Reconfiguration Rate Research Articles

Curcumin Prevents Aggregation in α-Synuclein by Increasing Reconfiguration Rate

α-Synuclein is a protein that is intrinsically disordered in vitro and prone to aggregation, particularly at high temperatures. In this work, we examined the ability of curcumin, a compound found in turmeric, to prevent aggregation of the protein. We found strong binding of curcumin to α-synuclein in the hydrophobic non-amyloid-β component region and complete inhibition of oligomers or fibrils. We also found that the reconfiguration rate within the unfolded protein was significantly increased at high temperatures. We conclude that α-synuclein is prone to aggregation because its reconfiguration rate is slow enough to expose hydrophobic residues on the same time scale that bimolecular association occurs. Curcumin rescues the protein from aggregation by increasing the reconfiguration rate into a faster regime.

Observation of Bistable Defects in Electron Irradiated N-Type 4H-SiC

DLTS measurements show bistable behavior of the previously reported EH5 peak in low- and high-energy electron irradiation 4H-SiC. Both reconfiguration processes (A ! B and B ! A) take place above 700 ±C. By isothermal annealing, the reconfiguration rates were determined and the reconfiguration energy was calculated to EA = 2.4±0.2 eV. Since the defect is present already after low-energy electron irradiation, which mainly affects the C atom in SiC, the EH5 peak may be related to defects associated with C-vacancies or C-interstitials

A Dynamic Dual Fixed-Point Arithmetic Architecture for FPGAs

In FPGA embedded systems, designers usually have to make a compromise between numerical precision and logical resources. Scientific computations in particular, usually require highly accurate calculations and are computing intensive. In this context, a designer is left with the task of implementing several arithmetic cores for parallel processing while supporting high numerical precision with finite logical resources. This paper introduces an arithmetic architecture that uses runtime partial reconfiguration to dynamically adapt its numerical precision, without requiring significant additional logical resources. The paper also quantifies the relationship between reduced logical resources and savings in power consumption, which is particularly important for FPGA implementations. Finally, our results show performance benefits when this approach is compared to alternative static solutions within bounds on the reconfiguration rate.

Rapidly reconfigurable slow-light system based on off-resonant Raman absorption

We present a slow-light system based on dual Raman absorption resonances in warm rubidium vapor. Each Raman absorption resonance is produced by a control beam in an off-resonant $\ensuremath{\Lambda}$ system. This system combines all optical control of the Raman absorption and the low-dispersion broadening properties of the double Lorentzian absorption slow light. The bandwidth, group delay, and central frequency of the slow-light system can all be tuned dynamically by changing the properties of the control beam. We demonstrate multiple pulse delays with low distortion and show that such a system has fast switching dynamics and thus fast reconfiguration rates.

Partial Reconfigurable FIR Filtering System Using Distributed Arithmetic

Dynamic partial reconfiguration (DPR) allows us to adapt hardware resources to meet time-varying requirements in power, resources, or performance. In this paper, we present two new DPR systems that allow for efficient implementations of 1D FIR filters on modern FPGA devices. To minimize the required partial reconfiguration region (PRR), both implementations are based on distributed arithmetic. For a smaller required PRR, the first system only allows changes to the filter coefficient values while keeping the rest of the architecture fixed. The second DPR system allows full FIR-filter reconfiguration while requiring a larger PR region. We investigate the proposed system performance in terms of the dynamic reconfiguration rates. At low reconfiguration rates, the DPR systems can maintain much higher throughputs. We also present an example that demonstrates that the system can maintain a throughput of 10 Mega-samples per second while fully reconfiguring about seventy times per second.

A Self-Reconfigurable Platform for Scalable DCT Computation Using Compressed Partial Bitstreams and BlockRAM Prefetching

In this paper, we propose a self-reconfigurable platform which can reconfigure the architecture of discrete cosine transform (DCT) computations during run-time using dynamic partial reconfiguration. The scalable architecture of DCT computations can compute different numbers of DCT coefficients in a zig-zag scan order to adapt to different requirements, such as power consumption, hardware resources, and performance. We propose a configuration manager, which is implemented in the embedded processor in order to adaptively control the reconfiguration of scalable DCT architecture during run-time. In addition, we use the Lempel-Ziv-Storer-Szymanski algorithm for compression of the partial bitstreams and on-chip BlockRAM as a cache to reduce latency overhead for loading the partial bitstreams from the off-chip memory for run-time reconfiguration. A hardware module is designed for parallel reconfiguration of the partial bitstreams. The experimental results show that our approach can reduce the external memory accesses by 69% and can achieve a 400 MB/s reconfiguration rate. Detailed trade-offs of power, throughput, and quality are investigated, and used as a criterion for self-reconfiguration.

Multihop Control Schemes in Switches With Reconfiguration Latency

Optical switching fabrics (OSFs) are receiving increasing attention in the design of high-speed packet switches, due to their excellent properties in terms of available bandwidth and reduced power consumption. However, for most optical devices, the latency needed to reconfigure input/output switch port connections may not be negligible with respect to the packet transmission time and can adversely affect switch performance, creating high delays and reduced throughput. We consider OSFs, and we propose a multihop approach to schedule packet transfers; i.e., packets are sent to the final destination port by exploiting transmission through intermediate ports. We show that the multihop approach is a promising technique to control the trade-off between delay and throughput, and it permits us to partly decouple the switch reconfiguration rate from the packet duration. We propose a general framework to solve the issue of multihop transmission in input-queued packet switches. Furthermore, we examine the multihop approach when the direct exchange of packets among ports is based on multidimensional regular topologies. We discuss which sequence of intermediate ports should be traversed to reach the final output port (i.e., the internal routing) and the switch time-scheduling problem (i.e., when a pair of ports can exchange packets). Performance is analyzed both analytically and by simulation.

Continuous Tunable Delays at 10-Gb/s Data Rates Using Self-Phase Modulation and Dispersion

We demonstrate all-optical tunable delays in optical fiber at communication data rates via dispersion and wavelength conversion using nonlinear spectral broadening and filtering. A second wavelength-conversion stage is implemented such that the output wavelength of the delay generator is the same as the input wavelength. With this scheme, we achieve continuously tunable delays over a range of 250 ps for 5.4-ps-long pulses at a data rate of 10 Gb/s. The delay generator does not exhibit any measurable pulse distortion and offers potential scalability to data rates as high as 60 Gb/s. The reconfiguration rate of the delay generator is limited by the tuning speed of the bandpass filter used in the wavelength-conversion stage.

Evaluation of Software-Implemented Fault-Tolerance (SIFT) Approach in Gracefully Degradable Multi-Computer Systems

This paper presents an analytical method for evaluating the reliability improvement for any size of multi-computer system based on Software-Implemented Fault-Tolerance (SIFT). The method is based on the equivalent failure rate Gamma, the single node failure rate lambda, the number of nodes in the system, N, the repair rate mu, the fault coverage factor c, the reconfiguration rate delta, and the percentage of blocking faults b <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and b <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The impact of these parameters on the reliability improvement has been evaluated for a gracefully degradable multi-computer system using our proposed analytical technique based on Markov chains. To validate our approach, we used the SIFT method which implements error detection at the node level, combined with a fast reconfiguration algorithm for avoiding faulty nodes. It is worth noting that the proposed method is applicable to any multi-computer systems' topology. The evaluation work presented in this paper focuses on the combination of analytical and experimental approaches, and more precisely on Markov chains. The SIFT method has been successfully implemented for a multi-computer system, nCube. The time overhead (reconfiguration & recomputation time) incurred by the injected fault, and the fault coverage factor c, are experimentally evaluated by means of a parallel version of the Software Object-Oriented Fault-Injection Tool (nSOFIT). The implemented SIFT approach can be used for real-time applications, when the time constraints should be met despite failures in the gracefully degradable multi-computer system

Understanding when location-hiding using overlay networks is feasible

Overlay networks (proxy networks) have been used as a communication infrastructure to allow applications to communicate with users without revealing their IP addresses. Such proxy networks are used to enhance application security; including protecting applications from direct attacks and infrastructure Denial-of-Service attacks. However, the conditions under which such approaches can hide application location are not well understood. To shed light on this question, we develop a formal framework for the proxy network approach to location-hiding which encompasses most of the proposed approaches. It is used to characterize how attacks, defenses, and correlated host vulnerabilities affect the feasibility of location-hiding. We find that existing approaches employing static structures (e.g., SOS and I3) cannot hide application location because attackers gain information monotonically and quickly penetrate the proxy network. However, adding defenses, such as proxy network reconfiguration or migration, which invalidate the information attackers have, makes location-hiding feasible against penetration attacks. Proxy-network depth and reconfiguration rates are critical factors for effectiveness. Furthermore, correlated vulnerabilities in many cases jeopardize location-hiding; however, by exploiting host diversity and intelligent proxy-network construction, the negative impact of correlation can be mitigated and location-hiding can be achieved. These results provide deeper understanding of the location-hiding problem and guidelines for proxy-network design.

An efficient reconfiguration scheme for fault-tolerant meshes

A new reconfiguration scheme, including a reconfiguration algorithm, is proposed in this paper to lift up the fault tolerance and system reconfiguration abilities for the mesh topology. The scheme adds redundancies––spare nodes and links––to the mesh network for necessary node replacement. By collocating a suitable number of spare nodes located at the best site of the network and joined by some well-connected spare links, our scheme is simple and yet effective in performing system reconfiguration. To carry out reconfiguration in a more regulated way, a reconfiguration algorithm is provided. The algorithm works dynamically and individually: system reconfiguration starts instantly upon the emergence of a fault and the replacement of a new faulty node is considered independently from previous replacements. Experimental performance evaluation shows that, with significantly reduced complexity, the proposed reconfiguration scheme is able to achieve desirable reconfiguration rates for the mesh network.

Extensional deformation, cohesive failure, and boundary conditions during sharkskin melt fracture

We measure the flow kinetics of a polyethylene extruded through the exit of a sapphire capillary tube in order to understand the nature of sharkskin, a surface roughness in the extruded material. Optical velocimetry shows that sharkskin can occur under a variety of polymer/wall boundary conditions; stick, slip, or oscillating stick/slip, demonstrating that the flow boundary condition is not the direct cause of sharkskin. Downstream of the exit, high-speed video microscopy reveals two distinct material failures during each sharkskin cycle, the first is cohesive and splits the material into two regions, the second one occurs at the polymer–wall interface. Upon modification of the surface with a polymer processing additive (PPA), we confirm strong slip at the wall and a suppression of sharkskin, but find that sharkskin does return at sufficiently high flow rates. The extensional strain rate at the onset of sharkskin is significantly higher in the case with PPA than that without. We then empirically define a “reconfiguration rate” and find it is comparable at the onset of sharkskin for the two surface conditions. We use data in the literature to show that the reconfiguration rate also predicts the relationship observed between the onset of sharkskin and the capillary radius.

Dynamic holographic telecommunications components based on spatial light modulation with pixelated χ(2) polymers in a Fabry-Pe´rot cavity

The provision of a range of wavelength division multiplexing (WDM) network component functionalities by ferroelectric liquid crystal (FLC) spatial light modulators (SLMs) has already been demonstrated in both transmissive and reflective arrangements. The FLC-SLM reconfiguration rate is limited to ~100 kHz by the liquid crystal response time. x(2) nonlinear optical polymers (NLOPs) might form the material basis of a future generation of faster and less costly SLMs for WDM applications, with response time limited only by electronic RC product. We present a theoretical analysis and the experimental characterization of single-pixel SLMs based on an ~2-?m film of commercially available x(2) NLOP in an asymmetric Fabry-Perot (AFP) cavity. Rigorous modeling enables optimization of the generic pixel design and specific pixel parameters, with the design guidelines and constraints dictated by the context of wideband WDM operation ~1.55 ?m. Polymer films are poled at a low field of ~35 V/?m and a 10-V modulating signal is applied. A modulation depth of 1.4% is provided by an AFP device of optimal pixel structure. Further characterization reveals a 3-dB width of transmitted intensity modulation ~10.8 nm near 1.55 ?m. The modeled behavior is extrapolated to yield two significant performance indicators. One indicator is that the holographic diffraction efficiency n of a full-scale pixelated AFP NLOP-SLM will be principally phase-modulation-dependent if the polymer Pockels coefficient r13 is of the order of 5 pm/V. For the preferred reflective geometry, the diffraction efficiency has a maximum value of ~13.5% cf. ~40% for a binary phase FLC-SLM. The second indicator is that for experimental devices, the 3-dB bandwidth of n~1.55 ?m will be only ~5 nm, but a~190 nm-thin cavity-optimized structure will have y3dB of ~30 nm.

Data transparent reconfigurable optical interconnections using polarization switching in VCSEL's induced by optical injection

We demonstrate a data transparent reconfigurable optical interconnection system based on optical injection controlled polarization switching in a master-slave vertical-cavity surface-emitting laser (VCSEL) configuration. A 140-Mb/s data stream generated by the slave VCSEL is redirected by an anisotropic diffractive optical element depending on the polarization state of the emitted light. The polarization of the slave laser is controlled by injecting an orthogonally polarized optical signal from a master laser. The current modulation of the master VCSEL and the subsequent polarization switching of the slave VCSEL occur at 40 MHz. In our setup, both the data rate and the optical interconnection reconfiguration rate are limited by the electronic drive circuitry and could in principle attain the gigahertz range.

Reconfigurable two-dimensional diffractive phase element with the fractional Talbot effect

We investigate the technical feasibility of the optical implementation of a four-phase-level diffractive element with two {0, pi}-phase spatial light modulators in a fractional Talbot configuration. The space-bandwidth product of the spatial light modulators is seen as the main theoretical limitation of the proposed approach. We investigate the robustness of technological and geometrical parameters on the diffraction efficiency of the whole system. Ferroelectric liquid-crystal silicon backplane spatial light modulators are chosen because of their high reconfiguration rates and good electro-optics interface. Similarly, we assess the influence of liquid-crystal technical parameters on system performance.

Data transparent reconfigurable optical interconnections based on polarization-switching VCSELs and polarization-selective diffractive optical elements

A polarization-switching VCSEL is combined with an anisotropic diffractive optical element to demonstrate, for the first time, reconfigurable free-space optical interconnects at a rate of 30 MHz. The same set of components is also used in a proof-of-principle demonstrator for data transparent reconfigurable optical interconnects at a bit rate of 1 MHz and a reconfiguration rate of 40 kHz.

Efficient beam steering in the 1.55 micron window using large-tilt FLC one-dimensional array

The recent development of wavelength division multiplexing requires novel transparent optical switches with moderate reconfiguration rates (typically the ms) for management and safety requirements at the optical -wavelength- level. One important fonction in such an optical switch is beam steering in the infrared 1.55 μm region. For that purpose, we propose to design a ferroelectric liquid crystal spatial light modulator (FLC SLM) acting as a programmable diffraction grating. Futhermore, a large-tilt angle FLC is used to make the device insensitive to the polarisation of the input wavefront. Prior to the realisation of the optical swich, we present here an experimental characterisation of the FLC beam deflector.

Microscopic theory of critical folding nuclei and reconfiguration activation barriers in folding proteins

An explicit droplet calculation is developed to address two aspects of the folding kinetics of large proteins: the thermodynamic folding barrier and the reconfiguration rate. First, a nonspecific folding nucleus is described as the instanton or droplet solution of a free energy functional derived for a minimally frustrated polymer Hamiltonian of the Gō type. Second, a theory for the barriers for transitions between trapped misfolded states is developed using a replica approach extended to inhomogeneous cases near the glass transition temperature of a random heteropolymer. Replica instantons are computed and their shape described. These two factors are then combined to give a microscopic theory of the folding time.

Implementation of an optical crossbar network based on directional switches

We have implemented an all-optical digital switching network based on ferroelectric liquid crystal arrays used as directional switches. It connects eight input to eight output channels simultaneously and randomly. The reconfiguration rate of the system can reach 100 kHz by using a parallel-driven 6 x 6 ferroelectric liquid crystal array. The modulation bandwidth in each channel depends only on the transmitters and receivers, not on the system itself.

Analysis of control subsystems for free-space photonic switching architectures

Four different methods of injecting control signals into photonic switches are compared. A control injection model based on time-division-multiplexed switching is developed, and the analysis studies the effects of the different control injection schemes on network performance, system complexity, and system packaging. Serious system-level limitations are identified for all the control injection schemes in switching networks with high reconfiguration rates.