The h Bar

1:04 AM

if you wanted to produce an image of a living human brain with enough clarity to discern each and every neuron and synapse without killing or damaging the brain tissue of the person involved, must the required technology be more than simply increasing the numbers in the specifications of an MRI or C-scan?

Mikhail

1:16 AM

@0xFFF1 So, the MRI spin flip (T2-limited resolution) is around 10 um. You/d have to do some super resolution witchcraft, maybe like STED to get higher resolution.

10 um is pretty terrible, compared to light microscopes, not to mention FIB-SEM, basically MRI doesn't have enough resolution and will never have enough resolution.

0xFFF1

same story for Cscans?

Mikhail

xrays have really high resolution, although it depends on your belief in the reversibility of fields

0xFFF1

high frequency EM waves bounce off bone though?

Mikhail

Not really

0xFFF1

hm

Mikhail

1:21 AM

xrays go through, mostly

Ultraviolet catastrophe

The ultraviolet catastrophe, also called the Rayleigh–Jeans catastrophe, was the prediction of late 19th century/early 20th century classical physics that an ideal black body at thermal equilibrium will emit radiation in all frequency ranges, emitting more energy as the frequency increases. By calculating the total amount of radiated energy (i.e., the sum of emissions in all frequency ranges), it can be shown that a blackbody would release an infinite amount of energy, contradicting the principles of conservation of energy and indicating that a new model for the behaviour of blackbodies was needed...

Problem is the signal is scrambled when it "bounces" around a lot

Also to get the coherence properties of an xray source that will let you do sub micron imaging, you gotta build a cyclotron (or simliar)

0xFFF1

how many zones of lines-of-sight do you have to peer into a living human cranium while only piercing soft tissue? Through the eye holes and nose hole, and underneath the jaw?

Mikhail

You have zero because the brain is covered?

0xFFF1

i mean there's ways in that dont have to go through bone

looking up cyclotron, looks like it's either so much energy, or too long an exposure to xrays to be safe

Mikhail

Its not about the intensity, its about the coherence requirements

0xFFF1

yeah, but we dont want to kill the person

at least, I dont

Mikhail

1:29 AM

You probably don't understand what I'm talking about. Its not about the intensity, its about getting the perfect xray out.

Even then its not clear if you can reverse the media turbidity.

0xFFF1

coherence is about being able to constrain the trajectory of a particle outgoing an accelerator, to get more information about the image that it produced from it bouncing back?

Mikhail

no

The illumination isn't perfect, its a bunch of waves with some spread. This spread reduces interferometric contrast (among other things). If you don't have the right coherence you see something like a low resolution shadow map.

So, when they do xray imaging of cells or semiconductors they hook up a microscope to end of a massive ring that makes the fuck sure the xray field has no spread in frequencies.

If they didn't do that, they wouldn't see anything.

0xFFF1

tubidity seems like a simple enough concept, a bunch of free particles in a fluid cause em packets to bounce around. This would obviously ruin the image quality

Mikhail

So, an image is the interference of a scattered and transmitted field. Turbidity in a sample ruins the ability of these field to interfere while also producing a third, "non-interferometric" signal.

0xFFF1

is that unwanted third part of the signal mostly random?

Mikhail

1:44 AM

That's a loaded question. Some people (perhaps me) believe that the mechanism that make it introduce true randomness and the signal is gone forever. Its also typically quite intense compared to the remaining interference portion (which vanishes all the way as you make your sample thicker).

0xFFF1

i suppose I should use the word random here in its common usage (variance that is beyond our control to calculate or modify). I think actual randomness doesn't exist. (IE the copenhagen interpretation is bullshit and we should instead use pilot-wave)

well, an image of an entire brain would be pretty thick

so there isn't hope of being able to resolve such an image? or just not with xrays?

Mikhail

So, if you use an xray you can get more depth penetration and the right resolution, the question is if the turbidity can be resolved.

0xFFF1

would taking the image multiple times under the same parameters help?

Mikhail

no

0xFFF1

then comparing

Mikhail

1:53 AM

The loss of coherence (in this case) comes from the variable path the photon will take moving through the sample.

Cows

5:08 AM

APES**T - THE CARTERS

►

Physics all night long

Taking this stuff to the next level

Koolman

7:24 AM

@JohnRennie Hii

I have a question

John Rennie

I'm working at the moment I'm afraid. Back in an hour or so.

Koolman

Why in C program we sometimes use return 0; or return 1; in the code ?

@JohnRennie np

reply me when you are free .

codesdope.com/blog/article/…

Slereah

@Koolman So that a program calling this program knows that it ended correctly

Koolman

Example is given in above link of C program

Slereah

Your program may be called by another program. Generally, it's considered that if it returns 0, it has ended correctly

If it returns another value, that value is an error code

For which hopefully you have documentation

Koolman

7:27 AM

@Slereah Where it return 0 ?

Slereah

yes

Koolman

@Slereah What do you mean by documentation ?

I am a beginner .

Slereah

Well in the best case scenario, the program should have a document indicating what the return values mean

Although for simple programs, such as the ones you're doing as a beginner, there's not much need to worry and you can just return 0

Koolman

@Slereah How could we know it will written 0 or any other integer

codesdope.com/blog/article/…

But in this code they have used both the integers

Anonymous

@Koolman You can obviously check in the console output...

Slereah

7:29 AM

At the level of the OS, a C program works somewhat like a function

You can call it with arguments

and it returns a numeric value

which you can check if you know what you're doing

Anonymous

Or yeah, just call it from another function

Koolman

@Blue Does on console output there it is written 0 or 1 ?

Anonymous

Should be written, yes

Slereah

That's why the main program is written like a function

int main (int argc, char *argv[])

although technically it's not mandatory

The main function can just return nothing

It depends what the purpose of the program is

In what kind of environment it has to run

Anonymous

@Koolman Why are you learning C tho? Part of syllabus?

Koolman

7:33 AM

@Blue Actually I have almost completed C but never thought of it .

Now I am starting with JAVA

Slereah

@Koolman stackoverflow.com/questions/8626109/…

Anonymous

What does "completing C" even mean? :P

Anonymous

Anyhow, I vouch for Python ;)

Sid

That ^

Slereah

Python isn't gr8

No typing

it can be a bit of a mess

Sid

7:35 AM

@Slereah Python has an easy learning curve.

Slereah

It comes at a grave price!

Koolman

@Slereah Also we sometimes use void main() and int main()

Slereah

yes

void is when you don't require your function to output anything

So that either your program doesn't get called by another program, or if it does, they can't know how the execution went

Anonymous

@Slereah It isn't strongly typed, true. But I really haven't faced many issues with it. In which type of cases does it cause a problem (other than it's difficult to keep track of which variable is of which type)?

Koolman

Thanks
Now I understood it

Sid

7:39 AM

@Blue That's one of the primary issue with it. But, it's not a dealbreaker for me.

Anonymous

Additionally jupyter notebooks, numpy and pandas are the best thing ever :)

Slereah

@Blue you just said it :p

Real men program in Ada!

that shit won't compile if there's any type error

Anonymous

Anyhow, I sort of got bored of picking up new programming languages now :P I'll stick to C and Python till they become the new COBOLs

Anonymous

@Slereah lol...nice

Sid

@Blue I don't have any liking to C. I will just do Python and R.

Anonymous

7:46 AM

The good thing about C and C++ is that almost every programming problem you'll ever face, is already coded in those two languages by someone, somewhere :P

Slereah

@Blue C has been the new COBOL for 50 years

Sid

I was just seeing my subjects for next semester and only a few look particularly interesting.

Slereah

C ain't going away

they're not gonna recode Linux in Java

Anonymous

lol

Slereah

The three things that never die are COBOL, FORTRAN and C

and of course the Space Jam website

warnerbros.com/archive/spacejam/movie/jam.html

Although I guess technically Ada also never dies, but it's a much more narrow field of application

Ada is all for like plane hardware and that kind of stuff

Sid

7:50 AM

@Slereah woodbetween.world/2017/07/…

Anonymous

@Sid Dude, I convinced my professor to learn C and forget FORTRAN :P Give me a medal (not that they have still forgotten their love for FORTRAN)

Anonymous

Well, tbh FORTRAN does have some advantages

Anonymous

But it has so many different versions that it gets difficult to keep track of

Anonymous

"You'll get the sample code and look at it, and it will be completely incomprehensible. They all are. All Fortran codes are incomprehensible."

Anonymous

This is soooo true, lol ^

Slereah

8:01 AM

FORTRAN is basically to do math

It's not very friendly for any other application

Anonymous

Indeed. When you just need to churn out the numbers...

Slereah

"Actual Fortran legacy code I received once.
All four of the comments are in French.
I dare you to figure out what it means."

I am shocked by this racism against my people

Anonymous

The French are (in)famous for many things :P

Slereah

"The convention is (usually) that names beginning with letters A-H or O-Z are implicitly floating point, while names beginning with letters I-N are implicitly integers."

My sides

Sid

@Blue Awards you gold medal. :P

There's also this

Secret

8:11 AM

analogy and catalogy

open(unit=1234, iostat=stat, file=file, status='old')
if (stat == 0) close(1234, status='delete')

quora.com/…

Anonymous

@ACuriousMind Is your new display picture for checking whether people will still address you as "Sir" on the main site? ;)

Secret

lol

Slereah

9:25 AM

"Perl is “some assembly required”. Python is “batteries included”. PHP is “kitchen sink, but it’s from Canada and both faucets are labeled C“."

3

"0x0+2 produces 4. The parser considers the 2 as both part of the hex literal and a separate decimal literal, treating this as 0x002 + 2. 0x0+0x2 displays the same problem. Strangely, 0x0 +2 is still 4, but 0x0+ 2 is correctly 2."

Jesus

Secret

IBM Think 2018: Mark Howell and James McLeod from Lloyds

►

Secret

10:32 AM

0

Q: Why do the laws of physics fail to predict the behavior of frustrators?

This is my attempt to make an earlier question less broad. This question takes the form of a thought experiment, and is based on this video. Suppose you are given: The positions, velocities, wavefunctions, masses, whatever you want to know of every single particle in the experiment Unlimited c...

seed of light should put a limit

Physics Meta

11:05 AM

0

Q: Can I ask if my calculation is correct?

Let's say I've been working in a calculation which is reasonable simple but I didn't found it done anywhere else. Can I post is in physics.SE and ask what the community think about it? I know in other SE communities that would not be allowed but in physics that might be, because check whether th...

discussion

rob

11:23 AM

@Slereah That's a funny way to spell "the parser is garbage"

Secret

12:25 PM

R.I.N.G.

Resentment
Induced
Nonlocal
Genocide

That will make a good thriller

Transcript for