2019
Matthias Noack, Erich Focht, Thomas Steinke	Heterogeneous Active Messages for Offloading on the NEC SX-Aurora TSUBASA	2019 IEEE International Parallel and Distributed Processing Symposium Workshops (IPDPSW), Heterogeneity in Computing Workshop (HCW 2019), 2019 (in press)	BibTeX
2018
Matthias Noack, Alexander Reinefeld, Tobias Kramer, Thomas Steinke	DM-HEOM: A Portable and Scalable Solver-Framework for the Hierarchical Equations of Motion	2018 IEEE International Parallel and Distributed Processing Symposium Workshops (IPDPSW), 19th IEEE Int. Workshop on Parallel and Distributed Scientific and Engineering Computing (PDSEC 2018), pp. 947-956, 2018, isbn: 978-1-5386-5555-9	BibTeX DOI
Florian Wende, Martijn Marsman, Jeongnim Kim, Fedor Vasilev, Zhengji Zhao, Thomas Steinke	OpenMP in VASP: Threading and SIMD	International Journal of Quantum Chemistry, p. e25851, 2018 (in press)	BibTeX DOI
2017
Matthias Noack, Florian Wende, Georg Zitzlsberger, Michael Klemm, Thomas Steinke	KART - A Runtime Compilation Library for Improving HPC Application Performance	High Performance Computing: ISC High Performance 2017 International Workshops, DRBSD, ExaComm, HCPM, HPC-IODC, IWOPH, IXPUG, P^3MA, VHPC, Visualization at Scale, WOPSSS, Frankfurt, Germany, June 18-22, 2017, Revised Selected Papers, Springer International Publishing, pp. 389-403, 2017 (preprint available as ZIB-Report 16-48)	PDF (ZIB-Report) BibTeX DOI
Helge Knoop, Tobias Gronemeier, Matthias Sühring, Peter Steinbach, Matthias Noack, Florian Wende, Thomas Steinke, Christoph Knigge, Siegfried Raasch, Klaus Ketelsen	Porting the MPI-parallelized LES model PALM to multi-GPU systems and many integrated core processors: an experience report	International Journal of Computational Science and Engineering. Special Issue on: Novel Strategies for Programming Accelerators, 2017 (accepted for publication on 2017-04-29)	BibTeX
2016
Robert Schmidtke, Guido Laubender, Thomas Steinke	Big Data Analytics on Cray XC Series DataWarp using Hadoop, Spark and Flink	CUG Proceedings, 2016	PDF BibTeX
C. Weinhold, A. Lackorzynski, J. Bierbaum, M. Küttler, M. Planeta, H. Härtig, A. Shiloh, E. Levy, T. Ben-Nun, A. Barak, T. Steinke, T. Schütt, J. Fajerski, A. Reinefeld, M. Lieber, W. E. Nagel	FFMK: A Fast and Fault-tolerant Microkernel-based System for Exascale Computing	SPPEXA Symposium 2016, 2016	BibTeX DOI
J. Fajerski, M. Noack, A. Reinefeld, F. Schintke, T. Schütt, T. Steinke	Fast In-Memory Checkpointing with POSIX API for Legacy Exascale-Applications	SPPEXA Symposium 2016, 2016	BibTeX DOI
Florian Wende, Martijn Marsman, Thomas Steinke	On Enhancing 3D-FFT Performance in VASP	CUG Proceedings, 2016	PDF BibTeX
Florian Wende, Matthias Noack, Thomas Steinke, Michael Klemm, Georg Zitzlsberger, Chris J. Newburn	*Portable SIMD Performance with OpenMP 4.x Compiler Directives**	Pierre-Francois Dutot, Denis Trystram (Eds.), Vol.Euro-Par 2016: Parallel Processing: 22nd International Conference on Parallel and Distributed Computing, LNCS, 2016, isbn: 978-3-319-43659-3	BibTeX DOI
2015
Florian Wende, Matthias Noack, Thorsten Schütt, Stephen Sachs, Thomas Steinke	Application Performance on a Cray XC30 Evaluation System with Xeon Phi Coprocessors at HLRN-III	Cray User Group, 2015	BibTeX
Wolfgang Baumann, Guido Laubender, Matthias Läuter, Alexander Reinefeld, Christian Schimmel, Thomas Steinke, Christian Tuma, Stefan Wollny	HLRN-III at Zuse Institute Berlin	Contemporary High Performance Computing: From Petascale toward Exascale, Volume Two, Jeffrey S. Vetter (Ed.), Chapman and Hall/CRC, pp. 81-114, 2015, isbn: 9781498700627	BibTeX
Florian Wende, Thomas Steinke, Alexander Reinefeld	The Impact of Process Placement and Oversubscription on Application Performance: A Case Study for Exascale Computing	Proceedings of the 3rd International Conference on Exascale Applications and Software, EASC 2015, A. Gray, L. Smith, M. Weiland (Eds.), pp. 13-18, 2015, isbn: 978 -0-9 926615 -1-9 (preprint available as ZIB-Report 15-05)	PDF PDF (ZIB-Report) BibTeX
2014
Matthias Noack, Florian Wende, Thomas Steinke, Frank Cordes	A Unified Programming Model for Intra- and Inter-Node Offloading on Xeon Phi Clusters	SC '14: Proceedings of the International Conference on High Performance Computing, Networking, Storage and Analysis. SC14, November 16-21, 2014, New Orleans, Louisiana, USA, 2014	BibTeX DOI
Sebastian Dreßler, Thomas Steinke	An Automated Approach for Estimating the Memory Footprint of Non-linear Data Objects	Euro-Par 2013: Parallel Processing Workshops, pp. 249-258, Vol.8374, Lecture Notes in Computer Science, 2014 (preprint available as ZIB-Report 13-46)	PDF (ZIB-Report) BibTeX DOI
Florian Wende, Frank Cordes, Thomas Steinke	Concurrent Kernel Execution on Xeon Phi within Parallel Heterogeneous Workloads	Euro-Par 2014: Parallel Processing. 20th International Conference, Porto, Portugal, August 25-29, 2014, Proceedings, pp. 788-799, Vol.8632, Lecture Notes in Computer Science, 2014	BibTeX DOI
Florian Wende, Thomas Steinke, Michael Klemm, Alexander Reinefeld	Concurrent Kernel Offloading	High Performance Parallelism Pearls, James Reinders, Jim Jeffers (Eds.), Morgan Kaufman, Elsevier, 2014, isbn: 978-0128021187 (in press)	BibTeX
Florian Wende, Guido Laubender, Thomas Steinke	Integration of Intel Xeon Phi Servers into the HLRN-III Complex: Experiences, Performance and Lessons Learned	CUG2014 Proceedings, 2014 (preprint available as ZIB-Report 14-15)	PDF PDF (ZIB-Report) BibTeX
Florian Wende, Thomas Steinke, Frank Cordes	Multi-threaded Kernel Offloading to GPGPU Using Hyper-Q on Kepler Architecture	ZIB-Report 14-19	PDF BibTeX URN
Jens Krüger, Richard Grunzke, Sandra Gesing, Sebastian Breuers, André Brinkmann, Luis de la Garza, Oliver Kohlbacher, Martin Kruse, Wolfgang E. Nagel, Lars Packschies, Ralph Müller-Pfefferkorn, Patrick Schäfer, Charlotta Schärfe, Thomas Steinke, Tobias Schlemmer, Klaus Dieter Warzecha, Andreas Zink, Sonja Herres-Pawlis	The MoSGrid Science Gateway - A Complete Solution for Molecular Simulations	Journal of Chemical Theory and Computation, 10(6), pp. 2232-2245, 2014	BibTeX DOI
2013
Sebastian Dreßler, Thomas Steinke	Automated Analysis of Complex Data Objects	28th International Supercomputing Conference, ISC 2013, Leipzig, Germany, June 16-20, 2013, 2013	BibTeX
	Special issue of the Journal of Parallel and Distributed Computing (JDPC) on novel architectures for high-performance computing	Journal of Parallel and Distributed Computing, 73(11), pp. 1415-1416, Simon McIntosh-Smith, Charles Gillan, Nico Sanna, Stan Scott, Thomas Steinke (Eds.), 2013	BibTeX DOI
Richard Grunzke, Sebastian Breuers, Sandra Gesing, Sonja Herres-Pawlis, Martin Kruse, Dirk Blunk, Luis de la Garza, Lars Packschies, Patrick Schäfer, Charlotta Schärfe, Tobias Schlemmer, Thomas Steinke, Bernd Schuller, Ralph Müller-Pfefferkorn, René Jäkel, Wolfgang Nagel, Malcolm Atkinson, Jens Krüger	Standards-based metadata management for molecular simulations	Concurrency and Computation: Practice and Experience, 2013	BibTeX DOI
Florian Wende, Thomas Steinke	Swendsen-Wang Multi-Cluster Algorithm for the 2D/3D Ising Model on Xeon Phi and GPU	Proceeding SC '13 Proceedings of SC13: International Conference for High Performance Computing, Networking, Storage and Analysis Article No. 83 ACM New York, NY, USA, 2013, 2013 (preprint available as ZIB-Report 13-44)	PDF (ZIB-Report) BibTeX DOI
2012
Richard Grunzke, Georg Birkenheuer, Dirk Blunk, Sebastian Breuers, André Brinkmann, Sandra Gesing, Sonja Herres-Pawlis, Oliver Kohlbacher, Jens Krüger, Martin Kruse, Ralph Müller-Pfefferkorn, Patrick Schäfer, Bernd Schuller, Thomas Steinke, Andreas Zink	A Data Driven Science Gateway for Computational Workflows	Proceedings of the UNICORE Summit, 2012	BibTeX
Sebastian Dreßler, Thomas Steinke	A Novel Hybrid Approach to Automatically Determine Kernel Interface Data Volumes	ZIB-Report 12-23	PDF BibTeX URN
Sandra Gesing, Sonja Herres-Pawlis, Georg Birkenheuer, André Brinkmann, Richard Grunzke, Peter Kacsuk, Oliver Kohlbacher, Miklos Kozlovszky, Jens Krüger, Ralph Müller-Pfefferkorn, Patrick Schäfer, Thomas Steinke	A Science Gateway Getting Ready for Serving the International Molecular Simulation Community	Proceedings of Science, Vol.PoS(EGICF12-EMITC2)050, 2012	BibTeX
Sandra Gesing, Richard Grunzke, Jens Krüger, Georg Birkenheuer, Martin Wewior, Patrick Schäfer, Bernd Schuller, Johannes Schuster, Sonja Herres-Pawlis, Sebastian Breuers, Akos Balasko, Miklos Kozlovszky, Anna Szikszay Fabri, Lars Packschies, Peter Kacsuk, Dirk Blunk, Thomas Steinke, André Brinkmann, Gregor Fels, Ralph Müller-Pfefferkorn, René Jäkel, Oliver Kohlbacher	A Single Sign-On Infrastructure for Science Gateways on a Use Case for Structural Bioinformatics	Journal of Grid Computing, 2012	BibTeX
Sebastian Dreßler, Thomas Steinke	Energy consumption of CUDA kernels with varying thread topology	Computer Science - Research and Development, pp. 1-9, 2012	BibTeX DOI
Khaled Benkrid, Esam El-Araby, Miaoqing Huang, Kentaro Sano, Thomas Steinke	High-Performance Reconfigurable Computing - editorial for Special Issue of the International Journal of Reconfigurable Computing	International Journal of Reconfigurable Computing, Vol.2012, pp. 1-2, 2012	BibTeX DOI
Georg Birkenheuer, Dirk Blunk, Sebastian Breuers, André Brinkmann, Ines dos Santos Vieira, Gregor Fels, Sandra Gesing, Richard Grunzke, Sonja Herres-Pawlis, Oliver Kohlbacher, Jens Krüger, Ulrich Lang, Lars Packschies, Ralph Müller-Pfefferkorn, Patrick Schäfer, Thomas Steinke, Klaus Warzecha, Martin Wewior	MoSGrid: efficient data management and a standardized data exchange format for molecular simulations in a grid environment	Journal of Cheminformatics, 4(Suppl 1), p. 21, 2012	BibTeX DOI
F. Wende, F. Cordes, T. Steinke	On Improving the Performance of Multi-threaded CUDA Applications with Concurrent Kernel Execution by Kernel Reordering	Application Accelerators in High Performance Computing (SAAHPC), 2012 Symposium on, pp. 74-83, 2012	BibTeX DOI
Sandra Gesing, Sonja Herres-Pawlis, Georg Birkenheuer, Andre Brinkmann, Richard Grunzke, Peter Kacsuk, Oliver Kohlbacher, Miklos Kozlovszky, Jens Krüger, Ralf Müller-Pfefferkorn, Patrick Schäfer, Thomas Steinke	The MoSGrid Community – From National to International Scale	EGI Community Forum 2012, 2012	BibTeX
2011
Georg Birkenheuer, Dirk Blunk, Sebastian Breuers, Andre Brinkmann, Ines dos Santos Vieira, Gregor Fels, Sandra Gesing, Richard Grunzke, Sonja Herres-Pawlis, Oliver Kohlbacher, Jens Krüger, Ulrich Lang, Lars Packschies, Ralf Müller-Pfefferkorn, Patrick Schäfer, Hans-Günther Schmalz, Thomas Steinke, Klaus Warzecha, Martin Wewior	A Molecular Simulation Grid as new tool for Computational Chemistry, Biology and Material Science	Journal of Cheminformatics 2011, 3(Suppl 1), 2011	BibTeX DOI
Sandra Gesing, Peter Kacsuk, Miklos Kozlovszky, Georg Birkenheuer, Dirk Blunk, Sebastian Breuers, Andre Brinkmann, Gregor Fels, Richard Grunzke, Sonja Herres-Pawlis, Jens Krüger, Lars Packschies, Ralf Müller-Pfefferkorn, Patrick Schäfer, Thomas Steinke, Anna Szikszay Fabri, Klaus Warzecha, Martin Wewior, Oliver Kohlbacher	A Science Gateway for Molecular Simulations	EGI (European Grid Infrastructure) User Forum 2011, Book of Abstracts, pp. 94-95, 2011	BibTeX
Sandra Gesing, Richard Grunzke, Akos Balasko, Georg Birkenheuer, Dirk Blunk, Sebastian Breuers, André Brinkmann, Gregor Fels, Sonja Herres-Pawlis, Peter Kacsuk, Miklos Kozlovszky, Jens Krüger, Lars Packschies, Patrick Schäfer, Bernd Schuller, Johannes Schuster, Thomas Steinke, Anna Szikszay Fabri, Martin Wewior, Ralph Müller-Pfefferkorn, Oliver Kohlbacher	Granular Security for a Science Gateway in Structural Bioinformatics	Proc. IWSG-Life 2011, 2011	BibTeX
Georg Birkenheuer, Dirk Blunk, Sebastian Breuers, Andre Brinkmann, Gregor Fels, Sandra Gesing, Richard Grunzke, Sonja Herres-Pawlis, Oliver Kohlbacher, Jens Krüger, Ulrich Lang, Lars Packschies, Ralf Müller-Pfefferkorn, Patrick Schäfer, Johannes Schuster, Thomas Steinke, Klaus Warzecha, Martin Wewior	MoSGrid: Progress of Workflow driven Chemical Simulations	Proc. of Grid Workflow Workshop 2011, Cologne, Germany, Vol.826, 2011	BibTeX
Frank Dickmann, Jürgen Falkner, Wilfried Gunia, Jochen Hampe, Michael Hausmann, Alexander Herrmann, Nick Kepper, Tobias Knoch, Svenja Lauterbach, Jörg Lippert, Kathrin Peter, Eberhard Schmitt, Ulrich Schwardmann, Juri Solodenko, Dietmar Sommerfeld, Thomas Steinke, Anette Weisbecker, Ulrich Sax	Solutions for biomedical grid computing – Case studies from the D-Grid project Services@MediGRID	Journal of Computational Science, -(0), 2011	BibTeX DOI
2010
Thomas Steinke, Kathrin Peter, Sebastian Borchert	Efficiency Considerations of Cauchy Reed-Solomon Implementations on Accelerator and Multi-Core Platforms	Symposium on Application Accelerators in High Performance Computing (SAAHPC), 2010	BibTeX
G. Birkenheuer, D. Blunk, S. Breuers, A. Brinkmann, I. d. Santos Vieira, G. Fels, S. Gesing, R. Grunzke, S. Herres-Pawlis, O. Kohlbacher, N. Kruber, J. Krüger, U. Lang, L. Packschies, R. Müller-Pfefferkorn, P. Schäfer, H.-G. Schmalz, Th. Steinke, K.-D. Warzecha, M. Wewior	MoSGrid – A Molecular Simulation Grid as a new tool in Computational Chemistry, Biology and Material Science	6. German Conference on Chemoinformatics, 2010	BibTeX
J. Krüger, G. Birkenheuer, D. Blunk, S. Breuers, A. Brinkmann, G. Fels, S. Gesing, R. Grunzke, S. Herres-Pawlis, O. Kohlbacher, N. Kruber, U. Lang, L. Packschies, R. Müller-Pfefferkorn, P. Schäfer, H.-G. Schmalz, Th. Steinke, K.-D. Warzecha, M. Wewior	Molecular Simulation Grid	6. German Conference on Chemoinformatics, 2010	BibTeX
Alexander Ziegler, Malte Ogurreck, Thomas Steinke, Felix Beckmann, Steffen Prohaska, Andreas Ziegler	Opportunities and challenges for digital morphology	Biology Direct, 5(1), p. 45, 2010	BibTeX DOI
P. May, A. Kreuchwig, T. Steinke, I. Koch	PTGL: a database for secondary structure-based protein topologies	Nucleic Acids Res., Vol.38, pp. D326-330, 2010	BibTeX
2009
Raphael Bauer, Kristian Rother, Peter Moor, Knut Reinert, Thomas Steinke, Janusz Bujnicki, Robert Preissner	Fast Structural Alignment of Biomolecules Using a Hash Table, N-Grams and String Descriptors	Algorithms, 2(2), pp. 692-709, 2009	BibTeX DOI
Dagmar Krefting, Julian Bart, Kamen Beronov, Olga Dzhimova, Jürgen Falkner, Michael Hartung, Andreas Hoheisel, Tobias Knoch, Thomas Lingner, Yassene Mohammed, Kathrin Peter, Erhard Rahm, Ulrich Sax, Dietmar Sommerfeld, Thomas Steinke, Thomas Tolxdorff, Michal Vossberg, Fred Viezens, Anette Weisbecker	MediGRID: Towards A User Friendly Secured Grid Infrastructure	Future Generation Computer Systems (FGCS), 25(3), pp. 281-289, 2009	BibTeX DOI
Frank Dickmann, Mathias Kaspar, Benjamin Löhnhardt, Nick Kepper, Fred Viezens, Frank Hertel, Michael Lesnussa, Yassene Mohammed, Andreas Thiel, Thomas Steinke, Johannes Bernarding, Dagmar Krefting, Tobias Knoch, Ulrich Sax	Visualization in Health Grid Environments: A Novel Service and Business Approach	GECON, pp. 150-159, Vol.5745, Lecture Notes in Computer Science, 2009	BibTeX DOI
2007
Patrick May, Gunnar Klau, Markus Bauer, Thomas Steinke	Accelerated microRNA-Precursor Detection Using the Smith-Waterman Algorithm on FPGAs	GCCB, W. Dubitzky (Ed.), pp. 19-32, Vol.4360, Lecture Notes in Bioinformatics, 2007	BibTeX
Michael Meyer, Thomas Steinke, Jürgen Sühnel	Density functional study of isoguanine tetrad and pentad sandwich complexes with alkali metal ions	Journal of Molecular Modeling, 13(2), pp. 335-345, 2007	BibTeX
Samatha Kottha, Kathrin Peter, Thomas Steinke, Julian Bart, Jürgen Falkner, Anette Weisbecker, Fred Viezens, Yassene Mohammed, Ulrich Sax, Andreas Hoheisel, Thilo Ernst, Dietmar Sommerfeld, Dagmar Krefting, Michael Vossberg	Medical Image Processing in MediGRID	German E-Science Conference, 2007	BibTeX
Eric Stahlberg, Michael Babst, Daryl Popig, Thomas Steinke	Molecular Dynamics with FPGAs: A Portable API Molecular Simulations with Hardware Accelerators: A Portable Interface Definition for FPGA Supported Acceleration	International Supercomputing Conference 2007 (ISC 2007), 2007	BibTeX
Eric Stahlberg, Daryl Popig, Debie Ryle, Michael Babst, Mohammed Anderson, Thomas Steinke	Molecular Simulations with Hardware Accelerators	Reconfigurable Systems Summer Institute 2007 (RSSI 2007), 2007	BibTeX
2006
B. Kolbeck, P. May, T. Schmidt-Goenner, T. Steinke, E. Knapp	Connectivity independent protein-structure alignment: a hierarchical approach	BMC Bioinformatics, Vol.7, p. 510, 2006	BibTeX
T. Steinke, A. Reinefeld	Experiences with High-Level Programming of FPGAs on Cray XD1	CUG Proceedings, 2006	BibTeX
Patrick May, Thomas Steinke	THESEUS - Protein Structure Prediction at ZIB	ZIB-Report 06-24	PDF BibTeX URN
Patrick May, Hans-Christian Ehrlich, Thomas Steinke	ZIB Structure Prediction Pipeline: Composing a Complex Biological Workflow Through Web Services	Euro-Par 2006 Workshops, Wolfgang Lehner, Norbert Meyer, Achim Streit, Craig Stewart (Eds.), pp. 1148-1158, Vol.4375, Lecture Notes in Computer Science, 2006	BibTeX
2005
Silke Trißl, Kristian Rother, Heiko Müller, Thomas Steinke, Ina Koch, Robert Preissner, Cornelius Frömmel, Ulf Leser	Columba: an integrated database of proteins, structures, and annotations	BMC Bioinformatics, Vol.6, pp. 81-92, 2005	BibTeX DOI
P. May, B. Kallies, T. Steinke	THESEUS – a parallel threading core for highthroughput protein structure prediction	Proceedings of the 7th Congress of the World Association of Theoretically Orientes Chemists (WARTOC), 2005	BibTeX
P. May, F. Krause, C. Ehrlich, J. Maaskola, T. Steinke	ZIB threading pipeline - A webservice-based, distributed structure prediction workflow.	Proceedings of the German Conference on Bioinformatics (GCB), pp. 125-126, 2005	BibTeX
2004
E. Michalsky, A. Goede, R. Preissner, P. May, T. Steinke	A distributed pipeline for structure prediction	CASP6 Abstract Book, Sixth Meeting on the Critical Assessment of Techniques for Protein Structure Prediction, Gaeta, Italy, pp. 112-114, 2004	BibTeX
Kristian Rother, Heiko Müller, Silke Trißl, Ina Koch, Thomas Steinke, Robert Preissner, Cornelius Frömmel, Ulf Leser	Columba: Multidimensional Data Integration of Protein Annotations	Data Integration in the Life Sciences, First International Workshop, DILS 2004, Leipzig, Germany, March 25-26, Erhard Rahm (Ed.), pp. 156-171, Vol.2994, Lecture Notes in Computer Science, 2004	BibTeX DOI
P. May, T. Steinke, M. Meyer	THESEUS: A Parallel Threading Core	Procs. 12th Internat. Conf. on Intelligent Systems for Mol. Bio. (ISMB) and 3rd European Conf. on Comp. Bio. (ECCB), Glasgow, p. 199, 2004	BibTeX
2003
K. Rother, S. Trissl, H. Müller, P. May, R. Heek, R. Preissner, T. Steinke, I. Koch, U. Leser, C. Frömmel	Columba - A Database of Annotations of Protein Structure	ECCB - Proceedings of the European Conference on Computational Biology in conjunction with the French National Conference on Bioinformatics, C. Christophe, H.-P. Lenhof, M.-F. Sagot (Eds.), pp. 109-110, 2003	BibTeX
F. Cordes, R. Preissner, T. Steinke	How Does a Protein Work?	BioTOPics J. of Biotechnology Berlin-Brandenburg, 18(2), pp. 4-5, 2003	BibTeX
2000
Michael Meyer, Thomas Steinke, Maria Brandl, Jürgen Sühnel	Density functional study of guanine and uracil quartets and of guanine quartet metal/ion complexes	ZIB-Report 00-16 (Appeared in: J. Comput. Chem. 22, 109-124 (2001))	PDF BibTeX URN
1997
Wolfgang Baumann, Hubert Busch, Jürgen Gottschewski, Thomas Steinke, Hinnerk Stüben	Berliner Landeshöchstleistungsrechner Parallelrechner Cray T3D/T3E: Betrieb, Nutzung, Projekte, Perspektiven für den Ausbau	ZIB-Report TR-97-08	PDF BibTeX URN
1996
Detlev Stalling, Thomas Steinke	Visualization of Vector Fields in Quantum Chemistry	ZIB-Report SC-96-01	PDF BibTeX URN