Valeria E Rac

Affiliations

Toronto Health Economics and Technology Assessment Collaborative, Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario, Canada.
Institute for Health Policy, Management, and Evaluation, University of Toronto, Toronto, Ontario, Canada.
Peter Munk Cardiac Centre, University Health Network, Toronto, Ontario, Canada.
Ted Rogers Centre for Heart Research, Toronto, Ontario, Canada.

Publications (33)

Trends in the Use of Cardiac Imaging for Patients With Heart Failure in Canada.

JAMA network open

Avec: Juarez R Braga , Howard Leong-Poi , Valeria E Rac , Peter C Austin , Heather J Ross , Douglas S Lee

Experiences and Perceptions of Patients and Providers Participating in Remote Titration of Heart Failure Medication Facilitated by Telemonitoring: Qualitative Study.

JMIR cardio

Avec: Veronica Artanian , Patrick Ware , Valeria E Rac , Heather J Ross , Emily Seto

Differences in demographics and outcomes based on method of consent for a randomised controlled trial on heat loss prevention in the delivery room.

Archives of disease in childhood. Fetal and neonatal edition

Avec: Sunita Vohra , Maureen Reilly , Valeria E Rac , Zafira Bhaloo , Denise Zayak , John Wimmer , Michael Vincer , Karla Ferrelli , Alex Kiss , Roger Soll , Michael Dunn

Understanding factors critical to the implementation of ehealth in chronic disease management: a realist review protocol.

BMJ open

Avec: Nida Shahid , Valeria E Rac , Joanna Bielecki , Whitney Berta

Inter-individual relationships within a Canadian SPOR research network: a social network study.

BMC health services research

Avec: Justin Lawarée , James M Bowen , Joyce Dogba , Valeria E Rac , Mathieu Ouimet

The Effect of Using a Remote Patient Management Platform in Optimizing Guideline-Directed Medical Therapy in Heart Failure Patients: A Randomized Controlled Trial.

JACC. Heart failure

Avec: Darshan H Brahmbhatt , Heather J Ross , Mary O'Sullivan , Veronica Artanian , Brigitte Mueller , Kyle Runeckles , Chun-Po Steve Fan , Valeria E Rac , Emily Seto , Auteur inconnu

Gender differences in the provision of key post-arrest interventions for out-of-hospital cardiac arrest (OHCA) patients-protocol for a systematic review.

Systematic reviews

Avec: Morgan Slater , Victoria M Sparrow-Downes , Precilla Veigas , Joanna M Bielecki , Valeria E Rac

SIESTA - Home sleep study with BresoDx for obstructive sleep apnea: a randomized controlled trial.

Sleep medicine

Avec: Michael Fitzpatrick , Valeria E Rac , Nicholas Mitsakakis , Lusine Abrahamyan , Petros Pechlivanoglou , Suzanne Chung , Steven M Carcone , Ba' Pham , Tetyana Kendzerska , Merrick Zwarenstein , Raymond Gottschalk , Charles George , Alia Kashgari , Murray Krahn

A 2020 Environmental Scan of Heart Failure Clinics in Ontario.

CJC open

Avec: Lakshmi Kugathasan , Troy Francis , Valeria E Rac , Harindra C Wijeysundera , Michael McDonald , Heather J Ross , Ana Carolina Alba

Raising the bar for patient experience during care transitions in Canada: A repeated cross-sectional survey evaluating a patient-oriented discharge summary at Ontario hospitals.

PloS one

Avec: Karen Okrainec , Audrey Chaput , Valeria E Rac , George Tomlinson , John Matelski , Mark Robson , Amy Troup , Murray Krahn , Shoshana Hahn-Goldberg

Support for health care workers and psychological distress: thinking about now and beyond the COVID-19 pandemic.

Health promotion and chronic disease prevention in Canada : research, policy and practice

Avec: Rima Styra , Laura Hawryluck , Allison McGeer , Michelle Dimas , Eileen Lam , Peter Giacobbe , Gianni Lorello , Neil Dattani , Jack Sheen , Valeria E Rac , Troy Francis , Peter E Wu , Wing-Si Luk , Jeya Nadarajah , Wayne L Gold

Mortality in patients with cardiogenic shock supported with VA ECMO: A systematic review and meta-analysis evaluating the impact of etiology on 29,289 patients.

The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation

Avec: Ana C Alba , Farid Foroutan , Tayler A Buchan , Juglans Alvarez , Aisling Kinsella , Kathryn Clark , Alice Zhu , Kimberley Lau , Caroline McGuinty , Natasha Aleksova , Troy Francis , Aleksandra Stanimirovic , Julie Vishram-Nielsen , Abdullah Malik , Heather J Ross , Eddy Fan , Valeria E Rac , Vivek Rao , Filio Billia

Gender-Based Differences in Outcomes Among Resuscitated Patients With Out-of-Hospital Cardiac Arrest.

Circulation

Avec: Purav Mody , Ambarish Pandey , Arthur S Slutsky , Matthew W Segar , Alex Kiss , Paul Dorian , Janet Parsons , Damon C Scales , Valeria E Rac , Sheldon Cheskes , Arlene S Bierman , Beth L Abramson , Sara Gray , Rob A Fowler , Katie N Dainty , Ahamed H Idris , Laurie Morrison

Digital Applications Targeting Medication Safety in Ambulatory High-Risk CKD Patients: Randomized Controlled Clinical Trial.

Clinical journal of the American Society of Nephrology : CJASN

Avec: Stephanie W Ong , Sarbjit V Jassal , Eveline C Porter , Kyoyoon K Min , Akib Uddin , Joseph A Cafazzo , Valeria E Rac , George Tomlinson , Alexander G Logan

Parallel Exploratory RCT of Polyethylene Wrap for Heat Loss Prevention in Infants Born at Less than 24 Weeks' Gestation.

Neonatology

Avec: Maureen C Reilly , Sunita Vohra , Valeria E Rac , Denise Zayack , John Wimmer , Michael Vincer , Karla Ferrelli , Alex Kiss , Roger F Soll , Michael Dunn

Automated digital counselling with social network support as a novel intervention for patients with heart failure: protocol for randomised controlled trial.

BMJ open

Avec: Rachel Grace Peiris , Heather Ross , Christopher T Chan , Stephanie Poon , Bourne Lewis Auguste , Valeria E Rac , Michael Farkouh , Michael McDonald , Janusz Kaczorowski , Jillianne Code , Juan Duero Posada , Stephanie Ong , Jeremy Kobulnik , George Tomlinson , Ella Huszti , JoAnne Arcand , Scott G Thomas , Ayub Akbari , Robert Maunder , Steven Grover , Emily Seto , Anne Simard , Brad Pope , Marc Bains , Carmen McIntyre , Chris Torbay , Fatima Syed , Robert P Nolan

Text message-based intervention, Keeping in Touch (KiT), to support youth as they transition to adult type 1 diabetes care: a protocol for a multisite randomised controlled superiority trial.

BMJ open

Avec: Geetha Sanmugalingham , Elise Mok , Joseph A Cafazzo , Laura Desveaux , Anne-Sophie Brazeau , Gillian L Booth , Marley Greenberg , Jessica Kichler , Valeria E Rac , Peter Austin , Ellen Goldbloom , Mélanie Henderson , Alanna Landry , Ian Zenlea , Madison Taylor , Meranda Nakhla , Rayzel Shulman

Understanding how and why upskilling programmes for unregulated care providers can support health equity in underserved communities: a realist review protocol.

BMJ open

Avec: Samah Hassan , Valeria E Rac , Brian David Hodges , Patti Leake , Saul Cobbing , Catharine Marie Gray , Nicola Bartley , Andrea Etherington , Munira Abdulwasi , Hei-Ching Kristy Cheung , Melanie Anderson , Nicole N Woods

Shared Decision-making in Head and Neck Surgery: A Review.

JAMA otolaryngology-- head & neck surgery

Avec: David Forner , Christopher W Noel , Andrew G Shuman , Paul Hong , Martin Corsten , Valeria E Rac , Arwen H Pieterse , David Goldstein

Tele-retina screening of diabetic retinopathy among at-risk populations: an economic analysis.

Canadian journal of ophthalmology. Journal canadien d'ophtalmologie

Avec: Aleksandra Stanimirovic , Troy Francis , Nida Shahid , Olivera Sutakovic , Rebecca Merritt , Michael H Brent , Valeria E Rac

Needs assessment for a decision support tool in oral cancer requiring major resection and reconstruction: a mixed-methods study protocol.

BMJ open

Avec: David Forner , Paul Hong , Martin Corsten , Valeria E Rac , Rosemary Martino , Andrew G Shuman , Douglas B Chepeha , Anna M Sawka , John R de Almeida , Jonathan C Irish , Dale H Brown , S Mark Taylor , Patrick J Gullane , Jonathan R Trites , Ralph Gilbert , Matthew H Rigby , Jolie Ringash , David Goldstein

Describing the state of a research network: A mixed methods approach to network evaluation.

Research Evaluation

Avec: James M Bowen , Mathieu Ouimet , Justin Lawarée , Joanna Bielecki , Ashley Rhéaume , Caylee Greenberg , Valeria E Rac

A scoping review reveals candidate quality indicators of knowledge translation and implementation science practice tools.

Journal of clinical epidemiology

Avec: Aunima R Bhuiya , Justin Sutherland , Rhonda Boateng , Téjia Bain , Becky Skidmore , Laure Perrier , Julie Makarski , Sarah Munce , Iveta Lewis , Ian D Graham , Jayna Holroyd-Leduc , Sharon E Straus , Henry T Stelfox , Lisa Strifler , Cynthia Lokker , Linda C Li , Fok-Han Leung , Maureen Dobbins , Lisa M Puchalski Ritchie , Janet E Squires , Valeria E Rac , Christine Fahim , Monika Kastner

Lifestyle approaches to hypertension for prevention of stroke and vascular cognitive impairment: a realist review protocol.

BMJ open

Avec: Sarah Ibrahim , Joanna Bielecki , Emine Kocabas , Sanjula Singh , Jasper R Senff , Leanne K Casaubon , Jonathan Rosand , Valeria E Rac , Aleksandra Pikula

Shared Decision Making for Surgical Care in the Era of COVID-19.

Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery

Avec: David Forner , Christopher W Noel , Ryan Densmore , David P Goldstein , Martin Corsten , Arwen H Pieterse , Andrew G Shuman , Paul Hong , Valeria E Rac

How Procurement Judges The Value of Medical Technologies: A Review of Healthcare Tenders.

International journal of technology assessment in health care

Avec: Fiona A Miller , Pascale Lehoux , Stuart Peacock , Valeria E Rac , Jeff Neukomm , Carolyn Barg , Jessica P Bytautas , Murray Krahn

Comparative effectiveness of the different components of care provided in heart failure clinics-protocol for a systematic review and network meta-analysis.

Systematic reviews

Avec: Morgan Slater , Joanna Bielecki , Ana Carolina Alba , Lusine Abrahamyan , George Tomlinson , Susanna Mak , Jane MacIver , Shelley Zieroth , Douglas Lee , William Wong , Murray Krahn , Heather Ross , Valeria E Rac

Surviving SARS and living through COVID-19: Healthcare worker mental health outcomes and insights for coping.

PloS one

Avec: Rima Styra , Laura Hawryluck , Allison Mc Geer , Michelle Dimas , Jack Sheen , Peter Giacobbe , Neil Dattani , Gianni Lorello , Valeria E Rac , Troy Francis , Peter E Wu , Wing-Si Luk , Enoch Ng , Jeya Nadarajah , Kaila Wingrove , Wayne L Gold

Impact of Remote Titration Combined With Telemonitoring on the Optimization of Guideline-Directed Medical Therapy for Patients With Heart Failure: Internal Pilot of a Randomized Controlled Trial.

JMIR cardio

Avec: Veronica Artanian , Heather J Ross , Valeria E Rac , Mary O'Sullivan , Darshan H Brahmbhatt , Emily Seto

Modes of coordination for health technology adoption: Health Technology Assessment agencies and Group Procurement Organizations in a polycentric regulatory regime.

Social science & medicine (1982)

Avec: Fiona A Miller , Pascale Lehoux , Valeria E Rac , Jessica P Bytautas , Murray Krahn , Stuart Peacock

Impact of Remote Titration Combined With Telemonitoring on the Optimization of Guideline-Directed Medical Therapy for Patients With Heart Failure: Protocol for a Randomized Controlled Trial.

JMIR research protocols

Avec: Veronica Artanian , Valeria E Rac , Heather J Ross , Emily Seto

Model for ASsessing the value of Artificial Intelligence in medical imaging (MAS-AI).

International journal of technology assessment in health care

Avec: Iben Fasterholdt , Tue Kjølhede , Mohammad Naghavi-Behzad , Thomas Schmidt , Quinnie T S Rautalammi , Malene G Hildebrandt , Anne Gerdes , Astrid Barkler , Kristian Kidholm , Valeria E Rac , Benjamin S B Rasmussen

Community consensus on core open science practices to monitor in biomedicine.

PLoS biology

Avec: Kelly D Cobey , Stefanie Haustein , Jamie Brehaut , Ulrich Dirnagl , Delwen L Franzen , Lars G Hemkens , Justin Presseau , Nico Riedel , Daniel Strech , Juan Pablo Alperin , Rodrigo Costas , Emily S Sena , Thed van Leeuwen , Clare L Ardern , Isabel O L Bacellar , Nancy Camack , Marcos Britto Correa , Roberto Buccione , Maximiliano Sergio Cenci , Dean A Fergusson , Cassandra Gould van Praag , Michael M Hoffman , Renata Moraes Bielemann , Ugo Moschini , Mauro Paschetta , Valentina Pasquale , Valeria E Rac , Dylan Roskams-Edris , Hermann M Schatzl , Jo Anne Stratton , David Moher

Réseau de co-auteurs

Heather J Ross 7 collaborations

Emily Seto 5 collaborations

Murray Krahn 5 collaborations

Troy Francis 5 collaborations

Veronica Artanian 4 collaborations

Joanna Bielecki 4 collaborations

George Tomlinson 4 collaborations

Alex Kiss 3 collaborations

David Forner 3 collaborations

Andrew G Shuman 3 collaborations

Paul Hong 3 collaborations

Martin Corsten 3 collaborations

Sunita Vohra 2 collaborations

John Wimmer 2 collaborations

Michael Vincer 2 collaborations

Karla Ferrelli 2 collaborations

Michael Dunn 2 collaborations

Nida Shahid 2 collaborations

Justin Lawarée 2 collaborations

James M Bowen 2 collaborations

Mathieu Ouimet 2 collaborations

Darshan H Brahmbhatt 2 collaborations

Mary O'Sullivan 2 collaborations

Morgan Slater 2 collaborations

Lusine Abrahamyan 2 collaborations

Michael McDonald 2 collaborations

Ana Carolina Alba 2 collaborations

Rima Styra 2 collaborations

Laura Hawryluck 2 collaborations

Michelle Dimas 2 collaborations

Peter Giacobbe 2 collaborations

Gianni Lorello 2 collaborations

Neil Dattani 2 collaborations

Jack Sheen 2 collaborations

Peter E Wu 2 collaborations

Wing-Si Luk 2 collaborations

Jeya Nadarajah 2 collaborations

Wayne L Gold 2 collaborations

Aleksandra Stanimirovic 2 collaborations

Joseph A Cafazzo 2 collaborations

Heather Ross 2 collaborations

Christopher W Noel 2 collaborations

Arwen H Pieterse 2 collaborations

David Goldstein 2 collaborations

Fiona A Miller 2 collaborations

Pascale Lehoux 2 collaborations

Stuart Peacock 2 collaborations

Jessica P Bytautas 2 collaborations

Juarez R Braga 1 collaboration

Howard Leong-Poi 1 collaboration

Peter C Austin 1 collaboration

Douglas S Lee 1 collaboration

Patrick Ware 1 collaboration

Maureen Reilly 1 collaboration

Zafira Bhaloo 1 collaboration

Denise Zayak 1 collaboration

Roger Soll 1 collaboration

Whitney Berta 1 collaboration

Joyce Dogba 1 collaboration

Brigitte Mueller 1 collaboration

Kyle Runeckles 1 collaboration

Chun-Po Steve Fan 1 collaboration

None None 1 collaboration

Victoria M Sparrow-Downes 1 collaboration

Precilla Veigas 1 collaboration

Joanna M Bielecki 1 collaboration

Michael Fitzpatrick 1 collaboration

Nicholas Mitsakakis 1 collaboration

Petros Pechlivanoglou 1 collaboration

Suzanne Chung 1 collaboration

Steven M Carcone 1 collaboration

Ba' Pham 1 collaboration

Tetyana Kendzerska 1 collaboration

Merrick Zwarenstein 1 collaboration

Raymond Gottschalk 1 collaboration

Charles George 1 collaboration

Alia Kashgari 1 collaboration

Lakshmi Kugathasan 1 collaboration

Harindra C Wijeysundera 1 collaboration

Karen Okrainec 1 collaboration

Audrey Chaput 1 collaboration

John Matelski 1 collaboration

Mark Robson 1 collaboration

Amy Troup 1 collaboration

Shoshana Hahn-Goldberg 1 collaboration

Allison McGeer 1 collaboration

Eileen Lam 1 collaboration

Ana C Alba 1 collaboration

Farid Foroutan 1 collaboration

Tayler A Buchan 1 collaboration

Juglans Alvarez 1 collaboration

Aisling Kinsella 1 collaboration

Kathryn Clark 1 collaboration

Alice Zhu 1 collaboration

Kimberley Lau 1 collaboration

Caroline McGuinty 1 collaboration

Natasha Aleksova 1 collaboration

Julie Vishram-Nielsen 1 collaboration

Abdullah Malik 1 collaboration

Eddy Fan 1 collaboration

Vivek Rao 1 collaboration

Filio Billia 1 collaboration

Purav Mody 1 collaboration

Ambarish Pandey 1 collaboration

Arthur S Slutsky 1 collaboration

Matthew W Segar 1 collaboration

Paul Dorian 1 collaboration

Janet Parsons 1 collaboration

Damon C Scales 1 collaboration

Sheldon Cheskes 1 collaboration

Arlene S Bierman 1 collaboration

Beth L Abramson 1 collaboration

Sara Gray 1 collaboration

Rob A Fowler 1 collaboration

Katie N Dainty 1 collaboration

Ahamed H Idris 1 collaboration

Laurie Morrison 1 collaboration

Stephanie W Ong 1 collaboration

Sarbjit V Jassal 1 collaboration

Eveline C Porter 1 collaboration

Kyoyoon K Min 1 collaboration

Akib Uddin 1 collaboration

Alexander G Logan 1 collaboration

Maureen C Reilly 1 collaboration

Denise Zayack 1 collaboration

Roger F Soll 1 collaboration

Rachel Grace Peiris 1 collaboration

Christopher T Chan 1 collaboration

Stephanie Poon 1 collaboration

Bourne Lewis Auguste 1 collaboration

Michael Farkouh 1 collaboration

Janusz Kaczorowski 1 collaboration

Jillianne Code 1 collaboration

Juan Duero Posada 1 collaboration

Stephanie Ong 1 collaboration

Jeremy Kobulnik 1 collaboration

Ella Huszti 1 collaboration

JoAnne Arcand 1 collaboration

Scott G Thomas 1 collaboration

Ayub Akbari 1 collaboration

Robert Maunder 1 collaboration

Steven Grover 1 collaboration

Anne Simard 1 collaboration

Brad Pope 1 collaboration

Marc Bains 1 collaboration

Carmen McIntyre 1 collaboration

Chris Torbay 1 collaboration

Fatima Syed 1 collaboration

Robert P Nolan 1 collaboration

Geetha Sanmugalingham 1 collaboration

Elise Mok 1 collaboration

Laura Desveaux 1 collaboration

Anne-Sophie Brazeau 1 collaboration

Gillian L Booth 1 collaboration

Marley Greenberg 1 collaboration

Jessica Kichler 1 collaboration

Peter Austin 1 collaboration

Ellen Goldbloom 1 collaboration

Mélanie Henderson 1 collaboration

Alanna Landry 1 collaboration

Ian Zenlea 1 collaboration

Madison Taylor 1 collaboration

Meranda Nakhla 1 collaboration

Rayzel Shulman 1 collaboration

Samah Hassan 1 collaboration

Brian David Hodges 1 collaboration

Patti Leake 1 collaboration

Saul Cobbing 1 collaboration

Catharine Marie Gray 1 collaboration

Nicola Bartley 1 collaboration

Andrea Etherington 1 collaboration

Munira Abdulwasi 1 collaboration

Hei-Ching Kristy Cheung 1 collaboration

Melanie Anderson 1 collaboration

Nicole N Woods 1 collaboration

Olivera Sutakovic 1 collaboration

Rebecca Merritt 1 collaboration

Michael H Brent 1 collaboration

Rosemary Martino 1 collaboration

Douglas B Chepeha 1 collaboration

Anna M Sawka 1 collaboration

John R de Almeida 1 collaboration

Jonathan C Irish 1 collaboration

Dale H Brown 1 collaboration

S Mark Taylor 1 collaboration

Patrick J Gullane 1 collaboration

Jonathan R Trites 1 collaboration

Ralph Gilbert 1 collaboration

Matthew H Rigby 1 collaboration

Jolie Ringash 1 collaboration

Ashley Rhéaume 1 collaboration

Caylee Greenberg 1 collaboration

Aunima R Bhuiya 1 collaboration

Justin Sutherland 1 collaboration

Rhonda Boateng 1 collaboration

Téjia Bain 1 collaboration

Becky Skidmore 1 collaboration

Laure Perrier 1 collaboration

Julie Makarski 1 collaboration

Sarah Munce 1 collaboration

Iveta Lewis 1 collaboration

Ian D Graham 1 collaboration

Jayna Holroyd-Leduc 1 collaboration

Sharon E Straus 1 collaboration

Henry T Stelfox 1 collaboration

Lisa Strifler 1 collaboration

Cynthia Lokker 1 collaboration

Linda C Li 1 collaboration

Fok-Han Leung 1 collaboration

Maureen Dobbins 1 collaboration

Lisa M Puchalski Ritchie 1 collaboration

Janet E Squires 1 collaboration

Christine Fahim 1 collaboration

Monika Kastner 1 collaboration

Sarah Ibrahim 1 collaboration

Emine Kocabas 1 collaboration

Sanjula Singh 1 collaboration

Jasper R Senff 1 collaboration

Leanne K Casaubon 1 collaboration

Jonathan Rosand 1 collaboration

Aleksandra Pikula 1 collaboration

Ryan Densmore 1 collaboration

David P Goldstein 1 collaboration

Jeff Neukomm 1 collaboration

Carolyn Barg 1 collaboration

Susanna Mak 1 collaboration

Jane MacIver 1 collaboration

Shelley Zieroth 1 collaboration

Douglas Lee 1 collaboration

William Wong 1 collaboration

Allison Mc Geer 1 collaboration

Enoch Ng 1 collaboration

Kaila Wingrove 1 collaboration

Iben Fasterholdt 1 collaboration

Tue Kjølhede 1 collaboration

Mohammad Naghavi-Behzad 1 collaboration

Thomas Schmidt 1 collaboration

Quinnie T S Rautalammi 1 collaboration

Malene G Hildebrandt 1 collaboration

Anne Gerdes 1 collaboration

Astrid Barkler 1 collaboration

Kristian Kidholm 1 collaboration

Benjamin S B Rasmussen 1 collaboration

Kelly D Cobey 1 collaboration

Stefanie Haustein 1 collaboration

Jamie Brehaut 1 collaboration

Ulrich Dirnagl 1 collaboration

Delwen L Franzen 1 collaboration

Lars G Hemkens 1 collaboration

Justin Presseau 1 collaboration

Nico Riedel 1 collaboration

Daniel Strech 1 collaboration

Juan Pablo Alperin 1 collaboration

Rodrigo Costas 1 collaboration

Emily S Sena 1 collaboration

Thed van Leeuwen 1 collaboration

Clare L Ardern 1 collaboration

Isabel O L Bacellar 1 collaboration

Nancy Camack 1 collaboration

Marcos Britto Correa 1 collaboration

Roberto Buccione 1 collaboration

Maximiliano Sergio Cenci 1 collaboration

Dean A Fergusson 1 collaboration

Cassandra Gould van Praag 1 collaboration

Michael M Hoffman 1 collaboration

Renata Moraes Bielemann 1 collaboration

Ugo Moschini 1 collaboration

Mauro Paschetta 1 collaboration

Valentina Pasquale 1 collaboration

Dylan Roskams-Edris 1 collaboration

Hermann M Schatzl 1 collaboration

Jo Anne Stratton 1 collaboration

David Moher 1 collaboration