Nested set model Updated 2025-07-16
This is particularly important in SQL: Nested set model in SQL, as it is an efficient way to transverse trees there, since querying parents every time would require multiple disk accesses.
The ASCII art visualizations from stackoverflow.com/questions/192220/what-is-the-most-efficient-elegant-way-to-parse-a-flat-table-into-a-tree/194031#194031 are worth reproducing.
As the sets:
__________________________________________________________________________
| Root 1 |
| ________________________________ ________________________________ |
| | Child 1.1 | | Child 1.2 | |
| | ___________ ___________ | | ___________ ___________ | |
| | | C 1.1.1 | | C 1.1.2 | | | | C 1.2.1 | | C 1.2.2 | | |
1 2 3___________4 5___________6 7 8 9___________10 11__________12 13 14
| |________________________________| |________________________________| |
|__________________________________________________________________________|Consider the following nested set:
0, 8, root
1, 7, mathematics
2, 3, geometry
3, 6, calculus
4, 5, derivative
5, 6, integral
6, 7, algebra
7, 8, physics Nested set model in SQL Updated 2025-07-16
How to implement Nested set model in SQL:
- stackoverflow.com/questions/192220/what-is-the-most-efficient-elegant-way-to-parse-a-flat-table-into-a-tree/42781302#42781302 contains the correct left/size representation and update queries, which makes it much easier to maintain the tree without having to worry about the sizes of siblings which are constant
- stackoverflow.com/questions/192220/what-is-the-most-efficient-elegant-way-to-parse-a-flat-table-into-a-tree/194031#194031 amazing ASCII art representations of the structure. Unfortunately uses a wonky left/right representation, rather than the much more natural left/size representation from the other post
Neuralink Updated 2025-07-16
- youtu.be/CLUWDLKAF1M?t=380 Shows a pig with the implant, and live signals are shown when its nose touches something.
- youtu.be/CLUWDLKAF1M?t=536 shows a pre-recorded pig study correlating really the joint positions while walking with the neuralink signals
NeuroMechFly Updated 2025-07-16
Dr. Strangelove Updated 2025-07-16
Dual space Updated 2025-07-16
The dual space of a vector space , sometimes denoted , is the vector space of all linear forms over with the obvious addition and scalar multiplication operations defined.
Since a linear form is completely determined by how it acts on a basis, and since for each basis element it is specified by a scalar, at least in finite dimension, the dimension of the dual space is the same as the , and so they are isomorphic because all vector spaces of the same dimension on a given field are isomorphic, and so the dual is quite a boring concept in the context of finite dimension.
Infinite dimension seems more interesting however, see: en.wikipedia.org/w/index.php?title=Dual_space&oldid=1046421278#Infinite-dimensional_case
Dulong-Petit law Updated 2025-07-16
It can be seen as the limit case of an Einstein solid at high temperatures. At lower temperatures, the heat capacity depends on temperature.
Dungeon Crawl Stone Soup Updated 2025-07-16
This website is really cool! crawl.akrasiac.org:8080/#lobby You can spectate players live and chat! Also has statistics.
Devs of this game are smart, they have one good in-tree tileset, unlike some other text-based games that didn't have an in-tree option...
Build on Ubuntu 21.10:
sudo apt install build-essential libncursesw5-dev bison flex liblua5.1-0-dev \
libsqlite3-dev libz-dev pkg-config python3-yaml binutils-gold python-is-python3 \
libsdl2-image-dev libsdl2-mixer-dev libsdl2-dev libfreetype6-dev libpng-dev \
fonts-dejavu-core advancecomp pngcrush
git clone --depth 1 --branch 0.28.0 https://github.com/crawl/crawl
cd crawl/crawl-ref/source
echo 0.28-a > util/release_ver
make -j`nproc` TILES=y
./crawlThis launches the UI version already for you.
Dutch university Updated 2025-07-16
Early expansions of hominins out of Africa Updated 2025-07-16
Early human migrations Updated 2025-07-16
Eat Just Updated 2025-07-16
Neutral atom quantum computer Updated 2025-07-16
Neutron star Updated 2025-10-14
Neutron stars are cool. What weird objects!
Newton dot notation Updated 2025-07-16
Nintendo 64 Updated 2025-07-16
This is the one that hit Ciro Santilli the hardest, coming in at the point in which he started to discern between games and the real world a little better. His parents bought it for him during a trip to Disney World in Florida in 1996 (?), since electronics were much cheaper in the USA.
So as Ciro became older, and turned into a software engineer, he started to become more and more morbidly curious about "N64 internals": tool-assisted speedrun, how the devkit looks like, how games were developed for it, hardware leaks, etc.
Luckily Ciro's mind is not interested enough by that useless shit for Ciro to seriously study it himself. But that's what YouTube is for, right? Why do useless stuff when other more useless people can do it for you?
E. Coli K-12 MG1655 gene thrL Updated 2025-07-16
The first gene in the E. Coli K-12 MG1655 genome. Remember however that bacterial chromosome is circular, so being the first doesn't mean much, how the choice was made: Section "E. Coli genome starting point".
Part of E. Coli K-12 MG1655 operon thrLABC.
At only 65 bp, this gene is quite small and boring. For a more interesting gene, have a look at the next gene, e. Coli K-12 MG1655 gene thrA.
Does something to do with threonine.
This is the first in the sequence thrL, thrA, thrB, thrC. This type of naming convention is quite common on related adjacent proteins, all of which must be getting transcribed into a single RNA by the same promoter. As mentioned in the analysis of the KEGG entry for e. Coli K-12 MG1655 gene thrA, those A, B and C are actually directly functionally linked in a direct metabolic pathway.
We can see that thrL, A, B, and C are in the same transcription unit by browsing the list of promoter at: biocyc.org/group?id=:ALL-PROMOTERS&orgid=ECOLI. By finding the first one by position we reach; biocyc.org/ECOLI/NEW-IMAGE?object=TU0-42486.
E. Coli K-12 MG1655 operon thrLABC Updated 2025-07-16
Contains the genes: e. Coli K-12 MG1655 gene thrL, e. Coli K-12 MG1655 gene thrA, e. Coli K-12 MG1655 gene thrB and e. Coli K-12 MG1655 gene thrC, all of which have directly linked functionality.
We can find it by searching for the species in the BioCyc promoter database. This leads to: biocyc.org/group?id=:ALL-PROMOTERS&orgid=ECOLI.
That page lists several components of the promoter, which we should try to understand!
Some of the transcription factors are proteins:
After the first gene in the codon, thrL, there is a rho-independent termination. By comparing:we understand that the presence of threonine or isoleucine variants, L-threonyl and L-isoleucyl, makes the rho-independent termination become more efficient, so the control loop is quite direct! Not sure why it cares about isoleucine as well though.
E. Coli Whole Cell Model by Covert Lab Default run variant Updated 2025-07-16
The default run variant, if you don't pass any options, just has the minimal growth conditions set. What this means can be seen at condition.
Notably, this implies a growth medium that includes glucose and salt. It also includes oxygen, which is not strictly required, but greatly benefits cell growth, and is of course easier to have than not have as it is part of the atmosphere!
But the medium does not include amino acids, which the bacteria will have to produce by itself.
NIST Atomic Spectra Database Updated 2025-07-16
Searching for "H" for hydrogen leads to: physics.nist.gov/cgi-bin/ASD/lines1.pl?spectra=H&limits_type=0&low_w=&upp_w=&unit=1&submit=Retrieve+Data&de=0&format=0&line_out=0&en_unit=0&output=0&bibrefs=1&page_size=15&show_obs_wl=1&show_calc_wl=1&unc_out=1&order_out=0&max_low_enrg=&show_av=2&max_upp_enrg=&tsb_value=0&min_str=&A_out=0&intens_out=on&max_str=&allowed_out=1&forbid_out=1&min_accur=&min_intens=&conf_out=on&term_out=on&enrg_out=on&J_out=on
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