1,1,1-Trichloro-2,2,2-trifluoroethane

Trichlorotrifluoroethane, also called 1,1,1-Trichloro-2,2,2-trifluoroethane or CFC-113a is a chlorofluorocarbon (CFC). It has the formula Cl₃C-CF₃.

Environmental effects

Ozone depletion

It is one of four man-made chemicals newly discovered in the atmosphere by a team at the University of East Anglia. But CFC-113a is the only known CFC whose abundance in the atmosphere is still growing. CFC-113a seems to have been accumulating unabated since 1960. Its source remains a mystery, but illegal manufacturing in China is suspected by some. Between 2010 and 2012, emissions of the gas jumped by 45 percent.

See also

References

R-390A

The R-390A /URR is a general coverage HF radio communications receiver designed by Collins Radio Company for the US military.

History

The R-390A military shortwave radio receiver was the result of a project undertaken by the U.S. Army Signal Corps in 1954 to replace the existing R-390 receiver then in use. The R-390 had done its job so well that the Corps decided continued use of this type of receiver necessitated an improved, reduced-cost version. There are many references to the R390A in the open literature during this period; a picture of the receiver appeared in the May 1959 issue of the amateur radio magazine QST.

Total production of the R-390A (as determined by the high serial numbers noted) is over 55,000 units. Initial production started in 1955 and ran through approximately 1970, and then was restarted in 1984 by Fowler Industries for Avondale Shipyards. Manufacturers and their approximate production numbers are:

Dichlorodifluoroethylene

A dichlorodifluoroethylene (systematically named dichlorodifluoroethene) is one of three compounds with the chemical formula C
2Cl
2F
2. Dichlorodifluoroethylenes are colourless gases, and are some of the simplest chlorodifluoroalkenes.

The structural isomers are used as intermediates or precursors in the production of other industrial chemicals.

1,1-Dichloro-2,2-difluoroethylene

1,1-Dichloro-2,2-difluoroethylene is a low-boiling liquid that is used a refrigerant. It may also be used as a solvent, but has practical limitations as such, because of its low boiling point (commercial listings, 19 °C; lit. 17 °C).

It is regarded as a hazardous chemical for being toxic by inhalation (see MSDS), and a low-boiling liquid, and it causes irritation when it comes into contact with the skin and mucous membranes. Its ASHRAE number is R-1112a, and its CAS number is 79-35-6. Concentrated 1,1-dichloro-2,2-difluoroethylene can be ignited with ease in the laboratory.

cis- And trans-1,2-dichloro-1,2-difluoroethylene

4 AM

4 AM is a point in time of the 12-hour clock which corresponds to 0400 in the 24-hour clock. 4 AM or 4am may also refer to:

Books

Music

Songs

See also

3AM (Matchbox Twenty song)

"3 A.M." (written "3 am" on the album and "3 AM" on the single) is the third single and the third track from Matchbox Twenty's debut album, Yourself or Someone Like You. It topped the Canadian RPM record charts in early 1998.

Background and content

This song was written by Rob Thomas, Jay Stanley, John Leslie Goff and Brian Yale while performing together in the early 1990s band Tabitha's Secret. The lyrics are inspired by Thomas as an adolescent having to live with a mother fighting to survive cancer.

Music video

The video (directed by Gavin Bowden) features the band sitting on sides of a street next to some telephone booths. A supermarket is also shown. The video switches from color video images to black-and-white images. During the introduction and the third verse of the song, Thomas walks in the middle of the street with some construction signs and lights. During the third verse, a car stops with a bare-chested man and a woman inside. The man walks out, revealing a catheter in his chest, and is handed three cigarettes by Thomas. Finally, during the last two choruses, the band is shown playing their instruments ending with an image of Thomas standing next to the telephone booths.

Canonical hours

In the practice of Christianity, canonical hours mark the divisions of the day in terms of periods of fixed prayer at regular intervals. A Book of Hours normally contains a version of, or selection from, such prayers.

The practice of daily prayers grew from the Jewish practice of reciting prayers at set times of the day: for example, in the Book of Acts, Peter and John visit the temple for the afternoon prayers (Acts 3:1). Psalm 119:164 states: "Seven times a day I praise you for your righteous laws" which is among the scriptural quotes in the attestation of Saint Symeon of Thessaloniki that commences "The times of prayer and the services are seven in number, like the number of gifts of the Spirit, since the holy prayers are from the Spirit."

This practice is believed to have been passed down through the centuries from the Apostles, with different practices developing in different places. As monasticism spread, the practice of specified hours and liturgical formats began to develop and become standardized. Around the year 484, Sabbas began the process of recording the liturgical practices around Jerusalem while the cathedral and parish rites in the Patriarchate of Constantinople evolved in an entirely different manner; the two were synthesized commencing in the eighth century to yield an office of great complexity. In 525, Benedict of Nursia set out one of the earliest schemes for the recitation of the Psalter at the Office. With the Cluniac reforms of the 11th century there was a new emphasis on liturgy and the canonical hours in the reformed Benedictine priories with the Abbey of Cluny at their head.