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A novel subcritical transition to turbulence in Taylor–Couette flow with counter-rotating cylinders
- Christopher J. Crowley, Michael C. Krygier, Daniel Borrero-Echeverry, Roman O. Grigoriev, Michael F. Schatz
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- Journal:
- Journal of Fluid Mechanics / Volume 892 / 10 June 2020
- Published online by Cambridge University Press:
- 02 April 2020, A12
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The transition to turbulence in Taylor–Couette flow often occurs via a sequence of supercritical bifurcations to progressively more complex, yet stable, flows. We describe a subcritical laminar–turbulent transition in the counter-rotating regime mediated by a transient intermediate state in a system with an axial aspect ratio of $\unicode[STIX]{x1D6E4}=5.26$ and a radius ratio of $\unicode[STIX]{x1D702}=0.905$. In this regime, flow visualization experiments and numerical simulations indicate the intermediate state corresponds to an aperiodic flow featuring interpenetrating spirals. Furthermore, the reverse transition out of turbulence leads first to the same intermediate state, which is now stable, before returning to an azimuthally symmetric laminar flow. Time-resolved tomographic particle image velocimetry is used to characterize the experimental flows; these measurements compare favourably to direct numerical simulations with axial boundary conditions matching those of the experiments.
Mental health capacity building in refugee primary health care settings in Sub-Saharan Africa: impact, challenges and gaps
- C. Echeverri, J. Le Roy, B. Worku, P. Ventevogel
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- Journal:
- Global Mental Health / Volume 5 / 2018
- Published online by Cambridge University Press:
- 28 August 2018, e28
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- Article
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Background.
In 2015, the United Nations High Commissioner for Refugees started a process of mental health capacity building in refugee primary health care settings in seven countries in Sub-Saharan Africa, ultimately aiming to decrease the treatment gap of mental, neurological and substance use (MNS) conditions in these operations. In 2015 and 2016, a specialized non-governmental organization, the War Trauma Foundation, trained 619 staff with the mental health gap action programme (mhGAP) Humanitarian Intervention Guide (HIG), a tool designed to guide clinical decision making in humanitarian settings.
Methods.This paper describes the results of a process evaluation of a real-life implementation project by an external consultant, one and a half years after starting the programme.
Results.The mhGAP-HIG capacity building efforts had various effects contributing to the integration of mental health in refugee primary health care. Facility-and community-based staff reported strengthened capacities to deliver mental health and psychosocial support interventions as well as changes in their attitude towards people suffering from MNS conditions. Service delivery and collaboration amongst different intervention levels improved. The scarcity of specialized staff in these settings was a major barrier, hindering the setting-up of supervision mechanisms.
Conclusion.Mental health training of non-specialized staff in complex humanitarian settings is feasible and can lead to increased competency of providers. However, capacity building is a ‘process’ and not an ‘event’ and mhGAP trainings are only one element in a spectrum of activities aimed at integrating mental health into general health care. Regular supervision and continuing on-the-job training are in fact critical to ensure sustainability.
Summary for Policy Makers
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- By Thomas B. Johansson, Lund University, Nebojsa Nakicenovic, International Institute for Applied Systems Analysis and Vienna University of Technology, Anand Patwardhan, Indian Institute of Technology-Bombay), Luis Gomez-Echeverri, International Institute for Applied Systems Analysis, Rangan Banerjee, Indian Institute of Technology, Sally M. Benson, Stanford University, Daniel H. Bouille, Bariloche Foundation, Abeeku Brew-Hammond, Kwame Nkrumah University of Science and Technology, Aleh Cherp, Central European University, Suani T. Coelho, National Reference Center on Biomass, University of São Paulo, Lisa Emberson, Stockholm Environment Institute, University of York, Maria Josefina Figueroa, Technical University, Arnulf Grubler, International Institute for Applied Systems Analysis, Austria and Yale University, Kebin He, Tsinghua University, Mark Jaccard, Simon Fraser University, Suzana Kahn Ribeiro, Federal University of Rio de Janeiro, Stephen Karekezi, AFREPREN/FWD, Eric D. Larson, Princeton University and Climate Central, Zheng Li, Tsinghua University, Susan McDade, United Nations Development Programme), Lynn K. Mytelka, United Nations University-MERIT, Shonali Pachauri, International Institute for Applied Systems Analysis, Keywan Riahi, International Institute for Applied Systems Analysis, Johan Rockström, Stockholm Environment Institute, Stockholm University, Hans-Holger Rogner, International Atomic Energy Agency, Joyashree Roy, Jadavpur University, Robert N. Schock, World Energy Council, UK and Center for Global Security Research, Ralph Sims, Massey University, Kirk R. Smith, University of California, Wim C. Turkenburg, Utrecht University, Diana Ürge-Vorsatz, Central European University, Frank von Hippel, Princeton University, Kurt Yeager, Electric Power Research Institute and Galvin Electricity Initiative
- Global Energy Assessment Writing Team
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- Book:
- Global Energy Assessment
- Published online:
- 05 September 2012
- Print publication:
- 27 August 2012, pp 3-30
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Summary
Introduction
Energy is essential for human development and energy systems are a crucial entry point for addressing the most pressing global challenges of the 21st century, including sustainable economic and social development, poverty eradication, adequate food production and food security, health for all, climate protection, conservation of ecosystems, peace and security. Yet, more than a decade into the 21st century, current energy systems do not meet these challenges.
A major transformation is therefore required to address these challenges and to avoid potentially catastrophic future consequences for human and planetary systems. The Global Energy Assessment (GEA) demonstrates that energy system change is the key for addressing and resolving these challenges. The GEA identifies strategies that could help resolve the multiple challenges simultaneously and bring multiple benefits. Their successful implementation requires determined, sustained and immediate action.
Transformative change in the energy system may not be internally generated; due to institutional inertia, incumbency and lack of capacity and agility of existing organizations to respond effectively to changing conditions. In such situations clear and consistent external policy signals may be required to initiate and sustain the transformative change needed to meet the sustainability challenges of the 21st century.
The industrial revolution catapulted humanity onto an explosive development path, whereby, reliance on muscle power and traditional biomass was replaced mostly by fossil fuels. In 2005, some 78% of global energy was based on fossil energy sources that provided abundant and ever cheaper energy services to more than half the people in the world.
Technical Summary
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- By Thomas B. Johansson, Lund University, Nebojsa Nakicenovic, International Institute for Applied Systems Analysis and Vienna University of Technology, Anand Patwardhan, Indian Institute of Technology, Luis Gomez-Echeverri, International Institute for Applied Systems Analysis, Doug J. Arent, National Renewable Energy Laboratory, Rangan Banerjee, Indian Institute of Technology, Sally M. Benson, Stanford University, Daniel H. Bouille, Bariloche Foundation, Abeeku Brew-Hammond, Kwame Nkrumah University of Science and Technology, Aleh Cherp, Central European University, Suani T. Coelho, National Reference Center on Biomass, University of São Paulo, Lisa Emberson, Stockholm Environment Institute, University of York, Maria Josefina Figueroa, Technical University, Arnulf Grubler, International Institute for Applied Systems Analysis, Austria and Yale University, Kebin He, Tsinghua University, Mark Jaccard, Simon Fraser University, Suzana Kahn Ribeiro, Federal University of Rio de Janeiro, Stephen Karekezi, AFREPREN/FWD, Eric D. Larson, Princeton University and Climate Central, Zheng Li, Tsinghua University, Susan McDade, United Nations Development Programme, Lynn K. Mytelka, United Nations University-MERIT, Shonali Pachauri, International Institute for Applied Systems Analysis, Keywan Riahi, International Institute for Applied Systems Analysis, Johan Rockström, Stockholm Environment Institute, Stockholm University, Hans-Holger Rogner, International Atomic Energy Agency, Joyashree Roy, Jadavpur University, Robert N. Schock, World Energy Council, UK and Center for Global Security Research, Ralph Sims, Massey University, Kirk R. Smith, University of California, Wim C. Turkenburg, Utrecht University, Diana Ürge-Vorsatz, Central European University, Frank von Hippel, Princeton University, Kurt Yeager, Electric Power Research Institute and Galvin Electricity Initiative
- Global Energy Assessment Writing Team
-
- Book:
- Global Energy Assessment
- Published online:
- 05 September 2012
- Print publication:
- 27 August 2012, pp 31-94
-
- Chapter
- Export citation
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Summary
Introduction
Energy is essential for human development and energy systems are a crucial entry point for addressing the most pressing global challenges of the 21st century, including sustainable economic, and social development, poverty eradication, adequate food production and food security, health for all, climate protection, conservation of ecosystems, peace, and security. Yet, more than a decade into the 21st century, current energy systems do not meet these challenges.
In this context, two considerations are important. The first is the capacity and agility of the players within the energy system to seize opportunities in response to these challenges. The second is the response capacity of the energy system itself, as the investments are long-term and tend to follow standard financial patterns, mainly avoiding risks and price instabilities. This traditional approach does not embrace the transformation needed to respond properly to the economic, environmental, and social sustainability challenges of the 21st century.
A major transformation is required to address these challenges and to avoid potentially catastrophic consequences for human and planetary systems. The GEA identifies strategies that could help resolve the multiple challenges simultaneously and bring multiple benefits. Their successful implementation requires determined, sustained, and immediate action.
The industrial revolution catapulted humanity onto an explosive development path, whereby reliance on muscle power and traditional biomass was replaced mostly by fossil fuels. In 2005, approximately 78% of global energy was based on fossil energy sources that provided abundant and ever cheaper energy services to more than half the world's population.