Proof calculusIn mathematical logic, a proof calculus or a proof system is built to prove statements. A proof system includes the components: Language: The set L of formulas admitted by the system, for example, propositional logic or first-order logic. Rules of inference: List of rules that can be employed to prove theorems from axioms and theorems. Axioms: Formulas in L assumed to be valid. All theorems are derived from axioms. Usually a given proof calculus encompasses more than a single particular formal system, since many proof calculi are under-determined and can be used for radically different logics.
Decision problemIn computability theory and computational complexity theory, a decision problem is a computational problem that can be posed as a yes–no question of the input values. An example of a decision problem is deciding by means of an algorithm whether a given natural number is prime. Another is the problem "given two numbers x and y, does x evenly divide y?". The answer is either 'yes' or 'no' depending upon the values of x and y. A method for solving a decision problem, given in the form of an algorithm, is called a decision procedure for that problem.
Constructive proofIn mathematics, a constructive proof is a method of proof that demonstrates the existence of a mathematical object by creating or providing a method for creating the object. This is in contrast to a non-constructive proof (also known as an existence proof or pure existence theorem), which proves the existence of a particular kind of object without providing an example. For avoiding confusion with the stronger concept that follows, such a constructive proof is sometimes called an effective proof.
Positron emission tomographyPositron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, regional chemical composition, and absorption. Different tracers are used for various imaging purposes, depending on the target process within the body. For example, -FDG is commonly used to detect cancer, NaF is widely used for detecting bone formation, and oxygen-15 is sometimes used to measure blood flow.
Jan ŽižkaJan Žižka z Trocnova a Kalicha (John Zizka of Trocnov and the Chalice; 1360 – 11 October 1424) was a Czech general – a contemporary and follower of Jan Hus and a Radical Hussite who led the Taborites. Žižka was a successful military leader and is now a Czech national hero. He was nicknamed "One-eyed Žižka", having lost one and then both eyes. Jan Žižka led Hussite forces against three crusades and never lost a single battle despite being completely blind in his last stages of life.
Ryszard KrynickiRyszard Krynicki (Polish: 'ryszard-kry'ńickJi; born 28 June 1943) is a Polish poet and translator, member of the Polish "New Wave" Movement. He is regarded as one of the most prominent post-war contemporary Polish poets. In 2015, he was awarded the Zbigniew Herbert International Literary Award as a recognition for his poetry works. He was born on 28 June 1943 in St. Valentin, Austria. After World War II, he moved to Poland, where he graduated from Marie Curie High School No. 2 in Gorzów Wielkopolski.
Tom Friedman (artist)Tom Friedman (born 1965) is an American conceptual sculptor. He was born in St. Louis, Missouri and received a BFA in graphic illustration from Washington University in St. Louis (1988) and an MFA in sculpture from the University of Illinois at Chicago (1990.). As a conceptual artist he works in diverse media including sculpture, painting, drawing, video, and installation. For over twenty years, Friedman has been investigating the viewer/object relationship, and "the space in between.
Svalbard and Jan MayenSvalbard and Jan Mayen (Svalbard og Jan Mayen, ISO 3166-1 alpha-2: SJ, ISO 3166-1 alpha-3: SJM, ISO 3166-1 numeric: 744) is a statistical designation defined by ISO 3166-1 for a collective grouping of two remote jurisdictions of Norway: Svalbard and Jan Mayen. While the two are combined for the purposes of the International Organization for Standardization (ISO) category, they are not administratively related. This has further resulted in the country code top-level domain being issued for Svalbard and Jan Mayen, and ISO 3166-2:SJ.
Giorgio JanGiorgio Jan (21 December 1791 in Vienna – 8 May 1866, Milan) was an Italian taxonomist, zoologist, botanist, herpetologist, and writer. He is also known as Georg Jan or Georges Jan. He was the first director of the natural history museum at Milan. After having been an assistant at the University of Vienna, Jan obtained the post of professor of botany at the university of Parma as well as becoming Director of the botanical garden. At that time, the duchy of Parma was no longer under Austrian jurisdiction following the Congress of Vienna after the defeat of Napoleon at Waterloo.
Jan ZachariasiewiczJan Chryzostom Zachariasiewicz (ˈjan xrɨˈzɔstɔm zaxarjaˈɕɛvit͡ʂ; 1823–1906; Zacharyasiewicz, Zacharjasiewicz) was a Polish novelist and journalist. Zachariasiewicz was born on 11 September 1823 in Radymno. During 1842–44 he was a prisoner of Špilberk Castle. Co-editor of Tygodnik Polski, where he published poem Machabeusze. For publishing this work and also for participation in Revolutions of 1848, Zachariasiewicz was imprisoned in Terezín for two years. He was a nephew or grandnephew of the bishop Franciszek Zachariasiewicz (1770–1845).
2008–09 Australian bushfire seasonThe Australian bushfire season ran from late December 2008 to April/May 2009. Above average rainfalls in December, particularly in Victoria, delayed the start of the season, but by January 2009, conditions throughout South eastern Australia worsened with the onset of one of the region's worst heat waves. On 7 February, extreme bushfire conditions precipitated major bushfires throughout Victoria, involving several large fire complexes, which continued to burn across the state for around one month.
Compact spaceIn mathematics, specifically general topology, compactness is a property that seeks to generalize the notion of a closed and bounded subset of Euclidean space. The idea is that a compact space has no "punctures" or "missing endpoints", i.e., it includes all limiting values of points. For example, the open interval (0,1) would not be compact because it excludes the limiting values of 0 and 1, whereas the closed interval [0,1] would be compact.
