? I'd also like to thin the cell wall a little -- not totally remove it, but rather make it more permissive to DIC microscopy.

I have access to a few good centrifuges, so I could probably repeatedly centrifuge solutions to remove debris and excess water. I already attempted this once (with lots of sonication) with lots of what I think is cellular debris (I hope it's not microbes) and clumps of intact cells that I can image to some degree. (It's very hard to see the nucleus -- though you normally can). The clump is several cells thick -- from two to four cells I think. Which isn't bad. I'd just like to have suggestions on how to improve it. John Riemann Soong (talk) 20:38, 24 June 2010 (UTC)
 * Are there any enzymes that you can use to selectively digest the cell wall, such as xylanase or cellulase? Graeme Bartlett (talk) 04:02, 25 June 2010 (UTC)
 * I could borrow some from another group. Do these enzymes resist degradation by sonication? John Riemann Soong (talk) 20:36, 25 June 2010 (UTC)

pros and cons of immortality
what are the pros and cons of immortality. note: not asking for medical advice, just curioujs —Preceding unsigned comment added by 85.181.145.173 (talk) 22:09, 24 June 2010 (UTC)
 * have you seen Immortality 77.86.123.157 (talk) 22:14, 24 June 2010 (UTC)
 * Don't expect a pension if you're going to be immortal... Physchim62 (talk) 22:17, 24 June 2010 (UTC)
 * That's not necessarily true, you just wouldn't get as good a pension. You would need an endowment, rather than an annuity. (Obviously unfunded pensions wouldn't work - they require a constant ratio of working people to retired people, and people working for a finite amount of time and then having eternal retirement would result in an ever decreasing ratio.) --Tango (talk) 22:28, 24 June 2010 (UTC)

Also at the top of this page it states "the reference desk does not answer requests for opinions .. do not start a debate" - this question can't really be answered scientifically without 'opinions'. Think for yourself. Have you made the slightest attempt to answer the question yourself? 77.86.123.157 (talk) 22:18, 24 June 2010 (UTC)


 * I don't agree with shouting this question down, and I think the link you provided before the shout-down was helpful and useful. Comet Tuttle (talk) 22:20, 24 June 2010 (UTC)


 * The article Immortality notes that the jellyfish Turritopsis nutricula has developed biological immortality one consequence of which is a worldwide population explosion of the organism. Mark that down as a con if you are considering biological immortality. However that can happen only in fiction so it seems we are being asked to brainstorm about a story plot. Immortality can also describe a person's reputation of which there are good and bad examples. Cuddlyable3 (talk) 22:54, 24 June 2010 (UTC)


 * You can't answer it meaningfully...even hypothetically...there just isn't enough information. For example:
 * Are people somehow immune from accidents? Since your chance of dying in an accidental manner is around 10 to 13 percent, you wouldn't actually live forever.
 * Are people somehow immune from absolutely all diseases? If the only thing this miracle process helps you with is not dying of old age, you should realize that maybe only 50% of people survive disease and accident to actually die of "ageing" (although that's a pretty fuzzy definition - you never really die of "old age" - it's always something specific like heart stoppage).  If you have a 50% chance of making it to 80 years old then you only have a 25% chance to make it to 160 years, a 12% chance to 240 years and so on.  Living forever means never fighting in a war, never driving a car, never crossing the street, never choking on a fishbone, never catching any kind of nasty virus, no cancer, etc.
 * Are you still fully fit and alert through this vastly extended life? Can you still work?  If we have a lot of people with failing faculties and inability to do heavy work then society is in horrible trouble...if they are all fit and alert - then that's a different matter.
 * Are people still able (and willing) to bear children at those ages? Again, this makes an immense difference to population growth rates (which would be serious in any case).
 * Can we assume that the other problems of over-population (global warming, water and food shortages, etc) would also be solved? If not, then the answers are vastly more dramatically serious than if those things too have magically "gone away".
 * In short, this is a speculative question - and we shouldn't attempt to answer it because our remit here at the ref desk says that we don't do that.
 * SteveBaker (talk) 23:04, 24 June 2010 (UTC)
 * I totally believe people will be able to live forever, or at least increase their lifespans by 5 or 10 times, possibly not in my lifetime, but within 100 years or so I think it's very plausible. So I believe this kind of thing will need to be worked out. But yeah, at this stage, it's still pretty much a speculative debate. Vespine (talk) 00:12, 25 June 2010 (UTC)
 * But just think about what you're saying! To have people live forever, you don't just have to solve the 'shortening telomere' problem of aging.  You also have to cure ALL diseases, end ALL wars, eliminate ALL causes of accidental death - oh and by the way: eliminate famine and resource/living-space limitations AND somehow take away people's ability to murder, commit suicide, etc.  If you plan to live forever then how do you avoid car accidents?  What are the odds of you surviving for more than a couple of hundred years without getting involved in a war or being murdered or choking on a fishbone or catching ebola or being struck by lightning or attacked by a rabid dog?  Without the technology to prevent all of those things, immortality is impossible.  As fast as we fix problems of aging, so diseases that you'd rarely live long enough to suffer from (cancer induced by normal background radiation, for example) become significant killers of the population.  Fixing all of those things to provide even a small probability of living (let's say) for 2000 years is a crazily impossible thing!  So sure, lifespans will probably continue to increase as our medical technology advances - and as it has done for the past several hundred years - but immortality takes a much more drastic step that seems unreasonably difficult. SteveBaker (talk) 13:52, 25 June 2010 (UTC)
 * I sure hope we've mastered space-based resource and energy harvesting before then!! APL (talk) 02:43, 25 June 2010 (UTC)


 * There is a huge body of science fiction work where the underlying theme can be roughly summarized as "I've achieved immortality, but it turns out that it sucks." See this TVTropes link for an incomplete, but long, list.
 * Frankly, I've always thought that these stories are a form of sour grapes. APL (talk) 02:34, 25 June 2010 (UTC)

Immortality cannot be experienced because there are only a finite number of states a brain can be in. So, even if you have a brain that exists forever, it can only generate some large but finite number of conscious experiences. In each of these subjective experiences, you have a finite memory of past events. What will happen if the brain survives forever is that some of these conscious experiences will be generated infinitely often. Count Iblis (talk) 03:11, 25 June 2010 (UTC)


 * I think that The Lord of the Rings tackles this issue in a serious and sober manner. Can't think of any others. Vranak (talk) 04:42, 25 June 2010 (UTC)
 * Maybe not exactly serious or sober, but the description of the Struldbrugs in Gulliver's Travels raises some issues about immortality. AndrewWTaylor (talk) 12:00, 25 June 2010 (UTC)
 * Immortality does not imply that the brain "survives forever". For example, nothing on this planet is more than 5 billion years old, and nothing will remain after another 5 billion years when the Sun becomes a red giant. A biologically realistic notion of immortality implies that the immortal being does not age (like many single-cell organisms that can divide indefinitely), or ages but continuously renews itself (like an aspen grove), or reverts to larval stage and starts again (like some jellyfish). All of those are immortal in the sense "not aging"; however, no living being is immortal in the sense of "cannot die". Anything that lives can die. --Dr Dima (talk) 07:11, 25 June 2010 (UTC)


 * If it is the immortality of the Struldbrugs I certainly don't want it. Imaging getting more and more aged and decrepit for ever. Dmcq (talk) 12:08, 25 June 2010 (UTC)


 * Immortality could cause "life" (which is by definition finite) to lose its meaning, as new experiences get less interesting and the level of variety approaches 0, and one would not be able to experience an afterlife if there is one and eventually there would be enough memories to cause brain inflammation. ~ A H  1 (TCU) 02:22, 26 June 2010 (UTC)


 * KSR's Mars trilogy addresses some of these issues -- not precisely with immortality, but with a drastic increases in longevity. One proposed solution to the population question was to award everyone a 0.5 right to bear a child, so that a couple could pool their rights and have one child.  This child would also receive such a right, and this way everyone would be permitted one child, but the population would at most double. -- 58.147.52.85 (talk) 11:58, 26 June 2010 (UTC)