A maser is a device that produces coherent electromagnetic waves through amplification by stimulated emission. Historically, “maser” derives from the original, upper-case acronym MASER, which stands for "Microwave Amplification by Stimulated Emission of Radiation". The lower-case usage arose from technological development having rendered the original denotation imprecise, because contemporary masers emit EM waves (microwave and radio frequencies) across a broader band of the electromagnetic spectrum; thus, the physicist Charles H. Townes’s suggested usage of “molecular” replacing “microwave”, for contemporary linguistic accuracy. In 1957, when the optical coherent oscillator was first developed, it was denominated ''optical maser'', but usually called laser (Light Amplification by Stimulated Emission of Radiation), the acronym Gordon Gould established in 1957.

History

Theoretically, the principle of the maser was described by Nikolay Basov and Alexander Prokhorov from Lebedev Institute of Physics at an ''All-Union Conference on Radio-Spectroscopy'' held by USSR Academy of Sciences in May 1952.

The results were subsequently published in October 1954. A precursor of the maser was the first ''show boosted'' hydrogen device built and tested by physicists Theodor V. Ionescu and Vasile Mihu in 1946. Independently, Charles H. Townes, J. P. Gordon, and H. J. Zeiger built the first ammonia maser at Columbia University in 1953. The device used stimulated emission in a stream of energized ammonia molecules to produce amplification of microwaves at a frequency of 24 gigahertz.

Townes later worked with Arthur L. Schawlow to describe the principle of the ''optical maser'', or ''laser'', which Theodore H. Maiman first demonstrated in 1960. For their research in this field Townes, Basov, and Prokhorov were awarded the Nobel Prize in Physics in 1964.

Technology

The maser is based on the principle of stimulated emission proposed by Albert Einstein in 1917. When atoms have been put into an excited energy state, they can amplify radiation at the proper frequency. By putting such an amplifying medium in a resonant cavity, feedback is created that can produce coherent radiation.

Some common types of masers

Atomic beam masers

*Ammonia maser

*Free Electron Maser

*Hydrogen maser

Gas masers

*Rubidium maser

Solid State masers

*Ruby maser

The dual noble gas maser is an example of a masing medium which is nonpolar.

Uses

Masers serve as high precision frequency references. These "atomic frequency standards" are one form of atomic clock. They are also used as electronic amplifiers in radio telescopes. Masers are being developed as directed-energy weapons.

Hydrogen maser

Today, the most important type of maser is the hydrogen maser which is currently used as an atomic frequency standard. Together with other types of atomic clocks, they constitute the "Temps Atomique International" or TAI. This is the international time scale, which is coordinated by the Bureau International des Poids et Mesures, or BIPM.

It was Norman Ramsey and his colleagues who first realized this device. Today's masers are identical to the original design. The maser oscillation relies on stimulated emission between two hyperfine levels of atomic hydrogen. Here is a brief description of how it works:

First, a beam of atomic hydrogen is produced. This is done by submitting the gas at low pressure to an RF discharge (see the picture on this page).

The next step is "state selection"—in order to get some stimulated emission, it is necessary to create a population inversion of the atoms. This is done in a way that is very similar to the famous Stern-Gerlach experiment. After passing through an aperture and a magnetic field, many of the atoms in the beam are left in the upper energy level of the lasing transition. From this state, the atoms can decay to the lower state and emit some microwave radiation.

A high quality factor microwave cavity confines the microwaves and reinjects them repeatedly into the atom beam. The stimulated emission amplifies the microwaves on each pass through the beam. This combination of amplification and feedback is what defines all oscillators. The resonant frequency of the microwave cavity is exactly tuned to the hyperfine structure of hydrogen: 1420 405 751.768 Hz.

A small fraction of the signal in the microwave cavity is coupled into a coaxial cable and then sent to a coherent receiver.

The microwave signal coming out of the maser is very weak (a few pW). The frequency of the signal is fixed and ''extremely'' stable. The coherent receiver is used to amplify the signal and change the frequency. This is done using a series of phase-locked loops and a high performance quartz oscillator.

Astrophysical masers

Maser-like stimulated emission also occurs in nature in interstellar space, and is frequently called superradiant emission to distinguish it from laboratory masers. Such emission is observed from molecules such as water (H₂O), hydroxyl radicals (OH), methanol (CH₃OH), formaldehyde (CH₂O), and silicon monoxide (SiO). Water molecules in star-forming regions can undergo a population inversion and emit radiation at 22 GHz, creating the brightest spectral line in the radio universe. Some water masers also emit radiation from a vibrational mode at 96 GHz.

Extremely powerful masers, associated with active galactic nuclei, are known as megamasers and are up to a million times more powerful than stellar masers.

Terminology

The meaning of the term ''maser'' has changed slightly since its introduction. Initially the acronym was universally given as "microwave amplification by stimulated emission of radiation," which described devices which emitted in the microwave region of the electromagnetic spectrum.

The principle and concept of stimulated emission has since been extended to more devices and frequencies. Thus the original acronym is sometimes modified, as suggested by Charles H. Townes, to "''molecular'' amplification by stimulated emission of radiation." Some have asserted that Townes's efforts to extend the acronym in this way were primarily motivated by the desire to increase the importance of his invention, and his reputation in the scientific community.

When the laser was developed, Townes and Schawlow and their colleagues at Bell Labs pushed the use of the term ''optical maser'', but this was largely abandoned in favor of ''laser'', coined by their rival Gordon Gould. In modern usage, devices that emit in the X-ray through infrared portions of the spectrum are typically called lasers, and devices that emit in the microwave region and below are commonly called ''masers'', regardless of whether they emit microwaves or other frequencies.

Gould originally proposed distinct names for devices that emit in each portion of the spectrum, including ''grasers'' (gamma ray lasers), ''xasers'' (x-ray lasers), ''uvasers'' (ultraviolet lasers), '' lasers'' (visible lasers), ''irasers'' (infrared lasers), ''masers'' (microwave masers), and ''rasers'' (RF masers). Most of these terms never caught on, however, and all have now become (apart from in science fiction) obsolete except for ''maser'' and ''laser''.

See also

Laser

List of laser types

Masers in science fiction

References

Further reading

J.R. Singer, ''Masers'', John Whiley and Sons Inc., 1959.

J. Vanier, C. Audoin, ''The Quantum Physics of Atomic Frequency Standards'', Adam Hilger, Bristol, 1989.

Cartoon Megas XLR 2005

External links

arXiv.org search for "maser"

Noble gas Maser

Bright Idea: The First Lasers

Invention of the Maser and Laser, American Physical Society

Shawlow and Townes Invent the Laser, Bell Labs

Category:Acronyms Category:American inventions Category:Laser types Category:Microwave technology Category:Optical devices

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The Type 66 is a 152 mm towed howitzer used by the People's Liberation Army of China.

The gun system is developed on the Soviet D-20 towed artillery .

References

Type 66 122MM TOWED GUN-HOWITZER

Category:152 mm artillery Category:Cold War field artillery Category:Artillery of the People's Republic of China Category:China – Soviet Union relations

Coordinates	44°43′″N37°46′″N
name	Carole Samaha}}

| image = | caption = | background = solo_singer | Born = 25th of July, Khonchara, Lebanon | genre = Arabic pop music | occupation = Singer, actress | years_active = 1999–present | associated_acts = Marwan Khoury | website = www.carolesamaha.com }}

Carole Samaha (}}) is a Lebanese musician and actress. She has released five studio albums. Samaha has a masters degree in acting and directing, which she earned in 1999. In 2004 she won the Arab Music Award for best female newcomer. She has also won multiple Murex d'Or awards and was nominated for Best Arabia Act in the 2008 MTV Europe Music Awards.

Biography

Early life

Samaha was born in Lebanon to Antoine Samaha of Kenshara and Nouhad Hawi of Dhour Choeuir. She grew up with her parents and two brothers, having only one dream since childhood, being on stage.

She started her career as an actress in the theatre as well as television

Musicals era

After introducing herself to Lebanese and Arab composers, she experienced a turning point in her career as she shifted from drama to musical theatre and found success.

Discography

2004
2006
2009

2011 Al- Shahroura

Videography

! Year	! Song	! Album	! Lebanese Charts	! Egyptian Charts	! Translation	! Notes
	Oughniat El Toufoula	''Oughniat El Toufoula''			Children Songs
Habib Alby				My Love
2004	Etalaa Feyi			Look At Me	casting ex-Mr. Lebanon Ghassan El Mawla
	Ghali Alayi				You Mean Alot To Me
Nezlet El Sitara			The Curtain Fell
Habbeit Delwa't			Now that i loved	movie soundtrack
	Esmaani				Listen to me
Zaelni Mennak			I'm upset with you
	Adwa'a El Shohra			Lights of Fame	sponsored by Pepsi
Ya Rab	''Ana wlleil'' - Marwan Khoury			Oh God	ft. Marwan Khoury
	Yama Layali	''Hdoudi Sama''			How Many Nights	sponsored by Pepsi
Jeet (Majnouni)				You Came (I Must Be Crazy)	movie soundtrack
Ali	''Hdoudi Sama''			Ali	promotional single
	Laily Lail	''The Gipsy Man Sings from the Middle East'' - Mario Reyes			–	ft. Mario Reyes, filmed in Morocco
Rag'aalak				Coming Back To You	promotional single
Zabahny			"Slaughtered" Me	promotional single
Ma Bkhaf			I Am Not Scared	first official single
	A'oul Ansak			I Try To Forget You	second official single
Khallik Bhalak			Stay Away

Awards

"Revelation of the year" (actress and singer) Murex d'Or in 2000. "Best female newcomer" Arab Music Award (2003) - This was the first year for which Arab Music Awards were awarded and the ceremony was held in Dubai in May 2004. "Best Polyvalent talent" (actress and singer) Murex d'Or in 2003. "Best Female Romantic Song" ("Tala3 Fiyyi") Murex d'Or in 2003. "Best album of the year" (''Adwa' Al Shohra'') ART Music Award in 2006. The ceremony was held in Cairo. "Best Lebanese Female Singer" Murex d'Or in 2007. "Best Lebanese Song" ("Ya Rab", with Marwan Khoury) Murex d'Or in 2007.

nominated for "Best Arab Act" in the MTV Europe Music Awards 2008 (along with Mohamed Hamaki, Karl Wolf, Abri and others).

"Best album of the year" (''Hdoudi Sama'', 2009) Murex d'Or in June 2010.

Samahe was honored for best music video – "Khalik Behalik" – at the 2011 Murex d'Or ceremony.

References

External links

Official Website

Official Facebook Page

Category:Living people Category:20th-century births Category:Lebanese female singers

ar:كارول سماحة fr:Carole Samaha he:קרול סמאחה

Mahmoud Saad محمود سعد is an Egyptian football player. Currently, he is the assistant coach of Zamalek. He was previously the manager of Zamalek, and of the Egyptian National Olympic Team in the 1992 Summer Olympics.

Titles as a Manager for Zamalek

1 Egyptian League Title for Zamalek 2 Egyptian Cup Titles for Zamalek 1 Egyptian Super Cup Title for Zamalek 4 African Champions League Titles For Zamalek 2 Afro-Asian Cup Titles For Zamalek 2 African Super Cup Titles For Zamalek

Titles as a player for Zamalek

1 Egyptian League Titles for Zamalek 3 Egyptian Cup Titles for Zamalek

References

Category:Zamalek players Category:Egyptian footballers Category:Egyptian football coaches Category:Lebanon national football team managers Category:Expatriate footballers in Lebanon Category:Egyptian football managers Category:Zamalek club managers Category:Year of birth missing (living people) Category:Living people

Coordinates	44°43′″N37°46′″N
name	Mohamed Mounir
background	solo_singer
birth name	Mohamed Mounir Mohamed Aba Yazeeb Gebriel Metwaly
alias	The King (El Malek)
born	October 10, 1954Aswan, Egypt
instrument	Vocals
genre	Nubian Music, Pop, Blues, Jazz, Reggae
occupation	Singer, Actor
years active	1977–present
label	Sonar, Sound of America, Digitec, FreeMusic, Mirage, Africana, Alam El Phan
notable instruments	}}

Mohamed Mounir () (born October 10, 1954) is a popular Egyptian singer and actor. He is one of the best-known musicians, both in Egypt and throughout the Middle East, with a musical career spanning more than three decades. He incorporates various genres into his music, including classical Arabic Music, Nubian music, blues, jazz and reggae. His lyrics are noted both for their philosophical content and for their passionate social and political commentary. He is affectionately known by his fans as “The King” in reference to his album and play "El Malek Howa El Malek" (The King is The King).

Early life

Born into a Nubian family in Aswan, Mounir spent most of his early childhood in the village of Manshyat Al Nubia, where he shared his fathers interests in both music and politics. As a teenager, he and his family were forced to relocate to Cairo when his village was lost in the floods that followed the construction of the Aswan Dam. It was here that he studied photography at the Faculty of Applied Arts at Helwan University. During this period, he would often sing for friends and family at social gatherings. His singing voice was noticed by the lyricist Abdel-Rehim Mansour, who would go on to introduce Mounir to the renowned folk singer Ahmed Mounib.

Musical career

Following his graduation, he was called up for military service in 1974, during which he continued his professional musical career by performing in various concerts. He performed his first such concert in 1975. Although the public were initially critical of Mounir for performing in casual attire at a time where Arab singers were expected to wear suits, they eventually warmed to his laid back image.

After completing his military service, Mounir released his 1977 debut solo album "Alemony Eneeki" on the Sonar record label. Mounir went on to release 5 more consecutive official albums and featured on one soundtrack album under the Sonar label. To date, Mounir has released a total 20 official albums and featured on 6 soundtrack albums under a number of different record labels.

Mounir’s single “Maddad” from this album caused controversy, as its lyrics could be interpreted as a call for intercession from the prophet Muhammad. Amongst Muslims, there are differing views as to whether the prophet can provide intercession between Allah and his believers. This resulted in the music video being banned from Egyptian television for a time. Mounir responded by saying "it is this fight against rigid thought that makes something out of you".

On his 2003 follow up album "Ahmar Shafayef" (Lipstick), he returned to his more familiar style of mainly secular lyrics. In the summer of 2003, following the release of his album Mounir toured Austria, Germany and Switzerland alongside the Austrian pop musician Hubert von Goisern, and later that year the duo performed a concert in Asyut.

In May 2004, he held a large concert at the pyramids, during which he was physically attacked by a drunken fan. Despite sustaining minor injuries, he continued his performance until the end of the concert.

He continued his trend of releasing secular albums infused with social commentary with the release of his 2005 album “Embareh Kan Omry Eshren” (Yesterday I Was Twenty), as well as on his latest album "Ta'm El Beyout" (Taste of Homes), released in 2008. Ta'm El Beyout was noted for its creativity but initially did not perform as well as expected in terms of album sales.

In 2008, Mounir postponed his New Year's Eve concert at Cairo Opera House in solidarity with the Palestinians suffering the effects of the Gaza War. He issued the statement: "delaying the concert is a message sent to the whole world, so that it would move forward and help the people in Gaza."

He headlined the Liverpool Arabic Arts Festival 2010 on the 9th July at the Liverpool Philharmonic Hall.

Acting career

As well as his singing career, Mounir also has an active acting career. Throughout his career he has appeared in 12 movies, 3 television series and 3 plays.

His movie career began in 1982, when he acted in and featured on the soundtrack album Youssef Chahine film “'Hadouta Masreia” (An Egyptian Story).

In 1997 he played the role of the bard in the Youssef Chahine French-Egyptian historical drama “Al Maseer” (Destiny), which screened out of competition at the 1997 Cannes Film Festival.

Mounir played the part of the blind poetry professor “Bashir” in the controversial 2005 film "Dunia". The movie is centered around the title character Dunia, a belly dancer and poet played by Egyptian actress Hanan Tork. When the film aired at the 2005 Cairo International Film Festival, it left the audience split between those supporting the film’s calls for intellectual freedom and its anti-female circumcision stance, and those disapproved of either the title character’s desire to physically express herself through dance, or of the filming of scenes in the Cairo’s slums which could be seen to tarnish Egypt's international image.

Discography

Official Albums

''Alemony Eneeki'' (Your Eyes Taught Me) - 1977

''Bnetweled'' (We Are Being Born) - 1978

''Shababeek'' (Windows) - 1981

''Etkalemy'' (Speak) - 1983

''Bareea'' (innocent) - 1986

''West El Dayra'' (In The Middle of The Circle) - 1987

''Shokolata'' (Chocolate) - 1989

''Ya Eskenderia'' (Oh, Alexandria) - 1990

''Meshwar'' (Trip) - 1991

''El Tool We El Loon We El Horya'' (The Length and Colour and Freedom) - 1992

''Eftah Albak'' (Open Your Heart) - 1994

''Momken'' (Maybe) - 1995

''Men Awel Lamsa'' (From The First Touch) - 1996

''El Farha'' (The Joy) - 1999

''Fe Eshq El Banat'' (On The Love of Girls) - 2000

''Ana Alby Masaken Shabya'' (My Heart is council housing) - 2001

''El Ard... El Salam'' (The Earth... Peace) - 2002

''Ahmar Shafayef'' (Lipstick) - 2003

''Embareh Kan Omry Eshren'' (Yesterday I Was Twenty) - 2005

''Ta'm El Beyout'' (Taste of Homes) - 2008

Soundtrack Albums

''Hadouta Masreia'' (An Egyptian Story) - 1982

''El Malek Howa El Malek'' (The King is The King) - 1988

''Maadarsh'' (I Can’t) - 1993

''El Maseer'' (Destiny) - 1997

''Habeebty'' (My Love) - 1998

''Dunia - Ode To Liberty'' - 2006

Filmography

Movies

Year	Film	Role	Notes
1982	''Hadouta Masreia'' (An Egyptian Tale)	Mahdi
1986	''Al Yawm Al Sades'' (The Sixth Day)	The Boatman
1987	''Al Tokk Wa Eswera'' (Ring and Bracelet)	Mr. Mohamed
1988	''Youm Mor We Youm Helw'' (A Bad Day & A Good Day)	Oraby
1990	''Shabab Ala Kaf Afreet'' (Youth on the palm of a ghost)
1991	''Ishtebah'' (Suspicion)	Medhat
1991	''Leih Ya Haram'' (Why Pyramid)	Ahmed Shafek
1992	''Hekayat Al Ghareb'' (Stranger Tale)	Saed
1994	''Al Bahth An Tut Ankh Amun'' (Search for Tutankhamen)	Gad
1997		Marwan (The Bard)
2006	''Dunia'' (World)''	Dr. Bashir
2006	''Mafesh Gher Keda'' (Nothing but this)	Himself

Television

“Bakkar”

“Ali Elewa”

“Gomhoreyat Zefta”

Theatre

''El Malek Howa El Malek''

''Al Shahateen''

''Masa' Al Kheer Ya Masr''

References

External links

Mohamed Mounir’s official website

Mohamed Mounir at the Internet Movie Database

Category:1954 births Category:Living people Category:Egyptian male singers Category:Egyptian singers Category:Egyptian actors Category:Egyptian people of Nubian descent

ar:محمد منير de:Mohamed Mounir es:Mohamed Mounir it:Mohamed Munir lt:Mohamedas Muniras arz:محمد منير