The Experts below are selected from a list of 31230 Experts worldwide ranked by ideXlab platform
Georgios Zervas - One of the best experts on this subject based on the ideXlab platform.
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pulse optical circuit switched data center architecture operating at nanosecond Timescales
Journal of Lightwave Technology, 2020Co-Authors: Joshua Benjamin, Thomas Gerard, Domanic Lavery, P Bayvel, Georgios ZervasAbstract:We introduce PULSE, a sub- $\mu$ s optical circuit switched data centre network architecture controlled by distributed hardware schedulers. PULSE is a flat architecture that uses parallel passive coupler-based broadcast and select networks. We employ a novel transceiver architecture, for dynamic wavelength-Timeslot selection, to achieve a Reconfiguration Time down to O(100 ps), establishing Timeslots of O(10 ns). A novel scheduling algorithm that has a clock period of 2.3 ns performs multiple iterations to maximize throughput, wavelength usage and reduce latency, enhancing the overall performance. In order to scale, the single-hop PULSE architecture uses sub-networks that are disjoint by using multiple transceivers for each node in 64 node racks. At the Reconfiguration circuit duration ( epoch = 120 ns), the scheduling algorithm is shown to achieve up to 93% throughput and 100% wavelength usage of 64 wavelengths, incurring an average latency that ranges from 0.7–1.2 $\mu$ s with best-case 0.4 $\mu$ s median and 5 $\mu$ s tail latency, limited by the Timeslot (20 ns) and epoch size (120 ns). We show how the 4096-node PULSE architecture allows up to 260 k optical channels to be re-used across sub-networks achieving a capacity of 25.6 Pbps with an energy consumption of 82 pJ/bit when using coherent receiver.
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pulse optical circuit switched data center architecture operating at nanosecond Timescales
arXiv: Networking and Internet Architecture, 2020Co-Authors: Joshua Benjamin, Thomas Gerard, Domanic Lavery, P Bayvel, Georgios ZervasAbstract:We introduce PULSE, a sub-microsecond optical circuit-switched data centre network architecture controlled by distributed hardware schedulers. PULSE is a flat architecture that uses parallel passive coupler-based broadcast and select networks. We employ a novel transceiver architecture, for dynamic wavelength-Timeslot selection, to achieve a Reconfiguration Time down to O(100ps), establishing Timeslots of O(10ns). A novel scheduling algorithm that has a clock period of 2.3ns performs multiple iterations to maximize throughput, wavelength usage and reduce latency, enhancing the overall performance. In order to scale, the single-hop PULSE architecture uses sub-networks that are disjoint by using multiple transceivers for each node in 64 node racks. At the Reconfiguration circuit duration (epoch = 120 ns), the scheduling algorithm is shown to achieve up to 93% throughput and 100% wavelength usage of 64 wavelengths, incurring an average latency that ranges from 0.7-1.2 microseconds with best-case 0.4 microsecond median and 5 microsecond tail latency, limited by the Timeslot (20 ns) and epoch size (120 ns). We show how the 4096-node PULSE architecture allows up to 260k optical channels to be re-used across sub-networks achieving a capacity of 25.6 Pbps with an energy consumption of 85 pJ/bit.
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real Time demonstration of software defined elastic interface for flexgrid networks
Optical Fiber Communication Conference, 2015Co-Authors: Arnaud Dupas, E Dutisseuil, Patricia Layec, Philipe Jenneve, Silvano Frigerio, Yan Yan, E Huguessalas, Georgios Zervas, Dimitra Simeonidou, Sebastien BigoAbstract:We demonstrate a real-Time Elastic Interface for future flex-grid networks with a software-defined symbol rate transmission. Using PDM-QPSK modulation, live experiments show a line rate adaptation from 10.7 to 107Gbit/s with a sub-millisecond Reconfiguration Time.
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real Time demonstration of software defined elastic interface for flexgrid networks
Optical Fiber Communication Conference, 2015Co-Authors: Arnaud Dupas, E Dutisseuil, Patricia Layec, Philipe Jenneve, Silvano Frigerio, Yan Yan, E Huguessalas, Georgios Zervas, Dimitra Simeonidou, Sebastien BigoAbstract:We demonstrate a real-Time Elastic Interface for future flex-grid networks with a software-defined symbol rate transmission. Using PDM-QPSK modulation, live experiments show a line rate adaptation from 10.7 to 107Gbit/s with a sub-millisecond Reconfiguration Time.
Benjamin Schuler - One of the best experts on this subject based on the ideXlab platform.
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quantifying internal friction in unfolded and intrinsically disordered proteins with single molecule spectroscopy
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Andrea Soranno, Sonja Mullerspath, Daniel Nettels, Brigitte Buchli, Ryan R Cheng, Shawn H Pfeil, Armin Hoffmann, Everett A Lipman, Dmitrii E. Makarov, Benjamin SchulerAbstract:Internal friction, which reflects the “roughness” of the energy landscape, plays an important role for proteins by modulating the dynamics of their folding and other conformational changes. However, the experimental quantification of internal friction and its contribution to folding dynamics has remained challenging. Here we use the combination of single-molecule Forster resonance energy transfer, nanosecond fluorescence correlation spectroscopy, and microfluidic mixing to determine the Reconfiguration Times of unfolded proteins and investigate the mechanisms of internal friction contributing to their dynamics. Using concepts from polymer dynamics, we determine internal friction with three complementary, largely independent, and consistent approaches as an additive contribution to the Reconfiguration Time of the unfolded state. We find that the magnitude of internal friction correlates with the compactness of the unfolded protein: its contribution dominates the Reconfiguration Time of approximately 100 ns of the compact unfolded state of a small cold shock protein under native conditions, but decreases for more expanded chains, and approaches zero both at high denaturant concentrations and in intrinsically disordered proteins that are expanded due to intramolecular charge repulsion. Our results suggest that internal friction in the unfolded state will be particularly relevant for the kinetics of proteins that fold in the microsecond range or faster. The low internal friction in expanded intrinsically disordered proteins may have implications for the dynamics of their interactions with cellular binding partners.
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probing the free energy surface for protein folding with single molecule fluorescence spectroscopy
Nature, 2002Co-Authors: Benjamin Schuler, Everett A Lipman, William A EatonAbstract:Protein folding is inherently a heterogeneous process because of the very large number of microscopic pathways that connect the myriad unfolded conformations to the unique conformation of the native structure. In a first step towards the long-range goal of describing the distribution of pathways experimentally, Forster resonance energy transfer1 (FRET) has been measured on single, freely diffusing molecules2,3,4. Here we use this method to determine properties of the free-energy surface for folding that have not been obtained from ensemble experiments. We show that single-molecule FRET measurements of a small cold-shock protein expose equilibrium collapse of the unfolded polypeptide and allow us to calculate limits on the polypeptide Reconfiguration Time. From these results, limits on the height of the free-energy barrier to folding are obtained that are consistent with a simple statistical mechanical model, but not with the barriers derived from simulations using molecular dynamics. Unlike the activation energy, the free-energy barrier includes the activation entropy and thus has been elusive to experimental determination for any kinetic process in solution.
Amin Vahdat - One of the best experts on this subject based on the ideXlab platform.
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A multiport microsecond optical circuit switch for data center networking
IEEE Photonics Technology Letters, 2013Co-Authors: Nathan Farrington, P. C. Sun, Joseph E. Ford, Alex Forencich, Yeshaiahu Fainman, George Porter, George C Papen, Amin VahdatAbstract:We experimentally evaluate the network-level switching Time of a functional 23-host prototype hybrid optical circuit-switched/electrical packet-switched network for datacenters called Mordia (Microsecond Optical Research Datacenter Interconnect Architecture). This hybrid network uses a standard electrical packet switch and an optical circuit-switched architecture based on a wavelength-selective switch that has a measured mean port-to-port network Reconfiguration Time of 11.5 including the signal acquisition by the network interface card. Using multiple parallel rings, we show that this architecture can scale to support the large bisection bandwidth required for future datacenters.
Nicola Calabretta - One of the best experts on this subject based on the ideXlab platform.
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Fully SDN-enabled all-optical architecture for data center virtualization with Time and space multiplexing
IEEE OSA Journal of Optical Communications and Networking, 2018Co-Authors: Koteswararao Kondepu, Fernando Agraz, C. Jackson, Y. Ou, A. Beldachi, Francesco Moscatelli, W. Miao, Valerija Kamchevska, Albert Pagès, Nicola CalabrettaAbstract:Virtual data center (VDC) solutions provide an environment that is able to quickly scale up, and where virtual machines and network resources can be quickly added on-demand through self-service procedures. VDC providers must support multiple simultaneous tenants with isolated networks on the same physical substrate. The provider must make efficient use of its available physical resources while providing high-bandwidth and low-latency connections to tenants with a variety of VDC configurations. This paper utilizes state-of-the-art optical network elements to provide high-bandwidth optical interconnections and develop a VDC architecture to slice the network and the compute resources dynamically, to efficiently divide the physical network between tenants. We present a data center virtualization architecture with a softwaredefined networking controlled all-optical data plane combining optical circuit switching and a Time-shared optical network. Developed network orchestration dynamically translates and provisions VDCs requests onto the optical physical layer. The experimental results show the provisioned bandwidth can be varied by adjusting the number of Time slots allocated in the Time-division multiplexing (TDM) network. These results lead to recommendations for provisioning TDM connections with different performance characteristics. Moreover, application-level optical switch Reconfiguration Time is also evaluated to fully understand the impact on application performance in VDC provision. The experimental demonstration confirmed that the developed VDC approach introduces negligible delay and complexity on the network side.
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novel flat datacenter network architecture based on scalable and flow controlled optical switch system
Optics Express, 2014Co-Authors: Wang W Miao, Stefano Di Lucente, Hjs Harm Dorren, Nicola CalabrettaAbstract:We propose and demonstrate an optical flat datacenter network based on scalable optical switch system with optical flow control. Modular structure with distributed control results in port-count independent optical switch Reconfiguration Time. RF tone in-band labeling technique allowing parallel processing of the label bits ensures the low latency operation regardless of the switch port-count. Hardware flow control is conducted at optical level by re-using the label wavelength without occupying extra bandwidth, space, and network resources which further improves the performance of latency within a simple structure. Dynamic switching including multicasting operation is validated for a 4x4 system. Error free operation of 40 Gb/s data packets has been achieved with only 1 dB penalty. The system could handle an input load up to 0.5 providing a packet loss lower that 10−5 and an average latency less that 500ns when a buffer size of 16 packets is employed. Investigation on scalability also indicates that the proposed system could potentially scale up to large port count with limited power penalty.
Dmitrii E. Makarov - One of the best experts on this subject based on the ideXlab platform.
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quantifying internal friction in unfolded and intrinsically disordered proteins with single molecule spectroscopy
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Andrea Soranno, Sonja Mullerspath, Daniel Nettels, Brigitte Buchli, Ryan R Cheng, Shawn H Pfeil, Armin Hoffmann, Everett A Lipman, Dmitrii E. Makarov, Benjamin SchulerAbstract:Internal friction, which reflects the “roughness” of the energy landscape, plays an important role for proteins by modulating the dynamics of their folding and other conformational changes. However, the experimental quantification of internal friction and its contribution to folding dynamics has remained challenging. Here we use the combination of single-molecule Forster resonance energy transfer, nanosecond fluorescence correlation spectroscopy, and microfluidic mixing to determine the Reconfiguration Times of unfolded proteins and investigate the mechanisms of internal friction contributing to their dynamics. Using concepts from polymer dynamics, we determine internal friction with three complementary, largely independent, and consistent approaches as an additive contribution to the Reconfiguration Time of the unfolded state. We find that the magnitude of internal friction correlates with the compactness of the unfolded protein: its contribution dominates the Reconfiguration Time of approximately 100 ns of the compact unfolded state of a small cold shock protein under native conditions, but decreases for more expanded chains, and approaches zero both at high denaturant concentrations and in intrinsically disordered proteins that are expanded due to intramolecular charge repulsion. Our results suggest that internal friction in the unfolded state will be particularly relevant for the kinetics of proteins that fold in the microsecond range or faster. The low internal friction in expanded intrinsically disordered proteins may have implications for the dynamics of their interactions with cellular binding partners.
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spatiotemporal correlations in denatured proteins the dependence of fluorescence resonance energy transfer fret derived protein Reconfiguration Times on the location of the fret probes
Journal of Chemical Physics, 2010Co-Authors: Dmitrii E. MakarovAbstract:There has been considerable effort to understand the inherent Time scale for conformational Reconfiguration of denatured proteins. Even a simple homopolymer, however, exhibits a spectrum of fluctuation Time scales rather than a unique characteristic Time. Consequently, different Time scales may be probed by different measurements. Motivated by recent single-molecule fluorescence resonance energy transfer experiments, here I have studied theoretically how the characteristic Time scale exhibited by fluctuations of the distance between two residues within an unfolded polypeptide depends on the choice of the residue pair. This Time scale was generally found to become shorter as the sequence separation between the residues is reduced. The maximum Reconfiguration Time, however, corresponds not to the residues being located at the ends of the chain but rather to each residue residing a short length apart from the ends. Comparison of these findings with recent single-molecule measurements suggests that the latter may bear signatures of transient residual structure.
