Split (1)

train · 367k rows

text stringlengths 9 2.4k
In 1999, CERN activated the Antiproton Decelerator, a device capable of decelerating antiprotons from to – still too "hot" to produce study-effective antihydrogen, but a huge leap forward. In late 2002 the ATHENA project announced that they had created the world's first "cold" antihydrogen. The ATRAP project released similar results very shortly thereafter. The antiprotons used in these experiments were cooled by decelerating them with the Antiproton Decelerator, passing them through a thin sheet of foil, and finally capturing them in a Penning–Malmberg trap. The overall cooling process is workable, but highly inefficient; approximately 25 million antiprotons leave the Antiproton Decelerator and roughly 25,000 make it to the Penning–Malmberg trap, which is about or 0.1% of the original amount. The antiprotons are still hot when initially trapped. To cool them further, they are mixed into an electron plasma. The electrons in this plasma cool via cyclotron radiation, and then sympathetically cool the antiprotons via Coulomb collisions. Eventually, the electrons are removed by the application of short-duration electric fields, leaving the antiprotons with energies less than . While the antiprotons are being cooled in the first trap, a small cloud of positrons is captured from radioactive sodium in a Surko-style positron accumulator. This cloud is then recaptured in a second trap near the antiprotons. Manipulations of the trap electrodes then tip the antiprotons into the positron plasma, where some combine with antiprotons to form antihydrogen. This neutral antihydrogen is unaffected by the electric and magnetic fields used to trap the charged positrons and antiprotons, and within a few microseconds the antihydrogen hits the trap walls, where it annihilates. Some hundreds of millions of antihydrogen atoms have been made in this fashion.
In 2005, ATHENA disbanded and some of the former members (along with others) formed the ALPHA Collaboration, which is also based at CERN. The ultimate goal of this endeavour is to test CPT symmetry through comparison of the atomic spectra of hydrogen and antihydrogen (see hydrogen spectral series). Most of the sought-after high-precision tests of the properties of antihydrogen could only be performed if the antihydrogen were trapped, that is, held in place for a relatively long time. While antihydrogen atoms are electrically neutral, the spins of their component particles produce a magnetic moment. These magnetic moments can interact with an inhomogeneous magnetic field; some of the antihydrogen atoms can be attracted to a magnetic minimum. Such a minimum can be created by a combination of mirror and multipole fields. Antihydrogen can be trapped in such a magnetic minimum (minimum-B) trap; in November 2010, the ALPHA collaboration announced that they had so trapped 38 antihydrogen atoms for about a sixth of a second. This was the first time that neutral antimatter had been trapped.
On 26 April 2011, ALPHA announced that they had trapped 309 antihydrogen atoms, some for as long as 1,000 seconds (about 17 minutes). This was longer than neutral antimatter had ever been trapped before. ALPHA has used these trapped atoms to initiate research into the spectral properties of antihydrogen. In 2016, a new antiproton decelerator and cooler called ELENA (Extra Low ENergy Antiproton decelerator) was built. It takes the antiprotons from the antiproton decelerator and cools them to 90 keV, which is "cold" enough to study. This machine works by using high energy and accelerating the particles within the chamber. More than one hundred antiprotons can be captured per second, a huge improvement, but it would still take several thousand years to make a nanogram of antimatter. The biggest limiting factor in the large-scale production of antimatter is the availability of antiprotons. Recent data released by CERN states that, when fully operational, their facilities are capable of producing ten million antiprotons per minute. Assuming a 100% conversion of antiprotons to antihydrogen, it would take 100 billion years to produce 1 gram or 1 mole of antihydrogen (approximately atoms of anti-hydrogen). However, CERN only produces 1% of the anti-matter Fermilab does, and neither are designed to produce anti-matter. According to Gerald Jackson, using technology already in use today we are capable of producing and capturing 20 grams of anti-matter particles per year at a yearly cost of 670 million dollars per facility.
Antihelium. Antihelium-3 nuclei () were first observed in the 1970s in proton–nucleus collision experiments at the Institute for High Energy Physics by Y. Prockoshkin's group (Protvino near Moscow, USSR) and later created in nucleus–nucleus collision experiments. Nucleus–nucleus collisions produce antinuclei through the coalescence of antiprotons and antineutrons created in these reactions. In 2011, the STAR detector reported the observation of artificially created antihelium-4 nuclei (anti-alpha particles) () from such collisions. The Alpha Magnetic Spectrometer on the International Space Station has, as of 2021, recorded eight events that seem to indicate the detection of antihelium-3. Preservation. Antimatter cannot be stored in a container made of ordinary matter because antimatter reacts with any matter it touches, annihilating itself and an equal amount of the container. Antimatter in the form of charged particles can be contained by a combination of electric and magnetic fields, in a device called a Penning trap. This device cannot, however, contain antimatter that consists of uncharged particles, for which atomic traps are used. In particular, such a trap may use the dipole moment (electric or magnetic) of the trapped particles. At high vacuum, the matter or antimatter particles can be trapped and cooled with slightly off-resonant laser radiation using a magneto-optical trap or magnetic trap. Small particles can also be suspended with optical tweezers, using a highly focused laser beam.
In 2011, CERN scientists were able to preserve antihydrogen for approximately 17 minutes. The record for storing antiparticles is currently held by the TRAP experiment at CERN: antiprotons were kept in a Penning trap for 405 days. A proposal was made in 2018 to develop containment technology advanced enough to contain a billion anti-protons in a portable device to be driven to another lab for further experimentation. Cost. Scientists claim that antimatter is the costliest material to make. In 2006, Gerald Smith estimated $250 million could produce 10 milligrams of positrons (equivalent to $25 billion per gram); in 1999, NASA gave a figure of $62.5 trillion per gram of antihydrogen. This is because production is difficult (only very few antiprotons are produced in reactions in particle accelerators) and because there is higher demand for other uses of particle accelerators. According to CERN, it has cost a few hundred million Swiss francs to produce about 1 billionth of a gram (the amount used so far for particle/antiparticle collisions). In comparison, to produce the first atomic weapon, the cost of the Manhattan Project was estimated at $23 billion with inflation during 2007.
Several studies funded by NASA Innovative Advanced Concepts are exploring whether it might be possible to use magnetic scoops to collect the antimatter that occurs naturally in the Van Allen belt of the Earth, and ultimately the belts of gas giants like Jupiter, ideally at a lower cost per gram. Uses. Medical. Matter–antimatter reactions have practical applications in medical imaging, such as positron emission tomography (PET). In positive beta decay, a nuclide loses surplus positive charge by emitting a positron (in the same event, a proton becomes a neutron, and a neutrino is also emitted). Nuclides with surplus positive charge are easily made in a cyclotron and are widely generated for medical use. Antiprotons have also been shown within laboratory experiments to have the potential to treat certain cancers, in a similar method currently used for ion (proton) therapy. Fuel. Isolated and stored antimatter could be used as a fuel for interplanetary or interstellar travel as part of an antimatter-catalyzed nuclear pulse propulsion or another antimatter rocket. Since the energy density of antimatter is higher than that of conventional fuels, an antimatter-fueled spacecraft would have a higher thrust-to-weight ratio than a conventional spacecraft.
If matter–antimatter collisions resulted only in photon emission, the entire rest mass of the particles would be converted to kinetic energy. The energy per unit mass () is about 10 orders of magnitude greater than chemical energies, and about 3 orders of magnitude greater than the nuclear potential energy that can be liberated, today, using nuclear fission (about per fission reaction or ), and about 2 orders of magnitude greater than the best possible results expected from fusion (about for the proton–proton chain). The reaction of of antimatter with of matter would produce (180 petajoules) of energy (by the mass–energy equivalence formula, ), or the rough equivalent of 43 megatons of TNT – slightly less than the yield of the 27,000 kg Tsar Bomba, the largest thermonuclear weapon ever detonated. Not all of that energy can be utilized by any realistic propulsion technology because of the nature of the annihilation products. While electron–positron reactions result in gamma ray photons, these are difficult to direct and use for thrust. In reactions between protons and antiprotons, their energy is converted largely into relativistic neutral and charged pions. The neutral pions decay almost immediately (with a lifetime of 85 attoseconds) into high-energy photons, but the charged pions decay more slowly (with a lifetime of 26 nanoseconds) and can be deflected magnetically to produce thrust.
Charged pions ultimately decay into a combination of neutrinos (carrying about 22% of the energy of the charged pions) and unstable charged muons (carrying about 78% of the charged pion energy), with the muons then decaying into a combination of electrons, positrons and neutrinos (cf. muon decay; the neutrinos from this decay carry about 2/3 of the energy of the muons, meaning that from the original charged pions, the total fraction of their energy converted to neutrinos by one route or another would be about ). Weapons. Antimatter has been considered as a trigger mechanism for nuclear weapons. A major obstacle is the difficulty of producing antimatter in large enough quantities, and there is no evidence that it will ever be feasible. Nonetheless, the U.S. Air Force funded studies of the physics of antimatter in the Cold War, and began considering its possible use in weapons, not just as a trigger, but as the explosive itself.
Casa Batlló () is a building in the center of Barcelona, Spain. It was designed by Antoni Gaudí, and is considered one of his masterpieces. A remodel of a previously built house, it was redesigned in 1904 by Gaudí (but the actual construction works hadn’t begun at this point) and has been refurbished several times since. Gaudí's assistants Domènec Sugrañes i Gras, Josep Canaleta and Joan Rubió also contributed to the renovation project. The local name for the building is "" (House of Bones), as it has a visceral, skeletal organic quality. It is located on the in the Eixample district, and forms part of a row of houses known as the (or , the "Block of Discord"), which consists of four buildings by noted architects of Barcelona. Like everything Gaudí designed, is only identifiable as in the broadest sense. The ground floor, in particular, has unusual tracery, irregular oval windows and flowing sculpted stone work. There are few straight lines, and much of the façade is decorated with a colorful mosaic made of broken ceramic tiles (). The roof is arched and was likened to the back of a dragon or dinosaur. A common theory about the building is that the rounded feature to the left of centre, terminating at the top in a turret and cross, represents the lance of Saint George (patron saint of Catalonia, Gaudí's home), which has been plunged into the back of the dragon.
In 2005, became an UNESCO World Heritage Site. History. Initial construction (1877). The building that is now was built in 1877, commissioned by Lluís Sala Sánchez. It was a classical building without remarkable characteristics within the eclecticism traditional by the end of the 19th century. The building had a basement, a ground floor, four other floors and a garden in the back. Batlló family. The house was bought by Josep Batlló in 1903. The design of the house made the home undesirable to buyers but the Batlló family decided to buy the place due to its centralized location. It is located in the middle of , which in the early 20th century was known as a very prestigious and fashionable area. It was an area where the prestigious family could draw attention to themselves. In 1906, Josep Batlló still owned the home. The Batlló family was very well known in Barcelona for its contribution to the textile industry in the city. Josep Batlló i Casanovas was a textile industrialist who owned a few factories in the city. Batlló married Amàlia Godó Belaunzarán, from the family that founded the newspaper "La Vanguardia". Josep wanted an architect that would design a house that was like no other and stood out as being audacious and creative. Both Josep and his wife were open to anything and they decided not to limit Gaudí. Josep did not want his house to resemble any of the houses of the rest of the Batlló family, such as Casa Pía, built by the Josep Vilaseca. He chose the architect who had designed Park Güell because he wanted him to come up with a risky plan. The family lived on the principal floor of until the middle of the 1950s.
Renovation (1904-1906). In 1904, Josep Batlló hired Gaudí to design his home; at first his plans were to tear down the building and construct a completely new house. Gaudí convinced Josep that a renovation was sufficient and was also able to submit the planning application the same year. The building was completed and refurbished in 1906. He completely changed the main apartment which became the residence for the Batlló family. He expanded the central well in order to supply light to the whole building and also added new floors. In the same year the Barcelona City Council selected the house as a candidate for that year's best building award. The award was given to another architect that year despite Gaudí's design. Refurbishments. Josep Batlló died in 1934 and the house was kept in order by the wife until her death in 1940. After the death of the two parents, the house was kept and managed by the children until 1954. In 1954, an insurance company named Seguros Iberia acquired Casa Batlló and set up offices there. In 1970, the first refurbishment occurred mainly in several of the interior rooms of the house. In 1983, the exterior balconies were restored to their original colour and a year later the exterior façade was illuminated in the ceremony of La Mercè.
Multiple uses. In 1993, the current owners of Casa Batlló bought the home and continued refurbishments throughout the whole building. Two years later, in 1995, Casa Batlló began to hire out its facilities for different events. More than 2,500 square meters of rooms within the building were rented out for many different functions. Due to the building's location and the beauty of the facilities being rented, the rooms of Casa Batlló were in very high demand and hosted many important events for the city. Design. Overview. The local name for the building is "Casa dels ossos" (House of Bones), as it has a visceral, skeletal organic quality. The building looks very remarkable — like everything Gaudí designed, only identifiable as Modernisme or Art Nouveau in the broadest sense. The ground floor, in particular, is rather astonishing with tracery, irregular oval windows and flowing sculpted stone work. It seems that the goal of the designer was to avoid straight lines completely. Much of the façade is decorated with a mosaic made of broken ceramic tiles (trencadís) that starts in shades of golden orange moving into greenish blues. The roof is arched and was likened to the back of a dragon or dinosaur. A common theory about the building is that the rounded feature to the left of centre, terminating at the top in a turret and cross, represents the lance of Saint George (patron saint of Catalonia, Gaudí's home), which has been plunged into the back of the dragon.
Loft. The loft is considered to be one of the most unusual spaces. It was formerly a service area for the tenants of the different apartments in the building which contained laundry rooms and storage areas. It is known for its simplicity of shapes and its Mediterranean influence through the use of white on the walls. It contains a series of sixty catenary arches that creates a space which represents the ribcage of an animal. Some people believe that the “ribcage” design of the arches is a ribcage for the dragon's spine that is represented in the roof. The Atrium (light well). The Atrium or the light well is in the central part of the house and delivers air and lighting to all corners of the house. Gaudí had an obsession with light and how it reflected off certain surfaces. The wall of the atrium has different tones of blue as well as a diamond textile pattern all around the walls. The blue tiles allow an equal distribution of light to all the floors. The well has windows with wooden splits to allow them to be open and closed for ventilation. Gaudí wanted to make the bottom of the well feel like the bottom of the sea. The skylight allows light to come in and reflect off the ceramic tiles into the windows to naturally illuminate the house. The blue tiles are more intensely colored at the top and get opaquer towards the bottom. The diamond textiles match the rest of the house's use of different, functional shapes.
Noble floor and museum. The noble floor is larger than seven-hundred square meters. It is the main floor of the building. The noble floor is accessed through a private entrance hall that uses skylights resembling tortoise shells and vaulted walls in curving shapes. On the noble floor there is a spacious landing with direct views of the blue tiling of the building well. On the Passeig de Gracia side is Batlló's study, a dining room, and a secluded spot for courting couples, decorated with a mushroom-shaped fireplace. The elaborate and animal-like décor continues throughout the whole noble floor. In 2002, as part of the celebration of the International Year of Gaudí, the house opened its doors to the public and people were allowed to visit the noble floor. Casa Batlló met with great unanticipated success, and visitors became eager to see the rest of the house. Two years later, in celebration of the one hundredth anniversary of the beginning of work on Casa Batlló, the fifth floor was restored and the house extended its visit to the loft and the well. In 2005, Casa Batlló became a UNESCO World Heritage Site.
Roof. The roof terrace is one of the most popular features of the entire house due to its famous dragon back design. Gaudí represents an animal's spine by using tiles of different colors on one side. The roof is decorated with four chimney stacks designed to prevent backdraughts. Exterior façade. The façade has three distinct sections which are harmoniously integrated. The lower ground floor with the main floor and two first-floor galleries are contained in a structure of Montjuïc sandstone with undulating lines. The central part, which reaches the last floor, is a multicolored section with protruding balconies. The top of the building is a crown, like a huge gable, which is at the same level as the roof and helps to conceal the room where there used to be water tanks. This room is currently empty. The top displays a trim with ceramic pieces that has attracted multiple interpretations. Roof tile. The roof's arched profile recalls the spine of a dragon with ceramic tiles for scales, and a small triangular window towards the right of the structure simulates the eye. Legend has it that it was once possible to see the Sagrada Família through this window, which was being built simultaneously. As of 2022, the partial view of the Sagrada Família is available from this vantage point, with its spires visible over newer buildings. The tiles were given a metallic sheen to simulate the varying scales of the monster, with the color grading from green on the right side, where the head begins, to deep blue and violet in the center, to red and pink on the left side of the building.
Tower and bulb. One of the highlights of the façade is a tower topped with a cross of four arms oriented to the cardinal directions. It is a bulbous, root-like structure that evokes plant life. There is a second bulb-shaped structure similarly reminiscent of a thalamus flower, which is represented by a cross with arms that are actually buds announcing the next flowering. The tower is decorated with monograms of Jesus (JHS), Maria (M with the ducal crown) and Joseph (JHP), made of ceramic pieces that stand out golden on the green background that covers the façade. These symbols show the deep religiosity of Gaudí, who was inspired by the contemporaneous construction of his basilica to choose the theme of the holy family. The bulb was broken when it was delivered, perhaps during transportation. Although the manufacturer committed to re-do the broken parts, Gaudí liked the aesthetic of the broken masonry and asked that the pieces be stuck to the main structure with lime mortar and held in with a brass ring. Central section.
The central part of the façade evokes the surface of a lake with water lilies, reminiscent of Monet's "Nymphéas", with gentle ripples and reflections caused by the glass and ceramic mosaic. It is a great undulating surface covered with plaster fragments of colored glass discs combined with 330 rounds of polychrome pottery. The discs were designed by Gaudí and Jujol between tests during their stay in Majorca, while working on the restoration of the Cathedral of Palma. Balcony. Finally, above the central part of the façade is a smaller balcony, also iron, with a different exterior aesthetic, closer to a local type of lily. Two iron arms were installed here to support a pulley to raise and lower furniture. Main floor. The façade of the main floor, made entirely in sandstone, and is supported by two columns. The design is complemented by joinery windows set with multicolored stained glass. In front of the large windows, as if they were pillars that support the complex stone structure, there are six fine columns that seem to simulate the bones of a limb, with an apparent central articulation; in fact, this is a floral decoration. The rounded shapes of the gaps and the lip-like edges carved into the stone surrounding them create a semblance of a fully open mouth, for which the Casa Batlló has been nicknamed the "house of yawns". The structure repeats on the first floor and in the design of two windows at the ends forming galleries, but on the large central window there are two balconies as described above.
Park Güell Park Güell ( ; ) is a privatized complex of parks, gardens and architectural elements in the Gràcia district of Barcelona, Catalonia, Spain. The site is located in the La Salut neighborhood on the southern side of a hill known as the Turó del Carmel, part of the Collserola mountain range. The separate Parc del Carmel is located on the northern side of the hill. In the midst of Barcelona's late 19th and early 20th-century urban expansion, Eusebi Güell, a Catalan industrialist and art patron, sought to commission a new park. Güell commissioned the design of the park to the renowned architect, Antoni Gaudí, widely regarded as a central figure of the aesthetic movement of Catalan modernism. Park Güell was built between 1900 and 1914 and was officially opened to the public in 1926. In 1984, UNESCO declared the park a World Heritage Site, recognizing it as part of the "Works of Antoni Gaudí" architectural series. Description. In addition to reflecting the distinct aesthetic sensibilities, artistic influences, and visual language present throughout Gaudí's career, Park Güell captures a particular moment in his artistic evolution. The park is associated with his naturalist phase, which occurred in the first decade of the 20th century. During this period, Gaudí's study of nature and organic shapes began to influence him creatively. Reflecting this shift, Gaudí introduced a series of new structural solutions rooted in geometric analysis.
Gaudí expanded upon these geometric forms to create his characteristically imaginative, ornamental style. Rooted in the Baroque, his works are characterized by a structural richness of forms and volumes, free of the rational rigidity of classical conventions. In designing Park Güell, Gaudí put these structural innovations into practice, for example by incorporating park benches that curve and undulate. Gaudi further elaborated on this characteristic style in the creation of the enormous Sagrada Família (Basilica and Expiatory Church of the Holy Family). Güell and Gaudí originally conceived the space not as a public park, but as a private community of luxurious homes equipped with all the latest modern amenities to fulfill the needs of its residents both artistically and physically. They envisioned a community strongly influenced by symbolism and Park Güell's common spaces (stairways, plazas, terraces, gardens) are designed to express physically the political and religious ideals of both patron and architect. For example, there are noticeable concepts originating from political Catalanism, most notably in the entrance stairway where the Catalan countries are represented, and Catholicism, as Monumento al Calvario, originally designed to be a chapel. In addition to Gaudí's reinterpretation of classical architectural elements such as columns, colonnades, and porticos, Park Güell also contains numerous references to Greek mythology. Some have suggested that Güell and Gaudí's conception of the park was inspired by the Temple of Apollo of Delphi.
The meaning of these symbols continues to be the subject of speculation. To some, Park Güell represents a spatial nexus of complex iconography that Gaudí intentionally applied to the project. Interpretations range from expressions of political vindication to religious exaltation, laden with mythologic, historical, and philosophical references. Others claim that Park Güell displays masonic influences in spite of the fact that both Güell and Gaudí embraced traditional Catholicism. Origins as a housing development. The park was originally part of a housing development project initiated by Count Eusebi Güell, which did not achieve commercial success. Influenced by the English garden city movement, the development incorporated the English term "Park" into its name (Catalan: "Parc Güell", Spanish: "Parque Güell"). The site selected was a rocky hill with sparse vegetation, known as "Muntanya Pelada" (English: Bare Mountain). A large country house, referred to as Larrard House or Muntaner de Dalt House,was already located on the property. The area bordered an upper-class neighborhood called La Salut ("The Health"). Güell aimed to utilize the site's fresh air and scenic views, positioning it as an attractive location away from industrial pollution. The original plan proposed dividing the land into sixty triangular lots intended for luxury housing. In 1906, Güell moved into Larrard House, a move understood to have been intended to promote the development. However, only two houses were ultimately constructed, and neither was designed by Antoni Gaudí.
One of these houses was built as a display home, but upon completion was put up for sale in 1904. However, because no buyers came forward, Güell suggested that Gaudí purchase the home with his own savings. Gaudí agreed and moved in with his family and his father in 1906. This house, in which Gaudí lived from 1906 until his death in 1926, was built in 1904 by Francesc Berenguer, himself a modernist architect and associate of Gaudí's. It contains original works by Gaudí and several of his collaborators. Since 1963, it has been open to the public as the Gaudí House Museum (Catalan: "Casa Museu Gaudí"). In 1969, it was declared to be a historical artistic monument of national interest. Municipal garden. Parc Güell has since been converted into a municipal garden. It is accessible by metro, although the closet metro stations (Vallcarca and Lesseps) are located some distance from the site at the base of Turó de Carmel. It can also be reached by city buses or commercial tourist buses. In October 2013 an entrance fee was introduced for the Monumental Zone (main entrance, terrace, viaducts, and areas featuring mosaics), though citizens of Barcelona may enter free of charge. Limited tickets are available, though these often sell out in advance. La Torre Rosa, Gaudí's home converted into a museum featuring furniture that he designed, can be visited for another entrance fee. However, there is a reduced rate for those wishing to see both Gaudí's house and the Sagrada Família Church.
The entrance is flanked by two gatehouses, both of which were designed by Gaudí. These two buildings make up the Porter's Lodge pavilion. One of these buildings contains a small room with a telephone booth. The other, while once being the porter's house, is now a permanent exhibition of the Barcelona City History Museum (Catalan: "Museu d'Història de Barcelona")"." The focal point of the park is the main terrace, enclosed by a long bench in the form of a sea serpent. The curves of the serpent bench from a number of enclaves, designed to foster social interaction. The design of the benches was the work not of Gaudí, but of his often overlooked collaborator Josep Maria Jujol. Another prominent feature found throughout the park are the series of elevated pathways, originally intended to service the houses, designed by Gaudí to jut out from the steep hillside or rest on Viaducts. These structures often serve as the roofs for lower footpaths in arcades formed underneath. To further minimize the intrusion of these roads, Gaudí had them constructed using a local stone, rendering them as an extension of landscape. Echoing natural forms, the columns and branching vaults supporting the roadways were carved to resemble tree trunks. Similar to his previous work on the Church of Colònia Güell, Gaudí used curved vaulting and the alignment of sloping columns to form inverted catenary arch shapes, which function as ideal compression structures.
At the park's high point, there is a stone hill composed of steps leading up to a platform on which stands three large crosses. This is a calvary, officially named "El Turó de les Tres Creus". Two of the crosses point north–south and east–west, while the third and tallest cross points skyward. From this vantage, it is possible to view the main city in panorama, including the Sagrada Família, Agbar Tower, and Montjuïc area in the distance. Park Güell supports a wide variety of wildlife, notably several of Barcelona's non-native parrots in addition to sightings of the short-toed eagle. The park also supports a population of hummingbird hawk moths.
Casa Milà Casa Milà (, ), popularly known as "La Pedrera" (, ; "the stone quarry") in reference to its unconventional rough-hewn appearance, is a "Modernista" building in Barcelona, Catalonia, Spain. It was the last private residence designed by architect Antoni Gaudí and was built between 1906 and 1912. The building was commissioned in 1906 by and his wife . At the time, it was controversial because of its undulating stone facade, twisting wrought iron balconies, and design by Josep Maria Jujol. Several structural innovations include a self-supporting stone façade, and a free-plan floor, underground garage and the spectacular terrace on the roof. In 1984, it was declared a World Heritage Site by UNESCO. Since 2013 it has been the headquarters of the Fundació Catalunya La Pedrera, which manages visits to the building, exhibitions and other cultural and educational activities at Casa Milà. Building history. Architect. Antoni Gaudí i Cornet was born on June 25, 1852, in Catalonia, Spain. As a child, Gaudí's health was poor, suffering from rheumatism. Because of this, he was afforded lengthy periods of time resting at his summer house in Riudoms. Here he spent a large portion of his time outdoors, allowing him to deeply study nature. This would become one of the major influences in his architecture to come.
Gaudí was a very practical man and a craftsman at his core. In his work he followed impulses and turned creative plans into reality. His openness to embrace new styles combined with a vivid imagination helped mold new styles of architecture and consequently helped push the limits of construction. Today he is regarded as a pioneer of the modern architecture style. In 1870, Gaudí moved to Barcelona to study architecture. He was an inconsistent student who showed flashes of brilliance. It took him eight years to graduate due to a mix of health complications, military service as well as other activities. After completion of his education he became a prolific architect as well as designing gardens, sculptures and all other decorative arts. Gaudí's most famous works consisted of several buildings: Parque Güell; Palacio Güell; Casa Mila; Casa Vicens. He also is attributed for his work on the Crypt of La Sagrada Familia and the Nativity facade. Gaudí's work at the time was both admired and criticized for his bold, innovative solutions.
Gaudí was injured on June 7, 1926, when he was run over by a tram. He later died in the hospital due to his injuries on June 10, 1926, at the age of 73. A few years after his death, his fame became renowned by critics and the general public alike. Building owners. Casa Milà was built for Roser Segimón and her husband Pere Milà. Roser Segimón was the wealthy widow of Josep Guardiola, an "Indiano" or "Americano", or former colonist returned from the Americas, who had made his fortune with a coffee plantation in Guatemala. Her second husband, Pere Milà, was a developer known for his flamboyant lifestyle. Construction process. In 1905, Milà and Segimón married and on June 9, Roser Segimón bought a house with garden which occupied an area of 1,835 square meters, located on Paseo de Gracia, 92. In September, they commissioned Gaudí for building them a new house with the idea of living in the main floor and renting out the rest of the apartments. On February 2, 1906, the project was presented to the Barcelona City Council and the works began, demolishing the pre-existing building instead of reforming it, as in the case of the Casa Batlló.
The building was completed in December 1910 and the owner asked Gaudí to make a certificate to inhabit the main floor, which the City Council authorized in October 1911, and the couple moved in. On October 31, 1912, Gaudí issued the certificate stating that, in accordance with his plans and his direction, the work had been completed and the whole house was ready to be rented. Critics and controversies. The building did not respect any rules of conventional style, for which Gaudí received much criticism. To begin with, the name "La Pedrera" is in fact a nickname assigned by the citizens who disapproved of its unusualness. The unique structure of the building and the relationship between the building's architect and Pere Milà became the object of ridicule for the people of Barcelona and many humorous publications of the time. Catholic symbols. Gaudí, a Catholic and a devotee of the Virgin Mary, planned for the Casa Milà to be a spiritual symbol. Overt religious elements include an excerpt from the Rosary on the cornice and planned statues of Mary, specifically Our Lady of the Rosary, and two archangels, St. Michael and St. Gabriel.
However, the Casa Milà was not built entirely to Gaudí's specifications. The local government ordered the demolition of elements that exceeded the height standard for the city, and fined the Milàs for many infractions of building codes. After Semana Trágica, an outbreak of anticlericalism in the city, Milà prudently decided to forgo the religious statues. Gaudí contemplated abandoning the project but a priest persuaded him to continue. Change of ownership. In 1940, Milà died. Segimon sold the property in 1946 for 18 million pesetas to Josep Ballvé i Pellisé, known for his department stores on , in partnership with the family of Pío Rubert Laporta. The Compañía Inmobiliaria Provenza, SA (CIPSA) was founded to administer the building. Roser Segimon continued to live on the main floor until her death in 1964. The new owners divided the first floor facing into five apartments instead of the original two. In 1953, they commissioned to convert 13 rubbish-filled attic laundry rooms to street-facing apartments, leaving a communal hallway on the side facing the courtyards. Some of these two or three room apartments had a loft and were designed and furnished in a typical early 1950s style using brick, ceramic and wood. Items of furniture, such as the , were reminiscent of Eero Saarinen's work.
The insurance company Northern took over the main floor in 1966. By then, Casa Milà had housed a bingo hall, an academy and the offices of Cementos Molins and Inoxcrom among others. Maintenance costs were high and the owners had allowed the building to become dilapidated, causing stones to loosen in 1971. Josep Anton Comas made some emergency repairs, especially to the paintings in the courtyards, while respecting the original design. Restoration. Gaudí's work was designated a historic and artistic monument on July 24, 1969. Casa Milà was in poor condition in the early 1980s. It had been painted a dreary brown and many of its interior color schemes had been abandoned or allowed to deteriorate, but it has been restored since including restoring many of the original colors. In 1984, the building became part of a World Heritage Site encompassing some of Gaudí's works. The Barcelonan city council tried to rent the main floor as an office for the 1992 Olympic bid. Finally, the day before Christmas 1986, Caixa Catalunya bought La Pedrera for 900 million pesetas. On February 19, 1987, urgently needed work began on the restoration and cleaning of the façade. The work was done by the architects Joseph Emilio Hernández-Cros and Rafael Vila. The renovated main floor opened in 1990 as part of the Cultural Olympiad of Barcelona. The floor became an exhibition room with an example of modernism in the Eixample.
Design. The building is 1,323 m2 per floor on a plot of 1,620 m2. Gaudí made the first sketches in his workshop in the Sagrada Família. He designed the house as a constant curve, both outside and inside, incorporating ruled geometry and naturalistic elements. Casa Milà consists of two buildings, which are structured around two courtyards that provide light to the nine stories: basement, ground floor, mezzanine, main (or noble) floor, four upper floors, and an attic. The basement was intended to be the garage, the main floor the residence of the Milàs (a flat of all 1,323 m2), and the rest distributed over 20 apartments. The resulting layout is shaped like an asymmetrical "8" because of the different shapes and sizes of the courtyards. The attic housed the laundry and drying areas, forming an insulating space for the building and simultaneously determining the levels of the roof. One of the most notable elements of the building is the roof, crowned with skylights, staircase exits, fans, and chimneys. All of these elements, constructed out of brick covered with lime, broken marble, or glass have a specific architectural function but are also real sculptures integrated into the building.
The apartments feature plastered ceilings with dynamic reliefs, handcrafted wooden doors, windows, and furniture, as well as hydraulic tiles and various ornamental elements. The stairways were intended as service entries, with the main access to the apartments by elevator except for the noble floor, where Gaudí added a prominent interior staircase. Gaudí wanted the people who lived in the flats to all know each other. Therefore, there were only elevators on every other floor, so people on different floors would meet one another. Structure. Casa Milà is characterized by its self-supporting stone facade, meaning that it is free of load-bearing walls. The facade connects to the internal structure of each floor by means of curved iron beams surrounding the perimeter of each floor. This construction system allows, on one hand, large openings in the facade which give light to the homes, and on the other, free structuring of the different levels, so that internal walls can be added and demolished without affecting the stability of the building. This allows the owners to change their minds at will and to modify, without problems, the interior layout of the homes.
Constructive and decorative items. Facade. The facade is composed of large blocks of limestone from the Garraf Massif on the first floor and from the Villefranche quarry for the higher levels. The blocks were cut to follow the plot of the projection of the model, then raised to their location and adjusted to align in a continuous curve to the pieces around them. The windows of La Pedrera are an integral part of the overall facade design. Gaudí made sure that the windows were of varying sizes, designed to optimize the amount of natural light that could enter the building. Viewed from the outside the building has three parts: the main body of the six-storey blocks with winding stone floors, two floors set a block back with a different curve, similar to waves, a smoother texture and whiter color, and with small holes that look like embrasures, and finally the body of the roof. Gaudí's original facade had some of its lower-level ironwork removed. In 1928, the tailor Mosella opened the first store in La Pedrera, and he eliminated the bars. This did not concern anyone, because in the middle of twentieth century, wrought ironwork had little importance. The ironwork was lost until a few years later, when Americans donated one of them to the MoMa, where it is on display.
With restoration initiatives launched in 1987, the facade was rejoined to some pieces of stone that had fallen. In order to respect the fidelity of the original, material was obtained from the Villefranche quarry, even though by then it was no longer operating. Hall and courtyards. The building uses a completely original solution to solve the issue of a lobby being too closed and dark. Its open and airy courtyards provide a place of transit and are directly visible to those accessing the building. There are two patios on the side of the Passeig de Gracia and of the street Provence. Patios, structurally, are key as supporting loads of interior facades. The floor of the courtyard is supported by pillars of cast iron. In the courtyard, there are traditional elliptical beams and girders but Gaudí applied an ingenious solution of using two concentric cylindrical beams with stretched radial beams, like the spokes of a bicycle. They form a point outside of the beam to two points above and below, making the function of the central girder a keystone and working in tension and compression simultaneously. This supported structure is twelve feet in diameter and is considered "the soul of the building" with a clear resemblance to Gothic crypts. The centerpiece was built in a shipyard by Josep Maria Carandell who copied a steering wheel, interpreting Gaudí's intent as to represent the helm of the ship of life.
Access is protected by a massive iron gate with a design attributed to Jujol. It was originally used by both people and cars, as access to the garage is in the basement, now an auditorium. The two halls are fully polychrome with oil paintings on the plaster surfaces, with eclectic references to mythology and flowers. During construction there was a problem including a basement as a garage for cars, the new invention that was thrilling the bourgeois at the time. The future neighbor Felix Anthony Meadows, owner of Industrial Linera, requested a change because his Rolls-Royce could not access it. Gaudí agreed to remove a pillar on the ramp that led into the garage so that Felix, who was establishing sales and factory in Parets del Vallès, could go to both places with his car from La Pedrera. For the floors of Casa Milà, Gaudí used a model of floor forms of square timbers with two colors, and the hydraulic pavement hexagonal pieces of blue and sea motifs that had originally been designed for the Batllo house. The wax was designed in gray by John Bertrand under the supervision of Gaudí who "touched up with their own fingers," in the words of the manufacturer Josep Bay.
Loft. Like in Casa Batlló, Gaudí shows the application of the catenary arch as a support structure for the roof, a form which he had already used shortly after graduating in the wood frameworks of Mataró's cooperative known as "L'Obrera Mataronense." In this case, Gaudí used the Catalan technique of timbrel, imported from Italy in the fourteenth century. The attic, where the laundry rooms were located, was a clear room under a Catalan vault roof supported by 270 parabolic vaults of different heights and spaced by about 80 cm. The roof resembles both the ribs of a huge animal and a palm, giving the roof-deck a very unconventional shape similar to a landscape of hills and valleys. The shape and location of the courtyards makes the arches higher when the space is narrowed and lower when the space expands. The builder Bayó explained its construction: "First the face of a wide wall was filled with mortar and plastered. Then Canaleta indicated the opening of each arch and Bayó put a nail at each starting point of the arch at the top of the wall. From these nails was dangled a chain so that the lowest point coincided with the deflection of the arch. Then the profile displayed on the wall by the chain was drawn and on this profile the carpenter marked and placed the corresponding centering, and the timbrel vault was started with three rows of plane bricks. Gaudí wanted to add a longitudinal axis of bricks connecting all vaults at their keystones".
Roof and chimneys. The work of Gaudí on the rooftop of La Pedrera brought his experience at Palau Güell together with solutions that were clearly more innovative – this time creating shapes and volumes with more body, more prominence, and less polychromasia. On the rooftop there are six skylights/staircase exits (four of which were covered with broken pottery and some that ended in a double cross typical of Gaudí), twenty-eight chimneys in several groupings, two half-hidden vents whose function is to renew the air in the building, and four domes that discharged to the facade. The staircases also house the water tanks; some of which are snail-shaped. The stepped roof of La Pedrera, called "the garden of warriors" by the poet Pere Gimferrer because the chimneys appear to be protecting the skylights, has undergone a radical restoration, removing chimneys added in interventions after Gaudí, television antennas, and other elements that degraded the space. The restoration brought back the splendor to the chimneys and the skylights that were covered with fragments of marble and broken Valencia tiles. One of the chimneys was topped with glass pieces – it was said that Gaudí did that the day after the inauguration of the building, taking advantage of the empty bottles from the party. It was restored with the bases of champagne bottles from the early twentieth century. The repair work has enabled the restoration of the original impact of the overhangs made of stone from Ulldecona with fragments of tiles. This whole set is more colorful than the facade, although here the creamy tones are dominant.
Furniture. Gaudí, as he had done in Casa Batlló, designed furniture specifically for the main floor. This was part of the concept artwork itself integral to modernism in which the architect assumed responsibility for global issues such as the structure and the facade, as well as every detail of the decor, designing furniture and accessories such as lamps, planters, floors or ceilings. This was another point of friction with Segimon, who complained that there was no straight wall to place her Steinway piano. Gaudí's response was blunt: "So play the violin." The result of these disagreements has been the loss of the decorative legacy of Gaudí, as most of the furniture was removed due to climate change and the changes she made to the main floor when Gaudí died. Some remain in private collections, including a curtain made of oak 4 m. long by 1.96 m. high in the Museum of Catalan Modernism; and a chair and desktop of Milà. Gaudí carved oak doors similar to what he had done for the Casa y Bardes, but these were only included on two floors as when Segimon discovered the price, she decided there would be no more at that quality.
Architecture. "Casa Milà" is part of the UNESCO World Heritage Site "Works of Antoni Gaudí". It was a predecessor of some buildings with a similar biomorphic appearance: Free exhibitions often are held on the first floor, which also provides some opportunity to see the interior design. There is a charge for entrance to the apartment on the fourth floor and the roof. The other floors are not open to visitors. Constructive similarities. Gaudí's La Pedrera was inspired by a mountain, but there is no agreement as to which mountain was the reference model. Joan Bergós thought it was the rocks of Fray Guerau in Prades mountains. Joan Matamala thought that the model could have been St. Miquel del Fai, while the sculptor Vicente Vilarubias believed it was inspired by the cliffs Torrent Pareis in Menorca. Other options include the mountains of Uçhisar in Cappadocia, suggested by Juan Goytisolo, or Mola Gallifa, suggested by Louis Permanyer, based on the fact that Gaudí visited the area in 1885 to escape an outbreak of cholera in Barcelona.
Some people say that the interior layout of La Pedrera comes from studies that Gaudí made of medieval fortresses. This image is reinforced by the seeming appearance of the rooftop chimneys as "sentinels" with great helmets. The structure of the iron door in the lobby does not follow any symmetry, straight or repetitive pattern. Rather, it evokes bubbles of soap that are formed between the hands or the structures of a plant cell. Criticism and controversy. The building's unconventional style made it the subject of much criticism. It was given the nickname "La Pedrera", meaning "the quarry". Casa Milà appeared in many satirical magazines. Joan Junceda presented it as a traditional "Easter cake" by means of cartoons in "Patufet". Joaquim Garcia made a joke about the difficulty of setting the damask wrought iron balconies in his magazine. Homeowners in Passeig de Gracia became angry with Milà and ceased to greet him, arguing that the weird building by Gaudí would lower the price of land in the area. Administrative problems.
Casa Milà also caused some administrative problems. In December 1907 the City Hall stopped work on the building because of a pillar which occupied part of the sidewalk, not respecting the alignment of facades. Again on August 17, 1908, more problems occurred when the building surpassed the predicted height and borders of its construction site by . The Council called for a fine of 100,000 pesetas (approximately 25% of the cost of work) or for the demolition of the attic and roof. The dispute was resolved a year and a half later, December 28, 1909, when the Commission certified that it was a monumental building and thus not required to have a 'strict compliance' with the bylaws. Design competitions. The owner entered La Pedrera in the annual sponsored by the Barcelona City Council ("Ayuntament"). Other entries in the competition included two works by Sagnier (Calle Mallorca 264, and one on Corsica and Av. Diagonal), the by architect , and the , designed by . Although the most dramatic and clear favorite was Casa Milà, the jury opined that even though the facades were complete, "there's still a lot left to do before it's fully completed, finalized and in a perfect state of appreciation." The winner in 1910 was Samanillo Perez, for his building which now houses the headquarters of the Circulo Ecuestre.
Design disagreements. Gaudí's relations with Segimon deteriorated during the construction and decoration of the house. There were many disagreements between them, one example being the monumental bronze virgin del Rosario, which Gaudí wanted as the statue on the front of the building in homage to the name of the owner, that the artist Carles Mani i Roig was to sculpt. The statue was not made although the words "Ave gratia M plena Dominus tecum" were written at the top of the facade. Continuing disagreements led Gaudí to take Milà to court over his fees. The lawsuit was won by Gaudí in 1916, and he gave the 105,000 pesetas he won in the case to charity, stating that "the principles mattered more than money." Milà was having to pay the mortgage. After Gaudí's death in 1926, Segimon got rid of most of the furniture that Gaudí had designed and covered over parts of Gaudí's designs with new decorations in the style of Louis XVI. La Pedrera was acquired in 1986 by and when restoration was done four years later, some of the original decorations re-emerged. When the Civil War broke out in July 1936, the Milàs were on vacation. Part of the building was collectivized by the Unified Socialist Party of Catalonia; the Milàs fled the area with some artwork.
Antiparticle In particle physics, every type of particle of "ordinary" matter (as opposed to antimatter) is associated with an antiparticle with the same mass but with opposite physical charges (such as electric charge). For example, the antiparticle of the electron is the positron (also known as an antielectron). While the electron has a negative electric charge, the positron has a positive electric charge, and is produced naturally in certain types of radioactive decay. The opposite is also true: the antiparticle of the positron is the electron. Some particles, such as the photon, are their own antiparticle. Otherwise, for each pair of antiparticle partners, one is designated as the normal particle (the one that occurs in matter usually interacted with in daily life). The other (usually given the prefix "anti-") is designated the "antiparticle". Particle–antiparticle pairs can annihilate each other, producing photons; since the charges of the particle and antiparticle are opposite, total charge is conserved. For example, the positrons produced in natural radioactive decay quickly annihilate themselves with electrons, producing pairs of gamma rays, a process exploited in positron emission tomography.
The laws of nature are very nearly symmetrical with respect to particles and antiparticles. For example, an antiproton and a positron can form an antihydrogen atom, which is believed to have the same properties as a hydrogen atom. This leads to the question of why the formation of matter after the Big Bang resulted in a universe consisting almost entirely of matter, rather than being a half-and-half mixture of matter and antimatter. The discovery of charge parity violation helped to shed light on this problem by showing that this symmetry, originally thought to be perfect, was only approximate. The question about how the formation of matter after the Big Bang resulted in a universe consisting almost entirely of matter remains an unanswered one, and explanations so far are not truly satisfactory, overall. Because charge is conserved, it is not possible to create an antiparticle without either destroying another particle of the same charge (as is for instance the case when antiparticles are produced naturally via beta decay or the collision of cosmic rays with Earth's atmosphere), or by the simultaneous creation of both a particle "and" its antiparticle (pair production), which can occur in particle accelerators such as the Large Hadron Collider at CERN.
Particles and their antiparticles have equal and opposite charges, so that an uncharged particle also gives rise to an uncharged antiparticle. In many cases, the antiparticle and the particle coincide: pairs of photons, Z0 bosons, mesons, and hypothetical gravitons and some hypothetical WIMPs all self-annihilate. However, electrically neutral particles need not be identical to their antiparticles: for example, the neutron and antineutron are distinct. History. Experiment. In 1932, soon after the prediction of positrons by Paul Dirac, Carl D. Anderson found that cosmic-ray collisions produced these particles in a cloud chamber – a particle detector in which moving electrons (or positrons) leave behind trails as they move through the gas. The electric charge-to-mass ratio of a particle can be measured by observing the radius of curling of its cloud-chamber track in a magnetic field. Positrons, because of the direction that their paths curled, were at first mistaken for electrons travelling in the opposite direction. Positron paths in a cloud-chamber trace the same helical path as an electron but rotate in the opposite direction with respect to the magnetic field direction due to their having the same magnitude of charge-to-mass ratio but with opposite charge and, therefore, opposite signed charge-to-mass ratios.
The antiproton and antineutron were found by Emilio Segrè and Owen Chamberlain in 1955 at the University of California, Berkeley. Since then, the antiparticles of many other subatomic particles have been created in particle accelerator experiments. In recent years, complete atoms of antimatter have been assembled out of antiprotons and positrons, collected in electromagnetic traps. Dirac hole theory. Solutions of the Dirac equation contain negative energy quantum states. As a result, an electron could always radiate energy and fall into a negative energy state. Even worse, it could keep radiating infinite amounts of energy because there were infinitely many negative energy states available. To prevent this unphysical situation from happening, Dirac proposed that a "sea" of negative-energy electrons fills the universe, already occupying all of the lower-energy states so that, due to the Pauli exclusion principle, no other electron could fall into them. Sometimes, however, one of these negative-energy particles could be lifted out of this Dirac sea to become a positive-energy particle. But, when lifted out, it would leave behind a "hole" in the sea that would act exactly like a positive-energy electron with a reversed charge. These holes were interpreted as "negative-energy electrons" by Paul Dirac and mistakenly identified with protons in his 1930 paper "A Theory of Electrons and Protons" However, these "negative-energy electrons" turned out to be positrons, and not protons.
This picture implied an infinite negative charge for the universea problem of which Dirac was aware. Dirac tried to argue that we would perceive this as the normal state of zero charge. Another difficulty was the difference in masses of the electron and the proton. Dirac tried to argue that this was due to the electromagnetic interactions with the sea, until Hermann Weyl proved that hole theory was completely symmetric between negative and positive charges. Dirac also predicted a reaction + → + , where an electron and a proton annihilate to give two photons. Robert Oppenheimer and Igor Tamm, however, proved that this would cause ordinary matter to disappear too fast. A year later, in 1931, Dirac modified his theory and postulated the positron, a new particle of the same mass as the electron. The discovery of this particle the next year removed the last two objections to his theory. Within Dirac's theory, the problem of infinite charge of the universe remains. Some bosons also have antiparticles, but since bosons do not obey the Pauli exclusion principle (only fermions do), hole theory does not work for them. A unified interpretation of antiparticles is now available in quantum field theory, which solves both these problems by describing antimatter as negative energy states of the same underlying matter field, i.e. particles moving backwards in time.
Particle–antiparticle annihilation. If a particle and antiparticle are in the appropriate quantum states, then they can annihilate each other and produce other particles. Reactions such as + → (the two-photon annihilation of an electron-positron pair) are an example. The single-photon annihilation of an electron-positron pair, + → , cannot occur in free space because it is impossible to conserve energy and momentum together in this process. However, in the Coulomb field of a nucleus the translational invariance is broken and single-photon annihilation may occur. The reverse reaction (in free space, without an atomic nucleus) is also impossible for this reason. In quantum field theory, this process is allowed only as an intermediate quantum state for times short enough that the violation of energy conservation can be accommodated by the uncertainty principle. This opens the way for virtual pair production or annihilation in which a one particle quantum state may "fluctuate" into a two particle state and back. These processes are important in the vacuum state and renormalization of a quantum field theory. It also opens the way for neutral particle mixing through processes such as the one pictured here, which is a complicated example of mass renormalization.
Properties. Quantum states of a particle and an antiparticle are interchanged by the combined application of charge conjugation formula_1, parity formula_2 and time reversal formula_3. formula_1 and formula_2 are linear, unitary operators, formula_3 is antilinear and antiunitary, formula_7. If formula_8 denotes the quantum state of a particle formula_9 with momentum formula_10 and spin formula_11 whose component in the z-direction is formula_12, then one has where formula_14 denotes the charge conjugate state, that is, the antiparticle. In particular a massive particle and its antiparticle transform under the same irreducible representation of the Poincaré group which means the antiparticle has the same mass and the same spin. If formula_15, formula_16 and formula_17 can be defined separately on the particles and antiparticles, then where the proportionality sign indicates that there might be a phase on the right hand side. As formula_21 anticommutes with the charges, formula_22, particle and antiparticle have opposite electric charges q and -q.
Quantum field theory. One may try to quantize an electron field without mixing the annihilation and creation operators by writing where we use the symbol "k" to denote the quantum numbers "p" and σ of the previous section and the sign of the energy, "E(k)", and "ak" denotes the corresponding annihilation operators. Of course, since we are dealing with fermions, we have to have the operators satisfy canonical anti-commutation relations. However, if one now writes down the Hamiltonian then one sees immediately that the expectation value of "H" need not be positive. This is because "E(k)" can have any sign whatsoever, and the combination of creation and annihilation operators has expectation value 1 or 0. So one has to introduce the charge conjugate "antiparticle" field, with its own creation and annihilation operators satisfying the relations where "k" has the same "p", and opposite σ and sign of the energy. Then one can rewrite the field in the form where the first sum is over positive energy states and the second over those of negative energy. The energy becomes
where "E0" is an infinite negative constant. The vacuum state is defined as the state with no particle or antiparticle, "i.e.", formula_28 and formula_29. Then the energy of the vacuum is exactly "E0". Since all energies are measured relative to the vacuum, H is positive definite. Analysis of the properties of "ak" and "bk" shows that one is the annihilation operator for particles and the other for antiparticles. This is the case of a fermion. This approach is due to Vladimir Fock, Wendell Furry and Robert Oppenheimer. If one quantizes a real scalar field, then one finds that there is only one kind of annihilation operator; therefore, real scalar fields describe neutral bosons. Since complex scalar fields admit two different kinds of annihilation operators, which are related by conjugation, such fields describe charged bosons. Feynman–Stückelberg interpretation. By considering the propagation of the negative energy modes of the electron field backward in time, Ernst Stückelberg reached a pictorial understanding of the fact that the particle and antiparticle have equal mass m and spin J but opposite charges q. This allowed him to rewrite perturbation theory precisely in the form of diagrams. Richard Feynman later gave an independent systematic derivation of these diagrams from a particle formalism, and they are now called Feynman diagrams. Each line of a diagram represents a particle propagating either backward or forward in time. In Feynman diagrams, anti-particles are shown traveling backwards in time relative to normal matter, and vice versa. This technique is the most widespread method of computing amplitudes in quantum field theory today. Since this picture was first developed by Stückelberg, and acquired its modern form in Feynman's work, it is called the Feynman–Stückelberg interpretation of antiparticles to honor both scientists.
Arabian Prince Kim Renard Nazel (born June 17, 1965), better known by his stage names Arabian Prince or Professor X, is an American rapper and record producer. He was a founding member of N.W.A and contributed to a few tracks from "N.W.A. and the Posse" (1987) and their debut studio album "Straight Outta Compton" (1989), the latter of which was released shortly after he left the group. Early life. Nazel was born in Compton, California, to the son of Joseph "Skippy" Nazel Jr., an African American author and radio talk show host. His musical background came from his mother, a piano teacher and classical musician. His family tried its best to shelter him, sending him to a Catholic school and keeping him busy with football to keep him away from the gangs. The younger Nazel got his first experience with making music at the radio station his father hosted his talk show on; Nazel used the radio station's equipment to put together mixtapes that he would sell at school. Nazel went on to graduate from Junípero Serra High School in nearby Gardena.
Music career. Nazel took the stage name of DJ Prince and started selling mixtapes at school. While working at a Petshop at a Lennox California Mall, its owner, Sam Nassif, asked him to DJ a party at a community dance hall. He kept performing there for several weekends and the success persuaded Nassif to invest even more in the place, renaming it "The Cave",(And Later "The Basement") where Nazel would continue to host for over three years and even after his N.W.A days. Nassif also funded DJ Prince's first record, "Strange Life". He changed his stage name when he was 15 years old at the Skateland USA, the same skating venue credited for launching N.W.A a few years later, due to a fan's suggestion. He said about his name: Arabian Prince started working with Bobby Jimmy & the Critters in 1984. He also produced the hit single and album for J.J. Fad, "Supersonic". In 1987, he was a founding member of N.W.A, helping with production on some tracks and appearing as a vocalist on "Panic Zone" from "N.W.A. and the Posse" (1987) and the last track off the group's debut studio album "Straight Outta Compton" (1989), "Something 2 Dance 2", a relatively radio-friendly song which was also removed from later pressings of the album due to a dispute. Arabian Prince left N.W.A in late 1988, shortly before the release of "Straight Outta Compton", over royalty and contract disagreements. "I started off as a solo artist", he said, "so I was aware of what a royalty statement was. I knew that when these many records were sold, there is a quarterly statement. When you look at it, you can see how much money was paid and then share it. This was not the case. We were also never paid for touring." Eazy-E, Ice Cube and MC Ren remained as the main performers, DJ Yella was the turntablist and Dr. Dre was the main producer.
After leaving N.W.A, Arabian Prince began a solo career. His first album, "Brother Arab", was released in 1989 with the single "She's Got A Big Posse"; "Where's My Bytches" followed in 1993. In the mid-2000s, he started releasing music again, with his Professor X project on the Dutch label Clone Records. "I could not release the record under Arabian Prince", he said, "because I already had a single out, so I called myself Professor X on that record." In 2007, he performed as a DJ on the 2K Sports Holiday Bounce Tour with artists from the Stones Throw label. In 2008, Stones Throw released a compilation of his electro-rap material from the 1980s. One of his songs was included on the 2007 video game, "College Hoops 2K8". In 2015, a biopic about N.W.A. titled "Straight Outta Compton" was released; however, Arabian Prince was not portrayed in the film. After the release film, Prince said to VladTV: "A lot of the scenes in real life, I was there—I'm just not there in the film, which I'm like, if you're gonna write me out of a movie, shoot some other scenes. Don't write scenes where I was there." Some of the pivotal scenes would be choosing the name for the band, the tour and the infamous Detroit concert. He also remembers himself as the main opposer to Jerry Heller about the royalties and the money, a role that in the film was instead given to Ice Cube. The following year, N.W.A. was inducted into the Rock and Roll Hall of Fame, but again, Arabian Prince was not included nor mentioned. In 2018, Arabian Prince appeared on the "AmeriKKKant" album of industrial-metal band Ministry. He made a second appearance on Ministry's 2021 album "Moral Hygiene". Other ventures. Aside from his music career, he worked in special effects, 3D animation and video games.
Associative property In mathematics, the associative property is a property of some binary operations that rearranging the parentheses in an expression will not change the result. In propositional logic, associativity is a valid rule of replacement for expressions in logical proofs. Within an expression containing two or more occurrences in a row of the same associative operator, the order in which the operations are performed does not matter as long as the sequence of the operands is not changed. That is (after rewriting the expression with parentheses and in infix notation if necessary), rearranging the parentheses in such an expression will not change its value. Consider the following equations: formula_1 Even though the parentheses were rearranged on each line, the values of the expressions were not altered. Since this holds true when performing addition and multiplication on any real numbers, it can be said that "addition and multiplication of real numbers are associative operations". Associativity is not the same as commutativity, which addresses whether the order of two operands affects the result. For example, the order does not matter in the multiplication of real numbers, that is, , so we say that the multiplication of real numbers is a commutative operation. However, operations such as function composition and matrix multiplication are associative, but not (generally) commutative.
Associative operations are abundant in mathematics; in fact, many algebraic structures (such as semigroups and categories) explicitly require their binary operations to be associative. However, many important and interesting operations are non-associative; some examples include subtraction, exponentiation, and the vector cross product. In contrast to the theoretical properties of real numbers, the addition of floating point numbers in computer science is not associative, and the choice of how to associate an expression can have a significant effect on rounding error. Definition. Formally, a binary operation formula_2 on a set is called associative if it satisfies the associative law: Here, ∗ is used to replace the symbol of the operation, which may be any symbol, and even the absence of symbol (juxtaposition) as for multiplication. The associative law can also be expressed in functional notation thus: formula_7 Generalized associative law. If a binary operation is associative, repeated application of the operation produces the same result regardless of how valid pairs of parentheses are inserted in the expression. This is called the generalized associative law.
The number of possible bracketings is just the Catalan number, formula_8 , for "n" operations on "n+1" values. For instance, a product of 3 operations on 4 elements may be written (ignoring permutations of the arguments), in formula_9 possible ways: If the product operation is associative, the generalized associative law says that all these expressions will yield the same result. So unless the expression with omitted parentheses already has a different meaning (see below), the parentheses can be considered unnecessary and "the" product can be written unambiguously as As the number of elements increases, the number of possible ways to insert parentheses grows quickly, but they remain unnecessary for disambiguation. An example where this does not work is the logical biconditional . It is associative; thus, is equivalent to , but most commonly means , which is not equivalent. Examples. Some examples of associative operations include the following. Propositional logic. Rule of replacement. In standard truth-functional propositional logic, "association", or "associativity" are two valid rules of replacement. The rules allow one to move parentheses in logical expressions in logical proofs. The rules (using logical connectives notation) are:
formula_16 and formula_17 where "formula_18" is a metalogical symbol representing "can be replaced in a proof with". Truth functional connectives. "Associativity" is a property of some logical connectives of truth-functional propositional logic. The following logical equivalences demonstrate that associativity is a property of particular connectives. The following (and their converses, since is commutative) are truth-functional tautologies. Joint denial is an example of a truth functional connective that is "not" associative. Non-associative operation. A binary operation formula_22 on a set "S" that does not satisfy the associative law is called non-associative. Symbolically, formula_23 For such an operation the order of evaluation "does" matter. For example: Also although addition is associative for finite sums, it is not associative inside infinite sums (series). For example, formula_28 whereas formula_29 Some non-associative operations are fundamental in mathematics. They appear often as the multiplication in structures called non-associative algebras, which have also an addition and a scalar multiplication. Examples are the octonions and Lie algebras. In Lie algebras, the multiplication satisfies Jacobi identity instead of the associative law; this allows abstracting the algebraic nature of infinitesimal transformations.
Other examples are quasigroup, quasifield, non-associative ring, and commutative non-associative magmas. Nonassociativity of floating point calculation. In mathematics, addition and multiplication of real numbers are associative. By contrast, in computer science, addition and multiplication of floating point numbers are "not" associative, as different rounding errors may be introduced when dissimilar-sized values are joined in a different order. To illustrate this, consider a floating point representation with a 4-bit significand: Even though most computers compute with 24 or 53 bits of significand, this is still an important source of rounding error, and approaches such as the Kahan summation algorithm are ways to minimise the errors. It can be especially problematic in parallel computing. Notation for non-associative operations. In general, parentheses must be used to indicate the order of evaluation if a non-associative operation appears more than once in an expression (unless the notation specifies the order in another way, like formula_30). However, mathematicians agree on a particular order of evaluation for several common non-associative operations. This is simply a notational convention to avoid parentheses.
A left-associative operation is a non-associative operation that is conventionally evaluated from left to right, i.e., formula_31 while a right-associative operation is conventionally evaluated from right to left: formula_32 Both left-associative and right-associative operations occur. Left-associative operations include the following: This notation can be motivated by the currying isomorphism, which enables partial application. Right-associative operations include the following: Non-associative operations for which no conventional evaluation order is defined include the following. History. William Rowan Hamilton seems to have coined the term "associative property" around 1844, a time when he was contemplating the non-associative algebra of the octonions he had learned about from John T. Graves.
The Apache Software Foundation The Apache Software Foundation ( ; ASF) is an American nonprofit corporation (classified as a 501(c)(3) organization in the United States) to support a number of open-source software projects. The ASF was formed from a group of developers of the Apache HTTP Server, and incorporated on March 25, 1999. it includes approximately 1000 members. The Apache Software Foundation is a decentralized open source community of developers. The software they produce is distributed under the terms of the Apache License, a permissive open-source license for free and open-source software (FOSS). The Apache projects are characterized by a collaborative, consensus-based development process and an open and pragmatic software license, which is to say that it allows developers, who receive the software freely, to redistribute it under non-free terms. Each project is managed by a self-selected team of technical experts who are active contributors to the project. The ASF is a meritocracy, implying that membership of the foundation is granted only to volunteers who have actively contributed to Apache projects.
Among the ASF's objectives are: to provide legal protection to volunteers working on Apache projects, and to prevent the "Apache" brand name from being used by other organizations without permission. The ASF also holds several ApacheCon conferences each year, highlighting Apache projects and related technology. History. The history of the Apache Software Foundation is linked to the Apache HTTP Server, development beginning in February 1993. A group of eight developers started working on enhancing the NCSA HTTPd daemon. They came to be known as the Apache Group. On March 25, 1999, the Apache Software Foundation was formed. The first official meeting of the Apache Software Foundation was held on April 13, 1999. The initial members of the Apache Software Foundation consisted of the Apache Group: Brian Behlendorf, Ken Coar, Miguel Gonzales, Mark Cox, Lars Eilebrecht, Ralf S. Engelschall, Roy T. Fielding, Dean Gaudet, Ben Hyde, Jim Jagielski, Alexei Kosut, Martin Kraemer, Ben Laurie, Doug MacEachern, Aram Mirzadeh, Sameer Parekh, Cliff Skolnick, Marc Slemko, William (Bill) Stoddard, Paul Sutton, Randy Terbush and Dirk-Willem van Gulik. After a series of additional meetings to elect board members and resolve other legal matters regarding incorporation, the effective incorporation date of the Apache Software Foundation was set to June 1, 1999.
Co-founder Brian Behlendorf states how the name 'Apache' was chosen: "I suggested the name Apache partly because the web technologies at the time that were launching were being called cyber this or spider that or something on those themes and I was like we need something a little more interesting, a little more romantic, not to be a cultural appropriator or anything like that, I had just seen a documentary about Geronimo and the last days of a Native American tribe called the Apaches right, who succumbed to the invasion from the West, from the United States, and they were the last tribe to give up their territory and for me that almost romantically represented what I felt we were doing with this web-server project..." Projects. Apache divides its software development activities into separate semi-autonomous areas called "top-level projects" (formally known as a "Project Management Committee" in the bylaws), some of which have a number of sub-projects. Unlike some other organizations that host FOSS projects, before a project is hosted at Apache it has to be licensed to the ASF with a grant or contributor agreement. In this way, the ASF gains the necessary intellectual property rights for the development and distribution of all its projects.
Board of directors. The board of directors of The Apache Software Foundation (ASF) is responsible for management and oversight of the business and affairs of the corporation in accordance with the Bylaws. This includes management of the corporate assets (funds, intellectual property, trademarks, and support equipment), appointment of a President and corporate officers managing the core operations of the ASF, and allocation of corporate resources for the benefit of Apache projects. Technical decision-making authority for every Apache project is assigned to their independent project management committee; the participants in each project provide direction, not the board. The board is elected annually by the ASF membership. Since March 6, 2025, the board of directors has been:
Americans with Disabilities Act of 1990 The Americans with Disabilities Act of 1990 or ADA () is a civil rights law that prohibits discrimination based on disability. It affords similar protections against discrimination to Americans with disabilities as the Civil Rights Act of 1964, which made discrimination based on race, religion, sex, national origin, and other characteristics illegal, and later sexual orientation and gender identity. In addition, unlike the Civil Rights Act, the ADA also requires covered employers to provide reasonable accommodations to employees with disabilities, and imposes accessibility requirements on public accommodations. In 1986, the National Council on Disability had recommended the enactment of an Americans with Disabilities Act and drafted the first version of the bill which was introduced in the House and Senate in 1988. A broad bipartisan coalition of legislators supported the ADA, while the bill was opposed by business interests (who argued the bill imposed costs on business) and conservative evangelicals (who opposed protection for individuals with HIV). The final version of the bill was signed into law on July 26, 1990, by President George H. W. Bush. It was later amended in 2008 and signed by President George W. Bush with changes effective as of January 1, 2009.
Disabilities included. Conditions classed as disabilities under the ADA include both mental and physical conditions. A condition does not need to be severe or permanent to be a disability. Equal Employment Opportunity Commission regulations provide a list of conditions that should easily be concluded to be disabilities: amputation, attention deficit hyperactivity disorder (ADHD), autism, bipolar disorder, blindness, cancer, cerebral palsy, deafness, diabetes, epilepsy, HIV/AIDS, intellectual disability, major depressive disorder, mobility impairments requiring a wheelchair, multiple sclerosis, muscular dystrophy, obsessive–compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and schizophrenia. Other mental or physical health conditions also may be disabilities, depending on what the individual's symptoms would be in the absence of "mitigating measures" such as medication, therapy, assistive devices, or other means of restoring function, during an "active episode" of the condition (if the condition is episodic).
Certain specific conditions that are widely considered anti-social, or tend to result in illegal activity, such as kleptomania, pedophilia, exhibitionism, voyeurism, etc. are excluded under the definition of "disability" in order to prevent abuse of the statute's purpose. Additionally, sexual orientation is no longer considered a disorder and is also excluded from the definition of "disability". However, in 2022, the United States Court of Appeals for the Fourth Circuit stated that the ADA covers individuals with gender dysphoria, which may aid transgender people in accessing legal protections they otherwise may be unable to. Titles. Title I—employment. The ADA states that a "covered entity" shall not discriminate against "a qualified individual with a disability". This applies to job application procedures, hiring, advancement and discharge of employees, job training, and other terms, conditions, and privileges of employment. "Covered entities" include employers with 15 or more employees, as well as employment agencies, labor organizations, and joint labor-management committees. There are strict limitations on when a covered entity can ask job applicants or employees disability-related questions or require them to undergo medical examination, and all medical information must be kept confidential.
Prohibited discrimination may include, among other things, firing or refusing to hire someone based on a real or perceived disability, segregation, and harassment based on a disability. Covered entities are also required to provide reasonable accommodations to job applicants and employees with disabilities. A reasonable accommodation is a change in the way things are typically done that the person needs because of a disability, and can include, among other things, special equipment that allows the person to perform the job, scheduling changes, and changes to the way work assignments are chosen or communicated. An employer is not required to provide an accommodation that would involve undue hardship (excessive difficulty or expense), and the individual who receives the accommodation must still perform the essential functions of the job and meet the normal performance requirements. An employee or applicant who currently engages in the illegal use of drugs is not considered qualified when a covered entity takes adverse action based on such use.
Part of Title I was found unconstitutional by the United States Supreme Court as it pertains to states in the case of "Board of Trustees of the University of Alabama v. Garrett" as violating the sovereign immunity rights of the several states as specified by the Eleventh Amendment to the United States Constitution. The Court determined that state employees cannot sue their employer for violating ADA rules. State employees can, however, file complaints at the Department of Justice or the Equal Employment Opportunity Commission, who can sue on their behalf. Title II—public entities (and public transportation). Title II prohibits disability discrimination by all public entities at the local level, e.g., school district, municipal, city, or county, and at state level. Public entities must comply with Title II regulations by the U.S. Department of Justice. These regulations cover access to all programs and services offered by the entity. Access includes physical access described in the ADA Standards for Accessible Design and programmatic access that might be obstructed by discriminatory policies or procedures of the entity.
Title II applies to public transportation provided by public entities through regulations by the U.S. Department of Transportation. It includes the National Railroad Passenger Corporation (Amtrak), along with all other commuter authorities. This section requires the provision of paratransit services by public entities that provide fixed-route services. ADA also sets minimum requirements for space layout in order to facilitate wheelchair securement on public transport. Title II also applies to all state and local public housing, housing assistance, and housing referrals. The Office of Fair Housing and Equal Opportunity is charged with enforcing this provision. Title III—public accommodations (and commercial facilities). Under Title III, no individual may be discriminated against on the basis of disability with regards to the full and equal enjoyment of the goods, services, facilities, or accommodations of any place of public accommodation by any person who owns, leases, or operates a place of public accommodation. Public accommodations include most places of lodging (such as inns and hotels), recreation, transportation, education, and dining, along with stores, care providers, and places of public displays.
Under Title III of the ADA, all new construction (construction, modification or alterations) after the effective date of the ADA (approximately July 1992) must be fully compliant with the Americans With Disabilities Act Accessibility Guidelines (ADAAG) found in the Code of Federal Regulations at 28 C.F.R., Part 36, Appendix "A". Title III also has applications to existing facilities. One of the definitions of "discrimination" under Title III of the ADA is a "failure to remove" architectural barriers in existing facilities. See . This means that even facilities that have not been modified or altered in any way after the ADA was passed still have obligations. The standard is whether "removing barriers" (typically defined as bringing a condition into compliance with the ADAAG) is "readily achievable", defined as "...easily accomplished without much difficulty or expense". The statutory definition of "readily achievable" calls for a balancing test between the cost of the proposed alteration and the wherewithal of the business and/or owners of the business. Thus, what might be "readily achievable" for a sophisticated and financially capable corporation might not be readily achievable for a small or local business.
There are exceptions to this title; many private clubs and religious organizations may not be bound by Title III. With regard to historic properties (those properties that are listed or that are eligible for listing in the National Register of Historic Places, or properties designated as historic under state or local law), those facilities must still comply with the provisions of Title III of the ADA to the "maximum extent feasible" but if following the usual standards would "threaten to destroy the historic significance of a feature of the building" then alternative standards may be used. Under 2010 revisions of Department of Justice regulations, newly constructed or altered swimming pools, wading pools, and spas must have an accessible means of entrance and exit to pools for disabled people. However, the requirement is conditioned on whether providing access through a fixed lift is "readily achievable". Other requirements exist, based on pool size, include providing a certain number of accessible means of entry and exit, which are outlined in Section 242 of the standards. However, businesses are free to consider the differences in the application of the rules depending on whether the pool is new or altered, or whether the swimming pool was in existence before the effective date of the new rule. Full compliance may not be required for existing facilities; Section 242 and 1009 of the 2010 Standards outline such exceptions.
Service animals. ADA provides explicit coverage for service animals. Guidelines protect persons with disabilities and indemnify businesses from damages related to granting access to service animals. Businesses are allowed to ask if the animal is a service animal and ask what tasks it is trained to perform, but are not allowed to ask the service animal to perform the task nor ask for an animal ID. They cannot ask what the person's disabilities are. A person with a disability cannot be removed from the premises unless one of two things happen: the animal is out of control and its owner cannot control it (e.g., a dog barking uncontrollably), or the animal is a direct threat to someone's health and safety. Allergies and fear of animals are not considered to be such a threat. Businesses that prepare or serve food must allow service animals and their owners on the premises even if state or local health laws otherwise prohibit animals. Businesses that prepare or serve food are not required to provide care, food, a relief area for service animals. Extra fees for service animals are forbidden. They cannot be discriminated against, such as by isolation from people at a restaurant.
People with disabilities cannot be treated as "less than" other customers. However, if a business normally charges for damages caused by the person to property, damage caused by a service animal can also require compensation. Auxiliary aids. The ADA provides explicit coverage for auxiliary aids. ADA says that "a public accommodation shall take those steps that may be necessary to ensure that no individual with a disability is excluded, denied services, segregated or otherwise treated differently than other individuals because of the absence of auxiliary aids and services, unless the public accommodation can demonstrate that taking those steps would fundamentally alter the nature of the goods, services, facilities, privileges, advantages, or accommodations being offered or would result in an undue burden, i.e., significant difficulty or expense." The term "auxiliary aids and services" includes: Captions are considered one type of auxiliary aid. Since the passage of the ADA, the use of captioning has expanded. Entertainment, educational, informational, and training materials are captioned for deaf and hard-of-hearing audiences at the time they are produced and distributed. The Television Decoder Circuitry Act of 1990 requires that all televisions larger than 13 inches sold in the United States after July 1993 have a special built-in decoder that enables viewers to watch closed-captioned programming. The Telecommunications Act of 1996 directs the Federal Communications Commission (FCC) to adopt rules requiring closed captioning of most television programming. The FCC's rules on closed captioning became effective January 1, 1998.
Title IV—telecommunications. Title IV of the ADA amended the Communications Act of 1934 primarily by adding section . This section requires that all telecommunications companies in the U.S. take steps to ensure functionally equivalent services for consumers with disabilities, notably those who are deaf or hard of hearing and those with speech impairments. When Title IV took effect in the early 1990s, it led to the installation of public teletypewriter (TTY) machines and other TDD (telecommunications devices for the deaf). Title IV also led to the creation, in all 50 states and the District of Columbia, of what was then called dual-party relay services and now are known as Telecommunications Relay Services (TRS), such as STS relay. Today, many TRS-mediated calls are made over the Internet by consumers who use broadband connections. Some are Video Relay Service (VRS) calls, while others are text calls. In either variation, communication assistants translate between the signed or typed words of a consumer and the spoken words of others. In 2006, according to the Federal Communications Commission (FCC), VRS calls averaged two million minutes a month.
Title V—miscellaneous provisions. Title V includes technical provisions. It discusses, for example, the fact that nothing in the ADA amends, overrides or cancels anything in Section 504. Additionally, Title V includes an anti-retaliation or coercion provision. The "Technical Assistance Manual" for the ADA explains this provision: History. The ADA has roots in Section 504 of the Rehabilitation Act of 1973. Drafting. The law began in the Virginia House of Delegates in 1985 as the Virginians with Disabilities Act—supported by Warren G. Stambaugh—which was passed by the state Virginia. It is the first iteration of the Americans with Disabilities Act. In 1986, the National Council on Disability (NCD), an independent federal agency, issued a report, Towards Independence, in which the Council examined incentives and disincentives in federal laws towards increasing the independence and full integration of people with disabilities into U.S. society. Among the disincentives to independence the Council identified was the existence of large remaining gaps in civil rights coverage for people with disabilities in the United States. A principal conclusion of the report was to recommend the adoption of comprehensive civil rights legislation, which became the ADA.
The idea of federal legislation enhancing and extending civil rights legislation to millions of Americans with disabilities gained bipartisan support in late 1988 and early 1989. In early 1989 both Congress and the newly inaugurated Bush White House worked separately, then jointly, to write legislation capable of expanding civil rights without imposing undue harm or costs on those already in compliance with existing rules and laws. Lobbying. Over the years, key activists and advocates played an important role in lobbying members of the U.S. Congress to develop and pass the ADA, including Justin Whitlock Dart Jr., Patrisha Wright and others. Wright is known as "the General" for her work in coordinating the campaign to enact the ADA. She is widely considered the main force behind the campaign lobbying for the ADA. Support and opposition. Support. Senator Bob Dole was a supporter and advocate for the bill. Opposition from religious groups. Conservative evangelicals opposed the ADA because the legislation protected individuals with HIV, which they associated with homosexuality.
The debate over the Americans with Disabilities Act led some religious groups to take opposite positions. The Association of Christian Schools International opposed the ADA in its original form, primarily because the ADA labeled religious institutions "public accommodations" and thus would have required churches to make costly structural changes to ensure access for all. The cost argument advanced by ACSI and others prevailed in keeping religious institutions from being labeled as "public accommodations". Church groups such as the National Association of Evangelicals testified against the ADA's Title I employment provisions on grounds of religious liberty. The NAE believed the regulation of the internal employment of churches was "... an improper intrusion [of] the federal government." Opposition from business interests. Many companies, corporations, and business groups opposed the Americans with Disabilities Act, arguing that the legislation would impose costs on businesses. Testifying before Congress, Greyhound Bus Lines stated that the act had the potential to "deprive millions of people of affordable intercity public transportation and thousands of rural communities of their only link to the outside world." The US Chamber of Commerce argued that the costs of the ADA would be "enormous" and have "a disastrous impact on many small businesses struggling to survive." The National Federation of Independent Business, an organization that lobbies for small businesses, called the ADA "a disaster for small business". Pro-business conservative commentators joined in opposition, writing that the Americans with Disabilities Act was "an expensive headache to millions" that would not necessarily improve the lives of people with disabilities.
"Capitol Crawl". Shortly before the act was passed, disability rights activists with physical disabilities coalesced in front of the Capitol Building, shed their crutches, wheelchairs, powerchairs and other assistive devices, and immediately proceeded to crawl and pull their bodies up all 100 of the Capitol's front steps, without warning. As the activists did so, many of them chanted "ADA now", and "Vote, Now". Some activists who remained at the bottom of the steps held signs and yelled words of encouragement at the "Capitol Crawlers". Jennifer Keelan, a second grader with cerebral palsy, was videotaped as she pulled herself up the steps, using mostly her hands and arms, saying "I'll take all night if I have to." This direct action is reported to have "inconvenienced" several senators and to have pushed them to approve the act. While there are those who do not attribute much overall importance to this action, the "Capitol Crawl" of 1990 is seen by some present-day disability activists in the United States as a central act for encouraging the ADA into law.
Final passage. Senator Tom Harkin (D-IA) authored what became the final bill and was its chief sponsor in the Senate. Harkin delivered part of his introduction speech in sign language, saying it was so his deaf brother could understand. President George H. W. Bush, on signing the measure on July 26, 1990, said: ADA Amendments Act, 2008. The ADA defines a covered disability as a physical or mental impairment that substantially limits one or more major life activities, a history of having such an impairment, or being regarded as having such an impairment. The Equal Employment Opportunity Commission (EEOC) was charged with interpreting the 1990 law with regard to discrimination in employment. The EEOC developed regulations limiting an individual's impairment to one that "severely or significantly restricts" a major life activity. The ADAAA directed the EEOC to amend its regulations and replace "severely or significantly" with "substantially limits", a more lenient standard. On September 25, 2008, President George W. Bush signed the ADA Amendments Act of 2008 (ADAAA) into law. The amendment broadened the definition of "disability", thereby extending the ADA's protections to a greater number of people. The ADAAA also added to the ADA examples of "major life activities" including, but not limited to, "caring for oneself, performing manual tasks, seeing, hearing, eating, sleeping, walking, standing, lifting, bending, speaking, breathing, learning, reading, concentrating, thinking, communicating, and working" as well as the operation of several specified "major bodily functions". The act overturned a 1999 US Supreme Court case that held that an employee was not disabled if the impairment could be corrected by mitigating measures; it specifically provides that such impairment must be determined without considering such ameliorative measures. It also overturned the court's finding that an impairment that substantially limits one major life activity must also limit others to be considered a disability.
In 2008, the United States House Committee on Education and Labor stated that the amendment "makes it absolutely clear that the ADA is intended to provide broad coverage to protect anyone who faces discrimination on the basis of disability." Thus the ADAAA led to broader coverage of impaired employees. Web Content Accessibility Guidelines, 2019. In October 2019, the Supreme Court declined to resolve a circuit split as to whether websites are covered by the ADA. The Court turned down an appeal from Domino's Pizza and let stand a U.S. 9th Circuit Court of Appeals ruling which held that the Americans with Disabilities Act protects access not just to brick-and-mortar public accommodations, but also to the websites and apps of those businesses. Impact. The ADA led to significant improvements in terms of access to public services, accessibility in the built environment, and societal understanding of disability. Employment. Between 1991 (after the enactment of the ADA) and 1995, the employment rate of men with disabilities dropped by 7.8% regardless of age, educational level, or type of disability, with the most affected being young, less-educated and intellectually disabled men. While no causal link between the ADA and that trend has been definitively identified, some researchers have characterized the ADA as ineffectual and argued that it caused this decline by raising the cost of doing business for employers, who quietly avoid hiring people with disabilities for fear of lawsuit. To these employers, hiring people with disabilities became too expensive as they had to spend extra on assistive technology.
In 2001, for men of all working ages and women under 40, Current Population Survey data showed a sharp drop in the employment of disabled workers, leading at least two economists to attribute the cause to the Act. By contrast, a study in 2003 found that while the Act may have led to short term reactions by employers, in the long term, there were either positive or neutral consequences for wages and employment. In 2005, the rate of employment among disabled people increased to 45% of the population of disabled people. "Professional plaintiffs". Since enforcement of the act began in July 1992, it has quickly become a major component of employment law. The ADA allows private plaintiffs to receive only injunctive relief (a court order requiring the public accommodation to remedy violations of the accessibility regulations) and attorneys' fees, and does not provide monetary rewards to private plaintiffs who sue non-compliant businesses. Unless a state law, such as the California Unruh Civil Rights Act, provides for monetary damages to private plaintiffs, persons with disabilities do not obtain direct financial benefits from suing businesses that violate the ADA.
The attorneys' fees provision of Title III does provide incentive for lawyers to specialize and engage in serial ADA litigation, but a disabled plaintiff does not obtain a financial reward from attorneys' fees unless they act as their own attorney, or as mentioned above, a disabled plaintiff resides in a state that provides for minimum compensation and court fees in lawsuits. Moreover, there may be a benefit to these private attorneys general who identify and compel the correction of illegal conditions: they may increase the number of public accommodations accessible to persons with disabilities. "Civil rights law depends heavily on private enforcement. Moreover, the inclusion of penalties and damages is the driving force that facilitates voluntary compliance with the ADA." Courts have noted: However, in states that have enacted laws that allow private individuals to win monetary awards from non-compliant businesses (as of 2008, these include California, Florida, Hawaii, and Illinois), "professional plaintiffs" are typically found. At least one of these plaintiffs in California has been barred by courts from filing lawsuits unless he receives prior court permission. Through the end of fiscal year 1998, 86% of the 106,988 ADA charges filed with and resolved by the Equal Employment Opportunity Commission, were either dropped or investigated and dismissed by EEOC but not without imposing opportunity costs and legal fees on employers.
Case law. There have been some notable cases regarding the ADA. For example, a major hotel room marketer (Hotels.com) with their business presence on the Internet was sued because their customers with disabilities could not reserve hotel rooms through their website without substantial extra efforts that persons without disabilities were not required to perform. Such lawsuits represent a major potential expansion of the ADA in that they (known as "bricks vs. clicks"), seek to expand the ADA's authority to cyberspace, where entities may not have actual physical facilities that are required to comply. "Green v. State of California". "Green v. State of California, No. S137770 (Cal. August 23, 2007)" was a case in which the California Supreme Court was faced with deciding whether an employee suing the state is required to prove they are able to perform "essential" job duties, regardless of whether or not there was "reasonable accommodation", or if the employer must prove the person suing was unable to do so. The court ruled the burden was on the employee, not the employer, and reversed a disputed decision by the lower courts. Plaintiff attorney David Greenberg brought forth considerations of the concept that, even in the state of California, employers do not have to employ a worker who is unable to perform "essential job functions" with "reasonable accommodation". Forcing employers to do so "would defy logic and establish a poor public policy in employment matters."
"National Federation of the Blind v. Target Corporation". "National Federation of the Blind v. Target Corp." was a case where a major retailer, Target Corp., was sued because their web designers failed to design its website to enable persons with low or no vision to use it. "Board of Trustees of the University of Alabama v. Garrett". "Board of Trustees of the University of Alabama v. Garrett" was a United States Supreme Court case about Congress's enforcement powers under the Fourteenth Amendment to the Constitution. It decided that Title I of the Americans with Disabilities Act was unconstitutional insofar as it allowed private citizens to sue states for money damages. "Barden v. The City of Sacramento". "Barden v. The City of Sacramento", filed in March 1999, claimed that the City of Sacramento failed to comply with the ADA when, while making public street improvements, it did not bring its sidewalks into compliance with the ADA. Certain issues were resolved in federal court. One issue, whether sidewalks were covered by the ADA, was appealed to the 9th Circuit Court of Appeals, which ruled that sidewalks were a "program" under the ADA and must be made accessible to persons with disabilities. The ruling was later appealed to the U.S. Supreme Court, which refused to hear the case, letting stand the ruling of the 9th Circuit.
"Bates v. United Parcel Service, Inc". "Bates v. United Parcel Service, Inc (UPS;" begun in 1999) was the first equal opportunity employment class action brought on behalf of Deaf and Hard of Hearing workers throughout the country concerning workplace discrimination. It established legal precedent for these employees to be fully covered under the ADA. Key findings included: The outcome was that UPS agreed to pay a $5.8 million award and agreed to a comprehensive accommodations program that was implemented in their facilities throughout the country. "Spector v. Norwegian Cruise Line Ltd.". "Spector v. Norwegian Cruise Line Ltd." was a case that was decided by the United States Supreme Court in 2005. The defendant argued that as a vessel flying the flag of a foreign nation it was exempt from the requirements of the ADA. This argument was accepted by a federal court in Florida and, subsequently, the Fifth Circuit Court of Appeals. However, the U.S. Supreme Court reversed the ruling of the lower courts on the basis that Norwegian Cruise Lines was a business headquartered in the United States whose clients were predominantly Americans and, more importantly, operated out of port facilities throughout the United States.
"Olmstead v. L.C.". "Olmstead v. L.C." was a case before the United States Supreme Court in 1999. The two plaintiffs, Lois Curtis and E.W., were institutionalized in Georgia for diagnosed "mental retardation" and schizophrenia. Clinical assessments by the state determined that the plaintiffs could be appropriately treated in a community setting rather than the state institution. The plaintiffs sued the state of Georgia and the institution for being inappropriately treated and housed in the institutional setting rather than being treated in one of the state's community-based treatment facilities. The Supreme Court decided under Title II of the ADA that mental illness is a form of disability and therefore covered under the ADA, and that unjustified institutional isolation of a person with a disability is a form of discrimination because it "...perpetuates unwarranted assumptions that persons so isolated are incapable or unworthy of participating in community life." The court added, "Confinement in an institution severely diminishes the everyday life activities of individuals, including family relations, social contacts, work options, economic independence, educational advancement, and cultural enrichment."
Therefore, under Title II no person with a disability can be unjustly excluded from participation in or be denied the benefits of services, programs or activities of any public entity. "Michigan Paralyzed Veterans of America v. The University of Michigan". "Michigan Paralyzed Veterans of America v. The University of Michigan" was a case filed before the United States District Court for the Eastern District of Michigan. It was filed on behalf of the Michigan Paralyzed Veterans of America against the University of Michigan claiming that Michigan Stadium violated the Americans with Disabilities Act in its $226-million renovation by failing to add enough seats for disabled fans or accommodate the needs for disabled restrooms, concessions and parking. Additionally, the distribution of the accessible seating was at issue, with nearly all the seats being provided in the end-zone areas. The U.S. Department of Justice assisted in the suit, which was settled in March 2008. The settlement required the stadium to add 329 wheelchair seats throughout the stadium by 2010, and an additional 135 accessible seats in clubhouses to go along with the existing 88 wheelchair seats. This case was significant because it set a precedent for the uniform distribution of accessible seating and gave the DOJ the opportunity to clarify previously unclear rules. The agreement now is a blueprint for all stadiums and other public facilities regarding accessibility.
"Paralyzed Veterans of America v. Ellerbe Becket Architects and Engineers". One of the first major ADA lawsuits, "Paralyzed Veterans of America v. Ellerbe Becket Architects and Engineers" (PVA 1996) was focused on the wheelchair accessibility of a stadium project that was still in the design phase, MCI Center (now known as Capital One Arena) in Washington, D.C. Previous to this case, which was filed only five years after the ADA was passed, the DOJ was unable or unwilling to provide clarification on the distribution requirements for accessible wheelchair locations in large assembly spaces. While Section 4.33.3 of ADAAG makes reference to lines of sight, no specific reference is made to seeing over standing patrons. The MCI Center, designed by Ellerbe Becket Architects & Engineers, was designed with too few wheelchair and companion seats, and the ones that were included did not provide sight lines that would enable the wheelchair user to view the playing area while the spectators in front of them were standing. This case and another related case established precedent on seat distribution and sight lines issues for ADA enforcement that continues to present day.
"Toyota Motor Manufacturing, Kentucky, Inc. v. Williams". "Toyota Motor Manufacturing, Kentucky, Inc. v. Williams", was a case in which the US Supreme Court interpreted the meaning of the phrase "substantially impairs" as used in the Americans with Disabilities Act. It reversed a Sixth Circuit Court of Appeals decision to grant partial summary judgment in favor of the respondent, Ella Williams, that classified her inability to perform manual job-related tasks as a disability. The Court held that the "major life activity" definition for evaluating the performance of manual tasks focuses the inquiry on whether Williams was unable to perform a range of tasks central to most people in carrying out the activities of daily living, not whether Williams was unable to perform her specific job tasks. Therefore, the determination of whether an impairment rises to the level of a disability is not limited to activities in the workplace solely, but rather to manual tasks in life in general. When the Supreme Court applied this standard, it found that the Court of Appeals had incorrectly determined the presence of a disability because it relied solely on her inability to perform specific manual work tasks, which was insufficient in proving the presence of a disability. The Court of Appeals should have taken into account the evidence presented that Williams retained the ability to do personal tasks and household chores, such activities being the nature of tasks most people do in their daily lives, and placed too much emphasis on her job disability. Since the evidence showed that Williams was performing normal daily tasks, it ruled that the Court of Appeals erred when it found that Williams was disabled. This ruling has since been legislatively overturned by the ADA Amendments Act of 2008 (ADAAA). In fact, Congress explicitly cited "Toyota v. Williams" in the text of the ADAAA itself as one of its driving influences for passing the ADAAA.
"US Airways, Inc. v. Barnett". "US Airways, Inc. v. Barnett" was decided by the US Supreme Court in 2002. This case held that even requests for accommodation that might seem reasonable on their face, e.g., a transfer to a different position, can be rendered unreasonable because it would require a violation of the company's seniority system. While the court held that, in general, a violation of a seniority system renders an otherwise reasonable accommodation unreasonable, a plaintiff can present evidence that, despite the seniority system, the accommodation is reasonable in the specific case at hand, e.g., the plaintiff could offer evidence that the seniority system is so often disregarded that another exception would not make a difference. Importantly, the court held that the defendant need not provide proof that this particular application of the seniority system should prevail, and that, once the defendant showed that the accommodation violated the seniority system, it fell to Barnett to show it was nevertheless reasonable.
In this case, Barnett was a US Airways employee who injured his back, rendering him physically unable to perform his cargo-handling job. Invoking seniority, he transferred to a less-demanding mailroom job, but this position later became open to seniority-based bidding and was bid on by more senior employees. Barnett requested the accommodation of being allowed to stay on in the less-demanding mailroom job. US Airways denied his request, and he lost his job. The Supreme Court decision invalidated both the approach of the district court, which found that the mere presence and importance of the seniority system was enough to warrant a summary judgment in favor of US Airways, as well as the circuit court's approach that interpreted 'reasonable accommodation' as 'effective accommodation.' "Access Now v. Southwest Airlines". "Access Now, Inc. v. Southwest Airlines Co." was a 2002 case where the District Court decided that the website of Southwest Airlines was not in violation of the Americans with Disabilities Act, because the ADA is concerned with things with a physical existence and thus cannot be applied to cyberspace. Judge Patricia A. Seitz found that the "virtual ticket counter" of the website was a virtual construct, and hence not a "public place of accommodation". As such, "To expand the ADA to cover 'virtual' spaces would be to create new rights without well-defined standards."
"Ouellette v. Viacom International Inc.". "Ouellette v. Viacom International Inc." (2011) held that a mere online presence does not subject a website to the ADA guidelines. Thus Myspace and YouTube were not liable for a dyslexic man's inability to navigate the site regardless of how impressive the "online theater" is. "Authors Guild v. HathiTrust". "Authors Guild v. HathiTrust" was a case in which the District Court decided that the HathiTrust digital library was a transformative, fair use of copyrighted works, making a large number of written text available to those with print disability. "Zamora-Quezada v. HealthTexas Medical Group". "Zamora-Quezada v. HealthTexas Medical Group" (begun in 1998) was the first time this act was used against HMOs when a novel lawsuit was filed by Texas attorney Robert Provan against five HMOs for their practice of revoking the contracts of doctors treating disabled patients. In 1999, these HMOs sought to dismiss Provan's lawsuit, but a federal court ruled against them, and the case was settled out of court. Many decisions relating to Provan's unique lawsuit against these HMOs have been cited in other court cases since.
"Campbell v. General Dynamics Government Systems Corp.". "Campbell v. General Dynamics Government Systems Corp." (2005) concerned the enforceability of a mandatory arbitration agreement contained in a dispute resolution policy linked to an e-mailed company-wide announcement, insofar as it applies to employment discrimination claims brought under the Americans with Disabilities Act. "Tennessee v. Lane". "Tennessee v. Lane", 541 U.S. 509 (2004), was a case in the Supreme Court of the United States involving Congress's enforcement powers under section 5 of the Fourteenth Amendment. George Lane was unable to walk after a 1997 car accident in which he was accused of driving on the wrong side of the road. A woman was killed in the crash, and Lane faced misdemeanor charges of reckless driving. The suit was brought about because he was denied access to appear in criminal court because the courthouse had no elevator, even though the court was willing to carry him up the stairs and then willing to move the hearing to the first floor. He refused, citing he wanted to be treated as any other citizen, and was subsequently charged with failure to appear, after appearing at a previous hearing where he dragged himself up the stairs. The court ruled that Congress did have enough evidence that disabled people were being denied those fundamental rights that are protected by the Due Process clause of the Fourteenth Amendment and had the enforcement powers under section 5 of the Fourteenth Amendment. It further ruled that "reasonable accommodations" mandated by the ADA were not unduly burdensome and disproportionate to the harm. Gender dysphoria. In 2022, the United States Court of Appeals for the Fourth Circuit stated that the ADA covers individuals with gender dysphoria, which may aid transgender people in accessing legal protections they otherwise may be unable to.
Americans with Disabilities Act of 1990/Findings and Purposes
Americans with Disabilities Act of 1990/Definitions
Americans with Disabilities Act of 1990/Title III
Apple I The Apple Computer 1 (Apple-1), later known predominantly as the Apple I, is an 8-bit motherboard-only personal computer designed by Steve Wozniak and released by the Apple Computer Company (now Apple Inc.) in 1976. The company was initially formed to sell the Apple Iits first product and would later become the world's largest technology company. The idea of starting a company and selling the computer came from Wozniak's friend and Apple co-founder Steve Jobs. A differentiator of the Apple I was that it included video display terminal circuitry on its circuit board, allowing it to connect to a low-cost composite video monitor or television, whereas others avoided this and used more expensive monitors because business was used to more characters per displayed/typewritten line. It and the Sol-20 were some of the first home computers to have this capability. To finance the Apple I's development, Wozniak and Jobs sold some of their possessions for a few hundred dollars. Wozniak demonstrated the first prototype in July 1976 at the Homebrew Computer Club in Palo Alto, California, impressing the Byte Shop, an early computer retailer. After securing an order for 50 computers, Jobs was able to order the parts on credit and deliver the first Apple products after ten days.
The Apple I was one of the first computers available that used the inexpensive MOS Technology 6502 microprocessor. An expansion included a BASIC interpreter, allowing users to utilize BASIC at home instead of at institutions with mainframe computers, greatly lowering the entry cost for computing with BASIC. Production was discontinued on September 30, 1977, after the June 10, 1977 introduction of its successor, the Apple II, which "Byte" magazine referred to as part of the "1977 Trinity" of personal computing (along with the PET 2001 from Commodore Business Machines and the TRS-80 Model I from Tandy Corporation). As relatively few computers were made before they were discontinued, coupled with their status as Apple's first product, surviving Apple I units are now displayed in computer museums. History. Development. In 1974, while visiting famous phone phreak John Draper in California, Steve Wozniak watched him connect a modem to the ARPANET – the precursor to the internet – and use a teleprinter to play chess with someone from Boston; this inspired him to make a cheap terminal that used an inexpensive keyboard from Sears and a standard TV. Later in March 1975, Wozniak started attending meetings of the Homebrew Computer Club, which was a major source of inspiration for him. New microcomputers such as the Altair 8800 inspired Wozniak to build a microprocessor into his video terminal circuit to make a complete computer. At the time the only appropriate CPUs available were the Intel 8080, and the Motorola 6800. Of these options, Wozniak preferred the 6800, though he was financially unable to obtain either. Instead, he began designing computers on paper until he could afford a CPU.
When the $25 MOS Technology 6502 was released in late 1975, Wozniak wrote a version of BASIC for it, then began to design a computer for it to run on. The 6502 was developed by many of the same engineers that designed the 6800, as many in Silicon Valley left employers to form their own companies. Wozniak's earlier 6800 computer design needed only minor changes to run on the new processor. By March 1, 1976, Wozniak completed the basic design of his computer. Wozniak originally offered the design to HP while working there, but it was rejected by the company on five occasions. When he demonstrated his computer at the Homebrew Computer Club, his friend and fellow club regular Steve Jobs was immediately interested in its commercial potential. Wozniak intended to share schematics of the machine for free; however, Jobs advised him to start a business together and sell bare printed circuit boards for the computer. Wozniak, at first skeptical, was later convinced by Jobs that even if they were not successful they could at least say to their grandchildren that they had had their own company. To raise the money they needed to build the first batch of the circuit boards, Wozniak sold his HP-65 scientific calculator while Jobs sold his Volkswagen van.
After the company was formed a month later, Jobs and Wozniak gave a presentation of the fully assembled "Apple Computer A" at the Homebrew Computer Club. Paul Terrell, who was starting a new computer shop in Mountain View, California, called the Byte Shop, saw the presentation and was impressed by the machine. Terrell told Jobs that he would order 50 units of the Apple I and pay $500 each on delivery, but only if they came fully assembledhe was not interested in buying bare printed circuit boards with no components. Jobs took the purchase order from the Byte Shop to national electronic parts distributor Cramer Electronics, and ordered the components needed. When asked by the credit manager how he would pay for the parts, Jobs replied, "I have this purchase order from the Byte Shop chain of computer stores for 50 of my computers and the payment terms are COD. If you give me the parts on net 30-day terms I can build and deliver the computers in that time frame, collect my money from Terrell at the Byte Shop and pay you."

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.