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2. Persistent effects of pre-Columbian plant domestication on Amazonian forest composition

Author

Levis, C., Costa, F. R. C., Bongers, F., Peña-Claros, M., Clement, C. R., Junqueira, A. B., Neves, E. G., Tamanaha, E. K., Figueiredo, F. O. G., Salomão, R. P., Castilho, C. V., Magnusson, W. E., Phillips, O. L., Guevara, J. E., Sabatier, D., Molino, J.-F., López, D. Cárdenas, Mendoza, A. M., Pitman, N. C. A., Duque, A., Vargas, P. Núñez, Zartman, C. E., Vasquez, R., Andrade, A., Camargo, J. L., Feldpausch, T. R., Laurance, S. G. W., Laurance, W. F., Killeen, T. J., Nascimento, H. E. Mendonça, Montero, J. C., Mostacedo, B., Amaral, I. L., Vieira, I. C. Guimarães, Brienen, R., Castellanos, H., Terborgh, J., de Jesus Veiga Carim, M., da Silva Guimarães, J. R., de Souza Coelho, L., de Almeida Matos, F. D., Wittmann, F., Mogollón, H. F., Damasco, G., Dávila, N., García-Villacorta, R., Coronado, E. N. H., Emilio, T., de Andrade Lima Filho, D., Schietti, J., Souza, P., Targhetta, N., Comiskey, J. A., Marimon, B. S., Marimon, B.-H., Neill, D., Alonso, A., Arroyo, L., Carvalho, F. A., de Souza, F. C., Dallmeier, F., Pansonato, M. P., Duivenvoorden, J. F., Fine, P. V. A., Stevenson, P. R., Araujo-Murakami, A., Aymard C., G. A., Baraloto, C., do Amaral, D. D., Engel, J., Henkel, T. W., Maas, P., Petronelli, P., Revilla, J. D. Cardenas, Stropp, J., Daly, D., Gribel, R., Paredes, M. Ríos, Silveira, M., Thomas-Caesar, R., Baker, T. R., da Silva, N. F., Ferreira, L. V., Peres, C. A., Silman, M. R., Cerón, C., Valverde, F. C., Di Fiore, A., Jimenez, E. M., Mora, M. C. Peñuela, Toledo, M., Barbosa, E. M., de Matos Bonates, L. C., Arboleda, N. C., de Sousa Farias, E., Fuentes, A., Guillaumet, J.-L., Jørgensen, P. Møller, Malhi, Y., de Andrade Miranda, I. P., Phillips, J. F., Prieto, A., Rudas, A., Ruschel, A. R., Silva, N., von Hildebrand, P., Vos, V. A., Zent, E. L., Zent, S., Cintra, B. B. L., Nascimento, M. T., Oliveira, A. A., Ramirez-Angulo, H., Ramos, J. F., Rivas, G., Schöngart, J., Sierra, R., Tirado, M., van der Heijden, G., Torre, E. V., Wang, O., Young, K. R., Baider, C., Cano, A., Farfan-Rios, W., Ferreira, C., Hoffman, B., Mendoza, C., Mesones, I., Torres-Lezama, A., Medina, M. N. U., van Andel, T. R., Villarroel, D., Zagt, R., Alexiades, M. N., Balslev, H., Garcia-Cabrera, K., Gonzales, T., Hernandez, L., Huamantupa-Chuquimaco, I., Manzatto, A. G., Milliken, W., Cuenca, W. P., Pansini, S., Pauletto, D., Arevalo, F. R., Reis, N. F. Costa, Sampaio, A. F., Giraldo, L. E. Urrego, Sandoval, E. H. Valderrama, Gamarra, L. Valenzuela, Vela, C. I. A., and ter Steege, H.

Published
2017

3. Diversity enhances carbon storage in tropical forests

Author

Poorter, L., van der Sande, M. T., Thompson, J., Arets, E. J. M. M., Alarcón, A., Álvarez-Sánchez, J., Ascarrunz, N., Balvanera, P., Barajas-Guzmán, G., Boit, A., Bongers, F., Carvalho, F. A., Casanoves, F., Cornejo-Tenorio, G., Costa, F. R. C., de Castilho, C. V., Duivenvoorden, J. F., Dutrieux, L. P., Enquist, B. J., Fernández-Méndez, F., Finegan, B., Gormley, L. H. L., Healey, J. R., Hoosbeek, M. R., Ibarra-Manriquez, G., Junqueira, A. B., Levis, C., Licona, J. C., Lisboa, L. S., Magnusson, W. E., Martínez-Ramos, M., Martínez-Yrizar, A., Martorano, L. G., Maskell, L. C., Mazzei, L., Meave, J. A., Mora, F., Muñoz, R., Nytch, C., Pansonato, M. P., Parr, T. W., Paz, H., Pérez-García, E. A., Rentería, L. Y., Rodríguez-Velazquez, J., Rozendaal, D. M. A., Ruschel, A. R., Sakschewski, B., Salgado-Negret, B., Schietti, J., Simões, M., Sinclair, F. L., Souza, P. F., Souza, F. C., Stropp, J., ter Steege, H., Swenson, N. G., Thonicke, K., Toledo, M., Uriarte, M., van der Hout, P., Walker, P., Zamora, N., and Peña-Claros, M.

Published
2015

7. How People Domesticated Amazonian Forests

Author

Levis, C., Flores, Bernardo, Moreira, Priscilla, Luize, Bruno G., Alves, Rubana, Franco-Moraes, Juliano, Lins, Juliana, Konings, Evelien, Pena Claros, M., Bongers, F., Costa, Flavia, Clement, Charles, Levis, C., Flores, Bernardo, Moreira, Priscilla, Luize, Bruno G., Alves, Rubana, Franco-Moraes, Juliano, Lins, Juliana, Konings, Evelien, Pena Claros, M., Bongers, F., Costa, Flavia, and Clement, Charles

Abstract

For millennia, Amazonian peoples have managed forest resources, modifying the natural environment in subtle and persistent ways. Legacies of past human occupation are striking near archaeological sites, yet we still lack a clear picture of how human management practices resulted in the domestication of Amazonian forests. The general view is that domesticated forests are recognizable by the presence of forest patches dominated by one or a few useful species favored by long-term human activities. Here, we used three complementary approaches to understand the long-term domestication of Amazonian forests. First, we compiled information from the literature about how indigenous and traditional Amazonian peoples manage forest resources to promote useful plant species that are mainly used as food resources. Then, we developed an interdisciplinary conceptual model of how interactions between these management practices across space and time may form domesticated forests. Finally, we collected field data from 30 contemporary villages located on and near archaeological sites, along four major Amazonian rivers, to compare with the management practices synthesized in our conceptual model. We identified eight distinct categories of management practices that contribute to form forest patches of useful plants: (1) removal of non-useful plants, (2) protection of useful plants, (3) attraction of non-human animal dispersers, (4) transportation of useful plants, (5) selection of phenotypes, (6) fire management, (7) planting of useful plants, and (8) soil improvement. Our conceptual model, when ethnographically projected into the past, reveals how the interaction of these multiple management practices interferes with natural ecological processes, resulting in the domestication of Amazonian forest patches dominated by useful species. Our model suggests that management practices became more frequent as human population increased during the Holocene. In the field, we found that useful peren

Published
2018

8. Letter to the editor: Forest conservation: Humans’ handprints

Author

Levis, C., Clement, R., Ter Steege, Hans, Bongers, F., Braga Junqueira, A., Pitman, Nigel C.A., Pena Claros, M., and Costa, Flavia R.C.

Subjects
Life Science, Bosecologie en Bosbeheer, Soil Biology, PE&RC, Forest Ecology and Forest Management, Bodembiologie
Published
2017

9. Computationally Inexpensive PV System Model as a Simulation Agent for Large Scale Integration Analysis

Author

Levis, C. and Hill, M.

Subjects
Grid and Energy System Integration, PV System Performance and Integration
Abstract

33rd European Photovoltaic Solar Energy Conference and Exhibition; 2733-2738, In recent years the proliferation of renewable energy systems, especially photovoltaic (PV), generating into the low voltage (LV) distribution network has been increasing and these systems are poised to contribute a significant portion of the energy supply. This poses a challenge for maintaining grid stability, which is traditionally reliant on large centralised synchronous machines. For large-scale integration of distributed PV generation, PV systems must be capable of providing grid support services (GSS) emulating the traditional system. This paper presents an accurate, reduced order, computationally inexpensive agent based model (ABM) of a three-phase PV inverter that will provide a platform for analysing advanced control strategies in a multi-agent LV distribution network. The ABM is designed to simulate the actions and interactions of autonomous/decentralised PV systems with GSS for voltage and frequency stability using droop controllers. The developed ABM is validated by comparing results from three independent step changes [Irradiation, frequency & voltage] with a full switching model in MATLAB/ Simscape Power Systems™. These resuts show similar system dynamics and a computational burden reduction of 135:1, hence, providing a simulation agent for large scale integration analysis.

Published
2017
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11. Estimating the global conservation status of over 15,000 Amazonian tree species

Author

Steege, HT, Pitman, NCA, Killeen, TJ, Laurance, WF, Peres, CA, Guevara, JE, Salomão, RP, Castilho, CV, Amaral, IL, Dionízia de Almeida Matos, F, de Souza Coelho, L, Magnusson, WE, Phillips, OLB, de Andrade Lima Filho, D, de Jesus Veiga Carim, M, Victória Irume, M, Martins, MP, Molino, J-F, Sabatier, D, Wittmann, F, Lopez, DC, da Silva Guimarães, JR, Monteagudo Mendoza, A, Vargas, PN, Manzatto, AG, Farias Costa Reis, N, Terborgh, J, Casula, KR, Montero, JC, Feldpausch, TR, Honorio Coronado, EN, Duque Montoya, AJ, Zartman, ZE, Mostacedo, B, Vasquez, R, Assis, RL, Brilhante Medeiros, M, Fragomeni Simon, M, Andrade, A, Camargo, JL, Laurance, SGW, Mendonça Nascimento, HE, Marimon, BS, Marimon Jr, B-H, Costa F, Targhetta, N, Guimarães Vieira, IC, Brienen, R, Castellanos, H, Duivenvoorden, JF, Mogollón, HF, Fernandez Piedade, MT, Aymard, GA, Comiskey, JA, Damasco, G, Dávila, N, García-Villacorta, R, Stevenson Diaz, PR, Vincentini, A, Emilio, T, Levis, C, Schietti, J, Souza, P, Alonso, A, Dallmeier, F, Valle Ferreira, L, Neill, D, Araujo-Murakami, A, Arroyo, L, Antunes Carvalho, F, Coelho Souza, F, Dantas do Amaral, D, Gribel, R, Garcia Luize, B, Petrati Pansonato, M, Venticinque, E, Fine, P, Toldeo, M, Baraloto, C, Cerón, C, Engel, J, Henkel, TW, Jimenez, EM, Maas, P, Peñuela Mora, MC, Petronelli, P, Cardenas Revilla, JD, Silveira, M, Stropp, J, Thomas-Caesar, R, Baker, TR, Daly, D, Ríos Paredes, M, Ferreira da Silva, N, Fuentes, A, Møller Jørgensen, P, Schöngart, J, Silman, MR, Castaño Arboleda, N, Ladvocat Cintra, B, Cornejo Valverde, F, Di Fiore, A, Fernando Phillips, J, van Andel, TR, von Hildebrand, P, Marques Barbosa, E, de Matos Bonates, LC, de Castro, D, de Sousa Farias, E, Gonzales, T, Guillaumet, J-L, Hoffman, B, Malhi, Y, de Andrade Miranda, IP, Prieto, M, Rudas, A, Ruschell, AR, Silva, N, Vela, CIA, Vos, VA, Zent, EL, Zent, S, Cano, A, Trindade Nascimento, M, Oliveira, AA, Ramirez-Angulo, H, Ferreira Ramos, J, Sierra, R, Tirado, M, Umaña Medina, MN, van der Heijden, G, Vilanova Torre, E, Vriesendorp, C, Wang, O, Young, KR, Baider, C, Balslev, H, de Castro, N, Farfan-Rios, W, Ferreira, C, Mendoza, C, Mesonos, I, Torres-Lezama, A, Urrego Giraldo, LE, Villarroel, D, Zagt, R, Alexiades, MN, Garcia-Cabrera, K, Hernandez, L, Huamantupa-Chuquimaco, I, Milliken, W, Palacios Cuenca, W, Pansini, S, Pauletto, D, Ramirez Arevalo, F, Sampaio, AF, and Valderrama Sandoval, EH

Abstract

Estimates of extinction risk for Amazonian plant and animal species are rare, and not often incorporated into land-use policy and conservation planning. Here we overlay spatial distribution models with historical and projected deforestation to show that at least 40% and up to 64% of all Amazonian tree species are likely to qualify as globally threatened under IUCN Red List criteria. If confirmed, these results would increase the number of threatened plant species on Earth by 22%. We further show that the trends observed in Amazonia apply to trees throughout the tropics, and predict that most of the world's >40,000 tropical tree species currently qualify as globally threatened. A gap analysis suggests that existing Amazonian protected areas and indigenous territories will protect viable populations of most threatened species if those areas suffer no further degradation, highlighting the key roles that protected areas, indigenous peoples, and improved governance can play in preventing large-scale extinctions in the tropics in this century.

Published
2015

12. Botrytis cinerea B05.10 Genome sequencing

Author

Amselem, J., Cuomo, C.A., van Kan, J.A.L., Viaud, M., Benito, E.P., Couloux, A., Coutinho, P.M., de Vries, R.P., Dyer, P.S., Fillinger, S., Fournier, E., Gout, L., Hahn, M., Kohn, L., Lapalu, N., Plummer, K.M., Pradier, J.M., Quévillon, E., Sharon, A., Simon, A., ten Have, A., Tudzynski, B., Tudzynski, P., Wincker, P., Andrew, M., Anthouard, V., Beever, R.E., Beffa, R., Benoit, I., Bouzid, O., Brault, B., Chen, Z., Choquer, M., Collemare, J., Cotton, P., Danchin, E.G., Da Silva, C., Gautier, A., Giraud, C., Giraud, T., Gonzalez, C., Grossetete, S., Güldener, U., Henrissat, B., Howlett, B.J., Kodira, C., Kretschmer, M., Lappartient, A., Leroch, M., Levis, C., Mauceli, E., Neuvéglise, C., Oeser, B., Pearson, M., Poulain, J., Poussereau, N., Quesneville, H., Rascle, C., Schumacher, J., Ségurens, B., Sexton, A., Silva, E., Sirven, C., Soanes, D.M., Talbot, N.J., Templeton, M., Yandava, C., Yarden, O., Zeng, Q., Rollins, J.A., Lebrun, M.H., Dickman, M., Amselem, J., Cuomo, C.A., van Kan, J.A.L., Viaud, M., Benito, E.P., Couloux, A., Coutinho, P.M., de Vries, R.P., Dyer, P.S., Fillinger, S., Fournier, E., Gout, L., Hahn, M., Kohn, L., Lapalu, N., Plummer, K.M., Pradier, J.M., Quévillon, E., Sharon, A., Simon, A., ten Have, A., Tudzynski, B., Tudzynski, P., Wincker, P., Andrew, M., Anthouard, V., Beever, R.E., Beffa, R., Benoit, I., Bouzid, O., Brault, B., Chen, Z., Choquer, M., Collemare, J., Cotton, P., Danchin, E.G., Da Silva, C., Gautier, A., Giraud, C., Giraud, T., Gonzalez, C., Grossetete, S., Güldener, U., Henrissat, B., Howlett, B.J., Kodira, C., Kretschmer, M., Lappartient, A., Leroch, M., Levis, C., Mauceli, E., Neuvéglise, C., Oeser, B., Pearson, M., Poulain, J., Poussereau, N., Quesneville, H., Rascle, C., Schumacher, J., Ségurens, B., Sexton, A., Silva, E., Sirven, C., Soanes, D.M., Talbot, N.J., Templeton, M., Yandava, C., Yarden, O., Zeng, Q., Rollins, J.A., Lebrun, M.H., and Dickman, M.

Abstract

Botrytis cinhttp://intrawebdev2.be-md.ncbi.nlm.nih.gov/projects/bp/bpedit.cgi?pid=264284#TabMainerea is an ascomycete fungus causing grey mould disease on many crops and harvested products (e.g. grape, strawberry, cucumber, rose), Botrytis cinhttp://intrawebdev2.be-md.ncbi.nlm.nih.gov/projects/bp/bpedit.cgi?pid=264284#TabMainerea is an ascomycete fungus causing grey mould disease on many crops and harvested products (e.g. grape, strawberry, cucumber, rose)

Published
2015

13. Hyperdominance in Amazonian forest carbon cycling

Author

Fauset, S., Arets, E.J.M.M., ter Steege, H., Pena Claros, M., Poorter, L., Levis, C., Toledo, M., Fauset, S., Arets, E.J.M.M., ter Steege, H., Pena Claros, M., Poorter, L., Levis, C., and Toledo, M.

Abstract

While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few ‘hyperdominant’ species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ˜1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region.

Published
2015

14. Estimating the global conservation status of more than 15,000 Amazonian tree species

Author

ter Steege, H., Pitman, N.C.A., Killeen, T.J., Levis, C., ter Steege, H., Pitman, N.C.A., Killeen, T.J., and Levis, C.

Abstract

Estimates of extinction risk for Amazonian plant and animal species are rare and not often incorporated into land-use policy and conservation planning. We overlay spatial distribution models with historical and projected deforestation to show that at least 36% and up to 57% of all Amazonian tree species are likely to qualify as globally threatened under International Union for Conservation of Nature (IUCN) Red List criteria. If confirmed, these results would increase the number of threatened plant species on Earth by 22%. We show that the trends observed in Amazonia apply to trees throughout the tropics, and we predict that most of the world’s >40,000 tropical tree species now qualify as globally threatened. A gap analysis suggests that existing Amazonian protected areas and indigenous territories will protect viable populations of most threatened species if these areas suffer no further degradation, highlighting the key roles that protected areas, indigenous peoples, and improved governance can play in preventing large-scale extinctions in the tropics in this century.

Published
2015

15. Soil physical restrictions and hydrology regulate stand age and wood biomass turnover rates of Purus-Madeira interfluvial wetlands in Amazonia

Author

Cintra, B. B. L., Schietti, J., Emillio, T., Martins, D., Moulatlet, G., Souza, P., Levis, C., Quesada, C. A., and Schöngart, J.

Subjects
Stand Structure, Allometry, Brasil, lcsh:QE1-996.5, lcsh:Life, Biogeochemistry, Concentration (composition), Madeira River, Forest Management, Turnover, lcsh:Geology, Purus River, lcsh:QH501-531, Age Class, Amazonia, lcsh:QH540-549.5, Forest Dynamics, Wetland, lcsh:Ecology, Biomass, Deforestation, Terrace, Amazon Basin
Abstract

In Amazonia, wetlands constitute about 30% of its entire basin, of which ancient fluvial terraces located in vast interfluvial regions cover a large portion. Although the increased number of permanent plots in the recent years has contributed to improved understanding of regional variation in forest dynamics across the Amazon Basin, the functioning of large lowland interfluvial wetlands remain poorly understood. Here we present the first field-based estimate for tree ages, wood biomass productivity and biomass turnover rates for eight 1 ha plots in wetland and non-flooded forests distributed along the BR-319 Highway along a distance of about 600 km crossing the Purus–Madeira rivers interfluvial region in central-southwestern Amazon Basin. We estimate stand age, wood biomass productivity and biomass turnover rates combining tree-ring data and an allometric equation based on diameter, tree height and wood density and relate these structural parameters to physical soil and hydrological restrictions. Wood biomass and productivity varied twofold among the plots, with wood biomass stocks ranging between 138–294 Mg ha−1 and productivity varying between 3.4–6.6 Mg ha−1 yr−1. Soil effective depth, topography, structure and mainly soil water saturation significantly affected stand age (64–103 yr) and forest dynamics in terms of annual biomass turnover rates (2.0–3.2%). On harsher soils characterized by a poor structure, low effective depth and high water saturation, biomass turnover rates were increased and forests stands were younger compared to well-drained sites. We suggest that soil constraints, especially soil water saturation, limit the development of the stand structure, resulting in forests with younger stand ages and higher biomass turnover rates compared to forests growing on well-drained soils. We do not find, however, any relation between physical soil restrictions or hydrology and wood biomass productivity, but there is a trend of increasing wood biomass productivity and phosphorus concentrations at the soil surface. Based on our results we establish hypotheses for different dynamical processes between forests growing on waterlogged and well-drained soils and discuss how these results can be applied in the background of conservation as well as the potential development of forest management plans in this region, which will experience increased deforestation due to the construction of the BR-319 Highway crossing the interfluvial region of the Purus–Madeira rivers.

Published
2013

16. Hyperdominance in the Amazonian tree flora

Author

Steege, H. ter, Pitman, C.A., Sabatier, D., Baraloto, C., Salomão, R.P., Guevara, J.E., Phillips, O.L., Castilho, C.V., Magnusson, W.E., Mollino, J.-F., Stevenson Diaz, P.R., Costa , F., Emilio, T., Levis, C., Schietti, J., Souza, P., Alonso, A., Dallmeier, F., Duque Montoya, A.J., Fernandez Piedade, M.T., Maas, P., Araujo-Murakami, A., Arroyo, L., Gribel, R., Fine, P.V.A., Peres, C.A., Toledo, M., Aymard C., G.A., Baker, T.R., Cerón, C., Engel, J., Petronelli, P., Henkel, T.W., Stropp, J., Zartman, C.E., Daly, D., Neill, D., Silveira, M., Ríos Paredes, M., Chave, J., de Andrade Lima Filho, D., Hoffman, B., Møller Jørgensen, P., Fuentes, A., Schöngart, J., Cornejo Valverde, F., Di Fiore, A., Jimenez, E.M., Peñuela Mora, M.C., Phillips, J.F., Rivas, G., Andel, T.R. (Tinde) van, Zent, E.L., Hildebrand, P. von, Malhi, Y., Prieto, A., Rudas, A., Ruschell, A., Silva, N., Vos, V., Zent, S., Oliveira, A.A., Wang, O., Cano Schutz, A., Gonzales, T., Trindade Nascimento, M., Ramirez-Angulo, H., Sierra, R., Tirado , M., Umaña Medina, M.N., Heijden, G. van der, Vela, C.I.A., Vilanova Torre, E., Young, K.R., Vriesendorp, C., Baider, C., Balslev, H., Ferreira, C., Mesones, I., Torres-Lezama, A., Urrego Giraldo, L.E., Zagt, R., Alexiades, M.N., Monteagudo, A., Hernandez, L., Huamantupa-Chuquimaco, I., Millikes, W., Palacios Cuenca, W., Pauletto, D., Valderrama Sandoval, E., Valenzuela Gamarra, L., Dexter, K.G., Feeley, K., Lopez-Gonzalez, G., Núñez Vargas, P., Silman, M.R., Montero, J.C., Feldpausch, T.R., Honorio Coronado, E.N., Killeen, T.J., Mostacedo, B., Vasquez, R., Assis, R.L., Terborgh, J., Wittmann, F., Andrade, A., Laurance, W.F., Laurance, S.G.W., Marimon, B.S., Marimon , (B.-H. Jr.), Célia Guimarães Vieira, I., Leão Amaral, I., Brienen, R., Castellanos, H., Cárdenas López, D., Duivenvoorden, J.F., Mogollón, H.F., Dionízia de Almeida Matos, F., Dávila, N., García-Villacorta, R., Steege, H. ter, Pitman, C.A., Sabatier, D., Baraloto, C., Salomão, R.P., Guevara, J.E., Phillips, O.L., Castilho, C.V., Magnusson, W.E., Mollino, J.-F., Stevenson Diaz, P.R., Costa , F., Emilio, T., Levis, C., Schietti, J., Souza, P., Alonso, A., Dallmeier, F., Duque Montoya, A.J., Fernandez Piedade, M.T., Maas, P., Araujo-Murakami, A., Arroyo, L., Gribel, R., Fine, P.V.A., Peres, C.A., Toledo, M., Aymard C., G.A., Baker, T.R., Cerón, C., Engel, J., Petronelli, P., Henkel, T.W., Stropp, J., Zartman, C.E., Daly, D., Neill, D., Silveira, M., Ríos Paredes, M., Chave, J., de Andrade Lima Filho, D., Hoffman, B., Møller Jørgensen, P., Fuentes, A., Schöngart, J., Cornejo Valverde, F., Di Fiore, A., Jimenez, E.M., Peñuela Mora, M.C., Phillips, J.F., Rivas, G., Andel, T.R. (Tinde) van, Zent, E.L., Hildebrand, P. von, Malhi, Y., Prieto, A., Rudas, A., Ruschell, A., Silva, N., Vos, V., Zent, S., Oliveira, A.A., Wang, O., Cano Schutz, A., Gonzales, T., Trindade Nascimento, M., Ramirez-Angulo, H., Sierra, R., Tirado , M., Umaña Medina, M.N., Heijden, G. van der, Vela, C.I.A., Vilanova Torre, E., Young, K.R., Vriesendorp, C., Baider, C., Balslev, H., Ferreira, C., Mesones, I., Torres-Lezama, A., Urrego Giraldo, L.E., Zagt, R., Alexiades, M.N., Monteagudo, A., Hernandez, L., Huamantupa-Chuquimaco, I., Millikes, W., Palacios Cuenca, W., Pauletto, D., Valderrama Sandoval, E., Valenzuela Gamarra, L., Dexter, K.G., Feeley, K., Lopez-Gonzalez, G., Núñez Vargas, P., Silman, M.R., Montero, J.C., Feldpausch, T.R., Honorio Coronado, E.N., Killeen, T.J., Mostacedo, B., Vasquez, R., Assis, R.L., Terborgh, J., Wittmann, F., Andrade, A., Laurance, W.F., Laurance, S.G.W., Marimon, B.S., Marimon , (B.-H. Jr.), Célia Guimarães Vieira, I., Leão Amaral, I., Brienen, R., Castellanos, H., Cárdenas López, D., Duivenvoorden, J.F., Mogollón, H.F., Dionízia de Almeida Matos, F., Dávila, N., and García-Villacorta, R.

Abstract

The vast extent of the Amazon Basin has historically restricted the study of its tree communities to the local and regional scales. Here, we provide empirical data on the commonness, rarity, and richness of lowland tree species across the entire Amazon Basin and Guiana Shield (Amazonia), collected in 1170 tree plots in all major forest types. Extrapolations suggest that Amazonia harbors roughly 16,000 tree species, of which just 227 (1.4%) account for half of all trees. Most of these are habitat specialists and only dominant in one or two regions of the basin. We discuss some implications of the finding that a small group of species—less diverse than the North American tree flora—accounts for half of the world’s most diverse tree community.

Published
2013
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17. Síndrome pulmonar por hantavirus en población infantil. Chile: Regiones IX y X. 1998-2000

Author

SOZA C., GUILLERMO, LORCA O., PEDRO, PUEBLA M., SERGIO, WENZEL M., MARISOL, NAVARRETE C., MARITZA, VILLAGRA C., ELIECER, MORA R., JUDITH, LEVIS C., SILVANA, and AVILES A., GABRIELA

Subjects
Pediatric disease, Hantavirus Pulmonary Syndrome, Chilean experience
Abstract

El síndrome pulmonar por hantavirus (SPH) ha estado presente en Chile desde 1993 y ha sido detectado desde 1997 en la IX Región. Es una grave zoonosis con alta mortalidad, que afecta a gente joven incluyendo niños. Se ha estimado oportuno dar a conocer nuestra experiencia en la atención de 6 pacientes pediátricos, atendidos en las unidades de Cuidados Intensivos y Aislamiento en el Hospital Regional de Temuco, entre enero de 1998 y enero de 2000 mediante un estudio descriptivo de la experiencia del equipo de salud en la atención de estos pacientes. La información clínico-epidemioló-gica se extrajo de las fichas clínicas y visitas a terreno. Se efectuó la confirmación etiológica por detección de anticuerpos específicos -IgM e IgG- mediante tests de ELISA y la pesquisa de genoma viral por reacción de polimerasa en cadena (TR RPC). Edad promedio 6 años 5 meses (rango: 2-10 años). relación varón/mujer: 4/2. Procedencia: de área rural cordillerana (n: 4), costera (n:2). Todos tuvieron exposición en casas deshabitadas o galpones. Período de incubación promedio: 14 días (rango: 7-21). Todos los pacientes tuvieron fiebre elevada, dolor abdominal intenso, vómitos, mialgias, compromiso respiratorio clínico y radiológico. Hallazgos hematológicos constantes: trombocito-penia, leucocitosis, inmunoblastos o linfocitosis con formas atípicas. La confirmación etiológica (IgM e IgG positivas) se alcanzó en todos. En dos pacientes se detectó en sangre la secuencia genética viral de hantavirus cepa Andes. Dos pacientes en los cuales se requirió ventilación mecánica y manejo del shock, finalmente fallecieron; los otros enfermos tuvieron una recuperación rápida. No existe una terapia específica conocida para el SPH, la prevención, una sospecha y diagnóstico oportunos y el tratamiento agresivo son las estrategias actuales para luchar contra esta enfermedad Hantavirus Pulmonary Syndrome (HPS) has been present in Chile since 1993 and it was first detected during 1997 in our region. It is a particularly serious zoonosis with a high mortality rate that affects young people including children. We refer our experience with 6 pediatric patients admitted into the Intensive Care and Pediatric Isolation units at Hospital Regional de Temuco (January 1998 to January 2000) including a description of our experience assisting these patients based on information obtained from clinical files and epidemiological visits. The hantavirus infection was confirmed by positive specific IgM and IgG ELISA tests. Search of viral genome was done by RT-PCR. The average age was 6 yrs - 5 ms (range: 2-10 yrs). The ratio of male/females was 4/2. The origin of the patients was: rural areas near the Andes Mountains (n: 4) and rural coast (n: 2). The exposure to infection was in uninhabited houses or barns. The average incubation period was: 14 days (range: 7-21). The symptoms were: high fever, intense abdominal pain, vomiting, myalgias, clinical and Rx respiratory distress in all. The main hematological findings were: thrombocytopenia, high leukocytes count, immunoblasts and atypical lymphocytic cells. All cases were confirmed by IgM and IgG positive tests. The Andes virus genomic sequence was found in blood of one pediatric patient and in his uncle. Two patients who required mechanical ventilation and shock management finally died, the other patients recovered rapidly. Hantavirus Pulmonary Syndrome has no specific treatment. Prevention, an opportune diagnostic suspicion and aggressive treatment are the current strategies to control this disease

Published
2000

18. Genomic Analysis of the Necrotrophic Fungal Pathogens Sclerotinia sclerotiorum and Botrytis cinerea

Author

Richardson, PM, Amselem, J, Cuomo, CA, van Kan, JAL, Viaud, M, Benito, EP, Couloux, A, Coutinho, PM, de Vries, RP, Dyer, PS, Fillinger, S, Fournier, E, Gout, L, Hahn, M, Kohn, LM, Lapalu, N, Plummer, KM, Pradier, J-M, Quevillon, E, Sharon, A, Simon, A, ten Have, A, Tudzynski, B, Tudzynski, P, Wincker, P, Andrew, M, Anthouard, V, Beever, RE, Beffa, R, Benoit, I, Bouzid, O, Brault, B, Chen, Z, Choquer, M, Collemare, J, Cotton, P, Danchin, EG, Da Silva, C, Gautier, A, Giraud, C, Giraud, T, Gonzalez, C, Grossetete, S, Gueldener, U, Henrissat, B, Howlett, BJ, Kodira, C, Kretschmer, M, Lappartient, A, Leroch, M, Levis, C, Mauceli, E, Neuveglise, C, Oeser, B, Pearson, M, Poulain, J, Poussereau, N, Quesneville, H, Rascle, C, Schumacher, J, Segurens, B, Sexton, A, Silva, E, Sirven, C, Soanes, DM, Talbot, NJ, Templeton, M, Yandava, C, Yarden, O, Zeng, Q, Rollins, JA, Lebrun, M-H, Dickman, M, Richardson, PM, Amselem, J, Cuomo, CA, van Kan, JAL, Viaud, M, Benito, EP, Couloux, A, Coutinho, PM, de Vries, RP, Dyer, PS, Fillinger, S, Fournier, E, Gout, L, Hahn, M, Kohn, LM, Lapalu, N, Plummer, KM, Pradier, J-M, Quevillon, E, Sharon, A, Simon, A, ten Have, A, Tudzynski, B, Tudzynski, P, Wincker, P, Andrew, M, Anthouard, V, Beever, RE, Beffa, R, Benoit, I, Bouzid, O, Brault, B, Chen, Z, Choquer, M, Collemare, J, Cotton, P, Danchin, EG, Da Silva, C, Gautier, A, Giraud, C, Giraud, T, Gonzalez, C, Grossetete, S, Gueldener, U, Henrissat, B, Howlett, BJ, Kodira, C, Kretschmer, M, Lappartient, A, Leroch, M, Levis, C, Mauceli, E, Neuveglise, C, Oeser, B, Pearson, M, Poulain, J, Poussereau, N, Quesneville, H, Rascle, C, Schumacher, J, Segurens, B, Sexton, A, Silva, E, Sirven, C, Soanes, DM, Talbot, NJ, Templeton, M, Yandava, C, Yarden, O, Zeng, Q, Rollins, JA, Lebrun, M-H, and Dickman, M

Abstract

Sclerotinia sclerotiorum and Botrytis cinerea are closely related necrotrophic plant pathogenic fungi notable for their wide host ranges and environmental persistence. These attributes have made these species models for understanding the complexity of necrotrophic, broad host-range pathogenicity. Despite their similarities, the two species differ in mating behaviour and the ability to produce asexual spores. We have sequenced the genomes of one strain of S. sclerotiorum and two strains of B. cinerea. The comparative analysis of these genomes relative to one another and to other sequenced fungal genomes is provided here. Their 38-39 Mb genomes include 11,860-14,270 predicted genes, which share 83% amino acid identity on average between the two species. We have mapped the S. sclerotiorum assembly to 16 chromosomes and found large-scale co-linearity with the B. cinerea genomes. Seven percent of the S. sclerotiorum genome comprises transposable elements compared to <1% of B. cinerea. The arsenal of genes associated with necrotrophic processes is similar between the species, including genes involved in plant cell wall degradation and oxalic acid production. Analysis of secondary metabolism gene clusters revealed an expansion in number and diversity of B. cinerea-specific secondary metabolites relative to S. sclerotiorum. The potential diversity in secondary metabolism might be involved in adaptation to specific ecological niches. Comparative genome analysis revealed the basis of differing sexual mating compatibility systems between S. sclerotiorum and B. cinerea. The organization of the mating-type loci differs, and their structures provide evidence for the evolution of heterothallism from homothallism. These data shed light on the evolutionary and mechanistic bases of the genetically complex traits of necrotrophic pathogenicity and sexual mating. This resource should facilitate the functional studies designed to better understand what makes these fungi such successful a

Published
2011

19. Genome analysis of the necrotrophic fungal pathogens Sclerotinia sclerotiorum and Botrytis cinerea

Author

Amselem, J., Cuomo, C.A., van Kan, J.A.L., Viaud, M., Benito, E.P., Couloux, A., Coutinho, P.M., de Vries, R.P., Dyer, P.S., Fillinger, S., Fournier, E., Gout, L., Hahn, M., Kohn, L., Lapalu, N., Plummer, K.M., Pradier, J.M., Quévillon, E., Sharon, A., Simon, A., ten Have, A., Tudzynski, B., Tudzynski, P., Wincker, P., Andrew, M., Anthouard, V., Beever, R.E., Beffa, R., Benoit, I., Bouzid, O., Brault, B., Chen, Z., Choquer, M., Collemare, J., Cotton, P., Danchin, E.G., Da Silva, C., Gautier, A., Giraud, C., Giraud, T., Gonzalez, C., Grossetete, S., Güldener, U., Henrissat, B., Howlett, B.J., Kodira, C., Kretschmer, M., Lappartient, A., Leroch, M., Levis, C., Mauceli, E., Neuvéglise, C., Oeser, B., Pearson, M., Poulain, J., Poussereau, N., Quesneville, H., Rascle, C., Schumacher, J., Ségurens, B., Sexton, A., Silva, E., Sirven, C., Soanes, D.M., Talbot, N.J., Templeton, M., Yandava, C., Yarden, O., Zeng, Q., Rollins, J.A., Lebrun, M.H., Dickman, M., Amselem, J., Cuomo, C.A., van Kan, J.A.L., Viaud, M., Benito, E.P., Couloux, A., Coutinho, P.M., de Vries, R.P., Dyer, P.S., Fillinger, S., Fournier, E., Gout, L., Hahn, M., Kohn, L., Lapalu, N., Plummer, K.M., Pradier, J.M., Quévillon, E., Sharon, A., Simon, A., ten Have, A., Tudzynski, B., Tudzynski, P., Wincker, P., Andrew, M., Anthouard, V., Beever, R.E., Beffa, R., Benoit, I., Bouzid, O., Brault, B., Chen, Z., Choquer, M., Collemare, J., Cotton, P., Danchin, E.G., Da Silva, C., Gautier, A., Giraud, C., Giraud, T., Gonzalez, C., Grossetete, S., Güldener, U., Henrissat, B., Howlett, B.J., Kodira, C., Kretschmer, M., Lappartient, A., Leroch, M., Levis, C., Mauceli, E., Neuvéglise, C., Oeser, B., Pearson, M., Poulain, J., Poussereau, N., Quesneville, H., Rascle, C., Schumacher, J., Ségurens, B., Sexton, A., Silva, E., Sirven, C., Soanes, D.M., Talbot, N.J., Templeton, M., Yandava, C., Yarden, O., Zeng, Q., Rollins, J.A., Lebrun, M.H., and Dickman, M.

Abstract

Sclerotinia sclerotiorum and Botrytis cinerea are closely related necrotrophic plant pathogenic fungi notable for their wide host ranges and environmental persistence. These attributes have made these species models for understanding the complexity of necrotrophic, broad host-range pathogenicity. Despite their similarities, the two species differ in mating behaviour and the ability to produce asexual spores. We have sequenced the genomes of one strain of S. sclerotiorum and two strains of B. cinerea. The comparative analysis of these genomes relative to one another and to other sequenced fungal genomes is provided here. Their 38–39 Mb genomes include 11,860–14,270 predicted genes, which share 83% amino acid identity on average between the two species. We have mapped the S. sclerotiorum assembly to 16 chromosomes and found large-scale co-linearity with the B. cinerea genomes. Seven percent of the S. sclerotiorum genome comprises transposable elements compared to

Published
2011

22. Engineering calculations for the Delta S method of solving the orbital allotment problem

Author

Kohnhorst, P. A, Levis, C. A, and Walton, E. K

Subjects
Astrodynamics
Abstract

The method of calculating single-entry separation requirements for pairs of satellites is extended to include the interference on the top link as well as on the down link. Several heuristic models for analyzing the effects of shaped-beam antenna designs on required satellite separations are introduced and demonstrated with gain contour plots. The calculation of aggregate interference is extended to include the effects of up-link interference. The relationship between the single-entry C/I requirements, used in determining satellite separation constraints for various optimization procedures, and the aggregate C/I values of the resulting solutions is discussed.

Published
1987

23. Engineering calculations for communications satellite systems planning

Author

Reilly, C. H, Levis, C. A, Buyukdura, O. M, and Mount-Campbell, C. A

Subjects
Communications And Radar
Abstract

Observed solution times were analyzed for the extended gradient and cyclic coordinate search procedures. The times used in the analysis come from computer runs made during a previously-reported experiment conducted to assess the quality of the solutions to a BSS synthesis problem found by the two search methods. The results of a second experiment with a Fixed Satellite Service (FSS) test problem are also presented. Computational results are summarized for mixed integer programming approaches for solving FSS synthesis problems. A promising heuristic algorithm is described. A synthesis model is discussed for orbital arc allotment optimization. Research plans for the near future are also presented.

Published
1986

24. Alternative mathematical programming formulations for FSS synthesis

Author

Reilly, C. H, Mount-Campbell, C. A, Gonsalvez, D. J. A, and Levis, C. A

Subjects
Computer Programming And Software
Abstract

A variety of mathematical programming models and two solution strategies are suggested for the problem of allocating orbital positions to (synthesizing) satellites in the Fixed Satellite Service. Mixed integer programming and almost linear programming formulations are presented in detail for each of two objectives: (1) positioning satellites as closely as possible to specified desired locations, and (2) minimizing the total length of the geostationary arc allocated to the satellites whose positions are to be determined. Computational results for mixed integer and almost linear programming models, with the objective of positioning satellites as closely as possible to their desired locations, are reported for three six-administration test problems and a thirteen-administration test problem.

Published
1986

25. Broadcasting satellite service synthesis using gradient and cyclic coordinate search procedures

Author

Reilly, C. H, Mount-Campbell, C. A, Gonsalvez, D. J, Martin, C. H, Levis, C. A, and Wang, C. W

Subjects
Communications And Radar
Abstract

Two search techniques are considered for solving satellite synthesis problems. Neither is likely to find a globally optimal solution. In order to determine which method performs better and what factors affect their performance, we design an experiment and solve the same problem under a variety of starting solution configuration-algorithm combinations. Since there is no randomization in the experiment, we present results of practical, rather than statistical, significance. Our implementation of a cyclic coordinate search procedure clearly finds better synthesis solutions than our implementation of a gradient search procedure does with our objective of maximizing the minimum C/I ratio computed at test points on the perimeters of the intended service areas. The length of the available orbital arc and the configuration of the starting solution are shown to affect the quality of the solutions found.

Published
1986

26. The role of service areas in the optimization of FSS orbital and frequency assignments

Author

Levis, C. A, Wang, C. W, Yamamura, Y, Reilly, C. H, and Gonsalvez, D. J

Subjects
Space Communications, Spacecraft Communications, Command And Tracking
Abstract

A relationship is derived, on a single-entry interference basis, for the minimum allowable spacing between two satellites as a function of electrical parameters and service-area geometries. For circular beams, universal curves relate the topocentric satellite spacing angle to the service-area separation angle measured at the satellite. The corresponding geocentric spacing depends only weakly on the mean longitude of the two satellites, and this is true also for alliptical antenna beams. As a consequence, if frequency channels are preassigned, the orbital assignment synthesis of a satellite system can be formulated as a mixed-integer programming (MIP) problem or approximated by a linear programming (LP) problem, with the interference protection requirements enforced by constraints while some linear function is optimized. Possible objective-function choices are discussed and explicit formulations are presented for the choice of the sum of the absolute deviations of the orbital locations from some prescribed ideal location set. A test problem is posed consisting of six service areas, each served by one satellite, all using elliptical antenna beams and the same frequency channels. Numerical results are given for the three ideal location prescriptions for both the MIP and LP formulations. The resulting scenarios also satisfy reasonable aggregate interference protection requirements.

Published
1985

27. The role of service areas in the optimization of FSS orbital and frequency assignments

Author

Levis, C. A, Wang, C.-W, Yamamura, Y, Reilly, C. H, and Gonsalvez, D. J

Subjects
Space Communications, Spacecraft Communications, Command And Tracking
Abstract

An implicit relationship is derived which relates the topocentric separation of two satellites required for a given level of single-entry protection to the separation and orientation of their service areas. The results are presented explicitly for circular beams and topocentric angles. A computational approach is given for elliptical beams and for use with longitude and latitude variables. It is found that the geocentric separation depends primarily on the service area separation, secondarily on a parameter which characterizes the electrical design, and only slightly on the mean orbital position of the satellites. Both linear programming and mixed integer programming algorithms are implemented. Possible objective function choices are discussed, and explicit formulations are presented for the choice of the sum of the absolute deviations of the orbital locations from some prescribed 'ideal' location set. A test problem involving six service areas is examined with results that are encouraging with respect to applying the linear programming procedure to larger scenarios.

Published
1986

28. Calculation of allowable orbital spacings for the fixed-satellite service

Author

Yamamura, Y and Levis, C. A

Subjects
Astrodynamics
Abstract

Minimum satellite separations are calculated which satisfy a given carrier-to-interference protection ratio for the Fixed-Satellite Service (FSS) on a single-entry basis, assuming circular antenna beams. The results are presented in the form of universal contour curves, in which antenna-centered angles are the coordinates, and also in terms of the more conventional longitude and latitude separations. It is shown that orbit capacity increases with decreasing service-area size and that, for practical service areas, capacity is increased if the longitude of a satellite does not differ too greatly from that of the service area it serves.

Published
1985

29. Engineering calculations for communications satellite systems planning

Author

Levis, C. A, Martin, C. H, Reilly, C. H, Gonsalvez, D. J, and Yamaura, Y

Subjects
Launch Vehicles And Space Vehicles
Abstract

An extended gradient search code for broadcasting satellite service (BSS) spectrum/orbit assignment synthesis is discussed. Progress is also reported on both single-entry and full synthesis computational aids for fixed satellite service (FSS) spectrum/orbit assignment purposes.

Published
1985

30. Engineering calculations for communications satellite systems planning

Author

Reilly, C. H, Levis, C. A, Mount-Campbell, C, Gonsalvez, D. J, Wang, C. W, and Yamamura, Y

Subjects
Communications And Radar
Abstract

Computer-based techniques for optimizing communications-satellite orbit and frequency assignments are discussed. A gradient-search code was tested against a BSS scenario derived from the RARC-83 data. Improvement was obtained, but each iteration requires about 50 minutes of IBM-3081 CPU time. Gradient-search experiments on a small FSS test problem, consisting of a single service area served by 8 satellites, showed quickest convergence when the satellites were all initially placed near the center of the available orbital arc with moderate spacing. A transformation technique is proposed for investigating the surface topography of the objective function used in the gradient-search method. A new synthesis approach is based on transforming single-entry interference constraints into corresponding constraints on satellite spacings. These constraints are used with linear objective functions to formulate the co-channel orbital assignment task as a linear-programming (LP) problem or mixed integer programming (MIP) problem. Globally optimal solutions are always found with the MIP problems, but not necessarily with the LP problems. The MIP solutions can be used to evaluate the quality of the LP solutions. The initial results are very encouraging.

Published
1985

31. Meteorological factors in Earth-Satellite propagation

Author

Levis, C. A, Damon, E. K, Lin, K. T, and Weller, A. E., III

Subjects
Communications And Radar
Abstract

A 5-meter paraboloidal antenna operated at 28 GHz showed gain changes of 2 dB due to rain. While precise estimation of the corresponding angle of arrival changes is difficult, they appear to have been on the order of 0.02 degrees. The attenuation at 28.6 GHz inferred from radiometry agreed well with that measured simultaneously over a satellite/Earth link at the same frequency. The radiometers so calibrated have been used to add to the available site diversity data base using a 9 km baseline. An improved empirical model of site diversity gain was obtained by applying regression techniques to available published data. A brief review of the literature has led to suggestions for two experimental programs, one dealing with multifrequency radiometry and the other with the effects of the stochastic properties of precipitation on wideband data transmission.

Published
1984

32. Engineering calculations for communications satellite systems planning

Author

Martin, C. H, Gonsalvez, D. J, Levis, C. A, and Wang, C. W

Subjects
Launch Vehicles And Space Vehicles
Abstract

Progress is reported on a computer code to improve the efficiency of spectrum and orbit utilization for the Broadcasting Satellite Service in the 12 GHz band for Region 2. It implements a constrained gradient search procedure using an exponential objective function based on aggregate signal to noise ratio and an extended line search in the gradient direction. The procedure is tested against a manually generated initial scenario and appears to work satisfactorily. In this test it was assumed that alternate channels use orthogonal polarizations at any one satellite location.

Published
1983

33. Meteorological factors in Earth-satellite propagation

Author

Levis, C. A, Taylor, R. C, Leonard, R, Lin, K. T, Pigon, B, and Weller, A

Subjects
Communications And Radar
Abstract

Using the COMSTAR D/4 28.56 GHz beacon as a source, a differential gain experiment was performed by connecting a 5-meter paraboloidal antenna and a 0.6-meter paraboloidal antenna alternately to the same receiver. Substantial differential gain changes were observed during some, but not all, rain events. A site-diversity experiment was implemented which consists of two 28.56 GHz radiometers separated by 9 km. The look-angle corresponds to that of the D/4 beacon, and data were obtained with one radiometer during several weeks of concurrent beacon operation to verify the system calibration. A theoretical study of the effect of scattering from a nonuniform rain distribution along the path is under way to aid in interpreting the results of this experiment. An improved empirical site diversity-gain model was derived from data in the literature relating to 34 diversity experiments. Work on the experiment control and data acquisition system is continuing with a view toward future experiments.

Published
1982

34. Engineering calculations for communications systems planning

Author

Levis, C. A, Martin, C. H, Wang, C. W, and Gonsalvez, D

Subjects
Communications And Radar
Abstract

The single entry interference problem is treated for frequency sharing between the broadcasting satellite and intersatellite services near 23 GHz. It is recommended that very long (more than 120 longitude difference) intersatellite hops be relegated to the unshared portion of the band. When this is done, it is found that suitable orbit assignments can be determined easily with the aid of a set of universal curves. An attempt to develop synthesis procedures for optimally assigning frequencies and orbital slots for the broadcasting satellite service in region 2 was initiated. Several discrete programming and continuous optimization techniques are discussed.

Published
1982

35. Preliminary analysis of 15 GHz scintillations on an ATS-5 satellite-to-ground path

Author

Levis, C. A and Ungvichian, V

Subjects
Space Communications, Spacecraft Communications, Command And Tracking
Abstract

Although the ATS 5 satellite failed to de-spin, a rather intricate analysis procedure allows the extraction of scintillation information at spectral rates from 20 to 60 Hz, as well as below 0.5 Hz. The procedure has been applied to 15.3 GHz signals. Distributions and spectra were obtained for a limited amount of data, representing a variety of meteorological conditions. A definite correlation of scintillation strength and variability with rainfall is apparent. The data analysis is continuing.

Published
1976

36. An optical radar for airborne use over natural waters

Author

Levis, C. A, Swarner, W. G, Prettyman, C, and Reinhardt, G. W

Subjects
Lasers And Masers
Abstract

An optical radar for detecting targets in natural waters was built and tested in the Gulf of Mexico. The transmitter consists of a Q switched neodymium glass laser, with output amplified and doubled in KDP to 0.53 micrometer wavelength. The receiver incorporates a noval optical spatial filter to reduce the dynamic range required of the photodetector to a reasonable value. Detection of targets to a depth of 26 meters (84 feet) was achieved with a considerable sensitivity margin. The sensitivity of the radar is highly dependent on the optical attenuation coefficient. In general, measured returns fell between the values predicted on the basis of monopath and multipath attenuation. By means of simple physical arguments, a radar equation for the system was derived. To validate this theoretical model, measurements of optical attenuation and of water surface behavior were also instrumented, and some of these results are given.

Published
1975

37. Distributed-switch Dicke radiometers

Author

Levis, C. A

Subjects
Instrumentation And Photography
Abstract

A radiometer on an orbiting spacecraft is described which derives high spatial resolution information from terrestrial and atmospheric regions. The N elements or subapertures on the spacecraft transduce electromagnetic energy into electric signals. Many or all of the elements are simultaneously illuminated by electromagnetic energy radiated from the same region. Identical, parallel processing channels are responsive to the N elements. Each of the channels includes a variable gain amplifier responsive to the signal transduced by its corresponding array elements. The gain of each amplifier is controlled as a function of the output difference when the channel is connected periodically to each of a pair of Dicke noise sources, such as resistors maintained at predetermined temperatures.

Published
1979

38. System implications of large radiometric array antennas

Author

Levis, C. A and Lin, H.-C

Subjects
Spacecraft Instrumentation
Abstract

Temperature sensitivity degradation due to antenna losses is recognized as a hindrance to extension of available remote-sensing radiometry techniques to larger systems for enhanced spatial resolution. The use of large antennas is also complicated by difficulties with bandwidth and integration time. Advantages of introducing active devices at the subarray level, with distributed Dicke switching or correlation detection, are examined, and their possible contribution to the design of effective imaging microwave radiometers for remote sensing of geophysical parameters (sea state, distribution of sea ice, cloud types and their distributions, soil moisture) is assessed.

Published
1977

39. Definition Study for Space Shuttle Experiments Involving Large, Steerable Millimeter-Wave Antenna Arrays

Author

Levis, C. A

Subjects
Communications And Radar
Abstract

The potential uses and techniques for the shuttle spacelab Millimeter Wave Large Aperture Antenna Experiment (MWLAE) are documented. Potential uses are identified: applications to radio astronomy, the sensing of atmospheric turbulence by its effect on water vapor line emissions, and the monitoring of oil spills by multifrequency radiometry. IF combining is preferable to RF combining with respect to signal to noise ratio for communications receiving antennas of the size proposed for MWLAE. A design approach using arrays of subapertures is proposed to reduce the number of phase shifters and mixers for uses which require a filled aperture. Correlation radiometry and a scheme utilizing synchronous Dicke switches and IF combining are proposed as potential solutions.

Published
1976

40. System implications of large radiometric array antennas

Author

Levis, C. A and Lin, H. C

Subjects
Electronics And Electrical Engineering
Abstract

Current radiometric earth and atmospheric sensing systems in the centimeter wavelength range generally employ a directive antenna connected through a single terminal pair to a Dicke receiver. It is shown that this approach does not lend itself to systems with greatly increased spatial resolution. Signal to noise considerations relating to antenna efficiency force the introduction of active elements at the subarray level; thus, if Dicke switching is to be used, it must be distributed throughout the system. Some possible approaches are suggested. The introduction of active elements at the subarray level is found to ease the design constraints on time delay elements, necessary for bandwidth, and on multiple beam generation, required in order to achieve sufficient integration time with high resolution.

Published
1976

48. A new class of tetraspanins in fungi

Author

Gourgues, M, primary, Clergeot, P.-H, additional, Veneault, C, additional, Cots, J, additional, Sibuet, S, additional, Brunet-Simon, A, additional, Levis, C, additional, Langin, T, additional, and Lebrun, M.-H, additional

Published
2002
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