OF
OF or Of may refer to:
Dioxygen difluoride
Dioxygen difluoride is a compound of fluorine and oxygen with the molecular formula O
2F
2. It exists as an orange solid that melts into a red liquid at −163 °C (110 K). It is an extremely strong oxidant and decomposes into oxygen and fluorine even at −160 °C (113 K) at a rate of 4% per day: its lifetime at room temperature is thus extremely short. Dioxygen difluoride reacts with nearly every chemical it encounters – even ordinary ice – leading to its onomatopoeic nickname "FOOF" (a play on its chemical structure).
The material has no practical applications, but has been of theoretical interest. One laboratory's use of it was the synthesis of plutonium hexafluoride at unprecedentedly low temperatures, which was significant because previous methods for its preparation needed temperatures so high that the plutonium hexafluoride created would rapidly decompose.
Preparation
Dioxygen difluoride can be obtained by subjecting a 1:1 mixture of gaseous fluorine and oxygen at low pressure (7–17 mmHg is optimal) to an electric discharge of 25–30 mA at 2.1–2.4 kV.
A similar method was used for the first synthesis by Otto Ruff in 1933. Another synthesis involves mixing O
2 and F
2 in a stainless steel vessel cooled to −196 °C (77.1 K), followed by exposing the elements to 3 MeV bremsstrahlung for several hours. A third method requires heating a mix of fluorine and oxygen to 700 °C (1,292 °F), and then rapidly cooling it using liquid oxygen. All of these methods involve synthesis according to the equation:
AACS encryption key controversy
A controversy surrounding the AACS cryptographic key arose in April 2007 when the Motion Picture Association of America and the Advanced Access Content System Licensing Administrator, LLC (AACS LA) began issuing cease and desist letters to websites publishing a 128-bit (16-byte) number, represented in hexadecimal as 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 (commonly referred to as 09 F9), a cryptographic key for HD DVDs and Blu-ray Discs. The letters demanded the immediate removal of the key and any links to it, citing the anti-circumvention provisions of the United States Digital Millennium Copyright Act (DMCA).
In response to widespread Internet postings of the key, the AACS LA issued various press statements, praising those websites that complied with their requests as acting in a "responsible manner", warning that "legal and technical tools" were adapting to the situation.
The controversy was further escalated in early May 2007, when aggregate news site Digg received a DMCA cease and desist notice and then removed numerous articles on the matter and banned users reposting the information. This sparked what some describe as a digital revolt or "cyber-riot", in which users posted and spread the key on Digg, and throughout the Internet en masse, thereby leading to a Streisand effect. The AACS LA described this situation as an "interesting new twist".
