- Kolloq - lists.ibr.cs.tu-bs.de

Erinnerung: Vortrag am 02.06.2015, 15:00 Uhr
by Informatik-Kolloquium 01 Jun '15

01 Jun '15

Die Dozenten der Informatik-Institute der Technischen Universität Braunschweig laden im Rahmen des Informatik-Kolloquiums zu folgendem Vortrag ein. Prof. Dr. Don Kulasiri, Prof. and Head of Systems Biology Center for Advanced Computational Solutions, Lincoln University, New Zealand: Integrated Systems Biology of Synaptic Plasticity Beginn: 02.06.2015, 15:00 Uhr Ort: TU Braunschweig, Inst. f. Geoökologie Webseite: http://www.ibr.cs.tu-bs.de/cal/kolloq/2015-06-02-kulasiri.html Kontakt: Prof. Hermann G. Matthies, PhD We discuss the pertinent aspects of a systems biology approach to synaptic plasticity. As an example, we take the functioning of the “memory molecule” and attempt to understand its role in synaptic pathways. The “memory molecule”, a synaptic protein, Ca2+/Calmodulin dependent protein kinase II (CaMKII), has complex state transitions and facilitates the emergence of long term potentiation (LTP), which is highly correlated to memory formation. Two of the state transitions are critical for LTP: (1) threonine 286 autophosphorylation of CaMKII; and (2) binding to N-methyl-D-aspartate receptor (NMDAR) in the postsynaptic density (PSD) to form CaMKII-NMDAR complex. Both of these state transitions retain the activity of CaMKII when the induction signal disappears which is very important for the long-lasting characteristics of LTP. However, the possible relationships between the state transitions in the emergence of LTP are not well understood. We develop a mathematical model of the formation of CaMKII-NMDAR complex with the full state transitions of CaMKII, including the autophosphorylation, based on ordinary differential equations. In addition, we formulate a probabilistic framework for the binding between CaMKII and NMDAR. The model gives accurate predictions of the behaviours of CaMKII in comparisons to the experimental observations. Using the model, we show that: (1) the formation of CaMKII-NMDAR complex is dependent not only on the binding affinity between CaMKII and NMDAR, but also on the translocation of CaMKII into PSD; and (2) the autophosphorylation is not a requirement for the formation of CaMKII-NMDAR complex, but is important for the rapid formation of CaMKII-NMDAR complex during LTP.

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Vortrag am 12.06.2015, 15:00 Uhr
by Informatik-Kolloquium 29 May '15

29 May '15

Die Dozenten der Informatik-Institute der Technischen Universität Braunschweig laden im Rahmen des Informatik-Kolloquiums zu folgendem Vortrag ein. Christian Cachin, IBM Research, Zürich: Separating Data and Control – BFT Storage with 2t+1 Data Replicas Beginn: 12.06.2015, 15:00 Uhr Ort: TU Braunschweig, Informatikzentrum, Mühlenpfordtstraße 23, 1. OG, Hörsaal M 161 Webseite: http://www.ibr.cs.tu-bs.de/cal/kolloq/2015-06-12-cachin.html Kontakt: Prof. Dr. Rüdiger Kapitza The overhead of Byzantine fault tolerant (BFT) storage is a primary concern that prevents its adoption in practice. The cost stems from the need to maintain at least 3t + 1 copies of the data at different storage replicas in the asynchronous model, so that t Byzantine replica faults can be tolerated. This work introduces MDStore, the first fully asynchronous BFT storage protocol that reduces the number of replicas that store the payload data to as few as 2t + 1 and maintains metadata at 3t + 1 replicas on (possibly) different servers. At the heart of MDStore lies a metadata service built upon a new abstraction called "timestamped storage." Timestamped storage allows for conditional writes (facilitating the implementation of the metadata service) and has consensus number one (making it implementable with wait-free semantics in an asynchronous system despite faults). In addition to its low replication overhead, MDStore offers strong guarantees by emulating a multi-writer multi-reader atomic register, providing wait-free termination, and tolerating any number of Byzantine readers and crash-faulty writers. Based on joint work with Elli Androulaki, Dan Dobre, and Marko Vukolić. Christian Cachin is a researcher in cryptography and security at IBM Research - Zurich. He graduated with a Ph.D. in Computer Science from ETH Zurich and has held visiting positions at MIT and at EPFL. Presently he serves as the President of the International Association for Cryptologic Research (IACR). An IEEE Fellow, ACM Distinguished Scientist, and recipient of multiple IBM Outstanding Technical Achievement Awards, he has co-authored the book "Introduction to Reliable and Secure Distributed Programming" and contributed to the OASIS Key Management Interoperability Protocol (KMIP) standard. His current research addresses the security of cloud computing, secure protocols for distributed systems, and cryptography.

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Vortrag am 05.06.2015, 15:00 Uhr
by Informatik-Kolloquium 22 May '15

22 May '15

Die Dozenten der Informatik-Institute der Technischen Universität Braunschweig laden im Rahmen des Informatik-Kolloquiums zu folgendem Vortrag ein. Jun.-Prof. Dr.-Ing. Kálmán Graffi, Heinrich-Heine-Universität Düsseldorf: Sicherheit und dezentrale Kommunikation in Zeiten der Überwachung Beginn: 05.06.2015, 15:00 Uhr Ort: TU Braunschweig, Informatikzentrum, Mühlenpfordtstraße 23, 1. OG, Hörsaal M 161 Webseite: http://www.ibr.cs.tu-bs.de/cal/kolloq/2015-06-05-graffi.html Kontakt: Prof. Dr.-Ing. Lars Wolf Digitale soziale Netzwerke und Echtzeitkommunikationsdienste haben in den vergangenen Jahren enormes Interesse erfahren. Facebook als größtes dieser Netzwerke verbindet Milliarden von Menschen und unterstützt sie in dem Austausch im Privaten und z.T. im Beruflichen. Während des Arabischen Frühlings wurde Facebook und ähnliche Netzwerke als Hauptkommunikationsmittel genutzt um die Aktivisten zu vernetzen, Visibilität zu schaffen und eine reichhaltige Kommunikation zu ermöglichen. Vielen war aber nicht bewusst, in wie weit die Überwachung dieses Kommunikationsmittels möglich ist und tatsächlich auch durchgeführt wird. Durch die Veröffentlichungen von Edward Snowden wurde uns bewusst dass ein Großteil der Kommunikationsdienste im Internet überwacht wird. Sichere Alternativen, die die Privatsphäre der Beteiligten schützen, sind aber nicht nur im Arabischen Raum, sondern auch in vielen weiteren Ländern z.T. lebenswichtig. In diesem Vortrag präsentieren wir diese sicheren, dezentralen Alternativen und zeigen auf welche Möglichkeiten man zur sicheren Kommunikation selbst unter Totalüberwachung und sogar Einschränkungen der Internetinfrastruktur hat. Insbesondere stellen wir unsere Lösungen aus der Peer-to-Peer-Forschung und aus der Forschung zu opportunistischen Netzwerken vor. Unser Rahmenwerk für vollständig dezentrale, sichere Kommunikation und Datenhaltung nennt sich LibreSocial und ist eine Software, die es ermöglicht soziale Netzwerke zu minimalen Kosten, sicher und unüberwachbar zu betreiben. Neuste Dienste, wie Audio-Video-Chats und Groupware, aber auch bekannte Dienste wie Statusnachrichten, Fotoalben und Emails werden in der sozialen Software vereint. Ob im globalen Betrieb oder im Einsatz in Unternehmen, Datenschutz und kontrollierte Qualität sind gewährleistet. Ferner zeigen wir Möglichkeiten auf, wie Smartphones durch lokale, sichere Vernetzung in die Lage versetzt werden können, Nachrichtenkommunikation und Datenhaltung selbst ohne verfügbare Internetanbindung für ansprechende Anwendungen anbieten zu können.

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Vortrag am 02.06.2015, 15:00 Uhr
by Informatik-Kolloquium 19 May '15

19 May '15

Die Dozenten der Informatik-Institute der Technischen Universität Braunschweig laden im Rahmen des Informatik-Kolloquiums zu folgendem Vortrag ein. Prof. Dr. Don Kulasiri, Prof. and Head of Systems Biology Center for Advanced Computational Solutions, Lincoln University, New Zealand: Integrated Systems Biology of Synaptic Plasticity Beginn: 02.06.2015, 15:00 Uhr Ort: TU Braunschweig, Inst. f. Geoökologie Webseite: http://www.ibr.cs.tu-bs.de/cal/kolloq/2015-06-02-kulasiri.html Kontakt: Prof. Hermann G. Matthies, PhD We discuss the pertinent aspects of a systems biology approach to synaptic plasticity. As an example, we take the functioning of the “memory molecule” and attempt to understand its role in synaptic pathways. The “memory molecule”, a synaptic protein, Ca2+/Calmodulin dependent protein kinase II (CaMKII), has complex state transitions and facilitates the emergence of long term potentiation (LTP), which is highly correlated to memory formation. Two of the state transitions are critical for LTP: (1) threonine 286 autophosphorylation of CaMKII; and (2) binding to N-methyl-D-aspartate receptor (NMDAR) in the postsynaptic density (PSD) to form CaMKII-NMDAR complex. Both of these state transitions retain the activity of CaMKII when the induction signal disappears which is very important for the long-lasting characteristics of LTP. However, the possible relationships between the state transitions in the emergence of LTP are not well understood. We develop a mathematical model of the formation of CaMKII-NMDAR complex with the full state transitions of CaMKII, including the autophosphorylation, based on ordinary differential equations. In addition, we formulate a probabilistic framework for the binding between CaMKII and NMDAR. The model gives accurate predictions of the behaviours of CaMKII in comparisons to the experimental observations. Using the model, we show that: (1) the formation of CaMKII-NMDAR complex is dependent not only on the binding affinity between CaMKII and NMDAR, but also on the translocation of CaMKII into PSD; and (2) the autophosphorylation is not a requirement for the formation of CaMKII-NMDAR complex, but is important for the rapid formation of CaMKII-NMDAR complex during LTP.

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Erinnerung: Vortrag am 04.05.2015, 15:00 Uhr
by Informatik-Kolloquium 03 May '15

03 May '15

Die Dozenten der Informatik-Institute der Technischen Universität Braunschweig laden im Rahmen des Informatik-Kolloquiums zu folgendem Vortrag ein. Nigel Lovell, Scientia Professor, UNSW Graduate School of Biomedical Engineering, Sydney, Australia: Towards Next Generation Bionic Interfaces Beginn: 04.05.2015, 15:00 Uhr Ort: TU Braunschweig, Informatikzentrum, Mühlenpfordtstraße 23, 4. OG, Raum 404 Webseite: http://www.ibr.cs.tu-bs.de/cal/kolloq/2015-05-04-lovell.html Kontakt: Prof. Dr. Reinhold Haux Many engineering challenges and scientific endeavours are focused on the interface between physical and biological domains. This presentation will focus on aspects of the bionic interface where electronic and mechanical devices interact with biological systems. Descriptions will also cover aspects of systems interfacing of wearable and implantable devices to encompass not just medical therapeutic devices but also diagnostic and physiological monitoring devices. Two technologies will be considered to illustrate the importance of the next generation of bionic interfaces. These will include an implantable device designed to restore aspects of patterned vision to those with profound vision loss – a so-called ‘bionic eye’ or visual neuroprosthesis, as well as a wearable ambulatory device with applications in fall detection and fall prediction. A critical consideration in designing a visual neuroprosthesis that affords improved visual acuity is engineering a stable, long-term, low impedance interface between the stimulating electrodes and the neural tissue; and associated with this, optimising stimulation paradigms to provide localised and punctate phosphenes with minimal cross-talk or interaction between electrodes. Various scientific and technological advances, including improvements in current steering and electrode coatings, will be explored. The next generation of bionic devices will also include implantable and wearable monitoring technologies. As an example, we will describe wearable ambulatory technologies based around inertial measurement units coupled with barometric pressure sensors for estimating risks of falling and for automatically detecting falls in the free-living environment.

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Vortrag am 04.05.2015, 15:00 Uhr
by Informatik-Kolloquium 23 Apr '15

23 Apr '15

Die Dozenten der Informatik-Institute der Technischen Universität Braunschweig laden im Rahmen des Informatik-Kolloquiums zu folgendem Vortrag ein. Nigel Lovell, Scientia Professor, UNSW Graduate School of Biomedical Engineering, Sydney, Australia: Towards Next Generation Bionic Interfaces Beginn: 04.05.2015, 15:00 Uhr Ort: TU Braunschweig, Informatikzentrum, Mühlenpfordtstraße 23, 4. OG, Raum 404 Webseite: http://www.ibr.cs.tu-bs.de/cal/kolloq/2015-05-04-lovell.html Kontakt: Prof. Dr. Reinhold Haux Many engineering challenges and scientific endeavours are focused on the interface between physical and biological domains. This presentation will focus on aspects of the bionic interface where electronic and mechanical devices interact with biological systems. Descriptions will also cover aspects of systems interfacing of wearable and implantable devices to encompass not just medical therapeutic devices but also diagnostic and physiological monitoring devices. Two technologies will be considered to illustrate the importance of the next generation of bionic interfaces. These will include an implantable device designed to restore aspects of patterned vision to those with profound vision loss – a so-called ‘bionic eye’ or visual neuroprosthesis, as well as a wearable ambulatory device with applications in fall detection and fall prediction. A critical consideration in designing a visual neuroprosthesis that affords improved visual acuity is engineering a stable, long-term, low impedance interface between the stimulating electrodes and the neural tissue; and associated with this, optimising stimulation paradigms to provide localised and punctate phosphenes with minimal cross-talk or interaction between electrodes. Various scientific and technological advances, including improvements in current steering and electrode coatings, will be explored. The next generation of bionic devices will also include implantable and wearable monitoring technologies. As an example, we will describe wearable ambulatory technologies based around inertial measurement units coupled with barometric pressure sensors for estimating risks of falling and for automatically detecting falls in the free-living environment.

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Erinnerung: Vortrag am 10.04.2015, 14:00 Uhr
by Informatik-Kolloquium 09 Apr '15

09 Apr '15

Die Dozenten der Informatik-Institute der Technischen Universität Braunschweig laden im Rahmen des Informatik-Kolloquiums zu folgendem Vortrag ein. Prof. Dr. Roland Meyer, TU Kaiserslautern: Robustness against Relaxed Memory Models Beginn: 10.04.2015, 14:00 Uhr Ort: TU Braunschweig, Informatikzentrum, Mühlenpfordtstraße 23, 1. OG, Hörsaal M 161 Webseite: http://www.ibr.cs.tu-bs.de/cal/kolloq/2015-04-09-glabbeek.html Kontakt: Prof. Dr.-Ing. Ina Schaefer For performance reasons, modern multiprocessors implement relaxed memory consistency models that admit out-of-program-order and non-store atomic executions. While data race-free programs are not sensitive to these relaxations, they pose a serious problem to the development of the underlying concurrency libraries. Library routines that work correctly under Sequential Consistency (SC) show undesirable effects when run under a relaxed memory model. These routines are not robust against the relaxations that the processor supports. To enforce robustness, the programmer has to add safety net instructions to the code that control the hardware --- a task that has proven to be difficult, even for experts. We recently developed algorithms that check and, if necessary, enforce robustness against prominent relaxed memory models like TSO implemented in x86 processors and Power implemented in IBM architectures. Given a program, our algorithms decide whether the actual behavior on the processor coincides with the SC semantics. If this is not the case, they synthesize safety net instructions that enforce robustness. When built into a compiler, our algorithms thus hide the relaxed memory model from the programmer and provide the illusion of Sequential Consistency. In this talk, we motivate the robustness problem and explain how to reduce it to an emptiness problem for a new automaton model.

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Erinnerung: Vortrag am 09.04.2015, 10:00 Uhr
by Informatik-Kolloquium 08 Apr '15

08 Apr '15

Die Dozenten der Informatik-Institute der Technischen Universität Braunschweig laden im Rahmen des Informatik-Kolloquiums zu folgendem Vortrag ein. Rob van Glabbeek, NICTA, Sydney, Australien: CCS, it’s not fair! Beginn: 09.04.2015, 10:00 Uhr Ort: TU Braunschweig, Informatikzentrum, Mühlenpfordtstraße 23, 1. OG, Hörsaal M 160 Webseite: http://www.ibr.cs.tu-bs.de/cal/kolloq/2015-04-09-glabbeek.html Kontakt: Prof. Dr.-Ing. Ina Schaefer Fair Schedulers cannot be implemented in CCS-like languages even under progress and certain fairness assumptions. In the process algebra community it is sometimes suggested that, on some level of abstraction, any distributed system can be modelled in standard process-algebraic specification formalisms like CCS. This sentiment is strengthened by results testifying that CCS, like many similar formalisms, is Turing powerful and provides a mechanism for interaction. This talk counters that sentiment by presenting a simple fair scheduler---one that in suitable variations occurs in many distributed systems---of which no implementation can be expressed in CCS, unless CCS is enriched with a fairness assumption. The same could be said for COSY, CSP, ACP, LOTOS, mCRL, the pi-calculus, etc. A cornerstone in the proof is that the fair scheduler cannot be implemented in terms of Petri nets. Since Dekker's and Peterson's mutual exclusion protocols implement fair schedulers, it follows that these protocols cannot be rendered correctly in CCS without imposing a fairness assumption. Peterson expressed this algorithm correctly in pseudocode without resorting to a fairness assumption, so it furthermore follows that CCS lacks the expressive power to accurately capture such pseudocode.

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Vortrag am 10.04.2015, 14:00 Uhr
by Informatik-Kolloquium 03 Apr '15

03 Apr '15

Die Dozenten der Informatik-Institute der Technischen Universität Braunschweig laden im Rahmen des Informatik-Kolloquiums zu folgendem Vortrag ein. Prof. Dr. Roland Meyer, TU Kaiserslautern: Robustness against Relaxed Memory Models Beginn: 10.04.2015, 14:00 Uhr Ort: TU Braunschweig, Informatikzentrum, Mühlenpfordtstraße 23, 1. OG, Hörsaal M 161 Webseite: http://www.ibr.cs.tu-bs.de/cal/kolloq/2015-04-09-glabbeek.html Kontakt: Prof. Dr.-Ing. Ina Schaefer For performance reasons, modern multiprocessors implement relaxed memory consistency models that admit out-of-program-order and non-store atomic executions. While data race-free programs are not sensitive to these relaxations, they pose a serious problem to the development of the underlying concurrency libraries. Library routines that work correctly under Sequential Consistency (SC) show undesirable effects when run under a relaxed memory model. These routines are not robust against the relaxations that the processor supports. To enforce robustness, the programmer has to add safety net instructions to the code that control the hardware --- a task that has proven to be difficult, even for experts. We recently developed algorithms that check and, if necessary, enforce robustness against prominent relaxed memory models like TSO implemented in x86 processors and Power implemented in IBM architectures. Given a program, our algorithms decide whether the actual behavior on the processor coincides with the SC semantics. If this is not the case, they synthesize safety net instructions that enforce robustness. When built into a compiler, our algorithms thus hide the relaxed memory model from the programmer and provide the illusion of Sequential Consistency. In this talk, we motivate the robustness problem and explain how to reduce it to an emptiness problem for a new automaton model.

1 0

Vortrag am 09.04.2015, 10:00 Uhr
by Informatik-Kolloquium 27 Mar '15

27 Mar '15

Die Dozenten der Informatik-Institute der Technischen Universität Braunschweig laden im Rahmen des Informatik-Kolloquiums zu folgendem Vortrag ein. Rob van Glabbeek, NICTA, Sydney, Australien: CCS, it’s not fair! Beginn: 09.04.2015, 10:00 Uhr Ort: TU Braunschweig, Informatikzentrum, Mühlenpfordtstraße 23, 1. OG, Hörsaal M 160 Webseite: http://www.ibr.cs.tu-bs.de/cal/kolloq/2015-04-09-glabbeek.html Kontakt: Prof. Dr.-Ing. Ina Schaefer Fair Schedulers cannot be implemented in CCS-like languages even under progress and certain fairness assumptions. In the process algebra community it is sometimes suggested that, on some level of abstraction, any distributed system can be modelled in standard process-algebraic specification formalisms like CCS. This sentiment is strengthened by results testifying that CCS, like many similar formalisms, is Turing powerful and provides a mechanism for interaction. This talk counters that sentiment by presenting a simple fair scheduler---one that in suitable variations occurs in many distributed systems---of which no implementation can be expressed in CCS, unless CCS is enriched with a fairness assumption. The same could be said for COSY, CSP, ACP, LOTOS, mCRL, the pi-calculus, etc. A cornerstone in the proof is that the fair scheduler cannot be implemented in terms of Petri nets. Since Dekker's and Peterson's mutual exclusion protocols implement fair schedulers, it follows that these protocols cannot be rendered correctly in CCS without imposing a fairness assumption. Peterson expressed this algorithm correctly in pseudocode without resorting to a fairness assumption, so it furthermore follows that CCS lacks the expressive power to accurately capture such pseudocode.

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