Cascade Switching Research Articles

Pinball attacks against Dynamic Channel assignment in wireless networks

In this paper, we expose a class of stealthy attacks, which we coin pinball attacks, that exploit the adaptive nature of Dynamic Channel Assignment algorithms in wireless networks. In a pinball attack, the attacker strategically induces interference in the neighborhood of certain nodes to cause a cascading channel switching behavior, thereby exploiting the topology of the network to his own advantage. The attacker’s problem is formulated as a Markov Decision Process in which the attacker seeks to maximize his long-term net rewards. To overcome the exponential size of the state space, we derive suboptimal attack policies through approximation methods. We expose the pinball attacks on two general setups that arise practically in wireless communication systems. In the first setup, each wireless node is an access point aiming to select a channel that has minimum interference with its neighbors. In the second setup, we consider wireless nodes with multiple antennas whereby every node should communicate with each of its neighbors on a separate channel. We formally establish the equivalence of both setups by showing that the identified pinball attack policies on one can be directly mapped to attack policies on the other. We present numerical results to assess the impact of the obtained pinball attack policies under various topologies, and show that they outperform other known attack policies over all topologies considered. We also propose a novel approach to scale up the attack to larger size networks with special structures.

Functional Characterization of Insulation Effect for Synthetic Gene Circuits in Mammalian Cells.

Insulators are noncoding gene regulatory elements in eukaryotic genome, which function as chromatin partitioning boundaries, and block interference across different chromatin domains. To facilitate modular construction of synthetic gene circuit that is usually composed of multiple transcription cassettes, unwanted cross-regulations between different cassettes should be avoided. Here, we developed a quantitative method to characterize the functional effect of three insulators on the cross-regulations of six promoters in mammalian cells. We showed that the unwanted cross-regulations displayed a threshold-like effect, and the threshold position varied along with the context of promoters and insulators. We tested the function of insulators in both cascade and sensory switch circuits assembled in episomal plasmid vectors, and showed that the insulation effect was mainly revealed on the first regulatory layer of the cascade circuit. A deviation on the response curve of the sensory switch circuit with or without insulators was observed, but response intensity of some sensory switch circuits were not affected. Therefore, our results provided a general guide on the selection of insulators with varying promoters in episomal synthetic gene circuits in mammalian cells, which may be useful to reduce the effect of the unwanted cross-regulations.

Distinguishing mechanisms underlying EMT tristability

BackgroundThe Epithelial-Mesenchymal Transition (EMT) endows epithelial-looking cells with enhanced migratory ability during embryonic development and tissue repair. EMT can also be co-opted by cancer cells to acquire metastatic potential and drug-resistance. Recent research has argued that epithelial (E) cells can undergo either a partial EMT to attain a hybrid epithelial/mesenchymal (E/M) phenotype that typically displays collective migration, or a complete EMT to adopt a mesenchymal (M) phenotype that shows individual migration. The core EMT regulatory network - miR-34/SNAIL/miR-200/ZEB1 - has been identified by various studies, but how this network regulates the transitions among the E, E/M, and M phenotypes remains controversial. Two major mathematical models – ternary chimera switch (TCS) and cascading bistable switches (CBS) - that both focus on the miR-34/SNAIL/miR-200/ZEB1 network, have been proposed to elucidate the EMT dynamics, but a detailed analysis of how well either or both of these two models can capture recent experimental observations about EMT dynamics remains to be done.ResultsHere, via an integrated experimental and theoretical approach, we first show that both these two models can be used to understand the two-step transition of EMT - E→E/M→M, the different responses of SNAIL and ZEB1 to exogenous TGF-β and the irreversibility of complete EMT. Next, we present new experimental results that tend to discriminate between these two models. We show that ZEB1 is present at intermediate levels in the hybrid E/M H1975 cells, and that in HMLE cells, overexpression of SNAIL is not sufficient to initiate EMT in the absence of ZEB1 and FOXC2.ConclusionsThese experimental results argue in favor of the TCS model proposing that miR-200/ZEB1 behaves as a three-way decision-making switch enabling transitions among the E, hybrid E/M and M phenotypes.

Architecture and performance of grouped ROADM rings with shared optical amplifier and grouped add/drop ports for hybrid data center network

We propose a novel reconfigurable optical add drop multiplexer (ROADM) rings architecture for the hybrid data center network where a pair of optical amplifiers is shared in a maximum number of ROADMs group to reduce cost. We show through simulation that the network proposal can almost achieve the same bit error rate performance of the conventional rings network with fully installed optical amplifiers, and 50% of optical amplifiers can be saved. The narrowing effect of cascading wavelength selective switches limits the number of ROADMs in such architecture to 54 regardless of the number of optical amplifiers provided. Based on those results, an ROADM with grouped add/drop ports is also proposed to further increase the capacity of network, which is 4 fold of the original ROADM rings architecture.

All-optical OXC transition strategy from WDM optical network to elastic optical network.

Elastic optical network (EON) has been proposed recently as a spectrum-efficient optical layer to adapt to rapidly-increasing traffic demands instead of current deployed wavelength-division-multiplexing (WDM) optical network. In contrast with conventional WDM optical cross-connect (OXCs) based on wavelength selective switches (WSSs), the EON OXCs are based on spectrum selective switches (SSSs) which are much more expensive than WSSs, especially for large-scale switching architectures. So the transition cost from WDM OXCs to EON OXCs is a major obstacle to realizing EON. In this paper, we propose and experimentally demonstrate a transition OXC (TOXC) structure based on 2-stage cascading switching architectures, which make full use of available WSSs in current deployed WDM OXCs to reduce number and port count of required SSSs. Moreover, we propose a contention-aware spectrum allocation (CASA) scheme for EON built with the proposed TOXCs. We show by simulation that the TOXCs reduce the network capital expenditure transiting from WDM optical network to EON about 50%, with a minor traffic blocking performance degradation and about 10% accommodated traffic number detriment compared with all-SSS EON OXC architectures.

Improvement in bias current redistribution in superconducting strip ion detectors with parallel configuration**Project supported by a Grant-in-Aid for Scientific Research (A) and (C) from the Japan Society for the Promotion of Science (Grant Nos. 22246056 and 24619013).

In time-of-flight mass spectrometry (TOF MS), superconducting strip ion detectors (SSIDs) in the parallel configuration are promising for ideal ion detection with a nanosecond-scale time response and a practical large sensitive area. In the parallel configuration, the bias current in one strip is diverted into other parallel strips after each detection event. Under high bias current conditions, the diverted bias current induces cascade switching of all parallel strips. Studies show that cascade switching degrades the ion count rate of SSIDs made from niobium and hence is disliked in TOF MS applications. To suppress the bias current redistribution, we connected resistors in a series with the individual parallel strips using aluminum-bonding wires. Their effect was studied by measuring the pulse height distributions.

TGF-β-induced epithelial-to-mesenchymal transition proceeds through stepwise activation of multiple feedback loops.

The process of epithelial-to-mesenchymal transition (EMT) is an essential type of cellular plasticity associated with a change from epithelial cells that function as a barrier consisting of a sheet of tightly connected cells to cells with properties of mesenchyme that are not attached to their neighbors and are highly motile. This phenotypic change occurs during development and also contributes to pathological processes, such as cancer progression. The molecular mechanisms controlling the switch between the fully epithelial and fully mesenchymal phenotypes and cells that have characteristics of both (partial EMT) are controversial, and multiple theoretical models have been proposed. To test these theoretical models, we systematically measured the changes in the abundance of proteins, mRNAs, and microRNAs (miRNAs) that represent the core regulators of EMT induced by transforming growth factor-β1 (TGF-β1) in the human breast epithelial cell line MCF10A at the population and single-cell levels. We provide experimental confirmation for a model of cascading switches in phenotypes associated with TGF-β1-induced EMT of MCF10A cells that involves two double-negative feedback loops: one between the transcription factor SNAIL1 and the miR-34 family and another between the transcription factor ZEB1 and the miR-200 family. Furthermore, our data showed that whereas the transition from epithelial to partial EMT was reversible for MCF10A cells, the transition from partial EMT to mesenchymal was mostly irreversible at high concentrations of TGF-β1.

Nano-optical observation of cascade switching in a parallel superconducting nanowire single photon detector

The device physics of parallel-wire superconducting nanowire single photon detectors is based on a cascade process. Using nano-optical techniques and a parallel wire device with spatially separate pixels, we explicitly demonstrate the single- and multi-photon triggering regimes. We develop a model for describing efficiency of a detector operating in the arm-trigger regime. We investigate the timing response of the detector when illuminating a single pixel and two pixels. We see a change in the active area of the detector between the two regimes and find the two-pixel trigger regime to have a faster timing response than the one-pixel regime.

The Triggered Behavior of a Controlled Corona Stabilized Cascade Switch

Corona stabilized switches have been shown to have advantages in pulse power switching applications due to their high repetition rates and low jitter. Work performed in recent years by the High Voltage Technologies Group within the Department of Electronic and Electrical Engineering at the University of Strathclyde has shown that the operating voltage range of such switches can be extended by using a multigap cascade configuration. One particular multigap topology, filled with pressurized atmospheric air, was shown to operate at 80 kV with a switching jitter of ~ 2 ns. It has since been shown that, by modifying the topology of the corona sources on the electrodes, it is possible to control the grading of the voltage distribution across the gaps in the cascade. The voltages across each gap and the self-break behavior of the cascade were found to be in close agreement with the values predicted from the corona emission characteristics for the tested electrode topologies. This paper reports on a further examination of the behavior of the corona controlled switching topology, where the triggered operation of the switch has been investigated for different voltage distributions across the cascade gaps.

All-Optical Reversible Logic Gates with Optically Controlled Bacteriorhodopsin Protein-Coated Microresonators

We present designs of all-optical reversible gates, namely, Feynman, Toffoli, Peres, and Feynman double gates, with optically controlled microresonators. To demonstrate the applicability, a bacteriorhodopsin protein-coated silica microcavity in contact between two tapered single-mode fibers has been used as an all-optical switch. Low-power control signals (<200 μW) at 532 nm and at 405 nm control the conformational states of the protein to switch a near infrared signal laser beam at 1310 or 1550 nm. This configuration has been used as a template to design four-port tunable resonant coupler logic gates. The proposed designs are general and can be implemented in both fiber-optic and integrated-optic formats and with any other coated photosensitive material. Advantages of directed logic, high Q-factor, tunability, compactness, low-power control signals, high fan-out, and flexibility of cascading switches in 2D/3D architectures to form circuits make the designs promising for practical applications.

Design of All-Optical Reconfigurable Logic Unit With Bacteriorhodopsin Protein Coated Microcavity Switches

We present a theoretical design of an all-optical reconfigurable logic unit based on optically controlled microcavity switches, for realization of all-optical computing circuits. It can execute different logic and arithmetic operations such as half and full adder or subtractor, by only changing the control inputs on the same circuit. Theoretical designs considering bacteriorhodopsin (BR) protein coated microcavities in tree architecture have been presented. The combined advantages of high Q-factor, tunability, compactness, switching of near-IR signals at telecom wavelengths (1310/1550 nm) with low-power control signals, and flexibility of cascading switches to form circuits, makes the designs promising for practical applications. They combine the ultrahigh sensitivity of both BR and microresonators to define a novel paradigm of all-optical computing based on hybrid nanobiophotonic integration.

Characterization of superconducting pulse discriminators based on parallel NbNnanostriplines

A superconducting pulse discriminator based on a cascade switch to the normal state ofparallel ultrathin NbN nanostrips has been fabricated and carefully investigated.Correct operation was achieved using 1 ns input pulses with amplitudes down to15 µA. The discriminator had a peak current gain of 12 and an FWHM timing jitter of 80 ps,limited by our measurement instrument resolution. These characteristics, together withsimple on-chip integration, small area and low dissipation, make this device suitable forapplications such as readout of fast cryogenic detectors and the output stage ofsuperconducting digital circuits.

Novel proposal for all-optical Fredkin logic gate with bacteriorhodopsin-coated microcavity and its applications

We present a design of the conservative, reversible, and universal all-optical Fredkin logic gate based on a single bacteriorhodopsin (BR)-protein-coated silica microcavity. The switching of a near-IR laser beam at 1310 or 1550 nm by photoactivating a silica microsphere coated with BR monolayers with a low power control signal at 532 nm, in contact between two tapered single-mode fibers, is used as a template for a four-port tunable resonant coupler Fredkin gate. The proposed gate has also been used to design low-power all-optical AND, OR, NOT, XOR, and X-NOR gates and full-adder and demultiplexer/multiplexer circuits. The advantages of high Q-factor, tunability, compactness, low-power control signals, high fan-out, and flexibility of cascading switches in 2-D to 3-D architectures to form circuits, makes the designs promising for practical applications. The proposed design provides a new paradigm for hybrid nanobiophotonic integration for all-optical computing.

The diapause decision as a cascade switch for adaptive developmental plasticity in body mass in a butterfly

Switch-induced developmental plasticity, such as the diapause decision in insects, is a major form of adaptation to variable environments. As individuals that follow alternative developmental pathways will experience different selective environments the diapause decision may evolve to a cascade switch that induces additional adaptive developmental differences downstream of the diapause decision. Here, we show that individuals following alternative developmental pathways in a Swedish population of the butterfly, Pararge aegeria, display differential optimization of adult body mass as a likely response to predictable differences in thermal conditions during reproduction. In a more northern population where this type of selection is absent no similar difference in adult mass among pathways was found. We conclude that the diapause decision in the southern population appears to act as a cascade switch, coordinating development downstream of the diapause decision, to produce adult phenotypes adapted to the typical thermal conditions of their expected reproductive period.

All-optical switching with bacteriorhodopsin protein coated microcavities and its application to low power computing circuits

We show all-optical switching of an input infrared laser beam at 1310 nm by controlling the photoinduced retinal isomerization to tune the resonances in a silica microsphere coated with three bacteriorhodopsin (BR) protein monolayers. The all-optical tunable resonant coupler re-routes the infrared beam between two tapered fibers in 50 μs using a low power (<200 μW) green (532 nm) and blue (405 nm) pump beams. The basic switching configuration has been used to design all-optical computing circuits, namely, half and full adder/subtractor, de-multiplexer, multiplexer, and an arithmetic unit. The design requires 2n−1 switches to realize n bit computation. The designs combine the exceptional sensitivities of BR and high-Q microcavities and the versatile tree architecture for realizing low power circuits and networks (approximately mW power budget). The combined advantages of high Q-factor, tunability, compactness, and low power control signals, with the flexibility of cascading switches to form circuits, and reversibility and reconfigurability to realize arithmetic and logic functions, makes the designs promising for practical applications. The designs are general and can be implemented (i) in both fiber-optic and integrated optic formats, (ii) with any other coated photosensitive material, or (iii) any externally controlled microresonator switch.

1 mm ultrafast superconducting stripline molecule detector

Superconducting stripline detectors (SSLDs) are promising for detecting keV molecules at nanosecond response times and with mass-independent detection efficiency. However, a fast response time is incompatible with practical centimeter detector size. A parallel configuration of striplines provides a means to address this problem. Experimental results and simulation for promisingly large 1-mm-square parallel niobium SSLDs show that nanosecond pulses are produced by superconducting-normal transition within only one of the parallel striplines instead of cascade switching of all the parallel striplines. Successful detection of a series of multimers of immunoglobulin G up to 584 kDa supports the mass-independent efficiency for mass spectrometry.

Timing jitter of cascade switch superconducting nanowire single photon detectors

We investigate the timing jitter in parallel superconducting NbN-nanowire single photon detectors based on a cascade switch mechanism. The measured timing jitter is asymmetric and has an oscillatory dependence on bias current. At the highest bias current the full width at half maximum was 1.5 times larger than an on-chip reference meander NbN nanowire. A physical model of the dynamics occurring during cascade switch is developed, that quantitatively accounts for our observations as a consequence of different nanowire critical currents within the detector.

A corona-stabilised plasma closing switch

Corona-stabilised plasma closing switches, filled with electronegative gases such as SF6 and air, have been used in pulsed-power applications as repetitive switching devices for the last 10 years. Their high repetition-rate capabilities coupled with their relatively simple design and construction have made them suitable alternatives to thyratrons and semi-conductor switches. As well as having repetitive switching capabilities, corona-stabilised plasma closing switches have the potential to operate at elevated voltages through the incorporation of multiple electrode sets. This allows high-voltage operation with inherent voltage grading between the electrodes. A further feature of such switches is that they can have relatively low jitter under triggered condition. This paper reports on some of the operational features of a new design of corona-stabilised, cascade switch that utilises air as the insulating gas. At pressures between 0 and 1 bar gauge the switch has be shown to operate over the voltage range of 40 to 100 kV with a jitter below 2 ns.

Large Signal Amplitude and Bias Range of Cascade Switch Superconducting Nanowire Single Photon Detectors

Cascade switch superconducting nanowire single photon detectors has been fabricated of ultrathin NbN films deposited by DC-magnetron sputtering at room temperature on MgO substrates. Detectors using 4 to 24 nanowires in parallel, having an area coverage of 5times mum2 and a filling factor of 40%, have been investigated. Signal amplitudes increase with the number of parallel nanowires and reaches 12.3 mV with a signal noise of 20 muV. The range of bias currents where the detectors emit signal pulses also increase with the number of parallel nanowires and exceeds the nanowire critical current.

Experimental characterization of NbN nanowire optical detectors with parallel stripline configuration

We have developed a novel geometrical configuration for NbN-based superconducting single photon optical detector (SSPD) that achieves two goals: a much lower intrinsic impedance, and a consequently greater bandwidth, and a much larger signal amplitude compared to the standard meandered configuration. This has been obtained by implementing a properly designed parallel stripline structure where a cascade switching mechanism occurs when one of the striplines is hit by an optical photon. The overall switching occurs synchronously and in a very short time, giving rise to a strong and fast voltage pulse. The SSPD have been realized using state of the art NbN deposition technology and e-beam lithography. The strips are 100 nm wide and 5 μm long and have been realized with 4 nm NbN film on sapphire and Si substrate. We report on experimental characterization of such novel devices. The performances of the proposed novel type of SSPD are compared with standard SSPD design and results in terms of signal amplitude, risetime and effective detection area.