title: Springbok content: on vigilance, more among the grazing springbok than among their browsing counterparts. Adults were found to be more vigilant than juveniles, and males more vigilant than females. Springbok passing through bushes tend to be more vulnerable to predator attacks as they can not be easily alerted, and predators usually conceal themselves in bushes. Another study calculated that the time spent in vigilance by springbok on the edges of herds is roughly double that spent by those in the centre and the open. Springbok were found to be more cautious in the late morning than at dawn or in the afternoon,


title: Springbok content: and more at night than in the daytime. Rates and methods of vigilance were found to vary with the aim of lowering risk from predators. During the rut, males establish territories, ranging from , which they mark by urinating and depositing large piles of dung. Males in neighbouring territories frequently fight for access to females, which they do by twisting and levering at each other with their horns, interspersed with stabbing attacks. Females roam the territories of different males. Outside of the rut, mixed-sex herds can range from as few as three to as many as 180 individuals, while all-male


title: Springbok content: bachelor herds are of typically no more than 50 individuals. Harem and nursery herds are much smaller, typically including no more than 10 individuals. In earlier times, when large populations of springbok roamed the Kalahari desert and Karoo, millions of migrating springbok formed herds hundreds of kilometres long that could take several days to pass a town. These mass treks, known as "trekbokken" in Afrikaans, took place during long periods of drought. Herds could efficiently retrace their paths to their territories after long migrations. "Trekbokken" is still observed occasionally in Botswana, though on a much smaller scale than earlier. Springbok


title: Springbok content: often go into bouts of repeated high leaps of up to into the air – a practice known as pronking (derived from the Afrikaans "pronk", "to show off") or stotting. In pronking, the springbok performs multiple leaps into the air in a stiff-legged posture, with the back bowed and the white flap lifted. When the male shows off his strength to attract a mate, or to ward off predators, he starts off in a stiff-legged trot, leaping into the air with an arched back every few paces and lifting the flap along his back. Lifting the flap causes the long


title: Springbok content: white hairs under the tail to stand up in a conspicuous fan shape, which in turn emits a strong scent of sweat. Although the exact cause of this behaviour is unknown, springbok exhibit this activity when they are nervous or otherwise excited. The most accepted theory for pronking is that it is a method to raise alarm against a potential predator or confuse it, or to get a better view of a concealed predator; it may also be used for display. Springbok are very fast antelopes, clocked at . They generally tend to be ignored by carnivores unless they are


title: Springbok content: breeding. Caracals, cheetahs, leopards, spotted hyenas, and wild dogs are major predators of the springbok. Southern African wildcats, black-backed jackals, black eagles, martial eagles, and tawny eagles target juveniles. Springbok are generally quiet animals, though they may make occasional low-pitched bellows as a greeting and high-pitched snorts when alarmed. A 2012 study on the effects of rainfall patterns and parasite infections on the body of the springbok in Etosha National Park observed that males and juveniles were in better health toward the end of the rainy season. Health of females was more affected by parasites than by rainfall; parasite count


title: Springbok content: in females peaked prior to and immediately after parturition. Studies show that springbok host helminths ("Haemonchus", "Longistrongylus" and "Trichostrongylus"), ixodid ticks ("Rhipicephalus" species), lice ("Damalinia" and "Linognathus" species). "Eimeria" species mainly affect juveniles. Springbok are primarily browsers and may switch to grazing occasionally; they feed on shrubs and young succulents (such as "Lampranthus" species) before they lignify. They prefer grasses such as "Themeda triandra". Springbok can meet their water needs from the food they eat, and are able to survive without drinking water through dry season. In extreme cases, they do not drink any water over the course of their


title: Springbok content: lives. Springbok may accomplish this by selecting flowers, seeds, and leaves of shrubs before dawn, when the food items are most succulent. In places such as the Etosha National Park, springbok seek out water bodies where they are available. Springbok gather in the wet season and disperse during the dry season, unlike other African mammals. Springbok mate year-round, though females are more likely to enter oestrus during the rainy season, when food is more plentiful. Females are able to conceive at as early as six to seven months, whereas males do not attain sexual maturity until two years; rut lasts


title: Springbok content: 5 to 21 days. When a female approaches a rutting male, the male holds his head and tail at level with the ground, lowers his horns, and makes a loud grunting noise to attract her. The male then urinates and sniffs the female's perineum. If the female is receptive, she urinates, as well, and the male makes a flehmen gesture, and taps his leg till the female leaves or permits him to mate. Copulation consists of a single pelvic thrust. Gestation lasts five to six months, after which a single calf (or rarely twins) is born. Most births take place


title: Springbok content: in the spring (October to November), prior to the onset of the rainy season. The infant weighs ; the female keeps her calf hidden in cover while she is away. Mother and calf rejoin the herd about three to four weeks after parturition; the young are weaned at five or six months. When the mother gives birth again, the previous offspring, now 6 to 12 months old, deserts her to join herds of adult springbok. Thus, a female can calve twice a year, and even thrice if one calf dies. Springbok live for up to 10 years in the wild.


title: Springbok content: Springbok inhabit the dry areas of south and southwestern Africa. Their range extends from northwestern South Africa through the Kalahari desert into Namibia and Botswana. The Transvaal marks the eastern limit of the range, from where it extends westward to the Atlantic and northward to southern Angola and Botswana. In Botswana, they mostly occur in the Kalahari desert in the southwestern and central parts of the country. They are widespread across Namibia and the vast grasslands of the Free State and the shrublands of Karoo in South Africa; however, they are confined to the Namib Desert in Angola. The historic


title: Springbok content: range of the springbok stretched across the dry grasslands, bushlands, and shrublands of south-western and southern Africa; springbok migrated sporadically in southern parts of the range. These migrations are rarely seen nowadays, but seasonal congregations can still be observed in preferred areas of short vegetation, such as the Kalahari desert. The springbok has been classified as least concern by the IUCN. No major threats to the long-term survival of the species are known. In fact, the springbok is one of the few antelope species with a positive population trend. Springbok occur in several protected areas across their range: Makgadikgadi and


title: Springbok content: Nxai National Park (Botswana); Kgalagadi Transfrontier Park between Botswana and South Africa; Etosha National Park and Namib-Naukluft Park (Namibia); Mokala and Karoo National Parks and a number of provincial reserves in South Africa. In 1999, Rod East of the IUCN SSC Antelope Specialist Group estimated the springbok population in South Africa at more than 670,000, noting that it might be an underestimate. However, estimates for Namibia, Angola, Botswana, Transvaal, Karoo, and the Free State (which gave a total population estimate of nearly 2,000,000 – 2,500,000 animals in southern Africa), were in complete disagreement with East's estimate. Springbok are under active


title: Springbok content: management in several private lands. Small populations have been introduced into private lands and provincial areas of KwaZulu-Natal. Springbok are hunted as game throughout Namibia, Botswana, and South Africa because of their attractive coats; they are common hunting targets due to their large numbers and the ease with which they can be supported on farmlands. The export of springbok skins, mainly from Namibia and South Africa, is a booming industry; these skins serve as taxidermy models. The meat is a prized fare, and is readily available in South African supermarkets. As of 2011, the springbok, the gemsbok, and the greater


title: Springbok content: kudu collectively account for around two-thirds of the game meat production from Namibian farmlands; nearly of the springbok meat is exported as mechanically deboned meat to overseas markets. The latissimus dorsi muscle of the springbok comprises 1.1–1.3% ash, 1.3–3.5% fat, 72–75% moisture and 18–22% protein. Stearic acid is the main fatty acid, accounting for 24–27% of the fatty acids. The cholesterol content varies from per of meat. The pH of the meat increases if the springbok is under stress or cropping is done improperly; consequently, the quality deteriorates and the colour darkens. The meat might be adversely affected if the


title: Springbok content: animal is killed by shooting. The meat may be consumed raw or used in prepared dishes. Biltong can be prepared by preserving the raw meat with vinegar, spices, and table salt, without fermentation, followed by drying. Springbok meat may also be used in preparing salami; a study found that the flavour of this salami is better than mutton salami, and feels oilier than salami of beef, horse meat, or mutton. The springbok has been a national symbol of South Africa since the white minority rule in the 20th century. It was adopted as a nickname or mascot by several South


title: Springbok content: African sports teams, most famously by the national rugby union team. The springbok is the national animal of South Africa. Even after the decline of apartheid, Nelson Mandela intervened to keep the name of the animal for the reconciliation of rugby fans, the majority of whom were whites. The cap badge of The Royal Canadian Dragoons has featured a springbok since 1913, a reference to the unit's involvement in the Second Boer War. Springbok The springbok (; "Antidorcas marsupialis") is a medium-sized antelope found mainly in southern and southwestern Africa. The sole member of the genus "Antidorcas", this bovid was


title: "Statue of Liberty" content: in, the committee resumed work on the pedestal. On June 17, 1885, the French steamer "Isère", arrived in New York with the crates holding the disassembled statue on board. New Yorkers displayed their new-found enthusiasm for the statue. Two hundred thousand people lined the docks and hundreds of boats put to sea to welcome the ship. After five months of daily calls to donate to the statue fund, on August 11, 1885, the "World" announced that $102,000 had been raised from 120,000 donors, and that 80 percent of the total had been received in sums of less than one dollar.


title: Selenocysteine content: in that position, have S chirality.) Proteins which contain one or more selenocysteine residues are called selenoproteins. Most selenoproteins contain a single selenocysteine residue. Selenoproteins which depend on selenocysteine's catalytic activity are called selenoenzymes. Selenoenzymes have been found to employ catalytic triad structures that influence the nucleophilicity of the active site selenocysteine. Selenocysteine has both a lower pKa (5.47) and a lower reduction potential than cysteine. These properties make it very suitable in proteins that are involved in antioxidant activity. Although it is found in the three domains of life, it is not universal in all organisms. Unlike other amino


title: "Symbionese Liberation Army" content: on all levels and for all of the people, and by any means necessary. To give back of all people their human and constitutional rights, liberty, equality and justice and the right to bear arms in the defense of these rights. To create a system where our aged are cared for with respect, love, and kindness and encouraged to become assets in their own ways to their nations and to their communal community. That the life that moves around them is not a frightening and murderous one and where life is not a fear, but rather one of love and


title: "Stevens–Johnson syndrome" content: can interact with the drug or its metabolite. Thus, only rare individuals are predisposed to develop SJS in response to a particular drug on the bases of their expression of specific T cell receptor types. While the evidence supporting this T cell receptor selectivity is limited, one study identified the preferential presence of the TCR-V-b and complementarity determining region 3 in T cell receptors found on the T cells in the blisters of patients with allopurinol-induced DRESS syndrome. This finding is compatible with the notion that specific types of T cell receptors are involved in the development of specific drug-induced


title: "Shania Twain" content: 10 and the Top 15 in France. The third single from the album would be the most successful in the US. The romantic ballad "Forever and for Always" was released as a single in April 2003 and peaked at No.4 on the country chart and No.1 on the Adult Contemporary chart, and made as well the "Billboard" Top 20. Again success was even bigger on the other side of the Atlantic with "Forever and For Always" again reaching the Top 10 in both, the UK and Germany. Further singles were "She's Not Just a Pretty Face", which was a country


title: Stethoscope content: Stethoscope The stethoscope is an acoustic medical device for auscultation, or listening to the internal sounds of an animal or human body. It typically has a small disc-shaped resonator that is placed against the chest, and two tubes connected to earpieces. It is often used to listen to lung and heart sounds. It is also used to listen to intestines and blood flow in arteries and veins. In combination with a sphygmomanometer, and is commonly used for measurements of blood pressure. Less commonly, "mechanic's stethoscopes", equipped with rod-shaped chest pieces, are used to listen to internal sounds made by machines


title: Stethoscope content: (for example, sounds and vibrations emitted by worn ball bearings), such as diagnosing a malfunctioning automobile engine by listening to the sounds of its internal parts. Stethoscopes can also be used to check scientific vacuum chambers for leaks, and various other small-scale acoustic monitoring tasks. A stethoscope that intensifies auscultatory sounds is called phonendoscope. The stethoscope was invented in France in 1816 by René Laennec at the Necker-Enfants Malades Hospital in Paris. It consisted of a wooden tube and was monaural. Laennec invented the stethoscope because he was uncomfortable placing his ear on women's chests to hear heart sounds. He


title: Stethoscope content: observed that a rolled piece of paper, placed between the patient's chest and his ear, could amplify heart sounds without requiring physical contact. Laennec's device was similar to the common ear trumpet, a historical form of hearing aid; indeed, his invention was almost indistinguishable in structure and function from the trumpet, which was commonly called a "microphone". Laennec called his device the "stethoscope" ("stetho-" + "-scope", "chest scope"), and he called its use "mediate auscultation", because it was auscultation with a tool intermediate between the patient's body and the physician's ear. (Today the word "auscultation" denotes all such listening, mediate


title: Stethoscope content: or not.) The first flexible stethoscope of any sort may have been a binaural instrument with articulated joints not very clearly described in 1829. In 1840, Golding Bird described a stethoscope he had been using with a flexible tube. Bird was the first to publish a description of such a stethoscope but he noted in his paper the prior existence of an earlier design (which he thought was of little utility) which he described as the snake ear trumpet. Bird's stethoscope had a single earpiece. In 1851, Irish physician Arthur Leared invented a binaural stethoscope and, in 1852, George Philip


title: Stethoscope content: Cammann perfected the design of the stethoscope instrument (that used both ears) for commercial production, which has become the standard ever since. Cammann also wrote a major treatise on diagnosis by auscultation, which the refined binaural stethoscope made possible. By 1873, there were descriptions of a differential stethoscope that could connect to slightly different locations to create a slight stereo effect, though this did not become a standard tool in clinical practice. Somerville Scott Alison described his invention of the stethophone at the Royal Society in 1858; the stethophone had two separate bells, allowing the user to hear and compare


title: Stethoscope content: sounds derived from two discrete locations. This was used to do definitive studies on binaural hearing and auditory processing that advanced knowledge of sound localization and eventually lead to an understanding of binaural fusion. The medical historian Jacalyn Duffin has argued that the invention of the stethoscope marked a major step in the redefinition of disease from being a bundle of symptoms, to the current sense of a disease as a problem with an anatomical system even if there are no noticeable symptoms. This re-conceptualization occurred in part, Duffin argues, because prior to stethoscopes, there were no non-lethal instruments for


title: Stethoscope content: exploring internal anatomy. Rappaport and Sprague designed a new stethoscope in the 1940s, which became the standard by which other stethoscopes are measured, consisting of two sides, one of which is used for the respiratory system, the other for the cardiovascular system. The Rappaport-Sprague was later made by Hewlett-Packard. HP's medical products division was spun off as part of Agilent Technologies, Inc., where it became Agilent Healthcare. Agilent Healthcare was purchased by Philips which became Philips Medical Systems, before the walnut-boxed, $300, original Rappaport-Sprague stethoscope was finally abandoned ca. 2004, along with Philips' brand (manufactured by Andromed, of Montreal, Canada)


title: Stethoscope content: electronic stethoscope model. The Rappaport-Sprague model stethoscope was heavy and short () with an antiquated appearance recognizable by their two large independent latex rubber tubes connecting an exposed leaf-spring-joined pair of opposing F-shaped chrome-plated brass binaural ear tubes with a dual-head chest piece. Several other minor refinements were made to stethoscopes until, in the early 1960s, David Littmann, a Harvard Medical School professor, created a new stethoscope that was lighter than previous models and had improved acoustics. In the late 1970s, 3M-Littmann introduced the tunable diaphragm: a very hard (G-10) glass-epoxy resin diaphragm member with an overmolded silicone flexible acoustic


title: Stethoscope content: surround which permitted increased excursion of the diaphragm member in a Z-axis with respect to the plane of the sound collecting area. The left shift to a lower resonant frequency increases the volume of some low-frequency sounds due to the longer waves propagated by the increased excursion of the hard diaphragm member suspended in the concentric accountic surround. Conversely, restricting excursion of the diaphragm by pressing the stethoscope diaphragm surface firmly against the anatomical area overlying the physiological sounds of interest, the acoustic surround could also be used to dampen excursion of the diaphragm in response to "z"-axis pressure against


title: Stethoscope content: a concentric fret. This raises the frequency bias by shortening the wavelength to auscultate a higher range of physiological sounds. In 1999, Richard Deslauriers patented the first external noise-reducing stethoscope, the DRG Puretone. It featured two parallel lumens containing two steel coils which dissipated infiltrating noise as inaudible heat energy. The steel coil "insulation" added .30 lb to each stethoscope. In 2005, DRG's diagnostics division was acquired by TRIMLINE Medical Products. Stethoscopes are often considered as a symbol of healthcare professionals, as various healthcare providers are often seen or depicted with stethoscopes hanging around their necks. A 2012 research paper


title: Stethoscope content: claimed that the stethoscope, when compared to other medical equipment, had the highest positive impact on the perceived trustworthiness of the practitioner seen with it. The advent of practical, widespread portable ultrasonography (point-of-care ultrasonography) in the late 1990s to early 2000s led some physicians to ask how soon it would be before stethoscopes would become obsolete. Others answered that they thought the relationship of the various tools (stethoscopes and digital devices) would change but that it would be a long time before stethoscopes were obsolete. A decade later, in 2016, the same two sides of the coin were still recognized.


title: Stethoscope content: One cardiologist said, "the stethoscope is dead", but a pediatrician said, "We are not at the place, and probably won't be for a very long time", where stethoscopes were obsolete. One consideration is that it depends on the segment of health care (emergency medical services, nursing, medicine) and the specialty. "Stethoscopes retain their value for listening to lungs and bowels for clues of disease, experts agree." But for the cardiovascular system, "auscultation is superfluous", one cardiologist said. Thus, it could be that cardiology in the secondary and tertiary care settings may abandon the stethoscope many years before primary care, pediatrics,


title: Stethoscope content: and physical therapy do. Acoustic stethoscopes are familiar to most people, and operate on the transmission of sound from the chest piece, via air-filled hollow tubes, to the listener's ears. The chest piece usually consists of two sides that can be placed against the patient for sensing sound: a diaphragm (plastic disc) or bell (hollow cup). If the diaphragm is placed on the patient, the body sounds vibrate the diaphragm, creating acoustic pressure waves which travel up the tubing to the listener's ears. If the bell is placed on the patient, the vibrations of the skin directly produce acoustic pressure


title: Stethoscope content: waves travelling up to the listener's ears. The bell transmits low-frequency sounds, while the diaphragm transmits higher frequency sounds. This two-sided stethoscope was invented by Rappaport and Sprague in the early part of the 20th century. One problem with acoustic stethoscopes was that the sound level was extremely low. This problem was surmounted in 1999 with the invention of the stratified continuous (inner) lumen, and the kinetic acoustic mechanism in 2002. An electronic stethoscope (or stethophone) overcomes the low sound levels by electronically amplifying body sounds. However, amplification of stethoscope contact artefacts and component cutoffs (frequency response thresholds of electronic


title: Stethoscope content: stethoscope microphones, pre-amps, amps, and speakers) limit electronically amplified stethoscopes' overall utility by amplifying mid-range sounds, while simultaneously attenuating high- and low- frequency range sounds. Currently, a number of companies offer electronic stethoscopes. Electronic stethoscopes require conversion of acoustic sound waves to electrical signals which can then be amplified and processed for optimal listening. Unlike acoustic stethoscopes, which are all based on the same physics, transducers in electronic stethoscopes vary widely. The simplest and least effective method of sound detection is achieved by placing a microphone in the chest piece. This method suffers from ambient noise interference and has fallen


title: Stethoscope content: out of favour. Another method, used in Welch-Allyn's Meditron stethoscope, comprises placement of a piezoelectric crystal at the head of a metal shaft, the bottom of the shaft making contact with a diaphragm. 3M also uses a piezo-electric crystal placed within foam behind a thick rubber-like diaphragm. The Thinklabs' Rhythm 32 uses an electromagnetic diaphragm with a conductive inner surface to form a capacitive sensor. This diaphragm responds to sound waves, with changes in an electric field replacing changes in air pressure. The Eko Core enables wireless transmission of heart sounds to a smartphone or tablet. Because the sounds are


title: Stethoscope content: transmitted electronically, an electronic stethoscope can be a wireless device, can be a recording device, and can provide noise reduction, signal enhancement, and both visual and audio output. Around 2001, Stethographics introduced PC-based software which enabled a phonocardiograph, graphic representation of cardiologic and pulmonologic sounds to be generated, and interpreted according to related algorithms. All of these features are helpful for purposes of telemedicine (remote diagnosis) and teaching. Electronic stethoscopes are also used with computer-aided auscultation programs to analyze the recorded heart sounds pathological or innocent heart murmurs. Some electronic stethoscopes feature direct audio output that can be used with


title: Stethoscope content: an external recording device, such as a laptop or MP3 recorder. The same connection can be used to listen to the previously recorded auscultation through the stethoscope headphones, allowing for more detailed study for general research as well as evaluation and consultation regarding a particular patient's condition and telemedicine, or remote diagnosis. There are some smartphone apps that can use the phone as a stethoscope. At least one uses the phone's own microphone to amplify sound, produce a visualization, and e-mail the results. These apps may be used for training purposes or as novelties, but have not yet gained acceptance


title: Stethoscope content: for professional medical use. The first stethoscope that could work with a smartphone application was introduced in 2015 A "fetal stethoscope" or "fetoscope" is an acoustic stethoscope shaped like a listening trumpet. It is placed against the abdomen of a pregnant woman to listen to the heart sounds of the fetus. The fetal stethoscope is also known as a Pinard horn after French obstetrician Adolphe Pinard (1844–1934). A Doppler stethoscope is an electronic device that measures the Doppler effect of ultrasound waves reflected from organs within the body. Motion is detected by the change in frequency, due to the Doppler


title: Stethoscope content: effect, of the reflected waves. Hence the Doppler stethoscope is particularly suited to deal with moving objects such as a beating heart. It was recently demonstrated that continuous Doppler enables the auscultation of valvular movements and blood flow sounds that are undetected during cardiac examination with a stethoscope in adults. The Doppler auscultation presented a sensitivity of 84% for the detection of aortic regurgitations while classic stethoscope auscultation presented a sensitivity of 58%. Moreover, Doppler auscultation was superior in the detection of impaired ventricular relaxation. Since the physics of Doppler auscultation and classic auscultation are different, it has been suggested


title: Stethoscope content: that both methods could complement each other. A military noise-immune Doppler based stethoscope has recently been developed for auscultation of patients in loud sound environments (up to 110 dB). A 3D-printed stethoscope is an open-source medical device meant for auscultation and manufactured via means of 3D printing. The 3D stethoscope was developed by Dr. Tarek Loubani and a team of medical and technology specialists. The 3D-stethoscope was developed as part of the Glia project, and its design is open source from the outset. The stethoscope gained widespread media coverage in Summer 2015. The need for a 3D-stethoscope was borne out


title: Stethoscope content: of a lack of stethoscopes and other vital medical equipment because of the blockade of the Gaza Strip, where Loubani, a Palestinian-Canadian, worked as an emergency physician during the 2012 conflict in Gaza. The 1960s-era "Littmann Cardiology 3" stethoscope became the basis for the 3D-printed stethoscope developed by Loubani. Stethoscopes usually have rubber earpieces, which aid comfort and create a seal with the ear, improving the acoustic function of the device. Stethoscopes can be modified by replacing the standard earpieces with moulded versions, which improve comfort and transmission of sound. Moulded earpieces can be cast by an audiologist or made


title: Stethoscope content: by the stethoscope user from a kit. Stethoscope The stethoscope is an acoustic medical device for auscultation, or listening to the internal sounds of an animal or human body. It typically has a small disc-shaped resonator that is placed against the chest, and two tubes connected to earpieces. It is often used to listen to lung and heart sounds. It is also used to listen to intestines and blood flow in arteries and veins. In combination with a sphygmomanometer, and is commonly used for measurements of blood pressure. Less commonly, "mechanic's stethoscopes", equipped with rod-shaped chest pieces, are used to


title: "Amsterdam Airport Schiphol" content: Airport, well known for its clear writing and thorough colour-coding; to avoid confusion, he prohibited any other signage in the shades of yellow and green used. The new terminal building replaced the older facilities once located on what is now the east side of the airport. The A-Pier (now C-pier) of the airport was modified in 1970 to allow Boeing 747 aircraft to use the boarding gates. A new pier (D, now called F) opened in 1977, dedicated to handling wide-body aircraft. The first railway station at the airport followed in 1978. The construction of a new Air Traffic Control


title: Supercontinent content: and the atmospheric oxygen content). There is also evidence for increased sedimentation concurrent with the timing of these mass oxygenation events, meaning that the organic carbon and pyrite at these times were more likely to be buried beneath sediment and therefore unable to react with the free oxygen. This sustained the atmospheric oxygen increases. During this time, there was an increase in molybdenum isotope fractionation. It was temporary, but supports the increase in atmospheric oxygen because molybdenum isotopes require free oxygen to fractionate. Between 2.45 and the second period of oxygenation occurred, it has been called the 'great oxygenation event.'


title: "Slide rule" content: calculators often lack. A slide rule will also display all the terms of a calculation along with the result, thus eliminating uncertainty about what calculation was actually performed. A slide rule requires the user to separately compute the order of magnitude of the answer in order to position the decimal point in the results. For example, 1.5 × 30 (which equals 45) will show the same result as 1,500,000 × 0.03 (which equals 45,000). This separate calculation is less likely to lead to extreme calculation errors, but forces the user to keep track of magnitude in short-term memory (which is


title: "Small beer" content: of 1797, thought that "For the drink of the more robust children water is preferable, and for the weaker ones, small beer ...". Larger educational establishments like Eton, Winchester, and Oxbridge colleges ran their own breweries. In 17th century England, it was an excise class which was determined by its wholesale price. From 1782 to 1802, table beer was defined as that which cost between six and eleven shillings per barrel and the duty on this class was three shillings. Cheaper beer was classed as small beer while the more expensive band was classed as strong beer. The distinction between


title: Submarine content: Submarine A submarine (or simply sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term most commonly refers to a large, crewed vessel. It is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. The noun "submarine" evolved as a shortened form of "submarine boat"; by naval tradition, submarines are usually referred to as "boats" rather than as "ships", regardless of their size ("boat" is usually reserved


title: Submarine content: for seagoing vessels of relatively small size). Although experimental submarines had been built before, submarine design took off during the 19th century, and they were adopted by several navies. Submarines were first widely used during World War I (1914–1918), and are now used in many navies large and small. Military uses include attacking enemy surface ships (merchant and military), attacking other submarines, aircraft carrier protection, blockade running, ballistic missile submarines as part of a nuclear strike force, reconnaissance, conventional land attack (for example using a cruise missile), and covert insertion of special forces. Civilian uses for submarines include marine science,


title: Submarine content: salvage, exploration and facility inspection and maintenance. Submarines can also be modified to perform more specialized functions such as search-and-rescue missions or undersea cable repair. Submarines are also used in tourism, and for undersea archaeology. Most large submarines consist of a cylindrical body with hemispherical (or conical) ends and a vertical structure, usually located amidships, which houses communications and sensing devices as well as periscopes. In modern submarines, this structure is the "sail" in American usage and "fin" in European usage. A "conning tower" was a feature of earlier designs: a separate pressure hull above the main body of the


title: Submarine content: boat that allowed the use of shorter periscopes. There is a propeller (or pump jet) at the rear, and various hydrodynamic control fins. Smaller, deep-diving and specialty submarines may deviate significantly from this traditional layout. Submarines use diving planes and also change the amount of water and air in ballast tanks to change buoyancy for submerging and surfacing. Submarines have one of the widest ranges of types and capabilities of any vessel. They range from small autonomous examples and one- or two-person vessels that operate for a few hours, to vessels that can remain submerged for six months—such as the


title: Submarine content: Russian , the biggest submarines ever built. Submarines can work at greater depths than are survivable or practical for human divers. Modern deep-diving submarines derive from the bathyscaphe, which in turn evolved from the diving bell. According to a report in "Opusculum Taisnieri" published in 1562: In 1578, the English mathematician William Bourne recorded in his book "Inventions or Devises" one of the first plans for an underwater navigation vehicle. A few years later the Scottish mathematician and theologian John Napier wrote in his "Secret Inventions" (1596) the following: "These inventions besides devises of sayling under water with divers, other


title: Submarine content: devises and strategems for harming of the enemyes by the Grace of God and worke of expert Craftsmen I hope to perform." It's unclear whether he ever carried out his idea. The first submersible of whose construction there exists reliable information was designed and built in 1620 by Cornelis Drebbel, a Dutchman in the service of James I of England. It was propelled by means of oars. By the mid-18th century, over a dozen patents for submarines/submersible boats had been granted in England. In 1747, Nathaniel Symons patented and built the first known working example of the use of a


title: Submarine content: ballast tank for submersion. His design used leather bags that could fill with water to submerge the craft. A mechanism was used to twist the water out of the bags and cause the boat to resurface. In 1749, the Gentlemen's Magazine reported that a similar design had initially been proposed by Giovanni Borelli in 1680. By this point of development, further improvement in design necessarily stagnated for over a century, until new industrial technologies for propulsion and stability could be applied. The first military submarine was the "Turtle" (1775), a hand-powered acorn-shaped device designed by the American David Bushnell to


title: Submarine content: accommodate a single person. It was the first verified submarine capable of independent underwater operation and movement, and the first to use screws for propulsion. In 1800, France built a human-powered submarine designed by American Robert Fulton, the . The French eventually gave up on the experiment in 1804, as did the British when they later considered Fulton's submarine design. In 1864, late in the American Civil War, the Confederate navy's became the first military submarine to sink an enemy vessel, the Union sloop-of-war . In the aftermath of its successful attack against the ship, the "Hunley" also sank, possibly


title: Submarine content: because it was too close to its own exploding torpedo. In 1866, the "Sub Marine Explorer" was the first submarine to successfully dive, cruise underwater, and resurface under the control of the crew. The design by German American Julius H. Kroehl (in German, "Kröhl") incorporated elements that are still used in modern submarines. In 1866, the "Flach" was built at the request of the Chilean government, by Karl Flach, a German engineer and immigrant. It was the fifth submarine built in the world and, along with a second submarine, was intended to defend the port of Valparaiso against attack by


title: Submarine content: the Spanish navy during the Chincha Islands War. The first submarine not relying on human power for propulsion was the French ("Diver"), launched in 1863, which used compressed air at 180 psi (1241 kPa). Narcís Monturiol designed the first air–independent and combustion–powered submarine, "Ictineo II', which was launched in Barcelona, Spain in 1864. The submarine became a potentially viable weapon with the development of the Whitehead torpedo, designed in 1866 by British engineer Robert Whitehead, the first practical self-propelled or 'locomotive' torpedo. The spar torpedo that had been developed earlier by the Confederate navy was considered to be impracticable, as


title: Submarine content: it was believed to have sunk both its intended target, and probably "H. L. Hunley", the submarine that deployed it. Discussions between the English clergyman and inventor George Garrett and the Swedish industrialist Thorsten Nordenfelt led to the first practical steam-powered submarines, armed with torpedoes and ready for military use. The first was "Nordenfelt I", a 56-tonne, vessel similar to Garrett's ill-fated "Resurgam" (1879), with a range of , armed with a single torpedo, in 1885. A reliable means of propulsion for the submerged vessel was only made possible in the 1880s with the advent of the necessary electric battery


title: Submarine content: technology. The first electrically powered boats were built by Isaac Peral y Caballero in Spain, Dupuy de Lôme and Gustave Zédé in France, and James Franklin Waddington in England. Peral's design featured torpedoes and other systems that later became standard in submarines. Submarines were not put into service for any widespread or routine use by navies until the early 1900s. This era marked a pivotal time in submarine development, and several important technologies appeared. A number of nations built and used submarines. Diesel electric propulsion became the dominant power system and equipment such as the periscope became standardized. Countries conducted


title: Submarine content: many experiments on effective tactics and weapons for submarines, which led to their large impact in World War I. The Irish inventor John Philip Holland built a model submarine in 1876 and a full-scale version in 1878, which were followed by a number of unsuccessful ones. In 1896 he designed the Holland Type VI submarine, which used internal combustion engine power on the surface and electric battery power underwater. Launched on 17 May 1897 at Navy Lt. Lewis Nixon's Crescent Shipyard in Elizabeth, New Jersey, "Holland VI" was purchased by the United States Navy on 11 April 1900, becoming the


title: Submarine content: Navy's first commissioned submarine, christened . Commissioned in June 1900, the French steam and electric employed the now typical double-hull design, with a pressure hull inside the outer shell. These 200-ton ships had a range of over underwater. The French submarine "Aigrette" in 1904 further improved the concept by using a diesel rather than a gasoline engine for surface power. Large numbers of these submarines were built, with seventy-six completed before 1914. The Royal Navy commissioned five s from Vickers, Barrow-in-Furness, under licence from the Holland Torpedo Boat Company from 1901 to 1903. Construction of the boats took longer than


title: Submarine content: anticipated, with the first only ready for a diving trial at sea on 6 April 1902. Although the design had been purchased entirely from the US company, the actual design used was an untested improvement to the original Holland design using a new petrol engine. These types of submarines were first used during the Russo-Japanese War of 1904–05. Due to the blockade at Port Arthur, the Russians sent their submarines to Vladivostok, where by 1 January 1905 there were seven boats, enough to create the world's first "operational submarine fleet". The new submarine fleet began patrols on 14 February, usually


title: Submarine content: lasting for about 24 hours each. The first confrontation with Japanese warships occurred on 29 April 1905 when the Russian submarine "Som" was fired upon by Japanese torpedo boats, but then withdrew. Military submarines first made a significant impact in World War I. Forces such as the U-boats of Germany saw action in the First Battle of the Atlantic, and were responsible for sinking , which was sunk as a result of unrestricted submarine warfare and is often cited among the reasons for the entry of the United States into the war. At the outbreak of war Germany had only


title: Submarine content: twenty submarines immediately available for combat, although these included vessels of the diesel-engined "U-19" class with the range (5,000 miles) and speed () to operate effectively around the entire British coast. By contrast the Royal Navy had a total of 74 submarines, though of mixed effectiveness. In August 1914, a flotilla of ten U-boats sailed from their base in Heligoland to attack Royal Navy warships in the North Sea in the first submarine war patrol in history. The U-boats' ability to function as practical war machines relied on new tactics, their numbers, and submarine technologies such as combination diesel-electric power


title: Submarine content: system developed in the preceding years. More submersibles than true submarines, U-boats operated primarily on the surface using regular engines, submerging occasionally to attack under battery power. They were roughly triangular in cross-section, with a distinct keel to control rolling while surfaced, and a distinct bow. During World War I more than 5,000 Allied ships were sunk by U-boats. The British tried to catch up to the Germans in terms of submarine technology with the creation of the K-class submarines. However, these were extremely large and often collided with each other forcing the British to scrap the K-class design shortly


title: Submarine content: after the war. During World War II, Germany used submarines to devastating effect in the Battle of the Atlantic, where it attempted to cut Britain's supply routes by sinking more merchant ships than Britain could replace. (Shipping was vital to supply Britain's population with food, industry with raw material, and armed forces with fuel and armaments.) While U-boats destroyed a significant number of ships, the strategy ultimately failed. Although the U-boats had been updated in the interwar years, the major innovation was improved communications, encrypted using the famous Enigma cipher machine. This allowed for mass-attack naval tactics ("Rudeltaktik", commonly known


title: Submarine content: as "wolfpack"), but was also ultimately the U-boats' downfall. By the end of the war, almost 3,000 Allied ships (175 warships, 2,825 merchantmen) had been sunk by U-boats. Although successful early in the war, ultimately the U-boat fleet suffered a casualty rate of 73%, almost all fatalities. Germany's U-boat fleet in World War II suffered heavy casualties, losing 793 U-boats and about 28,000 submariners, out of 41,000; a casualty rate of about 70%. The Imperial Japanese Navy operated the most varied fleet of submarines of any navy, including "Kaiten" crewed torpedoes, midget submarines ( and es), medium-range submarines, purpose-built supply


title: Submarine content: submarines and long-range fleet submarines. They also had submarines with the highest submerged speeds during World War II (s) and submarines that could carry multiple aircraft (s). They were also equipped with one of the most advanced torpedoes of the conflict, the oxygen-propelled Type 95. Nevertheless, despite their technical prowess, Japan chose to use its submarines for fleet warfare, and consequently were relatively unsuccessful, as warships were fast, maneuverable and well-defended compared to merchant ships. The submarine force was the most effective anti-ship weapon in the American arsenal. Submarines, though only about 2 percent of the U.S. Navy, destroyed over


title: Submarine content: 30 percent of the Japanese Navy, including 8 aircraft carriers, 1 battleship and 11 cruisers. US submarines also destroyed over 60 percent of the Japanese merchant fleet, crippling Japan's ability to supply its military forces and industrial war effort. Allied submarines in the Pacific War destroyed more Japanese shipping than all other weapons combined. This feat was considerably aided by the Imperial Japanese Navy's failure to provide adequate escort forces for the nation's merchant fleet. During World War II, 314 submarines served in the US Navy, of which nearly 260 were deployed to the Pacific. When the Japanese attacked Hawaii


title: Submarine content: in December 1941, 111 boats were in commission; 203 submarines from the , , and es were commissioned during the war. During the war, 52 US submarines were lost to all causes, with 48 directly due to hostilities. US submarines sank 1,560 enemy vessels, a total tonnage of 5.3 million tons (55% of the total sunk). The Royal Navy Submarine Service was used primarily in the classic Axis blockade. Its major operating areas were around Norway, in the Mediterranean (against the Axis supply routes to North Africa), and in the Far East. In that war, British submarines sank 2 million


title: Submarine content: tons of enemy shipping and 57 major warships, the latter including 35 submarines. Among these is the only documented instance of a submarine sinking another submarine while both were submerged. This occurred when engaged ; the "Venturer" crew manually computed a successful firing solution against a three-dimensionally maneuvering target using techniques which became the basis of modern torpedo computer targeting systems. Seventy-four British submarines were lost, the majority, forty-two, in the Mediterranean. The first launch of a cruise missile (SSM-N-8 Regulus) from a submarine occurred in July 1953, from the deck of , a World War II fleet boat modified


title: Submarine content: to carry the missile with a nuclear warhead. "Tunny" and its sister boat, , were the United States' first nuclear deterrent patrol submarines. In the 1950s, nuclear power partially replaced diesel-electric propulsion. Equipment was also developed to extract oxygen from sea water. These two innovations gave submarines the ability to remain submerged for weeks or months. Most of the naval submarines built since that time in the US, the Soviet Union/Russian Federation, Britain, and France have been powered by nuclear reactors. In 1959–1960, the first ballistic missile submarines were put into service by both the United States () and the


title: Submarine content: Soviet Union () as part of the Cold War nuclear deterrent strategy. During the Cold War, the US and the Soviet Union maintained large submarine fleets that engaged in cat-and-mouse games. The Soviet Union lost at least four submarines during this period: was lost in 1968 (a part of which the CIA retrieved from the ocean floor with the Howard Hughes-designed ship "Glomar Explorer"), in 1970, in 1986, and in 1989 (which held a depth record among military submarines—). Many other Soviet subs, such as (the first Soviet nuclear submarine, and the first Soviet sub to reach the North Pole)


title: Submarine content: were badly damaged by fire or radiation leaks. The US lost two nuclear submarines during this time: due to equipment failure during a test dive while at its operational limit, and due to unknown causes. During India's intervention in the Bangladesh Liberation War, the Pakistan Navy's sank the Indian frigate . This was the first sinking by a submarine since World War II. During the same war, the , a "Tench"-class submarine on loan to Pakistan from the US, was sunk by the Indian Navy. It was the first submarine combat loss since World War II. In 1982 during the


title: Submarine content: Falklands War, the Argentine cruiser was sunk by the British submarine , the first sinking by a nuclear-powered submarine in war. Before and during World War II, the primary role of the submarine was anti-surface ship warfare. Submarines would attack either on the surface, using deck guns or submerged, using torpedoes. They were particularly effective in sinking Allied transatlantic shipping in both World Wars, and in disrupting Japanese supply routes and naval operations in the Pacific in World War II. Mine-laying submarines were developed in the early part of the 20th century. The facility was used in both World Wars.


title: Submarine content: Submarines were also used for inserting and removing covert agents and military forces, for intelligence gathering, and to rescue aircrew during air attacks on islands, where the airmen would be told of safe places to crash-land so the submarines could rescue them. Submarines could carry cargo through hostile waters or act as supply vessels for other submarines. Submarines could usually locate and attack other submarines only on the surface, although managed to sink with a four torpedo spread while both were submerged. The British developed a specialized anti-submarine submarine in WWI, the R class. After WWII, with the development of


title: Submarine content: the homing torpedo, better sonar systems, and nuclear propulsion, submarines also became able to hunt each other effectively. The development of submarine-launched ballistic missile and submarine-launched cruise missiles gave submarines a substantial and long-ranged ability to attack both land and sea targets with a variety of weapons ranging from cluster bombs to nuclear weapons. The primary defense of a submarine lies in its ability to remain concealed in the depths of the ocean. Early submarines could be detected by the sound they made. Water is an excellent conductor of sound (much better than air), and submarines can detect and track


title: Submarine content: comparatively noisy surface ships from long distances. Modern submarines are built with an emphasis on stealth. Advanced propeller designs, extensive sound-reducing insulation, and special machinery help a submarine remain as quiet as ambient ocean noise, making them difficult to detect. It takes specialized technology to find and attack modern submarines. Active sonar uses the reflection of sound emitted from the search equipment to detect submarines. It has been used since WWII by surface ships, submarines and aircraft (via dropped buoys and helicopter "dipping" arrays), but it reveals the emitter's position, and is susceptible to counter-measures. A concealed military submarine is


title: Submarine content: a real threat, and because of its stealth, can force an enemy navy to waste resources searching large areas of ocean and protecting ships against attack. This advantage was vividly demonstrated in the 1982 Falklands War when the British nuclear-powered submarine sank the Argentine cruiser . After the sinking the Argentine Navy recognized that they had no effective defense against submarine attack, and the Argentine surface fleet withdrew to port for the remainder of the war, though an Argentine submarine remained at sea. Although the majority of the world's submarines are military, there are some civilian submarines, which are used


title: Submarine content: for tourism, exploration, oil and gas platform inspections, and pipeline surveys. Some are also used in illegal activities. The Submarine Voyage ride opened at Disneyland in 1959, but although it ran under water it was not a true submarine, as it ran on tracks and was open to the atmosphere. The first tourist submarine was , which went into service in 1964 at Expo64. By 1997 there were 45 tourist submarines operating around the world. Submarines with a crush depth in the range of are operated in several areas worldwide, typically with bottom depths around , with a carrying capacity


title: Submarine content: of 50 to 100 passengers. In a typical operation a surface vessel carries passengers to an offshore operating area and loads them into the submarine. The submarine then visits underwater points of interest such as natural or artificial reef structures. To surface safely without danger of collision the location of the submarine is marked with an air release and movement to the surface is coordinated by an observer in a support craft. A recent development is the deployment of so-called narco submarines by South American drug smugglers to evade law enforcement detection. Although they occasionally deploy true submarines, most are


title: Submarine content: self-propelled semi-submersibles, where a portion of the craft remains above water at all times. In September 2011, Colombian authorities seized a 16-meter-long submersible that could hold a crew of 5, costing about $2 million. The vessel belonged to FARC rebels and had the capacity to carry at least 7 tonnes of drugs. All surface ships, as well as surfaced submarines, are in a positively buoyant condition, weighing less than the volume of water they would displace if fully submerged. To submerge hydrostatically, a ship must have negative buoyancy, either by increasing its own weight or decreasing its displacement of water.


title: Submarine content: To control their displacement, submarines have ballast tanks, which can hold varying amounts of water and air. For general submersion or surfacing, submarines use the forward and aft tanks, called Main Ballast Tanks (MBT), which are filled with water to submerge or with air to surface. Submerged, MBTs generally remain flooded, which simplifies their design, and on many submarines these tanks are a section of interhull space. For more precise and quick control of depth, submarines use smaller Depth Control Tanks (DCT) – also called hard tanks (due to their ability to withstand higher pressure), or trim tanks. The amount


title: Submarine content: of water in depth control tanks can be controlled to change depth or to maintain a constant depth as outside conditions (chiefly water density) change. Depth control tanks may be located either near the submarine's center of gravity, or separated along the submarine body to prevent affecting trim. When submerged, the water pressure on a submarine's hull can reach for steel submarines and up to for titanium submarines like , while interior pressure remains relatively unchanged. This difference results in hull compression, which decreases displacement. Water density also marginally increases with depth, as the salinity and pressure are higher. This


title: Submarine content: change in density incompletely compensates for hull compression, so buoyancy decreases as depth increases. A submerged submarine is in an unstable equilibrium, having a tendency to either sink or float to the surface. Keeping a constant depth requires continual operation of either the depth control tanks or control surfaces. Submarines in a neutral buoyancy condition are not intrinsically trim-stable. To maintain desired trim, submarines use forward and aft trim tanks. Pumps can move water between the tanks, changing weight distribution and pointing the sub up or down. A similar system is sometimes used to maintain stability. The hydrostatic effect of


title: Submarine content: variable ballast tanks is not the only way to control the submarine underwater. Hydrodynamic maneuvering is done by several surfaces, which can be moved to create hydrodynamic forces when a submarine moves at sufficient speed. The stern planes, located near the propeller and normally horizontal, serve the same purpose as the trim tanks, controlling the trim, and are commonly used, while other control surfaces may not be present on all submarines. The fairwater planes on the sail and/or bow planes on the main body, both also horizontal, are closer to the center of gravity, and are used to control depth


title: Submarine content: with less effect on the trim. When a submarine performs an emergency surfacing, all depth and trim methods are used simultaneously, together with propelling the boat upwards. Such surfacing is very quick, so the sub may even partially jump out of the water, potentially damaging submarine systems. Modern submarines are cigar-shaped. This design, visible in early submarines, is sometimes called a "teardrop hull". It reduces the hydrodynamic drag when submerged, but decreases the sea-keeping capabilities and increases drag while surfaced. Since the limitations of the propulsion systems of early submarines forced them to operate surfaced most of the time, their


title: Submarine content: hull designs were a compromise. Because of the slow submerged speeds of those subs, usually well below 10 kt (18 km/h), the increased drag for underwater travel was acceptable. Late in World War II, when technology allowed faster and longer submerged operation and increased aircraft surveillance forced submarines to stay submerged, hull designs became teardrop shaped again to reduce drag and noise. was a unique research submarine that pioneered the American version of the teardrop hull form (sometimes referred to as an "Albacore hull") of modern submarines. On modern military submarines the outer hull is covered with a layer of


title: Submarine content: sound-absorbing rubber, or anechoic plating, to reduce detection. The occupied pressure hulls of deep diving submarines such as are spherical instead of cylindrical. This allows a more even distribution of stress at the great depth. A titanium frame is usually affixed to the pressure hull, providing attachment for ballast and trim systems, scientific instrumentation, battery packs, syntactic flotation foam, and lighting. A raised tower on top of a submarine accommodates the periscope and electronics masts, which can include radio, radar, electronic warfare, and other systems including the snorkel mast. In many early classes of submarines (see history), the control room,


title: Submarine content: or "conn", was located inside this tower, which was known as the "conning tower". Since then, the conn has been located within the hull of the submarine, and the tower is now called the "sail". The conn is distinct from the "bridge", a small open platform in the top of the sail, used for observation during surface operation. "Bathtubs" are related to conning towers but are used on smaller submarines. The bathtub is a metal cylinder surrounding the hatch that prevents waves from breaking directly into the cabin. It is needed because surfaced submarines have limited freeboard, that is, they


title: Submarine content: lie low in the water. Bathtubs help prevent swamping the vessel. Modern submarines and submersibles, as well as the oldest ones, usually have a single hull. Large submarines generally have an additional hull or hull sections outside. This external hull, which actually forms the shape of submarine, is called the outer hull ("casing" in the Royal Navy) or light hull, as it does not have to withstand a pressure difference. Inside the outer hull there is a strong hull, or pressure hull, which withstands sea pressure and has normal atmospheric pressure inside. As early as World War I, it was


title: Submarine content: realized that the optimal shape for withstanding pressure conflicted with the optimal shape for seakeeping and minimal drag, and construction difficulties further complicated the problem. This was solved either by a compromise shape, or by using two hulls; internal for holding pressure, and external for optimal shape. Until the end of World War II, most submarines had an additional partial cover on the top, bow and stern, built of thinner metal, which was flooded when submerged. Germany went further with the Type XXI, a general predecessor of modern submarines, in which the pressure hull was fully enclosed inside the light


title: Submarine content: hull, but optimized for submerged navigation, unlike earlier designs that were optimized for surface operation. After World War II, approaches split. The Soviet Union changed its designs, basing them on German developments. All post–World War II heavy Soviet and Russian submarines are built with a double hull structure. American and most other Western submarines switched to a primarily single-hull approach. They still have light hull sections in the bow and stern, which house main ballast tanks and provide a hydrodynamically optimized shape, but the main cylindrical hull section has only a single plating layer. Double hulls are being considered for


title: Submarine content: future submarines in the United States to improve payload capacity, stealth and range. The pressure hull is generally constructed of thick high-strength steel with a complex structure and high strength reserve, and is separated with watertight bulkheads into several compartments. There are also examples of more than two hulls in a submarine, like the , which has two main pressure hulls and three smaller ones for control room, torpedoes and steering gear, with the missile launch system between the main hulls. The dive depth cannot be increased easily. Simply making the hull thicker increases the weight and requires reduction of


title: Submarine content: onboard equipment weight, ultimately resulting in a "bathyscaphe". This is acceptable for civilian research submersibles, but not military submarines. WWI submarines had hulls of carbon steel, with a maximum depth. During WWII, high-strength alloyed steel was introduced, allowing depths. High-strength alloy steel remains the primary material for submarines today, with depths, which cannot be exceeded on a military submarine without design compromises. To exceed that limit, a few submarines were built with titanium hulls. Titanium can be stronger than steel, lighter, and is not ferromagnetic, important for stealth. Titanium submarines were built by the Soviet Union, which developed specialized high-strength


title: Submarine content: alloys. It has produced several types of titanium submarines. Titanium alloys allow a major increase in depth, but other systems must be redesigned to cope, so test depth was limited to for the , the deepest-diving combat submarine. An may have successfully operated at , though continuous operation at such depths would produce excessive stress on many submarine systems. Titanium does not flex as readily as steel, and may become brittle after many dive cycles. Despite its benefits, the high cost of titanium construction led to the abandonment of titanium submarine construction as the Cold War ended. Deep–diving civilian submarines


title: Submarine content: have used thick acrylic pressure hulls. The deepest deep-submergence vehicle (DSV) to date is "Trieste". On 5 October 1959, "Trieste" departed San Diego for Guam aboard the freighter "Santa Maria" to participate in "Project Nekton", a series of very deep dives in the Mariana Trench. On 23 January 1960, "Trieste" reached the ocean floor in the Challenger Deep (the deepest southern part of the Mariana Trench), carrying Jacques Piccard (son of Auguste) and Lieutenant Don Walsh, USN. This was the first time a vessel, manned or unmanned, had reached the deepest point in the Earth's oceans. The onboard systems indicated


title: Submarine content: a depth of , although this was later revised to and more accurate measurements made in 1995 have found the Challenger Deep slightly shallower, at . Building a pressure hull is difficult, as it must withstand pressures at its required diving depth. When the hull is perfectly round in cross-section, the pressure is evenly distributed, and causes only hull compression. If the shape is not perfect, the hull is bent, with several points heavily strained. Inevitable minor deviations are resisted by stiffener rings, but even a one-inch (25 mm) deviation from roundness results in over 30 percent decrease of maximal


title: Submarine content: hydrostatic load and consequently dive depth. The hull must therefore be constructed with high precision. All hull parts must be welded without defects, and all joints are checked multiple times with different methods, contributing to the high cost of modern submarines. (For example, each attack submarine costs US$2.6 billion, over US$200,000 per ton of displacement.) The first submarines were propelled by humans. The first mechanically driven submarine was the 1863 French , which used compressed air for propulsion. Anaerobic propulsion was first employed by the Spanish "Ictineo II" in 1864, which used a solution of zinc, manganese dioxide, and potassium


title: Submarine content: chlorate to generate sufficient heat to power a steam engine, while also providing oxygen for the crew. A similar system was not employed again until 1940 when the German Navy tested a hydrogen peroxide-based system, the Walter turbine, on the experimental V-80 submarine and later on the naval and type XVII submarines. Until the advent of nuclear marine propulsion, most 20th-century submarines used batteries for running underwater and gasoline (petrol) or diesel engines on the surface, and for battery recharging. Early submarines used gasoline, but this quickly gave way to kerosene (paraffin), then diesel, because of reduced flammability. Diesel-electric became


title: Submarine content: the standard means of propulsion. The diesel or gasoline engine and the electric motor, separated by clutches, were initially on the same shaft driving the propeller. This allowed the engine to drive the electric motor as a generator to recharge the batteries and also propel the submarine. The clutch between the motor and the engine would be disengaged when the submarine dived, so that the motor could drive the propeller. The motor could have multiple armatures on the shaft, which could be electrically coupled in series for slow speed and in parallel for high speed (these connections were called "group


title: Submarine content: down" and "group up", respectively). Early submarines used a direct mechanical connection between the engine and propeller, switching between diesel engines for surface running, and battery-driven electric motors for submerged propulsion. In 1928, the United States Navy's Bureau of Engineering proposed a diesel-electric transmission. Instead of driving the propeller directly while running on the surface, the submarine's diesel drove a generator that could either charge the submarine's batteries or drive the electric motor. This made electric motor speed independent of diesel engine speed, so the diesel could run at an optimum and non-critical speed. One or more diesel engines could


title: Submarine content: be shut down for maintenance while the submarine continued to run on the remaining engine or battery power. The US pioneered this concept in 1929, in the S-class submarines , , and . The first production submarines with this system were the "Porpoise" class of the 1930s, and it was used on most subsequent US diesel submarines through the 1960s. No other navy adopted the system before 1945, apart from the Royal Navy's U-class submarines, though some submarines of the Imperial Japanese Navy used separate diesel generators for low speed running. Other advantages of such an arrangement were that a


title: Submarine content: submarine could travel slowly with the engines at full power to recharge the batteries quickly, reducing time on the surface or on snorkel. It was then possible to isolate the noisy diesel engines from the pressure hull, making the submarine quieter. Additionally, diesel-electric transmissions were more compact. During World War II the Germans experimented with the idea of the "schnorchel" (snorkel) from captured Dutch submarines, but didn't see the need for them until rather late in the war. The "schnorchel" was a retractable pipe that supplied air to the diesel engines while submerged at periscope depth, allowing the boats to


title: Submarine content: cruise and recharge their batteries while maintaining a degree of stealth. It was far from a perfect solution, however. There were problems with the device's valve sticking shut or closing as it dunked in rough weather; since the system used the entire pressure hull as a buffer, the diesels would instantaneously suck huge volumes of air from the boat's compartments, and the crew often suffered painful ear injuries. Speed was limited to , lest the device snap from stress. The "schnorchel" also created noise that made the boat easier to detect with sonar, yet more difficult for the on-board sonar


title: Submarine content: to detect signals from other vessels. Finally, Allied radar eventually became sufficiently advanced that the "schnorchel" mast could be detected beyond visual range. While the snorkel renders a submarine far less detectable, it is not perfect. In clear weather, diesel exhaust can be seen on the surface to a distance of about three miles, while "periscope feather" (the wave created by the snorkel or periscope moving through the water) is visible from far off in calm sea conditions. Modern radar is also capable of detecting a snorkel in calm sea conditions. The problem of the diesels causing a vacuum in


title: Submarine content: the submarine when the head valve is submerged still exists in later model diesel submarines, but is mitigated by high-vacuum cut-off sensors that shut down the engines when the vacuum in the ship reaches a pre-set point. Modern snorkel induction masts use a fail-safe design using compressed air, controlled by a simple electrical circuit, to hold the "head valve" open against the pull of a powerful spring. Seawater washing over the mast shorts out exposed electrodes on top, breaking the control, and shutting the "head valve" while it is submerged. US submarines did not adopt the use of snorkels until


title: Submarine content: after WWII. One new technology that is being introduced starting with the Japanese Navy's eleventh "Sōryū"-class submarine (JS "Ōryū") is a more modern battery, the lithium-ion battery. These batteries have about double the electric storage of traditional batteries, and by changing out the lead-acid batteries in their normal storage areas plus filling up the large hull space normally devoted to AIP engine and fuel tanks with many tons of lithium-ion batteries, modern submarines can actually return to a "pure" diesel-electric configuration yet have the added underwater range and power normally associated with AIP equipped submarines. During World War II, German


title: Submarine content: Type XXI submarines (also known as ""Elektroboote"") were the first submarines designed to operate submerged for extended periods. Initially they were to carry hydrogen peroxide for long-term, fast air-independent propulsion, but were ultimately built with very large batteries instead. At the end of the War, the British and Soviets experimented with hydrogen peroxide/kerosene (paraffin) engines that could run surfaced and submerged. The results were not encouraging. Though the Soviet Union deployed a class of submarines with this engine type (codenamed by NATO), they were considered unsuccessful. The United States also used hydrogen peroxide in an experimental midget submarine, X-1. It


title: Submarine content: was originally powered by a hydrogen peroxide/diesel engine and battery system until an explosion of her hydrogen peroxide supply on 20 May 1957. X-1 was later converted to use diesel-electric drive. Today several navies use air-independent propulsion. Notably Sweden uses Stirling technology on the and s. The Stirling engine is heated by burning diesel fuel with liquid oxygen from cryogenic tanks. A newer development in air-independent propulsion is hydrogen fuel cells, first used on the German Type 212 submarine, with nine 34 kW or two 120 kW cells and soon to be used in the new Spanish s. Steam power


title: Submarine content: was resurrected in the 1950s with a nuclear-powered steam turbine driving a generator. By eliminating the need for atmospheric oxygen, the time that a submarine could remain submerged was limited only by its food stores, as breathing air was recycled and fresh water distilled from seawater. More importantly, a nuclear submarine has unlimited range at top speed. This allows it to travel from its operating base to the combat zone in a much shorter time and makes it a far more difficult target for most anti-submarine weapons. Nuclear-powered submarines have a relatively small battery and diesel engine/generator powerplant for emergency


title: Submarine content: use if the reactors must be shut down. Nuclear power is now used in all large submarines, but due to the high cost and large size of nuclear reactors, smaller submarines still use diesel-electric propulsion. The ratio of larger to smaller submarines depends on strategic needs. The US Navy, French Navy, and the British Royal Navy operate only nuclear submarines, which is explained by the need for distant operations. Other major operators rely on a mix of nuclear submarines for strategic purposes and diesel-electric submarines for defense. Most fleets have no nuclear submarines, due to the limited availability of nuclear


title: Submarine content: power and submarine technology. Diesel-electric submarines have a stealth advantage over their nuclear counterparts. Nuclear submarines generate noise from coolant pumps and turbo-machinery needed to operate the reactor, even at low power levels. Some nuclear submarines such as the American can operate with their reactor coolant pumps secured, making them quieter than electric subs. A conventional submarine operating on batteries is almost completely silent, the only noise coming from the shaft bearings, propeller, and flow noise around the hull, all of which stops when the sub hovers in mid-water to listen, leaving only the noise from crew activity. Commercial submarines


title: Submarine content: usually rely only on batteries, since they operate in conjunction with a mother ship. Several serious nuclear and radiation accidents have involved nuclear submarine mishaps. The reactor accident in 1961 resulted in 8 deaths and more than 30 other people were over-exposed to radiation. The reactor accident in 1968 resulted in 9 fatalities and 83 other injuries. The accident in 1985 resulted in 10 fatalities and 49 other radiation injuries. Oil-fired steam turbines powered the British K-class submarines, built during World War I and later, to give them the surface speed to keep up with the battle fleet. The K-class


title: Submarine content: subs were not very successful, however. Toward the end of the 20th century, some submarines—such as the British "Vanguard" class—began to be fitted with pump-jet propulsors instead of propellers. Though these are heavier, more expensive, and less efficient than a propeller, they are significantly quieter, providing an important tactical advantage. Magnetohydrodynamic drive (MHD) was portrayed as the operating principle behind the titular submarine's nearly silent propulsion system in the film adaptation of "The Hunt for Red October". However, in the novel the "Red October" did not use MHD, but rather something more similar to the above-mentioned pump-jet. The success of


title: Submarine content: the submarine is inextricably linked to the development of the torpedo, invented by Robert Whitehead in 1866. His invention is essentially the same now as it was 140 years ago. Only with self-propelled torpedoes could the submarine make the leap from novelty to a weapon of war. Until the perfection of the guided torpedo, multiple "straight-running" torpedoes were required to attack a target. With at most 20 to 25 torpedoes stored on board, the number of attacks was limited. To increase combat endurance most World War I submarines functioned as submersible gunboats, using their deck guns against unarmed targets, and


title: Submarine content: diving to escape and engage enemy warships. The importance of guns encouraged the development of the unsuccessful Submarine Cruiser such as the French and the Royal Navy's and M-class submarines. With the arrival of Anti-submarine warfare (ASW) aircraft, guns became more for defense than attack. A more practical method of increasing combat endurance was the external torpedo tube, loaded only in port. The ability of submarines to approach enemy harbours covertly led to their use as minelayers. Minelaying submarines of World War I and World War II were specially built for that purpose. Modern submarine-laid mines, such as the British


title: Submarine content: Mark 5 Stonefish and Mark 6 Sea Urchin, can be deployed from a submarine's torpedo tubes. After World War II, both the US and the USSR experimented with submarine-launched cruise missiles such as the SSM-N-8 Regulus and P-5 Pyatyorka. Such missiles required the submarine to surface to fire its missiles. They were the forerunners of modern submarine-launched cruise missiles, which can be fired from the torpedo tubes of submerged submarines, for example the US BGM-109 Tomahawk and Russian RPK-2 Viyuga and versions of surface–to–surface anti-ship missiles such as the Exocet and Harpoon, encapsulated for submarine launch. Ballistic missiles can also


title: Submarine content: be fired from a submarine's torpedo tubes, for example missiles such as the anti-submarine SUBROC. With internal volume as limited as ever and the desire to carry heavier warloads, the idea of the external launch tube was revived, usually for encapsulated missiles, with such tubes being placed between the internal pressure and outer streamlined hulls. The strategic mission of the SSM-N-8 and the P-5 was taken up by submarine-launched ballistic missile beginning with the US Navy's Polaris missile, and subsequently the Poseidon and Trident missiles. Germany is working on the torpedo tube-launched short-range IDAS missile, which can be used against


title: Submarine content: ASW helicopters, as well as surface ships and coastal targets. A submarine can have a variety of sensors, depending on its missions. Modern military submarines rely almost entirely on a suite of passive and active sonars to locate targets. Active sonar relies on an audible "ping" to generate echoes to reveal objects around the submarine. Active systems are rarely used, as doing so reveals the sub's presence. Passive sonar is a set of sensitive hydrophones set into the hull or trailed in a towed array, normally trailing several hundred feet behind the sub. The towed array is the mainstay of


title: Submarine content: NATO submarine detection systems, as it reduces the flow noise heard by operators. Hull mounted sonar is employed in addition to the towed array, as the towed array can't work in shallow depth and during maneuvering. In addition, sonar has a blind spot "through" the submarine, so a system on both the front and back works to eliminate that problem. As the towed array trails behind and below the submarine, it also allows the submarine to have a system both above and below the thermocline at the proper depth; sound passing through the thermocline is distorted resulting in a lower


title: Submarine content: detection range. Submarines also carry radar equipment to detect surface ships and aircraft. Submarine captains are more likely to use radar detection gear than active radar to detect targets, as radar can be detected far beyond its own return range, revealing the submarine. Periscopes are rarely used, except for position fixes and to verify a contact's identity. Civilian submarines, such as the or the Russian "Mir" submersibles, rely on small active sonar sets and viewing ports to navigate. The human eye cannot detect sunlight below about underwater, so high intensity lights are used to illuminate the viewing area. Early submarines


title: Submarine content: had few navigation aids, but modern subs have a variety of navigation systems. Modern military submarines use an inertial guidance system for navigation while submerged, but drift error unavoidably builds over time. To counter this, the crew occasionally uses the Global Positioning System to obtain an accurate position. The periscope—a retractable tube with a prism system that provides a view of the surface—is only used occasionally in modern submarines, since the visibility range is short. The and s use photonics masts rather than hull-penetrating optical periscopes. These masts must still be deployed above the surface, and use electronic sensors for


title: Submarine content: visible light, infrared, laser range-finding, and electromagnetic surveillance. One benefit to hoisting the mast above the surface is that while the mast is above the water the entire sub is still below the water and is much harder to detect visually or by radar. Military submarines use several systems to communicate with distant command centers or other ships. One is VLF (very low frequency) radio, which can reach a submarine either on the surface or submerged to a fairly shallow depth, usually less than . ELF (extremely low frequency) can reach a submarine at greater depths, but has a very


title: Submarine content: low bandwidth and is generally used to call a submerged sub to a shallower depth where VLF signals can reach. A submarine also has the option of floating a long, buoyant wire antenna to a shallower depth, allowing VLF transmissions by a deeply submerged boat. By extending a radio mast, a submarine can also use a "burst transmission" technique. A burst transmission takes only a fraction of a second, minimizing a submarine's risk of detection. To communicate with other submarines, a system known as Gertrude is used. Gertrude is basically a sonar telephone. Voice communication from one submarine is transmitted


title: Submarine content: by low power speakers into the water, where it is detected by passive sonars on the receiving submarine. The range of this system is probably very short, and using it radiates sound into the water, which can be heard by the enemy. Civilian submarines can use similar, albeit less powerful systems to communicate with support ships or other submersibles in the area. With nuclear power or air-independent propulsion, submarines can remain submerged for months at a time. Conventional diesel submarines must periodically resurface or run on snorkel to recharge their batteries. Most modern military submarines generate breathing oxygen by electrolysis


title: Submarine content: of water (using a device called an "Elektrolytic Oxygen Generator"). Atmosphere control equipment includes a CO scrubber, which uses an amine absorbent to remove the gas from air and diffuse it into waste pumped overboard. A machine that uses a catalyst to convert carbon monoxide into carbon dioxide (removed by the CO scrubber) and bonds hydrogen produced from the ship's storage battery with oxygen in the atmosphere to produce water, is also used. An atmosphere monitoring system samples the air from different areas of the ship for nitrogen, oxygen, hydrogen, R-12 and R-114 refrigerants, carbon dioxide, carbon monoxide, and other


title: Submarine content: gases. Poisonous gases are removed, and oxygen is replenished by use of an oxygen bank located in a main ballast tank. Some heavier submarines have two oxygen bleed stations (forward and aft). The oxygen in the air is sometimes kept a few percent less than atmospheric concentration to reduce fire danger. Fresh water is produced by either an evaporator or a reverse osmosis unit. The primary use for fresh water is to provide feedwater for the reactor and steam propulsion plants. It is also available for showers, sinks, cooking and cleaning once propulsion plant needs have been met. Seawater is


title: Submarine content: used to flush toilets, and the resulting "black water" is stored in a sanitary tank until it is blown overboard using pressurized air or pumped overboard by using a special sanitary pump. The blackwater–discharge system is difficult to operate, and the German Type VIIC boat was lost with casualties because of human error while using this system. Water from showers and sinks is stored separately in "grey water" tanks and discharged overboard using drain pumps. Trash on modern large submarines is usually disposed of using a tube called a Trash Disposal Unit (TDU), where it is compacted into a galvanized


title: Submarine content: steel can. At the bottom of the TDU is a large ball valve. An ice plug is set on top of the ball valve to protect it, the cans atop the ice plug. The top breech door is shut, and the TDU is flooded and equalized with sea pressure, the ball valve is opened and the cans fall out assisted by scrap iron weights in the cans. The TDU is also flushed with seawater to ensure it is completely empty and the ball valve is clear before closing the valve. A typical nuclear submarine has a crew of over 80;


title: Submarine content: conventional boats typically have fewer than 40. The conditions on a submarine can be difficult because crew members must work in isolation for long periods of time, without family contact. Submarines normally maintain radio silence to avoid detection. Operating a submarine is dangerous, even in peacetime, and many submarines have been lost in accidents. Most navies prohibited women from serving on submarines, even after they had been permitted to serve on surface warships. The Royal Norwegian Navy became the first navy to allow women on its submarine crews in 1985. The Royal Danish Navy allowed female submariners in 1988. Others


title: Submarine content: followed suit including the Swedish Navy (1989), the Royal Australian Navy (1998), the Spanish Navy (1999), the German Navy (2001) and the Canadian Navy (2002). In 1995, Solveig Krey of the Royal Norwegian Navy became the first female officer to assume command on a military submarine, HNoMS "Kobben". On 8 December 2011, British Defence Secretary Philip Hammond announced that the UK's ban on women in submarines was to be lifted from 2013. Previously there were fears that women were more at risk from a build-up of carbon dioxide in the submarine. But a study showed no medical reason to exclude


title: Submarine content: women, though pregnant women would still be excluded. Similar dangers to the pregnant woman and her fetus barred women from submarine service in Sweden in 1983, when all other positions were made available for them in the Swedish Navy. Today, pregnant women are still not allowed to serve on submarines in Sweden. However, the policymakers thought that it was discriminatory with a general ban and demanded that women should be tried on their individual merits and have their suitability evaluated and compared to other candidates. Further, they noted that a woman complying with such high demands is unlikely to become


title: Submarine content: pregnant. In May 2014, three women became the RN's first female submariners. Women have served on US Navy surface ships since 1993, and , began serving on submarines for the first time. Until presently, the Navy allowed only three exceptions to women being on board military submarines: female civilian technicians for a few days at most, women midshipmen on an overnight during summer training for Navy ROTC and Naval Academy, and family members for one-day dependent cruises. In 2009, senior officials, including then-Secretary of the Navy Ray Mabus, Joint Chief of Staff Admiral Michael Mullen, and Chief of Naval Operations


title: Submarine content: Admiral Gary Roughead, began the process of finding a way to implement women on submarines. The US Navy rescinded its "no women on subs" policy in 2010. Both the US and British navies operate nuclear-powered submarines that deploy for periods of six months or longer. Other navies that permit women to serve on submarines operate conventionally powered submarines, which deploy for much shorter periods—usually only for a few months. Prior to the change by the US, no nation using nuclear submarines permitted women to serve on board. In 2011, the first class of female submarine officers graduated from Naval Submarine


title: Submarine content: School's Submarine Officer Basic Course (SOBC) at the Naval Submarine Base New London. Additionally, more senior ranking and experienced female supply officers from the surface warfare specialty attended SOBC as well, proceeding to fleet Ballistic Missile (SSBN) and Guided Missile (SSGN) submarines along with the new female submarine line officers beginning in late 2011. By late 2011, several women were assigned to the "Ohio"-class ballistic missile submarine . On 15 October 2013, the US Navy announced that two of the smaller "Virginia"-class attack submarines, and , would have female crew-members by January 2015. In an emergency, submarines can transmit a


title: Submarine content: signal to other ships. The crew can use Submarine Escape Immersion Equipment to abandon the submarine. The crew can prevent a lung injury from the pressure change known as pulmonary barotrauma by exhaling during the ascent. Following escape from a pressurized submarine, the crew is at risk of developing decompression sickness. An alternative escape means is via a Deep Submergence Rescue Vehicle that can dock onto the disabled submarine. 1900/Russo-Japanese War 1904–1905 Submarine A submarine (or simply sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term most


title: "Special Operations Executive" content: as a result of his hard work, and appointed Sir Charles Hambro, head of Hambros Bank, to replace him. He also transferred Jebb back to the Foreign Office. Hambro had been a close friend of Churchill before the war and had won the Military Cross in the First World War. He retained several other interests, for example remaining chairman of Hambros and a director of the Great Western Railway. Some of his subordinates and associates expressed reservations that these interests distracted him from his duties as director. Selborne and Hambro nevertheless cooperated closely until August 1943, when they fell out


title: Suburb content: densities on newly approved housing schemes in parts of South East England. The goal is to "build sustainable communities" rather than housing estates. However, commercial concerns tend to delay the opening of services until a large number of residents have occupied the new neighbourhood. In Mexico, suburbs are generally similar to their United States counterparts. Houses are made in many different architectural styles which may be of European, American and International architecture and which vary in size. Suburbs can be found in Guadalajara, Mexico City, Monterrey, and most major cities. Lomas de Chapultepec is an example of an affluent suburb,


title: "Super Bowl XXXIII" content: Elam's 38-yard field goal attempt sailed wide right. Chandler responded on the next 2 plays with a 29-yard completion to receiver Tony Martin and a 12-yard scramble to advance the ball to the Denver 41-yard line. But then linebacker John Mobley sacked Chandler for a 6-yard loss, and cornerback Darrius Johnson intercepted Chandler's pass and returned it 28 yards to the Falcons 42-yard line on the next play. Denver then drove to the 29-yard line, but Elam missed another field goal attempt, this one from 47 yards. After the missed field goal, the Falcons drove to the Denver 21-yard line


title: Spaghetti content: Spaghetti Spaghetti (; sing. "spaghetto") is a long, thin, solid, cylindrical pasta. "Spaghettoni" is a thicker form of spaghetti, while "capellini" is a very thin spaghetti. It is a staple food of traditional Italian cuisine. Like other pasta, spaghetti is made of milled wheat and water and sometimes enriched with vitamins and minerals. Authentic Italian spaghetti is made from durum wheat semolina, but elsewhere it may be made with other kinds of flour. Typically the pasta is white because refined flour is used, but whole wheat flour may be added. Originally, spaghetti was notably long, but shorter lengths gained in


title: Spaghetti content: popularity during the latter half of the 20th century and now it is most commonly available in lengths. A variety of pasta dishes are based on it, and it is frequently served with tomato sauce or meat or vegetables. "Spaghetti" is the plural form of the Italian word "spaghetto", which is a diminutive of "spago", meaning "thin string" or "twine". The first written record of pasta comes from the Talmud in the 5th century AD and refers to dried pasta that could be cooked through boiling, which was conveniently portable. Some historians think that Berbers introduced pasta to Europe during


title: Spaghetti content: a conquest of Sicily. In the West, it may have first been worked into long, thin forms in Sicily around the 12th century, as the Tabula Rogeriana of Muhammad al-Idrisi attested, reporting some traditions about the Sicilian kingdom. The popularity of spaghetti spread throughout Italy after the establishment of spaghetti factories in the 19th century, enabling the mass production of spaghetti for the Italian market. In the United States around the end of the 19th century, spaghetti was offered in restaurants as "Spaghetti Italienne" (which likely consisted of noodles cooked past "al dente", and a mild tomato sauce flavored with


title: Spaghetti content: easily found spices and vegetables such as cloves, bay leaves, and garlic) and it was not until decades later that it came to be commonly prepared with oregano or basil. Spaghetti is made from ground grain (flour) and water. Whole-wheat and multigrain spaghetti are also available. At its simplest, spaghetti can be formed using no more than a rolling pin and a knife. A home pasta machine simplifies the rolling and makes the cutting more uniform. Fresh spaghetti would normally be cooked within hours of being formed. Commercial versions of 'fresh' spaghetti are manufactured. The bulk of dried spaghetti is


title: Spaghetti content: produced in factories using auger extruders. While essentially simple, the process requires attention to detail to ensure that the mixing and kneading of the ingredients produces a homogeneous mix, without air bubbles. The forming dies have to be water cooled to prevent spoiling of the pasta by overheating. Drying of the newly formed spaghetti has to be carefully controlled to prevent strands sticking together, and to leave it with sufficient moisture so that it is not too brittle. Packaging for protection and display has developed from paper wrapping to plastic bags and boxes. Fresh or dry spaghetti is cooked in


title: Spaghetti content: a large pot of salted, boiling water and then drained in a colander (). In Italy, spaghetti is generally cooked "al dente" (Italian for "to the tooth"), fully cooked but still firm to the bite. It may also be cooked to a softer consistency. "Spaghettoni" is a thicker spaghetti which takes more time to cook. "Spaghettini" is a thinner form which takes less time to cook. "Capellini" is a very thin form of spaghetti (it is also called "angel hair spaghetti" or "angel hair pasta") which cooks very quickly. Utensils used in spaghetti preparation include the spaghetti scoop and spaghetti


title: Spaghetti content: tongs. An emblem of Italian cuisine, spaghetti is frequently served with tomato sauce, which may contain various herbs (especially oregano and basil), olive oil, meat, or vegetables. Other spaghetti preparations include amatriciana or carbonara. Grated hard cheeses, such as Pecorino Romano, Parmesan and Grana Padano, are often sprinkled on top. In some countries, spaghetti is sold in cans/tins with sauce. In the United States, it is sometimes served with chili con carne. Unlike in Italy, abroad spaghetti is often served with Bolognese sauce. In the Philippines, an immensely popular variant is the Filipino spaghetti, which is distinctively sweet with the


title: Spaghetti content: tomato sauce sweetened with banana ketchup or sugar. It typically uses a large amount of "giniling" (ground meat), sliced hotdogs, and cheese. The dish dates back to the period between the 1940s to the 1960s. During the American Commonwealth Period, a shortage of tomato supplies in the Second World War forced the development of the banana ketchup. Spaghetti was introduced by the Americans and was tweaked to suit the local Filipino predilection for sweet dishes. "Sapaketti phat khi mao" (Spaghetti fried drunken noodle style) is a popular dish in Thai cuisine. By 1955, annual consumption of spaghetti in Italy doubled