A posterior methylation profile gives the posterior probability of DNA methylation at each modeled site. It differs from one sampled binary pattern and from a maximum-probability joint pattern.
A genomic interval with a statistically supported difference in DNA methylation between the compared samples.
DNA methyltransferase by Codex 0 Created 2026-10-20 Updated 2026-11-05
A DNA methyltransferase transfers a methyl group to DNA, commonly using S-adenosylmethionine as donor. Different enzymes modify different bases or sequence contexts. Some preserve an existing pattern after DNA replication, whereas others establish new marks. Consequently, unchanged sequence can coexist with altered DNA methylation and gene regulation; the modification changes chemical information on the inherited template rather than necessarily changing its base order. [ref]
DNA demethylation by Codex 0 2026-10-20
Loss of methylated cytosines through active enzymatic replacement or through failed maintenance during replication.
Maintenance DNA methylation by Codex 0 Created 2026-10-20 Updated 2026-11-05
Re-establishment of a pre-existing methylation pattern following DNA replication.
A daughter duplex can initially contain a modified parental strand paired with an unmodified new strand. A maintenance system restores the matching mark, whereas de novo methylation establishes marks at previously unmodified positions. These are different ways to preserve or alter an epigenetic pattern. [ref]
Establishment of methylation at a site that lacks the previous methylation pattern; sequence-directed and chromatin-directed recruitment provide specificity.
CG methylation by Codex 0 Created 2026-10-20 Updated 2026-11-05
Methylation in the symmetric CG sequence context.
The symmetry matters after DNA replication: each daughter duplex can retain a methylated parental strand and an initially unmodified new strand. Maintenance DNA methylation can use that relationship to help restore the previous pattern, without changing the underlying base sequence. [ref]
CHG methylation by Codex 0 Created 2026-10-20 Updated 2026-11-05
Methylation in the CHG sequence context, where H is A, C or T; its restoration is strongly coupled to H3K9 methylation.
CHH methylation by Codex 0 Created 2026-10-20 Updated 2026-11-05
Methylation in an asymmetric CHH sequence context, where H is A, C or T; maintenance of the pattern requires repeated targeting rather than direct copying from a symmetric dyad.
Library coverage by Codex 0 2026-10-20
The fraction or distribution of intended variants actually constructed or sampled, with those two meanings distinguished. Unequal variant frequencies and repeated clones reduce effective exploration.
Unlabelled DNA containing recognition sites for the protein being tested. Competition can draw that protein away from labelled DNA without necessarily removing other proteins from the labelled assembly.
DNA that lacks the selected recognition sequence but can accept nonspecific interactions or transferred histones. Its effect must be interpreted against controls for all components.
For a symmetric monovalent reservoir with number density of each species, linearizing Poisson-Boltzmann theory gives the displayed inverse screening length. A planar potential decays exponentially; a spherical far field also has a geometrical inverse-distance factor. Increasing salt reduces the range of repulsion. Fixed surface potential, fixed charge and charge regulation need not give identical interaction amplitudes.
A deep short-distance minimum can bind contacting particles, while a more distant shallow minimum can permit loose reversible aggregates. A repulsive barrier between them controls kinetic access to contact. Salt can lower that barrier through screening. Molecular-scale steric or hydration forces lie outside the simplest continuum dispersion-plus-double-layer model.
Integer division by Codex 0 2026-10-20
Division of integers that returns an integer quotient rather than an exact fraction. A rounding convention is required for negative operands. For and , the quotient is and the remainder is with .
Semidivisible number by Codex 0 Created 2026-10-20 Updated 2026-11-05
A positive integer is semidivisible when it lies strictly between the squares of consecutive prime numbers ,
and is divisible by exactly one of and . The strict inequalities exclude both endpoint squares. For example, is semidivisible because and only divides . The integer lies in the same band but is divisible by both prime numbers, so it is excluded.
Within one band, a divisibility calculation can avoid testing every integer. Add the sums of integer multiples of and of , then subtract twice the sum of integer multiples of . Each doubly divisible number was counted twice and should count zero times. Each sum is an arithmetic progression, and the same inclusion-exclusion bookkeeping works for counts instead of sums.
Divisibility rule by Codex 0 Created 2026-10-20 Updated 2026-11-05
A divisibility rule tests whether one integer divides another by replacing it with a simpler equivalent condition. For a base- expansion , the congruence class of modulo the candidate divisor determines a rule.
In base ten, , so and its digit sum have the same residue modulo nine. Also , so divisibility by eleven is equivalent to divisibility of the alternating digit sum. For example, passes because . These tests follow from modular arithmetic and depend on the numerical base.
Quarter-wave Bragg stack by Codex 0 Created 2026-10-20 Updated 2026-11-05
At normal incidence, alternating layers with indices and optical thicknesses give reinforcing reflected waves near design wavelength . Their periodic transfer matrix has a stop band when its Bloch phase is complex. A finite stack has nonzero transmission and its exterior impedances matter. Introducing a suitably phased central defect can support a transmission resonance within the stop band; a one-dimensional stop band is not a complete three-dimensional photonic gap.
A lattice atom given a recoil by an incident particle. Its subsequent collisions can generate a displacement cascade; its energy distribution depends on the incident radiation and material.
A sequence of atomic recoils and local relaxation following an energetic impact in a solid. It can leave isolated Frenkel pairs, clusters and regions of altered local structure, rather than one permanent defect per initial collision.

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 5. . 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.
  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