A dental formula is a summary of a mammal's teeth.

Almost all mammals have four kinds of teeth:
incisors
canines
premolars
molars

Teeth numbers and form have adapted to different feeding methods. Over time, different mammal groups have evolved distinct dental features, in the number and type of teeth, and in the shape and size of the chewing surface.

The number of teeth of each type is written as a dental formula for one side of the mouth, or quadrant, with the upper and lower teeth shown on separate rows. The number of teeth in a mouth is twice that listed as there are two sides.

In each set, incisors (I) are indicated first, canines (C) second, premolars (P) third, and finally molars (M), giving I:C:P:M. So for example, the formula 188.8.131.52 for upper teeth indicates 2 incisors, 1 canine, 2 premolars, and 3 molars on one side of the upper mouth.

The deciduous dental formula is notated in lowercase lettering preceded by the letter d: e.g. di:dc:dm. An animal's dentition for either deciduous or permanent teeth can thus be expressed as a dental formula, written in the form of a fraction: I.C.P.M / I.C.P.M.

Since the teeth are always listed in the same order, the letters can be dropped, thus:
Human: deciduous teeth: 212/212; adult = 2123/2123. Both childhood molars are replaced by adult premolars. Adult total is double the formula = 32.
Opossum: 5134/4134 (one less incisor on each side of the lower jaw).
Felines: 3131/3121. The last upper premolar and first lower molar of the cat are 'carnassials', used to slice meat and skin. The carnassials are always the fourth upper premolar and the first lower molar.
Horse 313-43/3133. The horse dentition is highly specialized for eating grass. Continuous growth from the roots counters teeth wear. The teeth fall into two clear groups: incisors seize the grass, molars grind the grass.
Both felines and horses have a large diastema, or gap, between their front teeth and their back teeth. This is a natural feature in many types of mammal.

References

Teeth
Mammals
Animal anatomy

]

Dental formula


In phonetics, the airstream mechanism is the method by which airflow is created in the vocal tract. Along with phonation and articulation, it is one of three main components of speech production. The airstream mechanism is mandatory for most sound production and constitutes the first part of this process, which is called initiation.

The organ generating the airstream is called the initiator and there are three initiators used phonemically in non-disordered human oral languages:
 the diaphragm together with the ribs and lungs (pulmonic mechanisms),
 the glottis (glottalic mechanisms), and
 the tongue (lingual or "velaric" mechanisms).
There are also methods of making sounds that do not require the glottis. These mechanisms are collectively called alaryngeal speech mechanisms (none of these speech mechanisms are used in non-disordered speech):

 the cheeks (buccal mechanisms, notated {ↀ} in VoQS). See buccal speech.
 after a laryngectomy, the esophagus may be used (notated {Œ} for simple esophageal speech, {Ю} for tracheo-esophageal speech in VoQS, and notated {И} for electrolaryngeal speech). See esophageal speech.
 the pharynx, and replacing the glottis using the tongue and the upper alveolus, the palate, or the pharyngeal wall. See pharyngeal speech.

Percussive consonants are produced without any airstream mechanism.

Types of airstream mechanism

Any of the three principal initiators − diaphragm, glottis or tongue − may act by either increasing or decreasing the pressure generating the airstream. These changes in pressure often correspond to outward and inward airflow, and are therefore termed egressive and ingressive respectively.

Of these six resulting airstream mechanisms, four are found lexically around the world:
 pulmonic egressive, where the air is pushed out of the lungs by the ribs and diaphragm. All human languages employ such sounds (such as vowels), and nearly three out of four use them exclusively.
 glottalic egressive, where the air column is compressed as the glottis moves upward. Such consonants are called ejectives. Ejective and ejective-like consonants occur in 16% of the languages.
 glottalic ingressive, where the air column is rarefied as the glottis moves downward. Such consonants are called implosives. Implosive and implosive-like consonants occur in 13% of the world's languages. Despite the name, the airstream may not actually flow inward: While the glottis moves downward, pulmonic air passes outward through it, but the reduction in pressure makes an audible difference to the sound.
 lingual ingressive, AKA velaric ingressive, where the air in the mouth is rarefied by a downward and sometimes rearward movement of the tongue. These are the click consonants. Clicks are regular sounds in ordinary (i.e. lexical) words in fewer than 2% of the world's languages, all in Africa.

These mechanisms may be combined into airstream contours, such as clicks which release into ejectives.

In normal vocabulary, the various Khoisan languages have pulmonic, ejective, and click consonants; the Chadic languages, some Mayan languages, and scattered Nilo-Saharan languages such as Gumuz, Uduk and Me'en have pulmonic, implosive, and ejective consonants, and the Nguni languages of the Bantu family utilize all four, – pulmonic, click, implosive, and ejective, – as does the Dahalo language of Kenya. Most other languages utilize at most two airstream mechanisms.

In interjections, the other two mechanisms may be employed. For example, in countries as diverse as Sweden, Turkey, and Togo, a pulmonic ingressive ("gasped" or "inhaled") vowel is used for back-channeling or to express agreement, and in France a lingual egressive (a "spurt") is used to express dismissal. The only language where such sounds are known to be contrastive in normal vocabulary is the extinct ritual language Damin (also the only language outside Africa with clicks); however, Damin appears to have been intentionally designed to differ from normal speech.

Pulmonic initiation
Initiation by means of the lungs (actually the diaphragm and ribs) is called pulmonic initiation. The vast majority of sounds used in human languages are pulmonic egressives. In most languages, including all the languages of Europe (excluding the Caucasus), all phonemes are pulmonic egressives.

The only attested use of a phonemic pulmonic ingressive is a lateral fricative in Damin, a ritual language formerly used by speakers of Lardil in Australia. This can be written with the extended version of the International Phonetic Alphabet as . !Xóõ has ingression as a phonetic detail in one series of its clicks, which are ingressive voiceless nasals with delayed aspiration, . Peter Ladefoged considers these to be among the most difficult sounds in the world. Other languages, for example in Taiwan, have been claimed to have pulmonic ingressives, but these claims have either proven to be spurious or to be occasional phonetic detail.

In interjections, but not in normal words, pulmonic ingressive vowels or words occur on all continents. This is commonly done for back-channeling (as with  in Ewe) or affirmation (as with  in Swedish). In English, an audible intake of breath, , or an indrawn consonant such as  or  is used in a conversation to indicate that someone is about to speak or is preparing to continue speaking. In some languages, such as Finnish and Amharic, entire phrases may be uttered with an ingressive airstream. (See ingressive sound.)

Glottalic initiation

It is possible to initiate airflow in the upper vocal tract by means of the vocal cords or glottis. This is known as glottalic initiation.

For egressive glottalic initiation, one lowers the glottis (as if to sing a low note), closes it as for a glottal stop, and then raises it, building up pressure in the oral cavity and upper trachea. Glottalic egressives are called ejectives. The glottis must be fully closed to form glottalic egressives, or the air column would flow backwards over it; it is therefore impossible to pronounce voiced ejectives. Ejective allophones of voiceless stops occur in many varieties of English at the ends of intonation units.

For ingressive glottalic initiation, the sequence of actions performed in glottalic pressure initiation is reversed:  one raises the glottis (as if to sing a high note), closes it, and then lowers it to create suction in the upper trachea and oral cavity. Glottalic ingressives are called implosives, although they may involve zero airflow rather than actual inflow. Because the air column would flow forwards over the descending glottis, it is not necessary to fully close it, and implosives may be voiced; indeed, voiceless implosives are exceedingly rare.

It is usual for implosives to be voiced. Instead of keeping the glottis tightly closed, it is tensed but left slightly open to allow a thin stream of air through. Unlike pulmonic voiced sounds, in which a stream of air passes through a usually-fixed glottis, in voiced implosives a mobile glottis passes over a nearly motionless air column to cause vibration of the vocal cords. Phonations that are more open than modal voice, such as breathy voice, are not conducive to glottalic sounds because in these the glottis is held relatively open, allowing air to readily flow through and preventing a significant pressure difference from building up behind the articulator.

Because the oral cavity is so much smaller than the lungs, vowels and approximants cannot be pronounced with glottalic initiation. So-called glottalized vowels and other sonorants use the more common pulmonic egressive airstream mechanism.

There is no clear divide between pulmonic and glottalic sounds. Some languages may have consonants which are intermediate. For example, glottalized consonants in London English, such as the t in rat , may be weakly ejective. Similarly, fully voiced stops in languages such as Thai, Zulu, and Maidu are weakly implosive. This ambiguity does not occur with the next airstream mechanism, lingual, which is clearly distinct from pulmonic sounds.

Lingual (velaric) initiation

The third form of initiation in human language is lingual or velaric initiation, where a sound is produced by a closure at two places of articulation, and the airstream is formed by movement of the body of the tongue. Lingual stops are more commonly known as clicks, and are almost universally ingressive. The word lingual is derived from Latin lingua, which means tongue.

To produce a lingual ingressive airstream, first close the vocal tract at two places: at the back of the tongue, as in a velar or uvular stop, and simultaneously with the front of the tongue or the lips, as in a coronal or bilabial stop. These holds may be voiceless, voiced, or nasalized. Then lower the body of the tongue to rarefy the air above it. The closure at the front of the tongue is opened first, as the click "release"; then the closure at the back is released for the pulmonic or glottalic click "accompaniment" or "efflux". This may be aspirated, affricated, or even ejective. Even when not ejective, it is not uncommon for the glottis to be closed as well, for a triply articulated consonant, and this third closure is released last to produce a glottalized click. Clicks are found in very few languages, notably the Khoisan languages of southern Africa and some nearby tongues such as Zulu. They are more often found in extra-linguistic contexts, such as the "tsk tsk" sound many Westerners use to express regret or pity (a dental click), or the clucking noise used by many equestrians to urge on their horses (a lateral click).

Lingual egressive initiation is performed by reversing the sequence of a lingual ingressive: the front and back of the tongue (or lips and back of the tongue) seal off the vocal cavity, and the cheeks and middle of the tongue move inward and upward to increase oral pressure. The only attested use of a lingual egressive is a bilabial nasal egressive click in Damin. Transcribing this also requires the use of the Extended IPA, .

Since the air pocket used to initiate lingual consonants is so small, it is not thought to be possible to produce lingual fricatives, vowels, or other sounds which require continuous airflow.

Clicks may be voiced, but they are more easily nasalized. This may be because the vocal cavity behind the rearmost closure, behind which the air passing through the glottis for voicing must be contained, is so small that clicks cannot be voiced for long. Allowing the airstream to pass through the nose enables a longer production.

Nasal clicks involve a combination of lingual and pulmonic mechanisms. The velum is lowered so as to direct pulmonic airflow through the nasal cavity during the lingual initiation. This nasal airflow may itself be egressive or ingressive, independently of the lingual initiation of the click. Nasal clicks may be voiced, but are very commonly unvoiced and even aspirated, which is rare for purely pulmonic nasals.

Airstream contours

In some treatments, complex clicks are posited to have airstream contours, in which the airstream changes between the front (click) and rear (non-click) release. There are two attested types: Linguo-pulmonic consonants, where the rear release is a uvular obstruent such as  or ; and linguo-glottalic consonants, where the rear release is an ejective such as  or .

Not only are simultaneous (rather than contour) implosive clicks possible, e.g. velar  and uvular , but velar implosive clicks are easier to produce than modally voiced clicks. However, they are not attested in any language.

Percussive consonants

Consonants may be pronounced without any airstream mechanism. These are percussive consonants, where the sound is generated by one organ striking another. Percussive consonants are not phonemic in any known language, though the extensions to the IPA for disordered speech provide symbols for a bilabial percussive  (smacking lips) and a bidental percussive  (gnashing teeth). The only percussive known to be used in nondisordered speech is a sublingual percussive  (a tongue slap) that appears allophonically in the release of alveolar clicks in the Sandawe language of Tanzania.

See also
Manner of articulation
Index of phonetics articles

References

External links
Eating the Wind: a satirical, but illustrative example of  sound symbolism and iconicity of airstream mechanisms.
: Robert Eklund (2008).  Pulmonic ingressive phonation: Diachronic and synchronic characteristics, distribution and function in animal and human sound production and in human speech. Journal of the International Phonetic Association, vol. 38, no. 3, pp. 235–324.
: Robert Eklund's website devoted to ingressive speech. Maps, sound files, and spectrograms.
 : Samples of ingressive pulmonic interjections from Northern Sweden

Phonetics

Airstream mechanism


Immaculata High School is a Roman Catholic high school in Ottawa, Ontario, Canada, operated by the Ottawa Catholic School Board. It is currently located along the Rideau Canal in Old Ottawa East neighbourhood of Ottawa. Like other Catholic schools, it is publicly funded under the Ontario school system.

History

Immaculata High School was founded as an all-girls school in 1928 by Reverend J.J. O'Gorman, acting under the advice of higher ecclesiastical authority. He named the school "Immaculata", and opened it with an initial enrollment of 85 run by a staff of 3 Grey Sisters as an alternative to public school education for girls of moderate income located at 211 Bronson Avenue.  The girls paid a monthly fee of one dollar — if their families could afford it.
The site for the new school was the former Christie mansion property on Bronson Avenue at the corner of Lisgar Street, which was purchased for $25,000. W.E. Noffke, a well-known Ottawa architect, designed the school with eight classrooms, a science lab, a home economics classroom, a gymnasium and a stage area, and office space. A passageway linked the school to the former Christie mansion, which became the first convent home for the Grey Sisters who taught at the school. During the construction of the school building, the students of the newly formed Immaculata High School attended classes at St. Patrick's Home, at the corner of Laurier Avenue and Kent Street. Sister Loyola was the first principal and the teachers were Sister Agnes of the Sacred Heart and Sister St. Geraldine.

By 1929, enrollment had increased to 160 students, and a new building with five classrooms, a science lab and a small library was constructed. In 1929, the first
commencement was held and a music department was established. In 1930, enrollment was 200 students and a commercial course was provided.

A home economics department and nine new classrooms were added in 1939 to meet the needs of the enrollment of 300 students, taught by nine Sisters.

In 1941, Principal Sister Mary Christine supervised a staff of 11. To meet the needs of the camera club, developing facilities and printing rooms were
added. In 1948, the enrolment at Immaculata was 425, and the staff now consisted of 17 Sisters.

The school's Dr. B. Kearns Memorial Wing, which opened in September 1950, added eight classrooms, including a double-sized commercial classroom and space for the
Music Department. In 1952, an addition to the Kearns Memorial Wing added three new classrooms, a students' library and a principal's office.

In 1954, a new convent was constructed on the north side of the property. The former convent was renovated into 2 classrooms and space for the Music Department, which had a staff of 4. The enrollment was 725 students and the school now had a staff of 22.

In 1962, a chapel/auditorium was built, a project led by principal Sister Mary Christine. In 1967, another building was constructed with 12 classrooms, labs and a gym. Despite this, however, by 1972 the enrollment of Immaculata had dropped to 400 students.

As Immaculata celebrated its golden anniversary in 1978, male students were enrolled for the first time. In 1984, grades 7 and 8 students were added. When Immaculata marked its 60th anniversary in 1988, James J. Shea was appointed as the school's first lay principal, overseeing an enrollment of 870 students.

After Immaculata celebrated its 65th anniversary in September 1994 (after 2 years of major renovations), the school moved to the current location at 140 Main Street. It has been declared an arts academy.

The high school's current location was originally built in 1929–1930 to house both St. Patrick's High School and St. Patrick's College (Ottawa), a now defunct Catholic post-secondary institution administered by the Oblate Fathers. In 1973, St. Patrick's sold the building to Algonquin College, who operated a satellite campus there until it sold the building to the Ottawa Roman Catholic Separate School Board to house Immaculata in 1994. Edward Cuhaci was the architect for the renovations undertaken in 1994.

In 2000, a satellite classroom site for Immaculata High School was set up in the basement of St. Mary's Home, to enable an initial enrollment of 10 pregnant teenagers from all schools in the city to continue with their academics during their pregnancies. The school held its first graduation in June 2000. In January 2002, the program, now called St. Mary's Home Community Outreach, moved into 780 rue de l'Eglise.

Immaculata High School celebrated its 75th anniversary in 2003. In 2007, Principal Thomas D'Amico was named one of Canada's Outstanding Principals. The school's sports team is the Immaculata Saints, and the school mascot is the saint bernard 'Bernie Mac'.

Principals
All of the Sisters who were principals were Grey Sisters of the Immaculate Conception:
Sister Loyola (1928) (while students attended classes at St. Patrick's Home)
Sister Agnes of the Sacred Heart (1928–1935) (first principal at Bronson Avenue site)
Sister Patrice Thompson (1935–1937)
Sister Darina Fackelman (1937–1941)
Sister Thomas Tremblay (1941–54)
Sister Cormickie Holland (1954–1967)
Sister Lucille Martin (1967–70)
Sister Anna Clare (1970–75 and 1976–82)
Sister Anne O'Brien (1975–76)
Sister Theresa Kelly (1982–87)
James J. Shea (1987–89)
Mary Durst (1989–95)
Evelyn Kelly (1989 (acting) and 1995–1997)
Bernard Swords (1998–2001)
Thomas Tremblay(2001–03)
Thomas D'Amico (2003–2010)
Christopher Mes (2010–2016)
Norma Mcdonald (2016–2018)
Sean Power (2018–2021)
Robert Garnett (2022–)

Notable alumni

 David Azzi, former CFL football player
 Ben Eager, former NHL hockey player
 Craig Lauzon, comedian, co-starring on Royal Canadian Air Farce
 Lynn Nightingale, figure skating champion
 Andrew Scheer, Canadian  Member of Parliament, former Speaker of the House of Commons and former leader of the Conservative Party of Canada
 Julie Van Dusen, reporter for CBC; covers political events
 Kaitlyn Alexander, non-binary actor/YouTuber/musician

See also
List of high schools in Ontario

References

150 years of Catholic Education in Ottawa-Carleton 1856-2006, Ottawa-Carleton Catholic School Board, 2006

External links

 School Website

Catholic secondary schools in Ontario
High schools in Ottawa
Educational institutions established in 1928
1928 establishments in Ontario
Middle schools in Ottawa

Immaculata High School (Ottawa)


Tehran (;   )
is the capital and most populous city of Iran, capital of Tehran province and Tehran county. Tehran city had a population of 9,039,000 in the estimate of 2022 and according to the 2018 estimate of the United Nations, it is the 34th most populous city in the world and the most populous city in West Asia. Tehran metropolis is the second most populated metropolis in the Middle East.

In the classical antiquity, part of the territory of present-day Tehran was occupied by Rhages (now Ray), a prominent Median city destroyed in the medieval Arab, Turkic, and Mongol invasions. Modern Ray was absorbed into the metropolitan area of Greater Tehran.

Tehran was first chosen as the capital of Iran by Agha Mohammad Khan of the Qajar dynasty in 1786, because of its proximity to Iran's territories in the Caucasus, then separated from Iran in the Russo-Iranian Wars, to avoid the vying factions of the previously ruling Iranian dynasties. The capital has been moved several times throughout history, however, and Tehran became the 32nd capital of Persia. Large-scale construction works began in the 1920s, and Tehran became a destination for mass migrations from all over Iran since the 20th century.

Tehran is home to many historical sites, including the royal complexes of Golestan, Sa'dabad, and Niavaran, where the last two dynasties of the former Imperial State of Iran were seated. Tehran's landmarks include the Azadi Tower, a memorial built under the reign of Mohammad Reza Shah of the Pahlavi dynasty in 1971 to mark the 2,500th anniversary of the Persian Empire, the Milad Tower, the world's sixth-tallest self-supporting tower, completed in 2007, and the Tabiat Bridge, completed in 2014.

Most of the population are Persian, with roughly 99% of them speaking the Persian language, alongside other ethnolinguistic groups in the city which became assimilated.

Tehran is served by Imam Khomeini International Airport, alongside the domestic Mehrabad Airport, a central railway station, Tehran Metro, a bus rapid transit system, trolleybuses, and a large network of highways.

Plans to relocate the capital from Tehran to another area due to air pollution and earthquakes have not been approved so far. A 2016 survey of 230 cities across the globe by Mercer ranked Tehran 203rd for quality of life. According to the Global Destinations Cities Index in 2016, Tehran is among the top ten fastest growing destinations. Tehran City Council declared 6 October the Tehran Day in 2016, celebrating the date when in 1907 the city officially became the capital of Iran.

Etymology
Various theories on the origin of the name Tehran have been put forward.

Iranian linguist Ahmad Kasravi, in an article "Shemiran-Tehran", suggested that Tehran and Kehran mean "the warm place", and Shemiran means "the cool place". He listed cities with the same base and suffix and studied the components of the word in ancient Iranian languages, and came to the conclusion that Tehran and Kehran meant the same thing in different Iranian language families, as the consonants "t" and "k" are close to each other in such languages. He also provided evidence that cities named "Shemiran" were colder than those named "Tehran" or "Kehran". He considered other theories not considering the ancient history of Iranian languages such as "Tirgan" theory and "Tahran" theory folk etymology.

The official City of Tehran website says that "Tehran" comes from the Persian words tah meaning "end", or "bottom", and ran meaning "[mountain] slope"—literally, the bottom of the mountain (ته کوه). Given Tehran's position at the foot of the Alborz mountains, this seems plausible.

So according to Zana Piranshahri, the word Tehran means a place where the "honeyberry" tree grows. Also the suffix ran is visible in many of the names of districts and villages of modern Tehran that are not unrelated to each other, such as Shemiran, Niavaran, Jamaran, Qasran and Shahran. In the Avestan language and also in the book of Avesta ran has had the meaning of "foothills" and "plain," which is still related to the name of the Rey city. The Zoroastrian Medes called their largest and most important town Rhaga or Rey, meaning the town which is situated in the plain and on a foothill. Therefore, the words "Rey" and "Ran" mean foothills, and the toponymic reason for this is the geographical position of Rey and Tehran, because both are located on foothills and in a plain.

In English, it was formerly spelt "Teheran".

History

Archaeological remains from the ancient city of Ray suggest that settlement in Tehran dates back over 6,000 years.

Classical era
Tehran is in the historical Media region of ( ) in northwestern Iran. By the time of the Median Empire, part of present-day Tehran was a suburb of the prominent Median city of Rhages ( ). In the Avesta's Videvdat (i, 15), Rhages is mentioned as the 12th sacred place created by Ohrmazd. In Old Persian inscriptions, Rhages appears as a province (Bistun 2, 10–18). From Rhages, Darius I sent reinforcements to his father Hystaspes, who was putting down a rebellion in Parthia (Bistun 3, 1–10). Some Middle Persian texts give Rhages as the birthplace of Zoroaster, although modern historians generally place the birth of Zoroaster in Khorasan Province.

Mount Damavand, the highest peak of Iran, which is located near Tehran, is an important location in Ferdowsi's Šāhnāme, an Iranian epic poem based on the ancient legends of Iran. It appears in the epics as the homeland of the protoplast Keyumars, the birthplace of King Manuchehr, the place where King Fereydun bound the dragon fiend Aždahāk (Bivarasp), and the place where Arash shot his arrow.

Medieval period
In 641, during the reign of the Sasanian Empire, Yazdgerd III issued his last appeal to the nation from Rhages, before fleeing to Khorasan. Rhages was dominated by the Parthian House of Mihran, and Siyavakhsh—the son of Mehran, the son of Bahram Chobin—who resisted the seventh-century Muslim invasion of Iran. Because of this resistance, when the Arabs captured Rhages, they ordered the town destroyed and rebuilt anew by traitor aristocrat Farrukhzad.

In the ninth century, Tehran was a well-known village, but less so than the city of Rhages, flourishing nearby. Rhages was described in detail by tenth-century Muslim geographers. Despite the interest that Arabian Baghdad displayed in Rhages, the number of Arabs in the city remained insignificant and the population mainly consisted of Iranians of all classes.

The Oghuz Turks invaded Rhages in 1035 and again in 1042, but the city was recovered under the Seljuks and the Khwarezmians. Medieval writer Najm od Din Razi declared the population of Rhages about 500,000 before the Mongol invasion. In the 13th century, the Mongols invaded Rhages, laid the city to ruins, and massacred many of its inhabitants. Others escaped to Tehran.

In July 1404, Castilian ambassador Ruy González de Clavijo visited Tehran on a journey to Samarkand, the capital of Turco-Mongol conqueror Timur, the ruler of Iran at the time. He described it in his diary as an unwalled region.

Early modern era
Italian traveler Pietro della Valle passed through Tehran overnight in 1618, and in his memoirs called the city Taheran. English traveler Thomas Herbert entered Tehran in 1627, and mentioned it as Tyroan. Herbert stated that the city had about 3,000 houses.

In the early 18th century, Karim Khan of the Zand dynasty ordered a palace and a government office built in Tehran, possibly to declare the city his capital; but he later moved his government to Shiraz. Eventually, Qajar king Agha Mohammad Khan chose Tehran as the capital of Iran in 1786.

Agha Mohammad Khan's choice of his capital was based on a similar concern for the control of both northern and southern Iran. He was aware of the loyalties of the inhabitants of former capitals Isfahan and Shiraz to the Safavid and Zand dynasties respectively, and was wary of the power of the local notables in these cities. Thus, he probably viewed Tehran's lack of a substantial urban structure as a blessing, because it minimized the chances of resistance to his rule by the notables and by the general public. Moreover, he had to remain within close reach of Azerbaijan and Iran's integral northern and southern Caucasian territories—at that time not yet irrevocably lost per the treaties of Golestan and Turkmenchay to the neighboring Russian Empire—which would follow in the course of the 19th century.

After 50 years of Qajar rule, the city still barely had more than 80,000 inhabitants. Up until the 1870s, Tehran consisted of a walled citadel, a roofed bazaar, and the three main neighborhoods of Udlajan, Chale-Meydan, and Sangelaj, where the majority resided.

The first development plan of Tehran in 1855 emphasized traditional spatial structure. The second, under the supervision of Dar ol Fonun in 1878, included new city walls, in the form of a perfect octagon with an area of 19 square kilometers, mimicking the Renaissance cities of Europe. Tehran was 19.79 square kilometers, and had expanded more than fourfold.

Late modern era

Growing awareness of civil rights resulted in the Constitutional Revolution and the first constitution of Iran in 1906. On 2 June 1907, the parliament passed a law on local governance known as the Baladie (municipal law), providing a detailed outline of issues such as the role of councils within the city, the members' qualifications, the election process, and the requirements to be entitled to vote. The then-Qajar monarch Mohammad Ali Shah abolished the constitution and bombarded the parliament with the help of the Russian-controlled Cossack Brigade on 23 June 1908. That was followed by the capture of the city by the revolutionary forces of Ali-Qoli Khan (Sardar Asad II) and Mohammad Vali Khan (Sepahsalar e Tonekaboni) on 13 July 1909. As a result, the monarch was exiled and replaced by his son Ahmad, and the parliament was re-established.

After World War I, the constituent assembly elected Reza Shah of the Pahlavi dynasty as the new monarch, who immediately suspended the Baladie law of 1907, replacing the decentralized and autonomous city councils with centralist approaches to governance and planning.

From the 1920s to the 1930s, under the rule of Reza Shah, the city was essentially rebuilt from scratch. Several old buildings, including parts of the Golestan Palace, Tekye Dowlat, and Tupkhane Square, were replaced with modern buildings influenced by classical Iranian architecture, particularly the buildings of the National Bank, the police headquarters, the telegraph office, and the military academy.

Changes to the urban fabric began with the street-widening act of 1933, which served as a framework for changes in all other cities. The Grand Bazaar was divided in half and many historic buildings were demolished and replaced by wide straight avenues, and the traditional texture of the city was replaced with intersecting cruciform streets that created large roundabouts in major public spaces such as the bazaar.

As an attempt to create a network for easy transportation within the city, the old citadel and city walls were demolished in 1937, replaced by wide streets cutting through the urban fabric. The new city map of Tehran in 1937 was heavily influenced by modernist planning patterns of zoning and gridiron networks.

During World War II, Soviet and British troops entered the city. In 1943, Tehran was the site of the Tehran Conference, attended by U.S. President Franklin D. Roosevelt, Soviet Premier Joseph Stalin, and British Prime Minister Winston Churchill.

The establishment of the planning organization of Iran in 1948 resulted in the first socioeconomic development plan to cover from 1949 to 1955. These plans not only failed to slow the unbalanced growth of Tehran but with the 1962 land reforms that Reza Shah's son and successor Mohammad Reza Shah named the White Revolution, Tehran's chaotic growth was further accentuated.

Throughout the 1960s and 1970s, Tehran developed rapidly under Mohammad Reza Shah. Modern buildings altered the face of Tehran and ambitious projects were planned for the following decades. To resolve the problem of social exclusion, the first comprehensive plan was approved in 1968. The consortium of Iranian architect Abd-ol-Aziz Farmanfarmaian and the American firm of Victor Gruen Associates identified the main problems blighting the city as high-density suburbs, air and water pollution, inefficient infrastructure, unemployment, and rural-urban migration. Eventually, the whole plan was marginalized by the 1979 Revolution and the subsequent Iran–Iraq War.

Tehran's most famous landmark, the Azadi Tower, was built by the order of the Shah in 1971. It was designed by Hossein Amanat, an architect whose design won a competition, combining elements of classical Sassanian architecture with post-classical Iranian architecture. Formerly known as the Shahyad Tower, it was built to commemorate the 2,500th anniversary of the Imperial State of Iran.

During the Iran–Iraq War in 1980 to 1988, Tehran was repeatedly targeted by airstrikes and Scud missile attacks.

The 435-meter-high Milad Tower, one of the proposed development projects of pre-revolutionary Iran, was completed in 2007, and has become a famous landmark of Tehran. Tabiat Bridge a 270-meter pedestrian overpass, designed by award-winning architect Leila Araghian, was completed in 2014.

Geography

Location and subdivisions

The metropolis of Tehran is divided into 22 municipal districts, each with its own administrative center. Of the 22 municipal districts, 20 are located in Tehran County's Central District, while districts 1 and 20 are respectively located in the counties of Shemiranat and Ray. Although administratively separate, the cities of Ray and Shemiran are often considered part of Greater Tehran.

Northern Tehran is the wealthiest part of the city, consisting of various districts such as Zafaraniyeh, Jordan, Elahiyeh, Pasdaran, Kamranieh, Ajodanieh, Farmanieh, Darrous, Niavaran, Jamaran, Aghdasieh, Mahmoodieh, Velenjak, Qeytarieh, Ozgol and Ekhtiarieh. While the center of the city houses government ministries and headquarters, commercial centers are located further north.

Climate

The northern area of Tehran has a Mediterranean climate (Köppen climate classification: Csa), with a cold semi-arid climate (BSk) elsewhere, with hot dry summers and cool rainy winters. Tehran's climate is largely defined by its geographic location, with the towering Alborz mountains to its north and the country's central desert to the south. It can be generally described as mild in spring and autumn, hot and dry in summer, and cold and wet in winter.

As the city has a large area, with significant differences in elevation among various districts, the weather is often cooler in the hilly north than in the flat southern part of Tehran. For instance, the  Valiasr Street runs from Tehran's railway station at  elevation above sea level in the south of the city to Tajrish Square at 1712.6 m (5612.3 ft) elevation above sea level in the north. However, the elevation can even rise up to  at the end of Velenjak in northern Tehran. The sparse texture, the existence of old gardens, orchards, green spaces along the highways and the lack of industrial activities in the north of the city have helped the air in the northern areas to be 2 to 3 degrees Celsius cooler than the southern areas of the city.

The main direction of the prevailing wind in Tehran is northwest to southeast. Other air currents that blow in the area of Tehran are:

 Tochal breeze: With the rapid cooling of the Alborz mountain range at night, a local high-pressure center is formed on Mount Tochal, and this cold current flows down the mountain due to its weight and high pressure; Thus, a gentle breeze blows into the city from the north at night.
 Southern and southeastern regional winds: these winds blow from the desert plains in the hot months of the year.
 Western winds: These winds are among the planetary winds that affect the city of Tehran more or less throughout the year and can be called the prevailing wind.

Air currents have a great effect on Tehran's weather. The prevailing wind blowing from the west causes the west of the city to always be exposed to fresh air; Although this wind brings smoke and pollution from the western industrial areas, its strong wind can take the polluted air out of the city of Tehran.

In most years, winter provides half of Tehran's total annual rainfall. March is the rainiest month of the year and about one-fifth of the annual rainfall occurs in it. Summer is also the least rainy season and September is the driest month of the year in Tehran. The average annual rainfall of the city is sometimes very different in the north and south regions. There are between 205 and 213 days of clear to partly cloudy weather in Tehran.

One of the most intense rains in Tehran happened on 21 April 1962 and this rain lasted for 10 hours. Meteorology also announced that the amount of rainfall on that one day in Tehran was equivalent to six years.

Summer is hot and dry with little rain, but relative humidity is generally low, making the heat tolerable. Average high temperatures are between  and  during summer months, and it can sometimes rise up to  during heat waves. Average low temperatures in summer are between  and , and it can occasionally drop to below   in the mountainous north of the city at night.

Winter is cold and occasionally snowy, with an average of 12.3 snow days annually in central Tehran and more than 23.7 snow days annually in northern Tehran. During the winter months, average high temperatures are between  and  and average low temperatures are between  and , and it can occasionally drop to below   during cold waves.

Most of the annual precipitation occurs from late autumn to mid-spring. March is the wettest month with an average precipitation of . The hottest month is July, with a mean minimum temperature of  and a mean maximum temperature of , and the coldest is January, with a mean minimum temperature of  and a mean maximum temperature of .

The highest recorded temperature was  on 3 July 1958 and the lowest recorded temperature was  on 8 January 1969.

In February 2005, heavy snow covered all parts of the city. Snow depth was recorded as  in the southern part of the city and  in the northern part of city. One newspaper reported that it had been the worst weather in 34 years. Ten thousand bulldozers and 13,000 municipal workers were deployed to keep the main roads open.

On 5 and 6 January 2008, a wave of heavy snow and low temperatures covered the city in a thick layer of snow and ice, forcing the Council of Ministers to officially declare a state of emergency and close down the capital from 6 January through 7 January.

On 3 February 2014, Tehran received heavy snowfall, specifically in the northern parts of the city, with a depth of . In one week of successive snowfalls, roads were made impassable in some areas, with the temperature ranging from   to  .

On 3 June 2014, a severe thunderstorm with powerful microbursts created a haboob, engulfing the city in sand and dust and causing five deaths, with more than 57 injured. This event also knocked down numerous trees and power lines. It struck between 5:00 and 6:00 p.m., dropping temperatures from   to   within an hour. The dramatic temperature drop was accompanied by wind gusts reaching nearly  .

Environmental issues

A plan to move the capital has been discussed many times in prior years, due mainly to the environmental issues of the region. Tehran is one of the world's most polluted cities and is also located near two major fault lines.

The city suffers from severe air pollution, 80% of it due to cars. The remaining 20% is due to industrial pollution. Other estimates suggest that motorcycles alone account for 30% of air and 50% of noise pollution in Tehran. Tehran is also considered one of the strongest sources of greenhouse gas emissions in the Middle East. Enhanced concentration of carbon dioxide over the city (that are likely originated from the anthropogenic urban sources in the city) is easily detectable from satellite observations throughout the year.

In 2010, the government announced that "for security and administrative reasons, the plan to move the capital from Tehran has been finalized." There are plans to relocate 163 state firms and several universities from Tehran to avoid damages from a potential earthquake.

The officials are engaged in a battle to reduce air pollution. It has, for instance, encouraged taxis and buses to convert from petrol engines to engines that run on compressed natural gas. Furthermore, the government has set up a "Traffic Zone" covering the city centre during peak traffic hours. Entering and driving inside this zone is only allowed with a special permit.

There have also been plans to raise people's awareness of the hazards of pollution. One method that is being employed is the installation of Pollution Indicator Boards all around the city to monitor the level of particulate matter (PM10), nitrogen dioxide (NO2), ozone (O3), sulfur dioxide (SO2), and carbon monoxide (CO).

Demographics

The city of Tehran had a population of 7,711,230 in 2,286,787 households at the time of the 2006 National Census. The following census in 2011 counted 8,154,051 people in 2,624,511 households. The latest census in 2016 showed a population of 8,693,706 people in 2,911,065 households.

With its cosmopolitan atmosphere, Tehran is home to diverse ethnic and linguistic groups from all over the country. The present-day dominant language of Tehran is the Tehrani variety of the Persian language, and the majority of people in Tehran identify themselves as Persians. However, before, the native language of the Tehran–Ray region was not Persian, which is linguistically Southwest Iranian and originates in Fars, but a now extinct Northwestern Iranian language.

Iranian Azeris form the second-largest ethnic group of the city, comprising about 10-15%  of the total population, while ethnic Mazanderanis are the third-largest, comprising about 5% of the total population. Tehran's other ethnic communities include Kurds, Armenians, Georgians, Bakhtyaris, Talysh, Baloch, Assyrians, Arabs, Jews, and Circassians.

According to a 2010 census conducted by the Sociology Department of the University of Tehran, in many districts of Tehran across various socio-economic classes in proportion to population sizes of each district and socio-economic class, 63% of the people were born in Tehran, 98% knew Persian, 75% identified themselves as ethnic Persian, and 13% had some degree of proficiency in a European language.

Tehran saw a drastic change in its ethnic-social composition in the early 1980s. After the political, social, and economic consequences of the 1979 Revolution and the years that followed, a number of Iranian citizens, mostly Tehranis, left Iran. The majority of Iranian emigrations have left for the United States, Germany, Sweden, and Canada.

With the start of the Iran–Iraq War (1980–1988), the second wave of inhabitants fled the city, especially during the Iraqi air offensives on the capital. With most major powers backing Iraq at the time, economic isolation gave yet more reason for many inhabitants to leave the city (and the country). Having left all they had and have struggled to adapt to a new country and build a life, most of them never came back when the war was over. During the war, Tehran also received a great number of migrants from the west and the southwest of the country bordering Iraq.

The unstable situation and the war in neighbouring Afghanistan and Iraq prompted a rush of refugees into the country who arrived in their millions, with Tehran being a magnet for much seeking work, who subsequently helped the city to recover from war wounds, working for far less pay than local construction workers. Many of these refugees are being repatriated with the assistance of the UNHCR, but there are still sizable groups of Afghan and Iraqi refugees in Tehran who are reluctant to leave, being pessimistic about the situation in their own countries. Afghan refugees are mostly Dari-speaking Tajik and Hazara, speaking a variety of Persian, and Iraqi refugees are mainly Mesopotamian Arabic-speakers who are often of Iranian and Persian ethnic heritage.

Religion

The majority of Tehranis are officially Twelver Shia Muslims, which has also been the state religion since the 16th-century Safavid conversion. Other religious communities in the city include followers of the Sunni and Mystic branches of Islam, various Christian denominations, Judaism, Zoroastrianism, and the Bahá'í Faith.

As per a 2003 survey, 60% of Tehranis consider religion to be "very important", 25% "important" and 13% "not important", while 41% of Tehranis identify as "very pious", 41% as "pious" and 16% as "not pious." A 2016 survey found out that, among Tehranis, 53.5% consider religion to be "very important / important", 31.1% to be "rather important", 10.5% to be "not very important" and 4.8% to be "not at all important."

There are many religious centres scattered around the city, from old to newly built centres, including mosques, churches, synagogues, and Zoroastrian fire temples. The city also has a very small third-generation Indian Sikh community with a local gurdwara that was visited by the Indian Prime Minister in 2012.

Economy

Tehran is the economic centre of Iran. About 30% of Iran's public-sector workforce and 45% of its large industrial firms are located in the city, and almost half of these workers are employed by the government. Most of the remainder of workers are factory workers, shopkeepers, laborers, and transport workers.

Few foreign companies operate in Tehran, due to the government's complex international relations. But prior to the 1979 Revolution, many foreign companies were active in Iran. Tehran's present-day modern industries include the manufacturing of automobiles, electronics and electrical equipment, weaponry, textiles, sugar, cement, and chemical products. It is also a leading centre for the sale of carpets and furniture. The oil refining companies of Pars Oil, Speedy, and Behran are based in Tehran.

Tehran relies heavily on private cars, buses, motorcycles, and taxis, and is one of the most car-dependent cities in the world. The Tehran Stock Exchange, which is a full member of the World Federation of Exchanges (WFE) and a founding member of the Federation of Euro-Asian Stock Exchanges, has been one of the world's best-performing stock exchanges in recent years.

Shopping

Tehran has a wide range of shopping centers, and is home to over 60 modern shopping malls. The city has a number of commercial districts, including those located at Valiasr, Davudie, and Zaferanie. The largest old bazaars of Tehran are the Grand Bazaar and the Bazaar of Tajrish. Iran Mall is the largest mall in the world in area.

Most of the international branded stores and upper-class shops are in the northern and western parts of the city. Tehran's retail business is growing with several newly built malls and shopping centres.

List of modern and most-visited Shopping Malls in Tehran Province:
 Mega Mall
 Bamland Shopping Center
 Palladium Shopping Center
 Sam Center
 Iran Mall
 Kourosh Mall
 Tirajeh Shopping Center
 Modern Elahiyeh Shopping Center
 Donyaye Noor Shopping Centre
 Tandis Shopping Center
 Ava Centre
 Atlas Mall
 Goldis Mall
 OPAL Shopping Center
 Rosha Department Store
 Sivan Center
 Arg Shopping Center
 Nasr Shopping Center
 Galleria Shopping Center
 Charso Mall
 Mirdamad Shopping Center
 Royal Address Complex
 Platin Shopping Center
 Sana Shopping Center
 Sepid Shopping Center Tehran
 Najm Khavar Mianeh
 Parsian Shopping Center
 Artemis Shopping Center
 Heravi Center Shopping Mall
 Tuba shopping center
 Lale Shopping Center
 Andisheh Shopping Center
 Sky Center
 Lotus Mall
 Saba Shopping Mall
 Seven Center Shopping Mall
 Kasa Shopping
 Platin Shopping Center

Tourism

Tehran, as one of the main tourist destinations in Iran, has a wealth of cultural attractions. It is home to royal complexes of Golestan, Saadabad and Niavaran, which were built under the reign of the country's last two monarchies.

There are several historic, artistic, and scientific museums in Tehran, including the
National Museum
Malek Museum
Cinema Museum at Ferdows Garden
Abgineh Museum
Museum of the Qasr Prison
Carpet Museum
Reverse Glass Painting Museum (vitray art)
Safir Office Machines Museum
Also the Museum of Contemporary Art, which hosts works of famous artists such as Van Gogh, Pablo Picasso, and Andy Warhol. The Iranian Imperial Crown Jewels, one of the largest jewel collections in the world, are also on display at Tehran's National Jewelry Museum.

A number of cultural and trade exhibitions take place in Tehran, which are mainly operated by the country's International Exhibitions Company. Tehran's annual International Book Fair is known to the international publishing world as one of the most important publishing events in Asia.

Hotel

 Espinas Palace Hotel
 Parsian Azadi Hotel
 Fereshteh Pasargad Hotel
 Laleh International Hotel
 Parsian Enghelab Hotel
 Parsian Esteghlal International Hotel
 Parsian Evin Hotel
 Ibis Hotel
 Espinas International Hotel
 Persian Plaza Hotel
 Hanna Boutique Hotel
 Homa Hotel
 Rexan Hotel
 Tehran Heritage Hostel
 Tehran Grand 1 Hotel
 Iran Cozy Hotel
 Pamchal Hotel
 Amatis Hotel
 Hotel Markazi Iran
 Marlik Hotel
 Ferdowsi Grand Hotel
 Atana Hotel
 Valiasr Hotel
 Taj Mahal Hotel
 Morvarid Hotel
 Hally Hotel
 Howeyzeh hotel
 Atlas Hotel
 Amir Hotel

Infrastructure

Highways and streets

Following the Islamic Revolution in 1979, the political system changed from constitutional monarchy to Islamic republic. Then the construction of political power in the country needed to change so that new spectrums of political power decision-making centers emerged in Iran. Motives, desires and actions of these new political power decision-making centers in Iran, made them rename streets and public places throughout the country, especially Tehran. For example Shahyad square changed to Azadi square and Pahlavi street changed to Valiasr street.

The metropolis of Tehran is equipped with a large network of highways and interchanges.

A number of streets in Tehran are named after international figures, including:
 Henri Corbin Street, central Tehran
 Simon Bolivar Boulevard, northwestern Tehran
 Edward Browne Street, near the University of Tehran
 Gandhi Street, northern Tehran
 Mohammad Ali Jenah Expressway, western Tehran
 Iqbal Lahori Street, eastern Tehran
 Patrice Lumumba Street, western Tehran
 Nelson Mandela Boulevard, northern Tehran
 Bobby Sands Street, western side of the British Embassy

Cars

According to the head of Tehran Municipality's Environment and Sustainable Development Office, Tehran was designed to have a capacity of about 300,000 cars, but more than five million cars are on the roads. The automotive industry has recently developed, but international sanctions influence the production processes periodically.

According to local media, Tehran has more than 200,000 taxis plying the roads daily, with several types of taxi available in the city. Airport taxis have a higher cost per kilometer as opposed to regular green and yellow taxis in the city.

Buses

Buses have served the city since the 1920s. Tehran's transport system includes conventional buses, trolleybuses, and bus rapid transit (BRT). The city's four major bus stations include the South Terminal, the East Terminal, the West Terminal, and the northcentral Beyhaghi Terminal.

The trolleybus system was opened in 1992, using a fleet of 65 articulated trolleybuses built by Czech Republic's Škoda. This was the first trolleybus system in Iran. In 2005, trolleybuses were operating on five routes, all starting at Imam Hossein Square. Two routes running northeastwards operated almost entirely in a segregated busway located in the middle of the wide carriageway along Damavand Street, stopping only at purpose-built stops located about every 500 metres along the routes, effectively making these routes trolleybus-BRT (but they were not called such). The other three trolleybus routes ran south and operated in mixed traffic. Both route sections were served by limited-stop services and local (making all stops) services. A 3.2-kilometer extension from Shoosh Square to Rah Ahan Square was opened in March 2010. Visitors in 2014 found that the trolleybus system had closed, apparently sometime in 2013. However, it reopened in March 2016, operating on a single 1.8-km route between Meydan-e-Khorasan (Khorasan Square) and Bozorgrah-e-Be'sat. Around 30 vehicles had been refurbished and returned to service. Extensions were planned.

Tehran's bus rapid transit (BRT) was officially inaugurated in 2008. It has 10 lines with some 215 stations in different areas of the city. , the BRT system had a network of , transporting 1.8 million passengers on a daily basis.

Bicycle

Bdood is a dockless bike-sharing company in Iran. Founded in 2017, it is available in the central and northwest regions of the capital city of Tehran. The company has plans to expand across the city in the future.

In the first phase, the application covers the flat areas of Tehran and they would be out of use in poor weather conditions.

Riders can use 29 parking lots for the bikes across Enqelab Avenue, Keshavarz Boulevard, Beheshti Street and Motahhari Avenue in which the bikes are available 24/7 for riders.

Railway and subway

Tehran has a central railway station that connects services round the clock to various cities in the country, along with a Tehran–Europe train line also running.

The feasibility study and conceptual planning of the construction of Tehran's subway system were started in the 1970s. The first two of the eight projected metro lines were opened in 2001.

Airport

Tehran is served by the international airports of Mehrabad and Imam Khomeini. Mehrabad Airport, an old airport in western Tehran that doubles as a military base, is mainly used for domestic and charter flights. Imam Khomeini Airport, located  south of the city, handles the main international flights.

Parks and green spaces

There are over 2,100 parks within the metropolis of Tehran, with one of the oldest being Jamshidie Park, which was first established as a private garden for Qajar prince Jamshid Davallu, and was then dedicated to the last empress of Iran, Farah Pahlavi. The total green space within Tehran stretches over 12,600 hectares, covering over 20 percent of the city's area. The Parks and Green Spaces Organization of Tehran was established in 1960, and is responsible for the protection of the urban nature present in the city.

Tehran's Birds Garden is the largest bird park in Iran. There is also a zoo located on the Tehran–Karaj Expressway, housing over 290 species within an area of about five hectares.

In 2009, the Ab-o-Atash Park ("Water and Fire park") was founded. Its main features are an open water fountain area for cooling in the hot climate, fire towers, and an amphitheatre.

Energy

Water

Greater Tehran with its population of more than 13 million is supplied by surface water from the Lar dam on the Lar River in the Northeast of the city, the Latyan dam on the Jajrood River in the North, the Karaj River in the Northwest, as well as by groundwater in the vicinity of the city.

Solar Energy

Solar panels have been installed in Tehran's Pardisan Park for green electricity production, said Masoumeh Ebtekar, head of the Department of Environment.

According to the national energy roadmap, the government plans to promote green technology to increase the nominal capacity of power plants from 74 gigawatts to over 120 gigawatts by the end of 2025.

Education

Tehran is the largest and most important educational center in Iran. There are a total of nearly 50 major colleges and universities in Greater Tehran.

Since the establishment of Dar ol Fonun by the order of Amir Kabir in the mid-19th century, Tehran has amassed a large number of institutions of higher education. Some of these institutions have played crucial roles in the unfolding of Iranian political events. Samuel M. Jordan, whom Jordan Avenue in Tehran was named after, was one of the founding pioneers of the American College of Tehran, which was one of the first modern high schools in the Middle East.

Among major educational institutions located in Tehran, Amirkabir University of Technology (Tehran Polytechnic), University of Tehran, Sharif University of Technology, and Tehran University of Medical Sciences are the most prestigious. Other major universities located in Tehran include Tehran University of Art, Allameh Tabatabaei University, K. N. Toosi University of Technology, Shahid Beheshti University (Melli University), Kharazmi University, Iran University of Science and Technology, Iran University of Medical Sciences, Islamic Azad University, International Institute of Earthquake Engineering and Seismology, Iran's Polymer and Petrochemical Institute, Shahed University, and Tarbiat Modarres University. Sharif University of Technology, Amirkabir University of Technology, Iran University of Science and Technology and K. N. Toosi University of Technology also located in Tehran are nationally well known for taking in the top undergraduate Engineering and Science students; and internationally recognized for training competent under graduate students. It has probably the highest percentage of graduates who seek higher education abroad.

Tehran is also home to Iran's largest military academy, and several religious schools and seminaries.

Culture

Architecture

The oldest surviving architectural monuments of Tehran are from the Qajar and Pahlavi eras. In Greater Tehran, monuments dating back to the Seljuk era remain as well; notably the Toqrol Tower in Ray. Rashkan Castle, dating back to the ancient Parthian Empire, of which some artifacts are housed at the National Museum; and the Bahram fire temple, which remains since the Sassanian Empire.

Tehran only had a small population until the late 18th century but began to take a more considerable role in Iranian society after it was chosen as the capital city. Despite the regular occurrence of earthquakes during the Qajar period and after, some historic buildings remain from that era.

Tehran is Iran's primate city, and is considered to have the most modernized infrastructure in the country. However, the gentrification of old neighbourhoods and the demolition of buildings of cultural significance have caused concerns.

Previously a low-rise city due to seismic activity in the region, modern high-rise developments in Tehran have been built in recent decades in order to service its growing population. There have been no major quakes in Tehran since 1830.

Tehran International Tower is the tallest skyscraper in Iran. It is 54-stories tall and located in the northern district of Yusef Abad.

The Azadi Tower, a memorial built under the reign of the Pahlavi dynasty, has long been the most famous symbol of Tehran. Originally constructed in commemoration of the 2,500th year of the foundation of the Imperial State of Iran, it combines elements of the architecture of the Achaemenid and Sassanid eras with post-classical Iranian architecture. The Milad Tower, which is the sixth tallest tower and the 24th-tallest freestanding structure in the world, is the city's other famous landmark tower. Leila Araghian's Tabiat Bridge, the largest pedestrian overpass in Tehran, was completed in 2014 and is also considered a landmark.

Theater

Under the reign of the Qajars, Tehran was home to the royal theatre of Tekye Dowlat, located to the southeast of the Golestan Palace, in which traditional and religious performances were observed. It was eventually demolished and replaced with a bank building in 1947, following the reforms during the reign of Reza Shah.

Before the 1979 Revolution, the Iranian national stage had become the most famous performing scene for known international artists and troupes in the Middle East, with the Roudaki Hall of Tehran constructed to function as the national stage for opera and ballet. The hall was inaugurated in October 1967 and named after prominent Persian poet Rudaki. It is home to the Tehran Symphony Orchestra, the Tehran Opera Orchestra, and the Iranian National Ballet Company.

The City Theater of Tehran, one of Iran's biggest theatre complexes, which contains several performance halls, was opened in 1972. It was built at the initiative and presidency of empress Farah Pahlavi, and was designed by architect Ali Sardar Afkhami, constructed within five years.

The annual events of Fajr Theater Festival and Tehran Puppet Theater Festival take place in Tehran.

Cinema

The first movie theater in Tehran was established by Mirza Ebrahim Khan in 1904. Until the early 1930s, there were 15 theaters in Tehran Province and 11 in other provinces.

In present-day Tehran, most of the movie theatres are located downtown. The complexes of Kourosh Cinema, Mellat Gallery and Cineplex, Azadi Cinema, and Cinema Farhang are among the most popular cinema complexes in Tehran.

Several film festivals are held in Tehran, including Fajr Film Festival, Children and Youth Film Festival, House of Cinema Festival, Mobile Film and Photo Festival, Nahal Festival, Roshd Film Festival, Tehran Animation Festival, Tehran Short Film Festival, and Urban Film Festival.

Concerts
There are a variety of concert halls in Tehran. An organization like the Roudaki Culture and Art Foundation has five different venues where more than 500 concerts take place this year. Vahdat Hall, Roudaki Hall, Ferdowsi Hall, Hafez Hall and Azadi Theater are the top five venues in Tehran, where classical, pop, traditional, rock or solo concerts take place.

Sports

Football and volleyball are the city's most popular sports, while wrestling, basketball, and futsal are also major parts of the city's sporting culture.

12 ski resorts operate in Iran, the most famous being Tochal, Dizin, and Shemshak, all within one to three hours from the city of Tehran.

Tochal's resort is the world's fifth-highest ski resort at over  above sea level at its highest point. It is also the world's nearest ski resort to a capital city. The resort was opened in 1976, shortly before the 1979 Revolution. It is equipped with an  gondola lift that covers a huge vertical distance. There are two parallel chair ski lifts in Tochal that reach  high near Tochal's peak (at ), rising higher than the gondola's seventh station, which is higher than any of the European ski resorts. From the Tochal peak, there are views of the Alborz range, including the  Mount Damavand, a dormant volcano.

Tehran is the site of the national stadium of Azadi, the biggest stadium by capacity in West Asia, where many of the top matches of Iran's Premier League are held. The stadium is a part of the Azadi Sport Complex, which was originally built to host the 7th Asian Games in September 1974. This was the first time the Asian Games were hosted in West Asia. Tehran played host to 3,010 athletes from 25 countries/NOCs, which was at the time the highest number of participants since the inception of the Games. That followed hosting the 6th AFC Asian Cup in June 1976, and then the first West Asian Games in November 1997. The success of the games led to the creation of the West Asian Games Federation (WAGF), and the intention of hosting the games every two years. The city had also hosted the final of the 1968 AFC Asian Cup. Several FIVB Volleyball World League courses have also been hosted in Tehran.

Food

There are many restaurants and cafes in Tehran, both modern and classic, serving both Iranian and cosmopolitan cuisine. Pizzerias, sandwich bars, and kebab shops make up the majority of food shops in Tehran.

Graffiti

Many styles of graffiti are seen in Tehran. Some are political and revolutionary slogans painted by governmental organizations, and some are works of art by ordinary citizens, representing their views on both social and political issues. However, unsanctioned street art is forbidden in Iran, and such works are usually short-lived.

During the 2009 Iranian presidential election protests, many graffiti works were created by people supporting the Green Movement. They were removed from the walls by the paramilitary Basij forces.

In recent years, Tehran Municipality has been using graffiti in order to beautify the city. Several graffiti festivals have also taken place in Tehran, including the one organized by the Tehran University of Art in October 2014.

Twin towns – sister cities

Tehran is twinned with:

 Ankara, Turkey
 Baghdad, Iraq
 Brasília, Brazil
 Budapest, Hungary
 Dushanbe, Tajikistan
 Havana, Cuba
 Khartoum, Sudan
 London, England, United Kingdom
 Los Angeles, United States
 Manila, Philippines
 Moscow, Russia
 Pretoria, South Africa
 Sarajevo, Bosnia and Herzegovina
 Tbilisi, Georgia
 Yerevan, Armenia

Cooperation agreements
Tehran cooperates with:
 Milan, Italy
 Seoul, South Korea
 Vienna, Austria

Panoramic views

See also
 Iran International Exhibitions Company
 Islamic City Council of Tehran
 List of people from Tehran
 Tehran City Council (1968–1979)

References

Bibliography

 Emerson, Charles. 1913: In Search of the World Before the Great War (2013) compares Tehran to 20 major world cities; pp. 309–24.

External links

 Google Map: Tehran
 Tehran Municipality website
 Tehran Geographic Information Center
 Tehranimages. A photographic project focusing on neglected pieces of architecture in downtown Tehran, Iran.
 Must see in Tehran

Capitals in Asia
Cities in Tehran Province
Iranian provincial capitals
Populated places along the Silk Road
Populated places in Tehran County
Articles containing video clips
Populated places with period of establishment missing

Tehran


Squadron Airborne (also titled "Squadron Airborn") is  a 1955 novel by Elleston Trevor. The plot revolves around the fighter pilots and auxiliary personnel of a fictional Spitfire squadron in September 1940. At the beginning of the story a newly trained 19-year-old pilot, Peter Stuyckes (pronounced "Stewks") arrives at Westhill (a fictitious Home Counties aerodrome near a fictitious town called Melbury), joining an established squadron already in the thick of the fighting. Less than a week later, after a number of aerial battles and many sub-plots concerning airmen and ground staff alike, the squadron is rotated to Lincolnshire for rest and refit, having suffered many casualties. This was the eighth novel to be released by Trevor under his own name although he had published many other titles under pseudonyms.

Plot summary
Pilot Officer Stuyckes arrives at Westhill and immediately suffers a mishap on a borrowed bicycle on presenting himself at his new Flight. This provokes mild amusement among his fellows and presages a near-disaster when, on being taken up for an introductory flight by Squadron Leader Charlie Mason, he is so preoccupied with making a textbook landing approach that he forgets to lower his undercarriage and has to be sarcastically reminded. Keen to make an impression, he succeeds in downing a German bomber on his first sortie but is attacked and seriously damaged, forcing him to make a belly landing for real although impressing the ground staff with how well he manages this.

While the green Stuyckes is adapting to life on the front line, it is seen that the more experienced members of Westhill Squadron (codenamed "Vestal" and never referred to by number in the book) have their own share of problems. Even Charlie Mason, regarded as invincible by many of the squadron, is beginning to suffer doubt before the end of the story, and many characters do worse:

 Bob White is suffering from battle fatigue, having earlier flown in France and over Dunkirk, and the conviction that he is fated to die soon. After he breaks down in a drunken rage, he is sent on leave to recover even though Mason and the station medical officer privately agree that he will probably kill himself anyway.
 Macklin, another veteran of the Battle of France, dies on Stuyckes' second sortie when his plane hits the ground (mentioned by another character during debriefing).
 Hodges, convinced that his wife has been killed in a Luftwaffe raid on Southampton but unable to make contact by telephone, first disposes of five enemy aircraft and then crashes his Spitfire into a sixth (in accordance with one of Mason's dicta, that given the balance of strength at that time in the battle, losing one fighter for five of the enemy destroyed is still a net loss for the R.A.F.). A later call from Southampton police confirms that Mrs Hodges has indeed died, but that Hodges could not possibly have known this.
 Brewer is attacked, cut off from the rest of the squadron, while his repeated calls for assistance ("Can anyone get that bastard?") go unanswered and apparently unheard, and eventually shot down by his persistent attacker.
 Spencer, Mason's closest friend, allows his attention to wander for a short time in a battle, leading him to spend three seconds in a Me109's gunsight and take a three-second burst from its spinner-cannon, destroying his Spitfire instantly. The previous night, Spencer had opted not to sleep with his girlfriend in order to get a good night's rest before returning to action, and Mason had told him that he was to be nominated for a Bar to his Distinguished Flying Cross. On going through Spencer's personal effects, Mason finds a letter stating that he, Spencer, had a premonition that he was to die soon and hoped that when it came it was quick and did not inconvenience the rest of the squadron. In connection with Hodges's earlier death, this leads Mason to wonder if he too will experience the same foreknowledge of his own death.
 Carsman, a tough Northerner transferred to Westhill as a replacement a few days after Stuyckes's arrival, is listed as a casualty along with Stuart and Rooke in the final chapter.

Stuyckes continues to experience an uphill struggle. On another early mission he is forced to bail out (sustaining superficial injuries after landing in a bramble patch), leading one of the WAAFs, twenty-year-old Daisy Caplin, who feels a strong sisterly attachment to him, to believe he has been killed when he does not return with the rest of the squadron. After a WAAF officer, who herself is hiding her own grief over a letter she is carrying in her uniform pocket, has interviewed Daisy and delicately inquired if she is illicitly pregnant (the phrase used is "Are you in trouble?"), Daisy sees Stuyckes walking around and only then learns that he had parachuted to safety and made his own way back to base.

At the end of the story, Stuyckes is in hospital after a more severe crash-landing, although making light of his injuries and well enough to pester the hospital staff to allow him to telephone Mason to inquire after the squadron's welfare. The squadron has already made its last operation before relocating to Lincolnshire and was able to fly off only seven aircraft (out of twelve) in response to a raid on the aerodrome itself, of whom at least three are mentioned as killed in Mason's conversation with Stuyckes. In addition to Mason himself and the injured Stuyckes, only two other pilots are mentioned as being alive, including one (Collins) who has been a byword for escaping by parachute throughout the story and has done so again.

Throughout the story, various romantic entanglements are explored. There is a suggestion that Stuyckes had his first sexual experience with a woman named Marcia on the night before he arrived at Westhill; two of the ground staff, both unhappily married, have a passionate affair which is abruptly ended by the transfer of one of them to Oban; and Mason himself becomes aware that Felicity, actually a local heiress working as a war volunteer in the WRVS while hosting five schoolboy evacuees, is strongly attracted to him. Despite the squadron's relocation to Lincolnshire, Mason resolves to return as soon as he has leave, as he finds himself returning Felicity's affection with equal force.

The book closes with the departure of the last survivors of the squadron, other than the hospitalised Stuyckes, and the arrival of a new squadron at the damaged but still operational aerodrome.

Technical error

In Chapter Seven, Leading Aircraftman Cornelius is paraded before Flight Lieutenant Robey to be disciplined for "breaking out of camp" (in this case, a short unauthorised absence, not via the official exit, to socialise privately with a WAAF). Robey punishes him with a reprimand. There are several issues with this:
 Cornelius and his fellows are relieved that the punishment is not more severe. In fact, a reprimand is considered a more serious punishment than would normally be imposed for a minor offence and the "Confined to Camp" punishment imposed on his girlfriend carries less weight although both speak of it as if it were more.
 A Leading Aircraftman is not an NCO and hence is too junior to be reprimanded.
 Robey is mentioned later as being specifically concerned not to harass engineers and fitters given the extreme hard work they are performing at this crucial stage of the Battle of Britain.

It is likely that the author confused the term "reprimand" with "admonishment". A person who is admonished is awarded a documented scolding which is considered far lighter than an official reprimand (and which can be applied to personnel below NCO rank). Later in the book, Cornelius is spoken to by Mason, after ignoring orders to take shelter while the station was under attack and Mason mentions a severe reprimand as a possible consequence for any repetition. (Mason also thanks Cornelius for his bravery and undertakes to recommend him for a decoration.)

Chronology
No dates are mentioned during the book, but the reference to a raid on Southampton and the arrival of unusually large Luftwaffe formations a few days later along with bombing attacks on towns would suggest that the story begins on or about the 10th of September 1940.

References

1955 British novels
British war novels
Novels set in England
Aviation novels
Novels by Elleston Trevor
Heinemann (publisher) books

Squadron Airborne


Miša David (June 6, 1942 – May 6, 2000) was a prominent architect and urban planner, one of the pioneers of 'participative urban planning' idea in former Yugoslavia. He graduated from The Faculty of Architecture, University of Belgrade in 1966. After attending a specialist course at the Centre for Environmental Studies in London (1972), he completed his MS Degree at The Faculty of Architecture, Belgrade (1975).

During his studies, together with a few of his close friends and colleagues, he created KMA (Klub Mladih Arhitekata – Association of Young Architects). Miša won a large number of awards on Yugoslavian architectural competitions and completed numerous urban plans and studies. He was also one of the founders and a charismatic director of Centre for Urban Development Planning- CEP (1975–1989), one of the most influential urban planning establishments on Yugoslavian soil of that era.

References

1942 births
2000 deaths
University of Belgrade Faculty of Architecture alumni
Yugoslav urban planners
20th-century architects
Yugoslav architects

Miša David


A lead castle, also called a lead cave or a lead housing, is a structure composed  of lead to provide   shielding against gamma radiation in a variety of applications in the nuclear industry and other activities which use ionizing radiation.

Applications

Shielding of radioactive materials
Castles are widely used to shield radioactive "sources" (see notes)  and radioactive materials, either in the laboratory or plant environment.  The purpose of the castle is to shield people from gamma radiation. Lead will not efficiently attenuate neutrons. If an experiment or pilot plant is to be observed, a viewing window of lead glass may be used to give gamma shielding but allow visibility.

Shielding of radiation detectors
Plant radiation detectors that are operating in a high ambient gamma background are sometimes shielded to prevent the background swamping the detector. Such a detector may be looking for alpha and beta particles, and gamma radiation will affect this.
Laboratory or health physics detectors, even if remote from nuclear operations, may require shielding if very low levels of radiation are to be detected. This is the case with, for instance, a scintillation counter measuring low levels of contamination on a swab or sample.

Construction
The castle can be made from individual bricks; usually with interlocking chevron edges to prevent "shine paths" of direct radiation through the gaps. They can also be made from lead produced in bespoke shapes by machining or casting. Such an example would be the annular ring castle commonly used for shielding scintillation counters.

A typical lead brick weighs about ten kilograms. Lead castles can be made of hundreds of bricks and weigh thousands of kilograms, so the floor must be able to withstand a heavy load. It is best to set up on a floor designed to carry the weight, or in the basement of a building built on a concrete slab. If the castle is not put directly on such a floor, it will require a suitably strong structure to safely support it.

Notes and references

External links

 Lead castle pictures

Lead
Nuclear physics
Nuclear safety and security
Radiation protection

Lead castle


Broca's area is a region in the brain of humans and other hominids. It is in the frontal lobe of the dominant hemisphere, usually the left. It works as part of "speech production".

Language processing has been linked to Broca's area after Pierre Paul Broca. Broca did autopsies on patients who had difficuty speaking when they were alive. He found damage to a particular area of the brain.  They had lost the ability to speak after injury to the posterior inferior frontal gyrus of the brain.

Since then, the region he identified has become known as Broca's area. The deficit in language production is Broca's aphasia, also called 'expressive aphasia'.

Functional magnetic resonance imaging (fMRI) studies have identified activation patterns in Broca's area associated with various language tasks. However, slow destruction of the Broca's area by brain tumors can leave speech relatively intact. This suggests that, given time, its functions can shift to nearby areas in the brain.

Related pages
 Cerebral hemisphere
 Lateralization of brain function
 Wernicke's area

References

Anatomy of the brain
Language

Broca's area


Alberto Suárez Laso (born December 19, 1977 in Riosa, Asturias) is a T12 athlete from Spain who competes in long distance races: the 5,000 meters, 10,000 meters, half marathon and marathon.  He is a world record holder in the men's T12 marathon, winning gold in the event at the 2011 IPC Athletics World Championships and the 2012 Summer Paralympics.

Personal
Suárez was born December 19, 1977 in Riosa, Asturias. , he resides in Oviedo, Asturias. He has a vision impairment.

Suárez won an award related to human values at the 2011 Asturian Best Sportspersons awards organized by the Asturian Sports Press Association,.  In 2012, he won the Asturian Sports Press Association award for best male athlete.

Athletics
Suárez is a T12, a blind runner, and he sometimes compete against runners without disabilities. He belongs to the Laso Oviedo Athletics Club. As of 2012, Chus Castaño is his coach. He is a world record in the marathon.

Suárez competed in the 2011 Gran Fondo Siete Aguas International Trophy President of the Council of Valencia. He competed in the 2011 Spanish Paralympic national athletics championships held in Gijón. He competed in the 2011 IPC Athletics World Championships in Christchurch New Zealand. He was one of two Spanish competitors in the marathon.  He was the first runner to finish the marathon and he made a world record by running the race with a time of 2.28:10.  He also finished third in the men's T12 10,000 meter race.

Suárez's goal for his running in 2012 was to finish first at the 2012 London Paralympics in the marathon. He race in the 2012 Riosa Sports Days. He competed at the 2012 Summer Paralympics, where hefinished firset in the men's T12 marathon and finished 6th in the men's T12 5,000 meter event.  His first place was Spain's eighth first place of the Games.  He finished the marathon in a time of 2:24.50, a new Paralympic Games record and World Record.

Suárez finished sixth in the 2013 Bareclona half marathon while racing against runners who did not have a disability. He set a personal best time in the half marathon at the race. He competed in the 2013 Divina Pastora 8 km Orotava held in the Canary Islands. He gave a speech two days before the race about physical activity, sport and eating patterns for athletes.

References

Other websites

Spanish long-distance runners
Living people
1977 births
Spanish Paralympic gold medalists
People from Asturias
2012 Summer Paralympics
Sportspeople with disabilities, type T12
Sportspeople with disabilities, type B2

Alberto Suárez Laso


Pwojè Pyebwa (Tree Project) is a tree-planting project in Haiti. It was designed, implemented, and initially run by cultural anthropologists. Different from reforestation projects, Pwojè Pyebwa promoted agroforestry—the strategic mixing of crops, trees, and animals. The agroforestry project in Haiti project was funded by the United States Agency for International Development USAID, but implemented through the Pan American Development Organization (PADF) and CARE. It was originally called the Agroforestry Outreach Project (AOP). The original project spanned a decade (1981–1991), but policies from Pwojè Pyebwa continued to direct PADF tree-planting through a second decade (1992–2000).

The project was executed throughout the country. Based on Haitian farmers' voluntary and widespread participation, the project has been deemed a success by many. Pwojè Pyebwa distributed free trees to farmers, and advised on the incorporation of trees into existing cropping arrangements based on anthropological research into the land tenure, agricultural systems, and the historical market-orientation of Haitian peasant farmers. The project eventually won the Praxis prize in applied anthropology. It is estimated that the project involved one-third of the entire rural Haitian population. Approximately 65 million trees were planted.

In 2009, follow-up research was conducted in the first area to receive tree seedlings. This research indicated that farmers continue to utilize trees from the project, and drew attention to already existing managed woodlots in the area. These Haitian farmer managed woodlots were documented as the result of historical shifts from exploited woodlands on public land toward the production of domestic firewood and eventually urban-bound charcoal, produced on private land; the woodlots were also examined contemporaneously as a unique Haitian agroforestry system.

References

Environment of Haiti

Pwojè Pyebwa


A cover system is a video game gameplay mechanic that allows a virtual avatar to hide from and avoid dangers, usually in a three-dimensional world. This method is a digital adaptation of the real-life military tactic of taking cover behind obstacles, for purposes of attaining protection from enemy ranged or area effect attacks, such as gunfire or explosions.

Definition

In gaming, a cover system lets a player character use stationary or moving obstacles to avoid damage. To be considered a cover system, there must be some physical interaction with the source of cover and the avatar. This means moving to stand in a position behind an object, as in traditional shooter games, while strictly speaking would be classified as "taking cover", does not qualify as an actual cover system in terms of video game mechanics. Some first-person shooters such as Soldier of Fortune bridged the gap somewhat, by allowing players to lean to the sides, allowing the player's avatar to lean out from behind objects to survey the environment or open fire on the enemy, without fully exposing the entirety of the player's own body to the enemy. In addition, the player character must have the ability to move in and out of the covering objects' proximity, leaving the player with moments of vulnerability, partially exposing themselves when they wish  to fire on the enemy. This excludes the exclusive use of portable shields as a cover system, though they may often be used to supplement a stationary source of cover, as seen in video games like Army of Two and Gears of War 2.

Other titles outside of first- and third-person shooters also offer implementations of a cover system. Tactical role-playing games such as X-COM enable the player-controlled characters to take advantage of walls and other objects in the environment to provide cover for their units, providing the effect of reducing the chance for that unit to be hit, or reducing the damage taken when hit by incoming fire. Elements of the user interface generally inform the player when cover is in effect, both when positioning player-controlled units, and when firing on enemies that are in cover

History

Origins (1975–1998)
Brian Ashcraft of Kotaku argues the idea of taking cover in video games is nearly as old as the shoot 'em up genre itself, originating from Taito's seminal 1978 arcade shooter Space Invaders, where the player's laser cannon could take cover behind destructible defense bunkers to avoid enemy fire. An even earlier example of the concept was Taito's 1975 shooter game Gun Fight, where the player characters could take cover behind destructible objects. In 1985, Data East's target shooting game Shootout had enemies who take cover behind objects or buildings and pop out from cover to fire back at the player.

Ryan Lambie, writing for Den of Geek, considers Namco's run and gun arcade game Rolling Thunder (1986) to be "the precursor to the modern cover shooter" due to how the player can hide behind crates, doors and other obstacles to avoid enemy fire. The mechanic of taking cover behind crates and jumping over them was later borrowed by Sega's arcade hit Shinobi (1987). Rolling Thunder 2 (1990) and Rolling Thunder 3 (1993) also allowed the player to enter doors to hide from enemies and dodge their gunfire. In 1988, Konami's Devastators, an early third-person shooter, featured a cover mechanic where destructible objects, such as sandbags and debris littered across the battlefield, could be used to take cover from enemy fire. In 1994, a cover mechanic was used in the game Blackthorne, which allowed the player to take cover by pressing against walls to avoid enemy fire.

Namco's 1995 3D light gun shooter arcade game Time Crisis introduced a dedicated cover button, specifically an "action" foot pedal, that could be used to take cover behind in-game objects. This cover mechanic helped Time Crisis distinguish itself from rival light gun shooters, like Sega's Virtua Cop, and took advantage of the players' hand-foot coordination to create a new arcade game experience. While Time Crisis was a first-person perspective shooter, cover would later be largely bound to third-person shooter titles, due to cover freeing up the camera and for it being easier to judge space when the character is visible on screen. Time Crisis, however, was able to use cover effectively due to being a rail shooter, where the path is already determined and there is no camera control.

Modern cover system (1999–2008)

WinBack, released by Koei for the Nintendo 64 in 1999, did not allow players to run-and-gun, but instead forced them to stop and shoot, with crates and corners providing cover for the player character to pop out from and fire his weapon.

In 2000, Raven released Soldier of Fortune for the PC which also featured its own lean-and-hide cover system which gave multiplayer combat far more depth. Using corners of walls, boxes, and other assorted obstacles to take cover from enemy fire was essential to successful gameplay.

In 2001's Metal Gear Solid 2: Sons of Liberty, Snake or Raiden able to take cover behind walls, boxes or crates and pop out to shoot at enemies, while the improved enemy AI allowed enemies to also take cover from the player character. The enemies would often take cover to call for backup, and during battle, they would take cover then pop out and shoot at the player or blindly throw grenades from behind their cover. In 2002, The Getaway for the PS2 featured a similar cover mechanic.

Kill.Switch is credited as the first game to feature the cover system as its core game mechanic, and introduced the blind fire mechanic to the cover system. It was also the earliest third-person shooter that required a button press to initiate the action of taking cover. This was the only game at the time to allow the in-game avatar to lean out and shoot, vault over cover, or blind fire during the cover sequence. This cover system was nicknamed 'Offensive Cover System' (OCS) by the developers. While this was considered a change in the shooter genre, reviewer Ricky Tucker felt that the game relied too heavily on the cover system with little other gameplay focus. He also said that the game felt "more like a prototype than a game" and didn't see any outstanding moments for the game despite the innovative cover design.

In 2005, CT Special Forces: Fire for Effect featured a cover system inspired by Kill Switch. Uncharted: Drake's Fortune, released in 2007, also began development that year, and took inspiration from Kill Switch for its cover system. In 2006, several shooters featured Kill Switch-inspired cover systems, including Rogue Trooper, a third-person shooter released in May based on the eponymous comic book series by 2000 AD, Tom Clancy's Rainbow Six: Vegas, a first-person shooter released in November that switched to a third-person over-the-shoulder view when initiating cover, and Killzone: Liberation, a third-person action game released in October. Other third-person shooters to feature a cover system that same year include WinBack 2: Project Poseidon, released in April, and Ghost Recon: Advanced Warfighter.

The most famous among them, however, was Gears of War, released by Epic Games in November 2006. It was a third-person shooter focused entirely on cover-based combat. While not the first to use a single button for moving in and out of cover, it used the mechanic more effectively with environments specifically designed with the cover system in mind. The cover system was considered revolutionary at the time and was credited for the massive success and sales of the game and its sequel, Gears of War 2. Its cover system was inspired by Kill Switch, whose lead designer was employed by Epic Games and was involved in the development of Gears of War. In turn, Gears of War inspired a new wave of video games using the third-person, single-button cover system. According to Stuart Lindsay, some games' cover systems are criticized because the cover system is created as an afterthought rather than the game being built around that feature.

Recent developments (2009–present)

After the video game cover system was popularized, several recent games have attempted to alter or further revolutionize the cover system in a unique way. One such game is the first-person shooter Killzone 2, which utilized a complete cover system that was used in the first-person perspective the entire time. Other first-person shooters like the Rainbow Six: Vegas series have traditionally changed to a third-person view when taking cover. A similar first-person cover approach was used by Rockstar Games in the eighth-generation release of Grand Theft Auto V, with an option to switch to a traditional third-person cover view when necessary as with Rainbow Six: Vegas.

A way games have changed the cover has been shifting the focus from participating in combat from behind cover to only using cover as a last resort. An example is 50 Cent: Blood on the Sand, which rewards players for assaulting enemies. Uncharted 2: Among Thieves uses cover abilities by allowing the player to hang onto cover vertically and use three dimensions of cover to avoid enemy fire. Dark Void uses a 360 degree threat radius, as the player character can fly. This is accomplished through vertical cover like scaling a mountainside or standard cover like walls.

Splinter Cell: Conviction in 2010 introduced cover to cover movement, which allows player character Sam Fisher to quickly move between covers by looking at the next cover and pressing a button. This mechanic was well received and has since been used in most of Ubisoft's third-person games like Ghost Recon: Future Soldier, Splinter Cell: Blacklist and Watch Dogs.
2011's Deus Ex: Human Revolution allows the protagonist Adam Jensen to quickly switch to another side of cover and quickly switch cover that's short distance on the left or on the right from him while in a third-person perspective. 2012's Hitman: Absolution, also published by Square Enix, and used again for Hitman (2016).

In contrast to some cover-based shooters, Vanquish, a 2010 third-person shooter developed by PlatinumGames, has bullets and missiles coming from all directions in a manner reminiscent of bullet hell shooters and cover is easily destroyed. Often a single shot is enough to remove the player's cover, forcing the player character to be on the move, while the game also penalizes the player on the scoreboard for the amount of time spent in cover. One of its innovations was the slide-boost mechanic that allows the player to slide-boost into and out of cover at high speeds (sometimes in slow motion using bullet time). According to director Shinji Mikami, the sliding boost mechanic was influenced by the 1970s anime series Casshern.

The action-RPG The Last Story includes a cover system that works with both 3rd-person shooting and melee combat systems, and the turn-based tactical XCOM: Enemy Unknown features cover systems as well.

Reception
The cover system has become a large part of modern third-person shooters. Nate Ahearn of Yahoo! News felt that cover systems changed the game experience for the better and reasoned this by claiming that cover systems were so vital because they allowed the player to view the character, creating a deeper connection between the gamer and the player character. In addition, Ahearn felt that having a cover system allowed the game to slow the pace and "really lets you flex the muscle of your fancy new graphics engine", giving games with cover systems advantages over fast-paced shooters.

Cover systems are not universally praised, however. Ben "Yahtzee" Croshaw has repeatedly criticized cover systems in his series Zero Punctuation, arguing that they ruin the flow of gameplay and comparing games that utilize them unfavorably to "retro" first-person shooters that focus on mobility, such as Quake and Duke Nukem 3D.

References

Video game development
Video game terminology
Virtual reality

Cover system