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"In physics, induced gamma emission (IGE) refers to the process of fluorescent emission of gamma rays from excited nuclei, usually involving a specific nuclear isomer. It is analogous to conventional fluorescence, which is defined as the emission of a photon (unit of light) by an excited electron in an atom or molecule. In the case of IGE, nuclear isomers can store significant amounts of excitation energy for times long enough for them to serve as nuclear fluorescent materials. There are over 800 known nuclear isomers but almost all are too intrinsically radioactive to be considered for applications. there were two proposed nuclear isomers that appeared to be physically capable of IGE fluorescence in safe arrangements: tantalum-180m and hafnium-178m2. History Energetics of IGE from 115In. Arrows are photons, (up) absorption, (down) emission. Horizontal lines represent excited states of In involved in IGE.Induced gamma emission is an example of interdisciplinary research bordering on both nuclear physics and quantum electronics. Viewed as a nuclear reaction it would belong to a class in which only photons were involved in creating and destroying states of nuclear excitation. It is a class usually overlooked in traditional discussions. In 1939 Pontecorvo and Lazard reported the first example of this type of reaction. Indium was the target and in modern terminology describing nuclear reactions it would be written 115In(γ,γ')115mIn. The product nuclide carries an "m" to denote that it has a long enough half life (4.5 h in this case) to qualify as being a nuclear isomer. That is what made the experiment possible in 1939 because the researchers had hours to remove the products from the irradiating environment and then to study them in a more appropriate location. With projectile photons, momentum and energy can be conserved only if the incident photon, X-ray or gamma, has precisely the energy corresponding to the difference in energy between the initial state of the target nucleus and some excited state that is not too different in terms of quantum properties such as spin. There is no threshold behavior and the incident projectile disappears and its energy is transferred into internal excitation of the target nucleus. It is a resonant process that is uncommon in nuclear reactions but normal in the excitation of fluorescence at the atomic level. Only as recently as 1988 was the resonant nature of this type of reaction finally proven. Such resonant reactions are more readily described by the formalities of atomic fluorescence and further development was facilitated by an interdisciplinary approach of IGE. There is little conceptual difference in an IGE experiment when the target is a nuclear isomer. Such a reaction as mX(γ,γ')X where mX is one of the five candidates listed above, is only different because there are lower energy states for the product nuclide to enter after the reaction than there were at the start. Practical difficulties arise from the need to ensure safety from the spontaneous radioactive decay of nuclear isomers in quantities sufficient for experimentation. Lifetimes must be long enough that doses from the spontaneous decay from the targets always remain within safe limits. In 1988 Collins and coworkers reported the first excitation of IGE from a nuclear isomer. They excited fluorescence from the nuclear isomer tantalum-180m with x-rays produced by an external beam radiotherapy linac. Results were surprising and considered to be controversial until the resonant states excited in the target were identified. Distinctive features *If an incident photon is absorbed by an initial state of a target nucleus, that nucleus will be raised to a more energetic state of excitation. If that state can radiate its energy only during a transition back to the initial state, the result is a scattering process as seen in the schematic figure. That is not an example of IGE. *If an incident photon is absorbed by an initial state of a target nucleus, that nucleus will be raised to a more energetic state of excitation. If there is a nonzero probability that sometimes that state will start a cascade of transitions as shown in the schematic, that state has been called a "gateway state" or "trigger level" or "intermediate state". One or more fluorescent photons are emitted, often with different delays after the initial absorption and the process is an example of IGE. *If the initial state of the target nucleus is its ground (lowest energy) state, then the fluorescent photons will have less energy than that of the incident photon (as seen in the schematic figure). Since the scattering channel is usually the strongest, it can "blind" the instruments being used to detect the fluorescence and early experiments preferred to study IGE by pulsing the source of incident photons while detectors were gated off and then concentrating upon any delayed photons of fluorescence when the instruments could be safely turned back on. *If the initial state of the target nucleus is a nuclear isomer (starting with more energy than the ground) it can also support IGE. However, in that case the schematic diagram is not simply the example seen for 115In but read from right to left with the arrows turned the other way. Such a "reversal" would require simultaneous (to within <0.25 ns) absorption of two incident photons of different energies to get from the 4 h isomer back up to the "gateway state". Usually the study of IGE from a ground state to an isomer of the same nucleus teaches little about how the same isomer would perform if used as the initial state for IGE. In order to support IGE an energy for an incident photon would have to be found that would "match" the energy needed to reach some other gateway state not shown in the schematic that could launch its own cascade down to the ground state. *If the target is a nuclear isomer storing a considerable amount of energy then IGE might produce a cascade that contains a transition that emits a photon with more energy than that of the incident photon. This would be the nuclear analog of upconversion in laser physics. *If the target is a nuclear isomer storing a considerable amount of energy then IGE might produce a cascade through a pair of excited states whose lifetimes are "inverted" so that in a collection of such nuclei, population would build up in the longer lived upper level while emptying rapidly from the shorter lived lower member of the pair. The resulting inversion of population might support some form of coherent emission analogous to amplified spontaneous emission (ASE) in laser physics. If the physical dimensions of the collection of target isomer nuclei were long and thin, then a form of gamma-ray laser might result. Potential applications =Energy-specific dosimeters= Since the IGE from ground state nuclei requires the absorption of very specific photon energies to produce delayed fluorescent photons that are easily counted, there is the possibility to construct energy-specific dosimeters by combining several different nuclides. This was demonstrated for the calibration of the radiation spectrum from the DNA-PITHON pulsed nuclear simulator. Such a dosimeter could be useful in radiation therapy where X-ray beams may contain many energies. Since photons of different energies deposit their effects at different depths in the tissue being treated, it could help calibrate how much of the total dose would be deposited in the actual target volume. =Aircraft power= hafnium crystalline bar In February 2003, the non-peer reviewed New Scientist wrote about the possibility of an IGE-powered airplane, a variant on nuclear propulsion.Nuclear-powered drone aircraft on drawing board - 19 February 2003 - New Scientist The idea was to utilize 178m2Hf (presumably due to its high energy to weight ratio) which would be triggered to release gamma rays that would heat air in a chamber for jet propulsion. This power source is described as a "quantum nucleonic reactor", although it is not clear if this name exists only in reference to the New Scientist article. =Nuclear weaponry= It is partly this theoretical density that has made the entire IGE field so controversial. It has been suggested that the materials might be constructed to allow all of the stored energy to be released very quickly in a "burst". The possible energy release of the gammas alone would make IGE a potential high power "explosive" on its own, or a potential radiological weapon. Fusion bomb ignition The density of gammas produced in this reaction would be high enough that it might allow them to be used to compress the fusion fuel of a fusion bomb. If this turns out to be the case, it might allow a fusion bomb to be constructed with no fissile material inside (i.e. a pure fusion weapon); it is the control of the fissile material and the means for making it that underlies most attempts to stop nuclear proliferation. See also *Gamma-ray laser *Hafnium controversy, use of stored energy in Hf-178m2 *Laser, induced light emission References Literature * External links *"Scary Things Come in Small Packages", Washington Post article of 2004 by Sharon Weinberger *Hf-isomer Summary Page of Results, C.B. Collins, University of Texas, Dallas *"Atomic Powered Global Hawk Jet Reving For Take-Off?", a SciScoop weblog entry *Conflicting Results on a Long-Lived Nuclear Isomer of Hafnium Have Wider Implications This Physics Today article provides a balanced view from 2004. *Reprints of articles about nuclear isomers in peer reviewed journals. - The Center for Quantum Electronics, The University of Texas at Dallas. Category:Nuclear interdisciplinary topics "
"Ewa Podleś Ewa Podleś (; born April 26, 1952) is a Polish coloratura contralto singer who has had an active international career both on the opera stage and in recital. She is known for the agility of her voice and a vocal range which spans more than three octaves. Life and career Podleś was born in Warsaw, Poland, and after studying at the Warsaw Academy of Music under Alina Bolechowska, made her stage debut as Rosina in Rossini's The Barber of Seville in 1975. She made her Metropolitan Opera debut on February 14, 1984, singing the title role in Handel's Rinaldo, but only for a few performances that year (from which only two were in the Met's house), and was notably absent from the Met for more than 24 years, since then pursuing her career elsewhere and performing regularly at many other opera houses in Europe and America. In 1996, she sang the part of the Marquise de Berkenfeld in Donizetti's La fille du régiment at La Scala, a performance which has been preserved on DVD.Bresnal, Barry (May 2010). "Review: Donizetti: La Fille du régiment". Fanfare. Retrieved 30 January 3013 via HighBeam Research . Her return to the Met took place on September 24, 2008, when she sang the role of La Cieca in Ponchielli's La Gioconda.La Gioconda, Met Performance CID 352574, MetOpera database Though known mainly for her interpretation of Baroque works, Podleś's repertoire ranges from Handel's Giulio Cesare (Cesare) to songs by Shostakovich. However, the coloratura contralto roles (some of them trouser roles) in Rossini's operas have been central to her repertoire. Critics have noted the expressive power of her voice and her ability to cope with the florid singing demanded of Rossini's heroes and heroines.Glass, Herbert (30 July 1995). "New Opera Recordings for a Song". Los Angeles Times. Retrieved 30 January 2013. Her voice has a wide range, spanning more than three octavesMidgette, Anne (16 October 1998). "A Voice as Rare in Type as in Beauty", The New York Times. Retrieved 30 January 2013. and has been called a "force of nature".Silverman, Mike (28 October 2009). "Contralto Ewa Podles in Rossini: A force of nature". Associated Press. Retrieved 30 January 2013. Her recent performances include roles of La Cieca in La Gioconda, Bertarido in Handel's Rodelinda, the title role in Rossini's Tancredi, the title role in Handel's Giulio Cesare, Isabella in Rossini's L'italiana in Algeri, Erda in Wagner's Ring Cycle (at the Seattle Opera), Klytämnestra in Richard Strauss's Elektra (with the Canadian Opera Company), Madame de la Haltière in Massenet's Cendrillon (at London's Royal Opera House), and the title role in Rossini's Ciro in Babilonia (in the work's US premiere at the Caramoor International Music Festival in July 2012 and at the Rossini Opera Festival in Pesaro, Italy, in August 2012). Podleś was scheduled to sing Azucena in Verdi's Il trovatore at the Atlanta Opera in 2009, but withdrew. After a seemingly final run of La fille du régiment at Barcelona's Liceu in May 2017,Novak, Josephine, "La fille du régiment at the Liceu", Metropolitan Barcelona, 30 May 2017. Podleś announced that, from 1 June, she was going to interrupt temporarily her stage career due to an upcoming orthopaedic operation, while carrying on, however, with her teaching activity. Yet, according to the singer's official website no further theatrical appearances are scheduled in 2018 and 2019.Ewa Podleś Official Website /Performances. Podleś and her husband, the pianist , live in Warsaw.Polskie Radio (27 February 2012). "Partnerstwo: Ewa Podleś i Jerzy Marchwiński". Retrieved 30 January 2013 Recordings Audio CD * Airs Célèbres (Handel, Vivaldi, Purcell, Gluck, and Marcello) with * Chopin: Mélodies with Abdel Rahman El Bacha * Chopin: Songs with Garrick Ohlsson * de Falla: El amor brujo with Krzysztof Penderecki * Duets (Mendelssohn, Brahms, Schumann) with Joanna Kozłowska and Jerzy Marchwinski (piano) * Gluck: Armide as La Haine with Marc Minkowski * Gluck: Orfeo ed Euridice as Orfeo with Peter Maag * Gluck: Orphée et Eurydice as Orphée with Patrick Peire * Handel Arias from Rinaldo and Orlando with Constantin Orbelian * Handel: Ariodante as Polinesso with Marc Minkowski * Mahler: Symphony No. 2: "Resurrection" with Jean-Claude Casadesus * Mahler: Symphony No. 3 with Antoni Wit * Mozart: Requiem with Michel Corboz and L'Ensemble vocal et instrumental de Lausanne * Offenbach: Orphée aux enfers as L'Opinion publique * Penderecki: Seven Gates of Jerusalem with Kazimierz Kord * Penderecki: Te Deum and Lacrimosa * Ewa Podleś & Garrick Ohlsson Live * Marta Ptaszynska: Concerto for Marimba; Songs of Despair and Loneliness * Prokofiev: Alexandr Nevsky with Jean-Claude Casadesus * Puccini: Il trittico with Bruno Bartoletti * Respighi: Il Tramonto with * Rossini Arias for Contralto with Pier Giorgio Morandi * Rossini Gala with * Rossini: Tancredi as Tancredi with Alberto Zedda * Russian Melodies with Constantin Orbelian * A Treasury of Polish Songs with DVD * Handel: Giulio Cesare in Egitto as Cornelia from Barcelona Opera * Donizetti: La fille du régiment as Marquise de Berkenfeld * Ponchielli: La Gioconda as La Cieca from Barcelona Opera * Rossini: Ciro in Babilonia as Ciro from Pesaro Rossini Opera Festival * Massenet: Cendrillon as Madame de la Haltière from Royal Opera Covent Garden * Tchaikovsky: The Queen of Spades as the Countess from a 2011 production of the Gran Teatre del Liceu, Barcelona References External links * * TheOperaCritic.com singer's page * Interview at MusicalCriticism.com * Interview at Culture Kiosque * Midgette, Anne (21 October 2008). "The Elemental Power of Ewa Podles". The Washington Post Category:1952 births Category:Living people Category:Operatic contraltos Category:Musicians from Warsaw Category:Polish opera singers Category:20th- century Polish opera singers Category:20th-century women opera singers Category:21st-century Polish opera singers Category:21st-century women opera singers "
"Ellen R. Spertus is Elinor Kilgore Snyder Professor of computer science at Mills College, Oakland, California, United States, and a former senior research scientist at Google. Spertus grew up in Glencoe, Illinois, where she attended New Trier High School. At MIT she received a Bachelor of Science (B.S.) in Computer Science and Engineering in 1990, a Master of Science (M.S.) in electrical engineering and computer science in 1992, and a Doctor of Philosophy (Ph.D.) in Electrical Engineering and Computer Science in 1998, with a Ph.D. thesis entitled ParaSite: mining the structural information on the World-Wide Web. She spent several summers between terms working for Microsoft. Spertus has written articles treating both technical and social subjects, often combining the two. In 1993, she was profiled in The New York Times as one of the "women who might change the face of the computer industry" and in a follow-up article in 2003. In 2001, she was named "The Sexiest Geek Alive". While at Google, Spertus spent her time working on App Inventor for Android, a block based development platform with a graphical user interface (GUI) that lets developers and amateurs create applications for Android. In May 2011, O'Reilly Media published the book App Inventor, which Spertus co- authored with David Wolber, Hal Abelson, and Liz Looney. Spertus was a lessee of one of the approximately 1,000 General Motors EV1s. She is married to computer scientist Keith Golden. In 2014, she went on Sabbatical from Mills to work with Google for the development of the Blockly programming environment. References External links * *, Mills College: Mathematics & Computer Science * Category:Year of birth missing (living people) Category:Living people Category:Massachusetts Institute of Technology alumni Category:Google employees Category:American women computer scientists Category:American computer scientists Category:New Trier High School alumni Category:Mills College faculty "