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Preliminary design of the INPE's Solar Vector Magnetograph
- L. E. A. Vieira, A. L. Clúa de Gonzalez, A. Dal Lago, C. Wrasse, E. Echer, F. L. Guarnieri, F. Reis Cardoso, G. Guerrero, J. Rezende Costa, J. Palacios, L. Balmaceda, L. Ribeiro Alves, L. da Silva, L. L. Costa, M. Sampaio, M. C. Rabello Soares, M. Barbosa, M. Domingues, N. Rigozo, O. Mendes, Jr., P. Jauer, R. Dallaqua, R. H. Branco, T. Stekel, W. Gonzalez, W. Kabata
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- Journal:
- Proceedings of the International Astronomical Union / Volume 10 / Issue S305 / December 2014
- Published online by Cambridge University Press:
- 24 July 2015, pp. 195-199
- Print publication:
- December 2014
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We describe the preliminary design of a magnetograph and visible-light imager instrument to study the solar dynamo processes through observations of the solar surface magnetic field distribution. The instrument will provide measurements of the vector magnetic field and of the line-of-sight velocity in the solar photosphere. As the magnetic field anchored at the solar surface produces most of the structures and energetic events in the upper solar atmosphere and significantly influences the heliosphere, the development of this instrument plays an important role in reaching the scientific goals of The Atmospheric and Space Science Coordination (CEA) at the Brazilian National Institute for Space Research (INPE). In particular, the CEA's space weather program will benefit most from the development of this technology. We expect that this project will be the starting point to establish a strong research program on Solar Physics in Brazil. Our main aim is acquiring progressively the know-how to build state-of-the-art solar vector magnetograph and visible-light imagers for space-based platforms to contribute to the efforts of the solar-terrestrial physics community to address the main unanswered questions on how our nearby Star works.
Contributors
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- By Rose Teteki Abbey, K. C. Abraham, David Tuesday Adamo, LeRoy H. Aden, Efrain Agosto, Victor Aguilan, Gillian T. W. Ahlgren, Charanjit Kaur AjitSingh, Dorothy B E A Akoto, Giuseppe Alberigo, Daniel E. Albrecht, Ruth Albrecht, Daniel O. Aleshire, Urs Altermatt, Anand Amaladass, Michael Amaladoss, James N. Amanze, Lesley G. Anderson, Thomas C. Anderson, Victor Anderson, Hope S. Antone, María Pilar Aquino, Paula Arai, Victorio Araya Guillén, S. Wesley Ariarajah, Ellen T. Armour, Brett Gregory Armstrong, Atsuhiro Asano, Naim Stifan Ateek, Mahmoud Ayoub, John Alembillah Azumah, Mercedes L. García Bachmann, Irena Backus, J. Wayne Baker, Mieke Bal, Lewis V. Baldwin, William Barbieri, António Barbosa da Silva, David Basinger, Bolaji Olukemi Bateye, Oswald Bayer, Daniel H. Bays, Rosalie Beck, Nancy Elizabeth Bedford, Guy-Thomas Bedouelle, Chorbishop Seely Beggiani, Wolfgang Behringer, Christopher M. Bellitto, Byard Bennett, Harold V. Bennett, Teresa Berger, Miguel A. Bernad, Henley Bernard, Alan E. Bernstein, Jon L. Berquist, Johannes Beutler, Ana María Bidegain, Matthew P. Binkewicz, Jennifer Bird, Joseph Blenkinsopp, Dmytro Bondarenko, Paulo Bonfatti, Riet en Pim Bons-Storm, Jessica A. Boon, Marcus J. Borg, Mark Bosco, Peter C. Bouteneff, François Bovon, William D. Bowman, Paul S. Boyer, David Brakke, Richard E. Brantley, Marcus Braybrooke, Ian Breward, Ênio José da Costa Brito, Jewel Spears Brooker, Johannes Brosseder, Nicholas Canfield Read Brown, Robert F. Brown, Pamela K. Brubaker, Walter Brueggemann, Bishop Colin O. Buchanan, Stanley M. Burgess, Amy Nelson Burnett, J. Patout Burns, David B. Burrell, David Buttrick, James P. Byrd, Lavinia Byrne, Gerado Caetano, Marcos Caldas, Alkiviadis Calivas, William J. Callahan, Salvatore Calomino, Euan K. Cameron, William S. Campbell, Marcelo Ayres Camurça, Daniel F. Caner, Paul E. Capetz, Carlos F. Cardoza-Orlandi, Patrick W. Carey, Barbara Carvill, Hal Cauthron, Subhadra Mitra Channa, Mark D. Chapman, James H. Charlesworth, Kenneth R. Chase, Chen Zemin, Luciano Chianeque, Philip Chia Phin Yin, Francisca H. Chimhanda, Daniel Chiquete, John T. Chirban, Soobin Choi, Robert Choquette, Mita Choudhury, Gerald Christianson, John Chryssavgis, Sejong Chun, Esther Chung-Kim, Charles M. A. Clark, Elizabeth A. Clark, Sathianathan Clarke, Fred Cloud, John B. Cobb, W. Owen Cole, John A Coleman, John J. Collins, Sylvia Collins-Mayo, Paul K. Conkin, Beth A. Conklin, Sean Connolly, Demetrios J. Constantelos, Michael A. Conway, Paula M. Cooey, Austin Cooper, Michael L. Cooper-White, Pamela Cooper-White, L. William Countryman, Sérgio Coutinho, Pamela Couture, Shannon Craigo-Snell, James L. Crenshaw, David Crowner, Humberto Horacio Cucchetti, Lawrence S. Cunningham, Elizabeth Mason Currier, Emmanuel Cutrone, Mary L. Daniel, David D. Daniels, Robert Darden, Rolf Darge, Isaiah Dau, Jeffry C. Davis, Jane Dawson, Valentin Dedji, John W. de Gruchy, Paul DeHart, Wendy J. Deichmann Edwards, Miguel A. De La Torre, George E. Demacopoulos, Thomas de Mayo, Leah DeVun, Beatriz de Vasconcellos Dias, Dennis C. Dickerson, John M. Dillon, Luis Miguel Donatello, Igor Dorfmann-Lazarev, Susanna Drake, Jonathan A. Draper, N. Dreher Martin, Otto Dreydoppel, Angelyn Dries, A. J. Droge, Francis X. D'Sa, Marilyn Dunn, Nicole Wilkinson Duran, Rifaat Ebied, Mark J. Edwards, William H. Edwards, Leonard H. Ehrlich, Nancy L. Eiesland, Martin Elbel, J. Harold Ellens, Stephen Ellingson, Marvin M. Ellison, Robert Ellsberg, Jean Bethke Elshtain, Eldon Jay Epp, Peter C. Erb, Tassilo Erhardt, Maria Erling, Noel Leo Erskine, Gillian R. Evans, Virginia Fabella, Michael A. Fahey, Edward Farley, Margaret A. Farley, Wendy Farley, Robert Fastiggi, Seena Fazel, Duncan S. Ferguson, Helwar Figueroa, Paul Corby Finney, Kyriaki Karidoyanes FitzGerald, Thomas E. FitzGerald, John R. Fitzmier, Marie Therese Flanagan, Sabina Flanagan, Claude Flipo, Ronald B. Flowers, Carole Fontaine, David Ford, Mary Ford, Stephanie A. Ford, Jim Forest, William Franke, Robert M. Franklin, Ruth Franzén, Edward H. Friedman, Samuel Frouisou, Lorelei F. Fuchs, Jojo M. Fung, Inger Furseth, Richard R. Gaillardetz, Brandon Gallaher, China Galland, Mark Galli, Ismael García, Tharscisse Gatwa, Jean-Marie Gaudeul, Luis María Gavilanes del Castillo, Pavel L. Gavrilyuk, Volney P. Gay, Metropolitan Athanasios Geevargis, Kondothra M. George, Mary Gerhart, Simon Gikandi, Maurice Gilbert, Michael J. Gillgannon, Verónica Giménez Beliveau, Terryl Givens, Beth Glazier-McDonald, Philip Gleason, Menghun Goh, Brian Golding, Bishop Hilario M. Gomez, Michelle A. Gonzalez, Donald K. Gorrell, Roy Gottfried, Tamara Grdzelidze, Joel B. Green, Niels Henrik Gregersen, Cristina Grenholm, Herbert Griffiths, Eric W. Gritsch, Erich S. Gruen, Christoffer H. Grundmann, Paul H. Gundani, Jon P. Gunnemann, Petre Guran, Vidar L. Haanes, Jeremiah M. Hackett, Getatchew Haile, Douglas John Hall, Nicholas Hammond, Daphne Hampson, Jehu J. Hanciles, Barry Hankins, Jennifer Haraguchi, Stanley S. Harakas, Anthony John Harding, Conrad L. Harkins, J. William Harmless, Marjory Harper, Amir Harrak, Joel F. Harrington, Mark W. Harris, Susan Ashbrook Harvey, Van A. Harvey, R. Chris Hassel, Jione Havea, Daniel Hawk, Diana L. Hayes, Leslie Hayes, Priscilla Hayner, S. Mark Heim, Simo Heininen, Richard P. Heitzenrater, Eila Helander, David Hempton, Scott H. Hendrix, Jan-Olav Henriksen, Gina Hens-Piazza, Carter Heyward, Nicholas J. Higham, David Hilliard, Norman A. Hjelm, Peter C. Hodgson, Arthur Holder, M. Jan Holton, Dwight N. Hopkins, Ronnie Po-chia Hsia, Po-Ho Huang, James Hudnut-Beumler, Jennifer S. Hughes, Leonard M. Hummel, Mary E. Hunt, Laennec Hurbon, Mark Hutchinson, Susan E. Hylen, Mary Beth Ingham, H. Larry Ingle, Dale T. Irvin, Jon Isaak, Paul John Isaak, Ada María Isasi-Díaz, Hans Raun Iversen, Margaret C. Jacob, Arthur James, Maria Jansdotter-Samuelsson, David Jasper, Werner G. Jeanrond, Renée Jeffery, David Lyle Jeffrey, Theodore W. Jennings, David H. Jensen, Robin Margaret Jensen, David Jobling, Dale A. Johnson, Elizabeth A. Johnson, Maxwell E. Johnson, Sarah Johnson, Mark D. Johnston, F. Stanley Jones, James William Jones, John R. Jones, Alissa Jones Nelson, Inge Jonsson, Jan Joosten, Elizabeth Judd, Mulambya Peggy Kabonde, Robert Kaggwa, Sylvester Kahakwa, Isaac Kalimi, Ogbu U. Kalu, Eunice Kamaara, Wayne C. Kannaday, Musimbi Kanyoro, Veli-Matti Kärkkäinen, Frank Kaufmann, Léon Nguapitshi Kayongo, Richard Kearney, Alice A. Keefe, Ralph Keen, Catherine Keller, Anthony J. Kelly, Karen Kennelly, Kathi Lynn Kern, Fergus Kerr, Edward Kessler, George Kilcourse, Heup Young Kim, Kim Sung-Hae, Kim Yong-Bock, Kim Yung Suk, Richard King, Thomas M. King, Robert M. Kingdon, Ross Kinsler, Hans G. Kippenberg, Cheryl A. 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Yee, Viktor Yelensky, Yeo Khiok-Khng, Gustav K. K. Yeung, Angela Yiu, Amos Yong, Yong Ting Jin, You Bin, Youhanna Nessim Youssef, Eliana Yunes, Robert Michael Zaller, Valarie H. Ziegler, Barbara Brown Zikmund, Joyce Ann Zimmerman, Aurora Zlotnik, Zhuo Xinping
- Edited by Daniel Patte, Vanderbilt University, Tennessee
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- The Cambridge Dictionary of Christianity
- Published online:
- 05 August 2012
- Print publication:
- 20 September 2010, pp xi-xliv
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PHYSIOLOGICAL BASIS OF YIELD VARIATION OF TEA (CAMELLIA SINENSIS) DURING DIFFERENT YEARS OF THE PRUNING CYCLE IN THE CENTRAL HIGHLANDS OF SRI LANKA
- W. A. J. M. DE COSTA, D. M. S. NAVARATNE, A. ANANDACOOMARASWAMY
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- Journal:
- Experimental Agriculture / Volume 45 / Issue 4 / October 2009
- Published online by Cambridge University Press:
- 02 September 2009, pp. 429-450
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The objective of this study was to elucidate the physiological basis of the significant yield decline that occurs during the fourth year of the pruning cycle of tea. Biomass partitioning, which was hypothesized to be a major factor in causing this yield decline, was measured by destructive harvests of entire tea bushes, in two contrasting, mature, field-grown tea cultivars (TRI 2025 and DT1) at the end of different years of the pruning cycle. In both cultivars, yield showed continuous increases from year 1 to 3, followed by reductions of 44% and 35% in TRI2025 and DT1 respectively in the fourth year. Patterns of biomass partitioning to roots, stems or branches did not correlate with the above yield variation whereas harvest index, canopy leaf area index and mature leaf dry weight showed variations which paralleled the yield variation. The fourth-year decline in harvest index was brought about by reductions in both shoot number per m2 and mean individual shoot weight, which indicate a reduction in sink strength. Both cultivars showed reductions in light-saturated photosynthetic rate of maintenance foliage during the second half of the pruning cycle, indicating reduced source capacity. Hence, a combined reduction of both sink strength and source capacity during the fourth year could have brought about the significant yield reduction in tea. A significant increase of root starch in the fourth year indicated a down-regulation of physiological activities of the bush towards the end of the pruning cycle. Mechanisms responsible for this down-regulation need to be elucidated by further research.
POSSIBILITY OF EARLY COMMENCEMENT OF TAPPING IN RUBBER (HEVEA BRASILIENSIS) USING DIFFERENT GENOTYPES AND TAPPING SYSTEMS
- H. K. L. K. GUNASEKARA, E. A. NUGAWELA, W. A. J. M. DE COSTA, D. P. S. T. G. ATTANAYAKE
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- Experimental Agriculture / Volume 43 / Issue 2 / April 2007
- Published online by Cambridge University Press:
- 28 March 2007, pp. 201-221
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The feasibility of commencing tapping (‘opening’) of rubber trees for latex extraction at a lower stem girth (40 and 45 cm) than the currently recommended 50 cm was investigated in three different genotypes. The possibility of combining early opening with low frequency tapping and yield stimulation using Ethrel (LFT + E) was also examined. One of the genotypes tested, RRIC 121, gave a higher dry rubber yield, both per tapping and cumulatively over a given period, when opened at 40 cm than at 50 cm. Of the other two genotypes, one (RRISL 211) showed a clear reduction in yield with early opening, while the other (RRIC 102) did not show a significant yield response. Among the three genotypes tested, RRIC 121 showed the minimum depression in trunk girth increment. Analysis of yield components showed that the response of a given genotype to early opening and LFT + E is determined by the interaction between latex volume per tapping and dry rubber content (DRC), which were negatively correlated. RRIC 121 had a significantly greater DRC, which enabled it to maintain a higher dry rubber yield under early opening and LFT + E despite producing a lower latex volume than both the other genotypes. In contrast, despite producing a substantially greater latex volume than the other two genotypes, RRISL 211 did not produce a higher dry rubber yield because of its lower DRC. The higher DRC was also responsible for the greater response of RRIC 121 to yield stimulation with Ethrel, which reduced the plugging index and increased the initial latex flow rate. Early commencement of tapping in combination with LFT + E is therefore possible in rubber when amenable genotypes are selected, offering the potential of improving the economics of rubber production, especially for smallholders, in West Asia.
GENOTYPIC VARIATION IN CANOPY PHOTOSYNTHESIS, LEAF GAS EXCHANGE CHARACTERISTICS AND THEIR RESPONSE TO TAPPING IN RUBBER (HEVEA BRASILIENSIS)
- H. K. L. K. GUNASEKARA, W. A. J. M. DE COSTA, E. A. NUGAWELA
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- Experimental Agriculture / Volume 43 / Issue 2 / April 2007
- Published online by Cambridge University Press:
- 28 March 2007, pp. 223-239
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The main objective of this study was to quantify the genotypic variation of photosynthetic and gas exchange parameters of Hevea and to examine their relationships to dry rubber yield and its components. Canopy photosynthesis (Pc) of the genotype RRISL 211 was 20 % greater than that of RRIC 121. This was primarily due to RRISL 211's greater light-saturated leaf photosynthetic rates and a greater leaf area index in the top canopy stratum. Tapping significantly increased Pc in RRISL 211, but not in RRIC 121. The genotypic variation in photosynthetic capacity was not reflected in the overall dry rubber yield, which did not differ between the two genotypes. However, analysis of yield components showed that while RRISL 211 may have preferentially partitioned a greater proportion of its additional assimilates to increasing the latex volume and extending the root system, RRIC 121 partitioned more assimilates to increasing its dry rubber content through greater biosynthesis of rubber. The higher plugging index and the greater post-tapping girth increment of RRIC 121 were probably responsible for observed increases in its dark respiration following tapping. Although RRISL 211 had a greater transpiration efficiency, this did not provide a yield advantage as the trees were growing in an environment with adequate rainfall throughout the year.
Agronomic regeneration of soil fertility in tropical Asian smallholder uplands for sustainable food production
- W. A. J. M. DE COSTA, U. R. SANGAKKARA
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- The Journal of Agricultural Science / Volume 144 / Issue 2 / April 2006
- Published online by Cambridge University Press:
- 10 February 2006, pp. 111-133
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Smallholder cropping systems are a vital component in the agricultural sectors of tropical Asia, especially in the developing nations. These systems are important for producing food and providing a livelihood to a major proportion of the populations of Asia. While the rice systems, usually cultivated under puddled conditions are considered stable, the upland or highland units, which provide a range of food, fibre and feed commodities, are generally situated on marginal lands. Low soil fertility, erosion, sub-optimal crop management and subsistence farming conditions characterize these units. Hence, these units require improved but low cost strategies to reverse the trend of lower productivity, loss of sustainability and most importantly, the loss of livelihood for the farming populations. Among the many strategies available, the regeneration of soil fertility through agronomic measures would be a useful and easily adoptable method of enhancing productivity of tropical Asian upland smallholding farming units. The methods available include the revival of age-old traditions such as adding organic matter directly to soils, green manuring and mimicking forest ecosystems through agroforestry. Agronomic measures using plants to enrich the soil and regenerate its supporting capacity are presented in the present paper. Relevant examples are cited to highlight the potential of these methods for regenerating productivity of the upland smallholder farming units and more importantly the agro-based livelihood of a large majority of the populations of tropical Asia.
Resource competition in contour hedgerow intercropping systems involving different shrub species with mature and young tea on sloping highlands in Sri Lanka
- W. A. J. M. DE COSTA, P. SURENTHRAN
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- Journal:
- The Journal of Agricultural Science / Volume 143 / Issue 5 / October 2005
- Published online by Cambridge University Press:
- 30 September 2005, pp. 395-405
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Tea (Camellia sinensis) in Sri Lanka is grown predominantly on sloping highlands. Incorporating trees as hedgerows along contours is aimed at reducing erosion and improving soil fertility through addition of prunings as mulch. However, there could be significant competition for essential growth resources between the hedgerows and tea. The primary objective of this study was to determine the influence of six hedgerow species (Calliandra calothyrsus, Senna [Cassia] spectabilis, Eupatorium inulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) on mature (6-year-old) and young (6-month-old) tea. This study had three on-farm, long-term (from Nov 1998 to Dec 2002) field experiments. Experiment 1 had 12 treatment combinations with the six shrub species and two mulching treatments (i.e. hedgerow prunings added to the tea plot as a mulch, and unmulched) on mature tea plus a sole tea crop as control. The same was repeated on young tea in Experiment 2 to determine whether resource competition on young tea was greater than that on mature tea. Experiment 3 examined the effects of removing tree root competition on tea by cutting a 1-m deep trench between hedgerows and tea.
In all experiments, total tea yields of hedgerow intercrops, cumulated over the 50-month experimental period, were significantly lower (by 3–50%) than sole tea crops, thus indicating significant resource competition except in the case of mulched hedgerow systems involving Eupatorium and mature tea (18% yield increase). Removal of below-ground competition significantly increased tea yields by 11–19%. Addition of hedgerow prunings as a mulch significantly increased yields of both mature and young tea by 13–21%. Tea yields of hedgerow systems with Calliandra, Flemingia and Eupatorium showed greater yield reductions in young tea than in mature tea, but the opposite was shown with other hedgerow species. There was a significant negative linear relationship between tea yield and pruned biomass of hedgerows. Tea yields of all experiments showed significant negative correlations with several hedgerow characters, which are indicators of their competitive ability. These included hedgerow root density, canopy lateral spread, height and cross-section. In a majority of hedgerow systems, the available phosphorus content of topsoil (0–20 cm depth) was up to 51% lower compared to sole crops. It is concluded that incorporation of contour hedgerows in to an existing tea crop could result in significant resource competition with tea and thereby cause tea yield to decrease. However, there is scope for selection of hedgerow species that minimize competition through spatial and temporal complementarity with tea in resource capture.
Maps of the Millimetre Sky from the BOOMERanG Experiment
- P. de Bernardis, G. De Troia, M. Giacometti, A. Iacoangeli, S. Masi, A. Melchiorri, F. Nati, F. Piacentini, G. Polenta, S. Ricciardi, P. A. R. Ade, P. D. Mauskopf, A. Balbi, P. Cabella, G. De Gasperis, P. Natoli, N. Vittorio, J. J. Bock, J. R. Bond, C. R. Contaldi, J. Borrill, A. Boscaleri, E. Pascale, W. C. Jones, A. E. Lange, P. Mason, V. V. Hristov, B. P. Crill, A. De-Oliveira Costa, M. Tegmark, K. Ganga, E. Hivon, T. Montroy, T. Kisner, J. E. Ruhl, A. H. Jaffe, C. MacTavish, C. B. Netterfield, D. Pogosyan, S. Prunet, G. Romeo
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- Journal:
- Symposium - International Astronomical Union / Volume 216 / 2005
- Published online by Cambridge University Press:
- 23 September 2016, pp. 35-42
- Print publication:
- 2005
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In the 1998-99 flight, BOOMERanG has produced maps of ∼4% of the sky at high Galactic latitudes, at frequencies of 90, 150, 240 and 410 GHz, with resolution ≳ 10'. The faint structure of the Cosmic Microwave Background at horizon and sub-horizon scales is evident in these maps. These maps compare well to the maps recently obtained at lower frequencies by the WMAP experiment. Here we compare the amplitude and morphology of the structures observed in the two sets of maps. We also outline the polarization sensitive version of BOOMERanG, which was flown early this year to measure the linear polarization of the microwave sky at 150, 240 and 350 GHz.
1995-1998 Large-Scale Campaigns on Λ Boo Star 29 Cygni
- D. E. Mkrtichian, A. V. Kusakin, V. A. Koval, M. C. Akan, C. Ibanoglu, E. Paunzen, W. W. Weiss, P. Lopez de Coca, A. Rolland, V. Costa, J. I. Olivares, M. A. Hobart, A. P. Hatzes, V. P. Malanushenko, A. Devlen, A. Ozturk, M. Paparó, K. Krisciunas, J. Percy, S. Thompson, G. Handle, V. I. Burnashev, A. I. Movchan
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- Journal:
- International Astronomical Union Colloquium / Volume 176 / 2000
- Published online by Cambridge University Press:
- 12 April 2016, pp. 494-495
- Print publication:
- 2000
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We present the main results of a photometric and spectroscopic study of the Λ Boo star 29 Cyg carried out from 1995 – 1998.
18. Commission des Longitudes par Télégraphie Sans fil
- Général G. Perrier, M. A. Lambert, MM. R. Baîllaud, Bianchi, W. Bowie, Coculesco, F. M. da Costa Lobo, de Lemos, Esclangon, Fayet, Fichot, Guyot, Hasimoto, Ivanov, J. Jackson, Jeffers, Spencer Jones, Jouaust, E. Kohlschütter, J. Krassowski, Lejay, Moreau, Niethammer, Nörlund, Nušl, Pavlov, Plakidis, Sampson, Silva, Sollenberger, R. M. Stewart, Stoyko, Tsiang, Volta, Watts, Witkowski, Zimmer
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- Journal:
- Transactions of the International Astronomical Union / Volume 6 / 1939
- Published online by Cambridge University Press:
- 25 April 2016, pp. 121-122
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- 1939
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La centralisation au Bureau international de l’Heure des résultats d’observations de l’Opération internationale de 1933 a été très lente, puisque les dernières données attendues ont été reçues vers la fin de 1937.
Le nombre des stations ayant coopéré à l’Opération internationale et ayant transmis leurs observations à l’organisme centralisateur s’élève à soixante et onze. Ainsi qu’il a été expliqué à notre Commission mixte, lors du Congrès de l’Union géodésique et géophysique internationale tenu à Édimbourg en 1936, ces stations ont été réparties en trois groupes:
Le Ier comprenant vingt Observatoires, disposant chacun de plusieurs horloges de première classe (soit à poids sous pression et à température constantes, soit à quartz piézoélectrique);