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#6238.

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#2464. What does the medical term Heart failure signify?

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2385) 49th Parallel

Gist

The 49th parallel most commonly refers to the 49th parallel north, a line of latitude that forms the international border between the United States and Canada for a significant portion of their boundary, a result of treaties in 1818 and 1846. This parallel also serves as the southern border for several Canadian provinces and the northern border for various U.S. states.

Summary

The 49th parallel north is a circle of latitude that is 49° north of Earth's equator. It crosses Europe, Asia, the Pacific Ocean, North America, and the Atlantic Ocean.

The city of Paris is about 15 kilometres (9 miles) south of the 49th parallel and is the largest city between the 48th and 49th parallels. Its main airport, Charles de Gaulle Airport, lies on the 49th parallel.

Roughly 2,030 kilometres (1,260 miles) of the Canada–United States border was designated to follow the 49th parallel from British Columbia to Manitoba on the Canada side, and from Washington to Minnesota on the U.S. side, more specifically from the Strait of Georgia to the Lake of the Woods. This international border was specified in the Anglo-American Convention of 1818 and the Oregon Treaty of 1846, though survey markers placed in the 19th century cause the border to deviate from the 49th parallel by up to 810 metres (0.503 miles).

From a point on the ground at this latitude, the sun is above the horizon for 16 hours, 12 minutes during the summer solstice and 8 hours, 14 minutes during the winter solstice.

This latitude also roughly corresponds to the minimum latitude in which astronomical twilight can last all night near the summer solstice. All-night astronomical twilight lasts about from June 9 to July 2. At midnight on the summer solstice, the altitude of the sun is about −17.56°.

Slightly less than one-eighth of the Earth's surface is north of the 49th parallel.

Details

When there’s a continent at stake, arguments over borders can make or break the peace across the whole region.

What happens when a continent has only two major nations? In the case of Canada and the United States of America, the 5,525 mile long line delineating the two nations is currently the longest undefended international boundary in the world, often cited as an example to the rest of the world of how two nations can cooperate.

Today, the countries are seen as model neighbours, but it took centuries of arguing, skirmishes, and outright wars to settle the matter of who got what in North America. Even after a century and a half of relative peace, today there are still a few areas that are still in dispute, and it doesn't show signs of being settled any time soon.

If you're interested in how this comparatively simple division of land occurred, here’s how it went down:

1700s

1775 - During the Revolutionary War, the American colonists hoped Quebec and Nova Scotia would be their allies against the British. The soon-to-be U.S. got impatient, though, and took matters into its own hands, invading its neighbor to the north and taking Montreal in the first big military maneuver of the war. A month later, they were pushed back in a major defeat known as the Battle of Quebec.

1783 - After the war, a victorious U.S. demanded that Great Britain give them Canada. Unsurprisingly, the British refused. The parties settled the boundaries, or so they thought, by using the 45th parallel as the northern border between New York and New Brunswick, and creating an imaginary line through the Great Lakes. No one knew much about what existed beyond the Mississippi River to the west, so those boundaries were left murky, to say the least.

1800s

1803 - The young United States made a very good deal with France, known as the Louisiana Purchase. For 15 million dollars, they bought a vast swath of territory that reached from Gulf of Mexico to the Rockies (or Stony Mountains, as they were called then). The British and the U.S. used the watershed between the Hudson Bay and the Mississippi/Missouri rivers to establish the northern border for the newly purchased lands. That turned out to be a bad idea, because the watershed was too flat to be measured accurately.

1812 - During the War of 1812, the United States invaded Canada again, not once, but twice, as a way of attacking British interests. Some Americans thought taking Canada would be a walk in the park, but they suffered a humiliating defeat in the Siege of Detroit, aided by the Native American Tecumseh. As well, British forces land near Washington D.C., burning the US Capitol and the Whitehouse.

In 1814, a treaty restored the original boundaries. Many Canadians fought during the war, which created a new sense of a national identity.

1818 - American settlers had streamed further west, encouraged by a belief in Manifest Destiny, which held that America was meant to stretch from coast to coast. That pressured Britain and the US to return to the border-negotiating table.

Surveyors were struggling against great odds to map exactly what existed in the largely rugged terrain. The powers-that-were decided to use a straight line - the 49th parallel - to demarcate the border up to the Rockies. Left unresolved was the mysterious land beyond, called Columbia in Canada and Oregon in the U.S.

For now, Britain and the U.S allowed it to remain open to whoever could survive out there. Surveying mistakes led to an anomaly that still exists, the Northwest Angle. It’s part of Minnesota, but if you want to go there by land, you have to travel through Canada, twice.

1846 - The agreement to keep the Oregon and Columbia territories neutral was falling apart. Thousands of Americans had stakes in the region, and the U.S. was pushing hard against Britain’s Hudson Bay Company, which controlled Canadian interests. President James K. Polk demanded that U.S. territory be extended northward, past the 49th parallel.

The slogan “54° 40’ or Fight” became a rallying cry for his supporters. In the end, the U.S. blinked, and Polk agreed to let the 49th parallel become the official dividing line for the westernmost areas of the two countries, resolving (almost) the last major piece of the Canadian-U.S. puzzle. Spats over small areas would continue for decades.

1867 - Canada is granted its independence from Great Britain. Based upon a drive for self-determination from the Canadian provinces, and a desire from Britain for Canada to defend itself against American encroachment, this process was peaceful and did not lead to a military dispute as seen in America's war of Independence.

The first Canadian prime minister Sir John A. MacDonald drives the creation of a transcontinental railroad in order to allow quick movements of troops to the western territories of Canada in case of American expansion.

1900s

1908 - A treaty between the two nations is signed, establishing a joint commission tasked with surveying and delineating the border between the two neighbours.

1925 - Canada and America agree to make the International Boundary Commission permanent, in order to maintain the land and monuments along the border.

One of its responsibilities is maintenance of the Peace Arch, which was built on the exact line between the two nations, in Washington State in the U.S. and British Columbia in Canada. On the U.S side, the monument reads "Children Of a Common Mother," and on the Canadian side "Brethren Dwelling together in Unity." And for the most part, both are true.

Current

The U.S. and Canada have agreed to disagree over a few remaining bits and bobs, including Machias Seal Island in the east, which has a Canadian lighthouse but is claimed by the U.S.

There is also the matter of the Northwest Passage, which Canada says is hers, but the U.S. says is international shipping waters. A small piece off territorial waters off the coast of the Yukon (a Canadian Territory) is claimed by the U.S. as a special economic zone.

As far as we know, there are no more plans to invade, however. It was a long road, but in the end, Canada and the United States reached a harmonious relationship that stretches from the Atlantic to the Pacific.

Additional Information

The 49th parallel serves as the border between the United States and Canada due to a series of historical agreements and treaties that shaped its establishment. The boundary is drawn along the 49th parallel from Lake of the Woods in the east to the Strait of Georgia in the west. Several key events led to this decision, making it a straightforward and agreed-upon solution for both nations.

The choice of the 49th parallel as a border was both practical and symbolic. It provided a simple, horizontal line that was straightforward to draw and maintain.

This choice allowed me and others involved to easily demarcate the land and limit disputes. The decision also meant a fair division of territory between the nations, which allowed for westward expansion without constant conflict.

Despite its simplicity, drawing a border along the 49th parallel wasn’t easy. The land includes plains, mountains, and everything in between, complicating the task. Surveyors, including those on my team, faced many obstacles, like harsh weather, as they worked over several decades to accurately map and mark this boundary.

2384) Seahorse

Gist

The seahorse is a marine fish of the genus Hippocampus and family Syngnathidae, named for its horse-like head and upright posture, resembling a miniature horse in the sea. These bony fish have distinctive features such as a prehensile tail, independently moving eyes, and segmented bony armour, and they are found in shallow coastal waters worldwide. 

Summary

A seahorse, (genus Hippocampus), any of about 50 species of marine fishes allied to pipefishes in the family Syngnathidae (order Gasterosteiformes). Seahorses are found in shallow coastal waters in latitudes from about 52° N to 45° S. Their habitats include coral reefs, mangroves, sea grass beds, and estuaries. They are unique in appearance, with their horselike head, prehensile tail, independently moving eyes, and brood pouch. They have long, tubular snouts and small, toothless mouths. Their bodies are covered with consecutive rings of bony plates. The name of the genus that contains seahorses is taken from the Greek words hippos (meaning “horse”) and kampos (meaning “sea monster”).

Seahorses vary in size, ranging in length from about 2 to 35 cm (about 0.8 to 14 inches). Adults of some of the smallest species—such as Denise’s pygmy seahorse (Hippocampus denise), found in the tropical western Pacific from Indonesia to Vanuatu, and Satomi’s pygmy seahorse (H. satomiae), found in the tropical Indian and Pacific Oceans from the Bay of Bengal to the Coral Sea—are less than 2 cm long. The largest species, the big-bellied seahorse (H. abdominalis), which inhabits the waters off South Australia and New Zealand, can grow up to 35 cm (13.8 inches) in length.

Seahorses are rather immobile, swimming more slowly than other fishes. When swimming they maintain a vertical position and propel themselves forward using a soft-rayed dorsal fin. They use pectoral fins located on the side of the head to maneuver. Some scientists contend that this upright swimming posture evolved shortly after the expansion of sea grasses in the western Pacific roughly 25 million years ago. These plants provided seahorses with useful hiding places to avoid enemies and to capture unsuspecting prey, and ancestors of the seahorse evolved to maximize the opportunities offered by this new habitat.

Seahorses are usually found clinging to plants or corals with their tails. Their sedentary habits coupled with excellent camouflage abilities render them successful ambush predators. When small organisms swim nearby, a seahorse may capture them by rapidly sucking them into the mouth. Seahorses also rely upon camouflage to avoid predators such as crabs and other fishes.

The reproductive behaviour of seahorses is notable in that the male carries the fertilized eggs. After an elaborate courtship, the female uses an ovipositor (egg duct) to place her eggs into a brood pouch located at the base of the male’s tail where the eggs are later fertilized. Depending on the species, the eggs remain in the pouch between 10 days and six weeks. During this time the male nurtures the developing young by regulating the chemistry of the fluid inside the pouch, slowly transforming it from that of his internal body fluids to that of salt water as pregnancy progresses. To nourish the growing young, the male also produces inorganic compounds and releases the hormone prolactin, which helps break down the proteins contributed by the female. Once the eggs hatch, the male convulses his body and expels the young through a single opening in the pouch. The young are miniature versions of their parents that receive no further care. The male can receive another brood of eggs almost immediately after giving birth. In some species a male and female will maintain a monogamous pair bond throughout the breeding season and produce many broods.

Commercially, seahorses are traded live as aquarium animals and dead for use in traditional medicines and as curios. Threatened by direct overfishing, accidental capture (bycatch) in other fisheries, and the destruction of their coastal habitats, some species—such as the Pacific seahorse (H. ingens)—face extinction.

Details:

Scientific classification

Kingdom:  Animalia
Phylum:  Chordata
Class:  Actinopterygii
Order:  Syngnathiformes
Family:  Syngnathidae
Subfamily:  Hippocampinae
Genus:  Hippocampus

A seahorse (also written sea-horse and sea horse) is any of 46 species of small marine bony fish in the genus Hippocampus. The genus name comes from the Ancient Greek hippókampos (ἱππόκαμπος), itself from híppos (ἵππος) meaning "horse" and kámpos meaning "sea monster" or "sea animal". Having a head and neck suggestive of a horse, seahorses also feature segmented bony armour, an upright posture and a curled prehensile tail. Along with the pipefishes and seadragons (Phycodurus and Phyllopteryx) they form the family Syngnathidae.

Evolution and fossil record

Anatomical evidence, supported by molecular, physical, and genetic evidence, demonstrates that seahorses are highly modified pipefish. The fossil record of seahorses, however, is very sparse. The best known and best studied fossils are specimens of Hippocampus guttulatus (though literature more commonly refers to them under the synonym of H. ramulosus), from the Marecchia River formation of Rimini Province, Italy, dating back to the Lower Pliocene, about 3 million years ago. The earliest known seahorse fossils are of two pipefish-like species, H. sarmaticus and H. slovenicus, from the coprolitic horizon of Tunjice Hills, a middle Miocene lagerstätte in Slovenia dating back about 13 million years.

Molecular dating implies that pipefish and seahorses diverged during the Late Oligocene. This has led to speculation that seahorses evolved in response to large areas of shallow water, newly created as the result of tectonic events. The shallow water would have allowed the expansion of seagrass habitats that served as camouflage for the seahorses' upright posture. These tectonic changes occurred in the western Pacific Ocean, pointing to an origin there, with molecular data suggesting two later, separate invasions of the Atlantic Ocean. In 2016, a study published in Nature found the seahorse genome to be the most rapidly evolving fish genome studied so far.

The evolution of seahorses from pipefish may have been an adaptation related to the biomechanics of prey capture. The unique posture of the seahorse allows them to capture small shrimps at larger distances than the pipefish is capable of.

Description

Seahorses range in size from 1.5 to 35 cm (0.6 to 13.8 in). They are named for their equine appearance, with bent necks and long snouted heads and a distinctive trunk and tail. Although they are bony fish, they do not have scales, but rather thin skin stretched over a series of bony plates, which are arranged in rings throughout their bodies. Each species has a distinct number of rings. The armor of bony plates also protects them against predators, and because of this outer skeleton, they no longer have ribs. Seahorses swim upright, propelling themselves using the dorsal fin, another characteristic not shared by their close pipefish relatives, which swim horizontally. Razorfish are the only other fish that swim vertically. The pectoral fins, located on either side of the head behind their eyes, are used for steering. They lack the caudal fin typical of fishes. Their prehensile tail is composed of square-like rings. They are adept at camouflage, and can grow and reabsorb spiny appendages depending on their habitat.

Unusual among fish, a seahorse has a flexible, well-defined neck. It also sports a crown-like spine or horn on its head, termed a "coronet", which is distinct for each species.

Seahorses swim extremely poorly, rapidly fluttering a dorsal fin and using pectoral fins to steer. The slowest-moving fish in the world is H. zosterae (the dwarf seahorse), with a top speed of about 1.5 m (5 ft) per hour. Since they are poor swimmers, they are most likely to be found resting with their prehensile tail wound around a stationary object. They have long snouts, which they use to drag up food, and their eyes can move independently of each other like those of a chameleon.

Habitat

Seahorses are mainly found in shallow tropical and temperate salt water throughout the world, from about 45°S to 45°N. They live in sheltered areas such as seagrass beds, estuaries, coral reefs, and mangroves. Four species are found in Pacific waters from North America to South America. In the Atlantic, Hippocampus erectus ranges from Nova Scotia to Uruguay. H. zosterae, known as the dwarf seahorse, is found in the Bahamas.

Colonies have been found in European waters such as the Thames Estuary.

Two species live in the Mediterranean Sea: H. guttulatus (the long-snouted seahorse), and H. hippocampus (the short-snouted seahorse). These species form territories; males stay within 1 sq m (10 sq ft) of habitat, while females range over about one hundred times that.

Feeding habits

Seahorses rely on stealth to ambush small prey such as copepods. They use pivot feeding to catch the copepod, which involves rotating their snout at high speed and then sucking in the copepod.
Seahorses use their long snouts to eat their food with ease. However, they are slow to consume their food and have extremely simple digestive systems that lack a stomach, so they must eat constantly to stay alive.[28] Seahorses are not very good swimmers, and for this reason they need to anchor themselves to seaweed, coral or anything else that will keep the seahorse in place. They do this by using their prehensile tails to grasp their object of choice. Seahorses feed on small crustaceans floating in the water or crawling on the bottom. With excellent camouflage, seahorses ambush prey that floats within striking range, sitting and waiting until an optimal moment. Mysid shrimp and other small crustaceans are favorites, but some seahorses have been observed eating other kinds of invertebrates and even larval fish. In a study of seahorses, the distinctive head morphology was found to give them a hydrodynamic advantage that creates minimal interference while approaching an evasive prey. Thus the seahorse can get very close to the copepods on which it preys. After successfully closing in on the prey without alerting it, the seahorse gives an upward thrust and rapidly rotates the head aided by large tendons that store and release elastic energy, to bring its long snout close to the prey. This step is crucial for prey capture, as oral suction only works at a close range. This two-phase prey capture mechanism is termed pivot-feeding. Seahorses have three distinctive feeding phases: preparatory, expansive, and recovery. During the preparatory phase, the seahorse slowly approaches the prey while in an upright position, after which it slowly flexes its head ventrally. In the expansive phase, the seahorse captures its prey by simultaneously elevating its head, expanding the buccal cavity, and sucking in the prey item. During the recovery phase, the jaws, head, and hyoid apparatus of the seahorse return to their original positions.

The amount of available cover influences the seahorse's feeding behaviour. For example, in wild areas with small amounts of vegetation, seahorses will sit and wait, but an environment with extensive vegetation will prompt the seahorse to inspect its environment, feeding while swimming rather than sitting and waiting. Conversely, in an aquarium setting with little vegetation, the seahorse will fully inspect its environment and makes no attempt to sit and wait.

Additional Information

Seahorses are members of the pipefish family. In addition to their iconic appearance, seahorses possess many interesting attributes. Among them are specialized structures in their skin cells, called chromatophores, which allow the mostly sessile seahorses to change color to mimic their surroundings. Well camouflaged as they cling to stalks of seagrass in their shallow habitats, seahorses can be hard to see.

Their truly remarkable biological claim to fame, however, is that male seahorses and sea dragons get pregnant and bear young—a unique adaptation in the animal kingdom.

After completing an elaborate courtship dance that may go on for hours or days, the female seahorse transfers her mature eggs into the male’s brood pouch, where they are fertilized. At the end of a gestation period usually lasting from two to four weeks, the pregnant male’s abdominal area begins to undulate rhythmically, and strong muscular contractions eject from a few dozen to as many as 1,000 fully formed baby seahorses into the surrounding water. After that, the offspring must fend for themselves. Large litters are necessary because only about 0.5 percent will survive to adulthood.

Many, if not all, of the 47 known seahorse species—14 of which were identified only in the 21st century—are in decline worldwide.

Because seahorses generally live in shallow, near-coastal waters, human activities including development, pollution, fisheries, and traditional medicine have reduced their numbers. At the same time, their universal appeal has worked against them; until recently, wild seahorses were often captured for the aquarium trade. The delicate creatures tend to fare poorly in aquaria, however. In recent years, captive-bred seahorses have shown promise as hardier tank-dwellers than their wild relatives.

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#5743. What does the noun optimization mean?

#5744. What does the adjective optimum mean?

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#9730.