The geometrical system described in the "Elements" was long known simply as "geometry" and was considered to be the only geometry possible. Today, that system is referred to as "Euclidean geometry", to distinguish it from other so-called "non-Euclidean geometries" which mathematicians discovered in the 19th century.
Occasionally in ancient times, writings were attributed to celebrated authors but were not written by them. It is in this way that the apocryphal books XIV and XV of the Elements were sometimes included in the collection. The spurious Book XIV was probably written by Hypsicles on the basis of a treatise by Apollonius of Perga. The book continues Euclid's comparison of regular solids inscribed in spheres. The chief result is that the ratio of the surfaces of the dodecahedron and icosahedron inscribed in the same sphere is the same as the ratio of their volumes.
The spurious Book XV was probably written, at least in part, by Isidore of Miletus. This book covers topics such as counting the number of edges and solid angles in the regular solids, and finding the measure of dihedral angles of faces that meet at an edge.
"Euclid's Elements – All thirteen books in one volume", based on Heath's translation, Green Lion Press, .
"The Elements: Books I-XIII-Complete and Unabridged" (2006), translated by Sir Thomas Heath, Barnes & Noble, .
Gene duplication
Gene duplication (or gene amplification) is any duplication of a region of DNA that contains a gene.
Gene duplication is important in supplying raw genetic material – new genes – to biological evolution. This has been recognized since the 1930s. Recent genomic sequence data show that duplicated genes are common in all organisms surveyed.
In classical genetics it may occur as an error in crossing-over during meiosis, or the duplication of an entire chromosome.
In non-classical genetics it may happen by a retrotransposition event.
The second copy of the gene is often relatively free from selective pressure. Mutations of it have no deleterious effects to its host organism. Thus it accumulates mutations faster than a functional single-copy gene, over generations.
A duplication is the opposite of a deletion. Duplications arise from unequal crossing-over that occurs during meiosis between misaligned homologous chromosomes. The product of this recombination are a duplication at the site of the exchange and a reciprocal deletion.
Gene duplication is believed to play a major role in evolution; this idea was first suggested 100 years ago. Susumu Ohno was one of the most famous developers of this theory in his classic book "Evolution by gene duplication" (1970). Ohno argued that gene duplication is the most important evolutionary force since the emergence of the last universal common ancestor (LUCA).
Major genome duplication events are not uncommon. It is believed that the entire yeast genome underwent duplication about 100 million years ago. Plants are the most prolific genome duplicators. For example, wheat is hexaploid (a kind of polyploid), meaning that it has six copies of its genome.
Normally, a big change in gene function is resisted because the original function is needed, but after a duplication one gene carries on the original function. Therefore, a change of function in the second copy is possible without loss of fitness.
This freedom from consequences allows for more mutations to be 'carried' in the population. Some of these might increase the fitness of the organism or code for a new function.
The two genes that exist after a gene duplication event are called paralogs and usually code for proteins with a similar function and/or structure. By contrast, orthologous genes are ones which code for proteins with similar functions but exist in different species, and are created from species-splitting.
Margins
In typesetting, the page margins (with header and footer) are the borders of the page outside of the regular text to be shown.
There are 4 main margins:
Other special margins can be used, beyond the typical 4, to provide additional margin settings on a page.
For webpages (such as on the Internet), the margins can be set by using CSS style sheet directives, such as:
Each page, and each image or formatted table on a page, can have the 4 margins set, separately.
Gladstone, South Australia
Gladstone is a small town in South Australia about 200 km north of Adelaide. In 2006 the population was 629.
It is in the middle of a farming area that grows wheat and raises sheep, but Gladstone is important because it has lots of very big buildings to store wheat, barley, durum wheat, peas, faba beans and fiesta beans. All together, these buildings store the biggest amount of grains in the Southern Hemisphere in a place not by the sea.
The railways are important to Gladstone so the grains can be moved to the sea and put on ships. The nearest place where this happens is Port Pirie.
The railways are also important to move the grains to the big cities in Australia. Gladstone is on the biggest railway line in Australia that goes between Sydney in the east and Perth in the west. Railway lines also go south to Adelaide, and north to other small towns. Now, all of the railway lines are 4 ft 8 1⁄2 in (1,435 mm) apart. This is called standard gauge. Before 1970, the railway lines going north were 3 ft 6 in (1,067 mm) apart (narrow gauge), and the railway lines going south were 5 ft 3 in (1,600 mm) apart (broad gauge). All three "gauges" joined together in Gladstone. Look at the photo to see this. This is very rare. Before 1970, there were only three places in the whole world where this happened.
Rosanna Arquette
Rosanna Arquette was born in New York City on August 10, 1959. She is an American actress and movie director. Her notable movies include "Desperately Seeking Susan", "Pulp Fiction" and many other movies. She's also been in TV shows. Many of her family members are also actors.
Broadcasting House
Broadcasting House is the headquarters and registered office of the BBC in Portland Place and Langham Place, London.
Broadcasting House is home to BBC Radio 3, BBC Radio 4, and BBC Radio 4 Extra and also houses the BBC Radio Theatre, where music and speech programmes (typically comedy for BBC Radio 4) are recorded in front of a studio audience. It is also the headquarters of the BBC itself and contains the offices of key figures within the organisation, such as the Director General.
The Original Construction of Broadcasting House took place in 1932, and opened on the 14 May 1932, 8 years after the corporation was created and was built as a housing for all their current operations, of offices and radio operations. Architect George Val Myer designed the building in collaboration with the BBC's civil engineer, M T Tudsbery. The original interiors were the work of the Australian-Irish architect Raymond McGrath. He set up and directed a team that included Serge Chermayeff and Wells Coates and designed the vaudeville studio, the associated green and dressing rooms, and the dance and chamber music studios in a flowing Art Deco style. It was later said of his efforts that "the designs for the BBC gave the first real fillip to industrial design in England".