cahya/wikipedia-simple-en huggingface dataset:
Potato gun

A potato gun or Potato cannon is a type of cannon that uses combustion or air pressure to fire a projectile. They are called potato guns because potatoes are a commonly used projectile.

There are two main types of potato guns. Combustion guns use a flammable fuel and igniter to move an object. Another type uses compressed air. Potato guns are usually built of PVC or ABS (a type of plastic) piping.

Combustion potato guns

Parts
Combustion potato guns have 4 parts. These are the barrel, combustion chamber, a cap, and an igniter.
Barrel: The barrel is the part of the gun which the projectile is fired from. It is usually a smaller diameter than the combustion chamber.
Combustion chamber: This is the part where the fuel is put. The igniter is also in the combustion chamber.
Igniter - A device which set the flammable fuel on fire. Electric grill igniters and magnesium latern lighters are often used. This could be called a trigger.
Cap - The cap is connected to the combustion chamber. It is removed to add fuel and replaced when the gun is fired.

Operation
the operator will put a projectile into the barrel. A ramrod is often used to push it all the way down to the end of the barrel. The projectile must fit tightly into the barrel so that the pressure of the expoding fuel is strong enough to move it. This is why potatoes are often used. With a large potato, the unneeded part of potato would be cut off when the potato is forced into the barrel. This creates a projectile that is almost the exact size as the inside of the barrel.
The cap is removed and a flammable fuel is put in the combustion chamber. Aerosol hairspray is a popular fuel because it ignites easily. Once fuel is added, the cap is replaced.
The cannon is pointed at its target and the igniter triggered. This causes the fuel to burn. The rapidly expanding gasses force the projectile out of the end of the barrel.

A potato cannon can move a 2" diameter potato projectile over 100 yards at a speed of 40 mph. This makes potato guns dangerous.

Air powered potato guns

Parts
 A source of compressed air (such as air compressor) 
 Barrel: 
 Air reservoir - This is where compressed air is held before being released. It serves the same job as the combustion chamber in the other version.
Release - a type of valve. It is placed between the air reservoir and the barrel. This could be called a trigger.

Operation
the operator will put a projectile into the barrel. A ramrod is often used to push it all the way down to the end of the barrel. The projectile must fit tightly into the barrel so that the pressure of the air is strong enough to move it.
The air reservoir is filled by connecting it to a compressed air source. The release be closed at this time.
the cannon is aimed and the release is pulled. This causes the compressed air to rush into the barrel. The high pressure forces the projectile out of the end of the barrel.

A air powered potato cannon is much stronger than a combustion cannon. A combustion potato gun will launch projectiles at a pressure of about 10-20 psi. Air powered guns often use pressures over 100 psi.

Other websites 
Instructables.com
Howstuffworks.com

Weapons
Parsec

A parsec is a unit of distance used in astronomy. It is the distance that light travels in 3.26 years, or just under 31 trillion kilometres (about 19 trillion miles). This is from the definition: a parsec is the distance from the Sun to an object which has a parallax angle of one arcsecond.

Distances measured in fractions of a parsec usually involve objects within the same star system. 

Surveying provides an everyday example of parallax. Go outside and look at a distant object. Hold your hand out with one finger raised and close one eye. Line up your finger so it covers the object from view. Then close that eye and open the other without moving your arm. Now, move your finger to block that eye's line of sight. The two positions your finger was at  can be used to find the distance from the object. This is what a survey crew does to figure out land plot boundaries. The mathematical technique used in the calculation is trigonometry. A parsec is so large that if you could see that far that you would be looking in to the past. You are looking 3.26 years in the past because it takes 3.26 years for the light to come from a parsec away.

Astronomical distances
Units of length
Deterministic algorithm

A deterministic algorithm is a computer science term. Functions are deterministic when if you never change what you give it (the input), that what you get out (the output) never changes either; and you can do this as many times as you want.

Algorithms
Puget Sound

Puget Sound is a sound in Western Washington. It is a large area of salt water that is partially cut off from the rest of the Pacific Ocean. Many of Washington's cities, like Seattle and Tacoma are next to the sound. Many boats travel on the sound. Some of the boats are Ferries which take people from the main part of Washington to the islands in the sound. Many boats come from across the ocean from places like Japan, and China to trade in Washington.

Geography of Seattle, Washington
Bodies of water of the United States
The Legacy of Heorot

The Legacy of Heorot is a science fiction novel written in 1987 by Larry Niven, Jerry Pournelle and Steven Barnes.

This is the first book in the Heorot series. It is about a human space colony at the star Tau Ceti.

Plot Summary 

Hundreds of years in the future, people travel to the star Tau Ceti. It takes 100 years to fly there. To live that long the people go to sleep and freeze each other. When they get there they unfreeze, but some people do not wake up. Some people wake up but are not as smart as they were.

They land on the fourth planet from the sun and build a town on a big island. Everything is peaceful until they are attacked by a large animal. The animal is like a cross between a frog and an alligator. It is big but also very fast and smart. They call it a Grendel. The Grendel kills several people but then it is killed.

The people get very scared and build fences, land mines, and guns. After a while they get less scared and think that the Grendel they killed was the only one. They build boats and get brave. Then another bigger Grendel kills some of the people in the boats. The People trap and kill this Grendel.

The People get really mad. They find out that Grendels have to stay near water because when a Grendel moves fast it makes a lot of heat. If it does not cool off it will die. They go all around the island and kill all the Grendels. This makes them very happy.

They feel safe and travel all around the island. They notice that the alien fish are big now. They think that without the Grendels around there will be lots of fish to eat. This makes them happy.

Everything is good until the fish get very big. When they get big enough they grow legs, breath air, and move very fast. The fish are baby Grendels. Now instead of a few big Grendels there are thousands of small ones.

Some people escape to the space ship. But, other stay to defend the town. They use the electric fences and land mines and guns to kill the little Grendels. After awhile the town gets too damaged to protect anymore. The people run away to a cave on a mountain. The Grendels follow them up a river and attack the cave. The people use kerosene to burn the Grendels. Also, they knock big rocks down onto them. After enough Grendels get killed, the other Grendels learn to run away instead of just attack. The people win.

Over time the people hunt down all the new Grendels and all the alien fish. Finally they are safe.

1987 books
Science fiction books
Horror novels
Xkcd

xkcd is a comic strip on the Internet. American cartoonist Randall Munroe draws and writes the comic. The comic is drawn in boxes. It is one of the most popular comics on the Internet. It is "a webcomic of romance, sarcasm, math and language". Sometimes, the readers of the comic act out things that Munroe puts in his comics. There are also messages in all comics that show up when moused over. In October 2007, the comic was viewed about 60 million times. The comic has won many awards. The name "xkcd" does not mean anything and was just made so people do not say it as a word.  there are more than 2400 different xkcd comics.

In November 2015, Munroe wrote a book named Thing Explainer,  using the same stick figure drawings from his comic. The book is about how things work, and is written in Simple English. It uses only one thousand different simple words. The idea for it came from a comic "Up goer Five" which is about the Saturn V rocket.

References 

Notes

Other websites 
 Main site
 A site for explaining the comics of xkcd

Webcomics
Lamar Advertising

Lamar Advertising is an outdoor advertising company. The company was founded in the year 1902. The company's headquarters is in Baton Rouge, Louisiana. Lamar operates in the United States of America, Canada and Puerto Rico. They sell advertising on billboards. They sell advertising on buses. They have digital billboards.

Departments 
Lamar has many parts called "departments". This is common in most companies. Here are some parts of Lamar.
 IT (it stands for Information Technology)
 Human Resources
 National Sales
 Plants (this is what Lamar calls its offices)

Other websites 
 Lamar

1902 establishments in the United States
Baton Rouge, Louisiana
Companies based in Louisiana
Advertising companies
Carl Pomerance

Carl Pomerance (born 1944, Joplin, Missouri) is a mathematician. Most of his work has been in number theory. He helped find the quadratic sieve which is a way to factor big numbers very fast. He teaches at Dartmouth College. He has Erdős number 1.

References

1944 births
Living people

Scientists from Missouri
People from Joplin, Missouri
American number theorists
Carnegie Mellon University

Carnegie Mellon University is a research university. It is in Pittsburgh, Pennsylvania. It is known for research in computer science. It is ranked #1 in the United States for computer science.

References

Association of American Universities
Colleges and universities in Pennsylvania
1900 establishments in the United States
Puzzle Quest: Challenge of the Warlords

Puzzle Quest: Challenge of the Warlords is an adventure puzzle video game made by Infinite Interactive and published by D3 Publisher in 2007.

Puzzle video games
2007 video games
Josh Groban

Joshua Winslow "Josh" Groban (born February 27, 1981) is an American singer, songwriter, musician, actor, and record producer. He has won awards.

Early life
Groban was born in Los Angeles, California. His parents are Lindy (nee Johnston), a school teacher, and Jack Groban, a businessman. He has a younger brother, Chris, who shares the same birthday, but four years younger. Groban's father was born Jewish, and is a descendant of Russian and Polish immigrants; he converted from Judaism to Christianity when marrying Groban's mother. Groban's mother's ancestry includes Norwegian (from Toten), German, and English; one of her own grandfathers had been Jewish. Groban's parents are Episcopalians.

Groban debuted as a singer in the seventh grade.

References

1981 births
Living people
American songwriters
American musicians
Singers from Los Angeles
Grammy Award winners
Slip End

Slip End is a medium sized village in South Bedfordshire, England. There is one school in the village - Slip End Lower School serving the community and surrounding areas from Reception to Year 4 Children.

There are two community venues in the village:

The Village Hall is at the centre of the village.
Peter Edwards Hall and playing fields is adjacent to the Church, St Andrews, next to the M1 motorway.

Other websites 
Slip End official website

Villages in Bedfordshire
Network bridge

A network bridge is a device which connects two parts of a network together at the data link layer (layer 2 of the OSI model). 

Network bridges work similarly to network switches, but the traffic is managed differently. A bridge will only send traffic from one side to the other if it is going to a destination on the other side. This is different to a layer 1 switch which sends all traffic from either side. Sometimes network bridges are called layer 2 switches. 

Since they need to look at the contents of the traffic going into them, they are much more complicated than a hub or repeater.

How is it different to a switch? 
Network Switches and Bridges are both Layer 2 devices. They  operate at the Data Link Layer (Layer 2) of the OSI Reference Model. Network Switches and Bridges have many similarities and similar  function. But Switches are considered as superior devices than bridges.

Following are the major differences between  network switches and bridges.

• Packet forwarding in Bridges are performed using software. Packet forwarding in Switches are performed using ASICs (Application Specific Integrated Circuits).

• Switches operate comparatively higher speeds that Bridges.

• Method of switching of a Bridge is store and forward. Method  of switching of a Switch can be store and forward, cut-through or fragment-free.

• Normally a Switch has more ports than a Bridge.

• Bridges can operate only in half duplex mode, but a Switch can operate both in half duplex or full duplex mode.

• Both Bridge and Switch has one collision domain per port, but switches have one broadcast domain per VLAN.

• Switches support full-duplex Local Area Network (LAN) communication.

Related pages
 Shortest Path Bridging

Computer networking
Alex Fraser (scientist)

Alex Fraser (1923–2002) was an Australian computer scientist. He helped develop the modelling of population genetics on computers.  His work made an impact on how we view evolutionary systems today.

1923 births
2002 deaths
Australian scientists
Scientists from London
Computer scientists
Great Northern War

The Great Northern War (1700–1721), was a war fought between Sweden and the coalition of Russia, Saxony, Poland, and Denmark-Norway. In 1715 Prussia and Hannover joined the war against Sweden. The King of Hannover was also King George II of Great Britain.

After the coalition attacked them, Sweden invaded Russia in 1709 which was not a good idea. The Russian Army retreated  so the Swedish Army had to chase them. When winter came it was the coldest winter that Europe had had in a hundred years and half of the Swedish soldiers died in the cold. Eventually the Swedish army caught up to the Russian army and they had a battle, called the battle of Poltava. Russia won the battle but most of the Swedish soldiers, including king Charles XII of Sweden, escaped and went to the Ottoman Empire. Peter, the king of Russia, didn't like this so he declared war on the Ottoman Empire.  He lost and had to give the town of Azov back to the Ottomans.

Charles XII left the Ottoman Empire in 1714 and went to Stralsund in Pomerania which was owned by Sweden at the time but was under siege.  Charles escaped back to Sweden just before the people in Stralsund surrendered. Then he invaded Norway (which was owned by Denmark at the time.) and was shot and killed there. With their king gone, the Swedish soldiers left Norway and went back to Sweden. On the way back many soldiers died.

When all that was happening Russia had been invading Sweden. Russia conquered  Estonia, Livonia and Ingria. By the time the remaining soldiers had come back from Norway, Russia had completely conquered Finland. Sweden still didn't want peace though, because they would have to give lots of land to Russia. Russia used a newly made fleet of ships to attack and raid the Swedish Coast and Sweden would still not give up.  Eventually the Russian and Swedish ships came together in the Battle of Grengam. Both sides thought they had won the battle so no treaty was signed until the Russians continued using their boats to damage the Swedish coast. Finally Sweden gave up in 1721. Sweden had made peace with Denmark in 1720 and in 1721 Sweden signed the treaty of Nystad.

Treaties 
In the Treaty of Nystad Sweden had to give land to other countries. Sweden had to give Estonia, Livonia and Ingria to Russia but could keep Finland. Sweden also signed other treaties. These were the treaty of Stockholm where Sweden gave Prussia Swedish Pomerania and the treaty of Fredericksborg where Sweden had to pay Denmark-Norway money for the damage the war had done.

This war was significant because it allowed Russia to become the dominant power in Northeastern Europe, instead of Sweden.

Wars involving Russia
CentOS

CentOS is a distribution (or distro) of Linux that is made to be similar to Red Hat. It was first made because the company that made Red Hat stopped making it free. Now, many people work on CentOS, and many more people use it on their computers. Often, CentOS is used on servers (computers which provide services to people or other computers) because it is stable (does not break often) and can be installed (put on a computer) in not much time, compared to other distributions such as Gentoo. On December 8th 2020, The CentOS Project announced the end of CentOS as it was previously known and announced CentOS Stream. AlmaLinux among others now provide 1:1 binary compatible releases with RHEL and the original CentOS. The original CentOS will reach end of life December 2021.

Other websites 
 Official website

Linux distributions
David Gilmour

David Jon Gilmour CBE (born 6 March 1946) is an English musician, record producer, songwriter. He is most famous for being a guitarist, singer and songwriter in the rock band Pink Floyd. Along with being in Pink Floyd, he has worked as a record producer for other musicians. Gilmour has also recorded and released albums as a solo performer.

Gilmour has always been active with many different charities. He was appointed CBE in 2003 for services to both music and for his charity work.

In 1996, Gilmour was inducted into the Rock and Roll Hall of Fame as a member of Pink Floyd.

In 2003, Gilmour was listed at number 82 in Rolling Stone Magazine's list of the "100 Greatest Guitarists of All Time" 

 Discography 
 David Gilmour (1978)
 About Face (1984)
 On an Island (2006)
 Live in Gdańsk (2008)
 Rattle That Lock (2015)
 Live at Pompeii'' (2017)

Notes 

1946 births
Living people
Commanders of the Order of the British Empire
English guitarists
English rock musicians
English singer-songwriters
Musicians from Cambridge
Pink Floyd
Thermal conductivity

Thermal conductivity is the ability of a material to conduct heat. Metals are good at heat conduction. The thermal conductivity of a material is a defining property that aids in the development of effective heating/cooling technologies. A value for thermal conductivity can be determined by measuring the rate at which heat can pass through a material. 

Thermal resistivity is the opposite of thermal conductivity. This means not conducting heat much. Materials with high resistivity are called "thermal insulators" and are used in clothing, thermoses, home insulation, and cars to keep people warm or in refrigerators, freezers, and thermoses to keep things cold. 

Thermal conductivity is often represented by the Greek letter "kappa", .  The units of thermal conductivity are watts per meter-kelvin.  Watts are a measure of power, meters are a measure of length, and kelvins are a measure of temperature.  From the units, we can see that thermal conductivity is a measure of how much power moves through a distance due to a temperature difference.

Some great thermal insulators are:
Vacuum, Aerogel, Polyurethane

Some great thermal conductors are:
Silver, Copper, Diamond

Silver is one of the most thermally conductive materials (and is relatively common), and because of this there are some cool experiments you can do with silver that show extremely well how thermal conduction works.

One example is when you put 2 spoons in boiling water, one spoon is steel and the other is silver. When you take the spoons out of the boiling water, the silver spoon is hotter than the steel spoon. The reason for this is that silver conducts heat better than steel. The silver spoon will also cool off faster because of this, as it is better at releasing heat.

Another example of silver's thermal conductivity is to put different materials on ice cubes.  An iron washer will just sit on the ice and slowly become colder.  A copper penny will melt through the ice cube and become colder faster.  A silver coin, spoon, or ring on the ice cube will sink into it almost as though the ice cube were made of thick syrup, and the silver will become ice cold almost instantly.  Again, this is because the silver is really good at drawing heat from the air and giving it to the ice cube.  Copper is also good at this, but not as much as silver.

Thermodynamics
Hydride

A hydride is a compound with hydrogen bonded to other elements. Except for a few of the Noble gases, all of the elements in the periodic table can form hydrides. The properties of hydrides can be very different, but some of the hydrides have similar properties. 

Metallic hydrides: compounds with ionic bonding. They are very reactive, making them difficult to dissolve. Most alkali metals and alkaline earth metals form ionic hydrides.

Metallic or Interstitial hydrides: These have metallic properties like good electrical conductivity and thermal conductivity. They are called interstitial because hydrogen can enter the metallic lattice (framework of metal atoms). Metallic hydrides are mostly formed from the metals in the groups 3 to 5 of the periodic table. Some of these are used in the nickel metal-hydride battery.

Covalent hydrides: These have covalent bonds between hydrogen and the other element. Most of the p-block elements form covalent hydrides. Many of these hydrides are unstable in air or water or when heated. Hydrocarbons are the hydrides of carbon, ammonia is a hydride of nitrogen, and water is a hydride of oxygen.

References

Chemistry
Horse the Band

Horse the Band is an American hardcore rock band from Lake Forest, California that was started in 1999. They are famous for using video-game style music in their songs.

Members

Current 
 Nathan Winneke - vocals (2003-present)
 David Isen - guitars, (1999-present)
 Erik Engstrom - keyboard (1999-present)
 Daniel Pouliot - drums, (2008-present)

Former 
 Dashiell Han Arkenstone- bass (2005-2008)
 Eli Green – drums (2005-2006)
 Andy Stokes – bass (2001-2005) 
 Jason Karuza – drums, (1999-2003)
 Christopher Prophet - drums, (2007-2008)
 Adam Crook – vocals (1999-2003)

Discography

Albums 
 Secret Rhythm of the Universe (2001)
 R. Borlax (2003, Pluto Records)
 The Mechanical Hand (2005, Combat Records; re-release, 2007, Koch Records)
 A Natural Death (2007, Koch Records)
 Desperate Living (2009, Vagrant Records)

EPs 
 I Am a Small Wooden Statue on a Patch of Crabgrass Next to a Dried Up Riverbed (2001)
 Beautiful Songs by Men (2002)
 Pizza (2006, Combat Records / LIF Records)

DVDs 
 The Effing 69 World Tour tour footage (2004)

Demos 
 Scabies, The Kangarooster, and You (1999)
Offa of Mercia

Offa was the King of Mercia from 757 until his death in July 796. 
Many historians regard Offa as the most powerful Anglo-Saxon king before Alfred the Great. Offa died in 796 and was succeeded by his son, Ecgfrith, who reigned for less than five months before Coenwulf of Mercia became king.

King of Mercia 

Offa was the son of Thingfrith, a descendant of Eowa of Mercia. Eowa was a king of Mercia who ruled along with his more famous brother Penda of Mercia. In 757 the king of Mercia,Athelbald, was murdered. There was a short civil war between others claiming the throne. An ealdorman named Beornred seized the throne of Mercia but Offa drove him out of Mercia and became king himself that same year. The alliances Athelbald had formed fell apart when Offa came to power. Offa had very little power outside of Mercia for the first several years of his reign.

Bretwalda (overlord) 
  
The Anglo-Saxon Chronicle makes no mention of Offa for the years between 757—777. No Mercian chronicles from this time period have survived. Charters are the only records that give any idea of Offa's power outside of Mercia. But he proved to be ruthless, bold and creative in bringing Kent, Sussex and Essex under his control. Aethelbert the king of Kent was apparently under Offa's influence before he died in 762. In 794 another Aethelbert, a king in East Anglia was beheaded at Offa's command. When Egbert of Wessex made a bid for the throne of Wessex in 786 Offa had him banished from England. He made Beorhtric king of Wessex instead. Egbert was welcomed at the court of Charlemagne for at least three years. In charters Offa issued in Kent, East Anglia, Sussex and Middlesex he simply used the style Rex Merciorum (Latin for king of Mercia). Only in three church charters does he expand his title to indicate he is overlord of all of England. 
   
Offa had diplomatic relations with Charlemagne. He was one of the few Anglo-Saxon monarchs to have dealings with continental rulers. Letters and presents were exchanged. But when Offa sought a marriage of his son to one of Charlemagne's daughters, relations were quickly cut off. Charlemagne had all Frankish ports closed to British ships. Offa, very involved in church affairs, presided over church councils personally in 786-7. In 787 he convinced the pope to create the position of archbishop of Lichfield in Mercia. He wanted his own archbishop who was closer at hand than the Archbishop of Canterbury. He reorganized the defenses of his kingdom. One of these defenses, Offa's Dyke was a massive earthworks between Mercia and the Welsh kingdoms to the west. Offa died in 796. His son, Ecgfrith, lasted only 141 days as king. Mercia was never again as powerful as it was during Offa's reign.

Notes

References 

Kings and queens
Year of birth unknown
796 deaths
Kings and Queens of Mercia
Face (professional wrestling)

In professional wrestling, a face is a good guy. 

A face should not cheat and most will not use weapons. They often try to make the crowd happy and excited. 

Often, a face will fight a heel (bad guy), so the crowd will cheer the face and boo the heel.

Professional wrestling

de:Liste von Wrestling-Begriffen#F
Fagaceae

The family Fagaceae, also called beech family, is a family of flowering plants. It comprises about 900 species of both evergreen and deciduous trees and shrubs, which are characterized by alternate simple leaves with pinnate venation, unisexual flowers in the form of catkins, and fruit in the form of nuts. 

Fagales
Heat sink

A heat sink is an object that cools another part that is too hot. It works with a CPU fan to do this. The heat sink is in contact with the part that should be cooled. It takes heat away and dissipates it, for example into the air around it.

Heat sinks are found in most computers. The chips inside a computer can get very hot. Therefore, they need to be cooled, so that they don't break. This is usually done with a heat sink. Heat sinks are also found in most high fidelity audio amplifiers.

Computer hardware

pt:Dissipador
Haka

The haka (; plural haka, in both Māori and English) is a ritual dance of the Maori, the native people of New Zealand. Sometimes, a haka is performed to excite friends and to scare enemies. In peace time, a haka is performed as a challenge. 

A haka can include:
voice (chanting)
feet (stamping and leaping)
hand (slapping, waving and clapping)
eyes (rolling)
tongue (poking out)

There are many different haka. Each tells a story. The most famous haka is Ka Mate. The Ka Mate haka is performed by many New Zealand sports teams before games. Another famous haka is 'Kapo O Pango' which is performed by New Zealand's rugby union team. This team is called the All Blacks. 

Women are not usually allowed to perform haka. Instead, they sing and chant in support.

References

New Zealand
War
Crisis on Infinite Earths

Crisis on Infinite Earths was a story told in American comic books in the year 1985. It lasted for 12 issues. Marv Wolfman wrote it and George Pérez drew it. It changed much about the history of the DC Universe, and allowed the editors of DC Comics to simplify  their then 55 year old history.

Comic books
American magazines
DC Comics
Magazines published in New York City
Four-stroke engine

The four-stroke engine is an internal combustion engine. The four strokes are:

Related pages
 Two-stroke engine

Motors
Pecan

The pecan (Carya illinoinensis) is a species of hickory nut, native to south-central North America, in the United States from southern Iowa, Illinois and Indiana east to western Kentucky, North Carolina and western Tennessee, south through Georgia, Alabama, Mississippi, Louisiana, Texas, Oklahoma and Arkansas; and in Mexico from Coahuila south to Jalisco and Veracruz.

"Pecan" is from an Algonquian word, meaning a nut requiring a stone to crack.

Pecans are often used in cooking in the Southern United States. A common dessert there is pecan pie.

References

Fagales
Edible nuts and seeds
Plants of North America
Tariff

A tariff is a tax charged on goods as they pass between one country and another. A tariff can be placed on goods being brought into the country (imports), and goods being exported from the country to another. It is usually done to make money for the government. It may also be done for protectionism. Protectionism makes it easier for local products to sell by making products from foreign countries more expensive.

Often, one government will have an agreement with another not to place any tariffs on goods that are traded between them. This kind of agreement is called free trade.

Related pages 
 Customs
 Indirect tax
 International trade

References 
 

Taxation
German Confederation

The German Confederation replaced the Holy Roman Empire in Central Europe. After the Holy Roman Empire fell, Germany had fallen into over 300 different small kingdoms. In 1815, the Congress of Vienna decided that these weak kingdoms were not strong enough to keep France from trying to take them over, which it had already done once under Napoleon. So the Congress combined all those little countries into 39 larger countries, which were still very small compared to the powerful countries of Europe. 

The problem was that the Congress did not want to make them too strong, or they'd start taking over other countries. So they put the 39 countries into a confederation which meant that they were all separate countries, but they agreed to help defend each other, and in some ways acted like one big country. The Confederation would not be strong enough to attack another country; only strong enough to preserve the European balance of power. 

The German Confederation lasted until 1866, when the members fought each other. The winners formed a new North German Confederation. In 1871 after winning the Franco-Prussian War, Otto von Bismarck, chancellor of Prussia, combined all the countries of Germany into the German Empire.

19th century in Austria
19th century in Germany
Former German countries
1815 establishments in Europe
1866 disestablishments
1860s disestablishments in Europe
WrestleMania XXVI

WrestleMania XXIV is the twenty-sixth yearly WrestleMania professional wrestling pay-per-view event put on by World Wrestling Entertainment (WWE). It took place on March 28th, 2010 at the University of Phoenix Stadium in Glendale, Arizona.

Matches

Production
Global Spectrum, University of Phoenix Stadium's operator, had worked in past years with World Wrestling Entertainment (WWE) to get the event to its venue. On January 18, 2008, Global Spectrum publicly announced that it wants to hold WrestleMania in 2010. The event became more widely known weeks prior when a photo of Wayne Gretzky wearing a shirt showing the event was seen in the Swedish newspaper Expressen. A press conference happened on February 24, 2009 at the University of Phoenix Stadium to officially tell people about the event for Glendale, Arizona at the University of Phoenix Stadium; this event is the first time WrestleMania would happen in the state of Arizona. Tickets for the event went on sale November 7, 2009 at 10:00am MST. Advertisements telling people about the date tickets would go on sale used the song "Welcome to the World" by Kevin Rudolf.

Along with WrestleMania XXVI, a group of events known as "WrestleMania Week" was held in the week before the event. The third yearly WrestleManiArt, an art show and auction featuring work by WWE superstars, was held on March 24. WrestleMania's yearly fan convention, WrestleMania Axxess, was held from March 25 through to March 27. On March 27, WWE hosted its yearly WWE Hall of Fame ceremony at the Dodge Theater, where the 2010 members were made an official member of the hall of fame.

Related pages
 List of WWE pay-per-view events

References

Other websites
 The Official Website of WrestleMania

WrestleMania 26
2010 in professional wrestling
Glendale, Arizona
2010s in Arizona
March events
Ice pellets

Ice pellets are known as sleet in North America, and hail in Great Britain. They are a type of frozen precipitation, little balls of ice. Large ice pellets are called hailstones.  Sometimes, ice pellets bounce when they hit the ground.

References

Precipitation
Howitzer

A howitzer is a special type of big gun used by an army. It has a short barrel, and is used fire a shell over a short distance. The barrel length of a howitzer is 15 to 25 times of the caliber. Howitzers are special because they're made to fire higher than a cannon but lower than a mortar. Howitzers are almost always used to shoot at targets on the ground, but they can be used for targets on water, or in the air. The name howitzer comes from an old Czech word, haufnice, which was a catapult that could fire many stones.

Related pages
List of howitzers

References
John Updike

John Updike (March 18, 1932 - January 27, 2009) was an American author of works including Rabbit, Run and Couples. He was born in Reading, Pennsylvania. He died of lung cancer in Danvers, Massachusetts in January 2009.

1932 births
2009 deaths
American Christians
American novelists
American poets
Cancer deaths in Massachusetts
Deaths from lung cancer
Writers from Pennsylvania
O. Henry Award winners
Clog (shoe)

A clog is a kind of shoe. There are different kinds of clogs. They can be shoes, sandals or completely made out of wood.

Footwear
Dendrite

Dendrites are the branches of neurons that receive signals from other neurons. The signals go into the cell body (or soma).

A cell may have hundreds of dendrites, but may have only one axon. The dendrites carry signals from other neurons into the soma, and the axon carries a single signal from the soma to the next neuron or to a muscle fiber.

A dendrite from one neuron and an axon from another neuron meet at a synapse, which is a very narrow gap between the two cells. When electrical impulses reach the end of an axon, they trigger the release of chemicals called neurotransmitters. These chemicals cross the synapse to the dendrite, where they trigger the flow of ions into or out of the cell.

The movement of the charged ions in the dendrite causes an electrical current, which spreads to the soma briefly before being restored to normal.

If the dendrites get lots of signals from axons, then it sets off a chain reaction. The chain reaction is a strong electrical current called an action potential that flows down the axon to the next synapse.

Fully differentiated neurons do not divide. However, stem cells in the adult brain may regenerate functional neurons throughout the life of an organism. Generally, once born, neurons do not divide. Many will live the whole lifetime of the animal.

References 

Anatomy of the nervous system
Red Hat

Red Hat, Inc. is an American software company. It makes open source software products. The company was founded in 1993. Red Hat has its headquarters in Raleigh, North Carolina, with other offices worldwide.

References

Other websites

 

 
 Red Hat contributions

 
Free software
American software companies
Companies based in North Carolina
1993 establishments in the United States
Raleigh, North Carolina
Mischief night

Mischief night is a tradition in some parts of the world; a night when people do mischief to their neighbours. This is usually 30 October, the day before Halloween night.

Traditional practice

Traditional mischiefs:

Knocking and tapping on doors and windows
Throwing paint
Putting treacle on door handles
Tying door handles together to stop them opening
Moving gates
Egging houses
Toilet papering houses

Current Day Practice
Sometimes combined with Trick or Treat.

In Detroit and other parts of Michigan, October 30 is called Devil's Night and includes vandalism and arson.

In northern New Jersey and the Philadelphia region, October 30 is referred to as "Mischief Night," where mischievous teens soap car windows, egg houses, adorn trees with toilet paper, and run away after ringing doorbells. In other parts of New Jersey, October 30 is also known as "Cabbage Night" or "Goosey Night."  In Camden, New Jersey.  Over 130 arsons were committed in that city on the night of October 30, 1991.

It is known as "Gate Night" in Trail, British Columbia, Winnipeg, Canada and as Mat Night in Quebec, Canada, always on the 30 October, the eve of Halloween. It is also commonly known as "Devil's Night" in many places throughout Canada.

In Yorkshire, it is also known as "mischievous night", "Miggy Night", "Tick-Tack Night", "Corn Night", "Trick Night" and "Micky Night". In Liverpool, it is known as "Mizzy Night"(but unlike in Yorkshire, where it is celebrated on October 30th). It was celebrated on Nov 4 in Merseyside during the 1970s, as well as in Manchester after the war.

Mischief night is becoming popular in Ireland, where teenagers get the week around Halloween off school. This means that many of the nights before 31 October are used by teenagers for vandalism.

Modern mischief includes toilet papering gardens and buildings, flouring and egging of cars, people, and homes, "forking" gardens, setting off fireworks and smashing pumpkins and jack-o'-lanterns.  Local shops do not sell eggs to chavs around the time of Halloween.  Sometimes the damage includes spray-painting of buildings and homes.

People play "Ding-Dong Ditch": in this 'game', people knock on doors and then run and hide.

Media
A 2006 film Mischief Night is based on a night in Leeds, UK.

Notes

References
 Confessions from a Mischief Night brat  BBC Yorkshire report — November 2006
 Police Patrol for Mischief Night BBC Merseyside report — November 2006
 Dialect Survey Results  US terms;prevalence and distribution

British culture
Crime
Observances
Shrove Tuesday

Shrove Tuesday is a holiday in which the christian has ash put on their head in the shape of a cross in the United Kingdom, Canada, The United States and Australia for the day before Ash Wednesday. Ash Wednesday is the first day of the Christian season of prayer and fasting called Lent.

On Shrove Tuesday people traditionally cook and eat pancakes. The reason for this was to use up foods such as fat, eggs and milk before Lent.

It is also called Pancake Tuesday or Pancake Day. In some other countries, such as the United States, it is called Mardi Gras.

In some cultures it has close ties with Mischief night.

Festivals
Sicilian language

The Sicilian language () is a language spoken in Sicily island and central Calabria. It is currently spoken by the majority of the inhabitants of Sicily and by emigrants.

Speakers
10 million people speak the language. It has three stocks: the Sicilian, the Calabro-Sicilian and Salentinu.

Differences with Italian
Compared to Italian, it is a distinctly separate form of verbal communication patterned by many years of foreign influence. Efforts to force Sicilians to speak conventional Italian include schools, television and radio. Italians maintain that Sicilian is simply a subset dialect of Italian, while Sicilians see their spoken word as a true and separate language. 

Romance languages
Sicily
Calabria
Portmanteau word

A portmanteau word () is made of other words, or parts of words. It comes from putting  two (or more) other words together, like motel, from motor and hotel.

Origin 
Portmanteau originally meant a type of suitcase with two separate parts for storage.
The first use as a word combination appeared in Lewis Carroll's book Through the Looking-Glass. There Humpty Dumpty explains that some of the unusual words in Jabberwocky are other words packed together into one word, as two parts of a portmanteau suitcase are packed together.

Examples 
Portmanteau itself is an example, combining the French words for carry (porter) and coat (manteau) into a coat carrier. Wikipedia is a portmanteau of wiki (Hawaiian for fast) and encyclopedia.

References

Related pages 
Neologism 

Words
Installation (computer programs)

Installation means to put a program on a computer so that the computer can run it.

Most programs are stored in special ways to make them smaller, or to gather all the different pieces of a program up into one big piece. Before it can be used, though, the program needs to have these changes undone. Some programs also need to know extra information about the computer it is going to run on, so while it is installing, it will figure out what it needs to know and write it down for later.

Software
Computers
Cohomology

Cohomology is something in higher math which is sometimes used to solve certain math problems.

Algebra

ru:Гомология (топология)#Когомологии
Laplace transform

The Laplace transform is a way to turn functions into other functions in order to do certain calculations more easily. This way of turning functions to other functions is very similar to U Substitution. The aim of this change is to be able to turn the hard work of integration into a simple algebraic addition and subtraction, just as logarithms allow one to add and subtract instead of multiplying and dividing. An example of its use is in ruin theory, which is a subject of actuarial science with regards to insurance.

Functions usually take a variable (say t) as an input, and give some output (say f). The Laplace transform converts these functions to take some other input (s) and give some other output (F). Because of certain shared properties of Laplace transforms, this makes it very easy to manipulate the original function into something useful.

The Laplace transform of a function , written as  or , is often formulated as:

where:
f(t) is the input function
 t is the old domain
s is the new domain

Related pages 

 Fourier transform

References 

Calculus
Lorentz factor

The Lorentz factor is the factor by which time, length, and mass change for an object moving at speeds close to the speed of light (relativistic speeds). It is named after the Dutch physicist Hendrik Lorentz.

The equation is:
 
where v is the speed of the object and c is the speed of light. The quantity (v/c) is often labeled  (beta) and so the above equation can be rewritten:

Classical relativity 
Classical or Galilean relativity is the idea that if you throw a ball at 50 mph while running at 5 mph, the ball travels 55 mph. Of course, the ball still moves away from you at 50 mph, so if one were to ask you, you saw the ball traveling 50 mph. Meanwhile, your friend Rory saw that you happened to be running at 5 mph. He would say that the ball was traveling 55 mph. Both of you are right, you just happened to be moving with the ball.

The speed of light, c, is 670,616,629 mph. So if you are in a car traveling half the speed of light (0.5c) and you turn on your headlights, the light moves away from you at 1 c... or is it 1.5 c? It ends up that c is c no matter what. The next section explains why it's not c - 0.5c.

Time dilation 
When a clock is in motion, it ticks slower by a tiny factor of . The famous twin paradox says that if there were two twins and twin A stayed on earth while twin B traveled near c for a few years, when twin B got back to earth, he would be many years younger than twin A (because he experienced less time). For example, if twin B left when he was 20 and traveled at .9c for 10 years, then when he got back to earth, twin B would be 30 (20 years + 10 years) and twin A would be almost 43:
 
Twin B would not notice that time had slowed at all. To him, if he looked out a window, it would seem like the universe was moving past him, and therefore slower (remember, to him, he's at rest). So time is relative.

Length contraction 
Things get shorter in the direction of movement when they travel at relativistic speeds. During twin B's journey, he would notice something strange about the universe. He would notice that it got shorter (contracted in the direction of his motion). And the factor by which things get shorter is .

Relativistic mass 
Relativistic mass also increases. It makes them harder to push. So by the time you reach 0.9999c, you need a very big force to make you go faster. This makes it impossible for anything to reach the speed of light.

Still, if you travel a bit slower, say 90% of the speed of light, your mass only grows by 2.3 times. So, while it may be impossible to reach the speed of light, it may still be possible to get close to it—that is, if you have enough fuel.

Relativity
Cyperaceae

The family Cyperaceae, or the sedges, is a taxon of flowering plants. They look like grasses or rushes, but are not. They are monocot plants (as are grasses), but belong to a different family. 

The family is large, with some 5,500 species described in about 109 genera. The largest is the Carex genus of "true sedges", with over 2,000 species.

Sedges include many wild marsh and grassland plants, and some cultivated ones such as water chestnut (Eleocharis dulcis) and papyrus sedge (Cyperus papyrus). These species are widely distributed, with many in tropical Asia and tropical South America. Sedges may be found growing in almost all environments. Many are wetlands, or have poor soils. Ecological communities dominated by sedges are known as sedgelands.

Features distinguishing members of the sedge family from grasses or rushes are stems with triangular cross-sections (with occasional exceptions) and leaves that are spirally arranged in three ranks (grasses have alternate leaves forming two ranks).

References 

Poales
Objective-C

Objective-C is an object-oriented programming language used to make computer programs for macOS and iOS devices.

History
Objective-C was created in the early 1980s by two programmers named Brad Cox and Tom Love. However, it didn't become popular until it was bought by NeXT in 1988 for their NeXTSTEP operating system. After NeXT was bought by Apple in 1996, it became the main programming language for Mac OS X and later the iPhone, iPod Touch and iPad. In recent years, swift has been more popular than Objective-C.

Basics
Objective-C is a strict superset of C, meaning that any code that can be written in C can be used in Objective-C programs without changing it. However, it adds some features of its own that can't be used in a traditional C program.

Messages
In Objective-C, functions are called using messages, a feature inspired by the SmallTalk programming language. Messages look like "blocks" of code similar to the one shown below:
[object messageToObject];
These blocks can be nested inside of each other as well, for example:
[[object messageToSendToObject] messageToSendToResultOfInnerMessage];

Interfaces and Implementations
Unlike other programming languages such as C and Java, Objective-C classes are divided into two separate parts: 
 Interface, which contains the initial declarations of variables and functions.
 Implementation, which contains the actual code for functions.

Usually, these are put in two different files, with the interface using the ".h" extension and the implementation using the ".m" extension.

Variations
Objective-C has variants that add features to the original Objective C programming language.

Objective-C++
Objective-C++ allows for C++ code to be used in Objective-C applications.

Objective-C 2.0
Objective-C 2.0 is an improved version of Objective-C. It adds many features, such as garbage collection (automatic memory management), fast enumeration and properties (the automatic generation of variable methods).

References

Programming languages