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Juggling Molecules with Linux
An anonymous reader writes "This article at LinuxDevices.com describes an interesting project at the University of Vermont in which researchers use real-time Linux to build a laser trap that manipulates individual molecules by means of a computer-controlled laser beam. The project makes use of RTLinux, a real-time enhanced version of Linux that allows the system to process interrupts every 50 microsecond, sample new data, and timeshare the laser beam position. 'If the computer failed to respond, for even a millisecond, then we would drop the balls,' explained one of the researchers. Gives a whole new meaning to BSOD, eh?"
I know several researchers who have been using realtime Linux on the desktop while performing studies regarding the user experience of systems with minimal latency. Their preliminary findings are that users much prefer the instantaneous response that a realtime system offers, even if the system does not perform as well when it comes to raw data crunching. For future desktop systems, heavily multithreaded, realtime apps are the way to go.
Cyric Zndovzny at your service.
I was under the impression that the whole idea of a laser trap is that you CAN'T drop the ball. Small particles get trapped in the beam due to photon pressure, if the particle shifts away from the center of the beam, it automatically is recentered. Then you can move the beam to manipulate the particle which is attached to a molecule. They use these to fold and unfold proteins, lipid layers, DNA, etc.
I mean, it's great that they're using a realtime kernel, but they really shouldn't NEED it.
-- sometimes AND gates turn me on.
I don't dispute your friends' findings, but I'm wondering why a RT based OS would really improve the user experience?
Here's why I ask: A RT system is typically real time for some dedicated purpose. Not all pieces of the system have to be RT; just the important bits. Now, an average user PC is NOT a specialized device at all. It can be running a number of applications and, except for cases where a given process has a higher priority, all the processes typically get an opportunity for equal time from the CPU. A desktop system with a RT OS would also fit this description too, right?
Now, given that: where's the RT aspect in all of this? What's actually RT in this situation? The pre-emptive multitasking loop? The UI event/response loop? The IO loop (assuming you could describe it that way)? The video update loop? What about this would give the user a better experience?
Please mod this post only if you think others should/n't read this. I have enough ego^H^H^Hkarma. Thanks!
One question: Typing error on your side? Do you mean 10ms or 10 us?
Because 10ms is hardly a latency to brag about... for any os...
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
Sorry, 10us.
Yes. When they only needed 10us latency, they didn't lose any. And that was on a 200MHz CPU.
A friend of mine implemented tetris using a laser to trap 1 mirometre glass beads. Short story + picture + video here. More explanation here.
How interesting. I just saw a lecture by one of the men that won a nobel prize for this very thing, Steven Chu. What is being done here is essentially what is called Optical Tweezers.
The way this works is that the laser is fired, in timed pulses at a molecule. When the laser hits it from an opposing direction, it starts to cancel out the kinetic energy that the molecule has, and therefore cooling it. (I think it was something to the order of 2.0 × 10^-06 degrees above absolute zero).
In a nutshell, this is what is going on:
-SteveAlmost Absolute Zero == Essentially No Movement == Essentially "Frozen" Object