Activator

Activator may refer to:

Enzyme activator

Enzyme activators are molecules that bind to enzymes and increase their activity. They are the opposite of enzyme inhibitors. These molecules are often involved in the allosteric regulation of enzymes in the control of metabolism. An example of an enzyme activator working in this way is fructose 2,6-bisphosphate, which activates phosphofructokinase 1 and increases the rate of glycolysis in response to the hormone insulin.

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References

Activator (phosphor)

In phosphors and scintillators, the activator is the element added as dopant to the crystal of the material to create desired type of nonhomogeneities.

In luminescence, only a small fraction of atoms, called emission centers or luminescence centers, emit light. In inorganic phosphors, these inhomogeneities in the crystal structure are created usually by addition of a trace amount of dopants, impurities called activators. (In rare cases dislocations or other crystal defects can play the role of the impurity.) The wavelength emitted by the emission center is dependent on the atom itself, its electronic configuration, and on the surrounding crystal structure.

The activators prolong the emission time (afterglow). In turn, other materials (such as nickel) can be used to quench the afterglow and shorten the decay part of the phosphor emission characteristics.

The electronic configuration of the activator depends on its oxidation state and is crucial for the light emission. Oxidation of the activator is one of the common mechanisms of phosphor degradation. The distribution of the activator in the crystal is also of high importance. Diffusion of the ions can cause depletion of the crystal from the activators with resulting loss of efficiency. This is another mechanism of phosphor degradation.

Katherine

Katherine and its variations is a feminine name. It is popular in Christian countries, as it was the name of one of the first Christian saints, Catherine of Alexandria.

Origin and meaning

The name originated from the Greek Αἰκατερίνα or Αἰκατερίνη (Aikaterina, Aikaterinē), which is of unknown etymology. The earliest known use of the Greek name is in reference to Saint Catherine of Alexandria. The theory that the name comes from Hecate, the name of the Greek goddess of magic, is regarded by the editors of the Oxford Dictionary of First Names as unconvincing, however this appears as merely an opinion of the editors and their text admits the etymology is unknown.

The name subsequently came to be associated with the Greek adjective καθαρός (katharos), meaning "pure", leading to the alternative spellings Katharine and Katherine. The former spelling, with a middle a, was more common in the past and is currently more popular in the United States than in Britain. Katherine, with a middle e, was first recorded in England in 1196 after being brought back from the Crusades.

The Vampire Diaries (novel series)

The Vampire Diaries is a young adult vampire horror series of novels created by L. J. Smith. The story centers on Elena Gilbert, a young high school girl who finds her heart eventually torn between two vampire brothers, Stefan and Damon Salvatore.

Publishing history

The series was originally published in 1991-1992 and it revolves around Stefan Salvatore and Elena Gilbert as the two main protagonists. The first three novels in the original series (The Awakening, The Struggle, and The Fury) all feature Stefan and Elena as the narrators of the series, while the last book in the original series, Dark Reunion, is from Bonnie McCullough's viewpoint.

After taking a long hiatus from writing, Smith published the first installment of "The Return" trilogy, Nightfall, on February 10, 2009. Shadow Souls, the second book of "The Return" trilogy, was released on March 16, 2010. The third and final book of "The Return" trilogy, Midnight, was released on March 15, 2011.

The trilogy after The Return trilogy, The Hunters, was written by a ghostwriter. In fact, Smith signed a "work for hire" contract back when she had written the original Vampire Diaries novel trilogy, which means Alloy owns the copyrights to the series. Smith had originally intended to call the books in "The Hunters" trilogy Phantom, Evensong and Eternity, but the third book was called Destiny Rising by the ghostwriter.Phantom was released on October 25, 2011,Moonsong on March 13, 2012, and Destiny Rising on October 23, 2012.

Katherine (Seton novel)

Katherine is a 1954 historical novel by American author Anya Seton. It tells the story of the historically important, 14th-century love affair in England between the eponymous Katherine Swynford and John of Gaunt, Duke of Lancaster, the third surviving son of King Edward III.

In 2003, Katherine was ranked 95 in the BBC's Big Read survey of Britain's best-loved novels. It is commonly regarded as a prime example of historical fiction, and has been continuously in print since its publication date.

Plot summary

Katherine tells the true story of Katherine de Roet, born the daughter of a minor Flemish herald, later knight. Katherine has no obvious prospects, except that her sister is a waiting-woman to Queen Philippa, wife of King Edward III, and the fiancée of Geoffrey Chaucer, then a minor court official. By virtue of this connection, Katherine meets and marries Sir Hugh Swynford of Lincolnshire and gives birth to a daughter, Blanchette, and a son, Thomas.