Stanford Smallville by Ciro Santilli 40 Updated 2025-07-16
Published as: arxiv.org/pdf/2304.03442.pdf Generative Agents: Interactive Simulacra of Human Behavior by Park et al.
Video 1.
AI Agents Behaving Like Humans by Prompt Engineering (2023)
. Source.
Lysozyme by Ciro Santilli 40 Updated 2025-07-16
Breaks up peptidoglycan present in the bacterial cell wall, which is thicker in Gram-positive bacteria, which is what this enzyme seems to target.
Part of the inate immune system.
It is present on basically everything that mammals and birds excrete, and it kills bacteria, both of which are reasons why it was discovered relatively early on.
  • reconstruction/ecoli/flat/condition/nutrient/minimal.tsv contains the nutrients in a minimal environment in which the cell survives:
    "molecule id" "lower bound (units.mmol / units.g / units.h)" "upper bound (units.mmol / units.g / units.h)"
    "ADP[c]" 3.15 3.15
    "PI[c]" 3.15 3.15
    "PROTON[c]" 3.15 3.15
    "GLC[p]" NaN 20
    "OXYGEN-MOLECULE[p]" NaN NaN
    "AMMONIUM[c]" NaN NaN
    "PI[p]" NaN NaN
    "K+[p]" NaN NaN
    "SULFATE[p]" NaN NaN
    "FE+2[p]" NaN NaN
    "CA+2[p]" NaN NaN
    "CL-[p]" NaN NaN
    "CO+2[p]" NaN NaN
    "MG+2[p]" NaN NaN
    "MN+2[p]" NaN NaN
    "NI+2[p]" NaN NaN
    "ZN+2[p]" NaN NaN
    "WATER[p]" NaN NaN
    "CARBON-DIOXIDE[p]" NaN NaN
    "CPD0-1958[p]" NaN NaN
    "L-SELENOCYSTEINE[c]" NaN NaN
    "GLC-D-LACTONE[c]" NaN NaN
    "CYTOSINE[c]" NaN NaN
    If we compare that to reconstruction/ecoli/flat/condition/nutrient/minimal_plus_amino_acids.tsv, we see that it adds the 20 amino acids on top of the minimal condition:
    "L-ALPHA-ALANINE[p]" NaN NaN
    "ARG[p]" NaN NaN
    "ASN[p]" NaN NaN
    "L-ASPARTATE[p]" NaN NaN
    "CYS[p]" NaN NaN
    "GLT[p]" NaN NaN
    "GLN[p]" NaN NaN
    "GLY[p]" NaN NaN
    "HIS[p]" NaN NaN
    "ILE[p]" NaN NaN
    "LEU[p]" NaN NaN
    "LYS[p]" NaN NaN
    "MET[p]" NaN NaN
    "PHE[p]" NaN NaN
    "PRO[p]" NaN NaN
    "SER[p]" NaN NaN
    "THR[p]" NaN NaN
    "TRP[p]" NaN NaN
    "TYR[p]" NaN NaN
    "L-SELENOCYSTEINE[c]" NaN NaN
    "VAL[p]" NaN NaN
    so we guess that NaN in the upper mound likely means infinite.
    We can try to understand the less obvious ones:
    • ADP: TODO
    • PI: TODO
    • PROTON[c]: presumably a measure of pH
    • GLC[p]: glucose, this can be seen by comparing minimal.tsv with minimal_no_glucose.tsv
    • AMMONIUM: ammonium. This appears to be the primary source of nitrogen atoms for producing amino acids.
    • CYTOSINE[c]: hmmm, why is external cytosine needed? Weird.
  • reconstruction/ecoli/flat/reconstruction/ecoli/flat/condition/timeseries/ contains sequences of conditions for each time. For example:
    • reconstruction/ecoli/flat/reconstruction/ecoli/flat/condition/timeseries/000000_basal.tsv contains:
      "time (units.s)" "nutrients"
      0 "minimal"
      which means just using reconstruction/ecoli/flat/condition/nutrient/minimal.tsv until infinity. That is the default one used by runSim.py, as can be seen from ./out/manual/wildtype_000000/000000/generation_000000/000000/simOut/Environment/attributes/nutrientTimeSeriesLabel which contains just 000000_basal.
    • reconstruction/ecoli/flat/reconstruction/ecoli/flat/condition/timeseries/000001_cut_glucose.tsv is more interesting and contains:
      "time (units.s)" "nutrients"
      0 "minimal"
      1200 "minimal_no_glucose"
      so we see that this will shift the conditions half-way to a condition that will eventually kill the bacteria because it will run out of glucose and thus energy!
    Timeseries can be selected with --variant nutrientTimeSeries X Y, see also: run variants.
    We can use that variant with:
    VARIANT="condition" FIRST_VARIANT_INDEX=1 LAST_VARIANT_INDEX=1 python runscripts/manual/runSim.py
  • reconstruction/ecoli/flat/condition/condition_defs.tsv contains lines of form:
    "condition" "nutrients"                "genotype perturbations" "doubling time (units.min)" "active TFs"
    "basal"     "minimal"                  {}                       44.0                        []
    "no_oxygen" "minimal_minus_oxygen"     {}                       100.0                       []
    "with_aa"   "minimal_plus_amino_acids" {}                       25.0                        ["CPLX-125", "MONOMER0-162", "CPLX0-7671", "CPLX0-228", "MONOMER0-155"]
    • condition refers to entries in reconstruction/ecoli/flat/condition/condition_defs.tsv
    • nutrients refers to entries under reconstruction/ecoli/flat/condition/nutrient/, e.g. reconstruction/ecoli/flat/condition/nutrient/minimal.tsv or reconstruction/ecoli/flat/condition/nutrient/minimal_plus_amino_acids.tsv
    • genotype perturbations: there aren't any in the file, but this suggests that genotype modifications can also be incorporated here
    • doubling time: TODO experimental data? Because this should be a simulation output, right? Or do they cheat and fix doubling by time?
    • active TFs: this suggests that they are cheating transcription factors here, as those would ideally be functions of other more basic inputs
NumPy by Ciro Santilli 40 Updated 2025-07-16
The people who work on this will go straight to heaven, no questions asked.
In this example, posts have tags. When a post is deleted, we check to see if there are now any empty tags, and now we want to delete any empty tags that the post deletion may have created.
If we are creating and deleting posts concurrently, a naive implementation might wrongly delete the tags of a newly created post.
This could be due to a concurrency issue of the following types.
Failure case 1:
  • thread 2: delete old post
  • thread 2: find all tags with 0 posts. Finds tag0 from the deleted old post which is now empty.
  • thread 1: create new post, which we want to have tag tag0
  • thread 1: try to create a new tag tag0, but don't because it already exists, this is done using SQLite's INSERT OR IGNORE INTO or PostgreSQL's INSERT ... ON CONFLICT DO NOTHING
  • thread 1: assign tag0 to the new post by adding an entry to the join table
  • thread 2: delete all tags with 0 posts. It still sees from its previous search that tag0 is empty, and deletes it, which then cascades into the join table
which would result in the new post incorrectly not having the tag0.
Failure case 2:
  • thread 2: delete old post
  • thread 2: find all tags with 0 posts
  • thread 1: create new post
  • thread 1: try to create a new tag tag0, but don't because it already exists
  • thread 2: delete all tags with 0 posts. It still sees from its previous search that tag0 is empty, and deletes it
  • thread 1: assign tag0 to the new post
which leads to a foreign key failure, because the tag does not exist anymore when the assignment happens.
Failure case 3:
  • thread 2: delete old post
  • thread 1: create new post, which we want to have tag tag0
  • thread 1: try to create a new tag tag0, and succeed because it wasn't present
  • thread 2: find all tags with 0 posts, finds the tag that was just created
  • thread 2: delete all tags with 0 posts, deleting the new tag
  • thread 1: assign tag0 to the new post
which leads to a foreign key failure, because the tag does not exist anymore when the assignment happens.
Sample executions:
  • node --unhandled-rejections=strict ./parallel_create_delete_empty_tag.js p 9 1000 'READ COMMITTED': PostgreSQL, 9 tags, DELETE/CREATE the tag0 test tag 1000 times, use READ COMMITTED
    Execution often fails, although not always. The failure is always:
    error: insert or update on table "PostTag" violates foreign key constraint "PostTag_tagId_fkey"
    because the:
    INSERT INTO "PostTag"
    tries to insert a tag that was deleted in the other thread, as it didn't have any corresponding posts, so this is the foreign key failure.
    TODO: we've never managed to observe the failure case in which tag0 is deleted. Is it truly possible? And if not, by which guarantee?
  • node --unhandled-rejections=strict ./parallel_create_delete_empty_tag.js p 9 1000 'READ COMMITTED' 'FOR UPDATE': do a SELECT ... FOR UPDATE before trying to INSERT.
    This is likely correct and the fastest correct method according to our quick benchmarking, about 20% faster than REPEATABLE READ.
    We are just now 100% sure it is corret becase we can't find out if the SELECT in the DELETE subquery could first select some rows, which are then locked by the tag creator, and only then locked by DELETE after selection. Or does it re-evaludate the SELECT even though it is in a subquery?
  • node --unhandled-rejections=strict ./parallel_create_delete_empty_tag.js p 9 1000 'REPEATABLE READ': repeatable read
    We've never observed any failures with this level. This should likely fix the foreign key issue according to the PostgreSQL docs, since:
    • the DELETE "Post" commit cannot start to be seen only in the middle of the thread 1 transaction
    • and then if DELETE happened, the thread 1 transaction will detect it, ROLLBACK, and re-run. TODO how does it detect the need rollback? Is it because of the foreign key? It is very hard to be sure about this kind of thing, just can't find the information. Related: postgreSQL serialization failure.
  • node --unhandled-rejections=strict ./parallel_create_delete_empty_tag.js p 9 1000 'SERIALIZABLE': serializable
  • node --unhandled-rejections=strict ./parallel_create_delete_empty_tag.js p 9 1000 'NONE': magic value, don't use any transaction. Can blow up of course, since even less restrictions than READ COMMITTED
All executions use 2 threads.
Some theoretical notes:
  • Failure case 3 is averted by a READ COMMITTED transaction, because thread 2 won't see the uncommitted tag that thread 1 created, and therefore won't be able to delete it
stackoverflow.com/questions/10935850/when-to-use-select-for-update from SELECT FOR UPDATE also talks about a similar example, and has relevant answers.
MRI is using NMR to image inside peoples bodies!
Video 1.
How does an MRI machine work? by Science Museum (2019)
Source. The best one can do in 3 minutes perhaps.
Video 2.
How MRI Works Part 1 by thePIRL (2018)
Source.
Video 3.
What happens behind the scenes of an MRI scan? by Strange Parts (2023)
. Source.
Video 4.
Dr Mansfield's MRI MEDICAL MARVEL by BBC
. Source. Broadcast in 1978. Description:
Tomorrow's World gave audiences a true world first as Dr Peter Mansfield of the University of Nottingham demonstrated the first full body prototype device for Magnetic resonance imaging (MRI), allowing us to see inside the human body without the use of X-rays.
Featuring the yet-to-be 2003 Nobel Prize in Physiology and Medicine Dr. Mansfield.
Ollama by Ciro Santilli 40 Updated 2025-07-16
Ollama is a highly automated open source wrapper that makes it very easy to run multiple Open weight LLM models either on CPU or GPU.
Its README alone is of great value, serving as a fantastic list of the most popular Open weight LLM models in existence.
Install with:
curl https://ollama.ai/install.sh | sh
The below was tested on Ollama 0.1.14 from December 2013.
Download llama2 7B and open a prompt:
ollama run llama2
On P14s it runs on CPU and generates a few tokens per second, which is quite usable for a quick interactive play.
As mentioned at github.com/jmorganca/ollama/blob/0174665d0e7dcdd8c60390ab2dd07155ef84eb3f/docs/faq.md the downloads to under /usr/share/ollama/.ollama/models/ and ncdu tells me:
--- /usr/share/ollama ----------------------------------
    3.6 GiB [###########################] /.ollama
    4.0 KiB [                           ]  .bashrc
    4.0 KiB [                           ]  .profile
    4.0 KiB [                           ]  .bash_logout
The file:
/usr/share/ollama/.ollama/models/manifests/hf.co/mlabonne/Meta-Llama-3.1-8B-Instruct-abliterated-GGUF/Q2_K
gives a the exact model name and parameters.
We can also do it non-interactively with:
/bin/time ollama run llama2 'What is quantum field theory?'
which gave me:
0.13user 0.17system 2:06.32elapsed 0%CPU (0avgtext+0avgdata 17280maxresident)k
0inputs+0outputs (0major+2203minor)pagefaults 0swaps
but note that there is a random seed that affects each run by default. ollama-expect is an attempt to make the output deterministic.
Some other quick benchmarks from Amazon EC2 GPU on a g4nd.xlarge instance which had an Nvidia Tesla T4:
0.07user 0.05system 0:16.91elapsed 0%CPU (0avgtext+0avgdata 16896maxresident)k
0inputs+0outputs (0major+1960minor)pagefaults 0swaps
and on Nvidia A10G in an g5.xlarge instance:
0.03user 0.05system 0:09.59elapsed 0%CPU (0avgtext+0avgdata 17312maxresident)k
8inputs+0outputs (1major+1934minor)pagefaults 0swaps
So it's not too bad, a small article in 10s.
It tends to babble quite a lot by default, but eventually decides to stop.

Pinned article: Introduction to the OurBigBook Project

Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
We have two killer features:
  1. topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculus
    Articles of different users are sorted by upvote within each article page. This feature is a bit like:
    • a Wikipedia where each user can have their own version of each article
    • a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
    This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
    Figure 1.
    Screenshot of the "Derivative" topic page
    . View it live at: ourbigbook.com/go/topic/derivative
  2. local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:
    This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
    Figure 2.
    You can publish local OurBigBook lightweight markup files to either https://OurBigBook.com or as a static website
    .
    Figure 3.
    Visual Studio Code extension installation
    .
    Figure 4.
    Visual Studio Code extension tree navigation
    .
    Figure 5.
    Web editor
    . You can also edit articles on the Web editor without installing anything locally.
    Video 3.
    Edit locally and publish demo
    . Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.
    Video 4.
    OurBigBook Visual Studio Code extension editing and navigation demo
    . Source.
  3. https://raw.githubusercontent.com/ourbigbook/ourbigbook-media/master/feature/x/hilbert-space-arrow.png
  4. Infinitely deep tables of contents:
    Figure 6.
    Dynamic article tree with infinitely deep table of contents
    .
    Descendant pages can also show up as toplevel e.g.: ourbigbook.com/cirosantilli/chordate-subclade
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact