5 results
The Permafrost Young Researchers Network (PYRN) is getting older: The past, present, and future of our evolving community
- Part of
- George Tanski, Helena Bergstedt, Alexandre Bevington, Philip Bonnaventure, Frédéric Bouchard, Caroline Coch, Simon Dumais, Alevtina Evgrafova, Oliver W. Frauenfeld, Jennifer Frederick, Michael Fritz, Denis Frolov, Silvie Harder, Ingo Hartmeyer, Joanne Heslop, Elin Högström, Margareta Johansson, Gleb Kraev, Elena Kuznetsova, Josefine Lenz, Alexey Lupachev, Florence Magnin, Jannik Martens, Alexey Maslakov, Anne Morgenstern, Alexandre Nieuwendam, Marc Oliva, Boris Radosavljevic, Justine Ramage, Andrea Schneider, Julia Stanilovskaya, Jens Strauss, Erin Trochim, Daniel J. Vecellio, Samuel Weber, Hugues Lantuit
-
- Journal:
- Polar Record / Volume 55 / Issue 4 / July 2019
- Published online by Cambridge University Press:
- 07 February 2019, pp. 216-219
-
- Article
- Export citation
-
A lasting legacy of the International Polar Year (IPY) 2007–2008 was the promotion of the Permafrost Young Researchers Network (PYRN), initially an IPY outreach and education activity by the International Permafrost Association (IPA). With the momentum of IPY, PYRN developed into a thriving network that still connects young permafrost scientists, engineers, and researchers from other disciplines. This research note summarises (1) PYRN’s development since 2005 and the IPY’s role, (2) the first 2015 PYRN census and survey results, and (3) PYRN’s future plans to improve international and interdisciplinary exchange between young researchers. The review concludes that PYRN is an established network within the polar research community that has continually developed since 2005. PYRN’s successful activities were largely fostered by IPY. With >200 of the 1200 registered members active and engaged, PYRN is capitalising on the availability of social media tools and rising to meet environmental challenges while maintaining its role as a successful network honouring the legacy of IPY.
Mean flow generation by an intermittently unstable boundary layer over a sloping wall
- Abouzar Ghasemi, Marten Klein, Andreas Will, Uwe Harlander
-
- Journal:
- Journal of Fluid Mechanics / Volume 853 / 25 October 2018
- Published online by Cambridge University Press:
- 22 August 2018, pp. 111-149
-
- Article
- Export citation
-
Direct numerical simulations (DNS) of the flow in various rotating annular confinements have been conducted to investigate the effects of wall inclination on secondary fluid motions due to an unstable boundary layer. The inner wall resembles a truncated cone (frustum) whose apex half-angle is varied from $18^{\circ }$ to $0^{\circ }$ (straight cylinder). The large inner radius $r_{1}$, the mean rotation rate $\unicode[STIX]{x1D6FA}_{0}$ and the kinematic viscosity $\unicode[STIX]{x1D708}$ were kept constant resulting in the constant Ekman number $E=\unicode[STIX]{x1D708}/(\unicode[STIX]{x1D6FA}_{0}r_{1}^{2})=4\times 10^{-5}$. Flows were excited by time-harmonic modulation of the inner wall’s rotation rate (so-called longitudinal libration) by prescribing the amplitude $\unicode[STIX]{x1D700}\unicode[STIX]{x1D6FA}_{0}$ and the forcing frequency $\unicode[STIX]{x1D714}=\unicode[STIX]{x1D6FA}_{0}$. By steepening the inner wall and hence reducing the effect of the local Coriolis force in the boundary layer three different flow regimes can be realized: a rotation-dominated, a libration-dominated and an intermediate regime. In the present study we focus on the libration-dominated regime. For small libration amplitudes (here $\unicode[STIX]{x1D700}=0.2$), a laminar Ekman–Stokes boundary layer (ESBL) is realized at the librating wall. With the aid of laminar boundary layer theory and DNS we show that the ESBL exhibits an oscillatory mass flux along the librating wall (Ekman property) and an oscillatory azimuthal velocity, which resembles a radially damped wave (Stokes property). For large libration amplitudes (here $\unicode[STIX]{x1D700}=0.8$), the DNS results exhibit an intermittently unstable ESBL, which turns centrifugally unstable during the prograde (faster) part of a libration period. This instability is due to the Stokes property and gives rise to Görtler vortices, which are found to be tilted with respect to the azimuth when the librating wall is at a finite angle relative to the axis of rotation. We show that this tilt is related to the Ekman property of the ESBL. This suggests that linear and nonlinear dynamics are equally important for this intermittent instability. Our DNS results indicate further that the Görtler vortices propagate into the fluid bulk where they generate an azimuthal mean flow. This mean flow is notably different from the mean flow driven in the case of the stable ESBL. A diagnostic analysis of the Reynolds-averaged Navier–Stokes (RANS) equations in the unstable flow regime hints at a competition between the radial and axial turbulent transport terms which act as generating and destructing agents for the azimuthal mean flow, respectively. We show that the balance of both terms depends on the wall inclination, that is, on the wall-tangential component of the Coriolis force.
Inertial wave excitation and focusing in a liquid bounded by a frustum and a cylinder
- Marten Klein, Torsten Seelig, Michael V. Kurgansky, Abouzar Ghasemi V., Ion Dan Borcia, Andreas Will, Eberhard Schaller, Christoph Egbers, Uwe Harlander
-
- Journal:
- Journal of Fluid Mechanics / Volume 751 / 25 July 2014
- Published online by Cambridge University Press:
- 18 June 2014, pp. 255-297
-
- Article
- Export citation
-
The mechanism of localized inertial wave excitation and its efficiency is investigated for an annular cavity rotating with $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\Omega _0$. Meridional symmetry is broken by replacing the inner cylinder with a truncated cone (frustum). Waves are excited by individual longitudinal libration of the walls. The geometry is non-separable and exhibits wave focusing and wave attractors. We investigated laboratory and numerical results for the Ekman number $E\approx 10^{-6}$, inclination $\alpha =5.71^\circ $ and libration amplitudes $\varepsilon \leq 0.2$ within the inertial wave band $0 < \omega < 2\Omega _0$. Under the assumption that the inertial waves do not essentially affect the boundary-layer structure, we use classical boundary-layer analysis to study oscillating Ekman layers over a librating wall that is at an angle $\alpha \neq 0$ to the axis of rotation. The Ekman layer erupts at frequency $\omega =f_{*}$, where $f_{*}\equiv 2 \Omega _0 \sin \alpha $ is the effective Coriolis parameter in a plane tangential to the wall. For the selected inclination this eruption occurs for the forcing frequency $\omega /\Omega _0=0.2$. For the librating lids eruption occurs at $\omega /\Omega _0=2$. The study reveals that the frequency dependence of the total kinetic energy $K_{\omega }$ of the excited wave field is strongly connected to the square of the Ekman pumping velocity $w_{{E}}(\omega )$ that, in the linear limit, becomes singular when the boundary layer erupts. This explains the frequency dependence of non-resonantly excited waves. By the localization of the forcing, the two configurations investigated, (i) frustum libration and (ii) lids together with outer cylinder in libration, can be clearly distinguished by their response spectra. Good agreement was found for the spatial structure of low-order wave attractors and periodic orbits (both characterized by a small number of reflections) in the frequency windows predicted by geometric ray tracing. For ‘resonant’ frequencies a significantly increased total bulk energy was found, while the energy in the boundary layer remained nearly constant. Inertial wave energy enters the bulk flow via corner beams, which are parallel to the characteristics of the underlying Poincaré problem. Numerical simulations revealed a mismatch between the wall-parallel mass fluxes near the corners. This leads to boundary-layer eruption and the generation of inertial waves in the corners.
Contributors
-
- By Zachary W. Adams, Margarita Alegría, Atalay Alem, Jordi Alonso, Victor Aparicio, Rifat Atun, Florence Baingana, Emily Baron, Marco Bertelli, Dinesh Bhugra, Sanchita Biswas, José Miguel Caldas de Almeida, Edwin Cameron, Somnath Chatterji, Erminia Colucci, Janice L. Cooper, Carla Kmett Danielson, Diego De Leo, Mary-Jo DelVecchio Good, Marten W. de Vries, Maureen S. Durkin, Xiangming Fang, Julia W. Felton, Sally Field, Andrea Fiorillo, Lance Gable, Teddy Gafna, Sandro Galea, Patrick Gatonga, Sofia Halperin-Goldstein, Yanling He, Grace A. Herbert, Sabrina Hermosilla, Simone Honikman, Takashi Izutsu, Ruwan M. Jayatunge, Janis H. Jenkins, Rachel Jenkins, Lynne Jones, Jayanthi Karunaratne, Ronald C. Kessler, Rob Keukens, Lincoln I. Khasakhala, Hanna Kienzler, Sarah Kippen Wood, M. Thomas Kishore, Robert Kohn, Natasja Koitzsch Jensen, Sheri Lapatin, Anna Lessios, Isabel Louro Bernal, Feijun Luo, Laura MacPherson, Matthew J. Maenner, Anne W. Mbwayo, David McDaid, Ingrid Meintjes, Victoria N. Mutiso, David M. Ndetei, Samuel O. Okpaku, Lijing Ouyang, Ramachandran Padmavati, Clare Pain, Duncan Pedersen, Jordan Pfau, Felipe Picon, Rodney D. Presley, Reima Pryor, Shoba Raja, Thara Rangaswamy, Jorge Rodriguez, Diana Rose, Moosa Salie, Norman Sartorius, Ester Shapiro, Manuela Silva, Daya Somasundaram, Katherine Sorsdahl, Dan J. Stein, Deborah M. Stone, Heather Stuart, Athula Sumathipala, Hema Tharoor, Rita Thom, Lay San Too, Atsuro Tsutsumi, Chris Underhill, Anne Valentine, Claire van der Westhuizen, Thandi van Heyningen, Robert van Voren, Inka Weissbecker, Gail Wyatt
- Edited by Samuel O. Okpaku
-
- Book:
- Essentials of Global Mental Health
- Published online:
- 05 March 2014
- Print publication:
- 27 February 2014, pp x-xiv
-
- Chapter
- Export citation
Risk of Rabies Infection and Adverse Effects of Postexposure Prophylaxis in Healthcare Workers and Other Patient Contacts Exposed to a Rabies Virus–Infected Lung Transplant Recipient
- Frauke Mattner, Cornelia Henke-Gendo, Andreas Martens, Christian Drosten, Thomas F. Schulz, Albert Heim, Sebastian Suerbaum, Sabine Kuhn, Juliane Bruderek, Petra Gastmeier, Martin Strueber
-
- Journal:
- Infection Control & Hospital Epidemiology / Volume 28 / Issue 5 / May 2007
- Published online by Cambridge University Press:
- 02 January 2015, pp. 513-518
- Print publication:
- May 2007
-
- Article
- Export citation
-
Background.
Rabies virus was inadvertently transmitted to a lung transplant recipient through donor lungs. The patient was given ventilatory assistance and cared for postoperatively for 6 weeks before a diagnosis of rabies virus infection was made. Postexposure prophylaxis (PEP) was offered to potentially exposed healthcare workers (HCWs).
Methods.Only HCWs classified as belonging to possible and/or proven contact groups (according to a standardized interview) received PEP. The risk of individual HCWs being exposed to rabies virus was reassessed on the basis of viral concentrations measured in the patient's excretions and body fluids. HCWs who were vaccinated as part of PEP were followed up prospectively according to a standardized procedure.
Results.Of 179 HCWs and other patient contacts, 132 met the eligibility criteria for PEP (118 [89.4%] with possible contact and 14 [10.6%] with proven contact with the patient's excretions and/or body fluids). One hundred thirty-one individuals started PEP, and 126 met the inclusion criteria for analysis. Of these, 48 (38%) developed at least 1 adverse effect (8 [6.3%] had fever, 37 [29.4%] had headache, 3 [2.4%] had lymphadenopathy, 17 [13.5%] had dizziness, and 6 [4.8%] had paresthesia). No HCW or other patient contact developed rabies or serious PEP-related adverse effects. Reassessment of the individual's risk of infection as a function of the viral concentration in the patient's excretions and/or body fluids (up to 5.12 × 107 copies/mL) revealed that 103 HCWs (78.0%) had contact with high-risk substances (89 [67.40%] had possible contact and 14 [10.7%] had proven contact).
Conclusion.HCWs can be exposed to significant viral concentrations in excretions and/or body fluids from rabies virus-infected lung transplant recipients. Because widespread use of PEP entails the possibility of significant health problems for HCWs considered to be at risk of contracting rabies, applying a rational indication for PEP is crucial.