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  • ASTROPHYSICS
  • Chemistry
  • Life and Medical Sciences
  • SPACE SCIENCES
  • Nature Publishing Group (NPG)  (3)
  • Kaduna (Nigeria)  (1)
  • 1
    Publication Date: 2013-04-05
    Description: The technological demand to push the gigahertz (10(9) hertz) switching speed limit of today's magnetic memory and logic devices into the terahertz (10(12) hertz) regime underlies the entire field of spin-electronics and integrated multi-functional devices. This challenge is met by all-optical magnetic switching based on coherent spin manipulation. By analogy to femtosecond chemistry and photosynthetic dynamics--in which photoproducts of chemical and biochemical reactions can be influenced by creating suitable superpositions of molecular states--femtosecond-laser-excited coherence between electronic states can switch magnetic order by 'suddenly' breaking the delicate balance between competing phases of correlated materials: for example, manganites exhibiting colossal magneto-resistance suitable for applications. Here we show femtosecond (10(-15) seconds) photo-induced switching from antiferromagnetic to ferromagnetic ordering in Pr0.7Ca0.3MnO3, by observing the establishment (within about 120 femtoseconds) of a huge temperature-dependent magnetization with photo-excitation threshold behaviour absent in the optical reflectivity. The development of ferromagnetic correlations during the femtosecond laser pulse reveals an initial quantum coherent regime of magnetism, distinguished from the picosecond (10(-12) seconds) lattice-heating regime characterized by phase separation without threshold behaviour. Our simulations reproduce the nonlinear femtosecond spin generation and underpin fast quantum spin-flip fluctuations correlated with coherent superpositions of electronic states to initiate local ferromagnetic correlations. These results merge two fields, femtosecond magnetism in metals and band insulators, and non-equilibrium phase transitions of strongly correlated electrons, in which local interactions exceeding the kinetic energy produce a complex balance of competing orders.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, Tianqi -- Patz, Aaron -- Mouchliadis, Leonidas -- Yan, Jiaqiang -- Lograsso, Thomas A -- Perakis, Ilias E -- Wang, Jigang -- England -- Nature. 2013 Apr 4;496(7443):69-73. doi: 10.1038/nature11934.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23552945" target="_blank"〉PubMed〈/a〉
    Keywords: Biology ; Chemistry ; Circular Dichroism ; Electronics ; Iron/chemistry ; *Magnetic Phenomena ; Magnetics ; Optics and Photonics ; Photosynthesis ; *Quantum Theory ; Temperature ; Time Factors
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
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    Fisheries Society of Nigeria | Kaduna (Nigeria)
    In:  http://aquaticcommons.org/id/eprint/23319 | 19325 | 2018-03-30 15:34:16 | 23319 | Fisheries Society of Nigeria
    Publication Date: 2021-07-14
    Description: The seasonal variations in the physicochemical parameters were studied from January, 2007 to December 2007, in Kontagora Reservoir, Niger State, Nigeria. The physico- chemical parameters were determined bi-monthly , using the following methods , temperature using mercury thermometer in degree centigrade, transparency using Secchi-disc , Pye Unicam model 292 meter used for pH and electrical conductivity. Dissolved oxygen by modified Winklerazide method, water hardness and Phosphate- phosphorus by method of Lind (1979), total alkalinity by standard method described by Boyd(l979) , Nitrate- Nitrogen by Phenoldisulphonic acid method. The rainy season mean values for water temperature, depth, pH, Nitrate-Nitrogen, were significantly (P〈0.05) higher than those for the dry season. However, for transparency, conductivity, dissolved oxygen, hardness, alkalinity, phosphate-phosphorus and total dissolved solid, the dry season mean values were higher than the rainy season mean value. As in most other Africa inland water bodies, there was seasonality in the physicochemical parameters variables. The torrential rains of the dam environment, the characteristics trade winds of the dry season, effect of deforestation, fertilizer application, herbicides, insecticide and other chemical factors might have contributed to the fluctuations of some of the physicochemical parameters detennined in the Reservoir.
    Description: Includes:- 2 tables.;1 fig.;39 refs.
    Keywords: Chemistry ; Nigeria ; Kontagora L. ; freshwater environment ; Physicochemical properties ; Seasonal variations
    Repository Name: AquaDocs
    Type: conference_item , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 189-195
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  • 3
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    Nature Publishing Group (NPG)
    Publication Date: 2010-10-15
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Crutzen, Paul J -- England -- Nature. 2010 Oct 14;467(7317):S10. doi: 10.1038/467S10a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20944610" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/chemistry ; Chemistry ; Human Activities ; Interdisciplinary Communication ; Mentors ; *Nobel Prize ; Ozone/analysis ; Politics ; Public Opinion ; Public Policy ; *Research Personnel
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
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    Nature Publishing Group (NPG)
    Publication Date: 2011-10-14
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lehn, Jean-Marie -- England -- Nature. 2011 Oct 12;478(7368):S8-9. doi: 10.1038/478S8a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21993827" target="_blank"〉PubMed〈/a〉
    Keywords: Chemistry ; Exobiology ; Hippocratic Oath ; Knowledge ; Motivation ; *Nobel Prize ; *Research Personnel/ethics/psychology/standards
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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