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Isotopes of thorium

Thorium has seven occurring isotopes but none are stable. One isotope, 232Th, is stable, with a half-life of 1.405×1010 years longer than the age of the Earth, slightly longer than the accepted age of the universe. This isotope makes up nearly all natural thorium, so thorium was considered to be mononuclidic. However, in 2013, IUPAC reclassified thorium as binuclidic, due to large amounts of 230Th in deep seawater. Thorium has a characteristic terrestrial isotopic composition and thus a standard atomic weight can be given. Thirty-one radioisotopes have been characterized, with the most stable being 232Th, 230Th with a half-life of 75,380 years, 229Th with a half-life of 7,917 years, 228Th with a half-life of 1.92 years. All of the remaining radioactive isotopes have half-lives that are less than thirty days and the majority of these have half-lives that are less than ten minutes. One isotope, 229Th, has a nuclear isomer with a remarkably low excitation energy measured to be 8.28 ± 0.17 eV. It has been proposed to perform laser spectroscopy of the 229Th nucleus and use the low-energy transition for the development of a nuclear clock of high accuracy.

The known isotopes of thorium range in mass number from 208 to 238. Thorium has been suggested for use in thorium-based nuclear power, it is radioactive, in many countries the use of thorium in consumer products is banned or discouraged. It is used in cathodes of vacuum tubes, for a combination of physical stability at high temperature and a low work energy required to remove an electron from its surface, it has, for about a century, been used in mantles of gas and vapor lamps such as gas lights and camping lanterns. Thorium was used in certain glass elements of Aero-Ektar lenses made by Kodak during World War II, thus they are mildly radioactive. Two of the glass elements in the f/2.5 Aero-Ektar lenses are 11% and 13% thorium by weight. The thorium-containing glasses were used because they have a high refractive index with a low dispersion, a desirable property. Many surviving Aero-Ektar lenses have a tea colored tint due to radiation damage to the glass; as these lenses were used for aerial reconnaissance, the radiation level is not high enough to fog film over a short period.

This would indicate. However, when not in use, it would be prudent to store these lenses as far as possible from inhabited areas. 228Th is an isotope of thorium with 138 neutrons. It was once named Radiothorium, due to its occurrence in the disintegration chain of thorium-232, it has a half-life of 1.9116 years. It undergoes alpha decay to 224Ra, it decays by the unusual route of cluster decay, emitting a nucleus of 20O and producing stable 208Pb. It is a daughter isotope of 232U. 228Th has an atomic weight of 228.0287411 grams/mole. 229Th is a radioactive isotope of thorium that decays by alpha emission with a half-life of 7917 years.229Th is produced by the decay of uranium-233, its principal use is for the production of the medical isotopes actinium-225 and bismuth-213. In 1976, gamma ray spectroscopy first indicated that 229Th has a nuclear isomer, 229mTh, with a remarkably low excitation energy. At that time the energy was inferred to be below 100 eV, purely based on the non-observation of the isomer's direct decay.

However, in 1990, further measurements led to the conclusion that the energy is certainly below 10 eV, making the isomer to be the one of lowest known excitation energy. In the following years, the energy was further constrained to 3.5 ± 1.0 eV, for a long time the accepted energy value. Such low energy soon raised some interest as it conceptually allows for direct laser excitation of the nuclear state, which leads to some interesting potential applications, e.g. the development of a nuclear clock of high accuracy or as a qubit for quantum computing. Nuclear laser excitation of 229mTh and therefore the development of a nuclear clock has so far been impeded by an insufficient knowledge about the isomeric properties. A precise knowledge of the isomeric energy is of particular importance in this context, as it determines the required laser technology and shortens the scanning times when searching for the direct excitation; this triggered a multitude of investigations, both theoretical and experimental, trying to determine the transition energy and to specify other properties of the isomeric state of 229Th.

The direct observation of photons emitted in the isomeric decay would help to pin down the isomeric energy value. Until today, there has been no conclusive report on the detection of photons emitted in the decay of 229mTh. Instead, improved gamma ray spectroscopy measurements using an advanced high-resolution X-ray microcalorimeter were carried out in 2007, yielding a new value for the transition energy of E = 7.6 ± 0.5 eV, corrected to E = 7.8 ± 0.5 eV in 2009. This shift in isomeric energy from 3.5 eV to 7.8 eV explains why several early attempts to directly observe the transition were unsuccessful. Still, most of the recent searches for light emitted in the isomeric decay failed to observe any signal, pointing towards a strong non-radiative decay channel. A direct detection of photons emitted in the isomeric decay was claimed in 2012 and again in 2018. However, both reports are subject to controversial discussions within the community. A direct detection of electrons being emitted in the internal conversion decay channel of 229mTh was achieved in 2016.

However, at the time the isomer's transition ener

List of actors who have played the Doctor

Since the beginning of the British science fiction television series Doctor Who in 1963, many actors have played the title character of The Doctor on television and in various BBC-licensed spin-offs on television, radio, audio plays and webcasts. The character's ability to periodically regenerate his appearance and personality has facilitated the ability of new actors to take over the role – in official and unofficial productions – while in most cases maintaining continuity with the television series; this list does not include Doctors who have appeared in fan films or amateur stage shows and audios, nor does it include rare occasions where a companion or other character has impersonated the Doctor. The incumbent is Jodie Whittaker, who succeeded Peter Capaldi in the role at the conclusion of the 2017 Christmas special. List of actors considered for the part of the Doctor Doctor Who spoofs The "Morbius Doctors"

Stephen Warfield Gambrill

Stephen Warfield Gambrill was an American politician. Born near Savage, Maryland, to Stephen Gambrill and Kate Gambrill, he attended the common schools and Maryland Agricultural College (now the University of Maryland, College Park, he graduated from the law department of Columbian College, Washington, D. C. in 1896, was admitted to the bar in 1897, practiced in Baltimore, Maryland. In 1900, he married Haddie D. Gorman. Gambrill served as a member of the Maryland House of Delegates from 1920 to 1922, served in the Maryland State Senate in 1924, he was elected from the fifth district of Maryland as a Democrat to the Sixty-eighth Congress to fill the vacancy caused by the death of Sidney E. Mudd II and was reelected to the Sixty-ninth and to the six succeeding Congresses, serving from November 4, 1924 until his death in Washington, D. C, he died on December 19, 1938 and is interred in Cedar Hill Cemetery, Maryland. List of United States Congress members who died in office United States Congress. "Stephen Warfield Gambrill".

Biographical Directory of the United States Congress

Disney's Halloween Treat

"Disney's Halloween Treat" is a 1982 Halloween-themed episode of Walt Disney which aired on October 30, 1982. The episode is narrated by a jack-o'-lantern puppet and features a compilation of Disney short cartoons involving spooky or supernatural themes as well as excerpted segments of various villains from Disney feature films; the opening and closing credits feature an orange colorized version of the 1929 Silly Symphony short The Skeleton Dance as well as its own title theme song, sung in the opening and closing credits. The lyrics were written by Galen R. Brandt with music by John Debney. Another similar special titled "A Disney Halloween" aired in 1983 which incorporated segments from both "Disney's Halloween Treat" and "Disney's Greatest Villains". "Disney's Halloween Treat". It was released on VHS in 1984; as of today, it has not been released on Blu-ray. "Madam Mim" – The Sword in the Stone "Night on Bald Mountain" sequence – Fantasia Clip of Pluto's Sweater Clip of Mickey's Parrot Donald Duck and the GorillaDonald Duck and his nephews Huey and Louie "Pluto's Judgement" sequence featuring three Pluto cartoons assembled together: Puss Cafe Cat Nap Pluto Pluto's Judgement Day "Captain Hook" – Peter Pan "Cruella de Vil" – One Hundred and One Dalmatians "The Evil Queen" – Snow White and the Seven Dwarfs "Si and Am" – Lady and the Tramp "Ichabod Crane and Headless Horseman" – The Adventures of Ichabod and Mr. Toad "Halloween Hall o' Fame" "A Disney Halloween" "Disney's Halloween Treat" on IMDb

Collins Waterfront Architectural District

The Collins Waterfront Architectural District is a historic district in Miami Beach, that includes 110 contributing buildings and structures built in the late 1940s, 1950s and 1960s, centering on Collins Avenue. The predominant styles include moderne, Art Deco and Mediterranean Revival architecture, as well as the local Miami Modern style; the chief contributing resources are large resort hotels. The district is bounded by the Atlantic Ocean on the east, by 24th Street, Indian Creek Drive, Pine Tree Drive and the Collins Canal; the district is part of Mid-Beach. The district was placed on the National Register of Historic Places on November 15, 2011. Miami Modern architecture List of Collins Waterfront Architectural District contributing properties Media related to Collins Waterfront Architectural District at Wikimedia Commons

Departments of Gabon

The provinces of Gabon are divided into forty-nine departments. The departments are listed below, by province: Komo Department Komo-Mondah Department Noya Department Komo-Océan Department Libreville The Department of Cap Estérias was deleted in 2013. Djoue Department Djououri-Aguilli Department Lekoni-Lekori Department Lekoko Department Leboumbi-Leyou Department Mpassa Department Plateaux Department Sebe-Brikolo Department Ogooué-Létili Department Lékabi-Léwolo Department Bayi-Brikolo Department Abanga-Bigne Department Ogooué et des Lacs Department Boumi-Louetsi Department Dola Department Douya-Onoy Department Louetsi-Wano Department Ndolou Department Ogoulou Department Tsamba-Magotsi Department Louetsi-Bibaka Department Mougalaba Department Basse-Banio Department Douigni Department Haute-Banio Department Mougoutsi Department Doutsila Department Mongo Department Ivindo Department Lope Department Mvoung Department Zadie Department Lolo-Bouenguidi Department Lombo-Bouenguidi Department Mouloundou Department Offoué-Onoye Department Bendje Department Etimboue Department Ndougou Department Haut-Komo Department Haut-Ntem Department Ntem Department Okano Department Woleu Department Provinces of Gabon Statoids, Departments of Gabon