Mitral annulus is dilated with preserved function in acromegaly regardless of its activity: Insights from the three-dimensional speckle-tracking echocardiographic MAGYAR-Path Study
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): Attila Nemes, Árpád Kormányos, Péter Domsik, Anita Kalapos, Csaba Lengyel, Nóra Ambrus, Zsuzsanna Valkusz (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

Mitral annular function in acromegaly: Still a lot to learn
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): Liliana Marta (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

Paravalvular leak closure: Still a challenge with unpredictable results
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): Ana Galrinho, Luísa M. Branco, António Fiarresga, Duarte Cacela, Lídia Sousa, Ruben Ramos, Rui C. Ferreira (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

Imaging techniques: Paving the way for paravalvular leak closure
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): Ana Pardo Sanz, José Luis Zamorano (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

Dexmedetomidine attenuates H2O2-induced apoptosis of rat cardiomyocytes independently of antioxidant enzyme expression
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): Xiaojian Weng, Wenjiao Shi, Xiaodan Zhang, Jianer Du (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

A novel cardioprotective strategy targeting mitochondrial reactive oxygen species production independent of antioxidant activity
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): Henrique Girão, Tania Martins-Marques (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

Influence of left ventricular systolic function on the long-term benefit of beta-blockers after ST-segment elevation myocardial infarction
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): Jesús Velásquez-Rodríguez, Vanesa Bruña, Lourdes Vicent, Felipe Díez-Delhoyo, María Jesús Valero-Masa, Iago Sousa-Casasnovas, Miriam Juárez, Carolina Devesa, Francisco Fernández-Avilés, Manuel Martínez-Sellés (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

Beta-blocker therapy after myocardial infarction or acute coronary syndrome: What we don’t know
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): José Ilídio Moreira (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

Current status of the treatment of degenerative mitral valve regurgitation
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): Gonçalo F. Coutinho, Manuel J. Antunes (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

An abnormal electrocardiogram in a hypothermic man
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): Paulo M. Araújo, Alzira Nunes, Sofia Torres, Carlos X. Resende, Pedro G. Diogo, Manuel Campelo, Maria J. Maciel (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

Heart retransplantation combined with kidney transplantation: A first in Portugal
Publication date: April 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 4Author(s): Bruno M.L. Rocha, Catarina Brízido, Gonçalo J.L. Cunha, Christopher Strong, Sara Ranchordas, António Tralhão, Diogo Santos, André Weigert, Carlos M.T. Aguiar, Miguel Sousa-Uva, Miguel Abecasis, Domingos Machado, António Martinho, Miguel Mendes, José P. Neves (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 16, 2021 Category: Cardiology Source Type: research

Left ventricular reverse remodeling and function by strain analysis in aortic stenosis: A CMR analysis of the EPICHEART study
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Diana Azevedo, Jennifer Mancio, Guilherme Pessoa-Amorim, David Monteiro, Nuno Almeida, Ricardo Ladeiras-Lopes, Rita Faria, Nuno Ferreira, Luís Vouga, Vasco Gama Ribeiro, Adelino Leite-Moreira, Nuno Bettencourt (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

Usefulness of advanced cardiovascular imaging in aortic valve replacement. Ready for prime time?
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Luís M. Moura (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

On-site percutaneous coronary intervention: Does it matter when treating patients with acute coronary syndromes?
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): José Ferreira Santos (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

Protein kinase D participates in cardiomyocyte hypertrophy by regulating extracellular signal-regulated and myocyte enhancer factor 2D
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Haitao Yuan, Qian Xiang, Le Yang, Jing Geng (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

Angiotensin II-induced cardiomyocyte hypertrophy: A complex response dependent on intertwined pathways
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Marta Consegal, Laura Valls-Lacalle, Antonio Rodríguez-Sinovas (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

The burden of infective endocarditis in Portugal in the last 30 years – a systematic review of observational studies
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Catarina de Sousa, Ruy M. Ribeiro, Fausto J. Pinto (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

Infective endocarditis in Portugal: Changing epidemiology but still a deadly disease
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Gilbert Habib (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

Impact of the creation of specialized units for patients with hypertrophic cardiomyopathy
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Martín Negreira-Caamaño, Jesús Piqueras-Flores, Inmaculada Vivo-Ortega, María Arántzazu-González-Marín, Manuel Muñoz-García, Alberto Jiménez-Lozano (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

Lipoprotein(a) in familial hypercholesterolemia: Tips from family history
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Beatrice Dal Pino, Francesco Sbrana, Michele Coceani, Federico Bigazzi, Tiziana Sampietro (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

Effectiveness of preoperative breathing exercise interventions in patients undergoing cardiac surgery: A systematic review
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Soraia Nicola Rodrigues, Helga Rafael Henriques, Maria Adriana Henriques (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

Exertional chest pain is sometimes more than just coronary atherosclerosis
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): G.J. Morgado, A.C. Gomes, I.R. Cruz, S. Carmona, P. Fazendas, I. João, A.I. Santos, L.R. Lopes, H. Pereira (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

Embolization of a left atrial appendage closure device
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Alzira Nunes, Diana Pissarra, Marta Tavares Silva, Pedro Bernardo Almeida, João Carlos Silva, Maria Júlia Maciel (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

de Winter pattern: Is it always so typical?
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Kenan Yalta, Ertan Yetkın, Gokay Taylan (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

The fall in acute coronary syndrome admissions during the COVID-19 Portuguese lockdown
Publication date: March 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 3Author(s): Daniel Candeias Faria, Miguel Borges Santos, Pedro Farto e Abreu (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 9, 2021 Category: Cardiology Source Type: research

Non‐pharmacological treatment of refractory angina: The coronary sinus reducer, the new kid on the block
Publication date: Available online 6 April 2021Source: Revista Portuguesa de Cardiologia (English Edition)Author(s): Sérgio Madeira, Catarina Brízido, Luís Raposo, João Brito, Nélson Vale, Sílvio Leal, Pedro de Araújo Gonçalves, Henrique Mesquita Gabriel, Rui Campante Teles, Manuel Almeida (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - April 7, 2021 Category: Cardiology Source Type: research

Comparative clinical performance of two types of drug-eluting stents with abluminal biodegradable polymer coating: Five-year results of the DESTINY randomized trial
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Guy F.A. Prado Jr, Alexandre A.C. Abizaid, George C. Meireles, Rogério Sarmento-Leite, Mauricio Prudente, Marcelo Cantarelli, Adriano D. Dourado, Jose Mariani Jr, Marco A. Perin, Costantino Costantini, Ricardo Costa, J. Ribamar Costa, Daniel Chamie, Carlos M. Campos, Expedito E. Ribeiro, Pedro A. Lemos (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

The third generation of drug-eluting stents: Reassuring data while we wait for the next one
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Sergio Bravo Baptista (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

Five years of Stent for Life in Portugal
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Hélder Pereira, Rita Calé, Ernesto Pereira, Sofia Mello, Sílvia Vitorino, Pedro Jerónimo de Sousa, Sílvia Monteiro, Fausto J. Pinto, Raquel Ramos, Pedro Coelho dos Santos, João Ferreira, João Silveira, João Morais, on behalf of the centers participating in the 'Stent for Life' Initiative Portugal (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

Convergent initiatives to change the current situation
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Rui Cruz Ferreira (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

Long-term outcomes after radiofrequency catheter ablation of the atrioventricular node: The experience of a Portuguese tertiary center
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Ana Mosalina Manuel, João Almeida, Paulo Fonseca, Joel Monteiro, Cláudio Guerreiro, Ana Raquel Barbosa, Pedro Teixeira, José Ribeiro, Elisabeth Santos, Filipa Rosas, José Ribeiro, Adelaide Dias, Daniel Caeiro, Olga Sousa, Madalena Teixeira, Marco Oliveira, Helena Gonçalves, João Primo, Pedro Braga (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

Pace and ablate: The ultimate treatment for atrial fibrillation?
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Pedro Carmo (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

Patient and caregiver productivity loss and indirect costs associated with cardiovascular events in Portugal
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Nuno Marques, Laetitia Gerlier, Mafalda Ramos, Helder Pereira, Sérgia Rocha, Ana Catarina Fonseca, Ana André, Ricardo Melo, Eduard Sidelnikov (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

Indirect costs associated with cardiovascular events in Portugal
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Miguel Gouveia (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

Portuguese electrophysiology: Consistent development
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Francisco Bello Morgado (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

A preliminary identification of PIN1 SNP linkage in patients with coronary heart disease from Handan, China
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Jing-Zhang Wang, Yu-Hua Zhang, Jing Bai, Wen-Tao Du, Xiang-Yang Zhang (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

Left ventricular pacing with a temporary pacemaker: Case report
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Marta Tavares-Silva, Carla de Sousa, Vítor Araújo, Luís Adão, Gonçalo Pestana, Roberto Pinto, Filipe Macedo, Maria Júlia Maciel (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

Late challenges after full plastic jacket in spontaneous coronary dissection
Publication date: February 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 2Author(s): Patrícia Marques-Alves, Manuel Oliveira-Santos, João Silva Marques, Lino Gonçalves (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 20, 2021 Category: Cardiology Source Type: research

Endocarditis due to Trichosporon beigelii 11 years after mitral valve replacement
Publication date: Available online 9 March 2021Source: Revista Portuguesa de Cardiologia (English Edition)Author(s): Renata Couto, Gustavo Couto, Ingrid Abrahão, Inaê Compagnoni, Tatiane Carnio, Julio Tolentino (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 9, 2021 Category: Cardiology Source Type: research

On the left side: The importance of the narrative of the heart for a better understanding of medicine
Publication date: Available online 6 March 2021Source: Revista Portuguesa de Cardiologia (English Edition)Author(s): Francisco Rosário (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - March 7, 2021 Category: Cardiology Source Type: research

Open letter to our reviewers: Justice is needed!
Publication date: January 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 1Author(s): Helena Donato, Nuno Cardim (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - February 24, 2021 Category: Cardiology Source Type: research

Quadricuspid aortic valve with a hidden left ostium: Case report and literature review
Publication date: January 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 1Author(s): Filipe R. Soares, Carlos Branco, Gonçalo F. Coutinho, David Prieto, Manuel J. Antunes (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - February 24, 2021 Category: Cardiology Source Type: research

ST-elevation acute coronary syndrome without obstructive coronary disease in a COVID-19 patient
Publication date: January 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 1Author(s): Tânia Proença, Mariana Paiva, Ricardo Alves Pinto, Miguel Martins Carvalho, Ricardo Lopes, Filipe Macedo (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - February 24, 2021 Category: Cardiology Source Type: research

Basal type ‘broken heart’ in a postpartum woman: Utility of speckle tracking echocardiography
Publication date: January 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 1Author(s): Nikolaos Miaris, Nearchos Kasinos, Archontoula Michelongona, Afroditi Konstantara, Dimitrios Barmpagiannis, Antonios Destounis, Panagiotis Zachos, Evangelia Nyktari, Anastasios Theodosis-Georgilas, Dimitrios Beldekos, Evangelos Pisimisis (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - February 24, 2021 Category: Cardiology Source Type: research

Relationships between paroxysmal atrial fibrillation, total oxidant status, and DNA damage
Publication date: January 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 1Author(s): Mustafa Begenc Tascanov, Zulkif Tanriverdi, Fatih Gungoren, Feyzullah Besli, Muslihittin Emre Erkus, İbrahim Halil Altiparmak, Ataman Gonel, Ismail Koyuncu, Recep Demirbag (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - February 24, 2021 Category: Cardiology Source Type: research

Oxidative stress and atrial fibrillation – association or causation?
Publication date: January 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 1Author(s): Francisco Moscoso Costa, Fu Siong Ng (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - February 24, 2021 Category: Cardiology Source Type: research

Cardiac rehabilitation in older patients: Indication or limitation?
Publication date: January 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 1Author(s): Marta Braga, Helena Nascimento, Roberto Pinto, Paulo Araújo, Alzira Nunes, Joana Rodrigues, Vítor Araújo, Fernando Parada-Pereira, Maria Júlia Maciel, Afonso Rocha (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - February 24, 2021 Category: Cardiology Source Type: research

Coronary artery calcium scoring and cardiovascular risk reclassification in patients undergoing coronary computed tomography angiography
Publication date: January 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 1Author(s): Daniel Matos, António Miguel Ferreira, Pedro de Araújo Gonçalves, Francisco Gama, Pedro Freitas, Sara Guerreiro, Gonçalo Cardoso, António Tralhão, Hélder Dores, João Abecasis, Hugo Marques, Carla Saraiva, Miguel Mendes (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - February 24, 2021 Category: Cardiology Source Type: research

Prime time for coronary calcium scoring: It should come, but will it?
Publication date: January 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 1Author(s): Nuno Bettencourt (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - February 24, 2021 Category: Cardiology Source Type: research

Brugada syndrome: Eligibility for subcutaneous implantable cardioverter-defibrillator after exercise stress test
Publication date: January 2021Source: Revista Portuguesa de Cardiologia (English Edition), Volume 40, Issue 1Author(s): Pedro von Hafe, Bebiana Faria, Geraldo Dias, Filipa Cardoso, Maria José Alves, Assunção Alves, Bernardete Rodrigues, Sílvia Ribeiro, Víctor Sanfins, António Lourenço (Source: Revista Portuguesa de Cardiologia)
Source: Revista Portuguesa de Cardiologia - February 24, 2021 Category: Cardiology Source Type: research