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Contrails or vapour trails are line-shaped clouds produced by aircraft engine exhaust or changes in air pressure at aircraft cruising altitudes several miles above the Earth's surface. Contrails are composed of water, in the form of ice crystals; the combination of water vapor in aircraft engine exhaust and the low ambient temperatures that exist at high altitudes allows the formation of the trails. Impurities in the engine exhaust from the fuel, including sulfur compounds provide some of the particles that can serve as sites for water droplet growth in the exhaust and, if water droplets form, they might freeze to form ice particles that compose a contrail, their formation can be triggered by changes in air pressure in wingtip vortices or in the air over the entire wing surface. Contrails, other clouds directly resulting from human activity, are collectively named homogenitus. Depending on the temperature and humidity at the altitude the contrails form, they may be visible for only a few seconds or minutes, or may persist for hours and spread to be several miles wide resembling natural cirrus or altocumulus clouds.

Persistent contrails are of particular interest to scientists because they increase the cloudiness of the atmosphere. The resulting cloud forms are formally described as homomutatus, may resemble cirrus, cirrocumulus, or cirrostratus, are sometimes called cirrus aviaticus. Persistent spreading contrails are suspected to have an effect on global climate. Engine exhaust is made up of many different chemical byproducts of incomplete hydrocarbon fuel combustion, including volatile organic compounds, inorganic gases, polycyclic aromatic hydrocarbons, oxygenated organics, alcohols and particles of soot and micron-sized metallic particles resulting from engine wear; as a function of engine type and basic combustion engine function, up to 30% of aircraft exhaust is raw, unburned fuel. At high altitudes as this water vapor emerges into a cold environment, the localized increase in water vapor can raise the relative humidity of the air past saturation point; the vapor condenses into tiny water droplets which freeze if the temperature is low enough.

These millions of tiny water droplets and/or ice crystals form the contrails. The time taken for the vapor to cool enough to condense accounts for the contrail forming some distance behind the aircraft. At high altitudes, supercooled water vapor requires a trigger to encourage deposition or condensation; the exhaust particles in the aircraft's exhaust act as this trigger, causing the trapped vapor to condense rapidly. Exhaust contrails form at high altitudes, they can form closer to the ground when the air is cold and moist. A 2013–2014 study jointly supported by NASA, the German aerospace center DLR, Canada's National Research Council NRC, determined that biofuels could reduce contrail generation; this reduction was explained by demonstrating that biofuels produce fewer soot particles, which are the nuclei around which the ice crystals form. The tests were performed by flying a DC-8 at cruising altitude with a sample-gathering aircraft flying in trail. In these samples, the contrail-producing soot particle count was reduced by 50 to 70 percent, using a 50% blend of conventional Jet A1 fuel and HEFA biofuel produced from camelina.

As a wing generates lift, it causes a vortex to form at the wingtip, at the tip of the flap when deployed These wingtip vortices persist in the atmosphere long after the aircraft has passed. The reduction in pressure and temperature across each vortex can cause water to condense and make the cores of the wingtip vortices visible; this effect is more common on humid days. Wingtip vortices can sometimes be seen behind the wing flaps of airliners during takeoff and landing, during landing of the Space Shuttle; the visible cores of wingtip vortices contrast with the other major type of contrails which are caused by the combustion of fuel. Contrails produced from jet engine exhaust are seen at high altitude, directly behind each engine. By contrast, the visible cores of wingtip vortices are seen only at low altitude where the aircraft is travelling after takeoff or before landing, where the ambient humidity is higher, they trail behind the wingtips and wing flaps rather than behind the engines. At high-thrust settings the fan blades at the intake of a turbofan engine reach transonic speeds, causing a sudden drop in air pressure.

This creates the condensation fog, observed by air travelers during takeoff. The tips of rotating surfaces sometimes produce visible contrails. Contrails, by affecting the Earth's radiation balance, act as a radiative forcing. Studies have found that contrails trap outgoing longwave radiation emitted by the Earth and atmosphere at a greater rate than they reflect incoming solar radiation. NASA conducted a great deal of detailed research on atmospheric and climatological effects of contrails, including effects on ozone, ice crystal formation, particle composition, during the Atmospheric Effects of Aviation Project. Global radiative forcing has been calculated from the reanalysis data, climatological models and radiative transfer codes, it is estimated to amount to 0.012 W/m² for 2005, with an uncertainty range of 0.005 to 0.026 W/m², with a low level of scientific understanding. Therefore, the overall net effect of contrails is positive, i.e. a warming effect. However, the effect

1997 Australian Individual Speedway Championship

The 1997 Australian Individual Speedway Championship was held at the Brisbane Exhibition Ground in Brisbane, Queensland on 28 December 1996. This was the final time. Defending champion Craig Boyce won his third and final Australian Championship, once again scoring a 15-point maximum from his five rides. Jason Crump finished second for the second straight year after defeating South Australian Champion Ryan Sullivan and former three time national champion Leigh Adams in a runoff when all three riders finished on 13 points. Australian Championship 28 December 1996 Brisbane, Queensland - Brisbane Exhibition Ground Referee: Qualification: The top four riders go through to the Overseas Final in Bradford, England. Australia national speedway team Sport in Australia

A Short History of Ethics

A Short History of Ethics: A History of Moral Philosophy from the Homeric Age to the Twentieth Century is a 1966 book on the history of moral philosophy by the Scottish philosopher Alasdair MacIntyre. It is the first of a series of books by MacIntyre on the development of ethics; the book covers Greek ethics including Plato and Aristotle, Christian moral thought including the work of Martin Luther and writers including Niccolò Machiavelli, Edmund Burke, Immanuel Kant, David Hume, Georg Wilhelm Friedrich Hegel, Karl Marx, Søren Kierkegaard, Arthur Schopenhauer and Friedrich Nietzsche. MacIntyre discusses twentieth century philosophers including G. E. Moore, John Dewey and R. M. Hare. According to a review in The Journal of Philosophy, one of MacIntyre's primary theses in the book is that "moral concepts change as social life changes" and therefore philosophers who believe there is one subject of ethical inquiry are mistaken. A review in the British Journal of Educational Studies describes the book as a "stimulating, if impressionistic, account of the history of ethics written from the point of view of his own convictions about the state of moral concepts".

In a review for The Philosophical Review, J. B. Schneewind describes the work as a "brilliant and provocative book", "not so much a history of ethics as an essay about the history of ethics". Schneewind criticises some elements of the book, noting the absence of any discussion of Henry Sidgwick and noting MacIntyre's lack of references or bibliography or of careful exposition of some of the issues of interpretation in the history of ethics

John M. Stahl

John Malcolm Stahl was an American film director and producer. He was born Jacob Morris Strelitsky in Baku to an eastern European Jewish family; when he was a child, his family left the Russian Empire and moved to the United States, settling in New York City. At a young age he took the name John Malcolm Stahl and began working, first as a theatre actor and in the city's growing motion picture industry, he directed his first silent film short in 1913. In 1919 he signed on with Louis B. Mayer Pictures in Hollywood. In 1924 he was part of the Mayer team. In 1927, Stahl was one of the thirty-six founding members of the Academy of Motion Picture Arts and Sciences. With the industry's transition to talkies and feature-length films, Stahl made the adjustment. From 1927 through 1929 Stahl was an executive at the short-lived independent studio Tiffany Pictures, renamed the company "Tiffany-Stahl Productions". In 1930 he joined Universal Pictures where he directed in 1934 the film Imitation of Life, nominated for an Academy Award for Best Picture.

The following year, he directed Magnificent Obsession, starring Robert Taylor. Both films were remade in the 1950s by director Douglas Sirk. John Stahl continued to produce and direct major productions as well as filler shorts up to the time of his death; some of his other notable directorial work was for The Keys of the Kingdom in 1944 and the 1945 film noir, Leave Her to Heaven starring Gene Tierney, nominated for Best Actress. Stahl died in Hollywood in 1950, he is interred at Forest Lawn Memorial Park Cemetery in California. He was married to actress and writer Frances Irene Reels from 1918 to her death in 1926, to actress Roxana McGowan from 1931 to his death. On February 8, 1960, for his contributions to the motion pictures industry, Stahl received a star on the Hollywood Walk of Fame at 6546 Hollywood Boulevard. Charles Barr, Bruce Babington; the Call of the Heart: John M Stahl and Hollywood Melodrama. John Libbey. ISBN 978-0-86196-736-0. John M. Stahl on IMDb John M. Stahl.

Derbyshire County Cricket Club in 1978

Derbyshire County Cricket Club in 1978 was the cricket season when the English club Derbyshire had been playing for one hundred and seven years. They reached the final of the Hedges Cup. In the County Championship, they won three matches to finish fourteenth in their seventy fourth season in the Championship, they did not progress beyond round 2 in the Gillette Cup. Derbyshire reached the final of the Hedges Cup, losing to Kent, they played twenty two matches in the County Championship, one against Cambridge University and one against the touring Pakistanis. They won three first class matches all in the Championship. In the Sunday league Derbyshire won six of the first eight matches but lost the remaining six that were played, they were knocked out in the second round of the Gillette Cup.. Eddie Barlow was in his second season as captain. A successful run in the Benson and Hedges cup saw Alan Hill as top scorer overall and Eddie Barlow taking most wickets overall; however in the first class game alone, Peter Kirsten was top scorer and Mike Hendrick took most wickets.

Bob Taylor County Championship Catches 24, Stumping 2 John Player League Catches 10, Stumping 1 Gillette Cup Catches 2, Stumping 1 Benson and Hedges Cup Catches 10, Stumping 1 Derbyshire County Cricket Club seasons 1978 English cricket season

Bekele Debele

Bekele Debele is an Ethiopian former long-distance runner who specialised in cross country running. His greatest achievement was winning the gold medal at the 1983 IAAF World Cross Country Championships, becoming only the second African man to do so. During his career he was selected for Ethiopia at every edition of the IAAF World Cross Country Championships from 1982 to 1989, he helped win the junior team title in 1982 and shared in the senior team medals from 1983 to 1989, including a three-year undefeated streak for the Ethiopian senior team from 1983 to 1985. He competed in the 10,000 metres and represented Ethiopia in that event at the 1983 World Championships in Athletics, he was the bronze medallist on the track at the Friendship Games, having missed the 1984 Summer Olympics due to Ethiopia's boycott of the games. Bekele was born into an Eastern Orthodox family of rural farmers in Shewa and was raised alongside his two brothers and two sisters, he was illiterate for much of his young life.

Due to his talent for running he was brought into the national military sports programme, typical during the reign of the Derg. There he received a basic education and proper training for long-distance running. Over his career, Bekele was coached by Roba Negussie, a former Olympic sprinter and top Ethiopian coach who served as coach for Ethiopia's Olympic long-distance running team. Bekele made his global debut at the 1982 IAAF World Cross Country Championships. Running in the junior race, he was part of the winning Ethiopian team, he won the San Blas Half Marathon at the start of 1983 with a time of 1:04:40 hours. He emerged as a top level runner shortly afterwards at the 1983 IAAF World Cross Country Championships, narrowly defeating both Carlos Lopes and Some Muge to become the world champion and take the team gold medal with Ethiopia. All three athletes recorded the same time in the closest finish at the competition, he became the second African man to win the title after Mohamed Kedir. That year he competed in the 10,000 metres at the inaugural 1983 World Championships in Athletics.

He ran a personal best of 27:49.30 minutes in the heats, but was a little slower in the final and placed tenth, just behind his team mate Kedir. Bekele returned to defend his title at the 1984 IAAF World Cross Country Championships but was beaten on that occasion, placing eighth overall. However, he still led the Ethiopians to the team title, he won the prestigious Cinque Mulini race the following month. He hoped to compete at the 1984 Summer Olympics, but a Soviet-led boycott of the event meant Ethiopia did not send a team there; the eastern bloc countries that boycotted the games set up their own competition instead and Bekele took the 10,000 m bronze medal at the Friendship Games. He ended the year with a win at the São Silvestre de Luanda 10K event. At the 1985 IAAF World Cross Country Championships he placed fourth behind fellow Ethiopian Wodajo Bulti and helped defend the men's team title, he continued to compete on the track an took a victory at Moscow's Brothers Znamensky Memorial meet.

He repeated his fourth-place finish at the 1986 IAAF World Cross Country Championships. Though his team mate Abebe Mekonnen was runner-up, the Ethiopian team was outclassed by a strong Kenyan squad, including winner John Ngugi, was relegated to second in the team rankings; the 1987 edition saw him fare poorly, finishing in 45th place, but he still reached the team podium as Ethiopia took third place. His worst international performance came at the 1988 IAAF World Cross Country Championships: he ended up 83rd overall and finished three minutes after world champion Ngugi, he was the slowest competitor in Ethiopia's silver medal-winning team. At the 1988 Cross de San Sebastián Bekele fought against John Ngugi in a sprint finish, but ended the race as runner-up behind the reigning world champion; this represented a brief improvement of form for what would be his final international outing at the 1989 IAAF World Cross Country Championships. At that event held in Stavanger he finished thirteenth and, alongside Tesfaye Tafa, he lifted Ethiopia into third place in the team competition.

A In an interview with El Pais in 1984 Bekele stated that his date of birth was 12 April 1962, rather than 12 March 1963, found in most other sources. Bekele Debele at World Athletics Video of 1983 World Cross Country Championships