If anyone gets to the 495th or so comment, as a former mathematician, I recommend a pen and paper. If it helps you to have it in ASCII text (for searching, etc...) then take a few minutes at the end of the day to transcribe it.
My rationale - A) Basic mathematical notation has evolved over a few hundred years to be concise and easily manipulated. It once was that equations were all described in text, so that even the description of the square root of a number was cumbersome ('a quantity, which when multiplied by itself yields the original...'). Expressing mathematical entities in textual psuedo notation, while quite a bit better than in prose, is a step backwards.
B) As you get more advanced in mathematics, you will most likely find the need for diagrams anyway (depending on the field). For instance, commutative diagrams in algebra, or all the bizarre pathologies in analysis (such as the 'walking ghosts'). There may be packages to do specific kinds of diagrams, but they will likely be unwieldy.
So get a nice pencil and paper. Or, like has been mentioned many times in this thread, get a Pulse pen. It's no worse than a pen ('cept for price), and you might find it useful.
(mini-review)
I recently got a Pulse pen, and while I'm no longer taking class notes, it's quite handy. It's a tiny bit large for my hand, but fairly comfortable still. You can search for the textual parts of your equations, and it mostly finds them. I've downloaded the MyScript OCR free trial (for Mac), but I don't think I'll buy it, since it does a poor job with my poor hand.
Your comments are valid, but if one is concerned about security, there are a number of steps to take. First, in regard to the STL (well, to be accurate, that part of the library which used to be called the STL), you can test and debug with a 'checked STL' implementation. Such an STL will detect all out of bounds accesses (not just when using 'at'). They can usually check a number of common iterator problems such as using invalidated iterators, an invalid iterator range (such as foreach(a.end(),a.begin()) ), mismatched iterators ( foreach(a.begin(),b.end()), and so on. STLPort provides one such implementation.
As for problems with uninitialized variables and order-of-initializer problems, one should compile with full warnings on. These types of problems are easy for the compiler to catch, and once warned, usually easy for you to fix.
I can think of one good reason to continue using templates in objective c++, despite the fact that they are ugly as all get out. Namely, they can be much faster than any form of dynamic dispatch. Now in most applications, that's just not going to matter that much, but in fields like scientific visualization, it can matter a lot.
Here is a real-life example: to do a direct volume render of a volume dataset, one can cast a ray into the data, sample at many (perhaps thousands) of points along the ray, and then composite the samples together to determine a pixel value. For a large dataset, rendering at HD resolution can require many billions of compositing operations.
Now, the code to cast the rays and determine the sampling points is pretty much set (for non-adaptive renderers), however it is likely that one may wish to composite the samples using different algorithms - absorption only (like x-ray), emissive only, absorptive/emissive (most realistic), or maximum-intensity projection (locate hotspots easily). Thus, one would like to be able to reuse the same raycasting and sampling code, but just vary the compositing algorithm. These algorithms are usually very simple (a handful of adds and multiplies), and so the overhead of dynamic dispatch is actually significant. By using a templated Raycast function, I can plug in different compositors and not only will there be no need for dynamic dispatch, but the code will be inlined by any decent compiler, getting rid of any branch instructions at all. This also allows further optimization (common subexpression elimination, for instance). I have not checked to see what the speedup is for this particular renderer (though I am curious now), but in similar situations in the past, I have seen about an order of magnitude difference in speed. (And that is using C++'s virtual functions, which are pretty low overhead. Not sure how they compare to ObjC's dynamic dispatch).
Again, most applications don't need this kind of speed. Even in scientific computing, there is plenty of room for dynamic dispatch, which can reduce code bloat and (at least to my eye) looks cleaner. But templates can be very valuable when performance matters.
Another example is the Blitz array library (www.oonumerics.org/blitz). One problem with naive implementations of array classes is that they can cause an inordinate amount of temporary array objects to be formed, so that an expression like: A = B*(x^2) + C*x +D where A,B,C and D are large arrays of the same size, causes at least three temporary arrays to be created, only to be deleted once the expression has been computed. Blitz uses a method called 'expression templates' to completely eliminate any temporaries, providing significant speedup .
Look, I understand how this may look like hype - we've had a lot of disease scares recently (not to mention asteroid-scares, bio-terror scares, and so on.) But I think you have to give the epidemiologists some leeway, for many reasons: 1. The death rate may be much higher than 4% 2. The infection rate may be higher than any of the diseases you mentioned 3. The time period from onset to death seems quite short, and 4. This is the very beginning of a possible pandemic.
I'll get to the 4th point in a bit. First....
#3 is fairly clear. SARS seems to have a much quicker death rate than any of the diseases you mentioned except for influenza (which I don't think has recently had such a high mortality rate.)
To address #2, SARS seems to have a drastically higher transmission rate than AIDS. Cancer and heart disease don't spread per se. However influenza does spread quickly as well
To argue #1, note that 4% of the people who have been infected with SARS have died, true. However, many of those people are still infected and may die yet. To get the fatality rate, you have to look at how many people have _recovered_ vs. those who have died, not how many people have been _infected_. This could be well over 10%. Combined with #2, notice that a disease with a 100% mortality rate which infects only 1% of the population is only half as dangerous as a disease which has only a 10% mortality rate which infects 20% of the population.
These last figures approximately mirror the 1918 flu epidemic, which killed 20-40 million people within a single year. Epidemiologists _are_ as scared as hell about another such influenza outbreak. That doesn't mean that SARS isn't a threat though.
So, now is time to address #4. Given that SARS seems to spread quite quickly and widely, may have a significant mortality rate, and kills fairly quickly, hopefully we agree that it could wreak havoc on the world. It may not be the worst epidemic, but it could still hurt us a lot. Now, we should take a look at epidemiology of the thing. When a disease starts to spread, the infection rate grows exponentially for a while. Then, as the susceptible portion of the population dries up, new infections slow down and taper off. The shape of the infected population over time is a logistic, or S-curve:
{cute ASCII graphic deleted due to/. filter}
The important thing to note about this curve (invisible in my ASCII rendering, I'm sure) is that initially it behaves like an exponential curve. Thus, it rises gradually for a while, hits a knee, and then shoots upwards.
All the best health-care practices in the world won't help us once that knee is passed. It is impossible to quarrantine even 5% of the worlds population, so if the infection ever gets to that level, only the most severe of measures could contain it (shutting down all forms of travel, essentially). After 10% of the world's population is infected there is nothing we can do to contain it. Also note that at around that point, hospitals will be overwhelmed, and thus won't be able to alleviate the symptoms of SARS, and thus the mortality rate may rise (right now hospitals can devote all their resources to keeping SARS victims alive until they recover)
So keep in mind that while SARS seems kind of lame now, in terms of how many people it has killed, it exhibits some disturbing characteristics. If those characteristics turn out to be real, then SARS could rival (in the worst case scenario) the plague or the 1918 flu. Now that is jumping the gun a bit, but the facts remain that: 1. SARS is potentially very dangerous. 2. It spreads quickly. 3. It may gain a foothold before we know for sure how dangerous it is.
The reason public health officials are treating this "candy-ass" disease so seriously, is that it really does have the potential to become that serious. And by the time we know that, there isn't much we will be able to do about it.
-matt
P.s. Public health is hard. Declare SARS as the next plague and if your're right, people take precautions, SARS fizzles, and the people assume you overreacted and ignore your warnings next time. Don't warn the public, and risk a pandemic.
Any sarcasm reserved for the first item on your list is mislaid. Many, many pets have RFID tags, and they aren't on the collar (where plain old metal tags do the trick) but actually implanted
in the pet (between the shoulder blades. It's called 'microchipping' your pet, and (after a slow start due to lack of standards) it is highly recommended by vets and shelters lost animals wriggle out of their collars quite frequently. Many humane societies and vets have universal scanners on hand, or at least access to them. The scanner returns a unique ID, which can be looked up in a national database (or even a North American database, I believe)
The actual RFID tag is a passive device, about the size of a grain of rice (kind of a big one) that gets injected between your pets shoulder blades.
I think occasionally they have been known to 'migrate' from that position, but there are almost no health issues.
Our vet implanted an 'Avid' chip (http://www/avidid.com. The vet charged us $30 U.S. Registering with the database is a one time $15 charge (now I'm reading from the website) and it costs $6 to change information in the database when you move.
As to privacy concerns with RFID in general, there are many reasons to be concerned, or at least watchful, of current trends, but I think this is a good application of technology.
From the specification, it seems that D is actually designed to be able to do quite a bit of low level programming. In the section on 'Interfacing to C', the spec states that you can use C's malloc and free without interference from the GC. (Yes, GC scares me a little too, so I was heartened by this.)
Not that I'd go a'kernel-hacking with D myself, but it seems possible.
That's a well put post, except for one glaring error:
On another topic, these long-standing, but
near-universally-believed-to-be-true conjectures
are often assumed to be true in order to prove
other theorems. i.e. a ground-breaking new
primality testing algorithm ASSUMES the truth of
the unproven Reimann Hypothesis.
A conjecture can not be used to prove a theorem (except in a strict mathematical sense which I'll describe in a bit). A proof is extremely rigorous, built up of elements of logic, axioms, and other (previously proven) theorems. Thus, while your hypothetical new primality testing algorithm can be very useful, it can not be PROVEN to be effective or correct until the Riemann Hypothesis is shown to be correct. Mathematics is extremely strict about this. In the (empirical) sciences and law a preponderance of evidence usually serves as proof, but absolutely not in math. So while your new primality testing algorithm may wow generations of computer scientists with its seemingly unerring accuracy, it still won't be proven, and might become completely useless for primes over a googleplex (10^(10^100)) or something. (Of course in that case, you'll end up proving the contrapositive of "If the Riemann hypothesis is true, then my algorithm determines primes.", and thus you'll have disproven the Riemann Hypothesis. Which may piss some people off)
On the other hand, it is not uncommon for a mathematician to prove a link between two conjectures - in fact, this is the story of how Fermat's last theorem was proved. You must note that FLT was a horrible name, and still is. FLT was, until 1993, merely a conjecture. In 1986 Andrew Wiles, who had been mildly obsessed with this FLT-conjecture throughout his whole life, came across a proof by Ken Ribet that linked FLT to the Taniyama-Shimura Conjecture, a complex mathematical statement which says nothing at all about FLT. Ribet actually proved a theorem - "If the Taniyama-Shimura Conjecture is true, then Fermat's Last Theorem is also true." . Andrew Wiles took one look Ribets theorem and got to work proving the Taniyama-Shimura conjecture, which he finished seven years later.
ViewSonic sent a demo unit out to our group here at the NCSA. To answer a couple of questions I've seen in these posts, it has two dual-DVI inputs, so you can use two dual output PCI cards or one quad output card (The one we have is a GeForce4 Quadro, or something similar). It can be run in Linux, and the speed with OpenGL is just fine. Note that the refresh rate of the monitor is just 16Hz or so, which is fast enough for us (when we're rendering 100GB datasets, 16fps would be a godsend) but may make gamers think twice (or more).
That said, it is beautiful to behold. It has a nice wide viewing angle, and is quite bright. They sent us the monitor with a CPU with windows and a gallery of images installed. The images looked very, very nice - you could barely see the pixels at all! But for some reason even though the images were all 3840x2400, we still had to pan around them. Guess what?
OK - a trip to Monitor Properties and we are seeing it at native resolution for real this time. It was almost like looking at a very clear picture, as a previous poster wondered. We had some images of the moon's surface that were better looking than any I've ever seen before, even on print. I'd post screenshots for you if I could.
It was so nice that one of my colleagues suggested to the ViewSonic people that they ship the monitor with a magnifying glass. He wasn't kidding either.
About text, like people keep mentioning, it is awful. In windows, which I find uses quite small text by default anyway, the text on the start bar was illegible without getting up close and peering. In Linux, setting an xterm's text size to Huge makes it legible if you squint. It really is a problem that OS developers need to address because its starting to bug me, even with my 1600x1200 15" laptop screen. Are the physical dimensions of the monitor availible to the OS (using EDIDs or something)?
They are starting to do this - an acquantaince of mine has a cell-phone with a small solar panel, which is indeed a trickle charger for the phone's battery. You can still charge it in a standard charger, but it does prolong the life of the battery. Apparently, these things are all the rage in California.
I'm not sure where he got his from, but I've seen them for sale at www.snpower.com. Only cell-phones, and I have no experience dealing with that particular company.
-matt
Here's a little history on partiview: Partiview started life as part of a project called Virtual Director at the National Center for Supercomputing. Partiview is a data visualization tool, not a simulator -i.e. the universes you explore in Partiview are created beforehand, usually from astronomical observation or from a supercomputer simulation. It is not restricted to astronomical or cosmological data either, as a previous poster noted. The author (and continuing developer) is Stuart Levy of the NCSA, with documentation provided by Peter Teuben.
Partiview does have many features that aid in visualizing stellar dynamics, such as locating interacting groups (stars, galaxies, or other cosmological structure), viewing star trails, and providing differential rotation for galaxies. It can also incorporate (precomputed) isosurfaces into a scene.
The viz code in Partiview is also used in Virtual Director (created by Marcus Thiebaux, maintained by Stuart Levy), which is a collaborative choreography tool designed to be used in immersive virtual environments, originally only for SGI CAVE systems. The Parti code is the real-time renderer we use to set up camera shots (or "paths"). Later, we take the paths and feed them into a high- quality off-line renderer to create wonderfully smooth animations. The virdir/parti combo has been used to create the IMAX film "Cosmic Voyage", planetarium shows (such as at Hayden), and some TV shows - most recently the Discovery Channel show "Unfolding Universe", which started airing this month.
However, using Virtual Director while running a CAVE simulator on a desktop is extremely difficult (you have to control 12 degrees of freedom with a 2D mouse). Therefore Stuart wrote the Partivew standalone executable to be able to develop his particle visualization code without going nuts trying to control the thing, and since then, Partiview has become a nice tool. It is, however, an industrial strength tool, and many of the interesting features are accessed via the command line (thus reading the manual is probably useful).
I could say a lot more about Virtual Director, and Partiview - (I am writing a new, cross platform version of Virtual Director. Or, at least I'm supposed to be, but I seem to be posting to/. instead). But if you are interested, look at the milkyway model. If the model is the same as the one were using here, it's made up of about 20 different datasets - from the Milky Way itself (extrapolated from a kindred Galaxy) to the Hiparcos data set ( observed locations of about 15k of our nearest stellar naighbors) and simulation of interstellar matter, I believe. (One tiny note - on the AMNH page, they seem to imply that they are the sole developer and distributer of Partiview. Partiview is still mainly an NCSA project,
In case documentation isn't provided, you can find it at: http://bima.astro.umd.edu/nemo/amnh/partiview .html.
My wife and I have both titanium wedding and engagement bands (from www.titaniumrings.com). Lovely.
While we both thought they were cool, my wife was very happy about them - she's a grad student in cognitive psych, and works with MRI's (actually FMRI's). Titanium is, I think, the only metal you can wear around an MRI (in fact, when surgery is done while a patient is in an MRI, the surgeons use titanium scalpels). The Ti/Al alloy seems to share that property, so she doesn't have to take her rings off when she goes to the magnet.
Yes a large percentage of cars are on the road at any given time. But also keep in mind that in and around cities, they are travelling at a snails pace (2.8mph according to the London Times survey cited in the report)
If this system can provide speeds averaging 20 mph, then the trip time will be 1/4 of what it was, meaning you would need fewer vehicles to get the same number of people to their destination in the same time. Of course, to reuse a pod during the morning rush, you would have to send it back to the suburbs empty, which cuts the advantage somewhat.
As to the original poster's comment that you would still need a car for travelling outside the system, you're absolutely right. At least in the U.S., people are not going to abandon car ownership - any attempt to force this system upon them to would lead to armed revolt.
However, many families may decide to own only one car instead of 2 or 3, and they would use that car much less often. Instead they will be making shorter trips in a smaller, more efficient vehicle. Much less pollution, much less road rage, quieter neighborhoods.
Not only can you overclock PowerPCs, but when G3 upgrade cards came out for older PowerMacs, some (notably PowerLogix) had thumbwheels on them to control bus speed/multiplier settings. No yanking of boards, no dropping jumpers into the dark recesses of the case. Shutdown, rotate the dials, startup.
One difference between V-Ger and the solar foci telescope is that the latter would have an ion drive. Ion drives, as I understand, can provide continuous thrust for a very long time with more fuel efficiency, so that the solar foci telescope could be constantly accelerating for the first 275 AU, and then decelerating the rest of the way.
Much higher top speeds, supposedly even relativistic speeds, can be reached by this method. Thus, the trip length may be vastly shorter than the rocket thruster+slingshot method that these older satellites use.
However, IANARS, so please correct me if I'm wrong.
Unfortunately, you can not use 6 LCD projectors
if you want to view stereo. There are two options for stereo viewing that are considered: passive and active stereo. The latter requires special shutter glasses (which come in prices of $20 to $600), and the former just requires simple polarized glasses like you get at a 3D Imax.
However, LCD projectors can not do active stereo. The projector displays the left eye view and the right eye view sequentially, and the active glasses (which must be somehow synchronized to the projector) block the right and left eyes sequentially. So at any given time, one eye is viwing an image, and the other sees pure black.
If the refresh rate is too low, then the stereo starts to become flickery. And uncomfortable to the eyes. You can view stereo with a 60Hz display, but for most people, five minutes is about all they can stand. At 96Hz, one can view stereo comfortably for quite a while. 120 hz is even nicer.
From what I understand, LCD panels can't achieve these speeds (something to do with the energy requirements, and especially the cooling requirements, going up exponentially with Hz)
One can use CRT projectors, or DLP projectors (I saw such a CAVE at EVL in Chicago, birthplace of the original CAVE)
With passive stereo, LCD's can be used - basically
you just shine 2 projectors fitted with polarized filters at each screen, spend about a week aligning everything, and you're ready to go (special lenses may be needed so that alignment can actually succeed)
Now, there actually are some other options - the least interesting one is anaglyphic stereo (red/blue glasses). We'll let that one slide.
However, many new auto-stereoscopic technologies (glasses-less) are being developed.
There is lenticular - based on the same principle as those doodads you used to get in cereal boxes, where the picture would change when you rotated the thing. Now those things only had 2 images, and you had to rotate it 30 degrees to change the image. But you can make 'em so fine that each eye sees a different image. Put a display behind it, and you have autostereo.
see here
One of the funkiest methods I've heard of being tried is to use pupil tracking. To understand this, you need to know that the eye is a very low resolution 'camera' for the most part. However, in the dead center of the retina, there is an extremely dense set of receptors called the fovea. It covers only about 1-2 degrees of arc, and this is where your eye picks up pretty much all of the detail.
Now, if you use pupil tracking (which can be done without the viewer having to wear any special equipment), then you can determine the region of the screen each eye's fovea is covering, and draw the corresponding image there. I haven't found an online reference to this yet, but I think it's a cool, if not a little difficult, solution to autostereo.
Heh- this actually IS a problem here, where we have a 6-wall CUBE (CAVE-like beast - an immersive VR environment).
Playing CAVEQuakeII in it is amazing - you have to
sidestep, duck, move around. It really gets your heart rate up.
Problem? No air holes.
(OK - they are working on it, but they don't like the idea of drilling holes in the walls. For now, they just leave the door ajar)
Actually, we have a couple of versions of CAVE Quake running at NCSA, with full head and wand(gun) tracking. I believe that the QIII game
engine is limited to scenery, but it is being worked on. QII is pretty fully functional.
I'm sorry that I can't post the link - we are all getting ready for SuperComputing '01, and I don't want to/. his machine. If someone else posts the link, please be considerate - we are on a very tight schedule and I don't know the capacity of the machine serving the page.
There is no treadmill (currently) hooked up, but
since you are head tracked, dodging, stepping out behind corners, etc works. To get into some spaces you actually have to duck down. Jumping is a bit of a chore though. Really.:)
Slashdot Mirror
If anyone gets to the 495th or so comment, as a former mathematician, I recommend a pen and paper. If it helps you to have it in ASCII text (for searching, etc...) then take a few minutes at the end of the day to transcribe it.
My rationale -
A) Basic mathematical notation has evolved over a few hundred years to be concise and easily manipulated. It once was that equations were all described in text, so that even the description of the square root of a number was cumbersome ('a quantity, which when multiplied by itself yields the original...'). Expressing mathematical entities in textual psuedo notation, while quite a bit better than in prose, is a step backwards.
B) As you get more advanced in mathematics, you will most likely find the need for diagrams anyway (depending on the field). For instance, commutative diagrams in algebra, or all the bizarre pathologies in analysis (such as the 'walking ghosts'). There may be packages to do specific kinds of diagrams, but they will likely be unwieldy.
So get a nice pencil and paper. Or, like has been mentioned many times in this thread, get a Pulse pen. It's no worse than a pen ('cept for price), and you might find it useful.
(mini-review)
I recently got a Pulse pen, and while I'm no longer taking class notes, it's quite handy. It's a tiny bit large for my hand, but fairly comfortable still. You can search for the textual parts of your equations, and it mostly finds them. I've downloaded the MyScript OCR free trial (for Mac), but I don't think I'll buy it, since it does a poor job with my poor hand.
Your comments are valid, but if one is concerned about security, there are a number of steps to take. First, in regard to the STL (well, to be accurate, that part of the library which used to be called the STL), you can test and debug with a 'checked STL' implementation. Such an STL will detect all out of bounds accesses (not just when using 'at'). They can usually check a number of common iterator problems such as using invalidated iterators, an invalid iterator range (such as foreach(a.end(),a.begin()) ), mismatched iterators ( foreach(a.begin(),b.end()), and so on. STLPort provides one such implementation.
As for problems with uninitialized variables and order-of-initializer problems, one should compile with full warnings on. These types of problems are easy for the compiler to catch, and once warned, usually easy for you to fix.
I can think of one good reason to continue using templates in objective c++, despite the fact that they are ugly as all get out. Namely, they can be much faster than any form of dynamic dispatch. Now in most applications, that's just not going to matter that much, but in fields like scientific visualization, it can matter a lot.
Here is a real-life example: to do a direct volume render of a volume dataset, one can cast a ray into the data, sample at many (perhaps thousands) of points along the ray, and then composite the samples together to determine a pixel value. For a large dataset, rendering at HD resolution can require many billions of compositing operations.
Now, the code to cast the rays and determine the sampling points is pretty much set (for non-adaptive renderers), however it is likely that one may wish to composite the samples using different algorithms - absorption only (like x-ray), emissive only, absorptive/emissive (most realistic), or maximum-intensity projection (locate hotspots easily). Thus, one would like to be able to reuse the same raycasting and sampling code, but just vary the compositing algorithm. These algorithms are usually very simple (a handful of adds and multiplies), and so the overhead of dynamic dispatch is actually significant. By using a templated Raycast function, I can plug in different compositors and not only will there be no need for dynamic dispatch, but the code will be inlined by any decent compiler, getting rid of any branch instructions at all. This also allows further optimization (common subexpression elimination, for instance). I have not checked to see what the speedup is for this particular renderer (though I am curious now), but in similar situations in the past, I have seen about an order of magnitude difference in speed. (And that is using C++'s virtual functions, which are pretty low overhead. Not sure how they compare to ObjC's dynamic dispatch).
Again, most applications don't need this kind of speed. Even in scientific computing, there is plenty of room for dynamic dispatch, which can reduce code bloat and (at least to my eye) looks cleaner. But templates can be very valuable when performance matters.
Another example is the Blitz array library (www.oonumerics.org/blitz). One problem with naive implementations of array classes is that they can cause an inordinate amount of temporary array objects to be formed, so that an expression like:
A = B*(x^2) + C*x +D
where A,B,C and D are large arrays of the same size, causes at least three temporary arrays to be created, only to be deleted once the
expression has been computed. Blitz uses a method called 'expression templates' to completely eliminate any temporaries, providing significant speedup .
Hope this answers your question.
-matt
Look, I understand how this may look like hype - we've had a lot of disease scares recently (not to mention asteroid-scares, bio-terror scares, and so on.) But I think you have to give the epidemiologists some leeway, for many reasons:
/. filter}
1. The death rate may be much higher than 4%
2. The infection rate may be higher than any of the diseases you mentioned
3. The time period from onset to death seems quite short, and
4. This is the very beginning of a possible pandemic.
I'll get to the 4th point in a bit. First....
#3 is fairly clear. SARS seems to have a much quicker death rate than any of the diseases you mentioned except for influenza (which I don't think has recently had such a high mortality rate.)
To address #2, SARS seems to have a drastically higher transmission rate than AIDS. Cancer and heart disease don't spread per se. However influenza does spread quickly as well
To argue #1, note that 4% of the people who have been infected with SARS have died, true. However, many of those people are still infected and may die yet. To get the fatality rate, you have to look at how many people have _recovered_ vs. those who have died, not how many people have been _infected_. This could be well over 10%.
Combined with #2, notice that a disease with a 100% mortality rate which infects only 1% of the population is only half as dangerous as a disease which has only a 10% mortality rate which infects 20% of the population.
These last figures approximately mirror the 1918 flu epidemic, which killed 20-40 million people within a single year. Epidemiologists _are_ as scared as hell about another such influenza outbreak. That doesn't mean that SARS isn't a threat though.
So, now is time to address #4. Given that SARS seems to spread quite quickly and widely, may have a significant mortality rate, and kills fairly quickly, hopefully we agree that it could wreak havoc on the world. It may not be the worst epidemic, but it could still hurt us a lot. Now, we should take a look at epidemiology of the thing.
When a disease starts to spread, the infection rate grows exponentially for a while. Then, as the susceptible portion of the population dries up, new infections slow down and taper off. The shape of the infected population over time is a logistic, or S-curve:
{cute ASCII graphic deleted due to
The important thing to note about this curve (invisible in my ASCII rendering, I'm sure) is that initially it behaves like an exponential curve. Thus, it rises gradually for a while, hits a knee, and then shoots upwards.
All the best health-care practices in the world won't help us once that knee is passed. It is impossible to quarrantine even 5% of the worlds population, so if the infection ever gets to that level, only the most severe of measures could contain it (shutting down all forms of travel, essentially). After 10% of the world's population is infected there is nothing we can do to contain it. Also note that at around that point, hospitals will be overwhelmed, and thus won't be able to alleviate the symptoms of SARS, and thus the mortality rate may rise (right now hospitals can devote all their resources to keeping SARS victims alive until they recover)
So keep in mind that while SARS seems kind of lame now, in terms of how many people it has killed, it exhibits some disturbing characteristics. If those characteristics turn out to be real, then SARS could rival (in the worst case scenario) the plague or the 1918 flu. Now that is jumping the gun a bit, but the facts remain that:
1. SARS is potentially very dangerous.
2. It spreads quickly.
3. It may gain a foothold before we know for sure how dangerous it is.
The reason public health officials are treating this "candy-ass" disease so seriously, is that it really does have the potential to become that serious. And by the time we know that, there isn't much we will be able to do about it.
-matt
P.s. Public health is hard. Declare SARS as the next plague and if your're right, people take precautions, SARS fizzles, and the people assume you overreacted and ignore your warnings next time. Don't warn the public, and risk a pandemic.
The actual RFID tag is a passive device, about the size of a grain of rice (kind of a big one) that gets injected between your pets shoulder blades. I think occasionally they have been known to 'migrate' from that position, but there are almost no health issues.
Our vet implanted an 'Avid' chip (http://www/avidid.com. The vet charged us $30 U.S. Registering with the database is a one time $15 charge (now I'm reading from the website) and it costs $6 to change information in the database when you move.
As to privacy concerns with RFID in general, there are many reasons to be concerned, or at least watchful, of current trends, but I think this is a good application of technology.
-matt
From the specification, it seems that D is actually designed to be able to do quite a bit of low level programming. In the section on 'Interfacing to C', the spec states that you can use C's malloc and free without interference from the GC. (Yes, GC scares me a little too, so I was heartened by this.)
Not that I'd go a'kernel-hacking with D myself, but it seems possible.
-matt
That's a well put post, except for one glaring error:
On another topic, these long-standing, but
near-universally-believed-to-be-true conjectures
are often assumed to be true in order to prove
other theorems. i.e. a ground-breaking new
primality testing algorithm ASSUMES the truth of
the unproven Reimann Hypothesis.
A conjecture can not be used to prove a theorem (except in a strict mathematical sense which I'll describe in a bit). A proof is extremely rigorous, built up of elements of logic, axioms, and other (previously proven) theorems. Thus, while your hypothetical new primality testing algorithm can be very useful, it can not be PROVEN to be effective or correct until the Riemann Hypothesis is shown to be correct. Mathematics is extremely strict about this. In the (empirical) sciences and law a preponderance of evidence usually serves as proof, but absolutely not in math. So while your new primality testing algorithm may wow generations of computer scientists with its seemingly unerring accuracy, it still won't be proven, and might become completely useless for primes over a googleplex (10^(10^100)) or something. (Of course in that case, you'll end up proving the contrapositive of "If the Riemann hypothesis is true, then my algorithm determines primes.", and thus you'll have disproven the Riemann Hypothesis. Which may piss some people off)
On the other hand, it is not uncommon for a mathematician to prove a link between two conjectures - in fact, this is the story of how Fermat's last theorem was proved. You must note that FLT was a horrible name, and still is. FLT was, until 1993, merely a conjecture. In 1986 Andrew Wiles, who had been mildly obsessed with this FLT-conjecture throughout his whole life, came across a proof by Ken Ribet that linked FLT to the Taniyama-Shimura Conjecture, a complex mathematical statement which says nothing at all about FLT. Ribet actually proved a theorem - "If the Taniyama-Shimura Conjecture is true, then Fermat's Last Theorem is also true." . Andrew Wiles took one look Ribets theorem and got to work proving the Taniyama-Shimura conjecture, which he finished seven years later.
-matt
That said, it is beautiful to behold. It has a nice wide viewing angle, and is quite bright. They sent us the monitor with a CPU with windows and a gallery of images installed. The images looked very, very nice - you could barely see the pixels at all! But for some reason even though the images were all 3840x2400, we still had to pan around them. Guess what?
OK - a trip to Monitor Properties and we are seeing it at native resolution for real this time. It was almost like looking at a very clear picture, as a previous poster wondered. We had some images of the moon's surface that were better looking than any I've ever seen before, even on print. I'd post screenshots for you if I could. It was so nice that one of my colleagues suggested to the ViewSonic people that they ship the monitor with a magnifying glass. He wasn't kidding either.
About text, like people keep mentioning, it is awful. In windows, which I find uses quite small text by default anyway, the text on the start bar was illegible without getting up close and peering. In Linux, setting an xterm's text size to Huge makes it legible if you squint. It really is a problem that OS developers need to address because its starting to bug me, even with my 1600x1200 15" laptop screen. Are the physical dimensions of the monitor availible to the OS (using EDIDs or something)?
Well, must go. -matt
They are starting to do this - an acquantaince of mine has a cell-phone with a small solar panel, which is indeed a trickle charger for the phone's battery. You can still charge it in a standard charger, but it does prolong the life of the battery. Apparently, these things are all the rage in California.
I'm not sure where he got his from, but I've seen them for sale at www.snpower.com. Only cell-phones, and I have no experience dealing with that particular company. -matt
Here's a little history on partiview:
Partiview started life as part of a project called Virtual Director
at the National Center for Supercomputing. Partiview is a data
visualization tool, not a simulator -i.e. the universes you explore
in Partiview are created beforehand, usually from astronomical observation
or from a supercomputer simulation. It is not restricted to
astronomical or cosmological data either, as a previous poster noted.
The author (and continuing developer) is Stuart Levy of the NCSA,
with documentation provided by Peter Teuben.
Partiview does have many features that aid in visualizing stellar
dynamics, such as locating interacting groups (stars, galaxies, or
other cosmological structure), viewing star trails, and providing
differential rotation for galaxies. It can also incorporate
(precomputed) isosurfaces into a scene.
The viz code in Partiview is also used in Virtual Director (created
by Marcus Thiebaux, maintained by Stuart Levy), which is a
collaborative choreography tool designed to be used in immersive
virtual environments, originally only for SGI CAVE systems.
The Parti code is the real-time renderer we use to set up camera shots
(or "paths"). Later, we take the paths and feed them into a high-
quality off-line renderer to create wonderfully smooth animations.
The virdir/parti combo has been used to create the IMAX film "Cosmic
Voyage", planetarium shows (such as at Hayden), and some TV shows -
most recently the Discovery Channel show "Unfolding Universe", which
started airing this month.
However, using Virtual Director while running a CAVE simulator on
a desktop is extremely difficult (you have to control 12 degrees
of freedom with a 2D mouse). Therefore Stuart wrote the Partivew
standalone executable to be able to develop his particle
visualization code without going nuts trying to control the thing,
and since then, Partiview has become a nice tool. It is, however,
an industrial strength tool, and many of the interesting features
are accessed via the command line (thus reading the manual is probably
useful).
I could say a lot more about Virtual Director, and Partiview - (I am
writing a new, cross platform version of Virtual Director. Or, at
least I'm supposed to be, but I seem to be posting to
But if you are interested, look at the milkyway model. If the model
is the same as the one were using here, it's made up of about 20
different datasets - from the Milky Way itself (extrapolated from
a kindred Galaxy) to the Hiparcos data set ( observed locations of
about 15k of our nearest stellar naighbors) and simulation of
interstellar matter, I believe.
(One tiny note - on the AMNH page, they seem to imply that they
are the sole developer and distributer of Partiview. Partiview
is still mainly an NCSA project,
In case documentation isn't provided, you can find it at:
http://bima.astro.umd.edu/nemo/amnh/partivie
-matt
My wife and I have both titanium wedding and engagement bands (from www.titaniumrings.com).
Lovely.
While we both thought they were cool, my wife was very happy about them - she's a grad student in cognitive psych, and works with MRI's (actually FMRI's). Titanium is, I think, the only metal you can wear around an MRI (in fact, when surgery is done while a patient is in an MRI, the surgeons use titanium scalpels). The Ti/Al alloy seems to share that property, so she doesn't have to take her rings off when she goes to the magnet.
Yes a large percentage of cars are on the road at any given time. But also keep in mind that in and around cities, they are travelling at a snails pace (2.8mph according to the London Times survey cited in the report)
If this system can provide speeds averaging 20 mph, then the trip time will be 1/4 of what it was, meaning you would need fewer vehicles to get the same number of people to their destination in the same time. Of course, to reuse a pod during the morning rush, you would have to send it back to the suburbs empty, which cuts the advantage somewhat.
As to the original poster's comment that you would still need a car for travelling outside the system, you're absolutely right. At least in the U.S., people are not going to abandon car ownership - any attempt to force this system upon them to would lead to armed revolt.
However, many families may decide to own only one car instead of 2 or 3, and they would use that car much less often. Instead they will be making shorter trips in a smaller, more efficient vehicle. Much less pollution, much less road rage, quieter neighborhoods.
Now if only it works...
Overclocking for the rest of us.
-matt
One difference between V-Ger and the solar foci telescope is that the latter would have an ion drive. Ion drives, as I understand, can provide continuous thrust for a very long time with more fuel efficiency, so that the solar foci telescope could be constantly accelerating for the first 275 AU, and then decelerating the rest of the way.
Much higher top speeds, supposedly even relativistic speeds, can be reached by this method. Thus, the trip length may be vastly shorter than the rocket thruster+slingshot method that these older satellites use.
However, IANARS, so please correct me if I'm wrong.
However, LCD projectors can not do active stereo. The projector displays the left eye view and the right eye view sequentially, and the active glasses (which must be somehow synchronized to the projector) block the right and left eyes sequentially. So at any given time, one eye is viwing an image, and the other sees pure black. If the refresh rate is too low, then the stereo starts to become flickery. And uncomfortable to the eyes. You can view stereo with a 60Hz display, but for most people, five minutes is about all they can stand. At 96Hz, one can view stereo comfortably for quite a while. 120 hz is even nicer.
From what I understand, LCD panels can't achieve these speeds (something to do with the energy requirements, and especially the cooling requirements, going up exponentially with Hz) One can use CRT projectors, or DLP projectors (I saw such a CAVE at EVL in Chicago, birthplace of the original CAVE)
With passive stereo, LCD's can be used - basically you just shine 2 projectors fitted with polarized filters at each screen, spend about a week aligning everything, and you're ready to go (special lenses may be needed so that alignment can actually succeed)
Now, there actually are some other options - the least interesting one is anaglyphic stereo (red/blue glasses). We'll let that one slide.
However, many new auto-stereoscopic technologies (glasses-less) are being developed.
There is lenticular - based on the same principle as those doodads you used to get in cereal boxes, where the picture would change when you rotated the thing. Now those things only had 2 images, and you had to rotate it 30 degrees to change the image. But you can make 'em so fine that each eye sees a different image. Put a display behind it, and you have autostereo. see here
One of the funkiest methods I've heard of being tried is to use pupil tracking. To understand this, you need to know that the eye is a very low resolution 'camera' for the most part. However, in the dead center of the retina, there is an extremely dense set of receptors called the fovea. It covers only about 1-2 degrees of arc, and this is where your eye picks up pretty much all of the detail.
Now, if you use pupil tracking (which can be done without the viewer having to wear any special equipment), then you can determine the region of the screen each eye's fovea is covering, and draw the corresponding image there. I haven't found an online reference to this yet, but I think it's a cool, if not a little difficult, solution to autostereo.
-matt
Problem? No air holes.
(OK - they are working on it, but they don't like the idea of drilling holes in the walls. For now, they just leave the door ajar)
Info about the new 6-Walled CUBE:
http://www.isl.uiuc.edu/Virtual%20Tour/TourPages/I SLtour.htm
Article about CAVEQuake:
www.gamespot.com/features/cave_quake2
Elazro
I'm sorry that I can't post the link - we are all getting ready for SuperComputing '01, and I don't want to /. his machine. If someone else posts the link, please be considerate - we are on a very tight schedule and I don't know the capacity of the machine serving the page.
There is no treadmill (currently) hooked up, but since you are head tracked, dodging, stepping out behind corners, etc works. To get into some spaces you actually have to duck down. Jumping is a bit of a chore though. Really. :)