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Antenna (radio)

In radio engineering, an antenna is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies an electric current to the antenna's terminals, the antenna radiates the energy from the current as electromagnetic waves. In reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, applied to a receiver to be amplified. Antennas are essential components of all radio equipment. An antenna is an array of conductors, electrically connected to the transmitter. Antennas can be designed to transmit and receive radio waves in all horizontal directions or preferentially in a particular direction. An antenna may include components not connected to the transmitter, parabolic reflectors, horns, or parasitic elements, which serve to direct the radio waves into a beam or other desired radiation pattern; the first antennas were built in 1888 by German physicist Heinrich Hertz in his pioneering experiments to prove the existence of waves predicted by the electromagnetic theory of James Clerk Maxwell.

Hertz placed dipole antennas at the focal point of parabolic reflectors for both transmitting and receiving. Starting in 1895, Guglielmo Marconi began development of antennas practical for long-distance, wireless telegraphy, for which he received a Nobel Prize; the words antenna and aerial are used interchangeably. The equivalent term “aerial” is used to mean an elevated horizontal wire antenna; the origin of the word antenna relative to wireless apparatus is attributed to Italian radio pioneer Guglielmo Marconi. In the summer of 1895, Marconi began testing his wireless system outdoors on his father's estate near Bologna and soon began to experiment with long wire "aerials" suspended from a pole. In Italian a tent pole is known as l'antenna centrale, the pole with the wire was called l'antenna; until wireless radiating transmitting and receiving elements were known as “terminals”. Because of his prominence, Marconi's use of the word antenna spread among wireless researchers and enthusiasts, to the general public.

Antenna may refer broadly to an entire assembly including support structure, etc. in addition to the actual functional components. A receiving antenna may include not only the passive metal receiving elements, but an integrated preamplifier or mixer at and above microwave frequencies. Antennas are required by any radio receiver or transmitter to couple its electrical connection to the electromagnetic field. Radio waves are electromagnetic waves which carry signals through the air at the speed of light with no transmission loss. Antennas can be classified as omnidirectional, radiating energy equally in all directions, or directional, where energy radiates more along one direction than others. A uniform omnidirectional antenna is not physically possible; some antenna types have a uniform radiation pattern in the horizontal plane, but send little energy upward or downward. A "directional" antenna is intended to maximize its coupling to the electromagnetic field in the direction of the other station.

A vertical antenna or whip antenna radiates in all directions horizontally, but sends less energy upward or downward. A dipole antenna oriented horizontally sends little energy in direction vectors parallel to the conductor; the dipole antenna, the basis for most antenna designs, is a balanced component, with equal but opposite voltages and currents applied at its two terminals. The vertical antenna is a monopole antenna, not balanced with respect to ground; the ground plays the role of the second conductor of a dipole. Since monopole antennas rely on a conductive surface, they may be mounted with a ground plane to approximate the effect of being mounted on the Earth's surface. More complex antennas increase the directivity of the antenna. Additional elements in the antenna structure, which need not be directly connected to the receiver or transmitter, increase its directionality. Antenna "gain" describes the concentration of radiated power into a particular solid angle of space. "Gain" is an chosen term, by comparison with amplifier "gain" which implies a net increase in power.

In contrast, for antenna "gain", the power increased in the desired direction is at the expense of power reduced in undesired directions. Unlike amplifiers, antennas are electrically “passive” devices which conserve total power, there is no increase in total power above that delivered from the power source, only improved distribution of that fixed total. A phased array consists of two or more simple antennas which are connected together through an electrical network; this involves a number of parallel dipole antennas with a certain spacing. Depending on the relative phase introduced by the network, the same combination of dipole antennas can operate as a "broadside array" or as an "end-fire array". Antenna arrays may employ any basic antenna type, such as loop or slot antennas; these elements are identical. A log-periodic dipole array consists of a number of dipole elements of different lengths in order to obtain a somewhat directional antenna having an wide ban

Hamilton Naki

Hamilton Naki was a laboratory assistant to cardiac surgeon Christiaan Barnard in South Africa. He was recognised for his surgical skills and for his ability to teach medical students and physicians such skills despite not having received a formal medical education, took a leading role in organ transplant research on animals. A controversy arose after his death in that at least five periodicals and the Associated Press retracted statements in their obituaries of Naki that claimed that he participated in the world's first human-to-human heart transplantation in 1967. Naki was born to a poor family in Ngcingwane, a village in Centani in the Eastern Cape province of South Africa, he received six years of education up to the age of 14. Beginning about 1940, he commuted from Langa, Cape Town to the University of Cape Town to work as a gardener rolling grass tennis courts. In 1954 Robert Goetz of the University's surgical faculty asked Naki to assist him with laboratory animals. Naki's responsibilities progressed from cleaning cages to performing anaesthesia.

Most of Naki's work under Goetz involved anaesthetising dogs, but Naki assisted in operating on a giraffe "to dissect the jugular venous valves to determine why giraffes do not faint when bending to drink."Several years after Goetz left, Naki started working for Christiaan Barnard in the laboratory as an assistant. Barnard had studied open-heart surgery techniques in the United States and was bringing those techniques to South Africa. Naki first performed anaesthesia on animals for Barnard, but was "appointed principal surgical assistant of the laboratory because of his remarkable skill and dexterity." Barnard was quoted as saying "If Hamilton had had the opportunity to study, he would have become a brilliant surgeon" and that Naki was "one of the great researchers of all time in the field of heart transplants". In 1968, Barnard's cardiac surgical research team moved out of the surgical laboratory, Naki helped develop the heterotopic or "piggyback" heart transplantation technique. In the 1970s, Naki left Barnard's team and returned to the surgical laboratory, this time working on liver transplantation.

His contributions at this time were described as follows: Rosemary Hickman, transplantation surgeon whom Naki assisted and taught in the laboratory, who worked with Naki for nearly 30 years: "Despite his limited conventional education, he had an amazing ability to learn anatomical names and recognize anomalies. His skills ranged from assisting to operating and he prepared the donor animal while another team worked on the recipient." Del Khan, head of Groote Schuur Hospital's organ transplant unit, whom Naki taught in the laboratory: "A liver transplant on a pig in the U. S. would involve a team of two or three medically qualified surgeons… Hamilton can do this all on his own." Ralph Kirsch, head of the Liver Research Centre at the University of Cape Town: “He was one of those remarkable men who come around once in a long time. As a man without any education, he mastered surgical techniques at the highest level and passed them on to young doctors." Barnard: "A liver transplant is much more difficult than a heart transplant… tell me that Hamilton can do all the various aspects of liver transplantation, which I can't do.

So technically, he is a better surgeon than I am."Naki taught many students during his career. Naki assisted Hickman until his retirement in 1991, after which he received "a gardener's pension: 760 rand, or about $275, a month." Naki was reported to be married with one daughter. He lived in a small one-room house without electricity or running water and sent "most of his pay to his wife and family, left behind in Transkei," but "could pay for only one of his five children to stay to the end of high school." He read the Bible frequently. After retirement, Naki helped the community of Kentani, where part of his family lived, for example "in the construction of a school and in the provision of a mobile clinic" by soliciting donations from his "medical contacts", he received public recognition of his medical work after his retirement, including: Metropolitan Eastern Cape Award, 2002. The Bronze Order of Mapungubwe, 2002, presented by President Thabo Mbeki. One of the highest South African civil honours, this Order is "awarded to South African citizens for excellence and exceptional achievement."

BTWSC Black S/Heroes Award, 2003. An honorary master's degree from the University of Cape Town in 2003, presented by Chancellor Graça Machel; the honorary degree was described as MSc in others. Inclusion in a "senior civil guard of honour" at the 2004 opening of the Parliament of South Africa. In August 2017, the plain opposite the Christian Barnard Hospital in Cape Town was renamed from Salazar Plain to Hamilton Naki Square, he died in Langa on 29 May 2005, aged 78, of "heart trouble." After Naki's death, obituaries published 9 June 2005 to 2 July 2005 in at least two medical journals, one magazine, two newspapers, an unknown number of newspapers publishing Associated Press stories, printed obituaries that made the following claims about Naki's participation in the world's first human-to-human heart transplantation: That Barnard had asked Groote Schuur Hospital for permission for Naki to be on the transplant t

1972 Atlanta Falcons season

The 1972 Atlanta Falcons season was the franchise's seventh year in the National Football League. The team failed to improve on their previous season's output of 7–6–1, finishing 7–7 and failing to reach the playoffs. Standing at 7–5 the Falcons traveled to San Francisco with the NFC West division title on the line. However, the Falcons were never in the game and saw their playoff hopes end with a 20–0 shutout loss. Facing the Kansas City Chiefs in their final game of the season, Running Back Dave Hampton surpassed the 1,000-yard mark. However, a play he is thrown for a six-yard loss and ends the season with 995 yards, as the Falcons lose and finish 7–7. 1972 Atlanta Falcons at

CMLL International Gran Prix (2019)

The CMLL International Gran Prix was a lucha libre, or professional wrestling, tournament produced and scripted by the Mexican professional wrestling promotion Consejo Mundial de Lucha Libre which took place on August 30, 2019 in Arena México, Mexico City, Mexico, CMLL's main venue. The 2019 International Gran Prix was the sixteenth time CMLL has held an International Gran Prix tournament since 1994. All International Gran Prix tournaments have been a one-night tournament, always as part of CMLL's Friday night CMLL Super Viernes shows; the International Gran Prix saw the team of (Cavernario, Negro Casas, El Cuatrero, Diamante Azul, Dragon Lee, Soberano Jr. and Volador Jr. represented Mexico while Big Daddy, Jay Briscoe, Luke Hawx, Kenny King, Mecha Wolf 450, Matt Taven and Oraculo represented the United States or Puerto Rico. The match came down to Negro Casas and Volador Jr. both representing Mexico, which saw Volador Jr. take advantage of the situation to pin Casas to claim the International Gran Prix trophy for a second time.

On the undercard the storyline between Último Guerrero and Ciber the Main Man drawing in Gilbert el Boricua as part of the evolving storyline. In 1994, the Mexican professional wrestling promotion Consejo Mundial de Lucha Libre created the International Gran Prix tournament which took place on April 15 that saw Rayo de Jalisco Jr. defeat King Haku to win the tournament. The tournament became annual tournament but after the 1998 tournament, the tournament became inactive. In 2002, the tournament returned with new rules; the 2019 tournament will be 16th in the series. The tournament traditionally sees a team of Mexican born CMLL wrestlers face off against foreign-born wrestlers, for the 2019 tournament this meant wrestlers from the United States or Puerto Rico; the 2019 Gran Prix show will feature an undisclosed number of professional wrestling matches scripted by CMLL with some wrestlers involved in scripted feuds. The wrestlers faces as they perform. Team Resto del MundoBig Daddy Jay Briscoe Delirious Luke Hawx Kenny King Mecha Wolf 450 Matt Taven Oraculo Team MexicoCavernario Negro Casas El Cuatrero Diamante Azul Dragon Lee Rush Soberano Jr. Volador Jr

Isma'il ibn Ja'far

Abu Muhammad Ismāʿīl ibn Jaʿfar al-Mubārak was the eldest son of Imam Ja'far al-Sadiq. He is known as Isma'il Al-Ãraj ibn Ja'far. Following Ja'far's death, the Shia community split between those who believed the Imamate was passed to Musa ibn Ja'far, who would become the Twelver Shia, those who believed that the Imamate passed to Isma'il ibn Ja'far, who would become the Isma'ili branch named after Isma'il. Isma'il was born in Shawwal 100 AH/719 AD, his mother, Fatima bint al-Hussain'l-Athram bin al-Hasan bin Ali, was the first wife of Ja'far al-Sadiq. He was the brother of Abdullah al-Aftah. Isma'ili sources say that, after the age of seven, as his father's designated successor, Isma'il was kept apart from his siblings, limited in his contact with the public, with his father taking personal responsibility for his education. Given his father's reputation as a scholar and the number of distinguished students who sought out his tuition, Isma'il would have received excellent training, it is said that whenever Ja'far was ill and unable to fulfill his duties as Imam, he deputized Isma'il, although his role was restricted to the confines of the home.

According to Daftary, Isma'il may have taken part in an anti-Abbasid plot in 755 and identified with the more activist, or militant Shi'a. He may have been summoned to the Caliph's court with others to face charges but was spared execution, unlike some of his fellow plotters. To protect him from persecution, his father publicly declared him deceased; the majority Twelver groups argue that Isma'il died during his father's Imamate in the year 138 AH/756 AD. In about 762, Isma'il may have left Medina for Basra, he is said to have had a full grasp of the inner message of Islam. He was succeeded by his son, Muhammad, as the 8th Isma'ili Imam, about 22 at the time; some Isma'ilis believe that Muhammad bin Isma'il became "hidden" and will return as the Mahdi, to establish universal peace and justice. According to Daftary, Isma'il may have led a revolt against the Abbasids in 815, "and died shortly afterwards", he lived in "southwestern Persia... from where he dispatched his own Dais to adjoining areas".

According to some Isma'ili sources, Isma'il ibn Ja'far is buried in Salamiyah, a city located in Syria. Other sources point to Al-Baqi' Madina as his burial place. Twelver Shia's and Sunni Muslims sources have contradicted this, stating that he was buried in Al-Baqi' Medina, the holy Islamic city located in Hijaz; the Isma'ili–Twelver split occurred during and after Imam Ja'far al-Sadiq's lifetime. It was thought that Imam Ja'far al-Sadiq's elder son, Isma'il ibn Ja'far. would be the next Imam, arguably found in both Ismā'īlī and Twelver sources. However, his untimely death prior to Imam Ja'far al-Sadiq's death, led to multiple splits and theories within the community. What came to be known as Isma'ilis, are those who believed that the Imamate should remain within the line of Isma'il ibn Ja’far, it was believed that the designation went to Isma'il ibn Ja'far, therefore the Imamate should continue through his lineage. His early supporters theorized that Isma'il ibn Ja’far’s death was staged, he went into hiding out of fear for his life from the Abbasid Caliph al-Mansūr.

They refused to acknowledge his death, some claimed to have seen him after his funeral. However, most Ismā'īlīs accepted Isma'il ibn Ja’far’s death, instead followed his son Muhammad ibn Isma'il as the next Imam, since the Imamate could still be continued through Isma'il ibn Ja’far’s lineage. On a theological level, Ismai'lis refuse to acknowledge Imams outside of the lineage of Ismail ibn Ja’far due to the notion of naṣṣ and ‘ișma; because Shi’as believe that the Imams are infallible and contain special knowledge of the Divine decree, it is inconceivable that Imam Ja'far al-Sādiq would have incorrectly chosen Imam Isma'il ibn Ja’far as his successor and retract his original naṣṣ. This would mean that Imam Ja'far al-Sādiq either made a major mistake which would make him fallible, or claims regarding other designations were forged narrations. Ithna-'Asharis, following the early death of Isma'il ibn Ja’far acknowledged the designation of Imam Ja'far al-Sādiq’s younger son, Mūsā al-Kāẓim, from his slave-wife, Ḥamīda al-Barbariyya.

Various hadith reports from the Twelver Shi’i collection contain narrations about the designation of Imam Mūsā al-Kāẓim, along with his exceptional character and wisdom from an early age. Witnesses include some of Imam Jafar al-Sadiq’s sons, ‘Ali and Isḥāq, who affirmed Mūsā al-Kāẓim’s naṣṣ. Other arguments made for Imam Mūsā al-Kāẓim include the passing down of special objects that belonged to the Prophet, ‘Ali and Fatima to the designated Imams. While the early followers of Imam Jafar al-Sadiq believed that Isma'il ibn Ja'far might have been the Imam due to his beloved status by his father, some argue that he was neither explicitly designated, nor meant to be, due to his early death. Another mainstream view purports a “change” or “abrogation” in the Divine Decree, known as badā’, in which God may abrogate a previous decree for something better; as a result, Imam Ja'far al-Sādiq’s infallibility is not called into question. The Ithna-‘Asharis continued to follow the Imamate from Mūsā al-Kāẓim’s lineage until their twelfth Imam went into Occultation.

They await their twelfth Imam as the final Mahdi. List of Ismaili imams Family tree of Muhammad#Family tree linking prophets to Imams

1989 San Diego Chargers season

The 1989 San Diego Chargers season was the franchise's 20th season in the National Football League, its 30th overall and the first season under head coach Dan Henning's. The team matched on their 6–10 record from 1988. After a falling out with Head Coach Mike Ditka, Jim McMahon was traded from the Chicago Bears to San Diego, he started 11 games for a dreadful 6–10 Chargers team in 1989. He went 4–7 in the games he started, though the team lost 4 of those games by a combined 11 points in spite of his spotty play at times, he only had 389 yds against the Houston Oilers in a Week 2 loss. He had a falling out with team players and Coach Dan Henning in his year with San Diego with his lackluster play and ego, he finished the year with 2,132 yds, 10 TDs and 10 INTs. He was released and moved on to backup Randall Cunningham on the Philadelphia Eagles in 1990. During the season, the Chargers started playing a non-disco cover version of their fight song, "San Diego Super Chargers". Leslie O'Neal, Pro Bowl Selection Lee Williams, Pro Bowl Selection