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The second Digimon series is direct continuation of the first one, and began airing on April 2, 2000. Three years later, with most of the original DigiDestined now in high school at age fourteen, the Digital World was supposedly secure and peaceful. However, a new evil has appeared in the form of the Digimon Emperor (Digimon Kaiser) who as opposed to previous enemies is a human just like the DigiDestined. The Digimon Emperor has been enslaving Digimon with Dark Rings and Control Spires and has somehow made regular Digivolution impossible. However, five set Digi-Eggs with engraved emblems had been appointed to three new DigiDestined along with T.K. and Kari, two of the DigiDestined from the previous series. This new evolutionary process, dubbed Armor Digivolution helps the new DigiDestined to defeat evil lurking in the Digital World. Eventually, the DigiDestined defeat the Digimon Emperor, more commonly known as Ken Ichijouji on Earth, only with the great sacrifice of Ken's own Digimon, Wormmon. Just when things were thought to be settled, new Digimon enemies made from the deactivated Control Spires start to appear and cause trouble in the Digital World. To atone for his past mistakes, Ken joins the DigiDestined, being a DigiDestined himself, with his Partner Wormmon revived to fight against them. They soon save countries including France and Australia from control spires and defeat MaloMyotismon (BelialVamdemon), the digivolved form of Myotismon (Vamdemon) from the previous series. They stop the evil from destroying the two worlds, and at the end, every person on Earth gains their own Digimon partner. |
The third Digimon series, which began airing on April 1, 2001, is set largely in a "real world" where the Adventure and Adventure 02 series are television shows, and where Digimon game merchandise (based on actual items) become key to providing power boosts to real Digimon which appear in that world. The plot revolves around three Tamers, Takato Matsuki, Rika Nonaka, and Henry Wong. It began with Takato creating his own Digimon partner by sliding a mysterious blue card through his card reader, which then became a D-Power. Guilmon takes form from Takato's sketchings of a new Digimon. (Tamers’ only human connection to the Adventure series is Ryo Akiyama, a character featured in some of the Digimon video games and who made an appearance in some occasions of the Adventure story-line.) Some of the changes in this series include the way the Digimon digivolve with the introduction of Biomerge-Digivolution and the way their "Digivices" work. In this series, the Tamers can slide game cards through their "Digivices" and give their Digimon partners certain advantages, as in the card game. This act is called "Digi-Modify" (Card Slash in the Japanese version). The same process was often used to Digivolve the Digimon, but as usual, emotions play a big part in the digivolving process. Unlike the two seasons before it and most of the seasons that followed, Digimon Tamers takes a darker and more realistic approach to its story featuring Digimon who do not reincarnate after their deaths and more complex character development in the original Japanese. The anime has become controversial over the decade, with debates about how appropriate this show actually is for its "target" audience, especially due to the Lovecraftian nature of the last arc. The English dub is more lighthearted dialogue-wise, though still not as much as previous series. |
The fourth Digimon series, which began airing on April 7, 2002, radically departs from the previous three by focusing on a new and very different kind of evolution, Spirit Evolution, in which the human characters use their D-Tectors (this series' Digivice) to transform themselves into special Digimon called Legendary Warriors, detracting from the customary formula of having digital partners. After receiving unusual phone messages from Ophanimon (one of the three ruling Digimon alongside Seraphimon and Cherubimon) Takuya Kanbara, Koji Minamoto, Junpei Shibayama, Zoe Orimoto, Tommy Himi, and Koichi Kimura go to a subway station and take a train to the Digital World. Summoned by Ophanimon, the Digidestined realize that they must find the ten legendary spirits and stop the forces of Cherubimon from physically destroying the Digital World. After finding the ten spirits of the Legendary Warriors and defeating Mercurymon, Grumblemon, Ranamon, and Arbormon, they finally end up fighting Cherubimon hoping to foil his effort to dominate the Digital World. After the defeat of Cherubimon, the Digidestined find they must face an even greater challenge as they try to stop the Royal Knights—Dynasmon and Crusadermon—from destroying the Digital World and using the collected data to revive the original ruler of the Digital World: the tyrannical Lucemon. Ultimately the Digidestined fail in preventing Lucemon from reawakening but they do manage to prevent him from escaping into the Real World. In the final battle, all of the legendary spirits the digidestined have collected thus far merge and create Susanoomon. With this new form, the digidestined are able to effectively defeat Lucemon and save the Digital World. In general, Frontier has a much lighter tone than that of Tamers, yet remains darker than Adventure and Adventure 02. |
After a three-year hiatus, a fifth Digimon series began airing on April 2, 2006. Like Frontier, Savers has no connection with the previous installments, and also marks a new start for the Digimon franchise, with a drastic change in character designs and story-line, in order to reach a broader audience. The story focuses on the challenges faced by the members of D.A.T.S. ("Digital Accident Tactics Squad"), an organization created to conceal the existence of the Digital World and Digimon from the rest of mankind, and secretly solve any Digimon-related incidents occurring on Earth. Later the D.A.T.S. is dragged into a massive conflict between Earth and the Digital World, triggered by an ambitious human scientist named Akihiro Kurata, determined to make use of the Digimon for his own personal gains. The English version was dubbed by Studiopolis and it premiered on the Jetix block on Toon Disney on October 1, 2007. Digivolution in Data Squad requires the human partner's DNA ("Digital Natural Ability" in the English version and "Digisoul" in the Japanese version) to activate, a strong empathy with their Digimon and a will to succeed. 'Digimon Savers' also introduces a new form of digivolving called Burst Mode which is essentially the level above Mega (previously the strongest form a digimon could take). Like previously in Tamers, this plot takes on a dark tone throughout the story and the anime was aimed, originally in Japan, at an older audience consisting of late teens and people in their early twenties from ages 16 to 21. Because of that, along with the designs, the anime being heavily edited and localized for western US audiences like past series, and the English dub being aimed mostly toward younger audiences of children aged 6 to 10 and having a lower TV-Y7-FV rating just like past dubs, Studiopolis dubbed the anime on Jetix with far more edits, changes, censorship, and cut footage. This included giving the Japanese characters full Americanized names and American surnames as well as applying far more Americanization (Marcus Damon as opposed to the Japanese Daimon Masaru), cultural streamlining and more edits to their version similar to the changes 4Kids often made (such as removal of Japanese text for the purpose of cultural streamlining). Despite all that, the setting of the country was still in Japan and the characters were Japanese in the dub. This series was the first to show any Japanese cultural concepts that were unfamiliar with American audiences (such as the manju), which were left unedited and used in the English dub. Also despite the heavy censorship and the English dub aimed at young children, some of the Digimon's attacks named after real weapons such as RizeGreymon's Trident Revolver are not edited and used in the English dub. Well Go USA released it on DVD instead of Disney. The North American English dub was televised on Jetix in the U.S. and on the Family Channel in Canada. |
Three and a quarter years after the end of the fifth series, a new sixth series was confirmed by Bandai for the Digimon anime, its official name of the series revealed in the June issue of Shueisha's V Jump magazine being Digimon Xros Wars. It began airing in Japan on TV Asahi from July 6, 2010 onwards. Reverting to the design style of the first four series as well as the plot taking on the younger, lighter tone present in series one, two and four throughout the story. The story follows a boy named Mikey Kudō (Taiki Kudo in Japan) who, along with his friends, ends up in the Digital World where they meet Shoutmon and his Digimon friends. Wielding a digivice known as a Fusion Loader (Xros Loader in Japan), Mikey is able to combine multiple Digimon onto one to enhance his power, Shoutmon being the usual core of the combination, using a technique known as 'DigiFuse' (Digi-Xros in Japan). Forming Team Fusion Fighters (Team Xros Heart in Japan), Mikey, Shoutmon and their friends travel through the Digital World to liberate it from the evil Bagra Army, led by Bagramon(Lord Bagra in English), and Midnight, a shady group led by AxeKnightmon with Nene as a figurehead before joining the Fusion Fighters. The Fusion Fighters also finds themselves at odds with Blue Flare, led by Christopher Aonuma (Kiriha Anouma in Japan). The second arc of Xros Wars was subtitled The Evil Death Generals and the Seven Kingdoms. It saw the main cast reshuffled with a new wardrobe while Angie (Akari in Japan) and Jeremy (Zenjiro in Japan) stay behind in the Human World; thus making Mikey, Christopher and Nene the lead protagonists as they set off to face the Seven Death Generals of the Bagra Army and AxeKnightmon's new pawn: Nene's brother Ewan (Yuu in Japan). A new evolution known as Super Digivolution was introduced at the end of the first arc. The English dub of the series began airing on Nickelodeon on September 7, 2013, which is produced by Saban Brands. |
On August 17, 2011, Shueisha's V-Jump magazine announced a sequel set one year later, a third arc of Xros Wars subtitled The Young Hunters Who Leapt Through Time, which aired from October 2, 2011 to March 25, 2012, following on from the previous arc. It focuses on a new protagonist, Tagiru Akashi and his partner Gumdramon who embark on a new journey with an older Mikey, Shoutmon, an older Ewan and the revived Damemon, along with other new comrades as they deal with a hidden dimension that lies between the Human World and the Digital World called DigiQuartz. The series finale reintroduces the heroes of the previous five seasons as they all come together and help the current heroes in the final battle due to the fact that the DigiQuartz is essentially a tear in Space and Time, allowing all of the Digimon universes to converge. |
A new Digimon series was announced 30 months after the end of Digimon Fusion at a 15th anniversary concert and theater event for the franchise in August 2014. The series announced the return of the protagonists from the original Digimon Adventure series, most of them now as high school students. A countdown clicking game was posted on the show's official website, offering news when specific clicks were met. On December 13, 2014 the series title and a key visual featuring character designs by Atsuya Uki were revealed with Keitaro Motonaga announced as director with a tentative premiere date of Spring, 2015. However, on May 6, 2015, it was announced that tri. would not be a television series, but rather a 6-part theatrical film series. The films are being streamed in episodic format outside Japan by Crunchyroll and Hulu from the same day they premiere on Japanese theaters. |
The series is set three years after the events of Digimon Adventure 02, when Digimon who turn rogue by a mysterious infection appear to wreak havoc in the Human World. Tai and the other DigiDestined from the original series reunite with their partners and start fighting back with support from the Japanese government, while Davis, Yolei, Cody and Ken are defeated by a powerful enemy called Alphamon and disappear without a trace. Tai and the others also meet another DigiDestined called Meiko Mochizuki and her partner Meicoomon who become their friends, until Meicoomon turns hostile as well and flees after an encounter with Ken, who reappears suddenly, once again as the Digimon Emperor. The film series also feature several DigiDestined having their partners Digivolve up to the Mega level for the first time, a feat only Tai and Matt had achieved previously. |
There have been nine Digimon movies released in Japan. The first seven were directly connected to their respective anime series; Digital Monster X-Evolution originated from the Digimon Chronicle merchandise line. All movies except X-Evolution and Ultimate Power! Activate Burst Mode have been released and distributed internationally. Digimon: The Movie, released in the U.S. and Canada territory by Fox Kids through 20th Century Fox on October 6, 2000, consists of the union of the first three Japanese movies. |
The European publishing company, Panini, approached Digimon in different ways in different countries. While Germany created their own adaptations of episodes, the United Kingdom (UK) reprinted the Dark Horse titles, then translated some of the German adaptations of Adventure 02 episodes. Eventually the UK comics were given their own original stories, which appeared in both the UK's official Digimon Magazine and the official UK Fox Kids companion magazine, Wickid. These original stories only roughly followed the continuity of Adventure 02. When the comic switched to the Tamers series the storylines adhered to continuity more strictly; sometimes it would expand on subject matter not covered by the original Japanese anime (such as Mitsuo Yamaki's past) or the English adaptations of the television shows and movies (such as Ryo's story or the movies that remained undubbed until 2005). In a money saving venture, the original stories were later removed from Digimon Magazine, which returned to printing translated German adaptations of Tamers episodes. Eventually, both magazines were cancelled. |
The Digimon series has a large number of video games which usually have their own independent storylines with a few sometimes tying into the stories of the anime series or manga series. The games consists of a number of genres including life simulation, adventure, video card game, strategy and racing games, though they are mainly action role-playing games. The games released in North America are: Digimon World, Digimon World 2, Digimon World 3, Digimon World 4, Digimon Digital Card Battle, Digimon Rumble Arena, Digimon Rumble Arena 2, Digimon Battle Spirit, Digimon Battle Spirit 2, Digimon Racing, Digimon World DS, Digimon World Data Squad, Digimon World Dawn and Dusk, Digimon World Championship, and Digimon Masters. |
In 2011, Bandai posted a countdown on a teaser site. Once the countdown was finished, it revealed a reboot of the Digimon World series titled Digimon World Re:Digitize. An enhanced version of the game released on Nintendo 3DS as Digimon World Re:Digitize Decode in 2013. Another role-playing game by the name Digimon Story: Cyber Sleuth is set for release in 2015 for PlayStation Vita. It is part of the Digimon Story sub-series, originally on Nintendo DS and has also been released with English subtitles in North America. |
A glacier (US /ˈɡleɪʃər/ or UK /ˈɡlæsiə/) is a persistent body of dense ice that is constantly moving under its own weight; it forms where the accumulation of snow exceeds its ablation (melting and sublimation) over many years, often centuries. Glaciers slowly deform and flow due to stresses induced by their weight, creating crevasses, seracs, and other distinguishing features. They also abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. |
On Earth, 99% of glacial ice is contained within vast ice sheets in the polar regions, but glaciers may be found in mountain ranges on every continent except Australia, and on a few high-latitude oceanic islands. Between 35°N and 35°S, glaciers occur only in the Himalayas, Andes, Rocky Mountains, a few high mountains in East Africa, Mexico, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earth's land surface. Continental glaciers cover nearly 13,000,000 km2 (5×10^6 sq mi) or about 98 percent of Antarctica's 13,200,000 km2 (5.1×10^6 sq mi), with an average thickness of 2,100 m (7,000 ft). Greenland and Patagonia also have huge expanses of continental glaciers. |
Glacial ice is the largest reservoir of freshwater on Earth. Many glaciers from temperate, alpine and seasonal polar climates store water as ice during the colder seasons and release it later in the form of meltwater as warmer summer temperatures cause the glacier to melt, creating a water source that is especially important for plants, animals and human uses when other sources may be scant. Within high altitude and Antarctic environments, the seasonal temperature difference is often not sufficient to release meltwater. |
Glacial bodies larger than 50,000 km2 (19,000 sq mi) are called ice sheets or continental glaciers. Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces. The only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of fresh water, enough that if both melted, global sea levels would rise by over 70 m (230 ft). Portions of an ice sheet or cap that extend into water are called ice shelves; they tend to be thin with limited slopes and reduced velocities. Narrow, fast-moving sections of an ice sheet are called ice streams. In Antarctica, many ice streams drain into large ice shelves. Some drain directly into the sea, often with an ice tongue, like Mertz Glacier. |
Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, Baffin and Ellesmere Islands in Canada, Southeast Alaska, and the Northern and Southern Patagonian Ice Fields. As the ice reaches the sea, pieces break off, or calve, forming icebergs. Most tidewater glaciers calve above sea level, which often results in a tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long cycles of advance and retreat that are much less affected by the climate change than those of other glaciers. |
Thermally, a temperate glacier is at melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below freezing point from the surface to its base, although the surface snowpack may experience seasonal melting. A sub-polar glacier includes both temperate and polar ice, depending on depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is often described by the temperature at its base alone. A cold-based glacier is below freezing at the ice-ground interface, and is thus frozen to the underlying substrate. A warm-based glacier is above or at freezing at the interface, and is able to slide at this contact. This contrast is thought to a large extent to govern the ability of a glacier to effectively erode its bed, as sliding ice promotes plucking at rock from the surface below. Glaciers which are partly cold-based and partly warm-based are known as polythermal. |
Glaciers form where the accumulation of snow and ice exceeds ablation. The area in which a glacier forms is called a cirque (corrie or cwm) - a typically armchair-shaped geological feature (such as a depression between mountains enclosed by arêtes) - which collects and compresses through gravity the snow which falls into it. This snow collects and is compacted by the weight of the snow falling above it forming névé. Further crushing of the individual snowflakes and squeezing the air from the snow turns it into 'glacial ice'. This glacial ice will fill the cirque until it 'overflows' through a geological weakness or vacancy, such as the gap between two mountains. When the mass of snow and ice is sufficiently thick, it begins to move due to a combination of surface slope, gravity and pressure. On steeper slopes, this can occur with as little as 15 m (50 ft) of snow-ice. |
Glaciers are broken into zones based on surface snowpack and melt conditions. The ablation zone is the region where there is a net loss in glacier mass. The equilibrium line separates the ablation zone and the accumulation zone; it is the altitude where the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. The upper part of a glacier, where accumulation exceeds ablation, is called the accumulation zone. In general, the accumulation zone accounts for 60–70% of the glacier's surface area, more if the glacier calves icebergs. Ice in the accumulation zone is deep enough to exert a downward force that erodes underlying rock. After a glacier melts, it often leaves behind a bowl- or amphitheater-shaped depression that ranges in size from large basins like the Great Lakes to smaller mountain depressions known as cirques. |
The top 50 m (160 ft) of a glacier are rigid because they are under low pressure. This upper section is known as the fracture zone and moves mostly as a single unit over the plastically flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in the fracture zone. Crevasses form due to differences in glacier velocity. If two rigid sections of a glacier move at different speeds and directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but in some cases can be 300 m (1,000 ft) or even deeper. Beneath this point, the plasticity of the ice is too great for cracks to form. Intersecting crevasses can create isolated peaks in the ice, called seracs. |
Crevasses can form in several different ways. Transverse crevasses are transverse to flow and form where steeper slopes cause a glacier to accelerate. Longitudinal crevasses form semi-parallel to flow where a glacier expands laterally. Marginal crevasses form from the edge of the glacier, due to the reduction in speed caused by friction of the valley walls. Marginal crevasses are usually largely transverse to flow. Moving glacier ice can sometimes separate from stagnant ice above, forming a bergschrund. Bergschrunds resemble crevasses but are singular features at a glacier's margins. |
Mean speeds vary greatly, but is typically around 1 m (3 ft) per day. There may be no motion in stagnant areas; for example, in parts of Alaska, trees can establish themselves on surface sediment deposits. In other cases, glaciers can move as fast as 20–30 m (70–100 ft) per day, such as in Greenland's Jakobshavn Isbræ (Greenlandic: Sermeq Kujalleq). Velocity increases with increasing slope, increasing thickness, increasing snowfall, increasing longitudinal confinement, increasing basal temperature, increasing meltwater production and reduced bed hardness. |
A few glaciers have periods of very rapid advancement called surges. These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous state. During these surges, the glacier may reach velocities far greater than normal speed. These surges may be caused by failure of the underlying bedrock, the pooling of meltwater at the base of the glacier — perhaps delivered from a supraglacial lake — or the simple accumulation of mass beyond a critical "tipping point". Temporary rates up to 90 m (300 ft) per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath a glacier. |
In glaciated areas where the glacier moves faster than one km per year, glacial earthquakes occur. These are large scale temblors that have seismic magnitudes as high as 6.1. The number of glacial earthquakes in Greenland peaks every year in July, August and September and is increasing over time. In a study using data from January 1993 through October 2005, more events were detected every year since 2002, and twice as many events were recorded in 2005 as there were in any other year. This increase in the numbers of glacial earthquakes in Greenland may be a response to global warming. |
Ogives are alternating wave crests and valleys that appear as dark and light bands of ice on glacier surfaces. They are linked to seasonal motion of glaciers; the width of one dark and one light band generally equals the annual movement of the glacier. Ogives are formed when ice from an icefall is severely broken up, increasing ablation surface area during summer. This creates a swale and space for snow accumulation in the winter, which in turn creates a ridge. Sometimes ogives consist only of undulations or color bands and are described as wave ogives or band ogives. |
Glaciers are present on every continent and approximately fifty countries, excluding those (Australia, South Africa) that have glaciers only on distant subantarctic island territories. Extensive glaciers are found in Antarctica, Chile, Canada, Alaska, Greenland and Iceland. Mountain glaciers are widespread, especially in the Andes, the Himalayas, the Rocky Mountains, the Caucasus, and the Alps. Mainland Australia currently contains no glaciers, although a small glacier on Mount Kosciuszko was present in the last glacial period. In New Guinea, small, rapidly diminishing, glaciers are located on its highest summit massif of Puncak Jaya. Africa has glaciers on Mount Kilimanjaro in Tanzania, on Mount Kenya and in the Rwenzori Mountains. Oceanic islands with glaciers occur on Iceland, Svalbard, New Zealand, Jan Mayen and the subantarctic islands of Marion, Heard, Grande Terre (Kerguelen) and Bouvet. During glacial periods of the Quaternary, Taiwan, Hawaii on Mauna Kea and Tenerife also had large alpine glaciers, while the Faroe and Crozet Islands were completely glaciated. |
The permanent snow cover necessary for glacier formation is affected by factors such as the degree of slope on the land, amount of snowfall and the winds. Glaciers can be found in all latitudes except from 20° to 27° north and south of the equator where the presence of the descending limb of the Hadley circulation lowers precipitation so much that with high insolation snow lines reach above 6,500 m (21,330 ft). Between 19˚N and 19˚S, however, precipitation is higher and the mountains above 5,000 m (16,400 ft) usually have permanent snow. |
Even at high latitudes, glacier formation is not inevitable. Areas of the Arctic, such as Banks Island, and the McMurdo Dry Valleys in Antarctica are considered polar deserts where glaciers cannot form because they receive little snowfall despite the bitter cold. Cold air, unlike warm air, is unable to transport much water vapor. Even during glacial periods of the Quaternary, Manchuria, lowland Siberia, and central and northern Alaska, though extraordinarily cold, had such light snowfall that glaciers could not form. |
Glacial abrasion is commonly characterized by glacial striations. Glaciers produce these when they contain large boulders that carve long scratches in the bedrock. By mapping the direction of the striations, researchers can determine the direction of the glacier's movement. Similar to striations are chatter marks, lines of crescent-shape depressions in the rock underlying a glacier. They are formed by abrasion when boulders in the glacier are repeatedly caught and released as they are dragged along the bedrock. |
Glacial moraines are formed by the deposition of material from a glacier and are exposed after the glacier has retreated. They usually appear as linear mounds of till, a non-sorted mixture of rock, gravel and boulders within a matrix of a fine powdery material. Terminal or end moraines are formed at the foot or terminal end of a glacier. Lateral moraines are formed on the sides of the glacier. Medial moraines are formed when two different glaciers merge and the lateral moraines of each coalesce to form a moraine in the middle of the combined glacier. Less apparent are ground moraines, also called glacial drift, which often blankets the surface underneath the glacier downslope from the equilibrium line. |
Before glaciation, mountain valleys have a characteristic "V" shape, produced by eroding water. During glaciation, these valleys are widened, deepened, and smoothed, forming a "U"-shaped glacial valley. The erosion that creates glacial valleys eliminates the spurs of earth that extend across mountain valleys, creating triangular cliffs called truncated spurs. Within glacial valleys, depressions created by plucking and abrasion can be filled by lakes, called paternoster lakes. If a glacial valley runs into a large body of water, it forms a fjord. |
At the start of a classic valley glacier is a bowl-shaped cirque, which has escarped walls on three sides but is open on the side that descends into the valley. Cirques are where ice begins to accumulate in a glacier. Two glacial cirques may form back to back and erode their backwalls until only a narrow ridge, called an arête is left. This structure may result in a mountain pass. If multiple cirques encircle a single mountain, they create pointed pyramidal peaks; particularly steep examples are called horns. |
Some rock formations in the path of a glacier are sculpted into small hills called roche moutonnée, or "sheepback" rock. Roche moutonnée are elongated, rounded, and asymmetrical bedrock knobs that can be produced by glacier erosion. They range in length from less than a meter to several hundred meters long. Roche moutonnée have a gentle slope on their up-glacier sides and a steep to vertical face on their down-glacier sides. The glacier abrades the smooth slope on the upstream side as it flows along, but tears loose and carries away rock from the downstream side via plucking. |
Large masses, such as ice sheets or glaciers, can depress the crust of the Earth into the mantle. The depression usually totals a third of the ice sheet or glacier's thickness. After the ice sheet or glacier melts, the mantle begins to flow back to its original position, pushing the crust back up. This post-glacial rebound, which proceeds very slowly after the melting of the ice sheet or glacier, is currently occurring in measurable amounts in Scandinavia and the Great Lakes region of North America. |
First recognized in 1900 by Max Planck, it was originally the proportionality constant between the minimal increment of energy, E, of a hypothetical electrically charged oscillator in a cavity that contained black body radiation, and the frequency, f, of its associated electromagnetic wave. In 1905 the value E, the minimal energy increment of a hypothetical oscillator, was theoretically associated by Einstein with a "quantum" or minimal element of the energy of the electromagnetic wave itself. The light quantum behaved in some respects as an electrically neutral particle, as opposed to an electromagnetic wave. It was eventually called the photon. |
Classical statistical mechanics requires the existence of h (but does not define its value). Eventually, following upon Planck's discovery, it was recognized that physical action cannot take on an arbitrary value. Instead, it must be some multiple of a very small quantity, the "quantum of action", now called the Planck constant. Classical physics cannot explain this fact. In many cases, such as for monochromatic light or for atoms, this quantum of action also implies that only certain energy levels are allowed, and values in between are forbidden. |
Equivalently, the smallness of the Planck constant reflects the fact that everyday objects and systems are made of a large number of particles. For example, green light with a wavelength of 555 nanometres (the approximate wavelength to which human eyes are most sensitive) has a frequency of 7014540000000000000♠540 THz (7014540000000000000♠540×1012 Hz). Each photon has an energy E = hf = 6981358000000000000♠3.58×10−19 J. That is a very small amount of energy in terms of everyday experience, but everyday experience is not concerned with individual photons any more than with individual atoms or molecules. An amount of light compatible with everyday experience is the energy of one mole of photons; its energy can be computed by multiplying the photon energy by the Avogadro constant, NA ≈ 7023602200000000000♠6.022×1023 mol−1. The result is that green light of wavelength 555 nm has an energy of 7005216000000000000♠216 kJ/mol, a typical energy of everyday life. |
In the last years of the nineteenth century, Planck was investigating the problem of black-body radiation first posed by Kirchhoff some forty years earlier. It is well known that hot objects glow, and that hotter objects glow brighter than cooler ones. The electromagnetic field obeys laws of motion similarly to a mass on a spring, and can come to thermal equilibrium with hot atoms. The hot object in equilibrium with light absorbs just as much light as it emits. If the object is black, meaning it absorbs all the light that hits it, then its thermal light emission is maximized. |
The assumption that black-body radiation is thermal leads to an accurate prediction: the total amount of emitted energy goes up with the temperature according to a definite rule, the Stefan–Boltzmann law (1879–84). But it was also known that the colour of the light given off by a hot object changes with the temperature, so that "white hot" is hotter than "red hot". Nevertheless, Wilhelm Wien discovered the mathematical relationship between the peaks of the curves at different temperatures, by using the principle of adiabatic invariance. At each different temperature, the curve is moved over by Wien's displacement law (1893). Wien also proposed an approximation for the spectrum of the object, which was correct at high frequencies (short wavelength) but not at low frequencies (long wavelength). It still was not clear why the spectrum of a hot object had the form that it has (see diagram). |
Prior to Planck's work, it had been assumed that the energy of a body could take on any value whatsoever – that it was a continuous variable. The Rayleigh–Jeans law makes close predictions for a narrow range of values at one limit of temperatures, but the results diverge more and more strongly as temperatures increase. To make Planck's law, which correctly predicts blackbody emissions, it was necessary to multiply the classical expression by a complex factor that involves h in both the numerator and the denominator. The influence of h in this complex factor would not disappear if it were set to zero or to any other value. Making an equation out of Planck's law that would reproduce the Rayleigh–Jeans law could not be done by changing the values of h, of the Boltzmann constant, or of any other constant or variable in the equation. In this case the picture given by classical physics is not duplicated by a range of results in the quantum picture. |
The black-body problem was revisited in 1905, when Rayleigh and Jeans (on the one hand) and Einstein (on the other hand) independently proved that classical electromagnetism could never account for the observed spectrum. These proofs are commonly known as the "ultraviolet catastrophe", a name coined by Paul Ehrenfest in 1911. They contributed greatly (along with Einstein's work on the photoelectric effect) to convincing physicists that Planck's postulate of quantized energy levels was more than a mere mathematical formalism. The very first Solvay Conference in 1911 was devoted to "the theory of radiation and quanta". Max Planck received the 1918 Nobel Prize in Physics "in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta". |
The photoelectric effect is the emission of electrons (called "photoelectrons") from a surface when light is shone on it. It was first observed by Alexandre Edmond Becquerel in 1839, although credit is usually reserved for Heinrich Hertz, who published the first thorough investigation in 1887. Another particularly thorough investigation was published by Philipp Lenard in 1902. Einstein's 1905 paper discussing the effect in terms of light quanta would earn him the Nobel Prize in 1921, when his predictions had been confirmed by the experimental work of Robert Andrews Millikan. The Nobel committee awarded the prize for his work on the photo-electric effect, rather than relativity, both because of a bias against purely theoretical physics not grounded in discovery or experiment, and dissent amongst its members as to the actual proof that relativity was real. |
Prior to Einstein's paper, electromagnetic radiation such as visible light was considered to behave as a wave: hence the use of the terms "frequency" and "wavelength" to characterise different types of radiation. The energy transferred by a wave in a given time is called its intensity. The light from a theatre spotlight is more intense than the light from a domestic lightbulb; that is to say that the spotlight gives out more energy per unit time and per unit space(and hence consumes more electricity) than the ordinary bulb, even though the colour of the light might be very similar. Other waves, such as sound or the waves crashing against a seafront, also have their own intensity. However, the energy account of the photoelectric effect didn't seem to agree with the wave description of light. |
The "photoelectrons" emitted as a result of the photoelectric effect have a certain kinetic energy, which can be measured. This kinetic energy (for each photoelectron) is independent of the intensity of the light, but depends linearly on the frequency; and if the frequency is too low (corresponding to a photon energy that is less than the work function of the material), no photoelectrons are emitted at all, unless a plurality of photons, whose energetic sum is greater than the energy of the photoelectrons, acts virtually simultaneously (multiphoton effect) Assuming the frequency is high enough to cause the photoelectric effect, a rise in intensity of the light source causes more photoelectrons to be emitted with the same kinetic energy, rather than the same number of photoelectrons to be emitted with higher kinetic energy. |
Niels Bohr introduced the first quantized model of the atom in 1913, in an attempt to overcome a major shortcoming of Rutherford's classical model. In classical electrodynamics, a charge moving in a circle should radiate electromagnetic radiation. If that charge were to be an electron orbiting a nucleus, the radiation would cause it to lose energy and spiral down into the nucleus. Bohr solved this paradox with explicit reference to Planck's work: an electron in a Bohr atom could only have certain defined energies En |
Bohr also introduced the quantity , now known as the reduced Planck constant, as the quantum of angular momentum. At first, Bohr thought that this was the angular momentum of each electron in an atom: this proved incorrect and, despite developments by Sommerfeld and others, an accurate description of the electron angular momentum proved beyond the Bohr model. The correct quantization rules for electrons – in which the energy reduces to the Bohr model equation in the case of the hydrogen atom – were given by Heisenberg's matrix mechanics in 1925 and the Schrödinger wave equation in 1926: the reduced Planck constant remains the fundamental quantum of angular momentum. In modern terms, if J is the total angular momentum of a system with rotational invariance, and Jz the angular momentum measured along any given direction, these quantities can only take on the values |
where the uncertainty is given as the standard deviation of the measured value from its expected value. There are a number of other such pairs of physically measurable values which obey a similar rule. One example is time vs. energy. The either-or nature of uncertainty forces measurement attempts to choose between trade offs, and given that they are quanta, the trade offs often take the form of either-or (as in Fourier analysis), rather than the compromises and gray areas of time series analysis. |
The Bohr magneton and the nuclear magneton are units which are used to describe the magnetic properties of the electron and atomic nuclei respectively. The Bohr magneton is the magnetic moment which would be expected for an electron if it behaved as a spinning charge according to classical electrodynamics. It is defined in terms of the reduced Planck constant, the elementary charge and the electron mass, all of which depend on the Planck constant: the final dependence on h1/2 (r2 > 0.995) can be found by expanding the variables. |
In principle, the Planck constant could be determined by examining the spectrum of a black-body radiator or the kinetic energy of photoelectrons, and this is how its value was first calculated in the early twentieth century. In practice, these are no longer the most accurate methods. The CODATA value quoted here is based on three watt-balance measurements of KJ2RK and one inter-laboratory determination of the molar volume of silicon, but is mostly determined by a 2007 watt-balance measurement made at the U.S. National Institute of Standards and Technology (NIST). Five other measurements by three different methods were initially considered, but not included in the final refinement as they were too imprecise to affect the result. |
There are both practical and theoretical difficulties in determining h. The practical difficulties can be illustrated by the fact that the two most accurate methods, the watt balance and the X-ray crystal density method, do not appear to agree with one another. The most likely reason is that the measurement uncertainty for one (or both) of the methods has been estimated too low – it is (or they are) not as precise as is currently believed – but for the time being there is no indication which method is at fault. |
The theoretical difficulties arise from the fact that all of the methods except the X-ray crystal density method rely on the theoretical basis of the Josephson effect and the quantum Hall effect. If these theories are slightly inaccurate – though there is no evidence at present to suggest they are – the methods would not give accurate values for the Planck constant. More importantly, the values of the Planck constant obtained in this way cannot be used as tests of the theories without falling into a circular argument. Fortunately, there are other statistical ways of testing the theories, and the theories have yet to be refuted. |
A watt balance is an instrument for comparing two powers, one of which is measured in SI watts and the other of which is measured in conventional electrical units. From the definition of the conventional watt W90, this gives a measure of the product KJ2RK in SI units, where RK is the von Klitzing constant which appears in the quantum Hall effect. If the theoretical treatments of the Josephson effect and the quantum Hall effect are valid, and in particular assuming that RK = h/e2, the measurement of KJ2RK is a direct determination of the Planck constant. |
The gyromagnetic ratio γ is the constant of proportionality between the frequency ν of nuclear magnetic resonance (or electron paramagnetic resonance for electrons) and the applied magnetic field B: ν = γB. It is difficult to measure gyromagnetic ratios precisely because of the difficulties in precisely measuring B, but the value for protons in water at 7002298150000000000♠25 °C is known to better than one part per million. The protons are said to be "shielded" from the applied magnetic field by the electrons in the water molecule, the same effect that gives rise to chemical shift in NMR spectroscopy, and this is indicated by a prime on the symbol for the gyromagnetic ratio, γ′p. The gyromagnetic ratio is related to the shielded proton magnetic moment μ′p, the spin number I (I = 1⁄2 for protons) and the reduced Planck constant. |
A further complication is that the measurement of γ′p involves the measurement of an electric current: this is invariably measured in conventional amperes rather than in SI amperes, so a conversion factor is required. The symbol Γ′p-90 is used for the measured gyromagnetic ratio using conventional electrical units. In addition, there are two methods of measuring the value, a "low-field" method and a "high-field" method, and the conversion factors are different in the two cases. Only the high-field value Γ′p-90(hi) is of interest in determining the Planck constant. |
The Faraday constant F is the charge of one mole of electrons, equal to the Avogadro constant NA multiplied by the elementary charge e. It can be determined by careful electrolysis experiments, measuring the amount of silver dissolved from an electrode in a given time and for a given electric current. In practice, it is measured in conventional electrical units, and so given the symbol F90. Substituting the definitions of NA and e, and converting from conventional electrical units to SI units, gives the relation to the Planck constant. |
The X-ray crystal density method is primarily a method for determining the Avogadro constant NA but as the Avogadro constant is related to the Planck constant it also determines a value for h. The principle behind the method is to determine NA as the ratio between the volume of the unit cell of a crystal, measured by X-ray crystallography, and the molar volume of the substance. Crystals of silicon are used, as they are available in high quality and purity by the technology developed for the semiconductor industry. The unit cell volume is calculated from the spacing between two crystal planes referred to as d220. The molar volume Vm(Si) requires a knowledge of the density of the crystal and the atomic weight of the silicon used. The Planck constant is given by |
There are a number of proposals to redefine certain of the SI base units in terms of fundamental physical constants. This has already been done for the metre, which is defined in terms of a fixed value of the speed of light. The most urgent unit on the list for redefinition is the kilogram, whose value has been fixed for all science (since 1889) by the mass of a small cylinder of platinum–iridium alloy kept in a vault just outside Paris. While nobody knows if the mass of the International Prototype Kilogram has changed since 1889 – the value 1 kg of its mass expressed in kilograms is by definition unchanged and therein lies one of the problems – it is known that over such a timescale the many similar Pt–Ir alloy cylinders kept in national laboratories around the world, have changed their relative mass by several tens of parts per million, however carefully they are stored, and the more so the more they have been taken out and used as mass standards. A change of several tens of micrograms in one kilogram is equivalent to the current uncertainty in the value of the Planck constant in SI units. |
The legal process to change the definition of the kilogram is already underway, but it had been decided that no final decision would be made before the next meeting of the General Conference on Weights and Measures in 2011. (For more detailed information, see kilogram definitions.) The Planck constant is a leading contender to form the basis of the new definition, although not the only one. Possible new definitions include "the mass of a body at rest whose equivalent energy equals the energy of photons whose frequencies sum to 7050135639273999999♠135639274×1042 Hz", or simply "the kilogram is defined so that the Planck constant equals 6966662606895999999♠6.62606896×10−34 J⋅s". |
Comcast Corporation, formerly registered as Comcast Holdings,[note 1] is an American multinational mass media company and is the largest broadcasting and largest cable company in the world by revenue. It is the second largest pay-TV company after the AT&T-DirecTV acquisition, largest cable TV company and largest home Internet service provider in the United States, and the nation's third largest home telephone service provider. Comcast services U.S. residential and commercial customers in 40 states and the District of Columbia. The company's headquarters are located in Philadelphia, Pennsylvania. |
Comcast operates multiple cable-only channels (including E! Entertainment Television, the Golf Channel, and NBCSN), over-the-air national broadcast network channels (NBC and Telemundo), the film production studio Universal Pictures, and Universal Parks & Resorts, with a global total of nearly 200 family entertainment locations and attractions in the U.S. and several other countries including U.A.E., South Korea, Russia and China, with several new locations reportedly planned and being developed for future operation. Comcast also has significant holding in digital distribution (thePlatform). In February 2014 the company agreed to merge with Time Warner Cable in an equity swap deal worth $45.2 billion. Under the terms of the agreement Comcast was to acquire 100% of Time Warner Cable. However, on April 24, 2015, Comcast terminated the agreement. |
Comcast has been criticized for multiple reasons. The company's customer satisfaction often ranks among the lowest in the cable industry. Comcast has violated net neutrality practices in the past; and, despite Comcast's commitment to a narrow definition of net neutrality, critics advocate a definition of which precludes distinction between Comcast's private network services and the rest of the Internet. Critics also point out a lack of competition in the vast majority of Comcast's service area; there is limited competition among cable providers. Given Comcast's negotiating power as a large ISP, some suspect that Comcast could leverage paid peering agreements to unfairly influence end-user connection speeds. Its ownership of both content production (in NBCUniversal) and content distribution (as an ISP) has raised antitrust concerns. These issues, in addition to others, led to Comcast being dubbed "The Worst Company in America" by The Consumerist in 2014 and 2010. |
Comcast is sometimes described as a family business. Brian L. Roberts, Chairman, President, and CEO of Comcast, is son of co-founder Ralph Roberts. Roberts owns or controls just over 1% of all Comcast shares but all of the Class B supervoting shares, which gives him an "undilutable 33% voting power over the company". Legal expert Susan P. Crawford has said this gives him "effective control over its [Comcast's] every step". In 2010, he was one of the highest-paid executives in the United States, with total compensation of about $31 million. |
The company is often criticized by both the media and its own staff for its less upstanding policies regarding employee relations. A 2012 Reddit post written by an anonymous Comcast call center employee eager to share their negative experiences with the public received attention from publications including The Huffington Post. A 2014 investigative series published by The Verge involved interviews with 150 of Comcast's employees. It sought to examine why the company has become so widely criticized by its customers, the media and even members of its own staff. The series claimed part of the problem is internal and that Comcast's staff endures unreasonable corporate policies. According to the report: "customer service has been replaced by an obsession with sales; technicians are understaffed while tech support is poorly trained; and the company is hobbled by internal fragmentation." A widely read article penned by an anonymous call center employee working for Comcast appeared in November 2014 on Cracked. Titled "Five Nightmares You Live While Working For America's Worst Company," the article also claimed that Comcast is obsessed with sales, doesn't train its employees properly and concluded that "the system makes good customer service impossible." |
Comcast has also earned a reputation for being anti-union. According to one of the company's training manuals, "Comcast does not feel union representation is in the best interest of its employees, customers, or shareholders". A dispute in 2004 with CWA, a labor union that represented many employees at Comcast's offices in Beaverton, Oregon, led to allegations of management intimidating workers, requiring them to attend anti-union meetings and unwarranted disciplinary action for union members. In 2011, Comcast received criticism from Writers Guild of America for its policies in regards to unions. |
Despite these criticisms, Comcast has appeared on multiple "top places to work" lists. In 2009, it was included on CableFAX magazine's "Top 10 Places to Work in Cable", which cited its "scale, savvy and vision". Similarly, the Philadelphia Business Journal awarded Comcast the silver medal among extra-large companies in Philadelphia, with the gold medal going to partner organization, Comcast-Spectacor. The Boston Globe found Comcast to be that city's top place to work in 2009. Employee diversity is also an attribute upon which Comcast receives strong marks. In 2008, Black Enterprise magazine rated Comcast among the top 15 companies for workforce diversity. Comcast was also named a "Top 2014 Workplace" by the Washington Post in their annual feature. |
The book value of the company nearly doubled from $8.19 a share in 1999 to $15 a share in 2009. Revenues grew sixfold from 1999's $6 billion to almost $36 billion in 2009. Net profit margin rose from 4.2% in 1999 to 8.4% in 2009, with operating margins improving 31 percent and return on equity doubling to 6.7 percent in the same time span. Between 1999 and 2009, return on capital nearly tripled to 7 percent. Comcast reported first quarter 2012 profit increases of 30% due to increase in high-speed internet customers. In February 2014, Comcast generated 1.1 billion in revenue during the first quarter due to the Sochi Olympics,. |
With $18.8 million spent in 2013, Comcast has the seventh largest lobbying budget of any individual company or organization in the United States. Comcast employs multiple former US Congressmen as lobbyists. The National Cable & Telecommunications Association, which has multiple Comcast executives on its board, also represents Comcast and other cable companies as the fifth largest lobbying organization in the United States, spending $19.8 million in 2013. Comcast was among the top backers of Barack Obama's presidential runs, with Comcast vice president David Cohen raising over $2.2 million from 2007 to 2012. Cohen has been described by many sources as influential in the US government, though he is no longer a registered lobbyist, as the time he spends lobbying falls short of the 20% which requires official registration. Comcast's PAC, the Comcast Corporation and NBCUniversal Political Action Committee, is the among the largest PACs in the US, raising about $3.7 million from 2011-2012 for the campaigns of various candidates for office in the United States Federal Government. Comcast is also a major backer of the National Cable and Telecommunications Association Political Action Committee, which raised $2.6 million from 2011-2012. Comcast spent the most money of any organization in support of the Stop Online Piracy and PROTECT IP bills, spending roughly $5 million to lobby for their passage. |
In 1963, Ralph J. Roberts in conjunction with his two business partners, Daniel Aaron and Julian A. Brodsky, purchased American Cable Systems as a corporate spin-off from its parent, Jerrold Electronics, for US $500,000. At the time, American Cable was a small cable operator in Tupelo, Mississippi, with five channels and 12,000 customers. Storecast Corporation of America, a product placement supermarket specialist marketing firm, was purchased by American Cable in 1965. With Storecast being a Muzak client, American Cable purchased its first Muzak franchise of many in Orlando, Florida. |
In 1994, Comcast became the third largest cable operator in the United States with around 3.5 million subscribers following its purchase of Maclean-Hunter's American division for $1.27 billion. The company's UK branch, Comcast UK Cable Partners, goes public while constructing a cable telecommunications network. With five other media companies, the corporation becomes an original investor in The Golf Channel. Following a bid in 1994 for $2.1 billion, Comcast increased its ownership of QVC from 15.5% of stock to a majority, in a move to prevent QVC from merging with CBS. Comcast later sold its QVC shares in 2004 to Liberty Media for $7.9 billion. |
Comcast sold Comcast Cellular to SBC Communications in 1999 for $400 million, releasing them from $1.27 billion in debt. Comcast acquired Greater Philadelphia Cablevision in 1999. In March 1999, Comcast offered to buy MediaOne for $60 billion. However, MediaOne decided to accept AT&T Corporation's offer of $62 billion instead. Comcast University started in 1999 as well as Comcast Interactive Capital Group to make technology and Internet related investments taking its first investment in VeriSign. |
In 2001, Comcast announced it would acquire the assets of the largest cable television operator at the time, AT&T Broadband, for US$44.5 billion. The proposed name for the merged company was "AT&T Comcast", but the companies ultimately decided to keep only the Comcast name. In 2002, Comcast acquired all assets of AT&T Broadband, thus making Comcast the largest cable television company in the United States with over 22 million subscribers. This also spurred the start of Comcast Advertising Sales (using AT&T's groundwork) which would later be renamed Comcast Spotlight. As part of this acquisition, Comcast also acquired the National Digital Television Center in Centennial, Colorado as a wholly owned subsidiary, which is today known as the Comcast Media Center. |
On February 11, 2004, Comcast announced a $54 billion bid for The Walt Disney Company, as well as taking on $12 billion of Disney's debt. The deal would have made Comcast the largest media conglomerate in the world. However, after rejection by Disney and uncertain response from investors, the bid was abandoned in April. The main reason for the buyout attempt was so that Comcast could acquire Disney's 80 percent stake in ESPN, which a Comcast executive called "the most important and valuable asset" that Disney owned. |
On April 8, 2005, a partnership led by Comcast and Sony Pictures Entertainment finalized a deal to acquire MGM and its affiliate studio, United Artists, and create an additional outlet to carry MGM/UA's material for cable and Internet distribution. On October 31, 2005, Comcast officially announced that it had acquired Susquehanna Communications a South Central Pennsylvania, -based cable television and broadband services provider and unit of the former Susquehanna Pfaltzgraff company, for $775 million cash. In this deal Comcast acquired approximately 230,000 basic cable customers, 71,000 digital cable customers, and 86,000 high-speed Internet customers. Comcast previously owned approximately 30 percent of Susquehanna Communications through affiliate company Lenfest. In December 2005, Comcast announced the creation of Comcast Interactive Media, a new division focused on online media. |
Comcast announced in May 2007 and launched in September 2008 a dashboard called SmartZone. Hewlett-Packard led "design, creation and management". Collaboration and unified messaging technology came from open-source vendor Zimbra. "SmartZone users will be able to send and receive e-mail, listen to their voicemail messages online and forward that information via e-mail to others, send instant messages and video instant messages and merge their contacts into one address book". There is also Cloudmark spam and phishing protection and Trend Micro antivirus. The address book is Comcast Plaxo software. |
In April 2005, Comcast and Time Warner Cable announced plans to buy the assets of bankrupted Adelphia Cable. The two companies paid a total of $17.6 billion in the deal that was finalized in the second quarter of 2006—after the U.S. Federal Communications Commission (FCC) completed a seven-month investigation without raising an objection. Time Warner Cable became the second largest cable provider in the U.S., ranking behind Comcast. As part of the deal, Time Warner and Comcast traded existing subscribers in order to consolidate them into larger geographic clusters. |
Media outlets began reporting in late September 2009 that Comcast was in talks to buy NBCUniversal. Comcast denied the rumors at first, while NBC would not comment on them. However, CNBC itself reported on October 1 that General Electric was considering spinning NBCUniversal off into a separate company that would merge the NBC television network and its cable properties such as USA Network, Syfy and MSNBC with Comcast's content assets. GE would maintain 49% control of the new company, while Comcast owned 51%. Vivendi, which owns 20%, would have to sell its stake to GE. It was reported that under the current deal with GE that it would happen in November or December. It was also reported that Time Warner would be interested in placing a bid, until CEO Jeffrey L. Bewkes directly denied interest, leaving Comcast the sole bidder. On November 1, 2009, The New York Times reported Comcast had moved closer to a deal to purchase NBCUniversal and that a formal announcement could be made sometime the following week. |
Following a tentative agreement on by December 1, on December 3, 2009, the parties announced that Comcast would buy a controlling 51% stake in NBCUniversal for $6.5 billion in cash and $7.3 billion in programming. GE would take over the remaining 49% stake in NBCUniversal, using $5.8 billion to buy out Vivendi's 20% minority stake in NBCUniversal. On January 18, 2011, the FCC approved the deal by a vote of 4 to 1. The sale was completed on January 28, 2011. In late December 2012, Comcast added the NBC peacock symbol to their new logo. On February 12, 2013, Comcast announced an intention to acquire the remaining 49% of General Electric's interest in NBCUniversal, which Comcast completed on March 19, 2013. |
On February 12, 2014, the Los Angeles Times reported that Comcast sought to acquire Time Warner Cable in a deal valued at $45.2 billion. On February 13, it was reported that Time Warner Cable agreed to the acquisition. This was to add several metropolitan areas to the Comcast portfolio, such as New York City, Los Angeles, Dallas-Fort Worth, Cleveland, Columbus, Cincinnati, Charlotte, San Diego, and San Antonio. Time Warner Cable and Comcast aimed to merge into one company by the end of 2014 and both have praised the deal, emphasizing the increased capabilities of a combined telecommunications network, and to "create operating efficiencies and economies of scale". |
Critics noted in 2013 that Tom Wheeler, the head of the FCC, which has to approve the deal, is the former head of both the largest cable lobbying organization, the National Cable & Telecommunications Association, and as largest wireless lobby, CTIA – The Wireless Association. According to Politico, Comcast "donated to almost every member of Congress who has a hand in regulating it." The US Senate Judiciary Committee held a hearing on the deal on April 9, 2014. The House Judiciary Committee planned its own hearing. On March 6, 2014 the United States Department of Justice Antitrust Division confirmed it was investigating the deal. In March 2014, the division's chairman, William Baer, recused himself because he was involved in a prior Comcast NBCUniversal acquisition. Several states' attorneys general have announced support for the federal investigation. On April 24, 2015, Jonathan Sallet, general counsel of the F.C.C., said that he was going to recommend a hearing before an administrative law judge, equivalent to a collapse of the deal. |
Comcast delivers third-party television programming content to its own customers, and also produces its own first-party content both for subscribers and customers of other competing television services. Fully or partially owned Comcast programming includes Comcast Newsmakers, Comcast Network, Comcast SportsNet, SportsNet New York, MLB Network, Comcast Sports Southeast/Charter Sports Southeast, NBC Sports Network, The Golf Channel, AZN Television, and FEARnet. On May 19, 2009, Disney and ESPN announced an agreement to allow Comcast Corporation to carry the channels ESPNU and ESPN3. The U.S. Olympic Committee and Comcast intended to team up to create The U.S. Olympic Network, which was slated to launch after the 2010 Vancouver Olympic Games. These plans were then put on hold by the U.S. Olympic Committee. The U.S. Olympic Committee and Comcast have ended the plans to create The U.S. Olympic Network. |
Comcast also owns many local channels. Comcast also has a variety network known as Comcast Network, available exclusively to Comcast and Cablevision subscribers. The channel shows news, sports, and entertainment and places emphasis in Philadelphia and the Baltimore/Washington, D.C. areas, though the channel is also available in New York, Pittsburgh, and Richmond. In August 2004, Comcast started a channel called Comcast Entertainment Television, for Colorado Comcast subscribers, and focusing on life in Colorado. It also carries some National Hockey League and National Basketball Association games when Altitude Sports & Entertainment is carrying the NHL or NBA. In January 2006, CET became the primary channel for Colorado's Emergency Alert System in the Denver Metro Area. In 2006, Comcast helped found the channel SportsNet New York, acquiring a minority stake. The other partners in the project were New York Mets and Time Warner Cable. |
In 1996, Comcast bought a controlling stake in Spectacor from the company's founder, Ed Snider. Comcast-Spectacor holdings now include the Philadelphia Flyers NHL hockey team, the Philadelphia 76ers National Basketball Association basketball team and two large multipurpose arenas in Philadelphia. Over a number of years, Comcast became majority owner of Comcast SportsNet, as well as Golf Channel and NBCSN (formerly the Outdoor Life Network, then Versus). In 2002, Comcast paid the University of Maryland $25 million for naming rights to the new basketball arena built on the College Park campus, the XFINITY Center. Before it was renamed for Comcast's cable subsidiary, XFINITY Center was called Comcast Center from its opening in 2002 through July 2014. |
In 2004 and 2007, the American Customer Satisfaction Index (ACSI) survey found that Comcast had the worst customer satisfaction rating of any company or government agency in the country, including the Internal Revenue Service. The ACSI indicates that almost half of all cable customers (regardless of company) have registered complaints, and that cable is the only industry to score below 60 in the ACSI. Comcast's Customer Service Rating by the ACSI surveys indicate that the company's customer service has not improved since the surveys began in 2001. Analysis of the surveys states that "Comcast is one of the lowest scoring companies in ACSI. As its customer satisfaction eroded by 7% over the past year, revenue increased by 12%." The ACSI analysis also addresses this contradiction, stating that "Such pricing power usually comes with some level of monopoly protection and most cable companies have little competition at the local level. This also means that a cable company can do well financially even though its customers are not particularly satisfied." |
Comcast was given an "F" for its corporate governance practices in 2010, by Corporate Library, an independent shareholder-research organization. According to Corporate Library, Comcast's board of directors ability to oversee and control management was severely compromised (at least in 2010) by the fact that several of the directors either worked for the company or had business ties to it (making them susceptible to management pressure), and a third of the directors were over 70 years of age. According to the Wall Street Journal nearly two-thirds of the flights of Comcast's $40 million corporate jet purchased for business travel related to the NBCU acquisition, were to CEO Brian Roberts' private homes or to resorts. |
In January 2015, a customer named Ricardo Brown received a bill from Comcast with his name changed to "Asshole Brown". Brown's wife, Lisa, believed a Comcast employee changed the name in response to the Browns' request to cancel their cable service, an incident in which she was refused a cancellation unless she paid a $60 fee and instead was routed to a retention specialist. Comcast refused to correct the name on their bill after bringing it to the attention of numerous customer service outlets for the company by explaining that Ricardo is the legal name of the customer, so the Browns turned to consumer advocate Christopher Elliott. Elliott posted the facts of the incident, along with a copy of the bill, on his blog. Shortly thereafter, Elliott contacted Comcast and Comcast offered the Browns an apology, a $60 refund, and a promise to track down and fire the responsible employee. The Browns instead requested a full refund for their negative experience and Comcast agreed to refund the family the last two years of service and provide the next two years of service at no charge. Comcast released a statement explaining: "We have spoken with our customer and apologized for this completely unacceptable and inappropriate name change. We have zero tolerance for this type of disrespectful behavior and are conducting a thorough investigation to determine what happened. We are working with our customer to make this right and will take appropriate steps to prevent this from happening again." |
Tuberculosis (TB) is an infectious disease usually caused by the bacterium Mycobacterium tuberculosis (MTB). Tuberculosis generally affects the lungs, but can also affect other parts of the body. Most infections do not have symptoms, known as latent tuberculosis. About 10% of latent infections progress to active disease which, if left untreated, kills about half of those infected. The classic symptoms of active TB are a chronic cough with blood-containing sputum, fever, night sweats, and weight loss. The historical term "consumption" came about due to the weight loss. Infection of other organs can cause a wide range of symptoms. |
One-third of the world's population is thought to be infected with TB. New infections occur in about 1% of the population each year. In 2014, there were 9.6 million cases of active TB which resulted in 1.5 million deaths. More than 95% of deaths occurred in developing countries. The number of new cases each year has decreased since 2000. About 80% of people in many Asian and African countries test positive while 5–10% of people in the United States population tests positive by the tuberculin test. Tuberculosis has been present in humans since ancient times. |
If a tuberculosis infection does become active, it most commonly involves the lungs (in about 90% of cases). Symptoms may include chest pain and a prolonged cough producing sputum. About 25% of people may not have any symptoms (i.e. they remain "asymptomatic"). Occasionally, people may cough up blood in small amounts, and in very rare cases, the infection may erode into the pulmonary artery or a Rasmussen's aneurysm, resulting in massive bleeding. Tuberculosis may become a chronic illness and cause extensive scarring in the upper lobes of the lungs. The upper lung lobes are more frequently affected by tuberculosis than the lower ones. The reason for this difference is not clear. It may be due either to better air flow, or to poor lymph drainage within the upper lungs. |
In 15–20% of active cases, the infection spreads outside the lungs, causing other kinds of TB. These are collectively denoted as "extrapulmonary tuberculosis". Extrapulmonary TB occurs more commonly in immunosuppressed persons and young children. In those with HIV, this occurs in more than 50% of cases. Notable extrapulmonary infection sites include the pleura (in tuberculous pleurisy), the central nervous system (in tuberculous meningitis), the lymphatic system (in scrofula of the neck), the genitourinary system (in urogenital tuberculosis), and the bones and joints (in Pott disease of the spine), among others. When it spreads to the bones, it is also known as "osseous tuberculosis", a form of osteomyelitis. Sometimes, bursting of a tubercular abscess through skin results in tuberculous ulcer. An ulcer originating from nearby infected lymph nodes is painless, slowly enlarging and has an appearance of "wash leather". A potentially more serious, widespread form of TB is called "disseminated tuberculosis", also known as miliary tuberculosis. Miliary TB makes up about 10% of extrapulmonary cases. |
The main cause of TB is Mycobacterium tuberculosis, a small, aerobic, nonmotile bacillus. The high lipid content of this pathogen accounts for many of its unique clinical characteristics. It divides every 16 to 20 hours, which is an extremely slow rate compared with other bacteria, which usually divide in less than an hour. Mycobacteria have an outer membrane lipid bilayer. If a Gram stain is performed, MTB either stains very weakly "Gram-positive" or does not retain dye as a result of the high lipid and mycolic acid content of its cell wall. MTB can withstand weak disinfectants and survive in a dry state for weeks. In nature, the bacterium can grow only within the cells of a host organism, but M. tuberculosis can be cultured in the laboratory. |
Using histological stains on expectorated samples from phlegm (also called "sputum"), scientists can identify MTB under a microscope. Since MTB retains certain stains even after being treated with acidic solution, it is classified as an acid-fast bacillus. The most common acid-fast staining techniques are the Ziehl–Neelsen stain and the Kinyoun stain, which dye acid-fast bacilli a bright red that stands out against a blue background. Auramine-rhodamine staining and fluorescence microscopy are also used. |
The M. tuberculosis complex (MTBC) includes four other TB-causing mycobacteria: M. bovis, M. africanum, M. canetti, and M. microti. M. africanum is not widespread, but it is a significant cause of tuberculosis in parts of Africa. M. bovis was once a common cause of tuberculosis, but the introduction of pasteurized milk has almost completely eliminated this as a public health problem in developed countries. M. canetti is rare and seems to be limited to the Horn of Africa, although a few cases have been seen in African emigrants. M. microti is also rare and is seen almost only in immunodeficient people, although its prevalence may be significantly underestimated. |
People with prolonged, frequent, or close contact with people with TB are at particularly high risk of becoming infected, with an estimated 22% infection rate. A person with active but untreated tuberculosis may infect 10–15 (or more) other people per year. Transmission should occur from only people with active TB – those with latent infection are not thought to be contagious. The probability of transmission from one person to another depends upon several factors, including the number of infectious droplets expelled by the carrier, the effectiveness of ventilation, the duration of exposure, the virulence of the M. tuberculosis strain, the level of immunity in the uninfected person, and others. The cascade of person-to-person spread can be circumvented by segregating those with active ("overt") TB and putting them on anti-TB drug regimens. After about two weeks of effective treatment, subjects with nonresistant active infections generally do not remain contagious to others. If someone does become infected, it typically takes three to four weeks before the newly infected person becomes infectious enough to transmit the disease to others. |
TB infection begins when the mycobacteria reach the pulmonary alveoli, where they invade and replicate within endosomes of alveolar macrophages. Macrophages identify the bacterium as foreign and attempt to eliminate it by phagocytosis. During this process, the bacterium is enveloped by the macrophage and stored temporarily in a membrane-bound vesicle called a phagosome. The phagosome then combines with a lysosome to create a phagolysosome. In the phagolysosome, the cell attempts to use reactive oxygen species and acid to kill the bacterium. However, M. tuberculosis has a thick, waxy mycolic acid capsule that protects it from these toxic substances. M. tuberculosis is able to reproduce inside the macrophage and will eventually kill the immune cell. |
The primary site of infection in the lungs, known as the "Ghon focus", is generally located in either the upper part of the lower lobe, or the lower part of the upper lobe. Tuberculosis of the lungs may also occur via infection from the blood stream. This is known as a Simon focus and is typically found in the top of the lung. This hematogenous transmission can also spread infection to more distant sites, such as peripheral lymph nodes, the kidneys, the brain, and the bones. All parts of the body can be affected by the disease, though for unknown reasons it rarely affects the heart, skeletal muscles, pancreas, or thyroid. |
Tuberculosis is classified as one of the granulomatous inflammatory diseases. Macrophages, T lymphocytes, B lymphocytes, and fibroblasts aggregate to form granulomas, with lymphocytes surrounding the infected macrophages. When other macrophages attack the infected macrophage, they fuse together to form a giant multinucleated cell in the alveolar lumen. The granuloma may prevent dissemination of the mycobacteria and provide a local environment for interaction of cells of the immune system. However, more recent evidence suggests that the bacteria use the granulomas to avoid destruction by the host's immune system. Macrophages and dendritic cells in the granulomas are unable to present antigen to lymphocytes; thus the immune response is suppressed. Bacteria inside the granuloma can become dormant, resulting in latent infection. Another feature of the granulomas is the development of abnormal cell death (necrosis) in the center of tubercles. To the naked eye, this has the texture of soft, white cheese and is termed caseous necrosis. |
In many people, the infection waxes and wanes. Tissue destruction and necrosis are often balanced by healing and fibrosis. Affected tissue is replaced by scarring and cavities filled with caseous necrotic material. During active disease, some of these cavities are joined to the air passages bronchi and this material can be coughed up. It contains living bacteria, so can spread the infection. Treatment with appropriate antibiotics kills bacteria and allows healing to take place. Upon cure, affected areas are eventually replaced by scar tissue. |
Diagnosing active tuberculosis based only on signs and symptoms is difficult, as is diagnosing the disease in those who are immunosuppressed. A diagnosis of TB should, however, be considered in those with signs of lung disease or constitutional symptoms lasting longer than two weeks. A chest X-ray and multiple sputum cultures for acid-fast bacilli are typically part of the initial evaluation. Interferon-γ release assays and tuberculin skin tests are of little use in the developing world. IGRA have similar limitations in those with HIV. |
The Mantoux tuberculin skin test is often used to screen people at high risk for TB. Those who have been previously immunized may have a false-positive test result. The test may be falsely negative in those with sarcoidosis, Hodgkin's lymphoma, malnutrition, and most notably, active tuberculosis. Interferon gamma release assays (IGRAs), on a blood sample, are recommended in those who are positive to the Mantoux test. These are not affected by immunization or most environmental mycobacteria, so they generate fewer false-positive results. However, they are affected by M. szulgai, M. marinum, and M. kansasii. IGRAs may increase sensitivity when used in addition to the skin test, but may be less sensitive than the skin test when used alone. |
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