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A lenticular galaxy (denoted S0) is a type of galaxy intermediate between an elliptical (denoted E) and a spiral galaxy in galaxy morphological classification schemes. It contains a large-scale disc but does not have large-scale spiral arms. Lenticular galaxies are disc galaxies that have used up or lost most of their... | Lenticular galaxy | Wikipedia | 426 | 319126 | https://en.wikipedia.org/wiki/Lenticular%20galaxy | Physical sciences | Galaxy morphological classification | null |
Lenticular galaxies are often considered to be a poorly understood transition state between spiral and elliptical galaxies, which results in their intermediate placement on the Hubble sequence. This results from lenticulars having both prominent disk and bulge components. The disk component is usually featureless, whic... | Lenticular galaxy | Wikipedia | 355 | 319126 | https://en.wikipedia.org/wiki/Lenticular%20galaxy | Physical sciences | Galaxy morphological classification | null |
Bars
Like spiral galaxies, lenticular galaxies can possess a central bar structure. While the classification system for normal lenticulars depends on dust content, barred lenticular galaxies are classified by the prominence of the central bar. SB01 galaxies have the least defined bar structure and are only classified a... | Lenticular galaxy | Wikipedia | 378 | 319126 | https://en.wikipedia.org/wiki/Lenticular%20galaxy | Physical sciences | Galaxy morphological classification | null |
Lenticular galaxies share kinematic properties with both spiral and elliptical galaxies. This is due to the significant bulge and disk nature of lenticulars. The bulge component is similar to elliptical galaxies in that it is pressure supported by a central velocity dispersion. This situation is analogous to a balloon,... | Lenticular galaxy | Wikipedia | 397 | 319126 | https://en.wikipedia.org/wiki/Lenticular%20galaxy | Physical sciences | Galaxy morphological classification | null |
The kinematics of disk galaxies are usually determined by Hα or 21-cm emission lines, which are typically not present in lenticular galaxies due to their general lack of cool gas. Thus kinematic information and rough mass estimates for lenticular galaxies often comes from stellar absorption lines, which are less reliab... | Lenticular galaxy | Wikipedia | 318 | 319126 | https://en.wikipedia.org/wiki/Lenticular%20galaxy | Physical sciences | Galaxy morphological classification | null |
Formation theories
The morphology and kinematics of lenticular galaxies each, to a degree, suggest a mode of galaxy formation. Their disk-like, possibly dusty, appearance suggests they come from faded spiral galaxies, whose arm features disappeared. However, some lenticular galaxies are more luminous than spiral galaxi... | Lenticular galaxy | Wikipedia | 445 | 319126 | https://en.wikipedia.org/wiki/Lenticular%20galaxy | Physical sciences | Galaxy morphological classification | null |
The analyses of Burstein and Sandage showed that lenticular galaxies typically have surface brightness much greater than other spiral classes. It is also thought that lenticular galaxies exhibit a larger bulge-to-disk ratio than spiral galaxies and this may be inconsistent with simple fading from a spiral. If S0s were ... | Lenticular galaxy | Wikipedia | 402 | 319126 | https://en.wikipedia.org/wiki/Lenticular%20galaxy | Physical sciences | Galaxy morphological classification | null |
The Eagle Nebula (catalogued as Messier 16 or M16, and as NGC 6611, and also known as the Star Queen Nebula) is a young open cluster of stars in the constellation Serpens, discovered by Jean-Philippe de Cheseaux in 1745–46. Both the "Eagle" and the "Star Queen" refer to visual impressions of the dark silhouette near th... | Eagle Nebula | Wikipedia | 394 | 319141 | https://en.wikipedia.org/wiki/Eagle%20Nebula | Physical sciences | Notable nebulae | null |
Images produced by Jeff Hester and Paul Scowen using the Hubble Space Telescope in 1995 greatly improved scientific understanding of processes inside the nebula. One of these became famous as the "Pillars of Creation", depicting a large region of star formation. Its small dark pockets are believed to be protostars (Bok... | Eagle Nebula | Wikipedia | 463 | 319141 | https://en.wikipedia.org/wiki/Eagle%20Nebula | Physical sciences | Notable nebulae | null |
Messier 4 or M4 (also known as NGC 6121 or the Spider Globular Cluster) is a globular cluster in the constellation of Scorpius. It was discovered by Philippe Loys de Chéseaux in 1745 and catalogued by Charles Messier in 1764. It was the first globular cluster in which individual stars were resolved.
Visibility
M4 is c... | Messier 4 | Wikipedia | 410 | 319150 | https://en.wikipedia.org/wiki/Messier%204 | Physical sciences | Notable star clusters | Astronomy |
The space velocity components are (U, V, W) = (, , ) km/s. This confirms an orbit around the Milky Way of a period of with eccentricity 0.80 ± 0.03: during periapsis it comes within from the galactic core, while at apoapsis it travels out to . The inclination is at (an angle of) from the galactic plane, thus it reac... | Messier 4 | Wikipedia | 410 | 319150 | https://en.wikipedia.org/wiki/Messier%204 | Physical sciences | Notable star clusters | Astronomy |
Messier 83 or M83, also known as the Southern Pinwheel Galaxy and NGC 5236, is a barred spiral galaxy approximately 15 million light-years away in the constellation borders of Hydra and Centaurus. Nicolas-Louis de Lacaille discovered M83 on 17 February 1752 at the Cape of Good Hope. Charles Messier added it to his cata... | Messier 83 | Wikipedia | 322 | 319153 | https://en.wikipedia.org/wiki/Messier%2083 | Physical sciences | Notable galaxies | Astronomy |
Supernovae
Six supernovae have been observed in M83:
SN 1923A (type unknown, mag. 14) was discovered by Carl Otto Lampland on 5 May 1923.
SN 1945B (type unknown, mag. 14.2) was discovered by William Liller on 13 July 1945.
SN 1950B (type unknown, mag. 14.5) was discovered by Guillermo Haro on 15 March 1950.
SN 195... | Messier 83 | Wikipedia | 397 | 319153 | https://en.wikipedia.org/wiki/Messier%2083 | Physical sciences | Notable galaxies | Astronomy |
A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano. Repeated eruptions result in the steady accu... | Shield volcano | Wikipedia | 506 | 319168 | https://en.wikipedia.org/wiki/Shield%20volcano | Physical sciences | Volcanology | Earth science |
Active shield volcanoes experience near-continuous eruptive activity over extremely long periods of time, resulting in the gradual build-up of edifices that can reach extremely large dimensions. With the exclusion of flood basalts, mature shields are the largest volcanic features on Earth. The summit of the largest sub... | Shield volcano | Wikipedia | 443 | 319168 | https://en.wikipedia.org/wiki/Shield%20volcano | Physical sciences | Volcanology | Earth science |
Rift zones are a prevalent feature on shield volcanoes that is rare on other volcanic types. The large, decentralized shape of Hawaiian volcanoes as compared to their smaller, symmetrical Icelandic cousins can be attributed to rift eruptions. Fissure venting is common in Hawaii; most Hawaiian eruptions begin with a so-... | Shield volcano | Wikipedia | 495 | 319168 | https://en.wikipedia.org/wiki/Shield%20volcano | Physical sciences | Volcanology | Earth science |
Flows from Hawaiian eruptions can be divided into two types by their structural characteristics: pāhoehoe lava which is relatively smooth and flows with a ropey texture, and ʻaʻā flows which are denser, more viscous (and thus slower moving) and blockier. These lava flows can be anywhere between thick. Aā lava flows mo... | Shield volcano | Wikipedia | 503 | 319168 | https://en.wikipedia.org/wiki/Shield%20volcano | Physical sciences | Volcanology | Earth science |
Features common in shield volcanism include lava tubes. Lava tubes are cave-like volcanic straights formed by the hardening of overlaying lava. These structures help further the propagation of lava, as the walls of the tube insulate the lava within. Lava tubes can account for a large portion of shield volcano activity;... | Shield volcano | Wikipedia | 444 | 319168 | https://en.wikipedia.org/wiki/Shield%20volcano | Physical sciences | Volcanology | Earth science |
Hawaiian–Emperor seamount chain
The largest and most prominent shield volcano chain in the world is the Hawaiian–Emperor seamount chain, a chain of hotspot volcanoes in the Pacific Ocean. The volcanoes follow a distinct evolutionary pattern of growth and death. The chain contains at least 43 major volcanoes, and Meiji... | Shield volcano | Wikipedia | 447 | 319168 | https://en.wikipedia.org/wiki/Shield%20volcano | Physical sciences | Volcanology | Earth science |
Cerro Azul is a shield volcano on the southwestern part of Isabela Island and is one of the most active in the Galapagos, with the last eruption between May and June 2008. The Geophysics Institute at the National Polytechnic School in Quito houses an international team of seismologists and volcanologists whose respons... | Shield volcano | Wikipedia | 498 | 319168 | https://en.wikipedia.org/wiki/Shield%20volcano | Physical sciences | Volcanology | Earth science |
In East Africa, volcanic activity is generated by the development of the East African Rift and from nearby hotspots. Some volcanoes interact with both. Shield volcanoes are found near the rift and off the coast of Africa, although stratovolcanoes are more common. Although sparsely studied, the fact that all of its volc... | Shield volcano | Wikipedia | 465 | 319168 | https://en.wikipedia.org/wiki/Shield%20volcano | Physical sciences | Volcanology | Earth science |
Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other proteins in the cell. Microfilaments are usually about 7 nm in diameter and m... | Microfilament | Wikipedia | 490 | 319342 | https://en.wikipedia.org/wiki/Microfilament | Biology and health sciences | Cell parts | Biology |
In vitro self-assembly
Measuring approximately 6 nm in diameter, microfilaments are the thinnest fibers of the cytoskeleton. They are polymers of actin subunits (globular actin, or G-actin), which as part of the fiber are referred to as filamentous actin, or F-actin. Each microfilament is made up of two helical, interl... | Microfilament | Wikipedia | 361 | 319342 | https://en.wikipedia.org/wiki/Microfilament | Biology and health sciences | Cell parts | Biology |
Subsequently, ADP-actin dissociates slowly from the pointed end, a process significantly accelerated by the actin-binding protein, cofilin. ADP bound cofilin severs ADP-rich regions nearest the (−)-ends. Upon release, the free actin monomer slowly dissociates from ADP, which in turn rapidly binds to the free ATP diffus... | Microfilament | Wikipedia | 431 | 319342 | https://en.wikipedia.org/wiki/Microfilament | Biology and health sciences | Cell parts | Biology |
Because actin monomers must be recycled to sustain high rates of actin-based motility during chemotaxis, cell signalling is believed to activate cofilin, the actin-filament depolymerizing protein which binds to ADP-rich actin subunits nearest the filament's pointed-end and promotes filament fragmentation, with concomit... | Microfilament | Wikipedia | 355 | 319342 | https://en.wikipedia.org/wiki/Microfilament | Biology and health sciences | Cell parts | Biology |
Specialized unique actin cytoskeletal structures are found adjacent to the plasma membrane. Four remarkable examples include red blood cells, human embryonic kidney cells, neurons, and sperm cells. In red blood cells, a spectrin-actin hexagonal lattice is formed by interconnected short actin filaments. In human embryon... | Microfilament | Wikipedia | 382 | 319342 | https://en.wikipedia.org/wiki/Microfilament | Biology and health sciences | Cell parts | Biology |
The actin filament network in non-muscle cells is highly dynamic. The actin filament network is arranged with the barbed-end of each filament attached to the cell's peripheral membrane by means of clamped-filament elongation motors, the above-mentioned "actoclampins", formed from a filament barbed-end and a clamping pr... | Microfilament | Wikipedia | 511 | 319342 | https://en.wikipedia.org/wiki/Microfilament | Biology and health sciences | Cell parts | Biology |
Dickinson and Purich recognized that prompt ATP hydrolysis could explain the forces achieved during actin-based motility. They proposed a simple mechanoenzymatic sequence known as the Lock, Load & Fire Model, in which an end-tracking protein remains tightly bound ("locked" or clamped) onto the end of one sub-filament ... | Microfilament | Wikipedia | 463 | 319342 | https://en.wikipedia.org/wiki/Microfilament | Biology and health sciences | Cell parts | Biology |
Some actoclampins (e.g., those involving Ena/VASP proteins, WASP, and N-WASP) apparently require Arp2/3-mediated filament initiation to form the actin polymerization nucleus that is then "loaded" onto the end-tracker before processive motility can commence. To generate a new filament, Arp2/3 requires a "mother" filamen... | Microfilament | Wikipedia | 233 | 319342 | https://en.wikipedia.org/wiki/Microfilament | Biology and health sciences | Cell parts | Biology |
The cattle egret (formerly genus Bubulcus) is a cosmopolitan clade of heron (family Ardeidae) in the genus Ardea found in the tropics, subtropics, and warm-temperate zones. According to the IOC bird list, it contains two species, the western cattle egret and the eastern cattle egret, although some authorities regard th... | Cattle egret | Wikipedia | 375 | 319522 | https://en.wikipedia.org/wiki/Cattle%20egret | Biology and health sciences | Pelecanimorphae | Animals |
Taxonomy
Before the description of the Bubulcus by Charles Lucien Bonaparte in 1855, the western cattle egret had already been described in 1758 by Carl Linnaeus in his Systema Naturae as Ardea ibis, and the eastern cattle egret had been described in 1783 by Pieter Boddaert as Cancroma coromanda. Their generic name Bub... | Cattle egret | Wikipedia | 417 | 319522 | https://en.wikipedia.org/wiki/Cattle%20egret | Biology and health sciences | Pelecanimorphae | Animals |
The cattle egret is a stocky heron with an wingspan; it is long and weighs . It has a relatively short, thick neck, a sturdy bill, and a hunched posture. The nonbreeding adult has mainly white plumage, a yellow bill, and greyish-yellow legs. During the breeding season, adults of the western cattle egret develop orang... | Cattle egret | Wikipedia | 481 | 319522 | https://en.wikipedia.org/wiki/Cattle%20egret | Biology and health sciences | Pelecanimorphae | Animals |
The species first arrived in North America in 1941 (these early sightings were originally dismissed as escapees), bred in Florida in 1953, and spread rapidly, breeding for the first time in Canada in 1962. It is now commonly seen as far west as California. It was first recorded breeding in Cuba in 1957, in Costa Rica i... | Cattle egret | Wikipedia | 468 | 319522 | https://en.wikipedia.org/wiki/Cattle%20egret | Biology and health sciences | Pelecanimorphae | Animals |
In addition to the natural expansion of its range, cattle egrets have been deliberately introduced into a few areas. The western cattle egret was introduced to Hawaii in 1959, and to the Chagos Archipelago in 1955. Successful releases were also made in the Seychelles and Rodrigues, but attempts to introduce them to Mau... | Cattle egret | Wikipedia | 375 | 319522 | https://en.wikipedia.org/wiki/Cattle%20egret | Biology and health sciences | Pelecanimorphae | Animals |
Breeding
The cattle egret nests in colonies, which are often found around bodies of water. The colonies are usually found in woodlands near lakes or rivers, in swamps, or on small inland or coastal islands, and are sometimes shared with other wetland birds, such as herons, egrets, ibises, and cormorants. The breeding s... | Cattle egret | Wikipedia | 465 | 319522 | https://en.wikipedia.org/wiki/Cattle%20egret | Biology and health sciences | Pelecanimorphae | Animals |
The dominant factor in nesting mortality is starvation. Sibling rivalry can be intense, and in South Africa, third and fourth chicks inevitably starve. In the dryer habitats with fewer amphibians, the diet may lack sufficient vertebrate content and may cause bone abnormalities in growing chicks due to calcium deficienc... | Cattle egret | Wikipedia | 485 | 319522 | https://en.wikipedia.org/wiki/Cattle%20egret | Biology and health sciences | Pelecanimorphae | Animals |
The cattle egret sometimes shows versatility in its diet. On islands with seabird colonies, it will prey on the eggs and chicks of terns and other seabirds. During migration, it has also been reported to eat exhausted migrating landbirds. Birds of the Seychelles race also indulge in some kleptoparasitism, chasing the c... | Cattle egret | Wikipedia | 457 | 319522 | https://en.wikipedia.org/wiki/Cattle%20egret | Biology and health sciences | Pelecanimorphae | Animals |
Not all interactions between humans and cattle egrets are beneficial. The cattle egret can be a safety hazard to aircraft due to its habit of feeding in large groups in the grassy verges of airports, and it has been implicated in the spread of animal infections such as heartwater, infectious bursal disease, and possibl... | Cattle egret | Wikipedia | 69 | 319522 | https://en.wikipedia.org/wiki/Cattle%20egret | Biology and health sciences | Pelecanimorphae | Animals |
An ocean liner is a type of passenger ship primarily used for transportation across seas or oceans. Ocean liners may also carry cargo or mail, and may sometimes be used for other purposes (such as for pleasure cruises or as hospital ships). The Queen Mary 2 is the only ocean liner still in service to this day, serving ... | Ocean liner | Wikipedia | 464 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
Ocean liners were the primary mode of intercontinental travel for over a century, from the mid-19th century until they began to be supplanted by airliners in the 1950s. In addition to passengers, liners carried mail and cargo. Ships contracted to carry British Royal Mail used the designation RMS. Liners were also the p... | Ocean liner | Wikipedia | 489 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
At the beginning of the 19th century, the Industrial Revolution and the inter-continental trade made the development of secure links between continents imperative. Being at the top among the colonial powers, the United Kingdom needed stable maritime routes to connect different parts of its empire: the Far East, India, ... | Ocean liner | Wikipedia | 440 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
The last step toward long-distance travel using steam power was taken in 1837 when left Liverpool on 4 April and arrived in New York eighteen days later on 22 April after a turbulent crossing. Too little coal was prepared for the crossing, and the crew had to burn cabin furniture in order to complete the voyage. The j... | Ocean liner | Wikipedia | 472 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
As the size of ships increased, the wooden hull became unreliable. The start of the use of iron hulls in 1845, and then of steel hulls, solved this problem. The first ship to be both iron-hulled and equipped with a screw propeller was , a creation of Brunel. Her career was disastrous and short. She was run aground and ... | Ocean liner | Wikipedia | 469 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
In 1870, the White Star Line's set a new standard for ocean travel by having its first-class cabins amidships, with the added amenity of large portholes, electricity and running water. The size of ocean liners increased from 1880 onward to meet the needs of migration to the United States and Australia.
and her siste... | Ocean liner | Wikipedia | 455 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
Although German liners dominated in terms of speed, British liners dominated in terms of size. and the Big Four of the White Star Line were the first liners to surpass Great Eastern as the largest passenger ships. Ultimately their owner was American (as mentioned above, White Star Line had been absorbed into J. P. Mor... | Ocean liner | Wikipedia | 501 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
The war caused the loss of many liners. Britannic, while serving as a hospital ship, sank in the Aegean Sea in 1916 after she struck a mine. Numerous incidents of torpedoing took place and large numbers of ships sank. Kaiser Wilhelm der Grosse was defeated and scuttled after a fierce battle with off the coast of west ... | Ocean liner | Wikipedia | 462 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
In 1929, Germany returned to the scene with the two ships of Norddeutscher Lloyd, and . Bremen won the Blue Riband from Britain's Mauretania after the latter had held it for twenty years. Soon, Italy also entered the scene. The Italian Line completed and in 1932, breaking the records of both luxury and speed (Rex wo... | Ocean liner | Wikipedia | 419 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
Many liners were sunk with great loss of life; the three worst disasters were the loss of the Cunarder in 1940 off Saint-Nazaire to German bombing while attempting to evacuate troops of the British Expeditionary Force from France, with the loss of more than 3,000 lives; the sinking of , after the ship was torpedoed by... | Ocean liner | Wikipedia | 391 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
Before World War II, aircraft had not posed a significant economic threat to ocean liners. Most pre-war aircraft were noisy, vulnerable to bad weather, and/or incapable of the range needed for transoceanic flights; all were expensive and had a small passenger capacity. The war accelerated development of large, long-ran... | Ocean liner | Wikipedia | 487 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
A proposed and planned ocean liner, the Titanic II, is a modern replica of the original RMS Titanic, which sank in 1912. The ship is owned by Blue Star Line and is bought by Australian businessman Clive Palmer. The ship is set to be launched by 2027.
Survivors
Four ocean liners built before the World War II survive t... | Ocean liner | Wikipedia | 209 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
Post-war ocean liners still existent include (1948), (1952), MV Brazil Maru (1954), (1958), (1961), (1962), Queen Elizabeth 2 (1967), and Queen Mary 2 (2003). Out of these eight ocean liners, only one is still active and three of them have since been preserved. The Rotterdam has been moored in Rotterdam as a museu... | Ocean liner | Wikipedia | 408 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
Since their beginning in the 19th century, ocean liners needed to meet growing demands. The first liners were small and overcrowded, leading to unsanitary conditions on board. Eliminating these phenomena required larger ships, to reduce the crowding of passengers, and faster ships, to reduce the duration of transatlant... | Ocean liner | Wikipedia | 270 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
In the early 1840s, the average speed of liners was less than 10 knots (a crossing of the Atlantic thus took about 12 days or more). In the 1870s, the average speed of liners increased to around 15 knots the duration of a transatlantic crossing shortened to around 7 days, owing to the technological progress made in the... | Ocean liner | Wikipedia | 493 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
The British and the German shipyards were the most famed in shipbuilding during the era of ocean liners. In Ireland, Harland & Wolff shipyard of Belfast were particularly innovative and succeeded in winning the trust of many shipping companies, such as White Star Line. These gigantic shipyards employed a large portion ... | Ocean liner | Wikipedia | 499 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
The ocean liner industry in France also consisted of two rival companies: the Compagnie Générale Transatlantique (commonly known as "Transat" or "French Line") and Messageries Maritimes. The CGT operated on the North Atlantic route with well-known liners such as and , while the MM operated in French colonies in Asia a... | Ocean liner | Wikipedia | 504 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
The South Atlantic was the route frequented by liners bound for South America, Africa, and sometimes Oceania. The White Star Line had some of its ships, such as the , on the Liverpool-Cape Town-Sydney route. There was not the same level of competition in the South Atlantic as there was in the North Atlantic. There were... | Ocean liner | Wikipedia | 397 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
National symbol
The construction of some ocean liners was a result of nationalism. The revival of power of the German navy stemmed from the clear affirmation of Kaiser Wilhelm II of Germany to see his country become a sea power. Thus, the of 1900 had the honor to bear the name of its mother country, an honor which she... | Ocean liner | Wikipedia | 503 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
Literature
Ocean liners have a strong impact on popular culture, whether during their era or afterwards. In 1867, Jules Verne recounted his experience aboard in his novel A Floating City. In 1898, writer Morgan Robertson wrote the short novel Futility, or the Wreck of the Titan, which features a British ocean liner Ti... | Ocean liner | Wikipedia | 229 | 319558 | https://en.wikipedia.org/wiki/Ocean%20liner | Technology | Naval transport | null |
In biology, a biological life cycle (or just life cycle when the biological context is clear) is a series of stages of the life of an organism, that begins as a zygote, often in an egg, and concludes as an adult that reproduces, producing an offspring in the form of a new zygote which then itself goes through the same ... | Biological life cycle | Wikipedia | 396 | 319610 | https://en.wikipedia.org/wiki/Biological%20life%20cycle | Biology and health sciences | Ecology | Biology |
The cycles differ in when mitosis (growth) occurs. Zygotic meiosis and gametic meiosis have one mitotic stage: mitosis occurs during the n phase in zygotic meiosis and during the 2n phase in gametic meiosis. Therefore, zygotic and gametic meiosis are collectively termed "haplobiontic" (single mitotic phase, not to be c... | Biological life cycle | Wikipedia | 460 | 319610 | https://en.wikipedia.org/wiki/Biological%20life%20cycle | Biology and health sciences | Ecology | Biology |
In archaeplastidans: some green algae (e.g., Chlamydomonas, Zygnema, Chara)
In stramenopiles: some golden algae
In alveolates: many dinoflagellates, e.g., Ceratium, Gymnodinium, some apicomplexans (e.g., Plasmodium)
In rhizarians: some euglyphids, ascetosporeans
In excavates: some parabasalids
In amoebozoans: Dict... | Biological life cycle | Wikipedia | 371 | 319610 | https://en.wikipedia.org/wiki/Biological%20life%20cycle | Biology and health sciences | Ecology | Biology |
In archaeplastidans: some green algae (e.g., Cladophora glomerata, Acetabularia)
In stramenopiles: some brown algae (the Fucales, however, their life cycle can also be interpreted as strongly heteromorphic-diplohaplontic, with a highly reduced gametophyte phase, as in the flowering plants), some xanthophytes (e.g., Va... | Biological life cycle | Wikipedia | 490 | 319610 | https://en.wikipedia.org/wiki/Biological%20life%20cycle | Biology and health sciences | Ecology | Biology |
Vegetative meiosis
Some red algae (such as Bonnemaisonia and Lemanea) and green algae (such as Prasiola) have vegetative meiosis, also called somatic meiosis, which is a rare phenomenon. Vegetative meiosis can occur in haplodiplontic and also in diplontic life cycles. The gametophytes remain attached to and part of th... | Biological life cycle | Wikipedia | 452 | 319610 | https://en.wikipedia.org/wiki/Biological%20life%20cycle | Biology and health sciences | Ecology | Biology |
A host in which parasites reproduce sexually is known as the definitive, final or primary host. In intermediate hosts, parasites either do not reproduce or do so asexually, but the parasite always develops to a new stage in this type of host. In some cases a parasite will infect a host, but not undergo any development,... | Biological life cycle | Wikipedia | 357 | 319610 | https://en.wikipedia.org/wiki/Biological%20life%20cycle | Biology and health sciences | Ecology | Biology |
Individual organisms participating in a biological life cycle ordinarily age and die, while cells from these organisms that connect successive life cycle generations (germ line cells and their descendants) are potentially immortal. The basis for this difference is a fundamental problem in biology. The Russian biologis... | Biological life cycle | Wikipedia | 393 | 319610 | https://en.wikipedia.org/wiki/Biological%20life%20cycle | Biology and health sciences | Ecology | Biology |
A bidet ( or ) is a bowl or receptacle designed to be sat upon in order to wash a person's genitalia, perineum, inner buttocks, and anus. The modern variety has a plumbed-in water supply and a drainage opening, and is thus a plumbing fixture subject to local hygiene regulations. The bidet is designed to promote persona... | Bidet | Wikipedia | 418 | 319653 | https://en.wikipedia.org/wiki/Bidet | Technology | Hydraulics and pneumatics | null |
A bidet shower (also known as "bidet spray", "bidet sprayer", or "health faucet") is a hand-held triggered nozzle, similar to that on a kitchen sink sprayer, that delivers a spray of water to assist in anal cleansing and cleaning the genitals after defecation and urination. In contrast to a bidet that is integrated wit... | Bidet | Wikipedia | 414 | 319653 | https://en.wikipedia.org/wiki/Bidet | Technology | Hydraulics and pneumatics | null |
Such attachable bidets (also called "combined toilets", "bidet attachments", or "add-on bidets") are controlled either mechanically, by turning a valve, or electronically. Electronic bidets are controlled with waterproof electrical switches rather than a manual valve. There are models that have a heating element which ... | Bidet | Wikipedia | 485 | 319653 | https://en.wikipedia.org/wiki/Bidet | Technology | Hydraulics and pneumatics | null |
In the US, UK, and some other countries, wet wipes are heavily marketed as an upgrade from dry toilet paper. However, this product has been criticized for its adverse environmental impact, due to the non-biodegradable plastic fibers composing most versions. Although the wipes are promoted as "flushable", they absorb wa... | Bidet | Wikipedia | 474 | 319653 | https://en.wikipedia.org/wiki/Bidet | Technology | Hydraulics and pneumatics | null |
In 1980, the first "paperless toilet" was launched in Japan by manufacturer Toto, a combination of toilet and bidet which also dries the user after washing. These combination toilet-bidets (washlet) with seat warmers, or attachable bidets are particularly popular in Japan and South Korea, and are found in approximately... | Bidet | Wikipedia | 461 | 319653 | https://en.wikipedia.org/wiki/Bidet | Technology | Hydraulics and pneumatics | null |
Historical antecedents and early functions of the bidet are believed to include devices used for contraception. Bidets are considered ineffective by today's standards of contraception, and their use for that function was quickly abandoned and forgotten following the advent of modern contraceptives such as the pill.
By... | Bidet | Wikipedia | 296 | 319653 | https://en.wikipedia.org/wiki/Bidet | Technology | Hydraulics and pneumatics | null |
In mathematics, a binary relation is called well-founded (or wellfounded or foundational) on a set or, more generally, a class if every non-empty subset has a minimal element with respect to ; that is, there exists an such that, for every , one does not have . In other words, a relation is well-founded if:
Some au... | Well-founded relation | Wikipedia | 501 | 319712 | https://en.wikipedia.org/wiki/Well-founded%20relation | Mathematics | Order theory | null |
As an example, consider the well-founded relation , where is the set of all natural numbers, and is the graph of the successor function . Then induction on is the usual mathematical induction, and recursion on gives primitive recursion. If we consider the order relation , we obtain complete induction, and course-of... | Well-founded relation | Wikipedia | 441 | 319712 | https://en.wikipedia.org/wiki/Well-founded%20relation | Mathematics | Order theory | null |
If is a well-founded relation and is an element of , then the descending chains starting at are all finite, but this does not mean that their lengths are necessarily bounded. Consider the following example:
Let be the union of the positive integers with a new element ω that is bigger than any integer. Then is a ... | Well-founded relation | Wikipedia | 332 | 319712 | https://en.wikipedia.org/wiki/Well-founded%20relation | Mathematics | Order theory | null |
The Rutherford scattering experiments were a landmark series of experiments by which scientists learned that every atom has a nucleus where all of its positive charge and most of its mass is concentrated. They deduced this after measuring how an alpha particle beam is scattered when it strikes a thin metal foil. The ... | Rutherford scattering experiments | Wikipedia | 471 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
Alpha particles and the Thomson atom
An alpha particle is a positively charged particle of matter that is spontaneously emitted from certain radioactive elements. Alpha particles are so tiny as to be invisible, but they can be detected with the use of phosphorescent screens, photographic plates, or electrodes. Rutherfo... | Rutherford scattering experiments | Wikipedia | 506 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
The counter that Geiger and Rutherford built proved unreliable because the alpha particles were being too strongly deflected by their collisions with the molecules of air within the detection chamber. The highly variable trajectories of the alpha particles meant that they did not all generate the same number of ions as... | Rutherford scattering experiments | Wikipedia | 480 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
The extreme scattering observed forced Rutherford to revise the model of the atom. The issue in Thomson's model was that the charges were too diffuse to produce a sufficiently strong electrostatic force to cause such repulsion. Therefore they had to be more concentrated. In Rutherford's new model, the positive charge ... | Rutherford scattering experiments | Wikipedia | 468 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
Rutherford's new atom model caused no stir. Rutherford explicitly ignores the electrons, only mentioning Hantaro Nagaoka's Saturnian model of electrons orbiting a tiny "sun", a model that had been previously rejected as mechanically unstable. By ignoring the electrons Rutherford also ignores any potential implications ... | Rutherford scattering experiments | Wikipedia | 339 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
Alpha particle scattering: 1906 and 1908 experiments
Rutherford's first steps towards his discovery of the nature of the atom came from his work to understand alpha particles.
In 1906, Rutherford noticed that alpha particles passing through sheets of mica were deflected by the sheets by as much as 2 degrees. Rutherford... | Rutherford scattering experiments | Wikipedia | 486 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
The results of the initial alpha particle scattering experiments were confusing. The angular spread of the particle on the screen varied greatly with the shape of the apparatus and its internal pressure. Rutherford suggested that Ernest Marsden, a physics undergraduate student studying under Geiger, should look for dif... | Rutherford scattering experiments | Wikipedia | 425 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
Geiger and Marsden then wanted to estimate the total number of alpha particles that were reflected. The previous setup was unsuitable for doing this because the tube contained several radioactive substances (radium plus its decay products) and thus the alpha particles emitted had varying ranges, and because it was dif... | Rutherford scattering experiments | Wikipedia | 487 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
From the measurements he took, Geiger came to the following conclusions:
the most probable angle of deflection increases with the thickness of the material
the most probable angle of deflection is proportional to the atomic mass of the substance
the most probable angle of deflection decreases with the velocity of th... | Rutherford scattering experiments | Wikipedia | 462 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
To test how the scattering varied with the angle of deflection (i.e. if s ∝ csc4). Geiger and Marsden built an apparatus that consisted of a hollow metal cylinder mounted on a turntable. Inside the cylinder was a metal foil (F) and a radiation source containing radon (R), mounted on a detached column (T) which allowed... | Rutherford scattering experiments | Wikipedia | 370 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
Geiger and Marsden reused the apparatus to measure how the scattering pattern varied with the square of the nuclear charge (i.e. if s ∝ Qn2). Geiger and Marsden did not know what the positive charge of the nucleus of their metals were (they had only just discovered the nucleus existed at all), but they assumed it was ... | Rutherford scattering experiments | Wikipedia | 439 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
In 1917, Rutherford and his assistant William Kay began exploring the passage of alpha particles through gases such as hydrogen and nitrogen. In this experiment, they shot a beam of alpha particles through hydrogen, and they carefully placed their detector—a zinc sulfide screen—just beyond the range of the alpha partic... | Rutherford scattering experiments | Wikipedia | 411 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
For an alpha particle:
(mass) = =
(for the alpha particle) = 2 × =
(for gold) = 79 × =
(initial velocity) = (for this example)
The distance from the alpha particle to the centre of the nucleus () at this point is an upper limit for the nuclear radius.
Substituting these in gives the value of about , or 2... | Rutherford scattering experiments | Wikipedia | 416 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
Single scattering by a heavy nucleus
From his results for a head on collision, Rutherford knows that alpha particle scattering occurs close to the centre of an atom, at a radius 10,000 times smaller than the atom. The electrons have negligible effect. He begins by assuming no energy loss in the collision, that is he ig... | Rutherford scattering experiments | Wikipedia | 507 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
The next step is to find a formula for . From Figure 2, is the sum of two distances related to the hyperbola, SO and OA. Using the following logic, these distances can be expressed in terms of angle and impact parameter .
The eccentricity of a hyperbola is a value that describes the hyperbola's shape. It can be ca... | Rutherford scattering experiments | Wikipedia | 502 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
This formula predicted the results that Geiger measured in the coming year. The scattering probability into small angles greatly exceeds the probability in to larger angles, reflecting the tiny nucleus surrounded by empty space. However, for rare close encounters, large angle scattering occurs with just a single target... | Rutherford scattering experiments | Wikipedia | 453 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
Modern treatments analyze this type of Coulomb scattering in the centre of mass reference frame. The six coordinates of the two particles (also called "bodies") are converted into three relative coordinates between the two particles and three centre-of-mass coordinates moving in space (called the lab frame). The inter... | Rutherford scattering experiments | Wikipedia | 510 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
An alternative method to find the scattering angle
This section presents an alternative method to find the relation between the impact parameter and deflection angle in a single-atom encounter, using a force-centric approach as opposed to the energy-centric one that Rutherford used.
The scattering geometry is shown i... | Rutherford scattering experiments | Wikipedia | 442 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
Why the plum pudding model was wrong
J. J. Thomson himself didn't study alpha particle scattering, but he did study beta particle scattering. In his 1910 paper "On the Scattering of rapidly moving Electrified Particles", Thomson presented equations that modelled how beta particles scatter in a collision with an atom. R... | Rutherford scattering experiments | Wikipedia | 507 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
where px is the average horizontal momentum, which is first reduced then restored as horizontal force changes direction as the alpha particle goes across the sphere. Since the deflection is very small, can be treated as equal to . The chord length , per Pythagorean theorem.
The average deflection angle sums the angl... | Rutherford scattering experiments | Wikipedia | 455 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
On average the positive sphere and the electrons alike provide very little deflection in a single collision. Thomson's model combined many single-scattering events from the atom's electrons and a positive sphere. Each collision may increase or decrease the total scattering angle. Only very rarely would a series of coll... | Rutherford scattering experiments | Wikipedia | 306 | 319834 | https://en.wikipedia.org/wiki/Rutherford%20scattering%20experiments | Physical sciences | Atomic physics | null |
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Between the generating station and consumer, electric power may flow through several substations at different vo... | Substation | Wikipedia | 432 | 320217 | https://en.wikipedia.org/wiki/Substation | Technology | Electricity transmission and distribution | null |
Transmission substation
A transmission substation connects two or more transmission lines. The simplest case is where all transmission lines have the same voltage. In such cases, substation contains high-voltage switches that allow lines to be connected or isolated for fault clearance or maintenance. A transmission sta... | Substation | Wikipedia | 479 | 320217 | https://en.wikipedia.org/wiki/Substation | Technology | Electricity transmission and distribution | null |
Collector substation
In distributed generation projects such as a wind farm or photovoltaic power station, a collector substation may be required. It resembles a distribution substation although power flow is in the opposite direction, from many wind turbines or inverters up into the transmission grid. Usually for econ... | Substation | Wikipedia | 442 | 320217 | https://en.wikipedia.org/wiki/Substation | Technology | Electricity transmission and distribution | null |
An important function performed by a substation is switching, which is the connecting and disconnecting of transmission lines or other components to and from the system. Switching events may be planned or unplanned. A transmission line or other component may need to be de-energized for maintenance or for new constructi... | Substation | Wikipedia | 454 | 320217 | https://en.wikipedia.org/wiki/Substation | Technology | Electricity transmission and distribution | null |
Location selection
Selection of the location of a substation must consider many factors. Sufficient land area is required for installation of equipment with necessary clearances for electrical safety, and for access to maintain large apparatus such as transformers. The site must have room for expansion due to load grow... | Substation | Wikipedia | 479 | 320217 | https://en.wikipedia.org/wiki/Substation | Technology | Electricity transmission and distribution | null |
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