Volatility

Volatility or volatile may refer to:

Chemistry

Computer science

Volatile (The Lime Spiders album)

Volatile is the second studio album from The Lime Spiders, released in 1988 through Virgin Records on vinyl.

Track listing

Personnel

The Lime Spiders

Additional musicians

References

Carbonic acid

Carbonic acid is a chemical compound with the chemical formula H₂CO₃ (equivalently OC(OH)₂). It is also a name sometimes given to solutions of carbon dioxide in water (carbonated water), because such solutions contain small amounts of H₂CO₃. In physiology, carbonic acid is described as volatile acid or respiratory acid, because it is the only acid excreted as a gas by the lungs.

Carbonic acid, which is a weak acid, forms two kinds of salts, the carbonates and the bicarbonates. In geology, carbonic acid causes limestone to dissolve producing calcium bicarbonate which leads to many limestone features such as stalactites and stalagmites.

The long-held belief that carbonic acid could not exist as a pure compound has reportedly been recently disproved by the preparation of the pure substance in both solid and gas form by University of Innsbruck researchers.

Chemical equilibrium

When carbon dioxide dissolves in water it exists in chemical equilibrium producing carbonic acid:

The hydration equilibrium constant at 25 °C is called K_h, which in the case of carbonic acid is [H₂CO₃]/[CO₂] ≈ 1.7×10⁻³ in pure water and ≈ 1.2×10⁻³ in seawater. Hence, the majority of the carbon dioxide is not converted into carbonic acid, remaining as CO₂ molecules. In the absence of a catalyst, the equilibrium is reached quite slowly. The rate constants are 0.039 s⁻¹ for the forward reaction (CO₂ + H₂O → H₂CO₃) and 23 s⁻¹ for the reverse reaction (H₂CO₃ → CO₂ + H₂O). Carbonic acid is used in the making of soft drinks, inexpensive and artificially carbonated sparkling wines, and other bubbly drinks. The addition of two molecules of water to CO₂ would give orthocarbonic acid, C(OH)₄, which exists only in minute amounts in aqueous solution.

Off

Off or OFF may refer to:

See also

Off!

Off! is an American hardcore punk supergroup, formed in Los Angeles in 2009.

History

Off! was formed in Los Angeles, California in late 2009 by Circle Jerks/Black Flag singer Keith Morris, Burning Brides frontman Dimitri Coats, Redd Kross bassist Steven Shane McDonald, and Rocket From The Crypt/Hot Snakes drummer Mario Rubalcaba. The idea to form the band came after Coats had worked as producer on a Circle Jerks album which fell apart. During that time, Coats and Morris had written several songs together which they used to start Off!. The group made its live debut at the 2010 South By Southwest Music Festival in Austin, Texas. Off!'s first Los Angeles show featured an original art installation by Raymond Pettibon at a downtown warehouse space.

The first release by Off! is a 7" vinyl EP called 1st EP, which debuted on October 13, 2010. That EP, along with three more EPs, were later released as a four 7" vinyl box set entitled First Four EPs on December 14, 2010. The collection contains sixteen songs and features artwork by Raymond Pettibon.

Environment variable

Environment variables are a set of dynamic named values that can affect the way running processes will behave on a computer.

They are part of the environment in which a process runs. For example, a running process can query the value of the TEMP environment variable to discover a suitable location to store temporary files, or the HOME or USERPROFILE variable to find the directory structure owned by the user running the process.

They were introduced in their modern form in 1979 with Version 7 Unix, so are included in all Unix operating system flavors and variants from that point onward including Linux and OS X. From PC DOS 2.0 in 1982, all succeeding Microsoft operating systems including Microsoft Windows, and OS/2 also have included them as a feature, although with somewhat different syntax, usage and standard variable names.

Details

In all Unix and Unix-like systems, each process has its own separate set of environment variables. By default, when a process is created, it inherits a duplicate environment of its parent process, except for explicit changes made by the parent when it creates the child. At the API level, these changes must be done between running fork and exec. Alternatively, from command shells such as bash, a user can change environment variables for a particular command invocation by indirectly invoking it via env or using the ENVIRONMENT_VARIABLE=VALUE <command> notation. All Unix operating system flavors, DOS, and Windows have environment variables; however, they do not all use the same variable names. A running program can access the values of environment variables for configuration purposes.

SOD1

Superoxide dismutase [Cu-Zn] also known as superoxide dismutase 1 or SOD1 is an enzyme that in humans is encoded by the SOD1 gene, located on chromosome 21. SOD1 is one of three human superoxide dismutases. It is implicated in apoptosis and amyotrophic lateral sclerosis.

Structure

SOD1 is a 32 kDa homodimer which forms a β-barrel and contains an intramolecular disulfide bond and a binuclear Cu/Zn site in each subunit. This Cu/Zn site holds the copper and a zinc ion and is responsible for catalyzing the disproportionation of superoxide to hydrogen peroxide and dioxygen. The maturation process of this protein is complex and not fully understood, involving the selective binding of copper and zinc ions, formation of the intra-subunit disulfide bond between Cys-57 and Cys-146, and dimerization of the two subunits. The copper chaperone for Sod1 (CCS) facilitates copper insertion and disulfide oxidation. Though SOD1 is synthesized in the cytosol can mature there, the fraction of expressed, and still immature, SOD1 targeted to the mitochondria must be inserted into the intermembrane space. There, it forms the disulfide bond, though not metallation, required for its maturation. The mature protein is highly stable, but unstable when in its metal-free and disulfide-reduced forms. This manifests in vitro, as the loss of metal ions results in increased SOD1 aggregation, and in disease models, where low metallation is observed for insoluble SOD1. Moreover, the surface-exposed reduced cysteines could participate in disulfide crosslinking and, thus, aggregation.