Mónica Fass, Máximo Rivarola, Guillermo F. Ehrenbolger, C. A. Maringolo, Juan Francisco Montecchia, F. J. Quiroz, Francisco García‐García, Joaquín Dopazo Blázquez, H. Esteban Hopp, Ruth A. Heinz, Norma Paniego, V. V. Lia,
Abstract Sclerotinia head rot (SHR), caused by the necrotrophic fungus Sclerotinia sclerotiorum , is one of the most devastating sunflower crop diseases. Despite its worldwide occurrence, the genetic determinants of plant resistance are still largely unknown. Here, we investigated the Sclerotinia-sunflower pathosystem by analysing temporal changes in gene expression in one susceptible and two tolerant inbred lines (IL) inoculated with the pathogen under field conditions. Differential expression analysis ...
Tópico(s): Sunflower and Safflower Cultivation
2020 - Nature Portfolio | Scientific Reports
Juan M. Morales, María Daniela Rivarola, Guillermo C. Amico, Tomás A. Carlo,
The outcome of the dispersal process in zoochorous plants is largely determined by the behavior of frugivorous animals. Recent simulation studies have found that fruit removal rates and mean dispersal distances are strongly affected by fruiting plant neighborhoods. We empirically tested the effects of conspecific fruiting plant neighborhoods, crop sizes, and plant accessibility on fruit removal rates and seed dispersal distances of a mistletoe species exclusively dispersed by an arboreal marsupial ...
Tópico(s): Animal Ecology and Behavior Studies
2012 - Wiley | Ecology
Francisco E. Fontúrbel, Marcela Franco, Mariano A. Rodríguez‐Cabal, María Daniela Rivarola, Guillermo C. Amico,
Tópico(s): Wildlife Ecology and Conservation
2012 - Springer Science+Business Media | The Science of Nature
Felipe López Rivarola, Guillermo Etse, Paula Folino,
In this paper, the necessary and sufficient conditions for fulfilling the thermodynamic consistency of computational homogenization schemes in the framework of hierarchical multiscale theories are defined. The proposal is valid for arbitrary homogenization based multiscale procedures, including continuum and discontinuum methods in either scale. It is demonstrated that the well-known Hill–Mandel variational criterion for homogenization scheme is a necessary, but not a sufficient condition for the ...
Tópico(s): Nonlocal and gradient elasticity in micro/nano structures
2017 - American Society of Mechanical Engineers | Journal of Engineering Materials and Technology
Daniel van Huyssteen, Felipe López Rivarola, Guillermo Etse, Paul Steinmann,
The virtual element method is an extension of the finite element method permitting arbitrary polygonal/polyhedral element geometry. The method’s mesh flexibility is well-known and is beginning to be exploited in the context of mesh adaptivity. In this work a variety of novel approaches to the computation of isotropic and anisotropic mesh refinement indicators suited to the VEM are presented and comparatively assessed for the case of two-dimensional linear elasticity on structured meshes. Additionally, ...
Tópico(s): Computational Fluid Dynamics and Aerodynamics
2022 - Elsevier BV | Computer Methods in Applied Mechanics and Engineering
María Elisa Rivarola, Guillermo Albrieu-Llinás, María Belén Pisano, Laura B. Tauro, Melisa Gorosito-Serrán, Cristian G. Beccaría, Adrián Díaz, Ana Vázquez, Agustín I. E. Quaglia, C Enric López, Lorena Spinsanti, Adriana Gruppi, Marta Contigiani,
Saint Louis encephalitis virus (SLEV) reemerged in South America, and caused encephalitis outbreaks at the beginning of the 21st century. To enhance our knowledge about SLEV virulence, we performed comparative pathogenesis studies in Swiss albino mice inoculated with two different variants, the epidemic strain CbaAr-4005 and the non-epidemic strain CorAn-9275. Only the infection of mice with SLEV strain CbaAr-4005 resulted in high viremia, invasion of peripheral tissues including the lungs, kidney, ...
Tópico(s): Vector-borne infectious diseases
2017 - Elsevier BV | Virology
Agustina Balazote Oliver, Guillermo C. Amico, María Daniela Rivarola, Juan M. Morales,
Dromiciops gliroides is an arboreal marsupial endemic to the southern temperate forest located between 36°S and 43°S in both Chile and Argentina. This species is a key seed disperser of many native plants, including the keystone mistletoe, Tristerix corymbosus. We studied the population fluctuation of D. gliroides and the possible effects of natural disturbances on the population. We estimated density, abundance, survival, and recruitment ratios for 7 years (2009–2011 and 2013–2016) at Reserva Llao ...
Tópico(s): Species Distribution and Climate Change
2017 - Oxford University Press | Journal of Mammalogy
Paula Fernández, Marcelo Soria, David Blesa, Julio Dirienzo, Sebastián Moschen, Máximo Rivarola, Bernardo Clavijo, Sergio González, Lucila Peluffo, Darío Príncipi, Guillermo A. A. Dosio, Luis Aguirrezábal, Francisco García‐García, Ana Conesa, H. Esteban Hopp, Joaquı́n Dopazo, Ruth Amelia Heinz, Norma Paniego,
Oligonucleotide-based microarrays with accurate gene coverage represent a key strategy for transcriptional studies in orphan species such as sunflower, H. annuus L., which lacks full genome sequences. The goal of this study was the development and functional annotation of a comprehensive sunflower unigene collection and the design and validation of a custom sunflower oligonucleotide-based microarray. A large scale EST (>130,000 ESTs) curation, assembly and sequence annotation was performed using Blast2GO ( ...
Tópico(s): Soybean genetics and cultivation
2012 - Public Library of Science | PLoS ONE
Felipe López Rivarola, Nicolás A. Labanda, Guillermo Etse,
Tópico(s): Numerical methods in engineering
2019 - Birkhäuser | Zeitschrift für angewandte Mathematik und Physik
María Elisa Rivarola, Laura B. Tauro, Guillermo Albrieu-Llinás, Marta Contigiani,
Saint Louis encephalitis virus caused an outbreak of febrile illness and encephalitis cases in Córdoba, Argentina, in 2005. During this outbreak, the strain CbaAr-4005 was isolated from Culex quinquefasciatus mosquitoes. We hypothesised that this epidemic variant would be more virulent in a mouse model than two other non-epidemic strains (78V-6507 and CorAn-9275) isolated under different epidemiological conditions. To test this hypothesis, we performed a biological characterisation in a murine model, ...
Tópico(s): Malaria Research and Control
2014 - Instituto Oswaldo Cruz, Ministério da Saúde | Memórias do Instituto Oswaldo Cruz
Domingo M. Rivarola, Guillermo Heisecke,
Tópico(s): Regional Development and Innovation
1969 - Institute of Economic and Social Development | Desarrollo Económico
Fátima Cardozo, Brenda Konigheim, Guillermo Albrieu-Llinás, María Elisa Rivarola, Javier Aguilar, Alejandra Rojas, Agustín I. E. Quaglia, Malvina Páez, Yvalena Guillén, Adrián Díaz, María Asunción Vallejos, Lilian Herebia, María Lidia Recalde, Marta Contigiani, Laura Mendoza,
Alphaviruses can produce febrile illness and encephalitis in dead-end hosts such as horses and humans. Within this genus, the Venezuelan Equine Encephalitis virus (VEEV) complex includes pathogenic epizootic subtypes and enzootic subtypes that are not pathogenic in horses (except subtype IE, Mexican strains), although they can cause febrile symptoms in humans. The Rio Negro virus (RNV-VEEV subtype VI) circulates in Argentina, where it was associated with undifferentiated febrile illness. Mayaro (MAYV) ...
Tópico(s): Vector-Borne Animal Diseases
2018 - Mary Ann Liebert, Inc. | Vector-Borne and Zoonotic Diseases
Daniel van Huyssteen, Felipe López Rivarola, Guillermo Etse, Paul Steinmann,
Tópico(s): Electromagnetic Simulation and Numerical Methods
2023 - Elsevier BV | Computer Methods in Applied Mechanics and Engineering
Alisha Narjeel Morales Paredes, Diego Guillermo Rivarola Monzon, Mishell Romero Mansilla, Roberto Edir Cartagena Ochavano, Yuliana Meneses Espejo, A. Boza,
El principal objetivo de este trabajo de investigación fue llevar a cabo una revisión de la eficacia de los programas de ejercicios de fuerza y equilibrio en la prevención de caídas en adultos mayores. Para ello, se realizó un proceso de recolección principalmente de las bases de datos PubMed y Sciencedirect, seleccionando las revistas de mayor impacto. La muestra consiste de 29 artículos seleccionados teniendo en cuenta las siguientes variables: año de publicación, objetivos, muestra, instrumentos ...
Tópico(s): Health and Lifestyle Studies
2024 - FEADEF | Retos
María Elisa Rivarola, Soledad de Olmos, Guillermo Albrieu-Llinás, Laura B. Tauro, Melisa Gorosito-Serrán, Brenda Konigheim, Marta Contigiani, Adriana Gruppi,
Saint Louis encephalitis virus (SLEV) is a neglected flavivirus that causes severe neurological disorders. The epidemic strain of SLEV, CbaAr-4005, isolated during an outbreak in Córdoba city (Argentina), causes meningitis and encephalitis associated with neurological symptoms in a murine experimental model. Here, we identified the affected brain areas and the damage triggered by this neurotropic arbovirus. We performed a detailed analysis of brain neurodegeneration associated with CbaAr-4005 SLEV ...
Tópico(s): Neuroinflammation and Neurodegeneration Mechanisms
2018 - Frontiers Media | Frontiers in Microbiology
Felipe López Rivarola, Nicolás A. Labanda, Matías Fernando Benedetto, Guillermo Etse,
The use of multiscale schemes for computational failure evaluations of quasi-brittle composites, particularly concrete, has become a promising challenge for evaluating the complex degradation mechanisms at different scales of observations. In the framework of standard finite element procedures, both concurrent and semi-concurrent multiscale procedures have so far been considered for analysing failure behaviour of quasi-brittle materials. When it comes to composite materials like concrete with heterogeneous ...
Tópico(s): Rock Mechanics and Modeling
2020 - Elsevier BV | Computers & Structures
Felipe López Rivarola, Matías Fernando Benedetto, Nicolás A. Labanda, Guillermo Etse,
A semi-concurrent multi scale approach for heterogeneous media discretized with the Virtual Element Method (VEM) is presented in this work. Extensive numerical results for both the linear diffusion and linear elasticity settings are performed to assess the quality of the discrete solution, highlighting the differences between a mesoscopic and a multiscale approach. The capabilities and advantages of using VEM in semi-concurrent multiscale analyses are demonstrated, especially when dealing with composite ...
Tópico(s): Numerical methods in engineering
2019 - Elsevier BV | Finite Elements in Analysis and Design
Alfredo Bullard González, Domingo M. Rivarola, Guillermo Cabieses Crovetto, Freddy Escobar Rozas,
The current round table gathers four renowned specialists infields such as Law and Economics, Civil Law, Litigation, and others, inorder to discuss the relevance and impact of the development of behavioral psychology and neuroscience in Law. thus, the guests addressthe criticism directed from the mentioned study fields to the modelof individual rationality that underlies traditional legal institutions.
Tópico(s): Social Issues and Policies in Latin America
2014 - Asociación Civil IUS ET VERITAS | IUS ET VERITAS
Edgardo G. J. Rivarola, Guillermo Chantada, L. Ezcurdia, Alejandra Negro, Ernesto Gil Deza, D. Cascallar, Donna A. Santillan, S. Carnaval, Eduardo L. Morgenfeld, Felipe G. Gercovich,
8573 Background: There are no national protocols for the treatment of children with CNS tumors in Argentina, so patients receive individualized treatment at each center. The aim of this study was to evaluate, from an audit perspective, the treatment prescribed to children with CNS tumors belonging to a large health insurance organization in Argentina. Methods: The files of all patients with CNS tumors for whom their oncologists requested chemotherapy from 2000 to 2003 were retrieved. All patients ...
Tópico(s): Childhood Cancer Survivors' Quality of Life
2004 - Lippincott Williams & Wilkins | Journal of Clinical Oncology
Edgardo G. J. Rivarola, Guillermo Chantada, L. Ezcurdia, Alejandra Negro, Ernesto Gil Deza, D. Cascallar, Donna A. Santillan, S. Carnaval, Eduardo L. Morgenfeld, Felipe G. Gercovich,
8573 Background: There are no national protocols for the treatment of children with CNS tumors in Argentina, so patients receive individualized treatment at each center. The aim of this study was to evaluate, from an audit perspective, the treatment prescribed to children with CNS tumors belonging to a large health insurance organization in Argentina. Methods: The files of all patients with CNS tumors for whom their oncologists requested chemotherapy from 2000 to 2003 were retrieved. All patients ...
Tópico(s): Health Systems, Economic Evaluations, Quality of Life
2004 - Lippincott Williams & Wilkins | Journal of Clinical Oncology
Alejandro Jenik, Manuel Rocca Rivarola, Dra Grad, Dra Machado, Dra Norma, E Rossato, Manuel Rocca, Javier Meritano, Guillermo Colantonio, Rocca Rivarola, Grad Machado,
El contacto piel a piel al nacer (COPAP) entre madres y recién nacidos a término sanos es fundamental en los estándares de la Iniciativa Hospital Amigo de la Madre y el Niño de Unicef.El COPAP inmediatamente después del nacimiento favorece la estabilidad cardiorrespiratoria, la prevalencia y duración de la lactancia materna y el vínculo madrehijo, y disminuye el estrés materno.Existe preocupación por los casos de colapso súbito inesperado posnatal durante el COPAP con el bebé en decúbito prono sobre ...
Tópico(s): Infant Development and Preterm Care
2020 - Sociedad Argentina de Pediatría | Archivos Argentinos de Pediatria
Daniel van Huyssteen, Felipe López Rivarola, Guillermo Etse, Paul Steinmann,
Tópico(s): Computational Fluid Dynamics and Aerodynamics
2024 - Elsevier BV | Computer Methods in Applied Mechanics and Engineering
Martín Caloia, Enrique Pereira, Carlos María Autorino, Horacio E. Rivarola, Diego González Scotti, Guillermo Arce,
the use of Andrews and Carson Elbow scoring system.In all patients the score was recorded before the operation and at the time of final examination.In addition patients were asked to grade the result of treatment subjectively as poor, fair, good or very good.Statistic significance of the obtained results was determined by the Student t-test for the paired variables.Results: Average age of patients in the observed group was 39 years.In 19 cases the dominant arm was involved.Average follow-up time ...
Tópico(s): Shoulder Injury and Treatment
2012 - Elsevier BV | Arthroscopy The Journal of Arthroscopic and Related Surgery
Naomi Wright, Andrew Leather, Niyi Ade‐Ajayi, Nick Sevdalis, Justine Davies, Dan Poenaru, Emmanuel A. Ameh, Adesoji Ademuyiwa, Kokila Lakhoo, Emily R. Smith, Abdel Douiri, Maria Elstad, Marcus Sim, Cristiana Riboni, Bruno Martínez-Leo, Melika Akhbari, Stephen Tabiri, Ashrarur Rahman Mitul, Dayang Anita Abdul Aziz, Camila Girardi Fachin, Alliance Niyukuri, Muhammad Arshad, Fowzia Ibrahim, Natalie Moitt, Mohamed Fahmy Doheim, Hannah R. Thompson, Harmony Ubhi, Isabelle Williams, Sophia Hashim, Godfrey Sama Philipo, Laura Herrera, Aayenah Yunus, Dominique Vervoort, Samuel Parker, Yousra-Imane Benaskeur, Osaid Alser, Nana Adofo-Ansong, Ahmad Alhamid, Hosni Salem, Mahmoud Saleh, Safa Elrais, Sadi A. Abukhalaf, Patricia Shinondo, Ibrahim Nour, Emrah Aydın, Agota Vaitkienė, Kelly Naranjo, Andile Dube, Sodumisa Ngwenya, Mina A Yacoub, Henang Kwasau, Gabriella Hyman, S M.elghazaly, Ibrahim Al‐Slaibi, Intisar Hisham, Helena Franco, Hana Arbab, Lubna Samad, Aqil Soomro, Muhammad Amjad Chaudhry, Safina Karim, Muhammad Adnan Khattak, Shireen Anne Nah, Doris Mae Dimatatac, Candy S. C. Choo, Niveshni Maistry, Ashrarur Rahman Mitul, Samiul Hasan, Sabbir Karim, Hina Yousuf, Taimur Qureshi, Ibrahim Nour, Raed Al-Taher, Osama Abdul Kareem Sarhan, Luis García‐Aparicio, J. Prat, Eva Blázquez-Gómez, Xavier Tarrado, Martí Iriondo, P Bragagnini Rodríguez, Segundo Rite Gracia, Lars Hagander, Emma Svensson, Sheila Agyeiwaa Owusu, Alhassan Abdul‐Mumin, Dominic Bagbio, Vijay Anand Ismavel, Ann Miriam, T Shajin, Marlene Anaya Domínguez, Monica Ivanov, Andreea Mădălina Șerban, Miliard Derbew, Mahmoud Elfiky, Maricarmen Olivos Perez, Marcia Abrunhosa Matias, Alexis Arnaud, Ahmed Negida, Sebastian King, Mohamad Rafi Fazli, Nadia Hamidi, Souhem Touabti, Rossana Francisco Chipalavela, Pablo Lobos, Brendan C. Jones, Damir Ljuhar, Georg Singer, Samiul Hasan, Annelien Cordonnier, Lorena Jáuregui, Zlatan Zvizdić, Janice Siu Chong Wong, Etienne St‐Louis, Qiang Shu, Yang Lui, Catalina Correa, Lucie Poš, Elvyn Alcántara, Erick Féliz, Luis Zea-Salazar, Liza Ali, Matthieu Peycelon, Nzanzu Kipata Anatole, Cherno S. Jallow, Judith Lindert, Dhruva Ghosh, Cathline Freya Adhiwidjaja, Ahmad Khaleghnejad Tabari, Saran Lotfollahzadeh, Haidar Mohammad Mussein, Fabrizio Vatta, Noemi Pasqua, David Kihiko, Hetal Gohil, Ibrahim Nour, Muhammed Elhadi, Suad Ahmed Almada, Gilvydas Verkauskas, Toni Risteski, Alejandro Peñarrieta Daher, Oumaima Outani, James Hamill, Taiwo Lawal, Jack Mulu, Benjamin Yapo, Lily Saldaña, Beda Espineda, Krystian Toczewski, Eugène Tuyishime, Isaac Ndayishimiye, Enaam Raboe, Philip Hammond, Gregor Walker, Ivona Djordjević, Milind Chitnis, Joonhyuk Son, Sanghoon Lee, Muaad Hussien, Sawazen Malik, Enas Musa Ismail, Ampaipan Boonthai, Nesrine Ben Hadj Dahman, Nigel Hall, Fabiola Ruth Castedo Camacho, Helena Sobrero, Marilyn Butler, Aliev Makhmud, Nathan M. Novotny, Ahmad G Hammouri, Maisara Al-Rayyes, Bruce Bvulani, Qais Muraveji, Muhammad Yousuf Murzaie, Ajmal Sherzad, Sayed Aman Haidari, Abdul Baqi Monawar, Ahmad Zia Samadi, Jesh Thiessen, Ntakarutimana Venant, Sonia Inamuco Hospital, Niyonkuru Jérémie, Jean Claude Mbonicura, Butoyi Jean Marie Vianney, Amezene Tadesse, Samuel Negash, Charles A. Roberts, John N. Jabang, Abdoulie Bah, Kajali Camamra, Armandou Correa, Babucarr J. Sowe, Annalisa Gai, Musa Jaiteh, Kwizera Jean Raymond, Jean Paul Mvukiyehe, Innocent Itangishaka, Emmanuel Kayibanda, Emery Manirambona, Joseph Lule, Ainhoa Costas‐Chavarri, Ian Shyaka, Albert Ndata, Georges Gasana, Yves Nezerwa, T Simeon, Jean De Dieu Muragijimana, Sakina Rashid, David Msuya, Joseph Elisante, Meghna Solanki, Emmanuel Manjira, Jay Lodhia, Mubashir Jusabani, Murad Tarmohamed, Sengua Koipapi, Touabti Souhem, Nabti Sara, Brahimi Sihem, Bouguermouh Dania, Iaiche Achour Toufik, Baghdadi Nour el islam Mounira, Alouani Habiba, Liliana Aragão, Victor Gonçalves, Marcelo Mauricio Lino Urquizo, María Florencia Varela, Pedro Mercado, Bonavia Horacio, Andrea Damiani, Carlos Mac, Daniel Putruele, Karen Liljesthrom, Marianela Bernaus, Cesar Jauri, Alejandrina Cripovich, Ezequiel Bianchin, Maria Gabriela Puig, Lorna Andreussi, Susana Iracelay, Dolores Marcos, Carina Herrera, N. Palacios, Romina Avile, Belen Serezo, Debora Montoya, Rodrigo Cepeda, Justo Vaquila, Sofficci Veronica, Liliana Pardo‐López, Pelussi Valeria, Lapalma Julio, Aranda Diego Martin, Palazzi Lucio, Comba Gabriel, Depetrini Marianella, José Alfredo Calderón Arancibia, Enrique Huespe, Gabriela Natalia Losa, Elsa Arancibia Gutiérrez, Humberto Scherl, Daniel Emilio Gonzalez, Valentina Baistrocchi, Yanina Silva, Marcelo Galdeano, Pablo Medard, Ines Sueiras, E Romero Manteola, Victor Hugo Defago, Carlos Mieres, Carlos Alberto, Fabio Cornelli, M. Molina, Pablo Ravetta, Celeste Carolina Patiño Gonzalez, Maria Belen Dallegre, Maria Tatiana Szklarz, Marcos Federico Leyba, Nahuel Ignacio Rivarola, María D. Charras, Adriana Morales, Paloma Caseb, Luzía Toselli, Carolina Millán, Maria del Carmen Junes, Oscar Di Siervi, J Gilardi, Soledad Simon, Carla Sofia Contreras, Nair Rojas, Lucia Beatriz Arnoletto, Otilia Blain, Mauro Bravo, Nancy P. Sanchez, Luciana Martina Herrera Pesara, Maria Eugenia Moreno, Carlos Ariel Sferco,
BackgroundCongenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated ...
Elsevier BV
G. Chacón, Felipe López Rivarola, Daniel van Huyssteen, P. Steinmann, Guillermo Etse,
Tópico(s): Dam Engineering and Safety
2024 - Springer Science+Business Media | Computational Mechanics
Los estudios de G. Guitarte sobre la lengua de América eran bien conocidos en el ámbito de los especialistas. Publicados en revistas, en actas deeventos científicos y homenajes académicos, todos ellos constituyeron contribuciones sustanciales al conocimiento del español de América y de la filología hispanoamericana en torno a asuntos que han ocupado y ocupan un lugar preferencial en las reflexiones sobre nuestra realidad idiomática: la impronta andaluza en la formación de la variedad americana y ...
Tópico(s): Cultural and political discourse analysis
1986 - Pontifical Catholic University of Peru | Lexis
Adrian Hearn, Alejandro Diaz-Dominguez, Amurábi Oliveira, A. J. Turner, Angelina Carr A N T O N I O G E N I V A L D O Cordeiro De Oliveira, Bettina Schmidt, Brenda Carranza, Caique Bellato, Carlos Strapazzon, Celso Terzetti, Claudia Zilla, David Fernández, D Della Rocca, Rivarola Donizete, Raqueline Brito da Cruz, Eduardo Dullo, Elaine Prodócimo, Ely Torres, Emily Pierini, Enrico Hammes, Everton de Oliveira Maraldi, Fabián Fechner, Fábio Mendia, Fabio Py, Fábio L. Stern, Guillermo Wilde, Hannah J. Gould, Heinz-Juergen Loth, Inga Scharf Da Silva, Jeroen Dewulf, Joana Bahia, Júlio Cesar Goulart Fonseca, Karina Kosicki Bellotti, Keith Mcneal, Ken Chitwood, Klaus Baumann, Michele Martini, Oren Golan, Orivaldo Lopes, Paul Freston, Paulo Mattos, Paulo Barrera, R Andrew, Chesnut Rafael, Shoji Renan, William Dos Santos, Renata Siuda-Ambroziak, Roberto Garcés, Marrero Roberto, Mauro Cortéz, Motta Rodrigo, Coppe Caldeira, Roland Spliesgart, Ruth Melkonian-Hoover, Sílvia Fernandes, Tim Jensen,
2021 - Springer Science+Business Media | International Journal of Latin American Religions