Paraphyletic subgroup Updated 2025-07-16
Parasites tend to have smaller DNAs Updated 2025-07-16
If you live in the relatively food abundant environment of another cell, then you don't have to be able to digest every single food source in existence, of defend against a wide range of predators.
So because DNA replication is a key limiting factor of bacterial replication time, you just reduce your genome to a minimum.
Power, Sex, Suicide by Nick Lane (2006) section "Gene loss as an evolutionary trajectory" puts it well:and also section "How to lose the cell wall without dying" page 184 has some related mentions:
One of the most extreme examples of gene loss is Rickettsia prowazekii, the cause of typhus. [...] Over evolutionary time Rickettsia has lost most of its genes, and now has a mere protein-coding genes left. [...] Rickettsia is a tiny bacterium, almost as small as a virus, which lives as a parasite inside other cells. It is so well adapted to this lifestyle that it can no longer survive outside its host cells. [...] It was able to lose most of its genes in this way simply because they were not needed: life inside other cells, if you can survive there at all, is a spoonfed existence.
While many types of bacteria do lose their cell wall during parts of their life cycle only two groups of prokaryotes have succeeded in losing their cell walls permanently, yet lived to tell the tale. It's interesting to consider the extenuating circumstances that permitted them to do so.[...]One group, the Mycoplasma, comprises mostly parasites, many of which live inside other cells. Mycoplasma cells are tiny, with very small genomes. M. genitalium, discovered in 1981, has the smallest known genome of any bacterial cell, encoding fewer than 500 genes. M. genitalium, discovered in 1981, has the smallest known genome of any bacterial cell, encoding fewer than 500 genes. [...] Like Rickettsia, Mycoplasma have lost virtually all the genes required for making nucleotides, amino acids, and so forth.
Paris Updated 2025-07-16
Ciro Santilli lived in Paris for a few years between 2013 and 2016, and he can confirm the uncontroversial fact that "Paris is Magic".
Not just one type of magic though. Every quarter in Paris has its own unique personality that sets it apart and gives it a different mood.
Ciro knows Paris not from its historical facts, but from the raw feeling of endless walks through its streets in different times of the year. Ciro is a walker.
Maybe one day Ciro will expand this section to try and convey into words his feelings of love for the city, but maybe the effort would be pointless. Maybe such feelings can only be felt by other free-roaming walker souls living in the city, and that is both beautiful and a shame.
Ciro had written the following in the past before he lived in smaller cities, started cycling and joined the Street reclamation movement he thought:Perhaps compared to São Paulo City, which is what he knew before that was true. But no, his standards have improved since. Paris has way too many cars. The noise of internal combustion engine vehicles is extremely annoying. And because there are too many personal vehicles, cars have to horn a lot to fight for space. Fuck cars. Paris has been making a big cycling push in the early 2020's, and that is great. But it is still far, far from good.
Paris is a friendly city to walkers, as it is not too large, and does not have too many extremely busy roads, you can basically cross all of it on foot.
Particle accelerator facility Updated 2025-07-16
Particle creation and annihilation Updated 2025-07-16
Predicted by the Dirac equation.
We've likely known since forever that photons are created: just turn on a light and see gazillion of them come out!
Photon creation is easy because photons are massless, so there is not minimum energy to create them.
The creation of other particles is much rarer however, and took longer to be discovered, one notable milestone being the discovery of the positron.
Particle physics Updated 2025-07-16
Currently an informal name for the Standard Model
Chronological outline of the key theories:
- Maxwell's equations
- Schrödinger equation
- Date: 1926
- Numerical predictions:
- hydrogen spectral line, excluding finer structure such as 2p up and down split: en.wikipedia.org/wiki/Fine-structure_constant
- Dirac equation
- Date: 1928
- Numerical predictions:
- hydrogen spectral line including 2p split, but excluding even finer structure such as Lamb shift
- Qualitative predictions:
- Antimatter
- Spin as part of the equation
- quantum electrodynamics
- Date: 1947 onwards
- Numerical predictions:
- Qualitative predictions:
- Antimatter
- spin as part of the equation
ImageNet1k download Updated 2025-07-16
The official page: www.image-net.org/challenges/LSVRC/index.php points to a download link on Kaggle: www.kaggle.com/competitions/imagenet-object-localization-challenge/data Kaggle says that the size is 167.62 GB!
To download from Kaggle, create an API token on kaggle.com, which downloads a The download speed is wildly server/limited and take A LOT of hours. Also, the tool does not seem able to pick up where you stopped last time.
kaggle.json file then:mkdir -p ~/.kaggle
mv ~/down/kaggle.json ~/.kaggle
python3 -m pip install kaggle
kaggle competitions download -c imagenet-object-localization-challengeAnother download location appears to be: huggingface.co/datasets/imagenet-1k on Hugging Face, but you have to login due to their license terms. Once you login you have a very basic data explorer available: huggingface.co/datasets/imagenet-1k/viewer/default/train.
Impact factor Updated 2025-07-16
Implicit metric signature in Einstein notation Updated 2025-07-16
Implosion-type fission weapon Updated 2025-07-16
Implosion-type fission weapons are more complicated than gun-type fission weapon because you have to precisely coordinate the detonation of a bunch of explosives.
Indian classical music Updated 2025-07-16
Infinity (1996 film) Updated 2025-07-16
Good film, it feels quite realistic.
It is a shame that they tried to include some particularly interesting stories but didn't have the time to develop them, e.g. Feynman explaining to the high school interns what they were actually doing. These are referred to only in passing, and likely won't mean anything to someone who hasn't read the book.
The film settings are particularly good, and give what feels like an authentic view of the times. Particularly memorable are the Indian caves shown the film. TODO name? Possibly Puye Cliff Dwellings. Puye apparently appears prominently up on another film about Los Alamos: The Atomic city (1952). It is relatively close to Los Alamos, about 30 km away.
The title is presumably a reference to infinities in quantum field theory? Or just to the infinity of love etc.? But anyways, the infinities in quantum field theory theory come to mind if you are into this kind of stuff and is sad because that work started after the war.
Inflation Updated 2025-07-16
Injective function Updated 2025-07-16
Innovate UK Updated 2025-07-16
In-order depth-first search Updated 2025-07-16
This is the order in which a binary search tree should be traversed for ordered output, i.e.:
- everything to the left is smaller than parent
- everything to the right is larger than parent
This ordering makes sense for binary trees and not k-ary trees in general because if there are more than two nodes it is not clear what the top node should go in the middle of.
This is unlike pre-order depth-first search and post-order depth-first search which generalize obviously to general trees.
Pauli exclusion principle Updated 2025-07-16
Initially a phenomenological guess to explain the periodic table. Later it was apparently proven properly with the spin-statistics theorem, physics.stackexchange.com/questions/360140/theoretical-proof-of-paulis-exclusion-principle.
And it was understood more and more that basically this is what prevents solids from collapsing into a single nucleus, not electrical repulsion: electron degeneracy pressure!
Bibliography:
- www.youtube.com/watch?v=EK_6OzZAh5k How Electron Spin Makes Matter Possible by PBS Space Time (2021)
Peer tutoring Updated 2025-07-16
Pendulum Updated 2025-07-16
Perturbation theory Updated 2025-07-16
Used a lot in quantum mechanics, where the equations are really hard to solve. There's even a dedicated wiki page for it: en.wikipedia.org/wiki/Perturbation_theory_(quantum_mechanics). Notably, Feynman diagrams are a way to represent perturbation calculations in quantum field theory.
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