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Author Topic:   using your cd-rom to test for anthrax
New Cat's Eye
Inactive Member


Message 31 of 45 (301690)
04-06-2006 4:43 PM
Reply to: Message 28 by riVeRraT
04-06-2006 3:29 PM


I agree with RR too
It seems to me like jar was just being an ass.

Does he not like you?


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jar
Member
Posts: 30988
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.4


Message 32 of 45 (301706)
04-06-2006 5:40 PM
Reply to: Message 25 by riVeRraT
04-06-2006 3:17 PM


Re: Thank God
Rat, please read Message 21.

In your OP you said:

You take a blank cd, put a drop of water on the inner circle, add the suspected substance. Bake in an oven at 75F for 20 minutes. Add a protective cover, and insert into your cd rom drive. With the software it uses the laser in the drive which has a resolution to 300 nanometers? to read the image left by the stain. Then a spectrograph of sorts pops up on your computer, and you can just compare images. I think it even tells you what it is, if it recognizes it.

That is what I was responding to. Anyone reading that who does not immediately hear the ringing gong of a BS detector needs some lessons in critical thinking.

Let's parse it.

First, the title of the thread is "using your cd-rom to test for anthrax". That was the first thing that made the red flares go off and the gongs start ringing. The idea of a home anthrax test is enough to make anyone suspect the remainder of the article.

Then you said:

You take a blank cd, put a drop of water on the inner circle, add the suspected substance.

Second flare goes off. Joe home owner is supposed to handle the stuff and dissolve it in water? But the drop on the inner circle which has no recording medium and also often has the printing for batch and part number? In addition, that area is beyond the reading track of most consumer CD drives, in fact the heads are specifically designed to avoid that area. Third and fourth BS flares go off.

The next sentence:

Bake in an oven at 75F for 20 minutes.

Bake in an oven at room temperature for 20 minutes? Rat, if you don't understand what that sent up yet another flare I don't know what more I can say. It is a totally silly idea. Why bake something at room temperature?

With the software it uses the laser in the drive which has a resolution to 300 nanometers? to read the image left by the stain. Then a spectrograph of sorts pops up on your computer, and you can just compare images. I think it even tells you what it is, if it recognizes it.

Okay, a possiblity as I have said before. But by the time you get to this point, so much BS has been detected that this seems like hardly worth pursuing.

I pretty much got it word for word how it happened, except maybe for the temp of the oven, which I may have not heard correctly.

Well, no you didn't get it even close. It is NOT something for folk to try at home. It does not appear that the material is placed in the unreadable part of the CD. It is still an experimental technigue that may someday hold promise for professional applications. And we won't even get into the temperature and oven bit.

If you weren't so busy trying to make me look like a fool, you might have learned something. I can't see how your approach is even remotely Christian.

I was not trying to make you look like a fool. I don't want you to feel like a fool. I never said you were a fool.

But You wrote the OP. I've tried many times in the past to point things out to you when it's obvious that you have missed the whole import of what was said. As I said, you wrote the OP.

You actually accepted the paragraph in your OP as a reasonable statement and did not see all the glaring errors in it. From this message it appears that you still don'r see just how silly that paragraph was. All I hope that I have done is to encourage you to examine ideas critically.


Aslan is not a Tame Lion
This message is a reply to:
 Message 25 by riVeRraT, posted 04-06-2006 3:17 PM riVeRraT has responded

Replies to this message:
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crashfrog
Inactive Member


Message 33 of 45 (301722)
04-06-2006 6:02 PM
Reply to: Message 15 by riVeRraT
04-06-2006 2:28 PM


Maybe the light is being blocked in a certain measurable manor?

There's no way the CD ROM could measure opacity. It doesn't have that kind of photodetector, and it's mounted in the wrong place.


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Replies to this message:
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crashfrog
Inactive Member


Message 34 of 45 (301726)
04-06-2006 6:10 PM
Reply to: Message 26 by riVeRraT
04-06-2006 3:19 PM


Re: interesting stuff/primary literature
According to crash this is impossible?

Look, it's a simple matter of optics. CD-ROM's read by bouncing a laser of wavelength w at a reflective disc rotating k*w distance away. Data is encoded onto the disc by depressing the reflective surface such that it is moved k*w+1/2w away from the laser, so that as the beam returns from the reflective disc, it's 180 degrees out of phase and so the beam cancels itself out. A simple photodiode detects the difference between the beam being reflected and the beam being out of phase.

Shooting the beam through a transparent disc to try to detect some biological colony isn't going to work, because there's no photodetector above the disc in a CD-ROM drive. And even if there were, what's the point of this? The best you get is a picture of a disc with fungus growing on it, and you can get that from putting it on a flatbed scanner.


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pink sasquatch
Member (Idle past 4189 days)
Posts: 1567
Joined: 06-10-2004


Message 35 of 45 (301728)
04-06-2006 6:15 PM
Reply to: Message 33 by crashfrog
04-06-2006 6:02 PM


Apparently, it does.
Rat: Maybe the light is being blocked in a certain measurable manor?

Frog: There's no way the CD ROM could measure opacity.

Actually, Crash, you had the description correct when you said:

They detect the way pits on the reflective CD surface cause the laser to interfere with itself on its way back to the photodetector.

The substance placed on the CD surface scatters the reflected light in a reproducible way depending on the substance, and the interference is detectable by a standard CD-ROM drive in a standard PC laptop. Read the primary paper Modulous linked.

Do people simply refuse to believe this because RiverRat brought it up?


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crashfrog
Inactive Member


Message 36 of 45 (301731)
04-06-2006 6:18 PM
Reply to: Message 35 by pink sasquatch
04-06-2006 6:15 PM


Re: Apparently, it does.
The substance placed on the CD surface scatters the reflected light in a reproducible way depending on the substance, and the interference is detectable by a standard CD-ROM drive in a standard PC laptop.

How? There's no detector at the top of the drive. All the optics are at the bottom.


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Replies to this message:
 Message 37 by pink sasquatch, posted 04-06-2006 6:22 PM crashfrog has responded

  
pink sasquatch
Member (Idle past 4189 days)
Posts: 1567
Joined: 06-10-2004


Message 37 of 45 (301732)
04-06-2006 6:22 PM
Reply to: Message 36 by crashfrog
04-06-2006 6:18 PM


Reflection.
How? There's no detector at the top of the drive. All the optics are at the bottom.

The substance being analyzed scatters the reflected light. Not transmitted light.

Again, I suggest you read the primary article. RiverRat may have been a bit off in the details of the technique, but I think he did pretty well considering he was remembering something he saw on a popular science show a week ago that he half-watched while playing with a kid.


This message is a reply to:
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NosyNed
Member
Posts: 8842
From: Canada
Joined: 04-04-2003


Message 38 of 45 (301749)
04-06-2006 7:24 PM
Reply to: Message 37 by pink sasquatch
04-06-2006 6:22 PM


Primary article
I couldn't find any primary. Just the Australians TV show blub.
This message is a reply to:
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crashfrog
Inactive Member


Message 39 of 45 (301787)
04-06-2006 9:35 PM
Reply to: Message 37 by pink sasquatch
04-06-2006 6:22 PM


Re: Reflection.
The substance being analyzed scatters the reflected light.

I don't understand what's doing the reflecting.


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jar
Member
Posts: 30988
From: Texas!!
Joined: 04-20-2004
Member Rating: 4.4


Message 40 of 45 (301789)
04-06-2006 9:39 PM
Reply to: Message 39 by crashfrog
04-06-2006 9:35 PM


Re: Reflection.
Probably the disc.


Aslan is not a Tame Lion
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Modulous
Member (Idle past 271 days)
Posts: 7789
From: Manchester, UK
Joined: 05-01-2005


Message 41 of 45 (301878)
04-07-2006 8:17 AM
Reply to: Message 38 by NosyNed
04-06-2006 7:24 PM


Re: Primary article
I posted a link to it, Message 24. Here it is again
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riVeRraT
Member (Idle past 86 days)
Posts: 5746
From: NY USA
Joined: 05-09-2004


Message 42 of 45 (301879)
04-07-2006 8:21 AM
Reply to: Message 32 by jar
04-06-2006 5:40 PM


Re: Thank God
Anyone reading that who does not immediately hear the ringing gong of a BS detector needs some lessons in critical thinking.

I am not going to even address your post.

What I usually do if someone posts something, and I think it is BS, or I don't understand it, I take some time to research it, and either learn about it, or debunk it for the person, in a nice way. Nobody knows everything, and we all need a little humble pie once and a while.

Just because I may not be able to word things well, does not mean I do not understand the concept, or what is going on. Too many dugs in my past maybe.


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riVeRraT
Member (Idle past 86 days)
Posts: 5746
From: NY USA
Joined: 05-09-2004


Message 43 of 45 (301882)
04-07-2006 8:32 AM
Reply to: Message 39 by crashfrog
04-06-2006 9:35 PM


Re: Reflection.
I don't understand what's doing the reflecting.

Ok, so I don't know EXACTLY how a cd laser actually reads the cd, but my little understand is that it reads binary code? So there is a series of 1's and 0's on the disc that compiles the information.

If the cd drive is reading reflected light back through an optical sensor in a form of resistance. Is it possible that the resistance can be variable, and not limited to just 1's and 0's? Then the reflected light through the anthrax can help determine it's thickness. You should be able to get a repeatable result.

Or if it is limited to just 1's and 0's, or light/no light, is it possible that the width of the anthrax residue is much greater than the resolution of the ability to read the refracted light?

I am not even sure what anthrax is. Isn't it some kind of organism? What is the width of one? Is it greater than the resolution of the laser?

Once you add it to water and cook it (BTW, I think it was 75 degrees, but Celsius, not Fahrenheit) does it crystallize, and leave a consistent pattern that the laser could easily read?

Also they said cd, or DVD, so my guess is that they are using a DVD drive, which can read finer resolutions.

Well anyway, to me it all seems possible.


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sequencelv
Inactive Member


Message 44 of 45 (305825)
04-21-2006 11:27 PM


Actually, just to clarify, the program being discussed does not use the clear inner ring of the compact disc, but from what I understand, the program actually burns some kind of information onto the disc itself, or maybe simply creates two visible sections on disc surface, I.E. "burnt" and "unburnt" data, leaving approximately a 1/2 inch section on the inner part of the readable(or reflective) area of the disc, which is where the sample is placed, then the disc IS put into an oven, or anything that maintains a constant level of heat, but not enough to damage the disc itself (hence the 75 degrees), simply to evaporate any water that may be on the disc, doesn't need to be an oven, but there is less chance of contaminating your sample if it is done quickly, and with less exposure to the open air in a room. The main reason for drying the sample is, A: obviously noone wants to ruin a cd drive by putting water in it, even if it is covered, who wants to risk it, right? And, B: I'm not sure if the program can read wet samples or not, or if it just makes it easier to read and analyze, but I am pretty sure the incorporated database only consists of DRY chemicals as of right now, and not just anthrax, but I believe it will identify several hundred chemical compositions, including talc, chalk, or any kind of dry chemical. I don't think they have integrated moist or wet chemicals yet, or if they ever will. Then a protective cover is placed on the disc, such as a D-Skin cover http://www.d-skin.com/, and then placed in the cd-rom drive for analysis.

Hope this might clarify any issues that anyone might not have understood from the original TV broadcast.
P.S. if anyone gets ahold of this software, lemme know, I cant wait to see if it actually works! Just kidding ;P

This message has been edited by sequencelv, 04-21-2006 11:31 PM

This message has been edited by sequencelv, 04-21-2006 11:37 PM


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riVeRraT
Member (Idle past 86 days)
Posts: 5746
From: NY USA
Joined: 05-09-2004


Message 45 of 45 (305895)
04-22-2006 10:08 AM
Reply to: Message 44 by sequencelv
04-21-2006 11:27 PM


Actually, just to clarify, the program being discussed does not use the clear inner ring of the compact disc,

I never said the clear inner ring.
That was something that jar assumed I meant. He assumes that I know nothing about how a cd-rom works.

I assumed that everyone here does know how a cd-rom works, so when I mentioned the first indside inch, I assumed that everyone would know that it was the first inch of the cd that is readable.

How is a cd reader going to read where the laser can't reach?

Just stupidity if you ask me.

People in here are only smart when they want to be.

If it was someone like rrhain or scraf who would have made that comment, everyone would have assumed it was the first readable inch, not the clear inner circle. That is why I never addressed jar comments. They were directed towards a 2 year old.

leaving approximately a 1/2 inch section on the inner part of the readable(or reflective) area of the disc, which is where the sample is placed,

I noticed that in the program, but I do think they said blank cd. But you know these programs don't always get the story right. Or if it was right, it wasn't taught clearly enough.

but not enough to damage the disc itself (hence the 75 degrees),

The 75 degrees, must have been celsius, since I found the model of the oven they use, or one that looks exactly like it, and the temp starts at 50 celsius. I don't think they mentioned farenhiet or celsius, and I just assumed, it was a controlled dry temp that was needed to just dry the drop of water. I figured it was the humidity that was more important in drying the water.

I'm not sure if the program can read wet samples or not,

Given the rpm's of a cd-rom, I don't think the wet sample will stay on.

Also that is another reason they use the inside of the cd, and not the outside, the actual speed inside is less, so the crystals won't fly off. Plus the program probably uses the variable speed of the cd rom to keep it slow.

I am pretty sure the incorporated database only consists of DRY chemicals as of right now, and not just anthrax, but I believe it will identify several hundred chemical compositions, including talc, chalk, or any kind of dry chemical.

When I watched the show, they said there was 150 samples so far.


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