title: Sydney Tamiia Poitier

text: Poitier began her career of acting in the late 1990s. In 2001, she landed her first role on television in the NBC drama series "First Years". The series was canceled after three episodes. In 2003, she starred in the UPN sitcom "Abby". That series was also canceled during its first season. Later that same year, she had a recurring role in "Joan of Arcadia", where she played Rebecca Askew, the love interest of Joan's older brother, Kevin (Jason Ritter). She was also a regular on the first season of "Veronica Mars". However, she left the show after only appearing in four episodes because of budget cuts.


title: Sydney Tamiia Poitier

text: In 2007, Poitier starred in "Death Proof", director Quentin Tarantino's segment of the movie "Grindhouse", as radio DJ Jungle Julia. The next year, she had a co-starring role in the new "Knight Rider" series, as FBI Agent Carrie Rivai. In 2011, she guest-starred on two episodes of "Private Practice".


title: Sydney Tamiia Poitier

text: Poitier starred as Detective Sam Shaw in the Canadian crime comedy series "Carter", which ran for two seasons in 2018 and 2019.


title: Huckleberry

text: Huckleberry is a name used in North America for several plants in the family Ericaceae, in two closely related genera: "Vaccinium" and "Gaylussacia". The huckleberry is the state fruit of Idaho.


title: Huckleberry

text: The name 'huckleberry' is a North American variation of the English dialectal name variously called 'hurtleberry' or 'whortleberry' () for the bilberry. In North America the name was applied to numerous plant variations all bearing small berries with colors that may be red, blue or black. It is the common name for various "Gaylussacia" species, and some "Vaccinium" species, such as "Vaccinium parvifolium", the "red huckleberry", and is also applied to other "Vaccinium" species which may also be called blueberries depending upon local custom, as in New England and parts of Appalachia.


title: Huckleberry

text: Four species of huckleberries in the genus "Gaylussacia" are common in eastern North America, especially "G. baccata", also known as the black huckleberry.


title: Huckleberry

text: From coastal Central California through Oregon to southern Washington and British Columbia, the red huckleberry ("V. parvifolium") is found in the maritime-influenced plant community. In the Pacific Northwest and mountains of Montana and Idaho, this huckleberry species and several others, such as the black "Vaccinium" huckleberry ("V. membranaceum") and blue (Cascade) huckleberry ("V. deliciosum"), grow in various habitats, such as mid-alpine regions up to above sea level, mountain slopes, forests, or lake basins. The plant grows best in damp, acidic soil having volcanic origin, attaining under optimal conditions heights of , usually ripening in mid-to-late summer or later at high elevations. Huckleberry was one of the few plant species to survive on the slopes of Mount St. Helens when the volcano erupted in 1980, and existed as a prominent mountain-slope bush in 2017.


title: Huckleberry

text: Where the climate is favorable, certain species of huckleberry, such as "V. membranaceum", "V. parvifolium" and "V. deliciosum", are used in ornamental plantings. The 'garden huckleberry' ("Solanum scabrum") is not a true huckleberry, but is instead a member of the nightshade family.


title: Huckleberry

text: Huckleberries grow wild on subalpine slopes, forests, bogs and lake basins of the northwestern United States and western Canada. The plant has shallow, radiating roots topped by a bush growing from an underground stem. Attempts to cultivate huckleberry plants from seeds have failed, with plants devoid of fruits. This may be due to inability for the plants to fully root and to replicate the native soil chemistry of wild plants.


title: Huckleberry

text: Huckleberries were traditionally collected by Native American and First Nations people along the Pacific coast, interior British Columbia, Idaho, and Montana for use as food or traditional medicine. The berries are small and round, in diameter, and look like large dark blueberries. In taste, they may be tart, with a flavor similar to that of a blueberry, especially in blue- and purple-colored varieties, and some have noticeably larger, bitter seeds. The fruit is versatile in various foods or beverages, including jam, pudding, candy, pie, ice cream, muffins, pancakes, salad dressings, juice, tea, soup, and syrup.


title: Huckleberry

text: Two huckleberry species, "V. membranaceum" and "V. ovatum", were studied for phytochemical content, showing that "V. ovatum" had greater total anthocyanin and polyphenols than did "V. membranaceum". Each species contained 15 anthocyanins (galactoside, glucoside, and arabinoside of delphinidin, cyanidin, petunidin, peonidin, and malvidin) but in different proportions.


title: Huckleberry

text: Huckleberry "Huck" Finn is a fictional character in the books "The Adventures of Tom Sawyer" (1876) and "Adventures of Huckleberry Finn" (1884), by American author and humorist, Mark Twain (Samuel Langhorne Clemens). Huckleberry Finn was portrayed to be about 12 or 13 years old, derived from Twain's boyhood friend, Tom Blankenship, as "ignorant, unwashed, insufficiently fed; but he had as good a heart as ever any boy had. His liberties were totally unrestricted. He was the only really independent person—boy or man—in the community, and by consequence he was tranquilly and continuously happy and envied by the rest of us." The cartoon character that shares the same name with Mark Twain's character is Huckleberry "Huck" Hound, an anthropomorphic Bluetick Coonhound created by Hanna-Barbera in 1958, in which the term "huckleberry" can be a slang expression for a rube or an amateur, or a mild expression of disapproval.


title: Huckleberry

text: Huckleberries hold a place in archaic American English slang. The phrase "a huckleberry over my persimmon" was used to mean "a bit beyond my abilities". "I'm your huckleberry" is a way of saying that one is just the right person for a given job. The range of slang meanings of huckleberry in the 19th century was broad, also referring to significant persons or nice persons.


title: The Number 23

text: The Number 23 is a 2007 American thriller film written by Fernley Phillips and directed by Joel Schumacher. Jim Carrey stars as a man who becomes obsessed with the 23 enigma once he reads about it in a strange book that seemingly mirrors his own life. The film was released in the United States on February 23, 2007. This is the second film to pair Schumacher and Carrey, the first being "Batman Forever". The film grossed $77.6 million, and has an approval rating of 7% on Rotten Tomatoes.


title: The Number 23

text: Walter Sparrow is an animal control officer married to Agatha, with their son, Robin. Walter fails to catch stray dog 'Ned' and is late to meet Agatha. Agatha ends up browsing a bookstore and begins reading a book titled "The Number 23" written by Topsy Kretts. She later gives Walter the book as a birthday present. Walter starts reading the book and notices similarities between himself and the main character, a detective who refers to himself as "Fingerling". As Walter continues reading, he envisions himself and those closest to him as the book's characters, himself as Fingerling and Agatha as Fabrizia, Fingerling's new girlfriend etc.


title: The Number 23

text: Fingerling gets dispatched to a suicidal woman, 'Suicide Blonde', who rants about her obsession with the number 23, that it "rules her world" before jumping from her apartment balcony to her death. Fingerling examines the apartment and begins to read her scribblings of the enigma and soon begins noticing the number 23 everywhere he goes, too. Walter visits the book store and learns the book is self-published and there are no other works or further information on Topsy Kretts. Walter starts becoming obsessed with the 23 enigma, the idea that all incidents and events are directly connected to the number 23. Robin seems taken in by the enigma whilst Agatha dismisses any significance about the number. As Fingerling's obsession with the number increases, so does Walter's and Fingerling begins having nightmares about killing Fabrizia.


title: The Number 23

text: Concerned with Walter's growing obsession, Agatha refers him to her friend, Isaac French, who suggests Walter is being paranoid and recommends Walter finish the book to find the answers he's looking for. Isaac offers to speak to Agatha in the meantime. Fingerling tells his department shrink about his nightmares and about the number. Dr. Miles Phoenix (Isaac) suggests he takes a break and offers to speak to Fabrizia. Fabrizia does not find Fingerling's vacation appealing. After Fingerling discovers Fabrizia has 23 pairs of shoes he destroys them, causing Fabrizia to storm out of their apartment, calling him insane. Not long after, Fingerling discovers Fabrizia is having an affair with Dr. Phoenix and Walter begins growing paranoid of Agatha and Isaac's friendship.


title: The Number 23

text: Walter has a nightmare that he's stabbed Agatha to death. Fearing what's happening to him, Walter leaves home and stays in the King Edward Hotel (room 23) to finish the book and clear his head. Miles discovers a murdered Fabrizia, stabbed to death. The police arrest Miles, who, not knowing if Fabrizia was role-playing or not, picked up the murder weapon. Fingerling flees the scene to a hotel where he, erratic, steps towards the hotel balcony, mirroring Suicide Blonde's final moments. The book ends abruptly, with no further information on Fingerling. Walter is convinced the number had gone after Fingerling and was now going after him.


title: The Number 23

text: Walter immediately spots Ned and chases him, blaming the dog for making him late and therefore having the curse in his life. Walter catches Ned and learns he's under the care of a local church, since Ned tends to visit the cemetery. Ned recently favors a certain tombstone, Laura Tollins, who died on her 23rd birthday, although her body was never found. Walter discovers the circumstances revolving Laura Tollins' death is similar to the book's events and believes Tollins' convicted killer is the book's author. Walter visits Kyle Flinch in prison and asks him what the number means. Kyle maintains his innocence, denying both killing Laura and writing the book. Since Kyle's name does not add to 23, Walter is convinced he's innocent. Robin, who has also read the book, finds a hidden address. Hoping it's the author's address, the family send 23 empty packages to the address occupant, in order to entrap them at the delivery office.


title: The Number 23

text: A suspicious looking man enters the post office and when Walter confronts him, the man is suddenly terrified, telling Walter he should be dead. The man attacks Walt with a box cutter before slicing his own throat. Agatha attempts to stop the bleeding and tells Walter to take Robin home. Before succumbing to his injuries, the man tells Agatha to go to an institute. Agatha sees that, like Walter, the man is obsessed with the 23 enigma. Agatha finds the man's former work ID badge and visits the institute which is now fenced off and abandoned. There, she discovers a patient box labelled W. Sparrow but before she can look further a figure approaches her, giving her a fright.


title: The Number 23

text: Meanwhile, Walter discovers a secret message within the book, telling him to go to his local park and dig beneath its steps. Walter and Robin visit the park and dig beneath its 23rd step discovering a skeleton. The two flee and call the police but upon returning, discover the body has been removed. Agatha meets them at the park, having been driven by Isaac. Driving home, Walter glimpses Agatha's muddy fingertips and realizes she moved the skeleton. Walter confronts Agatha, believing she is the author who had murdered the book's publisher to protect herself and removed the skeleton. Agatha at first admits only to moving the skeleton, but finally admits what she learned at the psychiatric hospital, that the book was written by Walter.


title: The Number 23

text: Agatha shows a confused Walter the patient box. Inside are sources Walter used to write his novel. Seeing his old items, Walter begins partially remembering his past and flees to the King Edward Hotel. There he rips down the wallpaper of room 23 and discovers his past scribblings, the missing final chapter of the book, Chapter 23. Walter reads and remembers. Young Walter's mother killed herself which caused his father to do the same. Walter's father, an accountant, failed to leave a suicide note, only his notebook, containing the 23 enigma. In college Walter met Laura Tollins, who was aroused by danger. Tollins started flirting with her teacher Kyle Flinch to mess with Walter and with Walter's numeral obsession returning, Tollins had an affair with Flinch and broke up with Walt via note but Walter 'deciphered' her message and was convinced she was in danger and that the number wanted to 'kill her'.


title: The Number 23

text: Walter visited Tollins to warn her but she threatened him with a knife and, after a few harsh words, cut his arm. Walter went into a frenzy and stabbed her multiple times. Walter then fled with her body and proceeded to bury it under the park steps. Kyle Flinch later arrived, picked up the knife, incriminating himself. Walter arrived at the King Edward Hotel and began typewriting his suicide note which quickly becomes the book, changing the details of his confession into a fantasy. Walter then wrote the true events all over the room's walls before jumping out the window. Walter survived his suicide attempt but due to his head trauma and survivors guilt is left with amnesia. Walter was rehabilitated at the institute and discharged. Meanwhile, one of its doctors had obtained Walter's novel and began to succumb to the enigma, eventually publishing it under the name Topsy Kretts.


title: The Number 23

text: Back in the present, Agatha finds Walter at the hotel. Walter remembers everything and tells Agatha he's a murderer but Agatha argues he isn't the same person. Walter tells Agatha to leave before he kills again. Walter flees the hotel and runs into the street. There, across the road Ned is staring at him. As Walter stares at the dog a bus comes towards him at full speed. Almost allowing himself to be run over, Walter steps out of the way at the last second when he realizes his son is watching, not wanting to repeat the cycle his own father created. Walter, hugged by both Agatha and Robin, finally exclaims that it's just a number.


title: The Number 23

text: Walter hands himself in to the police and awaits sentencing and is told a judge will likely go easy on him due to handing himself in. A funeral procession takes place in front of Tollins' grave, where it is implied her body has finally been laid to rest.


title: The Number 23

text: "The Number 23" has an approval rating of 7% on Rotten Tomatoes based on 189 reviews; the average rating is 3.50/10. The site's consensus reads: "Jim Carrey has been sharp in a number of non-comedic roles, but this lurid, overheated, and self serious potboiler is not one of them. "The Number 23" is clumsy, unengaging, and mostly confusing." Audiences surveyed by CinemaScore gave the film a grade of "B−" on scale of A+ to F.


title: The Number 23

text: Of the few critics who liked the film, Richard Roeper and critic George Pennachio of KABC-TV in Los Angeles stand out, as they gave the film a "two thumbs up" rating on the television show "Ebert & Roeper" (Pennachio was standing in for Roger Ebert due to Ebert's illness). However, Michael Phillips, filling in for Ebert on the Worst of 2007 show (aired January 12, 2008) put "The Number 23" at No. 7 in his list of the worst (Roeper did not include it in his list).


title: The Number 23

text: Peter Travers of "Rolling Stone" declared the film the year's worst star vehicle on his list of the Worst Movies of 2007, while Colm Andrew of the "Manx Independent" said the film "delivers a rambling, confusing narrative with only a few stylistic elements thrown in". The film was nominated for two Teen Choice Awards. For his performance, Carrey was nominated for the Golden Raspberry Award for Worst Actor at the 28th Golden Raspberry Awards, but lost to Eddie Murphy for "Norbit".


title: The Number 23

text: On its opening weekend, "The Number 23" took in $14,602,867, coming in behind "Ghost Rider"s second weekend. After five weeks of release, the film grossed $35,193,167 at the domestic box office and $42,373,648 overseas, for a worldwide total of $77,566,815. The film was released in the United Kingdom on February 23, 2007, and opened on #3, behind "Charlotte's Web" and "Hot Fuzz".


title: The Number 23

text: The film was released on Region 1 DVD on July 24, 2007; The release contains both the theatrical version and an extended version, which runs an additional four minutes. This is the last in New Line's Infinifilm series. Special features include deleted scenes, such as a much more abstract alternate opening and an alternate ending that gives a few more details about Walter's prison sentence and hints at the possibility that the son could be subject to the same obsessions as his father. The disc also includes interviews with mathematicians, psychologists, and numerologists.


title: Rules of Engagement (TV series)

text: Rules of Engagement is an American sitcom television series that ran on CBS from February 5, 2007, to May 20, 2013, originally airing as a mid-season replacement.


title: Rules of Engagement (TV series)

text: The series was produced by Adam Sandler's Happy Madison Productions in association with CBS Television Studios and Sony Pictures Television (SPT controls the North American rights while CBS controls the international rights).


title: Rules of Engagement (TV series)

text: Although the show received negative reviews throughout its run, it earned 3 Primetime Emmy Award nominations and always earned reasonably good ratings, helping the show reach 100 episodes (typically the minimum needed for syndication) over seven seasons.


title: Rules of Engagement (TV series)

text: Two couples and their single friend deal with the complications of dating, promise and marriage. It portrays different interpersonal relationship in various stages, starring Patrick Warburton and Megyn Price as a long-married couple, Oliver Hudson and Bianca Kajlich as newly engaged sweethearts, and David Spade and Adhir Kalyan (the latter added in season 3) as their still-single friends. They often meet at "The Island Diner".


title: Rules of Engagement (TV series)

text: The show was heavily promoted by CBS during Super Bowl XLI and launched the following night, the first of seven episodes in its first season. The pilot episode remains the highest rated episode of the show. The series was renewed for a second season, which began as a mid-season replacement for "The New Adventures of Old Christine" on Monday, September 24, 2007, with production halted after nine episodes on November 6, 2007, in the wake of a writers' strike. After the strike ended, CBS announced that the show would return April 14, 2008, with a further six episodes.


title: Rules of Engagement (TV series)

text: Seasons three and four were both mid-season entries launched in March 2009 and March 2010. On May 18, 2010, it was announced that CBS had renewed "Rules of Engagement" for a 5th season. It was later announced that this season would start in September, in contrast to its usual midseason start, and received an expanded 24-episode order. (The fifth season was the first and only season to have a full-season order.) The first 15 episodes aired on Monday nights, usually in the 8:30 pm Eastern/7:30 pm Central time slot following "How I Met Your Mother". Then on February 24, 2011, the series moved to Thursdays at 8:30 pm Eastern/7:30 pm Central, following "The Big Bang Theory", after the cancellation of "$#*! My Dad Says". On January 31, 2011, CBS ordered an additional two episodes of the series to prepare for the possibility of "Two and a Half Men" going into hiatus following Charlie Sheen's real-life issues, taking the episode order to 26. Two of these episodes were held back and aired as part of the sixth season.


title: Rules of Engagement (TV series)

text: On May 17, 2011, the series was renewed for a sixth season to begin airing in fall 2011. One day later, CBS announced that "Rules of Engagement" would move to Saturday nights at 8:00 pm Eastern/7:00 pm Central as part of the network's new "Comedytime Saturday" block; the first time in six years that an original CBS program would air on that night. It also marked the fourth night on which the series would air, with it previously airing on Mondays, Wednesdays (two airings), and Thursdays. On October 7, 2011, however, it was announced that "Rules of Engagement" would move back to its 8:30PM EST Thursday timeslot following "The Big Bang Theory", replacing new sitcom "How to Be a Gentleman" which was moved to the new Saturday time slot. The episode order was cut from the original 18, down to 13 (plus two unaired episodes from season five) on November 14, 2011.


title: Rules of Engagement (TV series)

text: Effective January 12, 2012, CBS removed "Rules of Engagement" from its Thursday lineup, replacing it with the new sitcom "Rob" starring Rob Schneider. "Rules" would return to its Thursday 8:30 PM time slot on March 29, after "Rob" had finished airing its 8-episode order, resulting in a total of 15 episodes in season 6.


title: Rules of Engagement (TV series)

text: On May 21, 2012, CBS renewed "Rules of Engagement" for a seventh season of 13 episodes to air mid-season, bringing the total number of produced 100 episodes. Season 7 began airing on Mondays at 8:30, starting February 4, 2013.


title: Rules of Engagement (TV series)

text: On May 10, 2013, "Rules of Engagement" was cancelled by CBS after seven seasons and 100 episodes. The series finale episode aired on May 20, 2013.


title: Rules of Engagement (TV series)

text: In June 2011, the series was picked up for syndication by local network affiliates, The CW Plus, and WGN America, making its debut on September 10, 2012. On Wednesday, January 2, 2013, the series began airing weekdays on TBS at 2/1c. Shortly thereafter, it moved to the early morning hour of 6 A.M. throughout the week. As of May 2016, the series has left the line-up entirely. All 7 seasons were available for streaming on Netflix until September 2018 when they were removed. The Roku Channel alternates (every few months) offering seasons 1 thru 4 and seasons 5 thru 7, free. As of March 2021, in addition to the alternating seasons that The Roku Channel offers, all seven seasons of Rules of Engagement are available for streaming via subscription on Fubu and Starz.


title: Rules of Engagement (TV series)

text: Sony Pictures Home Entertainment owns the rights to release DVDs in Region 1. The fifth season of the series was made available beginning February 7, 2012, exclusively as a made-on-demand release from Sony Pictures Home Entertainment, in conjunction with amazon.com. Similarly, the sixth season received a MOD release from online retailers, on October 2, 2012.


title: Rules of Engagement (TV series)

text: Paramount Home Entertainment, in conjunction with CBS Home Entertainment, began releasing the series on DVD internationally in 2011. Season One was released in the UK (Region 2 DVD) on April 4, 2011. In region 4, the entire series has been released, as individual season sets.


title: Rules of Engagement (TV series)

text: Note: Following the events of Charlie Sheen's departure from "Two and a Half Men", CBS ordered an additional two episodes for "Rules of Engagement"’s fifth season, bringing the total number of episodes to 26 from the initial 24 ordered. Despite the episodes, "Scavenger Hunt" and "Cheating," airing during the sixth season, they were originally produced for the fifth season, and are included in the fifth season collection. Therefore, the sixth season's DVD release features the 13 episodes produced over that time period, versus the 15 that were broadcast by CBS.


title: Rules of Engagement (TV series)

text: Polish channel TVN started filming its own version of the show, called "Reguły Gry" (literally meaning "Rules of the Game" in Polish). It premiered on 16 February 2012 on TVN sister channel TVN 7 as its first original production.


title: Sneaky Pete

text: Sneaky Pete is an American crime drama series created by David Shore and Bryan Cranston. The series follows Marius Josipović (Giovanni Ribisi), a released convict who adopts the identity of his cellmate, Pete Murphy, to avoid his past life. The series also stars Marin Ireland, Shane McRae, Libe Barer, Michael Drayer, Peter Gerety and Margo Martindale. The pilot debuted on August 7, 2015, and was followed by a full series order that September. Shore left the project in early 2016 and was replaced by Graham Yost, who served as executive producer and showrunner for the remaining nine episodes. The first season premiered in its entirety on January 13, 2017, exclusively on Amazon Prime Video. On January 19, 2017, Amazon announced that "Sneaky Pete" had been renewed for a second season, which was released on March 9, 2018. On July 28, 2018, Amazon announced that the series had been renewed for a third season, which was released on May 10, 2019.


title: Sneaky Pete

text: "Sneaky Pete" follows "Marius, a con man who gets out of prison only to find himself hunted by the vicious gangster he once robbed. With nowhere else to turn, Marius takes cover from his past by assuming the identity of his cellmate, Pete and then "reunites" with Pete's estranged family — who have no reason to suspect he is not their long-lost loved one".


title: Sneaky Pete

text: In November 2014, CBS gave a production commitment to "Sneaky Pete". A formal pilot for the show was shot in New York in March 2015. On May 8, CBS decided to pass on the pilot, while also canceling David Shore's other series on the network, "Battle Creek". Just two days later, it was reported that the pilot might be moving to cable networks, with many expressing interest.


title: Sneaky Pete

text: In June, it was reported that Amazon was in negotiations to pick up the pilot, with some tweaking and possible minor reshoots before being made available to the viewers. The pilot was released on Amazon on August 7, 2015 and was ordered to series on September 2, 2015.


title: Sneaky Pete

text: In March 2016, it was announced that Shore would be leaving the project, and would be replaced by Graham Yost, who would be taking over as executive producer and showrunner. Start of production of the full series was pushed back to allow for the transition.


title: Sneaky Pete

text: The first season of "Sneaky Pete" received positive reviews from critics. Rotten Tomatoes gave the first season a 97% 'Certified Fresh' rating, based on 31 critic reviews, with the critical consensus "Suspenseful, smart, and terrifically cast, "Sneaky Pete" is part dramedy, part crime caper, and all in all entertaining." Metacritic gave the first season a 77 out of 100 score based on 22 critic reviews, indicating "generally favorable reviews".


title: Sneaky Pete

text: The second season of "Sneaky Pete" received positive critical reviews as well. Rotten Tomatoes gave the second season a 92% 'Fresh' rating, based on 12 critic reviews, with the critical consensus ""Sneaky Pete"'s sophomore season replicates its predecessor's finesse with narrative sleight of hand and deliciously twisted capers, although Bryan Cranston's gravitas is sorely missed."


title: Sneaky Pete

text: The third season of "Sneaky Pete" continued to receive positive critical reviews, with Rotten Tomatoes giving it 100% 'Fresh' rating, based on 5 critic reviews.


title: Sneaky Pete

text: Margo Martindale was nominated for her performance for Best Supporting Actress in a Drama Series at the


title: Sage Northcutt

text: Sage Northcutt (March 1, 1996) is an American professional mixed martial artist who is currently competing in the Lightweight division of ONE Championship, although he has competed in the Welterweight division as well. He has also previously competed for the Ultimate Fighting Championship (UFC).


title: Sage Northcutt

text: Northcutt has been training MMA since the age of 4 and competed all over the world from a young age. His father, Mark, is a black belt in shuri-ryū karate, and his older sister, Colbey, is an amateur kickboxing champion and a professional mixed martial artist currently signed to ONE Championship. At the age of 9, Northcutt became the youngest person ever to be on the cover of "Sport Karate Magazine". Northcutt has won a total of 77 world youth championships in karate. He was also an undefeated kickboxer, with his record standing at 15–0.


title: Sage Northcutt

text: Northcutt attended Seven Lakes High School for his first two years of high school before transferring to Katy High School during his sophomore year. Northcutt was inducted into the "Black Belt Magazine" Hall of Fame in 2012 at age 15. In high school Northcutt trained and competed in wrestling, and also trained with Texas A&M university’s NCWA wrestling club before dropping out to pursue his mixed martial arts career.


title: Sage Northcutt

text: In 2013, Northcutt began competing on the Legacy Fighting Championship amateur mixed martial arts (MMA) series, amassing an amateur record of 5-1 with his only loss coming on his first bout against Charles Sheppard by technical-knockout (TKO) in the first round. At the age of 18, he turned pro and racked up a 5–0 record in 16 months.


title: Sage Northcutt

text: Northcutt was featured in the debut episode of Dana White's "Looking For A Fight". After a victory at Legacy Fighting Championship 44, he was signed to the UFC.


title: Sage Northcutt

text: In his UFC debut, Northcutt also made his lightweight debut when he faced Francisco Treviño on October 3, 2015, at UFC 192. He won via technical-knockout (TKO) in 57 seconds.


title: Sage Northcutt

text: Northcutt's second UFC fight was against Cody Pfister on December 10, 2015, at UFC Fight Night 80. Northcutt won the fight via guillotine choke in the second round.


title: Sage Northcutt

text: Northcutt was expected to face Andrew Holbrook on January 30, 2016, at . However, after Holbrook withdrew from the bout citing an injury eight days prior to the event, Northcutt would instead make his welterweight debut against Bryan Barberena. Northcutt lost the bout via submission (arm-triangle choke) in the second round.


title: Sage Northcutt

text: Northcutt made a return to lightweight and faced Enrique Marín on July 9, 2016, at UFC 200, where he won via unanimous decision.


title: Sage Northcutt

text: Northcutt had his second welterweight bout when he faced Mickey Gall on December 17, 2016, at . He lost the contest via submission in the second round.


title: Sage Northcutt

text: Northcutt was expected to face Claudio Puelles in a lightweight bout on July 29, 2017, at UFC 214. However, Puelles pulled out of the fight in mid-June citing injury and was replaced by John Makdessi. In turn, the fight was canceled on July 14 due to injuries to both fighters.


title: Sage Northcutt

text: Northcutt faced Michel Quiñones on November 11, 2017, at UFC Fight Night 120. He won the fight via unanimous decision.


title: Sage Northcutt

text: Northcutt faced Thibault Gouti on February 18, 2018, at UFC Fight Night 126. He won the fight via unanimous decision.


title: Sage Northcutt

text: Northcutt faced Zak Ottow on July 14, 2018, at UFC Fight Night 133. He won the fight via knockout in the second round. Appearing on The Ariel Helwani Show early September 2018, Northcutt confirmed his contract expired following the fight with Ottow, making him a free agent. In the same appearance, Northcutt said he planned to listen for offers from various promotions.


title: Sage Northcutt

text: On November 26, 2018, Dana White confirmed on "UFC Unfiltered" that the UFC did not opt to renew Sage Northcutt's contract. White cited reasons, claiming, "Sage is young, and Sage needs some work. Let him get some work in some other organizations, and we will see where this kid ends up in a couple of years. Maybe we will pick him back up again."


title: Sage Northcutt

text: On November 30, 2018, it was announced that Northcutt had signed with ONE Championship. On February 26, 2019, it was announced that Northcutt was scheduled to make his promotional debut against Cosmo Alexandre on May 17, 2019, in . Northcutt lost the fight by knockout 29 seconds into the first round, marking his first professional loss by knockout. The blow resulted in eight facial fractures which required prompt surgical repair.


title: Sage Northcutt

text: On November 22, 2019, Northcutt announced that he would be moving down two weight classes to compete at featherweight (155 lbs) in ONE Championship. “I learned my lesson about fighting a weight class too big, going back down to 155, and it’ll be better for me,” Northcutt said in an interview with MMA News.


title: Sage Northcutt

text: Northcutt was scheduled to fight Shinya Aoki in a Lightweight bout, after a near two-year layoff, at ONE on TNT 4, on April 28, 2021. However, Northcutt withdrew from the bout due to lingering COVID-19 effects and was replaced by Eduard Folayang.


title: Sage Northcutt

text: Northcutt was majoring in petroleum engineering at Texas A&M University. In January 2017, Northcutt announced he would withdraw from Texas A&M University to train mixed martial arts full-time. Northcutt is a Christian. Northcutt married actress Amanda Leighton on December 5, 2020.


title: Senescence

text: Senescence () or biological aging is the gradual deterioration of functional characteristics in living organisms. The word "senescence" can refer to either cellular senescence or to senescence of the whole organism. Organismal senescence involves an increase in death rates and/or a decrease in fecundity with increasing age, at least in the latter part of an organism's life cycle.


title: Senescence

text: Senescence is the inevitable fate of almost all multicellular organisms with germ-soma separation, but it can be delayed. The discovery, in 1934, that calorie restriction can extend lifespan by 50% in rats, and the existence of species having negligible senescence and potentially immortal organisms such as "Hydra", have motivated research into delaying senescence and thus age-related diseases. Rare human mutations can cause accelerated aging diseases.


title: Senescence

text: Environmental factors may affect aging – for example, overexposure to ultraviolet radiation accelerates skin aging. Different parts of the body may age at different rates. Two organisms of the same species can also age at different rates, making biological aging and chronological aging distinct concepts.


title: Senescence

text: "Organismal senescence" is the aging of whole organisms. Actuarial senescence can be defined as an increase in mortality and/or a decrease in fecundity with age. The Gompertz–Makeham law of mortality says that the age-dependent component of the mortality rate increases exponentially with age.


title: Senescence

text: Aging is characterized by the declining ability to respond to stress, increased homeostatic imbalance, and increased risk of aging-associated diseases including cancer and heart disease. Aging has been defined as "a progressive deterioration of physiological function, an intrinsic age-related process of loss of viability and increase in vulnerability."


title: Senescence

text: In 2013, a group of scientists defined nine hallmarks of aging that are common between organisms with emphasis on mammals:


title: Senescence

text: The environment induces damage at various levels, e.g. damage to DNA, and damage to tissues and cells by oxygen radicals (widely known as free radicals), and some of this damage is not repaired and thus accumulates with time. Cloning from somatic cells rather than germ cells may begin life with a higher initial load of damage. Dolly the sheep died young from a contagious lung disease, but data on an entire population of cloned individuals would be necessary to measure mortality rates and quantify aging.


title: Senescence

text: The evolutionary theorist George Williams wrote, "It is remarkable that after a seemingly miraculous feat of morphogenesis, a complex metazoan should be unable to perform the much simpler task of merely maintaining what is already formed."


title: Senescence

text: Different speeds with which mortality increases with age correspond to different maximum life span among species. For example, a mouse is elderly at 3 years, a human is elderly at 80 years, and ginkgo trees show little effect of age even at 667 years.


title: Senescence

text: Almost all organisms senesce, including bacteria which have asymmetries between "mother" and "daughter" cells upon cell division, with the mother cell experiencing aging, while the daughter is rejuvenated. There is negligible senescence in some groups, such as the genus "Hydra". Planarian flatworms have "apparently limitless telomere regenerative capacity fueled by a population of highly proliferative adult stem cells." These planarians are not biologically immortal, but rather their death rate slowly increases with age. Organisms that are thought to be biologically immortal would, in one instance, be the "Turritopsis" "dohrnii", also known as the "immortal jellyfish", due to its ability to revert to its youth when it undergoes stress during adulthood. The reproductive system is observed to remain intact, and even the gonads of the "Turritopsis" "dohrnii" are existing.


title: Senescence

text: Some species exhibit "negative senescence", in which reproduction capability increases or is stable, and mortality falls with age, resulting from the advantages of increased body size during aging.


title: Senescence

text: More than 300 different theories have been posited to explain the nature and causes of aging. A good theory would both explain past observations and predict the results of future experiments.


title: Senescence

text: Theories of aging fall into two broad categories, evolutionary theories of aging and mechanistic theories of aging. Evolutionary theories of aging primarily explain why aging happens, but do not concern themselves with the molecular mechanism(s) that drive the process. All evolutionary theories of aging rest on the basic mechanisms that the force of natural selection declines with age. Mechanistic theories of aging can be divided into theories that propose aging is programmed, and damage accumulation theories, i.e. those that propose aging to be caused by specific molecular changes occurring over time.


title: Senescence

text: One theory was proposed by George C. Williams and involves antagonistic pleiotropy. A single gene may affect multiple traits. Some traits that increase fitness early in life may also have negative effects later in life. But, because many more individuals are alive at young ages than at old ages, even small positive effects early can be strongly selected for, and large negative effects later may be very weakly selected against. Williams suggested the following example: Perhaps a gene codes for calcium deposition in bones, which promotes juvenile survival and will therefore be favored by natural selection; however, this same gene promotes calcium deposition in the arteries, causing negative atherosclerotic effects in old age. Thus, harmful biological changes in old age may result from selection for pleiotropic genes that are beneficial early in life but harmful later on. In this case, selection pressure is relatively high when Fisher's reproductive value is high and relatively low when Fisher's reproductive value is low.


title: Senescence

text: Senescent cells within a multicellular organism can be purged by competition between cells, but this increases the risk of cancer. This leads to an inescapable dilemma between two possibilities—the accumulation of physiologically useless senescent cells, and cancer—both of which lead to increasing rates of mortality with age.


title: Senescence

text: The disposable soma theory of aging was proposed by Thomas Kirkwood in 1977. The theory suggests that aging occurs due to a strategy in which an individual only invests in maintenance of the soma for as long as it has a realistic chance of survival. A species that uses resources more efficiently will live longer, and therefore be able to pass on genetic information to the next generation. The demands of reproduction are high, so less effort is invested in repair and maintenance of somatic cells, compared to germline cells, in order to focus on reproduction and species survival.


title: Senescence

text: Programmed theories of aging posit that aging is adaptive, normally invoking selection for evolvability or group selection.


title: Senescence

text: The reproductive-cell cycle theory suggests that aging is regulated by changes in hormonal signaling over the lifespan.


title: Senescence

text: Only a very small minority of scientists believe aging to be programmed, and the vast majority believe aging is due to some kind of damage accumulation.


title: Senescence

text: One of the most prominent theories of aging was first proposed by Harman in 1956. It posits that free radicals produced by dissolved oxygen, radiation, cellular respiration and other sources cause damage to the molecular machines in the cell and gradually wear them down. This is also known as oxidative stress.


title: Senescence

text: There is substantial evidence to back up this theory. Old animals have larger amounts of oxidized proteins, DNA and lipids than their younger counterparts.


title: Senescence

text: One of the earliest aging theories was the "Rate of Living Hypothesis" described by Raymond Pearl in 1928 (based on earlier work by Max Rubner), which states that fast basal metabolic rate corresponds to short maximum life span.


title: Senescence

text: While there may be some validity to the idea that for various types of specific damage detailed below that are by-products of metabolism, all other things being equal, a fast metabolism may reduce lifespan, in general this theory does not adequately explain the differences in lifespan either within, or between, species. Calorically restricted animals process as much, or more, calories per gram of body mass, as their "ad libitum" fed counterparts, yet exhibit substantially longer lifespans. Similarly, metabolic rate is a poor predictor of lifespan for birds, bats and other species that, it is presumed, have reduced mortality from predation, and therefore have evolved long lifespans even in the presence of very high metabolic rates. In a 2007 analysis it was shown that, when modern statistical methods for correcting for the effects of body size and phylogeny are employed, metabolic rate does not correlate with longevity in mammals or birds.


title: Senescence

text: With respect to specific types of chemical damage caused by metabolism, it is suggested that damage to long-lived biopolymers, such as structural proteins or DNA, caused by ubiquitous chemical agents in the body such as oxygen and sugars, are in part responsible for aging. The damage can include breakage of biopolymer chains, cross-linking of biopolymers, or chemical attachment of unnatural substituents (haptens) to biopolymers.


title: Senescence

text: Under normal aerobic conditions, approximately 4% of the oxygen metabolized by mitochondria is converted to superoxide ion, which can subsequently be converted to hydrogen peroxide, hydroxyl radical and eventually other reactive species including other peroxides and singlet oxygen, which can, in turn, generate free radicals capable of damaging structural proteins and DNA. Certain metal ions found in the body, such as copper and iron, may participate in the process. (In Wilson's disease, a hereditary defect that causes the body to retain copper, some of the symptoms resemble accelerated senescence.) These processes termed oxidative stress are linked to the potential benefits of dietary polyphenol antioxidants, for example in coffee, red wine and tea.


title: Senescence

text: Sugars such as glucose and fructose can react with certain amino acids such as lysine and arginine and certain DNA bases such as guanine to produce sugar adducts, in a process called "glycation". These adducts can further rearrange to form reactive species, which can then cross-link the structural proteins or DNA to similar biopolymers or other biomolecules such as non-structural proteins. People with diabetes, who have elevated blood sugar, develop senescence-associated disorders much earlier than the general population, but can delay such disorders by rigorous control of their blood sugar levels. There is evidence that sugar damage is linked to oxidant damage in a process termed "glycoxidation".


title: Senescence

text: Free radicals can damage proteins, lipids or DNA. Glycation mainly damages proteins. Damaged proteins and lipids accumulate in lysosomes as lipofuscin. Chemical damage to structural proteins can lead to loss of function; for example, damage to collagen of blood vessel walls can lead to vessel-wall stiffness and, thus, hypertension, and vessel wall thickening and reactive tissue formation (atherosclerosis); similar processes in the kidney can lead to kidney failure. Damage to enzymes reduces cellular functionality. Lipid peroxidation of the inner mitochondrial membrane reduces the electric potential and the ability to generate energy. It is probably no accident that nearly all of the so-called "accelerated aging diseases" are due to defective DNA repair enzymes.


title: Senescence

text: It is believed that the impact of alcohol on aging can be partly explained by alcohol's activation of the HPA axis, which stimulates glucocorticoid secretion, long-term exposure to which produces symptoms of aging.


title: Senescence

text: Natural selection can support lethal and harmful alleles, if their effects are felt after reproduction. The geneticist J. B. S. Haldane wondered why the dominant mutation that causes Huntington's disease remained in the population, and why natural selection had not eliminated it. The onset of this neurological disease is (on average) at age 45 and is invariably fatal within 10–20 years. Haldane assumed that, in human prehistory, few survived until age 45. Since few were alive at older ages and their contribution to the next generation was therefore small relative to the large cohorts of younger age groups, the force of selection against such late-acting deleterious mutations was correspondingly small. Therefore, a genetic load of late-acting deleterious mutations could be substantial at mutation–selection balance. This concept came to be known as the selection shadow.


title: Senescence

text: Peter Medawar formalised this observation in his mutation accumulation theory of aging. "The force of natural selection weakens with increasing age—even in a theoretically immortal population, provided only that it is exposed to real hazards of mortality. If a genetic disaster... happens late enough in individual life, its consequences may be completely unimportant". Age-independent hazards such as predation, disease, and accidents, called 'extrinsic mortality', mean that even a population with negligible senescence will have fewer individuals alive in older age groups.


title: Senescence

text: If different individuals age at different rates, then fecundity, mortality, and functional capacity might be better predicted by biomarkers than by chronological age. However, graying of hair, skin wrinkles and other common changes seen with aging are not better indicators of future functionality than chronological age. Biogerontologists have continued efforts to find and validate biomarkers of aging, but success thus far has been limited. Levels of CD4 and CD8 memory T cells and naive T cells have been used to give good predictions of the expected lifespan of middle-aged mice.


title: Senescence

text: There is interest in an epigenetic clock as a biomarker of aging, based on its ability to predict human chronological age. Basic blood biochemistry and cell counts can also be used to accurately predict the chronological age. It is also possible to predict the human chronological age using the transcriptomic aging clocks.


title: Senescence

text: A number of genetic components of aging have been identified using model organisms, ranging from the simple budding yeast "Saccharomyces cerevisiae" to worms such as "Caenorhabditis elegans" and fruit flies ("Drosophila melanogaster"). Study of these organisms has revealed the presence of at least two conserved aging pathways.


title: Senescence

text: Gene expression is imperfectly controlled, and it is possible that random fluctuations in the expression levels of many genes contribute to the aging process as suggested by a study of such genes in yeast. Individual cells, which are genetically identical, nonetheless can have substantially different responses to outside stimuli, and markedly different lifespans, indicating the epigenetic factors play an important role in gene expression and aging as well as genetic factors.


title: Senescence

text: A set of rare hereditary (genetics) disorders, each called progeria, has been known for some time. Sufferers exhibit symptoms resembling accelerated aging, including wrinkled skin. The cause of Hutchinson–Gilford progeria syndrome was reported in the journal "Nature" in May 2003.


title: Senescence

text: This report suggests that DNA damage, not oxidative stress, is the cause of this form of accelerated aging.


title: Schumann resonances

text: The Schumann resonances (SR) are a set of spectrum peaks in the extremely low frequency (ELF) portion of the Earth's electromagnetic field spectrum. Schumann resonances are global electromagnetic resonances, generated and excited by lightning discharges in the cavity formed by the Earth's surface and the ionosphere.


title: Schumann resonances

text: The global electromagnetic resonance phenomenon is named after physicist Winfried Otto Schumann who predicted it mathematically in 1952.


title: Schumann resonances

text: Schumann resonances are the principal background in the part of the electromagnetic spectrum from 3 Hz through 60 Hz, and appear as distinct peaks at extremely low frequencies (ELF) around 7.83 Hz (fundamental), 14.3, 20.8, 27.3, and 33.8 Hz.


title: Schumann resonances

text: Schumann resonances occur because the space between the surface of the Earth and the conductive ionosphere acts as a closed, although variable-sized waveguide. The limited dimensions of the Earth cause this waveguide to act as a resonant cavity for electromagnetic waves in the ELF band. The cavity is naturally excited by electric currents in lightning.


title: Schumann resonances

text: In the normal mode descriptions of Schumann resonances, the fundamental mode is a standing wave in the Earth–ionosphere cavity with a wavelength equal to the circumference of the Earth. The lowest-frequency mode has the highest intensity, and the frequency of all modes can vary slightly owing to solar-induced perturbations to the ionosphere (which compress the upper wall of the closed cavity) amongst other factors. The higher resonance modes are spaced at approximately 6.5 Hz intervals (as may be seen by feeding numbers into the formula), a characteristic attributed to the atmosphere's spherical geometry. The peaks exhibit a spectral width of approximately 20% on account of the damping of the respective modes in the dissipative cavity.


title: Schumann resonances

text: Observations of Schumann resonances have been used to track global lightning activity. Owing to the connection between lightning activity and the Earth's climate it has been suggested that they may be used to monitor global temperature variations and variations of water vapor in the upper troposphere. Schumann resonances have been used to study the lower ionosphere on Earth and it has been suggested as one way to explore the lower ionosphere on celestial bodies. Some have proposed that lightning on other planets might be detectable and studied by means of Schumann resonance signatures of those planets.


title: Schumann resonances

text: Effects on Schumann resonances have been reported following geomagnetic and ionospheric disturbances. More recently, discrete Schumann resonance excitation has been linked to transient luminous events — sprites, ELVES, jets, and other upper-atmospheric lightning. A new field of interest using Schumann resonances is related to short-term earthquake prediction.


title: Schumann resonances

text: Interest in Schumann resonances renewed in 1993 when E.R. Williams showed a correlation between the resonance frequency and tropical air temperatures, suggesting the resonance could be used to monitor global warming. In geophysical survey, Schumann resonances are used to locate offshore hydrocarbon deposits.


title: Schumann resonances

text: In 1893, George Francis FitzGerald noted that the upper layers of the atmosphere must be fairly good conductors. Assuming that the height of these layers is about 100 km above ground, he estimated that oscillations (in this case the lowest mode of the Schumann resonances) would have a period of 0.1 second. Because of this contribution, it has been suggested to rename these resonances "Schumann–FitzGerald resonances". However FitzGerald's findings were not widely known as they were only presented at a meeting of the British Association for the Advancement of Science, followed by a brief mention in a column in "Nature".


title: Schumann resonances

text: The first suggestion that an ionosphere existed, capable of trapping electromagnetic waves, is attributed to Heaviside and Kennelly (1902). It took another twenty years before Edward Appleton and Barnett in 1925 were able to prove experimentally the existence of the ionosphere.


title: Schumann resonances

text: Although some of the most important mathematical tools for dealing with spherical waveguides were developed by G. N. Watson in 1918, it was Winfried Otto Schumann who first studied the theoretical aspects of the global resonances of the earth–ionosphere waveguide system, known today as the Schumann resonances. In 1952–1954 Schumann, together with H. L. König, attempted to measure the resonant frequencies. However, it was not until measurements made by Balser and Wagner in 1960–1963 that adequate analysis techniques were available to extract the resonance information from the background noise. Since then there has been an increasing interest in Schumann resonances in a wide variety of fields.


title: Schumann resonances

text: Lightning discharges are considered to be the primary natural source of Schumann resonance excitation; lightning channels behave like huge antennas that radiate electromagnetic energy at frequencies below about 100 kHz. These signals are very weak at large distances from the lightning source, but the Earth–ionosphere waveguide behaves like a resonator at ELF frequencies and amplifies the spectral signals from lightning at the resonance frequencies.


title: Schumann resonances

text: In an ideal cavity, the resonant frequency of the formula_1-th mode formula_2 is determined by the Earth radius formula_3 and the speed of light formula_4.


title: Schumann resonances

text: The real Earth–ionosphere waveguide is not a perfect electromagnetic resonant cavity. Losses due to finite ionosphere electrical conductivity lower the propagation speed of electromagnetic signals in the cavity, resulting in a resonance frequency that is lower than would be expected in an ideal case, and the observed peaks are wide. In addition, there are a number of horizontal asymmetries—day-night difference in the height of the ionosphere, latitudinal changes in the Earth's magnetic field, sudden ionospheric disturbances, polar cap absorption, variation in the Earth radius of ± 11 km from equator to geographic poles, etc. that produce other effects in the Schumann resonance power spectra.


title: Schumann resonances

text: Today Schumann resonances are recorded at many separate research stations around the world. The sensors used to measure Schumann resonances typically consist of two horizontal magnetic inductive coils for measuring the north-south and east-west components of the magnetic field, and a vertical electric dipole antenna for measuring the vertical component of the electric field. A typical passband of the instruments is 3–100 Hz. The Schumann resonance electric field amplitude (~300 microvolts per meter) is much smaller than the static fair-weather electric field (~150 V/m) in the atmosphere.


title: Schumann resonances

text: Similarly, the amplitude of the Schumann resonance magnetic field (~1 picotesla) is many orders of magnitude smaller than the Earth's magnetic field (~30–50 microteslas). Specialized receivers and antennas are needed to detect and record Schumann resonances. The electric component is commonly measured with a ball antenna, suggested by Ogawa et al., in 1966, connected to a high-impedance amplifier. The magnetic induction coils typically consist of tens- to hundreds-of-thousands of turns of wire wound around a core of very high magnetic permeability.


title: Schumann resonances

text: From the very beginning of Schumann resonance studies, it was known that they could be used to monitor global lightning activity. At any given time there are about 2000 thunderstorms around the globe. Producing approximately fifty lightning events per second, these thunderstorms are directly linked to the background Schumann resonance signal.


title: Schumann resonances

text: Determining the spatial lightning distribution from Schumann resonance records is a complex problem: in order to estimate the lightning intensity from Schumann resonance records it is necessary to account for both the distance to lightning sources and the wave propagation between the source and the observer. A common approach is to make a preliminary assumption on the spatial lightning distribution, based on the known properties of lightning climatology. An alternative approach is placing the receiver at the North or South Pole, which remain approximately equidistant from the main thunderstorm centers during the day.


title: Schumann resonances

text: One method not requiring preliminary assumptions on the lightning distribution is based on the decomposition of the average background Schumann resonance spectra, utilizing ratios between the average electric and magnetic spectra and between their linear combination. This technique assumes the cavity is spherically symmetric and therefore does not include known cavity asymmetries that are believed to affect the resonance and propagation properties of electromagnetic waves in the system.


title: Schumann resonances

text: The best documented and the most debated features of the Schumann resonance phenomenon are the diurnal variations of the background Schumann resonance power spectrum.


title: Schumann resonances

text: A characteristic Schumann resonance diurnal record reflects the properties of both global lightning activity and the state of the Earth–ionosphere cavity between the source region and the observer. The vertical electric field is independent of the direction of the source relative to the observer, and is therefore a measure of global lightning.


title: Schumann resonances

text: The diurnal behavior of the vertical electric field shows three distinct maxima, associated with the three "hot spots" of planetary lightning activity: one at 9 UT (Universal Time) linked to the daily peak of thunderstorm activity from Southeast Asia; one at 14 UT linked to the peak of African lightning activity; and one at 20 UT linked to the peak of South American lightning activity. The time and amplitude of the peaks vary throughout the year, linked to seasonal changes in lightning activity.


title: Schumann resonances

text: In general, the African peak is the strongest, reflecting the major contribution of the African "chimney" to global lightning activity. The ranking of the two other peaks—Asian and American—is the subject of a vigorous dispute among Schumann resonance scientists. Schumann resonance observations made from Europe show a greater contribution from Asia than from South America, while observations made from North America indicate the dominant contribution comes from South America.


title: Schumann resonances

text: Williams and Sátori suggest that in order to obtain "correct" Asia-America chimney ranking, it is necessary to remove the influence of the day/night variations in the ionospheric conductivity (day-night asymmetry influence) from the Schumann resonance records. The "corrected" records presented in the work by Sátori, et al. show that even after the removal of the day-night asymmetry influence from Schumann resonance records, the Asian contribution remains greater than American.


title: Schumann resonances

text: Similar results were obtained by Pechony et al. who calculated Schumann resonance fields from satellite lightning data. It was assumed that the distribution of lightning in the satellite maps was a good proxy for Schumann excitations sources, even though satellite observations predominantly measure in-cloud lightning rather than the cloud-to-ground lightning that are the primary exciters of the resonances. Both simulations—those neglecting the day-night asymmetry, and those taking this asymmetry into account—showed the same Asia-America chimney ranking. On the other hand, some optical satellite and climatological lightning data suggest the South American thunderstorm center is stronger than the Asian center.


title: Schumann resonances

text: The reason for the disparity among rankings of Asian and American chimneys in Schumann resonance records remains unclear, and is the subject of further research.


title: Schumann resonances

text: In the early literature the observed diurnal variations of Schumann resonance power were explained by the variations in the source-receiver (lightning-observer) geometry. It was concluded that no particular systematic variations of the ionosphere (which serves as the upper waveguide boundary) are needed to explain these variations. Subsequent theoretical studies supported the early estimations of the small influence of the ionosphere day-night asymmetry (difference between day-side and night-side ionosphere conductivity) on the observed variations in Schumann resonance field intensities.


title: Schumann resonances

text: The interest in the influence of the day-night asymmetry in the ionosphere conductivity on Schumann resonances gained new strength in the 1990s, after publication of a work by Sentman and Fraser. Sentman and Fraser developed a technique to separate the global and the local contributions to the observed field power variations using records obtained simultaneously at two stations that were widely separated in longitude. They interpreted the diurnal variations observed at each station in terms of a combination of a diurnally varying global excitation modulated by the local ionosphere height.


title: Schumann resonances

text: Their work, which combined both observations and energy conservation arguments, convinced many scientists of the importance of the ionospheric day-night asymmetry and inspired numerous experimental studies. However, recently it was shown that results obtained by Sentman and Fraser can be approximately simulated with a uniform model (without taking into account ionosphere day-night variation) and therefore cannot be uniquely interpreted solely in terms of ionosphere height variation.


title: Schumann resonances

text: Schumann resonance amplitude records show significant diurnal and seasonal variations which in general coincide in time with the times of the day-night transition (the terminator). This time-matching seems to support the suggestion of a significant influence of the day-night ionosphere asymmetry on Schumann resonance amplitudes. There are records showing almost clock-like accuracy of the diurnal amplitude changes.


title: Schumann resonances

text: On the other hand, there are numerous days when Schumann resonance amplitudes do not increase at sunrise or do not decrease at sunset. There are studies showing that the general behavior of Schumann resonance amplitude records can be recreated from diurnal and seasonal thunderstorm migration, without invoking ionospheric variations. Two recent independent theoretical studies have shown that the variations in Schumann resonance power related to the day-night transition are much smaller than those associated with the peaks of the global lightning activity, and therefore the global lightning activity plays a more important role in the variation of the Schumann resonance power.


title: Schumann resonances

text: It is generally acknowledged that source-observer effects are the dominant source of the observed diurnal variations, but there remains considerable controversy about the degree to which day-night signatures are present in the data. Part of this controversy stems from the fact that the Schumann resonance parameters extractable from observations provide only a limited amount of information about the coupled lightning source-ionospheric system geometry. The problem of inverting observations to simultaneously infer both the lightning source function and ionospheric structure is therefore extremely underdetermined, leading to the possibility of non-unique interpretations.


title: Schumann resonances

text: One of the interesting problems in Schumann resonances studies is determining the lightning source characteristics (the "inverse problem"). Temporally resolving each individual flash is impossible because the mean rate of excitation by lightning, ~50 lightning events per second globally, mixes up the individual contributions together. However, occasionally extremely large lightning flashes occur which produce distinctive signatures that stand out from the background signals. Called "Q-bursts", they are produced by intense lightning strikes that transfer large amounts of charge from clouds to the ground and often carry high peak current.


title: Schumann resonances

text: Q-bursts can exceed the amplitude of the background signal level by a factor of 10 or more and appear with intervals of ~10 s, which allows them to be considered as isolated events and determine the source lightning location. The source location is determined with either multi-station or single-station techniques and requires assuming a model for the Earth–ionosphere cavity. The multi-station techniques are more accurate, but require more complicated and expensive facilities.


title: Schumann resonances

text: It is now believed that many of the Schumann resonances transients (Q bursts) are related to the transient luminous events (TLEs). In 1995, Boccippio et al. showed that sprites, the most common TLE, are produced by positive cloud-to-ground lightning occurring in the stratiform region of a thunderstorm system, and are accompanied by Q-burst in the Schumann resonances band. Recent observations reveal that occurrences of sprites and Q bursts are highly correlated and Schumann resonances data can possibly be used to estimate the global occurrence rate of sprites.


title: Schumann resonances

text: Williams [1992] suggested that global temperature may be monitored with the Schumann resonances. The link between Schumann resonance and temperature is lightning flash rate, which increases nonlinearly with temperature. The nonlinearity of the lightning-to-temperature relation provides a natural amplifier of the temperature changes and makes Schumann resonance a sensitive "thermometer". Moreover, the ice particles that are believed to participate in the electrification processes which result in a lightning discharge have an important role in the radiative feedback effects that influence the atmosphere temperature. Schumann resonances may therefore help us to understand these feedback effects. A paper was published in 2006 linking Schumann resonance to global surface temperature, which was followed up with a 2009 study.


title: Schumann resonances

text: Tropospheric water vapor is a key element of the Earth's climate, which has direct effects as a greenhouse gas, as well as indirect effects through interaction with clouds, aerosols and tropospheric chemistry. Upper tropospheric water vapor (UTWV) has a much greater impact on the greenhouse effect than water vapor in the lower atmosphere, but whether this impact is a positive or a negative feedback is still uncertain.


title: Schumann resonances

text: The main challenge in addressing this question is the difficulty in monitoring UTWV globally over long timescales. Continental deep-convective thunderstorms produce most of the lightning discharges on Earth. In addition, they transport large amount of water vapor into the upper troposphere, dominating the variations of global UTWV. Price [2000] suggested that changes in the UTWV can be derived from records of Schumann resonances.


title: Schumann resonances

text: Within the Solar System there are five candidates for Schumann resonance detection besides the Earth: Venus, Mars, Jupiter, Saturn, and Saturn's biggest moon Titan.


title: Schumann resonances

text: Modeling Schumann resonances on the planets and moons of the Solar System is complicated by the lack of knowledge of the waveguide parameters. No "in situ" capability exists today to validate the results.


title: Schumann resonances

text: The strongest evidence for lightning on Venus comes from the electromagnetic waves first detected by Venera 11 and 12 landers. Theoretical calculations of the Schumann resonances at Venus were reported by Nickolaenko and Rabinowicz [1982] and Pechony and Price [2004]. Both studies yielded very close results, indicating that Schumann resonances should be easily detectable on that planet given a lightning source of excitation and a suitably located sensor.


title: Schumann resonances

text: In the case of Mars there have been terrestrial observations of radio emission spectra that have been associated with Schumann resonances. The reported radio emissions are not of the primary electromagnetic Schumann modes, but rather of secondary modulations of the nonthermal microwave emissions from the planet at approximately the expected Schumann frequencies, and have not been independently confirmed to be associated with lightning activity on Mars. There is the possibility that future lander missions could carry in situ instrumentation to perform the necessary measurements. Theoretical studies are primarily directed to parameterizing the problem for future planetary explorers.


title: Schumann resonances

text: Detection of lightning activity on Mars has been reported by Ruf et al. [2009]. The evidence is indirect and in the form of modulations of the nonthermal microwave spectrum at approximately the expected Schumann resonance frequencies. It has not been independently confirmed that these are associated with electrical discharges on Mars. In the event confirmation is made by direct, in situ observations, it would verify the suggestion of the possibility of charge separation and lightning strokes in the Martian dust storms made by Eden and Vonnegut [1973] and Renno et al. [2003].


title: Schumann resonances

text: Martian global resonances were modeled by Sukhorukov [1991], Pechony and Price [2004], and Molina-Cuberos et al. [2006]. The results of the three studies are somewhat different, but it seems that at least the first two Schumann resonance modes should be detectable. Evidence of the first three Schumann resonance modes is present in the spectra of radio emission from the lightning detected in Martian dust storms.


title: Schumann resonances

text: It was long ago suggested that lightning discharges may occur on Titan, but recent data from Cassini–Huygens seems to indicate that there is no lightning activity on this largest satellite of Saturn. Due to the recent interest in Titan, associated with the Cassini–Huygens mission, its ionosphere is perhaps the most thoroughly modeled today. Schumann resonances on Titan have received more attention than on any other celestial body, in works by Besser et al. [2002], Morente et al. [2003], Molina-Cuberos et al. [2004], Nickolaenko et al. [2003], and Pechony and Price [2004]. It appears that only the first Schumann resonance mode might be detectable on Titan.


title: Schumann resonances

text: Since the landing of the Huygens probe on Titan's surface in January 2005, there have been many reports on observations and theory of an atypical Schumann resonance on Titan. After several tens of fly-bys by Cassini, neither lightning nor thunderstorms were detected in Titan's atmosphere. Scientists therefore proposed another source of electrical excitation: induction of ionospheric currents by Saturn's co-rotating magnetosphere. All data and theoretical models comply with a Schumann resonance, the second eigenmode of which was observed by the Huygens probe. The most important result of this is the proof of existence of a buried liquid water-ammonia ocean under a few tens of km of the icy subsurface crust.


title: Schumann resonances

text: Lightning activity has been optically detected on Jupiter. Existence of lightning activity on that planet was predicted by Bar-Nun [1975] and it is now supported by data from Galileo, Voyagers 1 and 2, Pioneers 10 and 11, and Cassini. Saturn is also confirmed to have lightning activity. Though three visiting spacecraft (Pioneer 11 in 1979, Voyager 1 in 1980, and Voyager 2 in 1981) failed to provide any convincing evidence from optical observations, in July 2012 the Cassini spacecraft detected visible lightning flashes, and electromagnetic sensors aboard the spacecraft detected signatures that are characteristic of lightning.


title: Schumann resonances

text: Little is known about the electrical parameters of the interior of Jupiter or Saturn. Even the question of what should serve as the lower waveguide boundary is a non-trivial one in case of the gaseous planets. There seem to be no works dedicated to Schumann resonances on Saturn. To date there has been only one attempt to model Schumann resonances on Jupiter.


title: Schumann resonances

text: Here, the electrical conductivity profile within the gaseous atmosphere of Jupiter was calculated using methods similar to those used to model stellar interiors, and it was pointed out that the same methods could be easily extended to the other gas giants Saturn, Uranus and Neptune. Given the intense lightning activity at Jupiter, the Schumann resonances should be easily detectable with a sensor suitably positioned within the planetary-ionospheric cavity.


title: Color theory

text: In the visual arts, color theory is the body of practical guidance for color mixing and the visual effects of a specific color combination. Color terminology based on the color wheel and its geometry separates colors into primary color, secondary color, and tertiary color. The understanding of color theory dates to antiquity. Aristotle (d. 322 BCE) and Claudius Ptolemy (d. 168 CE) already discussed which and how colors can be produced by mixing other colors. The influence of light on color was investigated and revealed further by al-Kindi (d. 873) and Ibn al-Haytham (d.1039). Ibn Sina (d. 1037), Nasir al-Din al-Tusi (d. 1274), and Robert Grosseteste (d. 1253) discovered that contrary to the teachings of Aristotle, there are multiple color paths to get from black to white. More modern approaches to color theory principles can be found in the writings of Leone Battista Alberti (c. 1435) and the notebooks of Leonardo da Vinci (c. 1490). A formalization of "color theory" began in the 18th century, initially within a partisan controversy over Isaac Newton's theory of color ("Opticks", 1704) and the nature of primary colors. From there it developed as an independent artistic tradition with only superficial reference to colorimetry and vision science.


title: Color theory

text: The foundations of pre-20th-century color theory were built around "pure" or ideal colors, characterized by different sensory experiences rather than attributes of the physical world. This has led to several inaccuracies in traditional color theory principles that are not always remedied in modern formulations.


title: Color theory

text: Another issue has been the tendency to describe color effects holistically or categorically, for example as a contrast between "yellow" and "blue" conceived as generic colors, when most color effects are due to contrasts on three relative attributes which define all colors:


title: Color theory

text: The visual impact of "yellow" vs. "blue" hues in visual design depends on the relative lightness and saturation of the hues.


title: Color theory

text: These confusions are partly historical and arose in scientific uncertainty about the color perception that was not resolved until the late 19th-century when the artistic notions were already entrenched. They also arise from the attempt to describe the highly contextual and flexible behavior of color perception in terms of abstract color sensations that can be generated equivalently by any visual media.


title: Color theory

text: Many historical "color theorists" have assumed that three "pure" primary colors can mix into "all possible colors", and any failure of specific paints or inks to match this ideal performance is due to the impurity or imperfection of the colorants. In reality, only imaginary "primary colors" used in colorimetry can "mix" or quantify all visible (perceptually possible) colors; but to do this, these imaginary primaries are defined as lying outside the range of visible colors; i.e., they cannot be seen. Any three real "primary" colors of light, paint or ink can mix only a limited range of colors, called a gamut, which is always smaller (contains fewer colors) than the full range of colors humans can perceive.


title: Color theory

text: Color theory was originally formulated in terms of three "primary" or "primitive" colors—red, yellow and blue (RYB)—because these colors were believed capable of mixing all other colors.


title: Color theory

text: The RYB primary colors became the foundation of 18th-century theories of color vision, as the fundamental sensory qualities that are blended in the perception of all physical colors, and conversely, in the physical mixture of pigments or dyes. These theories were enhanced by 18th-century investigations of a variety of purely psychological color effects, in particular the contrast between "complementary" or opposing hues that are produced by color afterimages and in the contrasting shadows in colored light. These ideas and many personal color observations were summarized in two founding documents in color theory: the "Theory of Colours" (1810) by the German poet Johann Wolfgang von Goethe, and "The Law of Simultaneous Color Contrast" (1839) by the French industrial chemist Michel Eugène Chevreul. Charles Hayter published "A New Practical Treatise on the Three Primitive Colours Assumed as a Perfect System of Rudimentary Information" (London 1826), in which he described how all colors could be obtained from just three.


title: Color theory

text: Subsequently, German and English scientists established in the late 19th century that color perception is best described in terms of a different set of primary colors—red, green and blue-violet (RGB)—modeled through the additive mixture of three monochromatic lights. Subsequent research anchored these primary colors in the differing responses to light by three types of color receptors or "cones" in the retina (trichromacy). On this basis the quantitative description of the color mixture or colorimetry developed in the early 20th century, along with a series of increasingly sophisticated models of color space and color perception, such as the opponent process theory.


title: Color theory

text: Across the same period, industrial chemistry radically expanded the color range of lightfast synthetic pigments, allowing for substantially improved saturation in color mixtures of dyes, paints, and inks. It also created the dyes and chemical processes necessary for color photography. As a result, three-color printing became aesthetically and economically feasible in mass printed media, and the artists' color theory was adapted to primary colors most effective in inks or photographic dyes: cyan, magenta, and yellow (CMY). (In printing, dark colors are supplemented by black ink, known as the CMYK system; in both printing and photography, white is provided by the color of the paper.) These CMY primary colors were reconciled with the RGB primaries, and subtractive color mixing with additive color mixing, by defining the CMY primaries as substances that "absorbed" only one of the retinal primary colors: cyan absorbs only red (−R+G+B), magenta only green (+R−G+B), and yellow only blue-violet (+R+G−B). It is important to add that the CMYK, or process, color printing is meant as an economical way of producing a wide range of colors for printing, but is deficient in reproducing certain colors, notably orange and slightly deficient in reproducing purples. A wider range of colors can be obtained with the addition of other colors to the printing process, such as in Pantone's Hexachrome printing ink system (six colors), among others.


title: Color theory

text: For much of the 19th-century artistic color theory either lagged behind scientific understanding or was augmented by science books written for the lay public, in particular "Modern Chromatics" (1879) by the American physicist Ogden Rood, and early color atlases developed by Albert Munsell ("Munsell Book of Color", 1915, see Munsell color system) and Wilhelm Ostwald (Color Atlas, 1919). Major advances were made in the early 20th century by artists teaching or associated with the German Bauhaus, in particular Wassily Kandinsky, Johannes Itten, Faber Birren and Josef Albers, whose writings mix speculation with an empirical or demonstration-based study of color design principles.


title: Color theory

text: For the mixing of colored light, Isaac Newton's color wheel is often used to describe complementary colors, which are colors that cancel each other's hue to produce an achromatic (white, gray or black) light mixture. Newton offered as a conjecture that colors exactly opposite one another on the hue circle cancel out each other's hue; this concept was demonstrated more thoroughly in the 19th century. An example of complementary colors would be red and green


title: Color theory

text: A key assumption in Newton's hue circle was that the "fiery" or maximum saturated hues are located on the outer circumference of the circle, while achromatic white is at the center. Then the saturation of the mixture of two spectral hues was predicted by the straight line between them; the mixture of three colors was predicted by the "center of gravity" or centroid of three triangle points, and so on.


title: Color theory

text: According to traditional color theory based on subtractive primary colors and the RYB color model, yellow mixed with purple, orange mixed with blue, or red mixed with green produces an equivalent gray and are the painter's complementary colors. These contrasts form the basis of Chevreul's law of color contrast: colors that appear together will be altered as if mixed with the complementary color of the other color. A piece of yellow fabric placed on a blue background will appear tinted orange because orange is the complementary color to blue.


title: Color theory

text: However, when complementary colors are chosen based on the definition by light mixture, they are not the same as the artists' primary colors. This discrepancy becomes important when color theory is applied across media. Digital color management uses a hue circle defined according to additive primary colors (the RGB color model), as the colors in a computer monitor are additive mixtures of light, not subtractive mixtures of paints.


title: Color theory

text: One reason the artist's primary colors work at all is due to the imperfect pigments being used have sloped absorption curves and change color with concentration. A pigment that is pure red at high concentrations can behave more like magenta at low concentrations. This allows it to make purples that would otherwise be impossible. Likewise, a blue that is ultramarine at high concentrations appears cyan at low concentrations, allowing it to be used to mix green. Chromium red pigments can appear orange, and then yellow, as the concentration is reduced. It is even possible to mix very low concentrations of the blue mentioned and the chromium red to get a greenish color. This works much better with oil colors than it does with watercolors and dyes.


title: Color theory

text: The old primaries depend on sloped absorption curves and pigment leakages to work, while newer scientifically derived ones depend solely on controlling the amount of absorption in certain parts of the spectrum.


title: Color theory

text: Another reason the correct primary colors were not used by early artists is they were not available as durable pigments. Modern methods in chemistry were needed to produce them.


title: Color theory

text: The distinction between "warm" and "cool" colors has been important since at least the late 18th century. The difference (as traced by etymologies in the Oxford English Dictionary), seems related to the observed contrast in landscape light, between the "warm" colors associated with daylight or sunset, and the "cool" colors associated with a gray or overcast day. Warm colors are often said to be hues from red through yellow, browns, and tans included; cool colors are often said to be the hues from blue-green through blue violet, most grays included. There is a historical disagreement about the colors that anchor the polarity, but 19th-century sources put the peak contrast between red-orange and greenish-blue.


title: Color theory

text: Color theory has described perceptual and psychological effects to this contrast. Warm colors are said to advance or appear more active in a painting, while cool colors tend to recede; used in interior design or fashion, warm colors are said to arouse or stimulate the viewer, while cool colors calm and relax. Most of these effects, to the extent they are real, can be attributed to the higher saturation and lighter value of warm pigments in contrast to cool pigments; brown is a dark, unsaturated warm color that few people think of as visually active or psychologically arousing.


title: Color theory

text: The traditional warm/cool association of a color is reversed relative to the color temperature of a theoretical radiating black body; the hottest stars radiate blue (cool) light, and the coolest radiate red (warm) light.


title: Color theory

text: This contrast is further seen in the psychological associations of colors with the Doppler effect seen in astronomical objects. Traditional psychological associations, where warm colors are associated with advancing objects and cool colors with receding objects, are directly opposite those seen in astrophysics, where stars or galaxies moving towards our viewpoint on Earth are blueshifted (advancing) and stars or galaxies moving away from Earth are redshifted (receding).


title: Color theory

text: Any color that lacks strong chromatic content is said to be "unsaturated", "achromatic", "near-neutral", or "neutral". Near neutrals include browns, tans, pastels, and darker colors. Near neutrals can be of any hue or lightness. Pure achromatic, or "neutral" colors include black, white and all grays.


title: Color theory

text: "Near neutrals" are obtained by mixing pure colors with white, black or grey, or by mixing two complementary colors. In color theory, neutral colors are easily modified by adjacent more saturated colors, and they appear to take on the hue complementary to the saturated color; e.g., next to a bright red couch, a gray wall will appear distinctly greenish, this is a property of human vision.


title: Color theory

text: Black and white have long been known to combine "well" with almost any other colors; black decreases the apparent "saturation" or "brightness" of colors paired with it and white shows off all hues to equal effect.


title: Color theory

text: When mixing colored light (additive color models), the achromatic mixture of spectrally balanced red, green, and blue (RGB) is always white, not gray or black. When we mix colorants, such as the pigments in paint mixtures, a color is produced which is always darker and lower in chroma, or saturation, than the parent colors. This moves the mixed color toward a neutral color—a gray or near-black. Lights are made brighter or dimmer by adjusting their brightness, or energy level; in painting, lightness is adjusted through mixture with white, black, or a color's complement.


title: Color theory

text: It is common among some painters to darken a paint color by adding black paint—producing colors called "shades"—or lighten a color by adding white—producing colors called "tints". However, it is not always the best way for representational painting, as an unfortunate result is for colors to also shift in hue. For instance, darkening a color by adding black can cause colors such as yellows, reds, and oranges, to shift toward the greenish or bluish part of the spectrum. Lightening a color by adding white can cause a shift towards blue when mixed with reds and oranges. Another practice when darkening a color is to use its opposite, or complementary, color (e.g. purplish-red added to yellowish-green) in order to neutralize it without a shift in hue and darken it if the additive color is darker than the parent color. When lightening a color this hue shift can be corrected with the addition of a small amount of an adjacent color to bring the hue of the mixture back in line with the parent color (e.g. adding a small amount of orange to a mixture of red and white will correct the tendency of this mixture to shift slightly towards the blue end of the spectrum).


title: Color theory

text: In painting and other visual arts, two-dimensional color wheels or three-dimensional color solids are used as tools to teach beginners the essential relationships between colors. The organization of colors in a particular color model depends on the purpose of that model: some models show relationships based on human color perception, whereas others are based on the color mixing properties of a particular medium such as a computer display or set of paints.


title: Color theory

text: The split-primary palette, also called color-bias theory, is a color-wheel model that attempts to explain, and to compensate for, the unsatisfactory results sometimes produced when mixing the traditional primary colors, red, yellow, and blue.


title: Color theory

text: Painters have long considered red, yellow, and blue to be primary colors. In practice, however, many of the mixtures produced from these colors lack chromatic intensity. Rather than adopting a more satisfactory set of primary colors, proponents of split-primary theory explain this lack of chroma by the purported presence of chemical impurities, small amounts of other colors, in the paints, or biases away from the ideal primary toward one or the other of the adjacent colors. Every red paint, for example, is said to be tainted with, or biased toward, either blue or yellow, every blue paint toward either red or green, and every yellow toward either green or orange. These biases are thought to result in mixtures that contain sets of complementary colors, darkening the resulting color. In order to obtain vivid mixed colors, according to split-primary theory, it is necessary to employ the primary colors whose biases both fall in the direction, on the color wheel, of the color to be mixed, combining, for example, green-biased blue with green-biased yellow to make bright green.


title: Color theory

text: Though widely accepted and taught, the split-primary system is based on false assumptions. The perceived bias of colors is not due to chemical impurities. Rather, the color of any given colorant is inherent to its chemical and physical properties, the purity of such a chemical being unrelated to whether it conforms to our arbitrary conception of an ideal hue. Moreover, the identity of gamut-optimizing primary colors is determined by human color vision. Although no set of three primaries can be mixed to obtain the complete color gamut perceived by humans, red, yellow, and blue are a poor choice if high chroma mixtures are desired. From their incorrect premises, proponents of split-primary theory conclude that extra colors are needed in order to mix a wide gamut of high-chroma colors, an idea belied by the longtime success of three-color photographic printing.


title: Color theory

text: Although flawed in principle, the split-primary system can be successful in practice, because the recommended blue-biased red and green-biased blue positions are often filled by near approximations of magenta and cyan, while orange-biased red and violet-biased blue serve as secondary colors, which may widen the gamut even further.


title: Color theory

text: This system is still popular among contemporary painters, as it is basically a simplified version of Newton's geometrical rule that colors closer together on the hue circle will produce more vibrant mixtures. However, with the range of contemporary paints available, many artists simply add more paints to their palette as desired for a variety of practical reasons. For example, they may add a scarlet, purple and/or green paint to expand the mixable gamut; and they include one or more dark colors (especially "earth" colors such as yellow ochre or burnt sienna) simply because they are convenient to have premixed. Printers commonly augment a CMYK palette with spot (trademark specific) ink colors.


title: Color theory

text: It has been suggested that "Colors seen together to produce a pleasing affective response are said to be in harmony". However, color harmony is a complex notion because human responses to color are both affective and cognitive, involving emotional response and judgment. Hence, our responses to color and the notion of color harmony is open to the influence of a range of different factors. These factors include individual differences (such as age, gender, personal preference, affective state, etc.) as well as cultural, sub-cultural, and socially-based differences which gives rise to conditioning and learned responses about color. In addition, context always has an influence on responses about color and the notion of color harmony, and this concept is also influenced by temporal factors (such as changing trends) and perceptual factors (such as simultaneous contrast) which may impinge on human response to color. The following conceptual model illustrates this 21st-century approach to color harmony:


title: Color theory

text: wherein color harmony is a function ("f") of the interaction between color/s (Col 1, 2, 3, …, "n") and the factors that influence positive aesthetic response to color: individual differences ("ID") such as age, gender, personality and affective state; cultural experiences ("CE"), the prevailing context ("CX") which includes setting and ambient lighting; intervening perceptual effects ("P") and the effects of time ("T") in terms of prevailing social trends.


title: Color theory

text: In addition, given that humans can perceive over 2.8 million different colors, it has been suggested that the number of possible color combinations is virtually infinite thereby implying that predictive color harmony formulae are fundamentally unsound. Despite this, many color theorists have devised formulae, principles or guidelines for color combination with the aim being to predict or specify positive aesthetic response or "color harmony".


title: Color theory

text: Color wheel models have often been used as a basis for color combination principles or guidelines and for defining relationships between colors. Some theorists and artists believe juxtapositions of complementary color will produce strong contrast, a sense of visual tension as well as "color harmony"; while others believe juxtapositions of analogous colors will elicit a positive aesthetic response. Color combination guidelines (or formulas) suggest that colors next to each other on the color wheel model (analogous colors) tend to produce a single-hued or monochromatic color experience and some theorists also refer to these as "simple harmonies".


title: Color theory

text: In addition, split complementary color schemes usually depict a modified complementary pair, with instead of the "true" second color being chosen, a range of analogous hues around it are chosen, i.e. the split complements of red are blue-green and yellow-green. A triadic color scheme adopts any three colors approximately equidistant around a color wheel model. Feisner and Mahnke are among a number of authors who provide color combination guidelines in greater detail.


title: Color theory

text: Color combination formulae and principles may provide some guidance but have limited practical application. This is due to the influence of contextual, perceptual, and temporal factors which will influence how color/s are perceived in any given situation, setting, or context. Such formulae and principles may be useful in fashion, interior and graphic design, but much depends on the tastes, lifestyle, and cultural norms of the viewer or consumer.


title: Color theory

text: As early as the ancient Greek philosophers, many theorists have devised color associations and linked particular connotative meanings to specific colors. However, connotative color associations and color symbolism tends to be culture-bound and may also vary across different contexts and circumstances. For example, red has many different connotative and symbolic meanings from exciting, arousing, sensual, romantic, and feminine; to a symbol of good luck; and also acts as a signal of danger. Such color associations tend to be learned and do not necessarily hold irrespective of individual and cultural differences or contextual, temporal or perceptual factors. It is important to note that while color symbolism and color associations exist, their existence does not provide evidential support for color psychology or claims that color has therapeutic properties.


title: Color theory

text: The monochromatic formula chooses only one color (or hue). Variations of the color are created by changing the value and saturation of the color. Since only one hue is used, the color and its variations are guaranteed to work.