Guqin Updated 2025-07-16
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Figure 1. Source.
Figure 2.
11th century painting of a guqin recital
. Source.
Figure 3.
Stringless guqin fan painting by Feng Chaoran (1943)
Stolen traight from www.silkqin.com/10ideo.htm on silkqin.com:
Wind in the pines and a babbling brook are nature's melody. A qin was brought along, but there is no need to play it
The The Gateless Barrier vibe and Chinese naturalism is just awesome.
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Hamilton's equations Updated 2025-07-16
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Analogous to what the Euler-Lagrange equation is to Lagrangian mechanics, Hamilton's equations give the equations of motion from a given input Hamiltonian:
(1)
So once you have the Hamiltonian, you can write down this system of partial differential equations which can then be numerically solved.
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Hanford site Updated 2025-07-16
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The B Reactor of the facility produced the plutonium used for Trinity and Fat Man, and then for many more thousand bombs during the Cold War. More precisely, this was done at
Located in Washington, in a dry place the middle of the mountainous areas of the Western United States, where basically no one lives. The Columbia river is however nearby, that river is quite large, and provided the water needed by their activities, notably for cooling the nuclear reactors. It is worth it having look on Google Maps to get a feel for the region.
Unlike many other such laboratories, this one did not become a United States Department of Energy national laboratories. It was likely just too polluted.
Figure 1.
Aerial image of the Hanford site in 1960
. Source.
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Hans Petter Langtangen Updated 2025-07-16
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It should be mentioned that when you start Googling for PDE stuff, you will reach Han's writings a lot under his GitHub Pages: hplgit.github.io/, and he is one of the main authors of the FEniCS Project.
Unfortunately he died of cancer in 2016, shame, he seemed like a good educator.
He also published to GitHub pages with his own crazy markdown-like multi-output markup language: github.com/hplgit/doconce.
Rest in peace, Hans.
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Harvard University Updated 2025-07-16
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How to diagnose a genius by Wilhelm Ostwald (1909) Updated 2025-07-16
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From the abstract:
Much money, his student went on to say, is spent by various Governments in attempting to discover those people whose thorough education may be expected to bring in a return of value to the State, and the question how best to discover latent genius is an eminently practical one. After cogitation, Prof. Ostwald came to the conclusion that it is those students who cannot be kept on the rails - that is, who are not contented with methodical teaching - who have within them the seeds of genius
Ciro Santilli couldn't agree more... notably students must have a flexible choice of what to learn.
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How to exit from repl in rshell? Updated 2025-07-16
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Ctrl + X. Documented by running help repl from the main shell.
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How to make animations of molecular biology processes Updated 2025-07-16
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Drew Berry recommends having a look at clarafi.
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How to run a MicroPython script from a file on the Raspberry Pi Pico W from the command line? Updated 2025-07-26
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The first/only way Ciro could find was with ampy: stackoverflow.com/questions/74150782/how-to-run-a-micropython-host-script-file-on-the-raspbery-pi-pico-from-the-host/74150783#74150783 That just worked and it worked perfectly!
pipx install adafruit-ampy
ampy --port /dev/ttyACM0 run blink.py
TODO: possible with rshell?
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How to show that a group is simple Updated 2025-07-16
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How to teach / Advertise your material Updated 2025-07-16
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Once you have crated something awesome, you have to advertise it, otherwise no one will ever find it.
This means:
  • whenever you walk into a classroom, give students a link to the material
    Then ask them if they want to talk about anything.
    Then leave the classroom and go produce more good material instead of wasting your time there :-)
  • whenever someone asks as question on an online forum, answer it, and link to the section of your material that also answers that question.
    The material will answer many of their future questions.
  • after you've done something awesome, Google possible relevant keywords that should hit it.
    This will lead you to other websites that talk about the same content.
    Then, leave comments on those pages linking to your stuff, or email the authors of those pages.
    It is borderline spam, but if the subject is closely related, it is a win for everyone.
Eventually, people will find you on the front page of Google searches, and then you will know that you've truly made something useful.
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How to teach / Give examples Updated 2025-07-16
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Keep the example/theory ratio high, very, very high.
For natural sciences, add as many reproducible experiment images/videos/descriptions as you can.
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How to teach / Projcts must aim for novelty Updated 2025-07-16
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How to teach / Use the Internet Updated 2025-07-16
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If you give a course in a classroom, you reach 10 people (the others were sleeping).
If you make a perfect course online, and answer questions online, you reach 10 thousand.
Not doing things online is a waste of time.
You are a highly trained professional, and your time is extremely valuable.
Even if it takes twice as long to create the material than giving course, you are still more efficient by a factor of 500.
It is as if there were 500 little copies of you working full time. It is a superpower.
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How to use an Oxford Nanopore MinION to extract DNA from river water and determine which bacteria live in it / Qiagen DNeasy PowerWater Kit Updated 2025-07-16
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Kit to extract clean DNA from water.
Figure 1.
Qiagen DNeasy PowerWater Kit open box.
Source.
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How to use an Oxford Nanopore MinION to extract DNA from river water and determine which bacteria live in it / Sample collection Updated 2025-07-16
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As you would expect, not much secret here, we just dumped a 1 liter glass bottle with a rope attached around the neck in a few different locations of the river, and pulled it out with the rope.
And, in the name of science, we even wore gloves to not contaminate the samples!
Figure 1.
Swans swimming in the river when during sample collection
. Source. Swam poo bacteria?
Figure 2.
Tying rope to bootle for river water sample collection
. Source.
Figure 3.
Dumping the bottle into the river to collect the water sample
. Source.
Figure 4.
Measuring the river water sample temperature with a mercury thermometer
. Source.
Figure 5.
Measuring the river water sample pH with a pH strip
. Source. The strip is compared with the color of a mobile app that gives the pH for a given strip color.
Figure 6.
Noting sample collection location on the water bottle
. Source.
Video 1.
Dumping the bottle into the river to collect the water sample
. Source. That was fun.
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How to view only posts by followed on Facebook feed? Updated 2025-07-16
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Circa 2023, the feed is an unbearable list of stupid suggestions, never-ending idiotic memes, and you just end up missing posts you actually care about from people you actually follow.
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Hugging Face Updated 2025-07-16
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Interesting website, hosts mostly:
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Human game used for AI training Updated 2025-07-16
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This section is about games initially designed for humans, but which ended up being used in AI development as well, e.g.:
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Hund's rules Updated 2025-07-16
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Allow us to determine with good approximation in a multi-electron atom which electron configuration have more energy. It is a bit like the Aufbau principle, but at a finer resolution.
Note that this is not trivial since there is no explicit solution to the Schrödinger equation for multi-electron atoms like there is for hydrogen.
For example, consider carbon which has electron configuration 1s2 2s2 2p2.
If we were to populate the 3 p-orbitals with two electrons with spins either up or down, which has more energy? E.g. of the following two:
m_L -1  0  1
    u_ u_ __
    u_ __ u_
    __ ud __
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