title: Renaissance Center

text: In July 2015, the complex was re-branded as "The GMRENCEN." Its logo was modernized and "Reflecting a New Detroit" was introduced as the new tagline. A photo-journalistic advertising campaign launched to "shine a spotlight on the people in Detroit who make remarkable contributions" to the city.


title: Renaissance Center

text: Despite the name, the hotel portion is not affiliated with the Renaissance Hotels chain, also owned by Marriott. An unrelated Renaissance Hotel does exist in the suburb of Novi however.


title: Renaissance Center

text: The idea was first conceived by Henry Ford II, the Ford Motor Company Chairman of the time. In 1970, to bring his idea to life, Ford teamed up with other business leaders to form the Detroit Renaissance. This was a private non-profit development organization which Ford headed in order to stimulate building activity and revitalize the economy of Detroit. Henry Ford II sold the concept of the RenCen to the City and community leaders. Detroit Mayor Roman Gribbs touted the project as "a complete rebuilding from bridge to bridge," referring to the area between the Ambassador Bridge, that connects Detroit to Windsor, Ontario, and the MacArthur Bridge, which connects the city with Belle Isle Park.


title: Renaissance Center

text: The Detroit Renaissance announced the first phase of construction in 1971, receiving primary financing from the Ford Motor Company. It soon became the world's largest private development with an anticipated 1971 cost of $500 million. The principal architect was John Portman, the architect behind the Westin Peachtree Plaza Hotel and the Peachtree Center in Atlanta, Georgia; the Embarcadero Center in San Francisco, California; and the Bonaventure Hotel in Los Angeles, California.


title: Renaissance Center

text: The "city within a city" arose. The first phase of Renaissance Center opened on July 1, 1976. For phase I, the facade of the first five towers was covered with of glass, and used about of concrete. This did not include the additional glass used for the atriums. It also cost $337 million to construct, employing 7,000 workers. The heating and cooling systems for the buildings were housed in two-story concrete berms facing Jefferson Avenue. Other phases that included residences, additional office and retail space were never constructed.


title: Renaissance Center

text: When the Renaissance Center opened, the cylindrical central tower was originally the flagship of Westin Hotels. The top three floors of the hotel hosted an upscale restaurant, The Summit, that rotated to allow a 360 degree view. The shopping center in the podium originally housed high-end boutiques, but now contains a greater complement of restaurants in the retail mix.


title: Renaissance Center

text: In 1977, managed by Western International Hotels, the central hotel tower of the Renaissance Center opened as the Detroit Plaza Hotel. It became the world's tallest all-hotel skyscraper surpassing its architectural twin, the Westin Peachtree Plaza Hotel in Atlanta. The hotel was later renamed The Westin Hotel Renaissance Center Detroit. In 1986, it was surpassed in height by The Westin Stamford in Singapore. Since, the Renaissance Center's central tower has held the distinction as the tallest all-hotel skyscraper in the Western Hemisphere.


title: Renaissance Center

text: On April 15, 1977, Henry Ford II and Detroit mayor Coleman Young unveiled a plaque commemorating the private investors whose funds made the project possible. Later that evening, 650 business and society leaders attended a benefit to celebrate the Renaissance Center's formal dedication. The money raised from the $300-per-couple tickets went to the Detroit Symphony Orchestra.


title: Renaissance Center

text: In 1980, Detroit hosted the Republican National Convention, during this event both presidential nominee Ronald Reagan and former President Gerald Ford stayed at the Renaissance Center.


title: Renaissance Center

text: The "city within a city" concept was duplicated in the suburb of Southfield, when the Southfield Town Center office complex - with five inter-connected golden skyscrapers and an overall area of - was constructed from 1975 to 1989. In the ensuing years, the Renaissance Center would face competition from the growing suburban office market.


title: Renaissance Center

text: In 1987, the elevated Detroit People Mover transit line began operation with a stop at the Renaissance Center.


title: Renaissance Center

text: In 1996, General Motors purchased the complex and moved its world headquarters from what is now the historic Cadillac Place state office complex in the New Center district, to the Renaissance Center, in downtown Detroit. Meanwhile, Ford Motor Company maintained offices in one of the towers in the center. Before the acquisition, Sibley's Shoes had its headquarters in the center.


title: Renaissance Center

text: Architects' initial design for the Renaissance Center focused on creating secure "interior spaces", while its design later expanded and improved to connect with the exterior spaces and waterfront through a reconfigured interior, open glass entryways, and a winter garden. By 2004, GM completed an extensive $500 million renovation of the Renaissance Center. This included a $100 million makeover for the hotel. Among GM's first actions was to remove the concrete berms facing Jefferson Avenue. The renovation includes a lighted glass walkway which encircles the interior mezzanine for ease of navigation, while the addition of the winter garden provides riverfront access and a view of Canada. A covered skyway over Jefferson Avenue connects to the Millender Center, Courtyard by Marriott - Downtown Detroit, and Coleman A. Young Municipal Center.


title: Renaissance Center

text: In July 2010, Blue Cross Blue Shield of Michigan announced plans to lease of Tower 500 and Tower 600 and relocate 3,000 of its employees from its building in Southfield, Michigan.


title: Renaissance Center

text: In January 2015, General Motors announced its intent to renovate much of the complex to make it more inviting as a destination for visitors to Detroit.


title: Renaissance Center

text: The Renaissance Center is owned by General Motors. The hotel in the central tower is now managed by the Marriott hotel chain and is called the Detroit Marriott at the Renaissance Center. The 1,298-room hotel is one of the largest operated by Marriott. The rooftop restaurant (which previously had revolved) received a $10 million renovation and was operated by The Epicurean Groups's Coach Insignia (closed in 2017). It served Coach wines, a product of the Fisher family whose legacy includes Fisher Body, a name which is part of GM history.


title: Renaissance Center

text: The Renaissance Center's renovation provides for the prospect of continued development and restorations throughout the city. Architectural critics have touted the city's architecture as among North America's finest.


title: Renaissance Center

text: In its first year of operation it generated over $1 billion in economic growth for the downtown. Detroit Renaissance continued to interact with the city, by contributing to a variety of projects within the downtown area in the ensuing decades.


title: Renaissance Center

text: The Renaissance Center is a riverfront property located along the Detroit River. Approximately one-mile north of the center are Comerica Park and Ford Field, the respective venues for the Detroit Tigers and Detroit Lions. The US portal of the Detroit-Windsor Tunnel emerges adjacent to the western boundary of the Renaissance Center. The Renaissance Center is also a station on the Detroit People Mover. Additionally a pedestrian skyway, over Jefferson Avenue, connects the complex to the Millender Center. Several blocks to the west of the Renaissance Center, along Jefferson Avenue, there are the Coleman A. Young Municipal Center, Hart Plaza, TCF Center (formerly Cobo Center, home to events such as the North American International Auto Show and Youmacon) and the Joe Louis Arena (former home of the Detroit Red Wings). The University of Detroit Mercy School of Law is located just across Jefferson Avenue. The Renaissance Center's modernist architecture balances the city's panoramic waterfront skyline, a frequent feature in photography taken from Windsor, Ontario, across the river. From the top of Renaissance Center's previous Coach Insignia restaurant (closed in 2017), patrons were able to peer down upon the neogothic spires of the One Detroit Center and the city's Financial District skyscrapers and stadiums. The view from the top extended for in all directions.


title: Renaissance Center

text: The centerpiece is the 73-story 727-foot (221.5 m) luxury hotel with 1,246 rooms and 52 suites (1298 total guest rooms). Its height is measured from its main Wintergarden entrance on Atwater Street which faces the International Riverfront where the complex measures taller. Entirely owned by General Motors, the complex has of space. The main Renaissance Center complex rises from a site. The complex is designed in the modern architectural style with glass as a main material.


title: Renaissance Center

text: Famous for its cylindrical design, the central hotel tower's diameter is . A lighted glass walkway radiates the mezzanine level and encircles the base of cylindrical hotel tower for ease of navigation. This ringed glass walkway is about wide and has a circumference of approximately or about one-eighth of a mile around. The ringed walkway's diameter is approximately . It links to several other walkways in the complex. The five-story Wintergarden atrium leads into the central area which has an eight-story atrium lobby with rounded concrete balconies and terraces. The Highlands is located on Floors 71 through 73, which includes a restaurant, scotch bar, and special events space. The hotel has no floors labeled 7, 8, or 13. The hotel features a major conference center with of meeting space including a Renaissance Ballroom for up to 2,200 guests with for events, one of the largest in the United States.


title: Renaissance Center

text: John Portman designed the five-building rosette with "interior spaces." In 1977, its central tower opened as the tallest hotel in the world. It remains the tallest all hotel skyscraper in the Western Hemisphere. The smaller cylinders on sides of all the towers house the elevators. The four surrounding 39-story office towers (100–400) each reach 522 feet (159 m) and have a total of of space. Each 39-story tower has a base five-story podium structure with for retail space for a total of . A portion of the central atrium area houses "GM World", a showcase for GM vehicles. Two 21-story towers (500–600), designed by Portman and constructed in 1981, reach 339 feet (103 m). GM gained control of Towers 500 and 600 in 2001. Tower 500 has of office space and an additional of retail space. Tower 600 has of office space and an additional of retail space.


title: Renaissance Center

text: Towers 100 and 200 front Jefferson Avenue. Towers 300 and 400 are on the main Wintergarden/Atwater Street entrance facing the Riverfront. The GM Renaissance Conference Center is located on the second floor of tower 300.


title: Renaissance Center

text: In December 2001, the General Motors unveiled the "Wintergarden" retail atrium. Designed by Skidmore, Owings & Merrill, it rises tall at its highest point opening direct access to the International Riverfront. In addition, the atrium contains of retail space and of contiguous main floor exhibit space which was used by the media during Super Bowl XL.


title: Renaissance Center

text: The design is consistent with the themes of Brutalist architecture, especially in the heavy massing of concrete on the lower floors, but the 2001 renovation has softened those features.


title: Renaissance Center

text: The redevelopment project included the work of many different architects including Skidmore, Owings & Merrill of Chicago, SmithGroup of Detroit, and Ghafari Associates of Dearborn who did the renovation of the office towers. The majority of the construction operations were led by Turner Construction Company. The structural glass and steel for the Wintergarden, the entrance lobby as well as the mezzanine glass walkway were contributed by Mero. The cost of the renovation does not include the cost for reconfiguring the streets around the Renaissance Center or the cost of the park along the International Riverfront.


title: Renaissance Center

text: The $500 million renovation of the Renaissance Center completed in 2003 has helped improve Detroit's economy. Together, GM's renovation of the Renaissance Center and the Detroit Riverwalk exceeded $1 billion; the project constituted a substantial investment in downtown. More than 10,000 people (of whom 6,000 are GM employees) work in the complex. Nearly 2,000 state workers now occupy GM's former office building, the restored Cadillac Place, in the historic New Center district.


title: Renaissance Center

text: The Wintergarden added to the Renaissance Center faces the Riverfront and provides panoramic views of the Windsor skyline. The complex connects offices, the hotel, retail specialty shops, restaurants, a jazz club, and a movie theater. The theater has since closed and been converted to offices. A pedestrian-friendly glass entryway has replaced the former concrete berms along Jefferson Avenue. The redevelopment provides the "GM World" display of vehicles, a restored hotel, a renovated rooftop restaurant, and the addition of GM's corporate logo to crown the top of the building. Construction of the lighted glass walkway facilitates ease of navigation encircling the interior mezzanine. Hines completed redevelopment of Towers 500 and 600 for GM in 2004.


title: Renaissance Center

text: The Riverfront Promenade was dedicated on December 17, 2004, and helped to usher in a return to recreational uses along Detroit's International Riverfront. GM played a key role in the transformation of the east riverfront with a donation of $135 million to the Detroit Riverfront Conservancy for the development of a world class riverfront promenade planned at $559 million, which included $50 million from the Kresge foundation. In 2011, the Detroit Wayne County Port Authority opened its new state of the art cruise ship dock and passenger terminal on Hart Plaza, adjacent to the Renaissance Center. Port authority bonds financed another 1,500 space parking garage adjacent to the Renaissance Center. Further upriver, the Roberts Riverwalk Hotel faces the east riverfront. In addition to the gradual continuation of the riverfront promenade, other planned projects complementing the Renaissance Center continue along the International Riverfont which include development of luxury condominiums, a cruise ship passenger terminal, retail, and entertainment venues.


title: Renaissance Center

text: In 2011, the Renaissance Center added colored LED lighting on the top of its towers (Towers 500 and 600 utilize traditional blue floodlights to illuminate their top floors). General Motors added a large illuminated LED corporate logo which also displays GM divisions. The animated logo and illuminated LED color bands around the towers can be used to support special events and may be seen from Comerica Park, home of the Detroit Tigers. The renovation of TCF Center convention and exhibit facility incorporates similar blue neon lighting along riverfront promenade.


title: Renaissance Center

text: In June 2015 the Ren Cen 4 Theatres theater complex announced that it was closing. With the end of Ren Cen 4, the city of Detroit has one first-run theater remaining, along with three independent theaters.


title: Renaissance Center

text: In July 2007 portions of Asian Village, a development of restaurants in Suite 2653 in the GM Center (200 Renaissance Center) with Asian cuisine offered, opened. The center was designed to evoke street food stalls within East and Southeast Asia.


title: Renaissance Center

text: The opening scenes of "Thunder in the Skies", the seventh episode of the BBC science-history documentary "Connections" by James Burke, were visibly filmed in the then-new Renaissance Center (1978).


title: Renaissance Center

text: In the film "Collision Course" starring Jay Leno and Pat Morita, the Renaissance Center is featured when Morita's character and Leno meet for the first time; Morita is considered a suspect and chased through the hotel (1989).


title: Renaissance Center

text: The 2008 crime thriller "Killshot" features an opening scene in which Mickey Rourke drives a blue Cadillac along Jefferson Avenue in Downtown Detroit where, in his role as hired hitman Armand Degas - nicknamed "Blackbird" - he enters the Marriott Hotel in the Renaissance Center to assassinate a mafia leader called "Papa", played by actor Hal Holbrook.


title: Renaissance Center

text: The film "Bird on a Wire" (starring Mel Gibson and Goldie Hawn) shot a chase scene inside the Renaissance Center (1990).


title: Renaissance Center

text: The opening scene of "Renaissance Man" shows Danny DeVito driving down Jefferson Avenue, late for a business meeting at the Renaissance Center, when he receives the phone call that fires him from his job. (1994).


title: Renaissance Center

text: In the Steven Soderbergh film adaptation of "Out of Sight", the main characters meet in the revolving restaurant atop the Renaissance Center. The scene was filmed on location (1998).


title: Renaissance Center

text: The Renaissance Center was featured in the Kevin Costner and Joan Allen film "The Upside of Anger". Costner's character plays a DJ for WRIF 101 FM, a real Detroit FM rock station, whose studio (in the film) is housed in the Renaissance Center (2004).


title: Renaissance Center

text: For the 2005 Major League Baseball All-Star Game, which was played at Comerica Park in Detroit, the center tower of the Renaissance Center was wrapped with an image of a large baseball smashing into the tower, with "4,612 FT" written below it to indicate the distance from home plate at Comerica Park. For Super Bowl XL, held at Detroit's Ford Field on February 5, 2006, a large National Football League logo was wrapped around the main tower just beneath the GM logo.


title: Renaissance Center

text: The Renaissance Center also hosted the major media for Super Bowl XL. GM offered the Wintergarden a venue for the annual Fash Bash, a fashion event and fundraiser coordinated by the Detroit Institute of Arts.


title: Renaissance Center

text: In a book by Adrian Humphreys titled "The Weasel: A Double Life in the Mob", the former driver of Jimmy Hoffa and a mob associate Marvin "The Weasel" Elkind stated that Hoffa is buried in the foundations of the Renaissance Center (2011).


title: Renaissance Center

text: The series finale of "Motor City Masters" was filmed in the GM World exhibit in the lower level of the Renaissance Center in 2014.


title: Renaissance Center

text: The alternate cover of the Eminem album "Recovery" features the Renaissance Center in the background.


title: Perfect is the enemy of good

text: Perfect is the enemy of good is an aphorism which means insistence on perfection often prevents implementation of good improvements. The Pareto principle or 80–20 rule explains this numerically. For example, it commonly takes 20% of the full time to complete 80% of a task while to complete the last 20% of a task takes 80% of the effort. Achieving absolute perfection may be impossible and so, as increasing effort results in diminishing returns, further activity becomes increasingly inefficient.


title: Perfect is the enemy of good

text: In the English-speaking world the aphorism is commonly attributed to Voltaire, who quoted an Italian proverb in his "Questions sur l'Encyclopédie" in 1770: "". It subsequently appeared in his moral poem, , which starts


title: Perfect is the enemy of good

text: Aristotle and other classical philosophers propounded the principle of the golden mean which counsels against extremism in general.


title: Perfect is the enemy of good

text: Its sense in English literature can be traced back to Shakespeare, In his tragedy, "King Lear" (1606), the Duke of Albany warns of "striving to better, oft we mar what's well" and in Sonnet 103:


title: Perfect is the enemy of good

text: The 1893 "Dictionary of Quotations from Ancient and Modern, English and Foreign Sources" lists a similar proverb, which it claims is of Chinese provenance: "Better a diamond with a flaw than a pebble without one."


title: Perfect is the enemy of good

text: More recent applications include Robert Watson-Watt propounding a "cult of the imperfect", which he stated as "Give them the third best to go on with; the second best comes too late, the best never comes"; economist George Stigler's assertion that "If you never miss a plane, you're spending too much time at the airport"; and, in the field of computer program optimization, Donald Knuth's statement that "Premature optimization is the root of all evil".


title: Ronald Acuña Jr.

text: Ronald José Acuña Blanco Jr. (born December 18, 1997) is a Venezuelan professional baseball outfielder for the Atlanta Braves of Major League Baseball (MLB). After signing with the Braves as an international free agent in 2014, Acuña made his MLB debut in 2018, and won the National League Rookie of the Year Award. The next season, Acuña was named an MLB All-Star, was the NL stolen base leader, and won a Silver Slugger Award.


title: Ronald Acuña Jr.

text: Acuña signed with the Atlanta Braves for $100,000 as an international free agent in July 2014. He made his professional debut in 2015 with the Gulf Coast Braves and was later promoted to the Danville Braves that season. In 55 games between the two teams he batted .269 with four home runs, 18 RBIs, and 16 stolen bases.


title: Ronald Acuña Jr.

text: In 2016, he slashed .312/.392/.429 with four home runs and 19 RBIs in only 42 games combined between the Gulf Coast Braves and Rome Braves due to an injury. After the season, he played for the Melbourne Aces of the Australian Baseball League and was named an ABL All-Star. Acuña made his first appearances in Grapefruit League games at the start of the 2017 season as an extra player originally assigned to minor league camp. He began the year with the Florida Fire Frogs of the Class A-Advanced Florida State League and was later promoted to the Mississippi Braves of the Class AA Southern League. Acuña was named to the All-Star Futures Game roster in July, and played the whole game, one of three World Team members to do so. He reported to the Gwinnett Braves of the Class AAA International League immediately after the All-Star break, making his International League debut against the Charlotte Knights, during which he hit an opposite-field home run in his second at bat. For the year, Acuña appeared in 139 games, hitting .325/.374/.522 with 21 homers, 82 RBIs and 44 stolen bases.


title: Ronald Acuña Jr.

text: After the 2017 minor league regular season ended, Acuña was invited to join the Arizona Fall League and was assigned to the Peoria Javelinas. He played 23 games in the AFL hitting .325/.414/.639 alongside seven home runs, winning the league championship and claiming league MVP honors, becoming the AFL's youngest most valuable player.


title: Ronald Acuña Jr.

text: "Baseball America" ranked Acuña as the No. 1 Major League Baseball prospect heading into the 2018 season. MLB.com ranked him second to Japanese pitcher/hitter Shohei Ohtani. Acuña began the year at major league spring training. Despite a .432 average and four home runs in spring training, Acuña was reassigned to minor league camp on March 19, 2018. He reported to the Gwinnett Stripers to begin the 2018 season.


title: Ronald Acuña Jr.

text: On April 25, 2018, the Braves promoted Acuña to the major leagues. This made him the youngest player in Major League Baseball at that time, claiming the distinction from teammate Ozzie Albies. Though Acuña wore uniform number 24 throughout his minor league career in honor of Miguel Cabrera, he made his major league debut on April 25, 2018, wearing number 13. Against the Cincinnati Reds, Acuña collected his first career hit off Kevin Shackelford. He finished the game 1 for 5 and scored the game-tying run in the eighth inning as the Braves won 5–4. The next day, also against the Reds, Acuña hit his first MLB home run off Homer Bailey. He finished the game 3 for 4 as the Braves won 7–4. On May 28, Acuña was placed on the 10-day disabled list due to a mild ACL sprain and a bruise in his left knee as well as back contusion. On June 21, the Braves optioned Acuña to Triple-A Gwinnett for a rehab assignment.


title: Ronald Acuña Jr.

text: Acuña regularly hit in the leadoff spot in the lineup after the All-Star break. His performance improved markedly as he implemented an adjustment to his batting stance at the suggestion of Kevin Seitzer. While playing against the Miami Marlins on August 13, 2018, Acuña became the fourth player in the history of Major League Baseball to hit a home run to lead off both games of a doubleheader. Additionally, he had hit a home run in his last four games, becoming the youngest player since 1920 to accomplish the feat. By hitting a home run off Trevor Richards on August 14, Acuña became the youngest major leaguer ever to hit home runs in five consecutive games, as well as the fifth batter in Atlanta Braves history to do so. Facing Adam Conley later that same game, Acuña hit his second home run of the night, marking the first time he had ever hit more than one home run in a game.


title: Ronald Acuña Jr.

text: In the finale of the Braves' series against the Marlins on August 15, Acuña faced José Ureña, who hit him with the first pitch of the game. Ureña was ejected from the game, while Acuña was replaced in the field at the top of the second inning. Acuña played the Braves' next game against the Colorado Rockies on August 16. When Acuña next played the Marlins on August 23, he hit another home run, and was subsequently struck by another pitch. His production during the month of August won him the Major League Baseball Rookie of the Month Award. On September 2, Acuña hit his seventh leadoff home run, tying a Braves team record, set by Marquis Grissom, for such home runs in a season. Three days later, Acuña broke the team's leadoff home run record in a game against the Boston Red Sox. With his 25th home run on September 9, Acuña became the seventh player in MLB history to hit that many home runs while under the age of 21. Later that month, it was announced that Acuña would be playing in the MLB Japan All-Star Series scheduled for November. With his fifteenth stolen base on September 22, 2018, Acuña became the fourth player in MLB history to record a 25–15 season, while aged 20 or below, alongside Alex Rodriguez, Orlando Cepeda, and Mike Trout. Overall with the 2018 Braves, Acuña appeared in 111 MLB games, batting .293 with 26 home runs and 64 RBIs.


title: Ronald Acuña Jr.

text: On October 7, in a National League Division Series game against the Los Angeles Dodgers, Acuña became the youngest player in MLB history to hit a postseason grand slam, aged 20 years 293 days, off Dodgers pitcher Walker Buehler. On November 12, he was named the National League Rookie of the Year.


title: Ronald Acuña Jr.

text: On April 2, 2019, Acuña and the Braves agreed to an eight-year contract worth $100 million. The extension included team options for the 2027 and 2028 seasons. Aged 21, Acuña became the youngest player in baseball history to sign a contract worth at least $100 million. Acuña's deal was the largest for any player with less than one year of major league service. By June 2019, Acuña had drawn attention for his power production. At midseason, he was named a starting outfielder for the National League in the 2019 Major League Baseball All-Star Game, and invited to take part in that year's Home Run Derby.


title: Ronald Acuña Jr.

text: On August 9, Acuña hit his thirtieth home run of the 2019 season while facing Marlins pitcher Tayron Guerrero. Acuña joined the 30–30 club on August 24, in a game against the New York Mets. He became the second-youngest player to reach the milestone, after Mike Trout. With his fortieth home run on September 19, Acuña became the youngest major leaguer to enter the 40–30 club. He reported a minor injury in the penultimate series of the Braves' 2019 season, and was rested for the remainder of the regular season.


title: Ronald Acuña Jr.

text: For the year, Acuña hit .280/.365/.518/.883, with 127 runs (leading the National League), 41 home runs, and 37 stolen bases (leading the NL). Acuña missed the 40–40 club by three stolen bases. He led the major leagues in power-speed number (38.9). Acuña and teammates Ozzie Albies and Freddie Freeman won the 2019 National League Silver Slugger Awards for outfield, second base, and first base, respectively.


title: Ronald Acuña Jr.

text: During a season shortened by the COVID-19 pandemic, the Braves won the division for the third time in a row, earning a league-record 20th division title. Near the end of the season, Acuña hit a 495-foot home run against the Red Sox; it was the longest MLB home run that year and the longest home run ever hit at Truist Park. In 2020, he batted .250/.406/.581, with 14 home runs and 29 RBIs in 160 at bats and led the league in at bats per home run. He was awarded his second consecutive Silver Slugger Award and finished in twelfth place in voting for the Most Valuable Player Award.


title: Ronald Acuña Jr.

text: On May 3, Acuña was named National League Player of the Month for April, batting .341/.443/.705 with eight home runs, three stolen bases, 18 RBIs, and 25 runs scored in 24 games. On May 19, Acuña hit his first career walk-off home run against the New York Mets to give the Braves a 5–4 win.


title: Ronald Acuña Jr.

text: On July 10, 2021, Acuña suffered a leg injury while trying to field a fly ball and was taken off the field on a motorized stretcher. An MRI showed a complete tear in his right anterior cruciate ligament, which prematurely ended his 2021 season. In 82 games, Acuña hit .283/.394/.596 with 24 home runs, 52 RBIs and 17 stolen bases in 2021. In 2021, he had the fastest sprint speed of all major league right fielders, at 29.4 feet/second. He led the major leagues with 72 runs scored at the time of his injury. Acuña was elected to start the 2021 All-Star Game alongside teammates Freddie Freeman and Ozzie Albies but was unable to participate due to the injury. Despite Acuña's injury, the Braves went on to win the 2021 World Series.


title: Ronald Acuña Jr.

text: Acuña did not participate in spring training games, as rehabilitation from his leg injury continued into the 2022 season. Acuña remained at the Braves' spring training facility and played in simulated games until being assigned to the Gwinnett Stripers during the third week of April. He was activated from the injured list on April 27. Acuña received the most votes of any National League player and was duly selected as a starting outfielder for the 2022 Major League Baseball All-Star Game. On July 11, 2022, it was announced that Acuña would participate in the 2022 Home Run Derby.


title: Ronald Acuña Jr.

text: A powerful right-handed batter, Acuña has all round batting range. Former major league hitter Sean Casey compared Acuña's batting style to Roberto Clemente, as his natural core power and rotational torque allows him to hit without a backswing, and keeping the knob of the bat pointing down at home plate (normally pointing towards the catcher during the backswing), yet still making contact and maintaining control of the barrel.


title: Ronald Acuña Jr.

text: On the basepaths, Acuña starts off like an infielder with a more upright stance, or a running back standing with a slight bend of the knees and hands on the knees to generate greater acceleration. According to Harold Reynolds, who adopted the Rickey Henderson technique for both baserunning and fielding, the stance also stops him from leaning or tipping off fielders for base stealing.


title: Ronald Acuña Jr.

text: Acuña's grandfather, Romualdo Blanco, and father, Ronald Acuña Sr., both played minor league baseball. Acuña Sr. represented Venezuela at the 2011 Pan American Games. Acuña Jr. is the eldest of four sons. A younger brother, Luisangel, is a shortstop in the Texas Rangers organization. An uncle, José Escobar, played for the Cleveland Indians in 1991, and several cousins have also played in Major League Baseball, namely Vicente Campos, Alcides Escobar, Edwin Escobar, and Kelvim Escobar. His son was born in 2020.


title: Logo

text: A logo (abbreviation of logotype; ) is a graphic mark, emblem, or symbol used to aid and promote public identification and recognition. It may be of an abstract or figurative design or include the text of the name it represents as in a wordmark.


title: Logo

text: In the days of hot metal typesetting, a logotype was one word cast as a single piece of type (e.g. "The" in ATF Garamond), as opposed to a ligature, which is two or more letters joined, but not forming a word. By extension, the term was also used for a uniquely set and arranged typeface or colophon. At the level of mass communication and in common usage, a company's logo is today often synonymous with its trademark or brand.


title: Logo

text: Douglas Harper's Online Etymology Dictionary states that the term 'logo' used in 1937 "probably a shortening of logogram".


title: Logo

text: Numerous inventions and techniques have contributed to the contemporary logo, including cylinder seals (c. 2300 BCE), coins (c. 600 BCE), trans-cultural diffusion of logographic languages, coats of arms, watermarks, silver hallmarks, and the development of printing technology.


title: Logo

text: As the industrial revolution converted western societies from agrarian to industrial in the 18th and 19th centuries, photography and lithography contributed to the boom of an advertising industry that integrated typography and imagery together on the page. Simultaneously, typography itself was undergoing a revolution of form and expression that expanded beyond the modest, serif typefaces used in books, to bold, ornamental typefaces used on broadsheet posters.


title: Logo

text: The arts were expanding in purpose—from expression and decoration of an artistic, storytelling nature, to a differentiation of brands and products that the growing middle classes were consuming. Consultancies and trades-groups in the commercial arts were growing and organizing; by 1890, the US had 700 lithographic printing firms employing more than 8,000 people. Artistic credit tended to be assigned to the lithographic company, as opposed to the individual artists who usually performed less important jobs.


title: Logo

text: Innovators in the visual arts and lithographic process—such as French printing firm Rouchon in the 1840s, Joseph Morse of New York in the 1850s, Frederick Walker of England in the 1870s, and Jules Chéret of France in the 1870s—developed an illustrative style that went beyond tonal, representational art to figurative imagery with sections of bright, flat colors. Playful children's books, authoritative newspapers, and conversational periodicals developed their own visual and editorial styles for unique, expanding audiences. As printing costs decreased, literacy rates increased, and visual styles changed, the Victorian decorative arts led to an expansion of typographic styles and methods of representing businesses.


title: Logo

text: The Arts and Crafts Movement of late-19th century, partially in response to the excesses of Victorian typography, aimed to restore an honest sense of craftsmanship to the mass-produced goods of the era. A renewal of interest in craftsmanship and quality also provided the artists and companies with a greater interest in credit, leading to the creation of unique logos and marks.


title: Logo

text: By the 1950s, Modernism had shed its roots as an avant-garde artistic movement in Europe to become an international, commercialized movement with adherents in the United States and elsewhere. The visual simplicity and conceptual clarity that were the hallmarks of Modernism as an artistic movement formed a powerful toolset for a new generation of graphic designers whose logos embodied Ludwig Mies van der Rohe’s dictum, "Less is more." Modernist-inspired logos proved successful in the era of mass visual communication ushered in by television, improvements in printing technology, and digital innovations.


title: Logo

text: The current era of logo design began in the 1870s with the first abstract logo, the Bass red triangle. , many corporations, products, brands, services, agencies, and other entities use an ideogram (sign, icon) or an emblem (symbol) or a combination of sign and emblem as a logo. As a result, only a few of the thousands of ideograms in circulation are recognizable without a name. An effective logo may consist of both an ideogram and the company name (logotype) to emphasize the name over the graphic, and employ a unique design via the use of letters, colors, and additional graphic elements.


title: Logo

text: Ideograms and symbols may be more effective than written names (logotypes), especially for logos translated into many alphabets in increasingly globalized markets. For instance, a name written in Arabic script might have little resonance in most European markets. By contrast, ideograms keep the general proprietary nature of a product in both markets. In non-profit areas, the Red Cross (varied as the Red Crescent in Muslim countries and as the Red Star of David in Israel) exemplifies a well-known emblem that does not need an accompanying name. The red cross and red crescent are among the best-recognized symbols in the world. National Red Cross and Red Crescent Societies and their Federation as well as the International Committee of the Red Cross include these symbols in their logos.


title: Logo

text: Branding can aim to facilitate cross-language marketing. Consumers and potential consumers can identify the Coca-Cola name written in different alphabets because of the standard color and "ribbon wave" design of its logo. The text was written in Spencerian Script, which was a popular writing style when the Coca-Cola Logo was being designed.


title: Logo

text: Since a logo is the visual entity signifying an organization, logo design is an important area of graphic design. A logo is the central element of a complex identification system that must be functionally extended to all communications of an organization. Therefore, the design of logos and their incorporation in a visual identity system is one of the most difficult and important areas of graphic design. Logos fall into three classifications (which can be combined). Ideographs, such as Chase Bank, are completely abstract forms; pictographs are iconic, representational designs; logotypes (or wordmarks) depict the name or company initials. These elements can be combined in a set position and relative size in a logo lock-up, so named because elements are "locked" together and should not be broken apart or resized individually. Because logos are meant to represent companies' brands or corporate identities and foster their immediate customer recognition, it is counterproductive to frequently redesign logos.


title: Logo

text: The logo design profession has substantially increased in numbers over the years since the rise of the Modernist movement in the United States in the 1950s. Three designers are widely considered the pioneers of that movement and of logo and corporate identity design: The first is Chermayeff & Geismar, which is the firm responsible for many iconic logos, such as Chase Bank (1964), Mobil Oil (1965), PBS (1984), NBC (1986), National Geographic (2003), and others. Due to the simplicity and boldness of their designs, many of their earlier logos are still in use today. The firm recently designed logos for the Library of Congress and the fashion brand Armani Exchange. Another pioneer of corporate identity design is Paul Rand, who was one of the originators of the Swiss Style of graphic design. He designed many posters and corporate identities, including the famous logos for IBM, UPS, and ABC. The third pioneer of corporate identity design is Saul Bass. Bass was responsible for several recognizable logos in North America, including both the Bell Telephone logo (1969) and successor AT&T Corporation globe (1983). Other well-known designs were Continental Airlines (1968), Dixie (1969), and United Way (1972). Later, he would produce logos for a number of Japanese companies as well.


title: Logo

text: An important development in the documentation of logo design is the study of French trademarks by historian Edith Amiot and philosopher Jean Louis Azizollah.


title: Logo

text: Color is a key element in logo design and plays an important and potentially vital role in brand differentiation. Colors can have immense consequences on our moods. They are remarkably dominant to the point that they can psychologically manipulate perspectives, emotions, and reactions. The importance of color in this context is due to the mechanics of human visual perception wherein color and contrast play critical roles in visual detail detection. In addition, we tend to acquire various color connotations and color associations through social and cultural conditioning, and these play a role in how we decipher and evaluate logo color. While color is considered important to brand recognition and logo design, it shouldn't conflict with logo functionality, and it needs to be remembered that color connotations and associations are not consistent across all social and cultural groups. For example, in the United States, red, white, and blue are often used in logos for companies that want to project patriotic feelings but other countries will have different sets of colors that evoke national pride.


title: Logo

text: Choosing an organisation's logo's color is an important decision because of its long term implications and its role in creating differentiation among competitors' logos. A methodology for identifying potential logo colors within an industry sector is color mapping, whereby existing logo colors are systematically identified, mapped, and evaluated (O'Connor, 2011).


title: Logo

text: Designing a good logo often requires involvement from a marketing team teaming with the graphic design studio. Before a logo is designed, there must be a clear definition of the concept and values of the brand as well as understanding of the consumer or target group. Broad steps in the logo design process include research, conceptualization, investigation of alternative candidates, refinement of a chosen design, testing across products, and finally adoption and production of the chosen mark.


title: Logo

text: In 1898, the French tire manufacturer Michelin introduced the Michelin Man, a cartoon figure presented in many different contexts, such as eating, drinking, and playing sports. By the early 21st century, large corporations such as MTV, Nickelodeon, Google, Morton Salt, and Saks Fifth Avenue had adopted "dynamic logos" that change over time from setting to setting.


title: Logo

text: A company that uses logotypes (wordmarks) may desire a logo that matches the firm's Internet address. For short logotypes consisting of two or three characters, multiple companies are found to employ the same letters. A "CA" logo, for example, is used by the French bank Credit Agricole, the Dutch clothing retailer C&A, and the US software corporation CA Technologies, but only one can have the Internet domain name CA.com.


title: Logo

text: In today's digital interface adaptive world, a logo will be formatted and re-formatted from large monitors to small handheld devices. With the constant size change and re-formatting, logo designers are shifting to a more bold and simple approach, with heavy lines and shapes, and solid colors. This reduces the confusion when mingled with other logos in tight spaces and when scaled between media. Social networks like Twitter, Facebook, LinkedIn, and Google+ use such logos.


title: Logo

text: Logos and their design may be protected by copyright, via various intellectual property organisations worldwide which make available application procedures to register a design to give it protection at law. For example, in the UK, the Intellectual Property Office (United Kingdom) govern registered designs, patents, and trademarks. Ordinarily, the trademark registration will not 'make claim' to colors used, meaning it is the visual design that will be protected, even if it is reproduced in a variety of other colors or backgrounds.


title: Logo

text: In some countries, especially civil law countries, the threshold of originality required for copyright protection can be quite high, so a logo that contains simple geometric shapes or text might not be eligible for copyright protection although it can be protected as a trademark.


title: Logo

text: For many teams, a logo or "crest" is an important way to recognize a team's history and can intimidate opponents.


title: Logo

text: For certain teams, the logo and color scheme are synonymous with the team's players. For example, Manchester United, the Toronto Maple Leafs, or New York Yankees all have a recognizable logo that can be identified by any fan of the respective sport.


title: Application layer

text: An application layer is an abstraction layer that specifies the shared communications protocols and interface methods used by hosts in a communications network. An "application layer" abstraction is specified in both the Internet Protocol Suite (TCP/IP) and the OSI model. Although both models use the same term for their respective highest-level layer, the detailed definitions and purposes are different.


title: Application layer

text: In the Internet protocol suite, the application layer contains the communications protocols and interface methods used in process-to-process communications across an Internet Protocol (IP) computer network. The application layer only standardizes communication and depends upon the underlying transport layer protocols to establish host-to-host data transfer channels and manage the data exchange in a client–server or peer-to-peer networking model. Though the TCP/IP application layer does not describe specific rules or data formats that applications must consider when communicating, the original specification (in ) does rely on and recommend the robustness principle for application design.


title: Application layer

text: In the OSI model, the definition of the application layer is narrower in scope. The OSI model defines the application layer as only the interface responsible for communicating with host-based and user-facing applications. OSI then explicitly distinguishes the functionality of two additional layers, the session layer and presentation layer, as separate levels below the application layer and above the transport layer. OSI specifies a strict modular separation of functionality at these layers and provides protocol implementations for each. In contrast, the Internet Protocol Suite compiles these functions into a single layer.


title: Application layer

text: Originally the OSI model consisted of two kinds of application layer services with their related protocols. These two sublayers are the common application service element (CASE) and specific application service element (SASE). Generally, an application layer protocol is realized by the use of the functionality of a number of application service elements. Some application service elements invoke different procedures based on the version of the session service available.


title: Application layer

text: The common application service element sublayer provides services for the application layer and request services from the session layer.


title: Application layer

text: The specific application service element sublayer provides application-specific services (protocols), such as:


title: Application layer

text: The IETF definition document for the application layer in the Internet Protocol Suite is RFC 1123. It provided an initial set of protocols that covered the major aspects of the functionality of the early Internet:


title: Trust, but verify

text: Trust, but verify () is a rhyming Russian proverb. The phrase became internationally known in English after Suzanne Massie, an American scholar, taught it to Ronald Reagan, then president of the United States, the latter of whom used it on several occasions in the context of nuclear disarmament discussions with the Soviet Union.


title: Trust, but verify

text: Suzanne Massie, an American scholar, met with Ronald Reagan many times while he was president of the United States between 1984 and 1987. She taught him the Russian proverb () meaning 'trust, but verify'. She advised him that "The Russians like to talk in proverbs. It would be nice of you to know a few. You are an actor – you can learn them very quickly." The proverb was adopted as a signature phrase by Reagan, who used it frequently when discussing United States relations with the Soviet Union.


title: Trust, but verify

text: After Reagan used the phrase to emphasize "the extensive verification procedures that would enable both sides to monitor compliance with the treaty", at the signing of the INF Treaty, on 8 December 1987, his counterpart General Secretary Mikhail Gorbachev responded, "You repeat that at every meeting". To this, Reagan answered, "I like it". While Reagan quoted Russian proverbs, Gorbachev quoted Ralph Waldo Emerson, who had been popular in the USSR when Gorbachev was in college, saying that "the reward of a thing well done is to have done it."


title: Trust, but verify

text: Following the 2013 Ghouta attacks, Secretary of State John Kerry told a news conference in Geneva that the United States and Russia had agreed on a framework to dispose of Syria's chemical weapons. He said "President Reagan's old adage about 'trust but verify' ... is in need of an update. And we have committed here to a standard that says 'verify and verify'."


title: Trust, but verify

text: In 1995, the similar phrase "Trust and Verify" was used as the motto of the On-Site Inspection Agency (now subsumed into the Defense Threat Reduction Agency).


title: Trust, but verify

text: In 2000, David T. Lindgren's book about how interpretation, or imagery analysis, of aerial and satellite images of the Soviet Union played a key role in superpowers and in arms control during the Cold War was titled "Trust But Verify: Imagery Analysis in the Cold War".


title: Trust, but verify

text: In 2001, the National Infrastructure Protection Center (NIPC), a national critical infrastructure threat investigation and response entity, published a paper entitled "Trust but verify" on how to protect oneself and their company from email viruses.


title: Trust, but verify

text: In 2015, both Democrats and Republicans invoked the phrase when arguing for and against the proposed Iran nuclear deal framework.


title: Trust, but verify

text: In the study of programming languages, the phrase has been used to describe the implementation of downcasting: the compiler trusts that the downcast term will be of the desired type, but this assumption is verified at runtime in order to avoid undefined behavior.


title: Trust, but verify

text: In 2019, this quote was used in third episode of HBO miniseries "Chernobyl", by the first deputy chairman of the KGB.


title: Trust, but verify

text: The phrase has been used in relation to India–China border disputes and also following the Galwan clash during the 2020 China–India skirmishes. Variants of the phrase were also reported in the Indian media, "distrust until fully and comprehensively verified", and "verify and still not trust".


title: Trust, but verify

text: On July 24, 2020, US Secretary of State Michael Pompeo referenced the proverb in a speech at the Richard Nixon Presidential Library saying that in dealing with China, the United States must instead 'distrust and verify'.


title: Trust, but verify

text: The origin of the phrase is obscure but understood to be a paraphrase of Vladimir Lenin and Joseph Stalin.


title: Chad Channing

text: Chad Channing (born January 31, 1967) is an American musician who is best known as the drummer of the grunge band Nirvana from 1988 until 1990, during which time they recorded and released their debut album "Bleach" and appears on "Polly" in the follow-up album "Nevermind". He currently sings and plays bass in the band Before Cars.


title: Chad Channing

text: Channing was born on January 31, 1967, in Santa Rosa, California, to Wayne and Burnyce Channing. Wayne was a radio disc jockey and the family was constantly moving all over the country due to different jobs being offered to him. At 13 Chad shattered his femur in an accident during gym class. Over the years of rehabilitation and surgeries he discovered music, beginning with a bass guitar that his parents bought him. The bass filled Chad's time as he was unable to go to school. When he was out of his leg casts, his parents bought him a drum set to help build strength in his legs.


title: Chad Channing

text: Channing joined a band with future Nirvana guitarist Jason Everman called Stonecrow in 1985. Later, while working as a sauté cook on Bainbridge Island, Washington, Channing started the band Tick-Dolly-Row with Chris Karr, John Hurd and Ben Shepherd, also a Bainbridge Islander, who would later become the bassist for Soundgarden. Tick-Dolly-Row shared a bill with Nirvana, who at the time were going under the name Bliss. Not long after, a mutual friend introduced Channing to Kurt Cobain and Krist Novoselic who were searching for a drummer. The three got together several times for jam sessions before they started playing shows.


title: Chad Channing

text: In June 1988, a few weeks after Channing joined Nirvana, they recorded their first single "Love Buzz", also marking their Sub Pop debut. Nirvana began the recording sessions for "Bleach" on Christmas Eve 1988, finishing toward the end of January 1989. Jason Everman, a friend of the band, agreed to pay the money for recording costs. Everman had known Channing since fifth grade, and the two had played in bands together in high school.


title: Chad Channing

text: "Bleach" was released on June 15, 1989. Channing played drums on the entire album with the exception of "Floyd the Barber" and "Paper Cuts" which featured drummer Dale Crover from a recording session prior to Channing joining the band. The 1992 re-release of Bleach included the song "Downer", which also had Crover on drums from the same recording session prior to Channing joining the band. In April 1990, Nirvana recorded eight songs at Smart Studios with producer Butch Vig for the band's sophomore album, although the session was not completed due to Cobain losing his voice. During the sessions, Cobain and Novoselic became disenchanted with Channing's drumming, and Channing expressed frustration at not being actively involved in songwriting. These creative and artistic differences culminated in Channing's departure after their April-May 1990 tour, a mutual decision within the band. Nirvana used the Smart Studios recordings as a demo to secure a new contract with a major label and the band re-recorded the tracks for a new studio album in the fall of 1990, recruiting Dave Grohl as their new drummer who adopted many of Channing's drum parts. Although uncredited (until the Deluxe edition), the version of "Polly" used on "Nevermind" is the original version the band recorded with Channing on percussion, the only song carried over from the previous session.


title: Chad Channing

text: Due to popularity and longevity, the rehashing of older work by Nirvana continued, both during the band's existence and following their demise. The 1992 compilation, "Incesticide", featured the tracks "Big Long Now", "Stain" and "Dive", which all credited Channing as drummer. Live versions of "Polly" and "Breed" that included Channing appeared on "From the Muddy Banks of the Wishkah", a live album released in 1996. The 2004 "With the Lights Out" box set featured a DVD of a December 1988 Nirvana rehearsal, as well as seven songs scattered across the first two discs of the set, all with Channing on drums.


title: Chad Channing

text: Following Nirvana's induction into the Rock and Roll Hall of Fame in December 2013, Channing said in an interview with the Radio.com website that he perceived the recognition as a gift for his daughter. However, Channing was later informed of his omission via text message, and was not included in the April 2014 induction, as the accolade only applied to Cobain, Novoselic and Grohl. Channing did attend the ceremony, and his replacement Dave Grohl made a point to publicly thank Channing for his contributions to the band and noted that some of Nirvana's most recognizable drum riffs were, in fact, written by Channing.


title: Chad Channing

text: After leaving Nirvana, Channing formed the Fire Ants who released the "Stripped" EP on Dekema Records in 1992, produced by Jack Endino, who had produced "Bleach". Members of the Fire Ants included Brian Wood (vocals) and Kevin Wood (guitars), brothers of the late Mother Love Bone singer Andrew Wood, and bassist Dan McDonald. Channing and McDonald collaborated again in 1998 with John Hurd and Erik Spicer, forming The Methodists who released the album "Cookie".


title: Chad Channing

text: Chad stepped from behind the drum set to front his new project Before Cars, which released the single "Old Chair" in 2006. They released their debut album "Walk Back" in 2008, again produced by Jack Endino. Channing supplies lead vocals and bass on all tracks as well as some acoustic guitar.


title: Psychological stress

text: In psychology, stress is a feeling of emotional strain and pressure. Stress is a type of psychological pain. Small amounts of stress may be beneficial, as it can improve athletic performance, motivation and reaction to the environment. Excessive amounts of stress, however, can increase the risk of strokes, heart attacks, ulcers, and mental illnesses such as depression and also aggravation of a pre-existing condition.


title: Psychological stress

text: Stress can be external and related to the environment, but may also be caused by internal perceptions that cause an individual to experience anxiety or other negative emotions surrounding a situation, such as pressure, discomfort, etc., which they then deem stressful.


title: Psychological stress

text: Hans Selye (1974) proposed four variations of stress. On one axis he locates good stress (eustress) and bad stress (distress). On the other is over-stress (hyperstress) and understress (hypostress). Selye advocates balancing these: the ultimate goal would be to balance hyperstress and hypostress perfectly and have as much eustress as possible.


title: Psychological stress

text: The term "eustress" comes from the Greek root "eu-" which means "good" (as in "euphoria"). Eustress results when a person perceives a stressor as positive.


title: Psychological stress

text: "Distress" stems from the Latin root "dis-" (as in "dissonance" or "disagreement"). Medically defined distress is a threat to the quality of life. It occurs when a demand vastly exceeds a person's capabilities.


title: Psychological stress

text: Stress is a non-specific response. It is neutral, and what varies is the degree of response. It is all about the context of the individual and how they perceive the situation. Hans Selye defined stress as “the nonspecific (that is, common) result of any demand upon the body, be the effect mental or somatic.” This includes the medical definition of stress as a physical demand and the colloquial definition of stress as a psychological demand. A stressor is inherently neutral meaning that the same stressor can cause either distress or eustress. It is individual differences and responses that induce either distress or eustress.


title: Psychological stress

text: A stressor is any event, experience, or environmental stimulus that causes stress in an individual. These events or experiences are perceived as threats or challenges to the individual and can be either physical or psychological. Researchers have found that stressors can make individuals more prone to both physical and psychological problems, including heart disease and anxiety.


title: Psychological stress

text: Stressors are more likely to affect an individual's health when they are "chronic, highly disruptive, or perceived as uncontrollable". In psychology, researchers generally classify the different types of stressors into four categories: 1) crises/catastrophes, 2) major life events, 3) daily hassles/microstressors, and 4) ambient stressors. According to Ursin (1988), the common factor between these categories is an inconsistency between expected events ("set value") and perceived events ("actual value") that cannot be resolved satisfactorily, which puts stress into the broader context of cognitive-consistency theory.


title: Psychological stress

text: This type of stressor is unforeseen and unpredictable and, as such, is completely out of the control of the individual. Examples of crises and catastrophes include: devastating natural disasters, such as major floods or earthquakes, wars, pandemics, etc. Though rare in occurrence, this type of stressor typically causes a great deal of stress in a person's life. A study conducted by Stanford University found that after natural disasters, those affected experienced a significant increase in stress level. Combat stress is a widespread acute and chronic problem. With the rapid pace and the urgency of firing first, episodes of accidentally killing friendly forces (“brother” killing “brother” or fratricide) may happen. Prevention requires stress reduction, emphasis on vehicle and other identification training, awareness of the tactical situation, and continual risk analysis by leaders at all levels.


title: Psychological stress

text: Common examples of major life events include: marriage, going to college, death of a loved one, birth of a child, divorce, moving houses, etc. These events, either positive or negative, can create a sense of uncertainty and fear, which will ultimately lead to stress. For instance, research has found the elevation of stress during the transition from high school to university, with college freshmen being about two times more likely to be stressed than final year students. Research has found major life events are somewhat less likely to be major causes of stress, due to their rare occurrences.


title: Psychological stress

text: The length of time since occurrence and whether or not it is a positive or negative event are factors in whether or not it causes stress and how much stress it causes. Researchers have found that events that have occurred within the past month generally are not linked to stress or illness, while chronic events that occurred more than several months ago are linked to stress and illness and personality change. Additionally, positive life events are typically not linked to stress and if so, generally only trivial stress while negative life events can be linked to stress and the health problems that accompany it. However, positive experiences and positive life changes can predict decreases in neuroticism.


title: Psychological stress

text: This category includes daily annoyances and minor hassles. Examples include: making decisions, meeting deadlines at work or school, traffic jams, encounters with irritating personalities, etc. Often, this type of stressor includes conflicts with other people. Daily stressors, however, are different for each individual, as not everyone perceives a certain event as stressful. For example, most people find public speaking to be stressful, but someone who has experience with it will not.


title: Psychological stress

text: Daily hassles are the most frequently occurring type of stressor in most adults. The high frequency of hassles causes this stressor to have the most physiological effect on an individual. Carolyn Aldwin, Ph.D., conducted a study at the Oregon State University that examined the perceived intensity of daily hassles on an individual's mortality. Aldwin's study concluded that there is a strong correlation between individuals who rate their hassles as very intense and a high level of mortality. One's perception of their daily stressors can have a modulating effect on the physiological impact of daily stressors.


title: Psychological stress

text: Travel-related stress results from three main categories: lost time, surprises (an unforeseen event such as lost or delayed baggage) and routine breakers (inability to maintain daily habits).


title: Psychological stress

text: As their name implies, these are global (as opposed to individual) low-grade stressors that are a part of the background environment. They are defined as stressors that are "chronic, negatively valued, non-urgent, physically perceptible, and intractable to the efforts of individuals to change them". Typical examples of ambient stressors are pollution, noise, crowding, and traffic. Unlike the other three types of stressor, ambient stressors can (but do not necessarily have to) negatively impact stress without conscious awareness.


title: Psychological stress

text: Studies conducted in military and combat fields show that some of the most potent stressors can be due to personal organizational problems in the unit or on the home front. Stress due to bad organizational practices is often connected to "Toxic Leadership", both in companies and in governmental organizations.


title: Psychological stress

text: Life events scales can be used to assess stressful things that people experience in their lives. One such scale is the Holmes and Rahe Stress Scale, also known as the Social Readjustment Rating Scale, or SRRS. Developed by psychiatrists Thomas Holmes and Richard Rahe in 1967, the scale lists 43 stressful events.


title: Psychological stress

text: To calculate one's score, add up the number of "life change units" if an event occurred in the past year. A score of more than 300 means that individual is at risk for illness, a score between 150 and 299 means risk of illness is moderate, and a score under 150 means that individual only has a slight risk of illness.


title: Psychological stress

text: Modern people may attempt to self-assess their own "stress-level"; third parties (sometimes clinicians) may also provide qualitative evaluations. Quantitative approaches such as Galvanic Skin Response or other measurements giving results which may correlate with perceived psychological stress include testing for one or more of the several stress hormones, for cardiovascular responses, or for immune response. There are some valid questionnaires to assess stress level such as, Higher Education Stress Inventory (HESI) is a valid questionnaire used in many communities for assessment the stress level of college students.


title: Psychological stress

text: There are many (psycho-)physiological measurement methods that correlate more or less well with psychological stress (mental or emotional) and are thus used as a possible indicator.


title: Psychological stress

text: In the physiological domain of oculomotor function alone, several physiological responses are suspected to detect different stress situations in a person-specific and objective manner (not by means of a survey). For example, via eye movement and gaze behavior, via pupil behavior and via eyelid blink behavior (Blinking).


title: Psychological stress

text: To measure the body's response to stress, psychologists tend to use Hans Selye's general adaptation syndrome. This biological model, often referred to as the "classic stress response", revolves around the concept of homeostasis. General adaptive syndrome, according to this system, occurs in three stages:


title: Psychological stress

text: This physiological stress response involves high levels of sympathetic nervous system activation, often referred to as the "fight or flight" response. The response involves pupil dilation, release of endorphins, increased heart and respiration rates, cessation of digestive processes, secretion of adrenaline, arteriole dilation, and constriction of veins.


title: Psychological stress

text: Psychological stress does not appear to be a risk factor for the onset of cancer, though it may worsen outcomes in those who already have cancer. Research has found that personal belief in stress as a risk factor for cancer was common in England, though awareness of risk factors overall was found to be low.


title: Psychological stress

text: There is likely a connection between stress and illness. Theories of a proposed stress–illness link suggest that both acute and chronic stress can cause illness, and studies have found such a link. According to these theories, both kinds of stress can lead to changes in behavior and in physiology. Behavioral changes can involve smoking- and eating-habits and physical activity. Physiological changes can be changes in sympathetic activation or hypothalamic pituitary adrenocorticoid activation, and immunological function. However, there is much variability in the link between stress and illness.


title: Psychological stress

text: There is some evidence that stress can make the individual more susceptible to physical illnesses like the common cold. "Although chronic (but not acute) stressful events are associated with greater susceptibility, the association between social diversity and colds is not altered after controlling for life events." Stressful events, such as job changes, correlate with insomnia, impaired sleeping, and health complaints. Research indicates the type of stressor (whether it is acute or chronic) and individual characteristics such as age and physical well-being before the onset of the stressor can combine to determine the effect of stress on an individual. An individual's personality characteristics (such as level of neuroticism), genetics, and childhood experiences with major stressors and traumas may also dictate their response to stressors. Stress may also cause headaches.


title: Psychological stress

text: Chronic stress and a lack of coping resources available or used by an individual can often lead to the development of psychological issues such as depression and anxiety (see below for further information). This is particularly true regarding chronic stressors. These are stressors that may not be as intense as an acute stressor like a natural disaster or a major accident, but they persist over longer periods of time. These types of stressors tend to have a more negative impact on health because they are sustained and thus require the body's physiological response to occur daily. This depletes the body's energy more quickly and usually occurs over long periods of time, especially when such microstressors cannot be avoided (for example: stress related to living in a dangerous neighborhood). See allostatic load for further discussion of the biological process by which chronic stress may affect the body. For example, studies have found that caregivers, particularly those of dementia patients, have higher levels of depression and slightly worse physical health than non-caregivers.


title: Psychological stress

text: Studies have also shown that perceived chronic stress and the hostility associated with Type A personalities are often correlated with much higher risks of cardiovascular disease. This occurs because of the compromised immune system as well as the high levels of arousal in the sympathetic nervous system that occur as part of the body's physiological response to stressful events. However, it is possible for individuals to exhibit hardiness a term referring to the ability to be both chronically stressed and healthy. Chronic stress can correlate with psychological disorders such as delusions. Pathological anxiety and chronic stress lead to structural degeneration and impaired functioning of the hippocampus.


title: Psychological stress

text: It has long been believed that negative affective states, such as feelings of anxiety and depression, could influence the pathogenesis of physical disease, which in turn, have direct effects on biological process that could result in increased risk of disease in the end. However, studies done by the University of Wisconsin-Madison and other places have shown this to be partly untrue; although perceived stress seems to increase the risk of reported poor health, the additional "perception" of stress as something harmful increases the risk even further. For example, when humans are under chronic stress, permanent changes in their physiological, emotional, and behavioral responses are most likely to occur. Such changes could lead to disease. Chronic stress results from stressful events that persist over a relatively long period of time, such as caring for a spouse with dementia, or results from brief focal events that continue to be experienced as overwhelming even long after they are over, such as experiencing a sexual assault.


title: Psychological stress

text: Experiments show that when healthy human individuals are exposed to acute laboratory stressors, they show an adaptive enhancement of some markers of natural immunity but a general suppression of functions of specific immunity. By comparison, when healthy human individuals are exposed to real-life chronic stress, this stress is associated with a biphasic immune response where partial suppression of cellular and humoral function coincides with low-grade, nonspecific inflammation.


title: Psychological stress

text: Even though psychological stress is often connected with illness or disease, most healthy individuals can still remain disease-free after confronting chronic stressful events. Also, people who do not believe that stress will affect their health do not have an increased risk of illness, disease, or death. This suggests that there are individual differences in vulnerability to the potential pathogenic effects of stress; individual differences in vulnerability arise due to both genetic and psychological factors. In addition, the age at which the stress is experienced can dictate its effect on health. Research suggests chronic stress at a young age can have lifelong impacts on the biological, psychological, and behavioral responses to stress later in life.


title: Psychological stress

text: When someone is stressed, many challenges can arise; a recognized challenge being communication difficulties. Here are some examples of how stress can hinder communication.


title: Psychological stress

text: These cultural differences can affect how people communicate when they are stressed. For example, a member of an individualistic culture would be hesitant to ask for pain medication for fear of being perceived as weak. A member of a collectivistic culture would not hesitate. They have been brought up in a culture where everyone helps each other and is one functional unit whereas the member of the individualistic culture is not as comfortable asking others for aid.


title: Psychological stress

text: Language barriers can cause stress as well as stress adding to language barriers. People may feel uncomfortable because of differences in syntax, vocabulary, different ways of showing respect, and different use of body language can make things difficult. Along with a desire for successful social interactions, being uncomfortable with the communication around a person can discourage them from communicating at all. This barrier can cause cultures to divide and could result to the reasoning why people are more comfortable talking to people within their culture.


title: Psychological stress

text: The System 1 – System 2 model of Daniel Kahneman (Thinking Fast and Slow) and others would distinguish between automatic responses, such as one's native language would be, and a foreign language that required System 2 work to translate. System 2 can become "depleted" by conscious mental effort, making it more difficult and stressful.


title: Psychological stress

text: Divorce, death, and remarriage are all disruptive events in a household. Although everyone involved is affected by events such as these, it can be most drastically seen in children. Due to their age, children have relatively undeveloped coping skills. For this reason a stressful event may cause some changes in their behavior. Falling in with a new crowd, developing some new and sometimes undesirable habits are just some of the changes stress may trigger in their lives.


title: Psychological stress

text: A particularly interesting response to stress is talking to an imaginary friend. A child may feel angry with a parent or their peers who they feel brought this change on them. They need someone to talk to but it definitely would not be the person with whom they are angry. That is when the imaginary friend comes in. They “talk” to this imaginary friend but in doing so they cut off communication with the real people around them.


title: Psychological stress

text: Researchers have long been interested in how an individual's level and types of social support impact the effect of stress on their health. Studies consistently show that social support can protect against physical and mental consequences of stress. This can occur through a variety of mechanisms. One model, known as the "direct effects" model, holds that social support has a direct, positive impact on health by increasing positive affect, promoting adaptive health behaviors, predictability and stability in life, and safeguarding against social, legal, and economic concerns that could negatively impact health. Another model, the "buffering effect", says that social support exerts greatest influence on health in times of stress, either by helping individuals appraise situations in less threatening manners or coping with the actual stress. Researchers have found evidence to support both these pathways.


title: Psychological stress

text: Social support is defined more specifically as psychological and material resources provided by a social network that are aimed at helping an individual cope with stress. Researchers generally distinguish among several types of social support: instrumental support – which refers to material aid (e.g., financial support or assistance in transportation to a physician's appointment), informational support (e.g., knowledge, education or advice in problem-solving), and emotional support (e.g., empathy, reassurance, etc.). Social support can reduce the rate of stress during pregnancy. Studies have found that those who had a large change in their life with a small amount of social support has a higher chance of complications. Whereas those with a largersupport system would have a chance for less complications.


title: Psychological stress

text: Stress management refers to a wide spectrum of techniques and psychotherapies aimed at controlling a person's levels of stress, especially chronic stress, usually for the purpose of improving everyday functioning. It involves controlling and reducing the tension that occurs in stressful situations by making emotional and physical changes.


title: Psychological stress

text: Decreasing stressful behaviors is a part of prevention. Some of the common strategies and techniques are: self-monitoring, tailoring, material reinforcement, social reinforcement, social support, self-contracting, contracting with significant other, shaping, reminders, self-help groups, and professional help.


title: Psychological stress

text: Although many techniques have traditionally been developed to deal with the consequences of stress, considerable research has also been conducted on the prevention of stress, a subject closely related to psychological resilience-building. A number of self-help approaches to stress-prevention and resilience-building have been developed, drawing mainly on the theory and practice of cognitive-behavioral therapy.


title: Psychological stress

text: Biofeedback may also play a role in stress management. A randomized study by Sutarto et al. assessed the effect of resonant breathing biofeedback (recognize and control involuntary heart rate variability) among manufacturing operators; depression, anxiety and stress significantly decreased.


title: Psychological stress

text: Studies have shown that exercise reduces stress. Exercise effectively reduces fatigue, improves sleep, enhances overall cognitive function such as alertness and concentration, decreases overall levels of tension, and improves self-esteem. Because many of these are depleted when an individual experiences chronic stress, exercise provides an ideal coping mechanism. Despite popular belief, it is not necessary for exercise to be routine or intense in order to reduce stress; as little as five minutes of aerobic exercise can begin to stimulate anti-anxiety effects. Further, a 10-minute walk may have the same psychological benefits as a 45-minute workout, reinforcing the assertion that exercise in any amount or intensity will reduce stress. Cycling and walking activities have lower stress scores when compared to all other activities.


title: Psychological stress

text: A multitude of theories have been presented in attempts to explain why exercise effectively reduces stress. One theory, known as the time-out hypothesis, claims that exercise provides distraction from the stressor. The time out hypothesis claims that exercise effectively reduces stress because it gives individuals a break from their stressors. This was tested in a recent study of college women who had identified studying as their primary stressor. The women were then placed under four conditions at varying times: "rest," "studying," "exercising," and "studying while exercising." The stress levels of the participants were measured through self-assessments of stress and anxiety symptoms after each condition. The results demonstrated that the "exercise" condition had the most significant reduction in stress and anxiety symptoms. These results demonstrate the validity of the time-out hypothesis. It is also important to note that exercise provided greater stress reduction than rest.


title: Psychological stress

text: The Lazarus and Folkman model suggests that external events create a form of pressure to achieve, engage in, or experience a stressful situation. Stress is not the external event itself, but rather an interpretation and response to the potential threat; this is when the coping process begins.


title: Psychological stress

text: There are various ways individuals deal with perceived threats that may be stressful. However, people have a tendency to respond to threats with a predominant coping style, in which they dismiss feelings, or manipulate the stressful situation.


title: Psychological stress

text: There are different classifications for coping, or defense mechanisms, however they all are variations on the same general idea: There are good/productive and negative/counterproductive ways to handle stress. Because stress is perceived, the following mechanisms do not necessarily deal with the actual situation that is causing an individual stress. However, they may be considered coping mechanisms if they allow the individual to cope better with the negative feelings/anxiety that they are experiencing due to the perceived stressful situation, as opposed to actually fixing the concrete obstacle causing the stress. The following mechanisms are adapted from the DSM-IV Adaptive Functioning Scale, APA, 1994.


title: Psychological stress

text: These skills are what one could call as “facing the problem head on”, or at least dealing with the negative emotions experienced by stress in a constructive manner. (generally adaptive)


title: Psychological stress

text: The final path model fitted well (CF1 = 1, RMSEA = 0.00) and showed that direct quality of life paths with β = -0.2, and indirect social support with β = -0.088 had the most effects on reduction of stress during pregnancy.


title: Psychological stress

text: These mechanisms cause the individual to have a diminished (or in some cases non-existent) awareness about their anxiety, threatening ideas, fears, etc., that come from being conscious of the perceived threat.


title: Psychological stress

text: Other inhibition coping mechanisms include undoing, dissociation, denial, projection, and rationalization. Although some people claim that inhibition coping mechanisms may eventually increase the stress level because the problem is not solved, detaching from the stressor can sometimes help people to temporarily release the stress and become more prepared to deal with problems later on.


title: Psychological stress

text: There is an alternative method to coping with stress, in which one works to minimize their anxiety and stress in a preventative manner.


title: Psychological stress

text: Prior to the introduction of the concept "stress" in the psychological sense 1955, people already identified a range of more nuanced ideas to describe and confront such emotions as worry, grief, concern, obsession, fear, annoyance, anxiety, distress, suffering and passion."Stress" has subsequently become a mainstay of pop psychology. Though stress is discussed throughout history from many distinct topics and cultures, there is no universal consensus over describing stress. This has led to multiple kinds of research, looking at the different aspects of psychological stress and how it changes over a lifespan.


title: Fertilisation

text: Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Processes such as insemination or pollination which happen before the fusion of gametes are also sometimes informally called fertilisation. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation.


title: Fertilisation

text: In Antiquity, Aristotle conceived the formation of new individuals through fusion of male and female fluids, with form and function emerging gradually, in a mode called by him as epigenetic.


title: Fertilisation

text: In 1784, Spallanzani established the need of interaction between the female's ovum and male's sperm to form a zygote in frogs. In 1827, von Baer observed a therian mammalian egg for the first time. Oscar Hertwig (1876), in Germany, described the fusion of nuclei of spermatozoa and of ova from sea urchin.


title: Fertilisation

text: The evolution of fertilisation is related to the origin of meiosis, as both are part of sexual reproduction, originated in eukaryotes. There are two conflicting theories on how the couple meiosis–fertilisation arose. One is that it evolved from prokaryotic sex (bacterial recombination) as eukaryotes evolved from prokaryotes. The other is that mitosis originated meiosis.


title: Fertilisation

text: The gametes that participate in fertilisation of plants are the sperm (male) and the egg (female) cell. Various families of plants have differing methods by which the gametes produced by the male and female gametophytes come together and are fertilised. In Bryophyte land plants, fertilisation of the sperm and egg takes place within the archegonium. In seed plants, the male gametophyte is called a pollen grain. After pollination, the pollen grain germinates, and a pollen tube grows and penetrates the ovule through a tiny pore called a micropyle. The sperm are transferred from the pollen through the pollen tube to the ovule where the egg is fertilised. In flowering plants, two sperm cells are released from the pollen grain, and a second fertilisation event involving the second sperm cell and the central cell of the ovule, which is a second female gamete.


title: Fertilisation

text: Unlike animal sperm which is motile, plant sperm is immotile and relies on the pollen tube to carry it to the ovule where the sperm is released. The pollen tube penetrates the stigma and elongates through the extracellular matrix of the style before reaching the ovary. Then near the receptacle, it breaks through the ovule through the micropyle (an opening in the ovule wall) and the pollen tube "bursts" into the embryo sac, releasing sperm. The growth of the pollen tube has been believed to depend on chemical cues from the pistil, however these mechanisms were poorly understood until 1995. Work done on tobacco plants revealed a family of glycoproteins called TTS proteins that enhanced growth of pollen tubes. Pollen tubes in a sugar free pollen germination medium and a medium with purified TTS proteins both grew. However, in the TTS medium, the tubes grew at a rate 3x that of the sugar-free medium. TTS proteins were also placed on various locations of semi in vevo pollinated pistils, and pollen tubes were observed to immediately extend toward the proteins. Transgenic plants lacking the ability to produce TTS proteins exhibited slower pollen tube growth and reduced fertility.


title: Fertilisation

text: The rupture of the pollen tube to release sperm in "Arabidopsis" has been shown to depend on a signal from the female gametophyte. Specific proteins called FER protein kinases present in the ovule control the production of highly reactive derivatives of oxygen called reactive oxygen species (ROS). ROS levels have been shown via GFP to be at their highest during floral stages when the ovule is the most receptive to pollen tubes, and lowest during times of development and following fertilisation. High amounts of ROS activate Calcium ion channels in the pollen tube, causing these channels to take up Calcium ions in large amounts. This increased uptake of calcium causes the pollen tube to rupture, and release its sperm into the ovule. Pistil feeding assays in which plants were fed diphenyl iodonium chloride (DPI) suppressed ROS concentrations in "Arabidopsis", which in turn prevented pollen tube rupture.


title: Fertilisation

text: Bryophyte is a traditional name used to refer to all embryophytes (land plants) that do not have true vascular tissue and are therefore called "non-vascular plants". Some bryophytes do have specialised tissues for the transport of water; however, since these do not contain lignin, they are not considered true vascular tissue.


title: Fertilisation

text: A fern is a member of a group of roughly 12,000 species of vascular plants that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular (i.e. having water-conducting vessels). They have stems and leaves, like other vascular plants. Most ferns have what are called fiddleheads that expand into fronds, which are each delicately divided.


title: Fertilisation

text: The gymnosperms are a group of seed producing plants that includes conifers, Cycads, Ginkgo, and Gnetales. The term "gymnosperm" comes from the Greek composite word γυμνόσπερμος (γυμνός gymnos, "naked" and σπέρμα sperma, "seed"), meaning "naked seeds", after the unenclosed condition of their seeds (called ovules in their unfertilised state). Their naked condition stands in contrast to the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, often modified to form cones, or at the end of short stalks as in Ginkgo.


title: Fertilisation

text: After being fertilised, the ovary starts to swell and develop into the fruit. With multi-seeded fruits, multiple grains of pollen are necessary for syngamy with each ovule. The growth of the pollen tube is controlled by the vegetative (or tube) cytoplasm. Hydrolytic enzymes are secreted by the pollen tube that digest the female tissue as the tube grows down the stigma and style; the digested tissue is used as a nutrient source for the pollen tube as it grows. During pollen tube growth towards the ovary, the generative nucleus divides to produce two separate sperm nuclei (haploid number of chromosomes) – a growing pollen tube therefore contains three separate nuclei, two sperm and one tube. The sperms are interconnected and dimorphic, the large one, in a number of plants, is also linked to the tube nucleus and the interconnected sperm and the tube nucleus form the "male germ unit".


title: Fertilisation

text: Double fertilisation is the process in angiosperms (flowering plants) in which two sperm from each pollen tube fertilise two cells in a female gametophyte (sometimes called an embryo sac) that is inside an ovule. After the pollen tube enters the gametophyte, the pollen tube nucleus disintegrates and the two sperm cells are released; one of the two sperm cells "fertilises" the egg cell (at the bottom of the gametophyte near the micropyle), forming a diploid (2n) zygote. This is the point when fertilisation actually occurs; pollination and fertilisation are two separate processes. The nucleus of the other sperm cell fuses with two haploid polar nuclei (contained in the central cell) in the centre of the gametophyte. The resulting cell is triploid (3n). This triploid cell divides through mitosis and forms the endosperm, a nutrient-rich tissue, inside the seed.


title: Fertilisation

text: The two central-cell maternal nuclei (polar nuclei) that contribute to the endosperm arise by mitosis from the single meiotic product that also gave rise to the egg. Therefore, maternal contribution to the genetic constitution of the triploid endosperm is double that of the embryo.


title: Fertilisation

text: One primitive species of flowering plant, "Nuphar polysepala", has endosperm that is diploid, resulting from the fusion of a sperm with one, rather than two, maternal nuclei. It is believed that early in the development of angiosperm linages, there was a duplication in this mode of reproduction, producing seven-celled/eight-nucleate female gametophytes, and triploid endosperms with a 2:1 maternal to paternal genome ratio.


title: Fertilisation

text: In many plants, the development of the flesh of the fruit is proportional to the percentage of fertilised ovules. For example, with watermelon, about a thousand grains of pollen must be delivered and spread evenly on the three lobes of the stigma to make a normal sized and shaped fruit.


title: Fertilisation

text: Cross-fertilisation and self-fertilisation represent different strategies with differing benefits and costs. An estimated 48.7% of plant species are either dioecious or self-incompatible obligate out-crossers. It is also estimated that about 42% of flowering plants exhibit a mixed mating system in nature.


title: Fertilisation

text: In the most common kind of mixed mating system, individual plants produce a single type of flower and fruits may contain self-fertilised, out-crossed or a mixture of progeny types. The transition from cross-fertilisation to self-fertilisation is the most common evolutionary transition in plants, and has occurred repeatedly in many independent lineages. About 10-15% of flowering plants are predominantly self-fertilising.


title: Fertilisation

text: Under circumstances where pollinators or mates are rare, self-fertilisation offers the advantage of reproductive assurance. Self-fertilisation can therefore result in improved colonisation ability. In some species, self-fertilisation has persisted over many generations. "Capsella rubella" is a self-fertilisating species that became self-compatible 50,000 to 100,000 years ago. "Arabidopsis thaliana" is a predominantly self-fertilising plant with an out-crossing rate in the wild of less than 0.3%; a study suggested that self-fertilisation evolved roughly a million years ago or more in "A. thaliana". In long-established self-fertilising plants, the masking of deleterious mutations and the production of genetic variability is infrequent and thus unlikely to provide a sufficient benefit over many generations to maintain the meiotic apparatus. Consequently, one might expect self-fertilisation to be replaced in nature by an ameiotic asexual form of reproduction that would be less costly. However the actual persistence of meiosis and self-fertilisation as a form of reproduction in long-established self-fertilising plants may be related to the immediate benefit of efficient recombinational repair of DNA damage during formation of germ cells provided by meiosis at each generation.


title: Fertilisation

text: The mechanics behind fertilisation has been studied extensively in sea urchins and mice. This research addresses the question of how the sperm and the appropriate egg find each other and the question of how only one sperm gets into the egg and delivers its contents. There are three steps to fertilisation that ensure species-specificity:


title: Fertilisation

text: Consideration as to whether an animal (more specifically a vertebrate) uses internal or external fertilisation is often dependent on the method of birth. Oviparous animals laying eggs with thick calcium shells, such as chickens, or thick leathery shells generally reproduce via internal fertilisation so that the sperm fertilises the egg without having to pass through the thick, protective, tertiary layer of the egg. Ovoviviparous and viviparous animals also use internal fertilisation. It is important to note that although some organisms reproduce via amplexus, they may still use internal fertilisation, as with some salamanders. Advantages to internal fertilisation include: minimal waste of gametes; greater chance of individual egg fertilisation, relatively "longer" time period of egg protection, and selective fertilisation; many females have the ability to store sperm for extended periods of time and can fertilise their eggs at their own desire.


title: Fertilisation

text: Oviparous animals producing eggs with thin tertiary membranes or no membranes at all, on the other hand, use external fertilisation methods. Such animals may be more precisely termed ovuliparous. Advantages to external fertilisation include: minimal contact and transmission of bodily fluids; decreasing the risk of disease transmission, and greater genetic variation (especially during broadcast spawning external fertilisation methods).


title: Fertilisation

text: Sperm find the eggs via chemotaxis, a type of ligand/receptor interaction. Resact is a 14 amino acid peptide purified from the jelly coat of "A. punctulata" that attracts the migration of sperm.