Search found 32 matches

by Yggdrasil
Wed Nov 04, 2009 5:05 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0658: "Orbitals"
Replies: 89
Views: 14687

Re: "Orbitals" Discussion

Does that mean bosons get to have orgies?
by Yggdrasil
Mon Oct 05, 2009 2:47 am UTC
Forum: Science
Topic: First law of thermodynamics
Replies: 2
Views: 761

Re: First law of thermodynamics

Alright guys, this is easy stuff that for some reason I'm stuck going in circles about. I need to determine the sign of q, w, delta U, and delta H for the system (liquid/vapour) in the following: A liquid at its boiling point is converted reversibly to its vapour, at constant temperature and 1 atm ...
by Yggdrasil
Wed Jul 01, 2009 6:04 am UTC
Forum: Science
Topic: You Might Be a Biology Major if...
Replies: 153
Views: 17174

Re: You Might Be a Biology Major if...

Velifer wrote:...you wash your hands before you go to the bathroom.


This applies to chemists as well (at least the ones doing experiments).


Meteorswarm wrote:YMBABM if you picked classes expressly to avoid premeds...


I tried this and ended up with a degree in physical chemistry :D
by Yggdrasil
Mon Jun 29, 2009 1:48 am UTC
Forum: Science
Topic: You might be a chemistry major if...
Replies: 139
Views: 38729

Re: You might be a chemistry major if...

In case of acid burns*, sodium bicarbonate (aka baking soda) is best. It's basic so it'll neutralize the acid, but it won't harm you like lye would (aqueous sodium bicarbonate give a buffered solution of pH ~7). Plus, it's cheap and easy to obtain even for home chemists. Every chemistry lab should h...
by Yggdrasil
Sun Jun 28, 2009 5:42 am UTC
Forum: Science
Topic: Quantum Physics: Wavefunctions
Replies: 11
Views: 1064

Re: Quantum Physics: Wavefunctions

To show that a discontinuous wavefunciton is unphysical, you just need to consider the momentum operator ( given by [math]-i \hbar \frac{d}{dx}[/math] for a 1D system). The discontinuity would require the particle to have infinite momentum, clearly an unphysical scenario.
by Yggdrasil
Fri Jun 26, 2009 5:04 am UTC
Forum: Science
Topic: You might be a chemistry major if...
Replies: 139
Views: 38729

Re: You might be a chemistry major if...

You know you are an organic chemist if... ... you've started and/or witnessed a fire in lab. ... you see a firetruck with its sirens on and quickly check whether it's headed in the direction of your lab. ... you wash your hands before going to the bathroom. ... all your shirts have holes. ... when s...
by Yggdrasil
Sun Jun 21, 2009 4:20 pm UTC
Forum: Science
Topic: Equilibrium vs. Rate constant question
Replies: 12
Views: 3503

Re: Equilibrium vs. Rate constant question

Equilibrium constants must be determined experimentally as well... Not really. You can determine them thermodynamically, from other data. ...other experimentally determined data... It's actually possible to calculate the equilibrium constant of some simple reactions from first principles using stat...
by Yggdrasil
Fri Jun 05, 2009 4:25 am UTC
Forum: Science
Topic: Accidentally ingesting insulin
Replies: 24
Views: 18645

Re: Accidentally ingesting insulin

If insulin could be taken into the bloodstream via oral ingestion, do you think type I diabetics would be taking insulin injections rather than just using insulin pills?
by Yggdrasil
Thu May 21, 2009 5:49 am UTC
Forum: Science
Topic: Have you ever wished a particular theory didn't work?
Replies: 59
Views: 3944

Re: Have you ever wished a particular theory didn't work?

As a microscopist, the fact that light diffracts and behaves like a wave is a very inconvenient fact as it places a limit on the resolution of conventional optical microscope, and prevents us from resolving features smaller than about 200nm. If light did not diffract than it would be much easier to ...
by Yggdrasil
Sun May 03, 2009 8:31 pm UTC
Forum: Science
Topic: orbitals nightmare ....
Replies: 6
Views: 1606

Re: orbitals nightmare ....

The four sp 3 orbitals are arranged in a tetrahedral geometry but individual sp 3 orbitals have a linear geometry similar to that of a p-orbital but lopsided. See the picture in the following link: http://grandinetti.org/Teaching/Chem121/Lectures/Hybridization/assets/sp.gif (I think the diagram in t...
by Yggdrasil
Fri Apr 10, 2009 4:43 am UTC
Forum: Science
Topic: help with a genetics problem?
Replies: 4
Views: 617

Re: help with a genetics problem?

A quick explanation that can maybe help you. Restriction enzymes are enzymes that physically chop DNA into fragments. These enzymes recognize specific sequences in DNA called restriction sites. Now, suppose that I have a 2,000 base pair long (2 kilobase-pairs or 2kb) piece of DNA that looks like thi...
by Yggdrasil
Fri Apr 10, 2009 4:13 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0567: "Urgent Mission"
Replies: 129
Views: 25650

Re: "Urgent Mission" Discussion

He's just jealous that he's not made of antimatter.
by Yggdrasil
Mon Mar 02, 2009 5:09 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0550: "Density"
Replies: 184
Views: 56570

Re: "Density" Discussion

... but then who was phone!?
by Yggdrasil
Wed Feb 25, 2009 6:25 am UTC
Forum: Science
Topic: We certainly are fucking incredible
Replies: 16
Views: 3027

Re: We certainly are fucking incredible

Biology grad student here. The movie appears to show the process of leukocyte extravasion , the process by which white blood cells exit the blood stream in order to respond to pathogens in the body. This process begins with weak interactions between cell adhesion molecules on the blood vessel wall a...
by Yggdrasil
Wed Feb 11, 2009 5:14 am UTC
Forum: General
Topic: ITT: We make xkcd slightly worse.
Replies: 8594
Views: 1344724

Re: ITT: We make xkcd slightly worse.

Spoiler:
cover_up.png
That's the last time we have sex during Shark Week.
cover_up.png (59.75 KiB) Viewed 3439 times


Worse in the, we really didn't need to know that, way.
by Yggdrasil
Mon Jan 26, 2009 4:36 am UTC
Forum: Serious Business
Topic: The least racist country?
Replies: 107
Views: 13639

Re: The least racist country?

Japan and Sweden might not have many race problems within their society, but certain foreigners coming in may face significant hostility. Despite it's relatively homogenous population, there are still certain ethnic groups in Japan that face discrimination. For example, until recently, people of bu...
by Yggdrasil
Sat Jan 17, 2009 7:53 pm UTC
Forum: Science
Topic: Science Websites
Replies: 69
Views: 191131

Re: Science Websites

MIT Open Courseware http://ocw.mit.edu/OcwWeb/web/home/home/index.htm Free material (and some video) from classes taught at MIT Open WetWare http://openwetware.org/wiki/Main_Page A wiki with lots of useful information, including many lab protocols, for molecular biology and biological engineering. N...
by Yggdrasil
Sat Jan 17, 2009 6:18 am UTC
Forum: Science
Topic: Most silly "constant of nature"
Replies: 64
Views: 4946

Re: Most silly "constant of nature"

Avogadro's number is related to a very important physical constant, the mass of a proton or neutron. To a rough approximation, one mole of protons is will have a mass of one gram. Of course, because of nuclear binding energies and other factors, things get more complicated when you need to consider ...
by Yggdrasil
Sun Jan 11, 2009 7:00 am UTC
Forum: Science
Topic: Light Reflection
Replies: 15
Views: 1368

Re: Light Reflection

The angle of reflection is equal to the angle of incidence because of Fermat's principle. According to Fermat's principle, light takes extremal paths (the paths of maximal or minimal time, usually it is the path of minimal time). If you take light emanating from point a, bouncing off of a mirror, an...
by Yggdrasil
Sun Dec 28, 2008 7:08 am UTC
Forum: Science
Topic: Second Law of Thermodynamics
Replies: 14
Views: 1776

Re: Second Law of Thermodynamics

Here's the way I think of entropy. Boltzmann defined the entropy S of a system in terms of the number of microstates Ω associated with certain "macroscopic states" of the system (this sounds confusing but maybe it'll be more clear with an example). The relation between the two is S = k ln ...
by Yggdrasil
Fri Dec 19, 2008 6:46 am UTC
Forum: Logic Puzzles
Topic: Two Children Riddle
Replies: 43
Views: 8445

Re: Two Children Riddle

Thinking a little more outside the box
Spoiler:
What about children of an egg-laying species, like birds? Although, I suppose they'd be called chicks and not kids. And they'd hatch instead or birth.
by Yggdrasil
Fri Dec 19, 2008 6:29 am UTC
Forum: General
Topic: ITT: We make xkcd slightly worse.
Replies: 8594
Views: 1344724

Re: ITT: We make xkcd slightly worse.

Spoiler:
11th_grade.png
Perl was my next door neighbor.
11th_grade.png (30.21 KiB) Viewed 4459 times
by Yggdrasil
Thu Oct 09, 2008 3:53 am UTC
Forum: General
Topic: ITT: We make xkcd slightly worse.
Replies: 8594
Views: 1344724

Re: ITT: We make xkcd slightly worse.

note the new title
by Yggdrasil
Thu Sep 18, 2008 3:01 am UTC
Forum: Science
Topic: Peptide conformation
Replies: 5
Views: 896

Re: Peptide conformation

The high ionic strength would also promote the hydrophobic effect which would act to bury the valines in a conformation with two beta strands stacked on eachother (remember on beta strands, every other residue ends up on the same side of the beta strand). The peptide would fold into a beta hairpin-l...
by Yggdrasil
Sun Aug 10, 2008 3:12 am UTC
Forum: Food
Topic: Food storage / spoilage / safety
Replies: 26
Views: 6866

Re: Food storage / spoilage / safety

At worst, you'll end up with Ebola, but more likely you'll just end up a bit pukey for a few days. I think you mean E. coli a common bacteria that can sometimes be pathogenic and cause food poisoning (though most strains are fairly harmless and are part of the natural fauna of your digestive tract)...
by Yggdrasil
Sat Aug 09, 2008 4:05 pm UTC
Forum: Logic Puzzles
Topic: Some Good ones for the kids?
Replies: 32
Views: 4321

Re: Some Good ones for the kids?

Some more scale problems: Easy: You are a drug manufacturer and you have 10 jars of pills, and each pill should weigh exactly 1g. However, one jar contains defective pills that are identical to the regular pills in every way except that they weigh 1.1g (and will kill your customers). By using only o...
by Yggdrasil
Sat Aug 09, 2008 6:17 am UTC
Forum: Logic Puzzles
Topic: Some Good ones for the kids?
Replies: 32
Views: 4321

Re: Some Good ones for the kids?

A classic riddle that is good for groups is Bobby's world. Bobby's world has a specific rule about what is and is not in Bobby's world. You give an examples about Bobby's world and the others try to figure out that rule. For example: In Bobby's world, there is fall but not winter. In Bobby's world, ...
by Yggdrasil
Thu Aug 07, 2008 2:16 am UTC
Forum: Science
Topic: Favorite Scientist?
Replies: 84
Views: 6603

Re: Favorite Scientist?

Although I'd have to put down Pauling as my favorite scientist (I'm a biochemist), Boltzmann probably comes in a close second and I'm surprised no one has mentioned him yet. After all, he came up with statistical mechanics even before we knew about atoms, molecules, or quantum.
by Yggdrasil
Sat Aug 02, 2008 8:35 pm UTC
Forum: Logic Puzzles
Topic: Probability puzzle... genetics based
Replies: 24
Views: 3282

Re: Probability puzzle... genetics based

I have yet another answer for the first zot problem. I think Titanium Dragon's solution is incorrect because it doesn't take into account the problem's statement to assume a 50% prior probability that blue is recessive. VectorZero's solution is close, but I think I can do better because VectorZero d...
by Yggdrasil
Thu Jul 03, 2008 6:40 pm UTC
Forum: Logic Puzzles
Topic: Probability puzzle... genetics based
Replies: 24
Views: 3282

Re: Probability puzzle... genetics based

P(A|B) = \frac{P(B | A)\, P(A)}{P(B)} whoah, i've never even seen that equation before... can someone explain? This equation is a simplified form of Bayes' Law or Bayes' theorem. Here's a link to the wikipedia article on the topic which contains the derivation: http:...
by Yggdrasil
Sat May 10, 2008 5:19 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0421: "Making Hash Browns"
Replies: 122
Views: 30292

Re: "Making Hash Browns" Discussion

Damnit. First Randall makes me crave bacon with #418 and now hash browns. What unhealthy, fried, breakfast food will Randall subliminally force into my mind the next time I make breakfast? (mmm, donuts...)
by Yggdrasil
Mon Mar 31, 2008 4:46 am UTC
Forum: Logic Puzzles
Topic: 3 door problem
Replies: 88
Views: 25814

Re: 3 door problem

Under the assumption that the host can open a door that has been picked previously but not currently held, I get a different answer that is just slightly different. Assuming that the host can pick a door you have picked previously: There are five scenarios to consider. 1) The prize is behind A. ...

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