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Nadir Divan-Beghi
The nadir (, ; ar, نظير, naẓīr, counterpart) is the direction pointing directly ''below'' a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface. The direction opposite of the nadir is the zenith. Definitions Space science Since the concept of ''being below'' is itself somewhat vague, scientists define the nadir in more rigorous terms. Specifically, in astronomy, geophysics and related sciences (e.g., meteorology), the nadir at a given point is the local vertical direction pointing in the direction of the force of gravity at that location. The term can also be used to represent the lowest point that a celestial object reaches along its apparent daily path around a given point of observation (i.e. the object's ''lower culmination''). This can be used to describe the position of the Sun, but it is only technically accurate for one latitude at a time and only possible at the low latitudes. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope thermoelectric generators (RTGs). Most satellites also have a method of communication to ground stations, called Transponder (satellite communications), transponders. Many satellites use a Satellite bus, standardized bus to save cost and work, the most popular of which is small CubeSats. Similar satellites can work together as a group, forming Satellite constellation, constellations. Because of the high launch cost to space, satellites are designed to be as lightweight and robust as possible. Most communication satellites are radio Broadcast relay station, relay stations in orbit and carry dozens of transponders, each with a bandwidth of tens of megahertz. Satellites are placed from the surface to orbit by launch vehicles, high enough to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nadir Of American Race Relations
The nadir of American race relations was the period in African American history and the history of the United States from the end of Reconstruction in 1877 through the early 20th century when racism in the country, especially racism against African Americans, was more open and pronounced than it had ever been during any other period in the nation's history. During this period, African Americans lost access to many of the civil rights they had gained during Reconstruction. Anti-black violence, lynchings, segregation, legalized racial discrimination, and expressions of white supremacy all increased. Historian Rayford Logan coined the phrase in his 1954 book ''The Negro in American Life and Thought: The Nadir, 1877–1901''. Logan tried to determine the period when "the Negro's status in American society" reached its lowest point. He argued for 1901 as its end, suggesting that race relations improved after that year; other historians, such as John Hope Franklin and Henry Arthur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mood (psychology)
In psychology, a mood is an affective state. In contrast to emotions or feelings, moods are less specific, less intense and less likely to be provoked or instantiated by a particular stimulus or event. Moods are typically described as having either a positive or negative valence. In other words, people usually talk about being in a good mood or a bad mood. There are many different factors that influence mood, and these can lead to positive or negative effects on mood. Mood also differs from temperament or personality traits which are even longer-lasting. Nevertheless, personality traits such as optimism and neuroticism predispose certain types of moods. Long term disturbances of mood such as clinical depression and bipolar disorder are considered mood disorders. Mood is an internal, subjective state but it often can be inferred from posture and other behaviors. "We can be sent into a mood by an unexpected event, from the happiness of seeing an old friend to the anger of discov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemotherapy
Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherapy may be given with a curative intent (which almost always involves combinations of drugs) or it may aim to prolong life or to reduce symptoms ( palliative chemotherapy). Chemotherapy is one of the major categories of the medical discipline specifically devoted to pharmacotherapy for cancer, which is called ''medical oncology''. The term ''chemotherapy'' has come to connote non-specific usage of intracellular poisons to inhibit mitosis (cell division) or induce DNA damage, which is why inhibition of DNA repair can augment chemotherapy. The connotation of the word chemotherapy excludes more selective agents that block extracellular signals (signal transduction). The development of therapies with specific molecular or genetic targets, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oncology
Oncology is a branch of medicine that deals with the study, treatment, diagnosis and prevention of cancer. A medical professional who practices oncology is an ''oncologist''. The name's etymological origin is the Greek word ὄγκος (''ónkos''), meaning "tumor", "volume" or "mass". Oncology is concerned with: * The diagnosis of any cancer in a person (pathology) * Therapy (e.g. surgery, chemotherapy, radiotherapy and other modalities) * Follow-up of cancer patients after successful treatment * Palliative care of patients with terminal malignancies * Ethical questions surrounding cancer care * Screening efforts: ** of populations, or ** of the relatives of patients (in types of cancer that are thought to have a hereditary basis, such as breast cancer) Diagnosis Medical histories remain an important screening tool: the character of the complaints and nonspecific symptoms (such as fatigue, weight loss, unexplained anemia, fever of unknown origin, paraneoplastic phenome ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ground Track
A ground track or ground trace is the path on the surface of a planet directly below an aircraft's or satellite's trajectory. In the case of satellites, it is also known as a suborbital track, and is the vertical projection of the satellite's orbit onto the surface of the Earth (or whatever body the satellite is orbiting). A satellite ground track may be thought of as a path along the Earth's surface that traces the movement of an imaginary line between the satellite and the center of the Earth. In other words, the ground track is the set of points at which the satellite will pass directly overhead, or cross the zenith, in the frame of reference of a ground observer.. Aircraft ground tracks In air navigation, ground tracks typically approximate an arc of a great circle, this being the shortest distance between two points on the Earth's surface. In order to follow a specified ground track, a pilot must adjust their heading in order to compensate for the effect of wind. Aircra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerial Photo
Aerial photography (or airborne imagery) is the taking of photographs from an aircraft or other airborne platforms. When taking motion pictures, it is also known as aerial videography. Platforms for aerial photography include fixed-wing aircraft, helicopters, unmanned aerial vehicles (UAVs or "drones"), balloons, blimps and dirigibles, rockets, pigeons, kites, or using action cameras while skydiving or wingsuiting. Handheld cameras may be manually operated by the photographer, while mounted cameras are usually remotely operated or triggered automatically. Aerial photography typically refers specifically to bird's-eye view images that focus on landscapes and surface objects, and should not be confused with air-to-air photography, where one or more aircraft are used as chase planes that "chase" and photograph other aircraft in flight. Elevated photography can also produce bird's-eye images closely resembling aerial photography (despite not actually being aerial shots) when ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite Image
Satellite images (also Earth observation imagery, spaceborne photography, or simply satellite photo) are images of Earth collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell images by licensing them to governments and businesses such as Apple Maps and Google Maps. History The first images from space were taken on Sub-orbital spaceflight, sub-orbital flights. The U.S-launched V-2 flight on October 24, 1946, took one image every 1.5 seconds. With an Apsis, apogee of 65 miles (105 km), these photos were from five times higher than the previous record, the 13.7 miles (22 km) by the Explorer II balloon mission in 1935. The first satellite (orbital) photographs of Earth were made on August 14, 1959, by the U.S. Explorer 6. The first satellite photographs of the Moon might have been made on October 6, 1959, by the Soviet satellite Luna 3, on a mission to photograph the far side of the Moon. The Blue Marble ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spacewalk
Extravehicular activity (EVA) is any activity done by an astronaut in outer space outside a spacecraft. In the absence of a breathable atmosphere of Earth, Earthlike atmosphere, the astronaut is completely reliant on a space suit for environmental support. EVA includes ''spacewalks'' and Moon, lunar or planetary surface exploration (commonly known from 1969 to 1972 as ''moonwalks''). In a stand-up EVA (SEVA), an astronaut stands through an open hatch but does not fully leave the spacecraft. EVA has been conducted by the Soviet Union/Russia, the United States, Canada, the European Space Agency and China. On March 18, 1965, Alexei Leonov became the first human to perform a spacewalk, exiting the Voskhod 2 capsule for 12 minutes and 9 seconds. On July 20, 1969, Neil Armstrong became the first human to perform a moonwalk, outside his lunar lander on Apollo 11 for 2 hours and 31 minutes. On the last three Moon missions, astronauts also performed deep-space EVAs on the return to Eart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronaut
An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally reserved for professional space travelers, the term is sometimes applied to anyone who travels into space, including scientists, politicians, journalists, and tourists. "Astronaut" technically applies to all human space travelers regardless of nationality. However, astronauts fielded by Russia or the Soviet Union are typically known instead as cosmonauts (from the Russian "kosmos" (космос), meaning "space", also borrowed from Greek). Comparatively recent developments in crewed spaceflight made by China have led to the rise of the term taikonaut (from the Mandarin "tàikōng" (), meaning "space"), although its use is somewhat informal and its origin is unclear. In China, the People's Liberation Army Astronaut Corps astronauts and their ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmosphere Of Earth
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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