Aarushhh/wikipedia-simple-splitted huggingface dataset:
Example: The function f((x,y)):ℝ²→ℝ defined by z=y is a surjection. Its graph is a plane in 3-dimensional space. The pre-image of  zo is the line y=zo in the x0y plane.

In 3D games, 3-dimensional space is projected onto a 2-dimensional screen with a surjection.

Related pages
Injective function
Bijective function

References

Other websites
  interactive quiz
  interactive

Functions and mappings
Algebra
In mathematics, the range is a concept which has various meanings in different topics:

 The range of a function , also written as  or , is the set of elements that the function outputs.
 In statistics, the range is the difference between the lowest and highest values. For example. in {4, 6, 9, 3, 7}, the lowest value is 3, and the highest is 9, so the range is 9-3 = 6. 
 In some occasions, the term "range" can also refer to the mathematical concept of interval.

Related pages 
 Surjective function

References 

Functions and mappings
Mathematics
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis, organic reactions build new organic molecules. Organic reactions produce many man-made chemicals such as drugs, plastics, food additives, and fabrics.

More websites
Organic reactions @ Synarchive.com 
Organic reaction flashcards from OSU 
list of named reactions from UConn 
organic reactions 
Organic chemistry help-Best of the Web 2008 
Organic chemistry help-Electronic Flashcards
Study-Organic-Chemistry.com
organic-reaction.com

References
Shikasta is a 1979 science fiction novel. The full title is Re: Colonised Planet 5, Shikasta. British Nobel Prize in Literature-winner Doris Lessing wrote it as the first book in her five-book Canopus in Argos series. Alfred A. Knopf published it first in the United States in October 1979. Jonathan Cape published the book in the United Kingdom in November 1979. Shikasta is also the name of the fictional planet featured in the novel.
The book has a subtitle, "Personal, psychological, historical documents relating to visit by Johor (George Sherban) Emissary (Grade 9) 87th of the Period of the Last Days". 'The novel is the history of the planet Shikasta under the influence of three galactic empires: Canopus, Sirius, and their shared enemy, Puttiora. The book is a series of reports by Canopean visitors to Shikasta. They record what happens on the planet which is very similar to Earth. The novel shows the Earth's prehistory, how things became worse, the "Century of Destruction" (the 20th-century), and the Apocalypse (World War III).
Shikasta uses stories and images from the Old Testament and is influenced by spiritual and mystical themes in Sufism. Lessing had become interested in this Islamic belief system in the mid-1960s. The book was a major shift of focus in Lessing's writing, from realism to science fiction. Many of her readers were unhappy with the change. Critics gave the book both good and bad reviews. Some were impressed by the way the book showed a wide view of humanity and the universe. One reviewer called it a brave "and disturbing work from one of the world's great living writers". Others reviewers disliked the novel because it was depressing and humanity had no free will. People's lives were controlled by galactic empires.
The story of Shikasta is retold in the third book of the Canopus series, The Sirian Experiments (1980). In that book, the story is told from the point of view of Sirius. Shikasta appears again in the fourth book in the series, The Making of the Representative for Planet 8 (1982). The Zones that are briefly mentioned in Shikasta are the subject of the second book in the series, The Marriages Between Zones Three, Four and Five (1980).

References

Science fiction books
1979 books
Each molecular orbital has a calculated energy level. Chemists sort the molecular orbitals (MOs) by energy levels. Chemists assume that the electrons will occupy the lowest energy level MOs first. For example, if a molecule has enough electrons to fill 15 MOs, the 15 MOs with the lowest energy levels will be occupied. The 15th MO on the list would be called the "highest occupied molecular orbital" (HOMO) and the 16th MO on the list would be the "lowest unoccupied molecular orbital" (LUMO). The difference in the HOMO's energy level and the LUMO's energy level is called the band gap. The band gap can sometimes serve as a measure of the excitability of the molecule: the smaller the energy, the more easily a molecule's electrons will be excited. For example, this can help predict whether a substance will have luminescence.

SOMO
A SOMO is a singly occupied molecular orbital such as half-filled HOMO of a radical.

Related pages
 Diels–Alder reaction
 Electron configuration
 Ligand
 Organic semiconductor
References

Physical chemistry
Roald Hoffmann (born July 18, 1937) is a Polish-born American theoretical chemist of Jewish descent. He won the 1981 Nobel Prize in Chemistry. He currently teaches at Cornell University in Ithaca, New York.

He was born in Zloczov, Poland (now Ukraine)

Hoffmann survived The Holocaust and moved to the United States in 1949.

References 

1937 births
Living people
American chemists
American Nobel Prize winners
Columbia University alumni
Harvard University alumni
Holocaust survivors
Cornell University faculty
Jewish American scientists
Jewish Nobel Prize winners
Naturalized citizens of the United States
Polish Jews
Polish Nobel Prize winners
Ukrainian Jews
Ukrainian Nobel Prize winners
In organic chemistry and biochemistry, substituent is the name for a single atom or for a group of atoms that take the position of another atom in a molecule. They replace this atom. This reaction is called a substitution reaction. The atom or group of atoms that gets replaced is called the leaving group.
 
The terms substituent, side chain, group, branch, or pendant group are used in the same way to describe branches from a parent structure. These terms have different meanings in polymer chemistry.  In polymers, side chains extend from a backbone structure, while they are attached to the alpha carbon atoms of the amino acid backbone in proteins.
Organic chemistry has rules for naming compounds with substituent groups. The substituent group is listed first with a suffix to describe how it is attached to the main carbon chain. The suffix -yl is used when naming organic compounds that contain a single bond replacing one hydrogen. -ylidene and -ylidyne are used for double bonds and triple bonds respectively. When naming hydrocarbons that contain a substituent, position numbers may be used. These number will indicate which carbon atom the substituent is attached to. One case where this information is needed is that of isomers.

The phrases most-substituted and least-substituted are often used to describe molecules and predict their products. For example:

  Markovnikov's rule predicts that the hydrogen adds to the carbon of the alkene functional group that has the greater number of hydrogen substituents.
  Zaitsev's rule predicts that the major reaction product is the alkene with the more highly substituted (more stable) double bond.
Structures 
In a structural diagram or formula, the letters R or X are used to represent a substituent group. An organic substituent such as methyl, ethyl, aryl can be written as R (or R1, R2, etc.)  This is a generic placeholder. The R derived from radical or rest. The R can represent as many atoms as the author wants. The first to use this symbol was Charles Frédéric Gerhardt in 1844.

The symbol X can represent electronegative substituents such as the halides.

Related pages 
Side chain
 Functional groups are a subset of substituents

References

Organic chemistry
Chemical nomenclature
The greater rhea, Rhea americana, is a flightless bird found in South America. The greater rhea is also known as grey, common rhea, or the American rhea. The species, first described by Carl Linnaeus in 1758, is found in Argentina, Bolivia, Brazil, Paraguay, and Uruguay.

The greater rhea takes its scientific name from the Greek goddess Rhea and the Latin word for "America".

It has a length of  and a wingspan of . Weighing , the greater rhea is the largest bird in South America.

References

Birds of South America
Ratites
Struthioniformes

ja:レア (鳥類)#アメリカ・レア
Petr Kalandra (March 10, 1950 – September 7, 1995) was a Czech musician, guitarist, harmonica player, vocalist and songwriter. He was member of A.S.P.M., Blues Session and Marsyas. He died in September 1995. In 2006 he was inducted into the Beatová síň slávy (Beat Hall of Fame).

References 

Blues musicians
1995 deaths
1950 births
Czech guitarists
Till Eulenspiegel's Merry Pranks (German: Till Eulenspiegels lustige Streiche) is a very well-known piece of music for orchestra by Richard Strauss.  It is a tone poem (a piece of music which tells some kind of story).  In this work, Richard Strauss describes the adventures of Till Eulenspiegel who was the character in a series of stories written in Germany many years ago.  Till Eulenspiegel was a kind of folk hero.  He was a naughty boy who got up to all kinds of tricks.  The music is very humorous and describes his adventures.

The music is played by a large orchestra.  There is a small clarinet (normally an E flat clarinet, although in Strauss's day he used a D clarinet) that describes the character of Till.  Till is also represented by a French horn.
The music
The music starts with the main theme, which is like saying: 'Once upon a time'.  The horn plays one of Till's themes and this is taken up by the orchestra.  The small clarinet is then heard, sounding like Till laughing.  He rides his horse through the market and knocks lots of things off the stalls, then flirts with the girls (the first violin plays a theme which suggests love).

Till gets on his horse again.  Then suddenly there is a funeral march.  Till has been caught and he is sentenced to death.  Till pleads to be let free and tries to joke his way out of his troubles, but the executioner takes no notice.  Till is taken to the gallows (small clarinet), the flutes rattle as he reaches the top.  The small clarinet describes his death scream, and then he is executed (strings playing pizzicato.  There is a short silence, then the music returns to the opening 'Once upon a Time' theme, but the music finishes with a little joke, as if saying that someone like Till can never be destroyed.
Compositions by Richard Strauss
Orchestral works
Beatová síň slávy (Beat Hall of Fame or shortly BSS) is something like the Rock and Roll Hall of Fame. Czech Radio Beat honors the greatest legends of Czech rock music.

Categories 
 Musician
 Dead Musician
 Band

Induction

Multiple inductees

References

Other websites 
 Beatová síň slávy 

Czech music
Music awards
The extranet is a part of intranet that selected people outside the company can use.

Related pages
 Internet
 Intranet

Internet
The Thomson's gazelle (Gazella thomsonii) is the most common gazelle in East Africa. It is a kind of small antelope. It is named after explorer Joseph Thomson and, as a result, is sometimes referred to as a "tommie". They can be found on ranches and farmland throughout East Africa, and survive long after other species have been killed off or migrated away.

Description 
Thomson's gazelles are commonly referred to as "tommies". Tommies stand at about half a meter (22-26 inches) tall and weigh in between 15 and 25 kilograms (35-55 pounds). Although very similar in appearance to the Grant's gazelle, they have some distinguishing features.

Predators 
The tommy has adapted to drier life on the open grass plains of East Africa, mainly southern Kenya and northern Tanzania. Although tommies have many predators, including cheetahs, lions, leopards, crocodiles and hyenas, they are frequently the last animals left on an abandoned ranch or farmland.
Their major predators are cheetahs, which can run faster, but gazelles can outlast them in long chases and are able to make turns more speedily. This small antelope-gazelle can run extremely fast, from , to 96 km/h (60 mph) and zigzag, a peculiarity which often saves it from predators. 

Sometimes they are also chased by leopards, lions and hyenas, but the gazelles are faster and more agile; these predators attack especially the young or infirm individuals. They can also be devoured by crocodiles and pythons, and their fawns are sometimes the prey of eagles, jackals, and baboons. A noticeable behaviour of Thomson's gazelles is their bounding leap, known as stotting or pronking, used to startle predators and display strength.

References

Mammals of Africa
Bovids
Matthew MacKenzie Robinson (July 18, 1914 – March 12, 2000) was an American track athlete. He was the older brother of professional baseball player Jackie Robinson.  Robinson was born in Cairo, Georgia.  He moved to Pasadena, California when he was young and lived there most of his life.  He ran track in high school and college.  While at Pasadena City College, he set junior college records in several events.   He won a silver medal at the 1936 Summer Olympics.  He came in second to Jesse Owens in the 200m.  Robinson later ran for the University of Oregon.  While there, he won National Collegiate Athletic Association and Amateur Athletic Union titles.  He is a member of the Oregon Sports Hall of Fame.  Robinson spent his later years working for the city of Pasadena as a garbage collector and mailman.  He tried to stop crime in the black neighborhoods of Pasadena.  Robinson died in Pasadena in 2000.  Several landmarks in Pasadena honor both Jackie and Mack Robinson, including the stadium at PCC.

References
References

1914 births
2000 deaths
African-American track and field athletes
Sportspeople from Georgia (U.S. state)
Sportspeople from California
People from Cairo, Georgia
In organic chemistry, a diene ( ) or diolefin ( ) is a hydrocarbon that contains two carbon pi bonds. 
Conjugated dienes are functional groups, with a general formula of CnH2n-2. Dienes and alkynes are functional isomers. Dienes occur occasionally in nature but are widely used in the polymer industry.

Classes

Dienes can be divided into three classes, depending on the relative location of the double bonds: 
Cumulated dienes have the double bonds sharing a common atom as in a group of compounds called allenes.
Conjugated dienes have conjugated double bonds separated by one single bond.
Unconjugated dienes have the double bonds separated by two or more single bonds. They are usually less stable than isomeric conjugated dienes. 

Compounds that contain more than two double bonds are called polyenes. Polyenes and dienes, share many of their properties.
Cycloadditions
An important reaction for conjugated dienes is the Diels–Alder reaction.  Many specialized dienes have been developed to exploit this reactivity for the synthesis of natural products, e.g. Danishefsky’s diene.

Other websites
IUPACs Gold Book definition of dienes dienes PDF 

Hydrocarbons
In chemistry, a conjugated system is a system of continuous and parallel p-orbitals with delocalized electrons. Conjugated systems are created by several multiple bonds, each separated by single bonds. In general, conjugated systems may lower the overall energy of the molecule and increase how steady it is. They can contain lone pairs, radicals or carbonium ions. The compound may be cyclic, acyclic, linear or mixed. In most cases, the atoms in a molecule are held together by single bonds (where orbitals from adjacent atoms overlap).  Molecules which have a conjugated system have unique properties different from normal compounds created by the sharing of the delocalized electrons among many atoms.

Conjugation is the overlap of one p-orbital with another across a sigma bond (or single bond) that is in between. (The d-orbitals of larger atoms can also contribute to a conjugated system).
A conjugated system has a region of overlapping p-orbitals, bridging the single bonds that are between. They allow a delocalization of pi electrons across all the adjacent aligned p-orbitals.
The pi electrons do not belong to a single bond or atom, but rather to a group of atoms.

The largest conjugated systems (with the greatest number of shared electrons) are in graphite, conductive polymers, and carbon nanotubes.

Mechanism
Mechanism

Different types of molecular structures can result in conjugation. For conjugation, all the neighboring atoms in a chain must have an available p-orbital. In many cases, conjugated systems are a series of a single bonds each followed by a double bond. Other systems exist. For example, furan (see picture) is a five-membered ring with two alternating double bonds and an oxygen in position 1. The Oxygen in furan has two lone pairs, one of which fills a p-orbital on that position. The lone pair electron makes conjugation possible on a five-membered ring. The presence of a nitrogen in the ring can be a source of pi orbitals needed for conjugation. Also, pi orbitals needed for conjugation can come from substituent groups α to the ring like: a carbonyl group (C=O), an imine group (C=N), a vinyl group (C=C), or an anion.
Chromophores
Conjugated systems are the main things that make up chromophores. Chromophores are light-absorbing parts of a molecule that can cause a compound to have a visible color. Chromophores are often present in various organic compounds and sometimes present in polymers that are colored or glow in the dark. Chromophores often consist of a series of conjugated bonds and/or ring systems, which can include C-C, C=C, C=O, or N=N bonds. Many times, chromophores have aromatic rings.

Common examples
Diene
Vitamin D
Vitamin A
Benzene
Conjugated linoleic acid

Related pages
Resonance (chemistry)
Hyperconjugation
Cross-conjugation
Polyene

References

Organic chemistry
Prince Semien Fielder (born May 9, 1984 in Ontario, California) is an American former Major League Baseball player. He currently plays for the Texas Rangers. He debuted in the MLB for the Milwaukee Brewers on June 13, 2005 when he was called up from the minor league Nashville Sounds. He was sent back down but was called up again on August 17, 2005 where he finished the season with the Brewers and was used as a pinch-hitter. Fielder is a 3-time All Star and is also one of 26 players in the 50 home run club.

Other websites 

 Prince Fielder's MLB player profile

1984 births
Living people
Sportspeople from Los Angeles
National League All-Stars
Texas Rangers players
American League All-Stars
People from Ontario, California
Kurt Alder (July 10, 1902 – June 20, 1958) was a German chemist and Nobel laureate.

Biography
Alder was born in the industrial area of Königshütte, Silesia (modern day Chorzów, Upper Silesia, Poland). He received his early schooling there. Alder left the area for political reasons when Königshütte became part of Poland in 1922. He studied chemistry at the University of Berlin from 1922, and later at the University of Kiel where his earned a PhD in 1926 for work supervised by Diels.
In 1930 Alder was appointed reader for chemistry at Kiel, and promoted to lecturer in 1934. In 1936 he left Kiel to join I G Farben Industrie at Leverkusen, where he worked on synthetic rubber. In 1940, he was appointed Professor of Experimental Chemistry and Chemical Technology at the  University of Cologne and Director of the Institute of Chemistry there. Throughout this time and despite the many obstacles to original research in Europe at the time, he continued a systematic program of investigations of his particular interests in the synthesis of organic compounds. In all he published more than 151 papers in this field.   

Alder received several honorary degrees and other awards, most famously the 1950 Nobel Prize in Chemistry which he shared with his teacher Diels for their work on what is now known as the Diels–Alder reaction. The lunar crater Alder is named in his honour. The insecticide aldrin, created through a Diels–Alder reaction, is also named for him.

References
References

Other websites
Nobel Prize biography 

1902 births
1958 deaths
German academics
German chemists
German Nobel Prize winners
People from former German territories
Kenichi Fukui (October 4, 1918–January 9, 1998) was a Japanese chemist. He won the 1981 Nobel Prize in Chemistry.

Early life
Fukui was the oldest of three sons of Ryokichi Fukui, who was a merchant. He was born in Nara, Japan. 

He graduated from Kyoto Imperial University in 1941.

Career
Fukui worked at the Army Fuel Laboratory of Japan during World War II.{  

In 1943, he was appointed a lecturer in fuel chemistry at Kyoto Imperial University. 

He was professor of physical chemistry at Kyoto University from 1951 to 1982.

He was president of the Kyoto Institute of Technology between 1982 and 1988.
Fukui shared the 1981 Nobel Prize with Roald Hoffmann.  Fukui and Hoffmann worked separately on the mechanisms of chemical reactions.  Fukui explained in his Nobel lecture that, 
"It is only after the remarkable appearance of the brilliant work by Woodward and Hoffmann that I have become fully aware that not only the density distribution but also the nodal property of the particular orbitals have significance in such a wide variety of chemical reactions."

Honors
 Japan Academy Medal, 1962 
 Nobel Prize in Chemistry, 1981 
 Order of Culture, 1981 
 Order of the Rising Sun, Grand Cordon, 1988 
 Royal Society (UK), foreign member, 1989

Related pages 
 List of Nobel Prize winners by country

References

1918 births
1998 deaths
Japanese chemists
Foreign Members of the Royal Society
People from Nara Prefecture
Japanese Nobel Prize winners
Kyoto University alumni
Kyoto University faculty
Woodward's rules are a set of rules about how organic chemical compounds absorb ultraviolet light.

They give information about the wavelength of the absorption maximum (symbol λmax ) in an ultraviolet-visible (UV) spectrum of a compound.  The rules are named after Robert Burns Woodward. He was a Harvard University professor who won the 1965 Nobel Prize in chemistry. The rules are sometimes called the Woodward-Fieser rules, to also honor Louis Fieser. 

The rules build the prediction on the type of chromophores present, the substituents on the chromophores, and changes due to the solvent. Examples are conjugated carbonyl compounds, conjugated dienes, and polyenes.

Implementation
One set of Woodward-Fieser rules for dienes is shown in table one. A diene is either homoannular with both double bonds contained in one ring or heteroannular with two double bonds distributed between two rings.

These rules predict the UV absorption maximum of compounds. Here are two examples:
In the compound on the left the base value is 214 nm (a heteroannular diene). This diene group has 4 alkyl substituents (labeled 1,2,3,4) and the double bond in one ring is exocyclic to the other (adding 5 nm for an exocyclic double bond). In the compound on the right, the diene is homoannular with 4 alkyl substituents. Both double bonds in the central B ring are exocyclic with respect to rings A and C.

References

Organic chemistry
Description
The Lemon shark gets its name from the fact that it is yellow in colour. The underside is usually white or a lighter yellowish colour. Besides yellow, the Lemon shark is also brown and olive grey in colour. The Lemon shark is stocky, blunt-nosed, and has two dorsal fins of similar size and shape. The first dorsal fin is low and positioned at the back of the pectoral fins, and the second dorsal is of similar shape and size and positioned at the front of the anal fin. The pelvic fin weakly concave (curving inwards) rear margins, and the pectoral fin's outer margin is slightly convex (curving outwards), and both fins are weakly falcate. The snout is round and shorter than the width of the mouth. There is no mid-dorsal ridge present on this species.
The upper teeth are narrow and broad with triangular smooth-edged cusps and finely serrated bases. These teeth get more oblique as they get closer to the corner of the mouth. The lower teeth are narrow and triangular with smooth-edged cusps.
Lemon shark scales are large and overlapping with 3 to 5 ridges. The middle ridge is high, sharp and separated by deep furrows, and the back margins are opposite the primary ridges. The basal plates and pedicels are broad. 
Lemon sharks usually range between the lengths of , and have a growth rate of 0.21 inches per year (0.54 cm per year). The maximum length that can be reached by this species is between . Pups are between 24-26 inches (60-65 cm) at birth.
Reproduction
The Lemon shark is viviparous, meaning that they give live birth. After a gestation period of 10 to 12 months, pregnant females enter shallow nursery areas in spring and summer to give birth to litters of 4 to 17 pups. The pups have a very slow growth rate and remain within nursery grounds for quite a long time, where they are in less danger from predators. The mangroves that the young mainly inhabit are highly productive waters, creating an excellent area for feeding, but also an area of very low oxygen content. However, the Lemon shark has many adaptations that increase oxygen uptake, such as blood with an unusually high affinity for oxygen. As they grow, their range increases dramatically, from  up to around . Maturity is reached at about 6 and a half years of age, and it is believed that the Lemon shark lives for up to 27 years.
Behaviour
When it comes to hunting, the Lemon shark is known to be very patient. They are able to use their yellow coloring to help them successfully hide in their natural habitat. They are often found swimming along the sand of the bottom of the water so they blend in easily. This makes it easy to hide from predators and also to be able to find prey.
It is believed that this shark has a special set up with the retina. This enables them to be able to see very clearly even in the murky depths under the water. The Lemon Shark can be aggressive to humans, and is known to have a powerful bite. Most of the attacks that have been noted were provoked, but not all. Since Lemon sharks can blend into their surroundings so well, it is easy for someone to accidentally disrupt the shark.
What is encouraging about the Lemon Shark is that they are able to do fairly well in captivity. That is not usually the case with species of sharks. Still, many experts worry that they won’t copy all they do in the wild in captivity so they don’t usually rely on such details and observations as facts if they can’t also be confirmed in the wild. They are very social, and they develop a hierarchy based on gender and size that is very complex.
The Lemon Shark is gentle in nature and doesn’t seem to be aggressive towards people, including divers. They have been known to bite humans but it is believed this is due to being provoked. They aren’t seen as a major threat to sharing the waters with humans.
Feeding
The Lemon shark's diet consists mainly of bony fish and crustaceans. Catfish, mullet, jacks, croakers, porcupine fish, cowfish, guitarfish, stingrays, eagle rays, crabs and crayfish make up most of the Lemon shark's diet. Also, this species will eat sea birds and smaller sharks. Lemon sharks will eat until full with the rate of digestion dependent on the amount of food consumed at a single time.

Habitat
The Lemon shark lives in the tropical and subtropical waters of the coastal areas of the Atlantic and Pacific Oceans. They stay in moderately shallow water, normally going no deeper than 80 meters (roughly 260 feet). They are often found in shallow waters near coasts and islands, by coral reefs, mangroves, bays, and sometimes even river mouths.
Human interaction
These sharks represent a small threat to humans. According to the International Shark Attack File, there have been only 10 unprovoked attacks by Lemon sharks, all occurring in Florida and the Caribbean. There have been no fatal attacks from this species. The Lemon shark does inhabit coastal waters which swimmers, surfers and divers commonly swim in. The low number of attacks by this species shows that it is a small threat to humans.
The Lemon shark is targeted by commercial and recreational fishermen along the U.S, Atlantic Ocean, Caribbean, and in the eastern Pacific Ocean. The US bottom longline fishery commonly targets this species and it is also caught as by-catch in both pelagic and gillnet fisheries. Their fins are highly prized and are exported to Asia for shark fin soup. Their skin may be used for leather and their meat is eaten by humans. There is some concern that populations in the western north Atlantic and eastern Pacific Ocean are in danger due to over-fishing.

References
References 

Sharks
The spined pygmy shark (Squaliolus laticaudus) is one of the smallest sharks in the world. It is only seven to eight inches long on average. Spined pygmy sharks are dark gray or black on top. Their bellies glow in the dark. These sharks live very deep in the water (down to 6,500 feet) but they migrate up to about 650 feet at night, to hunt.

Spined pygmy sharks are harmless to humans.

References 

Sharks
The nurse shark (Ginglymostoma cirratum) is a bottom-dwelling shark, and is the only known species in the genus Ginglymostoma. They range in length from , and weigh .
Nurse sharks feed on crustaceans, mollusks, sea snakes, fish, coral, and tunicates.
The Nurse shark is common in the coastal tropical and subtropical waters of the eastern Pacific and the Atlantic Ocean.
Nurse sharks are nocturnal, and are very sluggish and are harmless unless bothered.

Description
Nurse sharks have two spineless, rounded dorsal fins, with the first dorsal fin being much larger than the second, and they have one anal fin. The first dorsal fin is located over the pelvic fins. The caudal fin is more than one quarter of the total shark's length. The sub-terminal mouth is placed well in front of the eyes, the spiracles are small, and there are long barbels on the mouth. The Nurse shark has nasoral grooves, but there is no perinasal groove.
Nurse sharks have the simplest type of tooth arrangement found in sharks. This means that there is no overlapping between the teeth, and that forward movements of teeth leading to shedding does not depend on other teeth. With sharks that have many overlapping teeth, the replacement of teeth cannot take place until the outer blocking teeth are lost. Young Nurse sharks can replace their teeth quicker than adults. Also, teeth replacing occurs faster in summer, when water temperatures are higher. Averaging 2.2-2.7 metres (7.2-9 feet) in total length, and weighing 75-105 kg (165-232 pounds), adult females reach a larger size than adult males which are around 2.1-2.6 metres (7-8.5 feet) long, and weigh around 90-120 kg (198-265 pounds). Females reach maturity at about 2.3 metres (7.6 feet), and males reach maturity at about 2.1 metres (7 feet). New-born Nurse sharks range in length from 28 to 30 cm (11 to 12 inches), with growth rates of 13 cm (5 inches) and 2.3 kg (5 pounds) per year
. Once the Nurse sharks reach maturity, their growth rates usually become much lower.
Distribution
The Nurse shark is common in the coastal tropical and subtropical waters of the eastern Pacific and the Atlantic Ocean. In the Atlantic, it ranges from Senegal to Gabon, Rhode Island to southern Brazil, and Mexico to Peru. Also, some Nurse sharks have been reported in the Gulf of Gascogne, in southwest France. This species is common in shallow waters throughout the West Indies, south Florida and the Florida Keys.
Behaviour
The Nurse shark is a nocturnal animal that rests on sandy bottoms or in caves or crevices in shallow waters during the day. They are usually found in groups of up to 40, as they lie very close together, sometimes even piling on one another.
Nurse sharks are very active during the night. In addition to swimming near the bottom, the Nurse shark can move around on the sea floor, using its flexible, muscular pectoral fins as limbs. Large juveniles and adults are usually found around deep coral reefs, and rocky areas at depths of up to 3-75 metres (10-246 feet) during the daytime, and then they migrate into shallower waters of less than 20 metres (66 feet) deep after darkness.
Young Nurse sharks up to 1.7 metres (6 feet) are usually found around shallow coral reefs, grass flats or mangrove islands in waters which are 1-4 metres (3-13 feet) deep. They often lie in groups within limestone holes or under rock ledges.
Nurse sharks are sluggish, and are not aggressive towards humans and will not attack unless they are provoked. If they are provoked, then they usually bite, but their bites are not deadly.

Feeding
The Nurse shark is a nocturnal predator, and hunts alone.  They feed on fish (such as catfish, mullets, and pufferfish)  stingrays, mollusks (such as octopuses, squids, and clams),  sea snakes, and tunicates. They move very slowly as they hunt along the bottom. They also consume algae, coral,  crustaceans (such as lobsters, shrimps, and crabs), sea urchins, snails and bivalves. 

The Nurse shark is one of the few species of sharks that can remain motionless in the water when it wants to. This not only helps it to conserve energy, it gives the Nurse shark an advantage when it comes to hunting. As it stays motionless, it's prey usually donesn't notice it, giving the Nurse shark a chance to ambush it's prey.
Reproduction
The mating season occurs once every 18 months, and lasts from the end of June till the end of July. They are ovoviviparous, with the gestation period lasting 6 months. Females can give birth to 21-29 pups at a time. However, sometimes the larger pups will feed on the smaller pups. As a result, only a small number of pups from each litter will live to the age of maturity. The young are born with spots, which fade as the sharks grow older. The average lifespan in the wild for these sharks is from 25 to 30 years.

Predators
Although the Nurse shark has no real predator, remains of Nurse sharks have been found in the stomachs of Tiger sharks, and Lemon sharks. Also, there have been reports of Bull sharks, and Great white sharks feeding on Nurse sharks.

Gallery

References 

Sharks
The spiny dogfish (Squalus acanthias) is one of the most common and well known species of dogfish. It is a small species of shark, with an average length of 28-39 inches (70–100 cm), and reaching a maximum weight of 9.8 kg.

The dogfish is found in the Atlantic and Pacific Ocean, and can be found from the surface to depths as deep as 1,460 metres. The spiny dogfish feeds mainly on pelagic fish such as herring, menhaden, capelin, sand lance, and mackerel.

Description
The spiny dogfish has a slim, long body and a flattened head. The snout is narrow, with a pointed tip. The eyes of this species are quite large. The first dorsal fin is located about halfway between the pectoral fins and the pelvic fins. The second dorsal fin is about two-thirds the size of the first one and is located behind the pelvic fins.
On the front of each dorsal fin there is a sharp spine attached to them, giving the spiny dogfish its name. The first spine is about half as long as the second spine. The pectoral fins form nearly perfect equilateral triangles, with rounded rear tips, and slightly concave rear margins. The pelvic fins are closer to the second dorsal fin than to the first dorsal fin. One the caudal fin, there is no notch on the upper lobe and the lower lobe is not well-developed. There is no anal fin on the Spiny dogfish.

The dorsal surface of the dogfish is slate-coloured and may have a brownish cast. There are rows of white spots along each side, from above the pectoral fins to above the pelvic fins. These spots are more visible on immature spiny dogfish, and they fade as the shark matures. With some individuals, the spots completely disappear. The edges of the dorsal fins and the caudal fin have a dusky-colour at birth, but this colour quickly fades. The ventral surface of the dogfish ranges from pale grey to pure white.
The average length of the spiny dogfish is 28-39 inches (70–100 cm), with adult males ranging from 24-35 inches (60–90 cm), and adult females ranging from 30-42 inches (76–107 cm). The maximum reported length of males is 39 inches (100 cm), and females is 49 inches (124 cm). Mature females can weigh as much as 3.2-4.5 kg (7-10 pounds), with a maximum recorded weight of 9.8 kg (22 pounds). The all-tackle game fish record is 7.14 kg (16 pounds), and was caught off the coast of Ireland in 1989.

Habitat
In the western Atlantic, the spiny dogfish ranges from Greenland to Argentina, and in the eastern Atlantic it is found from Iceland and the Murmanski Coast (Russia) to South Africa, including the Mediterranean Sea and the Black Sea. In the western Pacific, the dogfish occurs from the Bering Sea to New Zealand, while in the eastern Pacific, this species is found from the Bering Sea to Chile.
Spiny dogfish are benthopelagic, meaning that they are found just above the bottom of the ocean. They are found from the surface to depths as deep as 1,460 metres. Spiny dogfish can be found in brackish water, but prefer seawater, and are commonly found in waters with the temperature of 7-15 °C. Spiny dogfish are found inshore and offshore, over continental and insular (island) shelve, and upper slopes. They are often found in enclosed bays and estuaries. They have been reported to enter freshwater but cannot survive there for more than a few hours.

Predators
Spiny dogfish have been found in the stomachs of cod, red hake, and goosefish, as well as other dogfish. Larger species of sharks, as well as seals and Killer whales also feed on the spiny dogfish. To defend itself, the dogfish curls into a ball, and strikes at predators with its spines on the dorsal fins.
Feeding
The spiny dogfish usually feeds in groups. They feed mainly on pelagic fish such as herring, menhaden, capelin, sand lance, and mackerel, often consuming large numbers of them. They have been known to bite through fishing nets to be able to feed on the caught fish, usually releasing most of the fish. This has given the dogfish a bad reputation among fishermen. Other food items of this species includes molluscs (such as squid and octopus), crustacea (such as shrimp and crab), jellyfish, sea cucumber, algae, smaller sharks, and shark egg cases.

Reproduction
The gestation period of the spiny dogfish lasts up to 2 years. Spiny dogfish are ovoviviparous, meaning that the embryos develop inside eggs inside the female, and are nourished by yolk-filled sacs. Finally, the female gives birth to 1-20 pups, each one measuring around 20 to 33 centimeters. The spiny dogfish lives to the age of 20–75 years.

Human interaction
thumb|right|250px|A catch of Spiny dogfish
The dogfish poses little threat to humans, but if it is not handled properly, the spines on its dorsal fins can give a harmful wound. Also, the spiny dogfish has earned itself a bad reputation among fishermen due to its habit of biting through fishing nets to get at any fish which is caught in the nets.

The spiny dogfish is the most common living shark, yet two populations in the northwest and northeast Atlantic are at great risk due to overfishing. This shark is caught for food, liver oil, and is used to make sand paper, vitamins, leather, fertiliser, and pet food. Between 1900 and 1910, when the dogfish was at its peak abundance, it was estimated that up to 27 million spiny dogfish were caught off the Massachusetts coast every year.

Conservation
Due to their long gestation period and the low number of pups they give birth to at a time, the spiny dogfish must be managed carefully. This species is extremely vulnerable to overfishing and is currently on the brink of collapse.
Commercial fishermen target mature females because they grow to larger sizes than males. The fishing of spiny dogfish increased dramatically in the U.S.A during the 1990s, resulting in the population of mature females to decrease by 75%, leading to low number of pups. In 2001, the Atlantic States Marine Fisheries Commission (ASMFC) voted to extend an emergency action that closes state waters to fish for the vulnerable dogfish. This was in response to heavy fishing that devastated dogfish populations during the 1990s.

In late 2000, a fishery management plan for the spiny dogfish began to develop, followed by its approval in November 2002. Federal and state recovery plans are currently in place but are continually challenged. The National Marine Fisheries Service, with new data predicting the collapse of the spiny dogfish populations, closed federal waters to dogfish fishing in July 2003. The spiny dogfish is currently listed as Vulnerable by the IUCN.

Gallery

References 

Sharks
The tiger beetles are a large group of beetles in the family Carabidae. About 2,600 species and subspecies are known, with the richest diversity in the Oriental (Indo-Malayan) region, followed by the Neotropics.

All tiger beetles are predators. 
They are known for their aggressive predatory habits and running speed. The fastest species of tiger beetle can run at a speed of 9 km/h (5.6 mph), which, relative to its body length, is about 22 times the speed of an Olympic sprinter, the equivalent of a human running at . 

Tiger beetles live everywhere in the world except the Antarctic and Tasmania. They have powerful jaws, called mandibles, which they use to hold and crush their prey. They have long legs, big eyes, and a wide head. All are colourful.  Their elytra are usually bright and have bold markings.

References 

Carabidae
The Plastic People of the Universe (or shortly PPU) is a rock band from Prague, Czechoslovakia (Today Czech Republic). In 60s and 70s was frontman bass player Milan "Mejla" Hlavsa (*1951-†2001) and current frontman is saxophonist Vratislav Brabenec (*1943). On his "debut" album Egon Bondy's Happy Hearts Club Banned, the group set to music poems by Egon Bondy. The band became famous when it was put in prison by the communist government.

Selected discography
Muž bez uší (live recordings 1969-72)
Vožralej jak slíva (live recordings 1973-75)
Egon Bondy's Happy Hearts Club Banned (1974)
Ach to státu hanobení (live recordings 1976-77)
Pašijové hry velikonoční (1978)
Jak bude po smrti (1979)
Co znamená vésti koně (1981)
Kolejnice duní (1977–82)
Hovězí porážka (1983–84)
Půlnoční myš (1985–86)
Líně s tebou spím - Lazy Love / In Memoriam Mejla Hlavsa (2001)
Pašijové hry / Passion Play (with Agon Orchestra) (2004)
Maska za maskou (The Mask Behind the Mask)(2009)

References

Other websites

Plastic People official site
Article from Prague Life
Interview with Paul Wilson
Interview/profile from the Washington Post's Express 

Czech musical groups
Vratislav Brabenec (born April 28, 1943, Prague, Protectorate of Bohemia and Moravia, today Czech Republic) is a Czech musician, saxophonist, clarinetist a vocalist. He is member of Czech underground band The Plastic People of the Universe. Brabanec joined the Plastic People in 1972. He insisted that they no longer play songs by groups like the Velvet Underground. Brabenec wanted them to play their own songs and perform them in the Czech language. The band became famous in 1972 when some of the members were put in prison by the communist government. Brabenec was sent to prison for eight months because his music was "antisocial", he was disturbing the peace, and he his music was corrupting Czech youth.

References

Other websites
Plastic People of the Universe official site

1943 births
Living people
Clarinetists
Musicians from Prague
The Plastic People of the Universe
Robert Fripp (born 16 May 1946, Wimborne Minster, Dorset, England) is an English guitarist, songwriter and record producer. He was ranked 42 on Rolling Stone magazine's 2003 list of the "100 Greatest Guitarists of All Time". He is founder member of rock band King Crimson.

Fripp has been married to Toyah Willcox since 1986. His uncle was Alfie Fripp.

References

1946 births
Living people
English rock guitarists
Musicians from Dorset
Nico (born Christa Päffgen; 16 October 1938 – 18 July 1988) was a German singer, songwriter, actress, and Warhol Superstar. She is featured on the first album by the New York rock band The Velvet Underground, The Velvet Underground & Nico.

She was born in Cologne. She grew up in Brandenburg and Berlin.

She made seven studio albums.

She died on holiday in the Spanish island of Ibiza, of a cerebral hemorrhage while riding her bicycle.

Nico was born Christa Päffgen. When she was 16 the photographer Herbert Tobias gave her the name Nico. Nico moved to Paris and began working for Vogue, Tempo, Vie Nuove, Mascotte Spettacolo, Camera, Elle, and other fashion magazines.

References

1938 births
1988 deaths
Contraltos
Deaths from cerebral hemorrhage
Entertainers from Berlin
German singers
People from Brandenburg
Actors from Cologne
Rock singers
U.S. Route 4 is a highway in the United States. It travels from East Greenbush, New York, near Albany to Portsmouth, New Hampshire.  It passes through the state of Vermont.  It has a total length of 250 miles.  Before being a US highway, Route 4 was part of several New England highways.

References

04
Karel Kryl (April 12, 1944 Kroměříž, Protectorate of Bohemia and Moravia, today Czech Republic – March 3, 1994 Passau, Germany) was a Czech singer-songwriter and poet. Kryl is sometimes called a "Básník s kytarou" (poet with a guitar).

Other websites

Karel Kryl official website

1944 births
1994 deaths
Czech poets
Czech guitarists
Czech singer-songwriters
Schooling and shoaling is a kind of collective animal behaviour by fish.

Any group of fish that stays together for social reasons is said to be shoaling, and if the shoal is swimming in the same direction together, it is schooling.p365 About one quarter of fish shoal all their lives, and about one half of fish shoal for part of their lives.

Fish get many benefits from shoaling. These include defence against predators: if fish swim in schools, it is less likely any one of them will be eaten. Also, it may help a fish find food, and a mate. The school may even swim faster than a lone fish. Fish generally prefer larger shoals, shoalmates of their own species, shoalmates similar in size and appearance to themselves, healthy fish, and kin (when recognized).

Any shoal member which stands out in appearance may be targeted by predators. This is called the oddity effect. This may explain why fish prefer to shoal with individuals which look like themselves.

Schooling
Schooling 

Some fish spend most of their time schooling. Tuna, herring and anchovy, spend all of their time shoaling or schooling, and become agitated if separated from the group. Others, such as Atlantic cod, school only some of the time. Cod and tuna are, in nature, large fish which can look after themselves. Still, they do shoal.

Shoaling fish can shift into a disciplined and coordinated school, then shift back to an amorphous shoal within seconds. Such shifts are triggered by changes of activity from feeding, resting, travelling or avoiding predators.

When schooling fish stop to feed, they break ranks and become shoals. Shoals are more vulnerable to predator attack. The shape a shoal or school takes depends on the type of fish and what the fish are doing. Schools that are travelling can form long thin lines, or squares or ovals or amoeboid shapes. Fast moving schools usually form a wedge shape, while shoals that are feeding tend to become circular.
Small fish are preyed on by larger fish, seabirds and marine mammals (Cetacea). Small fish form schools, and may swim with their mouths open to filter feed on plankton. These schools can become huge, moving along coastlines and migrating across open oceans. The shoals are concentrated fuel resources for the great marine predators.

These immense gatherings fuel the ocean food web. Most forage fish are pelagic fish, which means they form their schools in open water, and not on or near the bottom (demersal fish). The predators are keenly focused on the shoals, acutely aware of their numbers and whereabouts, and make migrations themselves, often in schools of their own, that can span thousands of miles to connect with, or stay connected with them.