Archived threads in /sci/ - Science & Math - 1260. page

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>>8454878
Recrystallized paracetamol from acetone

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>>8454883
Sulfur recrystallized from toleuene

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>>8454885
Some KMnO4

Killed more people in the last century than all the wars combined.
That's pretty bad.

>>8454858
After researching it I've come to the conclusion that it's not unhealthy at all, certain groups that try to push a biased scientific view of smoking basically cherry pick the shit out of their studies and data, while completely downplaying the role that certain transmittable diseases have in causing so called smoking-related illnesses. It's called confounding by infectious disease.

http://sphweb.bumc.bu.edu/otlt/MPH-Modules/BS/BS704-EP713_Confounding-EM/BS704-EP713_Confounding-EM4.html

Of course groups like the FDA and WHO don't ever want to consider this so they can claim shit like smoking or meat causes cancer.

>>8454974
$1 has been deposited into your account.

>>8454800
What is it like being a grad student***

Yea, it sucked. I didn't for 8 days on a streak and my sleep quota was 5hrs/night.

>>8454874
>didn't take a shower

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>>8454794
lol, sounds like Riemann sums/Integration indeed;
guess he wanted to sound superior than all us Calculus dolts...
Or maybe he's incompetent.
*shrug*

Was it his whole thesis or just something he used in passing ? I mean Riemann sums *are* used to compute integrals, I dunno why kids here are so shocked to hear that grad students use elementary tools (especially in non-math fields).
Research is not about revolutionizing science every day, it's about using knowledge that exists to answer your own dumb questions.

>>8454844
You should not have to present something as basic as integration to a thesis defense committee and the rest of the audience at the graduate level. Maybe in a freshman course but not graduate. If someone doesn't know how integration works tell them to ask a freshman calc student to explain it to them

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>>8454788
That is some cool shit, where are you going to uni? I interned in rock mechanics this summer, so I ran a lot of compressive strength tests with rock cores. Worked pretty closely with a concrete engineer though.

>>8454788
>undergrad research
not a real thing

>>8454807
New York city college of technology

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>>8454741
folding cube in question

Read up on everything you mentioned and came to the same conclusion you did. I agree that this volume is clearly changing while the faces remain rigid. Do you have the original Connelly article / Bellows conjecture? Maybe we don't understand something about the class of non-convex polyhedra they're using.

>>8454782
I found the original proof:
https://www.math.ucdavis.edu/~deloera/MISC/BIBLIOTECA/trunk/Connelly/Connelly3.pdf
In it they speak of a "flex" of a surface (triangulated).
For the definition of a "flex" i find the following article which defines it for graphs representing polyhedra
http://erikdemaine.org/papers/LinkageTR/paper.pdf
with Connelly as co-writer, leading me to think this must be the proper definition.

However, this doesn't help at all. As you can see in the definition in the image, we have that a "flex" is defined as a set of continuous functions (in 3-space) such that
[eqn]p(t) = (p_1(t),\dots,p_n(t))[/eqn]
[eqn]p(0) = p[/eqn]
[eqn]||p_i(t) - p_j(t)|| \text{ is constant over $t$ if $p_i$ and $p_j$ are connected}[/eqn]

All three seem to apply in our case.

However, in the beginning of the first article, it does say "Consider a triangulated polyhedral surface S in three-space". The top and bottom of our cube are not triangles, but surely we can replace the top and bottom with some pyramid shape, and nothing would change in the "bellows" part of the polyhedron.

>>8454720
That's the one that the axiom of infinity cannot be proven via first principles right?

The inductive set and naturals model a very large finite set pretty well without worrying about just how big that very large set is.
Sure you could prove that induction works on every finite set via first principles...but I'm lazy and that sounds boring.
ne?

>>8454747

>he hasn't read Hume

>>8454720

>If you tried to doubt everything you would not get as far as doubting anything. The game of doubting itself presupposes certainty.

>>8454717

What other way is there? Like what is it that they actually teach you to do?
Maybe I'm just old... but I'm only 24...

>>8454723
Go to sleep grandpa

>>8454717
I honestly just don't know how to write it out. Fuck the public school system failed me, i basically winged it through high school. I think my algebra 1 teacher thought I was downright retarded or she wanted my dick. She literally just answered my work for me.

reading them "fast" generally won't help you. you need to absorb the material and take notes while you read

>in b4 miscellaneous brainlet remarks

>>8454714
But I end up writing books full of notes this way.

Don't, faggot. Read at a comfortable place and try to actually comprehend what you're reading, speedreading is a meme. Take notes for long-term retention.

>>8454718
Well, then trim them down. Use abbreviations, aim for 2-3 lines per paragraph, cut out the unnecessary shit.

>Austrian school of economics

this is the meme

>>8454661
;_;

>>8454660
This is the science and maths board. Try /biz/.

>>8454582
please stop reposting this garbage

>>8454582
Just fucking STOP!

>>8454582
>>>/x/

>>8454574
eigenvectors and eigenvalues

>>8454574
Matrix Algebra or Vector Space Theory?

>>8454574
when you realize, that matrices are fucked up, if they map more/any other than the zero vector onto the zero vector, because you can't invert such a matrix (their linearity forbids to map a zero vector to a non-zero vector). therefore you need to check, if your matrix is fucked up, and that's why there exist such things like a determinants

>>8454569
>completely invulnerable
Well there's no such thing so this is a meaningless question

I guess it would just make the sphere vibrate a lot or just end up with a lot of light reflecting inside. I mean I don't know what you'll allow to happen to your made up magic material.

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>>8454569
The energy would be dissipated either through heat, radiationor and vibration.

It´s the same thing that happens in the universe, since both the universe and the sphere are isolated systems.

>>8454556
delete this thread and then yourself

>>8454558
fucking hater answer question i just wanna know if lack of oxygen made me a retard

>>8454556
i think i have this, after a fight i got in. but not to that degree i'm unable to breath or something through nose. one of my nostrils is just capable of taking less air than the other. i'm not a mouth breather and my concentrating skill didn't get any worse

>>8454496
When i stopped believing on a test that measures your math skills

And when i realized if i dedicated some hours to math i could be good at it and i suck at everything else

>>8454508
Mine was same but opposite as I wanted to strengthen my Physics.
I was shit at math so had to develop it first then lookup at Physics

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>>8454508
tfw the exact same brother