/sqt/ - stupid questions thread

are there different "kinds" of pain?

for instance, a normal headache feels very different from the pain of a hangover

headache - a more intense pain
hangover - a sort of dull ache, that you can actually forget about if you are distracted enough, but still feels really shitty all day and the dull ache is always there

Check out the terms just to the left of the circled things

Does a single scientific study mean anything?

Like let's say there's a study on a subject and they got the result x, and there's no other study on the subject. Is the study's result valuable on it's own?

The inferior hypogastric plexus innervates your rectum and is sensitive to stretching.

When a sufficient amount of gas has escaped and your rectum has returned to normal size, the stretching sensation ends and your body actualizes the ceasing of the fart.

It's valuable but not as evidence of a claim, only as evidence that further research should be completed for different variations of the previous research or to eliminate possible flaws in the previous research.

Yes, different nerves and their terminal branches detect different sensations.

Heat, Cold, Cut, Stretch, Irritation, Noiception and Inflammation just to name a few.

Sensation from nerves is the result of action potentials, action potentials firing at accelerated rates cause increased sensation, a high enough rate signals pain, any of the previous sensations can be signaled into excess and thus discomfort.

Ok that's what I thought. Thank you my sir. I'd suck you off as an expression of my gratitude if you lived close.

I appreciate the offer for sexual acts, but instead: remember that scientific research is not conducted to prove a hypothesis is true, but rather to evaluate the chance that a hypothesis is wrong.

Yeah that's true. When they test Einstein's theories they try to disprove them and they fail, right?

Also the reason I asked was this article inverse.com/article/37463-conspiracy-beliefs-illusory-pattern-perception and I thought it was just such a fucking tub of bullshit. I didn't read the research article itself though. And this article reminded me about news websites using a single study as evidence of claims. I always thought there was something incorrect about doing it but kept forgetting to verify it with others.

>if you see red, that means that you should be on the lookout for danger.

False, red color distinction is a valuable trait for plant/food distinction, not a danger signal.

I don't recall most wolves, bears, big cats, spiders, snakes or various death-animals being red, now or prehistorically.

>European Journal of Social Psychology

At this point I would meme: Stopped reading there.

Unfortunately though I did continue reading and then investigated the linked 'research article'.

What I found was nothing more than what most psychological studies consist of, lose research constraints, weak trends but low p-values.

While their research was completed competently and the data is accurate (low p) their positive trends are fairly nonexistent, I didn't see many if any >.50.

Not only that, but the concept itself is flawed inherently. Gestalt principles are considered evident, but only the statement that 'the human brain will form patterns from "random" structures in order to better categorize information' is inherently true.

Resultant from that statement though we have to consider the definition of 'random' patterns. In the study, the participants were showed 'random' patterned paintings, which if painted by other humans would break the definition of 'random' has the human painting the piece would also be influenced by their own brains pattern impulses. That fact alone invalidates the entire study.

Most fatal to the study though is the violation of a simple highschool level science clause: Correlation is not causation, and is not extrapolated upon at all in the 'study'.

This article is really nothing more politicized clickbait aimed at invalidating inconvenient truths. Those truths being that the world isn't an inherently nice place, that people in power often abuse those without power and use misinformation to do so.

TL;DR:

Humans are cruel, those who can't handle that information write garbage articles on Inverse.

Is there anything wrong here? Was it proven correctly in pic related?

Common tricks in real analysis proofs are 'adding zero' and 'multiplying by one'.

Also, aren't they just assuming that some list of conspiracy theories is false?

They don't care whether or not it's false, theyre pushing a narrative.

I tried not to focus on that flaw because objectively it's still a bad research article, but yes, you are correct. Even in havens of logic such as Veeky Forums it's better to criticize things logically, lots of people don't like reading that they're wrong outright and will then deafen themselves to the supporting logic of an argument.

can someone explain to me using an equation why the specific heat of water vapor is less than water liquid? I understand it realistically and it makes sense but I want some valid evidencee

There are errors in the application of the rules of set equivalences but more importantly this is not how to prove this sort of thing. To prove a set identity, you want to use an 'element chasing argument'. This meas you suppose some element x is in the set on the left hand side, follow it, and show that it must be also in the set on the right hand side, then vice versa.

How?

Is pain, a form of your body communicating to you that there is a problem that needs to be solved, and considering the amount of pain determines the intensity of the problem?

Pain doesn't exist and your reality is now crashing down

On both RHS and LHS the first 'alternate representation' lines are wrong. Do it the right way, by element chasing.

Is a basis in linear algebra like a generator of a group in abstract algebra?

Am I fucking stupid?

[math]U_t = U_{xx} + U_x [/math]
[math]U(0,t) = 1[/math]
[math]U_x(1,t) = 0[/math]
[math]U(x,0) = x(1-x)[/math]

I'm asking for the steady state solution.
[math] U_t = 0 [/math]
[math] U_{xx} - U_x = 0[/math]
[math] U = c_1e^x+c_2[/math]

Plugging in BC's
[math]c_1+c_2=1[/math]
[math]c_1e=0[/math]
[math= c_1=0, c_2 = 1[/math]
[math]U=1[/math]

I feel like this is too simple to be right.

[math]c_1=0, c_2=1[/math]

should a brainlet learn logic?

People got disease D and there is a test T for it.
D+ means having AIDS.
D- means being healthy.

P(D+) = 0,01
P(D-) = 0,99

Now about the test: T+ means HIV+
Sensitivity P(T+ | D+) = 0,98
Specificity P(T- | D-) = 0,98
therefore:
P(T- | D+) = 0,02
P(T+ | D-) = 0,02

I need to find the positive predictive value for when two tests are done when

a) the tests are correlated
b) rho=0,7

I figured that for rho=0 the PPV for two tests is 0,4475. For a single test it's 0,4475. But I can't figure out a and b.

Anyone here knows some pharmacology? When people say something like "dopamine receptor agonist"...is the receptor presynaptic or postsynaptic? A presynaptic receptor (e.g. autoreceptor) may trigger a decrease in the production of the neurotransmmiter (so an inhibitory response), while an agonizer for postsynaptic receptor may encourage firing (so excitatory).

Am I misunderstanding something?

Find a function that is continuous and bounded on [0,infinity) but not uniformly continuous on [0,infinity).

I understand it has to do with a function having several different slopes, but how is this possible while being bounded?

Provide an example or briefly explain why the request is impossible: A nonempty bounded set whose set of limit points is a nonempty open set

I know the set of limit points is always closed, but sets can be closed and open. I feel like this can't be done. Help?

Also: A nonempty open set with no limit points.

This seems impossible, since if a set is open, any arbitrarily small epsilon neighborhood around a point A is nonempty (excluding the point A in question). Doesn't this mean A is a limit point since points nudge up arbitrarily close to it?

Can someone explain to me how to solve this problem?

During a thermodynamic process, the state variables of an ideal gas measured in m^3, KPa and C, varied in the following way:

P2 = 2P1
V2 = 2V1
T2 = 9T1

What is the final temperature of the gas?

I have absolutely no idea how to solve it and I feel like I'm seriously overlooking something.

can infintesimals be thought of as similar to R^2 with lex ordering?

You are overlooking data, user. Where the fuck are the initial values of anything

There literally are none. There's a hint on the page, but that's it:

>Here are some clues to answer the third question.
>The ratio between the temperatures at the final and initial states, T2 / T1, takes the given value if the temperatures are given in Celsius degrees. The temperatures in kelvins, as they should be used in the ideal gas equation, are (T1 + 273.15) and (T2 + 273.15).
>Write up the gas equation for the initial and final states
>Eliminate P2, V2, and T2 from the second equation
>Then eliminate the ratio P1V1/nR
>That leaves a linear equation with T1 being the only unknown in it.

But no matter what I do, I'm pretty sure I'm missing something, like the initial values being carried on from the last question but they forgot to say.

sin(sqrt(x))

It's bounded because sin is clamped, and if you take the derivative you get

cos(sqrt(x))*1/(2sqrt(x))

^I haven't done that in a while, so it could be wrong. The point is, as x approaches 0 your derivative goes infinite, which I think is how uniform continuity is defined.

The trick is the use a function which oscillates more and more as you go towards infinity.

This is wrong. Uniform continuity is defined as
>for every epsilon > 0, there is a delta > 0 such that for every x and y, if |x-y| < delta, then |f(x)-f(y)|

Yeah I saw that on Wikipedia. So is my function valid for his question or not? Sorry if my interpretation of the definition was too simple.

No, because it is not a uniformly continuous function.
The easiest way to show this is to split up the domain. Any continuous function on a compact domain is uniform continuous, so sin(sqrt(x)) is uniformly continuous on [0,1]. Then on [1/2,infinty), sin(sqrt(x)) has a bounded derivative, and thus it's uniformly continuous on that domain as well.
Then given epsilon > 0, you get delta_1>0 from the first domain, then delta_2>0 from the second domain. Put delta=min(1/2,delta_1,delta_2). Then if |x-y|

PV/T=constant
find relationship between TK1 and TK2
simultaneous equation with known TC2=9TC1
Final result should be 1400 ish

Sorry but I still don't get it. Its OK, I'll just let those 5 marks go.

Well I thought the goal was something NOT uniformly continuous.

I'm sorry, I made a typo, it is uniformly continuous and what I wrote after shows it is uniformly continuous.

So basically, the derivative being infinite as you approach 0 from the right has nothing to do with uniform continuity?

To restate what I said before, it is true that if the derivative is bounded, then the function is uniformly continuous. The converse of this, that if the function is uniformly continuous, then the derivative is bounded, is false. The function sin(sqrt(x)) demonstrates this.

Alright, thanks. What about sin(x^x)?

And going back to your explanation, I think I get it now. I guess I was thinking about it backwards or something?

I think that would work, though computing the derivative of x^x is mildly annoying. Something like sin(x^2) would work just as well and is simpler to compute.

Yeah true... thanks for the explanation. So is there any more intuitive way to comprehend uniform continuity/discontinuity other than ?

>mildly annoying
No it isn't. y=x^x, take ln of both sides and then differentiation and solve for y'. Once you do it once you have the formula. You don't need to do it by hand every time unless you're autistically retarded

H-How about this?
I've redo it with the element chasing from .

For continuity, it's that when you fix a point x, small changes around x result in small changes in f(x). However, how small the change is might depend on where you are in the domain. I think this is easiest to see with the function f(x) = 1/x on (0,1). As x->0, for a fixed epsilon, I need smaller and smaller delta to satisfy the definition of continuity.
For uniform continuity, there is one uniform delta that works for every point in the domain. So for something like f(x) = 3x, choosing delta = epsilon/3 will work for every point in the domain, it doesn't matter where.
So in summary: with uniform continuity, if x and y are close together, then f(x) and f(y) are close together, and it doesn't matter where in the domain x and y are. For regular continuity, you need to fix a point in the domain before you can choose a delta.

are sponges the only totipotent animal? are cnidarians indeterminate when they're developed?

I've dropped every math class i've taken at least once at my jc. precalc, calc, calc 2, and now i've gone and dropped calc 2 twice. can i ever transfer with these blemishes? i'm a cs major looking to go to a CSU or UC.

This is still bad. You need to use words in your proofs and you can't use set operators on formulas. Read this and practice mimicking their proofs.
math.cmu.edu/~wgunther/127m12/notes/day9.pdf

>gonna get this one wrong because it doesn't specify if the adult is American or not

should I feel bad or ashamed that my parents can afford to pay for my education and rent while I study

>le meme
I can't tell if you're actually being stupid but assume your country unless stated otherwise

Well, did you drop them after the drop deadline (i.e., do you have on your transcript that you withdrew from them)? Or did you just drop them like a week in or something?

A basis is a minimal generating set for the vector space (i.e., there is no subset of the basis that is also a generating set)

Haven't worked through it in detail, but I think this should work. Consider [math]\mathbb{Q}[/math] with the standard metric. Then [math]B(q,\alpha)[/math] with [math]\alpha[/math] irrational is bounded and clopen. Since it's closed, every limit point is contained in the set. Additionally, every point in the set is a limit point of the set. So the set of its limit points is just [math]B(q,\alpha)[/math] itself, which is open.

Consider the discrete topology.

No. Let that inspire you to do something good with it. Trust me, it is not healthy to dwell on that or feel jealous about people who saved up Starbucks money, worked while schooling and ended up self-funded. They're not better people, they just have a better story.

Write [h] or [H] after the filename in LaTeX. This is easy googling user.

Heads up its a HW question. I'm not asking you to do my HW, but please explain the concept to me because I'm incredibly confused.

What frequency of light can be generated if a single electron tunnels through a potential barrier V?

I'm super confused because I thought that the energy of the electron doesn't change after it tunnels through a barrier? I thought that tunneling only had to do with electron flux, hence the wave functions are the same before the electron hits the barrier and after the electron tunnels through the barrier, and electrons that make it through the potential barrier have the exact same energies as the incident electrons.

Do I have a fundamental misunderstanding of the concept?

X-ray Machine can't make picture of brain because it only shows skull.
But CT scan uses also x-rays and it can make picture of brain. What is different?

Hey Veeky Forums, Armyfag here.
I want to go to college when I'm out in a couple years, but I've realized I've forgotten almost everything I learned in high school, as I never apply any of it in my daily life. I figured this would make things hard in an Engineering related degree which I'll be pursuing once I'm out. My question is, is there any good resource collection to relearn most high school level courses, free online? I don't want a certificate or anything, just to brush back up on everything from geometry to calculus.

CT scans use contrast agents to increase absorptivity of X-rays in different tissues.

Their data processing is also more specially intricate and can, over time, build up a more complicated image than a simple 2D-X-ray. Wikipedia has some cool cutaways of the inside of CT scanners.

How was this found?

the equation (2.15) is

$$
x^2y'' +xy' + (x^2-a^2)y = 0
$$

bump

Khan academy has everything you need senpai

This is good for simple maths

Feynman lectures are free online and are well regarded for fundamental physics (if you want that) they can be quite hard though and most of it is above high school level but is fun nonetheless. You could try some of the very early parts of the series.

kys

Why would anyone write such a cumbersome proof?
Here is the proof for abstract inner product spaces.
[math] \frac{\langle u,v \rangle}{\lVert v \rVert ^2} v [/math] is the projection of u onto v; you take the dot product and divide by ||v|| which gives you the length of the projection and v/||v|| gives the direction of v.
w is just u minus the projection.
The projection and w are obviously orthogonal.

Hey sci, learning set theory now and ran across this problem. Pic related is supposedly the answer, but shouldn't the power of an empty set be the empty set in parenthesis? then why does the answer puts instead the empty set in parenthesis within + an empty set, all in parenthesis?

Yes and no, pain is just an overstimulated sensation, not communicating that there is a problem necessarily, our brain just interprets it that way oftentimes.

Hot sauce is a great example, capsicum aggravates heat and noiception sensations to the point of pain, though no actual damage is occurring outside of some irritation, this is fairly unique to mammals with physiology developed for high levels of plant consumption. Dogs on the other hand have a difficult time with 'heat' sensation from hot sauce, any time you see them reacting to it, is generally result of high amounts of 'bitter' being sensed not the actual communication of 'burning' experienced by humans.

The empty set is a subset of all sets (a vacuous truth), so it is contained in every power set.

but shouldn't by definition the power of V0 (an empty set) be an empty set in parenthesis? It looks like it went a step too far in defining V1.

Sorry user, 90% of Veeky Forums are mathmagicians so natural science is often in short supply.

When you say "dopamine receptor agonist" the 'dopamine receptor' part is only referring to the type of receptor activated.

As an agonist, it is probably either a hormone or a neurotransmitter, because we are talking about dopamine we know it's a neurotransmitter.

From there we can clearly define that a "dopamine receptor agonist" is a neurotransmitter that eventually signals for dopamine to be released.

Following basic pre-synapse/post-synapse rules, we know that the pre-synaptic neuron is the neurotransmitter producer and the post-synaptic neuron is the neurotransmitter receiver.

The answer to your immediate question is post-synaptic.

Concerning autoreceptors, they don't immediately apply to your question, but obviously are essential to the negative feedback loop. Read this article for an explanation of the dopamine autoreceptor relationships: ncbi.nlm.nih.gov/pubmed/24463000

Hope this helps, pharma is not my specialty.

Actually you're right. It seems the book mode a mistake. A simple way to check that would be: if X has n elements, then P(X) has 2^n elements. V0 has 0 elements, which means V1 should have just 1 element.

Alright, thanks.

Yeah it's not even from the book it's a solution guide so the guy just fucked up i guess.

>because we are talking about dopamine we know it's a neurotransmitter.
But I mean it can also be a drug no? Psychopharmacology is the context I'm most interested in; sorry I didn't make that clear.

>Concerning autoreceptors, they don't immediately apply to your question
Would you say it applies if we're talking drugs?

>Hope this helps, pharma is not my specialty.
Anything helps user; thanks for replying!

How to stop being a brainlet?

Hi guys, feeling a bit lost on a mechanical physics problem.
A particle undergoes simple harmonic motion (oscillation) with a frequency of 10hz. Find the displacement (or position) x as a function of time given the following information: x(0) = 0.25m and x 0 (0) = v 0 =0.1m/s.

What I have so far:
x(t) = .25cos(10t) + 0.1/10 sin (10t)
Am I on the right track? Or should I use
d^2x/dt^2 = -k/mx
P-p-pls respond

>Or should I use
>d^2x/dt^2 = -k/mx
Are you still in high school or retarded...
d^2x/dt^2 = -k/mx with boundary conditions gives x(t) = .25cos(10t) + 0.1/10 sin (10t)

Jeez man, physics obviously is not my forte, was forced to take this class. And my professor barely teaches us anything.
Anyways, mind pointing me in the right direction?, also in the problem I made a typo, it is X'(0) = vₒ = 0.1m/s

dual n back exercises

so d^2x/dt^2 = -k/mx is a differential equation that has the solution
x(t) = A cos(Bt) + C sin(Dt)
the frequency is 10hz, so B = D = 2pi/10 (or maybe 2pi*10 idk)
x(0) = A cos(0) + C sin(0) = A = 0.25m
this fixes A
x'(0) = -AB sin(0) + CD cos(0) = CD = 0.1
this fixes C

>I'm asking for the steady state solution.
>Ut=0
This is wrong. Steady state solution is when t->inf. You already had enough equations to solve the differential equation in the 4 lines before it. You solve it, apply the boundary conditions, then apply the limit.

This helped so much. Thanks.

The problem:

I need a way to calculate the coordinates (latitude/longitude) from the center point within the green circle.

What I have:
-> A pre processed segmented satellite image compressed in a jpg file.

-> The lat/lon from the center of the image

-> The distance in pixels from the center of the image to the center of the circle

PS: no geo data attached to the image :(

What the FUCK is a tensor and why is there no explanation that doesn't take a fucking page to write or is just "lol it transforms like this, don't worry about what it is xD"

youtube.com/watch?v=f5liqUk0ZTw