User:Cesiumfrog

identity
physics postgrad

quartz
''The quartz article is quite interesting, there's a lot of depth to the topic, and it could certainly do with better graphics. Unit cell image should have fatter atoms, and split the atom where it encounters the edge. What is the symmetry, in technical and lay terms? (Don't put the unit cell in a square box unless this is appropriate.) The graphics should be gifs, probably with thumbnail dimensions, and should gyrate slightly to convey the proper 3D depth. Overlay ghostly tetraheda on the unit cell. Continue tetrahedra in the background, to convey how the cell repeats and the greater structure e.g. helices (maybe even with ghostly superimposed -Si-O-Si-O- helix drawn like a spring). Want to talk about crystal-disorder in context of beta-quartz (aka high quartz).

Quartz is the most stable and common form of silica. Quartz (like any silica) consists of almost equal weights of oxygen (53%) and silicon (47%), and has chemical formula SiO2.

The microscopic structure of quartz can be visualised as a network of SiO4 tetrahedra, with each oxygen atom shared between two tetrahedra. It forms a crystal made by repeating a unit cell which contains three of these tetrahedra. These tetrahedra are arranged as to form helices down the principle (c-)axis of the crystal. Quartz crystals occur (with the same frequency) in two different types (called left- and right-quartz) corresponding to left-handed or right-handed helices, which effects optical activity.

descent
''A contribution to evidence of common descent is suggested by. A creationist argument is: yes, we acknowledge that there are similarities between species, but that only proves the creator reused design modules like any clever designer would; yes, we even acknowledge that species are arranged into heirarchical taxonomies (e.g., by the relatedness of their DNA), but this still does not prove those heirarchies are an artifact of common descent rather than a feature of the original design process (and the evolutionist is loath to reply strongly, knowing that there exist complicating exceptions of horizontal gene transfer such as by viruses). In short, even if the difference between two species corresponds with (among other representations) a known sequence of physically plausible mutations, the creationist disputes the one will find evidence that those same mutations occured in that same sequence over a long history rather than having existed by fiat from the beginning. (So what we want is to say that the chance of it being that way from the beginning rather than as an artifact of evolution is high sigma.) Indeed, this is the basic position of seventh day adventists in particular, to accept that evolution may indeed be occuring to some organisms today (as has been persuasively demonstrated already), but still to maintain that species originated recently by design rather than by evolution, and so to assume vaguery and errors in the fields that deal in historical aspects (most not being experts on the geology behind strata formation nor on the nuclear physics behind radiodating), believing future science will vindicate their scripture. This example is nice because it reduces to clean mathematics, and is not interdependent on those other (imagined messy) fields. Of course I'd also love to see examples that demonstrate the sophistication of those fields in addressing the question of common descent, just that I personally haven't presently yet heard any ones sufficiently fine.''

Detailed historical records are preserved in the genomes of living species. Genetic analysis thus not only reconfirms the hierarchical relatedness of present species, but reveals that they diverged from common species gradually over time.

Major chromosomal rearrangements are a mutation which causes one chromosome to become genetically isolated. For example, if a long section of DNA becomes inverted then during meiosis the inverted section tends not to undergo cross over with any uninverted homologous chromosomes (and the original mutant individuals would not be as fertile otherwise since such crossing over would inflict deletions). Thus the rearranged chromosome evolves as though its carriers were already isolated in a separate species, even though the evolving genetic material of the other chromosomes continues to be shared throughout the entire population.

As small differences gradually accrue between the rearranged chromosome and its counterparts...

So, one possibility is one subset lucks upon more advantagous mutations, and totally outcompetes the other from that population. Alternatively, the difference becomes too large. If AB becomes unviable, AA and BB diverge fairly cleanly. If ABxAA become incompatible, that'd still be a huge drain on, producing separate populations (presumably AAxAA is fine, it must be that AAxBB=AB becomes unviable and so BB diverges entirely, since... if AB were fine then as XXxAB=XX,AB and ABxAB=AB,AA,BB.. if BB were unviable then AB would also suffer in fertility gah idunno

They look at each gene, and especially at whether or not each point mutation also affects what protein is coded for.

causes of human evolution
''I think such a page is warranted, because it receives so much attention in popular science.

Skin-colour - sunlight connection:

Dark skin necessary on savannah (after forests of Africa disappeared) to prevent loss of folate by excess UV, after hair lost for heat dissipation. Folate is important for fertility of male and female adults; folate deficiency in pregnancy is a major cause of spina bifida. Folate supplements in bread of countries like Australia (recent immigration of light skinned people to high UV exposure region).

Light skin necessary in low light regions, to permit sufficient synthesis of vitamin D particularly in infants, to prevent rickets (skeletal deformities in children). Vitamin D deficiency is particularly common in dark skinned people that have recently immigrated to low sunlight regions such as the UK, or in Innuit that have recently discontinued a diet involving raw liver, and was addressed in the cities of England during the industrial revolution using codliver oil. Neanderthal genetics indicates parallel evolution of light skin under the same circumstances. Mutation of pigmentation genes (to cause lighter skin) also paralleled in zebra fish experiments.

Skin cancer not relevent - post reproductive, contradicted by Innuit.


 * Source: Secrets of the Human Body: Skin Deep, SBS Documentaries

Aquatic phase hypothesised to explain hairlessness, but comprehensively discredited.

Language (esp. grammar). Perhaps postulated for the great leap forward (culture).

Cooking (fire), greatly increases availability of dietary energy..

Persistance hunting. Humans have novel advantages over long distances in Africa.

Menopause. Unusual among animals, facilitates elders.

Apparently human fists were selected for adaptation to striking among males (constraining thumb geometry). Other apes walk on their second knuckle and strike with open hands.

Iwama aikido
Draft at separate page

Banana equivalent dose
''This article got really crazy while the Fukushima disaster was in the headlines. It wasn't the best before, and it got a lot worse. Did a major cleanup, reorganisation, and expansion (inc. referencing). Also, tried to make room for competing viewpoints (ie., those who wanted to decry the topic as flawed, and in doing so were interfering with the basic presentation). Much of the changes were supported by as yet unenacted talk points (that page grew at a prodigious rate). Although, doing so much in one shot at that time may have stepped on some toes, and risked sending the effort to waste.''

DNBK
''The Dai Nippon Butoku Kai article obviously needs work. For example, it says it was dissolved by allied powers (and this links in to the so called banning of martial arts in post war japan) but I've read that this was never actually the case: that they obviously wanted to declare this organisation illegal but could not because doing so would bar too many people from assisting in the new government, so instead ordered it to institute certain reforms, and it responded surprisingly by voluntarily disbanding (and martial arts were never officially banned in entireity from the top, although there was genuine basis for confusion in that chaotic era). Moreover, the article fails to convey how fascinating the topic is. Basically, on a national scale martial artforms were organised and (in combination with ordinary schools of the populace) put to military use: massive entangling of military, education, government, and arts. Later it was revived as a "national health" organisation, as if it were only concerned that its people did calisthenics, and is now called IMAF, as if not Japan-centric, with imperial family at top levels even then. It was also responsible for the standardisation of martial arts gi and ranking systems (likely even originated the kyu+dan combination), by means of preconditions for official recognition. Kyu was apparently previously used instead of dan in police sword, presume it also has a broader history in education? And is "Omoto-sponsored Budo Senyokai (Society for the Promotion of Martial Arts) headed by Ueshiba" related at all?''

Don't rank a category
This is the incubation for an essay.

The problem is that this can only be valid if the categorisation scheme is unambiguously specified. Otherwise it conveys no information. Instead describe the size of the focus category, never its ranking among other categories.

The rank assigned to a category changes depending on how all the other categories are divided up.

Even if one category is bigger than everything else combined, it is still poor practice to call it the "leading category". Although such a description would technically be accurate (since it remains true regardless of the rest of the categorisation scheme) it is still less informative to than the alternative (i.e., it is better to instead say that it comprises more than 50% of the whole).

Consider the mortality statistics for Exampleton:

Consider the black body spectrum. By wavelength, the peak intensity is x. By frequency, the peak is y. x is not y. In physics, it is very well known that frequency and wavelength are related by the formula... (If this seems surprising to you, note that the reason it happens is because the relation between wavelength and frequency is not linear, and this may give you a small inkling as to why physicists are so preoccupied with linear things such as tensors or Dirac equations.) Implying a measure.

Exception is when there is implicitly a canonical categorisation scheme. For example, Lithium is the third element and hydrogen is the lightest element: the mention of chemical elements implies that we are categorising (and by default also enumerating) atoms according to their number of protons.

Tetrad formalism
''This old stub might be fun to work on. Standard GR normally isn't described this way, but it is obviously an instance of the tetrad formalism, just with the choice of tetrad to be the coordinate derivative fields. (Formalism: it's basically just a different notation for the same thing.) Moreover, since there isn't always a chart that covers the whole manifold, one is constantly changing between tetrads (at the same time as coordinates), so the so called change from coordinated to tetrads is just an instance of something already know how to do. But noncoordinate tetrads can be useful. Particularly, the orthonormal tetrad is just a different terminology in which to make the observation that it is always possible to find a vector basis in which the metric is minkowskii - just that that basis won't correspond to any coordinate basis unless there is no curvature. But of course, the representations of all tensors can be different in the Apparently also relevant to spin and Einstein-Cartan theory and the completeness of GR. And most interestingly, seems to have a strong link to gauge theory (in fact, choosing a tetrad makes a gauge freedom explicit, for example choosing one set of orthonormal frames when one obviously could have picked another).''

Religious articles
There's a disapproved thing called a POVfork, and religious topics are rife with them, there's sore need of significant merging, etc.

How would I restructure the Bible article? Previously the basic breakdown was Jewish/Christian, which is basically just a POVfork without creating the separate article (in the loosest terms, since actually the separate article exists, alas times over). Replace with Hebrew Bible / Deuterocanon / New Testament breakdown; make this a subset of a content section. Also, the lead is just a million ways of saying that there isn't a unique bible, move that into separate "cannon" section, and use a table-graph to explain it (there's certainly enough other articles to back up this). The divine inspiration section should more generally be termed "religious importance" or similar. And then, try to include some note of the significance to mormonism, islam, bahai, etc. After all that, not sure whether existing content would call for (shorter) jewish/christian sections still?


 * Canon differences
 * Graph (table) showing on one axis: books of moses, remainder of the hebrew bible, deuterocanon, new testament; and on the other axis: samaritans, judaism, catholicism and orthodox, and protestants. (Possibly subdivide deutero, but not strictly necessary, since the text can address it in more detail. Similarly with more categories on the second axis.) Discuss that the numbering of the books is also divergent. So the number of books is.. Also note difference between what is included for publication, and what is canon (e.g., gideon leaves a lot out, and some printings include some extra stuff just for reference, and many highlight in red implying those quotes have higher priority than the surrounds authored by followers.)


 * Etymology
 * injel/evangelion/gospel/goodnews, bible/books, hebrew-/maso-/oldtest-, greek/hebrew/english for OT section titles


 * Content
 * hebrew bible
 * books of moses
 * deuterocanon
 * new testament
 * gospels
 * supplementary scripture
 * oral torah
 * "According to some Jews during the Hellenistic period, such as the Sadducees, only a minimal oral tradition of interpreting the words of the Torah existed, which did not include extended biblical interpretation. According to the Pharisees, however, God revealed both a Written Torah and an Oral Torah to Moses, the Oral Torah consisting of both stories and legal traditions. In Rabbinic Judaism, the Oral Torah is essential for understanding the Written Torah literally (as it includes neither vowels nor punctuation) and exegetically. The Oral Torah has different facets, principally Halacha (laws), the Aggadah (stories), and the Kabbalah (esoteric knowledge). Major portions of the Oral Law have been committed to writing, notably the Mishnah; the Tosefta; Midrash, such as Midrash Rabbah, the Sifre, the Sifra, and the Mechilta; and both the Babylonian and Jerusalem Talmuds as well. It may have even influenced early Christianity.
 * supplementary scripture
 * oral torah
 * "According to some Jews during the Hellenistic period, such as the Sadducees, only a minimal oral tradition of interpreting the words of the Torah existed, which did not include extended biblical interpretation. According to the Pharisees, however, God revealed both a Written Torah and an Oral Torah to Moses, the Oral Torah consisting of both stories and legal traditions. In Rabbinic Judaism, the Oral Torah is essential for understanding the Written Torah literally (as it includes neither vowels nor punctuation) and exegetically. The Oral Torah has different facets, principally Halacha (laws), the Aggadah (stories), and the Kabbalah (esoteric knowledge). Major portions of the Oral Law have been committed to writing, notably the Mishnah; the Tosefta; Midrash, such as Midrash Rabbah, the Sifre, the Sifra, and the Mechilta; and both the Babylonian and Jerusalem Talmuds as well. It may have even influenced early Christianity.


 * Orthodox Judaism continues to accept the Oral Torah in its totality, but "in fact, it is only ultra-Orthodox Jews who accept this concept in its literal totality". Masorti and Conservative Judaism state that the Oral Tradition is to some degree divinely inspired, and that rabbis today must adapt and apply its principles to changing conditions, even if this results in changes in Jewish practice. Reform Judaism also gives some credence to the Talmud containing the legal elements of the Oral Torah, but, as with the written Torah, asserts that both were inspired by, but not dictated by, God. Reconstructionist Judaism denies any connection of the Torah, Written or Oral, with God, viewing it instead as the nation's literary and moral genius.  Karaite Judaism holds strictly to the Written Torah but not the Oral Torah, maintaining that all of the divine commandments handed down to Moses by God were recorded in the written Torah, without additional Oral Law or explanation.


 * The article Jewish commentaries on the Bible discusses the Jewish understanding of the Bible, including Bible commentaries from the ancient Targums to classical Rabbinic literature, the midrash literature, the classical medieval commentators, and modern day Jewish Bible commentaries."
 * book of mormon
 * koran - extent of retelling,
 * other


 * religious traditions
 * Jewish views on the bible
 * development of the jewish cannon - note that important stuff has happened since the LXX translation.
 * Christian views on the bible
 * Islam. Note belief seems to be that the "injel" was divinely authored, given to the prophet jesus, and then spoken to the disciples, who introduced errors and so all existing versions of the gospel etc are corrupted but nonetheless holy books, whose adherents are to be granted mercy.
 * mormon. ..
 * Ba'hai


 * critical study
 * historical accuracy

The point is, the more content that can be pulled out of the "jewish" section and "christian" section, and combined into some other section which is not specific to any particular religious tradition, then the less we can be accused of POVforking. Why is POVforking bad? Partly because it encourages each part of the topic's treatment to be closeminded and biased, rather than exposing the reader to a comprehensive and integrated treatment which gives due weight (and only due weight) to a well-founded spectrum of viewpoints. Moreover, a major service of encyclopedias is to unify knowledge, so that insights made by experts within one community are communicated to be available for all communities (speeding progress and minimising duplication).

Numerics: There also desperately needs to be some facts on the length of the bible, and number of verses.

eggs
the article on eggs needs logical structuring.
 * eggs of different animal families
 * evolutionary overview
 * bird
 * fish
 * insect (at some point make note of how long triop eggs are viable)
 * non-animal (making brief note of ~ovum plus motile sperm, homologues)


 * classification of egg-laying reproduction
 * merge the oviparity article here

The intro also needs serious work, to explain that it is basically a single large cell initially, either ovum or zygote, but it remains an egg as the embryo develops until it casts off any shell and thus ends this sessile first phase of development. Note about mass of the cell notwithstanding length, and sterility wrt sulphur bacteria. An egg is the rounded object in which a baby animal develops.
 * classification of egg size and yoke
 * human use

nudibranch
Taxonomy confusing. There's this major dorid/eolid distinction, which doesn't quite seem to correspond with current cladistics, and nobody seems to mention where it came from.

Seems that Linnaeas named "doris argo" 1767 (now platydoris argo but still in dorididae and platydoris do seem to have the basic dorid form) and "limax papillosa" 1761 (now aeolidia papillosa, which is a definite eolid shaggy-carpet form, limax meaning literally slug and is now only a genus of air breathing land slugs). In fact, "doris" genera in 1758. Probably refers to greek mythological nymphs (medusa.. does sound like his naming scheme). Also: So linnaeas definitely is to be credited with doris genus, and the broader conceptual type of dorid nudibranchs arose as some of his other doris species got later bumped to other genera.
 * Scyllaea pelagica Linnaeus, 1758 -- Sargassum Nudibranch (looks like a scrap of seaweed, now in dendro.. in cladobranchia),
 * Calpurnus verrucosus (Linnaeus, 1758) This is not nudibranch or sea slug -- looks like a marine snail
 * Neosimnia spelta (Linnaeus, 1758) This is not nudibranch or sea slug -- looks like a nudi,but w/o projections.
 * Philine aperta (Linnaeus, 1767) sand slug
 * Aplysia Linnaeus, 1767 the sea hare genus
 * Onchidoris bilamellata 1767 rough-mantled doris except that wasn't the original genus name -- it was Doris bilamellata (Linnaeus, 1758), has roughly dorid appearance except gills in row not ring, Onchidoris apparently coined 1816.
 * Cadlina laevis (still in doridoidea if not dorididae -- has dorid appearance) was Doris laevis Linnaeus, 1767

Cuvier seems the one to credit with eolids/aeolids. Linnaeas had recognised the archetypical eolid as not-a-dorid, but had simply called it a slug, which seems a touch crude. After Cuvier its genus was aeolidia. Of course, Cuvier obviously hasn't got the tree fully worked out yet, since he leaves tritonia (now in dendro.. like the scyllaea nudibranchs) alongside aeolidia, and alongside doris also has tethys & scyllaea (both dendro..) and phyllidia (now in the big clade doridacea, but also doesn't look dorid).

eolides/œolidia.

Anyway, that's only the 1798 work, where he seemed undecided. His 1817 work on molluscs, with really neat drawings and dissection drawings, makes has chapters for genera: tritonia; doris; scyllaea + eolide + glaucus (the latter being that most spectacular eolid which hunts bluebottles); tethys; phyllidia; and other types of non-nudis. Maybe eolid only grew in prominence later, as it became the base type with which other non-dorid groups tended to accumulate.

originally Cuvier seems to have had dorid be one order of non-hard-shelled gastropod (containing the doris argo species), and further suggested a refinement in which œolidia was a suborder, and tritonia was another suborder. However, his non-hard-shelled gastropods included not only land slugs and sea hares and other sea slugs but also 3 additional orders now considered nudis, plus a parasitic arthropod (anchor worms, which concededely appear to have lost any exoskeleton).

Thing is, the now-discredited class orthiwhatever apparently hadn't even been employed by cuvier, so its obviously super-primitive.

e.g. :

"Under the old classification system by Johannes Thiele in 1931 Gastropoda were divided into the Prosobranchia, Pulmonata and Opisthobranchia. The later two were later combined into a single order. ....... A new study of rRNA gene sequences, published in 2005, could not resolve monophyly versus paraphyly of the Opisthobranchia [7]

Order Opisthobranchia Milne-Edwards, 1848 - sea slugs: Suborder Cephalaspidea P. Fischer, 1883 - headshield slugs and bubble shells Suborder Sacoglossa von Ihering, 1876 - sap-sucking slugs and bivalved gastropods Suborder Aplysiomorpha P. Fischer, 1883 - sea hares Suborder Notaspidea P. Fischer, 1883 - sidegill slugs Suborder Thecosomata Blainville, 1824 sea butterflies with shells Suborder Gymnosomata Blainville, 1824 - sea angels, no shells Suborder Nudibranchia Blainville, 1814 - nudibranchs Infraorder Anthobranchia F?russac, 1819 Infraorder Cladobranchia Willan & Morton, 1984" - So, need to wait for 1814 (and blainville generally) to get the nudibranch concept, which presumably is mostly as per today, and presumably the substructure begins to form around 1819 (would be interesting to see how that goes, since its over a hundred years gap then before cladobranchia gets recognised).

(1899ish Bargh(?) mistakenly establishes doridoxidae as dorids.)

Presume expansion of dorids straightforward, categorisation as nudis also suspect relatively straightforward. Curious what dorids were initially opposed from. How eolids expanded. What happened in 1984? (at that stage, infraorders seem to well establish dorid/eolid) I understand it was only 2001 (Schrodl et al) that by dissection of the rare doridoxida shifted them from what had been understood as dorids (anthobranchia) to what I presuppose had been viewed as eolids: cladobranchia/actenidiacea/cladohepatica. 2001 seems to break the nice division, that's big. (2005 the sisters to nudis get identified, which is all smooth sailing.) And then 2010 the whole nudipleura rocks into a new location as opisthobranchia crumbles.

In 1984: Cephalaspidea contained: Acteonacea Philinacea Bullacea Acochlidiacea Anaspidea - sea hares Sacoglossa - algae suckers. look nudi-like, but aern't. "Pteropoda" Thecosomata Gymnosomata Notaspidea - includes pleurobranchs Nudibranchia The two divisions attributed to Odhner (1939?). --
 * cladobranchia: gills outgrowths over mantle, often with intestine as cerata
 * Dendronotacea
 * Arminacea - shallow burrowing
 * Aeolidacea
 * Anthobranchia: gill tuft round anus
 * Doridacea
 * The clade Nudibranchia is the largest clade within the heterobranchs, with more than 3,000 described species.

Problems are:
 * the meaning/structure of heterobranchs appears to have changed significantly in the last 5 years
 * it is flatly false: e.g., the clade nudipleura (which contains nudibranchia) must be larger.
 * where is the number 3k sourced from?

Alternatives in 1984: --- [www.seaworld.org/animal-info/animal-bytes/animalia/eumetazoa/coelomates/protostomes/mollusca/sea-slugs.pdf] "Nudibranchs, which are considered the true sea slugs"..."• Nudibranchia (the “true” nudibranchs): Infraorder Anthobranchia (dorid – posterior gills); Infraorder Cladobranchia (eolid – with cerata)" ---
 * "The true NUDIBRANCHIA[..,] the dominant opisthobranchs are the most colourful of all gastropods." Incidentally, note opistho is a subclass, nudibr. an order, clado/antho are suborders, and there is a total of four superfamilies. I think nudibr.'s level might earlier have been only suborder, which is an issue the page could make explicit someplace.
 * "This is the largest, most highly advanced and most adaptively diverse order of the Opisthobranchia." (unfortunately op..)
 * "Nudibranchs bear evidence (says T.E. Thompson) of polyphyletic descent[...] Their common point of agreement lies in the loss of all trace of the shell and the slug-like external symmetry [...] 'So pervasive is the mosaic of convergent evolution exhibited by the nudibranchs, that the inter-relationships of the dendronotacean, arminacean, aeolidacian and doridacean suborders may never be fully understood'."
 * "ANTHOBRANCHIA with a flower-like circlet of gills surrounding the median dorsal anus, and consisting of the flat bodied dorid nudibranchs, and CLADOBRANCHIA where the anus remains on the right side and the gills are formed by various kinds of outgrowth from the body wall: lateral rows of dendritic appendages in DENRONOTACEA, or finger-like cerata in AEOLIDACEA and (in much modified forms) in ARMINACEA." might be useful describing the division

summary
 * Linnaeus (-1767) has genus a number of sea slugs, including doris (dates to 1758 and which will later be split up into doridae or some such etc), a typical eolid (which at that time is just called limax--slug) and scyllaea (a dendro).
 * Cuvier 1798 begins to group nudis, by having aeolidia (renaming that limax) and tritonia as two sub-groups of doris. Doris is still alongside scyllaea as well as tethys (another dendro), phyllidia (an uncharacteristic dorid), and various non-nudi genera.
 * Cuvier 1817 has a group for scyllaea + eolide + glaucus (spectacular surface eolid), which is alongside genera for doris, tritonia, and various non-nudi genera.
 * 1814 Blaine supposed to introduce Nudibranchia grouping. (1819: anthobranchia for the dorids)
 * (1899ish Bargh(?) mistakenly establishes doridoxidae as dorids.)
 * Odhner ~1939 (probably "Opisthobranchiate Mollusca from the Western and Northern Coasts of Norway") credited with the dorid/eolid division
 * Willan & Morton, 1984: clado set up to contain aeolid, dendro and armin.. (diggers). We have an order w/ two suborders. At some point clado becomes synonymous with eolid.
 * (2001 doridoxidae switches into clado, which breaks the dorid/eolid thing a bit really)
 * 2005 nudis placed in nudipleura
 * 2010 opisthobranchia crumbles (positioning nudipleura)

essay on destructive editing
In major restructuring edits, what tends to draw opposition (in the extreme form of wholesale reverts/rollbacks) is the obliteration of particular content which other individual editors considered useful (or were otherwise attached to). Much discussion and conflict is avoided, and the improvements are more likely to "take", if they are disentangled from and unencumbered with the content removals.

Some alternatives:
 * Compartmentalise unfavoured content, demoting it to a subsection at the bottom of the article.
 * Leave a cooling-off period: after restructuring the article, let it sit a few weeks before removing content. (This way the structural improvement acquires a kind of consensus, and is less likely to get included in any reversion of the later edits.)
 * Never combine content removal into the same edit with other improvements. Doing so makes it difficult for the content to be rescued without also rolling back the other improvements. Which means those other improvements are likely to be rejected automatically.
 * Avoid rewriting content that already exists.
 * Try to separate restructuring and paragraph-rewrites into separate edits.
 * Be very careful not to drop good references. It was hard to collect them, and they are the most important part of the article (since all the rest could just have been written by anybody!). Prefer not to drop any references, even though you may not have access to read them yourself.
 * If rewriting, make sure that your version is undeniably an improvement over the previous. If its going to be subjective and hence controversial, the author of the previous version is likely to contest your edit. Don't try to take ownership of the phrasing without any reason for the change.
 * Initially, rather than reducing any part of the scope of the paragraph, consider initially just moving some sentences lower down.
 * If content is inappropriate to the article but still likely to be of some use to readers, try to save it.
 * For example, with blocks of unsourced material which appear to have been contributed by a topic expert, move it to the talk page for incubation. Leave a note encouraging others to try to find sources so that it can potentially be developed into an article-appropriate state (and frankly it can still be useful to readers in the meantime, even if it does prove too original).
 * If the content is good but tangential, spin it off into another (new or existing) article. If you can't be bothered finding a good place to fit it in, again either tack it on to the bottom of the page for someone else to improve further, or dump it on a talk page with a brief note of explanation.
 * Use cleanup templates liberally. Mark stuff with citation needed, or with cleanup banners. Most likely someone else will either find supporting sources (improving the article) or ditch the section (in which case consensus has been demonstrated and you didn't need to be the controversial one).

Themes:
 * This is about a technique for developing consensus in a collaborative project. It would be naive to focus on the end result while ignoring the group psychology of the process. In an ideal world maybe your fellow editors wouldn't act in the way which this essay anticipates, but they aren't under your control (and wikilawyering to try to force them would only antagonise). People who invested effort writing a paragraph or found it personally useful aren't likely to appreciate you obliterating it, regardless of how tenuous the policy-justifications for them resisting the change may be.
 * The perfect is the enemy of the good. Different editors are unlikely to agree on the perfect, so don't try to make the article your version of perfect right from the start, instead incrementally make it more good.
 * Careful you aren't throwing out the baby with the bathwater. Don't make it hard for others to avoid doing so either.
 * Ultimately, each revision must answer: is this an uncontroversial improvement on the preceding revision. So don't do things to increase the likelihood of this being controversial.
 * Plot a trajectory which avoids needing a step that some may see as a disimprovement. (Obviously, don't blank content in preparation of a replacement version you intent to produce soon. Restructure first, demoting but not deleting anything until after it can be seen in context of the new structure and new material.)

geodesy
The articles surrounding datum (geodesy) are in need of cleanup. The current structuring is rife with misunderstanding.
 * A datum is an ellipsoid, defined by its size and how flattened it is. (Also need at least a couple points to tie it on to the globe. In principle this may be the rotation axis, the center of mass, and the greenwich meridian.) Its purpose is to impose one 2d grid (ie. lat/long) over a planet.
 * A geoid is a gravitational equipotential surface. Measurable by spirit-levelling networks (or by point grav. meters?).
 * The planet is not a sphere. Nor is it an ellipsoid. (Can prove the equilibrium shape of a spinning fluid is different from an ellipsoid.) In fact, the geoid isn't regular at all. (eg. affected even by local mineral deposits.) Geoid is expressed using spherical harmonics.
 * Two concepts of lattitude. We want the angle between the axis and the normal. (Navigators really mean the geoid normal but..)
 * On top of the geoid, there is also the elevations and topography. Importantly, the sea also has persistent topography. (Several causes: prevailing current, climate, geography vs tide.) Thus, MSL (let alone LAT/ISLW) are certainly not the geoid.
 * Vertical datum. May be a mismash of MSL interpolated from certain eras and stations, rather than geoid.
 * Time dimension. The whole thing is moving. Plates movement of order m/decade, with stretching/squashing. Land creeps down hills. Vertical component: post-glacial bounce, sea/climate, etc. May want positions as of where they were on an epoch. (Potentially lots of extra data grids involved.)
 * Legal boundaries prioritise survey marks over coordinates.

Multiple image template
Want to have a height parameter, since needing to know the pixel dimensions of each image is inconvenient.

Trouble is getting it to work on every browser. (Trying styles to fix chrome behaviour.. Theory: colspan=0 isn't supported in chrome, so must explicitly feed count. Also for chrome, need the table-caption display.)

schizophrenia
This is a field where, as the poster child for large genetic association studies, work is suddenly speeding up. But need to filter through the hype. For example, is long argued that a cluster of diseases underlied by separate mechanisms are being lumped into the same diagnosis. Family pedigrees tend to involve other mental illnesses (e.g. bipolar appears to share common genetic risk variants), and even patient histories tend to involve e.g. ADD childhood diagnoses, but also need to emphasise non-genetic component from twin studies. Article needs more on the etiology.


 * Immune hypothesis: support is a) long-noted mutual inverse correlation with rheumatoid arthritis, and b) by far the most significant genetic correlation is the MHC (primarily considered an immune function gene). Note MHC alone correlates the wrong way (positively) between these conditions therefore does not explain the observations.
 * Dopamine hypothesis: this was the traditional hypothesis, seems based on the fact that traditional antipsychotics target this system of neurotransmission.
 * NMDA hypothesis: support includes ketamine analogue (which extends to EEG/MMN biomarker and incidentally is reverse of autism).

Integration
If a parallelogram is specified by two arbitrary vectors then, almost by definition, its area is given by the magnitude of the cross product.

If a parallelepiped is specified by three arbitrary vectors then (from the geometric definitions of dot and cross products) its volume is given by the scalar triple product $$\pm\,\mathbf a \cdot (\mathbf b \times \mathbf c)$$.

By considering the transformation to an arbitrary basis from an orthonormal basis, it can be shown that the volume of the parallelepiped is given by the absolute value of a pseudotensor $$(\sqrt g\ o\epsilon_{ijk} dx^i \otimes dx^j \otimes dx^k)(\mathbf a, \mathbf b, \mathbf c)$$ where $$g$$ is the determinant of the metric components and ...

To take a volume integral involves parcelling the space up into cells. Given any coordinate system, a natural scheme is to cut along the contour lines of the coordinate fields. In the infinitesimal limit, these cells are parallelepipeds. The vectors corresponding with these parallelepipeds are the usual contravariant basis vectors (defined as partial derivative operators where all but one coordinate field is held constant..).

..it turns out that the volume (or area or hypervolume..) element is $$\sqrt g\, d^n x$$, involving the square root of the determinant of the manifold's metric.

$$ \vec U (\vec \mathbf x) = \int \frac {\alpha (1-2\nu)} {2 \pi G} \Delta p \frac {\vec \mathbf x - \vec \mathbf x'} {||\vec \mathbf x - \vec \mathbf x'||^3} \mathop{\mathrm d vol'} $$

$$ \vec U({\vec \mathbf x}) \propto \Delta p({\vec \mathbf x}) * \frac {\hat \mathbf x} {||{\vec \mathbf x}||^2} $$

Divergence
The key idea of a flux is that the contributions from opposite sides of a surface will cancel. (The flux in through a door is the reverse of the flux out through the same door.) This means that internal (pinched) surfaces make no contribution. Hence, for any arbitrary parcelling, the outer surface integral is identical to the sum of surface integrals of all the cells.

Taking this idea to its limit, parcel a volume into infinitesimal cells... For any operator $$\mathcal O$$ that depends linearly on a the normal $$\mathbf \hat n$$ to a surface, define the divergence:

$$ \nabla\cdot\mathcal O \equiv \lim_{\Omega\rightarrow\varnothing} \frac 1 { \int \limits_\Omega dV } \int \limits_{\partial \Omega} \mathcal O(\mathbf{\hat n}) dS $$

such that a surface integral can be expressed as a volume integral:

$$ \int \limits_{\partial \Omega} \mathcal O(\mathbf{\hat n}) dS = \int \limits_\Omega \nabla\cdot\mathcal O \ dV $$

It turns out that this is given by the trace of the covariant derivative..

Newtonian
Internal friction must vanish for uniform linear motion. Assume all terms linearly proportional to the velocity gradients (plausible in the limit of small gradients). Internal friction must also vanish for uniform rotation. This requires a symmetry.

The simplest non-rigid solid is elastic: strain deformation is linearly proportional to shear force. However for a simple fluid, a constant shear produces limitless deformation. So a simple Newtonian fluid is defined as isotropic and having shear proportional to rate of strain. $$\sigma_{ij}=-(p+\frac 2 3 \mu \nabla\cdot v)\delta_{ij} + \mu(\partial_i v_j + \partial_j v_i)$$

Navier Stokes
To begin with, be careful to note the dimension of vector spaces (2, 3 or 4), and the rank of tensors (0, 1, 2..).

The navier stokes equations can be derived from consideration of conservation laws applied to a sample test volume of fluid (an almost arbitrary 2+1 dimensional hypersurface).

Mass within a sample volume only changes in accordance with flow through its boundary, presuming there is no other source or sink. This can be expressed in terms of integrals of the density:

$$\frac d {dt} \int \limits_\Omega \rho dV = - \int \limits_{\partial\Omega} \rho\ \mathbf u \cdot d \mathbf S $$

Momentum is similarly conserved except for the influence of external forces, which may be either contact forces or body forces. The body force may be electromagnetic or may be inertial, including gravity (i.e. newtonian minus centrifugal) and coriolis. Note this is a rank-1 tensor equation on a 3-dimensional vector space.

$$\frac d {dt} \int \limits_\Omega \rho \mathbf u\ dV = - \int \limits_{\partial\Omega} \rho \mathbf u \otimes \mathbf u \cdot d \mathbf S + \int \limits_\Omega \rho \mathbf b\ dV + \int \limits_{\partial\Omega}  \mathbf T(d\mathbf S) $$

Leibnix integral rule (the total derivative of an integral is the integral of the integrand's partial derivative) permits rewriting the left hand side. Makes sense that partial derivative commutes with summation, and that the specification of an area exhausts the spatial dependencies.

Gauss' divergence theorem relates the flux from an enclosed volume to the fluxes from each part, and specifically the flux from each infinitesimal part. The latter (in terms scaled per unit volume) is defined as the divergence. The key idea is that flux is necessarily counterbalanced on opposing surfaces. In other words, "flux through the surface" can really mean any quantity that depends linear on the components of the surface normal vector. In particular, it is satisfied by any tensor which contracts one slot with the surface normal vector.

Of course to be useful in converting between surface and volume integrals, it is necessary to know the form for the divergence. This implicitly depends on the scheme used to parcel a volume into small bits. The parcelling is particularly easy to perform in a rectangular grid, and there the combinations of fluxes on opposite sides are identical to a partial derivative (that is, the opposite infinitesimal areas per volume equate to a difference per length). So for a tensor that has been contracted (in a particular slot) with the surface normal, you end up with something like a trace of the covariant derivative of the original tensor (where the contraction is between the surface-normal slot and the direction of the derivative).

$$ \int \limits_\Omega \frac {\partial \rho} {\partial t} \ dV = - \int \limits_{\Omega}  \nabla \cdot (\rho \mathbf u )\ dV $$

$$ \int \limits_\Omega \frac {\partial \rho \mathbf u}{\partial t} \ dV = - \int \limits_{\Omega}   \nabla \cdot (\rho \mathbf u \otimes \mathbf u)\ dV + \int \limits_\Omega \rho \mathbf b\ dV + \int \limits_{\Omega}  \nabla \cdot \mathbf T\ dV $$

This is trivially converted to differential equations (dropping mention of the hypersurface).

$$ 0 = \partial_t \rho + \nabla\cdot(\rho\mathbf u) $$

$$ 0 = \partial_t \rho \mathbf u +  \nabla \cdot (\rho \mathbf u \otimes \mathbf u) - \rho \mathbf b -  \nabla \cdot \mathbf T $$

For the mass equation, can use properties of divergences to expand in terms of a gradient. This can also be expressed in terms of a total derivative along a flow-line.

$$ 0 = \partial_t \rho + \rho \ \nabla\cdot\mathbf u + \mathbf u \cdot \nabla \rho \quad=\quad D_t \rho |_{\mathbf u} + \mathbf u \cdot \nabla \rho $$

We can also expand the momentum equation. And simplify it by substituting in the mass equation.

$$ 0 = ( \rho \partial_t \mathbf u + \mathbf u \partial_t \rho) + \mathbf u \cdot \nabla \rho + \rho \mathbf u \ \nabla \cdot \mathbf u - \rho \mathbf b - \nabla \cdot \mathbf T $$

$$ 0 = \rho \left( \partial_t + \mathbf u\cdot\nabla \right) \mathbf u  + \mathbf u \left( \partial_t + \mathbf u \cdot\nabla  \right)\rho - \rho \mathbf b - \nabla \cdot \mathbf T $$ $$ 0 = \rho D_t \mathbf u |_{\mathbf u} + \mathbf u \left( \partial_t + \mathbf u \cdot\nabla  \right)\rho - \rho \mathbf b - \nabla \cdot \mathbf T $$

In 3D differential form:

$$\left. \frac d {dt} \mathbf u \right|_\mathbf u = - \frac 1 \rho \nabla p + \mathbf b + \frac \mu \rho \nabla^2 \mathbf u $$

Numerics
$$\frac{q_{n+1}-q_n}{\Delta t}=G(q_n)+q_{n+1}H(q_n)$$

$$\therefore q_{n+1}=\frac{q_n+ G(q_n)\Delta t}{1-H(q_n)\Delta t} = \hat O [q_n] $$

$$\hat O_{}[ q ] \qquad [[q]_{+\Delta t}]_{+\Delta t} \qquad \underset {\scriptscriptstyle{\ +\Delta t}} \hat O [q] $$

$$q^*_{n+1} = {\scriptstyle \frac 1 2} q^*_n + {\scriptstyle \frac 1 2}\ \hat O \left[ \hat O [ q^*_n ] \right] $$

$$q = a (w - w_\min ) ^ p + c$$

$$O_{RK}(x) = \frac {x + O^2 (x)}2\ \textrm{where}\ O=O_{SI} O_{fE}$$

Steady uniform flow
Steady flow implies the time derivatives vanish.

Uniform flow implies the longitudinal derivatives vanish.

Now, the mass-conservation component of the shallow water equations simplifies to stating (in absence of any sources or sinks) that the product of the water depth and the transverse flow velocity is constant along the transverse direction. Given a boundary condition with no transverse flow, this implies that there is no transverse flow anywhere (including the physical constraint that even where the depth is zero there still obviously cannot be nonzero flow).

$$ \partial_x v_x h = 0 \Rightarrow v_x = 0 $$

This fact helps to simplify the remaining equations. (For example, the transverse friction term vanishes.)

The transverse momentum component of the equations simplifies to implying that the water stage is constant along any transverse section.

$$ \partial_x \frac {gh^2}2 = -gh\frac{\partial z}{\partial x} \Rightarrow \frac{\partial \frac 1 2 h^2}{\partial h}\frac{\partial h}{\partial x} = h \partial_x z \Rightarrow \partial_x (h+z) = 0 $$

The longitudinal component of the equations balances gravity against friction (as everything except these source terms vanishes). This forms a relationship between the flow velocity and the slope gradient.

$$ 0 = -gh \frac {\partial z}{\partial y} - gh S_{f_y} \Rightarrow n^2 v_y^2 = -\frac{\partial x}{\partial y} h^{\frac 4 3} $$

Lastly, the total flow is obtained by integrating the flow through the wet area of a transverse cross-section. This gives a way of calculating the total flow as a function of the water stage.

$$ Q = \int u\,h\ dy = ... = f(w) $$

Weak solution theory
User:Cesiumfrog/Weak solution

Weak solution theory is a branch of mathematics which generalises the concept of differential equations to admit some solutions which are distributions other than differentiable functions. It underpins the widely used finite element method.
 * Generalised derivative. The weak (or generalised) derivative is a definition for a derivative which does not require the target to be differentiable. (Essentially, derivatives of distributions that aren't at all points technically differentiable.) It is based on integration by parts. When is it equivalent (presumably for most differentiable functions)?
 * Weak solution.
 * Variational formulation: The variational formulation of a PDE permits additional solutions
 * Examples.

Climbing Protection
In climbing, protection (jargon "pro") is devices to attach a rope to the terrain, such as nuts, cams, bolts, and pitons. Protection attaches strongly so that the rope can be used to catch a falling climber. Protection helps reduce the danger of falling, and is used in combination with other climbing and safety equipment such as helmets, sunscreen and belay devices. Some forms of protection are generally pre-placed, and others may be placed as the climber ascends (e.g., for trad climbing).

Styles of climbing
Different styles of climbing may involve differences in the types and applications of protection.

In trad climbing, protection is placed during the ascent and afterward it is removed to leave the rock unchanged. In sport climbing, the climber uses pre-placed bolts.

History
In early use of ropes for rock climbing and mountaineering, instead of any placed protection, the route was traversed so as to thread the rope on the uphill side behind any trees or rock pillars.

Bolts (e.g. rock drilling and expansion bolts) were used in Europe in the 1920s (e.g., the first ascent of Pére Eternal in 1927).

A cam-based device for ascending ropes, the Jumar, had been developed in 1958.

In 1967-1973 Greg Lowe experimented with various spring loaded camming devices, such as the two-arm "crack jumar" and the single-lobe "cam nut". The tricam developed as a variation of this cam nut design (but omitting the spring and rigid stem).

Conventional (e.g. four-lobe with retracting trigger) spring-loaded camming devices ("friends") were brought to market by Wild Country. Originally these used a rigid stem.