The charge is not static. It says "velocity of one meter per second". That means it's moving- if it wasn't moving, there would be no force on it, despite the magnetic field.
One electron has a charge of 1.6E-19 Coloumbs, so you are talking about the equivalent of 6.7E18 electrons moving at 1m/s. One coulomb is the amount of charge that passes through a point in a wire in one second which is carrying one Amp of current.
The instantaneous force being described would be perpendicular to both the motion of the particle and that of the magnetic field. Make a gun with your right hand, let your index finger point in the direction of the charge, let the field point in the direction of your thumb. Stick out your middle finger so it makes a right angle with both digits, and that is the direction of the force.
Yes and no. Most MRI systems for humans operate at about 1.5 Tesla. I know of at least one 8 Tesla system, but that is experimental. The higher the static field (i.e. the 25 Tesla), the better the resolution of your system can be.
No one knows the effects of an 25 Tesla magnet on biological tissues. In addition, in order to get useable information out of an MRI system, one must hit it with radiofrequency (RF) waves. The higher the static field is, the higher these frequencies are going to be. A 7-tesla magnet uses frequences around 300 MHz. Therefore, by extrapolation (which I believe is right, since I know that a 9T system uses about 383 MHz), a 25 Hz system would need about 1.1 GHz. This might very well be extremely detrimental to biological tissue. In other words, to do MRI, you'd have to cook your sample.
Finally, to truly achieve a resolution advantage, you will need very powerful gradients. The gradients one would need to take advantage of such a system would be gigantic, at least tens if not hundreds of Tesla per meter. This would be very difficult to design for samples as large as a human body, if not impossible with today's technology, and at the very least extremely expensive.
Personally, I can see a 25 Tesla magnet being useful, just not for MRI. Perhaps for NMR being using not for imaging purposes, but in the study of non-soft condensed matter systems (i.e. not biological or organic, but solid state). It would be useful for examining superconductivity also.
As of 4:00PM Sept. 3, 2003, there are already well over 30 bids on the I-Tune, and bidding has exceeded $20. The original price was only $0.99. Very interesting.
You are correct about Landis. I met him back in 1995 when I was a summer intern at NASA. He works in the Photovoltaic Branch in Cleveland's Glenn Research Center.
I just want to reply to some of the people bashing Case as not caring about its students, spending money on name recognition, etc. While there may be some truth to these claims, they are being wildly exaggerated. I graduated from CWRU 3 years ago, and found my professors there to be extremely caring, and still maintain contact with them and ask them for advice. They have helped immensely with establishing my career path (I'm currently in grad school). There may still be a need for better teaching professors, but this is a result of Case being a primarily research-oriented institution for decades.
As for the tuition gripe, yes it is true that tuition has gone up, and that some of that money has been spent on trying to better the school and increase its name recognition. But tuition has gone up across the board, so the CWRU increases are nothing special- I'm willing to bet that they were less than the Ohio State tuition bumbs percentagewise. Secondly, the money spent on name recognition and the like seems to be working- here is this wireless network construction on Slashdot's frontpage.
So all in all, while Case will have its detractors, I think it is an up and coming institution. Trying to break new ground does not come cheap, and success is not guaranteed, but the spoils of achievement are well worth the risk.
This is a very good point. I realized before I posted that a diode is non-linear, but I was more or less trying to figure out where they got that 80% number. Hopefully, someone will mod these up...
I guess it depends on how you measure 'electricity'. If you measure it in terms of energy (the most sensible), than you save 40%, because energy and power are linearly related.
However, if you measure in terms of current, you might get a different answer. Assuming that both bulbs have the same resistence (a shaky presumption at best), we can calculate the current being used by the LED compared to the incandescent via power=(current)^2 * (resistance). This leads to a 60W LED using 77.46% of the current a 100W bulb uses (square root of 3/5).
The problem with the second method is that measuring electricity by current is perhaps not the best method to apply in this case. Plus you have to assume an equal resistance (which is doubtful). But perhaps that is how they arrived at their 80% figure.
"After another minute I was so bored that I picked it up to see what it had done... the wipe was completely clean but it was starting to push dirt in front of it. The ground clearance is so low that the dirt can't go under it to reach the wipe!"
Now that's what I call quality engineering. And I love the analog 'processor'!
While there is little doubt that executive administrations pick and choose the statisitics they base their policy choices on, this President has been particularly bad. Republicans and Democrats have twisted scientific data and opinions to suit their own desires, but President Bush has a habit of forcing his religious moral on the rest of us, and helping out his big business pals using 'scientists' as justification. The level of this type of behavior is unprecedented.
Well, I heard that there is one place here in town that has it, but so far I've had no luck in finding it. And a little bird told me that Coors might be bringing Caffrey's back sometime soon. Who knows if that means within a year, or within five, but the sooner the better.
What about newsgroups? I hear about people trading very large amounts of data via newsgroups all the time, including entire CD's. It seems to be more reliable than peer-to-peer, and it's private. And what about the IRC? I've heard of people getting software shipped to them before it's even released to the general public because of good contacts on IRC channels!
BTW, what is up with the formatting on Slashdot? The comment form REFUSED to accept the URL correctly, it kept putting a space in the word 'raid'. That sucks a lot, and there is no reason for it work like that. How can anyone post a URL?
There is some sort of forum there, and people are going crazy about how Tilley's rights were violated when the government seized his stuff. Personally, I don't see that as seizure of property as much as it is seizure of evidence- the guy supposedly had cash lying around everywhere in common objects like coffee cans. Besides, how is the government supposed to test his devices if it doesn't have them?
Seems like they are putting this one out early. But I don't find this to be a trend in just MMORPG, but in ANY game being released these days. BF1942 is still releasing patches, and 'expansion packs', and on the singleplayer side of things, so is Civ3, which took over 6 months to release the final patch (which is still buggy). What happened to the good old days of rigourous in house testing and beta release? I guess those days are long gone, bound for nostalgic recollections of old school gamers...
Current MRI magnets operate at about 1 Tesla, with a bore large enough to accomdate a human head, or even a whole human body. In the future, there is a good chance that we will be using more powerful magnets, which may exacerbate the effect this company is trying to compensate for. The question is, will the thickness of their coating suffice when we are using higher power magnets? For instance, at the Ohio State University Medical Center, the world's most powerful medical MRI unit is in the first stages of testing. It operates at 8 Tesla, which is CONSIDERABLY more powerful than 1 Tesla. The thing is so strong that it will erase your credit cards from 20 to 30 feet away, through a wall. Just a thought about the future of MRI.
Slashdot Mirror
One electron has a charge of 1.6E-19 Coloumbs, so you are talking about the equivalent of 6.7E18 electrons moving at 1m/s. One coulomb is the amount of charge that passes through a point in a wire in one second which is carrying one Amp of current.
The instantaneous force being described would be perpendicular to both the motion of the particle and that of the magnetic field. Make a gun with your right hand, let your index finger point in the direction of the charge, let the field point in the direction of your thumb. Stick out your middle finger so it makes a right angle with both digits, and that is the direction of the force.
No one knows the effects of an 25 Tesla magnet on biological tissues. In addition, in order to get useable information out of an MRI system, one must hit it with radiofrequency (RF) waves. The higher the static field is, the higher these frequencies are going to be. A 7-tesla magnet uses frequences around 300 MHz. Therefore, by extrapolation (which I believe is right, since I know that a 9T system uses about 383 MHz), a 25 Hz system would need about 1.1 GHz. This might very well be extremely detrimental to biological tissue. In other words, to do MRI, you'd have to cook your sample.
Finally, to truly achieve a resolution advantage, you will need very powerful gradients. The gradients one would need to take advantage of such a system would be gigantic, at least tens if not hundreds of Tesla per meter. This would be very difficult to design for samples as large as a human body, if not impossible with today's technology, and at the very least extremely expensive.
Personally, I can see a 25 Tesla magnet being useful, just not for MRI. Perhaps for NMR being using not for imaging purposes, but in the study of non-soft condensed matter systems (i.e. not biological or organic, but solid state). It would be useful for examining superconductivity also.
As of 4:00PM Sept. 3, 2003, there are already well over 30 bids on the I-Tune, and bidding has exceeded $20. The original price was only $0.99. Very interesting.
You are correct about Landis. I met him back in 1995 when I was a summer intern at NASA. He works in the Photovoltaic Branch in Cleveland's Glenn Research Center.
I'm in physics, as a matter of fact. My favorite profs were Chottiner, Mathur, Kash, and Singer.
As for the tuition gripe, yes it is true that tuition has gone up, and that some of that money has been spent on trying to better the school and increase its name recognition. But tuition has gone up across the board, so the CWRU increases are nothing special- I'm willing to bet that they were less than the Ohio State tuition bumbs percentagewise. Secondly, the money spent on name recognition and the like seems to be working- here is this wireless network construction on Slashdot's frontpage.
So all in all, while Case will have its detractors, I think it is an up and coming institution. Trying to break new ground does not come cheap, and success is not guaranteed, but the spoils of achievement are well worth the risk.
This is a very good point. I realized before I posted that a diode is non-linear, but I was more or less trying to figure out where they got that 80% number. Hopefully, someone will mod these up...
However, if you measure in terms of current, you might get a different answer. Assuming that both bulbs have the same resistence (a shaky presumption at best), we can calculate the current being used by the LED compared to the incandescent via power=(current)^2 * (resistance). This leads to a 60W LED using 77.46% of the current a 100W bulb uses (square root of 3/5).
The problem with the second method is that measuring electricity by current is perhaps not the best method to apply in this case. Plus you have to assume an equal resistance (which is doubtful). But perhaps that is how they arrived at their 80% figure.
Now that's what I call quality engineering. And I love the analog 'processor'!
While there is little doubt that executive administrations pick and choose the statisitics they base their policy choices on, this President has been particularly bad. Republicans and Democrats have twisted scientific data and opinions to suit their own desires, but President Bush has a habit of forcing his religious moral on the rest of us, and helping out his big business pals using 'scientists' as justification. The level of this type of behavior is unprecedented.
Well, I heard that there is one place here in town that has it, but so far I've had no luck in finding it. And a little bird told me that Coors might be bringing Caffrey's back sometime soon. Who knows if that means within a year, or within five, but the sooner the better.
I'd rather have a Caffrey's myself, but they don't have it in the States anymore, not since 1999 or so.
What about newsgroups? I hear about people trading very large amounts of data via newsgroups all the time, including entire CD's. It seems to be more reliable than peer-to-peer, and it's private. And what about the IRC? I've heard of people getting software shipped to them before it's even released to the general public because of good contacts on IRC channels!
Can you add a hard disk after purchase?
Seriously. 11 comments and it has already been /.'ed. Amazing.
Thanks sebi and AC. Very helpful. Tilley 101
http://www.greaterthings.com/News/Tilley/fraud/rai d/index.html
http://www.greaterthings.com/News/Tilley/fraud/rai d/index.html
There is some sort of forum there, and people are going crazy about how Tilley's rights were violated when the government seized his stuff. Personally, I don't see that as seizure of property as much as it is seizure of evidence- the guy supposedly had cash lying around everywhere in common objects like coffee cans. Besides, how is the government supposed to test his devices if it doesn't have them?
Seems like they are putting this one out early. But I don't find this to be a trend in just MMORPG, but in ANY game being released these days. BF1942 is still releasing patches, and 'expansion packs', and on the singleplayer side of things, so is Civ3, which took over 6 months to release the final patch (which is still buggy). What happened to the good old days of rigourous in house testing and beta release? I guess those days are long gone, bound for nostalgic recollections of old school gamers...
lol... i didn't notice that. and no, I know BillGates is not a /.er.
None of us mere ./ mortals will ever be able to afford this, unless your name is BillGates or some other such fantastically rich nerd.
Damnit Jim, I'm a doctor, not a bricklayer!
Free software being used to keep people from getting free bandwidth. How ironic.
C&W is in the red, so to speak, hence the red bars!
Current MRI magnets operate at about 1 Tesla, with a bore large enough to accomdate a human head, or even a whole human body. In the future, there is a good chance that we will be using more powerful magnets, which may exacerbate the effect this company is trying to compensate for. The question is, will the thickness of their coating suffice when we are using higher power magnets? For instance, at the Ohio State University Medical Center, the world's most powerful medical MRI unit is in the first stages of testing. It operates at 8 Tesla, which is CONSIDERABLY more powerful than 1 Tesla. The thing is so strong that it will erase your credit cards from 20 to 30 feet away, through a wall. Just a thought about the future of MRI.