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Electric potential energy

Electric potential energy, or Electrostatic potential energy, is a potential energy that results from conservative Coulomb forces and is associated with the configuration of a particular set of point charges within a defined system. An object may have electric potential energy by virtue of two key elements: its own electric charge and its relative position to other electrically charged objects; the term "electric potential energy" is used to describe the potential energy in systems with time-variant electric fields, while the term "electrostatic potential energy" is used to describe the potential energy in systems with time-invariant electric fields. The electric potential energy of a system of point charges is defined as the work required assembling this system of charges by bringing them close together, as in the system from an infinite distance; the electrostatic potential energy, UE, of one point charge q at position r in the presence of an electric field E is defined as the negative of the work W done by the electrostatic force to bring it from the reference position rref to that position r. where E is the electrostatic field and dr' is the displacement vector in a curve from the reference position rref to the final position r.

The electrostatic potential energy can be defined from the electric potential as follows: The electrostatic potential energy, UE, of one point charge q at position r in the presence of an electric potential Φ is defined as the product of the charge and the electric potential. Where Φ is the electric potential generated by the charges, a function of position r; the SI unit of electric potential energy is the joule. In the CGS system the erg is the unit of energy, being equal to 10−7 J. Electronvolts may be used, 1 eV = 1.602×10−19 J. The electrostatic potential energy, UE, of one point charge q at position r in the presence of a point charge Q, taking an infinite separation between the charges as the reference position, is: where k e = 1 4 π ε 0 is Coulomb's constant, r is the distance between the point charges q & Q, q & Q are the charges; the following outline of proof states the derivation from the definition of electric potential energy and Coulomb's law to this formula. The electrostatic potential energy, UE, of one point charge q in the presence of n point charges Qi, taking an infinite separation between the charges as the reference position, is: where k e = 1 4 π ε 0 is Coulomb's constant, ri is the distance between the point charges q & Qi, q & Qi are the signed values of the charges.

The electrostatic potential energy UE stored in a system of N charges q1, q2... qN at positions r1, r2... rN is: where, for each i value, Φ is the electrostatic potential due to all point charges except the one at ri, is equal to: Φ = k e ∑ j = 1 N q j r i j, where rij is the distance between qj and qi. The electrostatic potential energy of a system containing only one point charge is zero, as there are no other sources of electrostatic force against which an external agent must do work in moving the point charge from infinity to its final location. A common question arises concerning the interaction of a point charge with its own electrostatic potential. Since this interaction doesn't act to move the point charge itself, it doesn't contribute to the stored energy of the system. Consider bringing a point charge, q, into its final position near a point charge, Q1; the electrostatic potential Φ due to Q1 is Φ = k e Q 1 r Hence we obtain, the electric potential energy of q in the potential of Q1 as U E = 1 4 π ε 0 q Q 1 r 1 where r1 is the separation between the two point charges.

The electrostatic potential energy of a system of three charges should not be confused with the electrostatic potential energy of Q1 due to two charges Q2 and Q3, because the latter doesn't include the electrostatic potential energy of the system of the two charges Q2 and Q3. The electrostatic potential energy stored in the system of three charges is: U E = 1 4 π ε 0 [ Q 1 Q 2 r 12


Onchopristis is a genus of extinct giant sclerorhynchid sawfish from the Lower Cretaceous to Upper Cretaceous of North America, North Africa and New Zealand. It had an elongated snout lined laterally with barbed teeth; the rostrum, or snout, was around 2.5 m long, lined with barbed teeth. In the type species, O. numidus, each tooth had one barb, but in O. dunklei there were two to five barbs on each tooth, two to three in O. d. praecursor. This sawfish was 8-10 meters long; as with modern sawfish, Onchopristis's eyes were on top of its head, to spot predators rather than prey, its mouth and gills were under its body. The rostrum most would have had electroreceptors to detect food in the water below them like most modern sharks and some rays. Onchopristis may have raked through the riverbed to find and eat prey. Dutheil, D. B. Brito, P. M. 2009. Articulated cranium of Onchopristis numidus from Morocco. In: Jalil, N.-E. 1st International Congress on North African Vertebrate Palaeontology, Program & Abstracts, Marrakech, 25–27 May 2009, p. 66.

Haug, E. Paléontologie. Documents Scientifiques de la mission saharienne. Publications de la Société de Géographie, p. 751-832

Robert Karolevitz

Robert Francis Karolevitz was an American author and humorist from Yankton, South Dakota. His writing focused on biography and history, among other topics, he has been described as "one of South Dakota’s most prolific authors." Karolevitz was born in South Dakota, to Frank and Martha Karolevitz. He grew up in Yankton, where he attended Sacred Heart School and graduated from Yankton High School in 1940, he fought in the United States Army Infantry in both Japan and the Philippines during World War II. He earned his bachelor's degree from South Dakota State University and his master's degree from the University of Oregon. In 1971, he received the Wrangler Award from the National Western Heritage Museum, he served as chairman of South Dakota's State Regional Advisory Group for Comprehensive Health Planning, a member of the Committee for Medical Advancement in South Dakota, a trustee of Sacred Heart Hospital in Yankton, a South Dakota State Historical Society board member. He played a major role in the establishment of both the medical school at the University of South Dakota and the Lewis and Clark Health Education and Service Center.

In 1973, he became one of the first people to be inducted into the South Dakota Hall of Fame. In 2006, he received the Robinson Award from the Governor of South Dakota. In 2014, he was named a "health pioneer" by the South Dakota Department of Health. Karolevitz married Phyllis Gunderson on January 4, 1951, they had two daughters: Martha Jill. Robert Karolevitz died on June 17, 2011 at Avera Sister James Care Center in Yankton

Maxime Biamou

Maxime Gérard Biamou Ngapmou Yoke is a French professional footballer who plays as a striker for League One club Coventry City. Born in Créteil, Biamou spent his early career in non-league football with Villemomble Sports and Sutton United, he signed for Coventry City in June 2017. In August 2018 he suffered an anterior cruciate ligament injury, was ruled out for a number of months. At the start of the 2019–20 season Coventry tried to play Biamou on the left wing. In a post-match interview conducted after a 2-0 win against Southend United in February 2020, Biamou praised the club for his footballing development, saying "I am a different player since I came to Coventry"; as of match played 25 February 2020 Coventry City EFL League Two play-offs: 2018

Mel Pejic

Melvyn Pejic is an English former footballer who played in the Football League for Hereford United, Stoke City and Wrexham. His brother Mike was a professional footballer as well as his son Shaun. Pejic was born in Chesterton and joined the youth teams of Stoke City in 1977 where his older brother Mike had just spent ten years, he made just one first team appearance for Stoke which came against Ipswich Town on 12 January 1980, he played at right back as Stoke lost 1–0. He signed for Hereford United. A serious knee ligament injury hampered his first two seasons at Edgar Street. However, in the next four seasons he missed only five matches and was voted Player of the Year for three successive seasons in 1983, 1984 and 1985, he became the only Hereford United Captain to lifted the Welsh Cup in 1990 when Hereford defeated Wrexham at Cardiff Arms Park. In a 12-season stint, he made 523 competitive appearances. Of these, 412 were in league matches, for which he holds the clubs Football League appearances record, where he scored 14 goals, puts him second in the all-time appearance list for the "Bulls", behind John Layton who played a total 549 times for the club during their non-league days.

He moved to Wrexham midway through the 1991–92 season, went on to make over 100 league appearances for the "Red Dragons" helping the Welsh side to gain promotion in 1992–93. Towards the end of his playing days he firstly completed his FA Diploma in the Treatment and Management of Injuries, before studying and gaining a Physiotherapy Degree from Salford University taking over first physio duties at Wrexham and under the managership of John Toshack the Wales national football team senior physiotherapists position, being promoted from a similar position with the Under 21 team. In August 2012, after three years as physiotherapist with Bolton Wanderers, Pejic joined Macclesfield Town. In November 2013 Pejic returned to Stoke City to work in the medical department at the club's academy. One of Mel's sons, Shaun played for Wrexham, his elder brother Mike was a footballer. Source: WrexhamThird Division runner-up: 1992–93

Howard Sochurek

Howard Sochurek, was an American photojournalist. Howard J. Sochurek was born in 1924 in Wisconsin, he graduated from Princeton University in 1942 enlisted on December 1 that year to fight in the Second World War. On return from war, Sochurek first found work with the Milwaukee Journal in 1950 secured a position as staff photographer with Life magazine, going on to work from their New York, Detroit, New Delhi and Paris offices, for National Geographic, photographing for stories on the Soviet Union, where in 1959 he covered a visit by Christian Dior fashion models to GUM, the ‘USSR’s premier department store’, on the Middle East, on nationalist Chinese ‘Boy Battalion’ soldiers in Formosa, traveling to Mongolia and Vietnam. At home, he photographed Pulitzer Prize-winning poet Robert Frost in 1957, Richard Nixon’s presidential election campaign, Henry Kissinger, black student activists with Martin Luther King Jr.. During the Korean War he was parachuted with the 187th Airborne RCT behind enemy lines to photograph American troops, was sent in 1952 to cover the First Indochina War, documenting the French defeat at Battle of Dien Bien Phu, subsequently, the Vietnam War.

In 1955 Sochurek was awarded the first Robert Capa Gold Medal. His image India: Willing hands bring progress, showing silhouetted construction workers on scaffolding, was selected by Edward Steichen for MoMA's globally-touring The Family of Man exhibition, Sochurek documented the installation of the exhibition for publicity. Sochurek was the first photojournalist to receive the Harvard research sabbatical, the Nieman Fellowship in 1959. Sochurek left Life in 1970 after two decades to work as a freelancer. On assignment for Life, Sochurek had been told to investigate advances in medical imaging. Seeing an opportunity, he secured a computer from NASA, used to produce images from the transmissions of spy and weather satellites, becoming one of the first photographers to use computers to image and colourise X-ray and CT scans, his reputation among medical circles grew, many doctors and pharmaceutical and other medical companies used his photographs in textbooks and advertisements. In retirement, Sochurek settled in Florida.

He died of liver cancer at the age of 69, in April 1994 in Miami at the Jackson Memorial Hospital, survived by his wife Tania and daughter Tania DeChiara. Sochurek, Medicine's new vision, Mack Pub. Co, ISBN 978-0-912734-25-5 Sochurek, Howard.