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Half-life is half-life; there isn't a process we can use to change that

OK, to begin, the following is simplified to skip some points of extreme nuisance, and to be suitable for non nuclear engineers (like me).

Radioactive decay isn't as simple as one might be forgiven for thinking given the simplistic concept "half-life". You might ideally start off with a pure form of a single isotope of a single element. In practice, you never do. Reactor fuel as it goes into the reactor is about 5% U235, 95% U238, with traces of other elements and isotopes. When it comes out of the reactor, it is a lesser percentage of U235, still a bunch of U238 left, plus a bunch of plutonium and a witch's brew of other isotopes of elements resulting from the nuclear "cooking" in the reactor involving neutron bombardment.

But for simplicity, let's take an imaginary bunch of U235.

The U235 decays to Th231 in a decay process with a half-life of 704 million years
The Th231 decays to Pa231 in a decay process with a half-life of 25.5 hours
The Pa231 decays to Ac227 in a decay process with a half-life of 32,500 years
The Ac227 decays to 98.6% Th227 and 1.4% Fr223 in a decay process with a half-life of 21.6 years
The Th227 decays to Ra223 in a decay process with a half-life of 18.2 days
The Ra223 decays to Rn219 in a decay process with a half-life of 11.4 days
The Rn219 decays to Po215 in a decay process with a half-life of 4.00 seconds
The Po215 decays to Pb211 in a decay process with a half-life of 1.78 milliseconds
The Pb211 decays to Bi211 in a decay process with a half-life of 36.1 minutes
The Bi211 decays to 99.7% Tl207 and 0.3% Po211 in a decay process with a half-life of 2.15 minutes
The Tl207 decays to Pb207 in a decay process with a half-life of 4.79 minutes
The Pb207 is stable and hangs around for the balance of eternity

The first thing to realize is that an instant after the imaginary start with pure Uranium235, and continuing for many billions of years, we have a constantly changing mix of various isotopes of elements, shading from pure U235, and asymptotically approaching (but never mathematically quite reaching) pure Lead207.

The constituents of that mix are busy decaying all at their own rates.

But the individual decay rates are mathematical models. A tiny little bit of that U235 has already changed all the way to Pb207 within the first hour, and a tiny little bit is still stuck at U235 after some billions of years. The rate of each individual decay process averages out to the half-life given by the particular model for that process.

So to get all the way to the point: yes, you actually can effectively change the rate of transmutation of the stuff that comes out of the reactor. You can re-enrich it back to a sufficiently rich mixture of uranium and plutonium oxides (and do some other reprocessing chores, such as cleaning out the fission poisons so it's usable again) and put it back in a reactor. Or you can separate out the plutonium and put it in a nuclear bomb and that will transmute really fast if you set it off. After you take out the plutonium it is at least theoretiucally possible to re-enrich the remainder back to 5% U235 and put THAT back in a reactor.

Note that the process during reactor operation is not the same as the decay process. In the reactor, you can "use up" a substantial percentage of the starting U235 in just a few years, in the process "creating" a bunch of plutonium (more than one isotope!) where there was none.

> I hope the next revolution in software engineering will probably be some more automatic way to handle errors, just like garbage collection was to memory handling.

That would be extremely nice; In the past I would of argued TINSTAAFL but now that 4-core 2.x GHz is starting to get common switching away from the fundamental root problem of "von Neumann architecture" might be an option. However I don't see anyone switching to the Harvard Architecture anytime soon which means yet another 40+ years of buffer overflows before people wise up ... simply because it is to costly for array bounds checking. :-/

You might find this read interesting:

* "The von Neumann Architecture of Computer Systems"
http://www.csupomona.edu/~hnri...

References:

* Von Neumann architecture http://en.wikipedia.org/wiki/V...
* Harvard architecture http://en.wikipedia.org/wiki/H...

--
"Beautiful Form Helps Function
Ugly Form Hinders Function"
One of the many reasons it is import to write beautiful code & algorithms.

Yes, it is an alpha emitter. But it and its decay products also produce plenty of gamma. See http://www.csupomona.edu/~pbsiegel/decaychain/U235.html . You build a detector to detect the gammas at the particular frequencies that U235 emits at and bam - you've got a detector that will detect U235 and nothing else. Also, gammas are highly penetrating, so unless that cargo container is lined with a significant amount of lead, you will detect something if its there.

As a random aside, supposedly Lazlo was based on one of the founding CS professors from Cal Poly Pomona, Dr. Laszlo from his time at Caltech. A strange guy, to be sure, but by far one of my favorite professors.

http://www.csupomona.edu/~tassi/gestures.htm

mutual incomprehensibility

While there is that other Cal Poly in Pomona, the "Learn By Doing" school is indeed the correct one. He's the Director of Cal Poly's Environmental Biotechnology Institute and Unocal Professor of Environmental Studies (more accolades here).

Oddly, his inspiration for brewing beer seems to be convincing his slightly inebriated father to provide money for a movie and a hamburger.

Ogham is a human writeable alphabet that looks a lot like what you put in your example. I thought it was ogham at first glance. It was found on standing stones in Celtic regions (Ireland, Britain, France) and consists of a groups of 1 to 5 lines either to left, right or centered on a main line. It was supposedly also used as a sign language alphabet with the body or walking stick replacing the main line and the fingers of a hand taking the place of the letters.

Here is the Wikipedia article:
http://en.wikipedia.org/wiki/Ogham
Here is a more concise article:
http://www.csupomona.edu/~jcclark/ogham/

Is this really making the light waves go faster, or is it just anomalous dispersion? I heard in one of my Physics lectures that you can make something happen that looks like superluminal motion, and it caused a bit of controversy when someone did it, but it's not actually the wave that's moving faster than c - it's actually the wave envelope, which is related to the amplitude of the wave. I could try and explain, but I'd only make things confusing (if I haven't already!), so I have found some animations you can look at, see here and here.

On the other hand, if the light really is going faster than c, then I am thoroughly impressed!

Not really. A search for any of:
An I war a maydyn,
An I war a maiden, or
When I was a wanton wench of twelve
does not find: http://www.csupomona.edu/~jcclark/emusic/lyrics/an _i_war.html
or the site it links to from which a zip of the midi is available.

From my experience learning styles are very important. I've been doing my teacher traing this year and have noticed how I learn. For me a picture or diagram on the board really helps me understand a concept. Another chap on the course was also a visual thinker and he'd come out of class completly blank, not having been able to absorb the large amount of spoken words.

There is a very good case to make is that the very high number of kids who fail at school is due to not paying attention to the way they learn. Are the kids looking board in class? Change the style of deliveray and see what happens.

I think this issues is of particular relavance to the slashdot crowd. There is probably a higher than average number of visual and tactile learners here. Probably also a good number of dyslexics and aspergics who do learn in very diferent ways.

Have a go at some of the online assesments for learing styles say http://www.csupomona.edu/~jekarayan/brain/brain/ or http://www.vark-learn.com/english/page.asp?p=quest ionnaire. It would be fun to pool results. Do slashdotters learn in a different way?

Mirror of the vid for everyone: http://www.csupomona.edu/~iwsnyder/robo_s.wmv The video is awesome. I love the nice touches, like the controls for the guns, and the self-lowering windshield.

DCE did a "proper" job by using the available fields of kerberos for the correct - documented - purpose.

the use of CDS being largely irrelevant was recognised by TOG in 1999: you need to pay IBM stacks of $$$ to get the code _but_ it was recognised: OpenGroup link here. fortunately, someone has created a set of free software plugins - nss and pam etc. already

AFS, OpenAFS, DFS - it's a long long story for another day, methinks :)

Well if this is the Cantonese "Ng" then it is pronounced like this. That is a wave file of the Cantonese pronunciation from the same CSU Pomona website.

And thanks to the respondents for their jovial spirit.

Okay, according to the Cal Poly Pomona Asian Name Pronunciation Guide the name "Ng" is Filipino and is pronounced as 'nahng'.

What SuperKenall said is correct. However, some languages have more differences than others.

All the .NET languages MS ships are all about the same; the only difference is syntax. .NET requires all compatible languages to adhere to the same capabilities so they can be 100% compatible with each other. Unfortunately, it also requires all the languages it supports to be dumbed down to the lowest common denominator. There is a very long list of things that had to be removed from ISO C++ to create Managed C++, because including them would make it incompatible with VB and C# (and .NET), such as multiple inheritance, templates (non-type params too), pointers, member pointers, etc.

Functionally, VB.NET, C#, J#, and Managed C++ all have exactly the same capibilities. They are all sequential, procedural, imperative, object-oriented languages that support single inheritance, interfaces, events, exceptions, type generics(they will in v2.0), reflection and share a common runtime library and work in a sandboxed VM. The ONLY differences between them are in syntax. So, it doesn't really matter which of these languages are used unless someone in the group doesn't know the syntax for a language in a source file they need to work on. The interfaces between them will be equivalent regardless of language.

Compare this to a functional language such as Common LISP or Scheme, or a declaritive rule-baed language like Prolog or Mercury. Mercury can compile to .NET (it normally compiles to C), but you can forget about a runtime system like Prolog being compatible with .NET. .NET doesn't understand functions that don't have an implementation until you've decided the direction the argumets are flowing (a very big part of declaritive languages), .NET doesn't understand state tracking and backtracking or multiple modes based on detirminism, .NET doesn't understand multiple possible results for a single variable (a list is the closest you can get; it isn't the same because you have to do all the handling yourself which defeats the purpose).
Haskell has to jump through hoops to get the needed multiple inheritance to work.
OTOH, there are some interesting projects like F#, an OCaml like functional language. It has some serious issues to be compatible with .NET, though.

It's like Microsoft offers you several languages, but they are all the same. The illusion of choices without really having any. They should just be like Java and admit that there might as well be one language-- seriously, Java could have all the multi-language support of .NET if there were bytecode compilers for other languages. .NET and Java are so alike in function anyways.

As for what languages should be used when, where and by whom: I don't know. I'm still trying to figure that out. I know that some are good and bad for certain things, but I also know that personal preference is important, too.

</rant>

...if the Mohs scale were linear, diamond's value would be about 42.
-- Mohs hardness scale

Parent is refering to the Mohs hardness scale in which diamond is used as the upper end of the scale at 10.

If this is harder than diamond then either the scale will have to be scaled to make this the new 10 or this will be set as some value greater than 10 depending on its relative hardness.

Is this another sign that dynamic languages are the future?

I would have to say yes, but the real reason I posted was to point out a Dynamic Interpreter I know of. I recently took a Compilier Design class at my College and the teacher teaches using an Interpreter that he wrote in Java.

The interesting part about his interpreter is that it creates production tables on the fly (linear time) where the latest production is used when there are duplicate entries. Thus it could be that as a production rule fires it could in fact change the meaning or syntax of another production as they are encountered.

For those interested the site is:
A Java-based interpreter of context-free languages with user-defined semantics.
http://www.csupomona.edu/~carich/gi/

Oh yeah? Compare this with this. They even got downtown in the right place :)

(I know, I know, but the resemblance is striking!)

That's because the majority of things in that map were just arbitrarily placed : "While the placement of most locations is arbitrary"

Well if we thin out the population of tech schools some, the more reputable colleges (in my case Cal Poly Pomona) will look a little better, and that degree will mean more. Therefore maybe IT degrees will mean something again...well we can hope anyways...

At my little state university my mathematics classes are full of apathetic ex CS majors. Most think that they can just sail through a mathematics major and land a low paying but safe teaching job. However many start to fall off when they get to the upperdivision classes where being a calculating machine doesn't help much. Mathematics (like CS) are really hard majors that are now not really worth it if you do not love the subject matter. Still from speaking to other students, this direction is lacking in most students at this level.

Actually, this is more relevant.

I like the logo, and I am nominating it for a Brown Ring of Quality.

Well I am a junior math major at a not so pristegious university and I would say that I am in the same boat. I posted a topic similar to this on the alt.math newsgroup and I got about 50/50 = "go for it" / "Stick w/ computers and keep math as a hobby"

If I were you I would take a few more classes until I make a lifelong commitment. Math is one of those subjects where the upper division work differs greatly from most of what you see in ugrad/hs.If that hasn't scared you enough then try the AMS Job Search just to see what type of positions seem to be open in your state.

www.csupomona.edu/~cmtrim