A conserved SREBP-1/phosphatidylcholine feedback circuit regulates lipogenesis in metazoans.

Science.gov (United States)

Walker, Amy K; Jacobs, René L; Watts, Jennifer L; Rottiers, Veerle; Jiang, Karen; Finnegan, Deirdre M; Shioda, Toshi; Hansen, Malene; Yang, Fajun; Niebergall, Lorissa J; Vance, Dennis E; Tzoneva, Monika; Hart, Anne C; Näär, Anders M

2011-11-11

Sterol regulatory element-binding proteins (SREBPs) activate genes involved in the synthesis and trafficking of cholesterol and other lipids and are critical for maintaining lipid homeostasis. Aberrant SREBP activity, however, can contribute to obesity, fatty liver disease, and insulin resistance, hallmarks of metabolic syndrome. Our studies identify a conserved regulatory circuit in which SREBP-1 controls genes in the one-carbon cycle, which produces the methyl donor S-adenosylmethionine (SAMe). Methylation is critical for the synthesis of phosphatidylcholine (PC), a major membrane component, and we find that blocking SAMe or PC synthesis in C. elegans, mouse liver, and human cells causes elevated SREBP-1-dependent transcription and lipid droplet accumulation. Distinct from negative regulation of SREBP-2 by cholesterol, our data suggest a feedback mechanism whereby maturation of nuclear, transcriptionally active SREBP-1 is controlled by levels of PC. Thus, nutritional or genetic conditions limiting SAMe or PC production may activate SREBP-1, contributing to human metabolic disorders. Copyright © 2011 Elsevier Inc. All rights reserved.

Cortical feedback control of olfactory bulb circuits.

Science.gov (United States)

Boyd, Alison M; Sturgill, James F; Poo, Cindy; Isaacson, Jeffry S

2012-12-20

Olfactory cortex pyramidal cells integrate sensory input from olfactory bulb mitral and tufted (M/T) cells and project axons back to the bulb. However, the impact of cortical feedback projections on olfactory bulb circuits is unclear. Here, we selectively express channelrhodopsin-2 in olfactory cortex pyramidal cells and show that cortical feedback projections excite diverse populations of bulb interneurons. Activation of cortical fibers directly excites GABAergic granule cells, which in turn inhibit M/T cells. However, we show that cortical inputs preferentially target short axon cells that drive feedforward inhibition of granule cells. In vivo, activation of olfactory cortex that only weakly affects spontaneous M/T cell firing strongly gates odor-evoked M/T cell responses: cortical activity suppresses odor-evoked excitation and enhances odor-evoked inhibition. Together, these results indicate that although cortical projections have diverse actions on olfactory bulb microcircuits, the net effect of cortical feedback on M/T cells is an amplification of odor-evoked inhibition. Copyright © 2012 Elsevier Inc. All rights reserved.

The stochastic behavior of a molecular switching circuit with feedback

Directory of Open Access Journals (Sweden)

Smith Eric

2007-05-01

Full Text Available Abstract Background Using a statistical physics approach, we study the stochastic switching behavior of a model circuit of multisite phosphorylation and dephosphorylation with feedback. The circuit consists of a kinase and phosphatase acting on multiple sites of a substrate that, contingent on its modification state, catalyzes its own phosphorylation and, in a symmetric scenario, dephosphorylation. The symmetric case is viewed as a cartoon of conflicting feedback that could result from antagonistic pathways impinging on the state of a shared component. Results Multisite phosphorylation is sufficient for bistable behavior under feedback even when catalysis is linear in substrate concentration, which is the case we consider. We compute the phase diagram, fluctuation spectrum and large-deviation properties related to switch memory within a statistical mechanics framework. Bistability occurs as either a first-order or second-order non-equilibrium phase transition, depending on the network symmetries and the ratio of phosphatase to kinase numbers. In the second-order case, the circuit never leaves the bistable regime upon increasing the number of substrate molecules at constant kinase to phosphatase ratio. Conclusion The number of substrate molecules is a key parameter controlling both the onset of the bistable regime, fluctuation intensity, and the residence time in a switched state. The relevance of the concept of memory depends on the degree of switch symmetry, as memory presupposes information to be remembered, which is highest for equal residence times in the switched states. Reviewers This article was reviewed by Artem Novozhilov (nominated by Eugene Koonin, Sergei Maslov, and Ned Wingreen.

Parts & Pools: A Framework for Modular Design of Synthetic Gene Circuits

Energy Technology Data Exchange (ETDEWEB)

Marchisio, Mario Andrea, E-mail: marchisio@hit.edu.cn [School of Life Science and Technology, Harbin Institute of Technology, Harbin (China)

2014-10-06

Published in 2008, Parts & Pools represents one of the first attempts to conceptualize the modular design of bacterial synthetic gene circuits with Standard Biological Parts (DNA segments) and Pools of molecules referred to as common signal carriers (e.g., RNA polymerases and ribosomes). The original framework for modeling bacterial components and designing prokaryotic circuits evolved over the last years and brought, first, to the development of an algorithm for the automatic design of Boolean gene circuits. This is a remarkable achievement since gene digital circuits have a broad range of applications that goes from biosensors for health and environment care to computational devices. More recently, Parts & Pools was enabled to give a proper formal description of eukaryotic biological circuit components. This was possible by employing a rule-based modeling approach, a technique that permits a faithful calculation of all the species and reactions involved in complex systems such as eukaryotic cells and compartments. In this way, Parts & Pools is currently suitable for the visual and modular design of synthetic gene circuits in yeast and mammalian cells too.

Parts & Pools: A Framework for Modular Design of Synthetic Gene Circuits

International Nuclear Information System (INIS)

Marchisio, Mario Andrea

2014-01-01

Published in 2008, Parts & Pools represents one of the first attempts to conceptualize the modular design of bacterial synthetic gene circuits with Standard Biological Parts (DNA segments) and Pools of molecules referred to as common signal carriers (e.g., RNA polymerases and ribosomes). The original framework for modeling bacterial components and designing prokaryotic circuits evolved over the last years and brought, first, to the development of an algorithm for the automatic design of Boolean gene circuits. This is a remarkable achievement since gene digital circuits have a broad range of applications that goes from biosensors for health and environment care to computational devices. More recently, Parts & Pools was enabled to give a proper formal description of eukaryotic biological circuit components. This was possible by employing a rule-based modeling approach, a technique that permits a faithful calculation of all the species and reactions involved in complex systems such as eukaryotic cells and compartments. In this way, Parts & Pools is currently suitable for the visual and modular design of synthetic gene circuits in yeast and mammalian cells too.

Feed-Forward versus Feedback Inhibition in a Basic Olfactory Circuit.

Directory of Open Access Journals (Sweden)

Tiffany Kee

2015-10-01

Full Text Available Inhibitory interneurons play critical roles in shaping the firing patterns of principal neurons in many brain systems. Despite difference in the anatomy or functions of neuronal circuits containing inhibition, two basic motifs repeatedly emerge: feed-forward and feedback. In the locust, it was proposed that a subset of lateral horn interneurons (LHNs, provide feed-forward inhibition onto Kenyon cells (KCs to maintain their sparse firing--a property critical for olfactory learning and memory. But recently it was established that a single inhibitory cell, the giant GABAergic neuron (GGN, is the main and perhaps sole source of inhibition in the mushroom body, and that inhibition from this cell is mediated by a feedback (FB loop including KCs and the GGN. To clarify basic differences in the effects of feedback vs. feed-forward inhibition in circuit dynamics we here use a model of the locust olfactory system. We found both inhibitory motifs were able to maintain sparse KCs responses and provide optimal odor discrimination. However, we further found that only FB inhibition could create a phase response consistent with data recorded in vivo. These findings describe general rules for feed-forward versus feedback inhibition and suggest GGN is potentially capable of providing the primary source of inhibition to the KCs. A better understanding of how inhibitory motifs impact post-synaptic neuronal activity could be used to reveal unknown inhibitory structures within biological networks.

Circuit simulation and physical implementation for a memristor-based colpitts oscillator

OpenAIRE

Hongmin Deng; Dongping Wang

2017-01-01

This paper implements two kinds of memristor-based colpitts oscillators, namely, the circuit where the memristor is added into the feedback network of the oscillator in parallel and series, respectively. First, a MULTISIM simulation circuit for the memristive colpitts oscillator is built, where an emulator constructed by some off-the-shelf components is utilized to replace the memristor. Then the physical system is implemented in terms of the MULTISIM simulation circuit. Circuit simulation an...

Design and Preliminary Results of a Feedback Circuit for Plasma Displacement Control in IR-T1 Tokamak

International Nuclear Information System (INIS)

TalebiTaher, A.; Ghoranneviss, M.; Tarkeshian, R.; Salem, M. K.; Khorshid, P.

2008-01-01

Since displacement is very important for plasma position control, in IR-T1 tokamak a combination of two cosine coils and two saddle sine coils is used for horizontal displacement measurement. According to the multiple moment theory, the output of these coils linearly depends to radial displacement of plasma column. A new circuit for adding these signals to feedback system designed and unwanted effects of other fields in final output compensated. After compensation and calibration of the system, the output of horizontal displacement circuits applied to feedback control system. By considers the required auxiliary vertical field, a proportional amplifier and driver circuit are constructed to drive power transistors these power transistors switch the feedback bank capacitors. In the experiment, a good linear proportionality between displacement and output observed by applying an appropriate feedback field, the linger confinement time in IR-T1 tokamak obtained, applying this system to discharge increased the plasma duration and realizes repetitive discharges

Automatic design of digital synthetic gene circuits.

Directory of Open Access Journals (Sweden)

Mario A Marchisio

2011-02-01

Full Text Available De novo computational design of synthetic gene circuits that achieve well-defined target functions is a hard task. Existing, brute-force approaches run optimization algorithms on the structure and on the kinetic parameter values of the network. However, more direct rational methods for automatic circuit design are lacking. Focusing on digital synthetic gene circuits, we developed a methodology and a corresponding tool for in silico automatic design. For a given truth table that specifies a circuit's input-output relations, our algorithm generates and ranks several possible circuit schemes without the need for any optimization. Logic behavior is reproduced by the action of regulatory factors and chemicals on the promoters and on the ribosome binding sites of biological Boolean gates. Simulations of circuits with up to four inputs show a faithful and unequivocal truth table representation, even under parametric perturbations and stochastic noise. A comparison with already implemented circuits, in addition, reveals the potential for simpler designs with the same function. Therefore, we expect the method to help both in devising new circuits and in simplifying existing solutions.

A SQUID gradiometer module with wire-wound pickup antenna and integrated voltage feedback circuit

Energy Technology Data Exchange (ETDEWEB)

Zhang Guofeng [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Peter Gruenberg Institute (PGI-8), Forschungszentrum Juelich (FZJ), D-52425 Juelich (Germany); Joint Research Laboratory on Superconductivity and Bioelectronics, Collaboration between CAS-Shanghai and FZJ, Shanghai 200050 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Yi, E-mail: y.zhang@fz-juelich.de [Peter Gruenberg Institute (PGI-8), Forschungszentrum Juelich (FZJ), D-52425 Juelich (Germany); Joint Research Laboratory on Superconductivity and Bioelectronics, Collaboration between CAS-Shanghai and FZJ, Shanghai 200050 (China); Zhang Shulin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Joint Research Laboratory on Superconductivity and Bioelectronics, Collaboration between CAS-Shanghai and FZJ, Shanghai 200050 (China); Krause, Hans-Joachim [Peter Gruenberg Institute (PGI-8), Forschungszentrum Juelich (FZJ), D-52425 Juelich (Germany); Joint Research Laboratory on Superconductivity and Bioelectronics, Collaboration between CAS-Shanghai and FZJ, Shanghai 200050 (China); and others

2012-10-15

The performance of the direct readout schemes for dc SQUID, Additional Positive Feedback (APF), noise cancellation (NC) and SQUID bootstrap circuit (SBC), have been studied in conjunction with planar SQUID magnetometers. In this paper, we examine the NC technique applied to a niobium SQUID gradiometer module with an Nb wire-wound antenna connecting to a dual-loop SQUID chip with an integrated voltage feedback circuit for suppression of the preamplifier noise contribution. The sensitivity of the SQUID gradiometer module is measured to be about 1 fT/(cm {radical}Hz) in the white noise range in a magnetically shielded room. Using such gradiometer, both MCG and MEG signals are recorded.

Circuit simulation and physical implementation for a memristor-based colpitts oscillator

Science.gov (United States)

Deng, Hongmin; Wang, Dongping

2017-03-01

This paper implements two kinds of memristor-based colpitts oscillators, namely, the circuit where the memristor is added into the feedback network of the oscillator in parallel and series, respectively. First, a MULTISIM simulation circuit for the memristive colpitts oscillator is built, where an emulator constructed by some off-the-shelf components is utilized to replace the memristor. Then the physical system is implemented in terms of the MULTISIM simulation circuit. Circuit simulation and experimental study show that this memristive colpitts oscillator can exhibit periodic, quasi-periodic, and chaotic behaviors with certain parameter's variances. Besides, in a sense, the circuit is robust with circuit parameters and device types.

Gene Circuit Analysis of the Terminal Gap Gene huckebein

Science.gov (United States)

Ashyraliyev, Maksat; Siggens, Ken; Janssens, Hilde; Blom, Joke; Akam, Michael; Jaeger, Johannes

2009-01-01

The early embryo of Drosophila melanogaster provides a powerful model system to study the role of genes in pattern formation. The gap gene network constitutes the first zygotic regulatory tier in the hierarchy of the segmentation genes involved in specifying the position of body segments. Here, we use an integrative, systems-level approach to investigate the regulatory effect of the terminal gap gene huckebein (hkb) on gap gene expression. We present quantitative expression data for the Hkb protein, which enable us to include hkb in gap gene circuit models. Gap gene circuits are mathematical models of gene networks used as computational tools to extract regulatory information from spatial expression data. This is achieved by fitting the model to gap gene expression patterns, in order to obtain estimates for regulatory parameters which predict a specific network topology. We show how considering variability in the data combined with analysis of parameter determinability significantly improves the biological relevance and consistency of the approach. Our models are in agreement with earlier results, which they extend in two important respects: First, we show that Hkb is involved in the regulation of the posterior hunchback (hb) domain, but does not have any other essential function. Specifically, Hkb is required for the anterior shift in the posterior border of this domain, which is now reproduced correctly in our models. Second, gap gene circuits presented here are able to reproduce mutants of terminal gap genes, while previously published models were unable to reproduce any null mutants correctly. As a consequence, our models now capture the expression dynamics of all posterior gap genes and some variational properties of the system correctly. This is an important step towards a better, quantitative understanding of the developmental and evolutionary dynamics of the gap gene network. PMID:19876378

Dynamic Coding of Signed Quantities in Cortical Feedback Circuits

Directory of Open Access Journals (Sweden)

Dana eBallard

2012-08-01

Full Text Available In the early sensory and motor areas of the cortex, individual neurons transmit information about specific sensory features via a peaked response. This concept has been crystallized as `labeled lines,' to denote that axons communicate the specific properties of their sensory or motor parent cell. Such cells also can be characterized as being polarized, that is, as representing a signed quantity that is either positive or negative. We show in a model simulation that there are two important consequences when learning receptive fields using such signed codings in circuits that subtract different inputs. The first is that, in feedback circuits using labeled lines, such arithmetic operations need to be distributed across multiple distinct pathways. The second consequence is that such pathways must be necessarily dynamic, i.e. that synapses can grow and retract when forming receptive fields. The model monitors the breaking and growing of new circuit connections when their synapses need to change polarities and predicts that the rate of such changes should be inversely correlated with the progress of receptive field formation.

Circuit simulation and physical implementation for a memristor-based colpitts oscillator

Directory of Open Access Journals (Sweden)

Hongmin Deng

2017-03-01

Full Text Available This paper implements two kinds of memristor-based colpitts oscillators, namely, the circuit where the memristor is added into the feedback network of the oscillator in parallel and series, respectively. First, a MULTISIM simulation circuit for the memristive colpitts oscillator is built, where an emulator constructed by some off-the-shelf components is utilized to replace the memristor. Then the physical system is implemented in terms of the MULTISIM simulation circuit. Circuit simulation and experimental study show that this memristive colpitts oscillator can exhibit periodic, quasi-periodic, and chaotic behaviors with certain parameter’s variances. Besides, in a sense, the circuit is robust with circuit parameters and device types.

Monolithically Integrated Light Feedback Control Circuit for Blue/UV LED Smart Package

NARCIS (Netherlands)

Koladouz Esfahani, Z.; Tohidian, M.; van Zeijl, H.W.; Kolahdouz, Mohammadreza; Zhang, G.Q.

2017-01-01

Given the performance decay of high-power light-emitting diode (LED) chips over time and package condition changes, having a reliable output light for sensitive applications is a point of concern. In this study, a light feedback control circuit, including blue-selective photodiodes, for

Microcontroller-based Feedback Control Laboratory Experiments

Directory of Open Access Journals (Sweden)

Chiu Choi

2014-06-01

Full Text Available this paper is a result of the implementation of the recommendations on enhancing hands-on experience of control engineering education using single chip, small scale computers such as microcontrollers. A set of microcontroller-based feedback control experiments was developed for the Electrical Engineering curriculum at the University of North Florida. These experiments provided hands-on techniques that students can utilize in the development of complete solutions for a number of servo control problems. Significant effort was devoted to software development of feedback controllers and the associated signal conditioning circuits interfacing between the microcontroller and the physical plant. These experiments have stimulated the interest of our students in control engineering.

Modular design of synthetic gene circuits with biological parts and pools.

Science.gov (United States)

Marchisio, Mario Andrea

2015-01-01

Synthetic gene circuits can be designed in an electronic fashion by displaying their basic components-Standard Biological Parts and Pools of molecules-on the computer screen and connecting them with hypothetical wires. This procedure, achieved by our add-on for the software ProMoT, was successfully applied to bacterial circuits. Recently, we have extended this design-methodology to eukaryotic cells. Here, highly complex components such as promoters and Pools of mRNA contain hundreds of species and reactions whose calculation demands a rule-based modeling approach. We showed how to build such complex modules via the joint employment of the software BioNetGen (rule-based modeling) and ProMoT (modularization). In this chapter, we illustrate how to utilize our computational tool for synthetic biology with the in silico implementation of a simple eukaryotic gene circuit that performs the logic AND operation.

Drosophila olfactory memory: single genes to complex neural circuits.

Science.gov (United States)

Keene, Alex C; Waddell, Scott

2007-05-01

A central goal of neuroscience is to understand how neural circuits encode memory and guide behaviour. Studying simple, genetically tractable organisms, such as Drosophila melanogaster, can illuminate principles of neural circuit organization and function. Early genetic dissection of D. melanogaster olfactory memory focused on individual genes and molecules. These molecular tags subsequently revealed key neural circuits for memory. Recent advances in genetic technology have allowed us to manipulate and observe activity in these circuits, and even individual neurons, in live animals. The studies have transformed D. melanogaster from a useful organism for gene discovery to an ideal model to understand neural circuit function in memory.

A framework for scalable parameter estimation of gene circuit models using structural information

KAUST Repository

Kuwahara, Hiroyuki

2013-06-21

Motivation: Systematic and scalable parameter estimation is a key to construct complex gene regulatory models and to ultimately facilitate an integrative systems biology approach to quantitatively understand the molecular mechanisms underpinning gene regulation. Results: Here, we report a novel framework for efficient and scalable parameter estimation that focuses specifically on modeling of gene circuits. Exploiting the structure commonly found in gene circuit models, this framework decomposes a system of coupled rate equations into individual ones and efficiently integrates them separately to reconstruct the mean time evolution of the gene products. The accuracy of the parameter estimates is refined by iteratively increasing the accuracy of numerical integration using the model structure. As a case study, we applied our framework to four gene circuit models with complex dynamics based on three synthetic datasets and one time series microarray data set. We compared our framework to three state-of-the-art parameter estimation methods and found that our approach consistently generated higher quality parameter solutions efficiently. Although many general-purpose parameter estimation methods have been applied for modeling of gene circuits, our results suggest that the use of more tailored approaches to use domain-specific information may be a key to reverse engineering of complex biological systems. The Author 2013.

A framework for scalable parameter estimation of gene circuit models using structural information

KAUST Repository

Kuwahara, Hiroyuki; Fan, Ming; Wang, Suojin; Gao, Xin

2013-01-01

Motivation: Systematic and scalable parameter estimation is a key to construct complex gene regulatory models and to ultimately facilitate an integrative systems biology approach to quantitatively understand the molecular mechanisms underpinning gene regulation. Results: Here, we report a novel framework for efficient and scalable parameter estimation that focuses specifically on modeling of gene circuits. Exploiting the structure commonly found in gene circuit models, this framework decomposes a system of coupled rate equations into individual ones and efficiently integrates them separately to reconstruct the mean time evolution of the gene products. The accuracy of the parameter estimates is refined by iteratively increasing the accuracy of numerical integration using the model structure. As a case study, we applied our framework to four gene circuit models with complex dynamics based on three synthetic datasets and one time series microarray data set. We compared our framework to three state-of-the-art parameter estimation methods and found that our approach consistently generated higher quality parameter solutions efficiently. Although many general-purpose parameter estimation methods have been applied for modeling of gene circuits, our results suggest that the use of more tailored approaches to use domain-specific information may be a key to reverse engineering of complex biological systems. The Author 2013.

Role of inhibitory feedback for information processing in thalamocortical circuits

International Nuclear Information System (INIS)

Mayer, Joerg; Schuster, Heinz Georg; Claussen, Jens Christian

2006-01-01

The information transfer in the thalamus is blocked dynamically during sleep, in conjunction with the occurrence of spindle waves. In order to describe the dynamic mechanisms which control the sensory transfer of information, it is necessary to have a qualitative model for the response properties of thalamic neurons. As the theoretical understanding of the mechanism remains incomplete, we analyze two modeling approaches for a recent experiment by Le Masson et al. [Nature (London) 417, 854 (2002)] on the thalamocortical loop. We use a conductance based model in order to motivate an extension of the Hindmarsh-Rose model, which mimics experimental observations of Le Masson et al. Typically, thalamic neurons posses two different firing modes, depending on their membrane potential. At depolarized potentials, the cells fire in a single spike mode and relay synaptic inputs in a one-to-one manner to the cortex. If the cell gets hyperpolarized, T-type calcium currents generate burst-mode firing which leads to a decrease in the spike transfer. In thalamocortical circuits, the cell membrane gets hyperpolarized by recurrent inhibitory feedback loops. In the case of reciprocally coupled excitatory and inhibitory neurons, inhibitory feedback leads to metastable self-sustained oscillations, which mask the incoming input, and thereby reduce the information transfer significantly

Automatic Design of Synthetic Gene Circuits through Mixed Integer Non-linear Programming

Science.gov (United States)

Huynh, Linh; Kececioglu, John; Köppe, Matthias; Tagkopoulos, Ilias

2012-01-01

Automatic design of synthetic gene circuits poses a significant challenge to synthetic biology, primarily due to the complexity of biological systems, and the lack of rigorous optimization methods that can cope with the combinatorial explosion as the number of biological parts increases. Current optimization methods for synthetic gene design rely on heuristic algorithms that are usually not deterministic, deliver sub-optimal solutions, and provide no guaranties on convergence or error bounds. Here, we introduce an optimization framework for the problem of part selection in synthetic gene circuits that is based on mixed integer non-linear programming (MINLP), which is a deterministic method that finds the globally optimal solution and guarantees convergence in finite time. Given a synthetic gene circuit, a library of characterized parts, and user-defined constraints, our method can find the optimal selection of parts that satisfy the constraints and best approximates the objective function given by the user. We evaluated the proposed method in the design of three synthetic circuits (a toggle switch, a transcriptional cascade, and a band detector), with both experimentally constructed and synthetic promoter libraries. Scalability and robustness analysis shows that the proposed framework scales well with the library size and the solution space. The work described here is a step towards a unifying, realistic framework for the automated design of biological circuits. PMID:22536398

Design and engineering of intracellular-metabolite-sensing/regulation gene circuits in Saccharomyces cerevisiae.

Science.gov (United States)

Wang, Meng; Li, Sijin; Zhao, Huimin

2016-01-01

The development of high-throughput phenotyping tools is lagging far behind the rapid advances of genotype generation methods. To bridge this gap, we report a new strategy for design, construction, and fine-tuning of intracellular-metabolite-sensing/regulation gene circuits by repurposing bacterial transcription factors and eukaryotic promoters. As proof of concept, we systematically investigated the design and engineering of bacterial repressor-based xylose-sensing/regulation gene circuits in Saccharomyces cerevisiae. We demonstrated that numerous properties, such as induction ratio and dose-response curve, can be fine-tuned at three different nodes, including repressor expression level, operator position, and operator sequence. By applying these gene circuits, we developed a cell sorting based, rapid and robust high-throughput screening method for xylose transporter engineering and obtained a sugar transporter HXT14 mutant with 6.5-fold improvement in xylose transportation capacity. This strategy should be generally applicable and highly useful for evolutionary engineering of proteins, pathways, and genomes in S. cerevisiae. © 2015 Wiley Periodicals, Inc.

Circuit-Host Coupling Induces Multifaceted Behavioral Modulations of a Gene Switch.

Science.gov (United States)

Blanchard, Andrew E; Liao, Chen; Lu, Ting

2018-02-06

Quantitative modeling of gene circuits is fundamentally important to synthetic biology, as it offers the potential to transform circuit engineering from trial-and-error construction to rational design and, hence, facilitates the advance of the field. Currently, typical models regard gene circuits as isolated entities and focus only on the biochemical processes within the circuits. However, such a standard paradigm is getting challenged by increasing experimental evidence suggesting that circuits and their host are intimately connected, and their interactions can potentially impact circuit behaviors. Here we systematically examined the roles of circuit-host coupling in shaping circuit dynamics by using a self-activating gene switch as a model circuit. Through a combination of deterministic modeling, stochastic simulation, and Fokker-Planck equation formalism, we found that circuit-host coupling alters switch behaviors across multiple scales. At the single-cell level, it slows the switch dynamics in the high protein production regime and enlarges the difference between stable steady-state values. At the population level, it favors cells with low protein production through differential growth amplification. Together, the two-level coupling effects induce both quantitative and qualitative modulations of the switch, with the primary component of the effects determined by the circuit's architectural parameters. This study illustrates the complexity and importance of circuit-host coupling in modulating circuit behaviors, demonstrating the need for a new paradigm-integrated modeling of the circuit-host system-for quantitative understanding of engineered gene networks. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Activity-regulated genes as mediators of neural circuit plasticity.

Science.gov (United States)

Leslie, Jennifer H; Nedivi, Elly

2011-08-01

Modifications of neuronal circuits allow the brain to adapt and change with experience. This plasticity manifests during development and throughout life, and can be remarkably long lasting. Evidence has linked activity-regulated gene expression to the long-term structural and electrophysiological adaptations that take place during developmental critical periods, learning and memory, and alterations to sensory map representations in the adult. In all these cases, the cellular response to neuronal activity integrates multiple tightly coordinated mechanisms to precisely orchestrate long-lasting, functional and structural changes in brain circuits. Experience-dependent plasticity is triggered when neuronal excitation activates cellular signaling pathways from the synapse to the nucleus that initiate new programs of gene expression. The protein products of activity-regulated genes then work via a diverse array of cellular mechanisms to modify neuronal functional properties. Synaptic strengthening or weakening can reweight existing circuit connections, while structural changes including synapse addition and elimination create new connections. Posttranscriptional regulatory mechanisms, often also dependent on activity, further modulate activity-regulated gene transcript and protein function. Thus, activity-regulated genes implement varied forms of structural and functional plasticity to fine-tune brain circuit wiring. Copyright © 2011 Elsevier Ltd. All rights reserved.

A framework for scalable parameter estimation of gene circuit models using structural information.

Science.gov (United States)

Kuwahara, Hiroyuki; Fan, Ming; Wang, Suojin; Gao, Xin

2013-07-01

Systematic and scalable parameter estimation is a key to construct complex gene regulatory models and to ultimately facilitate an integrative systems biology approach to quantitatively understand the molecular mechanisms underpinning gene regulation. Here, we report a novel framework for efficient and scalable parameter estimation that focuses specifically on modeling of gene circuits. Exploiting the structure commonly found in gene circuit models, this framework decomposes a system of coupled rate equations into individual ones and efficiently integrates them separately to reconstruct the mean time evolution of the gene products. The accuracy of the parameter estimates is refined by iteratively increasing the accuracy of numerical integration using the model structure. As a case study, we applied our framework to four gene circuit models with complex dynamics based on three synthetic datasets and one time series microarray data set. We compared our framework to three state-of-the-art parameter estimation methods and found that our approach consistently generated higher quality parameter solutions efficiently. Although many general-purpose parameter estimation methods have been applied for modeling of gene circuits, our results suggest that the use of more tailored approaches to use domain-specific information may be a key to reverse engineering of complex biological systems. http://sfb.kaust.edu.sa/Pages/Software.aspx. Supplementary data are available at Bioinformatics online.

The role of feedback resistors and tid effects in the ASET response of a high speed current feedback amplifier

International Nuclear Information System (INIS)

Roig, F.; Dusseau, L.; Privat, A.; Vaille, J.R.; Boch, J.; Saigne, F.; Ribeiro, P.; Auriel, G.; Roche, N.J.H.; Marec, R.; Calvel, P.; Bezerra, F.; Ecoffet, R.; Azais, B.

2014-01-01

The influence of external circuit designs on ASET shapes in a high speed current feedback amplifier (CFA) (AD844) is investigated by means of the pulsed laser single event effect (PLSEE) simulation technique. Changes of the feedback resistors modify circuit's electrical parameters such as closed-loop gain and bandwidth, affecting amplifier stability and so ASET shapes. Qualitative explanations based on general electronic rules and feedback theories enable the understanding of a CFA operation establishing a correlation between the evolution of external feedback resistor values and ASET parameters. TID effects on the ASET sensitivity in AD844 CFA are also investigated in this work highlighting different behaviors according to the impacted bipolar transistor in the integrated circuit. (authors)

Localization and Imaging of Integrated Circuit Defect Using Simple Optical Feedback Detection

Directory of Open Access Journals (Sweden)

Vernon Julius Cemine

2004-12-01

Full Text Available High-contrast microscopy of semiconductor and metal edifices in integrated circuits is demonstrated by combining laser-scanning confocal reflectance microscopy, one-photon optical-beam-induced current (1P-OBIC imaging, and optical feedback detection via a commercially available semiconductor laser that also serves as the excitation source. The confocal microscope has a compact in-line arrangement with no external photodetector. Confocal and 1P-OBIC images are obtained simultaneously from the same focused beam that is scanned across the sample plane. Image pairs are processed to generate exclusive high-contrast distributions of the semiconductor, metal, and dielectric sites in a GaAs photodiode array sample. The method is then utilized to demonstrate defect localization and imaging in an integrated circuit.

Equations for studies of feedback stabilization

International Nuclear Information System (INIS)

Boozer, A.H.

1998-01-01

Important ideal magnetohydrodynamic (MHD) instabilities grow slowly when a conducting wall surrounds a toroidal plasma. Feedback stabilization of these instabilities may be required for tokamaks and other magnetic confinement concepts to achieve adequate plasma pressure and self-driven current for practical fusion power. Equations are derived for simulating feedback stabilization, which require the minimum information about an ideal plasma for an exact analysis. The equations are solved in the approximation of one unstable mode, one wall circuit, one feedback circuit, and one sensor circuit. The analysis based on a single unstable mode is shown to be mathematically equivalent to the standard analysis of feedback of the axisymmetric vertical instability of tokamaks. Unlike that analysis, the method presented here applies to multiple modes that are coupled by the wall and to arbitrary toroidal mode numbers. copyright 1998 American Institute of Physics

Modulation of distributed feedback (DFB) laser diode with the autonomous Chua's circuit: Theory and experiment

Science.gov (United States)

Talla Mbé, Jimmi Hervé; Woafo, Paul

2018-03-01

We report on a simple way to generate complex optical waveforms with very cheap and accessible equipments. The general idea consists in modulating a laser diode with an autonomous electronic oscillator, and in the case of this study, we use a distributed feedback (DFB) laser diode pumped with an electronic Chua's circuit. Based on the adiabatic P-I characteristics of the laser diode at low frequencies, we show that when the total pump is greater than the laser threshold, it is possible to convert the electrical waveforms of the Chua's circuit into optical carriers. But, if that is not the case, the on-off dynamical behavior of the laser permits to obtain many other optical waveform signals, mainly pulses. Our numerical results are consistent with experimental measurements. The work presents the advantage of extending the range of possible chaotic dynamics of the laser diodes in the time domains (millisecond) where it is not usually expected with conventional modulation techniques. Moreover, this new technique of laser diodes modulation brings a general benefit in the physical equipment, reduces their cost and congestion so that, it can constitute a step towards photonic integrated circuits.

Novel matched amplifiers with low noise positive feedback. Part II: Resistive-capacitive feedback

Science.gov (United States)

Bruck, Y.; Zakharenko, V.

2010-02-01

This article is a continuation of consideration for an amplifier with resistive positive feedback (RPF) (Bruck (2008), 'Novel Matched LNA with Low Noise Positive Feedback. Part 1: General Features and Resistive Feedback', International Journal of Electronics, 95, 441-456). We propose here new configuration schematics of a transformer-less selective LNA with resistive-capacitive positive feedback (RCPF). A circuit of an amplifier with a transistor connected into a circuit with a common base (CB) configuration is analysed in detail. RCPF and RPF circuits are compared. It is shown that the LNA RCPF provides any pass-band, a good level of input and output matching, a minimum noise temperature which is significantly lower than that of the LNA RPF, a rather high linearity, and stability of amplification. The simulation results and some experimental data for the amplifiers intended for use in the LOFAR radiotelescope (Konovalenko et al. (2003), 'Thirty Element Array Antenna as a Prototype of a Huge Low-Frequency Radio Telescope,' Experimental Astronomy, 16, 149-164; Konovalenko (2007), 'Ukrainian Contribution to LOFAR', A scientific workshop, organised by LOFAR/ASTRON' Emmen, Netherlands, 23-27. http://www.lofar.org/workshop) are given. It is assumed that such devices are of a special interest for high-frequency integral circuits (IC).

Implementation of chaotic secure communication systems based on OPA circuits

International Nuclear Information System (INIS)

Huang, C.-K.; Tsay, S.-C.; Wu, Y.-R.

2005-01-01

In this paper, we proposed a novel three-order autonomous circuit to construct a chaotic circuit with double scroll characteristic. The design idea is to use RLC elements and a nonlinear resistor. The one of salient features of the chaotic circuit is that the circuit with two flexible breakpoints of nonlinear element, and the advantage of the flexible breakpoint is that it increased complexity of the dynamical performance. Here, if we take a large and suitable breakpoint value, then the chaotic state can masking a large input signal in the circuit. Furthermore, we proposed a secure communication hyperchaotic system based on the proposed chaotic circuits, where the chaotic communication system is constituted by a chaotic transmitter and a chaotic receiver. To achieve the synchronization between the transmitter and the receiver, we are using a suitable Lyapunov function and Lyapunov theorem to design the feedback control gain. Thus, the transmitting message masked by chaotic state in the transmitter can be guaranteed to perfectly recover in the receiver. To achieve the systems performance, some basic components containing OPA, resistor and capacitor elements are used to implement the proposed communication scheme. From the viewpoints of circuit implementation, this proposed chaotic circuit is superior to the Chua chaotic circuits. Finally, the test results containing simulation and the circuit measurement are shown to demonstrate that the proposed method is correct and feasible

Paper-based synthetic gene networks.

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Pardee, Keith; Green, Alexander A; Ferrante, Tom; Cameron, D Ewen; DaleyKeyser, Ajay; Yin, Peng; Collins, James J

2014-11-06

Synthetic gene networks have wide-ranging uses in reprogramming and rewiring organisms. To date, there has not been a way to harness the vast potential of these networks beyond the constraints of a laboratory or in vivo environment. Here, we present an in vitro paper-based platform that provides an alternate, versatile venue for synthetic biologists to operate and a much-needed medium for the safe deployment of engineered gene circuits beyond the lab. Commercially available cell-free systems are freeze dried onto paper, enabling the inexpensive, sterile, and abiotic distribution of synthetic-biology-based technologies for the clinic, global health, industry, research, and education. For field use, we create circuits with colorimetric outputs for detection by eye and fabricate a low-cost, electronic optical interface. We demonstrate this technology with small-molecule and RNA actuation of genetic switches, rapid prototyping of complex gene circuits, and programmable in vitro diagnostics, including glucose sensors and strain-specific Ebola virus sensors.

Paper-based Synthetic Gene Networks

Science.gov (United States)

Pardee, Keith; Green, Alexander A.; Ferrante, Tom; Cameron, D. Ewen; DaleyKeyser, Ajay; Yin, Peng; Collins, James J.

2014-01-01

Synthetic gene networks have wide-ranging uses in reprogramming and rewiring organisms. To date, there has not been a way to harness the vast potential of these networks beyond the constraints of a laboratory or in vivo environment. Here, we present an in vitro paper-based platform that provides a new venue for synthetic biologists to operate, and a much-needed medium for the safe deployment of engineered gene circuits beyond the lab. Commercially available cell-free systems are freeze-dried onto paper, enabling the inexpensive, sterile and abiotic distribution of synthetic biology-based technologies for the clinic, global health, industry, research and education. For field use, we create circuits with colorimetric outputs for detection by eye, and fabricate a low-cost, electronic optical interface. We demonstrate this technology with small molecule and RNA actuation of genetic switches, rapid prototyping of complex gene circuits, and programmable in vitro diagnostics, including glucose sensors and strain-specific Ebola virus sensors. PMID:25417167

MicroRNA-7/NF-κB signaling regulatory feedback circuit regulates gastric carcinogenesis

Science.gov (United States)

Zhao, Xiao-Di; Lu, Yuan-Yuan; Guo, Hao; Xie, Hua-Hong; He, Li-Jie; Shen, Gao-Fei; Zhou, Jin-Feng; Li, Ting; Hu, Si-Jun; Zhou, Lin; Han, Ya-Nan; Liang, Shu-Li; Wang, Xin; Wu, Kai-Chun; Shi, Yong-Quan; Nie, Yong-Zhan

2015-01-01

MicroRNAs play essential roles in gene expression regulation during carcinogenesis. Here, we investigated the role of miR-7 and the mechanism by which it is dysregulated in gastric cancer (GC). We used genome-wide screenings and identified RELA and FOS as novel targets of miR-7. Overexpression of miR-7 repressed RELA and FOS expression and prevented GC cell proliferation and tumorigenesis. These effects were clinically relevant, as low miR-7 expression was correlated with high RELA and FOS expression and poor survival in GC patients. Intriguingly, we found that miR-7 indirectly regulated RELA activation by targeting the IκB kinase IKKε. Furthermore, IKKε and RELA can repress miR-7 transcription, which forms a feedback circuit between miR-7 and nuclear factor κB (NF-κB) signaling. Additionally, we demonstrate that down-regulation of miR-7 may occur as a result of the aberrant activation of NF-κB signaling by Helicobacter pylori infection. These findings suggest that miR-7 may serve as an important regulator in GC development and progression. PMID:26261179

Firing-rate based network modeling of the dLGN circuit: Effects of cortical feedback on spatiotemporal response properties of relay cells.

Science.gov (United States)

Mobarhan, Milad Hobbi; Halnes, Geir; Martínez-Cañada, Pablo; Hafting, Torkel; Fyhn, Marianne; Einevoll, Gaute T

2018-05-01

Visually evoked signals in the retina pass through the dorsal geniculate nucleus (dLGN) on the way to the visual cortex. This is however not a simple feedforward flow of information: there is a significant feedback from cortical cells back to both relay cells and interneurons in the dLGN. Despite four decades of experimental and theoretical studies, the functional role of this feedback is still debated. Here we use a firing-rate model, the extended difference-of-Gaussians (eDOG) model, to explore cortical feedback effects on visual responses of dLGN relay cells. For this model the responses are found by direct evaluation of two- or three-dimensional integrals allowing for fast and comprehensive studies of putative effects of different candidate organizations of the cortical feedback. Our analysis identifies a special mixed configuration of excitatory and inhibitory cortical feedback which seems to best account for available experimental data. This configuration consists of (i) a slow (long-delay) and spatially widespread inhibitory feedback, combined with (ii) a fast (short-delayed) and spatially narrow excitatory feedback, where (iii) the excitatory/inhibitory ON-ON connections are accompanied respectively by inhibitory/excitatory OFF-ON connections, i.e. following a phase-reversed arrangement. The recent development of optogenetic and pharmacogenetic methods has provided new tools for more precise manipulation and investigation of the thalamocortical circuit, in particular for mice. Such data will expectedly allow the eDOG model to be better constrained by data from specific animal model systems than has been possible until now for cat. We have therefore made the Python tool pyLGN which allows for easy adaptation of the eDOG model to new situations.

GATA Factor-Dependent Positive-Feedback Circuit in Acute Myeloid Leukemia Cells

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Koichi R. Katsumura

2016-08-01

Full Text Available The master regulatory transcription factor GATA-2 triggers hematopoietic stem and progenitor cell generation. GATA2 haploinsufficiency is implicated in myelodysplastic syndrome (MDS and acute myeloid leukemia (AML, and GATA2 overexpression portends a poor prognosis for AML. However, the constituents of the GATA-2-dependent genetic network mediating pathogenesis are unknown. We described a p38-dependent mechanism that phosphorylates GATA-2 and increases GATA-2 target gene activation. We demonstrate that this mechanism establishes a growth-promoting chemokine/cytokine circuit in AML cells. p38/ERK-dependent GATA-2 phosphorylation facilitated positive autoregulation of GATA2 transcription and expression of target genes, including IL1B and CXCL2. IL-1β and CXCL2 enhanced GATA-2 phosphorylation, which increased GATA-2-mediated transcriptional activation. p38/ERK-GATA-2 stimulated AML cell proliferation via CXCL2 induction. As GATA2 mRNA correlated with IL1B and CXCL2 mRNAs in AML-M5 and high expression of these genes predicted poor prognosis of cytogenetically normal AML, we propose that the circuit is functionally important in specific AML contexts.

Signal detection circuit design of HCN measurement system based on TDLAS

Science.gov (United States)

He, Chungui; Zhang, Yujun; Chen, Chen; Lu, Yibing; Liu, Guohua; Gao, Yanwei; You, Kun; He, Ying; Zhang, Kai; Liu, Wenqing

2016-10-01

Hydrogen cyanide gas leakage may exist in the petrochemical industry, smelting plant, and other industrial processes, causing serious harm to the environment, and even threatening the safety of personnel. So the continuous detection of HCN gas plays an important role in the prevention of risk in production process and storage environment that existing hydrogen cyanide gas. The Tunable Diode Laser Technology (TDLAS) has advantages of non-contact, high sensitivity, high selectivity, and fast response time, etc., which is one of the ideal method of gas detection technologies and can be used to measure the hydrogen cyanide concentration. This paper studies the HCN detection system based on TDLAS technology, selects the absorption lines of hydrogen cyanide in 6539.12cm-1, and utilizes the center wavelength of 1.529μm distributed feedback (DFB) laser as a light source. It is discussed in detail on technical requirements of a high frequency modulated laser signal detection circuit, including noise level, gain, and bandwidth. Based on the above theory, the high frequency modulation preamplifier circuit and main amplifier circuit are designed for InGaAs photoelectric detector. The designed circuits are calculation analyzed with corresponding formula and simulation analyzed based on the Multisim software.

Correction: The role of coupled positive feedback in the expression of the SPI1 type three secretion system in Salmonella.

Directory of Open Access Journals (Sweden)

Supreet Saini

2010-08-01

Full Text Available Salmonella enterica serovar Typhimurium is a common food-borne pathogen that induces inflammatory diarrhea and invades intestinal epithelial cells using a type three secretion system (T3SS encoded within Salmonella pathogenicity island 1 (SPI1. The genes encoding the SPI1 T3SS are tightly regulated by a network of interacting transcriptional regulators involving three coupled positive feedback loops. While the core architecture of the SPI1 gene circuit has been determined, the relative roles of these interacting regulators and associated feedback loops are still unknown. To determine the function of this circuit, we measured gene expression dynamics at both population and single-cell resolution in a number of SPI1 regulatory mutants. Using these data, we constructed a mathematical model of the SPI1 gene circuit. Analysis of the model predicted that the circuit serves two functions. The first is to place a threshold on SPI1 activation, ensuring that the genes encoding the T3SS are expressed only in response to the appropriate combination of environmental and cellular cues. The second is to amplify SPI1 gene expression. To experimentally test these predictions, we rewired the SPI1 genetic circuit by changing its regulatory architecture. This enabled us to directly test our predictions regarding the function of the circuit by varying the strength and dynamics of the activating signal. Collectively, our experimental and computational results enable us to deconstruct this complex circuit and determine the role of its individual components in regulating SPI1 gene expression dynamics.

Electrothermal Feedback and Absorption-Induced Open-Circuit-Voltage Turnover in Solar Cells

Science.gov (United States)

Ullbrich, Sascha; Fischer, Axel; Tang, Zheng; Ávila, Jorge; Bolink, Henk J.; Reineke, Sebastian; Vandewal, Koen

2018-05-01

Solar panels easily heat up upon intense solar radiation due to excess energy dissipation of the absorbed photons or by nonradiative recombination of charge carriers. Still, photoinduced self-heating is often ignored when characterizing lab-sized samples. For light-intensity-dependent measurements of the open-circuit voltage (Suns-VO C ), allowing us to characterize the recombination mechanism, sample heating is often not considered, although almost 100% of the absorbed energy is converted into heat. Here, we show that the frequently observed stagnation or even decrease in VOC at increasingly high light intensities can be explained by considering an effective electrothermal feedback between the recombination current and the open-circuit voltage. Our analytical model fully explains the experimental data for various solar-cell technologies, comprising conventional inorganic semiconductors as well as organic and perovskite materials. Furthermore, the model can be exploited to determine the ideality factor, the effective gap, and the temperature rise from a single Suns-VOC measurement at ambient conditions.

Parameter estimation methods for gene circuit modeling from time-series mRNA data: a comparative study.

Science.gov (United States)

Fan, Ming; Kuwahara, Hiroyuki; Wang, Xiaolei; Wang, Suojin; Gao, Xin

2015-11-01

Parameter estimation is a challenging computational problem in the reverse engineering of biological systems. Because advances in biotechnology have facilitated wide availability of time-series gene expression data, systematic parameter estimation of gene circuit models from such time-series mRNA data has become an important method for quantitatively dissecting the regulation of gene expression. By focusing on the modeling of gene circuits, we examine here the performance of three types of state-of-the-art parameter estimation methods: population-based methods, online methods and model-decomposition-based methods. Our results show that certain population-based methods are able to generate high-quality parameter solutions. The performance of these methods, however, is heavily dependent on the size of the parameter search space, and their computational requirements substantially increase as the size of the search space increases. In comparison, online methods and model decomposition-based methods are computationally faster alternatives and are less dependent on the size of the search space. Among other things, our results show that a hybrid approach that augments computationally fast methods with local search as a subsequent refinement procedure can substantially increase the quality of their parameter estimates to the level on par with the best solution obtained from the population-based methods while maintaining high computational speed. These suggest that such hybrid methods can be a promising alternative to the more commonly used population-based methods for parameter estimation of gene circuit models when limited prior knowledge about the underlying regulatory mechanisms makes the size of the parameter search space vastly large. © The Author 2015. Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

Sub-circuits of a gene regulatory network control a developmental epithelial-mesenchymal transition.

Science.gov (United States)

Saunders, Lindsay R; McClay, David R

2014-04-01

Epithelial-mesenchymal transition (EMT) is a fundamental cell state change that transforms epithelial to mesenchymal cells during embryonic development, adult tissue repair and cancer metastasis. EMT includes a complex series of intermediate cell state changes including remodeling of the basement membrane, apical constriction, epithelial de-adhesion, directed motility, loss of apical-basal polarity, and acquisition of mesenchymal adhesion and polarity. Transcriptional regulatory state changes must ultimately coordinate the timing and execution of these cell biological processes. A well-characterized gene regulatory network (GRN) in the sea urchin embryo was used to identify the transcription factors that control five distinct cell changes during EMT. Single transcription factors were perturbed and the consequences followed with in vivo time-lapse imaging or immunostaining assays. The data show that five different sub-circuits of the GRN control five distinct cell biological activities, each part of the complex EMT process. Thirteen transcription factors (TFs) expressed specifically in pre-EMT cells were required for EMT. Three TFs highest in the GRN specified and activated EMT (alx1, ets1, tbr) and the 10 TFs downstream of those (tel, erg, hex, tgif, snail, twist, foxn2/3, dri, foxb, foxo) were also required for EMT. No single TF functioned in all five sub-circuits, indicating that there is no EMT master regulator. Instead, the resulting sub-circuit topologies suggest EMT requires multiple simultaneous regulatory mechanisms: forward cascades, parallel inputs and positive-feedback lock downs. The interconnected and overlapping nature of the sub-circuits provides one explanation for the seamless orchestration by the embryo of cell state changes leading to successful EMT.

Feedback loop compensates for rectifier nonlinearity

Science.gov (United States)

1966-01-01

Signal processing circuit with two negative feedback loops rectifies two sinusoidal signals which are 180 degrees out of phase and produces a single full-wave rectified output signal. Each feedback loop incorporates a feedback rectifier to compensate for the nonlinearity of the circuit.

High efficiency inverter and ballast circuits

International Nuclear Information System (INIS)

Nilssen, O.K.

1984-01-01

A high efficiency push-pull inverter circuit employing a pair of relatively high power switching transistors is described. The switching on and off of the transistors is precisely controlled to minimize power losses due to common-mode conduction or due to transient conditions that occur in the process of turning a transistor on or off. Two current feed-back transformers are employed in the transistor base drives; one being saturable for providing a positive feedback, and the other being non-saturable for providing a subtractive feedback

A plausible neural circuit for decision making and its formation based on reinforcement learning.

Science.gov (United States)

Wei, Hui; Dai, Dawei; Bu, Yijie

2017-06-01

A human's, or lower insects', behavior is dominated by its nervous system. Each stable behavior has its own inner steps and control rules, and is regulated by a neural circuit. Understanding how the brain influences perception, thought, and behavior is a central mandate of neuroscience. The phototactic flight of insects is a widely observed deterministic behavior. Since its movement is not stochastic, the behavior should be dominated by a neural circuit. Based on the basic firing characteristics of biological neurons and the neural circuit's constitution, we designed a plausible neural circuit for this phototactic behavior from logic perspective. The circuit's output layer, which generates a stable spike firing rate to encode flight commands, controls the insect's angular velocity when flying. The firing pattern and connection type of excitatory and inhibitory neurons are considered in this computational model. We simulated the circuit's information processing using a distributed PC array, and used the real-time average firing rate of output neuron clusters to drive a flying behavior simulation. In this paper, we also explored how a correct neural decision circuit is generated from network flow view through a bee's behavior experiment based on the reward and punishment feedback mechanism. The significance of this study: firstly, we designed a neural circuit to achieve the behavioral logic rules by strictly following the electrophysiological characteristics of biological neurons and anatomical facts. Secondly, our circuit's generality permits the design and implementation of behavioral logic rules based on the most general information processing and activity mode of biological neurons. Thirdly, through computer simulation, we achieved new understanding about the cooperative condition upon which multi-neurons achieve some behavioral control. Fourthly, this study aims in understanding the information encoding mechanism and how neural circuits achieve behavior control

A Printed Organic Circuit System for Wearable Amperometric Electrochemical Sensors.

Science.gov (United States)

Shiwaku, Rei; Matsui, Hiroyuki; Nagamine, Kuniaki; Uematsu, Mayu; Mano, Taisei; Maruyama, Yuki; Nomura, Ayako; Tsuchiya, Kazuhiko; Hayasaka, Kazuma; Takeda, Yasunori; Fukuda, Takashi; Kumaki, Daisuke; Tokito, Shizuo

2018-04-23

Wearable sensor device technologies, which enable continuous monitoring of biological information from the human body, are promising in the fields of sports, healthcare, and medical applications. Further thinness, light weight, flexibility and low-cost are significant requirements for making the devices attachable onto human tissues or clothes like a patch. Here we demonstrate a flexible and printed circuit system consisting of an enzyme-based amperometric sensor, feedback control and amplification circuits based on organic thin-film transistors. The feedback control and amplification circuits based on pseudo-CMOS inverters were successfuly integrated by printing methods on a plastic film. This simple system worked very well like a potentiostat for electrochemical measurements, and enabled the quantitative and real-time measurement of lactate concentration with high sensitivity of 1 V/mM and a short response time of a hundred seconds.

Integrated genomic and gene expression profiling identifies two major genomic circuits in urothelial carcinoma.

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David Lindgren

Full Text Available Similar to other malignancies, urothelial carcinoma (UC is characterized by specific recurrent chromosomal aberrations and gene mutations. However, the interconnection between specific genomic alterations, and how patterns of chromosomal alterations adhere to different molecular subgroups of UC, is less clear. We applied tiling resolution array CGH to 146 cases of UC and identified a number of regions harboring recurrent focal genomic amplifications and deletions. Several potential oncogenes were included in the amplified regions, including known oncogenes like E2F3, CCND1, and CCNE1, as well as new candidate genes, such as SETDB1 (1q21, and BCL2L1 (20q11. We next combined genome profiling with global gene expression, gene mutation, and protein expression data and identified two major genomic circuits operating in urothelial carcinoma. The first circuit was characterized by FGFR3 alterations, overexpression of CCND1, and 9q and CDKN2A deletions. The second circuit was defined by E3F3 amplifications and RB1 deletions, as well as gains of 5p, deletions at PTEN and 2q36, 16q, 20q, and elevated CDKN2A levels. TP53/MDM2 alterations were common for advanced tumors within the two circuits. Our data also suggest a possible RAS/RAF circuit. The tumors with worst prognosis showed a gene expression profile that indicated a keratinized phenotype. Taken together, our integrative approach revealed at least two separate networks of genomic alterations linked to the molecular diversity seen in UC, and that these circuits may reflect distinct pathways of tumor development.

Piezoelectric drive circuit

Science.gov (United States)

Treu, C.A. Jr.

1999-08-31

A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes. 7 figs.

Brain reflections: A circuit-based framework for understanding information processing and cognitive control.

Science.gov (United States)

Gratton, Gabriele

2018-03-01

Here, I propose a view of the architecture of the human information processing system, and of how it can be adapted to changing task demands (which is the hallmark of cognitive control). This view is informed by an interpretation of brain activity as reflecting the excitability level of neural representations, encoding not only stimuli and temporal contexts, but also action plans and task goals. The proposed cognitive architecture includes three types of circuits: open circuits, involved in feed-forward processing such as that connecting stimuli with responses and characterized by brief, transient brain activity; and two types of closed circuits, positive feedback circuits (characterized by sustained, high-frequency oscillatory activity), which help select and maintain representations, and negative feedback circuits (characterized by brief, low-frequency oscillatory bursts), which are instead associated with changes in representations. Feed-forward activity is primarily responsible for the spread of activation along the information processing system. Oscillatory activity, instead, controls this spread. Sustained oscillatory activity due to both local cortical circuits (gamma) and longer corticothalamic circuits (alpha and beta) allows for the selection of individuated representations. Through the interaction of these circuits, it also allows for the preservation of representations across different temporal spans (sensory and working memory) and their spread across the brain. In contrast, brief bursts of oscillatory activity, generated by novel and/or conflicting information, lead to the interruption of sustained oscillatory activity and promote the generation of new representations. I discuss how this framework can account for a number of psychological and behavioral phenomena. © 2017 Society for Psychophysiological Research.

Implementation Considerations, Not Topological Differences, Are the Main Determinants of Noise Suppression Properties in Feedback and Incoherent Feedforward Circuits.

Science.gov (United States)

Buzi, Gentian; Khammash, Mustafa

2016-06-01

Biological systems use a variety of mechanisms to deal with the uncertain nature of their external and internal environments. Two of the most common motifs employed for this purpose are the incoherent feedforward (IFF) and feedback (FB) topologies. Many theoretical and experimental studies suggest that these circuits play very different roles in providing robustness to uncertainty in the cellular environment. Here, we use a control theoretic approach to analyze two common FB and IFF architectures that make use of an intermediary species to achieve regulation. We show the equivalence of both circuits topologies in suppressing static cell-to-cell variations. While both circuits can suppress variations due to input noise, they are ineffective in suppressing inherent chemical reaction stochasticity. Indeed, these circuits realize comparable improvements limited to a modest 25% variance reduction in best case scenarios. Such limitations are attributed to the use of intermediary species in regulation, and as such, they persist even for circuit architectures that combine both IFF and FB features. Intriguingly, while the FB circuits are better suited in dealing with dynamic input variability, the most significant difference between the two topologies lies not in the structural features of the circuits, but in their practical implementation considerations.

Implementation Considerations, Not Topological Differences, Are the Main Determinants of Noise Suppression Properties in Feedback and Incoherent Feedforward Circuits.

Directory of Open Access Journals (Sweden)

Gentian Buzi

2016-06-01

Full Text Available Biological systems use a variety of mechanisms to deal with the uncertain nature of their external and internal environments. Two of the most common motifs employed for this purpose are the incoherent feedforward (IFF and feedback (FB topologies. Many theoretical and experimental studies suggest that these circuits play very different roles in providing robustness to uncertainty in the cellular environment. Here, we use a control theoretic approach to analyze two common FB and IFF architectures that make use of an intermediary species to achieve regulation. We show the equivalence of both circuits topologies in suppressing static cell-to-cell variations. While both circuits can suppress variations due to input noise, they are ineffective in suppressing inherent chemical reaction stochasticity. Indeed, these circuits realize comparable improvements limited to a modest 25% variance reduction in best case scenarios. Such limitations are attributed to the use of intermediary species in regulation, and as such, they persist even for circuit architectures that combine both IFF and FB features. Intriguingly, while the FB circuits are better suited in dealing with dynamic input variability, the most significant difference between the two topologies lies not in the structural features of the circuits, but in their practical implementation considerations.

Implementation Considerations, Not Topological Differences, Are the Main Determinants of Noise Suppression Properties in Feedback and Incoherent Feedforward Circuits

Science.gov (United States)

Buzi, Gentian; Khammash, Mustafa

2016-01-01

Biological systems use a variety of mechanisms to deal with the uncertain nature of their external and internal environments. Two of the most common motifs employed for this purpose are the incoherent feedforward (IFF) and feedback (FB) topologies. Many theoretical and experimental studies suggest that these circuits play very different roles in providing robustness to uncertainty in the cellular environment. Here, we use a control theoretic approach to analyze two common FB and IFF architectures that make use of an intermediary species to achieve regulation. We show the equivalence of both circuits topologies in suppressing static cell-to-cell variations. While both circuits can suppress variations due to input noise, they are ineffective in suppressing inherent chemical reaction stochasticity. Indeed, these circuits realize comparable improvements limited to a modest 25% variance reduction in best case scenarios. Such limitations are attributed to the use of intermediary species in regulation, and as such, they persist even for circuit architectures that combine both IFF and FB features. Intriguingly, while the FB circuits are better suited in dealing with dynamic input variability, the most significant difference between the two topologies lies not in the structural features of the circuits, but in their practical implementation considerations. PMID:27257684

Mixed-mode chaotic circuit with Wien-bridge configuration: The results of experimental verification

International Nuclear Information System (INIS)

Kilic, Recai

2007-01-01

In this paper, we deal with the experimentally implementation of inductorless Wien bridge-based mixed-mode chaotic circuit (MMCC) which is capable to exhibit both linear and nonlinear oscillations. The results of experimental implementation agree with the results of theoretical and computer simulation presented in literature. Since the proposed implementation of MMCC circuit uses different design blocks such as Wien bridge-based autonomous circuit part, CFOA (current feedback operational amplifier)-based floating inductance simulator, CFOA-based Chua's diode and switching mechanism, it offers very versatile chaotic circuit model for studying autonomous and nonautonomous chaotic dynamics

Active damping of LLCL-filter resonance based on LC-trap voltage and capacitor current feedback

DEFF Research Database (Denmark)

Huang, Min; Wang, Xiongfei; Loh, Poh Chiang

2015-01-01

. In this paper, different feedback coefficients like the proportional, derivative, integral, high pass and low pass feedback coefficients of the filter capacitor current and the LC-trap circuit voltage are investigated for damping the filter resonance. Active damping methods are analyzed by using the concept...

Mixed-mode chaotic circuit with Wien-bridge configuration: The results of experimental verification

Energy Technology Data Exchange (ETDEWEB)

Kilic, Recai [Erciyes University, Department of Electronic Engineering, 38039 Kayseri (Turkey)]. E-mail: kilic@erciyes.edu.tr

2007-05-15

In this paper, we deal with the experimentally implementation of inductorless Wien bridge-based mixed-mode chaotic circuit (MMCC) which is capable to exhibit both linear and nonlinear oscillations. The results of experimental implementation agree with the results of theoretical and computer simulation presented in literature. Since the proposed implementation of MMCC circuit uses different design blocks such as Wien bridge-based autonomous circuit part, CFOA (current feedback operational amplifier)-based floating inductance simulator, CFOA-based Chua's diode and switching mechanism, it offers very versatile chaotic circuit model for studying autonomous and nonautonomous chaotic dynamics.

Feedback control of persistent-current oscillation based on the atomic-clock technique

Science.gov (United States)

Yu, Deshui; Dumke, Rainer

2018-05-01

We propose a scheme of stabilizing the persistent-current Rabi oscillation based on the flux qubit-resonator-atom hybrid structure. The low-Q L C resonator weakly interacts with the flux qubit and maps the persistent-current Rabi oscillation of the flux qubit onto the intraresonator electric field. This oscillating electric field is further coupled to a Rydberg-Rydberg transition of the 87Rb atoms. The Rabi-frequency fluctuation of the flux qubit is deduced from measuring the atomic population via the fluorescence detection and stabilized by feedback controlling the external flux bias. Our numerical simulation indicates that the feedback-control method can efficiently suppress the background fluctuations in the flux qubit, especially in the low-frequency limit. This technique may be extensively applicable to different types of superconducting circuits, paving a way to long-term-coherence superconducting quantum information processing.

Circuit Design and Implementation of Micro-Displacement Measurement System of Laser Self-Mixing Interference

Directory of Open Access Journals (Sweden)

Guang Ya LIU

2014-02-01

Full Text Available In this paper we put forward the basic structure of a micro-displacement measuring system based on the basic theory of laser feedback, and designed a hardware circuit of the system, including the LD driver and modulation circuit, photoelectric signal amplifier and filter circuit, which meet the requirements of the follow-up experimental study by theoretical analysis and Multisim simulation to the circuit.

Genome engineering using a synthetic gene circuit in Bacillus subtilis.

Science.gov (United States)

Jeong, Da-Eun; Park, Seung-Hwan; Pan, Jae-Gu; Kim, Eui-Joong; Choi, Soo-Keun

2015-03-31

Genome engineering without leaving foreign DNA behind requires an efficient counter-selectable marker system. Here, we developed a genome engineering method in Bacillus subtilis using a synthetic gene circuit as a counter-selectable marker system. The system contained two repressible promoters (B. subtilis xylA (Pxyl) and spac (Pspac)) and two repressor genes (lacI and xylR). Pxyl-lacI was integrated into the B. subtilis genome with a target gene containing a desired mutation. The xylR and Pspac-chloramphenicol resistant genes (cat) were located on a helper plasmid. In the presence of xylose, repression of XylR by xylose induced LacI expression, the LacIs repressed the Pspac promoter and the cells become chloramphenicol sensitive. Thus, to survive in the presence of chloramphenicol, the cell must delete Pxyl-lacI by recombination between the wild-type and mutated target genes. The recombination leads to mutation of the target gene. The remaining helper plasmid was removed easily under the chloramphenicol absent condition. In this study, we showed base insertion, deletion and point mutation of the B. subtilis genome without leaving any foreign DNA behind. Additionally, we successfully deleted a 2-kb gene (amyE) and a 38-kb operon (ppsABCDE). This method will be useful to construct designer Bacillus strains for various industrial applications. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

Dynamics of gene expression with positive feedback to histone modifications at bivalent domains

Science.gov (United States)

Huang, Rongsheng; Lei, Jinzhi

2018-03-01

Experiments have shown that in embryonic stem cells, the promoters of many lineage-control genes contain “bivalent domains”, within which the nucleosomes possess both active (H3K4me3) and repressive (H3K27me3) marks. Such bivalent modifications play important roles in maintaining pluripotency in embryonic stem cells. Here, to investigate gene expression dynamics when there are regulations in bivalent histone modifications and random partition in cell divisions, we study how positive feedback to histone methylation/demethylation controls the transition dynamics of the histone modification patterns along with cell cycles. We constructed a computational model that includes dynamics of histone marks, three-stage chromatin state transitions, transcription and translation, feedbacks from protein product to enzymes to regulate the addition and removal of histone marks, and the inheritance of nucleosome state between cell cycles. The model reveals how dynamics of both nucleosome state transition and gene expression are dependent on the enzyme activities and feedback regulations. Results show that the combination of stochastic histone modification at each cell division and the deterministic feedback regulation work together to adjust the dynamics of chromatin state transition in stem cell regenerations.

Physically based arc-circuit interaction

International Nuclear Information System (INIS)

Zhong-Lie, L.

1984-01-01

An integral arc model is extended to study the interaction of the gas blast arc with the test circuit in this paper. The deformation in the waveshapes of arc current and voltage around the current zero has been formulated to first approximation by using a simple model of arc voltage based on the arc core energy conservation. By supplementing with the time scale for the radiation, the time rates of arc processes were amended. Both the contributions of various arc processes and the influence of circuit parameters to the arc-circuit interaction have been estimated by this theory. Analysis generated a new method of calculating test circuit parameters which improves the accurate simulation of arc-circuit interaction. The new method agrees with the published experimental results

Logarithmic circuit with wide dynamic range

Science.gov (United States)

Wiley, P. H.; Manus, E. A. (Inventor)

1978-01-01

A circuit deriving an output voltage that is proportional to the logarithm of a dc input voltage susceptible to wide variations in amplitude includes a constant current source which forward biases a diode so that the diode operates in the exponential portion of its voltage versus current characteristic, above its saturation current. The constant current source includes first and second, cascaded feedback, dc operational amplifiers connected in negative feedback circuit. An input terminal of the first amplifier is responsive to the input voltage. A circuit shunting the first amplifier output terminal includes a resistor in series with the diode. The voltage across the resistor is sensed at the input of the second dc operational feedback amplifier. The current flowing through the resistor is proportional to the input voltage over the wide range of variations in amplitude of the input voltage.

Dichotomy of nonlinear systems: Application to chaos control of nonlinear electronic circuit

International Nuclear Information System (INIS)

Wang Jinzhi; Duan Zhisheng; Huang Lin

2006-01-01

In this Letter a new method of chaos control for Chua's circuit and the modified canonical Chua's electrical circuit is proposed by using the results of dichotomy in nonlinear systems. A linear feedback control based on linear matrix inequality (LMI) is given such that chaos oscillation or hyperchaos phenomenon of circuit systems injected control signal disappear. Numerical simulations are presented to illustrate the efficiency of the proposed method

MOS voltage automatic tuning circuit

OpenAIRE

李, 田茂; 中田, 辰則; 松本, 寛樹

2004-01-01

Abstract ###Automatic tuning circuit adjusts frequency performance to compensate for the process variation. Phase locked ###loop (PLL) is a suitable oscillator for the integrated circuit. It is a feedback system that compares the input ###phase with the output phase. It can make the output frequency equal to the input frequency. In this paper, PLL ###fomed of MOSFET's is presented.The presented circuit consists of XOR circuit, Low-pass filter and Relaxation ###Oscillator. On PSPICE simulation...

Negative Resistance Circuit for Damping an Array of Coupled FitzHugh-Nagumo Oscillators

DEFF Research Database (Denmark)

Tamaševičius, Arūnas; Adomaitienė, Elena; Bumelienė, Skaidra

2015-01-01

An analog circuit, based on a negative impedance converter and a capacitor, for damping oscillations in an array of mean-field coupled neuronal FitzHugh–Nagumo (FHN) type oscillators is described. The circuit is essentially a two-terminal feedback controller. When coupled to an array of the FHN...

Synthetic biology devices and circuits for RNA-based 'smart vaccines': a propositional review.

Science.gov (United States)

Andries, Oliwia; Kitada, Tasuku; Bodner, Katie; Sanders, Niek N; Weiss, Ron

2015-02-01

Nucleic acid vaccines have been gaining attention as an alternative to the standard attenuated pathogen or protein based vaccine. However, an unrealized advantage of using such DNA or RNA based vaccination modalities is the ability to program within these nucleic acids regulatory devices that would provide an immunologist with the power to control the production of antigens and adjuvants in a desirable manner by administering small molecule drugs as chemical triggers. Advances in synthetic biology have resulted in the creation of highly predictable and modular genetic parts and devices that can be composed into synthetic gene circuits with complex behaviors. With the recent advent of modified RNA gene delivery methods and developments in the RNA replicon platform, we foresee a future in which mammalian synthetic biologists will create genetic circuits encoded exclusively on RNA. Here, we review the current repertoire of devices used in RNA synthetic biology and propose how programmable 'smart vaccines' will revolutionize the field of RNA vaccination.

Distributed force feedback in the spinal cord and the regulation of limb mechanics.

Science.gov (United States)

Nichols, T Richard

2018-03-01

This review is an update on the role of force feedback from Golgi tendon organs in the regulation of limb mechanics during voluntary movement. Current ideas about the role of force feedback are based on modular circuits linking idealized systems of agonists, synergists, and antagonistic muscles. In contrast, force feedback is widely distributed across the muscles of a limb and cannot be understood based on these circuit motifs. Similarly, muscle architecture cannot be understood in terms of idealized systems, since muscles cross multiple joints and axes of rotation and further influence remote joints through inertial coupling. It is hypothesized that distributed force feedback better represents the complex mechanical interactions of muscles, including the stresses in the musculoskeletal network born by muscle articulations, myofascial force transmission, and inertial coupling. Together with the strains of muscle fascicles measured by length feedback from muscle spindle receptors, this integrated proprioceptive feedback represents the mechanical state of the musculoskeletal system. Within the spinal cord, force feedback has excitatory and inhibitory components that coexist in various combinations based on motor task and integrated with length feedback at the premotoneuronal and motoneuronal levels. It is concluded that, in agreement with other investigators, autogenic, excitatory force feedback contributes to propulsion and weight support. It is further concluded that coexistent inhibitory force feedback, together with length feedback, functions to manage interjoint coordination and the mechanical properties of the limb in the face of destabilizing inertial forces and positive force feedback, as required by the accelerations and changing directions of both predator and prey.

Modulation of dynamic modes by interplay between positive and negative feedback loops in gene regulatory networks

Science.gov (United States)

Wang, Liu-Suo; Li, Ning-Xi; Chen, Jing-Jia; Zhang, Xiao-Peng; Liu, Feng; Wang, Wei

2018-04-01

A positive and a negative feedback loop can induce bistability and oscillation, respectively, in biological networks. Nevertheless, they are frequently interlinked to perform more elaborate functions in many gene regulatory networks. Coupled positive and negative feedback loops may exhibit either oscillation or bistability depending on the intensity of the stimulus in some particular networks. It is less understood how the transition between the two dynamic modes is modulated by the positive and negative feedback loops. We developed an abstract model of such systems, largely based on the core p53 pathway, to explore the mechanism for the transformation of dynamic behaviors. Our results show that enhancing the positive feedback may promote or suppress oscillations depending on the strength of both feedback loops. We found that the system oscillates with low amplitudes in response to a moderate stimulus and switches to the on state upon a strong stimulus. When the positive feedback is activated much later than the negative one in response to a strong stimulus, the system exhibits long-term oscillations before switching to the on state. We explain this intriguing phenomenon using quasistatic approximation. Moreover, early switching to the on state may occur when the system starts from a steady state in the absence of stimuli. The interplay between the positive and negative feedback plays a key role in the transitions between oscillation and bistability. Of note, our conclusions should be applicable only to some specific gene regulatory networks, especially the p53 network, in which both oscillation and bistability exist in response to a certain type of stimulus. Our work also underscores the significance of transient dynamics in determining cellular outcome.

A transimpedance amplifier using a novel current mode feedback loop

CERN Document Server

Anghinolfi, Francis; Delagnes, E; Jarron, Pierre; Scharfetter, L H H

1995-01-01

We present a transimpedance amplifier stage based on a novel current mode feedback topology. This circuit employs NMOS and PMOS transistors exclusively and requires neither capacitor for stabilizing the transimpedance loop nor resistor for the transresistance feedback and transistor loading. This amplifier circuit is fully compatible with submicron digital CMOS processes. The active feedback network consists of two grounded-gate MOS devices which split the output current in both the feedback and output branches. The transresistance and the phase margin are adjustable through external DC signals. The measured rise time of the impulse response of the amplifier implemented in an industrial 0,7µm CMOS process is 18 ns for a transresistance of 180 k‡ and 30 ns for a transresistance of 560 k‡. The measured Equivalent Noise Charge (ENC) is 800 rms e¯ for an input capacitance of 20 pF with the transresistance adjusted to 560 k‡.

A voltage biased superconducting quantum interference device bootstrap circuit

International Nuclear Information System (INIS)

Xie Xiaoming; Wang Huiwu; Wang Yongliang; Dong Hui; Jiang Mianheng; Zhang Yi; Krause, Hans-Joachim; Braginski, Alex I; Offenhaeusser, Andreas; Mueck, Michael

2010-01-01

We present a dc superconducting quantum interference device (SQUID) readout circuit operating in the voltage bias mode and called a SQUID bootstrap circuit (SBC). The SBC is an alternative implementation of two existing methods for suppression of room-temperature amplifier noise: additional voltage feedback and current feedback. Two circuit branches are connected in parallel. In the dc SQUID branch, an inductively coupled coil connected in series provides the bias current feedback for enhancing the flux-to-current coefficient. The circuit branch parallel to the dc SQUID branch contains an inductively coupled voltage feedback coil with a shunt resistor in series for suppressing the preamplifier noise current by increasing the dynamic resistance. We show that the SBC effectively reduces the preamplifier noise to below the SQUID intrinsic noise. For a helium-cooled planar SQUID magnetometer with a SQUID inductance of 350 pH, a flux noise of about 3 μΦ 0 Hz -1/2 and a magnetic field resolution of less than 3 fT Hz -1/2 were obtained. The SBC leads to a convenient direct readout electronics for a dc SQUID with a wider adjustment tolerance than other feedback schemes.

A Simple Negative Interaction in the Positive Transcriptional Feedback of a Single Gene Is Sufficient to Produce Reliable Oscillations

Science.gov (United States)

Miró-Bueno, Jesús M.; Rodríguez-Patón, Alfonso

2011-01-01

Negative and positive transcriptional feedback loops are present in natural and synthetic genetic oscillators. A single gene with negative transcriptional feedback needs a time delay and sufficiently strong nonlinearity in the transmission of the feedback signal in order to produce biochemical rhythms. A single gene with only positive transcriptional feedback does not produce oscillations. Here, we demonstrate that this single-gene network in conjunction with a simple negative interaction can also easily produce rhythms. We examine a model comprised of two well-differentiated parts. The first is a positive feedback created by a protein that binds to the promoter of its own gene and activates the transcription. The second is a negative interaction in which a repressor molecule prevents this protein from binding to its promoter. A stochastic study shows that the system is robust to noise. A deterministic study identifies that the dynamics of the oscillator are mainly driven by two types of biomolecules: the protein, and the complex formed by the repressor and this protein. The main conclusion of this paper is that a simple and usual negative interaction, such as degradation, sequestration or inhibition, acting on the positive transcriptional feedback of a single gene is a sufficient condition to produce reliable oscillations. One gene is enough and the positive transcriptional feedback signal does not need to activate a second repressor gene. This means that at the genetic level an explicit negative feedback loop is not necessary. The model needs neither cooperative binding reactions nor the formation of protein multimers. Therefore, our findings could help to clarify the design principles of cellular clocks and constitute a new efficient tool for engineering synthetic genetic oscillators. PMID:22205920

PEP-II Transverse Feedback Electronics Upgrade

International Nuclear Information System (INIS)

Weber, J.; Chin, M.; Doolittle, L.; Akre, R.

2005-01-01

The PEP-II B Factory at the Stanford Linear Accelerator Center (SLAC) requires an upgrade of the transverse feedback system electronics. The new electronics require 12-bit resolution and a minimum sampling rate of 238 Msps. A Field Programmable Gate Array (FPGA) is used to implement the feedback algorithm. The FPGA also contains an embedded PowerPC 405 (PPC-405) processor to run control system interface software for data retrieval, diagnostics, and system monitoring. The design of this system is based on the Xilinx(R) ML300 Development Platform, a circuit board set containing an FPGA with an embedded processor, a large memory bank, and other peripherals. This paper discusses the design of a digital feedback system based on an FPGA with an embedded processor. Discussion will include specifications, component selection, and integration with the ML300 design

PEP-II Transverse Feedback Electronics Upgrade

International Nuclear Information System (INIS)

Weber, J.M.; Chin, M.J.; Doolittle, L.R.; Akre, R.

2006-01-01

The PEP-II B Factory at the Stanford Linear Accelerator Center (SLAC) requires an upgrade of the transverse feedback system electronics. The new electronics require 12-bit resolution and a minimum sampling rate of 238 Msps. A Field Programmable Gate Array (FPGA) is used to implement the feedback algorithm. The FPGA also contains an embedded PowerPC 405 (PPC-405) processor to run control system interface software for data retrieval, diagnostics, and system monitoring. The design of this system is based on the Xilinx(reg s ign) ML300 Development Platform, a circuit board set containing an FPGA with an embedded processor, a large memory bank, and other peripherals. This paper discusses the design of a digital feedback system based on an FPGA with an embedded processor. Discussion will include specifications, component selection, and integration with the ML300 design

PEP-II Transverse Feedback Electronics Upgrade

CERN Document Server

Weber, Jonah; Chin, Michael; Doolittle, Lawrence

2005-01-01

The PEP-II B Factory at the Stanford Linear Accelerator Center (SLAC) requires an upgrade of the transverse feedback system electronics. The new electronics require 12-bit resolution and a minimum sampling rate of 238 Msps. A Field Programmable Gate Array (FPGA) is used to implement the feedback algorithm. The FPGA also contains an embedded PowerPC 405 (PPC-405) processor to run control system interface software for data retrieval, diagnostics, and system monitoring. The design of this system is based on the Xilinx® ML300 Development Platform, a circuit board set containing an FPGA with an embedded processor, a large memory bank, and other peripherals. This paper discusses the design of a digital feedback system based on an FPGA with an embedded processor. Discussion will include specifications, component selection, and integration with the ML300 design.

Robust control of chaos in Chua's circuit based on internal model principle

International Nuclear Information System (INIS)

Lee, Keum W.; Singh, Sahjendra N.

2007-01-01

The paper treats the question of robust control of chaos in Chua's circuit based on the internal model principle. The Chua's diode has polynomial non-linearity and it is assumed that the parameters of the circuit are not known. A robust control law for the asymptotic regulation of the output (node voltage) along constant and sinusoidal reference trajectories is derived. For the derivation of the control law, the non-linear regulator equations are solved to obtain a manifold in the state space on which the output error is zero and an internal model of the k-fold exosystem (k = 3 here) is constructed. Then a feedback control law using the optimal control theory or pole placement technique for the stabilization of the augmented system including the Chua's circuit and the internal model is derived. In the closed-loop system, robust output node voltage trajectory tracking of sinusoidal and constant reference trajectories are accomplished and in the steady state, the remaining state variables converge to periodic and constant trajectories, respectively. Simulation results are presented which show that in the closed-loop system, asymptotic trajectory control, disturbance rejection and suppression of chaotic motion in spite of uncertainties in the system are accomplished

Model-based evaluation of the short-circuited tripolar cuff configuration.

Science.gov (United States)

Andreasen, Lotte N S; Struijk, Johannes J

2006-05-01

Recordings of neural information for use as feedback in functional electrical stimulation are often contaminated with interfering signals from muscles and from stimulus pulses. The cuff electrode used for the neural recording can be optimized to improve the S/I ratio. In this work, we evaluate a model of both the nerve signal and the interfering signals recorded by a cuff, and subsequently use this model to study the signal to interference ratio of different cuff designs and to evaluate a recently introduced short-circuited tripolar cuff configuration. The results of the model showed good agreement with results from measurements in rabbits and confirmed the superior performance of the short-circuited tripolar configuration as compared with the traditionally used tripolar configuration.

Impaired coupling of local and global functional feedbacks underlies abnormal synchronization and negative symptoms of schizophrenia.

Science.gov (United States)

Noh, Kyungchul; Shin, Kyung Soon; Shin, Dongkwan; Hwang, Jae Yeon; Kim, June Sic; Jang, Joon Hwan; Chung, Chun Kee; Kwon, Jun Soo; Cho, Kwang-Hyun

2013-04-10

Abnormal synchronization of brain oscillations is found to be associated with various core symptoms of schizophrenia. However, the underlying mechanism of this association remains yet to be elucidated. In this study, we found that coupled local and global feedback (CLGF) circuits in the cortical functional network are related to the abnormal synchronization and also correlated to the negative symptom of schizophrenia. Analysis of the magnetoencephalography data obtained from patients with chronic schizophrenia during rest revealed an increase in beta band synchronization and a reduction in gamma band power compared to healthy controls. Using a feedback identification method based on non-causal impulse responses, we constructed functional feedback networks and found that CLGF circuits were significantly reduced in schizophrenia. From computational analysis on the basis of the Wilson-Cowan model, we unraveled that the CLGF circuits are critically involved in the abnormal synchronization and the dynamical switching between beta and gamma bands power in schizophrenia. Moreover, we found that the abundance of CLGF circuits was negatively correlated with the development of negative symptoms of schizophrenia, suggesting that the negative symptom is closely related to the impairment of this circuit. Our study implicates that patients with schizophrenia might have the impaired coupling of inter- and intra-regional functional feedbacks and that the CLGF circuit might serve as a critical bridge between abnormal synchronization and the negative symptoms of schizophrenia.

The test of VLSI circuits

Science.gov (United States)

Baviere, Ph.

Tests which have proven effective for evaluating VLSI circuits for space applications are described. It is recommended that circuits be examined after each manfacturing step to gain fast feedback on inadequacies in the production system. Data from failure modes which occur during operational lifetimes of circuits also permit redefinition of the manufacturing and quality control process to eliminate the defects identified. Other tests include determination of the operational envelope of the circuits, examination of the circuit response to controlled inputs, and the performance and functional speeds of ROM and RAM memories. Finally, it is desirable that all new circuits be designed with testing in mind.

Parameter tolerance of the SQUID bootstrap circuit

International Nuclear Information System (INIS)

Zhang Guofeng; Dong Hui; Xie Xiaoming; Jiang Mianheng; Zhang Yi; Krause, Hans-Joachim; Braginski, Alex I; Offenhäusser, Andreas

2012-01-01

We recently demonstrated and analysed the voltage-biased SQUID bootstrap circuit (SBC) conceived to suppress the preamplifier noise contribution in the absence of flux modulation readout. Our scheme contains both the additional voltage and current feedbacks. In this study, we analysed the tolerance of the SBC noise suppression performance to spreads in SQUID and SBC circuit parameters. Analytical results were confirmed by experiments. A one-time adjustable current feedback can be used to extend the tolerance to spreads such as those caused by the integrated circuit fabrication process. This should help to improve the fabrication yield of SBC devices integrated on one chip—as required for multi-channel SQUID systems.

A Sequential Circuit-Based IP Watermarking Algorithm for Multiple Scan Chains in Design-for-Test

Directory of Open Access Journals (Sweden)

C. Wu

2011-06-01

Full Text Available In Very Large Scale Integrated Circuits (VLSI design, the existing Design-for-Test(DFT based watermarking techniques usually insert watermark through reordering scan cells, which causes large resource overhead, low security and coverage rate of watermark detection. A novel scheme was proposed to watermark multiple scan chains in DFT for solving the problems. The proposed scheme adopts DFT scan test model of VLSI design, and uses a Linear Feedback Shift Register (LFSR for pseudo random test vector generation. All of the test vectors are shifted in scan input for the construction of multiple scan chains with minimum correlation. Specific registers in multiple scan chains will be changed by the watermark circuit for watermarking the design. The watermark can be effectively detected without interference with normal function of the circuit, even after the chip is packaged. The experimental results on several ISCAS benchmarks show that the proposed scheme has lower resource overhead, probability of coincidence and higher coverage rate of watermark detection by comparing with the existing methods.

Differential transimpedance amplifier circuit for correlated differential amplification

Science.gov (United States)

Gresham, Christopher A [Albuquerque, NM; Denton, M Bonner [Tucson, AZ; Sperline, Roger P [Tucson, AZ

2008-07-22

A differential transimpedance amplifier circuit for correlated differential amplification. The amplifier circuit increase electronic signal-to-noise ratios in charge detection circuits designed for the detection of very small quantities of electrical charge and/or very weak electromagnetic waves. A differential, integrating capacitive transimpedance amplifier integrated circuit comprising capacitor feedback loops performs time-correlated subtraction of noise.

Triple inverter pierce oscillator circuit suitable for CMOS

Science.gov (United States)

Wessendorf,; Kurt, O [Albuquerque, NM

2007-02-27

An oscillator circuit is disclosed which can be formed using discrete field-effect transistors (FETs), or as a complementary metal-oxide-semiconductor (CMOS) integrated circuit. The oscillator circuit utilizes a Pierce oscillator design with three inverter stages connected in series. A feedback resistor provided in a feedback loop about a second inverter stage provides an almost ideal inverting transconductance thereby allowing high-Q operation at the resonator-controlled frequency while suppressing a parasitic oscillation frequency that is inherent in a Pierce configuration using a "standard" triple inverter for the sustaining amplifier. The oscillator circuit, which operates in a range of 10 50 MHz, has applications for use as a clock in a microprocessor and can also be used for sensor applications.

Micromachined diffraction based optical microphones and intensity probes with electrostatic force feedback

Science.gov (United States)

Bicen, Baris

Measuring acoustic pressure gradients is critical in many applications such as directional microphones for hearing aids and sound intensity probes. This measurement is especially challenging with decreasing microphone size, which reduces the sensitivity due to small spacing between the pressure ports. Novel, micromachined biomimetic microphone diaphragms are shown to provide high sensitivity to pressure gradients on one side of the diaphragm with low thermal mechanical noise. These structures have a dominant mode shape with see-saw like motion in the audio band, responding to pressure gradients as well as spurious higher order modes sensitive to pressure. In this dissertation, integration of a diffraction based optical detection method with these novel diaphragm structures to implement a low noise optical pressure gradient microphone is described and experimental characterization results are presented, showing 36 dBA noise level with 1mm port spacing, nearly an order of magnitude better than the current gradient microphones. The optical detection scheme also provides electrostatic actuation capability from both sides of the diaphragm separately which can be used for active force feedback. A 4-port electromechanical equivalent circuit model of this microphone with optical readout is developed to predict the overall response of the device to different acoustic and electrostatic excitations. The model includes the damping due to complex motion of air around the microphone diaphragm, and it calculates the detected optical signal on each side of the diaphragm as a combination of two separate dominant vibration modes. This equivalent circuit model is verified by experiments and used to predict the microphone response with different force feedback schemes. Single sided force feedback is used for active damping to improve the linearity and the frequency response of the microphone. Furthermore, it is shown that using two sided force feedback one can significantly suppress

A Two-Layer Gene Circuit for Decoupling Cell Growth from Metabolite Production.

Science.gov (United States)

Lo, Tat-Ming; Chng, Si Hui; Teo, Wei Suong; Cho, Han-Saem; Chang, Matthew Wook

2016-08-01

We present a synthetic gene circuit for decoupling cell growth from metabolite production through autonomous regulation of enzymatic pathways by integrated modules that sense nutrient and substrate. The two-layer circuit allows Escherichia coli to selectively utilize target substrates in a mixed pool; channel metabolic resources to growth by delaying enzymatic conversion until nutrient depletion; and activate, terminate, and re-activate conversion upon substrate availability. We developed two versions of controller, both of which have glucose nutrient sensors but differ in their substrate-sensing modules. One controller is specific for hydroxycinnamic acid and the other for oleic acid. Our hydroxycinnamic acid controller lowered metabolic stress 2-fold and increased the growth rate 2-fold and productivity 5-fold, whereas our oleic acid controller lowered metabolic stress 2-fold and increased the growth rate 1.3-fold and productivity 2.4-fold. These results demonstrate the potential for engineering strategies that decouple growth and production to make bio-based production more economical and sustainable. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Logarithmic current-measuring transistor circuits

DEFF Research Database (Denmark)

Højberg, Kristian Søe

1967-01-01

Describes two transistorized circuits for the logarithmic measurement of small currents suitable for nuclear reactor instrumentation. The logarithmic element is applied in the feedback path of an amplifier, and only one dual transistor is used as logarithmic diode and temperature compensating...... transistor. A simple one-amplifier circuit is compared with a two-amplifier system. The circuits presented have been developed in connexion with an amplifier using a dual m.o.s. transistor input stage with diode-protected gates....

Switched Flip-Flop based Preprocessing Circuit for ISFETs

Directory of Open Access Journals (Sweden)

Martin Kollár

2005-03-01

Full Text Available In this paper, a preprocessing circuit for ISFETs (Ion-sensitive field-effecttransistors to measure hydrogen-ion concentration in electrolyte is presented. A modifiedflip-flop is the main part of the circuit. The modification consists in replacing the standardtransistors by ISFETs and periodically switching the supply voltage on and off.Concentration of hydrogen ions to be measured discontinues the flip-flop value symmetry,which means that by switching the supply voltage on the flip-flop goes to one of two stablestates, ‘one’ or ‘zero’. The recovery of the value symmetry can be achieved by changing abalanced voltage, which is incorporated to the flip-flop, to bring the flip-flop to a 50%position (probability of ‘one’ equals to probability of ‘zero’. Thus, the balanced voltagereflects the measured concentration of hydrogen ions. Its magnitude is set automatically byusing a feedback circuit whose input is connected to the flip-flop output. The preprocessingcircuit, as the whole, is the well-known δ modulator in which the switched flip-flop servesas a comparator and a sampling circuit. The advantages of this approach in comparison tothose of standard approaches are discussed. Finally, theoretical results are verified bysimulations with TSPICE and a good agreement is reported.

Design of an improved RCD buffer circuit for full bridge circuit

Science.gov (United States)

Yang, Wenyan; Wei, Xueye; Du, Yongbo; Hu, Liang; Zhang, Liwei; Zhang, Ou

2017-05-01

In the full bridge inverter circuit, when the switch tube suddenly opened or closed, the inductor current changes rapidly. Due to the existence of parasitic inductance of the main circuit. Therefore, the surge voltage between drain and source of the switch tube can be generated, which will have an impact on the switch and the output voltage. In order to ab sorb the surge voltage. An improve RCD buffer circuit is proposed in the paper. The peak energy will be absorbed through the buffer capacitor of the circuit. The part energy feedback to the power supply, another part release through the resistor in the form of heat, and the circuit can absorb the voltage spikes. This paper analyzes the process of the improved RCD snubber circuit, According to the specific parameters of the main circuit, a reasonable formula for calculating the resistance capacitance is given. A simulation model will be modulated in Multisim, which compared the waveform of tube voltage and the output waveform of the circuit without snubber circuit with the improved RCD snubber circuit. By comparing and analyzing, it is proved that the improved buffer circuit can absorb surge voltage. Finally, experiments are demonstrated to validate that the correctness of the RC formula and the improved RCD snubber circuit.

When more is less: Feedback effects in perceptual category learning ☆

Science.gov (United States)

Maddox, W. Todd; Love, Bradley C.; Glass, Brian D.; Filoteo, J. Vincent

2008-01-01

Rule-based and information-integration category learning were compared under minimal and full feedback conditions. Rule-based category structures are those for which the optimal rule is verbalizable. Information-integration category structures are those for which the optimal rule is not verbalizable. With minimal feedback subjects are told whether their response was correct or incorrect, but are not informed of the correct category assignment. With full feedback subjects are informed of the correctness of their response and are also informed of the correct category assignment. An examination of the distinct neural circuits that subserve rule-based and information-integration category learning leads to the counterintuitive prediction that full feedback should facilitate rule-based learning but should also hinder information-integration learning. This prediction was supported in the experiment reported below. The implications of these results for theories of learning are discussed. PMID:18455155

Design of analog pixels front-end active feedback

Science.gov (United States)

Kmon, P.; Kadlubowski, L. A.; Kaczmarczyk, P.

2018-01-01

The paper presents the design of the active feedback used in a charge-sensitive amplifier. The predominant advantages of the presented circuit are its ability for setting wide range of pulse-time widths, small silicon area occupation and low power consumption. The feedback also allows sensor leakage current compensation and, thanks to an additional DC amplifier, it minimizes the output DC voltage variations, which is especially important in the DC coupled recording chain and for processes with limited supply voltage. The paper provides feedback description and its operation principle. The proposed circuit was designed in the CMOS 130nm technology.

Current feedback operational amplifiers and their applications

CERN Document Server

Senani, Raj; Singh, A K; Singh, V K

2013-01-01

This book describes a variety of current feedback operational amplifier (CFOA) architectures and their applications in analog signal processing/generation. Coverage includes a comprehensive survey of commercially available, off-the-shelf integrated circuit CFOAs, as well as recent advances made on the design of CFOAs, including design innovations for bipolar and CMOS CFOAs.  This book serves as a single-source reference to the topic, as well as a catalog of over 200 application circuits which would be useful not only for students, educators and researchers in apprising them about the recent developments in the area but would also serve as a comprehensive repertoire of useful circuits for practicing engineers who might be interested in choosing an appropriate CFOA-based topology for use in a given application.

Moderator purification and design modifications based on operation feedback

International Nuclear Information System (INIS)

Das, S.; Chakrabarti, A.K.; Shirolkar, K.M.; Sharma, V.K.

1994-01-01

Heavy water is used as a moderator in the Pressurized Heavy Water Reactors using natural uranium as a fissile fuel. The purification system is provided to maintain the purity of moderator heavy water so as to minimise the radiolytic decomposition of heavy water due to nuclear radiation which otherwise would lead to hazardous concentration of deuterium in the moderator cover gas. The presence of dissolved impurity in the moderator increases the radiolysis rate by impeding the reverse reaction and hence these must be removed. The purification system in general controls the chemistry of moderator by minimizing the corrosion of piping in the circuit and along with the liquid poison injection system adjusts the concentration of the poisons in the moderator. This paper describes the evolution of the purification system for the 500 MWe PHWRs based on various operating requirements and feedback from the operating stations. (author)

Feedback in Videogame-based Adaptive Training

Science.gov (United States)

2011-05-01

G. (1985). The geometry tutor. Proceedings of the International Joint Conference on Artificial Intelligence . Los Altos, CA: Kaufmann. Anderson, R...Technical Report 1287 Feedback in Videogame -based Adaptive Training Iris D. Rivera Florida Institute of Technology...REPORT TYPE Final 3. DATES COVERED (from. . . to) August 2008 – April 2010 4. TITLE AND SUBTITLE Feedback in Videogame -based Adaptive

Sensitive detection of proteasomal activation using the Deg-On mammalian synthetic gene circuit.

Science.gov (United States)

Zhao, Wenting; Bonem, Matthew; McWhite, Claire; Silberg, Jonathan J; Segatori, Laura

2014-04-08

The ubiquitin proteasome system (UPS) has emerged as a drug target for diverse diseases characterized by altered proteostasis, but pharmacological agents that enhance UPS activity have been challenging to establish. Here we report the Deg-On system, a genetic inverter that translates proteasomal degradation of the transcriptional regulator TetR into a fluorescent signal, thereby linking UPS activity to an easily detectable output, which can be tuned using tetracycline. We demonstrate that this circuit responds to modulation of UPS activity in cell culture arising from the inhibitor MG-132 and activator PA28γ. Guided by predictive modelling, we enhanced the circuit's signal sensitivity and dynamic range by introducing a feedback loop that enables self-amplification of TetR. By linking UPS activity to a simple and tunable fluorescence output, these genetic inverters will enable a variety of applications, including screening for UPS activating molecules and selecting for mammalian cells with different levels of proteasome activity.

A Small-Molecule Inducible Synthetic Circuit for Control of the SOS Gene Network without DNA Damage.

Science.gov (United States)

Kubiak, Jeffrey M; Culyba, Matthew J; Liu, Monica Yun; Mo, Charlie Y; Goulian, Mark; Kohli, Rahul M

2017-11-17

The bacterial SOS stress-response pathway is a pro-mutagenic DNA repair system that mediates bacterial survival and adaptation to genotoxic stressors, including antibiotics and UV light. The SOS pathway is composed of a network of genes under the control of the transcriptional repressor, LexA. Activation of the pathway involves linked but distinct events: an initial DNA damage event leads to activation of RecA, which promotes autoproteolysis of LexA, abrogating its repressor function and leading to induction of the SOS gene network. These linked events can each independently contribute to DNA repair and mutagenesis, making it difficult to separate the contributions of the different events to observed phenotypes. We therefore devised a novel synthetic circuit to unlink these events and permit induction of the SOS gene network in the absence of DNA damage or RecA activation via orthogonal cleavage of LexA. Strains engineered with the synthetic SOS circuit demonstrate small-molecule inducible expression of SOS genes as well as the associated resistance to UV light. Exploiting our ability to activate SOS genes independently of upstream events, we further demonstrate that the majority of SOS-mediated mutagenesis on the chromosome does not readily occur with orthogonal pathway induction alone, but instead requires DNA damage. More generally, our approach provides an exemplar for using synthetic circuit design to separate an environmental stressor from its associated stress-response pathway.

Quality-factor amplification in piezoelectric MEMS resonators applying an all-electrical feedback loop

International Nuclear Information System (INIS)

Manzaneque, T; Hernando-García, J; Sánchez-Rojas, J L; Ababneh, A; Schwarz, P; Seidel, H; Schmid, U

2011-01-01

An all-electrical velocity feedback control to enhance the quality factor of piezoelectric aluminium nitride (AlN)-based microcantilevers and microbridges was implemented. Two alternatives to obtain a velocity-proportional signal were demonstrated depending on the top electrode configuration. For a straightforward electrode design in one-port configuration (i.e. self-actuation and self-sensing), a velocity signal, proportional to the piezoelectric current, was used in the feedback loop by cancelling out the dielectric current electronically. For top electrodes allowing a two-port configuration (i.e. one for actuation and one for sensing), the piezoelectric current is directly extracted and its relationship with velocity is analysed taking the symmetry of the modal shape into account. Standard operational amplifier-based configurations for the feedback circuits were implemented on a printed circuit board. Quality factors were determined from the transient electrical response of the devices. Comparable results were obtained from the displacement spectrum applying a laser Doppler vibrometer. Quality factors as high as 2 × 10 5 , corresponding to an enhancement factor of about 200, were achieved in air for the lowest gain margin achievable before the circuit becomes unstable, making this kind of device more competitive for mass sensor applications due to enhanced spectral resolution.

Interface Prostheses With Classifier-Feedback-Based User Training.

Science.gov (United States)

Fang, Yinfeng; Zhou, Dalin; Li, Kairu; Liu, Honghai

2017-11-01

It is evident that user training significantly affects performance of pattern-recognition-based myoelectric prosthetic device control. Despite plausible classification accuracy on offline datasets, online accuracy usually suffers from the changes in physiological conditions and electrode displacement. The user ability in generating consistent electromyographic (EMG) patterns can be enhanced via proper user training strategies in order to improve online performance. This study proposes a clustering-feedback strategy that provides real-time feedback to users by means of a visualized online EMG signal input as well as the centroids of the training samples, whose dimensionality is reduced to minimal number by dimension reduction. Clustering feedback provides a criterion that guides users to adjust motion gestures and muscle contraction forces intentionally. The experiment results have demonstrated that hand motion recognition accuracy increases steadily along the progress of the clustering-feedback-based user training, while conventional classifier-feedback methods, i.e., label feedback, hardly achieve any improvement. The result concludes that the use of proper classifier feedback can accelerate the process of user training, and implies prosperous future for the amputees with limited or no experience in pattern-recognition-based prosthetic device manipulation.It is evident that user training significantly affects performance of pattern-recognition-based myoelectric prosthetic device control. Despite plausible classification accuracy on offline datasets, online accuracy usually suffers from the changes in physiological conditions and electrode displacement. The user ability in generating consistent electromyographic (EMG) patterns can be enhanced via proper user training strategies in order to improve online performance. This study proposes a clustering-feedback strategy that provides real-time feedback to users by means of a visualized online EMG signal input as well

Robust control of chaos in Chua's circuit based on internal model principle

Energy Technology Data Exchange (ETDEWEB)

Lee, Keum W. [Department of Electrical and Computer Engineering, University of Nevada Las Vegas, 4505 Maryland Parkway, Las Vegas, NV, 89154-4026 (United States); Singh, Sahjendra N. [Department of Electrical and Computer Engineering, University of Nevada Las Vegas, 4505 Maryland Parkway, Las Vegas, NV, 89154-4026 (United States)]. E-mail: sahaj@ee.unlv.edu

2007-03-15

The paper treats the question of robust control of chaos in Chua's circuit based on the internal model principle. The Chua's diode has polynomial non-linearity and it is assumed that the parameters of the circuit are not known. A robust control law for the asymptotic regulation of the output (node voltage) along constant and sinusoidal reference trajectories is derived. For the derivation of the control law, the non-linear regulator equations are solved to obtain a manifold in the state space on which the output error is zero and an internal model of the k-fold exosystem (k = 3 here) is constructed. Then a feedback control law using the optimal control theory or pole placement technique for the stabilization of the augmented system including the Chua's circuit and the internal model is derived. In the closed-loop system, robust output node voltage trajectory tracking of sinusoidal and constant reference trajectories are accomplished and in the steady state, the remaining state variables converge to periodic and constant trajectories, respectively. Simulation results are presented which show that in the closed-loop system, asymptotic trajectory control, disturbance rejection and suppression of chaotic motion in spite of uncertainties in the system are accomplished.

Moderator purification and design modifications based on operation feedback

Energy Technology Data Exchange (ETDEWEB)

Das, S; Chakrabarti, A K; Shirolkar, K M; Sharma, V K [Nuclear Power Corporation, Bhabha Atomic Research Centre, Mumbai (India)

1994-06-01

Heavy water is used as a moderator in the Pressurized Heavy Water Reactors using natural uranium as a fissile fuel. The purification system is provided to maintain the purity of moderator heavy water so as to minimise the radiolytic decomposition of heavy water due to nuclear radiation which otherwise would lead to hazardous concentration of deuterium in the moderator cover gas. The presence of dissolved impurity in the moderator increases the radiolysis rate by impeding the reverse reaction and hence these must be removed. The purification system in general controls the chemistry of moderator by minimizing the corrosion of piping in the circuit and along with the liquid poison injection system adjusts the concentration of the poisons in the moderator. This paper describes the evolution of the purification system for the 500 MWe PHWRs based on various operating requirements and feedback from the operating stations. (author). 2 refs., 3 figs., 1 tab.

Circuit for Driving Piezoelectric Transducers

Science.gov (United States)

Randall, David P.; Chapsky, Jacob

2009-01-01

The figure schematically depicts an oscillator circuit for driving a piezoelectric transducer to excite vibrations in a mechanical structure. The circuit was designed and built to satisfy application-specific requirements to drive a selected one of 16 such transducers at a regulated amplitude and frequency chosen to optimize the amount of work performed by the transducer and to compensate for both (1) temporal variations of the resonance frequency and damping time of each transducer and (2) initially unknown differences among the resonance frequencies and damping times of different transducers. In other words, the circuit is designed to adjust itself to optimize the performance of whichever transducer is selected at any given time. The basic design concept may be adaptable to other applications that involve the use of piezoelectric transducers in ultrasonic cleaners and other apparatuses in which high-frequency mechanical drives are utilized. This circuit includes three resistor-capacitor networks that, together with the selected piezoelectric transducer, constitute a band-pass filter having a peak response at a frequency of about 2 kHz, which is approximately the resonance frequency of the piezoelectric transducers. Gain for generating oscillations is provided by a power hybrid operational amplifier (U1). A junction field-effect transistor (Q1) in combination with a resistor (R4) is used as a voltage-variable resistor to control the magnitude of the oscillation. The voltage-variable resistor is part of a feedback control loop: Part of the output of the oscillator is rectified and filtered for use as a slow negative feedback to the gate of Q1 to keep the output amplitude constant. The response of this control loop is much slower than 2 kHz and, therefore, does not introduce significant distortion of the oscillator output, which is a fairly clean sine wave. The positive AC feedback needed to sustain oscillations is derived from sampling the current through the

Pluripotency gene network dynamics: System views from parametric analysis.

Science.gov (United States)

Akberdin, Ilya R; Omelyanchuk, Nadezda A; Fadeev, Stanislav I; Leskova, Natalya E; Oschepkova, Evgeniya A; Kazantsev, Fedor V; Matushkin, Yury G; Afonnikov, Dmitry A; Kolchanov, Nikolay A

2018-01-01

Multiple experimental data demonstrated that the core gene network orchestrating self-renewal and differentiation of mouse embryonic stem cells involves activity of Oct4, Sox2 and Nanog genes by means of a number of positive feedback loops among them. However, recent studies indicated that the architecture of the core gene network should also incorporate negative Nanog autoregulation and might not include positive feedbacks from Nanog to Oct4 and Sox2. Thorough parametric analysis of the mathematical model based on this revisited core regulatory circuit identified that there are substantial changes in model dynamics occurred depending on the strength of Oct4 and Sox2 activation and molecular complexity of Nanog autorepression. The analysis showed the existence of four dynamical domains with different numbers of stable and unstable steady states. We hypothesize that these domains can constitute the checkpoints in a developmental progression from naïve to primed pluripotency and vice versa. During this transition, parametric conditions exist, which generate an oscillatory behavior of the system explaining heterogeneity in expression of pluripotent and differentiation factors in serum ESC cultures. Eventually, simulations showed that addition of positive feedbacks from Nanog to Oct4 and Sox2 leads mainly to increase of the parametric space for the naïve ESC state, in which pluripotency factors are strongly expressed while differentiation ones are repressed.

Nuclear Power Plants Secondary Circuit Piping Wall-Thinning Management in China

International Nuclear Information System (INIS)

Zhong Zhimin; Li Jinsong; Zheng Hui

2012-01-01

Research and field feedbacks showed that nuclear power plants secondary circuit steam and water piping are more sensitive than that of fuel plant to the attack of flow-accelerated corrosion (FAC). FAC, Liquid droplet impingement or cavitation erosion will cause secondary circuit piping local wall-thinning in NPPs. Without effective management, the wall-thinning in those high energy piping will cause leakage or pipe rupture during nuclear power plant operation, more seriously cause unplanned shut down, injured and fatality, or heavy economic losses. This paper briefly introduces the history, development and state of the art of secondary circuit piping wall-thinning management in China NPPs. Then, the effectiveness of inspection grid size selecting was analyzed in detail based on field feedbacks. EPRI recommendatory inspection grid, JSME code recommendatory grid and plant specific inspection grid were compared and the detection probabilities of local wall-thinning were estimated. Then, the development and application of NPPs Secondary Circuit Piping Wall Thickness Management Information System, developed, operated and maintained by our team, was briefly introduced and the statistical analysis results of 11 PWR units were shared. It was conclude that the long term, systemic, effective wall-thinning management strategy of high energy piping was very important to the safety and economic operation of NPPs. Furthermore, take into account the actual situation of China nuclear power plants, some advice and suggestion on developing effective nuclear power plant secondary circuit steam and water piping wall-thinning management system are put forward from code development, design and manufacture, operation management, pipeline and locations selection, inspection method selection and application, thickness measurement result evaluation, residual life predication and decision making, feedbacks usage, personnel training and etc. (author)

Developmental checkpoints and feedback circuits time insect maturation

DEFF Research Database (Denmark)

Rewitz, Kim Furbo; Yamanaka, Naoki; O'Connor, Michael B.

2013-01-01

as external cues, to time production and release of ecdysone. Based on results discussed here, we suggest that developmental progression to adulthood is controlled by checkpoints that regulate the genetic timing program enabling it to adapt to different environmental conditions. These checkpoints utilize...... a number of signaling pathways to modulate ecdysone production in the prothoracic gland. Release of ecdysone activates an autonomous cascade of both feedforward and feedback signals that determine the duration of the ecdysone pulse at each developmental transitions. Conservation of the genetic mechanisms...... that coordinate the juvenile-adult transition suggests that insights from the fruit fly Drosophila will provide a framework for future investigation of developmental timing in metazoans....

Dynamical consequences of bandpass feedback loops in a bacterial phosphorelay.

Directory of Open Access Journals (Sweden)

Shaunak Sen

Full Text Available Under conditions of nutrient limitation, Bacillus subtilis cells terminally differentiate into a dormant spore state. Progression to sporulation is controlled by a genetic circuit consisting of a phosphorelay embedded in multiple transcriptional feedback loops, which is used to activate the master regulator Spo0A by phosphorylation. These transcriptional regulatory interactions are "bandpass"-like, in the sense that activation occurs within a limited band of Spo0A∼P concentrations. Additionally, recent results show that the phosphorelay activation occurs in pulses, in a cell-cycle dependent fashion. However, the impact of these pulsed bandpass interactions on the circuit dynamics preceding sporulation remains unclear. In order to address this question, we measured key features of the bandpass interactions at the single-cell level and analyzed them in the context of a simple mathematical model. The model predicted the emergence of a delayed phase shift between the pulsing activity of the different sporulation genes, as well as the existence of a stable state, with elevated Spo0A activity but no sporulation, embedded within the dynamical structure of the system. To test the model, we used time-lapse fluorescence microscopy to measure dynamics of single cells initiating sporulation. We observed the delayed phase shift emerging during the progression to sporulation, while a re-engineering of the sporulation circuit revealed behavior resembling the predicted additional state. These results show that periodically-driven bandpass feedback loops can give rise to complex dynamics in the progression towards sporulation.

Novel charge sensitive preamplifier without high-value feedback resistor

International Nuclear Information System (INIS)

Xi Deming

1992-01-01

A novel charge sensitive preamplifier is introduced. The method of removing the high value feedback resistor, the circuit design and analysis are described. A practical circuit and its measured performances are provided

A parity checker circuit based on microelectromechanical resonator logic elements

Energy Technology Data Exchange (ETDEWEB)

Hafiz, Md Abdullah Al, E-mail: abdullah.hafiz@kaust.edu.sa [CEMSE Division, King Abdullah University of Science and Technology, Thuwal (Saudi Arabia); Li, Ren [CEMSE Division, King Abdullah University of Science and Technology, Thuwal (Saudi Arabia); Younis, Mohammad I. [PSE Division, King Abdullah University of Science and Technology, Thuwal (Saudi Arabia); Fariborzi, Hossein [CEMSE Division, King Abdullah University of Science and Technology, Thuwal (Saudi Arabia)

2017-03-03

Micro/nano-electromechanical resonator based logic computation has attracted significant attention in recent years due to its dynamic mode of operation, ultra-low power consumption, and potential for reprogrammable and reversible computing. Here we demonstrate a 4-bit parity checker circuit by utilizing recently developed logic gates based on MEMS resonators. Toward this, resonance frequencies of shallow arch shaped micro-resonators are electrothermally tuned by the logic inputs to constitute the required logic gates for the proposed parity checker circuit. This study demonstrates that by utilizing MEMS resonator based logic elements, complex digital circuits can be realized. - Highlights: • A 4-bit parity checker circuit is proposed and demonstrated based on MEMS resonator based logic elements. • Multiple copies of MEMS resonator based XOR logic gates are used to construct a complex logic circuit. • Functionality and feasibility of micro-resonator based logic platform is demonstrated.

Biophysical network modeling of the dLGN circuit: Effects of cortical feedback on spatial response properties of relay cells.

Directory of Open Access Journals (Sweden)

Pablo Martínez-Cañada

2018-01-01

Full Text Available Despite half-a-century of research since the seminal work of Hubel and Wiesel, the role of the dorsal lateral geniculate nucleus (dLGN in shaping the visual signals is not properly understood. Placed on route from retina to primary visual cortex in the early visual pathway, a striking feature of the dLGN circuit is that both the relay cells (RCs and interneurons (INs not only receive feedforward input from retinal ganglion cells, but also a prominent feedback from cells in layer 6 of visual cortex. This feedback has been proposed to affect synchronicity and other temporal properties of the RC firing. It has also been seen to affect spatial properties such as the center-surround antagonism of thalamic receptive fields, i.e., the suppression of the response to very large stimuli compared to smaller, more optimal stimuli. Here we explore the spatial effects of cortical feedback on the RC response by means of a a comprehensive network model with biophysically detailed, single-compartment and multicompartment neuron models of RCs, INs and a population of orientation-selective layer 6 simple cells, consisting of pyramidal cells (PY. We have considered two different arrangements of synaptic feedback from the ON and OFF zones in the visual cortex to the dLGN: phase-reversed ('push-pull' and phase-matched ('push-push', as well as different spatial extents of the corticothalamic projection pattern. Our simulation results support that a phase-reversed arrangement provides a more effective way for cortical feedback to provide the increased center-surround antagonism seen in experiments both for flashing spots and, even more prominently, for patch gratings. This implies that ON-center RCs receive direct excitation from OFF-dominated cortical cells and indirect inhibitory feedback from ON-dominated cortical cells. The increased center-surround antagonism in the model is accompanied by spatial focusing, i.e., the maximum RC response occurs for smaller stimuli

Biophysical network modeling of the dLGN circuit: Effects of cortical feedback on spatial response properties of relay cells

Science.gov (United States)

Martínez-Cañada, Pablo; Halnes, Geir; Fyhn, Marianne

2018-01-01

Despite half-a-century of research since the seminal work of Hubel and Wiesel, the role of the dorsal lateral geniculate nucleus (dLGN) in shaping the visual signals is not properly understood. Placed on route from retina to primary visual cortex in the early visual pathway, a striking feature of the dLGN circuit is that both the relay cells (RCs) and interneurons (INs) not only receive feedforward input from retinal ganglion cells, but also a prominent feedback from cells in layer 6 of visual cortex. This feedback has been proposed to affect synchronicity and other temporal properties of the RC firing. It has also been seen to affect spatial properties such as the center-surround antagonism of thalamic receptive fields, i.e., the suppression of the response to very large stimuli compared to smaller, more optimal stimuli. Here we explore the spatial effects of cortical feedback on the RC response by means of a a comprehensive network model with biophysically detailed, single-compartment and multicompartment neuron models of RCs, INs and a population of orientation-selective layer 6 simple cells, consisting of pyramidal cells (PY). We have considered two different arrangements of synaptic feedback from the ON and OFF zones in the visual cortex to the dLGN: phase-reversed (‘push-pull’) and phase-matched (‘push-push’), as well as different spatial extents of the corticothalamic projection pattern. Our simulation results support that a phase-reversed arrangement provides a more effective way for cortical feedback to provide the increased center-surround antagonism seen in experiments both for flashing spots and, even more prominently, for patch gratings. This implies that ON-center RCs receive direct excitation from OFF-dominated cortical cells and indirect inhibitory feedback from ON-dominated cortical cells. The increased center-surround antagonism in the model is accompanied by spatial focusing, i.e., the maximum RC response occurs for smaller stimuli when

Thyristor based short circuit current injection in isolated grids

OpenAIRE

Hoff, Bjarte; Sharma, Pawan; Østrem, Trond

2017-01-01

This paper proposes a thyristor based short circuit current injector for providing short circuit current in isolated and weak grids, where sufficient fault current to trigger circuit breakers may not be available. This will allow the use of conventional miniature circuit breakers, which requires high fault current for instantaneous tripping. The method has been validated through experiments.

Analog circuit design art, science, and personalities

CERN Document Server

Williams, Jim

1991-01-01

Analog Circuit Design: Art, Science, and Personalities discusses the many approaches and styles in the practice of analog circuit design. The book is written in an informal yet informative manner, making it easily understandable to those new in the field. The selection covers the definition, history, current practice, and future direction of analog design; the practice proper; and the styles in analog circuit design. The book also includes the problems usually encountered in analog circuit design; approach to feedback loop design; and other different techniques and applications. The text is

Photonic integrated circuits unveil crisis-induced intermittency.

Science.gov (United States)

Karsaklian Dal Bosco, Andreas; Akizawa, Yasuhiro; Kanno, Kazutaka; Uchida, Atsushi; Harayama, Takahisa; Yoshimura, Kazuyuki

2016-09-19

We experimentally investigate an intermittent route to chaos in a photonic integrated circuit consisting of a semiconductor laser with time-delayed optical feedback from a short external cavity. The transition from a period-doubling dynamics to a fully-developed chaos reveals a stage intermittently exhibiting these two dynamics. We unveil the bifurcation mechanism underlying this route to chaos by using the Lang-Kobayashi model and demonstrate that the process is based on a phenomenon of attractor expansion initiated by a particular distribution of the local Lyapunov exponents. We emphasize on the crucial importance of the distribution of the steady-state solutions introduced by the time-delayed feedback on the existence of this intermittent dynamics.

CMOS-based carbon nanotube pass-transistor logic integrated circuits

Science.gov (United States)

Ding, Li; Zhang, Zhiyong; Liang, Shibo; Pei, Tian; Wang, Sheng; Li, Yan; Zhou, Weiwei; Liu, Jie; Peng, Lian-Mao

2012-01-01

Field-effect transistors based on carbon nanotubes have been shown to be faster and less energy consuming than their silicon counterparts. However, ensuring these advantages are maintained for integrated circuits is a challenge. Here we demonstrate that a significant reduction in the use of field-effect transistors can be achieved by constructing carbon nanotube-based integrated circuits based on a pass-transistor logic configuration, rather than a complementary metal-oxide semiconductor configuration. Logic gates are constructed on individual carbon nanotubes via a doping-free approach and with a single power supply at voltages as low as 0.4 V. The pass-transistor logic configurarion provides a significant simplification of the carbon nanotube-based circuit design, a higher potential circuit speed and a significant reduction in power consumption. In particular, a full adder, which requires a total of 28 field-effect transistors to construct in the usual complementary metal-oxide semiconductor circuit, uses only three pairs of n- and p-field-effect transistors in the pass-transistor logic configuration. PMID:22334080

Transcriptional feedback regulation of YUCCA genes in response to auxin levels in Arabidopsis.

Science.gov (United States)

Suzuki, Masashi; Yamazaki, Chiaki; Mitsui, Marie; Kakei, Yusuke; Mitani, Yuka; Nakamura, Ayako; Ishii, Takahiro; Soeno, Kazuo; Shimada, Yukihisa

2015-08-01

The IPyA pathway, the major auxin biosynthesis pathway, is transcriptionally regulated through a negative feedback mechanism in response to active auxin levels. The phytohormone auxin plays an important role in plant growth and development, and levels of active free auxin are determined by biosynthesis, conjugation, and polar transport. Unlike conjugation and polar transport, little is known regarding the regulatory mechanism of auxin biosynthesis. We discovered that expression of genes encoding indole-3-pyruvic acid (IPyA) pathway enzymes is regulated by elevated or reduced active auxin levels. Expression levels of TAR2, YUC1, YUC2, YUC4, and YUC6 were downregulated in response to synthetic auxins [1-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D)] exogenously applied to Arabidopsis thaliana L. seedlings. Concomitantly, reduced levels of endogenous indole-3-acetic acid (IAA) were observed. Alternatively, expression of these YUCCA genes was upregulated by the auxin biosynthetic inhibitor kynurenine in Arabidopsis seedlings, accompanied by reduced IAA levels. These results indicate that expression of YUCCA genes is regulated by active auxin levels. Similar results were also observed in auxin-overproduction and auxin-deficient mutants. Exogenous application of IPyA to Arabidopsis seedlings preincubated with kynurenine increased endogenous IAA levels, while preincubation with 2,4-D reduced endogenous IAA levels compared to seedlings exposed only to IPyA. These results suggest that in vivo conversion of IPyA to IAA was enhanced under reduced auxin levels, while IPyA to IAA conversion was depressed in the presence of excess auxin. Based on these results, we propose that the IPyA pathway is transcriptionally regulated through a negative feedback mechanism in response to active auxin levels.

Simulation model for transcervical laryngeal injection providing real-time feedback.

Science.gov (United States)

Ainsworth, Tiffiny A; Kobler, James B; Loan, Gregory J; Burns, James A

2014-12-01

This study aimed to develop and evaluate a model for teaching transcervical laryngeal injections. A 3-dimensional printer was used to create a laryngotracheal framework based on de-identified computed tomography images of a human larynx. The arytenoid cartilages and intrinsic laryngeal musculature were created in silicone from clay casts and thermoplastic molds. The thyroarytenoid (TA) muscle was created with electrically conductive silicone using metallic filaments embedded in silicone. Wires connected TA muscles to an electrical circuit incorporating a cell phone and speaker. A needle electrode completed the circuit when inserted in the TA during simulated injection, providing real-time feedback of successful needle placement by producing an audible sound. Face validation by the senior author confirmed appropriate tactile feedback and anatomical realism. Otolaryngologists pilot tested the model and completed presimulation and postsimulation questionnaires. The high-fidelity simulation model provided tactile and audio feedback during needle placement, simulating transcervical vocal fold injections. Otolaryngology residents demonstrated higher comfort levels with transcervical thyroarytenoid injection on postsimulation questionnaires. This is the first study to describe a simulator for developing transcervical vocal fold injection skills. The model provides real-time tactile and auditory feedback that aids in skill acquisition. Otolaryngologists reported increased confidence with transcervical injection after using the simulator. © The Author(s) 2014.

Current feedback operational amplifiers as fast charge sensitive preamplifiers for photomultiplier read out

Energy Technology Data Exchange (ETDEWEB)

Giachero, A; Gotti, C; Maino, M; Pessina, G, E-mail: claudio.gotti@mib.infn.it [INFN - Sezione di Milano-Bicocca, I-20126, Milano (Italy)

2011-05-01

Fast charge sensitive preamplifiers were built using commercial current feedback operational amplifiers for fast read out of charge pulses from a photomultiplier tube. Current feedback opamps prove to be particularly well suited for this application where the charge from the detector is large, of the order of one million electrons, and high timing resolution is required. A proper circuit arrangement allows very fast signals, with rise times down to one nanosecond, while keeping the amplifier stable. After a review of current feedback circuit topology and stability constraints, we provide a 'recipe' to build stable and very fast charge sensitive preamplifiers from any current feedback opamp by adding just a few external components. The noise performance of the circuit topology has been evaluated and is reported in terms of equivalent noise charge.

Robust dynamical pattern formation from a multifunctional minimal genetic circuit

Directory of Open Access Journals (Sweden)

Carrera Javier

2010-04-01

Full Text Available Abstract Background A practical problem during the analysis of natural networks is their complexity, thus the use of synthetic circuits would allow to unveil the natural mechanisms of operation. Autocatalytic gene regulatory networks play an important role in shaping the development of multicellular organisms, whereas oscillatory circuits are used to control gene expression under variable environments such as the light-dark cycle. Results We propose a new mechanism to generate developmental patterns and oscillations using a minimal number of genes. For this, we design a synthetic gene circuit with an antagonistic self-regulation to study the spatio-temporal control of protein expression. Here, we show that our minimal system can behave as a biological clock or memory, and it exhibites an inherent robustness due to a quorum sensing mechanism. We analyze this property by accounting for molecular noise in an heterogeneous population. We also show how the period of the oscillations is tunable by environmental signals, and we study the bifurcations of the system by constructing different phase diagrams. Conclusions As this minimal circuit is based on a single transcriptional unit, it provides a new mechanism based on post-translational interactions to generate targeted spatio-temporal behavior.

Rocchio-based relevance feedback in video event retrieval

NARCIS (Netherlands)

Pingen, G.L.J.; de Boer, M.H.T.; Aly, Robin; Amsaleg, Laurent; Guðmundsson, Gylfi Þór; Gurrin, Cathal; Jónsson, Björn Þór; Satoh, Shin’ichi

This paper investigates methods for user and pseudo relevance feedback in video event retrieval. Existing feedback methods achieve strong performance but adjust the ranking based on few individual examples. We propose a relevance feedback algorithm (ARF) derived from the Rocchio method, which is a

Encyclopedia of bacterial gene circuits whose presence or absence correlate with pathogenicity--a large-scale system analysis of decoded bacterial genomes.

Science.gov (United States)

Shestov, Maksim; Ontañón, Santiago; Tozeren, Aydin

2015-10-13

Bacterial infections comprise a global health challenge as the incidences of antibiotic resistance increase. Pathogenic potential of bacteria has been shown to be context dependent, varying in response to environment and even within the strains of the same genus. We used the KEGG repository and extensive literature searches to identify among the 2527 bacterial genomes in the literature those implicated as pathogenic to the host, including those which show pathogenicity in a context dependent manner. Using data on the gene contents of these genomes, we identified sets of genes highly abundant in pathogenic but relatively absent in commensal strains and vice versa. In addition, we carried out genome comparison within a genus for the seventeen largest genera in our genome collection. We projected the resultant lists of ortholog genes onto KEGG bacterial pathways to identify clusters and circuits, which can be linked to either pathogenicity or synergy. Gene circuits relatively abundant in nonpathogenic bacteria often mediated biosynthesis of antibiotics. Other synergy-linked circuits reduced drug-induced toxicity. Pathogen-abundant gene circuits included modules in one-carbon folate, two-component system, type-3 secretion system, and peptidoglycan biosynthesis. Antibiotics-resistant bacterial strains possessed genes modulating phagocytosis, vesicle trafficking, cytoskeletal reorganization, and regulation of the inflammatory response. Our study also identified bacterial genera containing a circuit, elements of which were previously linked to Alzheimer's disease. Present study produces for the first time, a signature, in the form of a robust list of gene circuitry whose presence or absence could potentially define the pathogenicity of a microbiome. Extensive literature search substantiated a bulk majority of the commensal and pathogenic circuitry in our predicted list. Scanning microbiome libraries for these circuitry motifs will provide further insights into the complex

Thermally-isolated silicon-based integrated circuits and related methods

Science.gov (United States)

Wojciechowski, Kenneth; Olsson, Roy H.; Clews, Peggy J.; Bauer, Todd

2017-05-09

Thermally isolated devices may be formed by performing a series of etches on a silicon-based substrate. As a result of the series of etches, silicon material may be removed from underneath a region of an integrated circuit (IC). The removal of the silicon material from underneath the IC forms a gap between remaining substrate and the integrated circuit, though the integrated circuit remains connected to the substrate via a support bar arrangement that suspends the integrated circuit over the substrate. The creation of this gap functions to release the device from the substrate and create a thermally-isolated integrated circuit.

Method of making thermally-isolated silicon-based integrated circuits

Science.gov (United States)

Wojciechowski, Kenneth; Olsson, Roy; Clews, Peggy J.; Bauer, Todd

2017-11-21

Thermally isolated devices may be formed by performing a series of etches on a silicon-based substrate. As a result of the series of etches, silicon material may be removed from underneath a region of an integrated circuit (IC). The removal of the silicon material from underneath the IC forms a gap between remaining substrate and the integrated circuit, though the integrated circuit remains connected to the substrate via a support bar arrangement that suspends the integrated circuit over the substrate. The creation of this gap functions to release the device from the substrate and create a thermally-isolated integrated circuit.

All-semiconductor metamaterial-based optical circuit board at the microscale

International Nuclear Information System (INIS)

Min, Li; Huang, Lirong

2015-01-01

The newly introduced metamaterial-based optical circuit, an analogue of electronic circuit, is becoming a forefront topic in the fields of electronics, optics, plasmonics, and metamaterials. However, metals, as the commonly used plasmonic elements in an optical circuit, suffer from large losses at the visible and infrared wavelengths. We propose here a low-loss, all-semiconductor metamaterial-based optical circuit board at the microscale by using interleaved intrinsic GaAs and doped GaAs, and present the detailed design process for various lumped optical circuit elements, including lumped optical inductors, optical capacitors, optical conductors, and optical insulators. By properly combining these optical circuit elements and arranging anisotropic optical connectors, we obtain a subwavelength optical filter, which can always hold band-stop filtering function for various polarization states of the incident electromagnetic wave. All-semiconductor optical circuits may provide a new opportunity in developing low-power and ultrafast components and devices for optical information processing

Design, Simulation and Characteristics Research of the Interface Circuit based on nano-polysilicon thin films pressure sensor

Science.gov (United States)

Zhao, Xiaosong; Zhao, Xiaofeng; Yin, Liang

2018-03-01

This paper presents a interface circuit for nano-polysilicon thin films pressure sensor. The interface circuit includes consist of instrument amplifier and Analog-to-Digital converter (ADC). The instrumentation amplifier with a high common mode rejection ratio (CMRR) is implemented by three stages current feedback structure. At the same time, in order to satisfy the high precision requirements of pressure sensor measure system, the 1/f noise corner of 26.5 mHz can be achieved through chopping technology at a noise density of 38.2 nV/sqrt(Hz).Ripple introduced by chopping technology adopt continuous ripple reduce circuit (RRL), which achieves the output ripple level is lower than noise. The ADC achieves 16 bits significant digit by adopting sigma-delta modulator with fourth-order single-bit structure and digital decimation filter, and finally achieves high precision integrated pressure sensor interface circuit.

Crossed SMPS MOSFET-based protection circuit for high frequency ultrasound transceivers and transducers.

Science.gov (United States)

Choi, Hojong; Shung, K Kirk

2014-06-12

The ultrasonic transducer is one of the core components of ultrasound systems, and the transducer's sensitivity is significantly related the loss of electronic components such as the transmitter, receiver, and protection circuit. In an ultrasonic device, protection circuits are commonly used to isolate the electrical noise between an ultrasound transmitter and transducer and to minimize unwanted discharged pulses in order to protect the ultrasound receiver. However, the performance of the protection circuit and transceiver obviously degrade as the operating frequency or voltage increases. We therefore developed a crossed SMPS (Switching Mode Power Supply) MOSFET-based protection circuit in order to maximize the sensitivity of high frequency transducers in ultrasound systems.The high frequency pulse signals need to trigger the transducer, and high frequency pulse signals must be received by the transducer. We therefore selected the SMPS MOSFET, which is the main component of the protection circuit, to minimize the loss in high frequency operation. The crossed configuration of the protection circuit can drive balanced bipolar high voltage signals from the pulser and transfer the balanced low voltage echo signals from the transducer. The equivalent circuit models of the SMPS MOSFET-based protection circuit are shown in order to select the proper device components. The schematic diagram and operation mechanism of the protection circuit is provided to show how the protection circuit is constructed. The P-Spice circuit simulation was also performed in order to estimate the performance of the crossed MOSFET-based protection circuit. We compared the performance of our crossed SMPS MOSFET-based protection circuit with a commercial diode-based protection circuit. At 60 MHz, our expander and limiter circuits have lower insertion loss than the commercial diode-based circuits. The pulse-echo test is typical method to evaluate the sensitivity of ultrasonic transducers

A Cytomorphic Chip for Quantitative Modeling of Fundamental Bio-Molecular Circuits.

Science.gov (United States)

2015-08-01

We describe a 0.35 μm BiCMOS silicon chip that quantitatively models fundamental molecular circuits via efficient log-domain cytomorphic transistor equivalents. These circuits include those for biochemical binding with automatic representation of non-modular and loading behavior, e.g., in cascade and fan-out topologies; for representing variable Hill-coefficient operation and cooperative binding; for representing inducer, transcription-factor, and DNA binding; for probabilistic gene transcription with analogic representations of log-linear and saturating operation; for gain, degradation, and dynamics of mRNA and protein variables in transcription and translation; and, for faithfully representing biological noise via tunable stochastic transistor circuits. The use of on-chip DACs and ADCs enables multiple chips to interact via incoming and outgoing molecular digital data packets and thus create scalable biochemical reaction networks. The use of off-chip digital processors and on-chip digital memory enables programmable connectivity and parameter storage. We show that published static and dynamic MATLAB models of synthetic biological circuits including repressilators, feed-forward loops, and feedback oscillators are in excellent quantitative agreement with those from transistor circuits on the chip. Computationally intensive stochastic Gillespie simulations of molecular production are also rapidly reproduced by the chip and can be reliably tuned over the range of signal-to-noise ratios observed in biological cells.

Automatic Control of Gene Expression in Mammalian Cells.

Science.gov (United States)

Fracassi, Chiara; Postiglione, Lorena; Fiore, Gianfranco; di Bernardo, Diego

2016-04-15

Automatic control of gene expression in living cells is paramount importance to characterize both endogenous gene regulatory networks and synthetic circuits. In addition, such a technology can be used to maintain the expression of synthetic circuit components in an optimal range in order to ensure reliable performance. Here we present a microfluidics-based method to automatically control gene expression from the tetracycline-inducible promoter in mammalian cells in real time. Our approach is based on the negative-feedback control engineering paradigm. We validated our method in a monoclonal population of cells constitutively expressing a fluorescent reporter protein (d2EYFP) downstream of a minimal CMV promoter with seven tet-responsive operator motifs (CMV-TET). These cells also constitutively express the tetracycline transactivator protein (tTA). In cells grown in standard growth medium, tTA is able to bind the CMV-TET promoter, causing d2EYFP to be maximally expressed. Upon addition of tetracycline to the culture medium, tTA detaches from the CMV-TET promoter, thus preventing d2EYFP expression. We tested two different model-independent control algorithms (relay and proportional-integral (PI)) to force a monoclonal population of cells to express an intermediate level of d2EYFP equal to 50% of its maximum expression level for up to 3500 min. The control input is either tetracycline-rich or standard growth medium. We demonstrated that both the relay and PI controllers can regulate gene expression at the desired level, despite oscillations (dampened in the case of the PI controller) around the chosen set point.

Spike timing precision of neuronal circuits.

Science.gov (United States)

Kilinc, Deniz; Demir, Alper

2018-04-17

Spike timing is believed to be a key factor in sensory information encoding and computations performed by the neurons and neuronal circuits. However, the considerable noise and variability, arising from the inherently stochastic mechanisms that exist in the neurons and the synapses, degrade spike timing precision. Computational modeling can help decipher the mechanisms utilized by the neuronal circuits in order to regulate timing precision. In this paper, we utilize semi-analytical techniques, which were adapted from previously developed methods for electronic circuits, for the stochastic characterization of neuronal circuits. These techniques, which are orders of magnitude faster than traditional Monte Carlo type simulations, can be used to directly compute the spike timing jitter variance, power spectral densities, correlation functions, and other stochastic characterizations of neuronal circuit operation. We consider three distinct neuronal circuit motifs: Feedback inhibition, synaptic integration, and synaptic coupling. First, we show that both the spike timing precision and the energy efficiency of a spiking neuron are improved with feedback inhibition. We unveil the underlying mechanism through which this is achieved. Then, we demonstrate that a neuron can improve on the timing precision of its synaptic inputs, coming from multiple sources, via synaptic integration: The phase of the output spikes of the integrator neuron has the same variance as that of the sample average of the phases of its inputs. Finally, we reveal that weak synaptic coupling among neurons, in a fully connected network, enables them to behave like a single neuron with a larger membrane area, resulting in an improvement in the timing precision through cooperation.

The rice YABBY1 gene is involved in the feedback regulation of gibberellin metabolism.

Science.gov (United States)

Dai, Mingqiu; Zhao, Yu; Ma, Qian; Hu, Yongfeng; Hedden, Peter; Zhang, Qifa; Zhou, Dao-Xiu

2007-05-01

Gibberellin (GA) biosynthesis is regulated by feedback control providing a mechanism for GA homeostasis in plants. However, regulatory elements involved in the feedback control are not known. In this report, we show that a rice (Oryza sativa) YABBY1 (YAB1) gene had a similar expression pattern as key rice GA biosynthetic genes GA3ox2 and GA20ox2. Overexpression of YAB1 in transgenic rice resulted in a semidwarf phenotype that could be fully rescued by applied GA. Quantification of the endogenous GA content revealed increases of GA(20) and decreases of GA(1) levels in the overexpression plants, in which the transcripts of the biosynthetic gene GA3ox2 were decreased. Cosuppression of YAB1 in transgenic plants induced expression of GA3ox2. The repression of GA3ox2 could be obtained upon treatment by dexamethasone of transgenic plants expressing a YAB1-glucocorticoid receptor fusion. Importantly, we show that YAB1 bound to a GA-responsive element within the GA3ox2 promoter. In addition, the expression of YAB1 was deregulated in GA biosynthesis and signaling mutants and could be either transiently induced by GA or repressed by a GA inhibitor. Finally, either overexpression or cosuppression of YAB1 impaired GA-mediated repression of GA3ox2. These data together suggest that YAB1 is involved in the feedback regulation of GA biosynthesis in rice.

Optogenetic dissection of neuronal circuits in zebrafish using viral gene transfer and the Tet system

Directory of Open Access Journals (Sweden)

Peixin Zhu

2009-12-01

Full Text Available The conditional expression of transgenes at high levels in sparse and specific populations of neurons is important for high-resolution optogenetic analyses of neuronal circuits. We explored two complementary methods, viral gene delivery and the iTet-Off system, to express transgenes in the brain of zebrafish. High-level gene expression in neurons was achieved by Sindbis and Rabies viruses. The Tet system produced strong and specific gene expression that could be modulated conveniently by doxycycline. Moreover, transgenic lines showed expression in distinct, sparse and stable populations of neurons that appeared to be subsets of the neurons targeted by the promoter driving the Tet activator. The Tet system therefore provides the opportunity to generate libraries of diverse expression patterns similar to gene trap approaches or the thy-1 promoter in mice, but with the additional possibility to pre-select cell types of interest. In transgenic lines expressing channelrhodopsin-2, action potential firing could be precisely controlled by two-photon stimulation at low laser power, presumably because the expression levels of the Tet-controlled genes were high even in adults. In channelrhodopsin-2-expressing larvae, optical stimulation with a single blue LED evoked distinct swimming behaviors including backward swimming. These approaches provide new opportunities for the optogenetic dissection of neuronal circuit structure and function.

Unstable oscillators based hyperchaotic circuit

DEFF Research Database (Denmark)

Murali, K.; Tamasevicius, A.; G. Mykolaitis, A.

1999-01-01

A simple 4th order hyperchaotic circuit with unstable oscillators is described. The circuit contains two negative impedance converters, two inductors, two capacitors, a linear resistor and a diode. The Lyapunov exponents are presented to confirm hyperchaotic nature of the oscillations in the circ...... in the circuit. The performance of the circuit is investigated by means of numerical integration of appropriate differential equations, PSPICE simulations, and hardware experiment.......A simple 4th order hyperchaotic circuit with unstable oscillators is described. The circuit contains two negative impedance converters, two inductors, two capacitors, a linear resistor and a diode. The Lyapunov exponents are presented to confirm hyperchaotic nature of the oscillations...

Dynamic feedback for multi-mode plasma instabilities

International Nuclear Information System (INIS)

Sen, A.K.

1978-01-01

Constant feedback, which has been used exclusively, fails to stabilize more than one mode of a plasma instability. It is shown that a suitable dynamic or frequency-dependent feedback can stabilize all modes. Methods are developed in which such a feedback structure can be chosen in terms of its poles and zeros in relation to those of the plasma transfer function in the complex frequency plane. The synthesis procedure for such a feedback structure, in the form of an integrated electronic circuit is also discussed. As an example, a dynamic feedback for multi-mode stabilization of a collisional drift wave instability is developed in detail. (author)

The inhibitory microcircuit of the substantia nigra provides feedback gain control of the basal ganglia output.

Science.gov (United States)

Brown, Jennifer; Pan, Wei-Xing; Dudman, Joshua Tate

2014-05-21

Dysfunction of the basal ganglia produces severe deficits in the timing, initiation, and vigor of movement. These diverse impairments suggest a control system gone awry. In engineered systems, feedback is critical for control. By contrast, models of the basal ganglia highlight feedforward circuitry and ignore intrinsic feedback circuits. In this study, we show that feedback via axon collaterals of substantia nigra projection neurons control the gain of the basal ganglia output. Through a combination of physiology, optogenetics, anatomy, and circuit mapping, we elaborate a general circuit mechanism for gain control in a microcircuit lacking interneurons. Our data suggest that diverse tonic firing rates, weak unitary connections and a spatially diffuse collateral circuit with distinct topography and kinetics from feedforward input is sufficient to implement divisive feedback inhibition. The importance of feedback for engineered systems implies that the intranigral microcircuit, despite its absence from canonical models, could be essential to basal ganglia function. DOI: http://dx.doi.org/10.7554/eLife.02397.001. Copyright © 2014, Brown et al.

Printed organic thin-film transistor-based integrated circuits

International Nuclear Information System (INIS)

Mandal, Saumen; Noh, Yong-Young

2015-01-01

Organic electronics is moving ahead on its journey towards reality. However, this technology will only be possible when it is able to meet specific criteria including flexibility, transparency, disposability and low cost. Printing is one of the conventional techniques to deposit thin films from solution-based ink. It is used worldwide for visual modes of information, and it is now poised to enter into the manufacturing processes of various consumer electronics. The continuous progress made in the field of functional organic semiconductors has achieved high solubility in common solvents as well as high charge carrier mobility, which offers ample opportunity for organic-based printed integrated circuits. In this paper, we present a comprehensive review of all-printed organic thin-film transistor-based integrated circuits, mainly ring oscillators. First, the necessity of all-printed organic integrated circuits is discussed; we consider how the gap between printed electronics and real applications can be bridged. Next, various materials for printed organic integrated circuits are discussed. The features of these circuits and their suitability for electronics using different printing and coating techniques follow. Interconnection technology is equally important to make this product industrially viable; much attention in this review is placed here. For high-frequency operation, channel length should be sufficiently small; this could be achievable with a combination of surface treatment-assisted printing or laser writing. Registration is also an important issue related to printing; the printed gate should be perfectly aligned with the source and drain to minimize parasitic capacitances. All-printed organic inverters and ring oscillators are discussed here, along with their importance. Finally, future applications of all-printed organic integrated circuits are highlighted. (paper)

Pulsed feedback defers cellular differentiation.

Directory of Open Access Journals (Sweden)

Joe H Levine

2012-01-01

Full Text Available Environmental signals induce diverse cellular differentiation programs. In certain systems, cells defer differentiation for extended time periods after the signal appears, proliferating through multiple rounds of cell division before committing to a new fate. How can cells set a deferral time much longer than the cell cycle? Here we study Bacillus subtilis cells that respond to sudden nutrient limitation with multiple rounds of growth and division before differentiating into spores. A well-characterized genetic circuit controls the concentration and phosphorylation of the master regulator Spo0A, which rises to a critical concentration to initiate sporulation. However, it remains unclear how this circuit enables cells to defer sporulation for multiple cell cycles. Using quantitative time-lapse fluorescence microscopy of Spo0A dynamics in individual cells, we observed pulses of Spo0A phosphorylation at a characteristic cell cycle phase. Pulse amplitudes grew systematically and cell-autonomously over multiple cell cycles leading up to sporulation. This pulse growth required a key positive feedback loop involving the sporulation kinases, without which the deferral of sporulation became ultrasensitive to kinase expression. Thus, deferral is controlled by a pulsed positive feedback loop in which kinase expression is activated by pulses of Spo0A phosphorylation. This pulsed positive feedback architecture provides a more robust mechanism for setting deferral times than constitutive kinase expression. Finally, using mathematical modeling, we show how pulsing and time delays together enable "polyphasic" positive feedback, in which different parts of a feedback loop are active at different times. Polyphasic feedback can enable more accurate tuning of long deferral times. Together, these results suggest that Bacillus subtilis uses a pulsed positive feedback loop to implement a "timer" that operates over timescales much longer than a cell cycle.

Cytokinins and auxins control the expression of a gene in Nicotiana plumbaginifolia cells by feedback regulation.

Science.gov (United States)

Dominov, J A; Stenzler, L; Lee, S; Schwarz, J J; Leisner, S; Howell, S H

1992-01-01

Both cytokinin (N6-benzyladenine [BA]) and auxin (2,4-dichlorophenoxyacetic acid [2,4-D]) stimulate the accumulation of an mRNA, represented by the cDNA pLS216, in Nicotiana plumbaginifolia suspension culture cells. The kinetics of RNA accumulation were different for the two hormones; however, the response to both was transient, and the magnitude of the response was dose dependent. Runoff transcription experiments demonstrated that the transient appearance of the RNA could be accounted for by feedback regulation of transcription and not by the induction of an RNA degradation system. The feedback mechanism appeared to desensitize the cells to further exposure of the hormone. In particular, cells became refractory to the subsequent addition of 2,4-D after the initial RNA accumulation response subsided. A very different response was observed when the second hormone was added to cells that had been desensitized to the first hormone. Under such conditions, BA produced a heightened response in cells desensitized to 2,4-D and vice versa. These findings support a model in which cytokinin further enhances the auxin response or prevents its feedback inhibition. The hormone-induced RNA accumulation was blocked by the protein kinase inhibitor staurosporin. On the other hand, the protein phosphatase inhibitor okadaic acid stimulated expression, and, in particular, okadaic acid was able to stimulate RNA accumulation in cells desensitized to auxin. This suggests that hormone activation involves phosphorylation of critical proteins on the hormone signaling pathway, whereas feedback inhibition may involve dephosphorylation of these proteins. The sequence of pLS216 is similar to genes in other plants that are stimulated by multiple agonists such as auxins, elicitors, and heavy metals, and to the gene encoding the stringent starvation protein in Escherichia coli. It is proposed that this gene family in various plants be called multiple stimulus response (msr) genes. PMID:1498603

Synchronization and parameter identification of one class of realistic chaotic circuit

International Nuclear Information System (INIS)

Chun-Ni, Wang; Jun, Ma; Run-Tong, Chu; Shi-Rong, Li

2009-01-01

In this paper, the synchronization and the parameter identification of the chaotic Pikovsky–Rabinovich (PR) circuits are investigated. The linear error of the second corresponding variables is used to change the driven chaotic PR circuit, and the complete synchronization of the two identical chaotic PR circuits is realized with feedback intensity k increasing to a certain threshold. The Lyapunov exponents of the chaotic PR circuits are calculated by using different feedback intensities and our results are confirmed. The case where the two chaotic PR circuits are not identical is also investigated. A general positive Lyapunov function V, which consists of all the errors of the corresponding variables and parameters and changeable gain coefficient, is constructed by using the Lyapunov stability theory to study the parameter identification and complete synchronization of two non-identical chaotic circuits. The controllers and the parameter observers could be obtained analytically only by simplifying the criterion dV/dt < 0 (differential coefficient of Lyapunov function V with respect to time is negative). It is confirmed that the two non-identical chaotic PR circuits could still reach complete synchronization and all the unknown parameters in the drive system are estimated exactly within a short transient period

IMPORTANT NOTICE: Cancellation of shuttle Circuit 3

CERN Multimedia

2013-01-01

Circuit 3 of the CERN Shuttle Service (Point 5), which has served CMS since the start of LS1, will be cancelled with effect from Tuesday 16 April. This decision has been taken in consultation with CMS, as the circuit was seldom used.   In response to increasing demand for Circuit 1 - Meyrin and feedback from passengers, the two Circuit 3 journeys will be switched to Circuit 1 – Meyrin (see new timetable below): Mornings: Four journeys instead of three. Circuit 1 now starts at 8:10 (instead of 8:19 a.m.) and runs until 9:27 a.m. (instead of 9:16 a.m.). Lunchtimes: Five journeys in place between 12:10 p.m. and 1:47 p.m. Evenings: Circuit starts at 5:23 p.m. (instead of 5:03 p.m.) and ends at 6:20 p.m. at Building 33. Please note that the circuit will depart from Building 13 instead of Building 33.  

Synthesis for robust synchronization of chaotic systems under output feedback control with multiple random delays

International Nuclear Information System (INIS)

Wen Guilin; Wang Qingguo; Lin Chong; Han Xu; Li Guangyao

2006-01-01

Synchronization under output feedback control with multiple random time delays is studied, using the paradigm in nonlinear physics-Chua's circuit. Compared with other synchronization control methods, output feedback control with multiple random delay is superior for a realistic synchronization application to secure communications. Sufficient condition for global stability of delay-dependent synchronization is established based on the LMI technique. Numerical simulations fully support the analytical approach, in spite of the random delays

A microcontroller-based interface circuit for lossy capacitive sensors

International Nuclear Information System (INIS)

Reverter, Ferran; Casas, Òscar

2010-01-01

This paper introduces and analyses a low-cost microcontroller-based interface circuit for lossy capacitive sensors, i.e. sensors whose parasitic conductance (G x ) is not negligible. Such a circuit relies on a previous circuit also proposed by the authors, in which the sensor is directly connected to a microcontroller without using either a signal conditioner or an analogue-to-digital converter in the signal path. The novel circuit uses the same hardware, but it performs an additional measurement and executes a new calibration technique. As a result, the sensitivity of the circuit to G x decreases significantly (a factor higher than ten), but not completely due to the input capacitances of the port pins of the microcontroller. Experimental results show a relative error in the capacitance measurement below 1% for G x x ) shows the effectiveness of the circuit

A parity checker circuit based on microelectromechanical resonator logic elements

KAUST Repository

Hafiz, Md Abdullah Al

2017-01-11

Micro/nano-electromechanical resonator based logic computation has attracted significant attention in recent years due to its dynamic mode of operation, ultra-low power consumption, and potential for reprogrammable and reversible computing. Here we demonstrate a 4-bit parity checker circuit by utilizing recently developed logic gates based on MEMS resonators. Toward this, resonance frequencies of shallow arch shaped micro resonators are electrothermally tuned by the logic inputs to constitute the required logic gates for the proposed parity checker circuit. This study demonstrates that by utilizing MEMS resonator based logic elements, complex digital circuits can be realized.

A parity checker circuit based on microelectromechanical resonator logic elements

KAUST Repository

Hafiz, Md Abdullah Al; Li, Ren; Younis, Mohammad I.; Fariborzi, Hossein

2017-01-01

Micro/nano-electromechanical resonator based logic computation has attracted significant attention in recent years due to its dynamic mode of operation, ultra-low power consumption, and potential for reprogrammable and reversible computing. Here we demonstrate a 4-bit parity checker circuit by utilizing recently developed logic gates based on MEMS resonators. Toward this, resonance frequencies of shallow arch shaped micro resonators are electrothermally tuned by the logic inputs to constitute the required logic gates for the proposed parity checker circuit. This study demonstrates that by utilizing MEMS resonator based logic elements, complex digital circuits can be realized.

Utility of an app-based system to improve feedback following workplace-based assessment.

Science.gov (United States)

Lefroy, Janet; Roberts, Nicola; Molyneux, Adrian; Bartlett, Maggie; Gay, Simon; McKinley, Robert

2017-05-31

To determine whether an app-based software system to support production and storage of assessment feedback summaries makes workplace-based assessment easier for clinical tutors and enhances the educational impact on medical students. We monitored our workplace assessor app's usage by Year 3 to 5 medical students in 2014-15 and conducted focus groups with Year 4 medical students and interviews with clinical tutors who had used the apps. Analysis was by constant comparison using a framework based on elements of van der Vleuten's utility index. The app may enhance the content of feedback for students. Using a screen may be distracting if the app is used during feedback discussions.    Educational impact was reduced by students' perceptions that an easy-to-produce feedback summary is less valuable than one requiring more tutor time and effort. Tutors' typing, dictation skills and their familiarity with mobile devices varied. This influenced their willingness to use the assessment and feedback mobile app rather than the equivalent web app. Electronic feedback summaries had more real and perceived uses than anticipated both for tutors and students including perceptions that they were for the school rather than the student. Electronic workplace-based assessment systems can be acceptable to tutors and can make giving detailed written feedback more practical but can interrupt the social interaction required for the feedback conversation. Tutor training and flexible systems will be required to minimise unwanted consequences. The educational impact on both tutors and students of providing pre-formulated advice within the app is worth further study.

Theoretical and experimental study of Chen chaotic system with notch filter feedback control

International Nuclear Information System (INIS)

Ming, Zhang Xiao; Jian-Hua, Peng; Ju-Fang, Chen

2010-01-01

Since the past two decades, the time delay feedback control method has attracted more and more attention in chaos control studies because of its simplicity and efficiency compared with other chaos control schemes. Recently, it has been proposed to suppress low-dimensional chaos with the notch filter feedback control method, which can be implemented in a laser system. In this work, we have analytically determined the controllable conditions for notch filter feedback controlling of Chen chaotic system in terms of the Hopf bifurcation theory. The conditions for notch filter feedback controlled Chen chaoitc system having a stable limit cycle solution are given. Meanwhile, we also analysed the Hopf bifurcation direction, which is very important for parameter settings in notch filter feedback control applications. Finally, we apply the notch filter feedback control methods to the electronic circuit experiments and numerical simulations based on the theoretical analysis. The controlling results of notch filter feedback control method well prove the feasibility and reliability of the theoretical analysis. (general)

Relevance Feedback in Content Based Image Retrieval: A Review

Directory of Open Access Journals (Sweden)

Manesh B. Kokare

2011-01-01

Full Text Available This paper provides an overview of the technical achievements in the research area of relevance feedback (RF in content-based image retrieval (CBIR. Relevance feedback is a powerful technique in CBIR systems, in order to improve the performance of CBIR effectively. It is an open research area to the researcher to reduce the semantic gap between low-level features and high level concepts. The paper covers the current state of art of the research in relevance feedback in CBIR, various relevance feedback techniques and issues in relevance feedback are discussed in detail.

Small circuits for cryptography.

Energy Technology Data Exchange (ETDEWEB)

Torgerson, Mark Dolan; Draelos, Timothy John; Schroeppel, Richard Crabtree; Miller, Russell D.; Anderson, William Erik

2005-10-01

This report examines a number of hardware circuit design issues associated with implementing certain functions in FPGA and ASIC technologies. Here we show circuit designs for AES and SHA-1 that have an extremely small hardware footprint, yet show reasonably good performance characteristics as compared to the state of the art designs found in the literature. Our AES performance numbers are fueled by an optimized composite field S-box design for the Stratix chipset. Our SHA-1 designs use register packing and feedback functionalities of the Stratix LE, which reduce the logic element usage by as much as 72% as compared to other SHA-1 designs.

Circuit Design of Surface Acoustic Wave Based Micro Force Sensor

Directory of Open Access Journals (Sweden)

Yuanyuan Li

2014-01-01

Full Text Available Pressure sensors are commonly used in industrial production and mechanical system. However, resistance strain, piezoresistive sensor, and ceramic capacitive pressure sensors possess limitations, especially in micro force measurement. A surface acoustic wave (SAW based micro force sensor is designed in this paper, which is based on the theories of wavelet transform, SAW detection, and pierce oscillator circuits. Using lithium niobate as the basal material, a mathematical model is established to analyze the frequency, and a peripheral circuit is designed to measure the micro force. The SAW based micro force sensor is tested to show the reasonable design of detection circuit and the stability of frequency and amplitude.

Qualitative and quantitative feedback in the context of competency-based education.

Science.gov (United States)

Tekian, Ara; Watling, Christopher J; Roberts, Trudie E; Steinert, Yvonne; Norcini, John

2017-12-01

Research indicates the importance and usefulness of feedback, yet with the shift of medical curricula toward competencies, feedback is not well understood in this context. This paper attempts to identify how feedback fits within a competency-based curriculum. After careful consideration of the literature, the following conclusions are drawn: (1) Because feedback is predicated on assessment, the assessment should be designed to optimize and prevent inaccuracies in feedback; (2) Giving qualitative feedback in the form of a conversation would lend credibility to the feedback, address emotional obstacles and create a context in which feedback is comfortable; (3) Quantitative feedback in the form of individualized data could fulfill the demand for more feedback, help students devise strategies on how to improve, allow students to compare themselves to their peers, recognizing that big data have limitations; and (4) Faculty development needs to incorporate and promote cultural and systems changes with regard to feedback. A better understanding of the role of feedback in competency-based education could result in more efficient learning for students.

PC-based digital feedback control for scanning force microscope

International Nuclear Information System (INIS)

Mohd Ashhar Khalid

2002-01-01

In the past, most digital feedback implementation for scanned-probe microscope were based on a digital signal processor (DSP). At present DSP plug-in card with the input-output interface module is still expensive compared to a fast pentium PC motherboard. For a magnetic force microscope (MFM) digital feedback has an advantage where the magnetic signal can be easily separated from the topographic signal. In this paper, a simple low-cost PC-based digital feedback and imaging system for Scanning Force Microscope (SFM) is presented. (Author)

Parameter estimation and determinability analysis applied to Drosophila gap gene circuits

Directory of Open Access Journals (Sweden)

Jaeger Johannes

2008-09-01

Full Text Available Abstract Background Mathematical modeling of real-life processes often requires the estimation of unknown parameters. Once the parameters are found by means of optimization, it is important to assess the quality of the parameter estimates, especially if parameter values are used to draw biological conclusions from the model. Results In this paper we describe how the quality of parameter estimates can be analyzed. We apply our methodology to assess parameter determinability for gene circuit models of the gap gene network in early Drosophila embryos. Conclusion Our analysis shows that none of the parameters of the considered model can be determined individually with reasonable accuracy due to correlations between parameters. Therefore, the model cannot be used as a tool to infer quantitative regulatory weights. On the other hand, our results show that it is still possible to draw reliable qualitative conclusions on the regulatory topology of the gene network. Moreover, it improves previous analyses of the same model by allowing us to identify those interactions for which qualitative conclusions are reliable, and those for which they are ambiguous.

Circadian pacemaking in cells and circuits of the suprachiasmatic nucleus.

Science.gov (United States)

Hastings, M H; Brancaccio, M; Maywood, E S

2014-01-01

The suprachiasmatic nucleus (SCN) of the hypothalamus is the principal circadian pacemaker of the brain. It co-ordinates the daily rhythms of sleep and wakefulness, as well as physiology and behaviour, that set the tempo to our lives. Disturbance of this daily pattern, most acutely with jet-lag but more insidiously with rotational shift-work, can have severely deleterious effects for mental function and long-term health. The present review considers recent developments in our understanding of the properties of the SCN that make it a robust circadian time-keeper. It first focuses on the intracellular transcriptional/ translational feedback loops (TTFL) that constitute the cellular clockwork of the SCN neurone. Daily timing by these loops pivots around the negative regulation of the Period (Per) and Cryptochrome (Cry) genes by their protein products. The period of the circadian cycle is set by the relative stability of Per and Cry proteins, and this can be controlled by both genetic and pharmacological interventions. It then considers the function of these feedback loops in the context of cytosolic signalling by cAMP and intracellular calcium ([Ca(2+) ]i ), which are both outputs from, and inputs to, the TTFL, as well as the critical role of vasoactive intestinal peptide (VIP) signalling in synchronising cellular clocks across the SCN. Synchronisation by VIP in the SCN is paracrine, operating over an unconventionally long time frame (i.e. 24 h) and wide spatial domain, mediated via the cytosolic pathways upstream of the TTFL. Finally, we show how intersectional pharmacogenetics can be used to control G-protein-coupled signalling in individual SCN neurones, and how manipulation of Gq/[Ca(2+) ]i -signalling in VIP neurones can re-programme the circuit-level encoding of circadian time. Circadian pacemaking in the SCN therefore provides an unrivalled context in which to understand how a complex, adaptive behaviour can be organised by the dynamic activity of a relatively

Feedback Blunting: Total Sleep Deprivation Impairs Decision Making that Requires Updating Based on Feedback

Science.gov (United States)

Whitney, Paul; Hinson, John M.; Jackson, Melinda L.; Van Dongen, Hans P.A.

2015-01-01

Study Objectives: To better understand the sometimes catastrophic effects of sleep loss on naturalistic decision making, we investigated effects of sleep deprivation on decision making in a reversal learning paradigm requiring acquisition and updating of information based on outcome feedback. Design: Subjects were randomized to a sleep deprivation or control condition, with performance testing at baseline, after 2 nights of total sleep deprivation (or rested control), and following 2 nights of recovery sleep. Subjects performed a decision task involving initial learning of go and no go response sets followed by unannounced reversal of contingencies, requiring use of outcome feedback for decisions. A working memory scanning task and psychomotor vigilance test were also administered. Setting: Six consecutive days and nights in a controlled laboratory environment with continuous behavioral monitoring. Subjects: Twenty-six subjects (22–40 y of age; 10 women). Interventions: Thirteen subjects were randomized to a 62-h total sleep deprivation condition; the others were controls. Results: Unlike controls, sleep deprived subjects had difficulty with initial learning of go and no go stimuli sets and had profound impairment adapting to reversal. Skin conductance responses to outcome feedback were diminished, indicating blunted affective reactions to feedback accompanying sleep deprivation. Working memory scanning performance was not significantly affected by sleep deprivation. And although sleep deprived subjects showed expected attentional lapses, these could not account for impairments in reversal learning decision making. Conclusions: Sleep deprivation is particularly problematic for decision making involving uncertainty and unexpected change. Blunted reactions to feedback while sleep deprived underlie failures to adapt to uncertainty and changing contingencies. Thus, an error may register, but with diminished effect because of reduced affective valence of the feedback

Hacking DNA copy number for circuit engineering.

Science.gov (United States)

Wu, Feilun; You, Lingchong

2017-07-27

DNA copy number represents an essential parameter in the dynamics of synthetic gene circuits but typically is not explicitly considered. A new study demonstrates how dynamic control of DNA copy number can serve as an effective strategy to program robust oscillations in gene expression circuits.

Load Capacity Improvements in Nucleic Acid Based Systems Using Partially Open Feedback Control

OpenAIRE

Kulkarni, Vishwesh; Kharisov, Evgeny; Hovakimyan, Naira; Kim, Jongmin

2014-01-01

Synthetic biology is facilitating novel methods and components to build in vivo and in vitro circuits to better understand and re-engineer biological networks. Recently, Kim and Winfree have synthesized a remarkably elegant network of transcriptional oscillators in vitro using a modular architecture of synthetic gene analogues and a few enzymes that, in turn, could be used to drive a variety of downstream circuits and nanodevices. However, these oscillators are sensitive to initial conditions...

Circuit-wide Transcriptional Profiling Reveals Brain Region-Specific Gene Networks Regulating Depression Susceptibility.

Science.gov (United States)

Bagot, Rosemary C; Cates, Hannah M; Purushothaman, Immanuel; Lorsch, Zachary S; Walker, Deena M; Wang, Junshi; Huang, Xiaojie; Schlüter, Oliver M; Maze, Ian; Peña, Catherine J; Heller, Elizabeth A; Issler, Orna; Wang, Minghui; Song, Won-Min; Stein, Jason L; Liu, Xiaochuan; Doyle, Marie A; Scobie, Kimberly N; Sun, Hao Sheng; Neve, Rachael L; Geschwind, Daniel; Dong, Yan; Shen, Li; Zhang, Bin; Nestler, Eric J

2016-06-01

Depression is a complex, heterogeneous disorder and a leading contributor to the global burden of disease. Most previous research has focused on individual brain regions and genes contributing to depression. However, emerging evidence in humans and animal models suggests that dysregulated circuit function and gene expression across multiple brain regions drive depressive phenotypes. Here, we performed RNA sequencing on four brain regions from control animals and those susceptible or resilient to chronic social defeat stress at multiple time points. We employed an integrative network biology approach to identify transcriptional networks and key driver genes that regulate susceptibility to depressive-like symptoms. Further, we validated in vivo several key drivers and their associated transcriptional networks that regulate depression susceptibility and confirmed their functional significance at the levels of gene transcription, synaptic regulation, and behavior. Our study reveals novel transcriptional networks that control stress susceptibility and offers fundamentally new leads for antidepressant drug discovery. Copyright © 2016 Elsevier Inc. All rights reserved.

Orbit Feedback Operation with RCBX (MD 1209)

CERN Document Server

Wenninger, Jorg; Nisbet, David; Ponce, Laurette; Louro Alves, Diogo Miguel; CERN. Geneva. ATS Department

2017-01-01

The LHC Orbit Feedback (OFB) is able to drive any orbit corrector circuit (COD) to steer the LHC orbit. But during the first feedback tests in 2010, all attempts to use the common triplet orbit correctors (MCBX) failed because the QPS system installed to protect those magnets triggered power aborts as soon as the OFB steered the beam with those CODs. The reason was most likely the violation of the RCBX circuit acceleration limits. For this reason the MCBX orbit correctors were never driven by the OFB in regular operation. Although the performance of the OFB is generally excellent, the quality of the beam steering around IRs could be improved if the OFB could correct the orbit with the MCBX to counteract locally triplet quadrupole movements. The aim of this MD was to make a new attempt to use the MCBX in the OFB. The test was successful at injection (no circuit trip) and failed during the ramp (QPS power abort). The PC voltages and QPS Ures signals revealed the presence of voltage spikes with a period of 10~s...

The MCD circuit based on FPGA

International Nuclear Information System (INIS)

Vu Quoc Trong

2003-01-01

Two MCD circuits based on different FPGA are presented as results of the study of the MAX+PLUS II software and FPGA devices. An external memory like 62256 and programmed EPM7064S will be able to form a MCD with 8 kilo channels. (NHA)

Feedback regulation of an Agrobacterium catalase gene katA involved in Agrobacterium-plant interaction.

Science.gov (United States)

Xu, X Q; Li, L P; Pan, S Q

2001-11-01

Catalases are known to detoxify H2O2, a major component of oxidative stress imposed on a cell. An Agrobacterium tumefaciens catalase encoded by a chromosomal gene katA has been implicated as an important virulence factor as it is involved in detoxification of H2O2 released during Agrobacterium-plant interaction. In this paper, we report a feedback regulation pathway that controls the expression of katA in A. tumefaciens cells. We observed that katA could be induced by plant tissue sections and by acidic pH on a minimal medium, which resembles the plant environment that the bacteria encounter during the course of infection. This represents a new regulatory factor for catalase induction in bacteria. More importantly, a feedback regulation was observed when the katA-gfp expression was studied in different genetic backgrounds. We found that introduction of a wild-type katA gene encoding a functional catalase into A. tumefaciens cells could repress the katA-gfp expression over 60-fold. The katA gene could be induced by H2O2 and the encoded catalase could detoxify H2O2. In addition, the katA-gfp expression of one bacterial cell could be repressed by other surrounding catalase-proficient bacterial cells. Furthermore, mutation at katA caused a 10-fold increase of the intracellular H2O2 concentration in the bacteria grown on an acidic pH medium. These results suggest that the endogenous H2O2 generated during A. tumefaciens cell growth could serve as the intracellular and intercellular inducer for the katA gene expression and that the acidic pH could pose an oxidative stress on the bacteria. Surprisingly, one mutated KatA protein, exhibiting no significant catalase activity as a result of the alteration of two important residues at the putative active site, could partially repress the katA-gfp expression. The feedback regulation of the katA gene by both catalase activity and KatA protein could presumably maintain an appropriated level of catalase activity and H2O2 inside A

Track Circuit Fault Diagnosis Method based on Least Squares Support Vector

Science.gov (United States)

Cao, Yan; Sun, Fengru

2018-01-01

In order to improve the troubleshooting efficiency and accuracy of the track circuit, track circuit fault diagnosis method was researched. Firstly, the least squares support vector machine was applied to design the multi-fault classifier of the track circuit, and then the measured track data as training samples was used to verify the feasibility of the methods. Finally, the results based on BP neural network fault diagnosis methods and the methods used in this paper were compared. Results shows that the track fault classifier based on least squares support vector machine can effectively achieve the five track circuit fault diagnosis with less computing time.

The Smallest Transistor-Based Nonautonomous Chaotic Circuit

DEFF Research Database (Denmark)

Lindberg, Erik; Murali, K.; Tamasevicius, Arunas

2005-01-01

A nonautonomous chaotic circuit based on one transistor, two capacitors, and two resistors is described. The mechanism behind the chaotic performance is based on “disturbance of integration.” The forward part and the reverse part of the bipolar transistor are “fighting” about the charging...

Investigation of flip-flop effects in a linear analog comparator-with-hysteresis circuit

International Nuclear Information System (INIS)

Roche, N.J.H.; Buchner, S.P.; Warner, J.H.; McMorrow, D.; Roig, F.; Auriel, G.; Dusseau, L.; Boch, J.; Saigne, F.; Azais, B.

2013-01-01

The impact of the positive feedback loop on analog single event transient (ASET) shapes was investigated for a comparator- with-hysteresis circuit. Simulation based on previous developed ASET simulation tool is used to model the impact of the power supply voltage, the input voltage level and the injected energy. Simulation results show that these kinds of circuits are sensitive to flip-flop effects. This phenomenon occurs if the input voltage is in the hysteresis band range. In this case, simulations show that the ASET can latch the output into a non-desired state by changing the state of the circuit on his transfer characteristic curves. Laser experiments were conducted and show that the simulation outputs are in agreement with the experimental collected data. (authors)

Feedback in formative OSCEs: comparison between direct observation and video-based formats

Science.gov (United States)

Junod Perron, Noëlle; Louis-Simonet, Martine; Cerutti, Bernard; Pfarrwaller, Eva; Sommer, Johanna; Nendaz, Mathieu

2016-01-01

Introduction Medical students at the Faculty of Medicine, University of Geneva, Switzerland, have the opportunity to practice clinical skills with simulated patients during formative sessions in preparation for clerkships. These sessions are given in two formats: 1) direct observation of an encounter followed by verbal feedback (direct feedback) and 2) subsequent review of the videotaped encounter by both student and supervisor (video-based feedback). The aim of the study was to evaluate whether content and process of feedback differed between both formats. Methods In 2013, all second- and third-year medical students and clinical supervisors involved in formative sessions were asked to take part in the study. A sample of audiotaped feedback sessions involving supervisors who gave feedback in both formats were analyzed (content and process of the feedback) using a 21-item feedback scale. Results Forty-eight audiotaped feedback sessions involving 12 supervisors were analyzed (2 direct and 2 video-based sessions per supervisor). When adjusted for the length of feedback, there were significant differences in terms of content and process between both formats; the number of communication skills and clinical reasoning items addressed were higher in the video-based format (11.29 vs. 7.71, p=0.002 and 3.71 vs. 2.04, p=0.010, respectively). Supervisors engaged students more actively during the video-based sessions than during direct feedback sessions (self-assessment: 4.00 vs. 3.17, p=0.007; active problem-solving: 3.92 vs. 3.42, p=0.009). Students made similar observations and tended to consider that the video feedback was more useful for improving some clinical skills. Conclusion Video-based feedback facilitates discussion of clinical reasoning, communication, and professionalism issues while at the same time actively engaging students. Different time and conceptual frameworks may explain observed differences. The choice of feedback format should depend on the educational

Feedback in formative OSCEs: comparison between direct observation and video-based formats

Directory of Open Access Journals (Sweden)

Noëlle Junod Perron

2016-11-01

Full Text Available Introduction: Medical students at the Faculty of Medicine, University of Geneva, Switzerland, have the opportunity to practice clinical skills with simulated patients during formative sessions in preparation for clerkships. These sessions are given in two formats: 1 direct observation of an encounter followed by verbal feedback (direct feedback and 2 subsequent review of the videotaped encounter by both student and supervisor (video-based feedback. The aim of the study was to evaluate whether content and process of feedback differed between both formats. Methods: In 2013, all second- and third-year medical students and clinical supervisors involved in formative sessions were asked to take part in the study. A sample of audiotaped feedback sessions involving supervisors who gave feedback in both formats were analyzed (content and process of the feedback using a 21-item feedback scale. Results: Forty-eight audiotaped feedback sessions involving 12 supervisors were analyzed (2 direct and 2 video-based sessions per supervisor. When adjusted for the length of feedback, there were significant differences in terms of content and process between both formats; the number of communication skills and clinical reasoning items addressed were higher in the video-based format (11.29 vs. 7.71, p=0.002 and 3.71 vs. 2.04, p=0.010, respectively. Supervisors engaged students more actively during the video-based sessions than during direct feedback sessions (self-assessment: 4.00 vs. 3.17, p=0.007; active problem-solving: 3.92 vs. 3.42, p=0.009. Students made similar observations and tended to consider that the video feedback was more useful for improving some clinical skills. Conclusion: Video-based feedback facilitates discussion of clinical reasoning, communication, and professionalism issues while at the same time actively engaging students. Different time and conceptual frameworks may explain observed differences. The choice of feedback format should depend on

Mobile Learning Based Worked Example in Electric Circuit (WEIEC) Application to Improve the High School Students' Electric Circuits Interpretation Ability

Science.gov (United States)

Yadiannur, Mitra; Supahar

2017-01-01

This research aims to determine the feasibility and effectivity of mobile learning based Worked Example in Electric Circuits (WEIEC) application in improving the high school students' electric circuits interpretation ability on Direct Current Circuits materials. The research method used was a combination of Four-D Models and ADDIE model. The…

Upper bounds for reversible circuits based on Young subgroups

DEFF Research Database (Denmark)

Abdessaied, Nabila; Soeken, Mathias; Thomsen, Michael Kirkedal

2014-01-01

We present tighter upper bounds on the number of Toffoli gates needed in reversible circuits. Both multiple controlled Toffoli gates and mixed polarity Toffoli gates have been considered for this purpose. The calculation of the bounds is based on a synthesis approach based on Young subgroups...... that results in circuits using a more generalized gate library. Starting from an upper bound for this library we derive new bounds which improve the existing bound by around 77%....

Exploring the use of tactile feedback in an ERP-based auditory BCI.

Science.gov (United States)

Schreuder, Martijn; Thurlings, Marieke E; Brouwer, Anne-Marie; Van Erp, Jan B F; Tangermann, Michael

2012-01-01

Giving direct, continuous feedback on a brain state is common practice in motor imagery based brain-computer interfaces (BCI), but has not been reported for BCIs based on event-related potentials (ERP), where feedback is only given once after a sequence of stimuli. Potentially, direct feedback could allow the user to adjust his strategy during a running trial to obtain the required response. In order to test the usefulness of such feedback, directionally congruent vibrotactile feedback was given during an online auditory BCI experiment. Users received either no feedback, short feedback pulses or continuous feedback. The feedback conditions showed reduced performance both on a behavioral task and in terms of classification accuracy. Several explanations are discussed that give interesting starting points for further research on this topic.

MEMS-based Circuits and Systems for Wireless Communication

CERN Document Server

Kaiser, Andreas

2013-01-01

MEMS-based Circuits and Systems for Wireless Communication provides comprehensive coverage of RF-MEMS technology from device to system level. This edited volume places emphasis on how system performance for radio frequency applications can be leveraged by Micro-Electro-Mechanical Systems (MEMS). Coverage also extends to innovative MEMS-aware radio architectures that push the potential of MEMS technology further ahead.  This work presents a broad overview of the technology from MEMS devices (mainly BAW and Si MEMS resonators) to basic circuits, such as oscillators and filters, and finally complete systems such as ultra-low-power MEMS-based radios. Contributions from leading experts around the world are organized in three parts. Part I introduces RF-MEMS technology, devices and modeling and includes a prospective outlook on ongoing developments towards Nano-Electro-Mechanical Systems (NEMS) and phononic crystals. Device properties and models are presented in a circuit oriented perspective. Part II focusses on ...

A simple structure wavelet transform circuit employing function link neural networks and SI filters

Science.gov (United States)

Mu, Li; Yigang, He

2016-12-01

Signal processing by means of analog circuits offers advantages from a power consumption viewpoint. Implementing wavelet transform (WT) using analog circuits is of great interest when low-power consumption becomes an important issue. In this article, a novel simple structure WT circuit in analog domain is presented by employing functional link neural network (FLNN) and switched-current (SI) filters. First, the wavelet base is approximated using FLNN algorithms for giving a filter transfer function that is suitable for simple structure WT circuit implementation. Next, the WT circuit is constructed with the wavelet filter bank, whose impulse response is the approximated wavelet and its dilations. The filter design that follows is based on a follow-the-leader feedback (FLF) structure with multiple output bilinear SI integrators and current mirrors as the main building blocks. SI filter is well suited for this application since the dilation constant across different scales of the transform can be precisely implemented and controlled by the clock frequency of the circuit with the same system architecture. Finally, to illustrate the design procedure, a seventh-order FLNN-approximated Gaussian wavelet is implemented as an example. Simulations have successfully verified that the designed simple structure WT circuit has low sensitivity, low-power consumption and litter effect to the imperfections.

Feedforward and feedback motor control abnormalities implicate cerebellar dysfunctions in autism spectrum disorder.

Science.gov (United States)

Mosconi, Matthew W; Mohanty, Suman; Greene, Rachel K; Cook, Edwin H; Vaillancourt, David E; Sweeney, John A

2015-02-04

Sensorimotor abnormalities are common in autism spectrum disorder (ASD) and among the earliest manifestations of the disorder. They have been studied far less than the social-communication and cognitive deficits that define ASD, but a mechanistic understanding of sensorimotor abnormalities in ASD may provide key insights into the neural underpinnings of the disorder. In this human study, we examined rapid, precision grip force contractions to determine whether feedforward mechanisms supporting initial motor output before sensory feedback can be processed are disrupted in ASD. Sustained force contractions also were examined to determine whether reactive adjustments to ongoing motor behavior based on visual feedback are altered. Sustained force was studied across multiple force levels and visual gains to assess motor and visuomotor mechanisms, respectively. Primary force contractions of individuals with ASD showed greater peak rate of force increases and large transient overshoots. Individuals with ASD also showed increased sustained force variability that scaled with force level and was more severe when visual gain was highly amplified or highly degraded. When sustaining a constant force level, their reactive adjustments were more periodic than controls, and they showed increased reliance on slower feedback mechanisms. Feedforward and feedback mechanism alterations each were associated with more severe social-communication impairments in ASD. These findings implicate anterior cerebellar circuits involved in feedforward motor control and posterior cerebellar circuits involved in transforming visual feedback into precise motor adjustments in ASD. Copyright © 2015 the authors 0270-6474/15/352015-11$15.00/0.

Aging and a genetic KIBRA polymorphism interactively affect feedback- and observation-based probabilistic classification learning.

Science.gov (United States)

Schuck, Nicolas W; Petok, Jessica R; Meeter, Martijn; Schjeide, Brit-Maren M; Schröder, Julia; Bertram, Lars; Gluck, Mark A; Li, Shu-Chen

2018-01-01

Probabilistic category learning involves complex interactions between the hippocampus and striatum that may depend on whether acquisition occurs via feedback or observation. Little is known about how healthy aging affects these processes. We tested whether age-related behavioral differences in probabilistic category learning from feedback or observation depend on a genetic factor known to influence individual differences in hippocampal function, the KIBRA gene (single nucleotide polymorphism rs17070145). Results showed comparable age-related performance impairments in observational as well as feedback-based learning. Moreover, genetic analyses indicated an age-related interactive effect of KIBRA on learning: among older adults, the beneficial T-allele was positively associated with learning from feedback, but negatively with learning from observation. In younger adults, no effects of KIBRA were found. Our results add behavioral genetic evidence to emerging data showing age-related differences in how neural resources relate to memory functions, namely that hippocampal and striatal contributions to probabilistic category learning may vary with age. Our findings highlight the effects genetic factors can have on differential age-related decline of different memory functions. Copyright © 2017 Elsevier Inc. All rights reserved.

Feedback stabilization of electrostatic reactive instabilities

International Nuclear Information System (INIS)

Richards, R.K.

1976-01-01

A general theory for the feedback stabilization of electrostatic reactive instabilities is developed which includes the effects of dissipation in the plasma and frequency dependence in the sensor-suppressor elements and in the external feedback circuit. This theory is compared to experiments involving particular reactive instability, an interchange mode, found in a magnetic mirror device; these results are found to be in good agreement with theory. One noteworthy result is that a frequency dependence in the overall gain and phase shift of the feedback loop can cause destabilization at large gain. Multimode feedback stabilization is studied using the spatial variation of two interchange modes to separate them such that each can be acted upon individually by the feedback system. The transfer function of the plasma is also examined. This analysis is used for mode identification and location of the pole positions. As an example of using feedback as a diagnostic tool, instability induced transport is studied. Here feedback is used to control the amplitude of fluctuations at saturation

Design and evaluation of a flow-to-frequency converter circuit with thermal feedback

International Nuclear Information System (INIS)

Pawlowski, Eligiusz

2017-01-01

A novel thermal flow sensor with a frequency output is presented. The sensor provides a pulse-train output whose frequency is related to the fluid flow rate around a self-heating thermistor. The integrating properties of the temperature sensor have been used, which allowed for realization of the pulse frequency modulator with a thermal feedback loop, stabilizing the temperature of the sensor placed in the flowing medium. The system assures a balance of the amount of heat supplied in the impulses to the sensor and the heat given up by the sensor in a continuous way to the flowing medium. Therefore the frequency of output pulse-train is proportional to the medium flow velocity around the sensor. The special feature of the presented solution is the total integration of the thermal sensor with the measurement signal conditioning system. i.e. the sensor and conditioning system are not separate elements of the measurement circuit, but constitute a whole in the form of a thermal heat-balance mode flow-to-frequency converter. The frequency signal from the converter may be directly connected to the microprocessor digital input, which with use of the standard built-in counters may convert the frequency into a numerical value of high precision. The sensor has been experimentally characterized as a function of the average flow velocity of air at room temperature. (paper)

PLS beam position measurement and feedback system

International Nuclear Information System (INIS)

Huang, J.Y.; Lee, J.; Park, M.K.; Kim, J.H.; Won, S.C.

1992-01-01

A real-time orbit correction system is proposed for the stabilization of beam orbit and photon beam positions in Pohang Light Source. PLS beam position monitoring system is designed to be VMEbus compatible to fit the real-time digital orbit feedback system. A VMEbus based subsystem control computer, Mil-1553B communication network and 12 BPM/PS machine interface units constitute digital part of the feedback system. With the super-stable PLS correction magnet power supply, power line frequency noise is almost filtered out and the dominant spectra of beam obtit fluctuations are expected to appear below 15 Hz. Using DSP board in SCC for the computation and using an appropriate compensation circuit for the phase delay by the vacuum chamber, PLS real-time orbit correction system is realizable without changing the basic structure of PLS computer control system. (author)

Dynamical Analysis, Synchronization, Circuit Design, and Secure Communication of a Novel Hyperchaotic System

Directory of Open Access Journals (Sweden)

Li Xiong

2017-01-01

Full Text Available This paper is devoted to introduce a novel fourth-order hyperchaotic system. The hyperchaotic system is constructed by adding a linear feedback control level based on a modified Lorenz-like chaotic circuit with reduced number of amplifiers. The local dynamical entities, such as the basic dynamical behavior, the divergence, the eigenvalue, and the Lyapunov exponents of the new hyperchaotic system, are all investigated analytically and numerically. Then, an active control method is derived to achieve global chaotic synchronization of the novel hyperchaotic system through making the synchronization error system asymptotically stable at the origin based on Lyapunov stability theory. Next, the proposed novel hyperchaotic system is applied to construct another new hyperchaotic system with circuit deformation and design a new hyperchaotic secure communication circuit. Furthermore, the implementation of two novel electronic circuits of the proposed hyperchaotic systems is presented, examined, and realized using physical components. A good qualitative agreement is shown between the simulations and the experimental results around 500 kHz and below 1 MHz.

Hybrid integrated circuit for charge-to-time interval conversion

Energy Technology Data Exchange (ETDEWEB)

Basiladze, S.G.; Dotsenko, Yu.Yu.; Man' yakov, P.K.; Fedorchenko, S.N. (Joint Inst. for Nuclear Research, Dubna (USSR))

The hybrid integrated circuit for charge-to time interval conversion with nanosecond input fast response is described. The circuit can be used in energy measuring channels, time-to-digital converters and in the modified variant in amplitude-to-digital converters. The converter described consists of a buffer amplifier, a linear transmission circuit, a direct current source and a unit of time interval separation. The buffer amplifier represents a current follower providing low input and high output resistances by the current feedback. It is concluded that the described converter excelled the QT100B circuit analogous to it in a number of parameters especially, in thermostability.

Single-flux-quantum logic circuits exploiting collision-based fusion gates

International Nuclear Information System (INIS)

Asai, T.; Yamada, K.; Amemiya, Y.

2008-01-01

We propose a single-flux-quantum (SFQ) logic circuit based on the fusion computing systems--collision-based and reaction-diffusion fusion computers. A fusion computing system consists of regularly arrayed unit cells (fusion gates), where each unit has two input arms and two output arms and is connected to its neighboring cells with the arms. We designed functional SFQ circuits that implemented the fusion computation. The unit cell was able to be made with ten Josephson junctions. Circuit simulation with standard Nb/Al-AlOx/Nb 2.5-kA/cm 2 process parameters showed that the SFQ fusion computing systems could operate at 10 GHz clock

Materials Integration and Doping of Carbon Nanotube-based Logic Circuits

Science.gov (United States)

Geier, Michael

Over the last 20 years, extensive research into the structure and properties of single- walled carbon nanotube (SWCNT) has elucidated many of the exceptional qualities possessed by SWCNTs, including record-setting tensile strength, excellent chemical stability, distinctive optoelectronic features, and outstanding electronic transport characteristics. In order to exploit these remarkable qualities, many application-specific hurdles must be overcome before the material can be implemented in commercial products. For electronic applications, recent advances in sorting SWCNTs by electronic type have enabled significant progress towards SWCNT-based integrated circuits. Despite these advances, demonstrations of SWCNT-based devices with suitable characteristics for large-scale integrated circuits have been limited. The processing methodologies, materials integration, and mechanistic understanding of electronic properties developed in this dissertation have enabled unprecedented scales of SWCNT-based transistor fabrication and integrated circuit demonstrations. Innovative materials selection and processing methods are at the core of this work and these advances have led to transistors with the necessary transport properties required for modern circuit integration. First, extensive collaborations with other research groups allowed for the exploration of SWCNT thin-film transistors (TFTs) using a wide variety of materials and processing methods such as new dielectric materials, hybrid semiconductor materials systems, and solution-based printing of SWCNT TFTs. These materials were integrated into circuit demonstrations such as NOR and NAND logic gates, voltage-controlled ring oscillators, and D-flip-flops using both rigid and flexible substrates. This dissertation explores strategies for implementing complementary SWCNT-based circuits, which were developed by using local metal gate structures that achieve enhancement-mode p-type and n-type SWCNT TFTs with widely separated and

Motivational beliefs, student effort, and feedback behaviour in computer-based formative assessment

NARCIS (Netherlands)

Timmers, C.F.; Braber-van den Broek, J.; van den Berg, Stéphanie Martine

2013-01-01

Feedback can only be effective when students seek feedback and process it. This study examines the relations between students' motivational beliefs, effort invested in a computer-based formative assessment, and feedback behaviour. Feedback behaviour is represented by whether a student seeks feedback

Quasi-Linear Circuit

Science.gov (United States)

Bradley, William; Bird, Ross; Eldred, Dennis; Zook, Jon; Knowles, Gareth

2013-01-01

This work involved developing spacequalifiable switch mode DC/DC power supplies that improve performance with fewer components, and result in elimination of digital components and reduction in magnetics. This design is for missions where systems may be operating under extreme conditions, especially at elevated temperature levels from 200 to 300 degC. Prior art for radiation-tolerant DC/DC converters has been accomplished utilizing classical magnetic-based switch mode converter topologies; however, this requires specific shielding and component de-rating to meet the high-reliability specifications. It requires complex measurement and feedback components, and will not enable automatic re-optimization for larger changes in voltage supply or electrical loading condition. The innovation is a switch mode DC/DC power supply that eliminates the need for processors and most magnetics. It can provide a well-regulated voltage supply with a gain of 1:100 step-up to 8:1 step down, tolerating an up to 30% fluctuation of the voltage supply parameters. The circuit incorporates a ceramic core transformer in a manner that enables it to provide a well-regulated voltage output without use of any processor components or magnetic transformers. The circuit adjusts its internal parameters to re-optimize its performance for changes in supply voltage, environmental conditions, or electrical loading at the output

Air-stable complementary-like circuits based on organic ambipolar transistors

NARCIS (Netherlands)

Anthopoulos, Thomas D.; Setayesh, Sepas; Smits, Edsger; Cantatore, Eugenio; Boer ,de Bert; Blom, Paul W. M.; de Leeuw, Dago M.; Cölle, Michael

2006-01-01

Air stable complementary-like circuits, such as voltage inverters (see figure) and ring oscillators, are fabricated using ambipolar organic transistors based on a nickel dithiolene derivative. In addition to the complementary-like character of the circuits, the technology is very simple and fully

Four quadrant control circuit for a brushless three-phase dc motor

Science.gov (United States)

Nola, Frank J. (Inventor)

1987-01-01

A control circuit is provided for a brushless three-phase dc motor which affords four quadrant control from a single command. The control circuit probes acceleration of the motor in both clockwise and counterclockwise directions and braking and generation in both clockwise and counterclockwise directions. In addition to turning on individual transistors of the transistor pairs connected to the phase windings of the motor for 120 deg periods while the other transistor of that pair is off, the control circuit also provides, in a future mode of operation, turning the two transistors of each pair on and off alternately at a phase modulation frequency during such a 120 deg period. A feedback signal is derived which is proportional to the motor current and which has a polarity consistent with the command signal, such that negative feedback results.

Effect- and Performance-Based Auditory Feedback on Interpersonal Coordination

Directory of Open Access Journals (Sweden)

Tong-Hun Hwang

2018-03-01

Full Text Available When two individuals interact in a collaborative task, such as carrying a sofa or a table, usually spatiotemporal coordination of individual motor behavior will emerge. In many cases, interpersonal coordination can arise independently of verbal communication, based on the observation of the partners' movements and/or the object's movements. In this study, we investigate how social coupling between two individuals can emerge in a collaborative task under different modes of perceptual information. A visual reference condition was compared with three different conditions with new types of additional auditory feedback provided in real time: effect-based auditory feedback, performance-based auditory feedback, and combined effect/performance-based auditory feedback. We have developed a new paradigm in which the actions of both participants continuously result in a seamlessly merged effect on an object simulated by a tablet computer application. Here, participants should temporally synchronize their movements with a 90° phase difference and precisely adjust the finger dynamics in order to keep the object (a ball accurately rotating on a given circular trajectory on the tablet. Results demonstrate that interpersonal coordination in a joint task can be altered by different kinds of additional auditory information in various ways.

The combination of positive and negative feedback loops confers exquisite flexibility to biochemical switches

International Nuclear Information System (INIS)

Pfeuty, Benjamin; Kaneko, Kunihiko

2009-01-01

A wide range of cellular processes require molecular regulatory pathways to convert a graded signal into a discrete response. One prevalent switching mechanism relies on the coexistence of two stable states (bistability) caused by positive feedback regulations. Intriguingly, positive feedback is often supplemented with negative feedback, raising the question of whether and how these two types of feedback can cooperate to control discrete cellular responses. To address this issue, we formulate a canonical model of a protein–protein interaction network and analyze the dynamics of a prototypical two-component circuit. The appropriate combination of negative and positive feedback loops can bring a bistable circuit close to the oscillatory regime. Notably, sharply activated negative feedback can give rise to a bistable regime wherein two stable fixed points coexist and may collide pairwise with two saddle points. This specific type of bistability is found to allow for separate and flexible control of switch-on and switch-off events, for example (i) to combine fast and reversible transitions, (ii) to enable transient switching responses and (iii) to display tunable noise-induced transition rates. Finally, we discuss the relevance of such bistable switching behavior, and the circuit topologies considered, to specific biological processes such as adaptive metabolic responses, stochastic fate decisions and cell-cycle transitions. Taken together, our results suggest an efficient mechanism by which positive and negative feedback loops cooperate to drive the flexible and multifaceted switching behaviors arising in biological systems

Multi-channel control circuit for real-time control of events in Aditya tokamak

Energy Technology Data Exchange (ETDEWEB)

Edappala, Praveenlal, E-mail: praveen@ipr.res.in; Shah, Minsha; Rajpal, Rachana; Tanna, R.L.; Ghosh, Joydeep; Chattopadhyay, P.K.; Jha, R.

2016-11-15

Highlights: • Low cost microcontroller based control circuit. • The control hardware can be programmed/configured very easily for different applications. • Microcontroller programming is done in assembly language so that precise timing can be achieved with micro seconds resolution. • Successful implementation of this circuit in noisy tokamak environment. • Efficient noise and burst elimination. • Can be integrated in to the other subsystems. • Low cost solution for implementing feedback control in small and medium size tokamaks and other experiments requiring feedback control. - Abstract: Tokamak plasma is prone to many random events having potential for causing severe damages to the machine, such as disruptions, production and elimination of high-energy runaway electrons etc. These events can be mitigated by obtaining pre-cursor signal leading to these events and then taking proper measures just before their onset to avoid their happenings, like disruptions can be mitigated by massive gas injection or putting a bias voltage on an electrode placed inside the plasma, the runaways can be mitigated by gas injection and by applying specific magnetic fields. Hence for real time control of these events, the pre-cursors should be electronically recorded and the mitigation techniques should be initiated by sending triggers to their individual operational systems. To implement these methodologies of real-time controlling of events in Aditya Tokamak, a low cost multi-channel Micro-Controller based timing circuit is designed and developed in-house. This circuit first compares the precursor signals fed into it with the pre-set values and gives a trigger output whenever the signals overshoot the pre-set values. The circuit readies itself for operation along with start of the tokamak discharge and waits up to an initial pre-determined delay and then initiates a trigger at the time of overshooting of precursor signal. The circuit is fully integrated and assembled in

Parameter estimation methods for gene circuit modeling from time-series mRNA data: a comparative study

KAUST Repository

Fan, M.

2015-03-29

Parameter estimation is a challenging computational problemin the reverse engineering of biological systems. Because advances in biotechnology have facilitated wide availability of time-series gene expression data, systematic parameter esti- mation of gene circuitmodels fromsuch time-series mRNA data has become an importantmethod for quantitatively dissecting the regulation of gene expression. By focusing on themodeling of gene circuits, we examine here the perform- ance of three types of state-of-the-art parameter estimation methods: population-basedmethods, onlinemethods and model-decomposition-basedmethods. Our results show that certain population-basedmethods are able to generate high- quality parameter solutions. The performance of thesemethods, however, is heavily dependent on the size of the param- eter search space, and their computational requirements substantially increase as the size of the search space increases. In comparison, onlinemethods andmodel decomposition-basedmethods are computationally faster alternatives and are less dependent on the size of the search space. Among other things, our results show that a hybrid approach that augments computationally fastmethods with local search as a subsequent refinement procedure can substantially increase the qual- ity of their parameter estimates to the level on par with the best solution obtained fromthe population-basedmethods whilemaintaining high computational speed. These suggest that such hybridmethods can be a promising alternative to themore commonly used population-basedmethods for parameter estimation of gene circuit models when limited prior knowledge about the underlying regulatorymechanismsmakes the size of the parameter search space vastly large. © The Author 2015. Published by Oxford University Press.

Toward a generalized and high-throughput enzyme screening system based on artificial genetic circuits.

Science.gov (United States)

Choi, Su-Lim; Rha, Eugene; Lee, Sang Jun; Kim, Haseong; Kwon, Kilkoang; Jeong, Young-Su; Rhee, Young Ha; Song, Jae Jun; Kim, Hak-Sung; Lee, Seung-Goo

2014-03-21

Large-scale screening of enzyme libraries is essential for the development of cost-effective biological processes, which will be indispensable for the production of sustainable biobased chemicals. Here, we introduce a genetic circuit termed the Genetic Enzyme Screening System that is highly useful for high-throughput enzyme screening from diverse microbial metagenomes. The circuit consists of two AND logics. The first AND logic, the two inputs of which are the target enzyme and its substrate, is responsible for the accumulation of a phenol compound in cell. Then, the phenol compound and its inducible transcription factor, whose activation turns on the expression of a reporter gene, interact in the other logic gate. We confirmed that an individual cell harboring this genetic circuit can present approximately a 100-fold higher cellular fluorescence than the negative control and can be easily quantified by flow cytometry depending on the amounts of phenolic derivatives. The high sensitivity of the genetic circuit enables the rapid discovery of novel enzymes from metagenomic libraries, even for genes that show marginal activities in a host system. The crucial feature of this approach is that this single system can be used to screen a variety of enzymes that produce a phenol compound from respective synthetic phenyl-substrates, including cellulase, lipase, alkaline phosphatase, tyrosine phenol-lyase, and methyl parathion hydrolase. Consequently, the highly sensitive and quantitative nature of this genetic circuit along with flow cytometry techniques could provide a widely applicable toolkit for discovering and engineering novel enzymes at a single cell level.

Dictionary-based image reconstruction for superresolution in integrated circuit imaging.

Science.gov (United States)

Cilingiroglu, T Berkin; Uyar, Aydan; Tuysuzoglu, Ahmet; Karl, W Clem; Konrad, Janusz; Goldberg, Bennett B; Ünlü, M Selim

2015-06-01

Resolution improvement through signal processing techniques for integrated circuit imaging is becoming more crucial as the rapid decrease in integrated circuit dimensions continues. Although there is a significant effort to push the limits of optical resolution for backside fault analysis through the use of solid immersion lenses, higher order laser beams, and beam apodization, signal processing techniques are required for additional improvement. In this work, we propose a sparse image reconstruction framework which couples overcomplete dictionary-based representation with a physics-based forward model to improve resolution and localization accuracy in high numerical aperture confocal microscopy systems for backside optical integrated circuit analysis. The effectiveness of the framework is demonstrated on experimental data.

Project Circuits in a Basic Electric Circuits Course

Science.gov (United States)

Becker, James P.; Plumb, Carolyn; Revia, Richard A.

2014-01-01

The use of project circuits (a photoplethysmograph circuit and a simple audio amplifier), introduced in a sophomore-level electric circuits course utilizing active learning and inquiry-based methods, is described. The development of the project circuits was initiated to promote enhanced engagement and deeper understanding of course content among…

Computer-based feedback in formative assessment

NARCIS (Netherlands)

van der Kleij, Fabienne

2013-01-01

Formative assessment concerns any assessment that provides feedback that is intended to support learning and can be used by teachers and/or students. Computers could offer a solution to overcoming obstacles encountered in implementing formative assessment. For example, computer-based assessments

A spiking neuron circuit based on a carbon nanotube transistor

International Nuclear Information System (INIS)

Chen, C-L; Kim, K; Truong, Q; Shen, A; Li, Z; Chen, Y

2012-01-01

A spiking neuron circuit based on a carbon nanotube (CNT) transistor is presented in this paper. The spiking neuron circuit has a crossbar architecture in which the transistor gates are connected to its row electrodes and the transistor sources are connected to its column electrodes. An electrochemical cell is incorporated in the gate of the transistor by sandwiching a hydrogen-doped poly(ethylene glycol)methyl ether (PEG) electrolyte between the CNT channel and the top gate electrode. An input spike applied to the gate triggers a dynamic drift of the hydrogen ions in the PEG electrolyte, resulting in a post-synaptic current (PSC) through the CNT channel. Spikes input into the rows trigger PSCs through multiple CNT transistors, and PSCs cumulate in the columns and integrate into a ‘soma’ circuit to trigger output spikes based on an integrate-and-fire mechanism. The spiking neuron circuit can potentially emulate biological neuron networks and their intelligent functions. (paper)

Nanosecond-Timescale Intra-Bunch-Train Feedback for the Linear Collider: Results of the FONT2 Run

International Nuclear Information System (INIS)

Barlow, R.; Dufau, M.; Kalinin, A.; Daresbury; Myatt, G.; Perry, C.; Oxford U.; Burrows, P.N.; Hartin, T.; Hussain, S.M.; Molloy, S.; White, G.R.; Queen Mary, U. of London; Adolphsen, C.; Frisch, J.C.; Hendrickson, L.; Jobe, R.K.; Markiewicz, T.; McCormick, D.J.; Nelson, J.; Ross, M.C.; Smith, S.; Smith, T.J.; SLAC

2005-01-01

We report on experimental results from the December 2003/January 2004 data run of the Feedback On Nanosecond Timescales (FONT) experiment at the Next Linear Collider Test Accelerator at SLAC. We built a second-generation prototype intra-train beam-based feedback system incorporating beam position monitors, fast analogue signal processors, a feedback circuit, fast-risetime amplifiers and stripline kickers. We applied a novel real-time charge-normalization scheme to account for beam current variations along the train. We used the system to correct the position of the 170-nanosecond-long bunchtrain at NLCTA. We achieved a latency of 53 nanoseconds, representing a significant improvement on FONT1 (2002), and providing a demonstration of intra-train feedback for the Linear Collider

Online tuning of impedance matching circuit for long pulse inductively coupled plasma source operation—An alternate approach

International Nuclear Information System (INIS)

Sudhir, Dass; Bandyopadhyay, M.; Chakraborty, A.; Kraus, W.; Gahlaut, A.; Bansal, G.

2014-01-01

Impedance matching circuit between radio frequency (RF) generator and the plasma load, placed between them, determines the RF power transfer from RF generator to the plasma load. The impedance of plasma load depends on the plasma parameters through skin depth and plasma conductivity or resistivity. Therefore, for long pulse operation of inductively coupled plasmas, particularly for high power (∼100 kW or more) where plasma load condition may vary due to different reasons (e.g., pressure, power, and thermal), online tuning of impedance matching circuit is necessary through feedback. In fusion grade ion source operation, such online methodology through feedback is not present but offline remote tuning by adjusting the matching circuit capacitors and tuning the driving frequency of the RF generator between the ion source operation pulses is envisaged. The present model is an approach for remote impedance tuning methodology for long pulse operation and corresponding online impedance matching algorithm based on RF coil antenna current measurement or coil antenna calorimetric measurement may be useful in this regard

Automatic circuit analysis based on mask information

International Nuclear Information System (INIS)

Preas, B.T.; Lindsay, B.W.; Gwyn, C.W.

1976-01-01

The Circuit Mask Translator (CMAT) code has been developed which converts integrated circuit mask information into a circuit schematic. Logical operations, pattern recognition, and special functions are used to identify and interconnect diodes, transistors, capacitors, and resistances. The circuit topology provided by the translator is compatible with the input required for a circuit analysis program

Silicon-based optical integrated circuits for terabit communication networks

International Nuclear Information System (INIS)

Svidzinsky, K K

2003-01-01

A brief review is presented of the development of silicon-based optical integrated circuits used as components in modern all-optical communication networks with the terabit-per-second transmission capacity. The designs and technologies for manufacturing these circuits are described and the problems related to their development and application in WDM communication systems are considered. (special issue devoted to the memory of academician a m prokhorov)

Quantum circuit implementation of cyclic mutually unbiased bases

Energy Technology Data Exchange (ETDEWEB)

Seyfarth, Ulrich; Dittmann, Niklas; Alber, Gernot [Institut fuer Angewandte Physik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany)

2013-07-01

Complete sets of mutually unbiased bases (MUBs) play an important role in the areas of quantum state tomography and quantum cryptography. Sets which can be generated cyclically may eliminate certain side-channel attacks. To profit from the advantages of these MUBs we propose a method for deriving a quantum circuit that implements the generator of a set into an experimental setup. For some dimensions this circuit is minimal. The presented method is in principle applicable for a larger set of operations and generalizes recently published results.

Haptic Feedback for the GPU-based Surgical Simulator

DEFF Research Database (Denmark)

Sørensen, Thomas Sangild; Mosegaard, Jesper

2006-01-01

The GPU has proven to be a powerful processor to compute spring-mass based surgical simulations. It has not previously been shown however, how to effectively implement haptic interaction with a simulation running entirely on the GPU. This paper describes a method to calculate haptic feedback...... with limited performance cost. It allows easy balancing of the GPU workload between calculations of simulation, visualisation, and the haptic feedback....

Design of nuclear pulse shaped circuit based on proportional counter

International Nuclear Information System (INIS)

Song Qianqian; Cheng Yi; Tuo Xianguo

2011-01-01

Use the self-developed proportional to sample gas tritium in environment and make the measurement. For this detector, a kind of pulse shape circuit based on second order active low pass filtering circuit realized filtering and shaping nuclear pulse by high-speed operational amplifier, with less stages that has been approved for filter Gaussian wave. Use Multisim 10.0 to simulate the different parameters of the filter circuit. The simulation result was consistent with the theoretical results. The experiments proved the feasibility of this circuit, and at the same time provided a convenient and reliable method for analysis and optimization of the nuclear pulse waveform in order for discriminating by MCA. (authors)

Power flow control based solely on slow feedback loop for heart pump applications.

Science.gov (United States)

Wang, Bob; Hu, Aiguo Patrick; Budgett, David

2012-06-01

This paper proposes a new control method for regulating power flow via transcutaneous energy transfer (TET) for implantable heart pumps. Previous work on power flow controller requires a fast feedback loop that needs additional switching devices and resonant capacitors to be added to the primary converter. The proposed power flow controller eliminates these additional components, and it relies solely on a slow feedback loop to directly drive the primary converter to meet the heart pump power demand and ensure zero voltage switching. A controlled change in switching frequency varies the resonant tank shorting period of a current-fed push-pull resonant converter, thus changing the magnitude of the primary resonant voltage, as well as the tuning between primary and secondary resonant tanks. The proposed controller has been implemented successfully using an analogue circuit and has reached an end-to-end power efficiency of 79.6% at 10 W with a switching frequency regulation range of 149.3 kHz to 182.2 kHz.

Analysis of different categories of feedback in two organizational ways in gymnastics Análisis de diferentes categorías del feedback en dos formas organizativas del medio gimnástico.

Directory of Open Access Journals (Sweden)

J. López Bedoya

2010-09-01

Full Text Available

The objetive of this study is to evaluate the relation of two organizational methods of learning and performance of one gymnastic skill and their influence in some categories of feedback. 35 subjets of both sexes, 10 and 12 years old, were tested. The results showed the importance of a continuous and circular organizational method based on mini-circuits, since it promotes both individual and prescriptive feedback, important ingredients for an efficient training.
KEY WORDS: gymnastics, learning, feedback.

PALABRAS CLAVE: gimnasia, aprendizaje, feedback.

A model for educational feedback based on clinical communication skills strategies: beyond the "feedback sandwich".

Science.gov (United States)

Milan, Felise B; Parish, Sharon J; Reichgott, Michael J

2006-01-01

Feedback is an essential tool in medical education, and the process is often difficult for both faculty and learner. There are strong analogies between the provision of educational feedback and doctor-patient communication during the clinical encounter. Relationship-building skills used in the clinical setting-Partnership, Empathy, Apology, Respect, Legitimation, Support (PEARLS)-can establish trust with the learner to better manage difficult feedback situations involving personal issues, unprofessional behavior, or a defensive learner. Using the stage of readiness to change (transtheoretical) model, the educator can "diagnose" the learner's stage of readiness and employ focused interventions to encourage desired changes. This approach has been positively received by medical educators in faculty development workshops. A model for provision of educational feedback based on communication skills used in the clinical encounter can be useful in the medical education setting. More robust evaluation of the construct validity is required in actual training program situations.

A SQUID Bootstrap Circuit with a Large Parameter Tolerance

International Nuclear Information System (INIS)

Zhang Guo-Feng; Kong Xiang-Yan; Xie Xiao-Ming; Zhang Yi; Krause Hans-Joachim; Offenhäusser Andreas

2013-01-01

The voltage biased (SQUID) bootstrap circuit (SBC) was recently introduced as an effective means to reduce the preamplifier noise contribution. We analyze the tolerances of the SBC noise suppression performance to spreads in SQUID and SBC circuit parameters. It is found that the tolerance to spread mainly caused by the integrated circuit fabrication process could be extended by a one-time adjustable current feedback. A helium-cooled niobium SQUID with a loop inductance of 350 pH is employed to experimentally verify the analysis. From this work, design criteria for fully integrated SBC devices with a high yield can be derived

Oscillation-based test in mixed-signal circuits

CERN Document Server

Sánchez, Gloria Huertas; Rueda, Adoración Rueda

2007-01-01

This book presents the development and experimental validation of the structural test strategy called Oscillation-Based Test - OBT in short. The results presented here assert, not only from a theoretical point of view, but also based on a wide experimental support, that OBT is an efficient defect-oriented test solution, complementing the existing functional test techniques for mixed-signal circuits.

Enhancement of galloping-based wind energy harvesting by synchronized switching interface circuits

Science.gov (United States)

Zhao, Liya; Liang, Junrui; Tang, Lihua; Yang, Yaowen; Liu, Haili

2015-04-01

Galloping phenomenon has attracted extensive research attention for small-scale wind energy harvesting. In the reported literature, the dynamics and harvested power of a galloping-based energy harvesting system are usually evaluated with a resistive AC load; these characteristics might shift when a practical harvesting interface circuit is connected for extracting useful DC power. In the family of piezoelectric energy harvesting interface circuits, synchronized switching harvesting on inductor (SSHI) has demonstrated its advantage for enhancing the harvested power from existing base vibrations. This paper investigates the harvesting capability of a galloping-based wind energy harvester using SSHI interfaces, with a focus on comparing the performances of Series SSHI (S-SSHI) and Parallel SSHI (P-SSHI) with that of a standard DC interface, in terms of power at various wind speeds. The prototyped galloping-based piezoelectric energy harvester (GPEH) comprises a piezoelectric cantilever attached with a square-sectioned bluff body made of foam. Equivalent circuit model (ECM) of the GPEH is established and system-level circuit simulations with SSHI and standard interfaces are performed and validated with wind tunnel tests. The benefits of SSHI compared to standard circuit become more significant when the wind speed gets higher; while SSHI circuits lose the benefits at small wind speeds. In both experiment and simulation, the superiority of P-SSHI is confirmed while S-SSHI demands further investigation. The power output is increased by 43.75% with P-SSHI compared to the standard circuit at a wind speed of 6m/s.

Java Based Symbolic Circuit Solver For Electrical Engineering Curriculum

Directory of Open Access Journals (Sweden)

Ruba Akram Amarin

2012-11-01

Full Text Available The interactive technical electronic book, TechEBook, currently under development at the University of Central Florida (UCF, introduces a paradigm shift by replacing the traditional electrical engineering course with topic-driven modules that provide a useful tool for engineers and scientists. The TechEBook comprises the two worlds of classical circuit books and interactive operating platforms such as iPads, laptops and desktops. The TechEBook provides an interactive applets screen that holds many modules, each of which has a specific application in the self learning process. This paper describes one of the interactive techniques in the TechEBook known as Symbolic Circuit Solver (SymCirc. The SymCirc develops a versatile symbolic based linear circuit with a switches solver. The solver works by accepting a Netlist and the element that the user wants to find the voltage across or current on, as input parameters. Then it either produces the plot or the time domain expression of the output. Frequency domain plots or Symbolic Transfer Functions are also produced. The solver gets its input from a Web-based GUI circuit drawer developed at UCF. Typical simulation tools that electrical engineers encounter are numerical in nature, that is, when presented with an input circuit they iteratively solve the circuit across a set of small time steps. The result is represented as a data set of output versus time, which can be plotted for further inspection. Such results do not help users understand the ultimate nature of circuits as Linear Time Invariant systems with a finite dimensional basis in the solution space. SymCirc provides all simulation results as time domain expressions composed of the basic functions that exclusively include exponentials, sines, cosines and/or t raised to any power. This paper explains the motivation behind SymCirc, the Graphical User Interface front end and how the solver actually works. The paper also presents some examples and

CMOS technology and current-feedback op-amps

DEFF Research Database (Denmark)

Bruun, Erik

1993-01-01

Some of the problems related to the application of CMOS technology to current-feedback operational amplifiers (CFB op-amps) are identified. Problems caused by the low device transconductance and by the absence of matching between p-channel and n-channel transistors are examined, and circuit...

Neurophysiological correlates of anhedonia in feedback processing

NARCIS (Netherlands)

G.W. Mies (Gabry); I. van den Berg (Ivo); I.H.A. Franken (Ingmar); M. Smits (Marion); M.W. Molen, van der (Maurits); F.M. van der Veen (Frederik)

2013-01-01

textabstractDisturbances in feedback processing and a dysregulation of the neural circuit in which the cingulate cortex plays a key role have been frequently observed in depression. Since depression is a heterogeneous disease, instead of focusing on the depressive state in general, this study

Neurophysiological correlates of anhedonia in feedback processing

NARCIS (Netherlands)

Mies, G.W.; Berg, I. van den; Franken, I.H.A.; Smits, M.; Molen, M.W. van der; Veen, F.M. van der

2013-01-01

Disturbances in feedback processing and a dysregulation of the neural circuit in which the cingulate cortex plays a keyrole have been frequently observed in depression. Since depression is a heterogeneous disease, instead of focusing on the depressive state in general, this study investigated the

Efficient/reliable dc-to-dc inverter circuit

Science.gov (United States)

Pasciutti, E. R.

1970-01-01

Feedback loop, which contains an inductor in series with a saturable reactor, is added to a standard inverter circuit to permit the inverter power transistors to be switched in a controlled and efficient manner. This inverter is applicable where the power source has either high or low impedance properties.

Establishment of a universal and rational gene detection strategy through three-way junction-based remote transduction.

Science.gov (United States)

Tang, Yidan; Lu, Baiyang; Zhu, Zhentong; Li, Bingling

2018-01-21

The polymerase chain reaction and many isothermal amplifications are able to achieve super gene amplification. Unfortunately, most commonly-used transduction methods, such as dye staining and Taqman-like probing, still suffer from shortcomings including false signals or difficult probe design, or are incompatible with multi-analysis. Here a universal and rational gene detection strategy has been established by translating isothermal amplicons to enzyme-free strand displacement circuits via three-way junction-based remote transduction. An assistant transduction probe was imported to form a partial hybrid with the target single-stranded nucleic acid. After systematic optimization the hybrid could serve as an associative trigger to activate a downstream circuit detector via a strand displacement reaction across the three-way junction. By doing so, the detection selectivity can be double-guaranteed through both amplicon-transducer recognition and the amplicon-circuit reaction. A well-optimized circuit can be immediately applied to a new target detection through simply displacing only 10-12 nt on only one component, according to the target. More importantly, this property for the first time enables multi-analysis and logic-analysis in a single reaction, sharing a single fluorescence reporter. In an applicable model, trace amounts of Cronobacter and Enterobacteria genes have been clearly distinguished from samples with no bacteria or one bacterium, with ultra-high sensitivity and selectivity.

A new method of removing the high value feedback resistor in the charge sensitive preamplifier

International Nuclear Information System (INIS)

Xi Deming

1993-01-01

A new method of removing the high value feedback resistor in the charge sensitive preamplifier is introduced. The circuit analysis of this novel design is described and the measured performances of a practical circuit are provided

Diagnosis of soft faults in analog integrated circuits based on fractional correlation

International Nuclear Information System (INIS)

Deng Yong; Shi Yibing; Zhang Wei

2012-01-01

Aiming at the problem of diagnosing soft faults in analog integrated circuits, an approach based on fractional correlation is proposed. First, the Volterra series of the circuit under test (CUT) decomposed by the fractional wavelet packet are used to calculate the fractional correlation functions. Then, the calculated fractional correlation functions are used to form the fault signatures of the CUT. By comparing the fault signatures, the different soft faulty conditions of the CUT are identified and the faults are located. Simulations of benchmark circuits illustrate the proposed method and validate its effectiveness in diagnosing soft faults in analog integrated circuits. (semiconductor integrated circuits)

Scheduling for Multiuser MIMO Downlink Channels with Ranking-Based Feedback

Science.gov (United States)

Kountouris, Marios; Sälzer, Thomas; Gesbert, David

2008-12-01

We consider a multi-antenna broadcast channel with more single-antenna receivers than transmit antennas and partial channel state information at the transmitter (CSIT). We propose a novel type of CSIT representation for the purpose of user selection, coined as ranking-based feedback. Each user calculates and feeds back the rank, an integer between 1 and W + 1, of its instantaneous channel quality information (CQI) among a set of W past CQI measurements. Apart from reducing significantly the required feedback load, ranking-based feedback enables the transmitter to select users that are on the highest peak (quantile) with respect to their own channel distribution, independently of the distribution of other users. It can also be shown that this feedback metric can restore temporal fairness in heterogeneous networks, in which users' channels are not identically distributed and mobile terminals experience different average signal-to-noise ratio (SNR). The performance of a system that performs user selection using ranking-based CSIT in the context of random opportunistic beamforming is analyzed, and we provide design guidelines on the number of required past CSIT samples and the impact of finite W on average throughput. Simulation results show that feedback reduction of order of 40-50% can be achieved with negligible decrease in system throughput.

A bio-inspired spatial patterning circuit.

Science.gov (United States)

Chen, Kai-Yuan; Joe, Danial J; Shealy, James B; Land, Bruce R; Shen, Xiling

2014-01-01

Lateral Inhibition (LI) is a widely conserved patterning mechanism in biological systems across species. Distinct from better-known Turing patterns, LI depend on cell-cell contact rather than diffusion. We built an in silico genetic circuit model to analyze the dynamic properties of LI. The model revealed that LI amplifies differences between neighboring cells to push them into opposite states, hence forming stable 2-D patterns. Inspired by this insight, we designed and implemented an electronic circuit that recapitulates LI patterning dynamics. This biomimetic system serve as a physical model to elucidate the design principle of generating robust patterning through spatial feedback, regardless of the underlying devices being biological or electrical.

An Improved Zero Potential Circuit for Readout of a Two-Dimensional Resistive Sensor Array.

Science.gov (United States)

Wu, Jian-Feng; Wang, Feng; Wang, Qi; Li, Jian-Qing; Song, Ai-Guo

2016-12-06

With one operational amplifier (op-amp) in negative feedback, the traditional zero potential circuit could access one element in the two-dimensional (2-D) resistive sensor array with the shared row-column fashion but it suffered from the crosstalk problem for the non-scanned elements' bypass currents, which were injected into array's non-scanned electrodes from zero potential. Firstly, for suppressing the crosstalk problem, we designed a novel improved zero potential circuit with one more op-amp in negative feedback to sample the total bypass current and calculate the precision resistance of the element being tested (EBT) with it. The improved setting non-scanned-electrode zero potential circuit (S-NSE-ZPC) was given as an example for analyzing and verifying the performance of the improved zero potential circuit. Secondly, in the S-NSE-ZPC and the improved S-NSE-ZPC, the effects of different parameters of the resistive sensor arrays and their readout circuits on the EBT's measurement accuracy were simulated with the NI Multisim 12. Thirdly, part features of the improved circuit were verified with the experiments of a prototype circuit. Followed, the results were discussed and the conclusions were given. The experiment results show that the improved circuit, though it requires one more op-amp, one more resistor and one more sampling channel, can access the EBT in the 2-D resistive sensor array more accurately.

Optimal Design of Rectification Circuit in Electronic Circuit Fault Self-repair Based on EHW and RBT

Institute of Scientific and Technical Information of China (English)

ZHANG Junbin; CAI Jinyan; MENG Yafeng

2018-01-01

Reliability of traditional electronic circuit is improved mainly by redundant fault-tolerant technol-ogy with large hardware resource consumption and limited fault self-repair capability. In complicated environment, electronic circuit faults appear easily. If on-site immedi-ate repair is not implemented, normal running of elec-tronic system will be directly affected. In order to solve these problems, Evolvable hardware (EHW) technology is widely used. The conventional EHW has some bottlenecks. The optimal design of Rectification circuit (RTC) is fur-ther researched on the basis of the previously proposed fault self-repair based on EHW and Reparation balance technology (RBT). Fault sets are selected by fault danger degree and fault coverage rate. The optimal designed RTC can completely repair faults in the fault set. Simulation re-sults prove that it has higher self-repair capability and less hardware resource.

Memristor-based nanoelectronic computing circuits and architectures

CERN Document Server

Vourkas, Ioannis

2016-01-01

This book considers the design and development of nanoelectronic computing circuits, systems and architectures focusing particularly on memristors, which represent one of today’s latest technology breakthroughs in nanoelectronics. The book studies, explores, and addresses the related challenges and proposes solutions for the smooth transition from conventional circuit technologies to emerging computing memristive nanotechnologies. Its content spans from fundamental device modeling to emerging storage system architectures and novel circuit design methodologies, targeting advanced non-conventional analog/digital massively parallel computational structures. Several new results on memristor modeling, memristive interconnections, logic circuit design, memory circuit architectures, computer arithmetic systems, simulation software tools, and applications of memristors in computing are presented. High-density memristive data storage combined with memristive circuit-design paradigms and computational tools applied t...

Peer Feedback to Facilitate Project-Based Learning in an Online Environment

Science.gov (United States)

Ching, Yu-Hui; Hsu, Yu-Chang

2013-01-01

There has been limited research examining the pedagogical benefits of peer feedback for facilitating project-based learning in an online environment. Using a mixed method approach, this paper examines graduate students' participation and perceptions of peer feedback activity that supports project-based learning in an online instructional design…

New Quartz Crystal Oscillators Using the Current-Feedback Operational Amplifier

OpenAIRE

Muhammad Taher Abuelma'atti; Ahmad Al-Ghazwani

2000-01-01

New crystal oscillators using the current-feedback operational-amplifier (CFOA) are presented. Each circuit uses one CFOA, a crystal and, at most, five externally connected passive elements. Experimental results are included.

Uplink Contention-based CSI Feedback with Prioritized Layers for a Multi-Carrier System

DEFF Research Database (Denmark)

Kaneko, Megumi; Hayashi, Kazunori; Popovski, Petar

2012-01-01

, several works have considered contention-based CSI feedback in the UL control channel. We propose such a feedback scheme for a generic MC system, based on the idea of variable collision protection, where the probability that a feedback information experiences a collision depends on its importance......Optimized resource allocation of the Downlink (DL) in wireless systems utilizing Multi-Carrier (MC) transmission requires Channel State Information (CSI) feedback for each user/subchannel to the Base Station (BS), consuming a high amount of Uplink (UL) radio resources. To alleviate this problem...

WPG-Controlled Quantum BDD Circuits with BDD Architecture on GaAs-Based Hexagonal Nanowire Network Structure

Directory of Open Access Journals (Sweden)

Hong-Quan ZHao

2012-01-01

Full Text Available One-dimensional nanowire quantum devices and basic quantum logic AND and OR unit on hexagonal nanowire units controlled by wrap gate (WPG were designed and fabricated on GaAs-based one-dimensional electron gas (1-DEG regular nanowire network with hexagonal topology. These basic quantum logic units worked correctly at 35 K, and clear quantum conductance was achieved on the node device, logic AND circuit unit, and logic OR circuit unit. Binary-decision-diagram- (BDD- based arithmetic logic unit (ALU is realized on GaAs-based regular nanowire network with hexagonal topology by the same fabrication method as that of the quantum devices and basic circuits. This BDD-based ALU circuit worked correctly at room temperature. Since these quantum devices and circuits are basic units of the BDD ALU combinational circuit, the possibility of integrating these quantum devices and basic quantum circuits into the BDD-based quantum circuit with more complicated structures was discussed. We are prospecting the realization of quantum BDD combinational circuitries with very small of energy consumption and very high density of integration.

Nonlinear Analysis of Ring Oscillator and Cross-Coupled Oscillator Circuits

KAUST Repository

Ge, Xiaoqing

2010-12-01

Hassan Khalil’s research results and beautifully written textbook on nonlinear systems have influenced generations of researchers, including the authors of this paper. Using nonlinear systems techniques, this paper analyzes ring oscillator and cross-coupled oscillator circuits, which are essential building blocks in digital systems. The paper first investigates local and global stability properties of an n-stage ring oscillator by making use of its cyclic structure. It next studies global stability properties of a class of cross-coupled oscillators which admit the representation of a dynamic system in feedback with a static nonlinearity, and presents su cient conditions for almost global convergence of the solutions to a limit cycle when the feedback gain is in the vicinity of a bifurcation point. The result are also extended to the synchronization of interconnected identical oscillator circuits.

Nonlinear Analysis of Ring Oscillator and Cross-Coupled Oscillator Circuits

KAUST Repository

Ge, Xiaoqing; Arcak, Murat; Salama, Khaled N.

2010-01-01

Hassan Khalil’s research results and beautifully written textbook on nonlinear systems have influenced generations of researchers, including the authors of this paper. Using nonlinear systems techniques, this paper analyzes ring oscillator and cross-coupled oscillator circuits, which are essential building blocks in digital systems. The paper first investigates local and global stability properties of an n-stage ring oscillator by making use of its cyclic structure. It next studies global stability properties of a class of cross-coupled oscillators which admit the representation of a dynamic system in feedback with a static nonlinearity, and presents su cient conditions for almost global convergence of the solutions to a limit cycle when the feedback gain is in the vicinity of a bifurcation point. The result are also extended to the synchronization of interconnected identical oscillator circuits.

Effect of vibrotactile feedback on an EMG-based proportional cursor control system.

Science.gov (United States)

Li, Shunchong; Chen, Xingyu; Zhang, Dingguo; Sheng, Xinjun; Zhu, Xiangyang

2013-01-01

Surface electromyography (sEMG) has been introduced into the bio-mechatronics systems, however, most of them are lack of the sensory feedback. In this paper, the effect of vibrotactile feedback for a myoelectric cursor control system is investigated quantitatively. Simultaneous and proportional control signals are extracted from EMG using a muscle synergy model. Different types of feedback including vibrotactile feedback and visual feedback are added, assessed and compared with each other. The results show that vibrotactile feedback is capable of improving the performance of EMG-based human machine interface.

LHC beam stability and feedback control

International Nuclear Information System (INIS)

Steinhagen, Ralph

2007-01-01

This report presents the stability and the control of the Large Hadron Collider's (LHC) two beam orbits and their particle momenta using beam-based feedback systems. The aim of this report is to contribute to a safe and reliable LHC commissioning and machine operation. The first part of the analysis gives an estimate of the expected sources of orbit and energy perturbations that can be grouped into environmental sources, machine-inherent sources and machine element failures: the slowest perturbation due to ground motion, tides, temperature fluctuations of the tunnel and other environmental influences are described in this report by a propagation model that is both qualitatively and quantitatively supported by geophone and beam motion measurements at LEP and other CERN accelerators. The second part of this analysis deals with the control of the two LHC beams' orbit and energy through automated feedback systems. Based on the reading of the more than 1056 beam position monitors (BPMs) that are distributed over the machine, a central global feedback controller calculates new deflection strengths for the more than 1060 orbit corrector magnets (CODs) that are suitable to correct the orbit and momentum around their references. this report provides an analysis of the BPMs and CODs involved in the orbit and energy feedback. The BPMs are based on a wide-band time normaliser circuit that converts the transverse beam position reading of each individual particle bunch into two laser pulses that are separated by a time delay and transmitted through optical fibres to an acquisition card that converts the delay signals into a digital position. A simple error model has been tested and compared to the measurement accuracy of LHC type BPMs, obtained through beam-based measurements in the SPS. The average beam position is controlled through 1060 superconducting and individually powered corrector dipole magnets. The proposed correction in 'time-domain' consists of a proportional

Optimal design of RTCs in digital circuit fault self-repair based on global signal optimization

Institute of Scientific and Technical Information of China (English)

Zhang Junbin; Cai Jinyan; Meng Yafeng

2016-01-01

Since digital circuits have been widely and thoroughly applied in various fields, electronic systems are increasingly more complicated and require greater reliability. Faults may occur in elec-tronic systems in complicated environments. If immediate field repairs are not made on the faults, elec-tronic systems will not run normally, and this will lead to serious losses. The traditional method for improving system reliability based on redundant fault-tolerant technique has been unable to meet the requirements. Therefore, on the basis of (evolvable hardware)-based and (reparation balance technology)-based electronic circuit fault self-repair strategy proposed in our preliminary work, the optimal design of rectification circuits (RTCs) in electronic circuit fault self-repair based on global sig-nal optimization is deeply researched in this paper. First of all, the basic theory of RTC optimal design based on global signal optimization is proposed. Secondly, relevant considerations and suitable ranges are analyzed. Then, the basic flow of RTC optimal design is researched. Eventually, a typical circuit is selected for simulation verification, and detailed simulated analysis is made on five circumstances that occur during RTC evolution. The simulation results prove that compared with the conventional design method based RTC, the global signal optimization design method based RTC is lower in hardware cost, faster in circuit evolution, higher in convergent precision, and higher in circuit evolution success rate. Therefore, the global signal optimization based RTC optimal design method applied in the elec-tronic circuit fault self-repair technology is proven to be feasible, effective, and advantageous.

Control strategy and hardware implementation for DC–DC boost power circuit based on proportional–integral compensator for high voltage application

Directory of Open Access Journals (Sweden)

Sanjeevikumar Padmanaban

2015-06-01

Full Text Available For high-voltage (HV applications, the designers mostly prefer the classical DC–DC boost converter. However, it lacks due to the limitation of the output voltage by the gain transfer ratio, decreased efficiency and its requirement of two sensors for feedback signals, which creates complex control scheme with increased overall cost. Furthermore, the output voltage and efficiency are reduced due to the self-parasitic behavior of power circuit components. To overcome these drawbacks, this manuscript provides, the theoretical development and hardware implementation of DC–DC step-up (boost power converter circuit for obtaining extra output-voltage high-performance. The proposed circuit substantially improves the high output-voltage by voltage-lift technology with a closed loop proportional–integral controller. This complete numerical model of the converter circuit including closed loop P-I controller is developed in simulation (Matlab/Simulink software and the hardware prototype model is implemented with digital signal processor (DSP TMS320F2812. A detailed performance analysis was carried out under both line and load regulation conditions. Numerical simulation and its verification results provided in this paper, prove the good agreement of the circuit with theoretical background.

Beam-based Feedback Simulations for the NLC Linac

International Nuclear Information System (INIS)

Hendrickson, Linda

2000-01-01

Extensive beam-based feedback systems are planned as an integral part of the Next Linear Collider (NLC) control system. Wakefield effects are a significant influence on the feedback design, imposing both architectural and algorithmic constraints. Studies are in progress to assure the optimal selection of devices and to refine and confirm the algorithms for the system design. The authors show the results of initial simulations, along with evaluations of system response for various conditions of ground motion and other operational disturbances

Chaos and multi-scroll attractors in RCL-shunted junction coupled Jerk circuit connected by memristor

Science.gov (United States)

Zhou, Ping; Ahmad, Bashir; Ren, Guodong; Wang, Chunni

2018-01-01

In this paper, a new four-variable dynamical system is proposed to set chaotic circuit composed of memristor and Josephson junction, and the dependence of chaotic behaviors on nonlinearity is investigated. A magnetic flux-controlled memristor is used to couple with the RCL-shunted junction circuit, and the dynamical behaviors can be modulated by changing the coupling intensity between the memristor and the RCL-shunted junction. Bifurcation diagram and Lyapunov exponent are calculated to confirm the emergence of chaos in the improved dynamical system. The outputs and dynamical behaviors can be controlled by the initial setting and external stimulus as well. As a result, chaos can be suppressed and spiking occurs in the sampled outputs under negative feedback, while applying positive feedback type via memristor can be effective to trigger chaos. Furthermore, it is found that the number of multi-attractors in the Jerk circuit can be modulated when memristor coupling is applied on the circuit. These results indicate that memristor coupling can be effective to control chaotic circuits and it is also useful to reproduce dynamical behaviors for neuronal activities. PMID:29342178

Chaos and multi-scroll attractors in RCL-shunted junction coupled Jerk circuit connected by memristor.

Science.gov (United States)

Ma, Jun; Zhou, Ping; Ahmad, Bashir; Ren, Guodong; Wang, Chunni

2018-01-01

In this paper, a new four-variable dynamical system is proposed to set chaotic circuit composed of memristor and Josephson junction, and the dependence of chaotic behaviors on nonlinearity is investigated. A magnetic flux-controlled memristor is used to couple with the RCL-shunted junction circuit, and the dynamical behaviors can be modulated by changing the coupling intensity between the memristor and the RCL-shunted junction. Bifurcation diagram and Lyapunov exponent are calculated to confirm the emergence of chaos in the improved dynamical system. The outputs and dynamical behaviors can be controlled by the initial setting and external stimulus as well. As a result, chaos can be suppressed and spiking occurs in the sampled outputs under negative feedback, while applying positive feedback type via memristor can be effective to trigger chaos. Furthermore, it is found that the number of multi-attractors in the Jerk circuit can be modulated when memristor coupling is applied on the circuit. These results indicate that memristor coupling can be effective to control chaotic circuits and it is also useful to reproduce dynamical behaviors for neuronal activities.

Circuit- and Diagnosis-Specific DNA Methylation Changes at γ-Aminobutyric Acid-Related Genes in Postmortem Human Hippocampus in Schizophrenia and Bipolar Disorder.

Science.gov (United States)

Ruzicka, W Brad; Subburaju, Sivan; Benes, Francine M

2015-06-01

Dysfunction related to γ-aminobutyric acid (GABA)-ergic neurotransmission in the pathophysiology of major psychosis has been well established by the work of multiple groups across several decades, including the widely replicated downregulation of GAD1. Prior gene expression and network analyses within the human hippocampus implicate a broader network of genes, termed the GAD1 regulatory network, in regulation of GAD1 expression. Several genes within this GAD1 regulatory network show diagnosis- and sector-specific expression changes within the circuitry of the hippocampus, influencing abnormal GAD1 expression in schizophrenia and bipolar disorder. To investigate the hypothesis that aberrant DNA methylation contributes to circuit- and diagnosis-specific abnormal expression of GAD1 regulatory network genes in psychotic illness. This epigenetic association study targeting GAD1 regulatory network genes was conducted between July 1, 2012, and June 30, 2014. Postmortem human hippocampus tissue samples were obtained from 8 patients with schizophrenia, 8 patients with bipolar disorder, and 8 healthy control participants matched for age, sex, postmortem interval, and other potential confounds from the Harvard Brain Tissue Resource Center, McLean Hospital, Belmont, Massachusetts. We extracted DNA from laser-microdissected stratum oriens tissue of cornu ammonis 2/3 (CA2/3) and CA1 postmortem human hippocampus, bisulfite modified it, and assessed it with the Infinium HumanMethylation450 BeadChip (Illumina, Inc). The subset of CpG loci associated with GAD1 regulatory network genes was analyzed in R version 3.1.0 software (R Foundation) using the minfi package. Findings were validated using bisulfite pyrosequencing. Methylation levels at 1308 GAD1 regulatory network-associated CpG loci were assessed both as individual sites to identify differentially methylated positions and by sharing information among colocalized probes to identify differentially methylated regions. A total of

Feedback Blunting: Total Sleep Deprivation Impairs Decision Making that Requires Updating Based on Feedback.

Science.gov (United States)

Whitney, Paul; Hinson, John M; Jackson, Melinda L; Van Dongen, Hans P A

2015-05-01

To better understand the sometimes catastrophic effects of sleep loss on naturalistic decision making, we investigated effects of sleep deprivation on decision making in a reversal learning paradigm requiring acquisition and updating of information based on outcome feedback. Subjects were randomized to a sleep deprivation or control condition, with performance testing at baseline, after 2 nights of total sleep deprivation (or rested control), and following 2 nights of recovery sleep. Subjects performed a decision task involving initial learning of go and no go response sets followed by unannounced reversal of contingencies, requiring use of outcome feedback for decisions. A working memory scanning task and psychomotor vigilance test were also administered. Six consecutive days and nights in a controlled laboratory environment with continuous behavioral monitoring. Twenty-six subjects (22-40 y of age; 10 women). Thirteen subjects were randomized to a 62-h total sleep deprivation condition; the others were controls. Unlike controls, sleep deprived subjects had difficulty with initial learning of go and no go stimuli sets and had profound impairment adapting to reversal. Skin conductance responses to outcome feedback were diminished, indicating blunted affective reactions to feedback accompanying sleep deprivation. Working memory scanning performance was not significantly affected by sleep deprivation. And although sleep deprived subjects showed expected attentional lapses, these could not account for impairments in reversal learning decision making. Sleep deprivation is particularly problematic for decision making involving uncertainty and unexpected change. Blunted reactions to feedback while sleep deprived underlie failures to adapt to uncertainty and changing contingencies. Thus, an error may register, but with diminished effect because of reduced affective valence of the feedback or because the feedback is not cognitively bound with the choice. This has important

Realization of a Temperature Based Automatic Controlled Domestic Electric Boiling System

OpenAIRE

Shengqi Yu; Jinwei Zhao

2017-01-01

This paper presents a kind of analog circuit based temperature control system, which is mainly composed by threshold control signal circuit, synchronization signal circuit and trigger pulse circuit. Firstly, the temperature feedback signal function is realized by temperature sensor TS503F3950E. Secondly, the main control circuit forms the cycle controlled pulse signal to control the thyristor switching model. Finally two reverse paralleled thyristors regulate the output p...

Reward signal in a recurrent circuit drives appetitive long-term memory formation.

Science.gov (United States)

Ichinose, Toshiharu; Aso, Yoshinori; Yamagata, Nobuhiro; Abe, Ayako; Rubin, Gerald M; Tanimoto, Hiromu

2015-11-17

Dopamine signals reward in animal brains. A single presentation of a sugar reward to Drosophila activates distinct subsets of dopamine neurons that independently induce short- and long-term olfactory memories (STM and LTM, respectively). In this study, we show that a recurrent reward circuit underlies the formation and consolidation of LTM. This feedback circuit is composed of a single class of reward-signaling dopamine neurons (PAM-α1) projecting to a restricted region of the mushroom body (MB), and a specific MB output cell type, MBON-α1, whose dendrites arborize that same MB compartment. Both MBON-α1 and PAM-α1 neurons are required during the acquisition and consolidation of appetitive LTM. MBON-α1 additionally mediates the retrieval of LTM, which is dependent on the dopamine receptor signaling in the MB α/β neurons. Our results suggest that a reward signal transforms a nascent memory trace into a stable LTM using a feedback circuit at the cost of memory specificity.

COA based robust output feedback UPFC controller design

Energy Technology Data Exchange (ETDEWEB)

Shayeghi, H., E-mail: hshayeghi@gmail.co [Technical Engineering Department, University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Shayanfar, H.A. [Center of Excellence for Power System Automation and Operation, Electrical Engineering Department, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Jalilzadeh, S.; Safari, A. [Technical Engineering Department, Zanjan University, Zanjan (Iran, Islamic Republic of)

2010-12-15

In this paper, a novel method for the design of output feedback controller for unified power flow controller (UPFC) using chaotic optimization algorithm (COA) is developed. Chaotic optimization algorithms, which have the features of easy implementation, short execution time and robust mechanisms of escaping from the local optimum, is a promising tool for the engineering applications. The selection of the output feedback gains for the UPFC controllers is converted to an optimization problem with the time domain-based objective function which is solved by a COA based on Lozi map. Since chaotic mapping enjoys certainty, ergodicity and the stochastic property, the proposed chaotic optimization problem introduces chaos mapping using Lozi map chaotic sequences which increases its convergence rate and resulting precision. To ensure the robustness of the proposed stabilizers, the design process takes into account a wide range of operating conditions and system configurations. The effectiveness of the proposed controller for damping low frequency oscillations is tested and demonstrated through non-linear time-domain simulation and some performance indices studies. The results analysis reveals that the designed COA based output feedback UPFC damping controller has an excellent capability in damping power system low frequency oscillations and enhance greatly the dynamic stability of the power systems.

Web-Based Trainer for Electrical Circuit Analysis

Science.gov (United States)

Weyten, L.; Rombouts, P.; De Maeyer, J.

2009-01-01

A Web-based system for training electric circuit analysis is presented in this paper. It is centered on symbolic analysis techniques and it not only verifies the student's final answer, but it also tracks and coaches him/her through all steps of his/her reasoning path. The system mimics homework assignments, enhanced by immediate personalized…

An Industrial Model Based Disturbance Feedback Control Scheme

DEFF Research Database (Denmark)

Kawai, Fukiko; Nakazawa, Chikashi; Vinther, Kasper

2014-01-01

This paper presents a model based disturbance feedback control scheme. Industrial process systems have been traditionally controlled by using relay and PID controller. However these controllers are affected by disturbances and model errors and these effects degrade control performance. The authors...... propose a new control method that can decrease the negative impact of disturbance and model errors. The control method is motivated by industrial practice by Fuji Electric. Simulation tests are examined with a conventional PID controller and the disturbance feedback control. The simulation results...

An Improved Zero Potential Circuit for Readout of a Two-Dimensional Resistive Sensor Array

Directory of Open Access Journals (Sweden)

Jian-Feng Wu

2016-12-01

Full Text Available With one operational amplifier (op-amp in negative feedback, the traditional zero potential circuit could access one element in the two-dimensional (2-D resistive sensor array with the shared row-column fashion but it suffered from the crosstalk problem for the non-scanned elements’ bypass currents, which were injected into array’s non-scanned electrodes from zero potential. Firstly, for suppressing the crosstalk problem, we designed a novel improved zero potential circuit with one more op-amp in negative feedback to sample the total bypass current and calculate the precision resistance of the element being tested (EBT with it. The improved setting non-scanned-electrode zero potential circuit (S-NSE-ZPC was given as an example for analyzing and verifying the performance of the improved zero potential circuit. Secondly, in the S-NSE-ZPC and the improved S-NSE-ZPC, the effects of different parameters of the resistive sensor arrays and their readout circuits on the EBT’s measurement accuracy were simulated with the NI Multisim 12. Thirdly, part features of the improved circuit were verified with the experiments of a prototype circuit. Followed, the results were discussed and the conclusions were given. The experiment results show that the improved circuit, though it requires one more op-amp, one more resistor and one more sampling channel, can access the EBT in the 2-D resistive sensor array more accurately.

Rail-to-rail low-power fully differential OTA utilizing adaptive biasing and partial feedback

DEFF Research Database (Denmark)

Tuan Vu, Cao; Wisland, Dag T.; Lande, Tor Sverre

A fully differential rail-to-rail Operational Transconductance Amplifier (OTA) with improved DC-gain and reduced power consumption is proposed in this paper. By using the adaptive biasing circuit and two differential inputs, a low stand-by current can be obtained together with reduced power...... consumption. The DC-gain of the proposed OTA is improved by adding a partial feedback loop. A Common-Mode Feedback (CMFB) circuit is required for fully differential rail-to-rail operation. Simulations show that the OTA topology has a low stand-by power consumption of 96μW and a high FoM of 3.84 [(V...

Design of synthetic biological logic circuits based on evolutionary algorithm.

Science.gov (United States)

Chuang, Chia-Hua; Lin, Chun-Liang; Chang, Yen-Chang; Jennawasin, Tanagorn; Chen, Po-Kuei

2013-08-01

The construction of an artificial biological logic circuit using systematic strategy is recognised as one of the most important topics for the development of synthetic biology. In this study, a real-structured genetic algorithm (RSGA), which combines general advantages of the traditional real genetic algorithm with those of the structured genetic algorithm, is proposed to deal with the biological logic circuit design problem. A general model with the cis-regulatory input function and appropriate promoter activity functions is proposed to synthesise a wide variety of fundamental logic gates such as NOT, Buffer, AND, OR, NAND, NOR and XOR. The results obtained can be extended to synthesise advanced combinational and sequential logic circuits by topologically distinct connections. The resulting optimal design of these logic gates and circuits are established via the RSGA. The in silico computer-based modelling technology has been verified showing its great advantages in the purpose.

Servo Platform Circuit Design of Pendulous Gyroscope Based on DSP

Science.gov (United States)

Tan, Lilong; Wang, Pengcheng; Zhong, Qiyuan; Zhang, Cui; Liu, Yunfei

2018-03-01

In order to solve the problem when a certain type of pendulous gyroscope in the initial installation deviation more than 40 degrees, that the servo platform can not be up to the speed of the gyroscope in the rough north seeking phase. This paper takes the digital signal processor TMS320F28027 as the core, uses incremental digital PID algorithm, carries out the circuit design of the servo platform. Firstly, the hardware circuit is divided into three parts: DSP minimum system, motor driving circuit and signal processing circuit, then the mathematical model of incremental digital PID algorithm is established, based on the model, writes the PID control program in CCS3.3, finally, the servo motor tracking control experiment is carried out, it shows that the design can significantly improve the tracking ability of the servo platform, and the design has good engineering practice.

Optical feedback-induced light modulation for fiber-based laser ablation.

Science.gov (United States)

Kang, Hyun Wook

2014-11-01

Optical fibers have been used as a minimally invasive tool in various medical fields. However, due to excessive heat accumulation, the distal end of a fiber often suffers from severe melting or devitrification, leading to the eventual fiber failure during laser treatment. In order to minimize thermal damage at the fiber tip, an optical feedback sensor was developed and tested ex vivo. Porcine kidney tissue was used to evaluate the feasibility of optical feedback in terms of signal activation, ablation performance, and light transmission. Testing various signal thresholds demonstrated that 3 V was relatively appropriate to trigger the feedback sensor and to prevent the fiber deterioration during kidney tissue ablation. Based upon the development of temporal signal signatures, full contact mode rapidly activated the optical feedback sensor possibly due to heat accumulation. Modulated light delivery induced by optical feedback diminished ablation efficiency by 30% in comparison with no feedback case. However, long-term transmission results validated that laser ablation assisted with optical feedback was able to almost consistently sustain light delivery to the tissue as well as ablation efficiency. Therefore, an optical feedback sensor can be a feasible tool to protect optical fiber tips by minimizing debris contamination and delaying thermal damage process and to ensure more efficient and safer laser-induced tissue ablation.

Circuit Regulates Speed Of dc Motor

Science.gov (United States)

Weaver, Charles; Padden, Robin; Brown, Floyd A., Jr.

1990-01-01

Driving circuit regulates speed of small dc permanent-magnet motor in tape recorder. Two nested feedback loops maintain speed within 1 percent of constant value. Inner loop provides coarse regulation, while outer loop removes most of variation in speed that remains in the presence of regulation by the inner loop. Compares speed of motor with commanded speed and adjusts current supplied to motor accordingly.

Utilization of process TEG for fabrication of HTS circuits

International Nuclear Information System (INIS)

Hato, T.; Okada, Y.; Maruyama, M.; Suzuki, H.; Wakana, H.; Adachi, S.; Kawabe, U.; Tanabe, K.

2006-01-01

We improved the fabrication process of high-temperature superconducting (HTS) sampler circuits with multilayer structures by utilizing a test elements group (TEG). Among a lot of difficulties in the HTS circuit fabrication process, loss of oxygen is one of the most significant problems. Since the film transition temperature (T c ) has a strong relationship with the resistance at room temperature, we fabricated a test pattern on the same wafer of the circuits and measured the resistance at room temperature by using a prober to estimate the T c of each layer. By introducing the measurement of the normal resistance after each process, we found better process conditions without a T c drop. Moreover, we constructed a low-temperature probing system, in which we can measure the junction TEG. The system enabled feedback of the fabrication condition soon after the junction process. The utilization of the process TEG contributed to reproducible fabrication of HTS circuits and that is a promising advance of the HTS circuit technology

Common-signal-induced synchronization in photonic integrated circuits and its application to secure key distribution.

Science.gov (United States)

Sasaki, Takuma; Kakesu, Izumi; Mitsui, Yusuke; Rontani, Damien; Uchida, Atsushi; Sunada, Satoshi; Yoshimura, Kazuyuki; Inubushi, Masanobu

2017-10-16

We experimentally achieve common-signal-induced synchronization in two photonic integrated circuits with short external cavities driven by a constant-amplitude random-phase light. The degree of synchronization can be controlled by changing the optical feedback phase of the two photonic integrated circuits. The change in the optical feedback phase leads to a significant redistribution of the spectral energy of optical and RF spectra, which is a unique characteristic of PICs with the short external cavity. The matching of the RF and optical spectra is necessary to achieve synchronization between the two PICs, and stable synchronization can be obtained over an hour in the presence of optical feedback. We succeed in generating information-theoretic secure keys and achieving the final key generation rate of 184 kb/s using the PICs.

Improvement of wireless power transmission efficiency of implantable subcutaneous devices by closed magnetic circuit mechanism.

Science.gov (United States)

Jo, Sung-Eun; Joung, Sanghoon; Suh, Jun-Kyo Francis; Kim, Yong-Jun

2012-09-01

Induction coils were fabricated based on flexible printed circuit board for inductive transcutaneous power transmission. The coil had closed magnetic circuit (CMC) structure consisting of inner and outer magnetic core. The power transmission efficiency of the fabricated device was measured in the air and in vivo condition. It was confirmed that the CMC coil had higher transmission efficiency than typical air-core coil. The power transmission efficiency during a misalignment between primary coil and implanted secondary coil was also evaluated. The decrease of mutual inductance between the two coils caused by the misalignment led to a low efficiency of the inductive link. Therefore, it is important to properly align the primary coil and implanted secondary coil for effective power transmission. To align the coils, a feedback coil was proposed. This was integrated on the backside of the primary coil and enabled the detection of a misalignment of the primary and secondary coils. As a result of using the feedback coil, the primary and secondary coils could be aligned without knowledge of the position of the implanted secondary coil.

Rational design of modular circuits for gene transcription: A test of the bottom-up approach

Directory of Open Access Journals (Sweden)

Giordano Emanuele

2010-11-01

Full Text Available Abstract Background Most of synthetic circuits developed so far have been designed by an ad hoc approach, using a small number of components (i.e. LacI, TetR and a trial and error strategy. We are at the point where an increasing number of modular, inter-changeable and well-characterized components is needed to expand the construction of synthetic devices and to allow a rational approach to the design. Results We used interchangeable modular biological parts to create a set of novel synthetic devices for controlling gene transcription, and we developed a mathematical model of the modular circuits. Model parameters were identified by experimental measurements from a subset of modular combinations. The model revealed an unexpected feature of the lactose repressor system, i.e. a residual binding affinity for the operator site by induced lactose repressor molecules. Once this residual affinity was taken into account, the model properly reproduced the experimental data from the training set. The parameters identified in the training set allowed the prediction of the behavior of networks not included in the identification procedure. Conclusions This study provides new quantitative evidences that the use of independent and well-characterized biological parts and mathematical modeling, what is called a bottom-up approach to the construction of gene networks, can allow the design of new and different devices re-using the same modular parts.

The Effectiveness of Pre-Service English Teachers’ Collaborative Genre-Based Writing Feedback

Directory of Open Access Journals (Sweden)

Didik Rinan Sumekto

2017-05-01

Full Text Available This study investigated the collaborative genre-based effectiveness among the pre-service English teachers (PSETs. Data collection used the genre-based writing feedback observation upon its reflection and instruction and need analysis questionnaire. The data analysis used multivariate statistics method to generalize the writing tests. The findings showed that the PSETs’ feedback supported the interaction, accountability, and interdependence. These aspects were due to the collaborative participation in groups, in which the PSETs worked with the flexibility, entirely performed the quality, andcontributed in positive attitude during the meetings and assignments. The feedback emphasized the learning improvement within the formative reflection through the general linear model (GLM repeated measures analysis, where F=6,114 and p<0,01. This study concludes that the collaborative genre-based writing feedback has the positive response from the PSETs. The determinant ranges gains in between 85% to 90% after a series of genre-based writing lectures were conducted.

Three-phase short circuit calculation method based on pre-computed surface for doubly fed induction generator

Science.gov (United States)

Ma, J.; Liu, Q.

2018-02-01

This paper presents an improved short circuit calculation method, based on pre-computed surface to determine the short circuit current of a distribution system with multiple doubly fed induction generators (DFIGs). The short circuit current, injected into power grid by DFIG, is determined by low voltage ride through (LVRT) control and protection under grid fault. However, the existing methods are difficult to calculate the short circuit current of DFIG in engineering practice due to its complexity. A short circuit calculation method, based on pre-computed surface, was proposed by developing the surface of short circuit current changing with the calculating impedance and the open circuit voltage. And the short circuit currents were derived by taking into account the rotor excitation and crowbar activation time. Finally, the pre-computed surfaces of short circuit current at different time were established, and the procedure of DFIG short circuit calculation considering its LVRT was designed. The correctness of proposed method was verified by simulation.

E-Pad: a comfortable electrocutaneous-based tactile feedback display

Science.gov (United States)

Wang, Jiabin; Zhao, Lu; Liu, Yue; Wang, Yongtian; Cai, Yi

2018-01-01

The devices with touchscreen are becoming more popular recently; however, most of them suffer from the crucial drawbacks of lacking accurate tactile feedback. A novel electrocutaneous-based tactile device with the name of E-pad is proposed to provide a dynamic and static low-voltage feedback for touchscreen. We optimize the key parameters of the output voltage and design custom-made hardwares to guarantee a comfortable user experience. Users could move their fingers freely across the touchscreen of the proposed device to really feel virtual objects. Two preliminary experiments are conducted to evaluate the interactive performance of the proposed device and the experimental results show that the proposed device can provide a comfortable and distinct tactile feedback.

A memristor-based nonvolatile latch circuit

International Nuclear Information System (INIS)

Robinett, Warren; Pickett, Matthew; Borghetti, Julien; Xia Qiangfei; Snider, Gregory S; Medeiros-Ribeiro, Gilberto; Williams, R Stanley

2010-01-01

Memristive devices, which exhibit a dynamical conductance state that depends on the excitation history, can be used as nonvolatile memory elements by storing information as different conductance states. We describe the implementation of a nonvolatile synchronous flip-flop circuit that uses a nanoscale memristive device as the nonvolatile memory element. Controlled testing of the circuit demonstrated successful state storage and restoration, with an error rate of 0.1%, during 1000 power loss events. These results indicate that integration of digital logic devices and memristors could open the way for nonvolatile computation with applications in small platforms that rely on intermittent power sources. This demonstrated feasibility of tight integration of memristors with CMOS (complementary metal-oxide-semiconductor) circuitry challenges the traditional memory hierarchy, in which nonvolatile memory is only available as a large, slow, monolithic block at the bottom of the hierarchy. In contrast, the nonvolatile, memristor-based memory cell can be fast, fine-grained and small, and is compatible with conventional CMOS electronics. This threatens to upset the traditional memory hierarchy, and may open up new architectural possibilities beyond it.

Clock generators for SOC processors circuits and architectures

CERN Document Server

Fahim, Amr

2004-01-01

This book explores the design of fully-integrated frequency synthesizers suitable for system-on-a-chip (SOC) processors. The text takes a more global design perspective in jointly examining the design space at the circuit level as well as at the architectural level. The comprehensive coverage includes summary chapters on circuit theory as well as feedback control theory relevant to the operation of phase locked loops (PLLs). On the circuit level, the discussion includes low-voltage analog design in deep submicron digital CMOS processes, effects of supply noise, substrate noise, as well device noise. On the architectural level, the discussion includes PLL analysis using continuous-time as well as discrete-time models, linear and nonlinear effects of PLL performance, and detailed analysis of locking behavior. The book provides numerous real world applications, as well as practical rules-of-thumb for modern designers to use at the system, architectural, as well as the circuit level.

Bio-inspired feedback-circuit implementation of discrete, free energy optimizing, winner-take-all computations.

Science.gov (United States)

Genewein, Tim; Braun, Daniel A

2016-06-01

Bayesian inference and bounded rational decision-making require the accumulation of evidence or utility, respectively, to transform a prior belief or strategy into a posterior probability distribution over hypotheses or actions. Crucially, this process cannot be simply realized by independent integrators, since the different hypotheses and actions also compete with each other. In continuous time, this competitive integration process can be described by a special case of the replicator equation. Here we investigate simple analog electric circuits that implement the underlying differential equation under the constraint that we only permit a limited set of building blocks that we regard as biologically interpretable, such as capacitors, resistors, voltage-dependent conductances and voltage- or current-controlled current and voltage sources. The appeal of these circuits is that they intrinsically perform normalization without requiring an explicit divisive normalization. However, even in idealized simulations, we find that these circuits are very sensitive to internal noise as they accumulate error over time. We discuss in how far neural circuits could implement these operations that might provide a generic competitive principle underlying both perception and action.

The Y-located gonadoblastoma gene TSPY amplifies its own expression through a positive feedback loop in prostate cancer cells

Energy Technology Data Exchange (ETDEWEB)

Kido, Tatsuo; Lau, Yun-Fai Chris, E-mail: Chris.Lau@UCSF.edu

2014-03-28

Highlights: • Y-encoded proto-oncoprotein TSPY amplifies its expression level via a positive feedback loop. • TSPY binds to the chromatin/DNA at exon 1 of TSPY gene. • TSPY enhances the gene expression in a TSPY exon 1 sequence dependent manner. • The conserved SET/NAP-domain is essential for TSPY transactivation. • Insights on probable mechanisms on TSPY exacerbation on cancer development in men. - Abstract: The testis-specific protein Y-encoded (TSPY) is a repetitive gene located on the gonadoblastoma region of the Y chromosome, and has been considered to be the putative gene for this oncogenic locus on the male-only chromosome. It is expressed in spermatogonial cells and spermatocytes in normal human testis, but abundantly in gonadoblastoma, testicular germ cell tumors and a variety of somatic cancers, including melanoma, hepatocellular carcinoma and prostate cancer. Various studies suggest that TSPY accelerates cell proliferation and growth, and promotes tumorigenesis. In this report, we show that TSPY could bind directly to the chromatin/DNA at exon 1 of its own gene, and greatly enhance the transcriptional activities of the endogenous gene in the LNCaP prostate cancer cells. Domain mapping analyses of TSPY have localized the critical and sufficient domain to the SET/NAP-domain. These results suggest that TSPY could efficiently amplify its expression and oncogenic functions through a positive feedback loop, and contribute to the overall tumorigenic processes when it is expressed in various human cancers.

Design and development of improved ballscrew and control circuit for reactivity mechanisms of 220 MWe PHWR operating stations

International Nuclear Information System (INIS)

Jain, A.K.; Rama Mohan, N.; Mathew, Jimmy; Mathur, M.K.; Roy, S.; Ingle, V.J.; Ghoshal, B.; Ashok Kumar, B.; Patil, D.C.; Dwivedi, K.P.; Bhambra, H.S.

2006-01-01

There has been persistent failure of Ballscrews used for Reactivity Mechanism in standardised 220 MWe PHWR units. The detailed review of failures indicated that on one hand the number of demands for operation of Absorber Rod and Regulating Rod had increased due to use of digital circuit in the drive control system as compared analog circuits used earlier. On the other hand, the existing design of ballscrew had some inherent weaknesses to withstand the loads generated during starting and stopping of the regulating rods. To solve these problems two-pronged approach was adopted. The control problem was traced to overshooting of the servomotor of Absorber Rod and Regulating Rod to the full speed at the time of starting and thereafter, settling to the required speed. This sudden overshooting produces a jerk in the drive mechanism. A modified circuit has been evolved to solve this problem. Also, Changing the dead band and gain of control circuits have reduced the number of rod movements. A 'new design' of Ballscrew assembly was finalised by NPCIL with a view to withstand the severe loads generated during starting and stopping of the regulating rods and to achieve enhanced service life under water-lubrication condition. Based on this design, prototype assemblies were successfully manufactured by two Indian manufacturers. The design was cleared for manufacturing of the bulk production of Ballscrew assemblies after evaluation of its performance during rigorous 'Acceptance Testing'. Two ballscrews of new design were installed in the KGS-1 reactor and are operating since July 2005. This paper covers operational feedback including ballscrew failures in various units, Design/Development of Modified Reactivity Mechanism Ballscrews and Control Circuit based on analysis of underlying causes of failures and feedback on performance of new design. (author)

Genome-wide analysis of E. coli cell-gene interactions.

Science.gov (United States)

Cardinale, S; Cambray, G

2017-11-23

The pursuit of standardization and reliability in synthetic biology has achieved, in recent years, a number of advances in the design of more predictable genetic parts for biological circuits. However, even with the development of high-throughput screening methods and whole-cell models, it is still not possible to predict reliably how a synthetic genetic construct interacts with all cellular endogenous systems. This study presents a genome-wide analysis of how the expression of synthetic genes is affected by systematic perturbations of cellular functions. We found that most perturbations modulate expression indirectly through an effect on cell size, putting forward the existence of a generic Size-Expression interaction in the model prokaryote Escherichia coli. The Size-Expression interaction was quantified by inserting a dual fluorescent reporter gene construct into each of the 3822 single-gene deletion strains comprised in the KEIO collection. Cellular size was measured for single cells via flow cytometry. Regression analyses were used to discriminate between expression-specific and gene-specific effects. Functions of the deleted genes broadly mapped onto three systems with distinct primary influence on the Size-Expression map. Perturbations in the Division and Biosynthesis (DB) system led to a large-cell and high-expression phenotype. In contrast, disruptions of the Membrane and Motility (MM) system caused small-cell and low-expression phenotypes. The Energy, Protein synthesis and Ribosome (EPR) system was predominantly associated with smaller cells and positive feedback on ribosome function. Feedback between cell growth and gene expression is widespread across cell systems. Even though most gene disruptions proximally affect one component of the Size-Expression interaction, the effect therefore ultimately propagates to both. More specifically, we describe the dual impact of growth on cell size and gene expression through cell division and ribosomal content

Monolithic microwave integrated circuits for sensors, radar, and communications systems; Proceedings of the Meeting, Orlando, FL, Apr. 2-4, 1991

Science.gov (United States)

Leonard, Regis F. (Editor); Bhasin, Kul B. (Editor)

1991-01-01

Consideration is given to MMICs for airborne phased arrays, monolithic GaAs integrated circuit millimeter wave imaging sensors, accurate design of multiport low-noise MMICs up to 20 GHz, an ultralinear low-noise amplifier technology for space communications, variable-gain MMIC module for space applications, a high-efficiency dual-band power amplifier for radar applications, a high-density circuit approach for low-cost MMIC circuits, coplanar SIMMWIC circuits, recent advances in monolithic phased arrays, and system-level integrated circuit development for phased-array antenna applications. Consideration is also given to performance enhancement in future communications satellites with MMIC technology insertion, application of Ka-band MMIC technology for an Orbiter/ACTS communications experiment, a space-based millimeter wave debris tracking radar, low-noise high-yield octave-band feedback amplifiers to 20 GHz, quasi-optical MESFET VCOs, and a high-dynamic-range mixer using novel balun structure.

Accelerometer Based Motional Feedback Integrated in a 2 3/4" Loudspeaker

DEFF Research Database (Denmark)

Bjerregaard, Ruben; Madsen, Anders Normann; Schneider, Henrik

2016-01-01

It is a well known fact that loudspeakers produce distortion when they are driven into large diaphragm displacements. Various methods exist to reduce distortion using forward compensation and feedback methods. Acceleration based motional feedback is one of these methods and was already thoroughly...

Effects of computer-based immediate feedback on foreign language listening comprehension and test-associated anxiety.

Science.gov (United States)

Lee, Shu-Ping; Su, Hui-Kai; Lee, Shin-Da

2012-06-01

This study investigated the effects of immediate feedback on computer-based foreign language listening comprehension tests and on intrapersonal test-associated anxiety in 72 English major college students at a Taiwanese University. Foreign language listening comprehension of computer-based tests designed by MOODLE, a dynamic e-learning environment, with or without immediate feedback together with the state-trait anxiety inventory (STAI) were tested and repeated after one week. The analysis indicated that immediate feedback during testing caused significantly higher anxiety and resulted in significantly higher listening scores than in the control group, which had no feedback. However, repeated feedback did not affect the test anxiety and listening scores. Computer-based immediate feedback did not lower debilitating effects of anxiety but enhanced students' intrapersonal eustress-like anxiety and probably improved their attention during listening tests. Computer-based tests with immediate feedback might help foreign language learners to increase attention in foreign language listening comprehension.

Circuit- and Diagnosis-Specific DNA Methylation Changes at γ-Aminobutyric Acid–Related Genes in Postmortem Human Hippocampus in Schizophrenia and Bipolar Disorder

Science.gov (United States)

Ruzicka, W. Brad; Subburaju, Sivan; Benes, Francine M.

2017-01-01

IMPORTANCE Dysfunction related to γ-aminobutyric acid (GABA)–ergic neurotransmission in the pathophysiology of major psychosis has been well established by the work of multiple groups across several decades, including the widely replicated downregulation of GAD1. Prior gene expression and network analyses within the human hippocampus implicate a broader network of genes, termed the GAD1 regulatory network, in regulation of GAD1 expression. Several genes within this GAD1 regulatory network show diagnosis- and sector-specific expression changes within the circuitry of the hippocampus, influencing abnormal GAD1 expression in schizophrenia and bipolar disorder. OBJECTIVE To investigate the hypothesis that aberrant DNA methylation contributes to circuit- and diagnosis-specific abnormal expression of GAD1 regulatory network genes in psychotic illness. DESIGN, SETTING, AND PARTICIPANTS This epigenetic association study targeting GAD1 regulatory network genes was conducted between July 1, 2012, and June 30, 2014. Postmortem human hippocampus tissue samples were obtained from 8patients with schizophrenia, 8 patients with bipolar disorder, and 8 healthy control participants matched for age, sex, postmortem interval, and other potential confounds from the Harvard Brain Tissue Resource Center, McLean Hospital, Belmont,Massachusetts. We extracted DNA from laser-microdissected stratum oriens tissue of cornu ammonis 2/3 (CA2/3) and CA1 postmortem human hippocampus, bisulfite modified it, and assessed it with the Infinium HumanMethylation450 BeadChip (Illumina, Inc). The subset of CpG loci associated with GAD1 regulatory network genes was analyzed in R version 3.1.0 software (R Foundation) using the minfi package. Findings were validated using bisulfite pyrosequencing. MAIN OUTCOMES AND MEASURES Methylation levels at 1308 GAD1 regulatory network–associated CpG loci were assessed both as individual sites to identify differentially methylated positions and by sharing

Demodulation Radio Frequency Interference Effects in Operational Amplifier Circuits

Science.gov (United States)

Sutu, Yue-Hong

A series of investigations have been carried out to determine RFI effects in analog circuits using monolithic integrated operational amplifiers (op amps) as active devices. The specific RFI effect investigated is how amplitude-modulated (AM) RF signals are demodulated in op amp circuits to produce undesired low frequency responses at AM-modulation frequency. The undesired demodulation responses were shown to be characterized by a second-order nonlinear transfer function. Four representative op amp types investigated were the 741 bipolar op amp, the LM10 bipolar op amp, the LF355 JFET-Bipolar op amp, and the CA081 MOS-Bipolar op amp. Two op amp circuits were investigated. The first circuit was a noninverting unity voltage gain buffer circuit. The second circuit was an inverting op amp configuration. In the second circuit, the investigation includes the effects of an RFI suppression capacitor in the feedback path. Approximately 30 units of each op amp type were tested to determine the statistical variations of RFI demodulation effects in the two op amp circuits. The Nonlinear Circuit Analysis Program, NCAP, was used to simulate the demodulation RFI response. In the simulation, the op amp was replaced with its incremental macromodel. Values of macromodel parameters were obtained from previous investigations and manufacturer's data sheets. Some key results of this work are: (1) The RFI demodulation effects are 10 to 20 dB lower in CA081 and LF355 FET-bipolar op amp than in 741 and LM10 bipolar op amp except above 40 MHz where the LM10 RFI response begins to approach that of CA081. (2) The experimental mean values for 30 741 op amps show that RFI demodulation responses in the inverting amplifier with a 27 pF feedback capacitor were suppressed from 10 to 35 dB over the RF frequency range 0.1 to 150 MHz except at 0.15 MHz where only 3.5 dB suppression was observed. (3) The NCAP program can predict RFI demodulation responses in 741 and LF355 unity gain buffer circuits

Chaos and multi-scroll attractors in RCL-shunted junction coupled Jerk circuit connected by memristor.

Directory of Open Access Journals (Sweden)

Jun Ma

Full Text Available In this paper, a new four-variable dynamical system is proposed to set chaotic circuit composed of memristor and Josephson junction, and the dependence of chaotic behaviors on nonlinearity is investigated. A magnetic flux-controlled memristor is used to couple with the RCL-shunted junction circuit, and the dynamical behaviors can be modulated by changing the coupling intensity between the memristor and the RCL-shunted junction. Bifurcation diagram and Lyapunov exponent are calculated to confirm the emergence of chaos in the improved dynamical system. The outputs and dynamical behaviors can be controlled by the initial setting and external stimulus as well. As a result, chaos can be suppressed and spiking occurs in the sampled outputs under negative feedback, while applying positive feedback type via memristor can be effective to trigger chaos. Furthermore, it is found that the number of multi-attractors in the Jerk circuit can be modulated when memristor coupling is applied on the circuit. These results indicate that memristor coupling can be effective to control chaotic circuits and it is also useful to reproduce dynamical behaviors for neuronal activities.

Isocost Lines Describe the Cellular Economy of Genetic Circuits.

Science.gov (United States)

Gyorgy, Andras; Jiménez, José I; Yazbek, John; Huang, Hsin-Ho; Chung, Hattie; Weiss, Ron; Del Vecchio, Domitilla

2015-08-04

Genetic circuits in living cells share transcriptional and translational resources that are available in limited amounts. This leads to unexpected couplings among seemingly unconnected modules, which result in poorly predictable circuit behavior. In this study, we determine these interdependencies between products of different genes by characterizing the economy of how transcriptional and translational resources are allocated to the production of proteins in genetic circuits. We discover that, when expressed from the same plasmid, the combinations of attainable protein concentrations are constrained by a linear relationship, which can be interpreted as an isocost line, a concept used in microeconomics. We created a library of circuits with two reporter genes, one constitutive and the other inducible in the same plasmid, without a regulatory path between them. In agreement with the model predictions, experiments reveal that the isocost line rotates when changing the ribosome binding site strength of the inducible gene and shifts when modifying the plasmid copy number. These results demonstrate that isocost lines can be employed to predict how genetic circuits become coupled when sharing resources and provide design guidelines for minimizing the effects of such couplings. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Nonlatching positive feedback enables robust bimodality by decoupling expression noise from the mean

Energy Technology Data Exchange (ETDEWEB)

Razooky, Brandon S. [Rockefeller Univ., New York, NY (United States). Lab. of Virology and Infectious Disease; Gladstone Institutes (Virology and Immunology), San Francisco, CA (United States); Univ. of California, San Francisco, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Univ. of Tennessee, Knoxville, TN (United States). Bredesen Center for Interdisciplinary; Cao, Youfang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hansen, Maike M. K. [Gladstone Institutes (Virology and Immunology), San Francisco, CA (United States); Perelson, Alan S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Simpson, Michael L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Univ. of Tennessee, Knoxville, TN (United States). Bredesen Center for Interdisciplinary; Weinberger, Leor S. [Gladstone Institutes (Virology and Immunology), San Francisco, CA (United States); Univ. of California, San Francisco, CA (United States). Dept. of Biochemistry and Biophysics; Univ. of California, San Francisco, CA (United States). QB3: California Inst. of Quantitative Biosciences; Univ. of California, San Francisco, CA (United States). Dept. of Pharmaceutical Chemistry

2017-10-18

Fundamental to biological decision-making is the ability to generate bimodal expression patterns where two alternate expression states simultaneously exist. Here in this study, we use a combination of single-cell analysis and mathematical modeling to examine the sources of bimodality in the transcriptional program controlling HIV’s fate decision between active replication and viral latency. We find that the HIV Tat protein manipulates the intrinsic toggling of HIV’s promoter, the LTR, to generate bimodal ON-OFF expression, and that transcriptional positive feedback from Tat shifts and expands the regime of LTR bimodality. This result holds for both minimal synthetic viral circuits and full-length virus. Strikingly, computational analysis indicates that the Tat circuit’s non-cooperative ‘non-latching’ feedback architecture is optimized to slow the promoter’s toggling and generate bimodality by stochastic extinction of Tat. In contrast to the standard Poisson model, theory and experiment show that non-latching positive feedback substantially dampens the inverse noise-mean relationship to maintain stochastic bimodality despite increasing mean-expression levels. Given the rapid evolution of HIV, the presence of a circuit optimized to robustly generate bimodal expression appears consistent with the hypothesis that HIV’s decision between active replication and latency provides a viral fitness advantage. More broadly, the results suggest that positive-feedback circuits may have evolved not only for signal amplification but also for robustly generating bimodality by decoupling expression fluctuations (noise) from mean expression levels.

Dichotomous noise models of gene switches

Energy Technology Data Exchange (ETDEWEB)

Potoyan, Davit A., E-mail: potoyan@rice.edu; Wolynes, Peter G., E-mail: pwolynes@rice.edu [Department of Chemistry and Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005 (United States)

2015-11-21

Molecular noise in gene regulatory networks has two intrinsic components, one part being due to fluctuations caused by the birth and death of protein or mRNA molecules which are often present in small numbers and the other part arising from gene state switching, a single molecule event. Stochastic dynamics of gene regulatory circuits appears to be largely responsible for bifurcations into a set of multi-attractor states that encode different cell phenotypes. The interplay of dichotomous single molecule gene noise with the nonlinear architecture of genetic networks generates rich and complex phenomena. In this paper, we elaborate on an approximate framework that leads to simple hybrid multi-scale schemes well suited for the quantitative exploration of the steady state properties of large-scale cellular genetic circuits. Through a path sum based analysis of trajectory statistics, we elucidate the connection of these hybrid schemes to the underlying master equation and provide a rigorous justification for using dichotomous noise based models to study genetic networks. Numerical simulations of circuit models reveal that the contribution of the genetic noise of single molecule origin to the total noise is significant for a wide range of kinetic regimes.

Performance of an X-ray spectroscopic system based on a double-gate double-feedback charge preamplifier

CERN Document Server

Fazzi, A

2000-01-01

The performance of a near room temperature X-ray spectroscopic system is reported. The system is based on a charge preamplifier with the first transistor having two separated gates. The preamplifier operates in a continuous reset mode without any physical resistor connected to the input node. The leakage current and the current due to the rate of X-rays is neutralized by an average current of holes, flowing under the control of an additional feedback, from the bottom to the top gate. The preamplifier is followed by a simple circuit which exactly cancels the long tail of the impulse response of a pure double-gate preamplifier. The compensation of this tail, due to the very principle of the preamplifier's continuous reset through the double-gate mechanism, improves substantially the high-rate performance of the system. The preamplifier based on a commercially available double-gate front JFET MX-40 (MOXTEK) coupled to a silicon drift detector produced at BNL achieved ENC of 13 electrons at -30 deg. C. The analys...

Nonlinear dynamics based digital logic and circuits.

Science.gov (United States)

Kia, Behnam; Lindner, John F; Ditto, William L

2015-01-01

We discuss the role and importance of dynamics in the brain and biological neural networks and argue that dynamics is one of the main missing elements in conventional Boolean logic and circuits. We summarize a simple dynamics based computing method, and categorize different techniques that we have introduced to realize logic, functionality, and programmability. We discuss the role and importance of coupled dynamics in networks of biological excitable cells, and then review our simple coupled dynamics based method for computing. In this paper, for the first time, we show how dynamics can be used and programmed to implement computation in any given base, including but not limited to base two.

Cycles of self-pulsations in a photonic integrated circuit.

Science.gov (United States)

Karsaklian Dal Bosco, Andreas; Kanno, Kazutaka; Uchida, Atsushi; Sciamanna, Marc; Harayama, Takahisa; Yoshimura, Kazuyuki

2015-12-01

We report experimentally on the bifurcation cascade leading to the appearance of self-pulsation in a photonic integrated circuit in which a laser diode is subjected to delayed optical feedback. We study the evolution of the self-pulsing frequency with the increase of both the feedback strength and the injection current. Experimental observations show good qualitative accordance with numerical results carried out with the Lang-Kobayashi rate equation model. We explain the mechanism underlying the self-pulsations by a phenomenon of beating between successive pairs of external cavity modes and antimodes.

Student generated assignments about electrical circuits in a computer simulation

NARCIS (Netherlands)

Vreman-de Olde, Cornelise; de Jong, Anthonius J.M.

2004-01-01

In this study we investigated the design of assignments by students as a knowledge-generating activity. Students were required to design assignments for 'other students' in a computer simulation environment about electrical circuits. Assignments consisted of a question, alternatives, and feedback on

Review of Polynomial Chaos-Based Methods for Uncertainty Quantification in Modern Integrated Circuits

Directory of Open Access Journals (Sweden)

Arun Kaintura

2018-02-01

Full Text Available Advances in manufacturing process technology are key ensembles for the production of integrated circuits in the sub-micrometer region. It is of paramount importance to assess the effects of tolerances in the manufacturing process on the performance of modern integrated circuits. The polynomial chaos expansion has emerged as a suitable alternative to standard Monte Carlo-based methods that are accurate, but computationally cumbersome. This paper provides an overview of the most recent developments and challenges in the application of polynomial chaos-based techniques for uncertainty quantification in integrated circuits, with particular focus on high-dimensional problems.

Automatic medical image annotation and keyword-based image retrieval using relevance feedback.

Science.gov (United States)

Ko, Byoung Chul; Lee, JiHyeon; Nam, Jae-Yeal

2012-08-01

This paper presents novel multiple keywords annotation for medical images, keyword-based medical image retrieval, and relevance feedback method for image retrieval for enhancing image retrieval performance. For semantic keyword annotation, this study proposes a novel medical image classification method combining local wavelet-based center symmetric-local binary patterns with random forests. For keyword-based image retrieval, our retrieval system use the confidence score that is assigned to each annotated keyword by combining probabilities of random forests with predefined body relation graph. To overcome the limitation of keyword-based image retrieval, we combine our image retrieval system with relevance feedback mechanism based on visual feature and pattern classifier. Compared with other annotation and relevance feedback algorithms, the proposed method shows both improved annotation performance and accurate retrieval results.

LHC beam stability and feedback control

Energy Technology Data Exchange (ETDEWEB)

Steinhagen, Ralph

2007-07-20

This report presents the stability and the control of the Large Hadron Collider's (LHC) two beam orbits and their particle momenta using beam-based feedback systems. The aim of this report is to contribute to a safe and reliable LHC commissioning and machine operation. The first part of the analysis gives an estimate of the expected sources of orbit and energy perturbations that can be grouped into environmental sources, machine-inherent sources and machine element failures: the slowest perturbation due to ground motion, tides, temperature fluctuations of the tunnel and other environmental influences are described in this report by a propagation model that is both qualitatively and quantitatively supported by geophone and beam motion measurements at LEP and other CERN accelerators. The second part of this analysis deals with the control of the two LHC beams' orbit and energy through automated feedback systems. Based on the reading of the more than 1056 beam position monitors (BPMs) that are distributed over the machine, a central global feedback controller calculates new deflection strengths for the more than 1060 orbit corrector magnets (CODs) that are suitable to correct the orbit and momentum around their references. this report provides an analysis of the BPMs and CODs involved in the orbit and energy feedback. The BPMs are based on a wide-band time normaliser circuit that converts the transverse beam position reading of each individual particle bunch into two laser pulses that are separated by a time delay and transmitted through optical fibres to an acquisition card that converts the delay signals into a digital position. A simple error model has been tested and compared to the measurement accuracy of LHC type BPMs, obtained through beam-based measurements in the SPS. The average beam position is controlled through 1060 superconducting and individually powered corrector dipole magnets. The proposed correction in 'time-domain' consists of a

CMOS based capacitance to digital converter circuit for MEMS sensor

Science.gov (United States)

Rotake, D. R.; Darji, A. D.

2018-02-01

Most of the MEMS cantilever based system required costly instruments for characterization, processing and also has large experimental setups which led to non-portable device. So there is a need of low cost, highly sensitive, high speed and portable digital system. The proposed Capacitance to Digital Converter (CDC) interfacing circuit converts capacitance to digital domain which can be easily processed. Recent demand microcantilever deflection is part per trillion ranges which change the capacitance in 1-10 femto farad (fF) range. The entire CDC circuit is designed using CMOS 250nm technology. Design of CDC circuit consists of a D-latch and two oscillators, namely Sensor controlled oscillator (SCO) and digitally controlled oscillator (DCO). The D-latch is designed using transmission gate based MUX for power optimization. A CDC design of 7-stage, 9-stage and 11-stage tested for 1-18 fF and simulated using mentor graphics Eldo tool with parasitic. Since the proposed design does not use resistance component, the total power dissipation is reduced to 2.3621 mW for CDC designed using 9-stage SCO and DCO.

Synthetic Biology: A Unifying View and Review Using Analog Circuits.

Science.gov (United States)

Teo, Jonathan J Y; Woo, Sung Sik; Sarpeshkar, Rahul

2015-08-01

We review the field of synthetic biology from an analog circuits and analog computation perspective, focusing on circuits that have been built in living cells. This perspective is well suited to pictorially, symbolically, and quantitatively representing the nonlinear, dynamic, and stochastic (noisy) ordinary and partial differential equations that rigorously describe the molecular circuits of synthetic biology. This perspective enables us to construct a canonical analog circuit schematic that helps unify and review the operation of many fundamental circuits that have been built in synthetic biology at the DNA, RNA, protein, and small-molecule levels over nearly two decades. We review 17 circuits in the literature as particular examples of feedforward and feedback analog circuits that arise from special topological cases of the canonical analog circuit schematic. Digital circuit operation of these circuits represents a special case of saturated analog circuit behavior and is automatically incorporated as well. Many issues that have prevented synthetic biology from scaling are naturally represented in analog circuit schematics. Furthermore, the deep similarity between the Boltzmann thermodynamic equations that describe noisy electronic current flow in subthreshold transistors and noisy molecular flux in biochemical reactions has helped map analog circuit motifs in electronics to analog circuit motifs in cells and vice versa via a `cytomorphic' approach. Thus, a body of knowledge in analog electronic circuit design, analysis, simulation, and implementation may also be useful in the robust and efficient design of molecular circuits in synthetic biology, helping it to scale to more complex circuits in the future.

Using circuit theory to model connectivity in ecology, evolution, and conservation.

Science.gov (United States)

McRae, Brad H; Dickson, Brett G; Keitt, Timothy H; Shah, Viral B

2008-10-01

Connectivity among populations and habitats is important for a wide range of ecological processes. Understanding, preserving, and restoring connectivity in complex landscapes requires connectivity models and metrics that are reliable, efficient, and process based. We introduce a new class of ecological connectivity models based in electrical circuit theory. Although they have been applied in other disciplines, circuit-theoretic connectivity models are new to ecology. They offer distinct advantages over common analytic connectivity models, including a theoretical basis in random walk theory and an ability to evaluate contributions of multiple dispersal pathways. Resistance, current, and voltage calculated across graphs or raster grids can be related to ecological processes (such as individual movement and gene flow) that occur across large population networks or landscapes. Efficient algorithms can quickly solve networks with millions of nodes, or landscapes with millions of raster cells. Here we review basic circuit theory, discuss relationships between circuit and random walk theories, and describe applications in ecology, evolution, and conservation. We provide examples of how circuit models can be used to predict movement patterns and fates of random walkers in complex landscapes and to identify important habitat patches and movement corridors for conservation planning.

A dynamic-biased dual-loop-feedback CMOS LDO regulator with fast transient response

International Nuclear Information System (INIS)

Wang Han; Sun Maomao

2014-01-01

This paper presents a low-dropout regulator (LDO) for portable applications with dual-loop feedback and a dynamic bias circuit. The dual-loop feedback structure is adopted to reduce the output voltage spike and the response time of the LDO. The dynamic bias circuit enhances the slew rate at the gate of the power transistor. In addition, an adaptive miller compensation technique is employed, from which a single pole system is realized and over a 59° phase margin is achieved under the full range of the load current. The proposed LDO has been implemented in a 0.6-μm CMOS process. From the experimental results, the regulator can operate with a minimum dropout voltage of 200 mV at a maximum 300 mA load and I Q of 113 μA. The line regulation and load regulation are improved to 0.1 mV/V and 3.4 μV/mA due to the sufficient loop gain provided by the dual feedback loops. Under a full range load current step, the voltage spikes and the recovery time of the proposed LDO is reduced to 97 mV and 0.142 μs respectively. (semiconductor integrated circuits)

Multiple-valued logic design based on the multiple-peak BiCMOS-NDR circuits

Directory of Open Access Journals (Sweden)

Kwang-Jow Gan

2016-06-01

Full Text Available Three different multiple-valued logic (MVL designs using the multiple-peak negative-differential-resistance (NDR circuits are investigated. The basic NDR element, which is made of several Si-based metal-oxide-semiconductor field-effect-transistor (MOS and SiGe-based heterojunction-bipolar-transistor (HBT devices, can be implemented by using a standard BiCMOS process. These MVL circuits are designed based on the triggering-pulse control, saw-tooth input signal, and peak-control methods, respectively. However, there are some transient states existing between the multiple stable levels for the first two methods. These states might affect the circuit function in practical application. As a result, our proposed peak-control method for the MVL design can be used to overcome these transient states.

DC feedback for wide band frequency fixed current source

Directory of Open Access Journals (Sweden)

Aoday Hashim Mohamad Al-Rawi

2013-03-01

Full Text Available Alternating current sources are mainly used in bioelectrical impedance devices. Nowadays 50 – 100 kHz bioelectrical impedance devices are commonly used for body composition analysis. High frequency bioelectrical impedance analysis devices are mostly used in bioimpedance tomography and blood analysis. High speed op-amps and voltage comparators are used in this circuit. Direct current feedback is used to prevent delay. An N-Channel J-FET transistor was used to establish the voltage controlled gain amplifier (VCG. A sine wave signal has been applied as input voltage. The value of this signal should be constant in 170 mV rms to keep the output current in about 1 mA rms. Four frequencies; 100 kHz, 1 MHz, 2 MHz and 3.2 MHz were applied to the circuit and the current was measured for different load resistances. The results showed that the current was stable for changes in the resistor load, bouncing around an average point as a result of bouncing DC feedback.

Integrated circuit-based electrochemical sensor for spatially resolved detection of redox-active metabolites in biofilms.

Science.gov (United States)

Bellin, Daniel L; Sakhtah, Hassan; Rosenstein, Jacob K; Levine, Peter M; Thimot, Jordan; Emmett, Kevin; Dietrich, Lars E P; Shepard, Kenneth L

2014-01-01

Despite advances in monitoring spatiotemporal expression patterns of genes and proteins with fluorescent probes, direct detection of metabolites and small molecules remains challenging. A technique for spatially resolved detection of small molecules would benefit the study of redox-active metabolites that are produced by microbial biofilms and can affect their development. Here we present an integrated circuit-based electrochemical sensing platform featuring an array of working electrodes and parallel potentiostat channels. 'Images' over a 3.25 × 0.9 mm(2) area can be captured with a diffusion-limited spatial resolution of 750 μm. We demonstrate that square wave voltammetry can be used to detect, identify and quantify (for concentrations as low as 2.6 μM) four distinct redox-active metabolites called phenazines. We characterize phenazine production in both wild-type and mutant Pseudomonas aeruginosa PA14 colony biofilms, and find correlations with fluorescent reporter imaging of phenazine biosynthetic gene expression.

Q-factor enhancement for self-actuated self-sensing piezoelectric MEMS resonators applying a lock-in driven feedback loop

International Nuclear Information System (INIS)

Kucera, M; Bittner, A; Schmid, U; Manzaneque, T; Sánchez-Rojas, J L

2013-01-01

This paper presents a robust Q-control approach based on an all-electrical feedback loop enhancing the quality factor of a resonant microstructure by using the self-sensing capability of a piezoelectric thin film actuator made of aluminium nitride. A lock-in amplifier is used to extract the feedback signal which is proportional to the piezoelectric current. The measured real part is used to replace the originally low-quality and noisy feedback signal to modulate the driving voltage of the piezoelectric thin-film actuator. Since the lock-in amplifier reduces the noise in the feedback signal substantially, the proposed enhancement loop avoids the disadvantage of a constant signal-to-noise ratio, which an analogue feedback circuit usually suffers from. The quality factor was increased from the intrinsic value of 1766 to a maximum of 34 840 in air. These promising results facilitate precise measurements for self-actuated and self-sensing MEMS cantilevers even when operated in static viscous media. (paper)

ttm-1 encodes CDF transporters that excrete zinc from intestinal cells of C. elegans and act in a parallel negative feedback circuit that promotes homeostasis.

Directory of Open Access Journals (Sweden)

Hyun Cheol Roh

2013-05-01

Full Text Available Zinc is an essential metal involved in a wide range of biological processes, and aberrant zinc metabolism is implicated in human diseases. The gastrointestinal tract of animals is a critical site of zinc metabolism that is responsible for dietary zinc uptake and distribution to the body. However, the role of the gastrointestinal tract in zinc excretion remains unclear. Zinc transporters are key regulators of zinc metabolism that mediate the movement of zinc ions across membranes. Here, we identified a comprehensive list of 14 predicted Cation Diffusion Facilitator (CDF family zinc transporters in Caenorhabditis elegans and demonstrated that zinc is excreted from intestinal cells by one of these CDF proteins, TTM-1B. The ttm-1 locus encodes two transcripts, ttm-1a and ttm-1b, that use different transcription start sites. ttm-1b expression was induced by high levels of zinc specifically in intestinal cells, whereas ttm-1a was not induced by zinc. TTM-1B was localized to the apical plasma membrane of intestinal cells, and analyses of loss-of-function mutant animals indicated that TTM-1B promotes zinc excretion into the intestinal lumen. Zinc excretion mediated by TTM-1B contributes to zinc detoxification. These observations indicate that ttm-1 is a component of a negative feedback circuit, since high levels of cytoplasmic zinc increase ttm-1b transcript levels and TTM-1B protein functions to reduce the level of cytoplasmic zinc. We showed that TTM-1 isoforms function in tandem with CDF-2, which is also induced by high levels of cytoplasmic zinc and reduces cytoplasmic zinc levels by sequestering zinc in lysosome-related organelles. These findings define a parallel negative feedback circuit that promotes zinc homeostasis and advance the understanding of the physiological roles of the gastrointestinal tract in zinc metabolism in animals.

Pilot study of a 'RIME'-based tool for giving feedback in a multi-specialty longitudinal clerkship.

Science.gov (United States)

DeWitt, Dawn; Carline, Jan; Paauw, Douglas; Pangaro, Louis

2008-12-01

The Reporter-Interpreter-Manager-Educator (RIME) evaluation framework is intuitive and reliable. Our preceptors' frustration with using summative tools for formative feedback and the hypothesis that the RIME vocabulary might improve students' and preceptors' experiences with feedback prompted us to develop and pilot a RIME-based feedback tool. The tool was based on the RIME vocabulary, which has previously been used for evaluation. As interpersonal skills and professionalism are difficult areas in which to give feedback, we added these as explicit categories. We piloted the tool in a longitudinal, 5-month, multi-specialty clerkship. Preceptors completed pre- and post-introductory workshop surveys. Students completed post-workshop and post-clerkship surveys. Preceptors (n = 14) and students (n = 8) preferred RIME-based feedback to 'usual feedback' (previously given using end-of-clerkship evaluation forms). After the initial workshop, preceptors expected that giving feedback, including critical feedback, would be easier. After the 5-month clerkship, students reported receiving more feedback than in previous clerkships and rated feedback given using this tool more highly (P = 0.002; effect size 1.2). Students also felt it helped them understand specifically how to improve their performance (P = 0.003; effect size 1.2). In this pilot study, preceptors and students preferred feedback with a specific RIME-based tool. Students felt such feedback was more useful and helped them identify specifically how to improve. Whether this method can improve student performance through improved feedback remains an area for further research.

The Effect of Emotional Feedback on Behavioral Intention to Use Computer Based Assessment

Science.gov (United States)

Terzis, Vasileios; Moridis, Christos N.; Economides, Anastasios A.

2012-01-01

This study introduces emotional feedback as a construct in an acceptance model. It explores the effect of emotional feedback on behavioral intention to use Computer Based Assessment (CBA). A female Embodied Conversational Agent (ECA) with empathetic encouragement behavior was displayed as emotional feedback. More specifically, this research aims…

Approximate circuits for increased reliability

Science.gov (United States)

Hamlet, Jason R.; Mayo, Jackson R.

2015-08-18

Embodiments of the invention describe a Boolean circuit having a voter circuit and a plurality of approximate circuits each based, at least in part, on a reference circuit. The approximate circuits are each to generate one or more output signals based on values of received input signals. The voter circuit is to receive the one or more output signals generated by each of the approximate circuits, and is to output one or more signals corresponding to a majority value of the received signals. At least some of the approximate circuits are to generate an output value different than the reference circuit for one or more input signal values; however, for each possible input signal value, the majority values of the one or more output signals generated by the approximate circuits and received by the voter circuit correspond to output signal result values of the reference circuit.

Rail-to-rail low-power fully differential OTA utilizing adaptive biasing and partial feedback

DEFF Research Database (Denmark)

Tuan Vu, Cao; Wisland, Dag T.; Lande, Tor Sverre

consumption. The DC-gain of the proposed OTA is improved by adding a partial feedback loop. A Common-Mode Feedback (CMFB) circuit is required for fully differential rail-to-rail operation. Simulations show that the OTA topology has a low stand-by power consumption of 96μW and a high FoM of 3.84 [(V...

Synchronous long-term oscillations in a synthetic gene circuit.

Science.gov (United States)

Potvin-Trottier, Laurent; Lord, Nathan D; Vinnicombe, Glenn; Paulsson, Johan

2016-10-27

Synthetically engineered genetic circuits can perform a wide variety of tasks but are generally less accurate than natural systems. Here we revisit the first synthetic genetic oscillator, the repressilator, and modify it using principles from stochastic chemistry in single cells. Specifically, we sought to reduce error propagation and information losses, not by adding control loops, but by simply removing existing features. We show that this modification created highly regular and robust oscillations. Furthermore, some streamlined circuits kept 14 generation periods over a range of growth conditions and kept phase for hundreds of generations in single cells, allowing cells in flasks and colonies to oscillate synchronously without any coupling between them. Our results suggest that even the simplest synthetic genetic networks can achieve a precision that rivals natural systems, and emphasize the importance of noise analyses for circuit design in synthetic biology.

Modelling of optoelectronic circuits based on resonant tunneling diodes

Science.gov (United States)

Rei, João. F. M.; Foot, James A.; Rodrigues, Gil C.; Figueiredo, José M. L.

2017-08-01

Resonant tunneling diodes (RTDs) are the fastest pure electronic semiconductor devices at room temperature. When integrated with optoelectronic devices they can give rise to new devices with novel functionalities due to their highly nonlinear properties and electrical gain, with potential applications in future ultra-wide-band communication systems (see e.g. EU H2020 iBROW Project). The recent coverage on these devices led to the need to have appropriated simulation tools. In this work, we present RTD based optoelectronic circuits simulation packages to provide circuit signal level analysis such as transient and frequency responses. We will present and discuss the models, and evaluate the simulation packages.

Wavy Channel TFT-Based Digital Circuits

KAUST Repository

Hanna, Amir

2016-02-23

We report a wavy channel (WC) architecture thin-film transistor-based digital circuitry using ZnO as a channel material. The novel architecture allows for extending device width by integrating vertical finlike substrate corrugations giving rise to 50% larger device width, without occupying extra chip area. The enhancement in the output drive current is 100%, when compared with conventional planar architecture for devices occupying the same chip area. The current increase is attributed to both the extra device width and 50% enhancement in field-effect mobility due to electrostatic gating effects. Fabricated inverters show that WC inverters can achieve two times the peak-to-peak output voltage for the same input when compared with planar devices. In addition, WC inverters show 30% faster rise and fall times, and can operate up to around two times frequency of the planar inverters for the same peak-to-peak output voltage. WC NOR circuits have shown 70% higher peak-to-peak output voltage, over their planar counterparts, and WC pass transistor logic multiplexer circuit has shown more than five times faster high-to-low propagation delay compared with its planar counterpart at a similar peak-to-peak output voltage.

Wavy Channel TFT-Based Digital Circuits

KAUST Repository

Hanna, Amir; Hussain, Aftab M.; Hussain, Aftab M.; Hussain, Aftab M.; Omran, Hesham; Alsharif, Sarah M.; Salama, Khaled N.; Hussain, Muhammad Mustafa

2016-01-01

We report a wavy channel (WC) architecture thin-film transistor-based digital circuitry using ZnO as a channel material. The novel architecture allows for extending device width by integrating vertical finlike substrate corrugations giving rise to 50% larger device width, without occupying extra chip area. The enhancement in the output drive current is 100%, when compared with conventional planar architecture for devices occupying the same chip area. The current increase is attributed to both the extra device width and 50% enhancement in field-effect mobility due to electrostatic gating effects. Fabricated inverters show that WC inverters can achieve two times the peak-to-peak output voltage for the same input when compared with planar devices. In addition, WC inverters show 30% faster rise and fall times, and can operate up to around two times frequency of the planar inverters for the same peak-to-peak output voltage. WC NOR circuits have shown 70% higher peak-to-peak output voltage, over their planar counterparts, and WC pass transistor logic multiplexer circuit has shown more than five times faster high-to-low propagation delay compared with its planar counterpart at a similar peak-to-peak output voltage.

Wavelet-Based Feature Extraction in Fault Diagnosis for Biquad High-Pass Filter Circuit

OpenAIRE

Yuehai Wang; Yongzheng Yan; Qinyong Wang

2016-01-01

Fault diagnosis for analog circuit has become a prominent factor in improving the reliability of integrated circuit due to its irreplaceability in modern integrated circuits. In fact fault diagnosis based on intelligent algorithms has become a popular research topic as efficient feature extraction and selection are a critical and intricate task in analog fault diagnosis. Further, it is extremely important to propose some general guidelines for the optimal feature extraction and selection. In ...

FPGA based mixed-signal circuit novel testing techniques

International Nuclear Information System (INIS)

Pouros, Sotirios; Vassios, Vassilios; Papakostas, Dimitrios; Hristov, Valentin

2013-01-01

Electronic circuits fault detection techniques, especially on modern mixed-signal circuits, are evolved and customized around the world to meet the industry needs. The paper presents techniques used on fault detection in mixed signal circuits. Moreover, the paper involves standardized methods, along with current innovations for external testing like Design for Testability (DfT) and Built In Self Test (BIST) systems. Finally, the research team introduces a circuit implementation scheme using FPGA

A fast circuit analysis program based on microcomputer

International Nuclear Information System (INIS)

Hu Guoji

1988-01-01

A fast circuit analysis program (FCAP) is introduced. The program may be used to analyse DC operating point, frequency and transient response of fast circuit. The feature is that the model of active element is not specified. Users may choose one of many equivalent circuits. Written in FORTRAN 77, FCAP can be run on IBM PC and its compatible computers. It can be used as an assistant tool of analysis and design for fast circuits

Monolithic microwave integrated circuits for sensors, radar, and communications systems; Proceedings of the Meeting, Orlando, FL, Apr. 2-4, 1991

Science.gov (United States)

Leonard, Regis F.; Bhasin, Kul B.

Consideration is given to MMICs for airborne phased arrays, monolithic GaAs integrated circuit millimeter wave imaging sensors, accurate design of multiport low-noise MMICs up to 20 GHz, an ultralinear low-noise amplifier technology for space communications, variable-gain MMIC module for space applications, a high-efficiency dual-band power amplifier for radar applications, a high-density circuit approach for low-cost MMIC circuits, coplanar SIMMWIC circuits, recent advances in monolithic phased arrays, and system-level integrated circuit development for phased-array antenna applications. Consideration is also given to performance enhancement in future communications satellites with MMIC technology insertion, application of Ka-band MMIC technology for an Orbiter/ACTS communications experiment, a space-based millimeter wave debris tracking radar, low-noise high-yield octave-band feedback amplifiers to 20 GHz, quasi-optical MESFET VCOs, and a high-dynamic-range mixer using novel balun structure. (For individual items see A93-25777 to A93-25814)

Universal power transistor base drive control unit

Science.gov (United States)

Gale, Allan R.; Gritter, David J.

1988-01-01

A saturation condition regulator system for a power transistor which achieves the regulation objectives of a Baker clamp but without dumping excess base drive current into the transistor output circuit. The base drive current of the transistor is sensed and used through an active feedback circuit to produce an error signal which modulates the base drive current through a linearly operating FET. The collector base voltage of the power transistor is independently monitored to develop a second error signal which is also used to regulate base drive current. The current-sensitive circuit operates as a limiter. In addition, a fail-safe timing circuit is disclosed which automatically resets to a turn OFF condition in the event the transistor does not turn ON within a predetermined time after the input signal transition.

Feedback Linearization Based Arc Length Control for Gas Metal Arc Welding

DEFF Research Database (Denmark)

Thomsen, Jesper Sandberg

2005-01-01

a linear system to be controlled by linear state feedback control. The advantage of using a nonlinear approach as feedback linearization is the ability of this method to cope with nonlinearities and different operating points. However, the model describing the GMAW process is not exact, and therefore......In this paper a feedback linearization based arc length controller for gas metal arc welding (GMAW) is described. A nonlinear model describing the dynamic arc length is transformed into a system where nonlinearities can be cancelled by a nonlinear state feedback control part, and thus, leaving only......, the cancellation of nonlinear terms might give rise to problems with respect to robustness. Robustness of the closed loop system is therefore nvestigated by simulation....

Logic circuits based on molecular spider systems.

Science.gov (United States)

Mo, Dandan; Lakin, Matthew R; Stefanovic, Darko

2016-08-01

Spatial locality brings the advantages of computation speed-up and sequence reuse to molecular computing. In particular, molecular walkers that undergo localized reactions are of interest for implementing logic computations at the nanoscale. We use molecular spider walkers to implement logic circuits. We develop an extended multi-spider model with a dynamic environment wherein signal transmission is triggered via localized reactions, and use this model to implement three basic gates (AND, OR, NOT) and a cascading mechanism. We develop an algorithm to automatically generate the layout of the circuit. We use a kinetic Monte Carlo algorithm to simulate circuit computations, and we analyze circuit complexity: our design scales linearly with formula size and has a logarithmic time complexity. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Design of EAST LHCD high power supply feedback control system based on PLC

International Nuclear Information System (INIS)

Hu Huaichuan; Shan Jiafang

2009-01-01

Design of EAST LHCD -35kV/5.6MW high power supply feedback control system based on PLC is described. Industrial computer and PLC are used to control high power supply in the system. PID arithmetic is adopted to achieve the feedback control of voltage of high power supply. Operating system is base on real-time operating system of QNX. Good controlling properties and reliable protective properties of the feedback control system are proved by the experiment results. (authors)

Analog Circuit Design Optimization Based on Evolutionary Algorithms

Directory of Open Access Journals (Sweden)

Mansour Barari

2014-01-01

Full Text Available This paper investigates an evolutionary-based designing system for automated sizing of analog integrated circuits (ICs. Two evolutionary algorithms, genetic algorithm and PSO (Parswal particle swarm optimization algorithm, are proposed to design analog ICs with practical user-defined specifications. On the basis of the combination of HSPICE and MATLAB, the system links circuit performances, evaluated through specific electrical simulation, to the optimization system in the MATLAB environment, for the selected topology. The system has been tested by typical and hard-to-design cases, such as complex analog blocks with stringent design requirements. The results show that the design specifications are closely met. Comparisons with available methods like genetic algorithms show that the proposed algorithm offers important advantages in terms of optimization quality and robustness. Moreover, the algorithm is shown to be efficient.

A New Simple Chaotic Circuit Based on Memristor

Science.gov (United States)

Wu, Renping; Wang, Chunhua

In this paper, a new memristor is proposed, and then an emulator built from off-the-shelf solid state components imitating the behavior of the proposed memristor is presented. Multisim simulation and breadboard experiment are done on the emulator, exhibiting a pinched hysteresis loop in the voltage-current plane when the emulator is driven by a periodic excitation voltage. In addition, a new simple chaotic circuit is designed by using the proposed memristor and other circuit elements. It is exciting that this circuit with only a linear negative resistor, a capacitor, an inductor and a memristor can generate a chaotic attractor. The dynamical behaviors of the proposed chaotic system are analyzed by Lyapunov exponents, phase portraits and bifurcation diagrams. Finally, an electronic circuit is designed to implement the chaotic system. For the sake of simple circuit topology, the proposed chaotic circuit can be easily manufactured at low cost.

Modeling and Analysis of a Fractional-Order Generalized Memristor-Based Chaotic System and Circuit Implementation

Science.gov (United States)

Yang, Ningning; Xu, Cheng; Wu, Chaojun; Jia, Rong; Liu, Chongxin

2017-12-01

Memristor is a nonlinear “missing circuit element”, that can easily achieve chaotic oscillation. Memristor-based chaotic systems have received more and more attention. Research shows that fractional-order systems are more close to real systems. As an important parameter, the order can increase the flexibility and degree of freedom of the system. In this paper, a fractional-order generalized memristor, which consists of a diode bridge and a parallel circuit with an equivalent unit circuit and a linear resistance, is proposed. Frequency and electrical characteristics of the fractional-order memristor are analyzed. A chain structure circuit is used to implement the fractional-order unit circuit. Then replacing the conventional Chua’s diode by the fractional-order generalized memristor, a fractional-order memristor-based chaotic circuit is proposed. A large amount of research work has been done to investigate the influence of the order on the dynamical behaviors of the fractional-order memristor-based chaotic circuit. Varying with the order, the system enters the chaotic state from the periodic state through the Hopf bifurcation and period-doubling bifurcation. The chaotic state of the system has two types of attractors: single-scroll and double-scroll attractor. The stability theory of fractional-order systems is used to determine the minimum order occurring Hopf bifurcation. And the influence of the initial value on the system is analyzed. Circuit simulations are designed to verify the results of theoretical analysis and numerical simulation.

Ancestral regulatory circuits governing ectoderm patterning downstream of Nodal and BMP2/4 revealed by gene regulatory network analysis in an echinoderm.

Directory of Open Access Journals (Sweden)

Alexandra Saudemont

2010-12-01

Full Text Available Echinoderms, which are phylogenetically related to vertebrates and produce large numbers of transparent embryos that can be experimentally manipulated, offer many advantages for the analysis of the gene regulatory networks (GRN regulating germ layer formation. During development of the sea urchin embryo, the ectoderm is the source of signals that pattern all three germ layers along the dorsal-ventral axis. How this signaling center controls patterning and morphogenesis of the embryo is not understood. Here, we report a large-scale analysis of the GRN deployed in response to the activity of this signaling center in the embryos of the Mediterranean sea urchin Paracentrotus lividus, in which studies with high spatial resolution are possible. By using a combination of in situ hybridization screening, overexpression of mRNA, recombinant ligand treatments, and morpholino-based loss-of-function studies, we identified a cohort of transcription factors and signaling molecules expressed in the ventral ectoderm, dorsal ectoderm, and interposed neurogenic ("ciliary band" region in response to the known key signaling molecules Nodal and BMP2/4 and defined the epistatic relationships between the most important genes. The resultant GRN showed a number of striking features. First, Nodal was found to be essential for the expression of all ventral and dorsal marker genes, and BMP2/4 for all dorsal genes. Second, goosecoid was identified as a central player in a regulatory sub-circuit controlling mouth formation, while tbx2/3 emerged as a critical factor for differentiation of the dorsal ectoderm. Finally, and unexpectedly, a neurogenic ectoderm regulatory circuit characterized by expression of "ciliary band" genes was triggered in the absence of TGF beta signaling. We propose a novel model for ectoderm regionalization, in which neural ectoderm is the default fate in the absence of TGF beta signaling, and suggest that the stomodeal and neural subcircuits that we

Feedback Signal from Motoneurons Influences a Rhythmic Pattern Generator.

Science.gov (United States)

Rotstein, Horacio G; Schneider, Elisa; Szczupak, Lidia

2017-09-20

Motoneurons are not mere output units of neuronal circuits that control motor behavior but participate in pattern generation. Research on the circuit that controls the crawling motor behavior in leeches indicated that motoneurons participate as modulators of this rhythmic motor pattern. Crawling results from successive bouts of elongation and contraction of the whole leech body. In the isolated segmental ganglia, dopamine can induce a rhythmic antiphasic activity of the motoneurons that control contraction (DE-3 motoneurons) and elongation (CV motoneurons). The study was performed in isolated ganglia where manipulation of the activity of specific motoneurons was performed in the course of fictive crawling ( crawling ). In this study, the membrane potential of CV was manipulated while crawling was monitored through the rhythmic activity of DE-3. Matching behavioral observations that show that elongation dominates the rhythmic pattern, the electrophysiological activity of CV motoneurons dominates the cycle. Brief excitation of CV motoneurons during crawling episodes resets the rhythmic activity of DE-3, indicating that CV feeds back to the rhythmic pattern generator. CV hyperpolarization accelerated the rhythm to an extent that depended on the magnitude of the cycle period, suggesting that CV exerted a positive feedback on the unit(s) of the pattern generator that controls the elongation phase. A simple computational model was implemented to test the consequences of such feedback. The simulations indicate that the duty cycle of CV depended on the strength of the positive feedback between CV and the pattern generator circuit. SIGNIFICANCE STATEMENT Rhythmic movements of animals are controlled by neuronal networks that have been conceived as hierarchical structures. At the basis of this hierarchy, we find the motoneurons, few neurons at the top control global aspects of the behavior (e.g., onset, duration); and within these two ends, specific neuronal circuits control

Silicon CMOS optical receiver circuits with integrated thin-film compound semiconductor detectors

Science.gov (United States)

Brooke, Martin A.; Lee, Myunghee; Jokerst, Nan Marie; Camperi-Ginestet, C.

1995-04-01

While many circuit designers have tackled the problem of CMOS digital communications receiver design, few have considered the problem of circuitry suitable for an all CMOS digital IC fabrication process. Faced with a high speed receiver design the circuit designer will soon conclude that a high speed analog-oriented fabrication process provides superior performance advantages to a digital CMOS process. However, for applications where there are overwhelming reasons to integrate the receivers on the same IC as large amounts of conventional digital circuitry, the low yield and high cost of the exotic analog-oriented fabrication is no longer an option. The issues that result from a requirement to use a digital CMOS IC process cut across all aspects of receiver design, and result in significant differences in circuit design philosophy and topology. Digital ICs are primarily designed to yield small, fast CMOS devices for digital logic gates, thus no effort is put into providing accurate or high speed resistances, or capacitors. This lack of any reliable resistance or capacitance has a significant impact on receiver design. Since resistance optimization is not a prerogative of the digital IC process engineer, the wisest option is thus to not use these elements, opting instead for active circuitry to replace the functions normally ascribed to resistance and capacitance. Depending on the application receiver noise may be a dominant design constraint. The noise performance of CMOS amplifiers is different than bipolar or GaAs MESFET circuits, shot noise is generally insignificant when compared to channel thermal noise. As a result the optimal input stage topology is significantly different for the different technologies. It is found that, at speeds of operation approaching the limits of the digital CMOS process, open loop designs have noise-power-gain-bandwidth tradeoff performance superior to feedback designs. Furthermore, the lack of good resisters and capacitors

Logic circuits based on individual semiconducting and metallic carbon-nanotube devices

International Nuclear Information System (INIS)

Ryu, Hyeyeon; Kaelblein, Daniel; Ante, Frederik; Zschieschang, Ute; Kern, Klaus; Klauk, Hagen; Weitz, R Thomas; Schmidt, Oliver G

2010-01-01

Nanoscale transistors employing an individual semiconducting carbon nanotube as the channel hold great potential for logic circuits with large integration densities that can be manufactured on glass or plastic substrates. Carbon nanotubes are usually produced as a mixture of semiconducting and metallic nanotubes. Since only semiconducting nanotubes yield transistors, the metallic nanotubes are typically not utilized. However, integrated circuits often require not only transistors, but also resistive load devices. Here we show that many of the metallic carbon nanotubes that are deposited on the substrate along with the semiconducting nanotubes can be conveniently utilized as load resistors with favorable characteristics for the design of integrated circuits. We also demonstrate the fabrication of arrays of transistors and resistors, each based on an individual semiconducting or metallic carbon nanotube, and their integration on glass substrates into logic circuits with switching frequencies of up to 500 kHz using a custom-designed metal interconnect layer.

Feedforward and feedback inhibition in neostriatal GABAergic spiny neurons.

Science.gov (United States)

Tepper, James M; Wilson, Charles J; Koós, Tibor

2008-08-01

There are two distinct inhibitory GABAergic circuits in the neostriatum. The feedforward circuit consists of a relatively small population of GABAergic interneurons that receives excitatory input from the neocortex and exerts monosynaptic inhibition onto striatal spiny projection neurons. The feedback circuit comprises the numerous spiny projection neurons and their interconnections via local axon collaterals. This network has long been assumed to provide the majority of striatal GABAergic inhibition and to sharpen and shape striatal output through lateral inhibition, producing increased activity in the most strongly excited spiny cells at the expense of their less strongly excited neighbors. Recent results, mostly from recording experiments of synaptically connected pairs of neurons, have revealed that the two GABAergic circuits differ markedly in terms of the total number of synapses made by each, the strength of the postsynaptic response detected at the soma, the extent of presynaptic convergence and divergence and the net effect of the activation of each circuit on the postsynaptic activity of the spiny neuron. These data have revealed that the feedforward inhibition is powerful and widespread, with spiking in a single interneuron being capable of significantly delaying or even blocking the generation of spikes in a large number of postsynaptic spiny neurons. In contrast, the postsynaptic effects of spiking in a single presynaptic spiny neuron on postsynaptic spiny neurons are weak when measured at the soma, and unable to significantly affect spike timing or generation. Further, reciprocity of synaptic connections between spiny neurons is only rarely observed. These results suggest that the bulk of the fast inhibition that has the strongest effects on spiny neuron spike timing comes from the feedforward interneuronal system whereas the axon collateral feedback system acts principally at the dendrites to control local excitability as well as the overall level of

Structure of the EGF receptor transactivation circuit integrates multiple signals with cell context

Energy Technology Data Exchange (ETDEWEB)

Joslin, Elizabeth J.; Shankaran, Harish; Opresko, Lee K.; Bollinger, Nikki; Lauffenburger, Douglas A.; Wiley, H. S.

2010-05-10

Transactivation of the epidermal growth factor receptor (EGFR) has been proposed to be a mechanism by which a variety of cellular inputs can be integrated into a single signaling pathway, but the regulatory topology of this important system is unclear. To understand the transactivation circuit, we first created a “non-binding” reporter for ligand shedding. We then quantitatively defined how signals from multiple agonists were integrated both upstream and downstream of the EGFR into the extracellular signal regulated kinase (ERK) cascade in human mammary epithelial cells. We found that transactivation is mediated by a recursive autocrine circuit where ligand shedding drives EGFR-stimulated ERK that in turn drives further ligand shedding. The time from shedding to ERK activation is fast (<5 min) whereas the recursive feedback is slow (>15 min). Simulations showed that this delay in positive feedback greatly enhanced system stability and robustness. Our results indicate that the transactivation circuit is constructed so that the magnitude of ERK signaling is governed by the sum of multiple direct inputs, while recursive, autocrine ligand shedding controls signal duration.

Integrated circuits and logic operations based on single-layer MoS2.

Science.gov (United States)

Radisavljevic, Branimir; Whitwick, Michael Brian; Kis, Andras

2011-12-27

Logic circuits and the ability to amplify electrical signals form the functional backbone of electronics along with the possibility to integrate multiple elements on the same chip. The miniaturization of electronic circuits is expected to reach fundamental limits in the near future. Two-dimensional materials such as single-layer MoS(2) represent the ultimate limit of miniaturization in the vertical dimension, are interesting as building blocks of low-power nanoelectronic devices, and are suitable for integration due to their planar geometry. Because they are less than 1 nm thin, 2D materials in transistors could also lead to reduced short channel effects and result in fabrication of smaller and more power-efficient transistors. Here, we report on the first integrated circuit based on a two-dimensional semiconductor MoS(2). Our integrated circuits are capable of operating as inverters, converting logical "1" into logical "0", with room-temperature voltage gain higher than 1, making them suitable for incorporation into digital circuits. We also show that electrical circuits composed of single-layer MoS(2) transistors are capable of performing the NOR logic operation, the basis from which all logical operations and full digital functionality can be deduced.

Anterograde transneuronal viral tract tracing reveals central sensory circuits from brown fat and sensory denervation alters its thermogenic responses.

Science.gov (United States)

Vaughan, Cheryl H; Bartness, Timothy J

2012-05-01

Brown adipose tissue (BAT) thermogenic activity and growth are controlled by its sympathetic nervous system (SNS) innervation, but nerve fibers containing sensory-associated neuropeptides [substance P, calcitonin gene-related peptide (CGRP)] also suggest sensory innervation. The central nervous system (CNS) projections of BAT afferents are unknown. Therefore, we used the H129 strain of the herpes simplex virus-1 (HSV-1), an anterograde transneuronal viral tract tracer used to delineate sensory nerve circuits, to define these projections. HSV-1 was injected into interscapular BAT (IBAT) of Siberian hamsters and HSV-1 immunoreactivity (ir) was assessed 24, 48, 72, 96, and 114 h postinjection. The 96- and 114-h groups had the most HSV-1-ir neurons with marked infections in the hypothalamic paraventricular nucleus, periaqueductal gray, olivary areas, parabrachial nuclei, raphe nuclei, and reticular areas. These sites also are involved in sympathetic outflow to BAT suggesting possible BAT sensory-SNS thermogenesis feedback circuits. We tested the functional contribution of IBAT sensory innervation on thermogenic responses to an acute (24 h) cold exposure test by injecting the specific sensory nerve toxin capsaicin directly into IBAT pads and then measuring core (T(c)) and IBAT (T(IBAT)) temperature responses. CGRP content was significantly decreased in capsaicin-treated IBAT demonstrating successful sensory nerve destruction. T(IBAT) and T(c) were significantly decreased in capsaicin-treated hamsters compared with the saline controls at 2 h of cold exposure. Thus the central sensory circuits from IBAT have been delineated for the first time, and impairment of sensory feedback from BAT appears necessary for the appropriate, initial thermogenic response to acute cold exposure.

Coupling a universal DNA circuit with graphene sheets/polyaniline/AuNPs nanocomposites for the detection of BCR/ABL fusion gene

Energy Technology Data Exchange (ETDEWEB)

Chen, Xueping [Key Laboratory of Laboratory Medical Diagnostics of Education, Department of Laboratory Medicine, Chongqing Medical University, Chongqing, 400016 (China); Wang, Li [Key Laboratory of Laboratory Medical Diagnostics of Education, Department of Laboratory Medicine, Chongqing Medical University, Chongqing, 400016 (China); Department of Medical Laboratory, Chongqing Emergency Medical Center (Chongqing The Fourth Hospital), Chongqing, 400016 (China); Sheng, Shangchun [The No.2 Peoples' Hospital of Yibin, Sichuan, 644000 (China); Wang, Teng; Yang, Juan [Key Laboratory of Laboratory Medical Diagnostics of Education, Department of Laboratory Medicine, Chongqing Medical University, Chongqing, 400016 (China); Xie, Guoming, E-mail: guomingxie@cqmu.edu.cn [Key Laboratory of Laboratory Medical Diagnostics of Education, Department of Laboratory Medicine, Chongqing Medical University, Chongqing, 400016 (China); Feng, Wenli, E-mail: fengwlcqmu@sina.com [Key Laboratory of Laboratory Medical Diagnostics of Education, Department of Laboratory Medicine, Chongqing Medical University, Chongqing, 400016 (China)

2015-08-19

This article described a novel method by coupling a universal DNA circuit with graphene sheets/polyaniline/AuNPs nanocomposites (GS/PANI/AuNPs) for highly sensitive and specific detection of BCR/ABL fusion gene (bcr/abl) in chronic myeloid leukemia (CML). DNA circuit known as catalyzed hairpin assembly (CHA) is enzyme-free and can be simply operated to achieve exponential amplification, which has been widely employed in biosensing. However, application of CHA has been hindered by the need of specially redesigned sequences for each single-stranded DNA input. Herein, a transducer hairpin (HP) was designed to obtain a universal DNA circuit with favorable signal-to-background ratio. To further improve signal amplification, GS/PANI/AuNPs with excellent conductivity and enlarged effective area were introduced into this DNA circuit. Consequently, by combining the advantages of CHA and GS/PANI/AuNPs, bcr/abl could be detected in a linear range from 10 pM to 20 nM with a detection limit of 1.05 pM. Moreover, this protocol showed excellent specificity, good stability and was successfully applied for the detection of real sample, which demonstrated its great potential in clinical application. - Highlights: • A transducer hairpin was designed to improve the versatility of DNA circuit. • GS/PANI/AuNPs were introduced to the DNA circuit for further signal amplification. • The established biosensor displayed high sensitivity and good specificity.

Design and Evaluation of Accelerometer based Motional Feedback

DEFF Research Database (Denmark)

Schneider, Henrik; Pranjic, Emilio; Agerkvist, Finn T.

2015-01-01

and enable radical design changes in the loudspeaker which can lead to efficiency improvements. In combination this has motivated a revisit of the accelerometer based motional feedback technique. Experimental results on a 8 inch subwoofer show that the total harmonic distortion can be significantly reduced...

Graphene-based THz modulator analyzed by equivalent circuit model

DEFF Research Database (Denmark)

Xiao, Binggang; Chen, Jing; Xie, Zhiyi

2016-01-01

A terahertz (THz) modulator based on graphene is proposed and analysed by use of equivalent transmission line of a homogeneous mediumand the local anisotropic model of the graphene conductivity. The result calculated by the equivalent circuit is consistent with that obtained byFresnel transfer...

A kind of video image digitizing circuit based on computer parallel port

International Nuclear Information System (INIS)

Wang Yi; Tang Le; Cheng Jianping; Li Yuanjing; Zhang Binquan

2003-01-01

A kind of video images digitizing circuit based on parallel port was developed to digitize the flash x ray images in our Multi-Channel Digital Flash X ray Imaging System. The circuit can digitize the video images and store in static memory. The digital images can be transferred to computer through parallel port and can be displayed, processed and stored. (authors)

The role of feedback in improving the effectiveness of workplace based assessments: a systematic review.

Science.gov (United States)

Saedon, Habiba; Salleh, Shizalia; Balakrishnan, Arun; Imray, Christopher H E; Saedon, Mahmud

2012-05-02

With recent emphasis placed on workplace based assessment (WBA) as a method of formative performance assessment, there is limited evidence in the current literature regarding the role of feedback in improving the effectiveness of WBA. The aim of this systematic review was to elucidate the impact of feedback on the effectiveness of WBA in postgraduate medical training. Searches were conducted using the following bibliographic databases to identify original published studies related to WBA and the role of feedback: Medline (1950-December 2010), Embase (1980-December 2010) and Journals@Ovid (English language only, 1996-December 2010). Studies which attempted to evaluate the role of feedback in WBA involving postgraduate doctors were included. 15 identified studies met the inclusion criteria and minimum quality threshold. They were heterogeneous in methodological design. 7 studies focused on multi source feedback, 3 studies were based on mini-clinical evaluation exercise, 2 looked at procedural based assessment, one study looked at workplace based assessments in general and 2 studies looked at a combination of 3 to 6 workplace based assessments. 7 studies originated from the United Kingdom. Others were from Canada, the United States and New Zealand. Study populations were doctors in various grades of training from a wide range of specialties including general practice, general medicine, general surgery, dermatology, paediatrics and anaesthetics. All studies were prospective in design, and non-comparative descriptive or observational studies using a variety of methods including questionnaires, one to one interviews and focus groups. The evidence base contains few high quality conclusive studies and more studies are required to provide further evidence for the effect of feedback from workplace based assessment on subsequent performance. There is, however, good evidence that if well implemented, feedback from workplace based assessments, particularly multisource feedback

The role of feedback in improving the effectiveness of workplace based assessments: a systematic review

Directory of Open Access Journals (Sweden)

Saedon Habiba

2012-05-01

Full Text Available Abstract Background With recent emphasis placed on workplace based assessment (WBA as a method of formative performance assessment, there is limited evidence in the current literature regarding the role of feedback in improving the effectiveness of WBA. The aim of this systematic review was to elucidate the impact of feedback on the effectiveness of WBA in postgraduate medical training. Methods Searches were conducted using the following bibliographic databases to identify original published studies related to WBA and the role of feedback: Medline (1950-December 2010, Embase (1980-December 2010 and Journals@Ovid (English language only, 1996-December 2010. Studies which attempted to evaluate the role of feedback in WBA involving postgraduate doctors were included. Results 15 identified studies met the inclusion criteria and minimum quality threshold. They were heterogeneous in methodological design. 7 studies focused on multi source feedback, 3 studies were based on mini-clinical evaluation exercise, 2 looked at procedural based assessment, one study looked at workplace based assessments in general and 2 studies looked at a combination of 3 to 6 workplace based assessments. 7 studies originated from the United Kingdom. Others were from Canada, the United States and New Zealand. Study populations were doctors in various grades of training from a wide range of specialties including general practice, general medicine, general surgery, dermatology, paediatrics and anaesthetics. All studies were prospective in design, and non-comparative descriptive or observational studies using a variety of methods including questionnaires, one to one interviews and focus groups. Conclusions The evidence base contains few high quality conclusive studies and more studies are required to provide further evidence for the effect of feedback from workplace based assessment on subsequent performance. There is, however, good evidence that if well implemented, feedback from

Visual motion imagery neurofeedback based on the hMT+/V5 complex: evidence for a feedback-specific neural circuit involving neocortical and cerebellar regions

Science.gov (United States)

Banca, Paula; Sousa, Teresa; Catarina Duarte, Isabel; Castelo-Branco, Miguel

2015-12-01

Objective. Current approaches in neurofeedback/brain-computer interface research often focus on identifying, on a subject-by-subject basis, the neural regions that are best suited for self-driven modulation. It is known that the hMT+/V5 complex, an early visual cortical region, is recruited during explicit and implicit motion imagery, in addition to real motion perception. This study tests the feasibility of training healthy volunteers to regulate the level of activation in their hMT+/V5 complex using real-time fMRI neurofeedback and visual motion imagery strategies. Approach. We functionally localized the hMT+/V5 complex to further use as a target region for neurofeedback. An uniform strategy based on motion imagery was used to guide subjects to neuromodulate hMT+/V5. Main results. We found that 15/20 participants achieved successful neurofeedback. This modulation led to the recruitment of a specific network as further assessed by psychophysiological interaction analysis. This specific circuit, including hMT+/V5, putative V6 and medial cerebellum was activated for successful neurofeedback runs. The putamen and anterior insula were recruited for both successful and non-successful runs. Significance. Our findings indicate that hMT+/V5 is a region that can be modulated by focused imagery and that a specific cortico-cerebellar circuit is recruited during visual motion imagery leading to successful neurofeedback. These findings contribute to the debate on the relative potential of extrinsic (sensory) versus intrinsic (default-mode) brain regions in the clinical application of neurofeedback paradigms. This novel circuit might be a good target for future neurofeedback approaches that aim, for example, the training of focused attention in disorders such as ADHD.

Peptide Logic Circuits Based on Chemoenzymatic Ligation for Programmable Cell Apoptosis.

Science.gov (United States)

Li, Yong; Sun, Sujuan; Fan, Lin; Hu, Shanfang; Huang, Yan; Zhang, Ke; Nie, Zhou; Yao, Shouzhou

2017-11-20

A novel and versatile peptide-based bio-logic system capable of regulating cell function is developed using sortase A (SrtA), a peptide ligation enzyme, as a generic processor. By modular peptide design, we demonstrate that mammalian cells apoptosis can be programmed by peptide-based logic operations, including binary and combination gates (AND, INHIBIT, OR, and AND-INHIBIT), and a complex sequential logic circuit (multi-input keypad lock). Moreover, a proof-of-concept peptide regulatory circuit was developed to analyze the expression profile of cell-secreted protein biomarkers and trigger cancer-cell-specific apoptosis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

CMOS-based optical energy harvesting circuit for biomedical and Internet of Things devices

Science.gov (United States)

Nattakarn, Wuthibenjaphonchai; Ishizu, Takaaki; Haruta, Makito; Noda, Toshihiko; Sasagawa, Kiyotaka; Tokuda, Takashi; Sawan, Mohamad; Ohta, Jun

2018-04-01

In this work, we present a novel CMOS-based optical energy harvesting technology for implantable and Internet of Things (IoT) devices. In the proposed system, a CMOS energy-harvesting circuit accumulates a small amount of photoelectrically converted energy in an external capacitor, and intermittently supplies this power to a target device. Two optical energy-harvesting circuit types were implemented and evaluated. Furthermore, we developed a photoelectrically powered optical identification (ID) circuit that is suitable for IoT technology applications.

Notes on basis band-pass circuits; Notes sur les circuits de base passe-bande

Energy Technology Data Exchange (ETDEWEB)

Ailloud, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1959-07-01

Resistor load amplifier stages, basic band-pass RC networks, conventional single-tuned circuits, have the same transfer function. Common properties and differences because diverse magnitude of parameters with proposed problems are exposed. Next the case of several cascaded stages (or networks) is examined when there is no reaction ones to another. (author) [French] Les etages amplificateurs a resistances, les circuits passe-bande RC elementaires, le circuit resonnant classique possedent la meme fonction de transfert. On fait ressortir les proprietes communes et les differences de comportement dues aux ordres de grandeur qu'il est possible de donner aux parametres en fonction des problemes a resoudre. On examine ensuite le cas de plusieurs etages (ou de plusieurs circuits) en cascade lorsqu'ils ne reagissent pas les uns sur les autres. (auteur)

Combining ChIP-chip and expression profiling to model the MoCRZ1 mediated circuit for Ca/calcineurin signaling in the rice blast fungus.

Directory of Open Access Journals (Sweden)

Soonok Kim

2010-05-01

Full Text Available Significant progress has been made in defining the central signaling networks in many organisms, but collectively we know little about the downstream targets of these networks and the genes they regulate. To reconstruct the regulatory circuit of calcineurin signal transduction via MoCRZ1, a Magnaporthe oryzae C2H2 transcription factor activated by calcineurin dephosphorylation, we used a combined approach of chromatin immunoprecipitation - chip (ChIP-chip, coupled with microarray expression studies. One hundred forty genes were identified as being both a direct target of MoCRZ1 and having expression concurrently differentially regulated in a calcium/calcineurin/MoCRZ1 dependent manner. Highly represented were genes involved in calcium signaling, small molecule transport, ion homeostasis, cell wall synthesis/maintenance, and fungal virulence. Of particular note, genes involved in vesicle mediated secretion necessary for establishing host associations, were also found. MoCRZ1 itself was a target, suggesting a previously unreported autoregulation control point. The data also implicated a previously unreported feedback regulation mechanism of calcineurin activity. We propose that calcium/calcineurin regulated signal transduction circuits controlling development and pathogenicity manifest through multiple layers of regulation. We present results from the ChIP-chip and expression analysis along with a refined model of calcium/calcineurin signaling in this important plant pathogen.

Corticocortical feedback increases the spatial extent of normalization.

Science.gov (United States)

Nassi, Jonathan J; Gómez-Laberge, Camille; Kreiman, Gabriel; Born, Richard T

2014-01-01

Normalization has been proposed as a canonical computation operating across different brain regions, sensory modalities, and species. It provides a good phenomenological description of non-linear response properties in primary visual cortex (V1), including the contrast response function and surround suppression. Despite its widespread application throughout the visual system, the underlying neural mechanisms remain largely unknown. We recently observed that corticocortical feedback contributes to surround suppression in V1, raising the possibility that feedback acts through normalization. To test this idea, we characterized area summation and contrast response properties in V1 with and without feedback from V2 and V3 in alert macaques and applied a standard normalization model to the data. Area summation properties were well explained by a form of divisive normalization, which computes the ratio between a neuron's driving input and the spatially integrated activity of a "normalization pool." Feedback inactivation reduced surround suppression by shrinking the spatial extent of the normalization pool. This effect was independent of the gain modulation thought to mediate the influence of contrast on area summation, which remained intact during feedback inactivation. Contrast sensitivity within the receptive field center was also unaffected by feedback inactivation, providing further evidence that feedback participates in normalization independent of the circuit mechanisms involved in modulating contrast gain and saturation. These results suggest that corticocortical feedback contributes to surround suppression by increasing the visuotopic extent of normalization and, via this mechanism, feedback can play a critical role in contextual information processing.

Chemoelectronic circuits based on metal nanoparticles

Science.gov (United States)

Yan, Yong; Warren, Scott C.; Fuller, Patrick; Grzybowski, Bartosz A.

2016-07-01

To develop electronic devices with novel functionalities and applications, various non-silicon-based materials are currently being explored. Nanoparticles have unique characteristics due to their small size, which can impart functions that are distinct from those of their bulk counterparts. The use of semiconductor nanoparticles has already led to improvements in the efficiency of solar cells, the processability of transistors and the sensitivity of photodetectors, and the optical and catalytic properties of metal nanoparticles have led to similar advances in plasmonics and energy conversion. However, metals screen electric fields and this has, so far, prevented their use in the design of all-metal nanoparticle circuitry. Here, we show that simple electronic circuits can be made exclusively from metal nanoparticles functionalized with charged organic ligands. In these materials, electronic currents are controlled by the ionic gradients of mobile counterions surrounding the ‘jammed’ nanoparticles. The nanoparticle-based electronic elements of the circuitry can be interfaced with metal nanoparticles capable of sensing various environmental changes (humidity, gas, the presence of various cations), creating electronic devices in which metal nanoparticles sense, process and ultimately report chemical signals. Because the constituent nanoparticles combine electronic and chemical sensing functions, we term these systems ‘chemoelectronic’. The circuits have switching times comparable to those of polymer electronics, selectively transduce parts-per-trillion chemical changes into electrical signals, perform logic operations, consume little power (on the scale of microwatts), and are mechanically flexible. They are also ‘green’, in the sense that they comprise non-toxic nanoparticles cast at room temperature from alcohol solutions.

Radiation-Hard Complementary Integrated Circuits Based on Semiconducting Single-Walled Carbon Nanotubes.

Science.gov (United States)

McMorrow, Julian J; Cress, Cory D; Gaviria Rojas, William A; Geier, Michael L; Marks, Tobin J; Hersam, Mark C

2017-03-28

Increasingly complex demonstrations of integrated circuit elements based on semiconducting single-walled carbon nanotubes (SWCNTs) mark the maturation of this technology for use in next-generation electronics. In particular, organic materials have recently been leveraged as dopant and encapsulation layers to enable stable SWCNT-based rail-to-rail, low-power complementary metal-oxide-semiconductor (CMOS) logic circuits. To explore the limits of this technology in extreme environments, here we study total ionizing dose (TID) effects in enhancement-mode SWCNT-CMOS inverters that employ organic doping and encapsulation layers. Details of the evolution of the device transport properties are revealed by in situ and in operando measurements, identifying n-type transistors as the more TID-sensitive component of the CMOS system with over an order of magnitude larger degradation of the static power dissipation. To further improve device stability, radiation-hardening approaches are explored, resulting in the observation that SWNCT-CMOS circuits are TID-hard under dynamic bias operation. Overall, this work reveals conditions under which SWCNTs can be employed for radiation-hard integrated circuits, thus presenting significant potential for next-generation satellite and space applications.

High voltage short plus generation based on avalanche circuit

International Nuclear Information System (INIS)

Hu Yuanfeng; Yu Xiaoqi

2006-01-01

Simulate the avalanche circuit in series with PSPICE module, design the high voltage short plus generation circuit by avalanche transistor in series for the sweep deflection circuit of streak camera. The output voltage ranges 1.2 KV into 50 ohm load. The rise time of the circuit is less than 3 ns. (authors)

Distributed Feedback Laser Based on Single Crystal Perovskite

Science.gov (United States)

Sun, Shang; Xiao, Shumin; Song, Qinghai

2017-06-01

We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry-Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3 microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

Integrated Power Flow and Short Circuit Calculation Method for Distribution Network with Inverter Based Distributed Generation

OpenAIRE

Yang, Shan; Tong, Xiangqian

2016-01-01

Power flow calculation and short circuit calculation are the basis of theoretical research for distribution network with inverter based distributed generation. The similarity of equivalent model for inverter based distributed generation during normal and fault conditions of distribution network and the differences between power flow and short circuit calculation are analyzed in this paper. Then an integrated power flow and short circuit calculation method for distribution network with inverte...

Identification of a new gene regulatory circuit involving B cell receptor activated signaling using a combined analysis of experimental, clinical and global gene expression data

Science.gov (United States)

Schrader, Alexandra; Meyer, Katharina; Walther, Neele; Stolz, Ailine; Feist, Maren; Hand, Elisabeth; von Bonin, Frederike; Evers, Maurits; Kohler, Christian; Shirneshan, Katayoon; Vockerodt, Martina; Klapper, Wolfram; Szczepanowski, Monika; Murray, Paul G.; Bastians, Holger; Trümper, Lorenz; Spang, Rainer; Kube, Dieter

2016-01-01

To discover new regulatory pathways in B lymphoma cells, we performed a combined analysis of experimental, clinical and global gene expression data. We identified a specific cluster of genes that was coherently expressed in primary lymphoma samples and suppressed by activation of the B cell receptor (BCR) through αIgM treatment of lymphoma cells in vitro. This gene cluster, which we called BCR.1, includes numerous cell cycle regulators. A reduced expression of BCR.1 genes after BCR activation was observed in different cell lines and also in CD10+ germinal center B cells. We found that BCR activation led to a delayed entry to and progression of mitosis and defects in metaphase. Cytogenetic changes were detected upon long-term αIgM treatment. Furthermore, an inverse correlation of BCR.1 genes with c-Myc co-regulated genes in distinct groups of lymphoma patients was observed. Finally, we showed that the BCR.1 index discriminates activated B cell-like and germinal centre B cell-like diffuse large B cell lymphoma supporting the functional relevance of this new regulatory circuit and the power of guided clustering for biomarker discovery. PMID:27166259

A Bayesian matching pursuit based scheduling algorithm for feedback reduction in MIMO broadcast channels

KAUST Repository

Shibli, Hussain J.

2013-06-01

Opportunistic schedulers rely on the feedback of all users in order to schedule a set of users with favorable channel conditions. While the downlink channels can be easily estimated at all user terminals via a single broadcast, several key challenges are faced during uplink transmission. First of all, the statistics of the noisy and fading feedback channels are unknown at the base station (BS) and channel training is usually required from all users. Secondly, the amount of network resources (air-time) required for feedback transmission grows linearly with the number of users. In this paper, we tackle the above challenges and propose a Bayesian based scheduling algorithm that 1) reduces the air-time required to identify the strong users, and 2) is agnostic to the statistics of the feedback channels and utilizes the a priori statistics of the additive noise to identify the strong users. Numerical results show that the proposed algorithm reduces the feedback air-time while improving detection in the presence of fading and noisy channels when compared to recent compressed sensing based algorithms. Furthermore, the proposed algorithm achieves a sum-rate throughput close to that obtained by noiseless dedicated feedback systems. © 2013 IEEE.

Three-Phase Short-Circuit Current Calculation of Power Systems with High Penetration of VSC-Based Renewable Energy

Directory of Open Access Journals (Sweden)

Niancheng Zhou

2018-03-01

Full Text Available Short-circuit current level of power grid will be increased with high penetration of VSC-based renewable energy, and a strong coupling between transient fault process and control strategy will change the fault features. The full current expression of VSC-based renewable energy was obtained according to transient characteristics of short-circuit current. Furtherly, by analyzing the closed-loop transfer function model of controller and current source characteristics presented in steady state during a fault, equivalent circuits of VSC-based renewable energy of fault transient state and steady state were proposed, respectively. Then the correctness of the theory was verified by experimental tests. In addition, for power grid with VSC-based renewable energy, superposition theorem was used to calculate AC component and DC component of short-circuit current, respectively, then the peak value of short-circuit current was evaluated effectively. The calculated results could be used for grid planning and design, short-circuit current management as well as adjustment of relay protection. Based on comparing calculation and simulation results of 6-node 500 kV Huainan power grid and 35-node 220 kV Huaisu power grid, the effectiveness of the proposed method was verified.

Optically controllable molecular logic circuits

International Nuclear Information System (INIS)

Nishimura, Takahiro; Fujii, Ryo; Ogura, Yusuke; Tanida, Jun

2015-01-01

Molecular logic circuits represent a promising technology for observation and manipulation of biological systems at the molecular level. However, the implementation of molecular logic circuits for temporal and programmable operation remains challenging. In this paper, we demonstrate an optically controllable logic circuit that uses fluorescence resonance energy transfer (FRET) for signaling. The FRET-based signaling process is modulated by both molecular and optical inputs. Based on the distance dependence of FRET, the FRET pathways required to execute molecular logic operations are formed on a DNA nanostructure as a circuit based on its molecular inputs. In addition, the FRET pathways on the DNA nanostructure are controlled optically, using photoswitching fluorescent molecules to instruct the execution of the desired operation and the related timings. The behavior of the circuit can thus be controlled using external optical signals. As an example, a molecular logic circuit capable of executing two different logic operations was studied. The circuit contains functional DNAs and a DNA scaffold to construct two FRET routes for executing Input 1 AND Input 2 and Input 1 AND NOT Input 3 operations on molecular inputs. The circuit produced the correct outputs with all possible combinations of the inputs by following the light signals. Moreover, the operation execution timings were controlled based on light irradiation and the circuit responded to time-dependent inputs. The experimental results demonstrate that the circuit changes the output for the required operations following the input of temporal light signals

Lyapunov-based Stability of Feedback Interconnections of Negative Imaginary Systems

KAUST Repository

Ghallab, Ahmed G.

2017-10-19

Feedback control systems using sensors and actuators such as piezoelectric sensors and actuators, micro-electro-mechanical systems (MEMS) sensors and opto-mechanical sensors, are allowing new advances in designing such high precision technologies. The negative imaginary control systems framework allows for robust control design for such high precision systems in the face of uncertainties due to unmodelled dynamics. The stability of the feedback interconnection of negative imaginary systems has been well established in the literature. However, the proofs of stability feedback interconnection which are used in some previous papers have a shortcoming due to a matrix inevitability issue. In this paper, we provide a new and correct Lyapunov-based proof of one such result and show that the result is still true.

Lyapunov-based Stability of Feedback Interconnections of Negative Imaginary Systems

KAUST Repository

Ghallab, Ahmed G.; Mabrok, Mohamed; Petersen, Ian R.

2017-01-01

Feedback control systems using sensors and actuators such as piezoelectric sensors and actuators, micro-electro-mechanical systems (MEMS) sensors and opto-mechanical sensors, are allowing new advances in designing such high precision technologies. The negative imaginary control systems framework allows for robust control design for such high precision systems in the face of uncertainties due to unmodelled dynamics. The stability of the feedback interconnection of negative imaginary systems has been well established in the literature. However, the proofs of stability feedback interconnection which are used in some previous papers have a shortcoming due to a matrix inevitability issue. In this paper, we provide a new and correct Lyapunov-based proof of one such result and show that the result is still true.

A web-based feedback study on optimization-based training and analysis of human decision making

Directory of Open Access Journals (Sweden)

Michael Engelhart

2017-05-01

Full Text Available The question “How can humans learn efficiently to make decisions in a complex, dynamic, and uncertain environment” is still a very open question. We investigate what effects arise when feedback is given in a computer-simulated microworld that is controlled by participants. This has a direct impact on training simulators that are already in standard use in many professions, e.g., for flight simulators for pilots, and a potential impact on a better understanding of human decision making in general. Our study is based on a benchmark microworld with an economic framing, the IWR Tailorshop. N=94 participants played four rounds of the microworld, each 10 months, via a web interface. We propose a new approach to quantify performance and learning, which is based on a mathematical model of the microworld and optimization. Six participant groups receive different kinds of feedback in a training phase, then results in a performance phase without feedback are analyzed. As a main result, feedback of optimal solutions in training rounds improved model knowledge, early learning, and performance, especially when this information is encoded in a graphical representation (arrows.

Microcontroller based instrumentation for heater control circuit of tin oxide based hydrogen sensor

International Nuclear Information System (INIS)

Premalatha, S.; Krithika, P.; Gunasekaran, G.; Ramakrishnan, R.; Ramanarayanan, R.R.; Prabhu, E.; Jayaraman, V.; Parthasarathy, R.

2015-01-01

A thin film sensor based on tin oxide developed in IGCAR is used to monitor very low levels of hydrogen (concentration ranging from 2 ppm to 80 ppm). The heater and the sensor patterns are integrated on a miniature alumina substrate and necessary electrical leads are taken out. For proper functioning of the sensor, the heater has to be maintained at a constant temperature of 350°C. The sensor output (voltage signal) varies with H 2 concentration. In fast breeder reactors, liquid sodium is used as coolant. The sensor is used to detect water/steam leak in secondary sodium circuit. During the start up of the reactor, steam leak into sodium circuit generates hydrogen gas as a product that doesn't dissolve in sodium, but escapes to the surge tank containing argon i.e. in cover gas plenum of sodium circuit. On-line monitoring of hydrogen in cover gas is done to detect an event of water/steam leakage. The focus of this project is on the instrumentation pertaining to the temperature control for the sensor heater. The tin oxide based hydrogen sensor is embedded in a substrate which consists of a platinum heater, essentially a resistor. There is no provision of embedding a temperature sensor on the heater surface due to the physical constraints, without which maintaining a constant heater temperature is a complex task

Sociability Deficits and Altered Amygdala Circuits in Mice Lacking Pcdh10, an Autism Associated Gene.

Science.gov (United States)

Schoch, Hannah; Kreibich, Arati S; Ferri, Sarah L; White, Rachel S; Bohorquez, Dominique; Banerjee, Anamika; Port, Russell G; Dow, Holly C; Cordero, Lucero; Pallathra, Ashley A; Kim, Hyong; Li, Hongzhe; Bilker, Warren B; Hirano, Shinji; Schultz, Robert T; Borgmann-Winter, Karin; Hahn, Chang-Gyu; Feldmeyer, Dirk; Carlson, Gregory C; Abel, Ted; Brodkin, Edward S

2017-02-01

Behavioral symptoms in individuals with autism spectrum disorder (ASD) have been attributed to abnormal neuronal connectivity, but the molecular bases of these behavioral and brain phenotypes are largely unknown. Human genetic studies have implicated PCDH10, a member of the δ2 subfamily of nonclustered protocadherin genes, in ASD. PCDH10 expression is enriched in the basolateral amygdala, a brain region implicated in the social deficits of ASD. Previous reports indicate that Pcdh10 plays a role in axon outgrowth and glutamatergic synapse elimination, but its roles in social behaviors and amygdala neuronal connectivity are unknown. We hypothesized that haploinsufficiency of Pcdh10 would reduce social approach behavior and alter the structure and function of amygdala circuits. Mice lacking one copy of Pcdh10 (Pcdh10 +/- ) and wild-type littermates were assessed for social approach and other behaviors. The lateral/basolateral amygdala was assessed for dendritic spine number and morphology, and amygdala circuit function was studied using voltage-sensitive dye imaging. Expression of Pcdh10 and N-methyl-D-aspartate receptor (NMDAR) subunits was assessed in postsynaptic density fractions of the amygdala. Male Pcdh10 +/- mice have reduced social approach behavior, as well as impaired gamma synchronization, abnormal spine morphology, and reduced levels of NMDAR subunits in the amygdala. Social approach deficits in Pcdh10 +/- male mice were rescued with acute treatment with the NMDAR partial agonist d-cycloserine. Our studies reveal that male Pcdh10 +/- mice have synaptic and behavioral deficits, and establish Pcdh10 +/- mice as a novel genetic model for investigating neural circuitry and behavioral changes relevant to ASD. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Neurophysiological correlates of anhedonia in feedback processing

Science.gov (United States)

Mies, Gabry W.; Van den Berg, Ivo; Franken, Ingmar H. A.; Smits, Marion; Van der Molen, Maurits W.; Van der Veen, Frederik M.

2013-01-01

Disturbances in feedback processing and a dysregulation of the neural circuit in which the cingulate cortex plays a key role have been frequently observed in depression. Since depression is a heterogeneous disease, instead of focusing on the depressive state in general, this study investigated the relations between the two core symptoms of depression, i.e., depressed mood and anhedonia, and the neural correlates of feedback processing using fMRI. The focus was on the different subdivisions of the anterior cingulate cortex (ACC). Undergraduates with varying levels of depressed mood and anhedonia performed a time-estimation task in which they received positive and negative feedback that was either valid or invalid (i.e., related vs. unrelated to actual performance). The rostral cingulate zone (RCZ), corresponding to the dorsal part of the ACC, was less active in response to feedback in more anhedonic individuals, after correcting for the influence of depressed mood, whereas the subgenual ACC was more active in these individuals. Task performance was not affected by anhedonia, however. No statistically significant effects were found for depressed mood above and beyond the effects of anhedonia. This study therefore implies that increasing levels of anhedonia involve changes in the neural circuitry underlying feedback processing. PMID:23532800

An 11 μ w, two-electrode transimpedance biosignal amplifier with active current feedback stabilization.

Science.gov (United States)

Inan, O T; Kovacs, G T A

2010-04-01

A novel two-electrode biosignal amplifier circuit is demonstrated by using a composite transimpedance amplifier input stage with active current feedback. Micropower, low gain-bandwidth product operational amplifiers can be used, leading to the lowest reported overall power consumption in the literature for a design implemented with off-the-shelf commercial integrated circuits (11 μW). Active current feedback forces the common-mode input voltage to stay within the supply rails, reducing baseline drift and amplifier saturation problems that can be present in two-electrode systems. The bandwidth of the amplifier extends from 0.05-200 Hz and the midband voltage gain (assuming an electrode-to-skin resistance of 100 kΩ) is 48 dB. The measured output noise level is 1.2 mV pp, corresponding to a voltage signal-to-noise ratio approaching 50 dB for a typical electrocardiogram (ECG) level input of 1 mVpp. Recordings were taken from a subject by using the proposed two-electrode circuit and, simultaneously, a three-electrode standard ECG circuit. The residual of the normalized ensemble averages for both measurements was computed, and the power of this residual was 0.54% of the power of the standard ECG measurement output. While this paper primarily focuses on ECG applications, the circuit can also be used for amplifying other biosignals, such as the electroencephalogram.

The super collider transverse feedback system for suppression of the emittance growth and beam instabilities

International Nuclear Information System (INIS)

Lebedev, V.A.

1993-01-01

A super collider transverse feedback system designed to suppress injection errors, emittance growth due to external noises, and beam instabilities is considered. It is supposed that the feedback system should consist of two circuits: an injection damper operating just after injection and a super damper. To damp the emittance growth, the superdamper has to operate with the ultimate decrement close to the revolution frequency. The physics of such a feedback system and its main limitations are discussed. 9 refs.; 21 figs.; 1 tab

A novel charge sensitive preamplifier without the feedback resistor

International Nuclear Information System (INIS)

Bertuccio, G.

1992-01-01

A novel charge sensitive preamplifier which has no resistor in parallel with the feedback capacitor is presented. No external device or circuit is required to discharge the feedback capacitor. The detector leakage and signal current flows away through the gate of the first JFET which works with its gate to source junction slightly forward biased. The DC stabilization of the preamplifier is accomplished by an additional feedback loop, which permits to equalize the current flowing through the forward baised gate to source junction and the current coming from the detector. An equivalent noise charge of less than 20 electrons r.m.s. has been measured at room temperature by using an input JFET with a transconductance to gate capacitance ratio of 4 mS/5.4 pF

Fault Diagnosis for Compensating Capacitors of Jointless Track Circuit Based on Dynamic Time Warping

Directory of Open Access Journals (Sweden)

Wei Dong

2014-01-01

Full Text Available Aiming at the problem of online fault diagnosis for compensating capacitors of jointless track circuit, a dynamic time warping (DTW based diagnosis method is proposed in this paper. Different from the existing related works, this method only uses the ground indoor monitoring signals of track circuit to locate the faulty compensating capacitor, not depending on the shunt current of inspection train, which is an indispensable condition for existing methods. So, it can be used for online diagnosis of compensating capacitor, which has not yet been realized by existing methods. To overcome the key problem that track circuit cannot obtain the precise position of the train, the DTW method is used for the first time in this situation to recover the function relationship between receiver’s peak voltage and shunt position. The necessity, thinking, and procedure of the method are described in detail. Besides the classical DTW based method, two improved methods for improving classification quality and reducing computation complexity are proposed. Finally, the diagnosis experiments based on the simulation model of track circuit show the effectiveness of the proposed methods.

Trace-based post-silicon validation for VLSI circuits

CERN Document Server

Liu, Xiao

2014-01-01

This book first provides a comprehensive coverage of state-of-the-art validation solutions based on real-time signal tracing to guarantee the correctness of VLSI circuits.  The authors discuss several key challenges in post-silicon validation and provide automated solutions that are systematic and cost-effective.  A series of automatic tracing solutions and innovative design for debug (DfD) techniques are described, including techniques for trace signal selection for enhancing visibility of functional errors, a multiplexed signal tracing strategy for improving functional error detection, a tracing solution for debugging electrical errors, an interconnection fabric for increasing data bandwidth and supporting multi-core debug, an interconnection fabric design and optimization technique to increase transfer flexibility and a DfD design and associated tracing solution for improving debug efficiency and expanding tracing window. The solutions presented in this book improve the validation quality of VLSI circuit...

Tutorial on beam-based feedback systems for linacs

International Nuclear Information System (INIS)

Hendrickson, L.; Allison, S.; Gromme, T.; Grossberg, P.; Himel, T.; Krauter, K.; MacKenzie, R.; Ross, M.; Sass, R.; Shoaee, H.

1994-08-01

A generalized fast feedback system stabilizes beams in the SLC. It performs measurements and modifies actuator settings to control beam states such as position, angle, energy and intensity on a pulse to pulse basis. An adaptive cascade feature allows communication between a series of linac loops, avoiding overcorrection problems. The system is based on the state space formalism of digital control theory. Due to the database-driven design, new loops are added without requiring software modifications. Recent enhancements support the monitoring and control of nonlinear states such as beam phase using excitation techniques. In over three years of operation, the feedback system has grown from its original eight loops to more than fifty loops, and it has been invaluable in stabilizing the machine

Exploration and design of smart home circuit based on ZigBee

Science.gov (United States)

Luo, Huirong

2018-05-01

To apply ZigBee technique in smart home circuit design, in the hardware design link of ZigBee node, TI Company's ZigBee wireless communication chip CC2530 was used to complete the design of ZigBee RF module circuit and peripheral circuit. In addition, the function demand and the overall scheme of the intelligent system based on smart home furnishing were proposed. Finally, the smart home system was built by combining ZigBee network and intelligent gateway. The function realization, reliability and power consumption of ZigBee network were tested. The results showed that ZigBee technology was applied to smart home system, making it have some advantages in terms of flexibility, scalability, power consumption and indoor aesthetics. To sum up, the system has high application value.

An educational laboratory virtual instrumentation suite assisted experiment for studying fundamentals of series resistance-inductance-capacitance circuit

Science.gov (United States)

Rana, K. P. S.; Kumar, Vineet; Mendiratta, Jatin

2017-11-01

One of the most elementary concepts in freshmen Electrical Engineering subject comprises the Resistance-Inductance-Capacitance (RLC) circuit fundamentals, that is, their time and frequency domain responses. For a beginner, generally, it is difficult to understand and appreciate the step and the frequency responses, particularly the resonance. This paper proposes a student-friendly teaching and learning approach by inculcating the multifaceted versatile software LabVIEWTM along with the educational laboratory virtual instrumentation suite hardware, for studying the RLC circuit time and frequency domain responses. The proposed approach has offered an interactive laboratory experiment where students can model circuits in simulation and hardware circuits on prototype board, and then compare their performances. The theoretical simulations and the obtained experimental data are found to be in very close agreement, thereby enhancing the conviction of students. Finally, the proposed methodology was also subjected to the assessment of learning outcomes based on student feedback, and an average score of 8.05 out of 10 with a standard deviation of 0.471 was received, indicating the overall satisfaction of the students.

A double-gate double-feedback JFET charge-sensitive preamplifier

International Nuclear Information System (INIS)

Fazzi, A.

1996-01-01

A new charge-sensitive preamplifier (CSP) without a physical resistance in the feedback is presented. The input device has to be a double-gate JFET. In this new preamplifier configuration the feedback capacitor is continuously discharged by means of a second DC current feedback loop closed through the bottom gate of the input JFET. The top gate-channel junction works as usual in reverse bias, the bottom gate-channel is forward biased. A fraction of the current injected by the bottom gate reaches the top gate discharging the feedback capacitor. The n-channel double-gate JFET is considered from the viewpoint of the restoring action as a parasitic p-n-p ''transversal'' bipolar junction transistor. The new preamplifier is also suited for detectors operating at room temperature with leakage current which may vary with time. The DC behaviour and the dynamic behaviour of the circuit is analyzed and new measurements presented. (orig.)

Inductance analyzer based on auto-balanced circuit for precision measurement of fluxgate impedance

Science.gov (United States)

Setiadi, Rahmondia N.; Schilling, Meinhard

2018-05-01

An instrument for fluxgate sensor impedance measurement based on an auto-balanced circuit has been designed and characterized. The circuit design is adjusted to comply with the fluxgate sensor characteristics which are low impedance and highly saturable core with very high permeability. The system utilizes a NI-DAQ card and LabVIEW to process the signal acquisition and evaluation. Some fixed reference resistances are employed for system calibration using linear regression. A multimeter HP 34401A and impedance analyzer Agilent 4294A are used as calibrator and validator for the resistance and inductance measurements. Here, we realized a fluxgate analyzer instrument based on auto-balanced circuit, which measures the resistance and inductance of the device under test with a small error and much lower excitation current to avoid core saturation compared to the used calibrator.

Gene set-based module discovery in the breast cancer transcriptome

Directory of Open Access Journals (Sweden)

Zhang Michael Q

2009-02-01

Full Text Available Abstract Background Although microarray-based studies have revealed global view of gene expression in cancer cells, we still have little knowledge about regulatory mechanisms underlying the transcriptome. Several computational methods applied to yeast data have recently succeeded in identifying expression modules, which is defined as co-expressed gene sets under common regulatory mechanisms. However, such module discovery methods are not applied cancer transcriptome data. Results In order to decode oncogenic regulatory programs in cancer cells, we developed a novel module discovery method termed EEM by extending a previously reported module discovery method, and applied it to breast cancer expression data. Starting from seed gene sets prepared based on cis-regulatory elements, ChIP-chip data, and gene locus information, EEM identified 10 principal expression modules in breast cancer based on their expression coherence. Moreover, EEM depicted their activity profiles, which predict regulatory programs in each subtypes of breast tumors. For example, our analysis revealed that the expression module regulated by the Polycomb repressive complex 2 (PRC2 is downregulated in triple negative breast cancers, suggesting similarity of transcriptional programs between stem cells and aggressive breast cancer cells. We also found that the activity of the PRC2 expression module is negatively correlated to the expression of EZH2, a component of PRC2 which belongs to the E2F expression module. E2F-driven EZH2 overexpression may be responsible for the repression of the PRC2 expression modules in triple negative tumors. Furthermore, our network analysis predicts regulatory circuits in breast cancer cells. Conclusion These results demonstrate that the gene set-based module discovery approach is a powerful tool to decode regulatory programs in cancer cells.

A cell-based design approach for RSFQ circuits using a binary decision diagram

International Nuclear Information System (INIS)

Yoshikawa, N.; Koshiyama, J.

1999-01-01

We propose a cell-based design approach for rapid single flux quantum (RSFQ) circuits based on a binary decision diagram (BDD). The BDD is a way to represent a logical function using a directed graph which consists of binary switches having one input and two outputs. Since complex logic circuits can be implemented in the form of regular arrays of the BDD binary switches, we can use a cell-based layout methodology for the design of the RSFQ circuits. In this study, we implemented the BDD binary switches by a D 2 flip-flop. In the BDD design approach we made a cell library which contains a binary switch, pulse splitters, confluence buffers and Josephson transmission lines. All cell layouts in the library have identical widths and heights, so that any logic function can be laid out by simple connection of the library cells. As a case study, we implemented a 1-bit RSFQ half-adder and a 3-bit encoder for a flash AD converter. (author)

Corticocortical feedback increases the spatial extent of normalization

Science.gov (United States)

Nassi, Jonathan J.; Gómez-Laberge, Camille; Kreiman, Gabriel; Born, Richard T.

2014-01-01

Normalization has been proposed as a canonical computation operating across different brain regions, sensory modalities, and species. It provides a good phenomenological description of non-linear response properties in primary visual cortex (V1), including the contrast response function and surround suppression. Despite its widespread application throughout the visual system, the underlying neural mechanisms remain largely unknown. We recently observed that corticocortical feedback contributes to surround suppression in V1, raising the possibility that feedback acts through normalization. To test this idea, we characterized area summation and contrast response properties in V1 with and without feedback from V2 and V3 in alert macaques and applied a standard normalization model to the data. Area summation properties were well explained by a form of divisive normalization, which computes the ratio between a neuron's driving input and the spatially integrated activity of a “normalization pool.” Feedback inactivation reduced surround suppression by shrinking the spatial extent of the normalization pool. This effect was independent of the gain modulation thought to mediate the influence of contrast on area summation, which remained intact during feedback inactivation. Contrast sensitivity within the receptive field center was also unaffected by feedback inactivation, providing further evidence that feedback participates in normalization independent of the circuit mechanisms involved in modulating contrast gain and saturation. These results suggest that corticocortical feedback contributes to surround suppression by increasing the visuotopic extent of normalization and, via this mechanism, feedback can play a critical role in contextual information processing. PMID:24910596

Text Based Analogy in Overcoming Student Misconception on Simple Electricity Circuit Material

Science.gov (United States)

Hesti, R.; Maknun, J.; Feranie, S.

2017-09-01

Some researcher have found that the use of analogy in learning and teaching physics was effective enough in giving comprehension in a complicated physics concept such as electrical circuits. Meanwhile, misconception become main cause that makes students failed when learning physics. To provide teaching physics effectively, the misconception should be resolved. Using Text Based Analogy is one of the way to identifying misconceptions and it is enough to assist teachers in conveying scientific truths in order to overcome misconceptions. The purpose of the study to investigate the use of text based analogy in overcoming students misconception on simple electrical circuit material. The samples of this research were 28 of junior high school students taken purposively from one high school in South Jakarta. The method use in this research is pre-experimental and design in one shot case study. Students who are the participants of sample have been identified misconception on the electrical circuit material by using the Diagnostic Test of Simple Electricity Circuit. The results of this study found that TBA can replace the misconceptions of the concept possessed by students with scientific truths conveyed in the text in a way that is easily understood so that TBA is strongly recommended to use in other physics materials.

Delay-area trade-off for MPRM circuits based on hybrid discrete particle swarm optimization

International Nuclear Information System (INIS)

Jiang Zhidi; Wang Zhenhai; Wang Pengjun

2013-01-01

Polarity optimization for mixed polarity Reed—Muller (MPRM) circuits is a combinatorial issue. Based on the study on discrete particle swarm optimization (DPSO) and mixed polarity, the corresponding relation between particle and mixed polarity is established, and the delay-area trade-off of large-scale MPRM circuits is proposed. Firstly, mutation operation and elitist strategy in genetic algorithm are incorporated into DPSO to further develop a hybrid DPSO (HDPSO). Then the best polarity for delay and area trade-off is searched for large-scale MPRM circuits by combining the HDPSO and a delay estimation model. Finally, the proposed algorithm is testified by MCNC Benchmarks. Experimental results show that HDPSO achieves a better convergence than DPSO in terms of search capability for large-scale MPRM circuits. (semiconductor integrated circuits)

Pulse oximeter improvement with an ADC-DAC feedback loop and a radial reflectance sensor.

Science.gov (United States)

Thompson, David; Wareing, Austin; Day, Dwight; Warren, Steve

2006-01-01

Pulse oximeter circuitry must meet several design constraints, including the ability to separate a small pulsatile signal component from a large signal baseline. This paper describes pulse oximeter design changes that produced order-of-magnitude improvements in signal quality. The primary changes were (a) the replacement of an analog sample-and-hold-based differentiator circuit with an ADC-DAC feedback loop and (b) the replacement of a side-by-side reflectance sensor design with a radial sensor arrangement that maximizes the pulsatile-to-baseline signal ratio.

The Emergence of Contesting Motives for Student Feedback-Based Evaluation in Australian Higher Education

Science.gov (United States)

Darwin, Stephen

2016-01-01

Student feedback-based evaluation performs a significant social role in framing perceptions of the quality of teaching in contemporary Australian higher education. Yet its emergence is a relatively recent phenomenon, having only been in widespread application since the mid-1980s. The early manifestations of student feedback-based evaluation came…

Npas4 regulates excitatory-inhibitory balance within neural circuits through cell-type-specific gene programs.

Science.gov (United States)

Spiegel, Ivo; Mardinly, Alan R; Gabel, Harrison W; Bazinet, Jeremy E; Couch, Cameron H; Tzeng, Christopher P; Harmin, David A; Greenberg, Michael E

2014-05-22

The nervous system adapts to experience by inducing a transcriptional program that controls important aspects of synaptic plasticity. Although the molecular mechanisms of experience-dependent plasticity are well characterized in excitatory neurons, the mechanisms that regulate this process in inhibitory neurons are only poorly understood. Here, we describe a transcriptional program that is induced by neuronal activity in inhibitory neurons. We find that, while neuronal activity induces expression of early-response transcription factors such as Npas4 in both excitatory and inhibitory neurons, Npas4 activates distinct programs of late-response genes in inhibitory and excitatory neurons. These late-response genes differentially regulate synaptic input to these two types of neurons, promoting inhibition onto excitatory neurons while inducing excitation onto inhibitory neurons. These findings suggest that the functional outcomes of activity-induced transcriptional responses are adapted in a cell-type-specific manner to achieve a circuit-wide homeostatic response. Copyright © 2014 Elsevier Inc. All rights reserved.

A counting-card circuit based on PCI bus

International Nuclear Information System (INIS)

Shi Jing; Li Yong; Chinese Academy of Sciences, Lanzhou; Su Hong; Dong Chengfu; Li Xiaogang; Ma Xiaoli

2004-01-01

A counting-card circuit based on PCI bus that we developed recently used for advanced personal computer will be introduced in this paper briefly. The maximum count capacity of this counting-card is 10 9 -1, ranging from 0 to 999 999 999, the maximum counting time range, 1 x 10 6 s, can be set in 1 cycle, the maximum counting rate is 20 MHz for positive input. (authors)

Integrated electrofluidic circuits: pressure sensing with analog and digital operation functionalities for microfluidics.

Science.gov (United States)

Wu, Chueh-Yu; Lu, Jau-Ching; Liu, Man-Chi; Tung, Yi-Chung

2012-10-21

Microfluidic technology plays an essential role in various lab on a chip devices due to its desired advantages. An automated microfluidic system integrated with actuators and sensors can further achieve better controllability. A number of microfluidic actuation schemes have been well developed. In contrast, most of the existing sensing methods still heavily rely on optical observations and external transducers, which have drawbacks including: costly instrumentation, professional operation, tedious interfacing, and difficulties of scaling up and further signal processing. This paper reports the concept of electrofluidic circuits - electrical circuits which are constructed using ionic liquid (IL)-filled fluidic channels. The developed electrofluidic circuits can be fabricated using a well-developed multi-layer soft lithography (MSL) process with polydimethylsiloxane (PDMS) microfluidic channels. Electrofluidic circuits allow seamless integration of pressure sensors with analog and digital operation functions into microfluidic systems and provide electrical readouts for further signal processing. In the experiments, the analog operation device is constructed based on electrofluidic Wheatstone bridge circuits with electrical outputs of the addition and subtraction results of the applied pressures. The digital operation (AND, OR, and XOR) devices are constructed using the electrofluidic pressure controlled switches, and output electrical signals of digital operations of the applied pressures. The experimental results demonstrate the designed functions for analog and digital operations of applied pressures are successfully achieved using the developed electrofluidic circuits, making them promising to develop integrated microfluidic systems with capabilities of precise pressure monitoring and further feedback control for advanced lab on a chip applications.

Four-terminal circuit element with photonic core

Science.gov (United States)

Sampayan, Stephen

2017-08-29

A four-terminal circuit element is described that includes a photonic core inside of the circuit element that uses a wide bandgap semiconductor material that exhibits photoconductivity and allows current flow through the material in response to the light that is incident on the wide bandgap material. The four-terminal circuit element can be configured based on various hardware structures using a single piece or multiple pieces or layers of a wide bandgap semiconductor material to achieve various designed electrical properties such as high switching voltages by using the photoconductive feature beyond the breakdown voltages of semiconductor devices or circuits operated based on electrical bias or control designs. The photonic core aspect of the four-terminal circuit element provides unique features that enable versatile circuit applications to either replace the semiconductor transistor-based circuit elements or semiconductor diode-based circuit elements.

The impact of computer-based feedback on students’ written work

Directory of Open Access Journals (Sweden)

Khaled El Ebyary

2010-12-01

automatic computer-based holistic scores and computer-based feedback (CBF on written work are available and therefore have the potential to deal with this issue. Criterion is one such tool that claims to be able to provide automated feedback at word, sentence, paragraph and text level, but there is still a need for more research into the practical value of providing feedback on L2 writing. Quantitative and qualitative data about feedback practice was collected from 31 instructors and 549 Egyptian trainee EFL teachers using pre-treatment questionnaires, interviews and focus groups. 24 of the trainees then received computer-based feedback using Criterion on two drafts of essays submitted on each of 4 topics. Data recorded by the software suggested a positive effect on the quality of students’ second drafts and subsequent submissions, and post-treatment questionnaires, interviews and focus groups showed a positive effect on the students’ attitudes towards feedback.

A circuit design for front-end read-out electronics of beam homogeneity measurement

International Nuclear Information System (INIS)

She Qianshun; Su Hong; Xu Zhiguo; Ma Xiaoli; Hu Zhengguo; Mao Ruishi; Xu Hushan

2011-01-01

It introduces a circuit design of beam homogeneity measurement for heavy ion beam in the monitoring needs, which convert multichannel weak current from 10 pA to 100 nA of the output of parallel plate avalanche counter (PPAC) for large area with sensitive two-dimensional position to voltage signal from -2 V to -20 mV by current-voltage-converter (IVC) circuit which composed of T-feedback resistor networks, combined with data acquisition and processing system realized the beam homogeneity measurement in heavy ion tumor therapy of the Institute of Modern Physics. Experiments have shown that the circuit with speed and high precision. This circuit can be used for read-out of the beam for the Multiwire Proportional Chamber, Faraday Cup and other weak current sources. (authors)

Periodicity, chaos, and multiple attractors in a memristor-based Shinriki's circuit

Energy Technology Data Exchange (ETDEWEB)

Kengne, J. [Laboratory of Automation and Applied Computer (LAIA), Department of Electrical Engineering, IUT-FV Bandjoun, University of Dschang, Dschang (Cameroon); Njitacke Tabekoueng, Z.; Kamdoum Tamba, V.; Nguomkam Negou, A. [Laboratory of Automation and Applied Computer (LAIA), Department of Electrical Engineering, IUT-FV Bandjoun, University of Dschang, Dschang (Cameroon); Department of Physics, Laboratory of Electronics and Signal Processing (LETS), Faculty of Science, University of Dschang, Dschang (Cameroon)

2015-10-15

In this contribution, a novel memristor-based oscillator, obtained from Shinriki's circuit by substituting the nonlinear positive conductance with a first order memristive diode bridge, is introduced. The model is described by a continuous time four-dimensional autonomous system with smooth nonlinearities. The basic dynamical properties of the system are investigated including equilibria and stability, phase portraits, frequency spectra, bifurcation diagrams, and Lyapunov exponents' spectrum. It is found that in addition to the classical period-doubling and symmetry restoring crisis scenarios reported in the original circuit, the memristor-based oscillator experiences the unusual and striking feature of multiple attractors (i.e., coexistence of a pair of asymmetric periodic attractors with a pair of asymmetric chaotic ones) over a broad range of circuit parameters. Results of theoretical analyses are verified by laboratory experimental measurements.

Transition from weak to strong measurements by nonlinear quantum feedback control

International Nuclear Information System (INIS)

Zhang Jing; Liu Yuxi; Wu Rebing; Li Chunwen; Tarn, Tzyh-Jong

2010-01-01

We find that feedback control may induce 'pseudo'-nonlinear dynamics in a damped harmonic oscillator, whose centroid trajectory in the phase space behaves like a classical nonlinear system. Thus, similar to nonlinear amplifiers (e.g., rf-driven Josephson junctions), feedback control on the harmonic oscillator can induce nonlinear bifurcation, which can be used to amplify small signals and further to measure quantum states of qubits. Using the cavity QED and the circuit QED systems as examples, we show how to apply our method to measuring the states of two-level atoms and superconducting charge qubits.

Design method of general-purpose driving circuit for CCD based on CPLD

International Nuclear Information System (INIS)

Zhang Yong; Tang Benqi; Xiao Zhigang; Wang Zujun; Huang Shaoyan

2005-01-01

It is very important for studying the radiation damage effects and mechanism systematically about CCD to develop a general-purpose test platform. The paper discusses the design method of general-purpose driving circuit for CCD based on CPLD and the realization approach. A main controller has being designed to read the data file from the outer memory, setup the correlative parameter registers and produce the driving pulses according with parameter request strictly, which is based on MAX7000S by using MAX-PLUS II software. The basic driving circuit module has being finished based on this method. The output waveform of the module is the same figure as the simulation waveform. The result indicates that the design method is feasible. (authors)

Evaluating the negative or valuing the positive? Neural mechanisms supporting feedback-based learning across development.

Science.gov (United States)

van Duijvenvoorde, Anna C K; Zanolie, Kiki; Rombouts, Serge A R B; Raijmakers, Maartje E J; Crone, Eveline A

2008-09-17

How children learn from positive and negative performance feedback lies at the foundation of successful learning and is therefore of great importance for educational practice. In this study, we used functional magnetic resonance imaging (fMRI) to examine the neural developmental changes related to feedback-based learning when performing a rule search and application task. Behavioral results from three age groups (8-9, 11-13, and 18-25 years of age) demonstrated that, compared with adults, 8- to 9-year-old children performed disproportionally more inaccurately after receiving negative feedback relative to positive feedback. Additionally, imaging data pointed toward a qualitative difference in how children and adults use performance feedback. That is, dorsolateral prefrontal cortex and superior parietal cortex were more active after negative feedback for adults, but after positive feedback for children (8-9 years of age). For 11- to 13-year-olds, these regions did not show differential feedback sensitivity, suggesting that the transition occurs around this age. Pre-supplementary motor area/anterior cingulate cortex, in contrast, was more active after negative feedback in both 11- to 13-year-olds and adults, but not 8- to 9-year-olds. Together, the current data show that cognitive control areas are differentially engaged during feedback-based learning across development. Adults engage these regions after signals of response adjustment (i.e., negative feedback). Young children engage these regions after signals of response continuation (i.e., positive feedback). The neural activation patterns found in 11- to 13-year-olds indicate a transition around this age toward an increased influence of negative feedback on performance adjustment. This is the first developmental fMRI study to compare qualitative changes in brain activation during feedback learning across distinct stages of development.

Making the Grade: Using Instructional Feedback and Evaluation to Inspire Evidence-Based Teaching

Science.gov (United States)

Brickman, Peggy; Gormally, Cara; Martella, Amedee Marchand

2016-01-01

Typically, faculty receive feedback about teaching via two mechanisms: end-of-semester student evaluations and peer observation. However, instructors require more sustained encouragement and constructive feedback when implementing evidence-based teaching practices. Our study goal was to characterize the landscape of current instructional-feedback…

Feedback Networks

OpenAIRE

Zamir, Amir R.; Wu, Te-Lin; Sun, Lin; Shen, William; Malik, Jitendra; Savarese, Silvio

2016-01-01

Currently, the most successful learning models in computer vision are based on learning successive representations followed by a decision layer. This is usually actualized through feedforward multilayer neural networks, e.g. ConvNets, where each layer forms one of such successive representations. However, an alternative that can achieve the same goal is a feedback based approach in which the representation is formed in an iterative manner based on a feedback received from previous iteration's...

Fast protection circuit for 1 MW Klystron based RF system of Low Energy High Intensity Proton Accelerator (LEHIPA)

International Nuclear Information System (INIS)

Shrotriya, Sandip; Shiju, A.; Patel, N.R.; Pande, Manjiri; Singh, P.

2014-01-01

This paper describes the details of a hardwired protection circuit designed and developed for 1 MW Klystron based Radio Frequency (RF) System. The hardwired protection circuit protects the klystron from fault conditions occurring in high power DC supplies, other bias supplies and inside the klystron itself. Fast response of the order of 1-2 microseconds is necessary in case of critical signals for the protection of such a high power system. The system needs to handle around 10 critical signals comprising of optical signals and different digital signals. In case of malfunction in the existing controller based interlock and protection system, klystron will be protected by this hardwired protection circuit. The hardwired circuit will provide redundant protection and protect the klystron from damage. This circuit and controller based protection system are operating in parallel. This paper describes details of a purely hardwired protection circuit developed for critical signals for achieving reliability and faster response time requirements of the RF system. (author)

Developing a Web-Based Developmental Feedback Program

National Research Council Canada - National Science Library

Douglas, Matthew

2003-01-01

Developmental feedback programs provide an opportunity to improve leadership practices by giving leaders feedback about their performance from a number of sources, This thesis expanded on Capt Doug Patton's pilot study (2002...

Programmed coherent coupling in a synthetic DNA-based excitonic circuit

Science.gov (United States)

Boulais, Étienne; Sawaya, Nicolas P. D.; Veneziano, Rémi; Andreoni, Alessio; Banal, James L.; Kondo, Toru; Mandal, Sarthak; Lin, Su; Schlau-Cohen, Gabriela S.; Woodbury, Neal W.; Yan, Hao; Aspuru-Guzik, Alán; Bathe, Mark

2018-02-01

Natural light-harvesting systems spatially organize densely packed chromophore aggregates using rigid protein scaffolds to achieve highly efficient, directed energy transfer. Here, we report a synthetic strategy using rigid DNA scaffolds to similarly program the spatial organization of densely packed, discrete clusters of cyanine dye aggregates with tunable absorption spectra and strongly coupled exciton dynamics present in natural light-harvesting systems. We first characterize the range of dye-aggregate sizes that can be templated spatially by A-tracts of B-form DNA while retaining coherent energy transfer. We then use structure-based modelling and quantum dynamics to guide the rational design of higher-order synthetic circuits consisting of multiple discrete dye aggregates within a DX-tile. These programmed circuits exhibit excitonic transport properties with prominent circular dichroism, superradiance, and fast delocalized exciton transfer, consistent with our quantum dynamics predictions. This bottom-up strategy offers a versatile approach to the rational design of strongly coupled excitonic circuits using spatially organized dye aggregates for use in coherent nanoscale energy transport, artificial light-harvesting, and nanophotonics.

InP-based three-dimensional photonic integrated circuits

Science.gov (United States)

Tsou, Diana; Zaytsev, Sergey; Pauchard, Alexandre; Hummel, Steve; Lo, Yu-Hwa

2001-10-01

Fast-growing internet traffic volumes require high data communication bandwidth over longer distances than short wavelength (850 nm) multi-mode fiber systems can provide. Access network bottlenecks put pressure on short-range (SR) telecommunication systems. To effectively address these datacom and telecom market needs, low cost, high-speed laser modules at 1310 and 1550 nm wavelengths are required. The great success of GaAs 850 nm VCSELs for Gb/s Ethernet has motivated efforts to extend VCSEL technology to longer wavelengths in the 1310 and 1550 nm regimes. However, the technological challenges associated with available intrinsic materials for long wavelength VCSELs are tremendous. Even with recent advances in this area, it is believed that significant additional development is necessary before long wavelength VCSELs that meet commercial specifications will be widely available. In addition, the more stringent OC192 and OC768 specifications for single-mode fiber (SMF) datacom may require more than just a long wavelength laser diode, VCSEL or not, to address numerous cost and performance issues. We believe that photonic integrated circuits, which compactly integrate surface-emitting lasers with additional active and passive optical components with extended functionality, will provide the best solutions to today's problems. Photonic integrated circuits (PICs) have been investigated for more than a decade. However, they have produced limited commercial impact to date primarily because the highly complicated fabrication processes produce significant yield and device performance issues. In this presentation, we will discuss a new technology platform for fabricating InP-based photonic integrated circuits compatible with surface-emitting laser technology. Employing InP transparency at 1310 and 1550 nm wavelengths, we have created 3-D photonic integrated circuits (PICs) by utilizing light beams in both surface normal and in-plane directions within the InP-based structure

Can performance feedback during instruction boost knowledge acquisition? Contrasting criterion-based and social comparison feedback

NARCIS (Netherlands)

Kolloffel, Bas Jan; de Jong, Anthonius J.M.

2016-01-01

Feedback indicating how well students are performing during a learning task can be very stimulating. In this study with a pre- and post-test design, the effects of two types of performance feedback on learning results were compared: feedback during a learning task was either stated in terms of how

An analytical approach to bistable biological circuit discrimination using real algebraic geometry.

Science.gov (United States)

Siegal-Gaskins, Dan; Franco, Elisa; Zhou, Tiffany; Murray, Richard M

2015-07-06

Biomolecular circuits with two distinct and stable steady states have been identified as essential components in a wide range of biological networks, with a variety of mechanisms and topologies giving rise to their important bistable property. Understanding the differences between circuit implementations is an important question, particularly for the synthetic biologist faced with determining which bistable circuit design out of many is best for their specific application. In this work we explore the applicability of Sturm's theorem--a tool from nineteenth-century real algebraic geometry--to comparing 'functionally equivalent' bistable circuits without the need for numerical simulation. We first consider two genetic toggle variants and two different positive feedback circuits, and show how specific topological properties present in each type of circuit can serve to increase the size of the regions of parameter space in which they function as switches. We then demonstrate that a single competitive monomeric activator added to a purely monomeric (and otherwise monostable) mutual repressor circuit is sufficient for bistability. Finally, we compare our approach with the Routh-Hurwitz method and derive consistent, yet more powerful, parametric conditions. The predictive power and ease of use of Sturm's theorem demonstrated in this work suggest that algebraic geometric techniques may be underused in biomolecular circuit analysis.

Electrochemical study of galvanic corrosion inhibitors in water-based and ethylene glycol-based heat transfer circuits

International Nuclear Information System (INIS)

Netter, Pierre

1981-01-01

This research thesis reports the search for and the efficiency assessment of mixes of inhibitors for coolant circuits of motor cars. After a discussion of the general properties of water-alcohol solvents (chemical properties, acid-base equilibriums) and of parameters affecting corrosion in coolant circuits, the author proposes an overview of the main inhibitors which are used to protect these circuits against corrosion, and discusses their action mechanism and efficiency. The different methods used to study the corrosion of these circuits are described, and the advantages and drawbacks of test methods are commented. The second part proposes a synthesis of the different corrosion electromechanical mechanisms which may occur with respect to the used metallic materials and to possible galvanic couplings. The next part describes the experimental installations. The last part focuses on the different protections obtained with the different used inhibitor class in terms of results obtained by gravimetric tests and visual examination of samples, current-voltage curves in hydrodynamic regime, and galvanic corrosion tests performed in laboratory or in situ in motor cars [fr

Evaluating the Evidence Base of Performance Feedback in Preservice Special Education Teacher Training

Science.gov (United States)

Cornelius, Kyena E.; Nagro, Sarah A.

2014-01-01

Performance feedback is commonly used during field experiences to improve desired teaching behaviors in preservice teachers. The authors identify eight single-subject studies examining the effects of performance feedback in preservice teachers to determine the evidence base for this practice. These eight studies are reviewed using quality…

Beam closed orbit feedback based on PID control

International Nuclear Information System (INIS)

Xuan Ke; Wang Lin; Liu Gongfa; Li Weimin; Li Chuan; Wang Jigang; Bao Xun; Xu Hongliang

2013-01-01

The algorithm in the feedback system has important influence on the performance of the beam orbit. Good feedback algorithm can greatly improve the beam orbit stability. In this paper, the theory of beam closed orbit correction, the principle of PID control and the beam closed orbit feedback correction using PID control were introduced. The simulation results were given. Compared with least-square method, the PID feedback algorithm makes the steady-state error smaller and more accurate, and enhances the beam orbit stability. (authors)

Integrated Circuit-Based Biofabrication with Common Biomaterials for Probing Cellular Biomechanics.

Science.gov (United States)

Sung, Chun-Yen; Yang, Chung-Yao; Yeh, J Andrew; Cheng, Chao-Min

2016-02-01

Recent advances in bioengineering have enabled the development of biomedical tools with modifiable surface features (small-scale architecture) to mimic extracellular matrices and aid in the development of well-controlled platforms that allow for the application of mechanical stimulation for studying cellular biomechanics. An overview of recent developments in common biomaterials that can be manufactured using integrated circuit-based biofabrication is presented. Integrated circuit-based biofabrication possesses advantages including mass and diverse production capacities for fabricating in vitro biomedical devices. This review highlights the use of common biomaterials that have been most frequently used to study cellular biomechanics. In addition, the influence of various small-scale characteristics on common biomaterial surfaces for a range of different cell types is discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Feedback Gating Control for Network Based on Macroscopic Fundamental Diagram

Directory of Open Access Journals (Sweden)

YangBeibei Ji

2016-01-01

Full Text Available Empirical data from Yokohama, Japan, showed that a macroscopic fundamental diagram (MFD of urban traffic provides for different network regions a unimodal low-scatter relationship between network vehicle density and network space-mean flow. This provides new tools for network congestion control. Based on MFD, this paper proposed a feedback gating control policy which can be used to mitigate network congestion by adjusting signal timings of gating intersections. The objective of the feedback gating control model is to maximize the outflow and distribute the allowed inflows properly according to external demand and capacity of each gating intersection. An example network is used to test the performance of proposed feedback gating control model. Two types of background signalization types for the intersections within the test network, fixed-time and actuated control, are considered. The results of extensive simulation validate that the proposed feedback gating control model can get a Pareto improvement since the performance of both gating intersections and the whole network can be improved significantly especially under heavy demand situations. The inflows and outflows can be improved to a higher level, and the delay and queue length at all gating intersections are decreased dramatically.

Research on laser detonation pulse circuit with low-power based on super capacitor

Science.gov (United States)

Wang, Hao-yu; Hong, Jin; He, Aifeng; Jing, Bo; Cao, Chun-qiang; Ma, Yue; Chu, En-yi; Hu, Ya-dong

2018-03-01

According to the demand of laser initiating device miniaturization and low power consumption of weapon system, research on the low power pulse laser detonation circuit with super capacitor. Established a dynamic model of laser output based on super capacitance storage capacity, discharge voltage and programmable output pulse width. The output performance of the super capacitor under different energy storage capacity and discharge voltage is obtained by simulation. The experimental test system was set up, and the laser diode of low power pulsed laser detonation circuit was tested and the laser output waveform of laser diode in different energy storage capacity and discharge voltage was collected. Experiments show that low power pulse laser detonation based on super capacitor energy storage circuit discharge with high efficiency, good transient performance, for a low power consumption requirement, for laser detonation system and low power consumption and provide reference light miniaturization of engineering practice.

Integrated Power Flow and Short Circuit Calculation Method for Distribution Network with Inverter Based Distributed Generation

Directory of Open Access Journals (Sweden)

Shan Yang

2016-01-01

Full Text Available Power flow calculation and short circuit calculation are the basis of theoretical research for distribution network with inverter based distributed generation. The similarity of equivalent model for inverter based distributed generation during normal and fault conditions of distribution network and the differences between power flow and short circuit calculation are analyzed in this paper. Then an integrated power flow and short circuit calculation method for distribution network with inverter based distributed generation is proposed. The proposed method let the inverter based distributed generation be equivalent to Iθ bus, which makes it suitable to calculate the power flow of distribution network with a current limited inverter based distributed generation. And the low voltage ride through capability of inverter based distributed generation can be considered as well in this paper. Finally, some tests of power flow and short circuit current calculation are performed on a 33-bus distribution network. The calculated results from the proposed method in this paper are contrasted with those by the traditional method and the simulation method, whose results have verified the effectiveness of the integrated method suggested in this paper.

Can Performance Feedback during Instruction Boost Knowledge Acquisition? Contrasting Criterion-Based and Social Comparison Feedback

Science.gov (United States)

Kollöffel, Bas; de Jong, Ton

2016-01-01

Feedback indicating how well students are performing during a learning task can be very stimulating. In this study with a pre- and post-test design, the effects of two types of performance feedback on learning results were compared: feedback during a learning task was either stated in terms of how well the students were performing relative to…

Spectrum optimization-based chaotification using time-delay feedback control

International Nuclear Information System (INIS)

Zhou Jiaxi; Xu Daolin; Zhang Jing; Liu Chunrong

2012-01-01

Highlights: ► A time-delay feedback controller is designed for chaotification. ► A spectrum optimization method is proposed to determine chaotification parameters. ► Numerical examples verify the spectrum optimization- based chaotification method. ► Engineering application in line spectrum reconfiguration is demonstrated. - Abstract: In this paper, a spectrum optimization method is developed for chaotification in conjunction with an application in line spectrum reconfiguration. A key performance index (the objective function) based on Fourier spectrum is specially devised with the idea of suppressing spectrum spikes and broadening frequency band. Minimization of the index empowered by a genetic algorithm enables to locate favorable parameters of the time-delay feedback controller, by which a line spectrum of harmonic vibration can be transformed into a broad-band continuous spectrum of chaotic motion. Numerical simulations are carried out to verify the feasibility of the method and to demonstrate its effectiveness of chaotifying a 2-DOFs linear mechanical system.

A perturbation-based model for rectifier circuits

Directory of Open Access Journals (Sweden)

Vipin B. Vats

2006-01-01

Full Text Available A perturbation-theoretic analysis of rectifier circuits is presented. The governing differential equation of the half-wave rectifier with capacitor filter is analyzed by expanding the output voltage as a Taylor series with respect to an artificially introduced parameter in the nonlinearity of the diode characteristic as is done in quantum theory. The perturbation parameter introduced in the analysis is independent of the circuit components as compared to the method presented by multiple scales. The various terms appearing in the perturbation series are then modeled in the form of an equivalent circuit. This model is subsequently used in the analysis of full-wave rectifier. Matlab simulation results are included which confirm the validity of the theoretical formulations. Perturbation analysis acts a helpful tool in analyzing time-varying systems and chaotic systems.

[Leptin and the feedback regulation of body weight].

Science.gov (United States)

Wang, X; Ye, G; Sun, J

1999-09-30

Body weight may be controlled by a negative feedback loop. Recent studies have identified that the ob gene product, leptin, apparently and exclusively expressed in adipose tissue, is a part of the negative feedback loop. Leptin is proposed to act as an afferent signal in the negative feedback loop to hypothalamus that limiting food-intake, controlling energy homeostasis and regulating the mass of adipose tissue. The dificiency of or resistance to leptin causes severe obesity.

The Patient Feedback Response Framework - Understanding why UK hospital staff find it difficult to make improvements based on patient feedback: A qualitative study.

Science.gov (United States)

Sheard, Laura; Marsh, Claire; O'Hara, Jane; Armitage, Gerry; Wright, John; Lawton, Rebecca

2017-04-01

Patients are increasingly being asked for feedback about their healthcare experiences. However, healthcare staff often find it difficult to act on this feedback in order to make improvements to services. This paper draws upon notions of legitimacy and readiness to develop a conceptual framework (Patient Feedback Response Framework - PFRF) which outlines why staff may find it problematic to respond to patient feedback. A large qualitative study was conducted with 17 ward based teams between 2013 and 2014, across three hospital Trusts in the North of England. This was a process evaluation of a wider study where ward staff were encouraged to make action plans based on patient feedback. We focus on three methods here: i) examination of taped discussion between ward staff during action planning meetings ii) facilitators notes of these meetings iii) telephone interviews with staff focusing on whether action plans had been achieved six months later. Analysis employed an abductive approach. Through the development of the PFRF, we found that making changes based on patient feedback is a complex multi-tiered process and not something that ward staff can simply 'do'. First, staff must exhibit normative legitimacy - the belief that listening to patients is a worthwhile exercise. Second, structural legitimacy has to be in place - ward teams need adequate autonomy, ownership and resource to enact change. Some ward teams are able to make improvements within their immediate control and environment. Third, for those staff who require interdepartmental co-operation or high level assistance to achieve change, organisational readiness must exist at the level of the hospital otherwise improvement will rarely be enacted. Case studies drawn from our empirical data demonstrate the above. It is only when appropriate levels of individual and organisational capacity to change exist, that patient feedback is likely to be acted upon to improve services. Copyright © 2017 The Authors. Published

Analysis and modelling of GaN Schottky-based circuits at millimeter wavelengths

International Nuclear Information System (INIS)

Pardo, D; Grajal, J

2015-01-01

This work presents an analysis of the capabilities of GaN Schottky diodes for frequency multipliers and mixers at millimeter wavelengths. By using a Monte Carlo (MC) model of the diode coupled to a harmonic balance technique, the electrical and noise performances of these circuits are investigated. Despite the lower electron mobility of GaN compared to GaAs, multipliers based on GaN Schottky diodes can be competitive in the first stages of multiplier chains, due to the excellent power handling capabilities of this material. The performance of these circuits can be improved by taking advantage of the lateral Schottky diode structures based on AlGaN/GaN HEMT technology. (paper)

The effect of sensory feedback on crayfish posture and locomotion: II. Neuromechanical simulation of closing the loop.

Science.gov (United States)

Bacqué-Cazenave, Julien; Chung, Bryce; Cofer, David W; Cattaert, Daniel; Edwards, Donald H

2015-03-15

Neuromechanical simulation was used to determine whether proposed thoracic circuit mechanisms for the control of leg elevation and depression in crayfish could account for the responses of an experimental hybrid neuromechanical preparation when the proprioceptive feedback loop was open and closed. The hybrid neuromechanical preparation consisted of a computational model of the fifth crayfish leg driven in real time by the experimentally recorded activity of the levator and depressor (Lev/Dep) nerves of an in vitro preparation of the crayfish thoracic nerve cord. Up and down movements of the model leg evoked by motor nerve activity released and stretched the model coxobasal chordotonal organ (CBCO); variations in the CBCO length were used to drive identical variations in the length of the live CBCO in the in vitro preparation. CBCO afferent responses provided proprioceptive feedback to affect the thoracic motor output. Experiments performed with this hybrid neuromechanical preparation were simulated with a neuromechanical model in which a computational circuit model represented the relevant thoracic circuitry. Model simulations were able to reproduce the hybrid neuromechanical experimental results to show that proposed circuit mechanisms with sensory feedback could account for resistance reflexes displayed in the quiescent state and for reflex reversal and spontaneous Lev/Dep bursting seen in the active state. Copyright © 2015 the American Physiological Society.

Functional roles for noise in genetic circuits.

Science.gov (United States)

Eldar, Avigdor; Elowitz, Michael B

2010-09-09

The genetic circuits that regulate cellular functions are subject to stochastic fluctuations, or 'noise', in the levels of their components. Noise, far from just a nuisance, has begun to be appreciated for its essential role in key cellular activities. Noise functions in both microbial and eukaryotic cells, in multicellular development, and in evolution. It enables coordination of gene expression across large regulons, as well as probabilistic differentiation strategies that function across cell populations. At the longest timescales, noise may facilitate evolutionary transitions. Here we review examples and emerging principles that connect noise, the architecture of the gene circuits in which it is present, and the biological functions it enables. We further indicate some of the important challenges and opportunities going forward.

PSPICE simulation of bipolar pulse converter based on short-circuited coaxial transmission line

International Nuclear Information System (INIS)

Shi Lei; Fan Yajun

2010-01-01

The operating principle of the bipolar pulse converter based on short-circuited coaxial transmission line type is given. The output bipolar pulses are simulated by using PSPICE program on condition of different electric length and different impedance of the short-circuited coaxial transmission line. The bipolar pulses are generated by using unipolar pulse with pulse width of 2 ns in experiment, the experimental result fit well with the simulation result. (authors)

Vision-Based Haptic Feedback for Remote Micromanipulation in-SEM Environment

Science.gov (United States)

Bolopion, Aude; Dahmen, Christian; Stolle, Christian; Haliyo, Sinan; Régnier, Stéphane; Fatikow, Sergej

2012-07-01

This article presents an intuitive environment for remote micromanipulation composed of both haptic feedback and virtual reconstruction of the scene. To enable nonexpert users to perform complex teleoperated micromanipulation tasks, it is of utmost importance to provide them with information about the 3-D relative positions of the objects and the tools. Haptic feedback is an intuitive way to transmit such information. Since position sensors are not available at this scale, visual feedback is used to derive information about the scene. In this work, three different techniques are implemented, evaluated, and compared to derive the object positions from scanning electron microscope images. The modified correlation matching with generated template algorithm is accurate and provides reliable detection of objects. To track the tool, a marker-based approach is chosen since fast detection is required for stable haptic feedback. Information derived from these algorithms is used to propose an intuitive remote manipulation system that enables users situated in geographically distant sites to benefit from specific equipments, such as SEMs. Stability of the haptic feedback is ensured by the minimization of the delays, the computational efficiency of vision algorithms, and the proper tuning of the haptic coupling. Virtual guides are proposed to avoid any involuntary collisions between the tool and the objects. This approach is validated by a teleoperation involving melamine microspheres with a diameter of less than 2 μ m between Paris, France and Oldenburg, Germany.

Prospects of luminescence based molecular scale logic gates and logic circuits

International Nuclear Information System (INIS)

Speiser, Shammai

2016-01-01

In recent years molecular electronics has emerged as a rapidly growing research field. The aim of this review is to introduce this subject as a whole with special emphasis on molecular scale potential devices and applications. As a particular example we will discuss all optical molecular scale logic gates and logic circuits based on molecular fluorescence and electronic excitation transfer processes. Charge and electronic energy transfers (ET and EET) are well-studied examples whereby different molecules can signal their state from one (the donor, D) to the other (the acceptor, A). We show how a half-adder logic circuit can be implemented on one molecule that can communicate its logic output as input to another half-adder molecule. This is achieved as an electronic energy transfer from a donor to an acceptor, thus implementing a molecular full adder. We discuss a specific pair, the rhodamine–azulene, for which there is considerable spectroscopic data, but the scheme is general enough to allow a wide choice of D and A pairs. We present results based on this pair, in which, for the first time, an all optical half-adder and full-adder logic circuits are implemented. - Highlights: • Molecular scale logic • Photoquenching • Full adder

Prospects of luminescence based molecular scale logic gates and logic circuits

Energy Technology Data Exchange (ETDEWEB)

Speiser, Shammai, E-mail: speiser@technion.ac.il

2016-01-15

In recent years molecular electronics has emerged as a rapidly growing research field. The aim of this review is to introduce this subject as a whole with special emphasis on molecular scale potential devices and applications. As a particular example we will discuss all optical molecular scale logic gates and logic circuits based on molecular fluorescence and electronic excitation transfer processes. Charge and electronic energy transfers (ET and EET) are well-studied examples whereby different molecules can signal their state from one (the donor, D) to the other (the acceptor, A). We show how a half-adder logic circuit can be implemented on one molecule that can communicate its logic output as input to another half-adder molecule. This is achieved as an electronic energy transfer from a donor to an acceptor, thus implementing a molecular full adder. We discuss a specific pair, the rhodamine–azulene, for which there is considerable spectroscopic data, but the scheme is general enough to allow a wide choice of D and A pairs. We present results based on this pair, in which, for the first time, an all optical half-adder and full-adder logic circuits are implemented. - Highlights: • Molecular scale logic • Photoquenching • Full adder.

Improving Hospital Services Based on Patient Experience Data: Current Feedback Practices and Future Opportunities.

Science.gov (United States)

Kaipio, Johanna; Stenhammar, Hanna; Immonen, Susanna; Litovuo, Lauri; Axelsson, Minja; Lantto, Minna; Lahdenne, Pekka

2018-01-01

Patient feedback is considered important for healthcare organizations. However, measurement and analysis of patient reported data is useful only if gathered insights are transformed into actions. This article focuses on gathering and utilization of patient experience data at hospitals with the aim of supporting the development of patient-centered services. The study was designed to explore both current practices of collecting and utilizing patient feedback at hospitals as well as future feedback-related opportunities. Nine people working at different hierarchical levels of three university hospitals in Finland participated in in-depth interviews. Findings indicate that current feedback processes are poorly planned and inflexible. Some feedback data are gathered, but not systematically utilized. Currently, it is difficult to obtain a comprehensive picture of the situation. One future hope was to increase the amount of patient feedback to be able to better generalize and utilize the data. Based on the findings the following recommendations are given: attention to both patients' and healthcare staff's perspectives when collecting feedback, employing a coordinated approach for collecting and utilizing patient feedback, and organizational transformation towards a patient-centric culture.

Study of CMOS micromachined self-oscillating loop utilizing a phase-locked loop-driving circuit

International Nuclear Information System (INIS)

Li, Hsin-Chih; Tseng, Sheng-Hsiang; Lu, Michael S.-C.; Huang, Po-Chiun

2012-01-01

This work describes the design and characterization of integrated CMOS (complementary metal oxide semiconductor) oscillators comprising a capacitively transduced micromechanical resonator and a phase-locked loop (PLL) driving circuit. Three oscillator schemes are studied and compared, including direct feedback, direct feedback containing a PLL and hybrid direct feedback plus a PLL. PLL is known for its capability in automatic tuning and tracking of a reference signal. Inclusion of a PLL is beneficial for sustaining oscillations at resonant frequencies within its capture range. The micromechanical resonator has a measured resonant frequency of 117.3 kHz. The CMOS PLL circuit has a closed-loop bandwidth of 1.8 kHz with a capture range between 111 kHz and 118.4 kHz. The start-up times for oscillation are shortened in the two schemes utilizing a PLL, since it provides an initial driving signal at its free-running frequency. The lock-in time is also reduced by increasing the proportion of PLL drive in the hybrid scheme. The measured noises for the three oscillator schemes are similar with a value of −75 dB below the resonant peak at a 10 Hz offset. (paper)

Deciphering molecular circuits from genetic variation underlying transcriptional responsiveness to stimuli.

Science.gov (United States)

Gat-Viks, Irit; Chevrier, Nicolas; Wilentzik, Roni; Eisenhaure, Thomas; Raychowdhury, Raktima; Steuerman, Yael; Shalek, Alex K; Hacohen, Nir; Amit, Ido; Regev, Aviv

2013-04-01

Individual genetic variation affects gene responsiveness to stimuli, often by influencing complex molecular circuits. Here we combine genomic and intermediate-scale transcriptional profiling with computational methods to identify variants that affect the responsiveness of genes to stimuli (responsiveness quantitative trait loci or reQTLs) and to position these variants in molecular circuit diagrams. We apply this approach to study variation in transcriptional responsiveness to pathogen components in dendritic cells from recombinant inbred mouse strains. We identify reQTLs that correlate with particular stimuli and position them in known pathways. For example, in response to a virus-like stimulus, a trans-acting variant responds as an activator of the antiviral response; using RNA interference, we identify Rgs16 as the likely causal gene. Our approach charts an experimental and analytic path to decipher the mechanisms underlying genetic variation in circuits that control responses to stimuli.

Static inverter with synchronous output waveform synthesized by time-optimal-response feedback

Science.gov (United States)

Kernick, A.; Stechschulte, D. L.; Shireman, D. W.

1976-01-01

Time-optimal-response 'bang-bang' or 'bang-hang' technique, using four feedback control loops, synthesizes static-inverter sinusoidal output waveform by self-oscillatory but yet synchronous pulse-frequency-modulation (SPFM). A single modular power stage per phase of ac output entails the minimum of circuit complexity while providing by feedback synthesis individual phase voltage regulation, phase position control and inherent compensation simultaneously for line and load disturbances. Clipped sinewave performance is described under off-limit load or input voltage conditions. Also, approaches to high power levels, 3-phase arraying and parallel modular connection are given.

'Speedy' superconducting circuits

International Nuclear Information System (INIS)

Holst, T.

1994-01-01

The most promising concept for realizing ultra-fast superconducting digital circuits is the Rapid Single Flux Quantum (RSFQ) logic. The basic physical principle behind RSFQ logic, which include the storage and transfer of individual magnetic flux quanta in Superconducting Quantum Interference Devices (SQUIDs), is explained. A Set-Reset flip-flop is used as an example of the implementation of an RSFQ based circuit. Finally, the outlook for high-temperature superconducting materials in connection with RSFQ circuits is discussed in some details. (au)

Spontaneous Synchronization in Two Mutually Coupled Memristor-Based Chua’s Circuits: Numerical Investigations

Directory of Open Access Journals (Sweden)

Eleonora Bilotta

2014-01-01

Full Text Available Chaotic dynamics of numerous memristor-based circuits is widely reported in literature. Recently, some works have appeared which study the problem of synchronization control of these systems in a master-slave configuration. In the present paper, the spontaneous dynamic behavior of two chaotic memristor-based Chua’s circuits, mutually interacting through a coupling resistance, was studied via computer simulations in order to study possible self-organized synchronization phenomena. The used memristor is a flux controlled memristor with a cubic nonlinearity, and it can be regarded as a time-varying memductance. The memristor, in effect, retains memory of its past dynamic and any difference in the initial conditions of the two circuits results in different values of the corresponding memductances. In this sense, due to the memory effect of the memristor, even if coupled circuits have the same parameters they do not constitute two completely identical chaotic oscillators. As is known, for nonidentical chaotic systems, in addition to complete synchronizations (CS other weaker forms of synchronization which provide correlations between the signals of the two systems can also occur. Depending on initial conditions and coupling strength, both chaotic and nonchaotic synchronization are observed for the system considered in this work.

Sample-angle feedback for diffraction anomalous fine-structure spectroscopy

International Nuclear Information System (INIS)

Cross, J.O.; Elam, W.T.; Harris, V.G.; Kirkland, J.P.; Bouldin, C.E.; Sorensen, L.B.

1998-01-01

Diffraction anomalous fine-structure (DAFS) experiments measure Bragg peak intensities as continuous functions of photon energy near a core-level excitation. Measuring the integrated intensity at each energy makes the experiments prohibitively slow; however, in many cases DAFS can be collected quickly by measuring only the peak intensity at the center of the rocking curve. A piezoelectric-actuator-driven stage has been designed and tested as part of a sample-angle feedback circuit for locking onto the maximum of the rocking curve while the energy is scanned. Although software peak-tracking requires only a simple calculation of diffractometer angles, it is found that the additional hardware feedback dramatically improves the reproducibility of the data

Student use of model-based reasoning when troubleshooting an electronic circuit

Science.gov (United States)

Lewandowski, Heather; Stetzer, Mackenzie; van de Bogart, Kevin; Dounas-Frazer, Dimitri

2016-03-01

Troubleshooting systems is an integral part of experimental physics in both research and educational settings. Accordingly, ability to troubleshoot is an important learning goal for undergraduate physics lab courses. We investigate students' model-based reasoning on a troubleshooting task using data collected in think-aloud interviews during which pairs of students from two institutions attempted to diagnose and repair a malfunctioning circuit. Our analysis scheme was informed by the Experimental Modeling Framework, which describes physicists' use of mathematical and conceptual models when reasoning about experimental systems. We show that system and subsystem models were crucial for the evaluation of repairs to the circuit and played an important role in some troubleshooting strategies. Finally, drawing on data from interviews with electronics instructors from a broad range of institution types, we outline recommendations for model-based approaches to teaching and learning troubleshooting skills.

Student use of model-based reasoning when troubleshooting an electric circuit

Science.gov (United States)

Dounas-Frazer, Dimitri

2016-05-01

Troubleshooting systems is an integral part of experimental physics in both research and educational settings. Accordingly, ability to troubleshoot is an important learning goal for undergraduate physics lab courses. We investigate students' model-based reasoning on a troubleshooting task using data collected in think-aloud interviews during which pairs of students from two institutions attempted to diagnose and repair a malfunctioning circuit. Our analysis scheme was informed by the Experimental Modeling Framework, which describes physicists' use of mathematical and conceptual models when reasoning about experimental systems. We show that system and subsystem models were crucial for the evaluation of repairs to the circuit and played an important role in some troubleshooting strategies. Finally, drawing on data from interviews with electronics instructors from a broad range of institution types, we outline recommendations for model-based approaches to teaching and learning troubleshooting skills.

Secondary access based on sensing and primary ARQ feedback in spectrum sharing systems

KAUST Repository

Hamza, Doha R.

2012-04-01

In the context of primary/secondary spectrum sharing, we propose a randomized secondary access strategy with access probabilities that are a function of both the primary automatic repeat request (ARQ) feedback and the spectrum sensing outcome. The primary terminal operates in a time slotted fashion and is active only when it has a packet to send. The primary receiver can send a positive acknowledgment (ACK) when the received packet is decoded correctly. Lack of ARQ feedback is interpreted as erroneous reception or inactivity. We call this the explicit ACK scheme. The primary receiver may also send a negative acknowledgment (NACK) when the packet is received in error. Lack of ARQ feedback is interpreted as an ACK or no-transmission. This is called the explicit NACK scheme. Under both schemes, when the primary feedback is interpreted as a NACK, the secondary user assumes that there will be retransmission in the next slot and accesses the channel with a certain probability. When the primary feedback is interpreted as an ACK, the secondary user accesses the channel with either one of two probabilities based on the sensing outcome. Under these settings, we find the three optimal access probabilities via maximizing the secondary throughput given a constraint on the primary throughput. We compare the performance of the explicit ACK and explicit NACK schemes and contrast them with schemes based on either sensing or primary ARQ feedback only. © 2012 IEEE.

A universal gyroscope driving circuit with 70dB amplitude control range

KAUST Repository

Abdelghany, Mohamed A.

2010-08-01

A CMOS variable gain driving circuit with output signal amplitude control for gyroscopes with wide range of quality factors is presented. The driving circuit can be used for gyroscopes with Q values higher than 500. The circuit uses a current-commutating switching mixer to control the gyroscope driving signal level. Conventional driving circuits use automatic gain control (AGC) which suffers from limited linear range and the need for an off-chip capacitor for the peak detector and loop filter. Two stage variable gain amplifier is used in the proposed design to ensure enough gain for oscillation for such a wide range of quality factors. Analog and digital amplitude control methods are used to cover wide range of driving signal amplitude with enough accuracy to hit the maximum driving signal level without sacrificing gyroscope linearity. Due to the high DC gain of the amplifier chain, DC offset resulting from mismatches might saturate the amplifier output. DC offset correction is employed using a secondary negative feedback loop. The proposed driving circuit is being fabricated in 0.6μm CMOS technology. © 2010 IEEE.

Tunable and broadband microwave frequency combs based on a semiconductor laser with incoherent optical feedback

International Nuclear Information System (INIS)

Zhao Mao-Rong; Wu Zheng-Mao; Deng Tao; Zhou Zhen-Li; Xia Guang-Qiong

2015-01-01

Based on a semiconductor laser (SL) with incoherent optical feedback, a novel all-optical scheme for generating tunable and broadband microwave frequency combs (MFCs) is proposed and investigated numerically. The results show that, under suitable operation parameters, the SL with incoherent optical feedback can be driven to operate at a regular pulsing state, and the generated MFCs have bandwidths broader than 40 GHz within a 10 dB amplitude variation. For a fixed bias current, the line spacing (or repetition frequency) of the MFCs can be easily tuned by varying the feedback delay time and the feedback strength, and the tuning range of the line spacing increases with the increase in the bias current. The linewidth of the MFCs is sensitive to the variation of the feedback delay time and the feedback strength, and a linewidth of tens of KHz can be achieved through finely adjusting the feedback delay time and the feedback strength. In addition, mappings of amplitude variation, repetition frequency, and linewidth of MFCs in the parameter space of the feedback delay time and the feedback strength are presented. (paper)

Phenotypic deconstruction of gene circuitry.

Science.gov (United States)

Lomnitz, Jason G; Savageau, Michael A

2013-06-01

It remains a challenge to obtain a global perspective on the behavioral repertoire of complex nonlinear gene circuits. In this paper, we describe a method for deconstructing complex systems into nonlinear sub-systems, based on mathematically defined phenotypes, which are then represented within a system design space that allows the repertoire of qualitatively distinct phenotypes of the complex system to be identified, enumerated, and analyzed. This method efficiently characterizes large regions of system design space and quickly generates alternative hypotheses for experimental testing. We describe the motivation and strategy in general terms, illustrate its use with a detailed example involving a two-gene circuit with a rich repertoire of dynamic behavior, and discuss experimental means of navigating the system design space.