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Gravitational acceleration

In physics, gravitational acceleration is the free fall acceleration of an object in vacuum — without any drag. This is the steady gain in speed caused by the force of gravitational attraction. At given GPS coordinates on the Earth's surface and a given altitude, all bodies accelerate in vacuum at the same rate; this equality is true regardless of the compositions of the bodies. At different points on Earth surface, the gravitational speed gain ranges from 9.764 m/s2 to 9.834 m/s2 depending on altitude and latitude, with a conventional standard value of 9.80665 m/s2. This does not take into account other effects, such as drag. Newton's law of universal gravitation states that there is a gravitational force between any two masses, equal in magnitude for each mass, is aligned to draw the two masses toward each other; the formula is: F = G m 1 m 2 r 2 where m 1 and m 2 are any two masses, G is the gravitational constant, r is the distance between the two point-like masses. Using the integral form of Gauss' Law this formula can be extended to any pair of objects of which one is more massive than the other — like a planet relative to any man-scale artefact.

The distances between planets and between the planets and the Sun are larger than the sizes of the sun and the planets. In consequence both the sun and the planets can be considered as point masses and the same formula applied to planetary motions. If one mass is much larger than the other, it is convenient to take it as observational reference and define it as source of a gravitational field of magnitude and orientation given by: g = − G M r 2 r ^ where' M' is the mass of the field source, r ^ is a unit vector directed from the field source to the sample mass; the negative sign just indicates. The attraction force F vector onto a sample mass' m' can be expressed as: F = m g Here g is the friction-less, free-fall acceleration sustained by the sampling mass' m' under the attraction of the gravitational source, it is a vector oriented toward the field source, of magnitude measured in acceleration units. The gravitational acceleration vector depends only on how massive the field source' M' is and on the distance'r' to the sample mass' m'.

It does not depend on the magnitude of the vanishing-small sampling mass. This model represents the "far-field" gravitational acceleration associated with a massive body; when the dimensions of a body are not trivial compared to the distances of interest, the principle of superposition can be used for differential masses for an assumed density distribution throughout the body in order to get a more detailed model of the "near-field" gravitational acceleration. For satellites in orbit, the far-field model is sufficient for rough calculations of altitude versus period, but not for precision estimation of future location after multiple orbits; the more detailed models include the bulging at the equator for the Earth, irregular mass concentrations for the Moon. The Gravity Recovery And Climate Experiment mission launched in 2002 consists of two probes, nicknamed "Tom" and "Jerry", in polar orbit around the Earth measuring differences in the distance between the two probes in order to more determine the gravitational field around the Earth, to track changes that occur over time.

The Gravity Recovery and Interior Laboratory mission from 2011-2012 consisted of two probes in polar orbit around the Moon to more determine the gravitational field for future navigational purposes, to infer information about the Moon's physical makeup. The type of gravity model used for the Earth depends upon the degree of fidelity required for a given problem. For many problems such as aircraft simulation, it may be sufficient to consider gravity to be a constant, defined as: g = 9.80665 metres per s2based upon data from World Geodetic System 1984, where g is understood to be pointing'down' in the local frame of reference. If it is desirable to model an object's weight on Earth as a function of latitude, one could use the following: g = g 45 − 1 2 ( g p o l e s − g e q u a t o

Irene Bernasconi

Irene Bernasconi was an Argentine marine biologist specializing in Echinoderm research and best known for her work in the Antarctic. She was the first echinoderm specialist in Argentina and spent 55 years conducting research into echinoderms found in the Argentine Sea, her main focus was sea stars however she conducted research into brittle stars and sea urchins. Over the course of her career, Bernasconi described a number of new species, her first taxonomic publication, in which new species from the genus Pteraster were described, was published in 1935. In 1941 she described two new species from the genus Luidia. Between 1937 and 1980, Bernasconi revised the taxonomy of a number of families: Pterasteridae, Odontasteridae, Ganeriidae and Echinasteridae. In 1965 she described the new genus of Vemaster along with four new species. Bernasconi was one of the first female Argentinean scientists to conduct research in Antarctica after travelling there in 1968, at the age of 72, she was accompanied by three other scientists Microbiologist Maria Adela Caria, Marine Biologist Elena Martinez Fontes and Botanist Carmen Pujals

Antonio Buero Vallejo

Antonio Buero Vallejo was a Spanish playwright associated with the Generation of'36 movement and considered the most important Spanish dramatist of the Spanish Civil War. During his career he won three National Theater Prizes, a National Theater Prize for all his career in 1980, the National Literature Prize in 1996, the Miguel de Cervantes Prize, Spain's highest literary honour, in 1986. From 1971 until his death he was a member of the Real Academia Española. From 1934 to 1936 Vallejo studied art and painting in Madrid. During the civil war, he served as a medical aid in the Republican army. After the war he was imprisoned for six years. After being released he wrote Story of a Stairway in 1949; this work presented a graphic picture of Spain after the Civil War and won the Lope de Vega Prize, establishing Vallejo as one of the foremost authors in Spain. While other authors left Spain to escape Franco's censorship, Vallejo stayed in Spain and used symbolism to criticize the government. In 1971, he was elected to the Royal Spanish Academy.

In 1994 he was awarded the Gold Medal of Merit in Fine Arts and the Gold Medal of the Society of Authors of Spain. He died due to a stroke on April 29, 2000, aged 83. A common theme in his work is Spain's problems after Franco. In the tragedies there is always a sense of hope for the future, his works make frequent use of the symbolism of the senses—for example, using the "fiery darkness," in which the protagonist cannot see, as a symbol of Spain's dark situation. Miguel de Cervantes Prize 1986 Historia de una escalera En la ardiente oscuridad La tejedora de sueños La señal que se espera Casi un cuento de hadas Madrugada Irene o el tesoro Las cartas boca abajo Hoy es fiesta Un soñador para un pueblo Las Meninas El concierto de San Ovidio Aventura en lo gris El tragaluz La doble historia del doctor Valmy El sueño de la razón La detonación Llegada de los dioses La Fundación Jueces en la noche Caimán Diálogo secreto Lázaro en el laberinto Música cercana Las trampas del azar Misión al pueblo desierto Café Gijón Antonio Buero Vallejo at Miguel de Cervantes Virtual Library Antonio Buero Vallejo at Castilla-La Mancha Library site

2020–21 ICC Men's T20 World Cup Africa Qualifier

The 2020–21 ICC Men's T20 World Cup Africa Qualifier is scheduled to be a tournament played as part of qualification process for the 2021 ICC Men's T20 World Cup, between March and September 2020. In April 2018, the International Cricket Council granted full international status to Twenty20 men's matches played between member sides from 1 January 2019 onwards. Therefore, all the matches in the Regional Qualifiers will be played as Twenty20 Internationals; the Africa Qualifier will have two sub-regional groups, with the top two teams in each group progressing to the Regional Final. Kenya and Nigeria, the two highest ranked teams as of 1 January 2020, progressed directly to the Regional Final. Group B of the Africa Qualifier tournament is scheduled to take place in Rwanda in June and July 2020. Group A of the Africa Qualifier tournament is scheduled to take place from 25 April to 4 May 2020, at a venue to be confirmed. Group B of the Africa Qualifier tournament is scheduled to take place in Rwanda in June and July 2020.

Six teams will contest the Africa Regional Final: Kenya Nigeria Group-A Winner Group-A Runner-Up Group-B Winner Group-B Runner-Up

Paphiopedilum robinsonianum

Paphiopedilum robinsonianum is a species of slipper orchid endemic to Sulawesi, where it is known from two mountains in the regency of Central Sulawesi. It is restricted to tropical montane forest habitat at 1400 metres altitude; the specific epithet robinsonianum should not be confused with robinsonii. Paphiopedilum robinsonii Ridl. is a synonym of Paphiopedilum bullenianum. Paphiopedilum Robinsonianum is an invalid hybrid name synonymous with P. Euryale. Paphiopedilum robinsonianum is named after the botanist, Dr. Alastair Robinson, who brought the species to the attention of other taxonomists specializing in Paphiopedilum orchids; the authors mention that late in the naming process, Robinson sent word from another botanist, Ch'ien Lee, indicating that the plant had been photographed in the wild on one previous occasion on a nearby mountain, thus showing that the species has a wider distribution than thought

1978 Pacific hurricane season

The 1978 Pacific hurricane season began May 15, 1978, in the eastern Pacific, June 1, 1978, in the central Pacific, ended on November 30, 1978. These dates conventionally delimit the period of time when tropical cyclones form in the eastern north Pacific Ocean. Activity this year was above-average, with eighteen named storms forming. Five of those were tropical storms, thirteen were hurricanes, six were major hurricanes that reached Category 3 or higher on the Saffir–Simpson scale. In the Central Pacific, a tropical depression and a major hurricane formed; this season is the fourth-most active season within the basin when calculating by ACE Index, as the season had an index of 207. Atlantic Hurricane Greta was renamed Olivia; the 1978 Pacific Hurricane Season was the first season on record to have an ACE total at least 200. A small tropical disturbance formed in the Gulf of Tehuantepec on May 27, it accelerated southwest, before turning north late the following day. At this time, thunderstorm activity increased in coverage, aided by an outflow channel to the Intertropical Convergence Zone the disturbance.

Early on May 30, the disturbance's center become better defined, resulting in an upgraded into a tropical storm by 1200 UTC. After curving northwest, Aletta intensified, at 0000 UTC on May 31, Aletta was declared a minimal hurricane. However, hours Aletta degenerated into a tropical storm. On the afternoon of May 31, Aletta turned north-northwest due to a trough over northwestern Mexico and a ridge over southern Mexico. At 1730 UTC, Aletta moved ashore just west-northwest of Zihuatanejo. After moving inland, Aletta dissipated. A tropical disturbance developed on June 15 around 800 mi west-southwest of Acapulco. After moving west-southwest, the disturbance became more defined until June 17, when it was upgraded into a tropical depression. At noon, te depression was elevated to Tropical Storm Bud. Late on June 18, Bud reached its peak intensity of 60 mph, only to start weakening the following day as it moved west-northwest over cooler water. Early on June 20, Bud weakened to a tropical depression.

Shortly thereafter, Bud ceased to exist as a tropical cyclone. Around the time Bud was developing, another tropical disturbance was developed 800 mi to the east of Bud, but around 250 mi west of Acapulco. Veering west-northwest, the small disturbance organized and was designated as a tropical depression at 0600 UTC June 17. Eighteen hours the depression strengthened into Tropical Storm Carlotta. Thereafter, the system turned west-southwest south of a subtropical ridge in Bud's footsteps. Several hours after the formation of an eye early on June 19, Carlotta intensified into a hurricane. After becoming a hurricane, Carlotta tracked west-northwest, intensified. At 0000 UTC June 20, Hurricane Carlotta abruptly intensified into a major hurricane. Around 36 hours Carlotta peaked as a low-end Category 4 hurricane on the Saffir-Simpson scale. On June 22, Carlotta started a gradual weakening trend as it turned northwest over cooler waters on June 22. Two days Carlotta weakened to a tropical storm. On 0600 UTC June 25, Carlotta degenerated into a tropical depression.

Twelve hours Carlotta dissipated. The fourth tropical disturbance of the season developed on June 24 200 mi southwest of Nicaragua. Tracking west-northwest, the disturbance was upgraded into a tropical depression on June 26; the next day, the depression became a tropical storm, before weakening back to a tropical depression late on June 27. At 1500 UTC June 28, Daniel regained tropical storm intensity. While accelerating westward, Daniel intensified into a hurricane late on June 29. Midday on June 30, Daniel intensified into a major hurricane, peaking with winds of 115 mph. After maintaining its intensity for 24 hours, Daniel began to weaken. Late on July 2, Daniel was downgraded into a tropical storm. By midday on July 3, Daniel fell to a tropical depression. Several hours the EPHC stopped tracking the cyclone; this storm began as a weak tropical disturbance on June 28. A tropical disturbance developed just to the east of Acapulco on July 3; the disturbance turned west, moving at 16kt began to intensify over 85.

F water. With satellite imagery showing a cyclonic circulation about in the center, the disturbance was upgraded to a tropical depression on July 6 about 750 n mi west of Acapulco; the depression was named Emilia. Emilia turned to the north-west and continued to intensify. Winds near the center of the storm increased to 60 mph by July 8 and reached their peak intensity of 65 mph by July 9; as Emilia continued to move north-west, the cargo ship Marcona Exporter was helpful in locating the center of the storm. By July 10, Emilia was downgraded to a tropical depression with 35 mph winds. Emilia was over cooler water and dissipated. Hurricane Fico was the longest-lived hurricane of the season and at the time was the longest-lasting Pacific hurricane on record, it developed from a tropical disturbance off the coast of Mexico on July 9. It moved northwestward and westward reaching peak winds of 140 mph on July 12. Moving nearly due westward, the intensity of Fico fluctuated from Category 1 to Category 4 status on the Saffir–Simpson scale for the following days, it passed about 170 miles south of Hawaii on July 20 with winds of 115 mph.

Fico weakened as it turned to the northwest over cooler waters, became an extratropical cyclone on July 28 to the northeast of Midway Is