Econstudentlog

Wikipedia articles of interest

i. Globular cluster (featured). What a thing like that looks like:

“A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is derived from the Latin globulus—a small sphere. A globular cluster is sometimes known more simply as a globular.

Globular clusters, which are found in the halo of a galaxy, contain considerably more stars and are much older than the less dense galactic, or open clusters, which are found in the disk. Globular clusters are fairly common; there are about 150[2] to 158[3] currently known globular clusters in the Milky Way, with perhaps 10 to 20 more still undiscovered.[4] Large galaxies can have more: Andromeda, for instance, may have as many as 500.[5] Some giant elliptical galaxies, particularly those at the centers of galaxy clusters, such as M87,[6] have as many as 13,000 globular clusters. These globular clusters orbit the galaxy out to large radii, 40 kiloparsecs (approximately 131,000 light-years) or more.[7]

Every galaxy of sufficient mass in the Local Group has an associated group of globular clusters, and almost every large galaxy surveyed has been found to possess a system of globular clusters.[8] The Sagittarius Dwarf and Canis Major Dwarf galaxies appear to be in the process of donating their associated globular clusters (such as Palomar 12) to the Milky Way.[9] This demonstrates how many of this galaxy’s globular clusters might have been acquired in the past.

Although it appears that globular clusters contain some of the first stars to be produced in the galaxy, their origins and their role in galactic evolution are still unclear.”

ii. Srinivasa Ramanujan (‘good article’). If you’ve seen Good Will Hunting the name will probably ring a bell. An interesting life, but much too short.

iii. Gastropoda.

“The Gastropoda or gastropods, more commonly known as snails and slugs, are a large taxonomic class within the phylum Mollusca. The class Gastropoda includes snails and slugs of all kinds and all sizes from microscopic to large. There are many thousands of species of sea snails and sea slugs, as well as freshwater snails and freshwater limpets, as well as land snails and land slugs.

The class Gastropoda contains a vast total of named species, second only to the insects in overall number. The fossil history of this class goes back to the Late Cambrian. There are 611 families of gastropods, of which 202 families are extinct, being found only in the fossil record.[3]

Gastropoda (previously known as univalves and sometimes spelled Gasteropoda) are a major part of the phylum Mollusca and are the most highly diversified class in the phylum, with 60,000 to 80,000[3][4] living snail and slug species. The anatomy, behavior, feeding and reproductive adaptations of gastropods vary significantly from one clade or group to another. Therefore, it is difficult to state many generalities for all gastropods. […]

At all taxonomic levels, gastropods are second only to the insects in terms of their diversity.[5] […]

Although the name “snail” can be, and often is, applied to all the members of this class, commonly this word means only those species with an external shell large enough that the soft parts can withdraw completely into it. Those gastropods without a shell, and those with only a very reduced or internal shell, are usually known as slugs.”

iv. Borel-Cantelli lemma.

v. Vijayanagara Empire. (featured)

“The Vijayanagara Empire referred to as the Kingdom of Bisnagar by the Portuguese, was an empire based in South India, in the Deccan Plateau region. It was established in 1336 by Harihara I and his brother Bukka Raya I of Sangama Dynasty.[1][2][3] The empire rose to prominence as a culmination of attempts by the southern powers to ward off Islamic invasions by the end of the 13th century. It lasted until 1646 although its power declined after a major military defeat in 1565 by the Deccan sultanates. The empire is named after its capital city of Vijayanagara, whose ruins surround present day Hampi, now a World Heritage Site in Karnataka, India.[4]

vi. Donner Party (featured).

“The Donner Party was a group of 87 American pioneers who in 1846 set off from Missouri in a wagon train headed west for California, only to find themselves trapped by snow in the Sierra Nevada. The subsequent casualties resulting from starvation, exposure, disease, and trauma were extremely high, and many of the survivors resorted to cannibalism.

The wagons left in May 1846. Encouraged to try a new, faster route across Utah and Nevada, they opted to take the Hastings Cutoff proposed by Lansford Hastings, who had never taken the journey with wagons. The Cutoff required the wagons to traverse Utah’s Wasatch Mountains and the Great Salt Lake Desert, and slowed the party considerably, leading to the loss of wagons, horses, and cattle. It also forced them to engage in heavy labor by clearing the path ahead of them, and created deep divisions between members of the party. They had planned to be in California by September, but found themselves trapped in the Sierra Nevada by early November.

Most of the party took shelter in three cabins that had been constructed two years earlier at Truckee Lake (now Donner Lake), while a smaller group camped several miles away. Food stores quickly ran out, and a group of 15 men and women attempted to reach California on snowshoes in December, but became disoriented in the mountains before succumbing to starvation and cold. Only seven members of the snowshoe party survived, by eating the flesh of their dead companions. Meanwhile, the Mexican American War delayed rescue attempts from California, although family members and authorities in California tried to reach the stranded pioneers but were turned back by harsh weather.

The first rescue group reached the remaining members, who were starving and feeble, in February 1847. Weather conditions were so bad that three rescue groups were required to lead the rest to California, the last arriving in March. Most of these survivors also had resorted to cannibalism. Forty-eight members of the Donner Party survived to live in California. Although a minor incident in the record of westward migration in North America, the Donner Party became notorious for the reported claims of cannibalism. Efforts to memorialize the Donner Party were underway within a few years; historians have described the episode as one of the most spectacular tragedies in California history and in the record of western migration.[1] […]

The group became lost and confused. After two more days without food, Patrick Dolan proposed that one of them should volunteer to die, to feed the others. Some suggested a duel, while another account describes an attempt to create a lottery to choose a member to sacrifice.[88][89] Eddy suggested they keep moving until someone simply fell, but a blizzard forced the group to halt. Antonio, the animal handler, was the first to die; Franklin Graves was the next casualty.[90][91]

As the blizzard progressed, Patrick Dolan began to rant deliriously, stripped off his clothes and ran into the woods. He returned shortly afterwards and died a few hours later. Not long after, possibly because 12-year-old Lemuel Murphy was near death, some of the group began to eat flesh from Dolan’s body. Lemuel’s sister tried to feed some to her brother, but he died shortly afterwards. Eddy, Salvador and Luis refused to eat. The next morning the group stripped the muscle and organs from the bodies of Antonio, Dolan, Graves, and Murphy and dried it to store for the days ahead, taking care to ensure that nobody would have to eat his or her relatives.[92][93]

After three days rest they set off again, searching for the trail. Eddy eventually succumbed to his hunger and ate human flesh, but that was soon gone. They began to take apart their snowshoes to eat the oxhide webbing, and discussed killing Luis and Salvador for food; after Eddy warned the Indians they quietly left.[94] During the night Jay Fosdick died, leaving only seven members of the party. Eddy and Mary Graves left to hunt, but when they returned with deer meat, Fosdick’s body had already been cut apart for food.[95][96] After several more days—25 since they had left Truckee Lake—they came across Salvador and Luis, who had not eaten for about nine days and were close to death. William Foster, believing the flesh of the Indians was the group’s last hope of avoiding imminent death from starvation, shot the pair.[97]

On January 12, the group stumbled into a Miwok camp looking so deteriorated that the Indians initially fled. The Miwoks gave them what they had to eat: acorns, grass, and pine nuts.[97] After a few days, Eddy continued on with the help of a Miwok to a ranch in a small farming community at the edge of the Sacramento Valley.[98][99] A hurriedly assembled rescue party found the other six survivors on January 17.”

vii.  Endosymbiont.

“An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis (Greek: ἔνδον endon “within”, σύν syn “together” and βίωσις biosis “living”). Examples are nitrogen-fixing bacteria (called rhizobia) which live in root nodules on legume roots, single-celled algae inside reef-building corals, and bacterial endosymbionts that provide essential nutrients to about 10–15% of insects.

Many instances of endosymbiosis are obligate; that is, either the endosymbiont or the host cannot survive without the other, such as the gutless marine worms of the genus Riftia, which get nutrition from their endosymbiotic bacteria. The most common examples of obligate endosymbiosis are mitochondria and chloroplasts. Some human parasites, e.g. : Wucherichia bancrofti and Mansonella perstans thrive in their hosts because of an obligate endosymbiosis with Wolbachi spp.. They can both be eliminated from their host by treatments that target this bacterium. However, not all endosymbioses are obligate. Also, some endosymbioses can be harmful to either of the organisms involved.

It is generally agreed that certain organelles of the eukaryotic cell, especially mitochondria and plastids such as chloroplasts, originated as bacterial endosymbionts. This theory is called the endosymbiotic theory, and was first articulated by the Russian botanist Konstantin Mereschkowski in 1905.[1]

November 20, 2012 - Posted by | astronomy, biology, history, mathematics, Physics, wikipedia

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