A mobile phone (also known as a hand phone, cell phone, or cellular telephone) is a small portable radio telephone.

The mobile phone can be used to communicate over long distances without wires. It works by communicating with a nearby base station (also called a "mobile tower") which connects it to the main phone network. When moving, if the mobile phone gets too far away from the cell it is connected to, that cell sends a message to another cell to tell the new cell to take over the call. This is called a "hand off," and the call continues with the new cell the phone is connected to. The hand-off is done so well and carefully that the user will usually never even know that the call was transferred to another cell.

As mobile phones became more popular, they began to cost less money, and more people could afford them. Monthly plans became available for rates as low as US$30 or US$40 a month. Cell phones have become so cheap to own that they have mostly replaced pay phones and phone booths except for urban areas with many people.

In the 21st century, a new type of mobile phone, called smartphones, have become popular. Since the 2010s, more people use smartphones than the old kind of mobile phone, which are called feature phones.

History
Mobile phones in the 1950s through 1970s were large and heavy, and most were built into cars. In the late 20th century technology improved so people could carry their phones with ease.

Although Dr. Martin Cooper from Motorola made the first call using a mobile phone in 1973 (using a handset weighing  2 kilograms), it did not use the type of cellular mobile phone network that we use today.

The first cellular mobile phone networks were created in 1979 in Japan. Now almost all urban areas, and many country areas, are covered by mobile phone networks.

Technology
A cell phone combines technologies, mainly telephone, radio, and computer. Most also have a digital camera inside.

Cell phones work as two-way radios. They send electromagnetic microwaves from base station to base station. The waves are sent through antennas. This is called wireless communication.

Early cell telephones used analog networks. They became rare late in the 20th century. Modern phones use digital networks.

The first digital networks are also known as second generation, or 2G, technologies. The most used digital network is GSM (Global System for Mobile communication). It is used mainly in Europe and Asia, while CDMA (Code-Division Multiple Access) networks are mainly used in North America. The difference is in communication protocol. Other countries like Japan have different 2G protocols. A few 2G networks are still used. 3G are more common, and many places have 4G.

The radio waves that the mobile phone networks use are split into different frequencies. The frequency is measured in Hz. Low frequencies can send the signal farther. Higher frequencies provide better connections and the voice communications are generally clearer. Four main frequencies are used around the world: 850, 900, 1800 and 1900 MHz. Europe uses 900 and 1800 MHz and North America uses 850 and 1900 MHz.

Today there are mobile phones that work on two, three or four frequencies. The most advanced phones  work on all frequencies. They are called 'world' phones and can be used everywhere.

Shapes

There are different kinds of phones. A flip phone flips open, and is best for calling. A bar phone is shaped like a candy bar, and the keys and screen are on one face. A slate phone is a phone that has almost no buttons, and uses a touchscreen. Most smartphones are slates. A slider phone slides on rails. It can slide out number keys or a mini keyboard, but some do both. A swivel spins on an axle.

How mobile phones work

When a mobile phone is switched on, its radio receiver finds a nearby mobile phone network base station, and its transmitter sends a request for service. Computers in the base station check if the phone is allowed to use the network. The base station covers an area called a cell. A phone can move between different cells, but will only communicate with one cell at a time. This is why mobile communications are sometimes called cellular communications.

Once connected to a station, the mobile phone can make calls. Because the network knows that the phone is connected to that particular cell, it can also route calls to the mobile phone. Sometimes the radio connection to the cell is lost, for example when you go underground. This means the phone cannot make or receive calls until the connection is made again.

Networks and payment

The network is the company that provides the phone service. In most areas there will be more than one mobile network. Customers choose networks based on how well the different networks work in their area, or by price.

There are two main ways to pay for mobile phone calls:

 Contract
 If you pay by contract you will pay the network money every month so that you can make calls. Usually you can talk for a lot of time for the monthly fee, but if you do not use the phone a lot you still pay the same money.
 Pay as you use
 If you pay as you use, you will pay for a fixed amount of call time credit which you then use up when phoning people. Once the credit is used up you must buy some more to use the phone. This can be cheaper if you do not use the phone a lot.

Mobile phones use different technical standards. GSM phones need a separate microchip, called a Subscriber Identity Module or SIM card, to work. The SIM has information like the phone number and payment account and this is needed to make or receive calls. The SIM may be supplied by the same company as the phone, or a different one. Sometimes you can change the network by using a SIM from another network, but some companies do not want this to happen and they lock the phone so that you have to use their SIM.

The others have a special radio inside them that only makes phone calls when the phone is activated. When someone buys a contract, the network gives them a code, that if they enter it into the phone, the phone will then make calls. It is usually impossible to switch to a different network's code on this type of phone. The majority of these CDMA phones are used in the United States and nearby countries.

Smartphones
Main page: Smartphone

A majority of new mobile phones from the 21st century are smartphones. These phones are basically  small computers. Besides calling, they can be used for email, browsing the internet, showing local maps, playing music and games, and many other functions that computers can perform.

Most smartphones run a common mobile operating system. This allows developers to make mobile apps that work on many different phones without needing to change the code. Examples of smartphones include Apple's iPhone (which uses iOS software) and Samsung's Galaxy series, one of many phones that use the Android platform made by Google.

Mobile case

Cases, which are designed to attach to, support, or otherwise hold a smartphone, are popular accessories. Some have a keyboard built in. Case measures are based on the display inches (e.g. 5 inch display). There are different types:

 Pouches and sleeves
 Holsters
 Shells
 Skins
 Bumpers
 Flip cases and wallets
 Leather case
 Screen protectors and body films

In the 21st century, a new type of mobile phone, called smartphones, have become popular. More people are using smartphones than the old kind of mobile phone, which are called feature phones covers

Holsters are commonly used alone for devices that include rubberized padding, and/or are made of plastic and without exposed rigid corners. Heavy duty cases are designed to protect from drops and scratches.

Related pages
 4G
 5G

References

Mobile phone


Charles Robert Darwin (12 February 1809 – 19 April 1882) was an English naturalist. He was born in Shrewsbury, Shropshire. He is famous for his work on the theory of evolution.

His book On the Origin of Species was published in 1859. In this book, he put forward much evidence that evolution had occurred. He also proposed natural selection as the way evolution had taken place.

Darwin did not know about genetics: he never read the work of Gregor Mendel. Nevertheless, Darwin's explanation of evolution was fundamentally correct. In contrast to Lamarck, Darwin's idea was that the giraffe's neck became longer because those with longer necks survived better.p177/9 These survivors passed their genes on, and in time the whole species got longer necks.

Voyage of the  Beagle

Darwin spent almost five years on board a Royal Navy exploring ship, the HMS Beagle. He was the guest naturalist, which meant that he was responsible for making collections and notes about the animals, plants, and the geology of the countries they visited. The ship's crew made charts of all the coastal areas, which could be used by the navy wherever it went in the world. At the time, Britain had by far the largest navy in the world, and an empire which was global.

Darwin collected everywhere the ship landed. He found huge fossils of recently extinct mammals, experienced an earthquake in Chile, and noticed the land had been raised. He knew of raised beaches elsewhere, high in the Andes, with fossil seashells and trees which had once grown on a sandy beach. Obviously the Earth was constantly changing, with land rising in some places, and sinking in others. He collected birds and insects, and sent shipments back to Cambridge for experts to identify.

Darwin was the first dedicated naturalist to visit the Galapagos Islands, off the west coast of Ecuador. He noticed that some of the birds were like mockingbirds on the mainland, but different enough to be placed in separate species. He began to wonder how so many new species came to be on these islands.

When Darwin got back to England, he edited a series of scientific reviews of the voyage, and wrote a personal journal which we know as The Voyage of the Beagle. It is one of the great natural history travel diaries.

In 1843 Darwin, who already had two children with his wife Emma, bought Down House in the village of Downe, Kent. He lived there for the rest of his life, and today the house and contents are open to the public.

Evolution
While on the H.M.S. Beagle, and later back home in London, Darwin had come across the ideas of the Rev. T.R. Malthus. Malthus had realised that, although humans could double their population every 25 years, it did not happen in practice. He thought the reason was that a struggle for existence (or resources) limited their numbers. If numbers increased, then famine, wars and diseases caused more deaths. Darwin, who knew that all living things could, in principle, increase their numbers, began to think about why some survived, while others did not.p264-268 His answer took years to develop.

The theory of evolution says that all living things on Earth, including plants, animals and microbes, come from a common ancestor by slowly changing throughout the generations. Darwin suggested that the way living things changed over time is through natural selection. This is the better survival and reproduction of those that best fit their environment. Fitting into the place where you live is called adapting. Those who fit best into the place where they live, the best adapted, have the best chance to survive and breed. Those who are less well-adapted tend not to survive. If they do not survive well enough to raise young, this means they do not pass on their genes. In this way, the species gradually changes.

The first chapter of the Origin deals with domesticated animals, such as cattle and dogs. Darwin reminded readers of the huge changes mankind had made in its domestic animals, which were once wild species. The changes were brought about by selective breeding – choosing animals with desirable characters to breed from. This had been done generation after generation, until our modern breeds were produced. Perhaps what man had done deliberately, might happen in nature, where some would leave more offspring than others.

Darwin noticed that although young plants or animals are very similar to their parents, no two are exactly the same and there is always a range of shape, size, colour, and so on. Some of these differences the plant or animal may have got from their own ancestors, but some are new and caused by mutations. When such differences made an organism more able to live in the wild, it would have a better chance to survive, and would pass on its genes to its offspring, and they to their offspring. Any difference that would cause the plant or animal to have less of a chance to live would be less likely to be passed on, and would eventually die out altogether. In this way groups of similar plants or animals (called species) slowly change in shape and form so that they can live more successfully and have more offspring who will survive them. So, natural selection had similarities to selective breeding, except that it would happen by itself, over a much longer time.

He first started thinking about this in 1838, but it took a full twenty years before his ideas became public. By 1844 he was able to write a draft of the main ideas in his notebook. Historians think that he did not talk about his theory because he was afraid of public criticism. He knew his theory, which did not discuss religion, raised questions about the literal truth of the Book of Genesis. Whatever the reason, he did not publish his theory in a book until 1859. In 1858 he heard that another biologist, Alfred Russel Wallace, had the same ideas about natural selection. Darwin and Wallace's ideas were first published in the Journal of the Linnaean Society in London, 1858. Then, Darwin published his book the next year. The name of the book was On the Origin of Species by means of Natural Selection, or the preservation of favoured races in the struggle for life. This is usually called The Origin of Species.

Other works
Darwin wrote a number of other books, most of which are also very important.

His books

 1838-43: Zoology of the voyage of H.M.S. Beagle: published between 1839 and 1843 in five Parts (and nineteen numbers) by various authors, edited and superintended by Charles Darwin, who contributed sections to two of the Parts:
 1838: Part 1 No. 1 Fossil Mammalia, by Richard Owen (Preface and Geological introduction by Darwin)
 1838: Part 2 No. 1 Mammalia, by George Robert Waterhouse (Geographical introduction and A notice of their habits and ranges by Darwin)
 1839: Journal and remarks (The Voyage of the Beagle)
 1842: The structure and distribution of Coral Reefs
 1844: Geological observations of volcanic islands
 1846: Geological observations on South America
 1849: Geology from A manual of scientific enquiry; prepared for the use of Her Majesty's Navy: and adapted for travellers in general. ed. John Herschel.
 1851: A Monograph of the Sub-class Cirripedia, with figures of all the species. The Lepadidae; or, Pedunculated Cirripedes. Living barnacles.
 1854: A Monograph of the Sub-class Cirripedia, with figures of all the species. The Balanidae (or Sessile Cirripedes); the Verrucidae, etc.
 1851: A Monograph on the Fossil Lepadidae, or, Pedunculated Cirripedes of Great Britain. Fossil barnacles.
 1854: A Monograph on the Fossil Balanidæ and Verrucidæ of Great Britain
 1859: On the Origin of Species by means of natural selection, or the preservation of favoured races in the struggle for life
 1862: On the various contrivances by which British and foreign Orchids are fertilised by insects (Fertilisation of orchids)
 1865: On the movements and habits of climbing plants (Linnean Society paper, published in book form in 1875)
 1868: The variation of animals and plants under domestication
 1871: The Descent of Man, and selection in relation to sex
 1872: The expression of emotions in Man and animals
 1875: Insectivorous plants
 1876: The effects of cross and self fertilisation in the vegetable kingdom
 1877: The different forms of flowers on plants of the same species
 1880: The power of movement in plants
 1881: The formation of vegetable mould through the action of worms.

The original manuscript books of the Origin of Species were returned to Cambridge University library in 2020. They were stolen 22 years before.

Related pages
 Erasmus Darwin
 Alfred Russel Wallace
 Charles Lyell
 Charles Darwin's books
 Darwin Day
 Darwinism
 Evolution

References

1809 births
1882 deaths

Agnostics
Alumni of the University of Cambridge
British abolitionists
British zoologists
Deaths from heart failure
English activists
English Anglicans
English botanists
English evolutionary biologists
English geologists
English naturalists
English science writers
People buried in Westminster Abbey
People from Shropshire

Charles Darwin


The London Borough of Croydon is a London Borough. It is in south London. The borough is the farthest south of Greater London, with the M25 circle motorway touching it at the bottom. In North Croydon the borough mainly borders the London Borough of Bromley to the east as well as the London Boroughs of Southwark and Lambeth to the north. The boroughs of Sutton and Merton are west of Croydon.

Croydon's main town centre is Croydon itself. The town offers the most office space in Southeast England apart from Central London. There are two shopping centres in Croydon which are named Centrale and the Witgift Centre. Croydon was named the 20th best shopping town in the UK. Croydon is currently being modernised (meaning new buildings are being built). Croydon College and John Ruskin College are the only schools for people over 16 years old.

The London Borough of Croydon asked the government for city status in 2000 and again in 2002 but it failed. If the government said yes it would have been the third council in Greater London to hold that status, the others being the City of London and the City of Westminster.

The borough is the home of two football clubs, Crystal Palace F.C. who are in the Football League Championship and Croydon F.C. who are in the Ryman League. Croydon is also known for having a lot of parks and open spaces like Mitcham Common and South Norwood Lakes.

Croydon is a tourist attraction in London. One of the reasons is because it is close to Gatwick Airport and because it has lots of entertainment and historic facilities including the Fairfield Halls, Warehouse Theatre, Croydon Airport (disused), Shirley Windmill, Croydon Palace and the Croydon Clocktower.

Places

The borough includes the following areas:
 Addington
 Addiscombe
 Ashburton
 Broad Green
 Coombe
 Coulsdon
 Croydon
 Crystal Palace
 Forestdale
 Hamsey Green
 Kenley
 New Addington
 Norbury
 Purley
 Sanderstead
 Selhurst
 Selsdon
 Shirley
 South Croydon
 South Norwood
 Thornton Heath
 Upper Norwood
 Waddon
 West Croydon
 Woodside
 Whyteleafe

Attractions

Croydon has many places that people enjoy visiting. There are a lot of places of interest such as Croydon Airport, which was the largest airport in London until its closure in September 1959. It was closed because of it was too small to handle the growing number of flights to Croydon so Heathrow and Gatwick took over. It has become a great place for air plane shows and sometimes is hosts along with Biggin Hill. Addington Palace is an 18th-century mansion that was the home of six archbishops.

Croydon Clocktower is an arts facility in Central Croydon that includes a cinema, library, museum and conference room. The building links into the official Town Hall of Croydon Council and some areas of the building, most notably the Braithwaite Hall, are part of the original complex. The Clocktower is the tower of the Town Hall. New buildings were built alongside the Town Hall and were opened by Queen Elizabeth II in 1994. Croydon Palace is where Archbishops of Canterbury used to stay during the summer. It is more than 500 years old.

The Warehouse Theatre is a professional producing producing studio theatre with up to a hundred seats in the centre of Croydon based in an oak-beamed former Victorian cement warehouse. The Fairfield Halls is an arts centre in Croydon which opened in 1962. It contains a concert hall, the Ashcroft Theatre (named for local actress Dame Peggy Ashcroft), the Arnhem Gallery civic hall (Croydon is twinned with Arnhem, a city in The Netherlands) and an art gallery. The large concert hall is used by the BBC for recordings.

Other websites
 Croydon Council - London Borough of Croydon
 Croydon Online - Website about area

London Borough of Croydon


P versus NP is one of the Millennium Problems, and of great interest to people working with computers and in mathematics. One way of asking it is, "Can every solved problem whose answer can be checked quickly by a computer, also be quickly solved by a computer?" Math problems are referred to as P or NP, whether they are solvable in a given finite set of time with the problem itself being the upper limit. P problems have their solution time bound to a polynomial and so are relatively fast for computers to solve, and so are considered "easy". NP problems are fast (and so "easy") for a computer to check, but are not necessarily easy to solve.

In 1956, Kurt Gödel wrote a letter to John von Neumann. In this letter, Gödel asked whether a certain NP complete problem could be solved in quadratic or linear time. In 1971, Stephen Cook introduced the precise statement of the P versus NP problem in his article "The complexity of theorem proving procedures".

Today, many people consider this problem to be the most important open problem in computer science. It is one of the seven Millennium Prize Problems selected by the Clay Mathematics Institute to carry a US$1,000,000 prize for a solution that invites a published recognition by the Clay Institute, and presumably one(s) that changes the whole of mathematics.

Because many of these problems touch upon related issues, and it is the dream of many mathematicians to invent unifying theories, many hope the Millennium Problems are interconnected.

Clarifications
A computer may be able to tell if an answer is right, but take longer to get the answer. For some interesting, practical questions of this kind, difficult answers are possible to check quickly. So NP problems may be thought of as being like riddles: it may be hard to come up with an answer to a riddle, but once one hears the answer, the answer seems obvious. In this comparison (analogy), the basic question is: are riddles really as hard as we think they are, or are we missing something? Is there a secret to always having an answer?

Because these kinds of P versus NP questions are so practically important, many mathematicians, scientists, and computer programmers want to prove the general proposition, that every quickly-checked problem can also be solved quickly. This question is important enough that the Clay Mathematical Institute will give $1,000,000 to anyone who successfully provides a proof or a valid explanation that disproves it.

Digging a little deeper, we see that all P problems are NP problems: it is easy to check that a solution is correct by solving the problem and comparing the two solutions. However, people want to know about the opposite: Are there any NP problems other than P problems, or are all NP problems just P problems? If NP problems are really not the same as P problems (P ≠ NP), it would mean that no general, fast ways to solve those NP problems can exist, no matter how hard we look. However, if all NP problems are P problems (P = NP), it would mean that new, very fast problem-solving methods do exist. We just have not found them yet.

Since the best efforts of scientists and mathematicians have not found general, easy methods for solving NP problems yet, many people believe that there are NP problems other than P problems (that is, that P ≠ NP is true). Most mathematicians also believe this to be true, but currently no one has proven it by rigorous mathematical analysis. If it can be proven that NP and P are the same (P = NP is true), it would have a huge impact on many aspects of day-to-day life. For this reason, the question of P versus NP is an important and widely studied topic.

Example
Suppose someone wants to build two towers, by stacking rocks of different mass. One wants to make sure that each of the towers has exactly the same mass. That means one will have to put the rocks into two piles that have the same mass. If one guesses a division of the rocks that one thinks will work, it would be easy for one to check if one was right.  (To check the answer, one can divide the rocks into two piles, then use a balance to see if they have the same mass.) Because it is easy to check this problem, called 'Partition' by computer scientists—easier than to solve it outright, as we will see—it is not a P problem.

How hard is it to solve, outright? If one starts with just 100 rocks, there are 2^{100-1}-1 = 633,825,300,114,114,700,748,351,602,687, or about 6.3 x 10^{29} possible ways (combinations) to divide these rocks into two piles. If one could check one unique combination of rocks every day, it would take 1.3 x 10^{22} or 1,300,000,000,000,000,000,000 years of effort. For comparison, physicists believe that the universe is about 1.4 x 10^{10} years old (450,000,000,000,000,000 or about 4.5 x 10^{17} seconds, or about one trillionth as old as the time it would take for our rock piling effort. That means that if one takes all of the time that has passed since the beginning of the universe, one would need to check more than two trillion (2,000,000,000,000) different ways of dividing the rocks every second, in order to check all of the different ways.

If one programmed a powerful computer, to test all of these ways to divide the rocks, one might be able to check  combinations per second using current systems. This means one would still need  very powerful computers, working since the origin of the universe, to test all the ways of dividing the rocks.

However, it may be possible to find a method of dividing the rocks into two equal piles without checking all combinations. The question "Does P equal NP?" is a shorthand for asking if any method like that can exist.

Why it matters
There are many important NP problems that people don't know how to solve in a way that is faster than testing every possible answer.  Here are some examples:

 A travelling salesman wants to visit 100 cities by driving, starting and ending his trip at home. He has a limited supply of gasoline, so he can only drive a total of 10,000 kilometers.  He wants to know if he can visit all of the cities without running out of gasoline.
 A school offers 100 different classes, and a teacher needs to choose one hour for each class' final exam. To prevent cheating, all of the students who take a class must take the exam for that class at the same time. If a student takes more than one class, then all of those exams must be at a different time. The teacher wants to know if he can schedule all of the exams in the same day so that every student is able to take the exam for each of their classes.
 A farmer wants to take 100 watermelons of different masses to the market. She needs to pack the watermelons into boxes. Each box can only hold 20 kilograms without breaking.  The farmer needs to know if 10 boxes will be enough for her to carry all 100 watermelons to market. (This is trivial, if no more than one watermelon weighs more than 2 kg then any 10 can be placed in each of the crates, if no more than ten watermelons weighs more than 2 kg then one of each of them can be placed in each crate, etc., to a fast solution; observation will be the key to any rapid solution such as this or the number set problem).
 A large art gallery has many rooms, and each wall is covered with many expensive paintings. The owner of the gallery wants to buy cameras to watch these paintings, in case a thief tries to steal any of them. He wants to know if 100 cameras will be enough for him to make sure that each painting can be seen by at least one camera.
 The clique problem: The principal of a school has a list of which students are friends with each other. She wants to find a group of 10% of the students that are all friends with each other.

Exponential Time
In the example above, we see that with  rocks, there are  ways to partition the set of rocks. With  rocks, there are  combinations. The function  is an exponential function. It's important to NP because it models the worst-case number of computations that are needed to solve a problem and, thus, the worst-case amount of time required.

And so far, for the hard problems, the solutions have required on the order of  computations. For any particular problem, people have found ways to reduce the number of computations needed. One might figure out that a way to do just 1% of the worst-case number of computation and that saves a lot of computing, but that is still  computations. And every extra rock still doubles the number of computations needed to solve the problem. There are insights that can produce methods to do even fewer computations producing variations of the model: e.g. . But the exponential function still dominates as  grows.

Consider the problem of scheduling exams (described above). But suppose, next, that there are 15000 students. There's a computer program that takes the schedules of all 15000 students. It runs in an hour and outputs an exam schedule so that all students can do their exams in one week. It satisfies lots of rules (no back-to-back exams, no more than 2 exams in any 28 hour period, ...) to limit the stress of exam week. The program runs for one hour at mid-term break and everyone knows his/her exam schedule with plenty of time to prepare.

The next year, though, there are 10 more students. If the same program runs on the same computer then that one hour is going to turn into  hours, because every additional student doubles the computations. That's  weeks! If there were 20 more students, then

 hours =  hours ~  days ~  years

Thus, for  students, it takes one hour. For  students, it takes  years.

As you can see, exponential functions grow really fast. Most mathematicians believe that the hardest NP problems require exponential time to solve.

NP-complete problems
Mathematicians can show that there are some NP problems that are NP-Complete.  An NP-Complete problem is at least as difficult to solve as any other NP problem. This means that if someone found a method to solve any NP-Complete problem quickly, they could use that same method to solve every NP problem quickly. All of the problems listed above are NP-Complete, so if the salesman found a way to plan his trip quickly, he could tell the teacher, and she could use that same method to schedule the exams. The farmer could use the same method to determine how many boxes she needs, and the woman could use the same method to find a way to build her towers.

Because a method that quickly solves one of these problems can solve them all, there are many people who want to find one. However, because there are so many different NP-Complete problems and nobody so far has found a way to solve even one of them quickly, most experts believe that solving NP-Complete problems quickly is not possible.

Basic Properties
In computational complexity theory, the complexity class NP-complete (abbreviated NP-C or NPC), is a class of problems having two properties:
 It is in the set of NP (non-deterministic polynomial time) problems: Any given solution to the problem can be verified quickly (in polynomial time).
 It is also in the set of NP-hard problems: Those which are at least as hard as the hardest problems in NP. Problems that are NP-hard do not have to be elements of NP; indeed, they may not even be decidable.

Formal overview
NP-complete is a subset of NP, the set of all decision problems whose solutions can be verified in polynomial time; NP may be equivalently defined as the set of decision problems solved in polynomial time on a machine. A problem p in NP is also in NPC if and only if every other problem in NP is transformed into p in polynomial time. NP-complete was to be used as an adjective: problems in the class NP-complete were as NP+complete problems.

NP-complete problems are studied because the ability to quickly verify solutions to a problem (NP) seems to correlate with the ability to quickly solve problem (P). It is found every problem in NP is quickly solved—as called the P = NP: problem set. The single problem in NP-complete is solved quickly, faster than every problem in NP also quickly solved, because the definition of an NP-complete problem states every problem in NP must be quickly reducible to every problem in NP-complete (it is reduced in polynomial time).

Examples
The Boolean satisfiability problem is known to be NP complete. In 1972, Richard Karp formulated 21 problems that are known to be NP-complete. These are known as  Karp's 21 NP-complete problems. They include problems such as the Integer programming problem, which applies linear programming techniques to the integers, the knapsack problem, or the vertex cover problem.

References

Conjectures
Theoretical computer science

P versus NP problem


Crosby, Stills & Nash (CSN) was an American folk rock supergroup made up of David Crosby, Stephen Stills and Graham Nash. They are known as Crosby, Stills, Nash & Young (CSNY) when joined by occasional fourth member Neil Young, who is from Canada.

Their songs include "Marrakesh Express", "Suite: Judy Blue Eyes", "Teach Your Children", "Ohio" (a protest song, against the Kent State shootings in early 1970), and "Just A Song Before I Go".

Coming together
In the 1960s, Stephen Stills and Neil Young were members of another band, called Buffalo Springfield. Crosby was a founding member of The Byrds, and British-born Graham Nash was a member of The Hollies. Crosby was fired from the Byrds late in 1967, and the Buffalo Springfield disbanded the next year. Nash went to California, where the others lived and worked, when the Hollies visited there in 1968. Nash and Crosby had met earlier in England, and got back in touch in California. Crosby and Stills had worked together on two songs, called "Wooden Ships" and "You Don't Have To Cry". Performing "You Don't Have To Cry" for Nash, he joined in on harmonies, and the three noticed they had a special sound together. Nash moved to California, and the three formed a band. They signed a recording contract with Atlantic Records.

Stills and Crosby were free to work together, and record for Atlantic, but Nash still belonged to the Hollies, who had a contract with Epic Records. A trade was worked out, between Atlantic and Epic. In exchange for losing Nash, Epic Records got to sign up another Atlantic band, Poco, formed by Richie Furay from the Buffalo Springfield.

CSN's first album was released in the spring of 1969, and quickly became a hit. The cover showed Crosby, Stills and Nash sitting on a couch outside an abandoned house. (They did not sit in their name order; they had not yet named the group. When they decided on their name, they wanted to take another picture sitting in order, but the house had already been torn down.) Stephen Stills had played most of the instruments on the album, with Dallas Taylor playing drums. This worked fine for recordings, but not for live appearances. More musicians were needed. A keyboardist and bass guitarist were hired.

Atlantic Records president Ahmet Ertegün suggested Neil Young, who now had his own band called Crazy Horse, as another guitarist for the group. Stills wasn't sure if Young would work out, but gave him a chance. He fit in so well that CSN made him a full-time member, and added his name to theirs. Young was able to both play with CSN, and keep his own place with Crazy Horse. Their second show as a quartet was at the Woodstock Festival, in August 1969. They toured for the next several months, and released a second album, Déjà Vu, early the next year. They made another performing tour, to support the album, which was also a huge hit.

Coming apart
The group was very successful, but its members had many different ideas, and could not always work well together. Tension grew between them, and they nearly disbanded. Young left to return to Crazy Horse, and tour with them on his own. Each of the four recorded a solo album during 1971, though, and each album became a hit. Nash and Crosby toured together, and Stills formed another band, called Manassas, with Chris Hillman of the Byrds. Another round of solo and duo albums was released during 1972, with Young's Harvest and its single "Heart Of Gold" becoming the biggest hits. Albums by the other members were not as successful, though they still sold well. Crosby and Nash got along very well, and worked together as a duo, while Stills joined Young and Crazy Horse to record Young's "War Song". Crosby also rejoined the Byrds, but the album they recorded together, Byrds, was not a hit.

The four tried to reunite in Hawaii during 1973 to make a new album, Human Highway, but things did not work out. Finally the next year, they reformed and started another tour, with a compilation album, So Far, issued to give them something new to promote. Their shows ran longer than three hours, and there was sometimes trouble. Stills was abusing cocaine, and it made him hard to get along with. The same old tensions also came back. A new CSN&Y project was dashed when Stills and Young erased Crosby and Nash's vocals from the master tapes. Crosby and Nash went off on their own. Stills and Young formed The Stills/Young Band, and released an album, but even that did not work out.

Stills and Young toured together during 1975 and 1976. In July 1976, Young left suddenly between shows, sending Stills a telegram that expressed his unhappiness, and told Stills to "Eat a peach." Stills and Young each had to complete tour dates separately. Meanwhile, Nash and Crosby kept recording and performing together. They also sang background vocals for other artists, including James Taylor ("Mexico") and Joni Mitchell ("Free Man In Paris").

Back together
During one of their shows, Crosby and Nash were joined onstage by Stills, to perform "Teach Your Children". The three worked things out, and reformed their trio. CSN was released in 1977, and "Just A Song Before I Go" became a new hit single.

In the next years, the trio worked together off and on, and also as solo artists. Young's music had become very different from that of the other band members, and he mostly worked with Crazy Horse, but he did collaborate now and then with CSN. Crosby had his own cocaine problems during the 1980s, and ended up serving a prison sentence. He was able to stop abusing cocaine, as Stills had earlier. CSN's later songs included "Wasted On The Way". Nash rejoined the Hollies for a reunion album in 1984, and played shows with them, but the reunion was not a success.

CSN played in Berlin, Germany at the time the Berlin Wall was torn down, at the end of the 1980s. They also played shows during the 1990s and early 2000s, and their 2000 tour was called the "CSNY2K" tour. They recorded other albums, but they were not nearly the hits their early ones had been, and they worked with outside writers, instead of writing all their own songs. Atlantic Records cancelled their contract.

Crosby, Stills and Nash still work together and apart, with Crosby and Nash having the longest and strongest partnership. Neil Young continues on as a solo artist, with and without Crazy Horse, exploring many different kinds of music.

Discography
 1969: Crosby, Stills & Nash (CSN)
 1970: Déjà Vu (CSNY)
 1971: 4 Way Street (CSNY) (live)
 1974: So Far (CSNY)
 1977: CSN (CSN)
 1982: Daylight Again (CSN)
 1983: Allies (CSN) (live and studio)
 1988: American Dream (CSNY)
 1990: Live It Up (CSN)
 1994: After the Storm (CSN)
 1999: Looking Forward (CSNY)
 2008: Déjà Vu Live (CSNY) (live)

American rock bands
Folk music groups
Musical groups from California
Musical groups established in 1968
1968 establishments in the United States
1960s establishments in California
Musical groups disestablished in 1970
1970 disestablishments in the United States
1970s disestablishments in California
Musical groups established in 1974
1974 establishments in California
Musical groups disestablished in the 1970s
1974 disestablishments in the United States
Musical groups established in 1977
1977 establishments in the United States

Crosby, Stills, Nash & Young


This article is about the drink, for the plant see yerba mate.

Mate is a traditional drink in some countries in South America, especially in Argentina, Paraguay, Uruguay, Chile, Bolivia and Brazil. The drink, which contains mateine (an analog of caffeine), is made by an infusion of dried leaves of yerba mate (Ilex paraguariensis). It is usually drunk with friends and served in a hollow calabash gourd with a "Bombilla", a special metallic drinking straw. The straw is also called a bomba in Portuguese, and a bombija in Arabic. It is traditionally made of  silver. The gourd is known as a mate or a guampa. In Brazil it called a cuia. Even if the water comes in a very modern thermos, the drink is traditionally drunk from mates or cuias. There are now modern "tea-bag" type infusions of mate called mate cocido which have been sold in Argentina for many years. They are drunk from a cup. They are sold under such trade names as "Cruz de Malta" (Maltese Cross) and in Brazil under the name "Mate Leão" (Lion Mate).

Like other brewed herbs, yerba mate leaves are dried, chopped, and ground into a powder called yerba. The bombilla is both a straw and a sieve. The end which is placed in the drink is wider, with small holes or slots that let the brewed liquid in, but block the chunky matter that makes up much of the mixture. A modern bombilla uses a straight tube with holes, or spring sleeve to act as a sieve. Bombilla means "light bulb" in Spanish, but locally it is "little pump" or "straw".

In some areas of the Middle Eastern countries of Syria and Lebanon it is also common to drink mate. The custom of drinking mate came from Arab emigrants from South America.  Syria is the world's biggest importer of yerba mate in the world, importing 15,000 tons of yerba mate a year.

How to prepare mate
Mate is made differently in different places, with many arguments about which way is the best. In nearly all methods, the gourd is nearly filled with yerba, and hot water (typically at 70–80 °C [160–180 °F] and never boiling) is added.

Arranging the yerba
The most common way to make mate involves a careful arrangement of the yerba in the gourd before adding hot water. The gourd is filled one-half to three-quarters of the way with yerba. Extra herbs may be added for either health or flavor benefits. This is most often done in Paraguay, where people get herbs from a local yuyera (herbalist). The mate is used as a base for their herbal infusions. When the gourd is filled, the preparer typically grasps it with their full hand. They  cover the opening  and roughly seal it with their palm.  Then the mate is turned upside-down, and shaken vigorously, but briefly and with gradually decreasing force, in this inverted position causing the finest, most powdery particles of the yerba to settle toward the preparer's palm and the top of the mate.

Once the yerba is settled, the mate is carefully brought to a near-sideways angle, with the opening tilted just slightly upward of the base.  The mate is then shaken very gently  with a side-to-side motion.  This further settles the yerba inside the gourd so that the finest particles move toward the opening and the yerba is  layered along one side.  The largest stems and other bits create a partition between the empty space on one side of the gourd and the lopsided pile of yerba on the other.

After arranging the yerba along one side of the gourd, the mate is carefully tilted back onto its base, minimizing further disturbances of the yerba as it is re-oriented to allow consumption.  Some avalanche-like settling is normal, but is not desirable.  The angled mound of yerba should remain, with its powdery peak still flat and mostly level with the top of the gourd.  A layer of stems along its slope will slide downward and accumulate in the space opposite the yerba (though at least a portion should remain in place).

All of this careful settling of the yerba ensures that each sip contains as little particulate matter as possible, creating a smooth-running mate. The finest particles will then be as distant as possible from the filtering end of the bombilla.  With each draw, the smaller particles would inevitably move toward the bombilla, but the larger particles and stems filter much of this out.  A sloped arrangement provides consistent concentration and flavor with each filling of the mate.

Insertion of the bombilla

Now the mate is ready to receive the bombilla.  Many people choose to pour warm water into the mate before adding the bombilla, while others insist that the bombilla is best inserted into dry yerba.  Wetting the yerba by gently pouring cool water into the empty space within the gourd until the water nearly reaches the top, and then allowing it to be absorbed into the yerba before adding the bombilla, allows the preparer to carefully shape and "pack" the yerba's slope with the bombilla's filtering end, which makes the overall form of the yerba within the gourd more resilient and solid.  Dry yerba, on the other hand, allows a cleaner and easier insertion of the bombilla, though care must be taken so as not to overly disturb the arrangement of the yerba.  Such a decision is entirely a personal or cultural preference.  The bombilla is inserted with your thumb on the upper end of the bombilla, at an angle roughly perpendicular to the slope of the yerba, so that its filtering end travels into the deepest part of the yerba and comes to rest near or against the opposite wall of the gourd.

Brewing
Now the yerba may be brewed.  If the bombilla was inserted into dry yerba, the mate must first be filled once with warm water as above, then be allowed to absorb it completely (which generally takes no more than two or three minutes).  Treating the yerba with cool water before the addition of hot water is essential, as it protects the herb from being scalded and from the chemical breakdown of some of its desirable nutrients.  Hot water may then be added by carefully pouring it, as with the cool water before, into the cavity opposite the yerba, until it reaches almost to the top of the gourd when the yerba is fully saturated.  Care should be taken to maintain the dryness of the swollen top of the yerba beside the edge of the gourd's opening.

Once the hot water has been added, the mate is ready for drinking. It may be refilled many times before becoming washed out (lavado) and losing its flavor. When this happens, the mound of yerba can be pushed from one side of the gourd to the other, allowing water to be added along its opposite side; this revives the mate for additional re-fillings.

Drinking the mate
Mate is traditionally drunk in a particular social setting, such as family gatherings or with friends. One person (known in Spanish as the cebador) assumes the task of server. Typically, the cebador fills the gourd and drinks the mate completely to ensure that it is free of particulate matter and of good quality. The server subsequently refills the gourd and passes it to the next drinker who likewise drinks it all, without thanking the server. The ritual proceeds around the circle in this fashion until the mate becomes lavado ("washed out" or "flat"), typically after the gourd has been filled about ten times or more depending on the yerba used (well-aged yerba mate is typically more potent, and therefore provides a greater number of refills). When one has had his fill of mate,  he or she politely thanks the cebador passing the mate back at the same time.

The drink has a pungent taste like a cross between green tea and coffee, with hints of tobacco and oak. Some drinkers like to add sugar or honey, creating mate dulce (sweet mate), instead of sugarless mate amargo (bitter mate). It is considered bad for the gourd (especially for the natural (squash or wood) ones) to be used for mate dulce so it is normal for households with drinkers of both kinds to have two separate gourds.

Traditionally, natural gourds are used, though wood vessels, bamboo tubes and gourd-shaped mates, made of ceramic or metal (stainless steel or even silver) are also common.  Gourds are commonly decorated with silver, sporting decorative or heraldic designs with floral motifs.

Both the wood vessels and the gourds must undergo curing to get a better taste before being used for the first time and to ensure the long life of the gourd.  Typically, to cure a gourd, the inside is first scraped with the tip of a bombilla to remove loose gourd particles. Mate herb and hot water is added next, and the mixture poured into the gourd. The mixture is left to sit overnight and the water is topped off periodically through the next 24 hours as the gourd absorbs the water. Finally the gourd is scraped out, emptied, and put in sunlight until completely dry.

It is common for a black mold to grow inside the gourd when it is stored. Some people will clean this out, others consider it an enhancement to the mate flavor.

Legendary Origins
The Guaraní people started drinking mate in the region that now includes Paraguay, southern Brazil,Uruguay, and north-east Argentina. The Guaraní have a legend that says that the Goddesses of the Moon and the Cloud came to the Earth one day to visit it but they instead found a Yaguareté (a kind of jaguar) that was going to attack them. An old man saves them, and, in compensation, the Goddesses gave the old man a new kind of plant, from which he could prepare a "drink of friendship".

Variants and trivia

There is another drink that can be prepared with specially cut dry leaves, very cold water and, optionally, lemon or another fruit juice, called tereré. It is very common in Paraguay.  Drinking and harvesting of Mate started in Paraguay in pre-Hispanic times. (Notice its scientific name, Ilex paraguayensis.)

In Brazil the traditional mate or cuia is usually big with a corresponding large hole. In Uruguay and Argentina (especially in the capital, Buenos Aires) the mate is small and has a small hole, and people sometimes add sugar for flavor. In Bolivia and Peru, mate de coca is often sipped instead of ordinary mate.

In Uruguay there is even a national law that prohibits drinking mate while driving, because it caused many accidents of people getting scalded with hot water while driving.  For the same reason, there is also a "forbidden to drink mate" sign in all public transportation buses.

In Uruguay and in the northeast of Argentina it is not uncommon to see people walking around the streets toting a mate and a thermos with hot water. In Montevideo, Uruguay's capital, it is possible to see some construction worker drinking mate while riding his bicycle early in the morning, on his way to work. In some parts of Argentina, gas stations sponsored by yerba mate producers provide free hot water to travellers, specifically for the purpose of drinking during the journey. There are disposable mate sets with a plastic mate and bombilla, and sets with a thermos flask and stacking containers for the yerba and sugar inside a fitted case.

In Brazil, traditionally prepared mate is known as chimarrão, although in areas near the border with Uruguay the word mate is also used. Nowadays, in Brazil,  mate is often toasted with sugar and prepared in a similar manner to tea, a custom that originated in Paraguay. Supermarkets, restaurants and fast food chains sell "tea bags" and prepacked "iced tea" packages and bottles. In Argentina, mate cocido (cooked mate) is made with a teabag or leaves and drunk from a cup or mug, with or without sugar and milk.

At the beginning of the 21st century most urban Chileans are not mate drinkers, but travel narratives such as Maria Graham's Journal of a Residence in Chile [2003(1824):8], show that there is a long history of mate drinking in central Chile. Many rural Chileans drink mate, in particular in the southern regions, particularly Chiloé and Magallanes, perhaps due to the influence of neighboring areas of Argentina.

According to a major retailer of mate in San Luis Obispo, California, by 2004 mate had grown to about 5% of the overall natural tea market in North America  . Bottled iced mate is widely available in California.

References

Other websites
Preparing the mate in 8 steps
Yerba Mate Association of the Americas (YMAA)

Drinks
Argentine food
Chilean food

Mate (drink)


A computer network is a group of two or more computers that are linked together. Networks are usually used to share resources, exchange files or communicate with other users.

A network is a set of nodes connected by communication links.  A node can be a computer, printer, or any other device capable of sending or receiving data from or to the other node in the network.

Other devices are often needed for the network to work correctly.  Examples for such devices include hubs and switches.  Different kinds of network can be connected to each other with a router.  In general, networks that use cables to connect can operate at higher speeds than those using wireless technology.

Computers in a network can be near each other, or far. A Local Area Network (LAN) connects computers which are close together.  Building a LAN is easier than connecting different networks (by a Wide Area Network).  The largest Wide Area Network is the Internet.

Computers can be part of several different networks. Networks can also be parts of bigger networks. The local area network in a small business is usually connected to the corporate network of the larger company.  These connections may allow access to the Internet.  For example, a shop may use it to show merchandise on its Web site through a web server, or to convert received orders into shipping instructions.

A network must be connected with appropriate hardware. This can be wired or wireless. For a simple LAN, computers, media and peripherals are sufficient. WANs (wide area networks) and some large LANs (local area networks) need some additional devices like a bridge, gateway or router to connect different small or large networks.

A network needs a communication protocol (a system for exchanging messages between computing systems.) Microsoft Windows, Linux and most other operating systems use TCP/IP. Apple Macintosh computers used Appletalk in the 20th century, but use TCP/IP now.

Network models

One large network of communication technology would be difficult to implement. As a result, we split up various components of the network into smaller modules or layers. The standard model of a network is the Open Systems Interconnection (OSI) model set by the International Organization Standard (ISO).

Other network models exist, though they are all split into similar layers. Each layer uses the services that the layer below provides, while providing services for the layer above it. Each layer can only communicate with the same layer on the destination device.

OSI model
OSI (Open Systems Interconnection) is a 7-layer network model specified by ISO (International Organization for Standardization) norm and is widely used all around the world. The concept of a seven-layer model was provided by the work  of Charles Bachman, Honeywell information Services. Various aspects of OSI design evolved from experiences with the ARPANET, NPLNET, EIN and CYCLADES networks and the work in IFIP WG6.1.

Layer 1

The physical layer defines electrical and physical specifications for devices. It also specifies modulated and baseband transmission.

Baseband
Baseband is digital data in their raw form (in binary, the language understood by the computer in the form of 0s and 1s - 1001 1101 1010 0011).  This allows very fast and reliable transmission over short distances; however, the media tend to make the bits interfere with each other, the range of baseband transmission is very limited.  It becomes worse with increasing speed.  Baseband technology is frequently used on LAN.
 UTP cable – max 100 m on 100 Mbit/s speed without repeater
 Optical fiber – max 1 km on 100 Mbit/s speed without repeater
Typical technology: Ethernet cables

Modulated transmission
In telecommunications, modulation is the process of conveying a message signal, for example a digital bit stream or an analog audio signal, inside another signal that can be physically transmitted. The device that provides modulation of the baseband signal is called a modulator, and the device that provides demodulation of the modulated signal back to baseband is called a demodulator. Today, the modulator and demodulator are integrated into one device called Modem (modulator-demodulator). Frequently used on WAN, WLAN, WWAN.

Typical technology: WI-FI, ADSL, cable TV connection (CATV)

Layer 2
The data link layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the physical layer.

Layer 3
The network layer provides the functional and procedural means of transferring variable length data sequences from a source host on one network to a destination host on a different network using the IP address.

IP address
An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication. At present there are two versions of protocols in use – IPv4 and IPv6.
 IPv4 uses 32-bit addressing which limits address space up to 4294967296 (232) possible unique addresses.
Example: IP-192.168.0.1 mask-255.255.255.0 means that the network address is 192.168.0.0 and the device address is 192.168.0.1
 IPv6 uses 128-bit addressing which limits address space up to 2128 possible addresses. It is deemed sufficient for the foreseeable future. Full IPv6 support is still in the implementation phase.

Layer 4
The transport layer provides transparent transfer of data between end users, providing reliable data transfer services to the upper layers. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) of the Internet Protocol Suite are commonly categorized as layer-4 protocols within OSI.
 TCP (transmission control protocol) provides reliable, ordered delivery of a stream of bytes from a program on one computer to another program on another computer. TCP is used for applications that strictly require reliable transfer (e-mail, WWW, file transfer (FTP), ...)
 UDP (user datagram protocol) uses a simple transmission model without implicit handshaking dialogues for providing reliability, ordering, or data integrity. UDP is used in applications where we require reduced latency over reliability (stream videos, VOIP, online games,...)

Layers 5-7
Commonly united into one layer in simplified network models, its main purpose is to interact with applications, encrypting and establishing dedicated connections if necessary.

Networking terms

Latency
Latency, incorrectly called ping, is a value that measures how much time packets need to travel to their destination. It is measured in milliseconds (ms). The tool that measures latency is called ping, commonly using special ICMP packets which are smaller than standard data packets so they do not weight the network by their presence.
 Immediate latency is measured every X seconds and immediately displayed. Its value constantly changes due to the natural properties of packet-switching network technology. High latency peaks have negative effects on most network applications which can adapt to average latency by allocating corresponding size of memory as buffer. High latency peaks lead to emptying of this buffer and to temporary freezing of applications. This freezing is commonly called lag.
 Average latency is the sum of immediate latency measured Y times every X seconds divided by Y. Average latency is used to estimate size of the buffer, mainly because it does not change so often. Buffer enables some applications such as stream videos to run smoothly even with high average latency, but it cannot protect us from high latency peaks.

Capacity (bandwidth)
Capacity is a measure of transfer capacity of a network and is measured in bits per second (bps or b/s), today commonly Mbps or Mb/s. It shows us how many data units are transferred each second. At present, the average bandwidth is far higher than is necessary and it is not a limiting factor in most cases.
 Uplink is how much bandwidth is used for transferring data from user to server (usually lower for end users).
 Downlink is how much bandwidth is used for transferring data from server to user (usually higher for end users).

Broadcast
Broadcast is a special transmission that is not meant for a single device but is addressed to all devices in specific network. It is mostly used to automatically issue IP addresses to devices by a DHCP server and to create an ARP table that maps the network and speeds up the traffic.

References

Computer network


Midway Atoll is an island in the Pacific Ocean and was the site of a famous battle in World War II, the Battle of Midway. The United States of America took control of the atoll in 1867 when nobody lived there. In the 21st century about 40 people live there, mostly working for the United States Fish and Wildlife Service.

Wildlife

Midway Atoll is now home to 67-70% of the world's Laysan Albatross population, and 34-39% of the global Black-footed Albatross.

While Midway supports nearly three million birds, each seabird species has carved out a specific site on the atoll in which to nest.  Seventeen different species of seabird can be found, the rarest of which is the Short-tailed Albatross, otherwise known as the "Golden Gooney."  Fewer than 2,200 are believed to exist due to excessive feather hunting in the late nineteenth century.

Over 250 different species of looli marine life are found in the  of lagoon and surrounding waters. The critically endangered Hawaiian monk seals raise their pups on the beaches. Monk seals are benthic foragers and rely on the Midway Atoll's reef fish, squid, octopus and crustaceans. Green sea turtles, another threatened species, occasionally nest on the island. The first was found in 2006 on Spitsy Rinaia Island and another in 2007 on Sand Island. A resident pod of 300 spinner dolphins live in the lagoons and nearshore waters.

Other websites

 Satellite Map and NOAA Chart of Midway  on BlooSee
 AirNav - Henderson Field Airport : Airport facilities and navigational aids.
 Diary from the middle of nowhere BBC's environment correspondent David Shukman reports on the threat of plastic rubbish drifting in the North Pacific Gyre to Midway. Accessed 2008-03-26.
 Midway Atoll National Wildlife Refuge (this article incorporated some content from this public domain site)
 NOAA Midway Island Hawaiian Monk Seal Captive Care & Release Project
 The Battle of Midway: Turning the Tide in the Pacific, a National Park Service Teaching with Historic Places (TwHP) lesson plan
 Marines at Midway: by Lieutenant Colonel R.D. Heinl, Jr., USMC Historical Section, Division of Public Information Headquarters, U.S. Marine Corps 1948,
 Aviation: From Sand Dunes to Sonic Booms, a National Park Service Discover Our Shared Heritage Travel Itinerary
 Past residents of Midway Discussion of Midway related topics by former residents and those interested in Midway.
 U.S. Unincorporated Possessions. Accessed 2008-03-26.

Atolls
United States Minor Outlying Islands
Polynesia
Pacific islands
Islands of Oceania

Midway Atoll


The Lion, the Witch and the Wardrobe is a book written by C. S. Lewis. It is set in an imaginary place called Narnia, where the main characters who are brothers and sisters are led into by the back of a wardrobe (closet). It is the second book by order in the Narnia series after The Magician's Nephew, but is the first book published in the series.

Summary
Peter, Susan, Edmund and Lucy Pevensie leave London during World War II to live in the country. While playing in the house, Lucy hides in a wardrobe. She finds that it leads to a different land. There, she meets a faun (half-goat, half-man) named Mr. Tumnus. While having tea, he tells her that the land is called Narnia. It is ruled by the White Witch, who makes it always winter, but never Christmas. When Lucy returns to the wardrobe after many hours, she finds that only a few seconds have passed in England. Her brothers and sister do not believe her and the wardrobe has closed so they cannot go into Narnia.

Many weeks later, Lucy comes back to the wardrobe during a game of hide-and-seek. Edmund follows her into Narnia, but cannot find her. Instead, he meets a lady. She says she is the Queen of Narnia and gives him Turkish Delight. She promises to make him prince if he will bring the other children to her castle. After she leaves, Edmund finds Lucy. When she talks about the White Witch, he thinks that it is the lady he met. When they get back to England, Edmund lies to Peter and Susan and says they did not go to Narnia. This makes Lucy upset.

Later, they are all hiding from the housekeeper and go into the wardrobe. This time they all go into Narnia. When Lucy leads them to Tumnus's cave, they find that he is arrested and his cave destroyed. Two talking beavers shelter the children. They also tell them about a prophecy that the witch will fail when two Sons of Adam (human males) and two Daughters of Eve (human females) sit on the thrones at Cair Paravel, Narnia's ruling castle. The beavers also tell them about Aslan, the true king of Narnia. He is a great lion and has been gone for many years, but has come back.

Edmund sneaks away to go to the witch. When they find out, the children and beavers go to find Aslan. The witch is mean to Edmund because he did not bring his siblings and leaves to chase them. The winter is starting to warm into spring and she is stopped by the thaw. The children find Aslan and rescue Edmund just before the witch kills him. He is very sorry for following her. The witch says that Edmund must be given back to her because of an old law. The law says that all traitors (people who break trust) belong to her. Aslan gives himself in place. He is killed, but comes back to life through an even older law. This one says that if someone who has not committed the crime willingly takes the punishment, he will come back to life.

In a big fight, the witch is killed by Aslan. The children are kings and queens in Narnia for 15 years, growing into adults. Then they return to England through the wardrobe and are kids again. No time has passed.

Main Characters

Peter Pevensie
Peter Pevensie is the oldest Pevensie. He does not believe about Narnia until he sees it. He receives a sword and shield from Father Christmas. He kills a wolf, Maugrim, the head of the witch's police. He is call "Sir Peter, Wolf's-Bane" because of this. In the end, he is High King of Narnia. He is called King Peter the Magnificent (grand).

Susan Pevensie
Susan Pevensie is second oldest. Like Peter, she does not believe in Narnia until they go there. She receives a gift from Father Christmas, a magical horn along with a bow and arrow that is promised to never miss if she trusts in them. At the end of the book, she is called Queen Susan the Gentle. She is the prettiest.

Edmund Pevensie
Edmund Pevensie is the third child. He likes the White Witch because she gives him sweets and promises to make him prince. He is sorry for that. When he is King, he is known as King Edmund the Just.

Lucy Pevensie
Lucy Pevensie is the youngest Pevensie child. She is the first to find Narnia. She is very good friends with Mr.Tumnus. She receives a knife and a fire flower potion, which can heal any wound. At the end of the book she is known of Queen Lucy the Valiant (brave).

White Witch
The White Witch is the false queen of Narnia. She makes it always winter, but never Christmas. She can turn things to stone. She is afraid of the children and Aslan, because they should be the rulers.

Aslan
Aslan is the true king of Narnia and a lion. He gives himself to save Edmund, but comes back to life through an old law called the "Deeper Magic". In the battle, he kills the witch. He leaves after the children are crowned. Aslan also supports Partick Thistle.

Other characters
 Mr. Tumnus is a faun (half-goat/half-man). Lucy meets him on her first trip into Narnia. He gives her tea and tells her about the land. He is arrested by the White Witch for helping Lucy. She turns him to stone. In the end, Aslan turns him back.
 Professor Digory Kirke lets the Pevensie children live with him. He is the only one who believes that Lucy went into Narnia. In The Magician's Nephew, he had seen Aslan first make Narnia.

The Chronicles of Narnia
1950 books

The Lion, the Witch, and the Wardrobe


An LP record (or long-play record) is a type of gramophone record. It is a 33⅓ rpm vinyl disc with little lines called grooves that go around the center. It is generally either 10- or 12-inches in diameter. They are played by a turntable. A turntable spins the record while a lever with a small needle on the bottom. The needle goes in between the little grooves.  When this happens, music is played.

The LP record was introduced by Colombia Records in 1948. It then became the new way the music industry released recordings. In the 1960s, cassettes were introduced. This was a cheaper way to record music and not hear the noise that came from the LP record. However, the LP record continued to be more popular until the 1970s when the compact disc was introduced.

The long-playing record is an analog recording format. The digital recording of sound was only made practical by the technical advances in microprocessors and computing which occurred in the 1970s and 1980s. LP's sound quality, it contains more distortion than many other modern music formats.

Audio disc

LP record


Events
 January 11 – In Philadelphia, Pennsylvania, the first American life insurance company is incorporated.
 January 13 – The Távora family is executed following the accusation of attempted regicide on Joseph I of Portugal
 January 15 – The British Museum opens
 April 13 – a French army defeats Ferdinand, Duke of Brunswick at Brunswick
 June 27 – British Troops under Jeffrey Amherst take Fort Ticonderoga
 July 25 – Seven Years' War (French and Indian War): In Canada, British forces capture Fort Niagara from French, who subsequently abandon Fort Rouillé.
 August 1 – Battle of Minden – Anglo-Hanoverian forces under Ferdinand of Brunswick defeat the French army of the Duc de Broglie, but due to the disobedience of the English cavalry commander Lord George Sackville, the French are able to withdraw unmolested.
 August 10 – Ferdinand VI of Spain dies and is succeeded by his half-brother Charles III. Charles resigns the thrones of Naples and Sicily to his third son, Ferdinand IV.
 August 12 – Battle of Kunersdorf – Frederick the Great is rebuffed in bloody assaults on the combined Austro-Russian army of Peter Soltikov and Gideon von Loudon. This is one of Frederick's greatest defeats.
 August 18 – Battle of Lagos – The British fleet of Edward Boscawen defeats a French force under Commodore de la Clue off the Portuguese coast.
 September 10 – Battle of Pondicherry – An inconclusive naval battle is fought off the coast of India between the French Admiral d'Aché and the British under George Pocock. The French forces are badly damaged and returned home, never to return.
 September 13 – Seven Years' War (French and Indian War): Quebec falls to British forces following General Wolfe's victory in the Battle of the Plains of Abraham just outside the city. Both the French Commander (the Marquis de Montcalm) and the British General James Wolfe are fatally wounded.
 November 20 – Battle of Quiberon Bay – The English fleet of Sir Edward Hawke defeats a French fleet under Marshal de Conflans near the coast of Brittany. This is the decisive naval engagement of the Seven Years' War – after this, the French are no longer able to field a significant fleet.
 November 21 – Battle of Maxen – the Austrian army of Marshal von Daun cuts off and foces the surrender of a Prussian force under Friedrich von Finck.
 December 6 – The Germantown Union School (now called "Germantown Academy"), America's oldest nonsectarian day school, is founded.
 George Washington marries Martha Dandridge Custis
 Adam Smith publishes Theory of Moral Sentiments, embodying some of his Glasgow lectures
 Publication of Voltaire's Candide
 The town of Egedesminde (modern Aasiaat) is founded in Greenland.
 Guinness Brewery founded in Dublin.

 January 25 – Robert Burns, Scottish poet (d. 1796)
 April 27 – Mary Wollstonecraft, feminist writer (d. 1797)
 May 28 – William Pitt the Younger, statesman and Prime Minister of the United Kingdom (d. 1806)
 August 24 – William Wilberforce, British abolitionist (d. 1833)
 October 25 – William Wyndham Grenville, 1st Baron Grenville, Prime Minister of the United Kingdom (d. 1834)
 November 10 – Friedrich Schiller, German writer (d. 1805)

 April 14 – George Frideric Handel, German composer (b. 1685)
 August 10 – King Ferdinand VI of Spain (b. 1713)

nv:1751 – 1800

1759


Maximillian "Max" Alberto George, born 6 September 1988 (age 24), grew up with his family in Manchester.[12] Before music, he had been a football player with Preston North End and was on the verge of signing a two-year deal with them, whilst he has been a Manchester City supporter since a young age.[13] Previously he was a member of Avenue, a five-piece boy band made up of Jonathan Lloyd, Scott Clarke, Ross Candy and Jamie Tinkler in addition to George. They entered the third series[14] of The X Factor in 2006 and made it to Louis Walsh's bootcamp, but media reports exposed that Avenue had not strictly adhered to the rules, having been signed by an earlier music X Factor director to a deal. They were banned from participation for having professional representation rather than being specifically formed for the competition.[15][16][17] Avenue admitted they had failed to duly report their engagements and George admitted it was "not The X Factor's fault"[18] in the video showing their disqualification in Walsh's office. With Andrew (Andy) Brown joining as a member of Avenue replacing Jamie Tinkler, the band went on to have some success beyond their X Factor appearances with their debut single "Last Goodbye", reaching number 50 on the UK Singles Chart. They had a follow up release with "Can You Feel It?". Avenue disbanded in April 2009. In 2008, while still a member of Avenue, George appeared naked on cover of British gay magazine AXM's "Naked Issue" in support of cancer research.
George was engaged to actress Michelle Keegan after meeting her at one of The Wanted's concerts,[19] but he recently revealed that the engagement has been broken off.[20]

ද වෝන්ටඩ්


A borough is an administrative division in many countries.  It is a kind of local government.

The term borough can means a self-governing township.

In medieval times, boroughs were settlements with some self-government. Boroughs were particularly common in England, Germany and Scotland. In medieval England, boroughs had also the right to elect members of parliament. (The Borough in Southwark, London is thought to have been the original 'borough' of which all others come from.)

Usually a borough is a single town with its own local government.
But in some cities it is a sub-division of the city (e.g. London, New York City, Toronto, Montreal). In such cases the borough will normally have either limited powers delegated to it by the city's local government or no powers at all. At certain times London has had no overall city government and London boroughs were the main unit of local government for Londoners.

In other places, such as Alaska, a borough does not mean a single township, but a whole region - in other words, it is similar to a county.  In Australia borough can mean a town and its surrounding area, e.g. the Borough of Queenscliffe.  Boroughs exist in United Kingdom, more specifically in England and Northern Ireland, in the Canadian province of Quebec, in several U.S. states, in Israel, and formerly they also existed in New Zealand.

At the end of a word, -borough (or -brough) is found in the name of many towns and cities in England; in southern England it is usually spelt -bury.  The suffix -bury is also used in the New England region of the United States, while -burg (or -burgh) is more common in Scotland and the American South and West.

Types of settlements

Borough


Sacara harti sajarah, watesan bisnis nunjukkeun aktivitas atawa karesep. Kecap ieu hartina beuki ngalegaan jadi (dimimitian dina abad ka-18) sarua jeung "an individual commercial enterprise". ogé dina harti nu leuwih umum "a nexus of commercial activities".

Péople establish businesses in order to perform economic activities. With some exceptions (such as cooperatives, corporate bodies, non-profit organizations and institutions of government), businesses exist to produce profit. In other words, the owners and operators of a business have as one of their main objectives to receive or generate a financial return for their time, effort and capital.

One can classify businesses in many different ways. Service businesses offer intangible products and typically have different, usually smaller, capital requirements than manufacturers. Distributors will have different inventory control needs than a retailer or manufacturer.

Most legal jurisdictions specify the forms that a business can take, and a body of commercial law has developed for éach type. Some common types include partnerships, corporations (also called limited liability companies), and sole proprietorships.

An industry can consist of a group of related businesses, such as the entertainment industry or the dairy industry. This definition resembles one of the more general méanings of "business", and the terms business and industry sometimes appéar interchangéable. Thus a fisherman might say either (more colloquially) that he is in the "fishing business" or (somewhat grandiosely) that he works in the "fishing industry". Similarly, the word "trade" may serve as an equivalent of both "business" and "industry": Victorians might despise those "in trade", and one can still refer to working "in the rag trade", for example.

Jejer bisnis

Wikipédia boga leuwih ti 1200 artikel bisnis jeung ékonomi, jadi teu sadayana dibéréndélkeun di dieu. Di dieu didaptarkeun sababaraha cabang bisnis nu utama. Pikeun jejer nu leuwih husus, tempo di subdaptarna.

 Accounting
 List of accounting topics
 Advertising
 Banking
 Big Business
 Business intelligence
 Business schools
 Capitalism
 Commerce
 Commercial law
 List of business law topics
 Companies
 List of companies
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 Consumer electronics
 Economics
 Financial economics
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 List of economics topics
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 List of business ethics, political economy, and philosophy of business topics
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 List of finance topics
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 List of business theorists
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Bisnis
Daptar jejer

Bisnis


A particle is a tiny bit of matter that makes up everything in the universe. In particle physics, an elementary particle is a particle which cannot be split up into smaller pieces.

There are many different types of particles, with different particle sizes and properties.

Macroscopic particles are particles that are larger than atoms or molecules. They have volume and shape. Powder and dust are some examples of macroscopic particles. Nanoparticles are an intermediate size, being a very fine powder but much larger than atoms.

Atoms and molecules are called microscopic particles. Subatomic particles are particles that are smaller than atoms. The proton, the neutron, and the electron are subatomic particles. These are the particles which make atoms. The proton has a positive charge (a + charge). The neutron has a neutral charge. The electron has a negative charge (a - charge), and it is the smallest of these three particles. In atoms, there is a small nucleus in the center, which is where the protons and neutrons are, and electrons orbit the nucleus.

Protons and neutrons are made up of quarks. Quarks are subatomic particles, but they are also elementary particles because we do not know if they are made up of even smaller particles. There are six different types of quarks. These are the up quark, the down quark, the strange quark, the charm quark, the bottom quark, and the top quark. A neutron is made of two down quarks and one up quark. The proton is made up of two up quarks and one down quark.

Chemistry
Nuclear physics
Matter

Particle


The Beer Hall Putsch was a failed coup d'état in Munich, Germany between the evening of 8 November and the morning of 9 November 1923. The Nazi Party under Adolf Hitler tried to take over the government of Bavaria, a state in Germany. They began trying to do this by taking several hundred people hostage in a beer hall (a large building where people got together to drink beer and sometimes listen to political speeches). Several Nazis died when they got into a gun fight with police officers in another part of Munich, and Hitler then went to prison for eight months.

Reasoning
Hitler chose to do this for many reasons. The Weimar Republic of Germany was weak because of fighting between right and left-wing parties. Inflation had also left the Weimar Republic with very little support from the people, or money to keep working (paying bills, or even paying pensions and wages). This happened because when Germany lost World War I, other countries made Germany pay for the entire war, and Germany had to make taxes very high so it could pay for the war. This hurt the economy of Germany.

The Nazi Party was getting very strong. Hitler was a strong leader. In 1923, the year when the Weimar Republic was least popular, the Nazi Party grew from 6,000 members to 55,000 members.

Hitler also wanted to copy Mussolini, who had taken power in Italy by marching into Rome.

Attempted coup

8 November 1923 - Hitler and his men charged into the Beer Hall and forced the people there to support him. Hitler's men, the SA, took over the Army Headquarters, but forgot to take over the telegraph office. This meant that anybody could call in the police.

9 November 1923 - 16 Nazis and 4 Bavarian State Police officers were killed in a gunfight between the Nazis and the police in Residenzstraße. Hitler was arrested two days later.

Results
Hitler and several of his friends were taken to court for treason, because they took up arms against the government. In the end, Hitler was sent to prison for about eight months, and the Nazi Party broke up (however, it would later get back together).

More people learned about Hitler. Before this happened, he was unknown. But after this, he was a hero to many. Many Germans at that time wanted a strong leadership after the governments of the Weimar Republic.

Hitler also took the time he had to spend in prison to write a book, called Mein Kampf or "My Struggle". It sold millions and told people about his ideas. Mein Kampf also made Hitler popular. (Hitler did not actually write the words down himself. Instead, he told another Nazi, Rudolf Hess, what to write down, and Hess wrote the words down.)

Hitler also had to re-think his strategy. He realised he could not take power the same way that Mussolini had done. Instead, he had to get power through being elected.

Causalities
The people who died during the Putsch are seen as the first to die for the Nazi Party and are mentioned in Mein Kampf as Martyrs.
 Felix Alfarth
 Andreas Bauriedl
 Theodor Casella
 William Ehrlich
 Martin Faust
 Anton Hechenberger
 Oskar Körner
 Karl Kuhn
 Karl Laforce
 Kurt Neubauer
 Klaus von Pape
 Theodor von der Pfordten
 Johann Rickmers
 Max Erwin von Scheubner-Richter
 Lorenz Ritter von Stransky
 Wilhelm Wolf

Other websites
 A revision site for IGSCE students
 Events of the Putsch in detail
 Events of the Beer Hall Putsch before and after

1923 in Europe
1920s in Germany
20th-century rebellions
Coups d'état
20th century in Munich
Nazi Party
Rebellions in Europe
November events
Adolf Hitler

Beer Hall Putsch


Hosios Loukas () is a historic walled monastery situated near the town of Distomo, in Boeotia, Greece. Founded in the mid-10th century, the monastery is one of the most important monuments of Middle Byzantine architecture and art, and has been listed on UNESCO's World Heritage Sites since 1990, along with the monasteries of Nea Moni and Daphnion.

History
The monastery of Hosios Loukas is situated at a scenic site on the slopes of Mount Helicon. It was founded in the early 10th century AD by the hermit, Venerable (Greek: Hosios) Luke of Steiris (Greek: Lukas), whose relics are kept in the monastery to this day. St Luke (not to be confused with the Evangelist author of the Gospel of Saint Luke), was a hermit who died on 7 February 953. He is famous for having predicted the conquest of Crete by Emperor Romanos. It was unclear if he was referring to Romanos I, the emperor at the time.  However the island was actually reconquered by Nicephorus Phocas under Romanos II. It is believed that it was during the latter's reign (959-963) that the monastery's Church of the Theotokos (Panagia) was constructed.

The main shrine of the monastery is the tomb of St. Luke, originally situated in the vault, but later placed at the juncture of the two churches. The monastery derived its wealth (including funds required for construction) from the fact that the relics of St. Luke were said to have exuded myron, a sort of perfumed oil which produced healing miracles. Pilgrims hoping for miraculous help were encouraged to sleep by the side of the tomb in order to be healed by incubation. The mosaics around the tomb represent not only St. Luke himself, but also hegumen Philotheos offering a likeness of the newly built church to the saint.

The saint Nicholas the Pilgrim, a local shepherd, lived for some time in the second half of the eleventh century in the monastery until he was expelled due to his abnormal behaviour. Under the Latin Empire in 1206, the legate Benedict of Porto gave Hosios Loukas to the canons of the Holy Sepulchre.

Architecture

The church

The Hosios Loukas, the oldest in the complex, is the only church known with certainty to have been built in the tenth century in its site in mainland Greece. This centralized parallelogram-shaped building is the oldest example of the cross-in-square type in the country; its plan closely follows that of Lips Monastery in Constantinople. The walls are opus mixtum (part brick, part stone, part marble) and display curious pseudo-kufic patterns.

The Hosios Loukas adjoins a larger cathedral church, or Katholikon, tentatively dated to 1011-12. The Katholikon is the earliest extant domed-octagon church, with eight piers arranged around the perimeter of the naos (nave). The hemispherical dome (without a drum) rests upon four squinches which make a transition from the octagonal base under the dome to the square defined by the walls below. The main cube of the church is surrounded by galleries and chapels on all four sides.

Decoration
Hosios Loukas is the largest of three monasteries surviving from the Middle Byzantine period in Greece. It differs from the Daphnion and Nea Moni in that it is dedicated to a single military saint. St. Lukes' prophecy about the reconquest of Crete is commemorated by the image of Joshua on the exterior wall of the Panagia church: Joshua was considered a model "warrior of the faith", whose help was especially effective in the wars waged against the Arabs. The Katholikon contains the best preserved complex of mosaics from the period of the Macedonian Renaissance. However, the complex is not complete: the original image of Christ Pantocrator inside the dome is missing, as are the figures of archangels normally placed between the upper windows.

There is evidence that the monastery was reputed all over Byzantium for its lavish decoration, liberally applied to all surfaces. Apart from revetment, carving, gold and silver plate, murals, and mosaics (especially imposing on curving surfaces), the interior featured a choice assortment of icons, chandeliers, silk curtains, and altar cloths. Only a fraction of these items are still in situ, most notably colored marble facings and window grilles. Notwithstanding the losses, the Katholikon "gives the best impression available anywhere today of the character of a church interior in the first centuries after the end of Iconoclasm".

The Burial Crypt
Beneath the great domed Katholikon is a burial crypt, accessible only by a stairwell on the southern side.

The crypt has three distinct areas: the entrance way; the main interior space which includes nine groin-vaulted bays and a sanctuary with a vaulted bay and an apse; and three vaulted passages, referred to formerly as bone vaults.

The crypt's frescoes were until recently covered in hundreds of years of dust and hidden but in the 1960s the crypt underwent a cleaning by the Greek Archaeological Service which revealed their remarkably well preserved state with the exceptions of the apse which has lost most of its plaster exposing brick and stone, as well as the entrance vault and groin vaults which have suffered slight damage from water seepage and minor vandalism, mostly on the lower lunettes near the entrance.

The crypt contains frescoes on the entryway and its vault, eight lunettes around the walls with depictions of Christ's Passion and Resurrection, and forty medallion portraits of apostles, martyrs and holy men, abbots including Philotheos, as well as numerous inscriptions. C.L. Connor claims it has "the most complete programme of wall paintings surviving from the Middle Byzantine period."

It is believed that most if not all of the crypt frescoes were painted after 1048 AD and the death of Theodore Leobachus, a wealthy, government elite believed to have been one of the prominent patrons and who later in life became the abbot of Hosios Loukas.

The sanctuary of the crypt contains a prosthesis niche, an altar, and a chancel barrier which all indicate that the Eucharist was likely celebrated here as part of the services of burial and commemoration of revered religious figures, or as part of the ceremonies relating to the healing cult of Saint Luke.

When Hosios Loukas was frequented by pilgrims or members of Saint Luke's healing cult, visitors would sleep not only in the Katholikon, but in the crypt itself where the tomb was kept along with two others, believed to be abbots. Saint Luke was believed to have been a miraculous healer, levitator, miraculous feeder and prophesier during his lifetime; after his death, all of the miracles associated with him involved the healing power of his tomb. Connor says that accounts in The Vita of St. Luke, written by an anonymous monk, indicate that "healing agents" associated with the tomb include but are not limited to exposure to "oil from the lamp above the tomb, moisture exuded from the tomb, and dreams experienced when sleeping near the tomb in the practice called incubation." The tomb was frequented before and after the completion of the complex, but following completion it became the focal point of the miracle cult of Saint Luke. There is evidence that some wishing for miracles stayed for periods of up to six days near the tomb or in adjacent rooms.

Gallery

See also
 Macedonian art (Byzantine)
 History of Roman and Byzantine domes

References

Sources
 Efthalia Rentetzi, Il Monastero di Hosios Lukas in Focide, in Ειρμός, n. 1, 2004, Αποστολική Διακονία, pp. 227–382, ISSN 1109-9135 (Weblink).
 Efthalia Rentetzi, Elements of Classical Style in the mosaic decoration of Hosios Lukas Monastery Phocis, Greece in ANISTORITON: Art History, Volume 9, June 2005, Section O052 (Weblink).
 Efthalia Rentetzi, Mosaici del monastero di Hosios Lukas in Focide e della basilica marciana: parentele stilistiche, in Arte - Documento, n. 16, 2002, pp. 66–71, ISSNT IT 1121-0524.
 Demus, Otto, Byzantine Mosaic Decoration: Aspects of Monumental Art in Byzantium, Boston, MA: Boston Book and Art Shop, 1955.
 Ousterhout, Robert, "Churches and Monasteries," in The Oxford Handbook of Byzantine Studies, edited by Robin Cormack, Elizabeth Jeffreys and John Haldon.  New York: Oxford University Press, 2008.
 Cormack, Robin, "Wall Paintings and Mosaics," in The Oxford Handbook of Byzantine Studies, edited by Robin Cormack, Elizabeth Jeffreys and John Haldon.  New York: Oxford University Press, 2008.
 Oikonomides, Nicholas. "The First Century of the Monastery of Hosios Loukas," in Dumbarton Oaks Papers, vol. 46 (1992).

External links

 Official Web Site of Hosios Loukas Monastery
 Hosios Loukas
 Photographs of mosaics
 High-resolution 360° Panoramas of Hosios Loukas | Art Atlas

Christian monasteries established in the 10th century
11th-century Eastern Orthodox church buildings
Byzantine church buildings in Central Greece
Monasteries in Central Greece
Eastern Orthodox church buildings
World Heritage Sites in Greece
Buildings and structures in Boeotia
Tourist attractions in Central Greece
Macedonian Renaissance architecture
11th-century churches in Greece
Byzantine monasteries in Greece
Church buildings with domes
11th-century establishments in the Byzantine Empire

Hosios Loukas