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The Pelagornithidae had extremely thin-walled bones widely pneumatized with the air sac extensions of the lungs. Most limb bone fossils are very much crushed for that reason. In life, the thin bones and extensive pneumatization enabled the birds to achieve large size while remaining below critical wing loadings. Though 25 kg/m2 (5 lb/ft2) is regarded as the maximum wing loading for powered bird flight, there is evidence that bony-toothed birds used dynamic soaring flight almost exclusively: the proximal end of the humerus had an elongated diagonal shape that could hardly have allowed for the movement necessary for the typical flapping flight of birds; their weight thus cannot be easily estimated. The attachment positions for the muscles responsible for holding the upper arm straightly outstretched were particularly well-developed, and altogether the anatomy seems to allow for an ability of holding the wings rigidly at the glenoid joint unmatched by any other known bird. This is especially prominent in the Neogene pelagornithids, and less developed in the older Paleogene forms. The sternum had the deep and short shape typical of dynamic soarers, and bony outgrowths at the keel's forward margin securely anchored the furcula.
The legs were proportionally short, the feet probably webbed and the hallux was vestigial or entirely absent; the tarsometatarsi (anklebones) resembled those of albatrosses while the arrangement of the front toes was more like in fulmars. Typical for pseudotooth birds was a second toe that attached a bit kneewards from the others and was noticeably angled outwards. The "teeth" were probably covered by the rhamphotheca in life, and there are two furrows running along the underside of the upper bill just inside the ridges which bore the "teeth". Thus, when the bill was closed only the upper jaw's "teeth" were visible, with the lower ones hidden behind them. Inside the eye sockets of at least some pseudotooth birds – perhaps only in the younger species – were well-developed salt glands. | Pelagornithidae | Wikipedia | 436 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
Altogether, almost no major body part of pelagornithids is known from a well-preserved associated fossil and most well-preserved material consists of single bones only; on the other hand the long occurrence and large size makes for a few rather comprehensive (though much crushed and distorted) remains of individual birds that were entombed by as they lay dead, complete with some fossilized feathers. Large parts of the skull and some beak pieces are found not too infrequently. In February 2009, an almost-complete fossilized skull of a presumed Odontopteryx from around the Chasicoan-Huayquerian boundary c. 9 million years ago (Ma) was unveiled in Lima. It had been found a few months earlier in Ocucaje District of Ica Province, Peru. According to paleontologist Mario Urbina, who discovered the specimen, and his colleagues Rodolfo Salas, Ken Campbell and Daniel T. Ksepka, the Ocucaje skull is the best-preserved pelagornithid cranium known as of 2009.
Ecology and extinction | Pelagornithidae | Wikipedia | 225 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
Unlike the true teeth of Mesozoic stem-birds like Archaeopteryx or Ichthyornis, the pseudoteeth of the pelagornithids do not seem to have had serrated or otherwise specialized cutting edges, and were useful to hold prey for swallowing whole rather than to tear bits off it. Since the teeth were hollow or at best full of cancellous bone and are easily worn or broken off in fossils, it is surmised they were not extremely resilient in life either. Pelagornithid prey would thus have been soft-bodied, and have encompassed mainly cephalopods and soft-skinned fishes. Prey items may have reached considerable size. Though some reconstructions show pelagornithids as diving birds in the manner of gannets, the thin-walled highly pneumatized bones which must have fractured easily judging from the state of fossil specimens make such a mode of feeding unlikely, if not outright dangerous. Rather, prey would have been picked up from immediately below the ocean surface while the birds were flying or swimming, and they probably submerged only the beak in most situations. Their quadrate bone articulation with the lower jaw resembled that of a pelican or other birds that can open their beak widely. Altogether, the pseudotooth birds would have filled an ecological niche almost identical to that of the larger fish-eating pteranodontian pterosaurs, whose extinction at the end of the Cretaceous may well have paved the way for the highly successful 50-million-year reign of the Pelagornithidae. Like them as well as modern albatrosses, the pseudotooth birds could have used the system of ocean currents and atmospheric circulation to take round-track routes soaring over the open oceans, returning to breed only every few years. Unlike albatrosses today, which avoid the tropical equatorial currents with their doldrums, Pelagornithidae were found in all sorts of climates, and records from around 40 Ma stretch from Belgium through Togo to the Antarctic. It is conspicuous that penguins and plotopterids – both wing-propelled divers that foraged over the continental shelf – are almost invariably found in the company of pseudotooth birds. Thus, pseudotooth birds seem to have gathered in some numbers in upwelling regions, presumably to feed but perhaps also to breed nearby. | Pelagornithidae | Wikipedia | 478 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
It is sometimes claimed that as with some other seabirds (e.g. the flightless Plotopteridae), the evolutionary radiation of cetaceans and pinnipeds outcompeted the pseudotooth birds and drove them into extinction. While this may be correct for the plotopterids, for pelagornithids it is not so likely for two reasons: First, the Pelagornithidae continued to thrive for 10 million years after modern-type baleen whales evolved, and in the Middle Miocene Pelagornis coexisted with Aglaocetus and Harrison's whale (Eobalaenoptera harrisoni) in the Atlantic off the Eastern Seaboard, while the Pacific Osteodontornis inhabited the same seas as Balaenula and Morenocetus; the ancestral smallish sperm whale genus Aulophyseter (and/or Orycterocetus) occurred in both Northern Hemisphere oceans at that time, while the mid-sized sperm whale Brygmophyseter roamed the North Pacific. As regards Miocene pinnipeds, a diversity of ancient walruses and ancestral fur seals like Thalassoleon inhabited the north-east, while the ancient leopard seal Acrophoca is a remarkable species known from the south-east Pacific. Secondly, pinnipeds are limited to near-shore waters while pseudotooth birds roamed the seas far and wide, like large cetaceans, and like all big carnivores all three groups were K-strategists with moderate to very low population densities. | Pelagornithidae | Wikipedia | 329 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
Thus, direct competition for food between bony-toothed birds and cetaceans or pinnipeds cannot have been very severe. As both the birds and pinnipeds would need level ground near the sea to raise their young, competition for breeding grounds may have affected the birds' population. In that respect, the specializations for dynamic soaring restricted the number of possible nesting sites for the birds, but on the other hand upland on islands or in coastal ranges could have provided breeding grounds for Pelagornithidae that was inaccessible for pinnipeds; just as many albatrosses today nest in the uplands of islands (e.g. the Galápagos or Torishima). The bony-toothed birds probably required strong updrafts for takeoff and would have preferred higher sites anyway for this reason, rendering competition with pinniped rookeries quite minimal. As regards breeding grounds, giant eggshell fragments from the Famara mountains on Lanzarote, Canary Islands, were tentatively attributed to Late Miocene pseudotooth birds. As regards the Ypresian London Clay of the Isle of Sheppey, wherein pelagornithid fossils are not infrequently found, it was deposited in a shallow epicontinental sea during a very hot time with high sea levels. The presumed breeding sites cannot have been as far offshore as many seabird rookeries are today, as the region was hemmed in between the Alps and the Grampian and Scandinavian Mountains, in a sea less wide than the Caribbean is today.
Neogene pseudotooth birds are common along the America coasts near the Appalachian and Cordilleran mountains, and these species thus presumably also bred not far offshore or even in the mountains themselves. In that respect the presence of medullary bone in the specimens from Lee Creek Mine in North Carolina, United States, is notable, as among birds this is generally only found in laying females, indicating that the breeding grounds were probably not far away. At least Pacific islands of volcanic origin would be eroded away in the last millions of years however, obliterating any remains of pelagornithid breeding colonies that might have once existed in the open ocean. Necker Island for example was of significant size 10 million years ago, when Osteodontornis roamed the Pacific. | Pelagornithidae | Wikipedia | 469 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
There is no obvious single reason for the pseudotooth birds' extinction. A scenario of general ecological change – exacerbated by the beginning ice age and changes in ocean currents due to plate tectonic shifts (e.g. the emergence of the Antarctic circumpolar current or the closing of the Isthmus of Panama) – is more likely, with the pseudotooth birds as remnants of the world's Paleogene fauna ultimately failing to adapt. In that respect it may be significant that some lineages of cetaceans, like the primitive dolphins of the Kentriodontidae or the shark-toothed whales, flourished contemporary with the Pelagornithidae and became extinct at about the same time. Also, the modern diversity of pinniped and cetacean genera evolved largely around the Mio-Pliocene boundary, suggesting that many ecological niches emerged or became vacant. In addition, whatever caused the Middle Miocene disruption and the Messinian Salinity Crisis did affect the trophic web of Earth's oceans not insignificantly either, and the latter event led to a widespread extinction of seabirds. Together, this combination of factors led to Neogene animals finally replacing the last remnants of the Paleogene fauna in the Pliocene. In that respect, it is conspicuous that the older pseudotooth birds are typically found in the same deposits as plotopterids and penguins, while younger forms were sympatric with auks, albatrosses, penguins and Procellariidae – which, however, underwent an adaptive radiation of considerable extent coincident (and probably caused by) with the final demise of the Paleogene-type trophic web. Although the fossil record is necessarily incomplete, as it seems cormorants and seagulls were very rarely found in association with the Pelagornithidae. | Pelagornithidae | Wikipedia | 381 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
Irrespective of the cause of their ultimate extinction, during the long time of their existence the pseudotooth birds furnished prey for large predators themselves. Few if any birds that coexisted with them were large enough to harm them while airborne; as evidenced by the Early Eocene Limnofregata, the frigatebirds coevolved with the Pelagornithidae and may well have harassed any of the small species for food on occasion, as they today harass albatrosses. From the Middle Miocene or Early Pliocene of the Lee Creek Mine, some remains of pseudotooth birds which probably fell victim to sharks while feeding are known. The large members of the abundant Lee Creek Mine shark fauna that hunted near the water's surface included the broadnose sevengill shark (Notorynchus cepedianus), Carcharias sand tiger sharks, Isurus and Cosmopolitodus mako sharks, Carcharodon white sharks, the snaggletooth shark Hemipristis serra, tiger sharks (Galeocerdo), Carcharhinus whaler sharks, the lemon shark (Negaprion brevirostris) and hammerhead sharks (Sphyrna), and perhaps (depending on the bird fossils' age) also Pristis sawfishes, Odontaspis sand tiger sharks, and Lamna and Parotodus benedeni mackerel sharks. It is notable that fossils of smaller diving birds – for example auks, loons and cormorants – as well as those of albatrosses are much more commonly found in those shark pellets than pseudotooth birds, supporting the assumption that the latter had quite low population densities and caught much of their food in mid-flight.
A study on Pelagornis flight performance suggests that, unlike modern seabirds, it relied on thermal soaring much like continental soaring birds and Pteranodon.
External appearance | Pelagornithidae | Wikipedia | 396 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
Nothing is known for sure about the colouration of these birds, as they left no living descendants. But some inferences can be made based on their phylogeny: if they were a member of the "higher waterbird" group (see below), they most probably had a plumage similar to that depicted in the reconstruction of Osteodontornis orri – Procellariiformes and Pelecaniformes in the modern sense (or Ciconiiformes, if Pelecaniformes are merged there) have hardly any carotenoid or structural colors at all in their plumage, and generally lack even phaeomelanins. Thus, the only colours commonly found in these birds are black, white and various shades of grey. Some have patches of iridescent feathers, or brownish or reddish hues, but these are rare and limited in extent, and those species in which they are found (e.g. bitterns, ibises or the hammerkop) are generally only found in freshwater habitat. | Pelagornithidae | Wikipedia | 212 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
If the pseudotooth birds are Galloanseres, phaeomelanins might be more likely to have occurred in their feathers, but it is notable that the most basal lineages of Anseriformes are typically grey-and-black or black-and-white. Among ocean-going birds in general, the upperside tends to be much darker than the underside (including the underwings) – though some petrels are dark grey all over, a combination of more or less dark grey upperside and white underside and (usually) head is a widespread colouration found in seabirds and may either be plesiomorphic for "higher waterbirds" or, perhaps more likely, be an adaptation to provide camouflage, in particular against being silhouetted against the sky if seen by prey in the sea. It is notable that at least the primary remiges, and often the other flight feathers too, are typically black in birds – even if the entire remaining plumage is completely white, as in some pelicans or in the Bali starling (Leucopsar rothschildi). This is due to the fact that melanins will polymerize, making all-black feathers very robust; as the largest forces encountered by bird feathers affect the flight feathers, the large amount of melanin gives them better resistance against being damaged in flight. In soaring birds as dependent on strong winds as the bony-toothed birds were, black wingtips and perhaps tails can be expected to have been present.
As regards the bare parts, all the presumed close relatives of the Pelagornithidae quite often have rather bright reddish colours, in particular on the bill. The phylogenetic uncertainties surrounding them do not allow to infer whether the bony-toothed birds had a throat sac similar to pelicans. If they did, it was probably red or orange, and may have been used in mating displays. Sexual dimorphism was probably almost nonexistent, as it typically is among the basal Anseriformes and the "higher waterbirds".
Taxonomy, systematics and evolution
The name "pseudodontorns" refers to the genus Pseudodontornis, which for some time served as the family's namesake. However, the presently used name Pelagornithidae pre-dates Pseudodontornithidae, and thus modern authors generally prefer "pelagornithids" over "pseudodontorns". The latter name is generally found in mid-20th-century literature however. | Pelagornithidae | Wikipedia | 511 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
Historically, the disparate bones of the pseudotooth birds were spread across six groups: a number of genera described from leg bones was placed in a family Cyphornithidae, and considered close allies of the pelican family (Pelecanidae). They were united with the latter in a superfamily Pelecanides in suborder Pelecanae, or later on (after the endings of taxonomic ranks were fixed to today's standard) Pelecanoidea in suborder Pelecani. Subsequently, some allied them with the entirely spurious "family" "Cladornithidae" in a "pelecaniform" suborder "Cladornithes". Those genera known from skull material were typically assigned to one or two families (Odontopterygidae and sometimes also Pseudodontornithidae) in a "pelecaniform" suborder Odontopteryges or Odontopterygia. Pelagornis meanwhile, described from wing bones, was traditionally placed in a monotypic "pelecaniform" family Pelagornithidae. This was often assigned either to the gannet and cormorant suborder Sulae (which was formerly treated as superfamily Sulides in suborder Pelecanae), or to the Odontopterygia. The sternum of Gigantornis was placed in the albatross family (Diomedeidae) in the order of tube-nosed seabirds (Procellariiformes).
The most extensive taxonomic and systematic confusion affected Dasornis. That genus was established based on a huge skull piece, which for long was placed in the Gastornithidae merely due to its size. Argillornis – nowadays recognized to belong in Dasornis – was described from wing bones, and generally included in the Sulae as part of the "Elopterygidae" – yet another invalid "family", and its type genus is generally not considered a modern-type bird by current authors. Some additional tarsometatarsus (ankle) bone fragments were placed in the genus Neptuniavis and assigned to the Procellariidae in the Procellariiformes. All these remains were only shown to belong in the pseudotooth bird genus Dasornis in 2008.
The most basal known pelagornithid is Protodontopteryx. | Pelagornithidae | Wikipedia | 496 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
Systematics and phylogeny
The systematics of bony-toothed birds are subject of considerable debate. Initially, they were allied with the (then-polyphyletic) "Pelecaniformes" (pelicans and presumed allies, such as gannets and frigatebirds) and the Procellariiformes (tube-nosed seabirds like albatrosses and petrels), because of their similar general anatomy. Some of the first remains of the massive Dasornis were mistaken for a ratite and later a gastornithid. They were even used to argue for a close relationship between these two groups – and indeed, the pelicans and tubenoses, as well as for example the other "Pelecaniformes" (cormorants and allies) which are preferably separated as Phalacrocoraciformes nowadays, the Ciconiiformes (storks and/or either herons and ibises or the "core" Pelecaniformes) and Gaviiformes (loons/divers) seem to make up a radiation, possibly a clade, of "higher waterbirds". However, the Pelagornithidae are not generally held to be a missing link between pelicans and albatrosses anymore, but if anything much closer to the former and only convergent to the latter in ecomorphology. | Pelagornithidae | Wikipedia | 291 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
In 2005, a cladistic analysis proposed a close relationship between pseudotooth birds and waterfowl (Anseriformes). These are not part of the "higher waterbirds" but of the Galloanserae, a basal lineage of neognath birds. Some features, mainly of the skull, support this hypothesis. For example, the pelagornithids lack a crest on the underside of the palatine bone, while the Neoaves – the sister clade of the Galloanserae which includes the "higher waterbirds" and the "higher landbirds" – have such a crest. Also, like ducks, geese and swans pelagornithids only have two and not three condyles on the mandibular process of the quadrate bone, with the middle condyle beakwards of the side condyle. Their basipterygoid articulation is similar to that of the Galloanseres. At the side of the parasphenoid lamina, there is a wide platform as in Anseriformes. The bony-toothed birds' attachment of the coronoideal part of the external mandible adductor muscles was located at the midline, the rostropterygoid process had a support at its base and the mesethmoid bone had a deep depression for the caudal concha, just as in waterfowl. | Pelagornithidae | Wikipedia | 286 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
As regards other parts of the skeleton, the proposed synapomorphies of pelagornithids and waterfowl are found mainly in the arm- and handbones: the ulna had a strongly convex upper backside at its elbow end – at the handward end of which the scapulotricipital muscles attached –, a point-tipped dorsal cotyle and only a shallow depression to house the meniscus between ulna and radius; towards the elbow, the intercondylar sulcus of the ulna becomes wide and is bordered by a long winding ridge on the belly side. The radius, meanwhile, has a convex ventral border to the humeral cotyle, which prominently continues the hind edge of the knob where the biceps brachii muscle attaches; towards the upper side of the radius bone the surface becomes flat and triangular handwards of the articular surface for the ulna. The carpometacarpus of both Anseriformes and pseudotooth birds has a prominent pisiform process, which extends from the carpal trochlea far fingerwards along the bone's forward side. On the carpometacarpus' underside, there is a long but narrow symphysis of the distal metacarpals, with the large metacarpal bone having a mid-ridge that at its outer end curves tailwards, and the thumb joint has a well-developed knob on the hind side of its articular surface. The leg and foot bones, as is to be expected from birds not as specialized for swimming as waterfowl are, show less similarities between Anseriformes and pseudotooth birds: on the tibiotarsus there is a wide incision between the condyles and the middle condyle is narrower than the side condyle and protrudes forwards; the tarsometatarsus has a low distal vascular foramen with recessed opening on its plantar surface and a middle toe trochlea that is elongated, slightly oblique, projects to the underside of the foot and is pointed at the tip. | Pelagornithidae | Wikipedia | 426 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
It is unclear what to make of these apomorphies supposedly uniting Anseriformes and bony-toothed birds, for on the other hand, the sternum, distal humerus, leg and foot bones of pelagornithids seem to show apomorphies typical of "higher waterbirds". While details of the braincase bones are held to be very informative phylogenetically, the skull features in which the two groups are similar are generally related to the point where the bill attaches to the skull, and thus might have been subject to the selective forces brought about by skimming food from the upper water layer. The apparent non-neoavian traits distinguishing pelagornithids could just as well be retained or atavistic plesiomorphies; as the "higher waterbirds" are very ancient Neoaves and none of the suspected basal members of their radiation (see also "Graculavidae") were included in the analysis, it is not known for sure when the derived conditions typical of modern Neoaves were acquired. Footbone traits are notoriously prone to selection forces in birds, with convergent evolution known to inhibit or even invalidate cladistic analyses; however, the apparent autapomorphies of the lower arm and hand bones are hard to explain by anything else than an actual relationship. The location of the salt glands inside the eye sockets of Osteodontornis, Pelagornis (and probably others) shows that whatever their relationships were, the pelagornithids adapted to an oceanic habitat independently from penguins and tubenoses, which instead have supraorbital salt glands. Their missing or vestigial hallux – like in ducks but unlike in pelicans which have all four toes fully developed and webbed – was held against a close relationship with pelicans. But as is known today, pelicans are closer to storks (which have a hallux but no webbing) than to pseudotooth birds and evolved their fully webbed toes independently. With both a webbed and a hypotrophied hallux being apomorphic and paraphyletic, its absence in pseudotooth birds does not provide much information on their relationship. | Pelagornithidae | Wikipedia | 457 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
While giant Galloanserae were common and diverse in the Paleogene in particular, these (Gastornis and mihirungs) were flightless terrestrial birds; it is perhaps significant though that the only other "bone-toothed" birds known so far are the two species of the moa-nalo genus Thambetochen, extinct giant flightless dabbling ducks from the Hawaiian Islands. In any case, the 2005 cladistic analysis uses a representative sample of Procellariiformes and recovers them as strongly supported clade in agreement with the current consensus. The presumed close relationship between bony-toothed birds and tubenoses can thus be disregarded after all. As regards "Pelecaniformes", the analysis does not recover the correct phylogeny and does not include the shoebill (Balaeniceps rex, a "missing link" between pelicans and storks) either; clearly, the adaptive radiation of the pelican-stork lineage is misleading the analysis here. In addition, the Galloanserae are not recovered as monophyletic. In 2007, a far more comprehensive cladistic analysis of bird anatomy including some fossil forms (though not the crucial Late Cretaceous taxa, which are usually known only from fragmentary remains) resolved the "higher waterbird" radiation somewhat better; still, the problem of leg and foot traits confounding the analysis was noticeable. | Pelagornithidae | Wikipedia | 294 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
As their relationships are still unresolved between Galloanserae and "higher waterbirds", the pseudotooth birds are here placed in the distinct order Odontopterygiformes as a compromise, rather than in a pelecaniform/ciconiiform or anseriform suborder Odontopterygia or even a family of the Anseriformes, Ciconiiformes or Pelecaniformes. Such a treatment is unlikely to be completely wrong in either case, as the pseudotooth birds are well distinct from the Presbyornithidae and Scopidae, today generally regarded as the very basal divergences of, respectively, the Anseriformes and the pelican-stork group. It also provides leeway should the proposed separation of the Pelagornithidae into several families turn out to be appropriate. It is perhaps notable that when Boris Spulski established the Odontopterygia in 1910, he did this partly because he noted some of the similarities between pseudotooth birds and waterfowl listed above. Dasornis was long mistaken for a gastornithid, now strongly suspected to be very close indeed to the Anseriformes. Also, the pelagornithid Palaeochenoides mioceanus was initially mistaken for an anseriform, and the same might hold true for the supposed Oligocene swan Guguschia nailiae. In the former case, however, a "much the more convincing" analysis for a placement outside the Galloanseres was published the year after its description already. Most unrecognised pelagornithid bones were initially assigned to "higher waterbird" families however, typically to the (then-paraphyletic) "Pelecaniformes", but in particular the tarsometatarsus was typically mistaken for that of a procellariiform. The Odontopterygiformes were first proposed when Osteodontornis was described from the first – and still the only known – reasonably complete skeleton of one of these birds. Hildegarde Howard found that, no matter that some of its features resembled other birds, the combination was quite unlike any neognath known. | Pelagornithidae | Wikipedia | 459 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
While the authors claim it is beyond the paper's scope, the study describing Protodontopteryx suggests that the proposed pro-galloansere traits might actually be plesiomorphic in relation to Aves. It also notes "striking" similarities between pelagornithids and Ichthyornis in terms of jaw anatomy, but still classifies them as neognaths due to the well-developed hypotarsal crests, a supratendineal bridge on the distal tibiotarsus and the caudally closed ilioischiadic foramen. The actual phylogenetic tree depicts them in a polytomy with both Galloanserae and Neoaves.
It has been suggested at times that the "teeth" of pelagornithids were homologous with true teeth on an at least molecular level, being derived from the same programs responsible for the formation of teeth in other dinosaurs. This might have an importance to their actual phylogenetic position.
A 2022 paper described Janavis, an ichthyornithine (advanced stem-bird) with a pterygoid bone similar to that of galloanserans. This implies that a galloanseran-like pterygoid is ancestral for crown-group birds as a whole, rather than a derived feature of neognaths. The authors noted that among the groups often regarded as galloanserans based on their pterygoid morphology (pelagornithids, dromornithids and gastornithids), some might instead constitute early-diverging crown-birds outside Galloanserae, or even be outside the avian crown group altogether.
Genera and unidentified specimens
Due to the fragmented and crushed state of most pseudotooth bird remains, it is not clear whether the roughly one dozen genera that have been named are all valid. Only the beaks are robust and distinctive enough to allow for good taxonomic delimitation, and even these are usually found as broken pieces. For example, Argilliornis and Neptuniavis were recently found to be arm and leg bones, respectively, of Dasornis, which until then was only known from skull bones. Size is generally regarded as reliable marker for generic diversity, but care just be taken to ascertain whether smallish specimens are not from young birds. | Pelagornithidae | Wikipedia | 474 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
Tentatively, the following genera are recognized:
Protodontopteryx (Early Paleocene of New Zealand)
Pseudodontornis (Late Paleocene ?–? Late Oligocene of Charleston, South Carolina, US) – polyphyletic (type species in Palaeochenoides/Pelagornis)?
"Odontoptila" (Late Paleocene/Early Eocene of Ouled Abdoun Basin, Morocco) – a nomen nudum; preoccupied
Odontopteryx (Late Paleocene/Early Eocene of Ouled Abdoun Basin, Morocco – Middle Eocene of Uzbekistan) – including "Neptuniavis" minor, may include "Pseudodontornis" longidentata, "P." tschulensis and Macrodontopteryx
Dasornis (London Clay Early Eocene of Isle of Sheppey, England) – including Argillornis, "Lithornis" emuinus and "Neptuniavis" miranda; may include "Odontopteryx gigas" (a nomen nudum), "Pseudodontornis" longidentata and Gigantornis
Macrodontopteryx (London Clay Early Eocene of England) – may include "Pseudodontornis" longidentata and/or belong in Odontopteryx
cf. Odontopteryx (Early Eocene of Virginia, US)
Gigantornis (Ameki Middle Eocene of Ameki, Nigeria) – may belong in Dasornis
cf. Odontopteryx (Middle Eocene of Mexico)
Pelagornithidae gen. et sp. indet. (Middle Eocene of Mount Discovery, Antarctica) – same as large Seymour Island specimen/Dasornis/Gigantornis?
Pelagornithidae gen. et sp. indet. (Middle Eocene of Etterbeek, Belgium) – Dasornis/Macrodontopteryx?
"Aequornis" (Middle Eocene of Kpogamé-Hahotoé, Togo) – a nomen nudum
Pelagornithidae gen. et spp. indet. (La Meseta Middle/Late Eocene of Seymour Island, Antarctica) – two species? Same as Mount Discovery specimen/Dasornis/Gigantornis, Odontopteryx?
Pelagornithidae gen. et sp. indet. (Late Eocene of France) | Pelagornithidae | Wikipedia | 508 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
Pelagornithidae gen. et sp. indet. (Late Eocene of Kazakhstan) – may belong in Zheroia
Pelagornithidae gen. et sp. indet. (Eocene of South Shetland Islands, South Atlantic)
cf. Dasornis (Late Eocene/Early Oligocene of Oregon, US) – Cyphornis?
cf. Macrodontopteryx (Early Oligocene of Hamstead, England) – may belong in Proceriavis
Pelagornithidae gen. et sp. indet. (Early Oligocene of Japan)
Caspiodontornis (Late Oligocene of Pirəkəşkül, Azerbaijan) – may belong in Guguschia
Palaeochenoides (Late Oligocene of South Carolina, US) – may include Pseudodontornis longirostris or belong in Pelagornis
Pelagornithidae gen. et sp. indet. (Late Oligocene of South Carolina, US)
Pelagornithidae gen. et sp. indet. (Yamaga Late Oligocene of Kitakyushu, Japan) – Osteodontornis?
Tympanonesiotes (Late Oligocene or Early Miocene of Cooper River, US)
Cyphornis (Early Miocene of Carmanah Point, Vancouver Island, Canada) – may include Osteodontornis
Osteodontornis (Early Miocene – Early Pliocene) – may belong in Cyphornis
Pelagornis (Early Miocene of Armagnac, France – Early Pleistocene of Ahl al Oughlam, Morocco) – may include Pseudodontornis longirostris, Palaeochenoides
Pelagornithidae gen. et spp. indet. (Early? Miocene – Early Pliocene of eastern US) – 2–3 species? Pelagornis?
cf. Osteodontornis (Capadare Middle Miocene of Cueva del Zumbador, Venezuela)
cf. Osteodontornis/Pelagornis (?Middle/Late Miocene of North Canterbury, New Zealand)
cf. Pelagornis (Bahía Inglesa Middle Miocene of Chile – Early Pliocene of Chile and Peru) – 2 species?
cf. Osteodontornis (Pisco Middle Miocene –? Early Pliocene of Peru) – 2 species? | Pelagornithidae | Wikipedia | 494 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
"Pseudodontornis" stirtoni (Miocene or Pliocene of Motunau Beach, New Zealand) – sometimes Neodontornis
Pelagornithidae gen. et sp. indet. (Yushima Early Pliocene of Maesawa, Japan) – Osteodontornis?
cf. "Pseudodontornis" stirtoni (Tangahoe Mudstone Middle Pliocene of Hawera New Zealand)
Pelagornithidae gen. et sp. indet. (Dainichi Early Pleistocene of Kakegawa, Japan) – Osteodontornis?
Pelagornis sp. (Late Pliocene of California, US: Boessenecker and Smith; 2011)
Some other Paleogene (and in one case possibly Late Cretaceous) birds, typically taxa known only from the most fragmentary remains, might also be pelagornithids. They are not usually placed here, but the fossils' large size and the known similarities of certain pseudotooth birds' bones to those of other lineages warrant further study. The genera in question are Laornis, Proceriavis, Manu and Protopelicanus. | Pelagornithidae | Wikipedia | 243 | 9205088 | https://en.wikipedia.org/wiki/Pelagornithidae | Biology and health sciences | Prehistoric birds | Animals |
The Astronomical Almanac is an almanac published by the United Kingdom Hydrographic Office; it also includes data supplied by many scientists from around the world. On page vii, the listed major contributors to its various Sections are: H.M Nautical Almanac Office, United Kingdom Hydrographic Office; the Nautical Almanac Office, United States Naval Observatory; the Jet Propulsion Laboratory, California Institute of Technology; the IAU Standards Of Fundamental Astronomy (SOFA) initiative; the Institut de Mécanique Céleste et des Calcul des Éphémerides, Paris Observatory; and the Minor Planet Center, Cambridge, Massachusetts.
It is considered a worldwide resource for fundamental astronomical data, often being the first publication to incorporate new International Astronomical Union resolutions. The almanac largely contains Solar System ephemerides based on the JPL Solar System integration "DE440" (created June 2020), and catalogs of selected stellar and extragalactic objects. The material appears in sections, each section addressing a specific astronomical category. The book also includes references to the material, explanations, and examples. It used to be available up to one year in advance of its date, however the current 2024 edition became available only one month in advance; in December 2023.
The Astronomical Almanac Online was a companion to the printed volume. It was designed to broaden the scope of the publication, not duplicate the data. In addition to ancillary information, the Astronomical Almanac Online extended the printed version by providing data best presented in machine-readable form.
The 2024 printed edition of the Almanac states on page iv: "The web companion to The Astronomical Almanac has been withdrawn as of January 2023."
Publication contents
Section A PHENOMENA: includes information on the seasons, phases of the Moon, configurations of the planets, eclipses, transits of Mercury or Venus, sunrise/set, moonrise/set times, and times for twilight. Preprints of many of these data appear in Astronomical Phenomena, another joint publication by USNO and HMNAO.
Section B TIME-SCALES AND COORDINATE SYSTEMS: contains calendar information, relationships between time scales, universal and sidereal times, Earth rotation angle, definitions of the various celestial coordinate systems, frame bias, precession, nutation, obliquity, intermediate system, the position and velocity of the Earth, and coordinates of Polaris. Preprints of many of these data also appear in Astronomical Phenomena. | Astronomical Almanac | Wikipedia | 495 | 7082456 | https://en.wikipedia.org/wiki/Astronomical%20Almanac | Technology | Astronomical technology | null |
Section C SUN; covers detailed positional information on the Sun, including the ecliptic and equatorial coordinates, physical ephemerides, geocentric rectangular coordinates, times of transit, and the equation of time.
Section D MOON: contains detailed positional information on the Moon including phases, mean elements of the orbit and rotation, lengths of mean months, ecliptic and equatorial coordinates, librations, and physical ephemerides.
Section E PLANETS: consist of detailed positional information on each of the major planets including osculating orbital elements, heliocentric ecliptic and geocentric equatorial coordinates, and physical ephemerides.
Section F NATURAL SATELLITES; covers positional information on the satellites of Mars, Jupiter, Saturn (including the rings), Uranus, Neptune, and Pluto.
Section G DWARF PLANETS AND SMALL SOLAR SYSTEM BODIES: includes positional and physical data on selected dwarf planets, positional information on bright minor planets and periodic comets.
Section H STARS AND STELLAR SYSTEMS: contains mean places for bright stars, double stars, UBVRI standards, ubvy and H beta standards, spectrophotometric standards, radial velocity standards, variable stars, exoplanet and host stars, bright galaxies, open clusters, globular clusters, ICRF2 radio source positions, radio flux calibrators, x-ray sources, quasars, pulsars, and gamma ray sources.
Section J OBSERVATORIES: was a worldwide index of observatory names, locations, MPC codes, and instrumentation in alphabetical order and by country. This section has now been removed as stated in the printed 2024 edition on page J1: "We are presently reserving Section J for possible new contents in future editions of The Astronomical Almanac." An explanation is given on page iv: "Section J: Observatories: This section has been removed as it is significantly out-of-date and it is not clear that a static listing of Observatories is a useful service any longer."
Section K TABLES AND DATA: includes Julian dates, selected astronomical constants, relations between time scales, coordinates of the celestial pole, reduction of terrestrial coordinates, interpolations methods, vectors and matrices.
Section L NOTES AND REFERENCES: gives notes on the data and references for source material found in the almanac.
Section M GLOSSARY: contains terms and definitions for many of the words and phrases, with emphasis on positional astronomy. | Astronomical Almanac | Wikipedia | 502 | 7082456 | https://en.wikipedia.org/wiki/Astronomical%20Almanac | Technology | Astronomical technology | null |
Publication history
The Astronomical Almanac is the direct descendant of the British and American navigational almanacs. The British Nautical Almanac and Astronomical Ephemeris had been published since 1766, and was renamed The Astronomical Ephemeris in 1960. The American Ephemeris and Nautical Almanac had been published since 1852. In 1981 the British and American publications were combined under the title The Astronomical Almanac."
Explanatory Supplement to the Astronomical Almanac
The Explanatory Supplement to the Astronomical Almanac, currently in its third edition (2013), provides detailed discussion of usage and data reduction methods used by the Astronomical Almanac. It covers its history, significance, sources, methods of computation, and use of the data. Because the Astronomical Almanac prints primarily positional data, this book goes into great detail on techniques to get astronomical positions. Earlier editions of the supplement were published in 1961 and in 1992. | Astronomical Almanac | Wikipedia | 187 | 7082456 | https://en.wikipedia.org/wiki/Astronomical%20Almanac | Technology | Astronomical technology | null |
In fluid mechanics, Kelvin's circulation theorem states:In a barotropic, ideal fluid with conservative body forces, the circulation around a closed curve (which encloses the same fluid elements) moving with the fluid remains constant with time.
The theorem is named after William Thomson, 1st Baron Kelvin who published it in 1869.
Stated mathematically:
where is the circulation around a material moving contour as a function of time . The differential operator is a substantial (material) derivative moving with the fluid particles. Stated more simply, this theorem says that if one observes a closed contour at one instant, and follows the contour over time (by following the motion of all of its fluid elements), the circulation over the two locations of this contour remains constant.
This theorem does not hold in cases with viscous stresses, nonconservative body forces (for example the Coriolis force) or non-barotropic pressure-density relations.
Mathematical proof
The circulation around a closed material contour is defined by:
where u is the velocity vector, and ds is an element along the closed contour.
The governing equation for an inviscid fluid with a conservative body force is
where D/Dt is the convective derivative, ρ is the fluid density, p is the pressure and Φ is the potential for the body force. These are the Euler equations with a body force.
The condition of barotropicity implies that the density is a function only of the pressure, i.e. .
Taking the convective derivative of circulation gives
For the first term, we substitute from the governing equation, and then apply Stokes' theorem, thus:
The final equality arises since owing to barotropicity. We have also made use of the fact that the curl of any gradient is necessarily 0, or for any function .
For the second term, we note that evolution of the material line element is given by
Hence
The last equality is obtained by applying gradient theorem.
Since both terms are zero, we obtain the result
Poincaré–Bjerknes circulation theorem
A similar principle which conserves a quantity can be obtained for the rotating frame also, known as the Poincaré–Bjerknes theorem, named after Henri Poincaré and Vilhelm Bjerknes, who derived the invariant in 1893 and 1898. The theorem can be applied to a rotating frame which is rotating at a constant angular velocity given by the vector , for the modified circulation | Kelvin's circulation theorem | Wikipedia | 504 | 7086534 | https://en.wikipedia.org/wiki/Kelvin%27s%20circulation%20theorem | Physical sciences | Fluid mechanics | Physics |
Here is the position of the area of fluid. From Stokes' theorem, this is:
The vorticity of a velocity field in fluid dynamics is defined by:
Then: | Kelvin's circulation theorem | Wikipedia | 35 | 7086534 | https://en.wikipedia.org/wiki/Kelvin%27s%20circulation%20theorem | Physical sciences | Fluid mechanics | Physics |
The Limousin, , is a French breed of beef cattle from the Limousin and Marche regions of France. It was formerly used mainly as a draught animal, but in modern times is reared for beef. A herd-book was established in France in 1886. With the mechanisation of agriculture in the twentieth century, numbers declined. In the 1960s there were still more than 250 000 head, but the future of the breed was not clear; it was proposed that it be merged with the other blonde draught breeds of south-western France – the Blonde des Pyrénées, the Blonde de Quercy and the Garonnaise – to form the new Blonde d'Aquitaine. Instead, a breeders' association was formed; new importance was given to extensive management, to performance recording and to exports. In the twenty-first century the Limousin is the second-most numerous beef breed in France after the Charolais. It is a world breed, raised in about eighty countries round the world, many of which have breed associations.
History
The Limousin originates in the Limousin, the area surrounding Limoges on the western flank of the Massif Central. It was originally a robust draught animal, used for agricultural work. As elsewhere, oxen at the end of their working lives were fattened and sent to slaughter, at times in major cities such as Bordeaux or Paris.
In 1791, Jacques-Joseph Saint-Martin, an agronomist from Limoges, acknowledged the importance of Limousin cattle in the markets of cities such as Paris, Lyon, and Toulouse. Limousin cattle actually came from the departments of Charente, Dordogne, Haute-Vienne, Vienne, Lot, Corrèze, and Creuse. The market for Limousin cattle declined slightly in the early 19th century, but livestock still remained a major activity in the region.
A large variation in the agricultural systems was operating in the Limousin region, defined by three types of district. These were productive, grain-producing areas, called d'engrais, undeveloped, marginal, predominantly forested land called forestiers, and developing land called d'élèves. Cattle, in particular cows, were used extensively for all types of agricultural work. | Limousin cattle | Wikipedia | 458 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
At the beginning of the 19th century, the Limousin region was characterised by the mediocrity of its animals. Texier-Olivier Louis, prefect of the Haute-Vienne, observed that Limousin cattle weighed 300 to 350 kg and measured 1.5 m at the withers. The defect was considered to be attributable to poor genetics, nutrition and breeding practices. In competitions, Limousin cattle were among the worst performers. The breed was considered to be a working breed, but poorly shaped and with poor milk.
To improve the breed, some Limousin breeders tried to cross their animals with Agenais, Norman or Charolais cattle, which were better shaped.
The Limousin breed was also not immune to the wave of Anglomania affecting France in the middle of the 19th century. Some wealthy farmers maintained Durham cattle, which were prized by the elite of the time. However, this practice was criticised by the agricultural society of Limoges. The society encouraged farmers to continue selecting animals that were most consistent with the characteristics of the Limousin breed, which was perfectly adapted to the region's environment, rather than trying to adapt other breeds. Furthermore, the vast majority of Limousin breeders could not afford to raise livestock in addition to their working animals, as was the case on larger properties that practiced crossing with Durham cattle.
Finally, the marginalisation of English animals in competitions from the late 1860s reinforced the case to improve the breed by itself. A herd-book was started in 1886.
At the beginning of the 19th century, a bonus was introduced to reward farmers who retained their best bulls, though they were not productive. The increase in weight of the animals began with improved grassland. The second half of the 19th century had the arrival of fertilizers and improved pastures such as clover and ryegrass, which not only improved the productivity of existing fields, but also transformed the moorland pasture. Vineyards affected by phylloxera were also being returned to pasture. | Limousin cattle | Wikipedia | 406 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
The results were not immediate. In 1862, cattle sold at La Souterraine weighed about 600 kg. The decline of Anglomania in favour of economic pragmatism, and the criticism and fall of the aristocracy aided the development of Limousin cattle. The crowning moment was the honour received by the bull Achilles Caillaud to open the competition in Paris for all breeds in 1886 (the year the Limousin Herd Book was created), and the grand champion prize of all breeds won three years later by Charles Léobardy for his team.
The First World War slowed down the growth of the Limousin breed, which carried through the interwar years despite a reorganisation of the herd book in 1923. Herd book registrations grew slowly, from 600,000 animals in 1890 to 800,000 in 1940.
The Limousin breed almost disappeared when the French government planned to combine it with the Garonne, Quercy, and Blonde des Pyrenées breeds, during the formation of the Blonde d'Aquitaine breed in 1962. All of these cattle belonged to the "blond and red" branch of cattle. Limousin breeders fiercely opposed the merger and the Limousin breed was retained.
The Limousin breed resumed its growth in the 1960s. The size of the French Limousin herd has increased sharply in recent years, with a 50% increase in numbers in France in 15 years. Today, it is the second-most numerous French beef breed, behind Charolais and ahead of Blonde d'Aquitaine. In 2004, of about 900,000 Limousin cows, 63,000 were recorded in the herd book. At that time, 20,000 bulls were used for breeding, 10% through artificial insemination, and 1,600 were recorded in the Herd Book. France's Limousin herd grew by 2.6% in 2014 to 2.69 million head as of 31 Dec., including 1.09 million cows.
DNA studies have identified close genetic relationships between Limousin cattle and other south-west European breeds. One study reported a possible common origin or recent gene flow between the Limousin and Charolais cattle breeds. whereas other studies indicated that a closer genetic relationship exists between Limousin, Gasconne, Aubrac, Bazadais, Salers, and Blonde d'Aquitaine cattle. | Limousin cattle | Wikipedia | 478 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
One historian reported that the Limousin breed's origins can be traced to the blonde Garonne breed in the fifth century AD. The Garonne breed from the south-west of France was merged into the Blonde d'Aquitaine breed in 1962. The grey Gasconne breed with which Limousin cattle have a close genetic relationship is also reported to have arrived in the south-west of France with the Visigoths also around the fifth century AD.
The Limousin belongs to the blond group of European cattle, in a sub-group which also includes the Alpha 16, the Maraîchine, the Nantaise and the Parthenaise.
The herd-book
Significance
The purest form of Limousins have ancestors that can all be traced to "Full French" entries in the herd-book (known in France as Le livre généalogique). These Limousins are known by different names. In the US, and Canada they are known as Fullbloods, in Australia and New Zealand as French Pure, and in European countries such as Britain as purebred or simply Limousin.
In France, two Full French Herd Book classes exist, namely Pureblood (pur sang in French, also translated to Fullblood) and Pure Bred (race pure in French). The Full French Pure Bred Herd Book class, as with all European Union (EU) member countries' herd books, is controlled by EU legislation.
Full French is a term used by the French Limousin breeders' association (known in France as Herd Book Limousin, abbreviated to HBL) to describe cattle that comply with:
Bred by French active member-associates of the HBL: The strictly enforced rules of the HBL require breeders to conduct on-farm performance testing of their animals and to have selected animals independently tested by approved official bodies.
Independently inspected and certified to be Full French according to the Breed Standard.
Cattle excluded from Full French certification include those imported into France, cattle that are polled (in French sans corne), and cattle that have undesirable double muscling genes (in French gene culard) inherited from non-Limousin base animals. | Limousin cattle | Wikipedia | 446 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
A less pure form of Limousin is bred up (also known as graded up) from a base animal over a defined number of generations. A parent of each generation's progeny must be registered as a Limousin in the respective country's herd book. In the US, Canada, Australia, and New Zealand, a graded up Limousin, after three generations for females and four generations for males, is known (confusingly with the legal European definition) as purebred, which is then eligible for recording in the respective countries' herd books alongside Fullblood and French Pure Limousins. Unlike the US, Canada, Australia, and New Zealand, which allow both purebred and Full French bulls and dams to be used for grading up, in Britain, grading up can only occur using Full French bulls. British graded up females when they reach fourth generation from a non-Limousin base cow can then be registered as Limousins in the British Limousin Pedigree Register. The British Limousin Pedigree Register is separate from the British Limousin Herd Book, which is reserved for animals that have complete Full French ancestry.
Evolution of Herd Book
Prior to July 2007
The herd-book was destroyed in the Second World War. When the French Government decided to merge the Limousin breed into the new Blonde d'Aquitaine breed in the 1960s, which was fiercely opposed by French Limousin breeders, the impetus to re-establish the herd-book was provided. Inspectors were appointed to identify "true to type" Limousins from the Limousin region. These were admitted to the new herd-book as foundation animals (in French titre initial, abbreviated to T.I.).
Following its re-establishment, the Herd Book was opened from time to time for the admission of T.I. females that on inspection satisfied the Full French breed standard. These animals were identified by the letters T.I. placed after their name. The process of admitting new T.I. animals to the Herd Book continued until June 2008. The Limousins recorded in the herd-book were known as Pureblood (literal translation of the French pur sang). The is normally the name given to English thoroughbred horses, although in the context of Limousins the English translation Fullblood is commonly used. | Limousin cattle | Wikipedia | 475 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
July 2007 to June 2008
EU legislation, pressure from French breeders of polled stock, and other developments, including requirements of European Limousin associations (the 11 countries of EUROLIM), contributed to a restructuring of the herd-book that commenced in July 2007.
During the period July 2007 to June 2008, the herd-book comprised a main section (section principale in French) divided into the original Pureblood (pur sang) class and a newly created Purebred (race pure) class. The Purebred class was added to enable the recording of polled animals, those that carried a double-muscling gene (muscle hypertrophy abbreviated to MH, or gene culard in French), and those that did not comply fully with the French Breed standard.
After June 2008
EU legislation allowed a supplementary section (section annexe in French) to be used to introduce genetics into existing breeds from other breeds in a grading up process aimed at "progressive improvement". According to the legislation, only females whose mother and maternal grandmother entered in a supplementary section, and whose father and two grandfathers are entered in the main section, can be regarded as purebred and entered in the main section of a herd book. Although this appears to be a simple two-stage grading up process, base females that start a new grading up line were also required by EU legislation to "be judged to conform to the breed standard". Since 2007, EU legislation allowed base animals to be males but infusion of their genetics into the main section is still only possible through their female progeny.
The restructured French Herd Book is described as having a third section called certified purebred (race pure certifié in French) intermediate between the first two for recording animals that do not comply with the breed standard (for example incorrectly coloured hair in certain places), have double muscling genes, or are polled. Limousins imported into France that comply with Council Directive 2009/157 are also recorded in sub-class 2 (sous-classe 2 in French) of the certified purebred class because they do not comply with the French HBL requirement of being Full French. | Limousin cattle | Wikipedia | 439 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Base animals selected for the two-stage grading up process to any EU herd book purebred class require a minimum of 3/4 Limousin content. Graded up females using the two-stage process then become eligible for entry into the main section of all EU herd book purebred classes as initial registration (or T.I.) Limousins when they reach 15/16 Limousin content. They are then legally identified as Limousin (i.e. 100% Limousin) – the breed code 34 often substitutes for the word Limousin in French discussions and reports on cattle breeding.
Only the Certified Purebred sub-class 2 and Registered Purebred class are identified as Limousin in France because cattle of non-Limousin origin had been introduced into the supplementary section of the Pureblood class. The growth and spread of the Limousin breed in France since the early 1980s meant that a past practice of selecting a base female on appearance alone was no longer a guarantee of its breed origin because of the potential for "crossing absorption". Base females inadvertently assessed as Limousin and recorded as T.I. animals in the main section of the Pureblood class included Parthenais and Charolais, which were presumably the source of the double-muscling genes found in the French Limousin Pureblood population. In 2008, the double muscling gene had been found in 3% of active bulls in France.
Currently, only cattle recorded in the French Limousin Certified Purebred sub-class 2 and Registered Purebred class satisfy the requirements of EU law on herd books and can be transferred as Limousins, including indirectly through their genetics (for example semen and embryos), to other EU countries and recorded in the respective herd books. Outside of the EU, the rules and regulations of Limousin breed associations do not yet differentiate between the French Pureblood and Purebred classes, with the Pureblood class remaining the origin of, and standard for, the purest form of Limousin.
Since the 1960s and until 2008, the French Pureblood class defined the standard against which Limousins throughout the world were measured. Although it would seem appropriate to preserve the integrity of the herd-book as the international Limousin breed standard by preventing the EU-mandated entry of animals that do not meet the Full French standard, restrictions to such entries remain forbidden under EU law and subsequent interpretations by the European Court of Justice. | Limousin cattle | Wikipedia | 506 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Immediately prior to the restructuring of the herd-book in 2008, French breeders had two months to nominate the class (Pureblood or Purebred) in which they wanted their cattle to be registered. Pureblood cattle have higher business value than Purebreds because they are preferred by French breeders. Also, Full French cattle benefit under a branded meat marketing label known as Blason Prestige Label Rouge, which has around 800 outlets in France.
Future
EU legislation on dehorning practices is expected to place greater pressure to breed polled cattle, which is being pursued in France by the GIE Polled Excellence group. Because no French Limousins had been identified with the polled gene, a breeding programme commenced in 2005 with polled Canadian bulls of phenotype closest to the French breed standard.
French breeders of polled Limousins claimed that the breed standard that prevented their animals being recorded in the French Herd Book provided an unfair export advantage to foreign countries that do not have similar restrictions. The French recording ban was removed in July 2007 with the introduction of the Purebred class, but so far no polled Limousin have yet been accepted and registered as Full French.
Characteristics
Limousin breed standard
The French Limousin breed standard is described in Article 1 of Title I of the Rules of Procedure of the French Limousin herd-book, 1 August 1991:
The Limousin is a large framed breed of beef cattle with a bright wheat-coloured coat, not too dark, a little lighter on the belly, the rear of the thighs, between the legs, on the anus, around the testicles or udder, and the tail tip. Absence of any spots or pigmentation, with pink mucous membranes. Short head, broad forehead and muzzle, lighter area around the eyes and muzzle, fine horns curved forward and slightly raised at the tip (if present). Short neck. Chest broad and rounded. Side round. Pelvis wide, especially at the pin bones, not too inclined. Bones of lower back and hips slightly protruding. Forequarter well-muscled, wide above and very muscular. Hindquarters thick, deep and rounded. Horns and hooves lighter coloured. Correct limbs. Fine supple hide. | Limousin cattle | Wikipedia | 447 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Characteristics considered unacceptable in the French breed standard:
Any pigmentation or black spots on muzzle, black or white hairs anywhere on the coat, particularly in the ears, at the end of the tail and around the muzzle.
White hairs anywhere.
An eliminating count of less than five for any of the different breed standard points.
A difficult or vicious disposition (tranquilising is forbidden).
Any obvious physical malformation.
The French Limousin breed standard is applied by international breed associations in slightly different forms. These range from mandatory compliance before an animal can be recorded in a country's herd book (mainly European countries) to voluntary application in others. For example, in Belgium, application of its breed standard mirrors in most detail the French use, and in the UK, compliance with its version of the Limousin breed standard is required by the UK breed association's bye-laws.
The USA, Canadian, Australian and New Zealand breed associations do not define a breed standard in their regulations, and application of any standard is voluntary. The only requirement for registration as a Fullblood in both North American herd book registers is that ancestors should have "full French ancestry", or trace directly to the "Herd Book Limousin in France". In Australia and New Zealand the French Pure herd book classification requires that animals carry "100% Pure French genetics". USA, Australian and New Zealand breed association regulations also allow graded up animals to be registered in their herd books as purebreds without a requirement to comply with a minimum French Limousin content. Grading up using these purebreds over base or lower grade animals has resulted in the gradual reduction in the French Limousin content of some purebreds, and an observable divergence from the French breed standard. The Canadian breed association by regulation prevents loss of French Limousin content from its registered purebreds by requiring that they "contain 90% or more Limousin blood".
In the US, Canada, Australia and New Zealand, breed development and selection is influenced principally by performance recording and genetic selection.
French performance recording and genetic prediction
The breed standard in France is applied in parallel to an intensively applied system of selection, performance recording and genetic prediction that was established gradually across the country commencing in the 1980s. The system appears to be similar to that used in Denmark. | Limousin cattle | Wikipedia | 470 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
All females recorded in the French Herd Book are controlled under this system, which focuses mainly on maternal qualities derived from measurements of calving ease, and growth and structure of calves. Females that achieve the best indexes for particular traits are then examined in detail by HBL technicians who assign grades based on morphology. The best females receive the qualification Reproductive Recognised (in French Reproductrice Reconnue, abbreviated to RR), which is awarded to the top 10%, or Reproductive Recommended (in French Reproductrice Recommandée, abbreviated to RRE) awarded to the top 1%. The qualifications aid the identification of superior animals.
For males, selection of the best breeders is more complex. The first step is weaning, when the morphology of calves and the known qualities of their parents are used to make an initial selection of animals that receive the qualification Reproductive Hope (in French Reproducteur Espoir, abbreviated to Espoir). Annually in excess of about 700 bull calves are then selected to enter the national evaluation station at , close to Limoges, just after weaning, when they are about seven months old. At Lanaud the animals are grouped together to compare their performance under identical feeding and environmental conditions to the age of 13–14 months. The differences observed between the animals are then related principally to their genetics, which is of interest to breeders because this is what is transmitted to a bull's progeny.
After completing evaluation at Lanaud, half of the young bulls are awarded the qualification Reproductive young (in French Reproducteur jeune, abbreviated to RJ) by the HBL. Most of these bulls are intended for natural service, and the best are subjected to evaluations of their progeny. In the same way as for females, the best bulls receive the qualification "Reproductive Recognised" (RR), awarded to the top 10%, or "Reproductive Recommended" (RRE), awarded to the top 1%.
In parallel with the Lanaud evaluation station there are three local stations at La Souterraine in the Creuse department of the Limousin region, Saint-Jal in Corrèze, also in the Limousin region, and Naucelle in Aveyron in the south of France. The local stations provide commercial beef producers in their region with bulls of high production potential for use by commercial farmers whose herds are not necessarily registered in the French herd book. | Limousin cattle | Wikipedia | 501 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
The best bulls go to artificial insemination (AI) cooperatives where semen is taken. AI allows the wide distribution of a bulls' genetics to the benefit of more farmers. However, in order to guarantee their genetic qualities, the bulls are subject to a strict selection scheme to increase the accuracy of the different genetic indexes. The best bulls identified at Lanaud are sent to another test station at Naves in Corrèze. Here they are tested more accurately and evaluated for feed conversion efficiency, growth and muscle development. Progeny of the top 10 bulls out of this testing, and the best natural service bulls, are then evaluated. Cows are inseminated to produce 60 to 80 calves per bull tested, which are in turn evaluated.
Male progeny go to a station in Pépieux in the south of France, where they are fed a ration of corn silage before being slaughtered at the age of 16 months. In addition to evaluations of growth and conformation in the live animals, carcases, including fat composition, are evaluated. The best bulls identified in progeny testing are formally given the award Young Beef Cattle (in French Viande Jeunes Bovins, abbreviated to JB). Female progeny go to a test station in Moussour in Corrèze, where they are inseminated with the same bulls and calve at two years in confinement before being put out to pasture with their calves. The test station evaluates weight, growth, morphology, fertility, calving ability and milking ability in order to assess their maternal qualities. The best bulls following the tests on their daughters are identified as Maternal Qualities (in French Qualités Maternelles, abbreviated to QM).
The qualifications RR and RRE are recorded with an animal's description in sales' catalogues and other promotional literature. As a further aid to purchasers of French Limousin genetics, additional qualifications provide a guide to the greatest likely production benefit based on an animal's genetics estimated from on-farm progeny testing. The qualifications are aligned with French market specifications for Limousin beef: | Limousin cattle | Wikipedia | 429 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
VS – awarded to sires recognised or recommended for weaner production.
VB – awarded to AI sires recognised or recommended for vealer production.
JB – awarded to AI sires recognised or recommended for general beef production.
QM – awarded to AI sires recognised or recommended for breeding stock production.
M – awarded to AI sires recognised or recommended for both general beef and breeding stock production.
P – awarded to females recognised or recommended for the production of early developing progeny.
T – awarded to females recognised or recommended for the production of late developing progeny.
Genetic basis for muscling in Limousin cattle
The Limousin cattle breed has been popular in France for more than two centuries because of its meat qualities and the breed's production efficiency. Since the early 1990s scientists have quantified these breed characteristics in comparisons with other breeds, and identified a natural variant of the myostatin gene found in Limousins which has a significant influence on them. The myostatin gene is found in all mammals and influences the production of a protein that controls muscle development. Variants of the gene produce proteins that are less effective at controlling muscle development, which results in increased muscle mass.
Limousin muscling is intermediate to that of British cattle breeds such as Aberdeen Angus, Hereford, and Shorthorn and the extreme double muscling found in the European Belgian Blue and Piedmontese breeds. Studies of double-muscled cattle identified natural mutations of the myostatin gene which produce inactivated proteins that are unable to control muscle development. In Belgian Blue and Piedmontese cattle this causes an increase in muscle mass of 20–25%. Subsequent studies identified a less extreme myostatin mutation known as F94L associated with Limousins. The resulting partially active protein results in Limousins having intermediate muscle development, which avoids the extreme muscling and associated disadvantages of double muscled cattle. | Limousin cattle | Wikipedia | 385 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
A Limousin/Jersey backcross study conducted in Australia and New Zealand to investigate the effects of the F94L myostatin variant concluded that the mutation had no significant effect on birth-weight and growth traits. Averaged over all backcross calves in the trial (total of 766), animals homozygous for the mutation had approximately 6% heavier carcases than animals without the mutation, 15% larger eye muscle (also known as rib eye) area, 13% heavier silverside weight, and 13% heavier total meat weight. Increased meat weight and size was accompanied by a 15% reduction in intra-muscular fat and 25% reduction in total fat weight. No other significant effects were observed. A second backcross study conducted in Japan of Limousin and Japanese Black breeds identified similar changes to meat and fat quantities in cattle homozygous for the F94L mutation.
Although the Australian/New Zealand study found that the F94L mutation was partially to significantly recessive in most traits, meaning cattle heterozygous for the mutation express less to significantly less than half of the effects noted for homozygous cattle, the Japanese study found that the meat and fat quantities in cattle heterozygous for the mutation were about midway between the two extremes.
Distribution of F94L myostatin variants in Limousin cattle
A number of international breed associations have been testing the F94L status of cattle registered in their herd books. The absence of F94L genes in some tested cattle might be a result of a sire or dam ancestor that had double muscling (MH) genes, or more likely that the myostatin gene was the normal or wild type variant found most commonly in beef cattle. In the latter case, loss of the F94L variant will arise when grading up to purebred when base animals are not Limousins.
Europe
Of the 14 Limousins tested during the research that led to the discovery of the F94L variant, 12 cattle were homozygous for the variant and two were heterozygous. The second myostatin genes in both heterozygous cases were each different myostatin MH variants of types normally found in Belgian Blue and Charolais cattle. | Limousin cattle | Wikipedia | 469 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Britain
British test results of sale bulls in February 2010 indicated that of 142 animals tested, just under 90% were homozygous for the F94L mutation, about 8.5% were heterozygous, and 1.5% did not have the mutation.
USA
Test results of approximately 1,100 cattle recorded in the North American Limousin Foundation herd book show the following distributions for three classes of animal. About 94.4% of Fullbloods, 62.3% of purebreds and 5.3% of Lim-Flex were homozygous for the F94L mutation.
Australia and New Zealand
Test results of 1028 cattle recorded in the Australian and New Zealand herd book indicate that 96.7% of Fullbloods (known in Australia as French Pure), 88.0% of purebreds, and 33.3% of a limited sample of Lim-Flex were homozygous for the F94L mutation.
Implications for cattle heterozygous for the F94L variant
Cattle heterozygous for the F94L myostatin mutation have a 50% probability of passing the mutation to their progeny. Because the mutation has greatest effect on carcase traits, only 50% of progeny of a heterozygous parent will inherit increased muscling associated with the mutation.
Furthermore, best linear unbiased prediction (BLUP) techniques used to estimate the genetic merit of stud cattle (for example, estimated breeding values (EBVs) and expected progeny differences (EPDs)) will be incorrect because they assume that no dominant genes contribute to modelled traits. | Limousin cattle | Wikipedia | 340 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Inconsistent inheritance of myostatin mutations (for example, F94L in Limousins, nt821 in Angus, and Q204X in Charolais) by progeny is expected to result in possible BLUP prediction errors for EBVs and EPDs equalling or exceeding worst case standard errors of prediction. For example, average rib eye area for Limousins in US Meat Animal Research Center (USMARC) trials during the 1980s and early 1990s is reported to be 12.3in2, and the reported possible difference in rib eye area in progeny arising from inheritance of either two F94L mutations or two normal myostatin genes from heterozygous parents is estimated to be 1.8in2 (12.3in2 x 15%). This difference, which is unpredictable without DNA testing, is nearly four times the possible change value for a 0% BIF accuracy, reported to be 0.46in2 for the rib eye EPD.
When one parent is heterozygous for the mutation, and the other homozygous for the mutation or the normal form of the myostatin gene, the expected average difference in rib eye area of progeny will be about 0.9in2 (12.3in2 x 7.5%), depending on whether the mutation or normal form of the gene is inherited from the heterozygous parent. In this case, the unpredictable variation in rib eye area represents about twice the possible change value for a 0% BIF accuracy.
Standard errors of prediction, also known as accuracy or possible change value in the context of EBV and EPD predictions, are dependent on the quality of information used to predict an animal's EBV or EPD for a given trait. Errors in estimating genetic merit are being addressed in research programmes that aim to supplement phenotypic data extensively used in current BLUP predictions with genotypic data. | Limousin cattle | Wikipedia | 402 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Comparisons with other breeds
A USMARC long-term multi-breed study of Limousins, three British (Red Poll, Hereford, Aberdeen Angus) and five other continental European (Braunvieh, Pinzgauer, Gelbvieh, Simmental, Charolais) cattle breeds reported that Limousin cattle were the most efficient and fastest of all breeds at converting feed into saleable meat even though Limousin's live weight growth was the slowest. This arose because saleable meat yield expressed as percentage of live weight was significantly higher in Limousins than in most other cattle breeds. Saleable meat yield was an average 34.9% of live weight for the three British cattle breeds, compared with 40.4% for the five other continental European breeds, and 46.0% for Limousins, for two market end points of 225 kg saleable meat at 8mm fat trim, and 210 kg saleable meat at 0mm fat trim. Live weight gain for the Limousins averaged 1.27 kg/day, compared with an average 1.29 kg/day for the British breeds and 1.38 kg/day for the other continental European cattle. Limousin saleable meat gain averaged 585g/day, with the balance being 687g/day of low value or waste product, such as bone, trimmed fat, internal organs, and hide. The British breeds produced significantly less saleable meat (average 451g/day) and significantly more low value product (841g/day), while consuming about twice the feed of the Limousins from entry to the trial (weaning) to the market end point (slaughter). The other continental European breeds produced on average less saleable meat (556g/day) and more low cost product (819g/day) while consuming about 25% more feed than the Limousins. Although the Simmental and Charolais produced marginally more saleable meat (590g/day) than Limousins, they produced significantly more low cost product (847g/day) and consumed 18% more feed. | Limousin cattle | Wikipedia | 436 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
For a market end point of 333 kg carcase weight, the Limousin carcases in the USMARC study were estimated to be on average 63.5% of live weight, compared with an average 59.7% (range 58.6% – 60.4%) for the eight other breeds. Similar figures for Limousin meat yield are reported in other sources.
The USMARC study indicated that Limousins were significantly the slowest of all breeds to achieve market end points of two measures of marbling score (70 to 160 days longer than the British breeds, and 65 to 70 days longer than the other continental European breeds) while feed conversion efficiency based on live weight gain was marginally poorer (12% less than the British breeds and comparable with the other continental European breeds). When feed conversion efficiency is adjusted to weight of saleable meat divided by feed consumed, Limousin feed conversion efficiency then exceeds both British and continental European breeds by 10–25%. The USMARC study also indicated that Limousins were very significantly the slowest of all breeds to achieve market specifications of three measures of rib eye fat (300 to 400 days longer than the British breeds, and 170 to 220 days longer than the other continental European breeds) while feed conversion efficiency based on live weight gain was poorer (25–30% less than the British breeds and 12–16% less than the other continental European breeds). When corrected to saleable meat divided by feed consumed, feed conversion efficiency was similar or marginally better for Limousins. At these end points, Limousins finished at markedly heavier live weights (up to 490 kg heavier than the British breeds, and 190 kg heavier than the other continental European breeds).
The latest USMARC study of Limousins, two of the British breeds and three of the continental European breeds from the original study, reported similar saleable meat yields/live weight for the British breeds (average 36.3%, compared with the earlier 34.9%) and other continental European breeds (average 38.7%, compared with 40.4%), but a significant reduction for Limousin (39.4% compared with 46.0%). However, feed conversion to saleable meat for Limousins for the six reported market end points still exceeded the average of the other two breed groups by up to one-fifth. | Limousin cattle | Wikipedia | 487 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Live weight and daily live weight gain are the simplest and most common of all traits to be measured and reported, which continues to mask Limousin's superior saleable meat production efficiency.
Breed differences are expected to have reduced since the USMARC studies in the 1980s and 1990s because of the wide-scale introduction and use of performance recording and genetic improvement programmes. The reduction in yield reported for Limousins is possibly a result of the loss of French Limousin content and of F94L myostatin mutations from the US purebred population, which would be an expected result of the purebred grading up process practiced there. Earlier USMARC studies are reported to have evaluated high content pure French Limousins.
Breed comparison studies of performance-tested bulls report Limousin's more efficient conversion of feed into live weight and confirm the breed's slower live weight gain when compared with other beef cattle breeds.
Limousins generally have lower levels of intra-muscular fat (marbling) and subcutaneous fat when compared with British breed cattle grown in similar conditions. Marbling, together with tenderness and flavour, has been associated with eating quality in some countries, and attracts a higher quality grading with associated premiums, although the link between marbling and palatability is not universally supported. In some countries, Limousin's lean, tender meat is considered to be of outstanding quality and marketed through specialist outlets. Beef producers targeting the higher marbling specifications of some markets, but who have concerns over the poorer feed conversion efficiency and yield associated with higher marbling British breed cattle, use Limousin sires over British breed cows, or British breed sires over Limousin cows, in crossbreeding programmes that aim to achieve a balance between the different and conflicting production demands.
Crossbreeding with Limousins
Crossbreeding increases production efficiency because of hybrid vigour, and allows complementary traits of parents to be combined to produce progeny better suited to different environments or markets. Crossbreeding through the use of Limousin terminal sires in purebred British breed cow herds allows the complementary traits of higher marbling and fat cover provided by the British breed cows, and required or preferred by some markets, to be combined with the higher yield and feed conversion efficiency of Limousin sires. | Limousin cattle | Wikipedia | 471 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Crossbred cows produce up to, and in some cases in excess of, 20% more weaned calf weight as a result of increased reproductive performance and maternal ability. Crossbred cow longevity is also increased by up to two years when compared with straightbred cows. However, the benefits of hybrid vigour in a crossbred cow decline in subsequent generations if progeny are mated to cattle of parentage similar to the cow, and increase if a new breed is introduced. Although studies acknowledge that the major production benefits of hybrid vigour occur in crossbred cow herds, the main use of Limousins outside of Europe continues to be as terminal sires in purebred British breed cow herds.
Genetic basis for crossbreeding
Progeny of two parents of different breeds are termed F1 hybrids, F1 crosses or first crosses. F1 hybrids generally have an extremely uniform phenotype and benefit from hybrid vigour. These advantages are observed in the breeding of a wide variety of animals and plants, and arise because progeny inherit one of each paired gene from each parent. When both parents are homozygous for different variants of genes (known as alleles), which is likely to be the case when a breed has been developed and selected over several generations, progeny will inherit both gene variants present in the parents. The F1 hybrid progeny will then be heterozygous for each gene variant, which in turn increases the likelihood that the genes will code for an optimal protein or enzyme. This is the genetic basis of hybrid vigour. While many gene variants have effects that are of little consequence to beef production, a few, such as the myostatin variants found in different cattle breeds, have a major effect.
Loss of hybrid vigour occurs and phenotype varies greatly in subsequent generations if F1 hybrids are interbred or backcrossed with animals genetically similar to the F1 parent. Interbred F1 hybrids produce progeny that can be either heterozygous for each gene variant, homozygous for one gene variant, or homozygous for the other gene variant. When one of the variants has a large effect on a trait, for example the effect of myostatin variants on muscularity, larger phenotypic variation will occur among the progeny. Backcross progeny have less phenotypic variation and comprise animals that are either heterozygous for each gene variant or homozygous for the variant found in the original F1 backcross parent. | Limousin cattle | Wikipedia | 512 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
A third form of progeny arises when F1 hybrids are bred with animals genetically dissimilar to their parents. If heterozygosity is maintained or increased as a result, hybrid vigour and other production benefits occurring in the F1 generation will be maintained or increased. Maintenance of heterozygosity is the key to maintaining the highest levels of hybrid vigour. This requires complex breeding programmes and high levels of management. Simplified crossbreeding programmes have been developed using hybrid or composite bulls, which was the motivation behind the development of Lim-Flex hybrids.
The two major Limousin hybrids are Brahmousin (a cross between Brahman and Limousin cattle) and Lim-Flex (a cross between Angus and Limousin cattle), which were both developed before the significance of the F94L myostatin variant had been quantified. When Limousins homozygous for the F94L myostatin mutation are used in crossbreeding, only one of the mutations will be inherited (that is, progeny will be heterozygous for the mutation), and a high level of phenotypic uniformity and hybrid vigour would be expected in the progeny. However, breeding using heterozygous animals as parents, which could include purebred Limousins of low percentage Full French content, and Lim-Flex and Brahmousin hybrids that have not been bred to a uniform (homozygous) standard over several generations, would produce progeny with inconsistent carcase characteristics and production value depending upon whether or not the F94L mutation was inherited.
The use of Lim-Flex and Brahmousin sires over a third breed of cow would benefit most from increased hybrid vigour, which should minimise any reduction in carcase value arising from the loss of the F94L mutation.
According to research into the effects of the F94L mutation, live weights of progeny are unaffected by random inheritance of the mutation.
Brahmousin
Brahmousin cattle are a hybrid purebred breed of Brahman and Limousin first created in the US in the late 1970s. The goal was to blend the best of the Limousin and Brahman traits to create a breed that has reproductive efficiency, mothering ability, good muscling and growth traits, and adaptability to varying environmental conditions. Brahmousin are now bred in the US, Indonesia, El Salvador, and Australia. | Limousin cattle | Wikipedia | 512 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
The first Brahmousin cattle were produced from a multiple embryo transfer from a French-imported Limousin dam. The resulting progeny were then crossed with Brahman cattle to achieve an F1 hybrid. Further crosses over a broader base led to the production of the 5/8 Limousin – 3/8 Brahman Brahmousin purebred, a mix which has been found to be the most widely accepted and most useful for the majority of the US. The American Brahmousin Council allows animals that are not purebred to be recorded as percentage animals as long as they are at least one-quarter Limousin and one-quarter Brahman. To be recorded as a purebred Brahmousin, the animal must then be sired by a registered purebred or fullblood Limousin bull, registered Brahman bull, or a registered purebred Brahmousin bull.
In Australia, Brahmousin are between one-quarter and three-quarters of the parent breeds with the objective of combining the muscle growth and meat quality of Limousins with the heat and parasite resistance, fast growth, and good mothering ability of the Brahman. Brahmousin is formally recognised as a cattle breed in Australia.
Lim-Flex
Unlike the Brahmousin, Lim-Flex does not have purebred breed status in any participating countries, which includes the US, Australia, New Zealand, and Canada. The need for the Lim-Flex hybrid arose in 2000 out of a perceived need by North American commercial cattle breeders for hybrid bulls that would assist in achieving end-product targets.
Lim-Flex is a registered certification mark awarded to Limousin:Angus crossbred or hybrid cattle in the US with content between 25% and 75% Limousin pedigree blood, and between 25% and 75% of either Angus or Red Angus pedigree blood, with a maximum allowable 1/8th of unknown or other breed. Lim-Flex provide genetic options ranging from high content fullblood and purebred Limousin with high levels of muscle and efficiency, to blended options with higher marbling and maternal characteristics associated with Angus cattle, to meet the needs of crossbreeding programmes. | Limousin cattle | Wikipedia | 453 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
The Lim-Flex certification mark has been adopted in Australia and New Zealand, where "commercial Lim-Flex must be 25 to 75 percent Limousin and 25 to 75 percent Angus or Red Angus", and in Canada, where they "must be 37.5 to 75 percent Limousin and 25 to 62.5 percent Angus or Red Angus, with a maximum allowance of another breed or unknown breed composition of 12.5 percent (1/8th)".
Appearance
Most Limousin cattle's coloration varies from light wheat to darker golden-red. Other coloration, mainly black, has been developed through cross-breeding and grading up from other breeds of cattle. In addition to altering natural coloration, other traits, such as polled (a genetic lack of horns), have been introduced through crossbreeding. Angus cattle have been the dominant source of black and polled genes now present in graded-up, high-content Limousins found throughout the world.
Temperament
Since the mid-1990s, Limousin breeders have worked extensively on improving disposition issues in Europe, North America, Australia and New Zealand. This has been aided by the high heritability of temperament and by the development of genetic measures of docility (among many other traits) predicted from field measurements and subsequent analysis using BLUP techniques to produce docility EBVs and EPDs. Significant improvement has been recorded in the temperament of Limousins, as can be observed from trait trends published by various international breed associations.
Distribution outside France | Limousin cattle | Wikipedia | 303 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Initial exports
Following the creation of the French Limousin Herd-Book in 1886, Limousins were exported to Brazil (1886), New Caledonia (1902), Uruguay (1910), Madagascar (1922), Argentina (1924), and Portugal (1929). However, the only herd that became established outside France during this period was in New Caledonia, which continued to import Limousins. It was not until after the reform of Limousin breeding in France in 1962 that significant numbers were exported around the world. Limousins were reintroduced in Argentina (1966) and Brazil (1978), and imported to other European countries such as Spain (1965), Italy (1968), the Netherlands (1969), Denmark (1970), and the United Kingdom (1971). Their introduction to the United Kingdom provided opportunities for Australia and New Zealand to import semen in 1972. Soon after, New Zealand allowed the importation of Limousins from both Ireland and the United Kingdom, and the first Full French cattle were imported to Australia from New Zealand in 1975.
An essential step in the global spread of the Limousin breed was made in 1968 with the importation of the first bull, Prince Pompadour, to Canada. The semen of this bull was made available to the United States in 1969. During the early 1970s, imports of animals to North America started to grow strongly. Today, the North American Limousin Foundation is the largest global Limousin breeders' association.
Current situation
Limousins ability to adapt to different environments contributed greatly to the breed's current success outside France. In most cases, Limousin bulls or their semen are now imported to improve locally bred Limousins. Today, the breed is present in about 70 countries around the world, and in all latitudes ranging from Finland in the north to South Africa in the south. Limousin breeders' associations exist in many of these countries, of which 29 are members of the International Limousin Council (ILC). The ILC was founded at Limoges in 1973 by Louis de Neuville, the Limousin breed ambassador. In 1989, EUROLIM was formed to bring together all of the herd books of European Limousins. | Limousin cattle | Wikipedia | 456 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Limousins in different countries are bred according to different selection practices or objectives, and are connected by limited international gene flows. Poor genetic connectedness between countries has negative implications for estimation accuracies of international genetic prediction programmes. As a result of genetic drift or different selection, each country's population of Limousins is becoming genetically differentiated, but which is counterbalanced to a limited extent by gene flows from other countries. A study of over 2.4million Limousin pedigree files of five European countries (France, Denmark, Ireland, Sweden, United Kingdom) showed moderate gene flows from France to the United Kingdom and Denmark, but negligible gene flows to Sweden. Except for gene flows originating from France, and some limited gene flows between Denmark and Sweden in the 1990s, bull and semen exchanges between European countries has been scarce, especially since about 2000. Cow and embryo flows have been even more scarce. Conversely, the genetic contribution of North American Limousins to European countries has increased since the late 1990s, which has occurred because of their use in breeding programmes to introduce the polled gene.
International Limousin genetics are now widely available in many countries for use in artificial insemination programmes, which has been facilitated by a large number of companies that specialise in the export and import of semen. Details of semen are published in extensively distributed catalogues. | Limousin cattle | Wikipedia | 280 | 2953081 | https://en.wikipedia.org/wiki/Limousin%20cattle | Biology and health sciences | Cattle | Animals |
Food groups categorise foods for educational purposes, usually grouping together foods with similar nutritional properties or biological classifications. Food groups are often used in nutrition guides, although the number of groups used can vary widely.
Food groups were a public health education concept invented to teach people eating very restricted, unvaried diets how to avoid becoming deficient in specific nutrients. They have since been adapted to also address diseases of affluence related to diet, such as obesity, diabetes and heart disease.
Historical food groups
Opson and sitos were Classical Greek food groups, mainly used for moral education, to teach sophrosyne. Mitahara, a concept of moderate diet found in early-first-millennium Sanskrit texts, categorizes food into groups and recommends eating a variety of healthy foods, while avoiding the unhealthy ones; it also considers foods to have emotional and moral effects. Indian foodways had a substantial influence on European organisations such as the Vegetarian Society], which cited Indian diets as proof that a healthy vegetarian diet was possible, and were actively involved in public debate on nutrition.
In the 20th century, food groups became widely used in public health education, as a tool to reduce nutritional deficiencies.
As early as the 1980s, researchers were criticizing food groups, saying that they were a concept useful for teaching people to avoid nutritional deficiencies, but that nutritional deficiencies were no longer major cause of diet-related disease in affluent societies. Since these are caused by unhealthy food, not by diets lacking of a specific nutrient, they thought that food groups would have to be entirely discarded, or entirely revamped to make them useful in nutritional education in post-industrial countries.
United States
The USDA promoted eight basic food groups prior to 1943, then seven basic food groups until 1956, then four food groups. A food pyramid was introduced in 1992, then MyPyramid in 2005, followed by MyPlate in 2011. Dietary guidelines were introduced in 2015 and slated to be rereleased every five years. The 2020 guidelines were to be released in spring 2020. Recommended Dietary Allowance recommends daily servings of each group for a healthy diet. In the United States for instance, the USDA has described food as being in from 4 to 11 different groups. | Food group | Wikipedia | 461 | 2953473 | https://en.wikipedia.org/wiki/Food%20group | Biology and health sciences | Health and fitness | null |
The most common food groups
Dairy, also called milk products and sometimes categorized with milk alternatives or meat, is typically a smaller category in nutrition guides, if present at all, and is sometimes listed apart from other food groups. Examples of dairy products include milk, butter, ghee, yogurt, cheese, cream and ice cream. The categorization of dairy as a food group with recommended daily servings has been criticized by, for example, the Harvard School of Public Health who point out that "research has shown little benefit, and considerable potential for harm, of such high dairy intakes. Moderate consumption of milk or other dairy products—one to two servings a day—is fine, and likely has some benefits for children. But it’s not essential for adults, for a host of reasons."
Fruits, sometimes categorized with vegetables, include apples, oranges, bananas, berries and lemons. Fruits contain carbohydrates, mostly in the form of non-free sugar, as well as important vitamins and minerals.
Cereals and legumes, sometimes categorized as grains, is often the largest category in nutrition guides. Cereal examples include wheat, rice, oats, barley, bread and pasta. Legumes are also known as pulses and include beans, soy beans, lentils and chickpeas. Cereals are a good source of starch and are often categorized with other starchy food such as potatoes. Legumes are good source of essential amino acids as well as carbohydrates.
Meat, sometimes labelled protein and occasionally inclusive of legumes and beans, eggs, meat analogues and/or dairy, is typically a medium- to smaller-sized category in nutrition guides. Examples include chicken, fish, turkey, pork and beef.
Confections, also called sugary foods and sometimes categorized with fats and oils, is typically a very small category in nutrition guides, if present at all, and is sometimes listed apart from other food groups. Examples include candy, soft drinks, and chocolate.
Vegetables, sometimes categorized with fruit and occasionally inclusive of legumes, is typically a large category second only to grains, or sometimes equal or superior to grains, in nutrition guides. Examples include spinach, carrots, onions, and broccoli. | Food group | Wikipedia | 466 | 2953473 | https://en.wikipedia.org/wiki/Food%20group | Biology and health sciences | Health and fitness | null |
Water is treated in very different ways by different food guides. Some exclude the category, others list it separately from other food groups, and yet others make it the center or foundation of the guide. Water is sometimes categorized with tea, fruit juice, vegetable juice and even soup, and is typically recommended in plentiful amounts. | Food group | Wikipedia | 65 | 2953473 | https://en.wikipedia.org/wiki/Food%20group | Biology and health sciences | Health and fitness | null |
Uncommon food groups
The number of "common" food groups varies depending on who is defining them. Canada's Food Guide, which has been in continual publication since 1942 and is the second most requested government document after the income tax form in Canada, recognizes only four official food groups, listing the remainder of foods as "another". | Food group | Wikipedia | 66 | 2953473 | https://en.wikipedia.org/wiki/Food%20group | Biology and health sciences | Health and fitness | null |
Ethylenediamine (abbreviated as en when a ligand) is the organic compound with the formula C2H4(NH2)2. This colorless liquid with an ammonia-like odor is a basic amine. It is a widely used building block in chemical synthesis, with approximately 500,000 tonnes produced in 1998. Ethylenediamine is the first member of the so-called polyethylene amines.
Synthesis
Ethylenediamine is produced industrially by treating 1,2-dichloroethane with ammonia under pressure at 180 °C in an aqueous medium:
In this reaction hydrogen chloride is generated, which forms a salt with the amine. The amine is liberated by addition of sodium hydroxide and can then be recovered by fractional distillation. Diethylenetriamine (DETA) and triethylenetetramine (TETA) are formed as by-products.
Another industrial route to ethylenediamine involves the reaction of ethanolamine and ammonia:
This process involves passing the gaseous reactants over a bed of nickel heterogeneous catalysts.
It can be prepared in the lab by the reaction of either ethylene glycol or ethanolamine and urea, followed by decarboxylation of the ethyleneurea intermediate.
Ethylenediamine can be purified by treatment with sodium hydroxide to remove water followed by distillation.
Applications
Ethylenediamine is used in large quantities for production of many industrial chemicals. It forms derivatives with carboxylic acids (including fatty acids), nitriles, alcohols (at elevated temperatures), alkylating agents, carbon disulfide, and aldehydes and ketones. Because of its bifunctional nature, having two amino groups, it readily forms heterocycles such as imidazolidines. | Ethylenediamine | Wikipedia | 388 | 2955396 | https://en.wikipedia.org/wiki/Ethylenediamine | Physical sciences | Amides and amines | Chemistry |
Precursor to chelation agents, drugs, and agrochemicals
A most prominent derivative of ethylenediamine is the chelating agent EDTA, which is derived from ethylenediamine via a Strecker synthesis involving cyanide and formaldehyde. Hydroxyethylethylenediamine is another commercially significant chelating agent. Numerous bio-active compounds and drugs contain the N–CH2–CH2–N linkage, including some antihistamines. Salts of ethylenebisdithiocarbamate are commercially significant fungicides under the brand names Maneb, Mancozeb, Zineb, and Metiram. Some imidazoline-containing fungicides are derived from ethylenediamine.
Pharmaceutical ingredient
Ethylenediamine is an ingredient in the common bronchodilator drug aminophylline, where it serves to solubilize the active ingredient theophylline. Ethylenediamine has also been used in dermatologic preparations, but has been removed from some because of causing contact dermatitis. When used as a pharmaceutical excipient, after oral administration its bioavailability is about 0.34, due to a substantial first-pass effect. Less than 20% is eliminated by renal excretion.
Ethylenediamine-derived antihistamines are the oldest of the five classes of first-generation antihistamines, beginning with piperoxan aka benodain, discovered in 1933 at the Pasteur Institute in France, and also including mepyramine, tripelennamine, and antazoline. The other classes are derivatives of ethanolamine, alkylamine, piperazine, and others (primarily tricyclic and tetracyclic compounds related to phenothiazines, tricyclic antidepressants, as well as the cyproheptadine-phenindamine family)
Role in polymers
Ethylenediamine, because it contains two amine groups, is a widely used precursor to various polymers. Condensates derived from formaldehyde are plasticizers. It is widely used in the production of polyurethane fibers. The PAMAM class of dendrimers are derived from ethylenediamine. | Ethylenediamine | Wikipedia | 475 | 2955396 | https://en.wikipedia.org/wiki/Ethylenediamine | Physical sciences | Amides and amines | Chemistry |
Tetraacetylethylenediamine
The bleaching activator tetraacetylethylenediamine is generated from ethylenediamine. The derivative N,N-ethylenebis(stearamide) (EBS) is a commercially significant mold-release agent and a surfactant in gasoline and motor oil.
Other applications
as a solvent, it is miscible with polar solvents and is used to solubilize proteins such as albumins and casein. It is also used in certain electroplating baths.
as a corrosion inhibitor in paints and coolants.
ethylenediamine dihydroiodide (EDDI) is added to animal feeds as a source of iodide.
chemicals for color photography developing, binders, adhesives, fabric softeners, curing agents for epoxies, and dyes.
as a compound to sensitize nitromethane into an explosive. This mixture was used at Picatinny Arsenal during World War II, giving the nitromethane and ethylenediamine mixture the nickname PLX, or Picatinny Liquid Explosive.
Coordination chemistry
Ethylenediamine is a well-known bidentate chelating ligand for coordination compounds, with the two nitrogen atoms donating their lone pairs of electrons when ethylenediamine acts as a ligand. It is often abbreviated "en" in inorganic chemistry. The complex [Co(en)3]3+ is a well studied example. Schiff base ligands easily form from ethylenediamine. For example, the diamine condenses with 4-Trifluoromethylbenzaldehyde to give to the diimine. The salen ligands, some of which are used in catalysis, are derived from the condensation of salicylaldehydes and ethylenediamine.
Related ligands
Related derivatives of ethylenediamine include ethylenediaminetetraacetic acid (EDTA), tetramethylethylenediamine (TMEDA), and tetraethylethylenediamine (TEEDA). Chiral analogs of ethylenediamine include 1,2-diaminopropane and trans-diaminocyclohexane. | Ethylenediamine | Wikipedia | 477 | 2955396 | https://en.wikipedia.org/wiki/Ethylenediamine | Physical sciences | Amides and amines | Chemistry |
Safety
Ethylenediamine, like ammonia and other low-molecular weight amines, is a skin and respiratory irritant. Unless tightly contained, liquid ethylenediamine will release toxic and irritating vapors into its surroundings, especially on heating. The vapors absorb moisture from humid air to form a characteristic white mist, which is extremely irritating to skin, eyes, lungs and mucous membranes. | Ethylenediamine | Wikipedia | 82 | 2955396 | https://en.wikipedia.org/wiki/Ethylenediamine | Physical sciences | Amides and amines | Chemistry |
Glomeromycota (often referred to as glomeromycetes, as they include only one class, Glomeromycetes) are one of eight currently recognized divisions within the kingdom Fungi, with approximately 230 described species. Members of the Glomeromycota form arbuscular mycorrhizas (AMs) with the thalli of bryophytes and the roots of vascular land plants. Not all species have been shown to form AMs, and one, Geosiphon pyriformis, is known not to do so. Instead, it forms an endocytobiotic association with Nostoc cyanobacteria. The majority of evidence shows that the Glomeromycota are dependent on land plants (Nostoc in the case of Geosiphon) for carbon and energy, but there is recent circumstantial evidence that some species may be able to lead an independent existence. The arbuscular mycorrhizal species are terrestrial and widely distributed in soils worldwide where they form symbioses with the roots of the majority of plant species (>80%). They can also be found in wetlands, including salt-marshes, and associated with epiphytic plants.
According to multigene phylogenetic analyses, this taxon is located as a member of the phylum Mucoromycota. Currently, the phylum name Glomeromycota is invalid, and the subphylum Glomeromycotina should be used to describe this taxon.
Reproduction
The Glomeromycota have generally coenocytic (occasionally sparsely septate) mycelia and reproduce asexually through blastic development of the hyphal tip to produce spores (Glomerospores,blastospore) with diameters of 80–500 μm. In some, complex spores form within a terminal saccule. Recently it was shown that Glomus species contain 51 genes encoding all the tools necessary for meiosis. Based on these and related findings, it was suggested that Glomus species may have a cryptic sexual cycle. | Glomeromycota | Wikipedia | 437 | 2955810 | https://en.wikipedia.org/wiki/Glomeromycota | Biology and health sciences | Basics | Plants |
Colonization
New colonization of AM fungi largely depends on the amount of inoculum present in the soil. Although pre-existing hyphae and infected root fragments have been shown to colonize the roots of a host successfully, germinating spores are considered to be the key players in new host establishment. Spores are commonly dispersed by fungal and plant burrowing herbivore partners, but some air dispersal capabilities are also known. Studies have shown that spore germination is specific to particular environmental conditions such as right amount of nutrients, temperature or host availability. It has also been observed that the rate of root system colonization is directly correlated to spore density in the soil. In addition, new data also suggests that AM fungi host plants also secrete chemical factors that attract and enhance the growth of developing spore hyphae towards the root system.
The necessary components for the colonization of Glomeromycota include the host's fine root system, proper development of intracellular arbuscular structures, and a well-established external fungal mycelium. Colonization is accomplished by the interactions between germinating spore hyphae and the root hairs of the host or by the development of appressoria between epidermal root cells. The process is regulated by specialized chemical signaling and changes in gene expression of both the host and AM fungi. Intracellular hyphae extend up to the cortical cells of the root and penetrate the cell walls but not the inner cellular membrane creating an internal invagination. The penetrating hyphae develop a highly branched structure called an arbuscule, which has low functional periods before degradation and absorption by the host's root cells. A fully developed arbuscular mycorrhizal structure facilitates the two-way movement of nutrients between the host and mutualistic fungal partner. The symbiotic association allows the host plant to respond better to environmental stresses, and the non-photosynthetic fungi to obtain carbohydrates produced by photosynthesis. | Glomeromycota | Wikipedia | 406 | 2955810 | https://en.wikipedia.org/wiki/Glomeromycota | Biology and health sciences | Basics | Plants |
Phylogeny
Initial studies of the Glomeromycota were based on the morphology of soil-borne sporocarps (spore clusters) found in or near colonized plant roots. Distinguishing features such as wall morphologies, size, shape, color, hyphal attachment and reaction to staining compounds allowed a phylogeny to be constructed. Superficial similarities led to the initial placement of genus Glomus in the unrelated family Endogonaceae. Following broader reviews that cleared up the sporocarp confusion, the Glomeromycota were first proposed in the genera Acaulospora and Gigaspora before being accorded their own order with the three families Glomaceae (now Glomeraceae), Acaulosporaceae and Gigasporaceae.
With the advent of molecular techniques this classification has undergone major revision. An analysis of small subunit (SSU) rRNA sequences indicated that they share a common ancestor with the Dikarya. Nowadays it is accepted that Glomeromycota consists of 4 orders.
Several species which produce glomoid spores (i.e. spores similar to Glomus) in fact belong to other deeply divergent lineages and were placed in the orders, Paraglomerales and Archaeosporales. This new classification includes the Geosiphonaceae, which presently contains one fungus (Geosiphon pyriformis) that forms endosymbiotic associations with the cyanobacterium Nostoc punctiforme and produces spores typical to this division, in the Archaeosporales.
Work in this field is incomplete, and members of Glomus may be better suited to different genera or families. | Glomeromycota | Wikipedia | 354 | 2955810 | https://en.wikipedia.org/wiki/Glomeromycota | Biology and health sciences | Basics | Plants |
Molecular biology
The biochemical and genetic characterization of the Glomeromycota has been hindered by their biotrophic nature, which impedes laboratory culturing. This obstacle was eventually surpassed with the use of root cultures and, most recently, a method which applies sequencing of single nucleus from spores has also been developed to circumvent this challenge. The first mycorrhizal gene to be sequenced was the small-subunit ribosomal RNA (SSU rRNA). This gene is highly conserved and commonly used in phylogenetic studies so was isolated from spores of each taxonomic group before amplification through the polymerase chain reaction (PCR).
A metatranscriptomic survey of the Sevilleta Arid Lands found that 5.4% of the fungal rRNA reads mapped to Glomeromycota. This result was inconsistent with previous PCR-based studies of community structure in the region, suggesting that previous PCR-based studies may have underestimated Glomeromycota abundance due to amplification biases. | Glomeromycota | Wikipedia | 214 | 2955810 | https://en.wikipedia.org/wiki/Glomeromycota | Biology and health sciences | Basics | Plants |
The foot per second (plural feet per second) is a unit of both speed (scalar) and velocity (vector quantity, which includes direction). It expresses the distance in feet (ft) traveled or displaced, divided by the time in seconds (s). The corresponding unit in the International System of Units (SI) is the meter per second.
Abbreviations include ft/s, fps, and the scientific notation ft s−1.
Conversions | Foot per second | Wikipedia | 91 | 2956372 | https://en.wikipedia.org/wiki/Foot%20per%20second | Physical sciences | Speed | Basics and measurement |
Heaviside–Lorentz units (or Lorentz–Heaviside units) constitute a system of units and quantities that extends the CGS with a particular set of equations that defines electromagnetic quantities, named for Oliver Heaviside and Hendrik Antoon Lorentz. They share with the CGS-Gaussian system that the electric constant and magnetic constant do not appear in the defining equations for electromagnetism, having been incorporated implicitly into the electromagnetic quantities. Heaviside–Lorentz units may be thought of as normalizing and , while at the same time revising Maxwell's equations to use the speed of light instead.
The Heaviside–Lorentz unit system, like the International System of Quantities upon which the SI system is based, but unlike the CGS-Gaussian system, is rationalized, with the result that there are no factors of appearing explicitly in Maxwell's equations. That this system is rationalized partly explains its appeal in quantum field theory: the Lagrangian underlying the theory does not have any factors of when this system is used. Consequently, electromagnetic quantities in the Heaviside–Lorentz system differ by factors of in the definitions of the electric and magnetic fields and of electric charge. It is often used in relativistic calculations, and are used in particle physics. They are particularly convenient when performing calculations in spatial dimensions greater than three such as in string theory.
Motivation
In the mid-late 19th century, electromagnetic measurements were frequently made in either the so-named electrostatic (ESU) or electromagnetic (EMU) systems of units. These were based respectively on Coulomb's and Ampere's Law. Use of these systems, as with to the subsequently developed Gaussian CGS units, resulted in many factors of appearing in formulas for electromagnetic results, including those without any circular or spherical symmetry.
For example, in the CGS-Gaussian system, the capacitance of sphere of radius is while that of a parallel plate capacitor is , where is the area of the smaller plate and is their separation.
Heaviside, who was an important, though somewhat isolated, early theorist of electromagnetism, suggested in 1882 that the irrational appearance of in these sorts of relations could be removed by redefining the units for charges and fields.
In his 1893 book Electromagnetic Theory,
Heaviside wrote in the introduction:
Length–mass–time framework | Heaviside–Lorentz units | Wikipedia | 497 | 4061767 | https://en.wikipedia.org/wiki/Heaviside%E2%80%93Lorentz%20units | Physical sciences | Measurement systems | Basics and measurement |
As in the Gaussian system (), the Heaviside–Lorentz system () uses the length–mass–time dimensions. This means that all of the units of electric and magnetic quantities are expressible in terms of the units of the base quantities length, time and mass.
Coulomb's equation, used to define charge in these systems, is in the Gaussian system, and in the HL system. The unit of charge then connects to , where 'HLC' is the HL unit of charge. The HL quantity describing a charge is then times larger than the corresponding Gaussian quantity. There are comparable relationships for the other electromagnetic quantities (see below).
The commonly used set of units is the called the SI, which defines two constants, the vacuum permittivity () and the vacuum permeability (). These can be used to convert SI units to their corresponding Heaviside–Lorentz values, as detailed below. For example, SI charge is . When one puts , , , and , this evaluates to , the SI-equivalent of the Heaviside–Lorentz unit of charge.
Comparison of Heaviside–Lorentz with other systems of units
This section has a list of the basic formulas of electromagnetism, given in the SI, Heaviside–Lorentz, and Gaussian systems.
Here and are the electric field and displacement field, respectively,
and are the magnetic fields,
is the polarization density,
is the magnetization,
is charge density,
is current density,
is the speed of light in vacuum,
is the electric potential,
is the magnetic vector potential,
is the Lorentz force acting on a body of charge and velocity ,
is the permittivity,
is the electric susceptibility,
is the magnetic permeability, and
is the magnetic susceptibility.
Maxwell's equations
The electric and magnetic fields can be written in terms of the potentials and .
The definition of the magnetic field in terms of , , is the same in all systems of units, but the electric field is in the SI system, but in the HL or Gaussian systems.
Other basic laws
Dielectric and magnetic materials
Below are the expressions for the macroscopic fields , , and in a material medium. It is assumed here for simplicity that the medium is homogeneous, linear, isotropic, and nondispersive, so that the susceptibilities are constants. | Heaviside–Lorentz units | Wikipedia | 506 | 4061767 | https://en.wikipedia.org/wiki/Heaviside%E2%80%93Lorentz%20units | Physical sciences | Measurement systems | Basics and measurement |
Note that The quantities , and are dimensionless, and they have the same numeric value. By contrast, the electric susceptibility is dimensionless in all the systems, but has for the same material:
The same statements apply for the corresponding magnetic quantities.
Advantages and disadvantages of Heaviside–Lorentz units
Advantages
The formulas above are clearly simpler in units compared to either or Gaussian units. As Heaviside proposed, removing the from the Gauss law and putting it in the Force law considerably reduces the number of places the appears compared to Gaussian CGS units.
Removing the explicit from the Gauss law makes it clear that the inverse-square force law arises by the field spreading out over the surface of a sphere. This allows a straightforward extension to other dimensions. For example, the case of long, parallel wires extending straight in the direction can be considered a two-dimensional system. Another example is in string theory, where more than three spatial dimensions often need to be considered.
The equations are free of the constants and that are present in the SI system. (In addition and are overdetermined, because .)
The below points are true in both Heaviside–Lorentz and Gaussian systems, but not SI.
The electric and magnetic fields and have the same dimensions in the Heaviside–Lorentz system, meaning it is easy to recall where factors of go in the Maxwell equation. Every time derivative comes with a , which makes it dimensionally the same as a space derivative. In contrast, in SI units is .
Giving the and fields the same dimension makes the assembly into the electromagnetic tensor more transparent. There are no factors of that need to be inserted when assembling the tensor out of the three-dimensional fields. Similarly, and have the same dimensions and are the four components of the 4-potential.
The fields , , , and also have the same dimensions as and . For vacuum, any expression involving can simply be recast as the same expression with . In SI units, and have the same units, as do and , but they have different units from each other and from and .
Disadvantages | Heaviside–Lorentz units | Wikipedia | 436 | 4061767 | https://en.wikipedia.org/wiki/Heaviside%E2%80%93Lorentz%20units | Physical sciences | Measurement systems | Basics and measurement |
Despite Heaviside's urgings, it proved difficult to persuade people to switch from the established units. He believed that if the units were changed, "[o]ld style instruments would very soon be in a minority, and then disappear ...". Persuading people to switch was already difficult in 1893, and in the meanwhile there have been more than a century's worth of additional textbooks printed and voltmeters built.
Heaviside–Lorentz units, like the Gaussian CGS units by which they generally differ by a factor of about 3.5, are frequently of rather inconvenient sizes. The ampere (coulomb/second) is reasonable unit for measuring currents commonly encountered, but the ESU/s, as demonstrated above, is far too small. The Gaussian CGS unit of electric potential is named a statvolt. It is about , a value which is larger than most commonly encountered potentials. The henry, the SI unit for inductance is already on the large side compared to most inductors; the Gaussian unit is 12 orders of magnitude larger.
A few of the Gaussian CGS units have names; none of the Heaviside–Lorentz units do.
Textbooks in theoretical physics use Heaviside–Lorentz units nearly exclusively, frequently in their natural form (see below), system's conceptual simplicity and compactness significantly clarify the discussions, and it is possible if necessary to convert the resulting answers to appropriate units after the fact by inserting appropriate factors of and . Some textbooks on classical electricity and magnetism have been written using Gaussian CGS units, but recently some of them have been rewritten to use SI units. Outside of these contexts, including for example magazine articles on electric circuits, Heaviside–Lorentz and Gaussian CGS units are rarely encountered.
Translating formulas between systems
To convert any formula between the SI, Heaviside–Lorentz system or Gaussian system, the corresponding expressions shown in the table below can be equated and hence substituted for each other. Replace by or vice versa. This will reproduce any of the specific formulas given in the list above.
As an example, starting with the equation
and the equations from the table
Moving the factor across in the latter identities and substituting, the result is
which then simplifies to | Heaviside–Lorentz units | Wikipedia | 486 | 4061767 | https://en.wikipedia.org/wiki/Heaviside%E2%80%93Lorentz%20units | Physical sciences | Measurement systems | Basics and measurement |
Mudskippers are any of the 23 extant species of amphibious fish from the subfamily Oxudercinae of the goby family Oxudercidae. They are known for their unusual body shapes, preferences for semiaquatic habitats, limited terrestrial locomotion and jumping, and the ability to survive prolonged periods of time both in and out of water.
Mudskippers can grow up to long, and most are a brownish green colour that ranges anywhere from dark to light. During mating seasons, the males will also develop brightly coloured spots in order to attract females, which can be red, green or blue. Unlike other fish, the mudskipper's eyes protrude from the top of its flat head. Their most noticeable feature however is their side pectoral fins that are located more forward and under their elongated body. These fins are jointed and function similarly to limbs, which allow the mudskipper to crawl from place to place. Although having the typical body form of any other gobiid fish, these front fins allow the mudskipper to actively "skip" across muddy surfaces (hence the common name) and even climb low-hanging tree branches and scrubs. Mudskippers have also been found to be able to leap distances of up to by laterally flexing and pushing with their tails.
Taxonomy
Oxudercinae is sometimes classified within the family Gobiidae (gobies). Recent molecular studies do not support this classification, as oxudercine gobies appear to be paraphyletic relative to amblyopine gobies (Gobiidae: Amblyopinae), thus being included in a distinct "Periophthalmus lineage", together with amblyopines. Mudskippers can be defined as oxudercine gobies that are "fully terrestrial for some portion of the daily cycle" (character 24 in Murdy, 1989). This would define the species of the genera Boleophthalmus, Periophthalmodon, Periophthalmus, and Scartelaos as "mudskippers". However, field observations of Zappa confluentus suggest that this monotypic genus should be included in the definition. | Mudskipper | Wikipedia | 452 | 4063480 | https://en.wikipedia.org/wiki/Mudskipper | Biology and health sciences | Acanthomorpha | Animals |
Behaviour
Mudskippers typically live in burrows in intertidal habitats, and exhibit unique adaptations to this environment that are not found in most intertidal fishes, which typically survive the retreat of the tide by hiding under wet seaweed or in tide pools. These burrows are most often characterised by their smooth and vaulted ceilings. The way the males dig these burrows has been found to be directly linked to their ability to survive submerged in almost anoxic water. It has also been found to play a crucial role in the development of the eggs within the burrow. Mudskippers are quite active when out of water, feeding and interacting with one another, for example, to defend their territories and court potential partners. Once the male has completed digging his burrow he will resurface and will begin attempting to attract a female through assorted yet typical displays. These displays consist of body undulations, different postures and energetic movements. Once the female has made her choice she will then proceed to follow the male into the burrow where she will lay hundreds of eggs and allow them to be fertilized. After fertilization occurs, the period of cohabitation between the male and female is rather short. Eventually, the female will leave and it is the male that ends up guarding the egg filled burrow from predators.
Mudskippers are amphibious. When leaving the water and moving into a more dry environment on land, they are still able to breathe using water that is trapped inside their large gill chambers. They are also able to absorb oxygen from the lining of their mouth and throat, allowing them to stay out of water for long periods of time. It has been discovered that they spend up to three quarters of their life on land. They are found in tropical, subtropical, and temperate regions, including the Indo-Pacific and the Atlantic coast of Africa.
Adaptations
Compared with fully aquatic gobies, these specialised fish present a range of anatomical and ethological adaptations that allow them to move effectively on land as well as in the water.
Terrestrial movement
As their name implies, these fish use their fins to move around in a series of skips.
Breathing | Mudskipper | Wikipedia | 435 | 4063480 | https://en.wikipedia.org/wiki/Mudskipper | Biology and health sciences | Acanthomorpha | Animals |
Mudskippers have the ability to breathe through their skin and the lining of their mouth (the mucosa) and throat (the pharynx); this is only possible when the mudskippers are wet, limiting them to humid habitats and requiring that they keep themselves moist. The ability to breathe through their skin is associated with increased capillary density in their skin. This mode of breathing, similar to that employed by amphibians, is known as cutaneous respiration. Another important adaptation that aids breathing while out of water is their enlarged gill chambers, where they retain a bubble of air. These chambers close tightly when the fish is above water, due to a ventromedial valve of the gill slit, keeping the gills moist, and allowing them to function while exposed to air. Gill filaments are stiff and do not coalesce when out of water.
Diet
The different species have adapted to various diets on the mudflats. Boleophthalmus boddarti is detritivorous, while others will eat small crabs, insects, snails and even other mudskippers.
Burrowing
Digging deep burrows in soft sediments allows the fish to thermoregulate, avoid marine predators during the high tide when the fish and burrow are submerged, and lay their eggs. When the burrow is submerged, several mudskipper species maintain an air pocket inside it, which allows them to breathe in conditions of very low oxygen concentration.
Ammonia regulation
To reduce toxic ammonia production, mudskippers can suppress amino acid breakdown when exposed to air. Another method they use involves the partial breakdown of amino acids leading to the production of alanine, which also reduces ammonia production.
Mudskippers can reduce the membrane permeability of their skin and acidify the water in their burrows to reduce levels of ammonia from the environment. | Mudskipper | Wikipedia | 378 | 4063480 | https://en.wikipedia.org/wiki/Mudskipper | Biology and health sciences | Acanthomorpha | Animals |
Blinking
Mudskippers evolved the ability to blink independently from terrestrial tetrapods. Their eyes are located high on their head compared to other gobies, and they blink by lowering their eyes as a membrane called the dermal cup rises to cover them. Although other fully aquatic goby species do not have the ability to blink, mudskippers did not evolve different muscles or glands to blink with; their blinking is accomplished with the same muscles in a different configuration. Rather than having specialized glands to produce eye lubricant, the fluid film on their cornea is likely composed of mucus secreted by their skin and water from their environment, possibly stored in the infraorbital space behind the dermal cup membrane. Mudskippers likely evolved blinking in response to conditions of terrestrial life, such as to keep their eyes wet out of water (they blink more frequently in high evaporation conditions and only when colliding with things in water) and to clean and protect the eye from debris, which may adhere to the eye or approach at a faster, more dangerous speed when in air versus when in water. Their eyes are not elevated when they are still juveniles, which are fully aquatic.
Species
The genus Periophthalmus is by far the most diverse and widespread genus of mudskipper. Eighteen species have been described. Periophthalmus argentilineatus is one of the most widespread and well-known species. It can be found in mangrove ecosystems and mudflats of East Africa and Madagascar east through the Sundarbans of Bengal, Southeast Asia to Northern Australia, southeast China, Taiwan, and the Ryukyus, to Samoa and Tonga Islands. It grows to a length of about 9.5 cm and is a carnivorous opportunist feeder. It feeds on small prey such as small crabs and other arthropods. However, a recent molecular study suggests that P. argentilineatus is in fact a complex of species, with at least three separate lineages, one in East Africa, and two in the Indo-Malayan region.
Another species, Periophthalmus barbarus, is the only oxudercine goby that inhabits the coastal areas of western Africa. | Mudskipper | Wikipedia | 455 | 4063480 | https://en.wikipedia.org/wiki/Mudskipper | Biology and health sciences | Acanthomorpha | Animals |
Hyneria is a genus of large prehistoric predatory lobe-finned fish which lived in fresh water during the Famennian stage of the Devonian period.
Etymology
The genus name Hyneria is a reference to the village of Hyner, Pennsylvania, near where the first specimen was found. The species epithet H. lindae is derived from the name of the wife of Keith Stewart Thomson, who described this fish.
Description
Hyneria was a large fish. H. lindae is estimated around in total length. An isolated cleithrum AM 6545 likely belongs to an individual of at least in length. The largest complete jaw reaches , but there is much larger fragment possibly from a jaw about twice that length, although that specimen may belong to a rhizodont instead. Assuming this jaw fragment does pertain to Hyneria, and assuming proportions similar to more complete tristichopterids, it suggests H. lindae could possibly reach lengths up to 3.5 metres (11 ft). A second species, H. udlezinye, was once estimated as having a length of between before being described. However, the species description estimates that the largest specimen belongs to an animal about . Its skull had heavy, ornamented dermal bones and its lower jaw was relatively long and shallow. The teeth were stout, with those of the premaxilla forming fangs upwards of . Its body was covered by cycloid scales. It had large sensory canals to aid in detection of possible prey, as the freshwater environment it inhabited likely was murky and had low visibility. Adult individuals retained juvenile features (i.e. partially unossified skeletons), suggesting that they were likely neotenic.
Discovery
The original fossils came from two localities in Pennsylvania, United States, one found between the villages of North Bend and Hyner and another near Emporium. They consisted of a disarticulated partial skull and fragments of the shoulder girdle. The fossils were found in the Catskill Formation of the Red Hill Shale, dating to the upper Devonian. These were the only remains known until 1993 when a renewed collecting effort discovered abundant new material. Hyneria is considered the largest and most common lobe-finned fish found in the Red Hill Shale. In February 2023 a second species of Hyneria, H. udlezinye, was named from remains discovered in the Waterloo Farm lagerstätte. These remains include the skull and shoulder girdle. | Hyneria | Wikipedia | 506 | 4064886 | https://en.wikipedia.org/wiki/Hyneria | Biology and health sciences | Prehistoric osteichthyans | Animals |
In numerical linear algebra, the method of successive over-relaxation (SOR) is a variant of the Gauss–Seidel method for solving a linear system of equations, resulting in faster convergence. A similar method can be used for any slowly converging iterative process.
It was devised simultaneously by David M. Young Jr. and by Stanley P. Frankel in 1950 for the purpose of automatically solving linear systems on digital computers. Over-relaxation methods had been used before the work of Young and Frankel. An example is the method of Lewis Fry Richardson, and the methods developed by R. V. Southwell. However, these methods were designed for computation by human calculators, requiring some expertise to ensure convergence to the solution which made them inapplicable for programming on digital computers. These aspects are discussed in the thesis of David M. Young Jr.
Formulation
Given a square system of n linear equations with unknown x:
where:
Then A can be decomposed into a diagonal component D, and strictly lower and upper triangular components L and U:
where
The system of linear equations may be rewritten as:
for a constant ω > 1, called the relaxation factor.
The method of successive over-relaxation is an iterative technique that solves the left hand side of this expression for x, using the previous value for x on the right hand side. Analytically, this may be written as:
where is the kth approximation or iteration of and is the next or k + 1 iteration of .
However, by taking advantage of the triangular form of (D+ωL), the elements of x(k+1) can be computed sequentially using forward substitution:
This can again be written analytically in matrix-vector form without the need of inverting the matrix :
Convergence
The choice of relaxation factor ω is not necessarily easy, and depends upon the properties of the coefficient matrix.
In 1947, Ostrowski proved that if is symmetric and positive-definite then for .
Thus, convergence of the iteration process follows, but we are generally interested in faster convergence rather than just convergence.
Convergence Rate
The convergence rate for the SOR method can be analytically derived.
One needs to assume the following
the relaxation parameter is appropriate:
Jacobi's iteration matrix has only real eigenvalues
Jacobi's method is convergent:
the matrix decomposition satisfies the property that for any and .
Then the convergence rate can be expressed as
where the optimal relaxation parameter is given by | Successive over-relaxation | Wikipedia | 504 | 4068447 | https://en.wikipedia.org/wiki/Successive%20over-relaxation | Mathematics | Linear algebra | null |
In particular, for (Gauss-Seidel) it holds that .
For the optimal we get , which shows SOR is roughly four times more efficient than Gauss–Seidel.
The last assumption is satisfied for tridiagonal matrices since for diagonal with entries and .
Algorithm
Since elements can be overwritten as they are computed in this algorithm, only one storage vector is needed, and vector indexing is omitted. The algorithm goes as follows:
Inputs: , ,
Output:
Choose an initial guess to the solution
repeat until convergence
for from 1 until do
set to 0
for from 1 until do
if ≠ then
set to
end if
end (-loop)
set to
end (-loop)
check if convergence is reached
end (repeat)
Note can also be written , thus saving one multiplication in each iteration of the outer for-loop.
Example
We are presented the linear system
To solve the equations, we choose a relaxation factor and an initial guess vector . According to the successive over-relaxation algorithm, the following table is obtained, representing an exemplary iteration with approximations, which ideally, but not necessarily, finds the exact solution, , in 38 steps.
A simple implementation of the algorithm in Common Lisp is offered below.
;; Set the default floating-point format to "long-float" in order to
;; ensure correct operation on a wider range of numbers.
(setf *read-default-float-format* 'long-float)
(defparameter +MAXIMUM-NUMBER-OF-ITERATIONS+ 100
"The number of iterations beyond which the algorithm should cease its
operation, regardless of its current solution. A higher number of
iterations might provide a more accurate result, but imposes higher
performance requirements.")
(declaim (type (integer 0 *) +MAXIMUM-NUMBER-OF-ITERATIONS+)) | Successive over-relaxation | Wikipedia | 374 | 4068447 | https://en.wikipedia.org/wiki/Successive%20over-relaxation | Mathematics | Linear algebra | null |
(defun get-errors (computed-solution exact-solution)
"For each component of the COMPUTED-SOLUTION vector, retrieves its
error with respect to the expected EXACT-SOLUTION vector, returning a
vector of error values.
---
While both input vectors should be equal in size, this condition is
not checked and the shortest of the twain determines the output
vector's number of elements.
---
The established formula is the following:
Let resultVectorSize = min(computedSolution.length, exactSolution.length)
Let resultVector = new vector of resultVectorSize
For i from 0 to (resultVectorSize - 1)
resultVector[i] = exactSolution[i] - computedSolution[i]
Return resultVector"
(declare (type (vector number *) computed-solution))
(declare (type (vector number *) exact-solution))
(map '(vector number *) #'- exact-solution computed-solution))
(defun is-convergent (errors &key (error-tolerance 0.001))
"Checks whether the convergence is reached with respect to the
ERRORS vector which registers the discrepancy betwixt the computed
and the exact solution vector.
---
The convergence is fulfilled if and only if each absolute error
component is less than or equal to the ERROR-TOLERANCE, that is:
For all e in ERRORS, it holds: abs(e) <= errorTolerance."
(declare (type (vector number *) errors))
(declare (type number error-tolerance))
(flet ((error-is-acceptable (error)
(declare (type number error))
(<= (abs error) error-tolerance)))
(every #'error-is-acceptable errors)))
(defun make-zero-vector (size)
"Creates and returns a vector of the SIZE with all elements set to 0."
(declare (type (integer 0 *) size))
(make-array size :initial-element 0.0 :element-type 'number)) | Successive over-relaxation | Wikipedia | 437 | 4068447 | https://en.wikipedia.org/wiki/Successive%20over-relaxation | Mathematics | Linear algebra | null |
(defun successive-over-relaxation (A b omega
&key (phi (make-zero-vector (length b)))
(convergence-check
#'(lambda (iteration phi)
(declare (ignore phi))
(>= iteration +MAXIMUM-NUMBER-OF-ITERATIONS+))))
"Implements the successive over-relaxation (SOR) method, applied upon
the linear equations defined by the matrix A and the right-hand side
vector B, employing the relaxation factor OMEGA, returning the
calculated solution vector.
---
The first algorithm step, the choice of an initial guess PHI, is
represented by the optional keyword parameter PHI, which defaults
to a zero-vector of the same structure as B. If supplied, this
vector will be destructively modified. In any case, the PHI vector
constitutes the function's result value.
---
The terminating condition is implemented by the CONVERGENCE-CHECK,
an optional predicate
lambda(iteration phi) => generalized-boolean
which returns T, signifying the immediate termination, upon achieving
convergence, or NIL, signaling continuant operation, otherwise. In
its default configuration, the CONVERGENCE-CHECK simply abides the
iteration's ascension to the ``+MAXIMUM-NUMBER-OF-ITERATIONS+'',
ignoring the achieved accuracy of the vector PHI."
(declare (type (array number (* *)) A))
(declare (type (vector number *) b))
(declare (type number omega))
(declare (type (vector number *) phi))
(declare (type (function ((integer 1 *)
(vector number *))
*)
convergence-check))
(let ((n (array-dimension A 0)))
(declare (type (integer 0 *) n))
(loop for iteration from 1 by 1 do
(loop for i from 0 below n by 1 do
(let ((rho 0))
(declare (type number rho))
(loop for j from 0 below n by 1 do
(when (/= j i)
(let ((a[ij] (aref A i j))
(phi[j] (aref phi j)))
(incf rho (* a[ij] phi[j])))))
(setf (aref phi i)
(+ (* (- 1 omega)
(aref phi i)) | Successive over-relaxation | Wikipedia | 507 | 4068447 | https://en.wikipedia.org/wiki/Successive%20over-relaxation | Mathematics | Linear algebra | null |
(* (/ omega (aref A i i))
(- (aref b i) rho))))))
(format T "~&~d. solution = ~a" iteration phi)
;; Check if convergence is reached.
(when (funcall convergence-check iteration phi)
(return))))
(the (vector number *) phi)) | Successive over-relaxation | Wikipedia | 82 | 4068447 | https://en.wikipedia.org/wiki/Successive%20over-relaxation | Mathematics | Linear algebra | null |
;; Summon the function with the exemplary parameters.
(let ((A (make-array (list 4 4)
:initial-contents
'(( 4 -1 -6 0 )
( -5 -4 10 8 )
( 0 9 4 -2 )
( 1 0 -7 5 ))))
(b (vector 2 21 -12 -6))
(omega 0.5)
(exact-solution (vector 3 -2 2 1)))
(successive-over-relaxation
A b omega
:convergence-check
#'(lambda (iteration phi)
(declare (type (integer 0 *) iteration))
(declare (type (vector number *) phi))
(let ((errors (get-errors phi exact-solution)))
(declare (type (vector number *) errors))
(format T "~&~d. errors = ~a" iteration errors)
(or (is-convergent errors :error-tolerance 0.0)
(>= iteration +MAXIMUM-NUMBER-OF-ITERATIONS+))))))
A simple Python implementation of the pseudo-code provided above.
import numpy as np
from scipy import linalg | Successive over-relaxation | Wikipedia | 246 | 4068447 | https://en.wikipedia.org/wiki/Successive%20over-relaxation | Mathematics | Linear algebra | null |
def sor_solver(A, b, omega, initial_guess, convergence_criteria):
"""
This is an implementation of the pseudo-code provided in the Wikipedia article.
Arguments:
A: nxn numpy matrix.
b: n dimensional numpy vector.
omega: relaxation factor.
initial_guess: An initial solution guess for the solver to start with.
convergence_criteria: The maximum discrepancy acceptable to regard the current solution as fitting.
Returns:
phi: solution vector of dimension n.
"""
step = 0
phi = initial_guess[:]
residual = linalg.norm(A @ phi - b) # Initial residual
while residual > convergence_criteria:
for i in range(A.shape[0]):
sigma = 0
for j in range(A.shape[1]):
if j != i:
sigma += A[i, j] * phi[j]
phi[i] = (1 - omega) * phi[i] + (omega / A[i, i]) * (b[i] - sigma)
residual = linalg.norm(A @ phi - b)
step += 1
print("Step {} Residual: {:10.6g}".format(step, residual))
return phi
# An example case that mirrors the one in the Wikipedia article
residual_convergence = 1e-8
omega = 0.5 # Relaxation factor
A = np.array([[4, -1, -6, 0],
[-5, -4, 10, 8],
[0, 9, 4, -2],
[1, 0, -7, 5]])
b = np.array([2, 21, -12, -6])
initial_guess = np.zeros(4)
phi = sor_solver(A, b, omega, initial_guess, residual_convergence)
print(phi)
Symmetric successive over-relaxation
The version for symmetric matrices A, in which
is referred to as Symmetric Successive Over-Relaxation, or (SSOR), in which
and the iterative method is
The SOR and SSOR methods are credited to David M. Young Jr.
Other applications of the method
A similar technique can be used for any iterative method. If the original iteration had the form
then the modified version would use | Successive over-relaxation | Wikipedia | 498 | 4068447 | https://en.wikipedia.org/wiki/Successive%20over-relaxation | Mathematics | Linear algebra | null |
However, the formulation presented above, used for solving systems of linear equations, is not a special case of this formulation if is considered to be the complete vector. If this formulation is used instead, the equation for calculating the next vector will look like
where . Values of are used to speed up convergence of a slow-converging process, while values of are often used to help establish convergence of a diverging iterative process or speed up the convergence of an overshooting process.
There are various methods that adaptively set the relaxation parameter based on the observed behavior of the converging process. Usually they help to reach a super-linear convergence for some problems but fail for the others. | Successive over-relaxation | Wikipedia | 139 | 4068447 | https://en.wikipedia.org/wiki/Successive%20over-relaxation | Mathematics | Linear algebra | null |
In geology, basement and crystalline basement are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at the surface, but often they are buried under miles of rock and sediment. The basement rocks lie below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin. In the same way, the sediments or sedimentary rocks on top of the basement can be called a "cover" or "sedimentary cover".
Crustal rocks are modified several times before they become basement, and these transitions alter their composition.
Continental crust
Basement rock is the thick foundation of ancient, and oldest, metamorphic and igneous rock that forms the crust of continents, often in the form of granite. Basement rock is contrasted to overlying sedimentary rocks which are laid down on top of the basement rocks after the continent was formed, such as sandstone and limestone. The sedimentary rocks which may be deposited on top of the basement usually form a relatively thin veneer, but can be more than thick. The basement rock of the crust can be thick or more. The basement rock can be located under layers of sedimentary rock, or be visible at the surface.
Basement rock is visible, for example, at the bottom of the Grand Canyon, consisting of 1.7- to 2-billion-year-old granite (Zoroaster Granite) and schist (Vishnu Schist). The Vishnu Schist is believed to be highly metamorphosed igneous rocks and shale, from basalt, mud and clay laid from volcanic eruptions, and the granite is the result of magma intrusions into the Vishnu Schist. An extensive cross section of sedimentary rocks laid down on top of it through the ages is visible as well.
Age
The basement rocks of the continental crust tend to be much older than the oceanic crust. The oceanic crust can be from 0–340 million years in age, with an average age of 64 million years. Continental crust is older because continental crust is light and thick enough so it is not subducted, while oceanic crust is periodically subducted and replaced at subduction and oceanic rifting areas.
Complexity | Basement (geology) | Wikipedia | 441 | 5417918 | https://en.wikipedia.org/wiki/Basement%20%28geology%29 | Physical sciences | Stratigraphy | Earth science |
The basement rocks are often highly metamorphosed and complex, and are usually crystalline. They may consist of many different types of rock – volcanic, intrusive igneous and metamorphic. They may also contain ophiolites, which are fragments of oceanic crust that became wedged between plates when a terrane was accreted to the edge of the continent. Any of this material may be folded, refolded and metamorphosed. New igneous rock may freshly intrude into the crust from underneath, or may form underplating, where the new igneous rock forms a layer on the underside of the crust. The majority of continental crust on the planet is around 1 to 3 billion years old, and it is theorised that there was at least one period of rapid expansion and accretion to the continents during the Precambrian.
Much of the basement rock may have originally been oceanic crust, but it was highly metamorphosed and converted into continental crust. It is possible for oceanic crust to be subducted down into the Earth's mantle, at subduction fronts, where oceanic crust is being pushed down into the mantle by an overriding plate of oceanic or continental crust.
Volcanism
When a plate of oceanic crust is subducted beneath an overriding plate of oceanic crust, as the underthrusting crust melts, it causes an upwelling of magma that can cause volcanism along the subduction front on the overriding plate. This produces an oceanic volcanic arc, like Japan. This volcanism causes metamorphism, introduces igneous intrusions, and thickens the crust by depositing additional layers of extrusive igneous rock from volcanoes. This tends to make the crust thicker and less dense, making it immune to subduction. | Basement (geology) | Wikipedia | 369 | 5417918 | https://en.wikipedia.org/wiki/Basement%20%28geology%29 | Physical sciences | Stratigraphy | Earth science |
Oceanic crust can be subducted, while continental crust cannot. Eventually, the subduction of the underthrusting oceanic crust can bring the volcanic arc close to a continent, with which it may collide. When this happens, instead of being subducted, it is accreted to the edge of the continent and becomes part of it. Thin strips or fragments of the underthrusting oceanic plate may also remain attached to the edge of the continent so that they are wedged and tilted between the converging plates, creating ophiolites. In this manner, continents can grow over time as new terranes are accreted to their edges, and so continents can be composed of a complex quilt of terranes of varying ages.
As such, the basement rock can become younger going closer to the edge of the continent. There are exceptions, however, such as exotic terranes. Exotic terranes are pieces of other continents that have broken off from their original parent continent and have become accreted to a different continent.
Cratons
Continents can consist of several continental cratons – blocks of crust built around an initial original core of continents – that gradually grew and expanded as additional newly created terranes were added to their edges. For instance, Pangea consisted of most of the Earth's continents being accreted into one giant supercontinent. Most continents, such as Asia, Africa and Europe, include several continental cratons, as they were formed by the accretion of many smaller continents.
Usage
In European geology, the basement generally refers to rocks older than the Variscan orogeny. On top of this older basement Permian evaporites and Mesozoic limestones were deposited. The evaporites formed a weak zone on which the harder (stronger) limestone cover was able to move over the hard basement, making the distinction between basement and cover even more pronounced.
In Andean geology the basement refers to the Proterozoic, Paleozoic and early Mesozoic (Triassic to Jurassic) rock units as the basement to the late Mesozoic and Cenozoic Andean sequences developed following the onset of subduction along the western margin of the South American Plate.
When discussing the Trans-Mexican Volcanic Belt of Mexico the basement include Proterozoic, Paleozoic and Mesozoic age rocks for the Oaxaquia, the Mixteco and the Guerrero terranes respectively. | Basement (geology) | Wikipedia | 498 | 5417918 | https://en.wikipedia.org/wiki/Basement%20%28geology%29 | Physical sciences | Stratigraphy | Earth science |
The term basement is used mostly in disciplines of geology like basin geology, sedimentology and petroleum geology in which the (typically Precambrian) crystalline basement is not of interest as it rarely contains petroleum or natural gas. The term economic basement is also used to describe the deeper parts of a cover sequence that are of no economic interest. | Basement (geology) | Wikipedia | 67 | 5417918 | https://en.wikipedia.org/wiki/Basement%20%28geology%29 | Physical sciences | Stratigraphy | Earth science |
Hemp, or industrial hemp, is a plant in the botanical class of Cannabis sativa cultivars grown specifically for industrial and consumable use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest growing plants on Earth. It was also one of the first plants to be spun into usable fiber 50,000 years ago. It can be refined into a variety of commercial items, including paper, rope, textiles, clothing, biodegradable plastics, paint, insulation, biofuel, food, and animal feed.
Although chemotype I cannabis and hemp (types II, III, IV, V) are both Cannabis sativa and contain the psychoactive component tetrahydrocannabinol (THC), they represent distinct cultivar groups, typically with unique phytochemical compositions and uses. Hemp typically has lower concentrations of total THC and may have higher concentrations of cannabidiol (CBD), which potentially mitigates the psychoactive effects of THC. The legality of hemp varies widely among countries. Some governments regulate the concentration of THC and permit only hemp that is bred with an especially low THC content into commercial production.
Etymology
The etymology is uncertain but there appears to be no common Proto-Indo-European source for the various forms of the word; the Greek term () is the oldest attested form, which may have been borrowed from an earlier Scythian or Thracian word. Then it appears to have been borrowed into Latin, and separately into Slavic and from there into Baltic, Finnish, and Germanic languages.
In the Germanic languages, following Grimm's law, the "k" would have changed to "h" with the first Germanic sound shift, giving Proto-Germanic *hanapiz, after which it may have been adapted into the Old English form, , . Barber (1991) however, argued that the spread of the name "kannabis" was due to its historically more recent plant use, starting from the south, around Iran, whereas non-THC varieties of hemp are older and prehistoric. Another possible source of origin is Assyrian , which was the name for a source of oil, fiber, and medicine in the 1st millennium BC. | Hemp | Wikipedia | 468 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Cognates of hemp in other Germanic languages include Dutch , Danish and Norwegian , Saterland Frisian , German , Icelandic and Swedish . In those languages "hemp" can refer to either industrial fiber hemp or narcotic cannabis strains.
Uses
Hemp is used to make a variety of commercial and industrial products, including rope, textiles, clothing, shoes, food, paper, bioplastics, insulation, and biofuel. The bast fibers can be used to make textiles that are 100% hemp, but they are commonly blended with other fibers, such as flax, cotton or silk, as well as virgin and recycled polyester, to make woven fabrics for apparel and furnishings. The inner two fibers of the plant are woodier and typically have industrial applications, such as mulch, animal bedding, and litter. When oxidized (often erroneously referred to as "drying"), hemp oil from the seeds becomes solid and can be used in the manufacture of oil-based paints, in creams as a moisturizing agent, for cooking, and in plastics. Hemp seeds have been used in bird feed mix as well. A survey in 2003 showed that more than 95% of hemp seed sold in the European Union was used in animal and bird feed.
Food
Hemp seeds can be eaten raw, ground into hemp meal, sprouted or made into dried sprout powder. Hemp seeds can also be made into a slurry used for baking or for beverages, such as hemp milk and tisanes. Hemp oil is cold-pressed from the seed and is high in unsaturated fatty acids.
In the UK, the Department for Environment, Food and Rural Affairs treats hemp as a purely non-food crop, but with proper licensing and proof of less than 0.3% THC concentration, hemp seeds can be imported for sowing or for sale as a food or food ingredient. In the US, hemp can be used legally in food products and, , was typically sold in health food stores or through mail order.
Nutrition
A portion of hulled hemp seeds supplies of food energy. They contain 5% water, 5% carbohydrates, 49% total fat, and 31% protein. | Hemp | Wikipedia | 467 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
The share of protein obtained from the hemp seeds can be increased in by processing the seeds, such as by dehulling the seeds, or by using the meal or cake (also called hemp seed flour), that is, the remaining fraction of hemp seed obtained after expelling its oil fraction. The proteins are mostly located in the inner layer of the seed, whereas the hull is poor in proteins, as it mostly contains the fiber.
Hemp seeds are notable in providing 64% of the Daily Value (DV) of protein per 100-gram serving. The three main proteins in hemp seeds are edestin (83% of total protein content), albumin (13%) and ß-conglycinin (up to 5%). Hemp seed proteins are highly digestible compared to soy proteins when untreated (unheated). The amino acid profile of hemp seeds is comparable to the profiles of other protein-rich foods, such as meat, milk, eggs, and soy. Protein digestibility-corrected amino acid scores were 0.49–0.53 for whole hemp seed, 0.46–0.51 for hemp seed meal, and 0.63–0.66 for hulled hemp seed. The most abundant amino acid in hemp seed is glutamic acid (3.74–4.58% of whole seed) followed by arginine (2.28–3.10% of whole seed). The whole hemp seed can be considered a rich-protein source containing a protein amount higher or similar than other protein-rich products, such as quinoa (13.0%), chia seeds (18.2–19.7%), buckwheat seeds (27.8%) and linseeds (20.9%). Nutritionally, the protein fraction of hemp seed is highly digestible comparing to other plant-based proteins such as soy protein. Hemp seed protein has a good profile of essential amino acids, still, this profile of amino acids is inferior to that of soy or casein. | Hemp | Wikipedia | 438 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Hemp seeds are a rich source of dietary fiber (20% DV), B vitamins, and the dietary minerals manganese (362% DV), phosphorus (236% DV), magnesium (197% DV), zinc (104% DV), and iron (61% DV). About 73% of the energy in hemp seeds is in the form of fats and essential fatty acids, mainly polyunsaturated fatty acids, linoleic, oleic, and alpha-linolenic acids. The ratio of the 38.100 grams of polyunsaturated fats per 100 grams is 9.301 grams of omega-3 to 28.698 grams of omega-6. Typically, the portion suggested on packages for an adult is 30 grams, approximately three tablespoons.
With its gluten content as low as 4.78 ppm, hemp is attracting attention as a gluten-free (<20 ppm) food material.
Despite the rich nutrient content of hemp seeds, the seeds contain antinutritional compounds, including phytic acid, trypsin inhibitors, and tannins, in statistically significant concentrations.
Storage
Hemp oil oxidizes and turns rancid within a short period of time if not stored properly; its shelf life is extended when it is stored in a dark airtight container and refrigerated. Both light and heat can degrade hemp oil.
Fiber
Hemp fiber has been used extensively throughout history, with production climaxing soon after being introduced to the New World. For centuries, items ranging from rope, to fabrics, to industrial materials were made from hemp fiber. Hemp was also commonly used to make sail canvas. The word "canvas" is derived from the word cannabis. Pure hemp has a texture similar to linen. Because of its versatility for use in a variety of products, today hemp is used in a number of consumer goods, including clothing, shoes, accessories, dog collars, and home wares. For clothing, in some instances, hemp is mixed with lyocell. Its benefits in terms for sustainability also increase its appeal in industries, such as the clothing industry. | Hemp | Wikipedia | 459 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Building material
Hemp as a building construction material provides solutions to a variety of issues facing current building standards. Its light weight, mold resistance, breathability, etc. makes hemp products versatile in a multitude of uses. Following the co-heating tests of NNFCC Renewable House at the Building Research Establishment (BRE), hemp is reported to be a more sustainable material of construction in comparison to most building methods used today. In addition, its practical use in building construction could result in the reduction of both energy consumption costs and the creation of secondary pollutants.
In 2022, hemp-lime, also known as hempcrete, was accepted as a building material, along with methodologies for its use, by the International Code Council, and was included in the 2024 edition of the International Residential Code as an appendix: "Appendix BL Hemp-Lime (Hempcrete) Construction". This inclusion in the IRC model code is expected to promote expansion of the use and legitimacy of hemp-lime in construction in the United States.
The hemp market was at its largest during the 17th century. In the 19th century and onward, the market saw a decline during its rapid illegalization in many countries. Hemp has resurfaced in green building construction, primarily in Europe. The modern-day disputes regarding the legality of hemp lead to its main disadvantages: importing and regulating costs. Final Report on the Construction of the Hemp Houses at Haverhill, UK conducts that hemp construction exceeds the cost of traditional building materials by £48per square meter.
Currently, the University of Bath researches the use of hemp-lime panel systems for construction. Funded by the European Union, the research tests panel design within their use in high-quality construction, on site assembly, humidity and moisture penetration, temperature change, daily performance and energy saving documentations. The program, focusing on Britain, France, and Spain markets aims to perfect protocols of use and application, manufacturing, data gathering, certification for market use, as well as warranty and insurance.
The most common use of hemp-lime in building is by casting the hemp-hurd and lime mix while wet around a timber frame with temporary shuttering and tamping the mix to form a firm mass. After the removal of the temporary shuttering, the solidified hemp mix is then ready to be plastered with lime plaster. | Hemp | Wikipedia | 495 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Sustainability
Hemp is classified under the green category of building design, primarily due to its positive effects on the environment. A few of its benefits include but are not limited to the suppression of weed growth, anti-erosion, reclamation properties, and the ability to remove poisonous substances and heavy metals from soil.
The use of hemp is beginning to gain popularity alongside other natural materials. This is because cannabis processing is done mechanically with minimal harmful effects on the environment. A part of what makes hemp sustainable is its minimal water usage and non-reliance on pesticides for proper growth. It is recyclable, non-toxic, and biodegradable, making hemp a popular choice in green building construction.
Hemp fiber is known to have high strength and durability, and has been known to be a good protector against vermin. The fiber has the capability to reinforce structures by embossing threads and cannabis shavers. Hemp has been involved more recently in the building industry, producing building construction materials including insulation, hempcrete, and varnishes.
Hemp made materials have low embodied energy. The plant has the ability to absorb large amounts of CO2, providing air quality, thermal balance, creating a positive environmental impact.
Hemp's properties allow mold resistance, and its porous materiality makes the building materials made of it breathable. In addition hemp possesses the ability to absorb and release moisture without deteriorating. Hemp can be non-flammable if mixed with lime and could be applied on numerous aspects of the building (wall, roofs, etc.) due to its lightweight properties.
Insulation
Hemp is commonly used as an insulation material. Its flexibility and toughness during compression allows for easier implementation within structural framing systems. The insulation material could also be easily adjusted to different sizes and shapes by being cut during the installation process. The ability to not settle and therefore avoiding cavity developments lowers its need for maintenance.
Hemp insulation is naturally lightweight and non-toxic, allowing for an exposed installation in a variety of spaces, including flooring, walling, and roofing. Compared to mineral insulation, hemp absorbs roughly double the amount of heat and could be compared to wood, in some cases even overpassing some of its types. | Hemp | Wikipedia | 460 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Hemp insulation's porous materiality allows for air and moisture penetration, with a bulk density going up to 20% without losing any thermal properties. In contrast, the commonly used mineral insulation starts to fail after 2%. The insulation evenly distributes vapor and allows for air circulation, constantly carrying out used air and replacing with fresh. Its use on the exterior of the structure, overlaid with breathable water-resistive barriers, eases the withdrawal of moisture from within the wall structure.
In addition, the insulation doubles as a sound barrier, weakening airborne sound waves passing through it.
Hempcrete
In addition to the CO2 absorbed during its growth period, hemp-lime, also known as hempcrete, continues absorption during the curing process. The mixture hardens when the silica contained in hemp shives mixes with hydraulic lime, resulting in the mineralization process called "carbonation"..
Though not a load-bearing material, hempcrete is most commonly used as infill in building construction due to its light weight (roughly seven times lighter than common concrete) and vapor permeability. The building material is made of hemp hurds (shiv or shives), hydraulic lime, and water mixed in varying ratios. The mix depends on the use of the material within the structure and could differ in physical properties. Surfaces such as flooring interact with a multitude of loads and would have to be more resistive, while walls and roofs are required to be more lightweight. The application of this material in construction requires minimal skill.
Hempcrete can be formed in-situ or formed into blocks. Such blocks are not strong enough to be used for structural elements and must be supported by brick, wood, or steel framing. In the end of the twentieth century, during his renovation of Maison de la Turquie in Nogent-sur-Seine, France, Charles Rasetti first invented and applied the use of hempcrete in construction. Shortly after, in the 2000s, Modece Architects used hemp-lime for test designs in Haverhill. The dwellings were studied and monitored for comparison with other building performances by BRE. Completed in 2009, the Center for the Built Environment's Renewable House was found to be among the most technologically advanced structures made of hemp-based material. A year later the first home made of hemp-based materials was completed in Asheville, North Carolina, US.
Oils and varnishes | Hemp | Wikipedia | 507 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Cannabis seeds have high-fat content and contain 30-35% of fatty acids. The extracted oil is suited for a variety of construction applications. The biodegradable hemp oil acts as a wood varnish, protecting flooring from mold, pests, and wear. Its use prevents the water from penetrating the wood while still allowing air and vapor to pass through. Its most common use can be seen in wood framing construction, one of the most common construction methods in the world. Because of its low UV-resistant rating, the finish is most often used indoors, on surfaces such as flooring and wood paneling.
Plaster
Hemp-based insulating plaster is created by combining hemp fibers with calcium lime and sand. This material, when applied on internal walls, ceilings, and flooring, can be layered up to ten centimeters in thickness. Its porous materiality allows the created plaster to regulate air humidity and evenly distribute it. The gradual absorption and release of water prevent the material from cracking and breaking apart. Similar to high-density fiber cement, hemp plaster can naturally vary in color and be manually pigmented.
Ropes and strands
Hemp ropes can be woven in various diameters, possessing high amounts of strength making them suitable for a variety of uses for building construction purposes. Some of these uses include installation of frames in building openings and connection of joints. The ropes also used in bridge construction, tunnels, traditional homes, etc. One of the earliest examples of hemp rope and other textile use can be traced back to 1500 BC Egypt.
Plastics
Cannabis geotextiles could be put in both wet and dry conditions. Hemp-based bioplastic is a biodegradable alternative to regular plastic and can potentially replace polyvinyl chloride (PVC), a material used for plumbing pipes.
Wood
Hemp growth lasts roughly 100 days, a much faster time period than an average tree used for construction purposes. While dry, the fibers could be pressed into tight wood alternatives to wood-frame construction, wall/ceiling paneling, and flooring. As an addition, hemp is flexible and versatile allowing it to be used in a greater number of ways than wood. Similarly, hemp wood could also be made of recycled hemp-based paper.
Composite materials | Hemp | Wikipedia | 460 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
A mixture of fiberglass, hemp fiber, kenaf, and flax has been used since 2002 to make composite panels for automobiles. The choice of which bast fiber to use is primarily based on cost and availability.
Various car makers are beginning to use hemp in their cars, including Audi, BMW, Ford, GM, Chrysler, Honda, Iveco, Lotus, Mercedes, Mitsubishi, Porsche, Saturn, Volkswagen and Volvo. For example, the Lotus Eco Elise
and the Mercedes C-Class both contain hemp (up to 20 kg in each car in the case of the latter).
Paper | Hemp | Wikipedia | 123 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Hemp paper are paper varieties consisting exclusively or to a large extent from pulp obtained from fibers of industrial hemp. The products are mainly specialty papers such as cigarette paper, banknotes and technical filter papers. Compared to wood pulp, hemp pulp offers a four to five times longer fiber, a significantly lower lignin fraction as well as a higher tear resistance and tensile strength. However, production costs are about four times higher than for paper from wood, since the infrastructure for using hemp is underdeveloped. If the paper industry were to switch from wood to hemp for sourcing its cellulose fibers, the following benefits could be utilized:
Hemp yields three to four times more usable fiber per hectare per annum than forests, and hemp does not need pesticides or herbicides.
Hemp has a much faster crop yield. It takes about 3–4 months for hemp stalks to reach maturity, while trees can take between 20 and 80 years. Not only does hemp grow at a faster rate, but it also contains a high level of cellulose. This quick return means that paper can be produced at a faster rate if hemp were used in place of wood.
Hemp paper does not require the use of toxic bleaching or as many chemicals as wood pulp because it can be whitened with hydrogen peroxide. This means using hemp instead of wood for paper would end the practice of poisoning Earth's waterways with chlorine or dioxins from wood paper manufacturing.
Hemp paper can be recycled up to 8 times, compared to just 3 times for paper made from wood pulp.
Compared to its wood pulp counterpart, paper from hemp fibers resists decomposition and does not yellow or brown with age. It is also one of the strongest natural fibers in the world - one of the reasons for its longevity and durability.
Several factors favor the increased use of wood substitutes for paper, especially agricultural fibers such as hemp. Deforestation, particularly the destruction of old growth forests, and the world's decreasing supply of wild timber resources are today major ecological concerns. Hemp's use as a wood substitute will contribute to preserving biodiversity. | Hemp | Wikipedia | 441 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
However, hemp has had a hard time competing with paper from trees or recycled newsprint. Only the outer part of the stem consists mainly of fibers which are suitable for the production of paper. Numerous attempts have been made to develop machines that efficiently and inexpensively separate useful fibers from less useful fibers, but none have been completely successful. This has meant that paper from hemp is still expensive compared to paper from trees.
Jewelry
Hemp jewelry is the product of knotting hemp twine through the practice of macramé. Hemp jewelry includes bracelets, necklaces, anklets, rings, watches, and other adornments. Some jewelry features beads made from crystals, glass, stone, wood and bones. The hemp twine varies in thickness and comes in a variety of colors. There are many different stitches used to create hemp jewelry, however, the half knot and full knot stitches are most common.
Cordage
Hemp rope was used in the age of sailing ships, though the rope had to be protected by tarring, since hemp rope has a propensity for breaking from rot, as the capillary effect of the rope-woven fibers tended to hold liquid at the interior, while seeming dry from the outside. Tarring was a labor-intensive process, and earned sailors the nickname "Jack Tar". Hemp rope was phased out when manila rope, which does not require tarring, became widely available. Manila is sometimes referred to as Manila hemp, but is not related to hemp; it is abacá, a species of banana.
Animal bedding
Hemp shives are the core of the stem, hemp hurds are broken parts of the core. In the EU, they are used for animal bedding (horses, for instance), or for horticultural mulch. Industrial hemp is much more profitable if both fibers and shives (or even seeds) can be used.
Water and soil purification
Hemp can be used as a "mop crop" to clear impurities out of wastewater, such as sewage effluent, excessive phosphorus from chicken litter, or other unwanted substances or chemicals. Additionally, hemp is being used to clean contaminants at the Chernobyl nuclear disaster site, by way of a process which is known as phytoremediation – the process of clearing radioisotopes and a variety of other toxins from the soil, water, and air.
Weed control | Hemp | Wikipedia | 499 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Hemp crops are tall, have thick foliage, and can be planted densely, and thus can be grown as a smother crop to kill tough weeds. Using hemp this way can help farmers avoid the use of herbicides, gain organic certification, and gain the benefits of crop rotation. However, due to the plant's rapid and dense growth characteristics, some jurisdictions consider hemp a prohibited and noxious weed, much like Scotch Broom.
Biofuels
Biodiesel can be made from the oils in hemp seeds and stalks; this product is sometimes called "hempoline". Alcohol fuel (ethanol or, less commonly, methanol) can be made by fermenting the whole plant.
Filtered hemp oil can be used directly to power diesel engines. In 1892, Rudolf Diesel invented the diesel engine, which he intended to power "by a variety of fuels, especially vegetable and seed oils, which earlier were used for oil lamps, i.e. the Argand lamp".
Production of vehicle fuel from hemp is very small. Commercial biodiesel and biogas is typically produced from cereals, coconuts, palm seeds, and cheaper raw materials like garbage, wastewater, dead plant and animal material, animal feces and kitchen waste.
Processing
Separation of hurd and bast fiber is known as decortication. Traditionally, hemp stalks would be water-retted first before the fibers were beaten off the inner hurd by hand, a process known as scutching. As mechanical technology evolved, separating the fiber from the core was accomplished by crushing rollers and brush rollers, or by hammer-milling, wherein a mechanical hammer mechanism beats the hemp against a screen until hurd, smaller bast fibers, and dust fall through the screen. After the Marijuana Tax Act was implemented in 1938, the technology for separating the fibers from the core remained "frozen in time". Recently, new high-speed kinematic decortication has come about, capable of separating hemp into three streams; bast fiber, hurd, and green microfiber.
Only in 1997, did Ireland, parts of the Commonwealth and other countries begin to legally grow industrial hemp again. Iterations of the 1930s decorticator have been met with limited success, along with steam explosion and chemical processing known as thermomechanical pulping.
Cultivation | Hemp | Wikipedia | 482 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Hemp is usually planted between March and May in the northern hemisphere, between September and November in the southern hemisphere. It matures in about three to four months, depending on various conditions.
Millennia of selective breeding have resulted in varieties that display a wide range of traits; e.g. suited for particular environments/latitudes, producing different ratios and compositions of terpenoids and cannabinoids (CBD, THC, CBG, CBC, CBN...etc.), fiber quality, oil/seed yield, etc. Hemp grown for fiber is planted closely, resulting in tall, slender plants with long fibers.
The use of industrial hemp plant and its cultivation was commonplace until the 1900s when it was associated with its genetic sibling a.k.a. Drug-Type Cannabis species (which contain higher levels of psychoactive THC). Influential groups misconstrued hemp as a dangerous "drug", even though hemp is not a recreational drug and has the potential to be a sustainable and profitable crop for many farmers due to hemp's medical, structural and dietary uses. In the United States, the public's perception of hemp as marijuana has blocked hemp from becoming a useful crop and product," in spite of its vital importance prior to World War II.
Ideally, according to Britain's Department for Environment, Food and Rural Affairs, the herb should be desiccated and harvested toward the end of flowering. This early cropping reduces the seed yield but improves the fiber yield and quality.
The seeds are sown with grain drills or other conventional seeding equipment to a depth of . Greater seeding depths result in increased weed competition. Nitrogen should not be placed with the seed, but phosphate may be tolerated. The soil should have available 89 to 135 kg/ha of nitrogen, 46 kg/ha phosphorus, 67 kg/ha potassium, and 17 kg/ha sulfur. Organic fertilizers such as manure are one of the best methods of weed control.
Cultivars
In contrast to cannabis for medical use, varieties grown for fiber and seed have less than 0.3% THC and are unsuitable for producing hashish and marijuana. Present in industrial hemp, cannabidiol is a major constituent among some 560 compounds found in hemp. | Hemp | Wikipedia | 468 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Cannabis sativa L. subsp. sativa var. sativa is the variety grown for industrial use, while C. sativa subsp. indica generally has poor fiber quality and female buds from this variety are primarily used for recreational and medicinal purposes. The major differences between the two types of plants are the appearance, and the amount of Δ9-tetrahydrocannabinol (THC) secreted in a resinous mixture by epidermal hairs called glandular trichomes, although they can also be distinguished genetically. Oilseed and fiber varieties of Cannabis approved for industrial hemp production produce only minute amounts of this psychoactive drug, not enough for any physical or psychological effects. Typically, hemp contains below 0.3% THC, while cultivars of Cannabis grown for medicinal or recreational use can contain anywhere from 2% to over 20%.
Harvesting
Smallholder plots are usually harvested by hand. The plants are cut at 2 to 3 cm above the soil and left on the ground to dry. Mechanical harvesting is now common, using specially adapted cutter-binders or simpler cutters.
The cut hemp is laid in swathes to dry for up to four days. This was traditionally followed by retting, either water retting (the bundled hemp floats in water) or dew retting (the hemp remains on the ground and is affected by the moisture in dew and by molds and bacterial action). | Hemp | Wikipedia | 292 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Pests
Several arthropods can cause damage or injury to hemp plants, but the most serious species are associated with the Insecta class. The most problematic for outdoor crops are the voracious stem-boring caterpillars, which include the European corn borer, Ostrinia nubilalis, and the Eurasian hemp borer, Grapholita delineana. As the names imply, they target the stems reducing the structural integrity of the plant. Another lepidopteran, the corn earworm, Helicoverpa zea, is known to damage flowering parts and can be challenging to control. Other foliar pests, found in both indoor and outdoor crops, include the hemp russet mite, Aculops cannibicola, and cannabis aphid, Phorodon cannabis. They cause injury by reducing plant vigor because they feed on the phloem of the plant. Root feeders can be difficult to detect and control because of their below surface habitat. A number of beetle grubs and chafers are known to cause damage to hemp roots, including the flea beetle and Japanese beetle, Popillia Japonica. The rice root aphid, Rhopalosiphum rufiabdominale, has also been reported but primarily affects indoor growing facilities. Integrated pest management strategies should be employed to manage these pests with prevention and early detection being the foundation of a resilient program. Cultural and physical controls should be employed in conjunction with biological pest controls, chemical applications should only be used as a last resort.
Diseases
Hemp plants can be vulnerable to various pathogens, including bacteria, fungi, nematodes, viruses and other miscellaneous pathogens. Such diseases often lead to reduced fiber quality, stunted growth, and death of the plant. These diseases rarely affect the yield of a hemp field, so hemp production is not traditionally dependent on the use of pesticides. | Hemp | Wikipedia | 396 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Environmental impact
Hemp is considered by a 1998 study in Environmental Economics to be environmentally friendly due to a decrease of land use and other environmental impacts, indicating a possible decrease of ecological footprint in a US context compared to typical benchmarks. A 2010 study, however, that compared the production of paper specifically from hemp and eucalyptus concluded that "industrial hemp presents higher environmental impacts than eucalyptus paper"; however, the article also highlights that "there is scope for improving industrial hemp paper production". Hemp is also claimed to require few pesticides and no herbicides, and it has been called a carbon negative raw material.
Results indicate that high yield of hemp may require high total nutrient levels (field plus fertilizer nutrients) similar to a high yielding wheat crop.
A United Nations report endorses the versatility and sustainability of hemp and its productive potential in developing countries. Hemp uses a quarter of the water required by cotton, and absorbs more carbon dioxide than other crops and most trees.
Producers
The world-leading producer of hemp is China, which produces more than 70% of the world output. France ranks second with about a quarter of the world production. Smaller production occurs in the rest of Europe, Chile, and North Korea. Over 30 countries produce industrial hemp, including Australia, Austria, Canada, Chile, China, Denmark, Egypt, Finland, Germany, Greece, Hungary, India, Italy, Japan, Korea, Netherlands, New Zealand, Poland, Portugal, Romania, Russia, Slovenia, Spain, Sweden, Switzerland, Thailand, Turkey, the United Kingdom and Ukraine.
The United Kingdom and Germany resumed commercial production in the 1990s. British production is mostly used as bedding for horses; other uses are under development. Companies in Canada, the UK, the United States, and Germany, among many others, process hemp seed into a growing range of food products and cosmetics; many traditional growing countries continue to produce textile-grade fiber. | Hemp | Wikipedia | 396 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
Air-dried stem yields in Ontario have from 1998 and onward ranged from 2.6 to 14.0 tons of dry, retted stalks per hectare (1–5.5 t/ac) at 12% moisture. Yields in Kent County, have averaged 8.75 t/ha (3.5 t/ac). Northern Ontario crops averaged 6.1 t/ha (2.5 t/ac) in 1998. Statistic for the European Union for 2008 to 2010 say that the average yield of hemp straw has varied between 6.3 and 7.3 ton per ha. Only a part of that is bast fiber. Around one ton of bast fiber and 2–3 tons of core material can be decorticated from 3–4 tons of good-quality, dry-retted straw. For an annual yield of this level is it in Ontario recommended to add nitrogen (N):70–110 kg/ha, phosphate (P2O5): up to 80 kg/ha and potash (K2O): 40–90 kg/ha.
The average yield of dry hemp stalks in Europe was 6 ton/ha (2.4 ton/ac) in 2001 and 2002.
FAO argue that an optimum yield of hemp fiber is more than 2 tons per ha, while average yields are around 650 kg/ha.
Australia
In the Australian states of Tasmania, Victoria, Queensland, Western Australia, New South Wales, and most recently, South Australia, the state governments have issued licenses to grow hemp for industrial use. The first to initiate modern research into the potential of cannabis was the state of Tasmania, which pioneered the licensing of hemp during the early 1990s. The state of Victoria was an early adopter in 1998, and has reissued the regulation in 2008.
Queensland has allowed industrial production under license since 2002, where the issuance is controlled under the Drugs Misuse Act 1986.
Western Australia enabled the cultivation, harvest and processing of hemp under its Industrial Hemp Act 2004, New South Wales now issues licenses under a law, the Hemp Industry Regulations Act 2008 (No 58), that came into effect as of 6 November 2008.
Most recently, South Australia legalized industrial hemp under South Australia's Industrial Hemp Act 2017, which commenced on 12 November 2017.
Canada
Commercial production (including cultivation) of industrial hemp has been permitted in Canada since 1998 under licenses and authorization issued by Health Canada. | Hemp | Wikipedia | 501 | 963313 | https://en.wikipedia.org/wiki/Hemp | Biology and health sciences | Rosales | Plants |
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