The Order of Alcántara (Spanish: Orden de Alcántara), also called the Knights of St. Julian, was originally a military order of León, founded in 1166 and confirmed by Pope Alexander III in 1177.

Alcántara, is a town on the Tagus (which is here crossed by a bridge - cantara in Arabic, hence the name). The town is situated on the plain of Extremadura, a great field of conflict for the Muslims and Christians of Iberian Peninsula in the 12th century. Alcántara was first taken in 1167 by the King of León, Ferdinand II. In 1174 it fell again into the hands of Abu Yaqub Yusuf, the third of the African Almohades; and was not recovered until 1214, when it was taken by Alfonso IX of León.

To defend this conquest, on a border exposed to many assaults, the king resorted to military orders. The Middle Ages knew neither standing armies nor garrisons, a deficiency that the military orders supplied, combining as they did military training with monastic stability. In 1214 Alcántara was first committed to the care of the Castilian Knights of Calatrava, who had lately received great support after their performance in 1212 at the battle of Las Navas de Tolosa against the Almohades. Alonzo of León wished to found at Alcántara a special branch of this celebrated order for his realm. However, four years later the Order decided that the post was too far from its Castilian headquarters. They gave up the scheme and transferred the castle, with the permission of the king, to a peculiar Leonese order still in a formative stage, known as Knights of St. Julian de Pereiro.

Alcántara is a municipality in the province of Cáceres, Extremadura, Spain, on the Tagus, near Portugal. The toponym is from the Arabic word al-QanTarah (القنطرة) meaning "the bridge".

Archaeological findings have attested human presence in the area from the Bronze Age; the first historical inhabitants were the Lusitanians, followed by the Celts, who came from east to the Pyrenees. To this period, and to the following Roman domination, belong remains of several castra (military camps), villas and the bridge which gives its name to the city. The Roman rule lasted from the 2nd century BC to the 5th century, when they were replaced by the Visigoths.

In the 8th century the Arabs conquered the Iberian peninsula, including Extremadura. In the 12th century the Muslim geographer al-Idrisi described the bridge as one of the world's marvels. In the 12th-13th centuries Alcántara was a frontier city, devoted to military activities and animal husbandry. After the collapse of the Caliphate of Córdoba, it belonged to several Islamic taifas (petty kingdoms).

In mathematics, big O notation is used to describe the limiting behavior of a function when the argument tends towards a particular value or infinity, usually in terms of simpler functions. It is a member of a larger family of notations that is called Landau notation, Bachmann–Landau notation (after Edmund Landau and Paul Bachmann), or asymptotic notation. In computer science, big O notation is used to classify algorithms by how they respond (e.g., in their processing time or working space requirements) to changes in input size.

Big O notation characterizes functions according to their growth rates: different functions with the same growth rate may be represented using the same O notation. A description of a function in terms of big O notation usually only provides an upper bound on the growth rate of the function. Associated with big O notation are several related notations, using the symbols o, Ω, ω, and Θ, to describe other kinds of bounds on asymptotic growth rates.

Big O notation is also used in many other fields to provide similar estimates.

Archibald John Motley, Junior (October 7, 1891, New Orleans, Louisiana – January 16, 1981,Chicago, Illinois) was an African-American painter. He studied painting at the School of the Art Institute of Chicago during the 1910s, graduating in 1918. He is most famous for his colorful chronicling of the African-American experience during the 1920s and 1930s, and is considered one of the major contributors to the Harlem Renaissance, or the New Negro Movement, a time in which African American art reached new heights not just in New York but across America. He specialized in portraiture and saw it “as a means of affirming racial respect and race pride.”

Unlike many other Harlem Renaissance artists, Archibald Motley, Jr. never lived in Harlem—-he was born in New Orleans and spent the majority of his life in Chicago. He graduated from Englewood High School in Chicago. He was offered a scholarship to study architecture by one of his father's friends, which he turned down in order to study art. He attended the Art Institute of Chicago where he received classical training but his modernist-realist works were out of step with the school's then-conservative bent. During his time at the Art Institute, Motley was mentored by painters Earl Beuhr and John W. Norton. and he did well enough to cause his father's friend to pay his tuition. While he was a student, in 1913, other students at the Institute "rioted" against the modernism on display at the Armory Show (a collection of the best new modern art). Motley graduated in 1918 but kept his modern, jazz-influenced paintings secret for some years thereafter.