open-index/open-wikipedia-markdown huggingface dataset:
Therapsid

**Therapsids**, previously known as the mammal-like reptiles, are a group of synapsids. 

The clade includes the mammals, which are descended from the cynodont therapsids.

## Features 
The jaws of therapsids had frontal incisors for nipping, large lateral canines for puncturing and tearing, and molars for shearing and tearing, and chopping food. 

Therapsid legs were positioned more vertically beneath their bodies than were the sprawling legs of Sauropsids and Pelycosaurs.

## Evolution 
The therapsids were seriously affected by the P/Tr extinction event. The successful gorgonopsians died out, and the remaining groups were much reduced. 

The dicynodonts were now a single family of large stocky herbivores, the Kannemeyeridae. The medium-sized cynodonts (including carnivorous and herbivorous forms), flourished worldwide in the early to middle Triassic. They died out across much of Pangea before the end of the Upper Triassic. Some survived for a while in the wet equatorial band and in the South.

At least three groups of eucynodonts survived. They appeared in the Upper Triassic. The extremely mammal-like family, the Tritylodonts, survived into the Lower Cretaceous. Another group, *Morganucodon* and its relatives, were mammaliaformes. That is, their descendants became the mammals.

## Taxonomy 
* **Class Synapsida**
* **ORDER THERAPSIDA** *
** **Suborder Biarmosuchia** *
** **Suborder Dinocephalia**
** **Suborder Anomodontia** *
*** Superfamily Venyukoviamorpha
*** **Infraorder Dicynodonta**
** (unranked) **Theriodontia** *
*** **Suborder Gorgonopsia**
*** **Suborder Therocephalia**
*** **Suborder Cynodontia** *
** **(unranked) Mammaliaformes** *
* **Class Mammalia**

## References
* Kemp T.S. 2005. *The origin and evolution of mammals*. Oxford University Press
* Benton M.J. 2004. *Vertebrate Paleontology*. 3rd ed. Blackwell, Oxford.
* Carroll R.L. 1988 *Vertebrate Paleontology & Evolution*. Freeman N.Y.
* Romer A.S. 1966. *Vertebrate Paleontology*. 3rd ed, University of Chicago Press.
Lockheed P-38 Lightning

The **P-38 Lightning** is a World War II fighter aircraft made by Lockheed. It was mainly used by the United States Air Force. It first flew in 1939. It was different from other fighters because it had two engines instead of one, and was twice the size of other fighters. The plane fought in the Pacific and in Europe. It could carry 4 50-caliber machine guns and a 20mm cannon. With a top speed of over 400 miles per hour the P-38 was one of the fastest fighters of its time. The P-38 is also accounted for capturing 90% of all aerial footage over Europe. By 1944, it was replaced by the faster P-51 Mustang in Europe. The P-38 was the only American fighter being built at the beginning and the end of the war. The Germans called it the "fork tailed devil."

The Lockheed P-38 Lightning was a **well equipped single-seat WWII fighter**. It had **2 powerful engines** allowing it to reach **high altitudes** and **speeds**. The **tail design** was unique compared to other aircraft of the time. The **Americans** used this aircraft in many of its **dogfights and long-range** enemy engagements. The P-38 created many **aces**, making it **favourable** over other aircraft.

## References
Messerschmitt Bf 109

The **Messerschmitt Bf 109** was a fighter aircraft usually called the **Me 109**. It was a German World War II aircraft.

Made by Messerschmitt, it first flew in 1935, and was used by the Luftwaffe during the Spanish Civil War and throughout World War II.  It was one of the first modern fighters of the time. It had an all-metal construction, a closed cockpit, and retractable landing gear. It was powered by a liquid-cooled, inverted-V12 aero engine.

The **Messerschmitt Bf-109**, was a powerful **single-propeller** aircraft, used by the Germans as **support** aircraft. The Bf-109 was a **worthy competito**r as Germany’s greatest aircraft, though the **Fw-190 proved more significant** for **some** enemy engagements. The camouflaged aircraft fought in the heat of the 1940 **Battle of Britain,** going head to head with the **English Spitfires**.

There were many variations designed for special purposes. Overall, the Me 109 was the most produced fighter aircraft in history, with a total of 33,984 airframes produced from 1936 up to April 1945.

The design of the plane caused some problems on the ground, and with take-off and landing. At least 10% of all Bf 109s were lost in takeoff and landing accidents, 1,500 of which occurred between 1939 and 1941. A new fixed tailwheel helped correct the problem.

Bf 109 was used by Luftwaffe together with FW 190. The Messerschmitt had two machine guns and one cannon while FW 190 had two machine guns and four cannons. Bf 109 was much lighter than FW 190, by 1500&nbsp;kg. Despite that Bf 109 was almost as fast as FW 190 (Fw 190 A-8 was only 16kph faster than Bf 109 G-6) and climbed at 17&nbsp;m/s, 2&nbsp;m/s faster than FW 190.

## Related pages
*P-51 Mustang
*Fw 190
*Hawker Hurricane
*Supermarine Spitfire

## References
Messerschmitt Me 262

The **Me 262** is a German fighter aircraft flown during late World War II. It was the first jet to be used in war. It began test flights in 1942, but was not used in combat by the German air force, the Luftwaffe, until 1944. Very few were built because Germany's enemies were bombing factories. It saw little action because the war was nearly over. The jet engines of the new machine often caused problems, that's why a lot of machines had deathly accidents.

Nicknamed Schwalbe (Swallow), the Messerschmidt Me 262 surpassed the performance of every other World War II fighter. Faster than the North American P-51 Mustang by 190 km/h (120 mph), the Schwalbe restored to the faltering German Luftwaffe. The Me-262 has two ʽJumo 004 B turbine enginesʼ with a top speed of 869.4 km/h (540 mph). It's armament includes two ʽMK 103 30 mm cannonsʼ, two ʽ108 30 mm cannonsʼ, and a pair of ʽMG 151/20 20 mm cannonsʼ.

## Related pages
* Jet aircraft

## References
Osmosis

**Osmosis** (/ɒzˈmoʊ.sɪs/) is the movement of solvent (liquid) molecules through a membrane, from one solution to another, which happens without an outside force. 

Solvent will move to the side that has a *higher concentration* of *solutes*, or dissolved particles — and thus a *lower concentration* of *solvent*. This happens because the membrane is selectively permeable:  the solvent can pass through, but the solute cannot. Solvent molecules move randomly, and so the concentrations on both sides become more equal.

Osmosis can be made to do work. **Osmotic pressure** is the external pressure that must be applied so that there is no net movement of solvent across the membrane. Osmotic pressure depends on the molar concentration of the solute.

Osmosis is important in biological (living) systems, as biological membranes are semipermeable. In general, these membranes are impermeable to large  molecules such as ions, proteins, and polysaccharides. They are  permeable to non-polar or hydrophobic molecules like lipids and small molecules like oxygen, carbon dioxide, nitrogen, and nitric oxide. Permeability depends on solubility, charge, or chemistry, as well as solute size. Water molecules travel through the plasma membrane, vacuole, or protoplast by diffusing across the phospholipid bilayer. 

Osmosis provides the main way water is gets in and out of cells. The turgor pressure of a cell is largely maintained by osmosis across the cell membrane between the cell interior and its environment.
## Hypotonic, isotonic, and hypertonic 
Solutions may have more or less solute per unit of solvent. The one with less is called *hypotonic.* When the two solutions have equal concentration, they are *isotonic.* The one with more is *hypertonic*. When the hypotonic solution is outside the cell, and hypertonic solution inside, the cell becomes swollen and distorted.

## Cell membranes 
The plasma membrane of a cell is semi-permeable, which means it allows the entry of certain molecules in or out. It lets small molecules pass through, but blocks larger molecules. The membrane also has ports or gateways which get certain macromolecules through. This is active transport, which uses energy and is selective. It is the outermost covering of the animal cell, made of proteins and lipids. Example: exchange of gases like oxygen and carbon dioxide.

## Related pages 
* Reverse osmosis
* Osmoregulation
Mikoyan-Gurevich MiG-17

The **MiG-17 Fresco** is a fighter aircraft made by Mikoyan, a Russian company. It first flew in 1950, and was supposed to replace the MiG-15 in the Korean War, but it did not arrive fast enough. It was used by the North Vietnamese in the Vietnam War. It carried 3 guns on it, and later versions carried missiles. Today, it is used as a trainer in other air forces.

## Related pages
*F-8 Crusader
*F-4 Phantom II
*MiG-21
Mikoyan

**Mikoyan** is a Russian company that designs fighter airplanes. The company was first formed in December 1939 as a design office called Mikoyan-Gurevich or MiG, this was because its designers were Artem Mikoyan and Mikhail Gurevich. Mikoyan will join other Russian airplane companies in a new company called United Aircraft Corporation.

## History 
In 1939 Russia was part of the Soviet Union and was communist. In the Soviet communist system there were two types of airplane companies, companies that designed aircraft known as design offices or OKB, and companies that made airplanes called zavods. Artom Mikoyan and Mikhail Gurevich had been designers in another design office helping a designer called Nikolai Polikarpov. One airplane design that Artem Mikoyan and Mikhail Gurevich worked on at Polikarpov was called the I-200. When Nikolai Polikarpov lost the trust of the Soviet leader Stalin, Artem Mikoyan and Mikhail Gurevich were given the I-200 design to finish. This airplane was given a new name and was called the Mikoyan-Gurevich MiG-1. As it was being made, ways to make the MiG-1 into a better airplane were found and airplanes with these changes became known as the MiG-3 and later the MiG-7. However even with changes the MiG fighter airplanes were not as good as the fighter airplanes designed by the design offices of Lavochkin or Yakovlev.

After World War II Mikoyan-Gurevich designed jet aircraft. In the Soviet system the airplane designs of the design offices would compete to see which was the best.  When the best design had been found the design would be built by the airplane manufacturing company.  Even though Mikoyan-Gurevich airplanes in World War II had not been as good as airplanes by Lavochkin or Yakovlev. Mikoyan-Gurevich jet aircraft won more of the competitions to be sent to the zavods and in the time of the Cold War Mikoyan-Gurevich, together with another design office called Sukhoi, became one of the two most important design offices of fighter planes in the Soviet Union.

In the Soviet system decisions were made to protect the government from its own soldiers. In many countries there is only one airforce, the Soviet Union had five airforces. Two of these airforces were the main users of Soviet fighter airplanes. One airforce was called *PVO Strany*, this airforce was used to defend the cities and land of the Soviet Union. One airforce was called *Frontal Aviation*, this airforce was used to defend the Soviet Union's ground soldiers against enemy fighter airplanes, and to attack enemy ground forces. Mikoyan-Gurevich became the main designer of aircraft for *Frontal Aviation*.

## Aircraft made 
Mikoyan has designed the following airplanes:

* Mikoyan MiG-1
* Mikoyan MiG-3 (also called MiG-7)
* MiG DIS
* MiG-9 Fargo
* MiG-15 Fagot
* MiG-17 Fresco
* MiG-19 Farmer
* MiG-21 Fishbed
* MiG-23 Flogger
* MiG-25 Foxbat
* MiG-27 Flogger
* MiG-29 Fulcrum
* MiG-31 Foxhound
Neptune (mythology)

**Neptune** (Latin: *Neptūnus*) is the god of water and the sea in ancient Roman religion and mythology. His Greek equivalent is the god Poseidon. The Roman conception of Neptune was mainly influenced by the Etruscan god Nethuns. Neptune was associated with fresh water as well as the sea, while Oceanus was the god of the world-ocean. Like his Greek equivalent, Neptune was also worshipped by the Romans as the god of horses, and, under the name *Neptune Equester*, he was a patron god of horse-racing.

The planet Neptune is named after this Roman god.

## References 
* Poseidon -- Greek version of Neptune

*
Fortuna

**Fortuna** is a municipality in the Region of Murcia, in Spain.

It has an area of 149.3 km² and a population of 10,665 people.
Fortuna (disambiguation)

**Fortuna** (*Latin and Spanish: "fortune"*) can mean:

* Fortuna, the Roman goddess of luck (from the Greek Tyche)

**Geographical**
* 19 Fortuna, an asteroid
* Fortuna, California, a town on the north coast of California
* Fortuna, North Dakota, a town in the northwest of North Dakota, near the Canadian border.
* Fortuna (SEPTA station)
* Fortuna, Murcia, a town in the province of Murcia in Spain

**People**
* Fortuna (Brazilian singer), a female singer and composer from Brazil of Jewish origin
* Wojciech Fortuna, a former ski jumper and Olympic gold medallist

**Sports**
* Fortuna Düsseldorf
* Fortuna Köln
* Fortuna Sittard

**Other**
* Fortuna (philosophy), Philosophy of the Fellowship of Fortuna Movement
* Fortuna (PRNG), a cryptographically secure pseudo-random number generator design by Niels Ferguson and Bruce Schneier
* Fortuna, a fictional planet from the *Star Fox* series of video games
* Fortuna (cigarette), a cigarette brand owned by Altadis
* "O Fortuna", widely recognizable opening movement of Carl Orff's *Carmina Burana*
* Fortuna Saga, an original sprite-based webcomic set in the world of *Final Fantasy VI*.
* A name for bagatelle, a game developed from billiard
Juno

**Juno** could mean:

* Juno (mythology), a major Roman goddess
* June, the month named after Juno
* 3 Juno, one of the largest main belt asteroids

## Music 
* Juno (band), an American indie rock band
* *Juno* (musical), a Broadway musical with score by Marc Blitzstein based on Sean O'Casey's play *Juno and the Paycock*
* Juno Reactor, a trance music project of Ben Watkins
* Juno Mak, a Cantopop artist
* Juno Award, a Canadian music award
* Roland Juno-60, Roland Juno-106 or Roland Juno-D (1983?-Present), synthesizers by Roland
* "Juno", a song by Funeral for a Friend, from their debut EP *Between Order & Model*. Later re-recorded for debut LP *Casually Dressed and Deep in Conversation* and released as a single under the name *Juneau*
* Juno Records, an online music store

## Vehicles 
* *Juno* (spacecraft), a planned NASA mission to Jupiter
* HMS *Juno*, the name of seven vessels of Royal Navy
* Jupiter-C (rocket), also known as Juno or Juno I
* Jupiter (missile) also known as Juno II
* Juno (1864&nbsp;– 1884), one of the eight South Devon Railway Dido class steam locomotives
* Juno, a Great Western Railway Banking Class 0-6-0ST steam locomotive.
* Juno, a Spanish ship sank in 1802. After its 1997 discovery in Assateague coast (Virginia) the Spanish government claimed ownership of the wreck.

## Other uses 
* *Juno* (movie) a 2007 comedy-drama movie directed by Jason Reitman
* Juno (Dune), a Titan in the fictional Dune universe
* Juno Beach, one of five beaches used as landing zones in the Battle of Normandy in World War II
* 3 Juno, the third asteroid to be discovered
** Juno clump, a probable asteroid family near 3 Juno
* Juno Online Services, an internet service provider in the United States
* Project Juno, a British commercial venture that sent Helen Sharman to space
* Juno, protagonist of the video game *Jet Force Gemini*
* MegaMan Juno, a villain in the video game *Mega Man Legends*
* Juno Skinner, a villain in the 1994 film *True Lies*
* Juno Lighting, a company that specializes in commercial and residential lighting
* Juno creator of Star Cross'd Destiny
* Juno the game by Mountain King Studios
* Juno, a powerful Denial of Service attack program, written in the C Programming Language
* Juno, a German cigarette brand produced by Reemtsma
* Juno Temple, an English actress
Sol Invictus

:*For the folk music band, see Sol Invictus (band).*
, circa 280, with *Sol Invictus* riding a quadriga, with legend SOLI INVICTO, "to the Unconquered Sun". Note how the Emperor (on the left) wears a radiated solar crown, worn also by the god (to the right).]]
 (British Museum)]]

**Sol Invictus** ("the Unconquered Sun") or, more fully, **Deus Sol Invictus** ("the Unconquered Sun God") was a religious title applied to at least three distinct deities during the later Roman Empire: El Gabal, Mithras, and Sol.

The earlier cult of Sol Indiges ("the native sun" or "the invoked sun") was agrarian. The title *Deus Sol Invictus* was formed similar to the imperial titulature *pius felix invictus* ("dutiful, fortunate, unconquered").

The Romans held a festival on December 25 called *Dies Natalis Solis Invicti*, "the birthday of the unconquered sun." The use of the title **Sol Invictus** allowed several solar deities to be worshipped together, including Elah-Gabal, a Syrian sun god; Sol, the patron god of Emperor Aurelian (AD 270-274); and Mithras, a soldiers' god of Persian origin. Emperor Elagabalus (218-222) introduced the festival, and it reached the height of its popularity under Aurelian, who promoted it as an empire-wide holiday that was a possible inspiration of Christmas.

## Notes 
## Further reading
*Halsberghe, L. 1972. *The Cult of Sol Invictus* (Leiden)

## Other websites 
*Encyclopedia Britannica Online: Sol
*Probus and Sol, includes images of coins 
*Roman-Emperors: Aurelian 
*Gibbon's Decline and Fall: Triumph of Aurelian
*Gibbon's references for Aurelian's Temple of Sol Invictus 
*Clement A. Miles, *Christmas in Ritual and Tradition, Christian and Pagan* (1912): December 25 and the Natalis Invicti
*Catholic Encyclopedia (1908): Christmas
*Ancient sources
Optical printer

An **optical printer** is a machine. It can be used to copy rolls of movies. It is made of one or more movie projectors, which are linked to a movie camera. It allows filmmakers to re-photograph one or more strips of movie. The optical printer is used for making special effects for motion pictures or for copying and restoring old movie material.

Common optical effects include fade outs and fade ins, dissolves, slow motion, fast motion, and matte work. More complicated work needs dozens of elements, all combined into a single scene. Ideally, the audience in a theater should not be able to notice any optical printer work, but this is not always the case. For economical reasons, especially in the 1950s, and later in TV series produced on movie, printer work was limited to only the actual parts of a scene needing the effect, so there is a clear change in the image quality when the transition occurs.

The first, simple optical printers were constructed in the early 1920s. Linwood G. Dunn developed the idea in the 1930s. The development continued well into the 1980s, when the printers were controlled with minicomputers.

Since the late 1980s, digital compositing began to replace optical effects. Since the mid nineties the conversion to digital effects has been almost total. Optical printing today is used most widely by artists working exclusively with movie. As a technique, it proves particularly useful for making copies of hand painted or physically manipulated movies.

## References
Charter trustees

**Charter trustees** are the English district councillors for an area that used to be a city.

They are allowed by the *Charter Trustees Act 1985*, so that some of the privileges and dignities of former city can be carried on.
## References
Charter Trustees Acts 1985 c45
Quirinus

In Roman mythology, **Quirinus** was an early god of the Roman state. In Augustan Rome, Quirinus was also a name of Janus, as *Janus Quirinus*.

## History 
Quirinus was originally most likely a Sabine god. The Sabines had a settlement near the site of what was to become Rome, and erected an altar to Quirinus on the *Collis Quirinalis*, the *Quirinal Hill*, one of the *Seven Hills of Rome*.  When the Romans settled there, they absorbed the cult of Quirinus into their early belief system — previous to direct Greek influence — and he was said to be the deified Romulus.  

In later times, however, Quirinus became far less important, losing his place to (Juno and Minerva and Mars' place). 

## Notes
Kreisfreie stadt

The name **kreisfreie Stadt** (plural: *kreisfreie Städte*) is used for German towns that have their own government. This town government is independent of the government of the next-higher level of authority, the *Landkreis*. Today, most of the cities that have this statute, are big cities, with 100.000 people living there, or more. The concept grew historically. That means that there are big cities, with more than 100.000 people that do not have the statute. There are also some cities who have only taken a part of the responsibilities of a Landkreis (or Kreis). The smallest city with the statute is Zweibrücken. About 35.000 people live there. The biggest of these cities is Munich, with about 1.3 million people. Hamburg and Berlin are bigger. They are city states, though. The city state of Bremen (state) is made of two *kreisfreie Städte*, the city of Bremen, and the city of Bremerhaven, about 60 km to the north. About half a million people live in Bremen (1.5 million in the agglomeration), about 117.000 people live in Bremerhaven.

But not every big city with more than 100.000 inhabitants is a *kreisfreie Stadt*. Some of them, for example Recklinghausen or Göttingen (both more 120.000 inhabitants) are part of a *Landkreis*.

There are very few cities, who only took part of the paperwork from the Landkreis. Some of these are called *Große selbständige Stadt* (Translates to *Big sovereign city*). They only seem to exist in Lower Saxony. They are:
Celle, Cuxhaven, Goslar, Hameln, Hildesheim, Lingen, and Lüneburg. Things like hunting permits cannot be delegated to the cities. Other things, like what to do with the trash have sometimes been delegated.

Similar concepts to that of the *kreisfreie Stadt* are Unitary authorities in the United Kingdom, or that of *independent city* in the United States.
Jet aircraft

**Jet aircraft** are aircraft with jet engines. Unlike propeller-powered aircraft, jet aircraft normally fly at altitudes as high as 100 to 1,5&nbsp;meters, about 33 to .  At these altitudes, jet engines can achieve maximum efficiency over long distances.   The engines in propeller powered aircraft achieve their maximum efficiency at much lower altitudes. 

## Gallery

File:Ohain USAF He 178 page60.jpg|A Heinkel He 178, the first jet aircraft 
File:All Nippon Airways Lockheed L-1011-385-1 Tristar 1 (JA8509 193P-1100) (5043455689).jpg|A wide body jet aircraft
File:KLM (SkyTeam livery), PH-BXO, Boeing 737-9K2 (15836383413).jpg|A Boeing 737, the world's best selling jet aircraft

## References
Downtown

]]
**Downtown** (called a **city centre** in British English) is a word used in North America which refers to the main part of a city. It is usually the central business district where most commercial and office areas are; many of them being in skyscrapers. Tourism also concentrates there.
Wireless LAN

wireless card.]]
In computing, **Wireless LAN (WLAN)** or **Wireless local area network** is a term to refer to a Local Area Network that does not need cables to connect the different devices. Instead, radio waves and  IEEE 802.11 are used to communicate.

## Benefits of Wireless LANs 
* People can access the network from where they want; they are no longer limited by the length of the cable.
* Some places and vehicles have a Wireless LAN hotspot. This lets people access the internet even outside their normal work environment, for example in a restaurant or train.
* Setting up a wireless LAN can be done with one box called wireless access point or wireless router. This box can handle many connections at the same time. Wired networks require cables to be laid. This can be difficult for certain places.
* Access points can serve a varying number of computers.

## Disadvantages of Wireless LANs 
* Wireless LANs use radio waves to communicate. Special care needs to be taken to encrypt information.  
* The signal is noisier than on wires, and more bandwidth needs to be spent on error correction. 
* A typical IEEE 802.11 access point has A *range* of meters from where devices can connect. To extend the range more access points are needed. 
* There are many reliability problems, especially those connected to interference from other devices.
* Wireless LANs are much slower than wired ones; this may not matter for most users though, because the bottleneck in a home network is usually the speed of the ADSL line or other Internet connection.

## Technologies used 
Today, most  technologies used for WLANs use Orthogonal Frequency Division Multiplexing. This means that several frequencies are used at the same time. Signals that are close to each other, but that belong to different channels do not disturb each other, as they use different coding schemes. Depending on the material used, it is possible to cover between 30 metres and 100 metres indoors; outdoors, the range is about 100-300m, if there are no obstacles.
Bluetooth

]] adapters such as this one allow some Personal computers to communicate via Bluetooth]]

**Bluetooth** is a protocol for wireless communication over short distances. It was developed in the 1990s, to reduce the number of cables.  Devices such as mobile phones, laptops, PCs, printers, digital cameras and video game consoles can connect to each other, and exchange information. This is done using radio waves. It can be done securely. Bluetooth is usually only used for relatively short distances, like a few metres. Some signals can be up to 100 metres.

## Comparing Bluetooth to Wireless LAN 
There are many situations today where either Bluetooth or Wireless LANs can be used. Examples include setting up networks, printing or transferring files and data from a PDA to a computer. Both are versions of unlicensed wireless technology. WLANs can span bigger distances and offer higher throughput. Bluetooth does not require expensive hardware. It also needs less power to operate.

Both use the same radio frequency range, but their modulation techniques are different. Both have been developed to replace cabling. Bluetooth wanted to get rid of the peripheral equipment cables, WLANs wanted to get rid of the cables needed to set up a LAN.

### Bluetooth devices 
 dongle with a 100m range.]]
Bluetooth exists in many products, such as telephones, the Wii or PlayStation 3. It has recently been built into some electronic watches, modems and headsets. The technology is useful when transferring information between two or more devices that are near each other in low-bandwidth situations. Bluetooth is commonly used to transfer sound data with telephones (i.e. with a Bluetooth headset) or byte data with hand-held computers (transferring files).

Bluetooth uses protocols that make it easy to discover devices that are nearby, and to set up a connection between these devices. Bluetooth devices can advertise all the services they offer. Using services becomes easier; a lot of the setup related to security, networking or permissions is automatic.

### Wireless LAN 
WLANs are more like traditional LANs. More configuration is needed to set up the network, and to make resources accessible by other devices in the network. WLAN devices also consume more power than Bluetooth ones. 
Sometimes WLANs are called wireless Ethernet. WLAN needs more resources to be set up, but it also offers faster transfer speeds. The security is also better than that offered by Bluetooth.

## References
Noraduz

**Noraduz** (or Noratus) is a site in the region of Gegharkunik in Armenia near Lake Sevan. It was formed a church dedicated to Sainte-mère-de-Dieu (built in the ninth century), and an exceptional site of medieval tombs. The tombstones are called Khachkars. Noraduz is the most important place for Khachkars in Armenia.

## Related pages
*Noraduz cemetery
*Khachkar

## References 
## Other websites 
*Noraduz - Khachkars Field 
*Noraduz Village
IEEE 802.11

**IEEE 802.11** is a series of protocols for wireless networking. Often these are called **Wireless LAN**, *WLAN*, or **Wi-Fi**. Such a protocol allows computers that have the needed radio parts to communicate with each other, without a cable. There are many types of Wi-Fi standards, known as 802.11 a, b, g, n, and recently ac & ad. These specifications are different in terms of speed and how far away you can use them.

## Later standards 
The first Wi-Fi standard was made in 1997.  It is called IEEE 802.11.  It allows communication with 1-2 MBit per second.  Today it is outdated, and rare.  Later standards add a letter to the name.  They are labelled IEEE  802.11a to IEEE 802.11g.  There are plans for ones labeled h, i, j, n, p and s.  They are all compatible with each other.

Newer standards have a Bit rate of 54 MBit/s.  About 40-50% of this is usable in real-life situations.  As of 2007, the standards most widely used are IEEE 802.11g, and IEEE 802.11b.

## Frequency bands 
Data communication is done in the 2.4 GHz band and the 5 GHz band.  The 2.4 GHz band is a general use band.  Microwave ovens and Bluetooth are among the things that emit radio waves in this band. The 2.4 GHz band has the problem that there are only very few channels that can be used at the same time, without the signals interfering. There are three usable channels there. When more than three networks operate in the same place, signals still get to the user correctly, but interference slows them. 

The 5 GHz band can solve some of these problems, but it introduces others. That band has 19 usable channels. Overall the band is less used. However there are more regulations. Most devices need to be able to choose their channel to minimize interference. Some channels require that those participating can do Transmitter Power Control. This means they adapt the strength of the signal to what is actually needed. This helps reduce the amount of interference between different networks.
1921 New York Yankees season

The **New York Yankees** during 1921 (the 1921 season) was the 19th season for the Yankees in New York, and overall it was their 21st season. The season ended in the team having a record (the number of wins and losses) of 98-55 (98 wins, 55 losses). This was the first pennant won in Yankees history. They won the American League game pennant, replacing the previous winners, Cleveland Indians. The manager of their team was Miller Huggins. The Yankees home games were played on the Polo Grounds.

## Season standings
## Schedule
## World Series
## References
*1921 New York Yankees team page at www.baseball-almanac.com

## Other websites
*Yankees game log courtesy baseball-almanac.com
*1921 New York Yankees
Hominidae

hominid exhibit at the Museum of Osteology, Oklahoma City]]
The **hominids** are members of the biological family **Hominidae** (the **great apes**). This family includes humans, chimpanzees, gorillas and orangutans. "Great ape" is a common name rather than a taxonomic label, and people use it in different ways. Sometimes people mean to include humans in the category of “great apes,” and sometimes they mean non-human apes. *Homo sapiens* is definitely a hominid, as judged by all modern reference works.

Hominids range in weight from 48&nbsp;kg to 270&nbsp;kg. Males are larger than females. Hominids are primates with no tails, strong bodies, and well-developed forearms. Their thumbs (and big toes, except in humans) oppose the fingers, and form a grip. All digits have flattened nails.

At present, the family Hominidae includes four genera and eight species. However, if fossil hominids were included, all of the Australopithecines and the genus *Homo* would be members of the Hominidae family. Today, nonhuman great apes live only in the rainforests of equatorial Africa, Sumatra and Borneo.

The first hominid fossils are from the Miocene period. Archaeologists found these in Asia and Europe. Also in Asia, they found fossils of a huge version of the orangutan called *Gigantopithecus*, which is now extinct. Fossils also show that Neanderthals were in Europe and western Asia for at least half a million years before modern humans appeared.

## Classification
Scholars do not agree on exactly how to classify the family Hominidae.

### Past versions
In the past, the family Hominidae have been classified this way:
*Family **Hominidae**: Great apes
** Subfamily Ponginae
*** Genus *Pongo*  orangutans
** Subfamily Homininae
*** Genus *Gorilla* – gorillas
*** Genus *Pan* – chimpanzees
*** *Australopithecus*† and other extinct relatives
*** Genus *Homo* – humans

### Modern version
A more recent classification shows humans and the Australopithecines as distinct from the rainforest apes. Two major reference works have supported this approach.

Superfamily Hominoidea
:Family Hylobatidae
:::Genus *Hylobates*
:Family **Hominidae**
::Subfamily Ponginae
:::Genus *Pongo*
::Subfamily Gorillinae
:::Genus *Gorilla*
::Subfamily Homininae
:::Tribe Panini
::::Genus *Pan*
:::Tribe Hominini
::::Subtribe Australopithecina/Hominina
:::::Genus *Ardipithecus*
:::::Genus *Australopithecus*
:::::Genus *Kenyanthropus*
:::::Genus *Sahelanthropus*
:::::Genus *Orrorin*
:::::Genus *Paranthropus*
:::::Genus *Homo*

## Related pages
* Human timeline
* Human evolution

## References
Acropolis of Athens

The **Acropolis of Athens** is  the most famous acropolis. It is a large hill, in the center of Athens, on which the Parthenon and other Greek buildings were built. It is often known as *The* Acropolis.
* The Acropolis is a group of ancient temples that were built on a high, rocky hill in Athens, Greece. The word acropolis even means 'high city' in Greek. Other cities have an acropolis, too, but the one in Athens is the most well-known.

* The Acropolis of Athens is the most striking and complete ancient Greek monumental complex still existing in our times. It is situated on a hill of average height (156m) that rises in the basin of Athens. Its overall dimensions are approximately 170 by 350m.
* The buildings were a citadel where people could escape to if the city was attacked. The Acropolis was mostly destroyed by 580 B.C. The people of Athens weren't going to rebuild it. However, a hundred years later, Themistocles and Pericles persuaded them to build it again.
** Over the centuries, the Acropolis was many things: a home to kings, a citadel, a mythical home of the gods, a religious center and a tourist attraction. It has withstood bombardment, massive earthquakes and vandalism yet still stands as a reminder of the rich history of Greece.
Canadian Hurricane Centre

The **Canadian Hurricane Centre** (CHC) is a Canadian agency that is responsible for monitoring and tracking tropical cyclones that come near or affects Canadian territory. The agency warns people about on-coming tropical cyclones and makes hurricane advisories when needed. Its headquarters are in Dartmouth, Nova Scotia.

CHC usually works together with its United States counterpart, the National Hurricane Center in Miami, to coordinate the tracks and positions of all storms that show a possible threat to Canada.

While Atlantic hurricanes are normally uncommon in Canada, they do approach or strike from time to time. Among recent events are Hurricane Bob, which struck New Brunswick, in 1991, Hurricane Luis which struck Newfoundland in September 1995, Hurricane Hortense which struck Nova Scotia in September 1996, Hurricane Michael which struck Newfoundland in October 2000, and Hurricane Juan, which struck Nova Scotia in September 2003.

## Other websites
*CHC website
*Official Canadian Weather Warnings 
*Hurricane Bulletins for your wireless device
Vulcan (Star Trek)

**Vulcans** are a humanoid species in the fictional *Star Trek* universe from the planet Vulcan. They are noted for their attempt to live by reason and logic with no interference from emotion. In one episode of Star Trek The Next Generation Android Data and Spock work together to solve a Romulan cypher. Spock remarks that Data has achieved the perfect Vulcan state of Pure Logic without emotion.  Data remarks that Spock despite his efforts  still feels emotion which Data is trying to achieve. They were the first extraterrestrial species encountered by humans. They became one of the founding members of the United Federation of Planets. Vulcans are featured in all twelve Star Trek series, six of which featured a Vulcan as a main character.

## Related pages
* Vulcan, Alberta - a town in Canada that has incorporated *Star Trek* themes due to its name.
* Stoicism

## Bibliography
* Star Trek: The Magazine v3#10 (February 2003 - "Romulan Propulsion Historical Overview" by Rick Sternbach & Tim Earls)
* Spock's World Diane Duane Pg. 359 Pocket Books, a division of Simon & Schuster Inc.  1230 Avenue of the Americas, NY, 10020 Paperback Edition 1989.
Keck Observatory

The **W. M. Keck Observatory** is a pair of two large, ground-based telescopes located at Mauna Kea, Hawaii. Sitting four km (more than two miles) above sea level, the paired telescopes are used to examine light from distant stars in great detail. The primary mirrors of each of the two telescopes are 10 meters (33 feet) across, making them slightly smaller than the Gran Telescopio Canarias primary mirrors.

However, all of the light collected by the Keck Observatory primary mirrors (75.76m2) is sent to the secondary mirror and the instruments, compared to GTC's primary mirror, which has an effective light-collection area of 73.4m2, or 25.4 square feet less than each of the Keck Observatory primary mirrors. Because of this fundamental difference in design, Keck Observatory's telescopes arguably remain the largest steerable, optical/infrared telescopes on Earth.

## Related pages
* La Silla Observatory
* Very Large Telescope

## Other websites 
* W.M. Keck Observatory (official site)
* The Mauna Kea Observatory (official site)
Lares

**Lares** (pl.) were ancient Roman deities who protected the house and the family - household gods.  See also Genius, Larvae, Di Penates, Manes.

Lares are presumed sons of Mercury and Lara, and deeply venerated by ancient Romans through small statues, usually put in higher places of the house, far from the floor, or even on the roof.  
In the early Roman times, in every house there was at least one little statue. Later, a sort of confusion connected their figure with those of Manes, deities of Hades (and the most virtuous dead persons of the family). Finally the confusion included the Penates (other minor deities) as well. 

## Related pages
* Turan, the Etruscan love goddess

## References
HED meteorite

The **HED meteorites** are a group of achondrite meteorite types:
* *Howardites*
* *Eucrites*
* *Diogenites*
 
These are all thought to have come from the crust of the asteroid 4 Vesta. Their differences are due to different geologic histories of the parent rock. Their crystallization ages are between 4.43 and 4.55 billion years ago, by their radioisotope ratios.

## References
Radiation pressure

**Radiation pressure** is the pressure exerted upon any surface exposed to electromagnetic radiation. If absorbed, the pressure is the energy flux density divided by the speed of light. If the radiation is totally reflected, the radiation pressure is doubled.  This happens because the waves that make up electromagnetic radiation carry momentum with them and pass that momentum on when they reach a surface.

A Crookes radiometer appears to demonstrate the pressure of light, but instead it demonstrate the energy that light brings to a surface.  The black side of each paddle absorbs most of the light's energy an causes the air near that surface to have a higher pressure.  So, while a Crookes radiometer turns because of pressure, it is air pressure caused by the heat energy that light brings to the device.  

## Solar radiation at Earth
The  radiation at Earth's distance from the Sun has an energy flux density of 1370 W/m2, and more than half of this energy reaches surface.  A calculation shows that this value of the flux would cause on an absorbing surface to experience 4.6 µPa of radiation pressure.  A convenient way to compare the Sun's energy flux and radiation pressure is to imagine the pressure and energy deposited on one square meter:

:Power = P = \left(1370 \frac{W}{m^2}\right)\cdot \left(1 m^2\right) = 1371\, W (or about 1.4 kilowatts.) 
:Force = \left(4.6\times 10^{-6} \frac{N}{m^2}\right)\cdot \left(1 m^2\right) = 4.6\times 10^{-6}N = 4.6 \mu N

To understand how small a micro-newton is, convert calculate how much mass you need on Earth to get that force using \vec F=M\vec g:
:Mass = \frac{F}{g}=\frac{4.6}{9.8}\times 10^{-6}\,kg=.00047 g (or about ½ milligram.)

The difference between the energy flux and the pressure is like the difference between the heat coming through a large window and the weight of a very small mosquito.

## References
## Further reading
* Demir, Dilek,**"A table-top demonstration of radiation pressure"**,2011, Diplomathesis, E-Theses univie (http://othes.univie.ac.at/16381/)
Kirkwood gap

**Kirkwood gaps** are areas of the asteroid belt where asteroids are unusually scarce, as seen in the graph on the right. They are caused by orbital resonances with Jupiter.

The gaps were first noticed in 1857 by Daniel Kirkwood, who also correctly explained their origin in the orbital resonances with Jupiter while a professor at Jefferson College in Canonsburg, Pennsylvania.

## References 
## Other websites 
* Article on Kirkwood gaps at Wolfram's scienceworld
* A method to create a short-term simulation .
Eucrite

**Eucrites** are achondritic stony meteorites that originate from the surface of the asteroid 4 Vesta, and as such are part of the HED meteorite group. They are the most common achondrite group with well over 100 distinct finds at present.

Eucrites consist of basaltic rock from the crust of 4 Vesta. They are mostly made up of Ca-poor pyroxene, pigeonite, and Ca-rich plagioclase (anorthite).

Eucrites are named from a Greek word meaning "easily distinguished".

## Other websites 
* HED Group - Meteorites from Vesta
Barrel (weapons)

A **barrel** is a part of a gun. It is a long metal tube and main pressure containing component of the weapon that the bullet or projectile goes through after it is fired. Guns can have many different sizes of barrels. Usually, longer barrels make it easier for the bullet to hit the target more often. Barrels usually have spiral grooves on the inside called rifling. Barrels with grooves spin the projectile around faster as it exits the gun. This makes the projectile more stable in flight and more accurate.

## References
Shell (projectile)

A **shell** is a type of projectile used in weapons. It is filled with explosive or other things such as an incendiary device. It is similar to a bomb but is made to be shot out of a gun. Shells are usually large caliber projectiles fired by artillery, armored vehicles (including tanks), and warships. A fuze detonates the explosive or releases whatever else the shell may be carrying.

Anti-tank guns fire thick shells without much explosive inside. Shells usually have the shape of a cylinder but taper towards the front end to form a point. However, special shells may use other shapes.

The kinds of explosives used (by NATO countries), in artillery shells: RDX, IMX-104, and TNT.

## References
Ion thruster

An **ion thruster** is a type of spacecraft thruster. It works by using static electricity or magnetism to push ions (atoms that have an electric charge) out of the back of the spacecraft. It takes a very long time for the spacecraft to speed up, but the fuel is used very efficiently. A thruster that has very high efficiency is said to have a high specific impulse.

It has to be carried into outer space by a regular rocket, because the ions don't push hard enough for it to escape the Earth's atmosphere, but after it gets to outer space it can travel a very long way. An ion thruster needs lots of electricity to work, so the spacecraft needs a very good way of producing electricity, such as solar panels or a nuclear reactor. In 2015 the thruster brought Dawn to the dwarf planet named Ceres.

## References
Elena V. Pitjeva

**Elena Vladimirovna Pitjeva** is a Russian theoretical physicist at the Institute of Applied Astronomy, Russian Academy of Sciences, St. Petersburg. She is noted for her work on ephemerides and is currently head of the Laboratory of Ephemeris Astronomy at the Institute of Applied Astronomy. Pitjeva is a member of the International Astronomical Union Commission 4: Ephemerides.

## Education
Pitjeva earned her undergraduate degree from the Faculty of Mathematics and Mechanics at A. A. Zhdanov Leningrad State University in 1972 in the specialty of astronomy. She earned an M.A. in theoretical physics in 1994 and a Ph.D. in theoretical physics in 2005. She was a student of Professor G.A. Krasinski.

## Publications (selection)
*
*
*

## References
## Other websites
*Laboratory of Ephemeris Astronomy, Institute of Applied Astronomy
Pistol

A **pistol**  is a handgun. The word may be used broadly to mean any handgun, or narrowly to mean only a magazine pistol, as distinct from a revolver. 
## Overview
In a magazine pistol, the cartridges are in a magazine, which is a metal or plastic box. The magazine is usually inside the handle of the pistol. When the pistol is fired, the empty cartridge pops out, and the next one comes up into position. The magazine is spring-loaded so it pushes the next bullet into place as the empty cartridge is ejected. For that reason pistols are sometimes called "semi-automatic". When the magazine runs out of cartridges, it can be reloaded by inserting more cartridges.
## Name
The term has long been variously used. For example, in the American Old West revolvers were used but were then (and even today by some) called pistols. The word "pistol" entered English before 1600, from the French. At that time it usually meant a single-shot handgun.
## Safety
One of the most important rules of gun safety is to keep guns out of the hands of children. Guns should be locked up and kept away from children and others who do not appreciate how deadly they are. A shooter should keep their fingers away from the trigger until the moment they intend to shoot. 
 
Pistols have a few disadvantages when compared to revolvers. They are more complicated and have more moving parts. A pistol may use heavier springs that younger and elderly shooters may find difficult to use.

Modern pistols usually only fire one shot every time you pull the trigger. Some special pistols, called machine pistols, can fire more than one shot at a time. Some famous pistols are the Colt M1911 and the Beretta 92. 

Pistols were not often used in the western United States during the 1800s. They used revolvers. The first  successful pistol being used then was the Borchardt C-93. It was designed in 1893, and became available in 1894.

## Related pages
* Air gun
* Revolver
* Firearms
* Second Amendment to the United States Constitution

## References 
## Other websites 
* Gun Law in the UK
* Gun laws around the world. Huffington Post
* Gun Control: What We Can Learn From Other Advanced Countries. Newsweek
* Strict local gun laws limit servicemembers’ ownership on overseas bases. Stars and Stripes