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1,860 results on '"WILLIAMSON, G."'

1. The multi-wavelength view of shocks in the fastest nova V1674 Her

Author

Sokolovsky, K. V., Johnson, T. J., Buson, S., Jean, P., Cheung, C. C., Mukai, K., Chomiuk, L., Aydi, E., Molina, B., Kawash, A., Linford, J. D., Mioduszewski, A. J., Rupen, M. P., Sokoloski, J. L., Williams, M. N., Steinberg, E., Vurm, I., Metzger, B. D., Page, K. L., Orio, M., Quimby, R. M., Shafter, A. W., Corbett, H., Bolzoni, S., DeYoung, J., Menzies, K., Romanov, F. D., Richmond, M., Ulowetz, J., Vanmunster, T., Williamson, G., Lane, D. J., Bartnik, M., Bellaver, M., Bruinsma, E., Dugan, E., Fedewa, J., Gerhard, C., Painter, S., Peterson, D. -M., Rodriguez, J. E., Smith, C., Sullivan, H., and Watson, S.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Classical novae are shock-powered multi-wavelength transients triggered by a thermonuclear runaway on an accreting white dwarf. V1674 Her is the fastest nova ever recorded (time to declined by two magnitudes is t_2=1.1 d) that challenges our understanding of shock formation in novae. We investigate the physical mechanisms behind nova emission from GeV gamma-rays to cm-band radio using coordinated Fermi-LAT, NuSTAR, Swift and VLA observations supported by optical photometry. Fermi-LAT detected short-lived (18 h) 0.1-100 GeV emission from V1674 Her that appeared 6 h after the eruption began; this was at a level of (1.6 +/- 0.4)x10^-6 photons cm^-2 s^-1. Eleven days later, simultaneous NuSTAR and Swift X-ray observations revealed optically thin thermal plasma shock-heated to kT_shock = 4 keV. The lack of a detectable 6.7 keV Fe K_alpha emission suggests super-solar CNO abundances. The radio emission from V1674 Her was consistent with thermal emission at early times and synchrotron at late times. The radio spectrum steeply rising with frequency may be a result of either free-free absorption of synchrotron and thermal emission by unshocked outer regions of the nova shell or the Razin-Tsytovich effect attenuating synchrotron emission in dense plasma. The development of the shock inside the ejecta is unaffected by the extraordinarily rapid evolution and the intermediate polar host of this nova., Comment: 20 pages, 9 figures, 3 tables. Accepted to MNRAS

Published
2023
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2. Strong floristic distinctiveness across Neotropical successional forests.

Author

Jakovac, Catarina, Meave, Jorge, Bongers, Frans, Letcher, Susan, Dupuy, Juan, Piotto, Daniel, Rozendaal, Danaë, Peña-Claros, Marielos, Craven, Dylan, Santos, Braulio, Siminski, Alexandre, Fantini, Alfredo, Rodrigues, Alice, Hernández-Jaramillo, Alma, Idárraga, Alvaro, Junqueira, André, Zambrano, Angelica, de Jong, Ben, Pinho, Bruno, Finegan, Bryan, Castellano-Castro, Carolina, Zambiazi, Daisy, Dent, Daisy, García, Daniel, Kennard, Deborah, Delgado, Diego, Broadbent, Eben, Ortiz-Malavassi, Edgar, Pérez-García, Eduardo, Lebrija-Trejos, Edwin, Berenguer, Erika, Marín-Spiotta, Erika, Alvarez-Davila, Esteban, de Sá Sampaio, Everardo, Melo, Felipe, Elias, Fernando, França, Filipe, Oberleitner, Florian, Mora, Francisco, Williamson, G, Colletta, Gabriel, Cabral, George, Derroire, Géraldine, Fernandes, Geraldo, van der Wal, Hans, Teixeira, Heitor, Vester, Henricus, García, Hernando, Vieira, Ima, Jiménez-Montoya, Jaider, de Almeida-Cortez, Jarcilene, Hall, Jefferson, Chave, Jerome, Zimmerman, Jess, Nieto, Jhon, Ferreira, Joice, Rodríguez-Velázquez, Jorge, Ruíz, Jorge, Barlow, Jos, Aguilar-Cano, José, Hernández-Stefanoni, José, Engel, Julien, Becknell, Justin, Zanini, Kátia, Lohbeck, Madelon, Tabarelli, Marcelo, Romero-Romero, Marco, Uriarte, Maria, Veloso, Maria, Espírito-Santo, Mário, van der Sande, Masha, van Breugel, Michiel, Martínez-Ramos, Miguel, Schwartz, Naomi, Norden, Natalia, Pérez-Cárdenas, Nathalia, González-Valdivia, Noel, Petronelli, Pascal, Balvanera, Patricia, Massoca, Paulo, Brancalion, Pedro, Villa, Pedro, Hietz, Peter, Ostertag, Rebecca, López-Camacho, René, César, Ricardo, Mesquita, Rita, Chazdon, Robin, Muñoz, Rodrigo, DeWalt, Saara, Müller, Sandra, Durán, Sandra, Martins, Sebastião, Ochoa-Gaona, Susana, Rodríguez-Buritica, Susana, Aide, T, Bentos, Tony, de S Moreno, Vanessa, Granda, Vanessa, and Thomas, Wayt

Abstract

Forests that regrow naturally on abandoned fields are important for restoring biodiversity and ecosystem services, but can they also preserve the distinct regional tree floras? Using the floristic composition of 1215 early successional forests (≤20 years) in 75 human-modified landscapes across the Neotropic realm, we identified 14 distinct floristic groups, with a between-group dissimilarity of 0.97. Floristic groups were associated with location, bioregions, soil pH, temperature seasonality, and water availability. Hence, there is large continental-scale variation in the species composition of early successional forests, which is mainly associated with biogeographic and environmental factors but not with human disturbance indicators. This floristic distinctiveness is partially driven by regionally restricted species belonging to widespread genera. Early secondary forests contribute therefore to restoring and conserving the distinctiveness of bioregions across the Neotropical realm, and forest restoration initiatives should use local species to assure that these distinct floras are maintained.

Published
2022

4. Biodiversity recovery of Neotropical secondary forests.

Author

Rozendaal, Danaë MA, Bongers, Frans, Aide, T Mitchell, Alvarez-Dávila, Esteban, Ascarrunz, Nataly, Balvanera, Patricia, Becknell, Justin M, Bentos, Tony V, Brancalion, Pedro HS, Cabral, George AL, Calvo-Rodriguez, Sofia, Chave, Jerome, César, Ricardo G, Chazdon, Robin L, Condit, Richard, Dallinga, Jorn S, de Almeida-Cortez, Jarcilene S, de Jong, Ben, de Oliveira, Alexandre, Denslow, Julie S, Dent, Daisy H, DeWalt, Saara J, Dupuy, Juan Manuel, Durán, Sandra M, Dutrieux, Loïc P, Espírito-Santo, Mario M, Fandino, María C, Fernandes, G Wilson, Finegan, Bryan, García, Hernando, Gonzalez, Noel, Moser, Vanessa Granda, Hall, Jefferson S, Hernández-Stefanoni, José Luis, Hubbell, Stephen, Jakovac, Catarina C, Hernández, Alma Johanna, Junqueira, André B, Kennard, Deborah, Larpin, Denis, Letcher, Susan G, Licona, Juan-Carlos, Lebrija-Trejos, Edwin, Marín-Spiotta, Erika, Martínez-Ramos, Miguel, Massoca, Paulo ES, Meave, Jorge A, Mesquita, Rita CG, Mora, Francisco, Müller, Sandra C, Muñoz, Rodrigo, de Oliveira Neto, Silvio Nolasco, Norden, Natalia, Nunes, Yule RF, Ochoa-Gaona, Susana, Ortiz-Malavassi, Edgar, Ostertag, Rebecca, Peña-Claros, Marielos, Pérez-García, Eduardo A, Piotto, Daniel, Powers, Jennifer S, Aguilar-Cano, José, Rodriguez-Buritica, Susana, Rodríguez-Velázquez, Jorge, Romero-Romero, Marco Antonio, Ruíz, Jorge, Sanchez-Azofeifa, Arturo, de Almeida, Arlete Silva, Silver, Whendee L, Schwartz, Naomi B, Thomas, William Wayt, Toledo, Marisol, Uriarte, Maria, de Sá Sampaio, Everardo Valadares, van Breugel, Michiel, van der Wal, Hans, Martins, Sebastião Venâncio, Veloso, Maria DM, Vester, Hans FM, Vicentini, Alberto, Vieira, Ima CG, Villa, Pedro, Williamson, G Bruce, Zanini, Kátia J, Zimmerman, Jess, and Poorter, Lourens

Subjects
Conservation of Natural Resources, Ecosystem, Biodiversity, Tropical Climate, Geography, Forests
Abstract

Old-growth tropical forests harbor an immense diversity of tree species but are rapidly being cleared, while secondary forests that regrow on abandoned agricultural lands increase in extent. We assess how tree species richness and composition recover during secondary succession across gradients in environmental conditions and anthropogenic disturbance in an unprecedented multisite analysis for the Neotropics. Secondary forests recover remarkably fast in species richness but slowly in species composition. Secondary forests take a median time of five decades to recover the species richness of old-growth forest (80% recovery after 20 years) based on rarefaction analysis. Full recovery of species composition takes centuries (only 34% recovery after 20 years). A dual strategy that maintains both old-growth forests and species-rich secondary forests is therefore crucial for biodiversity conservation in human-modified tropical landscapes.

Published
2019

13. Wet and dry tropical forests show opposite successional pathways in wood density but converge over time

Author

Poorter, Lourens, Rozendaal, Danaë M. A., Bongers, Frans, de Almeida-Cortez, Jarcilene S., Almeyda Zambrano, Angélica María, Álvarez, Francisco S., Andrade, José Luís, Villa, Luis Felipe Arreola, Balvanera, Patricia, Becknell, Justin M., Bentos, Tony V., Bhaskar, Radika, Boukili, Vanessa, Brancalion, Pedro H. S., Broadbent, Eben N., César, Ricardo G., Chave, Jerome, Chazdon, Robin L., Colletta, Gabriel Dalla, Craven, Dylan, de Jong, Ben H. J., Denslow, Julie S., Dent, Daisy H., DeWalt, Saara J., García, Elisa Díaz, Dupuy, Juan Manuel, Durán, Sandra M., Espírito Santo, Mário M., Fandiño, María C., Fernandes, Geraldo Wilson, Finegan, Bryan, Moser, Vanessa Granda, Hall, Jefferson S., Hernández-Stefanoni, José Luis, Jakovac, Catarina C., Junqueira, André B., Kennard, Deborah, Lebrija-Trejos, Edwin, Letcher, Susan G., Lohbeck, Madelon, Lopez, Omar R., Marín-Spiotta, Erika, Martínez-Ramos, Miguel, Martins, Sebastião V., Massoca, Paulo E. S., Meave, Jorge A., Mesquita, Rita, Mora, Francisco, de Souza Moreno, Vanessa, Müller, Sandra C., Muñoz, Rodrigo, Muscarella, Robert, de Oliveira Neto, Silvio Nolasco, Nunes, Yule R. F., Ochoa-Gaona, Susana, Paz, Horacio, Peña-Claros, Marielos, Piotto, Daniel, Ruíz, Jorge, Sanaphre-Villanueva, Lucía, Sanchez-Azofeifa, Arturo, Schwartz, Naomi B., Steininger, Marc K., Thomas, William Wayt, Toledo, Marisol, Uriarte, Maria, Utrera, Luis P., van Breugel, Michiel, van der Sande, Masha T., van der Wal, Hans, Veloso, Maria D. M., Vester, Hans F. M., Vieira, Ima C. G., Villa, Pedro Manuel, Williamson, G. Bruce, Wright, S. Joseph, Zanini, Kátia J., Zimmerman, Jess K., and Westoby, Mark

Published
2019
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14. An Amazonian Forest and Its Fragments as a Laboratory of Global Change

Author

Laurance, William F., Camargo, José L. C., Fearnside, Philip M., Lovejoy, Thomas E., Williamson, G. Bruce, Mesquita, Rita C. G., Meyer, Christoph F. J., Bobrowiec, Paulo E. D., Laurance, Susan G. W., Caldwell, Martyn M., Series editor, Díaz, Sandra, Series editor, Heldmaier, Gerhard, Series editor, Jackson, Robert B., Series editor, Lange, Otto L., Series editor, Levia, Delphis F., Series editor, Mooney, Harold A., Series editor, Schulze, Ernst-Detlef, Series editor, Sommer, Ulrich, Series editor, Nagy, Laszlo, editor, Forsberg, Bruce R., editor, and Artaxo, Paulo, editor

Published
2016
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20. Australian Fire Danger Rating System Research Prototype: a climatology†.

Author

Sauvage, S., Fox-Hughes, P., Matthews, S., Kenny, B. J., Hollis, J. J., Grootemaat, S., Runcie, J. W., Holmes, A., Harris, R. M. B., Love, P. T., and Williamson, G.

Subjects
FIRE risk assessment, WILDFIRES, CLIMATE research, FIRE weather, PROTOTYPES
Abstract

Background: Historical records of fire weather phenomena provide valuable insights into spatial and temporal trends which can inform further research and are important tools for planning. Aims: We outline a 19-year climatology of a Research Prototype (AFDRSRP), of the new Australian Fire Danger Rating System, documenting its spatial and temporal characteristics. Methods: The analysis utilises the Australian Bureau of Meteorology's high-resolution reanalysis suite (BARRA), together with fuel data provided by Australian fire agencies. We examine the spatial and temporal distribution of the AFDRSRP. Distributions are categorised by fuel type, analysing relative variability across time and space. Key results: The results validate the broad behaviour of the new system and provide insight into the variation of fire danger throughout Australia, adding detail to the understanding of timing of peak fire danger both diurnally and annually. Conclusions: While the AFDRSRP differs from the operational system in its fire danger rating categories and tuning of algorithms, it nonetheless provides useful insights into the operational implementation. Implications: These results will be essential for planning during fire seasons. We present a 19-year climatology of the Australian Fire Danger Rating System: Research Prototype (AFDRSRP), recently implemented operationally throughout Australia. The climatology describes the typical spatial and temporal behaviour of the AFDRSRP. It is important for users to improve familiarity with the new system, and to ensure it performs as expected. This article belongs to the Collection Australian Fire Danger Rating System. [ABSTRACT FROM AUTHOR]

Published
2024
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28. Use of naturally occurring system disturbances to estimate the fault current contribution of induction motors

Author

Williamson, G. E.

Subjects
621.34
Abstract

The contribution of induction motor loads to short circuit currents can be significant and so must be considered when evaluating system fault levels. Standard procedures for calculating short circuit currents of induction motors require detailed machine data which may not be available. An algorithm has been developed to estimate the fault contribution of induction motor loads. The estimation technique is based on an analysis of load responses to naturally occurring disturbances. Neither disruptive staged tests or detailed information of the load or the network are required. The algorithm has been applied in practice by using the Fault Level Monitor, which records system disturbances. The fault infeed estimation algorithm has been examined using simulation studies and field tests. Results are presented which show good agreement between the values obtained from the algorithm and from conventional techniques.

Published
1995

29. The multiwavelength view of shocks in the fastest nova V1674 Her

Author

Sokolovsky, K V, primary, Johnson, T J, additional, Buson, S, additional, Jean, P, additional, Cheung, C C, additional, Mukai, K, additional, Chomiuk, L, additional, Aydi, E, additional, Molina, B, additional, Kawash, A, additional, Linford, J D, additional, Mioduszewski, A J, additional, Rupen, M P, additional, Sokoloski, J L, additional, Williams, M N, additional, Steinberg, E, additional, Vurm, I, additional, Metzger, B D, additional, Page, K L, additional, Orio, M, additional, Quimby, R M, additional, Shafter, A W, additional, Corbett, H, additional, Bolzoni, S, additional, DeYoung, J, additional, Menzies, K, additional, Romanov, F D, additional, Richmond, M, additional, Ulowetz, J, additional, Vanmunster, T, additional, Williamson, G, additional, Lane, D J, additional, Bartnik, M, additional, Bellaver, M, additional, Bruinsma, E, additional, Dugan, E, additional, Fedewa, J, additional, Gerhard, C, additional, Painter, S, additional, Peterson, D-M, additional, Rodriguez, J E, additional, Smith, C, additional, Sullivan, H, additional, and Watson, S, additional

Published
2023
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31. Demographic Drivers of Aboveground Biomass Dynamics During Secondary Succession in Neotropical Dry and Wet Forests

Author

Rozendaal, Danaë M. A., Chazdon, Robin L., Arreola-Villa, Felipe, Balvanera, Patricia, Bentos, Tony V., Dupuy, Juan M., Hernández-Stefanoni, J. Luis, Jakovac, Catarina C., Lebrija-Trejos, Edwin E., Lohbeck, Madelon, Martínez-Ramos, Miguel, Massoca, Paulo E. S., Meave, Jorge A., Mesquita, Rita C. G., Mora, Francisco, Pérez-García, Eduardo A., Romero-Pérez, I. Eunice, Saenz-Pedroza, Irving, van Breugel, Michiel, Williamson, G. Bruce, and Bongers, Frans

Published
2017
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32. Environmental gradients and the evolution of successional habitat specialization: a test case with 14 Neotropical forest sites

Author

Letcher, Susan G., Lasky, Jesse R., Chazdon, Robin L., Norden, Natalia, Wright, S. Joseph, Meave, Jorge A., Pérez-García, Eduardo A., Muñoz, Rodrigo, RomeroPérez, Eunice, Andrade, Ana, Andrade, José Luis, Balvanera, Patricia, Becknell, Justin M., Bentos, Tony V., Bhaskar, Radika, Bongers, Frans, Boukili, Vanessa, Brancalion, Pedro H. S., César, Ricardo G., Clark, Deborah A., Clark, David B., Craven, Dylan, DeFrancesco, Alexander, Dupuy, Juan M., Finegan, Bryan, GonzálezJiménez, Eugenio, Hall, Jefferson S., Harms, Kyle E., Hernández-Stefanoni, José Luis, Hietz, Peter, Kennard, Deborah, Killeen, Timothy J., Laurance, Susan G., LebrijaTrejos, Edwin E., Lohbeck, Madelon, Martínez-Ramos, Miguel, Massoca, Paulo E. S., Mesquita, Rita C. G., Mora, Francisco, Muscarella, Robert, Paz, Horacio, PinedaGarcía, Fernando, Powers, Jennifer S., Quesada-Monge, Ruperto, Rodrigues, Ricardo R., Sandor, Manette E., Sanaphre-Villanueva, Lucía, Schüller, Elisabeth, Swenson, Nathan G., Tauro, Alejandra, Uriarte, María, van Breugel, Michiel, VargasRamírez, Orlando, Viani, Ricardo A. G., Wendt, Amanda L., and Williamson, G. Bruce

Published
2015

38. Using Hierarchical Community Structure to Improve Community-Based Message Routing

Author

Stabeler, M., Lee, C., Williamson, G., and Padraig Cunningham

Abstract

Information about community structure can be useful in a variety of mobile web applications. For instance, it has been shown that community-based methods can be more effective than alternatives for routing messages in delay-tolerant networks. In this paper we present initial research that shows that information on hierarchical structures in communities can further improve the effectiveness of message routing. This is interesting because despite much previous work on the topic, there have been few concrete applications which exploit hierarchical community structure.

Published
2021
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41. Risk Factor Information Systems

Author

O’Carroll, Patrick W., Powell-Griner, Eve, Holtzman, Deborah, Williamson, G. David, Hannah, Kathryn J., editor, Ball, Marion J., editor, O’Carroll, Patrick W., editor, Ripp, Laura H., editor, Yasnoff, William A., editor, Ward, M. Elizabeth, editor, and Martin, Ernest L., editor

Published
2003
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43. Strong floristic distinctiveness across Neotropical successional forests

Author

Jakovac, Catarina C., Meave, Jorge A., Bongers, Frans, Letcher, Susan G., Dupuy, Juan Manuel, Piotto, Daniel, Rozendaal, Danaë M. A., Peña-Claros, Marielos, Craven, Dylan, Santos, Braulio A., Siminski, Alexandre, Fantini, Alfredo C., Rodrigues, Alice C., Hernández-Jaramillo, Alma, Idárraga, Alvaro, Junqueira, André B., Almeyda Zambrano, Angélica María, De Jong, Ben H.J., Ximenes Pinho, Bruno, Finegan, Bryan, Castellanos-Castro, Carolina, Zambiazi, Daisy Christiane, Dent, Daisy H., Hernán García, Daniel, Kennard, Deborah K., Delgado, Diego, Broadbent, Eben North, Ortiz-Malavasi, Edgar, Pérez-Garcia, Eudardo A., Lebrija-Trejos, Edwin, Berenguer, Erika, Marin-Spiotta, Erika, Álvarez-Dávila, Esteban, Valadares de Sá Barretto, Everardo, Melo, Felipe P.L., Elias, Fernando, França, Filipe, Oberleitner, Florian, Mora, Francisco, Williamson, G. Bruce, Dalla Colletta, Gabriel, Cabral, George A. L., Derroire, Géraldine, et al., Jakovac, Catarina C., Meave, Jorge A., Bongers, Frans, Letcher, Susan G., Dupuy, Juan Manuel, Piotto, Daniel, Rozendaal, Danaë M. A., Peña-Claros, Marielos, Craven, Dylan, Santos, Braulio A., Siminski, Alexandre, Fantini, Alfredo C., Rodrigues, Alice C., Hernández-Jaramillo, Alma, Idárraga, Alvaro, Junqueira, André B., Almeyda Zambrano, Angélica María, De Jong, Ben H.J., Ximenes Pinho, Bruno, Finegan, Bryan, Castellanos-Castro, Carolina, Zambiazi, Daisy Christiane, Dent, Daisy H., Hernán García, Daniel, Kennard, Deborah K., Delgado, Diego, Broadbent, Eben North, Ortiz-Malavasi, Edgar, Pérez-Garcia, Eudardo A., Lebrija-Trejos, Edwin, Berenguer, Erika, Marin-Spiotta, Erika, Álvarez-Dávila, Esteban, Valadares de Sá Barretto, Everardo, Melo, Felipe P.L., Elias, Fernando, França, Filipe, Oberleitner, Florian, Mora, Francisco, Williamson, G. Bruce, Dalla Colletta, Gabriel, Cabral, George A. L., Derroire, Géraldine, and et al.

Abstract

Forests that regrow naturally on abandoned fields are important for restoring biodiversity and ecosystem services, but can they also preserve the distinct regional tree floras? Using the floristic composition of 1215 early successional forests (≤20 years) in 75 human-modified landscapes across the Neotropic realm, we identified 14 distinct floristic groups, with a between-group dissimilarity of 0.97. Floristic groups were associated with location, bioregions, soil pH, temperature seasonality, and water availability. Hence, there is large continental-scale variation in the species composition of early successional forests, which is mainly associated with biogeographic and environmental factors but not with human disturbance indicators. This floristic distinctiveness is partially driven by regionally restricted species belonging to widespread genera. Early secondary forests contribute therefore to restoring and conserving the distinctiveness of bioregions across the Neotropical realm, and forest restoration initiatives should use local species to assure that these distinct floras are maintained.

Published
2022

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