Ring (chemistry)

Four cycloalkanes, all of which exhibit simple rings

In chemistry, a ring is an ambiguous term referring either to a simple cycle of atoms and bonds in a molecule or to a connected set of atoms and bonds in which every atom and bond is a member of a cycle (also called a ring system). A ring system that is a simple cycle is called a monocycle or simple ring, and one that is not a simple cycle is called a polycycle or polycyclic ring system. A simple ring contains the same number of sigma bonds as atoms, and a polycyclic ring system contains more sigma bonds than atoms.
A molecule containing one or more rings is called a cyclic compound, and a molecule containing two or more rings (either in the same or different ring systems) is termed a polycyclic compound. A molecule containing no rings is called an acyclic or open-chain compound.


1 Homocyclic and heterocyclic rings
2 Rings and ring systems
3 See also
4 References

Homocyclic and heterocyclic rings[edit]
A homocycle or homocyclic ring is a ring in which all atoms are of the same chemical element.[1] A heterocycle or heterocyclic ring is a ring containing atoms of at least two different elements, i.e. a non-homocyclic ring.[2] A carbocycle or carbocyclic ring is a homocyclic ring in which all of the atoms are carbon.[3] An important class of carbocycles are alicyclic rings,[4] and an important subclass of these are cycloalkanes.
Rings and ring systems[edit]
In common usage the terms “ring” and “ring system” are frequently interchanged, with the appropriate definition depending upon context. Typically a “ring” denotes a simple ring, unless otherwise qualified, as in terms like “polycyclic ring”, “fused ring”, “spiro ring” and “indole ring”, where clearly a polycyclic ring system is intended. Likewise, a “ring system” typically denotes a polycyclic ring system, except in terms like “monocyclic ring system” or “pyridine ring system”. To reduce ambiguity, IUPAC’s recommendations on organic nomenclature avoid the use of the term “ring” by using phrases such as “monocyclic parent” and “polycyclic ring system”.[5]
See also[edit]

Cyclic compound
Polycyclic compound
Heterocyclic compound
Bicyclic molecule
Spiro compound


^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”) (1997). Online corrected version:  (1995) “Homocyclic compounds”.
^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”) (1997). Online corrected version:  (1995

Felicità (album)


Studio album by Al Bano and Romina Power




Dario Farina

Al Bano and Romina Power chronology

Aria pura
Che angelo sei

Felicità (Italian for Happiness) is a studio album by Italian duo Al Bano and Romina Power, released in 1982 by Baby Records. The album was an international commercial success and included two of their biggest hits, “Felicità” and “Sharazan”.
In some territories, it was confusingly released under the title of their previous album, Aria pura, even though the two LPs contained different material.[1] In the Soviet Union, it was released as Al Bano and Romina Power (Russian: Аль Бано и Ромина Пауэр) and the track listing omitted “Prima notte d’amore” and “Caro Gesù”.[2] The duo also recorded a Spanish language version of the album, Felicidad.[3]


1 Track listing

1.1 Original Italian release
1.2 Spanish release (Felicidad)

2 Chart performance
3 References

Track listing[edit]
Original Italian release[edit]

Side A

“Aria pura” – 3:12
“Felicità” – 3:13
“Prima notte d’amore” – 2:55
“Sharazan” – 4:45
“Il ballo del qua qua” – 2:52

Side B

“Angeli” – 3:25
“E fu subito amore” – 3:59
“Canto di libertà” – 2:45
“Caro Gesù” – 3:30
“Arrivederci a Bahia” – 3:02

Spanish release (Felicidad)[edit]

Side A

“Felicidad” – 3:13
“Nestra primera noche” – 2:55
“Canto de libertad” – 2:45
“Il ballo del qua qua” – 2:52
“Arrivederci en Bahia” – 3:02

Side B

“Aire puro” – 3:12
“Oye Jesús” – 3:30
“Vivirlo otra vez” – 3:59
“Angeles” – 3:25

Chart performance[edit]

Chart (1982)





^ “Al Bano & Romina Power – Aria Pura at Discogs”. www.discogs.com. Retrieved 2015-08-24. 
^ “Al Bano & Romina Power – Аль Бано и Ромина Пауэр (Vinyl, LP, Album) at Discogs”. www.discogs.com. Retrieved 2015-08-24. 
^ “Al Bano Y Romina Power* – Felicidad (Cantan En Español) (Vinyl, LP, Album) at Discogs”. www.discogs.com. Retrieved 2015-08-24. 
^ “Offizielle Deutsche Charts” (in German). www.offiziellecharts.de. Retrieved 2015-07-30. 
^ “Hit Parade Italia – ALBUM 1982” (in Italian). www.hitparadeitalia.it. Retrieved 2015-08-24. 
^ “Discografie Al Bano & Romina Power” (in Dutch). dutchcharts.nl. Retrieved 2015-07-30. 


National Institute of Dental and Craniofacial Research

The National Institute of Dental and Craniofacial Research (NIDCR) is a branch of the U.S. National Institutes of Health. The institute aims to improve the oral, dental, and craniofacial health through research and the distribution of important health information to the American people.


1 History
2 NIDCR Directors [1]
3 Notes and references
4 External links

In 1931, the United States Public Health Service established a Dental Hygiene Unit at the National Institutes of Health. Designated as the first dental research worker, Dr. H. Trendley Dean studied the communities affected by the oral disease known as mottled enamel. Following the implementation of a water fluoridation trial in Grand Rapids, Michigan, the National Institute of Dental Research (NIDR), was established by President Harry S. Truman on June 24, 1948. The first grants and fellowships that supported dental research were awarded the following year.
In an effort to expand the NIDR, plans to finance the construction of a building for the institute were approved by President Dwight D. Eisenhower in 1958. The National Institute of Dental Research also established the Laboratory of Biochemistry to further the research regarding the structure and functions of various proteins. In continuing with this expansion, a grant to develop several dental research facilities at various universities was approved in 1967. This program hoped to establish research and training environments, as well as promote interdisciplinary approaches to combating oral diseases.
In addition to the Laboratory of Biochemistry, other laboratories were established in the years 1974 and 1975. These newly established laboratories focused on the field of oral medicine as well as the fields of microbiology and immunology. Another effort to expand research was implemented a decade later. The Dentist Scientist Award Program aimed to provide dentists with opportunities and incentive to pursue independent research regarding oral health.
In 1986, the most extensive survey on the dental health of American adults was completed by the NIDR. This study was the first to examine oral health diseases on a large and detailed scale. Following this survey, in 1993, the National Oral Health Information Clearinghouse was established. The purpose of this database is to provide resources for health professionals, patients, and the general public regarding oral health. In continuing with its mission to distribute important h