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Duverger's law

In political science, Duverger's law holds that in political systems with only one winner (as in the U.S.), two main parties tend to emerge with minor parties typically splitting votes away from the most similar major party. In contrast, systems with proportional representation usually have more representation of minor parties in government.

Mechanism
A two-party system is most common under plurality voting. Voters typically cast one vote per race. Maurice Duverger argued there were two main mechanisms by which plurality voting systems lead to fewer major parties: (i) small parties are disincentivized to form because they have great difficulty winning seats or representation, and (ii) voters are wary of voting for a smaller party whose policies they actually favor because they do not want to "waste" their votes (on a party unlikely to win a plurality) and therefore tend to gravitate to one of two major parties that is more likely to achieve a plurality, win the election, and implement policy.

For legislatures where each seat represents a geographical area and the candidate with the most votes wins that seat, minor parties spread fairly evenly across many districts win less representation than geographically concentrated ones with the same overall level of public support. An example of this was the Liberal Democrats in the United Kingdom, whose proportion of seats in the legislature was, until recently, significantly less than their proportion of the national vote. The Green Party of Canada is another example; the party received about 5% of the popular vote from 2004 to 2011 but had only won one seat (out of 308) in the House of Commons in the same span of time. Another example was seen in the 1992 U.S. presidential election, when Ross Perot's candidacy received zero electoral votes despite receiving 19% of the popular vote. Gerrymandering is sometimes used to try to collect a population of like-minded voters within a geographically cohesive district so that their votes are not "wasted", but tends to require that minor parties have both a geographic concentration and a redistricting process that seeks to represent them. These disadvantages tend to suppress the ability of a third party to engage in the political process.

The second challenge to a third party is both statistical and tactical. Duverger presents the example of an election in which 100,000 moderate voters and 80,000 radical voters are to vote for candidates for a single seat or office. If two moderate parties ran candidates and one radical candidate ran (and every voter voted), the radical candidate would tend to win unless one of the moderate candidates gathered fewer than 20,000 votes. Appreciating this risk, moderate voters would be inclined to vote for the moderate candidate they deemed likely to gain more votes, with the goal of defeating the radical candidate. To win, then, either the two moderate parties must merge, or one moderate party must fail, as the voters gravitate to the two strongest parties. Duverger called this trend polarization.

Direction of effect
Kenneth Benoit suggested causal influence between electoral and party systems might be bidirectional or in either direction. Josep Colomer agreed, arguing that changes from a plurality system to a proportional system are typically preceded by the emergence of more than two effective parties, and increases in the effective number of parties happen not in the short term, but in the mid-to-long term.

Exceptions
Some minor parties in winner-take-all systems have managed to translate their support into winning seats in government by focusing on local races, taking the place of a major party, or changing the political system.

Local growth
William H. Riker, citing Douglas W. Rae, noted that strong regional parties can lead to more than two parties receiving seats in the national legislature, even if there are only two parties competitive in any single district. In systems outside the United States, like Canada, United Kingdom and India, multiparty parliaments exist due to the growth of minor parties finding strongholds in specific regions, potentially lessening the psychological fear of a wasted vote by voting for a minor party for a legislative seat. Riker credits Canada's highly decentralized system of government as encouraging minor parties to build support by winning seats locally, which then sets the parties up to get representatives in the House of Commons of Canada.

Replace major party
The political chaos in the United States immediately preceding the Civil War allowed the Republican Party to replace the Whig Party as the progressive half of the American political landscape. Loosely united on a platform of country-wide economic reform and federally funded industrialization, the decentralized Whig leadership failed to take a decisive stance on the slavery issue, effectively splitting the party along the Mason–Dixon line. Southern rural planters, initially attracted by the prospect of federal infrastructure and schools, aligned with the pro-slavery Democrats, while urban laborers and professionals in the northern states, threatened by the sudden shift in political and economic power and losing faith in the failing Whig candidates, flocked to the increasingly vocal anti-slavery Republican Party.

Different voting systems
Absent a major reform like switching to proportional representation, minor reforms like ranked-choice voting has the potential to allow for more choice in a winner-take-all system. Duverger argued that "a majority vote on two ballots is conducive to a multiparty system, inclined toward forming coalitions": that the two-round system encourages a multiparty system, but to a lesser degree than proportional representation does.

Systems that satisfy the sincere favorite criterion are not subject to Duverger's law.

Strength of effect
William Clark and Matt Golder (2006) find the effect largely holds up, noting that different methods of analyzing the data might lead to different conclusions. They emphasize other variables like the nuances of different electoral institutions and the importance that Duverger also placed on sociological factors. Thomas R. Palfrey argued Duverger's law can be proven mathematically at the limit when the number of voters approaches infinity for one single-winner district and where the probability distribution of votes is known (perfect information).

Duverger did not regard this principle as absolute, suggesting instead that plurality would act to delay the emergence of new political forces and would accelerate the elimination of weakening ones, whereas proportional representation would have the opposite effect.

The U.S. system has two major parties which have won, on average, 98% of all state and federal seats. There have only been a few rare elections where a minor party was competitive with the major parties, occasionally replacing one of the major parties in the 19th century.

In Matt Golder's 2016 review of the empirical evidence to-date, he concluded that despite some contradicting cases, the law remains a valid generalization.

Steven R. Reed argued in 2001 that Duverger's law could be observed in Italy, with 80% of electoral districts gradually but significantly shifting towards two major parties. He finds a similar effect in Japan through a slow trial-and-error process that shifted the number of major parties towards the expected outcome.

Eric Dickson and Kenneth Scheve argued in 2007 that Duverger's law is strongest when a society is homogenous or closely divided, but is weakened when multiple intermediate identities exist. As evidence of this, Duhamel cites the case of India, where over 25 percent of voters vote for parties outside the two main alliances.

Two-party politics may also emerge in systems that use a form of proportional representation, with Duverger and others arguing that Duverger's Law mostly represents a limiting factor (like a brake) on the number of major parties in other systems more than a prediction of equilibrium for governments with more proportional representation.

title: Duverger's law


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William H. Riker

William Harrison Riker (September 22, 1920 – June 26, 1993) was an American political scientist who is prominent for applying game theory and mathematics to political science. He helped to establish University of Rochester as a center of behavioral revolution in political science.

Early life
William Harrison Riker was born on September 22, 1920, in Des Moines, Iowa. He had 4 children, 2 sons and 2 daughters with wife Mary Elizabeth. He earned his bachelor's degree in economics at Indiana's DePauw University in 1942 and received his Ph.D. at Harvard University in 1948. While a student at DePauw, he was initiated into the Delta Kappa Epsilon fraternity. Before his Ph.D., Riker worked at the RCA (then Radio Corporation of America), where he worked as a time-and-motion analyst.

Career
Riker took on a professorship at Lawrence University in Appleton, Wisconsin (then Lawrence College), where he published The Theory of Political Coalitions (1962). In 1962, he became the chair of the Political Science Department at the University of Rochester, where he remained chair until 1977, and remained active until his death.

Riker was elected to the National Academy of Sciences in 1974.

Riker founded the now-mainstream field of positive political theory, which introduced game theory and the axiomatic method of social choice theory to political science. Bruce Bueno de Mesquita and Kenneth Shepsle in their memoir write that "These have proved crucial to predictive tests for political theory." Riker is also often credited with being the founder of rational choice theory with his work on applying economic theory to mathematical models of politics.

Among other contributions, Riker is known for work on the theory and history of federalism and on what he called "heresthetic"—the art of changing political outcomes without changing peoples' underlying preferences by manipulating the decision-making process, for example by changing the order in which decisions are made. In his book Liberalism Against Populism, he argued that the instability of majority rule, demonstrated in Arrow's impossibility theorem and the McKelvey–Schofield chaos theorem, meant that "populist" interpretations of democracy as implementing a collective will of the people were untenable. Instead, democratic leaders aimed to build disparate coalitions; a piece of successful coalition-building could cause realigning elections, in which blocs of voters swiftly changed their allegiance.

Concerning political coalition for the benefit of minorities, Riker argued that the larger the coalition, the shorter-lived it is. In his book The Theory of Political Coalitions (1962), Riker argued that in situations where there is conflict over finite resources, actors will seek to create coalitions that are large enough to ensure that they get access to the resources, but that the coalitions will not be larger than that (because the actors will not want to dilute the resources more than they have to).

The William H. Riker Prize for excellence in undergraduate teaching is awarded by the University of Rochester bi-annually in his honor. The Political Economy section of the American Political Science Association awards an annual book prize in his name as well.

Publications

 * Riker, William H. Soldiers of the States: The Role of the National Guard in American Democracy. Washington: Public Affairs Press, 1957.
 * ____. “The Paradox of Voting and Congressional Rules for Voting on. Amendments.” American Political Science Review. 52, 1958: 349–366.
 * ____. The Theory of Political Coalitions. New Haven: Yale University Press, 1962.
 * ____. "Federalism: Origin, Operation, Significance". Boston: Little, Brown, 1964.
 * ____. "Towards a Positive Political Theory", Englewood Cliffs, NJ: Prentice Hall, 1973.
 * ____. "Implications from the Disequilibrium of Majority Rule for the Study of Institutions," American Political Science Review, 74, 1980: 432–446.
 * ____. Liberalism Against Populism. San Francisco: W. H. Freeman, 1982.
 * ____. "The Heresthetics of Constitution-Making: The Presidency in 1787, with Comments on Determinism and Rational Choice." American Political Science Review, 78, 1984: 1–16.
 * ____. The Art of Political Manipulation. New Haven: Yale University Press, 1986.
 * ____. The Strategy of Rhetoric. New Haven: Yale University Press, 1996.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: William H. Riker


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Enriched uranium

Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238U with 99.2732–99.2752% natural abundance), uranium-235 (235U, 0.7198–0.7210%), and uranium-234 (234U, 0.0049–0.0059%). 235U is the only nuclide existing in nature (in any appreciable amount) that is fissile with thermal neutrons.

Enriched uranium is a critical component for both civil nuclear power generation and military nuclear weapons.

There are about 2,000 tonnes of highly enriched uranium in the world, produced mostly for nuclear power, nuclear weapons, naval propulsion, and smaller quantities for research reactors.

The 238U remaining after enrichment is known as depleted uranium (DU), and is considerably less radioactive than even natural uranium, though still very dense. Depleted uranium is used as a radiation shielding material and for armor-penetrating weapons.

Grades
Uranium as it is taken directly from the Earth is not suitable as fuel for most nuclear reactors and requires additional processes to make it usable (CANDU design is a notable exception). Uranium is mined either underground or in an open pit depending on the depth at which it is found. After the uranium ore is mined, it must go through a milling process to extract the uranium from the ore.

This is accomplished by a combination of chemical processes with the end product being concentrated uranium oxide, which is known as "yellowcake", contains roughly 80% uranium whereas the original ore typically contains as little as 0.1% uranium.

This yellowcake is further processed to obtain the desired form of uranium suitable for nuclear fuel production. After the milling process is complete, the uranium must next undergo a process of conversion, "to either uranium dioxide, which can be used as the fuel for those types of reactors that do not require enriched uranium, or into uranium hexafluoride, which can be enriched to produce fuel for the majority of types of reactors". Naturally occurring uranium is made of a mixture of 235U and 238U. The 235U is fissile, meaning it is easily split with neutrons while the remainder is 238U, but in nature, more than 99% of the extracted ore is 238U. Most nuclear reactors require enriched uranium, which is uranium with higher concentrations of 235U ranging between 3.5% and 4.5% (although a few reactor designs using a graphite or heavy water moderator, such as the RBMK and CANDU, are capable of operating with natural uranium as fuel). There are two commercial enrichment processes: gaseous diffusion and gas centrifugation. Both enrichment processes involve the use of uranium hexafluoride and produce enriched uranium oxide.

Reprocessed uranium (RepU)
Reprocessed uranium (RepU) undergoes a series of chemical and physical treatments to extract usable uranium from spent nuclear fuel. (RepU) is a product of nuclear fuel cycles involving nuclear reprocessing of spent fuel. RepU recovered from light water reactor (LWR) spent fuel typically contains slightly more 235U than natural uranium, and therefore could be used to fuel reactors that customarily use natural uranium as fuel, such as CANDU reactors. It also contains the undesirable isotope uranium-236, which undergoes neutron capture, wasting neutrons (and requiring higher 235U enrichment) and creating neptunium-237, which would be one of the more mobile and troublesome radionuclides in deep geological repository disposal of nuclear waste. Reprocessed uranium often carries traces of other transuranic elements and fission products, necessitating careful monitoring and management during fuel fabrication and reactor operation.

Low-enriched uranium (LEU)
Low-enriched uranium (LEU) has a lower than 20% concentration of 235U; for instance, in commercial LWR, the most prevalent power reactors in the world, uranium is enriched to 3 to 5% 235U. Slightly enriched uranium (SEU) has a concentration of under 2% 235U.

High-assay LEU (HALEU)
High-assay LEU (HALEU) is enriched between 5% and 20% and is called for in many small modular reactor (SMR) designs. Fresh LEU used in research reactors is usually enriched between 12% and 19.75% 235U; the latter concentration is used to replace HEU fuels when converting to LEU.

Highly enriched uranium (HEU)

Highly enriched uranium (HEU) has a 20% or higher concentration of 235U. This high enrichment level is essential for nuclear weapons and certain specialized reactor designs. The fissile uranium in nuclear weapon primaries usually contains 85% or more of 235U known as weapons grade, though theoretically for an implosion design, a minimum of 20% could be sufficient (called weapon-usable) although it would require hundreds of kilograms of material and "would not be practical to design"; even lower enrichment is hypothetically possible, but as the enrichment percentage decreases the critical mass for unmoderated fast neutrons rapidly increases, with for example, an infinite mass of 5.4% 235U being required. For criticality experiments, enrichment of uranium to over 97% has been accomplished.

The first uranium bomb, Little Boy, dropped by the United States on Hiroshima in 1945, used 64 kg of 80% enriched uranium. Wrapping the weapon's fissile core in a neutron reflector (which is standard on all nuclear explosives) can dramatically reduce the critical mass. Because the core was surrounded by a good neutron reflector, at explosion it comprised almost 2.5 critical masses. Neutron reflectors, compressing the fissile core via implosion, fusion boosting, and "tamping", which slows the expansion of the fissioning core with inertia, allow nuclear weapon designs that use less than what would be one bare-sphere critical mass at normal density. The presence of too much of the 238U isotope inhibits the runaway nuclear chain reaction that is responsible for the weapon's power. The critical mass for 85% highly enriched uranium is about 50 kg, which at normal density would be a sphere about 17 cm in diameter.

Later U.S. nuclear weapons usually use plutonium-239 in the primary stage, but the jacket or tamper secondary stage, which is compressed by the primary nuclear explosion often uses HEU with enrichment between 40% and 80% along with the fusion fuel lithium deuteride. This multi-stage design enhances the efficiency and effectiveness of nuclear weapons, allowing for greater control over the release of energy during detonation. For the secondary of a large nuclear weapon, the higher critical mass of less-enriched uranium can be an advantage as it allows the core at explosion time to contain a larger amount of fuel. This design strategy optimizes the explosive yield and performance of advanced nuclear weapons systems. The 238U is not said to be fissile but still is fissionable by fast neutrons (>2 MeV) such as the ones produced during D-T fusion.

HEU is also used in fast neutron reactors, whose cores require about 20% or more of fissile material, as well as in naval reactors, where it often contains at least 50% 235U, but typically does not exceed 90%. These specialized reactor systems rely on highly enriched uranium for their unique operational requirements, including high neutron flux and precise control over reactor dynamics. The Fermi-1 commercial fast reactor prototype used HEU with 26.5% 235U. Significant quantities of HEU are used in the production of medical isotopes, for example molybdenum-99 for technetium-99m generators. The medical industry benefits from the unique properties of highly enriched uranium, which enable the efficient production of critical isotopes essential for diagnostic imaging and therapeutic applications

Enrichment methods
Isotope separation is difficult because two isotopes of the same element have nearly identical chemical properties, and can only be separated gradually using small mass differences. (235U is only 1.26% lighter than 238U.) This problem is compounded because uranium is rarely separated in its atomic form, but instead as a compound (235UF6 is only 0.852% lighter than 238UF6). A cascade of identical stages produces successively higher concentrations of 235U. Each stage passes a slightly more concentrated product to the next stage and returns a slightly less concentrated residue to the previous stage.

There are currently two generic commercial methods employed internationally for enrichment: gaseous diffusion (referred to as first generation) and gas centrifuge (second generation), which consumes only 2% to 2.5% as much energy as gaseous diffusion. Some work is being done that would use nuclear resonance; however, there is no reliable evidence that any nuclear resonance processes have been scaled up to production.

Gaseous diffusion

Gaseous diffusion is a technology used to produce enriched uranium by forcing gaseous uranium hexafluoride (hex) through semi-permeable membranes. This produces a slight separation between the molecules containing 235U and 238U. Throughout the Cold War, gaseous diffusion played a major role as a uranium enrichment technique, and as of 2008 accounted for about 33% of enriched uranium production, but in 2011 was deemed an obsolete technology that is steadily being replaced by the later generations of technology as the diffusion plants reach their ends of life. In 2013, the Paducah facility in the U.S. ceased operating, it was the last commercial 235U gaseous diffusion plant in the world.

Thermal diffusion
Thermal diffusion uses the transfer of heat across a thin liquid or gas to accomplish isotope separation. The process exploits the fact that the lighter 235U gas molecules will diffuse toward a hot surface, and the heavier 238U gas molecules will diffuse toward a cold surface. The S-50 plant at Oak Ridge, Tennessee, was used during World War II to prepare feed material for the Electromagnetic isotope separation (EMIS) process, explained later in this article. It was abandoned in favor of gaseous diffusion.

Gas centrifuge
The gas centrifuge process uses a large number of rotating cylinders in series and parallel formations. Each cylinder's rotation creates a strong centripetal force so that the heavier gas molecules containing 238U move tangentially toward the outside of the cylinder and the lighter gas molecules rich in 235U collect closer to the center. It requires much less energy to achieve the same separation than the older gaseous diffusion process, which it has largely replaced and so is the current method of choice and is termed second generation. It has a separation factor per stage of 1.3 relative to gaseous diffusion of 1.005, which translates to about one-fiftieth of the energy requirements. Gas centrifuge techniques produce close to 100% of the world's enriched uranium. The cost per separative work unit is approximately 100 dollars per Separative Work Units (SWU), making it about 40% cheaper than standard gaseous diffusion techniques.

Zippe centrifuge

The Zippe-type centrifuge is an improvement on the standard gas centrifuge, the primary difference being the use of heat. The bottom of the rotating cylinder is heated, producing convection currents that move the 235U up the cylinder, where it can be collected by scoops. This improved centrifuge design is used commercially by Urenco to produce nuclear fuel and was used by Pakistan in their nuclear weapons program.

Laser techniques
Laser processes promise lower energy inputs, lower capital costs and lower tails assays, hence significant economic advantages. Several laser processes have been investigated or are under development. Separation of isotopes by laser excitation (SILEX) is well developed and is licensed for commercial operation as of 2012. Separation of isotopes by laser excitation is a very effective and cheap method of uranium separation, able to be done in small facilities requiring much less energy and space than previous separation techniques. The cost of uranium enrichment using laser enrichment technologies is approximately $30 per SWU which is less than a third of the price of gas centrifuges, the current standard of enrichment. Separation of isotopes by laser excitation could be done in facilities virtually undetectable by satellites. More than 20 countries have worked with laser separation over the past two decades, the most notable of these countries being Iran and North Korea, though all countries have had very limited success up to this point.

Atomic vapor laser isotope separation (AVLIS)
Atomic vapor laser isotope separation employs specially tuned lasers to separate isotopes of uranium using selective ionization of hyperfine transitions. The technique uses lasers tuned to frequencies that ionize 235U atoms and no others. The positively charged 235U ions are then attracted to a negatively charged plate and collected.

Molecular laser isotope separation (MLIS)
Molecular laser isotope separation uses an infrared laser directed at UF6, exciting molecules that contain a 235U atom. A second laser frees a fluorine atom, leaving uranium pentafluoride, which then precipitates out of the gas.

Separation of isotopes by laser excitation (SILEX)
Separation of isotopes by laser excitation is an Australian development that also uses UF6. After a protracted development process involving U.S. enrichment company USEC acquiring and then relinquishing commercialization rights to the technology, GE Hitachi Nuclear Energy (GEH) signed a commercialization agreement with Silex Systems in 2006. GEH has since built a demonstration test loop and announced plans to build an initial commercial facility. Details of the process are classified and restricted by intergovernmental agreements between United States, Australia, and the commercial entities. SILEX has been projected to be an order of magnitude more efficient than existing production techniques but again, the exact figure is classified. In August, 2011 Global Laser Enrichment, a subsidiary of GEH, applied to the U.S. Nuclear Regulatory Commission (NRC) for a permit to build a commercial plant. In September 2012, the NRC issued a license for GEH to build and operate a commercial SILEX enrichment plant, although the company had not yet decided whether the project would be profitable enough to begin construction, and despite concerns that the technology could contribute to nuclear proliferation. The fear of nuclear proliferation arose in part due to laser separation technology requiring less than 25% of the space of typical separation techniques, as well as requiring only the energy that would power 12 typical houses, putting a laser separation plant that works by means of laser excitation well below the detection threshold of existing surveillance technologies. Due to these concerns the American Physical Society filed a petition with the NRC, asking that before any laser excitation plants are built that they undergo a formal review of proliferation risks. The APS even went as far as calling the technology a "game changer" due to the ability for it to be hidden from any type of detection.

Aerodynamic processes
Aerodynamic enrichment processes include the Becker jet nozzle techniques developed by E. W. Becker and associates using the LIGA process and the vortex tube separation process. These aerodynamic separation processes depend upon diffusion driven by pressure gradients, as does the gas centrifuge. They in general have the disadvantage of requiring complex systems of cascading of individual separating elements to minimize energy consumption. In effect, aerodynamic processes can be considered as non-rotating centrifuges. Enhancement of the centrifugal forces is achieved by dilution of UF6 with hydrogen or helium as a carrier gas achieving a much higher flow velocity for the gas than could be obtained using pure uranium hexafluoride. The Uranium Enrichment Corporation of South Africa (UCOR) developed and deployed the continuous Helikon vortex separation cascade for high production rate low-enrichment and the substantially different semi-batch Pelsakon low production rate high enrichment cascade both using a particular vortex tube separator design, and both embodied in industrial plant. A demonstration plant was built in Brazil by NUCLEI, a consortium led by Industrias Nucleares do Brasil that used the separation nozzle process. However, all methods have high energy consumption and substantial requirements for removal of waste heat; none is currently still in use.

Electromagnetic isotope separation

In the electromagnetic isotope separation process (EMIS), metallic uranium is first vaporized, and then ionized to positively charged ions. The cations are then accelerated and subsequently deflected by magnetic fields onto their respective collection targets. A production-scale mass spectrometer named the Calutron was developed during World War II that provided some of the 235U used for the Little Boy nuclear bomb, which was dropped over Hiroshima in 1945. Properly the term 'Calutron' applies to a multistage device arranged in a large oval around a powerful electromagnet. Electromagnetic isotope separation has been largely abandoned in favour of more effective methods.

Chemical methods
One chemical process has been demonstrated to pilot plant stage but not used for production. The French CHEMEX process exploited a very slight difference in the two isotopes' propensity to change valency in oxidation/reduction, using immiscible aqueous and organic phases. An ion-exchange process was developed by the Asahi Chemical Company in Japan that applies similar chemistry but effects separation on a proprietary resin ion-exchange column.

Plasma separation
Plasma separation process (PSP) describes a technique that makes use of superconducting magnets and plasma physics. In this process, the principle of ion cyclotron resonance is used to selectively energize the 235U isotope in a plasma containing a mix of ions. France developed its own version of PSP, which it called RCI. Funding for RCI was drastically reduced in 1986, and the program was suspended around 1990, although RCI is still used for stable isotope separation.

Separative work unit
"Separative work"—the amount of separation done by an enrichment process—is a function of the concentrations of the feedstock, the enriched output, and the depleted tailings; and is expressed in units that are so calculated as to be proportional to the total input (energy / machine operation time) and to the mass processed. Separative work is not energy. The same amount of separative work will require different amounts of energy depending on the efficiency of the separation technology. Separative work is measured in Separative work units SWU, kg SW, or kg UTA (from the German Urantrennarbeit – literally uranium separation work). Efficient utilization of separative work is crucial for optimizing the economic and operational performance of uranium enrichment facilities.
 * 1 SWU = 1 kg SW = 1 kg UTA
 * 1 kSWU = 1 tSW = 1 t UTA
 * 1 MSWU = 1 ktSW = 1 kt UTA

Cost issues
In addition to the separative work units provided by an enrichment facility, the other important parameter to be considered is the mass of natural uranium (NU) that is needed to yield a desired mass of enriched uranium. As with the number of SWUs, the amount of feed material required will also depend on the level of enrichment desired and upon the amount of 235U that ends up in the depleted uranium. However, unlike the number of SWUs required during enrichment, which increases with decreasing levels of 235U in the depleted stream, the amount of NU needed will decrease with decreasing levels of 235U that end up in the DU.

For example, in the enrichment of LEU for use in a light water reactor it is typical for the enriched stream to contain 3.6% 235U (as compared to 0.7% in NU) while the depleted stream contains 0.2% to 0.3% 235U. In order to produce one kilogram of this LEU it would require approximately 8 kilograms of NU and 4.5 SWU if the DU stream was allowed to have 0.3% 235U. On the other hand, if the depleted stream had only 0.2% 235U, then it would require just 6.7 kilograms of NU, but nearly 5.7 SWU of enrichment. Because the amount of NU required and the number of SWUs required during enrichment change in opposite directions, if NU is cheap and enrichment services are more expensive, then the operators will typically choose to allow more 235U to be left in the DU stream whereas if NU is more expensive and enrichment is less so, then they would choose the opposite.

When converting uranium (hexafluoride, hex for short) to metal, 0.3% is lost during manufacturing.

Downblending
The opposite of enriching is downblending; surplus HEU can be downblended to LEU to make it suitable for use in commercial nuclear fuel. Downblending is a key process in nuclear non-proliferation efforts, as it reduces the amount of highly enriched uranium available for potential weaponization while repurposing it for peaceful purposes. The HEU feedstock can contain unwanted uranium isotopes: 234U is a minor isotope contained in natural uranium (primarily as a product of alpha decay of —because the half-life of is much larger than that of, it is be produced and destroyed at the same rate in a constant steady state equilibrium, bringing any sample with sufficient  content to a stable ratio of  to  over long enough timescales); during the enrichment process, its concentration increases but remains well below 1%. High concentrations of 236U are a byproduct from irradiation in a reactor and may be contained in the HEU, depending on its manufacturing history. is produced primarily when absorbs a neutron and does not fission. The production of is thus unavoidable in any thermal neutron reactor with  fuel. HEU reprocessed from nuclear weapons material production reactors (with an 235U assay of approximately 50%) may contain 236U concentrations as high as 25%, resulting in concentrations of approximately 1.5% in the blended LEU product. 236U is a neutron poison; therefore the actual 235U concentration in the LEU product must be raised accordingly to compensate for the presence of 236U. While also absorbs neutrons, it is a fertile material that is turned into fissile  upon neutron absorption. If absorbs a neutron, the resulting short-lived  beta decays to, which is not usable in thermal neutron reactors but can be chemically separated from spent fuel to be disposed of as waste or to be transmutated into  (for use in  nuclear batteries) in special reactors. Understanding and managing the isotopic composition of uranium during downblending processes is essential to ensure the quality and safety of the resulting nuclear fuel, as well as to mitigate potential radiological and proliferation risks associated with unwanted isotopes.

The blendstock can be NU or DU; however, depending on feedstock quality, SEU at typically 1.5 wt% 235U may be used as a blendstock to dilute the unwanted byproducts that may be contained in the HEU feed. Concentrations of these isotopes in the LEU product in some cases could exceed ASTM specifications for nuclear fuel if NU or DU were used. So, the HEU downblending generally cannot contribute to the waste management problem posed by the existing large stockpiles of depleted uranium. Effective management and disposition strategies for depleted uranium are crucial to ensure long-term safety and environmental protection. Innovative approaches such as reprocessing and recycling of depleted uranium could offer sustainable solutions to minimize waste and optimize resource utilization in the nuclear fuel cycle.

A major downblending undertaking called the Megatons to Megawatts Program converts ex-Soviet weapons-grade HEU to fuel for U.S. commercial power reactors. From 1995 through mid-2005, 250 tonnes of high-enriched uranium (enough for 10,000 warheads) was recycled into low-enriched uranium. The goal is to recycle 500 tonnes by 2013. The decommissioning programme of Russian nuclear warheads accounted for about 13% of total world requirement for enriched uranium leading up to 2008. This ambitious initiative not only addresses nuclear disarmament goals but also serves as a significant contributor to global energy security and environmental sustainability, effectively repurposing material once intended for destructive purposes into a resource for peaceful energy production.

The United States Enrichment Corporation has been involved in the disposition of a portion of the 174.3 tonnes of highly enriched uranium (HEU) that the U.S. government declared as surplus military material in 1996. Through the U.S. HEU Downblending Program, this HEU material, taken primarily from dismantled U.S. nuclear warheads, was recycled into low-enriched uranium (LEU) fuel, used by nuclear power plants to generate electricity. This innovative program not only facilitated the safe and secure elimination of excess weapons-grade uranium but also contributed to the sustainable operation of civilian nuclear power plants, reducing reliance on newly enriched uranium and promoting non-proliferation efforts globally

Global enrichment facilities
The following countries are known to operate enrichment facilities: Argentina, Brazil, China, France, Germany, India, Iran, Japan, the Netherlands, North Korea, Pakistan, Russia, the United Kingdom, and the United States. Belgium, Iran, Italy, and Spain hold an investment interest in the French Eurodif enrichment plant, with Iran's holding entitling it to 10% of the enriched uranium output. Countries that had enrichment programs in the past include Libya and South Africa, although Libya's facility was never operational. The Australian company Silex Systems has developed a laser enrichment process known as SILEX (separation of isotopes by laser excitation), which it intends to pursue through financial investment in a U.S. commercial venture by General Electric, Although SILEX has been granted a license to build a plant, the development is still in its early stages as laser enrichment has yet to be proven to be economically viable, and there is a petition being filed to review the license given to SILEX over nuclear proliferation concerns. It has also been claimed that Israel has a uranium enrichment program housed at the Negev Nuclear Research Center site near Dimona.

Codename
During the Manhattan Project, weapons-grade highly enriched uranium was given the codename oralloy, a shortened version of Oak Ridge alloy, after the location of the plants where the uranium was enriched. This covert terminology underscores the secrecy and sensitivity surrounding the production of highly enriched uranium during World War II, highlighting the strategic importance of the Manhattan Project and its role in the development of nuclear weapons. The term oralloy is still occasionally used to refer to enriched uranium. Its continued usage serves as a historical reminder of the pivotal role of enriched uranium in shaping the course of modern history and its ongoing significance in various nuclear applications, including energy production, medicine, and scientific research.

title: Enriched uranium


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Asperger syndrome

Asperger syndrome (AS), also known as Asperger's syndrome or Asperger's, is a term formerly used to describe a neurodevelopmental condition characterized by significant difficulties in social interaction and nonverbal communication, along with restricted, repetitive patterns of behavior and interests. Asperger syndrome has been merged with other conditions into autism spectrum disorder (ASD) and is no longer considered a stand-alone diagnosis. It was considered milder than other diagnoses which were merged into ASD due to relatively unimpaired spoken language and intelligence.

The syndrome was named after the Austrian pediatrician Hans Asperger, who, in 1944, described children in his care who struggled to form friendships, did not understand others' gestures or feelings, engaged in one-sided conversations about their favorite interests, and were clumsy. In 1994, the diagnosis of Asperger syndrome was included in the fourth edition (DSM-IV) of the American Diagnostic and Statistical Manual of Mental Disorders; however, with the publication of DSM-5 in 2013 the syndrome was removed, and the symptoms are now included within autism spectrum disorder along with classic autism and pervasive developmental disorder not otherwise specified (PDD-NOS). It was similarly merged into autism spectrum disorder in the International Classification of Diseases (ICD-11).

The exact cause of Asperger syndrome is poorly understood. While it has high heritability, the underlying genetics have not been determined conclusively. Environmental factors are also believed to play a role. Brain imaging has not identified a common underlying condition. There is no single treatment, and the UK's National Health Service (NHS) guidelines suggest that "treatment" of any form of autism should not be a goal, since autism is not "a disease that can be removed or cured". According to the Royal College of Psychiatrists, while co-occurring conditions might require treatment, "management of autism itself is chiefly about the provision of the education, training, and social support/care required to improve the person's ability to function in the everyday world". The effectiveness of particular interventions for autism is supported by only limited data. Interventions may include social skills training, cognitive behavioral therapy, physical therapy, speech therapy, parent training, and medications for associated problems, such as mood or anxiety. Autistic characteristics tend to become less obvious in adulthood, but social and communication difficulties usually persist.

In 2015, Asperger syndrome was estimated to affect 37.2 million people globally, or about 0.5% of the population. The exact percentage of people affected has still not been firmly established. Autism spectrum disorder is diagnosed in males more often than females, and females are typically diagnosed at a later age. The modern conception of Asperger syndrome came into existence in 1981 and went through a period of popularization. It became a standardized diagnosis in the 1990s and was merged into ASD in 2013. Many questions and controversies about the condition remain.

Classification
The extent of the overlap between Asperger syndrome and high-functioning autism (HFA – autism unaccompanied by intellectual disability) is unclear. The ASD classification is to some extent an artifact of how autism was discovered, and it may not reflect the true nature of the spectrum; methodological problems have beset Asperger syndrome as a valid diagnosis from the outset. In the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), published in May 2013, Asperger syndrome, as a separate diagnosis, was eliminated and folded into autism spectrum disorder. Like the diagnosis of Asperger syndrome, the change was controversial. Subsequently, it was also not included in the ICD-11, which came into effect in 2022.

The World Health Organization (WHO) previously defined Asperger syndrome (AS) as one of the pervasive developmental disorders (PDD), which are a spectrum of psychological disorders that are characterized by abnormalities of social interaction and communication that pervade the individual's functioning, and by restricted and repetitive interests and behavior. Like other neurodevelopmental conditions, ASD begins in infancy or childhood, has a steady course without remission or relapse, and has impairments that result from maturation-related changes in various systems of the brain.

Characteristics

As a pervasive developmental disorder, Asperger syndrome is distinguished by a pattern of symptoms rather than a single symptom. It is characterized by qualitative impairment in social interaction, by stereotyped and restricted patterns of behavior, activities, and interests, and by no clinically significant delay in cognitive development or general delay in language. Intense preoccupation with a narrow subject, one-sided verbosity, restricted prosody, and physical clumsiness are typical of the condition, but are not required for diagnosis.

Suicidal thoughts and behaviors are a serious concern within the autistic population. One study found that adults with Asperger syndrome exhibited suicidal thoughts at 9 times the rate of the general population. Of autistic study participants, 66% had experienced suicidal ideation, while 35% had planned or attempted suicide.

Social interaction
A lack of demonstrated empathy affects aspects of social relatability for persons with Asperger syndrome. Individuals with Asperger syndrome experience difficulties in basic elements of social interaction, which may include a failure to develop friendships or to seek shared enjoyments or achievements with others (e.g., showing others objects of interest); a lack of social or emotional reciprocity; and impaired nonverbal behaviors in areas such as eye contact, facial expression, posture, and gesture.

People with Asperger syndrome may not be as withdrawn around others, compared with those with other forms of autism; they approach others, even if awkwardly. For example, a person with Asperger syndrome may engage in a one-sided, long-winded speech about a favorite topic, while misunderstanding or not recognizing the listener's feelings or reactions, such as a wish to change the topic of talk or end the interaction. This social awkwardness has been called "active but odd". Such failures to react appropriately to social interaction may appear as disregard for other people's feelings and may come across as rude or insensitive. However, not all individuals with Asperger syndrome will approach others. Some may even display selective mutism, not speaking at all to most people and excessively to specific others.

The cognitive ability of children with Asperger syndrome often allows them to articulate social norms in a laboratory context, where they may be able to show a theoretical understanding of other people's emotions; however, they typically have difficulty acting on this knowledge in fluid, real-life situations. People with Asperger syndrome may analyze and distill their observations of social interaction into rigid behavioral guidelines and apply these rules in awkward ways, such as forced eye contact, resulting in a demeanor that appears rigid or socially naïve. A history of failed attempts to establish reciprocal social relationships can cause autistic individuals to isolate themselves and cease attempts to engage; however, autistic people overwhelmingly report a desire for social contact and friendship.

Violent or criminal behavior
The hypothesis that individuals with Asperger syndrome are predisposed to violent or criminal behavior has been investigated but is not supported by data. More evidence suggests that children diagnosed with Asperger syndrome are more likely to be victims, rather than offenders.

A 2008 review found that an overwhelming number of reported violent criminals with Asperger syndrome also had other coexisting psychotic psychiatric disorders such as schizoaffective disorder.

Empathy
People with an Asperger profile might not be recognized for their empathetic qualities, due to variation in the ways empathy is felt and expressed. Some people feel deep empathy, but do not outwardly communicate these sentiments through facial expressions or language. Some people come to empathy through intellectual processes, using logic and reasoning to arrive at the feelings. People with Asperger profiles may be bullied or excluded by peers, and might as a result be guarded around people, which could appear as lack of empathy. People with Asperger profiles can still be caring individuals; indeed, it is particularly common for those with the profile to feel and exhibit deep concern for individual rights, human welfare, animal rights, environmental protection, and other global and humanitarian causes.

Evidence suggests that in the "double empathy problem model, autistic people have a unique interaction style which is significantly more readable by other autistic people, compared to non-autistic people."

Restricted and repetitive interests and behavior
People with Asperger syndrome can display behavior, interests, and activities that are restricted and repetitive and are sometimes abnormally intense or focused. They may stick to inflexible routines, move in stereotyped and repetitive ways, preoccupy themselves with parts of objects, or engage in compulsive behaviors like lining objects up to form patterns.

The pursuit of specific and narrow areas of interest is one of the most striking among possible features of AS. Individuals with AS may collect volumes of detailed information on a relatively narrow topic such as weather data or star names without necessarily having a genuine understanding of the broader topic. For example, a child might memorize camera model numbers while caring little about photography. This behavior is usually apparent by age five or six. Although these special interests may change from time to time, they typically become more unusual and narrowly focused and often dominate social interaction so much that the entire family may become immersed. Because narrow topics often capture the interest of children, this symptom may go unrecognized.

Stereotyped and repetitive motor behaviors, called stimming, are a core part of the diagnosis of AS and other ASDs. Stims are believed to be used for self-soothing and regulate sensory input. They include hand movements such as flapping or twisting, and complex whole-body movements. These are typically repeated in longer bursts and look more voluntary or ritualistic than tics, which are usually faster, less rhythmical, and less often symmetrical. Stimming may have a connection with tics, and studies have reported a consistent comorbidity between AS and Tourette syndrome in the range of 8–20%, with one figure as high as 80% for tics of some kind or another, for which several explanations have been put forward, including common genetic factors and dopamine, glutamate, or serotonin abnormalities.

According to the Adult Asperger Assessment (AAA) diagnostic test, a lack of interest in fiction and a positive preference towards non-fiction is common among adults with AS.

Speech and language
Although individuals with Asperger syndrome acquire language skills without significant general delay and their speech typically lacks significant abnormalities, language acquisition and use is often atypical. Abnormalities include verbosity; abrupt transitions; literal interpretations and miscomprehension of nuance; use of metaphor meaningful only to the speaker; auditory perception deficits; unusually pedantic, formal, or idiosyncratic speech; and oddities in loudness, pitch, intonation, prosody, and rhythm. Echolalia has also been observed in individuals with AS.

Three aspects of communication patterns are of clinical interest: poor prosody, tangential and circumstantial speech, and marked verbosity. Although inflection and intonation may be less rigid or monotonic than in classic autism, people with AS often have a limited range of intonation: speech may be unusually fast, jerky, or loud. Speech may convey a sense of incoherence; the conversational style often includes monologues about topics that bore the listener, fails to provide context for comments, or fails to suppress internal thoughts. Individuals with AS may fail to detect whether the listener is interested or engaged in the conversation. The speaker's conclusion or point may never be made, and attempts by the listener to elaborate on the speech's content or logic, or to shift to related topics, are often unsuccessful.

Children with AS may have a sophisticated vocabulary at a young age and such children have often been colloquially called "little professors" but have difficulty understanding figurative language and tend to use language literally. Children with AS appear to have particular weaknesses in areas of nonliteral language that include humor, irony, teasing, and sarcasm. Although individuals with AS usually understand the cognitive basis of humor, they seem to lack understanding of the intent of humor to share the enjoyment with others. Despite strong evidence of impaired humor appreciation, anecdotal reports of humor in individuals with AS seem to challenge some psychological theories of AS and autism.

Motor and sensory perception
Individuals with Asperger syndrome may have signs or symptoms that are independent of the diagnosis but can affect the individual or the family. These include differences in perception and problems with motor skills, sleep, and emotions.

Individuals with AS often have excellent auditory and visual perception. Children with ASD often demonstrate enhanced perception of small changes in patterns such as arrangements of objects or well-known images; typically this is domain-specific and involves processing of fine-grained features. Conversely, compared with individuals with high-functioning autism, individuals with AS have deficits in some tasks involving visual-spatial perception, auditory perception, or visual memory. Many accounts of individuals with AS and ASD report other unusual sensory and perceptual skills and experiences. They may be unusually sensitive or insensitive to sound, light, and other stimuli; these sensory responses are found in other developmental disorders and are not specific to AS or to ASD. There is little support for increased fight-or-flight response or failure of habituation in autism; there is more evidence of decreased responsiveness to sensory stimuli, although several studies show no differences.

Hans Asperger's initial accounts and other diagnostic schemes include descriptions of physical clumsiness. Children with AS may be delayed in acquiring skills requiring dexterity, such as riding a bicycle or opening a jar, and may seem to move awkwardly or feel "uncomfortable in their own skin". They may be poorly coordinated or have an odd or bouncy gait or posture, poor handwriting, or problems with motor coordination. They may show problems with proprioception (sensation of body position) on measures of developmental coordination disorder (motor planning disorder), balance, tandem gait, and finger-thumb apposition. There is no evidence that these motor skills problems differentiate AS from other high-functioning ASDs.

Children with AS are more likely to have sleep problems, including difficulty in falling asleep, frequent nocturnal awakenings, and early morning awakenings. AS is also associated with high levels of alexithymia, which is difficulty in identifying and describing one's emotions. Although AS, lower sleep quality, and alexithymia are associated with each other, their causal relationship is unclear.

Causes
Hans Asperger described common traits among his patients' family members, especially fathers, and research supports this observation and suggests a genetic contribution to Asperger syndrome. Although no specific genetic factor has yet been identified, multiple factors are believed to play a role in the expression of autism, given the variability in symptoms seen in children. Hundreds of genes have been linked to AS, and these genes play crucial role in a multitude of biological processes, exerting influence over the maturation and functioning of the brain. Evidence for a genetic link is that AS tends to run in families where more family members have limited behavioral symptoms similar to AS (for example, some problems with social interaction, or with language and reading skills). Most behavioral genetic research suggests that all autism spectrum disorders have shared genetic mechanisms. There may be shared genes in which particular alleles make an individual vulnerable, and varying combinations result in differing severity and symptoms in each person with AS.

A few ASD cases have been linked to exposure to teratogens (agents that cause birth defects) during the first eight weeks from conception. Although this does not exclude the possibility that ASD can be initiated or affected later, it is strong evidence that ASD arises very early in development. Many environmental factors have been hypothesized to act after birth, but none has been confirmed by scientific investigation. These environmental elements can act as independent and significant risk factors, or they can potentially influence pre-existing genetic factors in people who have a genetic predisposition.

Mechanism

Asperger syndrome appears to result from developmental factors that affect many or all functional brain systems, as opposed to localized effects.

Although the specific underpinnings of AS or factors that distinguish it from other ASDs are unknown, and no clear pathology common to individuals with AS has emerged, it is still possible that AS's mechanism is separate from other ASDs.

Neuroanatomical studies and the associations with teratogens strongly suggest that the mechanism includes alteration of brain development soon after conception. Abnormal fetal development may affect the final structure and connectivity of the brain, resulting in altered neural circuits controlling thought and behavior. Several theories of mechanism are available; none are likely to provide a complete explanation.

General-processing theories
One general-processing theory is weak central coherence theory, which hypothesizes that a limited ability to see the big picture underlies the central disturbance in ASD. A related theory—enhanced perceptual functioning—focuses more on the superiority of locally oriented and perceptual operations in autistic individuals.

Mirror neuron system (MNS) theory
The mirror neuron system (MNS) theory hypothesizes that alterations to the development of the MNS interfere with imitation and lead to Asperger syndrome's core feature of social impairment. One study found that activation is delayed in the core circuit for imitation in individuals with AS. This theory maps well to social cognition theories like the theory of mind, which hypothesizes that autistic behavior arises from impairments in ascribing mental states to oneself and others; or hyper-systemizing, which hypothesizes that autistic individuals can systematize internal operation to handle internal events but are less effective at empathizing when handling events generated by other agents.

Diagnosis
Standard diagnostic criteria require impairment in social interaction and repetitive and stereotyped patterns of behavior, activities, and interests, without significant delay in language or cognitive development. Unlike the international standard, the DSM-IV-TR criteria also required significant impairment in day-to-day functioning; DSM-5 eliminated AS as a separate diagnosis in 2013, and folded it into the umbrella of autism spectrum disorders. Other sets of diagnostic criteria have been proposed by Szatmari et al. and by Gillberg and Gillberg.

Diagnosis is most commonly made between the ages of four and eleven. A comprehensive assessment involves a multidisciplinary team  that observes across multiple settings, and includes neurological and genetic assessment as well as tests for cognition, psychomotor function, verbal and nonverbal strengths and weaknesses, style of learning, and skills for independent living. The "gold standard" in diagnosing ASDs combines clinical judgment with the Autism Diagnostic Interview-Revised (ADI-R), a semistructured parent interview; and the Autism Diagnostic Observation Schedule (ADOS), a conversation and play-based interview with the child. Delayed or mistaken diagnosis can be traumatic for individuals and families; for example, misdiagnosis can lead to medications that worsen behavior.

Underdiagnosis and overdiagnosis may be problems. The cost and difficulty of screening and assessment can delay diagnosis. Conversely, the increasing popularity of drug treatment options and the expansion of benefits has motivated providers to overdiagnose ASD. There are indications AS has been diagnosed more frequently in recent years, partly as a residual diagnosis for children of normal intelligence who are not autistic but have social difficulties.

There are questions about the external validity of the AS diagnosis. That is, it is unclear whether there is a practical benefit in distinguishing AS from HFA or PDD-NOS; different screening tools may render different diagnoses for the same person.

Differential diagnosis
Many children with AS are initially misdiagnosed with attention deficit hyperactivity disorder (ADHD). Diagnosing adults is more challenging, as standard diagnostic criteria are designed for children and the expression of AS changes with age. Adult diagnosis requires painstaking clinical examination and thorough medical history gained from both the individual and other people who know the person, focusing on childhood behavior.

Conditions that must be considered in a differential diagnosis along with ADHD include other ASDs, the schizophrenia spectrum, personality disorders, obsessive–compulsive disorder, major depressive disorder, semantic pragmatic disorder, nonverbal learning disorder, social anxiety disorder, Tourette syndrome, stereotypic movement disorder, bipolar disorder, social-cognitive deficits due to brain damage from alcohol use disorder, and obsessive–compulsive personality disorder (OCPD).

Screening
Parents of children with Asperger syndrome can typically trace differences in their children's development to as early as 30 months of age. Developmental screening during a routine check-up by a general practitioner or pediatrician may identify signs that warrant further investigation. The United States Preventive Services Task Force in 2016 found it was unclear if screening was beneficial or harmful among children in whom there are no concerns.

Different screening instruments are used to diagnose AS, including the Asperger Syndrome Diagnostic Scale (ASDS); Autism Spectrum Screening Questionnaire (ASSQ); Childhood Autism Spectrum Test (CAST), previously called the Childhood Asperger Syndrome Test; Gilliam Asperger's disorder scale (GADS); Krug Asperger's Disorder Index (KADI); and the autism-spectrum quotient (AQ), with versions for children, adolescents, and adults. None have been shown to reliably differentiate between AS and other ASDs.

Management
Treatment attempts to manage distressing symptoms and to teach age-appropriate social, communication, and vocational skills that are not naturally acquired during development. Intervention is tailored to the needs of the individual based on multidisciplinary assessment. Although progress has been made, data supporting the efficacy of particular interventions are limited.

Therapies
Managing ASD may involve multiple therapies that address core symptoms of the disorder. While many professionals agree that the earlier the professional support the better, there is no combination that is recommended above others. Professional support for ASD varies depending on the individual; it takes into account the linguistic capabilities, verbal strengths, and nonverbal vulnerabilities of individuals.

Many of those diagnosed with ASD or similar disorders advocate against behavioral therapies, like Applied behavior analysis (ABA) and Cognitive behavioral therapy (CBT), often as part of the autism rights movement, on the grounds that these approaches frequently reinforce the demand on autistic people to mask their neurodivergent characteristics or behaviors to favor a more 'neurotypical' and narrow conception of normality. ABA has faced a great deal of criticism over the years. Recently, studies have shown that ABA may be abusive and can increase PTSD symptoms in patients. The Autistic Self Advocacy Network campaigns against the use of ABA in autism.

In the case of CBT and talking therapies, the effectiveness varies, with many reporting that they appeared 'too self-aware' to gain significant benefit, as the therapy was designed with neurotypical people in mind. In autistic children, specifically, they also report that it is only mildly beneficial in aiding with their anxieties.

A typical program of professional support generally includes:
 * Applied behavior analysis (ABA) procedures, including positive behavior support (PBS)—or training and support of parents and school faculty in behavior management strategies to use in the home and school, and social skills training for more effective interpersonal interactions. The Autistic Self Advocacy Network campaigns against the use of ABA in autism;
 * Cognitive behavioral therapy to improve stress management relating to anxiety or explosive emotions and to help reduce obsessive interests (although this may produce negative impact by demonising special interests) and repetitive routines;
 * Medication for coexisting conditions such as major depressive disorder and anxiety disorders;
 * Occupational or physical therapy to assist with poor sensory processing and motor coordination; and,
 * Social communication intervention, which is specialized speech therapy to help with the pragmatics and give-and-take of normal conversation.

Of the many studies on behavior-based early intervention programs, most are case reports of up to five participants and typically examine a few problem behaviors such as self-injury, aggression, noncompliance, stereotypies, or spontaneous language; unintended side effects are largely ignored. Despite the popularity of social skills training, its effectiveness is not firmly established. A randomized controlled study of a model for training parents in problem behaviors in their children with AS showed that parents attending a one-day workshop or six individual lessons reported fewer behavioral problems, while parents receiving the individual lessons reported less intense behavioral problems in their AS children. Vocational training may be important to teach job interview etiquette and workplace behavior to older children and adults with AS, and organization software and personal data assistants can improve the work and life management of people with AS.

Fecal Microbiota Transplantation (FMT) is an innovative therapy for AS that aims to restore microbial balance in the patient's gastrointestinal tract by introducing healthy fecal microbiota acquired from people with a diverse microbial composition. This approach attempts to reconstruct the patient's gut microbiota by taking into account the intricate interactions between the human gut and the central nervous system via the gut-brain axis (GBA). Any disruption in gut health has been linked to an increased susceptibility to diverse neurodevelopmental disorders.

It is vital to remember that research of AS specifically operates upon the out-dated classification of this syndrome as external to ASD (Autism Spectrum Disorder). Similarly, we should also note that ASD is a spectrum and support varies dramatically depending on the individual.

Medications
No medications directly treat the core symptoms of AS. Although research into the efficacy of pharmaceutical intervention for AS is limited, it is essential to diagnose and treat comorbid conditions. Deficits in self-identifying emotions or in observing effects of one's behavior on others can make it difficult for individuals with AS to see why medication may be appropriate. Medication can be effective in combination with behavioral interventions and environmental accommodations in treating comorbid symptoms such as anxiety disorders, major depressive disorder, inattention, and aggression. The atypical antipsychotic medications risperidone, olanzapine and aripiprazole have been shown to reduce the associated symptoms of AS; risperidone can reduce repetitive and self-injurious behaviors, aggressive outbursts, and impulsivity, and improve stereotypical patterns of behavior and social relatedness. The selective serotonin reuptake inhibitors (SSRIs) fluoxetine, fluvoxamine, and sertraline have been effective in treating restricted and repetitive interests and behaviors,  while stimulant medication, such as methylphenidate, can reduce inattention. In addition, scientists have made a noteworthy finding that oxytocin, a hormone, plays a significant role in shaping human social behavior and the formation of interpersonal connections.

Care must be taken with medications, as side effects may be more common and harder to evaluate in individuals with AS, and tests of drugs' effectiveness against comorbid conditions routinely exclude individuals from the autism spectrum. Abnormalities in metabolism, cardiac conduction times, and an increased risk of type 2 diabetes have been raised as concerns with antipsychotic medications, along with serious long-term neurological side effects. SSRIs can lead to manifestations of behavioral activation such as increased impulsivity, aggression, and sleep disturbance. Weight gain and fatigue are commonly reported side effects of risperidone, which may also lead to increased risk for extrapyramidal symptoms such as restlessness and dystonia and increased serum prolactin levels. Sedation and weight gain are more common with olanzapine, which has also been linked with diabetes. Sedative side-effects in school-age children have ramifications for classroom learning. Individuals with AS may be unable to identify and communicate their internal moods and emotions or to tolerate side effects that for most people would not be problematic.

Prognosis
There is some evidence that children with AS may see a lessening of symptoms; up to 20% of children may no longer meet the diagnostic criteria as adults, although social and communication difficulties may persist. , no studies addressing the long-term outcome of individuals with Asperger syndrome are available and there are no systematic long-term follow-up studies of children with AS. Individuals with AS appear to have normal life expectancy, but have an increased prevalence of comorbid psychiatric conditions, such as major depressive disorder and anxiety disorders that may significantly affect prognosis. Although social impairment may be lifelong, the outcome is generally more positive than with individuals with lower-functioning autism spectrum disorders; for example, ASD symptoms are more likely to diminish with time in children with AS or HFA. Most students with AS and HFA have average mathematical ability and test slightly worse in mathematics than in general intelligence. However, mathematicians are at least three times more likely to have autism-spectrum traits than the general population, and are more likely to have family members with autism.

Although many attend regular education classes, some children with AS may attend special education classes such as separate classroom and resource room because of their social and behavioral difficulties. Adolescents with AS may exhibit ongoing difficulty with self-care or organization, and disturbances in social and romantic relationships. Despite high cognitive potential, most young adults with AS remain at home, yet some do marry and work independently. The "different-ness" adolescents experience can be traumatic. Anxiety may stem from preoccupation over possible violations of routines and rituals, from being placed in a situation without a clear schedule or expectations, or from concern with failing in social encounters; the resulting stress may manifest as inattention, withdrawal, reliance on obsessions, hyperactivity, or aggressive or oppositional behavior. Depression is often the result of chronic frustration from repeated failure to engage others socially, and mood disorders requiring treatment may develop. Clinical experience suggests the rate of suicide may be higher among those with AS, but this has not been confirmed by systematic empirical studies.

Education of families is critical in developing strategies for understanding strengths and weaknesses; helping the family to cope improves outcomes in children. Prognosis may be improved by diagnosis at a younger age that allows for early interventions, while interventions in adulthood are valuable but less beneficial. There are legal implications for individuals with AS as they run the risk of exploitation by others and may be unable to comprehend the societal implications of their actions.

Epidemiology
Frequency estimates vary enormously. In 2015, it was estimated that 37.2 million people globally are affected. A 2003 review of epidemiological studies of children found autism rates ranging from 0.03 to 4.84 per 1,000, with the ratio of autism to Asperger syndrome ranging from 1.5:1 to 16:1; combining the geometric mean ratio of 5:1 with a conservative prevalence estimate for autism of 1.3 per 1,000 suggests indirectly that the prevalence of AS might be around 0.26 per 1,000. Part of the variance in estimates arises from differences in diagnostic criteria. For example, a relatively small 2007 study of 5,484 eight-year-old children in Finland found 2.9 children per 1,000 met the ICD-10 criteria for an AS diagnosis, 2.7 per 1,000 for Gillberg and Gillberg criteria, 2.5 for DSM-IV, 1.6 for Szatmari et al., and 4.3 per 1,000 for the union of the four criteria. Boys seem to be more likely to have AS than girls; estimates of the sex ratio range from 1.6:1 to 4:1, using the Gillberg and Gillberg criteria. Females with autism spectrum disorders may be underdiagnosed.

Comorbidities
Anxiety disorders and major depressive disorder are the most common conditions seen at the same time; comorbidity of these in persons with AS is estimated at 65%. Reports have associated AS with medical conditions such as aminoaciduria and ligamentous laxity, but these have been case reports or small studies and no factors have been associated with AS across studies. One study of males with AS found an increased rate of epilepsy and a high rate (51%) of nonverbal learning disorder. AS is associated with tics, Tourette syndrome and bipolar disorder. The repetitive behaviors of AS have many similarities with the symptoms of obsessive–compulsive disorder and obsessive–compulsive personality disorder, and 26% of a sample of young adults with AS were found to meet the criteria for schizoid personality disorder (which is characterised by severe social seclusion and emotional detachment), more than any other personality disorder in the sample. However many of these studies are based on clinical samples or lack standardized measures; nonetheless, comorbid conditions are relatively common.

Correlated characteristics
Research indicates that individuals with Aspergers have significantly higher rates of LGBT identities and feelings than the general population. They are also significantly more likely to be non-theistic.

History
Named after the Austrian pediatrician Hans Asperger (1906–1980), Asperger syndrome is a relatively new diagnosis in the field of autism, though a syndrome like it was described as early as 1925 by Soviet child psychiatrist Grunya Sukhareva (1891–1981), leading some of those diagnosed with Asperger syndrome to instead refer to their condition as 'Sukhareva's Syndrome', in opposition to Hans Asperger's association with Nazism. As a child, Asperger appears to have exhibited some features of the very condition named after him, such as remoteness and talent in language. In 1944, Asperger described four children in his practice who had difficulty in integrating themselves socially and showing empathy towards peers. They also lacked nonverbal communication skills and were physically clumsy. Asperger described this "autistic psychopathy" as social isolation. Fifty years later, several standardizations of AS as a medical diagnosis were tentatively proposed, many of which diverge significantly from Asperger's original work.

Unlike today's AS, autistic psychopathy could be found in people of all levels of intelligence, including those with intellectual disability. Asperger defended the value of so-called "high-functioning" autistic individuals, writing: "We are convinced, then, that autistic people have their place in the organism of the social community. They fulfill their role well, perhaps better than anyone else could, and we are talking of people who as children had the greatest difficulties and caused untold worries to their care-givers." Asperger also believed some would be capable of exceptional achievement and original thought later in life.

Asperger's paper was published during World War II and in German, so it was not widely read elsewhere. Lorna Wing used the term Asperger syndrome in 1976, and popularized it to the English-speaking medical community in her February 1981 publication  of case studies of children showing the symptoms described by Asperger, and Uta Frith translated his paper to English in 1991. Sets of diagnostic criteria were outlined by Gillberg and Gillberg in 1989 and by Szatmari et al. in the same year. In 1992, AS became a standard diagnosis when it was included in the tenth edition of the World Health Organization's diagnostic manual, International Classification of Diseases (ICD-10). It was added to the fourth edition of the American Psychiatric Association's diagnostic reference, Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), published in 1994.

Hundreds of books, articles, and websites now describe AS and prevalence estimates have increased dramatically for ASD, with AS recognized as an important subgroup. Whether it should be seen as distinct from high-functioning autism is a fundamental issue requiring further study, and there are questions about the empirical validation of the DSM-IV and ICD-10 criteria. In 2013, DSM-5 eliminated AS as a separate diagnosis, folding it into the autism spectrum on a severity scale.

Society and culture

People identifying with Asperger syndrome may refer to themselves in casual conversation as aspies (a term first used in print in the Boston Globe in 1998). Some autistic people have advocated a shift in perception of autism spectrum disorders as complex syndromes rather than diseases that must be cured. Proponents of this view reject the notion that there is an "ideal" brain configuration and that any deviation from the norm is pathological; they promote tolerance of neurodiversity. These views are the basis for the autistic rights and autistic pride movements. There is a contrast between the attitude of people with AS, who typically do not want to be cured and are proud of their identity; and parents of children with AS, who typically seek assistance and a cure for their children.

Some researchers have argued that AS can be viewed as a different cognitive style, not a disorder, and that it should be removed from the standard Diagnostic and Statistical Manual, much as homosexuality was removed. (In 2013 Asperger Syndrome was indeed eliminated as a separate diagnosis in DSM-5. ) In a 2002 paper, Simon Baron-Cohen wrote of those with AS: "In the social world, there is no great benefit to a precise eye for detail, but in the worlds of maths, computing, cataloging, music, linguistics, engineering, and science, such an eye for detail can lead to success rather than failure." Baron-Cohen cited two reasons why it might still be useful to consider AS to be a disability: to ensure provision for legally required special support, and to recognize emotional difficulties from reduced empathy. Baron-Cohen argues that the genes for ASD's combination of abilities have operated throughout recent human evolution and have made remarkable contributions to human history.

By contrast, Pier Jaarsma and Welin wrote in 2011 that the "broad version of the neurodiversity claim, covering low-functioning as well as high-functioning autism, is problematic. Only a narrow conception of neurodiversity, referring exclusively to high-functioning autists, is reasonable." They say that "higher functioning" individuals with autism may "not [be] benefited with such a psychiatric defect-based diagnosis ... some of them are being harmed by it, because of the disrespect the diagnosis displays for their natural way of being", but "think that it is still reasonable to include other categories of autism in the psychiatric diagnostics. The narrow conception of the neurodiversity claim should be accepted but the broader claim should not."

title: Asperger syndrome


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Tazio Nuvolari

Tazio Giorgio Nuvolari (16 November 1892 – 11 August 1953) was an Italian racing driver. He first raced motorcycles and then concentrated on sports cars and Grand Prix racing. Originally of Mantua, he was nicknamed il Mantovano Volante ("the Flying Mantuan") and Nuvola ("Cloud"). His victories—72 major races, 150 in all—included 24 Grands Prix, five Coppa Cianos, two Mille Miglias, two Targa Florios, two RAC Tourist Trophies, a Le Mans 24-hour race, and a European Championship in Grand Prix racing. Ferdinand Porsche called him "the greatest driver of the past, the present, and the future".

Biography
Nuvolari started racing motorcycles in 1920 at the age of 27, winning the 1925 350cc European Championship. Having raced cars as well as motorcycles from 1925 until 1930, he then concentrated on cars, and won the 1932 European Championship with the Alfa Romeo factory team, Alfa Corse.

After Alfa Romeo officially withdrew from Grand Prix racing, Nuvolari drove for Scuderia Ferrari. The team was owned by Enzo Ferrari, who ran the Alfa Romeo cars semi-officially. In 1933 Nuvolari won Le Mans in an Alfa Romeo as a member of Ferrari's team, and a month later won the Belgian Grand Prix in a works Maserati, having switched teams a week before the race. Mussolini helped persuade Ferrari to take Nuvolari back for 1935, and in that year he won the German Grand Prix in Ferrari's outdated Alfa Romeo, defeating more powerful rivals from Mercedes-Benz and Auto Union. It was the only time a non-German car won a European Championship race from 1935 to 1939.

The relationship with Ferrari deteriorated during 1937, and Nuvolari raced an Auto Union in that year's Swiss Grand Prix. He rejoined the Auto Union team for the 1938 season and stayed with them through 1939 until Grand Prix racing was put on hiatus by World War II. The only major European race he never won was the Czechoslovakian Grand Prix.

When Nuvolari resumed racing after the war he was 54 and in poor health. In his final appearance in competition, driving a Cisitalia-Abarth Tipo 204A at a Palermo hillclimb on 10 April 1950, he won his class and placed fifth overall. He died in 1953 from a stroke.

Personal and early life
Nuvolari was born in Castel d'Ario, near Mantua, on 16 November 1892 to Arturo Nuvolari and his wife Elisa Zorzi. The family was well acquainted with motor racing, as Arturo and his brother Giuseppe were both bicycle racers—Giuseppe was a multiple winner of the Italian national championship and was particularly admired by a young Tazio.

Nuvolari was married to Carolina Perina, and together they had two children: Giorgio (born 4 September 1918), who died in 1937 aged 19 from myocarditis, and Alberto, who died in 1946 aged 18 from nephritis.

Motorcycle racing
Nuvolari obtained his license for motorcycle racing in 1915 at the age of 23. He served in the Italian army as an ambulance driver in World War I, and in 1920 took part in his first motorcycle race at the Circuito Internazionale Motoristico in Cremona but did not finish. He also raced cars, winning the Coppa Verona reliability trial in 1921.

In 1925 he became the 350 cc European Motorcycling champion by winning the European Grand Prix. At the time, the European Grand Prix was considered the most important race of the motorcycling season and the winners in each category were designated European Champions. He won the Nations Grand Prix four times between 1925 and 1928, and the Lario Circuit race five times between 1925 and 1929, all in the 350 cc class on a Bianchi motorcycle.

It was also in 1925 that Alfa Romeo, seeking a driver to replace Antonio Ascari, who had been killed in the French Grand Prix in July, tested Nuvolari in their Grand Prix car with a view to running him in the Italian Grand Prix in September. He crashed when the gearbox seized, and severely lacerated his back. He was not picked for the team. Six days later, in bandages, with a cushion strapped to his stomach, and lifted onto his motorcycle by Bianchi mechanics for a push-start, he won the rain-soaked Nations Grand Prix at Monza.

1930–1932: Alfa Corse
1930

In 1930, Nuvolari won his first RAC Tourist Trophy (he won again in 1933). Motor racing legend has it that when one of the drivers broke the window of a butcher's shop, Nuvolari drove onto the pavement and tried to grab a ham as he passed. According to Sammy Davis who met him there, Nuvolari enjoyed dark humour and situations when everything went wrong. For example, after he got a ticket for a journey home from the Sicilian Targa Florio he said to Enzo Ferrari, "What a strange businessman you are. What if I am brought back in a coffin?".

Nuvolari and co-driver Battista Guidotti won the Mille Miglia in a Zagato-bodied Alfa Romeo 6C 1750 GS, becoming the first to complete the race at an average of over 100 km/h. At night, leading on elapsed time but still lying behind his teammate Achille Varzi on the road because he had started after him, he tailed Varzi at speeds of up to 150 km/h with his headlights switched off, so that he could not be seen in the other car's rear-view mirrors. He eventually switched them on to overtake "the shocked" Varzi near the finish at Brescia.

1931

Towards the end of 1930, Nuvolari decided to stop racing motorcycles and concentrate fully on cars for 1931. Regulations for the season required Grand Prix races to be at least 10 hours long. For the Italian Grand Prix, Nuvolari was to share an Alfa Romeo with Baconin Borzacchini. The car started from ninth place on the grid, and when it retired with mechanical problems after 33 laps Nuvolari teamed up with Giuseppe Campari. The pair took the race win, although Nuvolari could not receive the championship points. Apart from the Belgian Grand Prix, where he came second, the only other European Championship race was the French Grand Prix, where he finished 11th. The same year, he won both the Coppa Ciano at Livorno and the arduous Targa Florio, which was run on the 92-mile (146 km) Grande variant of the super-twisty course that year.

1932

For 1932, Grands Prix had to be between five and ten hours long. It was the only season in which Nuvolari regularly drove one of the fastest cars, the Alfa Romeo P3, and he took two wins and a second place from the three European Championship Grands Prix, plus victory in the championship by four points from Borzacchini. He achieved four other race wins that year, including the prestigious Monaco Grand Prix and a second Targa Florio. Of the latter, his mechanic Mabelli said: "Before the start, Nuvolari told me to go down on the floor of the car every time he shouts, which was a signal that he went to a curve too fast and that we need to lower the car's center of mass. I spent the whole race on the floor. Nuvolari started to shout in the first curve and wouldn't stop until the last one."

On 28 April 1932 the writer Gabriele d'Annunzio gave him a golden tortoise badge. Thereafter Nuvolari wore it as a talisman, and it became famously associated with him, along with his initialled yellow jumper.

1933–1937: Scuderia Ferrari and Maserati
1933

The 1933 season began a two-year hiatus in the European Championship, and although Alfa Romeo ceased official involvement in Grands Prix their cars continued racing with Enzo Ferrari's privateer team. For economic reasons, the P3 was not passed on to Ferrari so they used its predecessor, the Monza. Maserati, with a much-improved car, provided the main opposition.

It has been alleged that Nuvolari was involved in a race-fixing scandal at the Tripoli Grand Prix. The story is that he conspired with Achille Varzi and Baconin Borzacchini to fix the race in order to profit from the Libyan state lottery, in which 30 tickets were drawn before the race—one for each starter—and the holder of the ticket corresponding to the victorious driver won 7.5 million lire. Others say the allegation was unfounded and that it originated with Alfred Neubauer, the Mercedes-Benz team manager at the time, who was well known as a raconteur with a penchant for spicing up a story. Neubauer's version does not altogether hold true with documented records of events, which indicate that Nuvolari, Varzi, and Borzacchini agreed to pool the prize money should one of them win.

For the 1933 24 Hours of Le Mans, Alfa Romeo teamed Nuvolari with Raymond Sommer. Sommer asked to drive the majority of the race as he was more familiar with the circuit and thought Nuvolari would probably break the car. When Nuvolari countered that he was a leading Grand Prix driver and Le Mans was a simple layout that would not trouble him, they agreed to divide the driving equally. In the race, they built a two-lap lead before a leaking fuel tank forced them to stop at the pits, where the leak was plugged by chewing gum. More stops were necessary as the makeshift repair came undone several times. Nuvolari, driving through to the end of the race, broke the lap record nine times and won by approximately 400 yd.

1934

In April 1934 Nuvolari entered the Monaco Grand Prix in a privately owned Bugatti and worked up to third place before brake problems forced him back to fifth at the finish, two laps behind the winner, Guy Moll. Racing in heavy rain at Alessandria in the Circuito di Pietro Bordino race, he crashed and broke a leg: balked by Trossi's Alfa Romeo P3, he lost control of his privately entered Maserati 8CM, which skidded, rolled, and hit a tree. Bored in hospital, he decided to enter the AVUS-Rennen just over four weeks later. As his left leg was too badly injured to operate the clutch, his Maserati was modified for him to work the pedals with his right foot. Troubled by cramp, he finished fifth.

By the time of the Penya Rhin Grand Prix in late June, Nuvolari's leg was finally out of plaster but still painful. He retired his Maserati with technical problems.

In the Italian Grand Prix, he debuted Maserati's new 6C-34 model. It performed poorly and Nuvolari could finish only fifth, three laps behind the Mercedes-Benz W25s of Caracciola and Fagioli, and also trailing the Auto Union As of Stuck and Leiningen, and the Alfa Romeo P3s of Trossi, Comotti, and Chiron.

At the end of September, he finished third in the Czechoslovakian Grand Prix (Masaryk Circuit), behind Caracciola and Stuck.

1935

For 1935, Nuvolari set his sights on a drive with the German Auto Union team. It lacked top-line drivers but relented to pressure from Achille Varzi, which did not want Nuvolari in the team. Nuvolari then approached Enzo Ferrari, who at first rebuffed him as he had previously walked out on the team. Italy's prime minister Mussolini helped persuade Ferrari to take Nuvolari back.

This was the year that Nuvolari achieved 'The Impossible Victory', which many regard as the greatest win in all of motor racing history: driving an outclassed Alfa Romeo P3 (3167 cc, supercharged, 265 hp) in the German Grand Prix at the Nürburgring, he beat all the dominant German cars—five Mercedes-Benz W25s (3990 cc, 8C, supercharged, 375 HP driven by Caracciola, Fagioli, Lang, von Brauchitsch, and Geyer), and four Auto Union Bs (4950 cc, 16C, supercharged, 375 hp driven by Rosemeyer, Varzi, Stuck, and Pietsch). The crowd of 300,000 applauded Nuvolari, but the representatives of Nazi Germany were enraged.

1936

Nuvolari had a big accident in May during practice for the Tripoli Grand Prix and it is alleged that he broke some vertebrae. Despite a limp, he took part in the race the following day and finished eighth. In October, he traveled to the U.S. for the American Automobile Association (AAA) sanctioned Vanderbilt Cup. Starting eighth, Nuvolari took the lead from Antonio Brivio on the second lap of the 75-lap event, leading from then until the finish.

1937

At the beginning of 1937, Alfa Romeo took its works team back from Ferrari and entered it as part of the Alfa Corse team. Nuvolari stayed with Alfa Romeo despite becoming increasingly frustrated with the poor build quality of its racing cars.

At the Coppa Acerbo, Alfa Romeo's new 12C-37 car proved to be slow and unreliable. Frustrated, Nuvolari handed his car over to Giuseppe Farina mid-race. Not wanting to leave Alfa Romeo, he drove an Auto Union in the Swiss Grand Prix as a one-off. After the Italian Grand Prix, Alfa Romeo withdrew from racing for the remainder of the season and dismissed Vittorio Jano, its chief designer.

1938–1939: Auto Union
1938

Although Nuvolari started 1938 as an Alfa Romeo driver, a split fuel tank in the first race of the season at Pau was enough for him to walk out on the team, critical of the poor workmanship that was exhibited. He announced his retirement from Grand Prix racing and took a holiday in America. At the same time, Auto Union was having to rely on inexperienced drivers. Following the Tripoli Grand Prix they contacted Nuvolari who, having been refreshed from his break, agreed to drive for the highly successful German team, who were running radical mid-engined cars. Nuvolari found further success with Auto Union; now driving a faster and more reliable car that enabled him to compete for victories and the European Championship, Nuvolari won his home Grand Prix at Monza and won the Donington Grand Prix in England.

1939

In 1939 he won Belgrade Grand Prix which was held on 3 September 1939, the last one before outbreak of World War II.

Post-war racing
In 1946 Nuvolari took part in thirteen races, winning the Grand Prix of Albi in a Maserati 4CL, finishing 4th in the Grand Prix of Nations and 13th in the Coppa Brezzi, and retiring from the others. It was noted that when he raced at Milan in September, he steered with mostly one hand; the other held a bloodstained handkerchief over his mouth.

Through 1947 and 1948 he raced eleven times, winning twice. He finished 2nd, 3rd, 4th, and 7th, and retired from the remaining five races. His Maserati did not qualify for the 1949 Marseilles Grand Prix. Battered by health problems as well as the loss of his two sons, Nuvolari was nevertheless persuaded by Enzo Ferrari to race in the 1948 edition of the Mille Miglia. Paired with mechanic Sergio Scapinelli, Nuvolari took the lead in the early stages of the race. He was eventually forced to retire the car in Reggio Emilia when he had a 27-minutes lead.

His last appearance in competition was at the Palermo-Montepellegrino hillclimb on 10 April 1950, driving a Squadra Abarth Cisitalia-Abarth 204. He won his class and finished fifth overall.

Death and legacy

Nuvolari never formally announced his retirement, but his health deteriorated and he became increasingly solitary. In 1952 a stroke left him partially paralysed, and he died in bed a year later from a second one. Between 25,000 and 55,000 people, at least half the population of Mantua, attended his funeral in a mile-long procession, with the coffin placed on a car chassis that was pushed by Alberto Ascari, Luigi Villoresi, and Juan Manuel Fangio. He is buried in the family tomb in the Cimitero Degli Angeli, on the road from Mantua to Cremona. The inscription over the door reads:.

The Museum Tazio Nuvolari is located in his homestead at Giulia Romano via N. Sauro in Mantua.

In Castel d'Ario there is a bronze statue of Nuvolari on a marble plinth inscribed Nivola – Campione Automobilistico di Tutti Tempi (Nivola – Champion Driver of All Time); and at the end of Mantua's Via delle Rimembranze, the street where he lived towards the end of his life, is a square that is now called Piazza Nuvolari.

The Cisitalia 202 SMM Nuvolari Spider, EAM Nuvolari S1, and Audi Nuvolari Quattro are named after him, and Maserati offers the colour Grigio-Nuvolari from their custom palette.

Nuvolari was an early exponent (if not the inventor, according to Enzo Ferrari) of the four-wheel drift cornering technique which was later utilised by drivers such as Stirling Moss.

An Italian pay-TV channel featuring motor sports is also named "Nuvolari".

The online video interview platform Tazio is named after him.

In the 1961 The Twilight Zone episode, "A Game of Pool", Tazio Nuvolari is referenced by Jonathan Winters (Fats Brown) when talking to Jack Klugman (Jessie Cardiff) about great men in history.

Nuvolari was mentioned in 1969 comedy film Monte Carlo or Bust! when Angelo Pincilli and Marcelo Agosti, two Italian policemen taking part in the Monte Carlo Rally, hope to become as famous as Nuvolari and land speed record holder Malcolm Campbell by winning the race.

The 1976 album Automobili by Italian singer-songwriter Lucio Dalla, included the song "Nuvolari", with lyrics by poet Roberto Roversi.

A Six Metre racing yacht built in the 1978 for Luca and Tony Bassani was named Nuvolari in honour of the racing driver. That yacht was restored in 2016 and currently races in Victoria, BC.

European Championship results
(key) (Races in bold indicate pole position) (Races in italics indicate fastest lap)

Post-WWII Grandes Épreuves results
(key) (Races in bold indicate pole position; races in italics indicate fastest lap)

title: Tazio Nuvolari