open-index/open-wikipedia-markdown huggingface dataset:
Migration period

The **migration period**, or **barbarian invasions** or **Völkerwanderung** happened in 300–700 AD in Europe, at the end of ancient history and during the Early Middle Ages.
.]]

The migrations included the Goths, Vandals, Franks, and other Germanic tribes; the Bulgars; and Slavic tribes. They may have been influenced by attacks of the Huns in the East and may also be connected to the Turkic migrations in Central Asia, overpopulation, or climate change. The migration period also included groups of Angles, Saxons, Frisians, and some Jutes to Britain.

The migrations would continue well into the Middle Ages, beyond 1000 AD, with successive waves of Slavs, Roma, Avars, Bulgars, Hungarians, Pechenegs, Cumans, and Tatars, which changed the ethnic makeup of Eastern Europe. Historians in Western Europe, however, tend to stress the migrations that were most relevant to that area.

## Related pages
* Human migration

## References 
## Other websites 
* J.B. Bury (1923). *History of the Later Roman Empire*
Apprenticeship

ing is learned through apprenticeship in Germany.]]

**Apprenticeship** is a system of training people who are learning how to do a job which needs special skill.  Someone who is learning in this way is called an "apprentice".  An apprentice will learn by working with someone who is already skilled at a job.  They are like a teacher and pupil.

## Development 
The system of apprenticeship has been used for many hundreds of years.  In the late Middle Ages the craft guilds and town governments used to watch and control the system.  A master craftsman had the right to employ young people to work for them and pay them a small salary.  In return the apprentice would be learning the trade.  Most apprentices were males, but female apprentices are more common nowadays, especially in crafts such as embroidery, silk-weaving etc..

## Related pages 
* Education

## Further reading
**Modern Apprenticeships: the way to work*, The Report of the Modern Apprenticeship Advisory Committee, 2001 http://www.dfes.gov.uk/ma.consultation 
**Apprenticeship in the British "Training Market"*, Paul Ryan and Lorna Unwin, University of Cambridge and University of Leicester, 2001 http://ner.sagepub.com/cgi/content/abstract/178/1/99 
**Creating a ‘Modern Apprenticeship’: a critique of the UK’s multi-sector, social inclusion approach* Alison Fuller and Lorna Unwin, 2003 (pdf) 
**Apprenticeship systems in England and Germany: decline and survival.* Thomas Deissinger in: *Towards a history of vocational education and training (VET) in Europe in a comparative perspective*, 2002 (pdf) 

## Other websites 
*The School of Applied Arts Apprentice program 
*Facts about Germany: Apprenticeships, Federal Foreign Office 
*Apprenticeships - a great idea (UK)
*''L'Apprenti*, in French
*Article on the history of apprenticeship in the U.S.  from EH.NET
*Academic Apprentices: Still an Ideal?, Barry Yeoman, *Duke Magazine''
San Francisco Bay

**San Francisco Bay** is a shallow bay in northern California, along the Pacific Ocean. It is an estuary because salt water from the ocean mixes with fresh water from rivers, especially the Sacramento and San Joaquin rivers. These rivers carry water from the Sierra Nevada mountains through the Central Valley. Water from about forty percent of California enters the bay.

The Sacramento and San Joaquin rivers enter the Suisun Bay. There water flows through the Carquinez Strait to meet with the Napa River at the entrance to San Pablo Bay. This connects at its south end to the San Francisco Bay. The San Francisco Bay is connected to the Pacific by a strait called the Golden Gate. However, this entire group of interconnected bays is often called "the San Francisco Bay".

San Francisco Bay lies in the US state of California and is surrounded by a region known as the San Francisco Bay Area, that includes the big cities of San Francisco, Oakland, and San Jose.

The Bay covers somewhere between 400 http://www.sfmuseum.org/hist9/mcgloin.html and 1,600 http://response.restoration.noaa.gov/cpr/watershed/sanfrancisco/sfb_html/sfbenv.html square miles (1,040 to 4,160 square kilometres), depending on which sub-bays (such as San Pablo Bay), estuaries, wetlands, and so on are included in the measurement.

## Photography 

Image:berkeleyfromclaremont800x600.jpg|The city of Berkeley, the Bay and Marin County in the background as seen from the Claremont Canyon reserve
Image:TamFromPinole.jpg|Mount Tamalpais view across San Pablo Bay at Point Pinole Regional Shoreline in Richmond

## References 
* 1999 Grolier Multimedia Encyclopedia.
* 1988 Encyclopædia Britannica.

## Other websites 
* *San Francisco Bay: Portrait of an Estuary*, David Sanger and John Hart, University of California Press
* Barging In - A Short History of Liveaboards on the Bay 
* Army Corps of Engineers Bay Model: Working scale model of the Bay 
* BoatingSF.com: Photos of SF Bay and its boats, plus online cruising guide
* SF Estuary Institute: San Francisco Bay Historical View Maps
Ahmed Yassin

**Ahmed Yassin** (Arabic: الشيخُ أَحْمَدُ إِسْمَاعِيلُ)  (June 1936 – March 22, 2004) was the founder and a spiritual leader of the militant Palestinian group Hamas.

## Life 
Ahmed Yassin was born on June 1936 in al-Jura, British Mandate of Palestine. He helped create Hamas and became its spiritual leader in 1987. To other members of Hamas he was a hero but he was blamed by the Israeli government for planning suicide bombings and other  against Israel. He claimed that was the only way of fighting occupation. He was confined to a wheelchair because he was paralyzed since age 12, he was also nearly blind and could barely hear. He was very powerful and influential.

Yassin's birth date is in dispute. He claimed he was born 1/1/1938, however, his passport indicated 1/1/1937. To some he was a hero, to some he was a well known member of a terrorist organization. He was also a symbolic figure for Palestinians to fight against Israel.

## Death 
Yassin was killed in an airstrike in Gaza City by the Israeli Army after he left a mosque in Gaza in the early morning hours. He was 67 years old.

## References
## Other websites 
* Israel Bombing of Refugee Camp 
* Yassin killed, Ahmed Yassin biography 
* Yassin's letter and kids named after him
Field (physics)

In physics, a **field** means that a physical quantity is assigned to every point in space (or, more generally, spacetime). A field is seen as extending throughout a large region of space so that it influences everything. The strength of a field usually varies over a region. Michael Faraday became the first to coin the term "field", in 1849.

For some fields, there is a number for each point in space. They are called *scalar fields*. For more complicated fields, there are more than one number for each point in space. They are called *vector fields* or *tensor fields*. For example, one can model a gravitational field by a vector field where a vector indicates the acceleration a mass would experience at each point in space. Other examples are temperature fields or air pressure fields, which are often illustrated on weather reports by isotherms and isobars by joining up the points of equal temperature or pressure respectively.

## Types of fields 
### Classical fields 
*Newtonian gravitation: describes the gravitational force as a mutual interaction between two masses.
*Electromagnetism:  electric and magnetic fields are not only fields of force which dictate the motion of particles, but also have an independent physical reality because they carry energy.
*Gravitation in general relativity: this is Einstein's theory of gravity. 
*Waves as fields

### Quantum fields 
It is now believed that quantum mechanics should underlie all physical phenomena.

### Field theory 
A field theory is a physical theory that describes how one or more physical fields interact with matter.

## Related pages 
* Elasticity
* Fluid dynamics
* General relativity
* Maxwell's equations
* Particle physics

## References 
* Landau, Lev D. and Lifshitz, Evgeny M. 1971. *Classical theory of fields*. 3rd ed, London: Pergamon.  Vol. 2 of the *Course of Theoretical Physics*.
Gradient

In vector calculus, the **gradient** of a multivariate function measures how steep a curve is. On a graph of the function, it is the slope of the tangent of that curve. More generally, it is a vector that points in the direction in which the function grows the fastest. Its coordinates are partial derivatives of that function. The gradient of a function *f* is often written as \nabla f or \operatorname{grad} f.

## Related pages 
* Laplace operator

## References
Gradient (disambiguation)

**Gradient** could mean:

* Gradient of a function, in vector calculus
* Slope or grade, referring to the inclination of a road or other geographic features
* Image gradient, a gradual change or blending of color

* In biology
** Concentration gradient, the ratio of solute concentration between two regions next to each other
** Electric gradient, the difference in electric charge between two regions next to each other
**  Pressure gradient, the difference in the exerted force per unit area in two regions next to each other
Archery

**Archery** is the practice of using a bow to shoot arrows. Archery has historically been used in hunting and combat and has become a  sport. A person practicing archery is called an *archer*, and one who enjoys or is an expert at archery is sometimes called an toxophilite.

## History
.]]
The earliest evidence of archery dates back more than 9,000 years. The bow probably was used in hunting first and later adopted as a tool of warfare. It was one of the earliest forms of artillery. 

Classical civilizations, notably the Persians, Macedonians, Nubians, Greeks, Parthians, Indians, Japanese, Chinese, and Koreans, had large numbers of archers in their armies. Archers in chariots were especially important in armies of ancient Egypt. Arrows were very destructive against massed formations, and the use of archers helped win battles. 

One of the primary sub-genres of archery is mounted archery. Japanese Samurai, North American tribes, Turkish nomadic groups, Persian armies and more honed the skill of hunting and warfare through mounted archery. The army of the Mongol Empire was mostly archers on horseback.

Though archery fell out of practical use, it never fully went away as a sport. As early as the 1480s in Britain, societies like the Ancient Society of Kilwinning Archers were having archery competitions.

## References 
## Other websites 
* Archery Interchange UK  The UK's largest online archery community.
* The Great Northwood Bowmen  Medieval Longbow Archery and re-enactment Society, re-enacting the 15th century, based in London. 
* Bowhunting Basics
* Archery Information 
* Archery Pictures
Metallic bond

.]]

A **metallic bond** is the sharing of many detached electrons between many positive ions, where the electrons act as a "glue" giving the substance a definite structure. It is unlike covalent or ionic bonding. 
Metals have low ionization energy.  Therefore, the valence electrons can be delocalized throughout the metals. Delocalized electrons are not associated with a particular nucleus of metal, instead, they are free to move throughout the whole crystalline structure forming a "sea" of electrons.

The electrons and the positive ions in the metal have a strong attractive force between them.  Therefore, metals often have high melting or boiling points. The principle is similar to that of ionic bonds.

Metallic bonds causes many of the traits of metals, such as strength, malleability, ductility, luster, conduction of heat and electricity.

Because the electrons move freely, the metal has some electrical conductivity. It allows the energy to pass quickly through the electrons, generating an electric current. Metals conduct heat for the same reason: the free electrons can transfer the energy at a faster rate than other substances with electrons that are fixed into position. There also are few non-metals that conduct electricity: graphite (because, like metals, it has free electrons), and ionic compounds that are molten or dissolved in water, which have free moving ions.

Metal atoms have at least one valence electron which they do not share with neighboring atoms, and they do not lose electrons to form ions. Instead, the outer energy levels (atomic orbitals) of the metal atoms overlap. They are similar to covalent bonds. Not all metals exhibit metallic bonding. For example, mercury ions () form covalent metal-metal bonds.

An alloy is a solution of metals. Most alloys are shiny like pure metals are.

## Related pages
* Chemical bond
* Covalent bond
* Ionic bond
* Coordination complex
* Alloy

## References
Signal transduction

A **signal transduction** in biology is a  cellular mechanism. It converts a stimulus into a response in the cell. There are two stages in this process:
#A signalling molecule attaches to a receptor protein on the cell membrane.
#A second messenger transmits the signal into the cell, and a change takes place in the cell.
So, signal transduction starts with a signal to a cell receptor, and ends with a change in cell function. In either step, the signal can be amplified. Thus, one signalling molecule can cause many responses.

These systems of communication between cells are extremely ancient, and are found in all metazoa.

## Related pages 
*Transduction (physiology)
*Ligand
*Cytokine
**Cytokine storm
*Neuroscience

## References
## Other websites 
* *Science*'s STKE - Signal transduction knowledge environment, from *Science*, published by AAAS.
* Cosma Shalizi's Signal transduction notebook
Flux (disambiguation)

**Flux** comes from Latin and means *flow*; it may mean:
* Flux, a scientific term describing the rate of flow of something through a surface
* Flux (software), a free for non-commercial usage suite of VRML/X3D viewing/authoring software
* Flux (metallurgy), a material that aids in smelting and soldering by assisting the flow of the molten metal
* Flow (psychology), often referred to as *flux*
* Flux (biochemistry), the rate of turnover of molecules through a metabolic pathway
* *Flux (novel)*, a book by Stephen Baxter
* Flux Magazine (US), a short-lived American music, comic book & video game magazine from the mid-1990s
* Flux Of Pink Indians, the name of a British anarcho-punk band, originally known as Flux of Pink Indians
* Fluxx, a card game
* Flux Capacitor, a fictional device from *Back to the Future* that "makes time travel possible"
* Fluxus, an art movement
* Flux Wildly, one of the main characters from the computer game Toonstruck
* Flux (magazine), a magazine published by students at the University of Oregon journalism school
* Flux (magazine), a magazine published in the United Kingdom
Flux

**Flux** is a term in physics and mathematics. It is broadly defined as "How much stuff goes through a thing" (or into an area). The word "flux" is similar to "flow".

For instance, in a butterfly net the amount of air passing through the net is the flux.

## Movement of substances 
In the study of transport phenomena (heat transfer, mass transfer and fluid dynamics), **flux** is defined as flow per unit area, where flow is the movement of some quantity per time. Flux, in this definition, is a vector.
 
There are many fluxes used in the study of transport phenomena. Each type of flux has its own distinct unit of measurement along with distinct physical constants. Six of the most common forms of flux from the transport literature are defined as:
#*Momentum flux*, the rate of transfer of momentum across a unit area (N·s·m−2·s−1). (Newtonian fluid, viscous flow)
#*Heat flux*, the rate of heat flow across a unit area (J·m−2·s−1). (Fourier's Law) (This definition of heat flux fits Maxwell's original definition.)
#*Chemical flux*, the rate of movement of molecules across a unit area (mol·m−2·s−1). (Fick's law of diffusion)
#*Volumetric flux*, the rate of volume flow across a unit area (m3·m−2·s−1). (Darcy's law)
#*Mass flux*, the rate of mass flow across a unit area (kg·m−2·s−1). (Either an alternate form of Fick's law that includes the molecular mass, or an alternate form of Darcy's law that includes the density).
#*Radiative flux*, the amount of energy moving in the form of photons at a certain distance from the source per steradian per second (J·m−2·s−1). Used in astronomy to study and classify stars.  Also acts as a generalization of heat flux, which is equal to the radiative flux when restricted to the infrared spectrum.
#*Magnetic flux*, the density of a magnetic field.

## Electromagnetism 
In the field of electromagnetism, flux is usually the integral of a vector quantity over a finite surface. The result of this integration is a scalar quantity. The magnetic flux is  the integral of the magnetic vector field over a surface, and the electric flux is defined similarly. Using this definition, the flux of the Poynting vector over a specified surface is the rate at which electromagnetic energy flows through that surface. Confusingly, the Poynting vector is sometimes called the *power flux*,  which is an example of the first usage of flux, above. It has units of watts per square metre (W/m2).

## Related pages
* Fluid dynamics

## References
## Further reading
*
Conversation analysis

**Conversation analysis** (commonly abbreviated as **CA**) is the study of talk in social interaction. CA tries to describe the structure and patterns of interaction, whether this is institutional (in the school, doctor's surgery, courts or elsewhere) or casual conversation. 

The term “conversation” to label this disciplinary movement is misleading if read in a colloquial sense, as many have. 

## Other websites 
* An Introduction to Conversation Analysis  (by  Discourse and Rhetoric Group,  Loughborough University)
* Online bibliography of pre-1990 CA literature
* Online bibliography of post-1989 CA literature 
* Online clearinghouse for the CA community
Mark-Anthony Turnage

**Mark-Anthony Turnage** (born Grays, Essex, 10 June 1960) is an English composer.  He is one of the most original composers in his country today.  

Turnage studied at the Royal College of Music and won all the major prizes.  He became famous when he wrote an opera called *Greek*.  It is typical of his musical style: quite lyrical but also very dramatic and aggressive.  His music is often inspired by jazz.  Other works include *Kai*, *Rockaby*, *Blood on the Floor*, *Dispelling the Fears*, *Drowned Out* and *Three Screaming Popes*.  He has written music for the English National Opera, City of Birmingham Symphony Orchestra and the Chicago Symphony Orchestra.  

## Other websites 
*http://www.boosey.com/pages/cr/composer/composer_main.asp?composerid=16405
Neuroscience

**Neuroscience** (or neurobiology) is the scientific study of the nervous system. It is the branch of biology which investigates every aspect of the brain and nervous system.

The nervous system is made of billions of neurons connected together and to other systems in the body.  The central nervous system includes the brain, spinal cord and retina. It is connected to the rest of the body via the peripheral nervous system.    

## Research themes 
Neuroscience research focusses on a set of themes and questions.  
* Behavior/cognition/language
* Biological rhythms
* Brain imaging or neuroimaging
* Cell biology
* Cell imaging & Electrophysiology
* Learning/memory
* Signal transduction
* Neurobiology of the neuron
* Neurotransmitter
* Sensation and perception
* Sleep
* Autonomic nervous system and homeostasis
* Arousal, attention and emotion
* Genetics of the nervous system
*Developmental biology of the nervous system 
*Diseases of the nervous system

## Related pages 
* Agonist
* Biology
* Cognitive neuropsychology
* Ethology
* Neurology
* Neurolinguistic programming
* Neuropsychology
* Psychiatry

## References
### Textbooks 
*
*
*Squire, L. *et al.* (2003). *Fundamental Neuroscience, 2nd edition*. Academic Press; 
*Byrne and Roberts (2004). *From Molecules to Networks*. Academic Press; 
*Sanes, Reh, Harris (2005). *Development of the Nervous System, 2nd edition*. Academic Press; 
*Siegel *et al.* (2005). *Basic Neurochemistry, 7th edition*. Academic Press; 
*Rieke, F. *et al.* (1999). *Spikes: Exploring the Neural Code*. The MIT Press; Reprint edition 

#### Online textbooks 
*Neuroscience 2nd ed. Dale Purves *et al*. Published by Sinauer Associates, Inc., 2001.
*Basic Neurochemistry: Molecular, Cellular, and Medical Aspects 6th ed. by George J. Siegel *et al*. Published by Lippincott, Williams & Wilkins, 1999.

### Popular works
* 
* Damasio, A. R. (1994). ''Descartes' Error: Emotion, Reason, and the Human Brain.* New York, Avon Books.  (Hardcover)  (Paperback)
* Gardner, H. (1976). *The Shattered Mind: The Person After Brain Damage.* New York, Vintage Books, 1976 
* Luria, A. R. (1997). *The Man with a Shattered World: The History of a Brain Wound.* Cambridge, Massachusetts, Harvard University Press.  (Hardcover)  (Paperback)
* Sacks, O. *The Man Who Mistook His Wife for a Hat*. Summit Books  (Hardcover)  (Paperback)
* Sacks, O. (1990). *Awakenings.* New York, Vintage Books. (See also Oliver Sacks)  (Hardcover)  (Paperback)
* Sternberg, E. (2007) *Are You a Machine? The Brain, the Mind and What it Means to be Human.* Amherst, NY: Prometheus Books.

## Other websites 
* High-Resolution Cytoarchitectural Primate Brain Atlases 
* Society for Neuroscience
* Neural Plasticity-Open Access Journal (Hindawi Publishing)
* Neuroscience. 2nd ed. by Purves *et al.'' (online textbook)
* Neuroscience for Kids
Guava

**Guavas** are plants in the genus *Psidium* of the family Myrtaceae. There are about 100 species of tropical shrubs and small trees in the genus.

They are native to Mexico, the Caribbean, Central America and the northern part of South America. Now they are found in all the tropical, and in some subtropical, regions because they are edible fruits.

Guava are also a kind of berry fruit on those plants. There are many kinds of guavas. The most common guava is the apple guava (*Psidium guajava*): it is so common that the word 'guava' usually refers to this species. Red guavas are called marooonguava. In 100 g of guava are 200 mg of vitamin C, which means that guavas have five times more vitamin C than oranges.
Resting potential

The **resting potential** of a cell is the membrane potential that would be maintained if there were no action potentials, synaptic potentials, or other active changes in the membrane potential. In most cells the resting potential has a negative value, which by convention means that there is excess negative charge inside compared to outside. The resting potential is mostly determined by the concentrations of the ions in the fluids on both sides of the cell membrane and the ion transport proteins that are in the cell membrane.

## Other websites 
*Neuroscience - online textbook by Purves, *et al.*
* Basic Neurochemistry Molecular, Cellular, and Medical Aspects by Siegel, *et al.*
* Bertil Hille *Ion channels of excitable membranes*, 3rd ed., Sinauer Associates, Sunderland, MA (2001). 
* Generation of resting membrane potential Wright, S.H., *Advances in Physiology Education*, **28**(1-4): 139-142, 2004,
Thrust (disambiguation)

**Thrust** is a reaction force described by Newton's Second and Third Law. For this meaning, see Thrust.

This word has other uses:
* For the land-speed record breaking car, see ThrustSSC and Thrust2
* For the computer game, see Thrust (computer game)
* For the rapper, see Thrust (rapper)
* For the Transformers characters, see Thrust (Transformers)
* For the Herbie Hancock fusion album, Thrust (album)
* For the semi-professional magazine which later changed its name to *Quantum*, see *Thrust (magazine)*
* Thrust fault in geology
Robert A. Heinlein

**Robert Anson Heinlein** (July 7, 1907 – May 8, 1988) was an American writer. He mostly wrote science fiction books. He won the Hugo Award four times. Probably his best-known novels are Starship Troopers (1959, Hugo Award, was made into a film), and Stranger in a Strange Land (1961, Hugo Award). Two other Hugo awards were for Double Star (1956) and The Moon is a Harsh Mistress (1966). Together with Isaac Asimov and Arthur C. Clarke he is seen as one of the *Big Three of Science Fiction*.

Heinlein employed his concept of the "World as Myth" in various works, notably his science fiction novel *The Number of the Beast,* which features a device which navigates through Block Time (aka Eternalism) in a plenum of innumerable alternate universes.

## References
List of video game genres

A video game genre is category of related games based on their gameplay (the rules and action of a game). Unlike genres of movies and novels, these genres are not based on a game's setting, main characters, or plot elements. However, horror games have been counted as a genre.

## List 
* Role-playing video game
** Massively multiplayer online role-playing game
** Action role-playing game
** Roguelike
* Action
** Shooter
*** First-person shooter
*** Third-person shooter
*** Shoot 'em up
** Platformer
** Beat 'em up
** Hack and slash
** Stealth
** Fighting
** Survival
*** Survival horror
*** Battle royale
* Action-adventure
* Adventure
** Interactive fiction
** Visual novel
* Simulation
** Life simulation game
*** Virtual pet
** Sports video game
* Strategy
** Real-time strategy
** Multiplayer online battle arena
** Tower defense
* Racing
** Sim racing
* Puzzle
Fable

A **fable** is a type of story which shows something in life or has a meaning to a word. A fable teaches a lesson or suggests a moral from it. A fable starts in the middle of the story, that means, jumps into the main event without detailed introduction of characters. The characters of a fable may be animals, plants and legendary creatures. When animals are used in fables, they think and talk like people, even though they act like animals. For example, in a fable a clay pot might say that it is frightened of being broken.

The stories told by fables are usually very simple. To understand a fable, the reader or listener does not need to know all about the characters, only one important thing. For this reason animals are often used in fables in a way that is easily understood because it is always the same. They keep the same *characteristics* from story to story.
* A lion is noble
* A rooster is boastful
* A peacock is proud
* A fox is cunning
* A wolf is fierce
* A horse is brave
* A donkey is hard-working

The most famous fables are those attributed to Aesop (6th century B.C.). Many fables are so well known that their morals have become English sayings.

For example:
* If a person says "sour grapes!" then they are referring to "The Fox and the Grapes". This fable is about a fox who saw a beautiful bunch of grapes hanging on a vine. He wanted to eat them but they were high up. He tried and tried to jump high enough to pull them down. When he was too tired to jump anymore, he went away saying "I'll bet those grapes were sour!"

:So, if a person sees a beautiful thing that they want, but cannot have, sometimes they say "I don't want it, anyway! I'll bet it is really no good!" This way of thinking is called *"sour grapes".*

"Crying wolf" is another well-known English saying. This comes from "The Boy Who Cried Wolf". This fable is about a boy who was sent to mind the sheep. The boy got lonely while minding the sheep, so he shouted "Wolf! Wolf!" The people came running. The next day, he did it again and they were very angry. On the third day the boy saw a wolf. He cried "Wolf! Wolf!" but no one came and the wolf ate him.

:So if a person always makes a great fuss to get attention, or if a person says something bad has happened when it has not, then it is called "crying wolf" and people will stop bothering to pay attention, even when things go really wrong.

## Related pages
* Children's literature
* Jean de La Fontaine
* Myth
* Fairy tale

## Other websites
* Animal Symbolism  List of frequently described animals and their characteristics
* The Dragon-Tyrant
* Fables - Collection and guide to fables for children 
* Imaginexus  A collection of interconnected stories that anyone can edit
* Beast Fable Society  An academic society focused on fables and related genres
Drainage

was partly changed into land by building polders and draining them. Old land is mostly green, new one is darker in color.]]
**Drainage** is the natural or artificial removal of surface and sub-surface water from a given area.  Many agricultural soils need drainage to improve production or to manage water supplies.

## Early history
The earliest archaeological record of an advanced system of drainage comes from the  Indus Valley Civilization from around 3100 BC in what is now Pakistan and North India. The ancient Indus systems of sewerage and drainage that were developed and used in cities throughout the civilization were far more advanced than any found in contemporary urban sites in the Middle East and even more efficient than those in some areas of modern Pakistan and India today. All houses in the major cities of Harappa and Mohenjo-daro had access to water and drainage facilities. Waste water was directed to covered drains, which lined the major streets.

## Reasons for artificial drainage 
Wetland soils may need drainage to be used for agriculture. In the northern USA and Europe, glaciation created numerous small lakes which gradually filled with humus to make marshes. Some of these were drained using open ditches and trenches.

The largest project of this type in the world has been in process for centuries in the Netherlands. The area between Amsterdam, Haarlem and Leiden was, in prehistoric times swampland and small lakes. Turf cutting (Peat mining), subsidence and shoreline erosion gradually caused the formation of one large lake, the Haarlemmermeer, or lake of Haarlem. The invention of wind powered pumping engines in the 15th century permitted drainage of some of the marginal land, but the final drainage of the lake had to await the design of large, steam powered pumps and agreements between regional authorities. The elimination of the lake occurred between 1849 and 1852, creating thousands of km2 of new land.

## Other websites 
*WebCom Systems , software created for designing soakaways and filter trenches.
*NDS , drainage calculator.
*Ancient drains, a series of images of the earliest drainage systems in the ancient Indus city of Mohenjo daro
*Stormwater DesignInformation on stormwater design 
**Draining for Profit, and Draining for Health* by George E. Waring, 1867, from Project Gutenberg
* Drainage photos
Polder

, Germany, aerial view (2012)]]
 is a Polder. Old land is mostly green, new land is darker in color.]]

**Empoldering** is a method of reclaiming land from the sea or from inland lakes, and a way to control floods.  Empoldering involves the use of a polder, a piece of land in a low-lying area that has been reclaimed from a body of water by building dikes and drainage canals.

Although empoldering is usually carried out in low-lying coastal areas, it can also be done in inland areas such as lakes and rivers.  It is common in countries like the Netherlands, where much of the country is below sea level and subject to flooding.  About one-fifth of the land in the Netherlands has been reclaimed from the sea.  Their largest and most successful project is the Zuiderzee Works.

Polders have two distinct features.  Firstly, they are enclosed by dikes to keep the water out.  The dikes also serve to protect the polder from erosion.  Secondly, polders are continually maintained by systems of drainage canals and pumps which prevent them from becoming waterlogged and hence, suitable for cultivation.

## Process 
Stage 1: Dike constructed around the area to be reclaimed to keep water from coming in.

Stage 2: The area is drained using pumps and drainage canals.

Stage 3: "Reeds" (a type of salt tolerant plant) are sown by aircraft to help the soil form.

Stage 4: After 3 years, reeds are burnt and the ash is used as fertilizers for the soil.

Stage 5: After a period of up to 15 years, the polder is ready for growing crops, building houses and constructing roads.

## Limits of land reclamation 
1. Cost of reclaiming from deeper waters 

2. Availability of sand 

3. Dispute over territorial boundaries
Doctor of Philosophy

The **Doctor of Philosophy**, (**PhD, Ph.D., DPhil** or **D.Phil.**) is a degree which a person gets from a university by finishing a doctorate program. In many areas of study, the PhD / DPhil is the highest degree that a person can earn. This is called the "terminal degree". There are PhD / DPhil degrees for many different fields. Examples of these include PhDs / DPhils in literature, philosophy, history, science, mathematics and engineering. Some PhD / DPhil degrees have existed for hundreds of years, such as a PhD / DPhil in Canon Law. Other PhD / DPhil degrees were developed in the 1970s and 1980s, such as the PhD / DPhil in computer science.

## Requirements for degree
To be admitted to a PhD / DPhil program, a person usually has to have completed their Bachelor's degree or master's degree that is related to the PhD / DPhil degree. For example, a person applying to be admitted to a PhD / DPhil degree in theater would normally have to have a master's degree such as a Master of Arts (MA) degree in theater, English literature or a related area.

## Elements of a PhD / DPhil degree
The PhD / DPhil degree usually takes between three and six years of full-time study to complete. They may or may not require a master's degree beforehand. Many PhD / DPhil degrees begin with a period of graduate courses. After the PhD / DPhil student has taken these courses, they take examinations to test what the student knows about their area of study. After the student passes the exams, they begin to do original research. The product is a long research report called a dissertation (or a "thesis"). Some PhD / DPhil degrees also require students to pass exams in languages (such as French, German or other languages). Many PhD / DPhil students teach undergraduate students or assist professors with research during their PhD / DPhil studies.

## As a requirement for university teaching 
Requirements for university teaching vary in different subjects and in different countries. A PhD / DPhil is necessary or usual to become a university professor in many fields, especially in science. However, many famous professors have not had higher degrees, though that is less common today. In some fields, there is no PhD / DPhil, and so another degree is required to become a university professor. For example, the highest degree in Fine Arts fields such as printmaking or graphic design is the Master of Fine Arts (MFA) degree. A person with an MFA degree can become a university professor in some Fine Arts fields.

## Other websites 
* The Mathematics PhD in the United Kingdom: Notes on its History Contains information/links of more general relevance than mathematics.
Marsh

In geography, a **marsh** is a type of wetland. It has grasses, rushes, reeds, typhas, sedges, and other herbaceous plants (possibly with low-growing woody plants) in a context of shallow water.  A marsh is different from a swamp, which has a greater proportion of open water surface, which is generally deeper than a marsh. In the US, the term 'swamp' is used for wetland dominated by trees rather than grasses and low herbs.

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The water of a marsh can be fresh, brackish or saline. Coastal marshes may be associated with estuaries and along waterways between coastal barrier islands and the inner coast.  Estuarine marshes often are based on soils consisting of sandy bottoms or bay muds.

Marshes are critically important wildlife habitat, often serving as breeding grounds for a wide variety of animal life.

## Related pages
*Fen
*Swamp
*Ecoregion

## Other websites 
* Marshes of the Lowcountry (South Carolina) -- Beaufort County Library
Ulan-Ude

**Ulan-Ude** (Russian:Ула́н-Удэ́; Buryat: Улаан-Үдэ), formerly **Verkhneudinsk** (), the capital city of the Buryat Republic, Russia. The city is located about 100&nbsp;km south-east of Lake Baikal. It sits at the foot of the Khamar-Daban and Khrebet Ulan-Burgasy mountain ranges, next to the confluence of the Selenga River and its tributary, the Uda. The city is divided into two parts by the Uda. Population 359,391 (2002 Census); 352,530 (1989 Census). It is the third largest city in East Siberia.  It is served by Ulan-Ude Airport (Mukhino) as well as the smaller Ulan-Ude Vostochny Airport.

Ulan-Ude was founded in 1666 by the Russian Cossacks. Due to its geographical position, the city grew rapidly and became a large trade centre which connected Russia with China and Mongolia. There are old merchants' mansions richly decorated with wood and stone carving in the historical center of Ulan-Ude, along the river banks. They represent beautiful examples of Russian classicism.  There is also a large and highly unusual head of Lenin in the central square.

## Gallery 

Image:Ulan ude station.jpg|Ulan-Ude train station on the Trans-Siberian railway
Image:Wooden house in ulan ude.jpg|A wooden house in Ulan-Ude

## Sources
## Other websites
Vitamin A

**Vitamin A** (also known as **retinol**, **vitamin A1**) is a vitamin, a group of organic chemicals including retinal and several carotenoids. The human body does not make these chemicals, and must take them from food. Egg yolks and liver are both rich in vitamin A, and so is dairy. The efficiency of the conversion depends on genetics and fat consumption. Leafy yellow, green, and red vegetables, and yellow fruits, such as mango, papaya, and apricots, are the main sources of beta-carotene. People who do not get enough of the vitamin may lose the ability to see in poor light and suffer from a weakened immune system. They may also have problems with memory, because vitamin A is important for the brain. People with malnutrition often have too little vitamin A. This is common in poor countries.   

### Hypervitaminosis A 
Too much vitamin A is also dangerous to health. Someone might get too much vitamin A from taking too many vitamin supplements or from eating too much A-rich food like liver.

Vitamin A does not need to be eaten every day. Because it can be stored in fat, anything that is not used by the body is stored for later. However, they have long, sometimes very long, periods between kills. In contrast, African big cats kill about every three or four days, and they do seem to avoid eating the liver.

## Related pages 
* Vitamin B
* Fentanyl

## References
Vitamin D

**Vitamin D** is a hormone. It is a steroid which is made in the body under the right conditions. To make it, the body needs sunlight, which acts on the lower layers of the skin. 

However, if the body does not make enough, it can be found from food sources in tiny amounts. In fact, many countries add it automatically to certain foods like milk. Supplements A recent panel of Vitamin D researchers concluded that *at least* 20-25 mcg (800-1000 IU) per day would help most adults.

Few foods naturally contain much D3. Fish do, especially oily ones, such as salmon, sardine and mackerel. Many kinds of edible mushrooms contain some D2, like shiitake. Mushrooms grown in full sunlight tend to have more.

## Related pages 
* Vitamin C (ascorbic acid) and vitamin E
* Hormones 
* Rickets

## References
## Other websites 
*Benefits and sources of Vitamin D 
*Benefits of Vitamin D 
*Factsheet on Vitamin D
*FDA takes Vitamin D drugs and feeds them to prisoners
Vitamin K

**Vitamin K** is a vitamin which is soluble in fat. It is probably best known for its role in the coagulation (clotting) of blood. However, it also serves other important functions in the body.

Vitamin K was discovered by a Danish chemist named Henrik Dam. He won the 1943 Nobel Prize in Physiology or Medicine for discovering its key role in the coagulation of blood. Since that time, Vitamin K's role in other physiologic functions has become known. One of the most important is its role in controlling where calcium goes in the body.

Without Vitamin K, there would be a loss of blood when a person bleeds, which can lead to unconsciousness or even death. Vitamin K can be found in green vegetables, such as spinach, lettuce, broccoli or cabbage. Babies are born without vitamin K2 in their gut and are inoculated (like a vaccine) with it at birth a lot of the time.

## Related pages 
* Blood
* Vitamin A (retinol) and vitamin D 

## References
Vitamin E

**Vitamin E** (which is also called **Tocopherol**

Some research suggests that vitamin E has anti-aging benefits.

## Related pages 
* Vitamin D and vitamin K
* Heart disease

## References
ONS coding system

The **ONS coding system** is a system used in the United Kingdom for dealing with census and other statistical data. It is used by the Office for National Statistics as a way to label each area of England and Wales. It is also used for parts of Northern Ireland.  The system uses a code for the larger census areas, counties and districts. It then breaks those areas down into smaller areas within the larger areas. Each of the smaller areas get a code that is based on the larger area. Areas are divided in this way until they get to the smallest size used for census data. An area must have at least 40 households, but they try to not divide an area into a size smaller than 100 households. 

## Example
## Other websites 
*ONS Open Geography Portal
*ONS Census 2021 Geographies
B vitamins

The **B vitamin complex** (also called **B vitamins**) are a group of 8 vitamins. They have an important job in the metabolism of cells. Each B vitamin is a cofactor (a coenzyme) for some key metabolic processes or it is a  needed to make one.

Originally, people thought they were just different forms of one vitamin (as with Vitamin D, for example). Later it turned out that they are separate vitamins that often can be found together. They are Vitamin B1/Thiamine, Vitamin B2/Riboflavin, Vitamin B3/Vitamin P/Vitamin PP/Niacin,Vitamin B5/Pantothenic acid, Vitamin B6, Vitamin B7/Vitamin H/Biotin, Vitamin B9/Vitamin M/Vitamin B-c/Folate and Vitamin B12. They are required for growth, and proper functioning of nerves and muscles. B vitamins are found in meat, milk, whole grains and fresh vegetables.

Vitamin B deficiencies have been shown to cause the following symptoms:

*mental problems
*heart palpitations
*heart arrhythmias
*exhaustion
*paranoia, vague fears, fear that something dreadful is about to happen, nervousness, ADD (attention deficiency), inability to concentrate
*thoughts of dying
*frustration
*inability to sleep
*restlessness
*tingling in hands
*tingling fingers and toes
*crying spells, inability to cope
*soreness all over

Well-known medical syndromes caused by thiamine deficiency are beri-beri, Wernicke–Korsakoff syndrome (WKS), and optic neuropathy.

## Related pages 
* Vitamin A (retinol) and C (ascorbic acid)

## References
Sexual abstinence

s are worn by some young people to show their commitment to abstinence. Someone who decides to avoid sex is called a celibate or volcel.

## Culture
Abstaining from sex before marriage can be called chastity. In some countries, it is illegal to have sex before marriage. Many religious and ethical systems forbid sexual activities between a person and anyone other than a spouse. These  include most denominational variations of Judaism, Christianity, and Islam. Other legal systems and societal norms  can promote abstinence. People who are abstinent even though they do not want to be are sometimes called incels or TFL (true forced loneliness). One form of sexual abstinence is fapstinence, avoiding masturbation.

## Reasons
People may choose to practice abstinence for other reasons. A common reason is because of the person's religious or philosophical beliefs. When done for religious reasons, it is called **celibacy**. Other people may choose abstinence in order to prevent pregnancy or sexually transmitted diseases. When someone is abstinent from sex but they don't want to be, its sometimes called *incel*, short for *involuntary celibacy*.

## Related pages
*Chastity
*Fornication
*Asexuality

## References
## Other websites 
* Chastity in Catholic Encyclopedia — a Christian view on chastity
Council of Jerusalem

The **Council of Jerusalem** or **apostolic council** is a common name for a meeting of early Christian leaders reported in the *Acts of the Apostles* chapter .  The meeting must have happened about  the year 50, at the latest some time before the death of James the Just in 62.

## The issues 
A common interpretation is that the council came together because there was disagreement within the Early Christian community between those who believed the church must observe the rules of traditional Judaism, and Paul of Tarsus, who believed there was no such necessity. The "rules of traditional Judaism," the Halakha of Rabbinic Judaism, were not finished at this time.

The central issue was circumcision, as the author of *Acts* relates the initial confrontation in Antioch, where Paul had been preaching:
:"And certain men which came down from Judaea taught the brethren, [and said], Except ye be circumcised after the manner of Moses, ye cannot be saved." (*Acts* 15:1) KJV

## Footnotes 
## Other websites 
* Acts 15 
* JersualemCouncil.org 
* NA26 Greek Acts 15 
* Catholic Encyclopedia: Judaizers
* Catholic Encyclopedia: Apostolic Canons
* Didache
* Apostolic Constitutions
* Didascalia Apostolorum
* Jewish Antiquities 20 
* New Perspective on Paul
* Early Christian Writings
* Jewish Encyclopedia: Hillel v. Shammai
* Jewish Encyclopedia: Didascalia
* Gentiles and Circumcision 

## Further reading 
* Ehrman, Bart D. *Lost Christianities: The Battle for Scripture and the Faiths We Never Knew* 2003
* Eisenman, Robert, 1997. *James the Brother of Jesus : The Key to Unlocking the Secrets of Early Christianity and the Dead Sea Scrolls.*  A cultural historian's dissenting view based on contemporary texts.
* Westerholm, Stephen. *Perspectives Old and New on Paul: The "Lutheran" Paul and His Critics* 2003
Central European Time

**Central European Time** is a time zone. It is one hour ahead of Coordinated Universal Time (what used to be called Greenwich Mean Time). Most countries in the central part of Europe and some countries in Africa follow it. 

In Europe, the countries of Ireland, Great Britain, Iceland and Portugal use Western European Time. All the other countries, up to Norway, Poland, Slovakia, Hungary, Bosnia and Herzegovina, Serbia and North Macedonia use Central European Time. 

Algeria and Tunisia in Africa use CET but do not observe daylight saving time.