for loop Updated +Created
The for loop is a subcase of the while loop.
One theoretical motivation for its existence is that it has the fundamental property that we are immediately certain it will terminate, unlike while loops with arbitrary conditions.
Primitive recursive functions are the complexity class that divides those two.
Fourier transform Updated +Created
Continuous version of the Fourier series.
Of course, every function defined on a finite line segment (i.e. a compact space).
Therefore, the Fourier transform can be seen as a generalization of the Fourier series that can also decompose functions defined on the entire real line.
As a more concrete example, just like the Fourier series is how you solve the heat equation on a line segment with Dirichlet boundary conditions as shown at: Section "Solving partial differential equations with the Fourier series", the Fourier transform is what you need to solve the problem when the domain is the entire real line.
Reactions to cirosantilli.com's design Updated +Created
People love green on black mostly.
news.ycombinator.com/item?id=38492304 about Section "CIA 2010 covert communication websites":
  • user thewildginger:
    Nothing like finding a webpage you can read from Lynx.
  • user socketcluster:
    Based on the choice of fonts and colors, you know this is a serious hacker website ;p
www.reddit.com/r/Monero/comments/1brryao/ciro_santilli_received_a_1000_xmr_donation_to/ from 1000 Monero donation:
  • user -TrustyDwarf-:
    Anyone mind to explain wtf this ugly piece of webpage reminding me of geocities from the 90s is about? I'd read it myself but I can't because it already gave me eye cancer.
  • user rbrunner7:
    It's all quite strange. Never mind the 90s design, people built good websites already back then with the tools at hand, but even their "About" isn't very clear. If you need 5 minutes to be reasonably sure what it is all about they are still doing it wrong.
  • automobi1e
    I'd rather take a look at the welding
Real coordinate space of dimension four Updated +Created
Real-time polymerase chain reaction Updated +Created
Also known as: Quantitative PCR (qPCR).
Like PCR, but the amplification machine measures the concentration of DNA at each step.
This describes one possible concentration detection method with fluorescent molecules that only become fluorescent when the DNA is double stranded (SYBR Green)
Video 1.
Polymerase Chain Reaction (PCR) - Quantitative PCR (qPCR) by Applied Biological Materials (2016)
Source.
This allows you to predict the exact initial concentration by extrapolating the exponential curve backwards.
TODO: vs non-real-time PCR. Why can't you just divide by 2 for every heating step to reach back the original concentration? Likely the reaction reach saturation at an unknown step.
TODO: vs non-real-time PCR in medical diagnostics: do you really need to know concentration for diagnostics? Isn't it enough to know if the virus is present or not?
RE (complexity) Updated +Created
Condensed matter university course Updated +Created
Entropy Updated +Created
OK, can someone please just stop the philosophy and give numerical predictions of how entropy helps you predict the future?
The original notion of entropy, and the first one you should study, is the Clausius entropy.
Video 1.
The Unexpected Side of Entropy by Daan Frenkel
. Source. 2021.
Video 2.
The Biggest Ideas in the Universe | 20. Entropy and Information by Sean Carroll (2020)
Source. In usual Sean Carroll fashion, it glosses over the subject. This one might be worth watching. It mentions 4 possible definitions of entropy: Boltzmann, Gibbs, Shannon (information theory) and John von Neumann (quantum mechanics).
Multiplication Updated +Created
Regulate the fuck out of advertising Updated +Created
It should be illegal to give someone money to advertise your product.
We should just use tags and upvote-based algorithms.
TODO find Sergey Brin quote bout advertising being a form of perverting search engine ranking neutrality. In other words, there are neutral metrics to what people find good, like links and upvotes. And then advertising is a way to pervert that to someone's profit.
Sometimes Ciro Santilli thinks advertising should be on-subscription only, but that is too restrictive, e.g. imagine the local business owner who wears a t-shirt of their business.
Video 1.
What Do I Think When I Think About Advertising by Daniele Grosso
. Source.
Bristol (synthesizer) Updated +Created
Simulates vintage hardware synthesizers, and includes some pretty complex ones!
Aims to show an UI that looks exactly like the synthesizers in question.
For example for the Minimoog on Ubuntu 20.04:
sudo apt install bristol
startBristol -mini -alsa
This is a really good piece of software. You can search on YouTube how some classic synths, work, and the immediately start playing them!
Transcription (biology) Updated +Created
bsub Updated +Created
Submit a new job. The most important command!
HIV Updated +Created
Messenger RNA Updated +Created
Resonance Updated +Created
Resonance is a really cool thing.
Examples:
Perhaps a key insight of resonance is that the reonant any lossy system tends to look like the resonance frequency quite quickly even if the initial condition is not the resonant condition itself, because everything that is not the resonant frequency interferes destructively and becomes noise. Some examples of that:
  • striking a bell or drum can be modelled by applying an impuse to the system
  • playing a pipe instrument comes down to blowing a piece that vibrates randomly, and then leads the pipe to vibrate mostly in the resonant frequency. Likely the same applies to bowed string instruments, the bow must be creating a random vibration.
  • playing a plucked string instrument comes down to initializing the system to an triangular wave form and then letting it evolve. TODO find a simulation of that!
Another cool aspect of resonance is that it was kind of the motivation for de Broglie hypothesis, as de Broglie was kind of thinking that electroncs might show discrete jumps on atomic spectra because of constructive interference.
Reverse transcriptase Updated +Created
Converts RNA to DNA, i.e. the inverse of transcription. Found in viruses such as Retrovirus, which includes e.g. HIV.

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