Bristol is a city and county in South West England with a population of 459,300. The wider district has the 10th-largest population in England; the urban area population of 724,000 is the 8th-largest in the UK. The city borders North Somerset and South Gloucestershire, with the cities of Bath and Gloucester to the south-east and north-east, respectively. South Wales lies across the Severn estuary. Iron Age hill forts and Roman villas were built near the confluence of the rivers Frome and Avon, around the beginning of the 11th century the settlement was known as Brycgstow. Bristol received a royal charter in 1155 and was divided between Gloucestershire and Somerset until 1373, when it became a county of itself. From the 13th to the 18th century, Bristol was among the top three English cities after London in tax receipts. Bristol was surpassed by the rapid rise of Birmingham and Liverpool in the Industrial Revolution. Bristol was a starting place for early voyages of exploration to the New World.
On a ship out of Bristol in 1497 John Cabot, a Venetian, became the first European since the Vikings to land on mainland North America. In 1499 William Weston, a Bristol merchant, was the first Englishman to lead an exploration to North America. At the height of the Bristol slave trade, from 1700 to 1807, more than 2,000 slave ships carried an estimated 500,000 people from Africa to slavery in the Americas; the Port of Bristol has since moved from Bristol Harbour in the city centre to the Severn Estuary at Avonmouth and Royal Portbury Dock. Bristol's modern economy is built on the creative media and aerospace industries, the city-centre docks have been redeveloped as centres of heritage and culture; the city has the largest circulating community currency in the UK—the Bristol pound, pegged to the Pound sterling. The city has two universities, the University of Bristol and the University of the West of England, a variety of artistic and sporting organisations and venues including the Royal West of England Academy, the Arnolfini, Spike Island, Ashton Gate and the Memorial Stadium.
It is connected to London and other major UK cities by road and rail, to the world by sea and air: road, by the M5 and M4. One of the UK's most popular tourist destinations, Bristol was selected in 2009 as one of the world's top ten cities by international travel publishers Dorling Kindersley in their Eyewitness series of travel guides; the Sunday Times named it as the best city in Britain in which to live in 2014 and 2017, Bristol won the EU's European Green Capital Award in 2015. The most ancient recorded name for Bristol is the archaic Welsh Caer Odor, consistent with modern understanding that early Bristol developed between the River Frome and Avon Gorge, it is most stated that the Saxon name Bricstow was a simple calque of the existing Celtic name, with Bric a literal translation of Odor, the common Saxon suffix Stow replacing Caer. Alternative etymologies are supported by numerous orthographic variations in medieval documents, with Samuel Seyer enumerating 47 alternative forms; the Old English form Brycgstow is used to derive the meaning place at the bridge.
Utilizing another form, Rev. Dr. Shaw derived the name from the Celtic words bras, or braos and tuile; the poet Thomas Chatterton popularised a derivation from Brictricstow linking the town to Brictric, a leading landholder in the area. It appears that the form Bricstow prevailed until 1204, the Bristolian'L' is what changed the name to Bristol. Archaeological finds, including flint tools believed to be between 300,000 and 126,000 years old made with the Levallois technique, indicate the presence of Neanderthals in the Shirehampton and St Annes areas of Bristol during the Middle Palaeolithic. Iron Age hill forts near the city are at Leigh Woods and Clifton Down, on the side of the Avon Gorge, on Kings Weston Hill near Henbury. A Roman settlement, existed at what is now Sea Mills. Isolated Roman villas and small forts and settlements were scattered throughout the area. Bristol was founded by 1000. By 1067 Brycgstow was a well-fortified burh, that year the townsmen beat off a raiding party from Ireland led by three of Harold Godwinson's sons.
Under Norman rule, the town had one of the strongest castles in southern England. Bristol was the place of exile for Diarmait Mac Murchada, the Irish king of Leinster, after being overthrown; the Bristol merchants subsequently played a prominent role in funding Richard Strongbow de Clare and the Norman invasion of Ireland. The port developed in the 11th century around the confluence of the Rivers Frome and Avon, adjacent to Bristol Bridge just outside the town walls. By the 12th century Bristol was an important port, handling much of England's trade with Ireland, including slaves. There was an important Jewish community in Bristol from the late 12th century through to the late 13th century when all Jews were expelled from England; the stone bridge built in 1247 was replaced by the current bridge during the 1760s. The town incorporated neighbouring suburbs and became a county in 1373, the first town in England to be given this status. During this period, Bristol became manufacturing centre. By the 14th centur
World War II
World War II known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries; the major participants threw their entire economic and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China, it included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, the only use of nuclear weapons in war. Japan, which aimed to dominate Asia and the Pacific, was at war with China by 1937, though neither side had declared war on the other. World War II is said to have begun on 1 September 1939, with the invasion of Poland by Germany and subsequent declarations of war on Germany by France and the United Kingdom.
From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Finland and the Baltic states. Following the onset of campaigns in North Africa and East Africa, the fall of France in mid 1940, the war continued between the European Axis powers and the British Empire. War in the Balkans, the aerial Battle of Britain, the Blitz, the long Battle of the Atlantic followed. On 22 June 1941, the European Axis powers launched an invasion of the Soviet Union, opening the largest land theatre of war in history; this Eastern Front trapped most crucially the German Wehrmacht, into a war of attrition. In December 1941, Japan launched a surprise attack on the United States as well as European colonies in the Pacific. Following an immediate U. S. declaration of war against Japan, supported by one from Great Britain, the European Axis powers declared war on the U.
S. in solidarity with their Japanese ally. Rapid Japanese conquests over much of the Western Pacific ensued, perceived by many in Asia as liberation from Western dominance and resulting in the support of several armies from defeated territories; the Axis advance in the Pacific halted in 1942. Key setbacks in 1943, which included a series of German defeats on the Eastern Front, the Allied invasions of Sicily and Italy, Allied victories in the Pacific, cost the Axis its initiative and forced it into strategic retreat on all fronts. In 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained its territorial losses and turned toward Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in Central China, South China and Burma, while the Allies crippled the Japanese Navy and captured key Western Pacific islands; the war in Europe concluded with an invasion of Germany by the Western Allies and the Soviet Union, culminating in the capture of Berlin by Soviet troops, the suicide of Adolf Hitler and the German unconditional surrender on 8 May 1945.
Following the Potsdam Declaration by the Allies on 26 July 1945 and the refusal of Japan to surrender under its terms, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki on 6 and 9 August respectively. With an invasion of the Japanese archipelago imminent, the possibility of additional atomic bombings, the Soviet entry into the war against Japan and its invasion of Manchuria, Japan announced its intention to surrender on 15 August 1945, cementing total victory in Asia for the Allies. Tribunals were set up by fiat by the Allies and war crimes trials were conducted in the wake of the war both against the Germans and the Japanese. World War II changed the political social structure of the globe; the United Nations was established to foster international co-operation and prevent future conflicts. The Soviet Union and United States emerged as rival superpowers, setting the stage for the nearly half-century long Cold War. In the wake of European devastation, the influence of its great powers waned, triggering the decolonisation of Africa and Asia.
Most countries whose industries had been damaged moved towards economic expansion. Political integration in Europe, emerged as an effort to end pre-war enmities and create a common identity; the start of the war in Europe is held to be 1 September 1939, beginning with the German invasion of Poland. The dates for the beginning of war in the Pacific include the start of the Second Sino-Japanese War on 7 July 1937, or the Japanese invasion of Manchuria on 19 September 1931. Others follow the British historian A. J. P. Taylor, who held that the Sino-Japanese War and war in Europe and its colonies occurred and the two wars merged in 1941; this article uses the conventional dating. Other starting dates sometimes used for World War II include the Italian invasion of Abyssinia on 3 October 1935; the British historian Antony Beevor views the beginning of World War II as the Battles of Khalkhin Gol fought between Japan and the fo
Joseph Jean Ferdinand Kutter is considered one of Luxembourg's most important painters. He was influenced by the Impressionists but developed his own distinctive Expressionist style. Kutter was born on 12 December 1894 in Luxembourg City where his father, Paul Kutter, was one of the city's early photographers. Hoping to become a painter, he first attended the Ecole d'Artisans in Luxembourg and the schools of decorative art in Strasbourg and Munich. From 1917 to 1918, he studied at the Munich Academy where he was introduced to a style of painting inspired by Wilhelm Leibl. From 1919, after being influenced by Cézanne, he presented his paintings at the Secessionist exhibitions in Munich. Although he returned to Luxembourg in 1924, he continued to exhibit in Munich until 1932 as a result of the negative criticism his nude paintings received in his home town. From 1925, he became interested in Flemish Expressionism, flourishing in Belgium and France. Encouraged by André de Ridder, a Belgian art critic and strong supporter of Expressionism, Kutter participated in the 1926 Salon d'Automne in Paris.
The same year, he became a founding member of the avant-garde Luxembourg secession movement, exhibiting at its salon in 1927. He continued to exhibit at the Salon d'automne in Paris, his abilities were recognized in France and Belgium, much less so in Germany. In 1933, he ceased exhibiting in Germany after being considered a degenerate. In 1936, he was commissioned to paint two large works of "Luxembourg" and "Clervaux" for the French International Exposition. While he was working on them, he began to suffer from a painful disease which the doctors were unable to diagnose. During his better periods, he painted his clowns which reveal his suffering and anxiety, he died on 2 January 1941 in Luxembourg City. In Kutter's paintings, the subjects stand in the foreground as if being photographed, his portraits, painted with strong brushstrokes show figures with excessively large noses, always attracting attention. From 1918, Kutter's paintings began to present Expressionist motifs in his landscapes and floral works where intense lines and colours became prominent.
Although Kutter spent a number of years in Germany, his work was influenced above all by trends in France and Belgium. His centre of attention was the human figure, he represented his subjects as sad, despairing clowns. The two large paintings he was commissioned to paint for Luxembourg's pavilion at the 1937 World Exposition in Pairs are excellent examples of his maturing Expressionist style. In his painting of "Luxembourg", his view of the city accentuates the stacked terracing of the houses, emphasizes the cubic appearance of the buildings, bestows a harsh appearance on the defensive walls and brings out the strength of the fortifications. "The Champion", National Museum of Art and History, depicts the Luxembourg racing cyclist Nicolas Frantz. "The Wooden Horse", National Museum of Art and History, Luxembourg. "Luxembourg", National Museum of Art and History, Luxembourg. "Clervaux", National Museum of Art and History, Luxembourg. Joseph-Emile Muller: Kutter. UNIL, Luxembourg, 1945 Ingeborg Kuhn-Regnier: Joseph Kutter.
Editions de l'Imprimerie 1990 t l'œuvre de Joseph Kutter. Promotion 4 a.s.b.l. Luxembourg, 1994 Jean Luc Koltz, Edmond Thill, Robert Wagner: Joseph Kutter, Luxembourg, 1894-1941. Grand-Duché de Luxembourg, Ministère des Affaires Culturelles, Musée National d'Histoire et d'Art, 1994 Jean Luc Koltz, Edmond Thill: Joseph Kutter. Catalogue raisonné de l'oeuvre. Editions Saint-Paul, Luxembourg, 2e éd. 2008
Lyndon B. Johnson
Lyndon Baines Johnson referred to as LBJ, was an American politician who served as the 36th president of the United States from 1963 to 1969. The 37th vice president of the United States from 1961 to 1963, he assumed the presidency following the assassination of President John F. Kennedy. A Democrat from Texas, Johnson served as a United States Representative and as the Majority Leader in the United States Senate. Johnson is one of only four people. Born in a farmhouse in Stonewall, Johnson was a high school teacher and worked as a congressional aide before winning election to the House of Representatives in 1937, he won election to the Senate in 1948 and was appointed to the position of Senate Majority Whip in 1951. He became the Senate Minority Leader in 1953 and the Senate Majority Leader in 1955, he became known for his domineering personality and the "Johnson treatment", his aggressive coercion of powerful politicians to advance legislation. Johnson ran for the Democratic nomination in the 1960 presidential election.
Although unsuccessful, he accepted the invitation of then-Senator John F. Kennedy of Massachusetts to be his running mate, they went on to win a close election over the Republican ticket of Richard Nixon and Henry Cabot Lodge Jr. On November 22, 1963, Kennedy was assassinated and Johnson succeeded him as president; the following year, Johnson won in a landslide. With 61.1 percent of the popular vote, Johnson won the largest share of the popular vote of any candidate since the uncontested 1820 election. In domestic policy, Johnson designed the "Great Society" legislation to expand civil rights, public broadcasting, Medicaid, aid to education, the arts and rural development, public services and his "War on Poverty". Assisted in part by a growing economy, the War on Poverty helped millions of Americans rise above the poverty line during his administration. Civil rights bills that he signed into law banned racial discrimination in public facilities, interstate commerce, the workplace and housing.
With the passage of the Immigration and Nationality Act of 1965, the country's immigration system was reformed, encouraging greater emigration from regions other than Europe. Johnson's presidency marked the peak of modern liberalism after the New Deal era. In foreign policy, Johnson escalated American involvement in the Vietnam War. In 1964, Congress passed the Gulf of Tonkin Resolution, which granted Johnson the power to use military force in Southeast Asia without having to ask for an official declaration of war; the number of American military personnel in Vietnam increased from 16,000 advisors in non-combat roles in 1963 to 525,000 in 1967, many in combat roles. American casualties soared and the peace process stagnated. Growing unease with the war stimulated a large, angry anti-war movement based chiefly among draft-age students on university campuses. Johnson faced further troubles when summer riots began in major cities in 1965 and crime rates soared, as his opponents raised demands for "law and order" policies.
While Johnson began his presidency with widespread approval, support for him declined as the public became frustrated with both the war and the growing violence at home. In 1968, the Democratic Party factionalized. Nixon was elected to succeed him, as the New Deal coalition that had dominated presidential politics for 36 years collapsed. After he left office in January 1969, Johnson returned to his Texas ranch, where he died of a heart attack at age 64, on January 22, 1973. Johnson is ranked favorably by many historians because of his domestic policies and the passage of many major laws that affected civil rights, gun control, wilderness preservation, Social Security, although he has drawn substantial criticism for his escalation of the Vietnam War. Lyndon Baines Johnson was born on August 27, 1908, near Stonewall, Texas, in a small farmhouse on the Pedernales River, he was the oldest of five children born to Samuel Ealy Johnson Rebekah Baines. Johnson had one brother, Sam Houston Johnson, three sisters.
The nearby small town of Johnson City, was named after LBJ's cousin, James Polk Johnson, whose forebears had moved west from Georgia. Johnson had English and Ulster Scots ancestry, he was maternally descended from pioneer Baptist clergyman George Washington Baines, who pastored eight churches in Texas, as well as others in Arkansas and Louisiana. Baines, the grandfather of Johnson's mother, was the president of Baylor University during the American Civil War. Johnson's grandfather, Samuel Ealy Johnson Sr. was raised as a Baptist and for a time was a member of the Christian Church. In his years the grandfather became a Christadelphian; as a politician, Johnson was influenced in his positive attitude toward Jews by the religious beliefs that his family his grandfather, had shared with him. Johnson's favorite Bible verse came from the King James Version of Isaiah 1:18. "Come now, let us reason together..." In school, Johnson was an awkward, talkative youth, elected president of his 11th-grade class.
He graduated in 1924 from Johnson City High School, where he participated in public speaking and baseball. At age 15, Johnson was the youngest member of his class. Pressured by his parents to attend college, he en
National Federation of the Blind
The National Federation of the Blind is an organization of blind people in the United States. It is the largest organization led by blind people in the United States, its national headquarters are in Maryland. Anyone, blind or sighted, is permitted to join the NFB, but a majority of members in its local chapters, state affiliates, nationwide divisions must be blind, as must its officers and board members at every level with exception of the National Organization of Parents of Blind Children; this structure is intended to ensure that the organization is run by blind people and reflects the collective views of its blind members, the NFB refers to itself as "the voice of the nation's blind." The philosophy of the organization is. We have our share of both geniuses and jerks, but most of us somewhere between, ordinary people living ordinary lives." The NFB works to promulgate its philosophy by educating and recruiting new members, working to educate the general public, interacting with legislators and policy makers at the local and national levels.
The positions of the National Federation of the Blind on issues are determined by its national convention, which meets annually and has between 2,500 and 3,000 delegates from the organization's affiliates in the fifty states, the District of Columbia, Puerto Rico. The policy positions of the NFB take the form of resolutions, which are voted upon by the convention. Like a union, the convention is subsidized by the organization making it affordable to those attending; the agenda of the National Convention is published on-line prior to its convention. Its logo consists of an outline of a walking person with a white cane; the NFB-style white cane is longer than most in order to allow the blind person to use a more natural walking position with their arms at their sides, rather than extended in front of them. The added length allows the blind person to walk more by giving more advanced information. In addition, the lighter weight of the fiberglass and carbon fiber canes, coupled with the metal tip, provides more information than the heavier aluminum style canes with plastic tips.
Federation members view the long white cane as a tool of independence and self-determination, rather than one of helplessness and dependency, as it provides greater mobility to the blind. Though detractors of the National Federation of the Blind assert that the NFB is anti guide dog, the NFB has a division dedicated to educating the public about the use of guide dogs, while promoting and fostering effective handling of guide dogs by its members; the National Association of Guide Dog Users is one of the largest and fastest growing divisions of the Federation. In 1940 sixteen people met in Wilkes-Barre, Pennsylvania, to develop a constitution that would unite organizations of blind people in seven states in a national federation that would serve as a vehicle for collective action to improve the prospects of the nation's blind citizens; the founder and president of the NFB for its first twenty years was Dr. Jacobus tenBroek, a professor and constitutional scholar; the NFB's first logo was a circle with the words "Security and Opportunity" forming a triangle at the center of the circle.
This expressed demands of the fledgling organization. TenBroek led early battles to obtain a modest stipend for blind people so they could live independently, equal access to jobs in the Civil Service and elsewhere where blind candidates had been prohibited from applying, equal access to housing and places of public accommodation; because of pressure exerted from within and differences of opinion about whether the organization should be a loose confederacy of strong state affiliates or a unified federal structure with state affiliates and local chapters, the NFB split into two groups in 1961. Those who left the NFB united to form the American Council of the Blind, an organization that continues to exist today. Jacobus tenBroek, who had served as president of the NFB for 20 years, resigned due to these problems, was succeeded by John Taylor, succeeded by Russell Kletzing the following year, but tenBroek became president again in 1966; the NFB replaced the handful of affiliates that had left, by the 1970s it had regained its momentum.
When Jacobus tenBroek died in 1968, he was succeeded in the presidency by Kenneth Jernigan, who served as president for most of the period until 1986 and who continued to be a blind leader and thinker with an international reputation until his death in 1998. Marc Maurer, a young lawyer, mentored by Jernigan, was elected president in 1986 and served as President until 2014 when he was replaced by Mark Riccobono, the current president of the organization. In 1978 Jernigan led the organization in establishing its national headquarters at 1800 Johnson Street in Baltimore, Maryland; the group remodeled and occupied the four floors of a block-long building, which they named the National Center for the Blind. The NFB broke ground in October 2001 for a twenty-million-dollar research and training institute now located adjacent to the National Center; the National Federation of the Blind Jernigan Institute opened for business in January 2004. Continuing to exert its influence, the NFB has taken over Braille Transcriber Certification from the Library of Congress, will receive up to $10 million from a US coin honoring Louis Braille and works to influence state training p
Dr. Lilli Nielsen was a Danish psychologist in the field of teaching blind children and those with multiple disabilities, she has written several books on the subject. Are You Blind? - This book focuses on the adult's interactions when working with children/adults with multiple disabilities. The needs of individuals with autistic-like tendencies or who exhibit self-injurious or aggressive behaviors are addressed; the Five Phases of Educational Treatment are presented in detail - a technique used to build trust and encourage skill attainment. Early Learning Step By Step - Parents and therapists who work with children and adults with multiple special needs will gain an understanding of how all individuals achieve readiness skills for learning. Environmental intervention can facilitate skill attainment through Active Learning equipment and techniques, including learning to move, coordinate hand movement, learning to chew/eat, dress/undress, play constructively. Educational Approaches - This book is a collection of Dr. Nielsen's papers, articles and research ideas.
It explains how she expanded the educational approaches for children and infants with vision impairments. Functional Scheme - This functional skill assessment and learning reassessment tool was developed by Dr. Nielsen to meet the needs of children and adults who are functioning at a developmental level under 48 months; the purpose of the tool is to create the best possible basis for developing an appropriate learning program for the learner. Space and Self - Dr. Nielsen details the meaning of spatial relations as it applies to the development of self-identity; the development and use of the “Little Room” is provided, with particular emphasis on promoting object conceptualization, self-identification and spatial relations in individuals with multiple special needs. Spatial Relations in Congenitally Blind Infants - This is Dr. Nielsen's dissertation on her scientific study, which resulted in the design of the "Little Room." The study investigated whether a specially designed environment would facilitate the development of early spatial relations in congenitally blind infants.
The Comprehending Hand - The ability to grasp is of fundamental importance for a child with special needs to get into contact with his/her surroundings and to enhance the development of the other senses. The book gives practical hints on how to adapt materials and surroundings to stimulate and encourage fine motor skill development; the FIELA Curriculum – 730 Learning Environments - Developed by Dr. Nielsen, The Flexible Individual Enriched Level Appropriate Curriculum offers 730 examples of developmentally appropriate activities for children and adults with multiple disabilities; this book is an "appetizer" to the thousands of learning environments and activities a child or adult needs to develop and learn to his potential. She was the second of seven children; when she was seven she was charged with the responsibility of taking care of her blind younger brother. She was a preschool teacher worked in a hospital, became a psychologist, was hired to teach the blind. In 1988 she earned a PhD in psychology at the University of Århus.
Lilli Nielsen has worked as special education adviser at Refsnaesskolen, National Institute to Blind and Partially Sighted Children and Youth in Denmark. She has been awarded the Knight Order of the Dannebrog. Dr. Lilli Nielsen died on the June 24, 2013, at the public hospital of Kolding after a short period of illness; the Active Learning approach emphasizes. All activity in the earliest stages of development "wires our brains" and establishes critical foundational concepts and skills necessary for all future learning. Individuals with multiple disabilities are at great risk from developing reliance on others to interact with the world around them, they learn to be a passive rather than active participant, waiting for adults to provide activity rather than seeking it out on their own. Children and adults with special needs develop stereotypical or aggressive behaviors in order to communicate with others or cope within the environments in which they are placed. Active Learning recognizes; the programming and intervention for facilitating learning must reflect this individuality.
Active Learning emphasizes creating a developmentally appropriate and enriched environment so that children and adults with multiple special needs become active learners. Dr. Nielsen's Active Learning approach addresses the breakdowns that can occur at the earliest stages of development due to an individual's inability to access the world because of disabilities including visual impairment, cerebral palsy, cognitive disabilities, hearing impairment and other disabilities. One of her most famous ideas is that of the "little room." This is a box, laid over a blind or disabled child that has toys and other stimuli hanging from it. The child can explore and play with the toys. Most will vocalize for the first time, due to the superior acoustics of the Little Room; as Nielsen wrote: "The purpose of the'Little Room' is to facilitate blind children's achievement of spatial relations and reaching behaviour, but it can be of considerable help for sighted low functioning children." The HOPSA-dress provides vertical orientation, without the need for weightbearing, to children with multiple disabilities.
Items with inter
Aluminium or aluminum is a chemical element with symbol Al and atomic number 13. It is a silvery-white, soft and ductile metal in the boron group. By mass, aluminium makes up about 8% of the Earth's crust; the chief ore of aluminium is bauxite. Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals. Aluminium is remarkable for its low density and its ability to resist corrosion through the phenomenon of passivation. Aluminium and its alloys are vital to the aerospace industry and important in transportation and building industries, such as building facades and window frames; the oxides and sulfates are the most useful compounds of aluminium. Despite its prevalence in the environment, no known form of life uses aluminium salts metabolically, but aluminium is well tolerated by plants and animals; because of these salts' abundance, the potential for a biological role for them is of continuing interest, studies continue.
Of aluminium isotopes, only 27Al is stable. This is consistent with aluminium having an odd atomic number, it is the only aluminium isotope that has existed on Earth in its current form since the creation of the planet. Nearly all the element on Earth is present as this isotope, which makes aluminium a mononuclidic element and means that its standard atomic weight equates to that of the isotope; the standard atomic weight of aluminium is low in comparison with many other metals, which has consequences for the element's properties. All other isotopes of aluminium are radioactive; the most stable of these is 26Al and therefore could not have survived since the formation of the planet. However, 26Al is produced from argon in the atmosphere by spallation caused by cosmic ray protons; the ratio of 26Al to 10Be has been used for radiodating of geological processes over 105 to 106 year time scales, in particular transport, sediment storage, burial times, erosion. Most meteorite scientists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.
The remaining isotopes of aluminium, with mass numbers ranging from 21 to 43, all have half-lives well under an hour. Three metastable states are known, all with half-lives under a minute. An aluminium atom has 13 electrons, arranged in an electron configuration of 3s23p1, with three electrons beyond a stable noble gas configuration. Accordingly, the combined first three ionization energies of aluminium are far lower than the fourth ionization energy alone. Aluminium can easily surrender its three outermost electrons in many chemical reactions; the electronegativity of aluminium is 1.61. A free aluminium atom has a radius of 143 pm. With the three outermost electrons removed, the radius shrinks to 39 pm for a 4-coordinated atom or 53.5 pm for a 6-coordinated atom. At standard temperature and pressure, aluminium atoms form a face-centered cubic crystal system bound by metallic bonding provided by atoms' outermost electrons; this crystal system is shared by some other metals, such as copper. Aluminium metal, when in quantity, is shiny and resembles silver because it preferentially absorbs far ultraviolet radiation while reflecting all visible light so it does not impart any color to reflected light, unlike the reflectance spectra of copper and gold.
Another important characteristic of aluminium is its low density, 2.70 g/cm3. Aluminium is a soft, lightweight and malleable with appearance ranging from silvery to dull gray, depending on the surface roughness, it is nonmagnetic and does not ignite. A fresh film of aluminium serves as a good reflector of visible light and an excellent reflector of medium and far infrared radiation; the yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium has stiffness of steel, it is machined, cast and extruded. Aluminium atoms are arranged in a face-centered cubic structure. Aluminium has a stacking-fault energy of 200 mJ/m2. Aluminium is a good thermal and electrical conductor, having 59% the conductivity of copper, both thermal and electrical, while having only 30% of copper's density. Aluminium is capable of superconductivity, with a superconducting critical temperature of 1.2 kelvin and a critical magnetic field of about 100 gauss.
Aluminium is the most common material for the fabrication of superconducting qubits. Aluminium's corrosion resistance can be excellent due to a thin surface layer of aluminium oxide that forms when the bare metal is exposed to air preventing further oxidation, in a process termed passivation; the strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper. This corrosion resistance is reduced by aqueous salts in the presence of dissimilar metals. In acidic solutions, aluminium reacts with water to form hydrogen, in alkaline ones to form aluminates—protective passivation under these conditions is negligible; because it is corroded by dissolved chlorides, such as common sodium chloride, household plumbing is never made from aluminium. However, because