Aarushhh/wikipedia-simple-splitted huggingface dataset:
The 1170s was a decade that started on 1 January 1170 and ended on 31 December 1179.

Events and trends 
 1170 – Assassination of Thomas à Becket
 1171 – Saladin ends the Islamic ruling of Fatimid, bringing back Sunni rule in Egypt.
 1179 – Third Council of the Lateran condemns Waldensians and Cathars as heretics (people who turn away from certain religious beliefs); reformation of clerical life

Significant people
The Arabs ( ʻarab) are an ethnic group widespread in the Middle East and North Africa. Arabic is one of the Semitic languages, which is also the name of the ethnic family which they belong to. Genealogically, Arabs are those who can trace their ancestry back to the people who first lived on the Arabian Peninsula.

Who is an Arab 
There are three points which decide whether someone is considered Arab or not:
 Political: whether they live in a country which is a member of the Arab League (or the Arab world); this definition covers more than 450 million people.
 Linguistic: whether their main language is Arabic; this definition covers more than 423 million people.
 Genealogical: whether they can trace their ancestry back to the people who first lived on the Arabian Peninsula.

Minorities are the Iraqi Turkmens in some Arab countries. The Iraqi Turkmen people are often considered Arab, but they are an Turkic people ethnic group with their own language and culture. The same goes for Berbers (Amazigh) and Bedouins.
There are many people who can be called Arabs by these points, but who do not think of themselves as Arab.  Examples include modern Egyptians (Coptics) and the Syriacs (Aramaics/Assyrians). Although they live in countries like Syria or Egypt which is part of the Arab League and speak the official language-Arabic, they are different cultural groups. They have their own languages, culture, identity and churches, such as the Coptic Church and the Syriac Catholic and Orthodox churches. Even though many have assimilated to Arab society, they have their own heritage that spans 3,000 years.
Traditional genealogy 
In Islamic and Jewish tradition, Arabs are a Semitic people from the Ishmaelites, who trace their ancestry from Ishmael, a son of the ancient patriarch Abraham and Hagar and of the sons from Abhraham and his wife Keturah. Medieval Arab genealogists separate the Arabs into two groups: the "original Arabs" (Bedouin) of South Arabia, descending from Qahtan (identified with the biblical Joktan) and the "Arabized Arabs" (musta`ribah) of North Arabia (The Levant), descending from Adnan who is descended from Ishmael.

Religion
Most Arabs today follow the religion of Islam, whose central prophet is Muhammad. Christianity makes up the largest religious minority - most of the Christians that do consider themselves Arabs belong to the Greek Orthodox Church with smaller numbers of Roman Catholics.

While Coptic and Maronite Catholic Christians are native Arabic-speakers, many reject the Arab pan-ethnicity, but are still considered Arab by outsider sources.
There are some small communities practicing Judaism and polytheism (the worship of many gods).

References

Other websites 
 A is for Arabs: What the world owes Arabs and Muslims 
 Maps of the Arab World 
 News from Arabic countries
 Business news from Arab countries
 Arabia in ancient history - with a discussion of the ancient usage of the word Arab
 Araboo.com - Arab Guide
 Arabic Search  - Arabic ThroughSearch

 
Ancient history
A mebibyte is a unit of measure. It represents 1024 * 1024 bytes. 

A mebibyte (a contraction of mega binary byte) is a unit of information or computer data storage, symbol MiB.

1 MiB = 220 bytes = 1,048,576 bytes = 1,024 kibibytes

The mebibyte is closely related to the megabyte (MB). Megabyte can either be a synonym for mebibyte, or refer to 106 bytes = 1,000,000 bytes, depending on context (see binary prefix for background). The two numbers are relatively close together, but mistaking the two has nevertheless led to problems. 

The unit MiB was defined by the International Electrotechnical Commission (IEC) in December 1998.  Use of mebibyte and related units is strongly endorsed by IEEE and CIPM and is becoming more common.

One mebibyte equals 1024 (= 210) kibibytes, and 1024 mebibytes equal one gibibyte.
Mibibyte is a common misspelling, presumably from the "i" in the abbreviation or confusion about how the surrounding prefixes (i.e., "kibi" and "gibi") were actually formed.  The "i" is actually from the end of the prefix.  Tebi- and pebi- are similarly abbreviated Ti- and Pi-, but they are not usually misspelled.

Related pages
Megabyte
Kibibyte
Gibibyte
Tebibyte

Other websites 
NIST Prefixes for binary multiples

Units of information
Clergy are people who have an office in a Christian church or other religion such as a rabbi or a priest. Clergy are often ordained before they are allowed to do their work.

Related pages 
 Clergyman
 Muslim clergy
 Rabbi
 Priest

Religious workers
Acre is a state in the Northern Region of Brazil. It borders other two states, Amazonas and Rondônia. It also borders two countries, Bolivia and Peru. Its capital city is Rio Branco. Other important cities are: Cruzeiro do Sul, Tarauacá, Sena Madureira, and Brasiléia.

The state is mostly covered by the Amazon Rainforest. There are many rivers in Acre. Some of the rivers are the Juruá, Purus River, Acre River, Tarauacá, Muru, Embirá, and Xapuri.

The economy is based on agriculture, cattle animal husbandry, and rubber production.

Until the start of the 20th century, Acre was a territory of Bolivia. Since the 19th century, most people from Acre were Brazilian people, and they created an independent state.

In 1889, the Bolivians tried to control the area again and there were fights.

On November 17, 1903, Acre become a Brazilian territory. On June 15, 1962, it was unified and became a state.

References
The roller coaster (some people say the simple form coaster) is a kind of theme park ride. A roller coaster is usually a small train. It has a number of carriages that travel on a track. This track has hills that go up and valleys that go down. Sometimes it has other features that will turn the train upside-down. The track can be made from wood or steel. Some roller coasters are made for children, so they do not travel very fast. Other roller coasters are made very tall and they travel very fast. Riders are generally held in place with a bar, a belt, or something similar.

Scientifically, a roller coaster works because of gravity, a force that pulls things down to the ground. Most roller coaster trains are pulled to the top of a hill on a chain. The train will slide down the track, which has a number of hills and valleys. As it slides downhill it goes faster, and it slows down when climbing.
History 
In the United States, LaMarcus Adna Thompson patented the first roller coaster on January 20, 1865. He named his ride the "Switchback Railway," and workers pulled the carriage to the top of the track. The first modern steel roller coaster was the Matterhorn Bobsleds at Disneyland. It opened in 1959.

Types of roller coasters 
Roller coaster rails are made of wood or steel.

Steel roller coasters can be separated into many more types. On a Wing Coaster riders sit on either side of a roller coaster track and nothing is above or below the riders.

On a flying roller coaster riders lie face down so they feel like they are flying. Cars hang below the track.
On a Floorless Coaster riders sit with no floor underneath them, so their feet can swing freely just above the track. 

Some roller coasters spin riders.

Both steel and wooden roller coasters can turn riders upside down.  This is called an inversion.
Son of Beast was the only wooden roller coaster to have an inversion.  However the loop was removed after an incident and after another incident, the ride was torn down.  In 2013, Hades 360 and Outlaw Run have inversions.  The Smiler has the world record for the most inversions.

Famous roller coasters

References

 Fuji-Q Highland'
 Nagashima Spa Land

Other websites
 Coasterpedia, the Roller Coaster Wiki
The Zimbabwe dollar was a currency for Zimbabwe from 1980 to 2009. Zimbabwe had the highest rate of inflation in the world. The rate of inflation grew to 231,150,888.87% in July 2008.

Because of hyperinflation, or inflation that is out of control, the Reserve Bank of Zimbabwe had to print banknotes with higher values to cope with the rising cost of living. In January 2009, Zimbabwe released a banknote for one hundred trillion dollars, or $100,000,000,000,000.

The Zimbabwe dollar had to be revalued three times due to the rising cost of living: in August 2006, August 2008 and February 2009. In August 2006, the first revaluation dollar was violent and too quick, meaning that many people lost their savings because they were unable to convert it into the new currency without fear of violence and corruption.

Since 12 April 2009, Zimbabwe stopped using the Zimbabwean dollar and adopted currencies from other countries, such as the United States Dollar and the Euro.

References
Notes

Sources
Sources

Zimbabwe
Former currencies
Bahia is a state in the northeast area of Brazil on the Atlantic Ocean coast.

Geography
The capital city of Bahia is Salvador. Other cities where many people live are Feira de Santana, Vitória da Conquista, Itabuna, Ilhéus, and Juazeiro. Almost all of Bahia is 200 m above the sea level. The São Francisco River is the longest river in Bahia. Salvador was the capital of Brazil from 1549 until 1763.

Economy
Bahia is the sixth richest Brazilian state. The economy of Bahia is based on industry, agriculture, animal husbandry, tourism, mining and services.

Culture
Bahia is said to have the greatest and most African influence, in terms of culture and customs, in Brazil.  Some of these are the martial art of capoeira and African-derived music such as samba, afoxé, and axé.

Acarajé is a popular street food. It is one of the symbols of the culture of Bahia.

References
Body modification (or body alteration) is when a person changes their body in a way that lasts forever or for a long time. There are many different kinds of body modification, like piercing, circumcision, or tattoos. Almost all cultures do some kind of body modification.

Arguments
People who do not like body modification sometimes call it "disfigurement" or "mutilation." They believe that if someone changes their body, it is wrong and they are doing something dangerous or unethical.

Why people do body modification
Body modification is done for different reasons. Religions might tell people that they should change their bodies to look a certain way. Other people with body modifications might just like the way the body modifications look, or how they feel good during sex.

Kinds of body modification

Common body modification
Body piercing is when a hole is made through the skin, and a piece of jewelry is put into the hole. Some piercings can be stretched so they fit larger, thicker kinds of jewelry.
 Tattooing is when ink is put under the skin to make a picture. Whole body tatooing and tattooing of the lips and eyes would be thought extreme by some.
 Scarification is when part of the skin is removed to create a scar.
 Branding is when the skin is burned to create a scar.

"Extreme" body modification
 Tongue splitting is when a person's tongue is split in two like a snake's.
 Subdermal implant is when a small object is placed right underneath a person's skin.
 Transdermal implant is when a small object is placed underneath a person's skin, but part of it pokes out of the skin and is visible.
 Extra ocular implant (eye jewellery) is when a tiny chip of metal is placed in someone's eye.

Other body modification
 Amputation is when a body part is cut off.

References 

Body art
Surgery
Skin
A serial killer is someone who murders several people at different times (similar killers of more than one person are mass murderers and spree killers). The victims are usually people the serial killer does not know, and the killer commits his crimes to get a certain kind of excitement or other feeling. They usually have no practical motive such as robbery or revenge.

Serial killer first became a commonly used phrase for this kind of killer in the 1970s. This was the result of the crimes of people like Ted Bundy and John Wayne Gacy. Jack the Ripper is thought by many to be one of the first serial killers that many people knew about, even though his victims were killed long before the phrase was invented.
Some of the worst serial killers have been doctors. Harold Shipman, a British general practitioner, is thought to have killed up to 250 of his patients. John Bodkin Adams, also British, is thought to have killed 163 patients. Burke and Hare, the 'resurrectionists', killed to sell bodies to a doctor, Robert Knox.

References
The World Wide Fund for Nature (WWF) is an international environmental organization. It was founded as the World Wildlife Fund, which is still its official name in Canada and the United States. 

Most of its offices are in Switzerland. Their mascot, or logo, is the Giant Panda. It is the world's largest independent wildlife management organization. It has over 5 million supporters worldwide, working in more than 90 countries. WWF supports 15,000 conservation and environmental projects around the world. It is a charity. About 90% of its fundraising money is from donations by private individuals and businesses.
The group says its mission is "to halt and reverse the destruction of our natural environment". Much of its work focuses on the conservation of three biomes that contain most of the world's biodiversity: forests, freshwater ecosystems, and oceans and coasts. Among other issues, it is also concerned with endangered species, pollution and climate change. The organization runs more than 1,200 field projects worldwide each year.

References 

International environmental organizations
Organizations based in Switzerland
Conservation
Charities
Nyon (district)
Deforestation is when forests are destroyed by cutting trees (logging) and not replanting them.  The most common reason is to clear the land to make farms and ranches.  They also cut trees for firewood and lumber and to make room for cities.  Deforestation destroys the habitat of many animals, leading to their death.  The loss is more severe in so called primary forests, which are forests that have yet been untouched by humans.  Deforestation also releases sequestered carbon.

Restoring trees in deforested places is called reforesting.

Causes of deforestation 

Land has other uses besides growing trees.  The biggest uses of land that was once forested are for farming and ranching.  Some land is also used for roads and buildings, especially in urban area. As the population grows, people need to remove more trees.  They also use the wood from the trees as lumber to make buildings and other things, or they burn the trees as firewood.
Forests do these things: 
 regulates the water cycle to some extent
 produces soil, and prevents soil erosion
 provides habitats for animals
 provides some of our oxygen (more is produced in the sea).
 regulates temperature to some extent 

Forests are often planted to protect against natural disasters.  When forests are lost, very often the soil they protected is also lost. This loss of soil is called erosion.

Trees are also important for carbon sequestration.  When the trees burn or rot, the carbon in them returns to the atmosphere in the form of carbon dioxide. Since carbon dioxide is a greenhouse gas, deforestation causes global warming.  Tropical deforestation is responsible for about 20% of world greenhouse gas emissions. Deforestation continues.

References

Related pages
Desertification
Illegal logging
Reforesting

Other websites
APP & APRIL announces end to deforestation in Indonesia

Forests
Environmental issues
Scuba diving is an activity where people (called "scuba divers", or simply "divers") can swim underwater. They can be underwater a long time by having a tank filled with compressed air. The tank is a large metal cylinder made of steel or aluminum.

The word scuba is an acronym from "Self-Contained Underwater Breathing  Apparatus".

History
In the 1600s, a diving bell would be lowered that had trapped air in it. A diving bell is like a large heavy upside-down bucket that holds air inside when lowered into the water. A diver would breathe that air and swim in an and out of the bell to work until the air became bad. Later fresh air was pumped to the diving bell through a hose, so the diver could stay longer.
The first diving suits used a heavy copper diving helmet with windows and a hose from an air pump. The helmet was clamped to a waterproof diving suit. Divers would wear heavy weights and walk on the seafloor as it was not safe to swim.  The air hose would send air to the helmet from a pump on land or on a boat above the diver. The air would pass through the helmet and out into the water through a valve, and the diver would breathe from the air in the helmet. This wasted a lot of air, but there was no way to only supply air when the diver needed it. This is called a free-flow system.
Jacques Cousteau was a Frenchman who developed several important parts of the scuba system and made it useful.  One part was a better regulator that only sent air when the diver breathed in.  This let the divers go farther on one tank.  It was made with a mouthpiece on a rubber hose, so a heavy helmet was not needed. It was light enough to use with fins and easily swim.  He also took many underwater movies and showed people what was under the water and why it needed to be protected.

There have been improvements to scuba equipment since Cousteau to make it safer and easier to use.
Equipment
 Scuba tank, (one or more) containing air.  The air is ordinary compressed air for most dives, but for longer dives a mixture of air with more oxygen, called nitrox can be used to avoid decompression sickness, also called the bends (a painful or deadly problem from going to the surface too fast). The tank is attached to the diver by a harness, which is often part of the BCD. For deeper dives a breathing gas containing helium can be used to prevent nitrogen narcosis, which can make the diver behave as if drunk, and is dangerous.
 Regulator for breathing the air from the tank.  This reduces the pressure of the air coming from the tank. It adjusts the air to the pressure of the water around the diver so they can breathe easily at any safe depth. There is also an air pressure gauge to show how much air is left in the tank.
BCD (buoyancy control device) to control whether the diver floats or sinks.  The diver can add air from an inflator valve or remove air by opening a dump valve. Divers may also wear weights to stop themselves from floating upwards when their diving suit is too buoyant. The BCD lets the diver adjust their buoyancy so they can be neutral (float in place) at a depth they want.  If the diver swims upward the air in the BCD will expand because the water pressure is less, and the diver must let some air out or float to the surface. If the diver swims down the air will compress and the diver must put in more air or sink to the bottom, so the diver must carefully control how much air is in the BCD whenever their depth changes.
 Depth gauge, to know how deep they are and there may be a watch to tell the time or a dive computer to show how slowly they must come up to be safe from decompression sickness.  A safe dive depends on how long and how deep the diver goes, and how long it has been since the last dive.
Most divers wear a diving suit to keep warm. This is usually a wetsuit made from foam neprene rubber, but for colder water a dry suit can be used.
 Divers wear a mask to see through, because the human eye cannot focus properly in water.
 Swimfins are worn on the feet to swim better. 
 A snorkel can be used for breathing at the surface when swimming face down
Certification
Divers face dangers that can hurt or kill them if they don't know what to do.  They can use up all their air, or get decompression sickness or nitrogen narcosis.  A person must be trained to use the equipment and dive safely. When they show that they can dive safely they get a certification card.  The biggest organization for certifying divers is PADI - Professional Association of Diving Instructors - but there are many others, depending on the country.  Some tourist places have a short course without certification and then the instructor will lead the diver in a shallow dive, all in one day.

Because of special dangers, there are advanced classes for things like diving in or around underwater shipwrecks, cave diving, and deep diving (more than 60 feet or 18 meters).

Related pages
 freediving - Diving without scuba equipment (holding your breath).  Snorkeling equipment is often used in freediving.  No certification is needed but it can still be dangerous.

References

Diving
A capillary is a blood vessel. It does not have the muscular/elastic tissue of other blood vessels. It has a single celled wall to help substances be transported through organisms.
Capillaries are small, and smaller than any other blood vessels. They are about 5-10 μms big, connect arteries and venules, and enable the moving of water, oxygen, carbon dioxide, as well as many other nutrients and waste chemicals  between blood and surrounding tissues.

Anatomy 
Blood moves from the heart to arteries, which branch and narrow into smaller arteries, and then branch more into capillaries. After oxygen has been moved to the tissue, capillaries join and widen to become small veins and then widen more to become veins, which return blood to the heart.

The "capillary bed" is the network of capillaries supplying an organ. The more metabolically active the cells, the more capillaries it will require to supply nutrients and carry away waste products.
Special arteries connect between arterioles and venules and are important in bypassing the flow of blood through the capillaries. True capillaries come from mainly from metarterioles and provide movement between cells and the circulation. The width of 8 μm forces the red blood cells to partly fold into bullet-like shapes in order to bypass them in single file.

Precapillary muscles are rings of smooth muscles at the start of true capillaries that handle blood flow into true capillaries and control blood flow through a body part or area.

Physiology 

The capillary wall is a one-layer tissue so thin that gas and other items such as oxygen, water, proteins and fats can pass through them driven by pressure differences. Waste items such as carbon dioxide and urea can move back into the blood to be carried away for removal from the body.
The capillary bed usually moves no more than 25% of the amount of blood it could contain, although this amount can be increased through auto regulation by making the smooth muscle relax in the arterioles that lead to the capillary bed as well as metarterioles making themselves smaller.

The capillaries do not have this smooth muscle in their own wall, and so any change in their width is passive.  Any signaling molecules they release (such as endothelin for constriction and nitric oxide for dilation) act on the smooth muscle cells in the walls of nearby, larger vessels, e.g. arterioles.

Capillary's ability to move items can be increased by the release of certain cytokines, such as in an the body defending itself from germs.

Related pages
Alveolar-capillary barrier
Blood brain barrier
Capillary action
Hagen-Poiseuille equation

References

Other websites 
 

Blood vessels
Viriato Clemente da Cruz, an Angolan poet and politician, was born in 1928 in Kikuvo (Porto Amboim), Angola and died in Beijing, China on 13 June 1973.

He is considered one of the most important Angolan poets of his time. He wrote poems in Portuguese and Angolan languages. He took part in the fight to free Angola from Portuguese rulers.

Political work
He was educated in Luanda, the capital of Angola, which was then ruled by Portugal. As a young man in 1957 he went to Paris, where he met Mario Pinto de Andrade, another Angolan poet and politician, who helped with his political ideas. In the 1960s they helped create the group called the Popular Movement for the Liberation of Angola (MPLA—from the Portuguese name ).
The MPLA was in not in Angola at this time, but was first in Conakry (the capital of Guinea) and then later in Leopoldville, Congo (now Kinshasa the capital of the DRC). Viriato da Cruz became secretary-general of the MPLA. After some time he and others, did not agree with some people in the group and this led to fighting in the streets of Leopoldville.

Exiled in China
Viriato da Cruz went to Beijing, China in the 1960s because of the fighting in the MPLA. At first, the Chinese government welcomed him. He was well known because he had helped create the MPLA. The Chinese wanted Viriato da Cruz to help them bring Maoist socialism to Africa.

This was a big problem for Viriato and his family. His ideas were not the same as the Maoists. He thought that stronger countries can not bring a socialist revolution to other places. He was very brave and did not change his ideas. This was against the Chinese Maoist idea of world revolution.
Viriato da Cruz wanted to leave China and return to Africa, but the Chinese government would not let him go and they were not good to him. This may be because he could have made trouble for their work in Africa.

Last years of life
The last years of the life of Viriato da Cruz were unhappy and difficult. He was weak, without much food, and he died on 13 Jun 1973. His dead body was taken away in a military vehicle and his burial was without any ceremony.

Some Angolan people think that this was shocking, because Viriato da Cruz worked hard for Angola and was one of the leaders of the liberation from Portugal.

Principal books
Poems (1961). Among these poems, Namoro, Sô Santo and Makézu are well-known.

1928 births
1973 deaths
Poets
Angolan politicians
Mollusks are an important phylum of invertebrate animals. Most of them are marine animals, which means they live in the ocean. They have huge numbers in-shore, that is, in shallow water. They are the largest marine phylum, with about 85,000 living species, 23% of all named marine organisms. They also occur in freshwater and on land.

Mollusks are extremely varied: they have great diversity. That may be why there is no word in English for the phylum as a whole. "In an evolutionary sense, mollusks are plastic material". They have much more variety than their ancient rivals, the brachiopods.

Most molluscs have shells, but some groups do not: octopods, slugs, and the gastropods known as sea slugs.

Diversity 
Many mollusks also live in freshwater and terrestrial habitats. They are highly diverse, not just in size and in anatomical structure, but also in behaviour and in habitat.
The phylum is usually divided into 9 or 10 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish and octopus, are among the most neurologically advanced of all invertebrates: they have good brains and complex behaviours. Either the giant squid or the colossal squid is the largest known invertebrate species. The gastropods (snails and slugs) are by far the most numerous molluscs in terms of classified species, and account for 80% of the total. The scientific study of mollusks is called malacology.

Main features 
The three most universal features defining modern mollusks are:
 a mantle with a cavity used for breathing and excretion,
 the presence of a radula, and
 the structure of the nervous system.
Other than these things, mollusks have so much variety that many textbooks use a "hypothetical ancestral mollusk" to summarize them (see below). This has a single, "limpet-like" shell on top, which is made of proteins and chitin reinforced with calcium carbonate. It is secreted by a mantle covering the whole upper surface. The underside of the animal consists of a single muscular "foot".

The mollusk's feeding system starts with a rasping "tongue", the radula. The complex digestive system uses mucus and microscopic, muscle-powered "hairs" called cilia. The generalized mollusk has two paired nerve cords, or three in bivalves. The brain, in species that have one, circles the oesophagus. Most mollusks have eyes, and all have sensors to detect chemicals, vibrations, and touch. The simplest type of molluscan reproductive system relies on external fertilization, but more complex variations occur. All produce eggs, from which may emerge trochophore larvae, more complex veliger larvae, or miniature adults.
A striking feature of molluscs is the use of the same organ for multiple functions. For example, the heart and nephridia ("kidneys") are important parts of the reproductive system, as well as the circulatory and excretory systems. In bivalves, the gills both "breathe" and produce a water current in the mantle cavity: this is important for excretion and reproduction. In reproduction, molluscs may change gender to accommodate the other breeding partner.

Good evidence exists for the appearance of gastropods, cephalopods and bivalves in the Cambrian period, 541 to 485.4 million years ago (mya). Before that, the evolutionary history of molluscs' emergence from the ancestral Lophotrochozoa is still unclear.
Mollusk species can also represent hazards or pests for human activities. The bite of the blue-ringed octopus is often fatal, and that of Octopus apollyon causes inflammation that can last for over a month. Stings from a few species of large tropical cone shells can also kill: their venom have become important tools in neurological research. Schistosomiasis (also known as bilharzia, bilharziosis or snail fever) is transmitted to humans via water snail hosts, and affects about 200 million people. Snails and slugs can also be serious agricultural pests, and accidental or deliberate introduction of some snail species into new environments has seriously damaged some ecosystems.

A "generalized mollusk"
Because mollusks have so many different shapes, many textbooks start the subject of molluscan anatomy by describing what is called an archi-mollusc, hypothetical generalized mollusc, or hypothetical ancestral mollusc (HAM) to illustrate the most common features in the phylum. The picture is rather similar to modern monoplacophorans: some think it may resemble very early mollusks.

The generalized mollusk is bilaterally symmetrical and has a single, "limpet-like" shell on top. The shell is secreted by a mantle covering the upper surface. The underside consists of a single muscular "foot". The visceral mass, or visceropallium, is the soft, nonmuscular metabolic region of the mollusc. It contains the body organs.
Taxonomy 
Classes of molluscs:
 Aplacophora: molluscs: the living ones are shell-less
 Bivalvia: Most shellfish; clams, oysters, scallops, mussels
 Cephalopoda: Squid, Octopus
 Gastropoda: whelks, limpets, snails, slugs, Nudibranchs
 Helcionelloida: (see below)
 Monoplacophora: molluscs with a cap-like shell
 Polyplacophora: Chitons
 †Rostroconchia: an extinct group
 Scaphopoda: the tusk shells

Helcionelloida 
It has become clear that the fossil taxon Helcionelloida does not belong to the class Gastropoda. It is now a separate class in the Mollusca. Parkhaev (2006, 2007) created the class Helcionelloida, whose members were previously treated as "Paleozoic mollusks of uncertain systematic position" by Bouchet & Rocroi.

Uses 
 Many mollusks are eaten as food: clams, oysters, scallops, mussels, squid (calamari) and land snails (escargot)
 Oysters sometimes make pearls, which are valuable and used to make necklaces. Other shells are collected for their beauty and sometimes used to make jewelry.

References
A sponge is a member of the phylum Porifera. It is a simple animal with many cells, but no mouth, muscles, heart or brain. It is sessile: it cannot move from place to place the way most animals can. A sponge is an animal that grows in one spot like most plants do. Nevertheless, sponges are quite successful.

The basic body plan is a jelly-like layer sandwiched between two thin layers of cells. Their bodies are full of pores and channels allowing water to circulate through them. Most of them feed on bacteria and other microorganisms. A few of them eat tiny crustaceans.

There are more than 10,000 species of sponge. Most sponges live in the ocean. A few live in fresh water. All sponges take in water through pores (little holes) in their bodies. The water goes out through a big tube in the center. Most sponges filter (take out) little bits of food from the water going through their bodies. Animals that get food this way are called filter feeders.
Sponges are the oldest animals with fossil evidence (from ~635 million years ago).

What makes them different 

Sponges are simple animals. A few things make them different from other animals. 
 A living sponge can change the shape of its body. Most cells in its body can move around; a few cells can even change from one type of cell to another.
 Like cnidarians (jellyfish, etc.) and ctenophores (comb jellies), and unlike all other known metazoans, sponges' bodies are made of a non-living jelly-like mass sandwiched between two main layers of cells.
 Sponges have no nervous system. Their middle jelly-like layers have many different types of cells. Some types of cell in their outer layers may move into the middle layer and change their functions.
Sponges can deter predators by releasing a chemically active compound that can contain toxins and also affect organisms competing with them.
Different kinds of sponges 
There are four classes of sponges. The difference between these kinds is in how their skeleton is made.

 Demosponges is a class that contains most of the sponges. The sponges in this class make their skeleton from spongin. Spongin is a special protein. All the large sponges are in this order. 
 Bony sponges use calcium carbonate to make the skeleton. They are known as Calcarea. They are usually very small, only 3-4 inches in height. Of the about 15,000 sponges known, about 400 are Calcarea.
 Glass sponges use silicon dioxide to make their skeletons. They are sometimes called Hexactinellida. Most of these live very deep in the ocean. There are about 500 different kinds of glass sponges, in 17 different families. These sponges make for about 7% of all known sponges.
 Homoscleromorpha are a class which was part of the Demosponges. Actually, they are well separated from the demosponges.

Life functions
Life functions

Movement 
Sponges are sessile, they live in one place, where they are fixed to the ground. A few sponges can change their position, they can move at speeds of between 1 mm and 4 mm a day. They do this like amoebae. A few species can contract their whole bodies. Many can close their openings/holes.
A few species live in waters where there is very little food available. They have therefore changed, and became predators. They eat small crustaceans and other small animals. Most of these sponges belong to the family Cladorhizidae, but a few members of the Guitarridae and Esperiopsidae are also carnivores. In most cases little is known about how they actually capture prey. Some species are thought to use either sticky threads or hooked spicules. Most carnivorous sponges live in deep waters, up to , and the development of deep-ocean exploration techniques is expected to lead to the discovery of several more. However one species has been found in Mediterranean caves at depths of 17-23m alongside the more usual filter feeding sponges. The cave-dwelling predators capture crustaceans under  long by entangling them with fine threads, digest them by enveloping them with further threads over the course of a few days, and then return to their normal shape; there is no evidence that they use venom.
Most known carnivorous sponges have completely lost the water flow system and choanocytes. However the genus Chondrocladia uses a highly modified water flow system to inflate balloon-like structures that are used for capturing prey.

Reproduction in Sponges

Asexual reproduction 
Sponges usually reproduce when little pieces break off. If such a piece has the right types of cells it can grow to become a new sponge. A few sponges can also use budding. With budding a small sponge grows on the parent; when it is done growing, it simply falls off. When the conditions are bad, some sponges can also grow lumps of unspecialised cells. These will not develop until the conditions improve again. They can then either make a new sponge, or they can use the skeleton of the parent sponge (that died).
Sexual reproduction 
Most sponges reproduce sexually. They can make sperm cells that are released into the water. These are either captured by another sponge, and are then transported to the egg cells of the parent. This is known as viviparous. Both cells are joined to form larvae, which can swim off to find a good place to settle.

The other way, known as oviparous is that both sperm cells and egg cells are released into the water. These then combine outside the sponges.

Use as tools
Use as tools

By dolphins 
A report in 1997 described how bottlenose dolphins in Shark Bay used sponges as tools: A dolphin may attach a marine sponge to its rostrum (snoutlike projection). It is thought the sponge is used to protect the rostrum when the dolphin is looking for food in the sandy sea bottom but scientists have not confirmed this. The behaviour, known as sponging, has only been seen in this bay, and is almost exclusively shown by females. A study in 2005 concluded that mothers teach the behaviour to their daughters, and that all the sponge-users are closely related. This suggests that it is a fairly recent innovation. Dolphins also use sponges as an exfoliator, rubbing their skin against the sponge attached to the rock to get rid of their old/dry skin.

By people
By people 

The calcium carbonate or silica spicules of most sponges make them too rough for most uses, but two genera, Hippospongia and Spongia, have soft, entirely fibrous skeletons. Early Europeans used soft sponges for many purposes including padding for helmets, portable drinking utensils and municipal water filters. Until synthetic sponges were invented, they were also used as cleaning tools, for painting, and as contraceptives. In the 20th century, overfishing is a problem. This has caused the animals, as well as the industry behind it to be close to extinction.

Many objects with sponge-like textures are now made of substances that do not come from poriferans. Synthetic "sponges" include personal and household cleaning tools; breast implants; contraceptive sponges.

The luffa "sponge", also spelled loofah, which is commonly sold for use in the kitchen or the bath, is not derived from an animal but from the fibrous "skeleton" of a gourd (Cucurbitaceae).

Gallery

References
References 

 
Basic English 850 words
A kibibyte (KiB) is a unit of information or computer storage. A kibibyte is 1024 bytes, 1024 kibibytes are a mebibyte.

Related pages
 Kilobyte
 Mebibyte
 Gibibyte
 Tebibyte

Units of information
Tomb Raider: The Cradle of Life is a 2003 action movie from Paramount Pictures. It is the second movie to star Angelina Jolie as the title character from the Tomb Raider video games.

2003 movies
American adventure movies
English-language movies
Paramount movies
Movies based on video games
2003 adventure movies
The amplitude or peak amplitude of a wave is a measure of how big its oscillation is.

Amplitudes are always measured as positive numbers (for example: 3.5, 1, 120) and are never negative (for example: -3.5, -1, -120). That's because distance can only be greater than zero or equal to zero; negative distance does not exist.

The distance from the top of one peak to the bottom of another is called peak-to-peak amplitude. Another way to describe peak-to-peak amplitude is to say that it is the distance between the maximum positive value and the maximum negative value of a wave is the maximum displacement of a wave from an equilibrium position

Related pages

 Waves and their properties:
 Frequency
 Period
 Wavelength
 Amplitude modulation
 Vibration control
 Vibration isolation

Wave physics
Mechanical vibrations
Ska is a popular music from Jamaica that began in the 1950s. Ska music that was first played at a slower tempo then became reggae in the late 1960s.

Ska music bands include singers, electric guitars, electric bass guitar, piano, organ, saxophone, trumpet, and trombone. In ska, the electric guitar and piano normally play short chords on the off-beat. If you go "one and two and three and four", the off-beat is the "and". 

A ska singer does a style of Jamaican singing called "toasting." When a singer is "toasting", they make sounds, repeat words, invent rhymes, and shout into the microphone. The Jamaican "toasting" style of singing and talking was adapted into rap music in the 1980s.
How Ska musicians dress 
Musicians who play ska dress in hats and suits. Many ska bands wear clothes with a chessboard pattern of black and white squares. Doc Martens are a common type of shoe. This pattern symbolizes the way that ska music mixes of Black and White musicans and styles of music.There was a British genre of ska-punk influenced by The Specials, Madness and the English Beat, that began to dress in kilts.

1980s Ska Revival 
Even though ska was developed in the 1950s, it became popular again in the 1980s in Britain. In the 1980s, ska bands such as The Specials, The Selecter, The Beat, UB40 and Madness played ska music.

1990s Ska mixed with punk rock 
In the 1990s, some bands mixed ska music with Punk rock to make ska-punk. This kind of ska music is from England and the United States. Some pop-punk bands from the 1990s mixed pop-punk with ska-punk.

Ska bands and singers
No Doubt
 The Mighty Mighty Bosstones
 The Specials
 The Selecter (British band)
 The Beat (British band)
 Madness (English band)
 Sublime
 Prince Buster (Jamaican singer)
 Desmond Dekker (Jamaican singer)
 The Bodysnatchers (female British band)
 The Skatalites (Jamaican band)
 Streetlight Manifesto (American band)
 The Toasters (American band)
 The Slackers (New York City band)
 Rusted Root (American band)
 Westbound Train (Boston band)
 Reel Big Fish
 Suburban Legends (American band)
 Catch 22 (American band)
 Less Than Jake
 Lord Creator (Jamaican singer)
 The King Blues (British band)

Related pages 
 Scat singing

References

Other websites 
 Going to a Ska Show? Here's What to Wear (LA Weekly)

Music genres
British culture
1950s establishments in North America
Jamaican culture
The Braille system is a way of writing things. It is named after Louis Braille, the French man who invented it. The system is used by blind people to read and write. The Braille system uses a set of raised bumps or dots that can be felt with a finger.  Each set of dots is a character in an alphabet, and the numbers and some punctuation.

Before Braille 
Louis Braille was not the first person to think about how to let the blind read and write. In the 17th century the Italian Jesuit Francesco Lana thought about different systems of writing for the blind. He invented a system of dashes that could be felt.
Charles Barbier used a similar system, because Napoleon wanted a code that soldiers could use to exchange messages silently and without light at night. Barbier called it night writing. Night writing uses two columns of six dots. It uses phonemes (separate sounds), not letters.  Barbier's system was too hard for soldiers to learn, and the military did not use it.  From the year 1821, he started to test his system in the school Haüy had founded. There it became very successful. Even though the system was difficult to learn, it did help the blind to read better than earlier systems. Barbier had understood that it was better to use a system that used dots over one that used lines.
Barbier met Braille when he visited the National Institute of the Blind. Braille saw the biggest problem of the code: The human finger cannot feel the whole symbol at one time. This makes it impossible to move rapidly from one symbol to the next. Braille's change was to use a 6 dot cell — the braille system — which completely changed how the blind would read and write.

The Braille alphabet 
Braille can be seen as the world's first binary way of character encoding. The system as originally invented by Braille has two parts
 Defining the letters of the French language with tuples (groups) of six bits or "dots".
 Showing these six-bit characters as raised dots in Braille cell.

Braille is used with different languages today. In each language, the letters are encoded differently, depending on the alphabet. The list of codes is known as braille code, or code page. There are also different braille codes in use for special purposes, like writing shorthand, mathematics or music.
To make it possible to read faster, certain transcriptions of Braille use shortened words, or contractions. This is known as Grade 2 Braille.

The Braille cell 

Braille uses cells of six raised dots, in two columns of three dots. The dot positions on the left are numbered one, to three, the ones on the right four to six, as shown in the picture.

Each symbol is coded with certain dots present, and others absent. The dots are approximately 0.02 inches (0.5 mm) high; inside the cell, the dots are about 0.1 inches (2.5 mm) apart. The space between the dots of two cells is about 0.15 inches (3.75 mm) horizontally and 0.2 inches (5 mm) vertically. A standard braille page is 11 inches by 11 inches and typically has between forty and forty-two braille cells per line and twenty-five lines.
Encoding 
As first made by Louis Braille, the first group of characters, using just the top 4 dots of the braille cell, represents letters "a" through "j" (this group of ten characters is called a decade).  Dot 3 (bottom left) is added to each of the "a" through "j" symbols to give letters "k" through "t".  Both of the bottom dots (dots 3 and 6) are added to the first decade to give letters "u", "v", "x", "y", and "z".  The letter "w" is left out of this group because French did not use the letter "w" when Louis Braille made his alphabet.  The fifth decade is the same as the first decade, but shifted down by a row (dots 1 and 4 are blank).

English braille has codes for the letters and some punctuation, and some double letter signs and word signs directly, but capitalization and numbers need a prefix symbol. In practice, braille produced in the United Kingdom does not use capital letters.
There are braille codes for representing shorthand (produced on a machine which embosses a paper tape) and for representing mathematics (Nemeth Braille) and musical notation (braille music).

Writing braille 
Braille can be made using a "slate" and a "stylus" in which each dot is created from the back of the page, writing in mirror image, by hand, or it may be produced on a special braille typewriter or "Perkins Brailler", or produced by a braille embosser attached to a computer.  It may also be made using a refreshable braille display.
Extensions 
The six bit braille code is very limited, it only allows 64 different possible combinations. This means that many things need more than one braille character to be coded. One example for this is how numbers are coded in English braille: First there is a symbol that says the next symbol is a number, and then there is the symbol for the number.  The symbol for number is usually given only once; every symbol that follows is treated as a number, until there is a space.
Braille has been extended to an 8 dot code, particularly for use with braille embossers and refreshable braille displays.  In 8 dot braille the added dots are added at the bottom of the cell, giving a cell 4 dots high by 2 dots wide.  The additional dots are called 7 (for the lower-left dot) and 8 (for the lower-right dot).  8-dot braille has the advantages that capital and lower cases of the letters are directly coded in the cell, a capital letter does not need two cells. All the printable ASCII characters can be represented in a single cell, and all 256 possible combinations of 8 bits are encoded by the Unicode standard.  Braille with six dots is frequently stored as braille ASCII.

Braille transcription

Grade 1 braille 

It is possible to transcribe braille by replacing each letter with the braille code for the letter. This is usually known as Grade 1 Braille. Grade 1 braille is mostly used by beginners.