Sample records for directed network modules

  1. Sequence dependence of phase-induced intensity noise in optical networks that employ direct modulation

    NASA Astrophysics Data System (ADS)

    Tur, M.; Legg, P. J.; Shabeer, M.; Andonovic, I.

    1995-02-01

    Phase-induced intensity noise in optical networks that employ directly modulated laser sources is observed to be bit-sequence dependent. This dependence is explained by optical frequency variations that are due to the heating history of the laser chip and is accurately modeled. This effect may permit suppression of phase-induced intensity noise in many types of fiber system with multipaths.

  2. Dynamic Network-Based Relevance Score Reveals Essential Proteins and Functional Modules in Directed Differentiation

    PubMed Central

    Wu, Chia-Chou; Lin, Che

    2015-01-01

    The induction of stem cells toward a desired differentiation direction is required for the advancement of stem cell-based therapies. Despite successful demonstrations of the control of differentiation direction, the effective use of stem cell-based therapies suffers from a lack of systematic knowledge regarding the mechanisms underlying directed differentiation. Using dynamic modeling and the temporal microarray data of three differentiation stages, three dynamic protein-protein interaction networks were constructed. The interaction difference networks derived from the constructed networks systematically delineated the evolution of interaction variations and the underlying mechanisms. A proposed relevance score identified the essential components in the directed differentiation. Inspection of well-known proteins and functional modules in the directed differentiation showed the plausibility of the proposed relevance score, with the higher scores of several proteins and function modules indicating their essential roles in the directed differentiation. During the differentiation process, the proteins and functional modules with higher relevance scores also became more specific to the neuronal identity. Ultimately, the essential components revealed by the relevance scores may play a role in controlling the direction of differentiation. In addition, these components may serve as a starting point for understanding the systematic mechanisms of directed differentiation and for increasing the efficiency of stem cell-based therapies. PMID:25977693

  3. Directly modulated laser parameters optimization for metropolitan area networks utilizing negative dispersion fibers

    Microsoft Academic Search

    José A. P. Morgado; Adolfo V. T. Cartaxo

    2003-01-01

    The optimization of an uncooled directly modulated laser operated at 10 Gbit\\/s for metropolitan area networks utilizing negative dispersion fibers is presented. The laser optimization is performed in order to accomplish two goals: maximizing the back-to-back sensitivity and the dispersion tolerance of negative dispersion single-mode fiber. Extensive numerical simulations reveal that a significant improvement of system performance can be achieved

  4. Module bay with directed flow

    DOEpatents

    Torczynski, John R. (Albuquerque, NM)

    2001-02-27

    A module bay requires less cleanroom airflow. A shaped gas inlet passage can allow cleanroom air into the module bay with flow velocity preferentially directed toward contaminant rich portions of a processing module in the module bay. Preferential gas flow direction can more efficiently purge contaminants from appropriate portions of the module bay, allowing a reduced cleanroom air flow rate for contaminant removal. A shelf extending from an air inlet slit in one wall of a module bay can direct air flowing therethrough toward contaminant-rich portions of the module bay, such as a junction between a lid and base of a processing module.

  5. Single package directly modulated laser bidirectional optical subassembly using a modified mini-dual-in-line package for 10 Gbps passive optical networks

    NASA Astrophysics Data System (ADS)

    Lee, Jong Jin; Kim, Jongdeog; Lee, Seihyoung

    2012-12-01

    A bidirectional optical subassembly comprised of a 2.5 Gbps distributed feedback (DFB) laser diode (LD) directly modulated laser transmitter and a 10 Gbps positive intrinsic negative photodiode receiver was developed for an optical network unit of a 10 Gbps passive optical network. Here, a low-cost mini-dual-in-line package was modified to contain whole components of a transmitter and receiver in a single space while satisfying the requirements of 10 Gbps micro-device package standards. The transmitter was fabricated to achieve high optical output power by placing a micro aspheric lens very close to the DFB LD and reducing the thermal resistance between an LD chip and heat sink to bring down the DFB LD chip temperature. As a result, the transmitter output power was 3.5 dB higher than a conventional transistor outline can BOSA due to a high optical coupling efficiency of more than 70% and a low thermal resistance for heat dissipation. The receiver sensitivity was -21 dBm at a bit error rate of 10-3 and the sensitivity penalty of the receiver due to signal crosstalk was less than 0.3 dB.

  6. A mean field neural network for hierarchical module placement

    NASA Technical Reports Server (NTRS)

    Unaltuna, M. Kemal; Pitchumani, Vijay

    1992-01-01

    This paper proposes a mean field neural network for the two-dimensional module placement problem. An efficient coding scheme with only O(N log N) neurons is employed where N is the number of modules. The neurons are evolved in groups of N in log N iteration steps such that the circuit is recursively partitioned in alternating vertical and horizontal directions. In our simulations, the network was able to find optimal solutions to all test problems with up to 128 modules.

  7. Explosive Percolation in Directed Networks

    E-print Network

    Anlage, Steven

    Explosive Percolation in Directed Networks Diego Alcala and Katherine Sytwu With Shane Squires ­ Directed and undirected networks ­ Percolation ­ Explosive percolation · Methodology · Results · Conclusion, infrastructure, etc. · Grow by the addition of links · New class of transitions: "explosive percolation" Taken

  8. Dynamic behaviors in directed networks

    NASA Astrophysics Data System (ADS)

    Park, Sung Min; Kim, Beom Jun

    2006-08-01

    Motivated by the abundance of directed synaptic couplings in a real biological neuronal network, we investigate the synchronization behavior of the Hodgkin-Huxley model in a directed network. We start from the standard model of the Watts-Strogatz undirected network and then change undirected edges to directed arcs with a given probability, still preserving the connectivity of the network. A generalized clustering coefficient for directed networks is defined and used to investigate the interplay between the synchronization behavior and underlying structural properties of directed networks. We observe that the directedness of complex networks plays an important role in emerging dynamical behaviors, which is also confirmed by a numerical study of the sociological game theoretic voter model on directed networks.

  9. A direct density modulation cathode in magnetron

    SciTech Connect

    Li, Wei; Zhang, Jun; Liu, Yong-gui; Yang, Han-wu; Shu, Ting [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073 (China)] [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073 (China)

    2013-09-15

    A direct Density Modulation Cathode (DMC) in magnetron is proposed in this paper. By removing the velocity modulation process, electron spokes corresponding to the dominant operating mode can be quickly formed when the DMC is used. Based on theoretical analysis, particle-in-cell simulations and experimental investigations are carried out for demonstration. The final results show that compared with conventional solid cathode and transparent cathode, the DMC can increase 68% and even 146% of relative microwave widths, respectively.

  10. A novel network module for medical devices

    Microsoft Academic Search

    Ping-Yu Chen

    2008-01-01

    In order to allow medical devices to upload the vital signs to a server on a network without manually configuring for end-users, a new network module is proposed. The proposed network module, called Medical Hub (MH), functions as a bridge to fetch the data from all connecting medical devices, and then upload these data to the server. When powering on,

  11. Demonstration of directly modulated silicon Raman laser

    E-print Network

    Jalali. Bahram

    Demonstration of directly modulated silicon Raman laser Ozdal Boyraz and Bahram Jalali Lett. 38, 1352-1354 (2002). 2. Ozdal Boyraz and Bahram Jalali, "Demonstration of a silicon Raman laser- 618 (2004). 10. Ozdal Boyraz, Dimitri Dimitropoulos and Bahram Jalali, "Observation of simultaneous

  12. Epidemic threshold in directed networks.

    PubMed

    Li, Cong; Wang, Huijuan; Van Mieghem, Piet

    2013-12-01

    Epidemics have so far been mostly studied in undirected networks. However, many real-world networks, such as the online social network Twitter and the world wide web, on which information, emotion, or malware spreads, are directed networks, composed of both unidirectional links and bidirectional links. We define the directionality ? as the percentage of unidirectional links. The epidemic threshold ?(c) for the susceptible-infected-susceptible (SIS) epidemic is lower bounded by 1/?(1) in directed networks, where ?(1), also called the spectral radius, is the largest eigenvalue of the adjacency matrix. In this work, we propose two algorithms to generate directed networks with a given directionality ?. The effect of ? on the spectral radius ?(1), principal eigenvector x(1), spectral gap (?(1)-|?(2)|), and algebraic connectivity ?(N-1) is studied. Important findings are that the spectral radius ?(1) decreases with the directionality ?, whereas the spectral gap and the algebraic connectivity increase with the directionality ?. The extent of the decrease of the spectral radius depends on both the degree distribution and the degree-degree correlation ?(D). Hence, in directed networks, the epidemic threshold is larger and a random walk converges to its steady state faster than that in undirected networks with the same degree distribution. PMID:24483506

  13. Real time network modulation for intractable epilepsy Behnaam Aazhang

    E-print Network

    Aazhang, Behnaam

    Real time network modulation for intractable epilepsy Behnaam Aazhang ! Electrical and Computer;Real time network modulation for intractable epilepsy Behnaam Aazhang ! Electrical and Computer;Real time network modulation for intractable epilepsy Behnaam Aazhang ! Electrical and Computer

  14. Modulation recognition using artificial neural networks

    Microsoft Academic Search

    A. K. Nandi; E. E. Azzouz

    1997-01-01

    This paper presents artificial neural networks (ANNs) for the recognition of either analogue or digital modulation types. Computer simulations of different types of band-limited, modulated signals corrupted by band-limited Gaussian noise sequence have been carried out to measure the performance of the ANN approach. The threshold SNR for the recognition of either analogue or digitally modulated signals with average success

  15. Network Models of Frequency Modulated Sweep Detection

    PubMed Central

    Skorheim, Steven; Razak, Khaleel; Bazhenov, Maxim

    2014-01-01

    Frequency modulated (FM) sweeps are common in species-specific vocalizations, including human speech. Auditory neurons selective for the direction and rate of frequency change in FM sweeps are present across species, but the synaptic mechanisms underlying such selectivity are only beginning to be understood. Even less is known about mechanisms of experience-dependent changes in FM sweep selectivity. We present three network models of synaptic mechanisms of FM sweep direction and rate selectivity that explains experimental data: (1) The ‘facilitation’ model contains frequency selective cells operating as coincidence detectors, summing up multiple excitatory inputs with different time delays. (2) The ‘duration tuned’ model depends on interactions between delayed excitation and early inhibition. The strength of delayed excitation determines the preferred duration. Inhibitory rebound can reinforce the delayed excitation. (3) The ‘inhibitory sideband’ model uses frequency selective inputs to a network of excitatory and inhibitory cells. The strength and asymmetry of these connections results in neurons responsive to sweeps in a single direction of sufficient sweep rate. Variations of these properties, can explain the diversity of rate-dependent direction selectivity seen across species. We show that the inhibitory sideband model can be trained using spike timing dependent plasticity (STDP) to develop direction selectivity from a non-selective network. These models provide a means to compare the proposed synaptic and spectrotemporal mechanisms of FM sweep processing and can be utilized to explore cellular mechanisms underlying experience- or training-dependent changes in spectrotemporal processing across animal models. Given the analogy between FM sweeps and visual motion, these models can serve a broader function in studying stimulus movement across sensory epithelia. PMID:25514021

  16. Name of Module: Network Optimization by Randomization

    E-print Network

    Wichmann, Felix

    abound in as diverse fields as communication protocols, network security, or distributed computing the essence of randomness for network protocol design: foiling the adversary, random sampling, load balancing of randomness when developing new network protocols. This module is principally designed to impart: technical

  17. PRESYNAPTIC NETWORKS. Single-cell-initiated monosynaptic tracing reveals layer-specific cortical network modules.

    PubMed

    Wertz, Adrian; Trenholm, Stuart; Yonehara, Keisuke; Hillier, Daniel; Raics, Zoltan; Leinweber, Marcus; Szalay, Gergely; Ghanem, Alexander; Keller, Georg; Rózsa, Balázs; Conzelmann, Karl-Klaus; Roska, Botond

    2015-07-01

    Individual cortical neurons can selectively respond to specific environmental features, such as visual motion or faces. How this relates to the selectivity of the presynaptic network across cortical layers remains unclear. We used single-cell-initiated, monosynaptically restricted retrograde transsynaptic tracing with rabies viruses expressing GCaMP6s to image, in vivo, the visual motion-evoked activity of individual layer 2/3 pyramidal neurons and their presynaptic networks across layers in mouse primary visual cortex. Neurons within each layer exhibited similar motion direction preferences, forming layer-specific functional modules. In one-third of the networks, the layer modules were locked to the direction preference of the postsynaptic neuron, whereas for other networks the direction preference varied by layer. Thus, there exist feature-locked and feature-variant cortical networks. PMID:26138975

  18. Direct modulation at L-band using a quadrature modulator with feedback

    NASA Technical Reports Server (NTRS)

    Datta, Ravi; Crozier, Stewart N.

    1995-01-01

    This paper describes how a high quality modulated signal can be generated directly at the frequency of transmission, using a standard quadrature modulator and other commercially-available, low-cost building blocks. The method uses a feedback technique for automatic correction of carrier leakage, differential gain and phase mismatch errors in the quadrature modulator, and other building blocks, by providing guidance to the digital baseband portion of the modulator. Experimental results are presented for direct modulation at 1.65 GHz.

  19. Optimal design of reverse osmosis module networks

    SciTech Connect

    Maskan, F.; Wiley, D.E.; Johnston, L.P.M.; Clements, D.J.

    2000-05-01

    The structure of individual reverse osmosis modules, the configuration of the module network, and the operating conditions were optimized for seawater and brackish water desalination. The system model included simple mathematical equations to predict the performance of the reverse osmosis modules. The optimization problem was formulated as a constrained multivariable nonlinear optimization. The objective function was the annual profit for the system, consisting of the profit obtained from the permeate, capital cost for the process units, and operating costs associated with energy consumption and maintenance. Optimization of several dual-stage reverse osmosis systems were investigated and compared. It was found that optimal network designs are the ones that produce the most permeate. It may be possible to achieve economic improvements by refining current membrane module designs and their operating pressures.

  20. The behaviour of basic autocatalytic signalling modules in isolation and embedded in networks

    SciTech Connect

    Krishnan, J. [Department of Chemical Engineering, Centre for Process Systems Engineering, Institute for Systems and Synthetic Biology, Imperial College London, London SW7 2AZ (United Kingdom); Mois, Kristina; Suwanmajo, Thapanar [Department of Chemical Engineering, Centre for Process Systems Engineering, Imperial College London, London SW7 2AZ (United Kingdom)

    2014-11-07

    In this paper, we examine the behaviour of basic autocatalytic feedback modules involving a species catalyzing its own production, either directly or indirectly. We first perform a systematic study of the autocatalytic feedback module in isolation, examining the effect of different factors, showing how this module is capable of exhibiting monostable threshold and bistable switch-like behaviour. We then study the behaviour of this module embedded in different kinds of basic networks including (essentially) irreversible cycles, open and closed reversible chains, and networks with additional feedback. We study the behaviour of the networks deterministically and also stochastically, using simulations, analytical work, and bifurcation analysis. We find that (i) there are significant differences between the behaviour of this module in isolation and in a network: thresholds may be altered or destroyed and bistability may be destroyed or even induced, even when the ambient network is simple. The global characteristics and topology of this network and the position of the module in the ambient network can play important and unexpected roles. (ii) There can be important differences between the deterministic and stochastic dynamics of the module embedded in networks, which may be accentuated by the ambient network. This provides new insights into the functioning of such enzymatic modules individually and as part of networks, with relevance to other enzymatic signalling modules as well.

  1. Directional borehole radar with dipole antenna array using optical modulators

    Microsoft Academic Search

    Satoshi Ebihara

    2004-01-01

    In this paper, we describe a directional borehole radar comprising a dipole antenna array with an optical modulator capable of determining the position of targets in three dimensions (3-D). Optical modulators using a Mach-Zehnder interferometer are used to transform electrical signals into optical signals at the feeding points of the dipole antennas. The advantages of using these modulators are that

  2. ONE-DIRECTED INDECOMPOSABLE PURE INJECTIVE MODULES OVER STRING ALGEBRAS

    E-print Network

    Prest, Mike

    ONE-DIRECTED INDECOMPOSABLE PURE INJECTIVE MODULES OVER STRING ALGEBRAS MIKE PREST (MANCHESTER;nite dimensional string algebras. 1. Introduction Let A be a #12;nite dimensional string algebra over-called string and band modules. Although the classi#12;cation of arbitrary in#12;nite dimensional modules over

  3. Downhole drilling network using burst modulation techniques

    DOEpatents

    Hall; David R. (Provo, UT), Fox; Joe (Spanish Fork, UT)

    2007-04-03

    A downhole drilling system is disclosed in one aspect of the present invention as including a drill string and a transmission line integrated into the drill string. Multiple network nodes are installed at selected intervals along the drill string and are adapted to communicate with one another through the transmission line. In order to efficiently allocate the available bandwidth, the network nodes are configured to use any of numerous burst modulation techniques to transmit data.

  4. Optical Learning Neural Network with a Pockels Readout Optical Modulator

    Microsoft Academic Search

    Masahiko Mori; Yutaka Yagai; Toyohiko Yatagai; Masanobu Watanabe

    1998-01-01

    We have constructed an optical neural-network system with learning capability by using a Pockels readout optical modulator. The system has a two-dimensional structure that permits easy optical alignment and can handle images without scanning. Learning signals are calculated optically with two liquid-crystal devices by a matrix matrix outer-product method. The calculated learning signals are added directly to the weights memorized

  5. Optical waveform generation using a directly modulated laser

    NASA Astrophysics Data System (ADS)

    Cartledge, John C.; Karar, Abdullah S.; Roberts, Kim

    2013-10-01

    The capability of a directly modulated laser (DML) can be dramatically enhanced through precise control of the drive current waveform based on digital signal processing (DSP) and a digital-to-analog convertor (DAC). In this paper, a novel method to pre-compensate fiber dispersion for metro and regional networks is described for a bit rate of 10.709 Gb/s using a DML. A look-up table (LUT) for the drive current is optimized for dispersion mitigation. The entries of the LUT are determined based on the effects of the DML adiabatic and transient chirp on pulse propagation, the nonlinear mapping between the input current and the output optical power, and the bandwidth of the DML package. A DAC operating at 2 samples per bit (21.418 GSa/s with 6 bit resolution) converts the digital samples at the output of the LUT to an analog current waveform driving the DML. Experimental results for a bit rate of 10.709 Gb/s and on-off keying demonstrate a transmission reach of 252 km using a DML intended for 2.5 Gb/s operation and 608 km using a chirp managed laser intended for 10 Gb/s operation. Using this approach (DSP + DAC), the generation of 10.709 Gb/s differential phase shift keying (DPSK) and 56 Gb/s 16-ary quadrature amplitude modulation, sub-carrier multiplexed (QAM SCM) optical signals using the direct modulation of a passive feedback laser is also presented. 6-bit DACs operating at sampling rates of 21.418 GSa/s and 28 GSa/s, respectively, was used to generate the requisite analog current waveform.

  6. SPACEWIRE HOT MODULES Session: SpaceWire Networks and Protocols

    E-print Network

    Keslassy, Isaac

    1 SPACEWIRE HOT MODULES Session: SpaceWire Networks and Protocols Long Paper Asaf Baron, Isask. Such modules are termed Hot Modules. SpaceWire uses wormhole routing to deliver packets comprising multiple at the presence of Hot Modules. In this paper we demonstrate that a single Hot Module can both dramatically reduce

  7. Transmission line directional protection using neural networks and filtering algorithms

    NASA Astrophysics Data System (ADS)

    Sanaye-Pasand, Majid

    2000-02-01

    Power transmission lines are the vital links in power systems providing the essential continuity of service from generating plants to the end users. To maintain stability in a power system it is imperative that any fault in the transmission system be identified by protective relays and the faulted line be isolated from the network with minimal delay. Faults on transmission lines need to be detected, classified and cleared as fast as possible. Moreover, the fault direction should be identified. Development of different modules of a transmission line protective relaying system is outlined in this dissertation. Different modules such as fault direction identification, fault detection and phase selection modules are designed, implemented and tested. Neural network technique is employed to design the transmission line fault direction identification module. Different neural network structures are used and four different directional modules are proposed. A new high speed algorithm, based on impedance measurement is proposed for fault detection and phase selection. Adaptive features are also added to the proposed relaying modules to enable them to track the changing operation conditions of the system. Off-line studies are performed with the proposed relaying modules on a simulated power system model. The system is subjected to different types of disturbances while it is operating at different operating conditions, and the performance of the proposed modules is evaluated. The results obtained indicate that the proposed relaying modules perform rapidly and correctly for different system conditions. The relaying algorithm has been implemented on a digital signal processor board. Using a power system model consisting of a micro-alternator connected to a constant voltage system extensive experimental studies are conducted and the performance of the relaying algorithm is investigated. The performance of the proposed modules is investigated further using recorded fault data from a high voltage power system. In this way, the performance of the newly designed relaying modules can be further verified in a more realistic environment. Results using various recorded field data are presented. The results presented in this dissertation confirm the feasibility of the proposed relaying modules.

  8. Parsimonious module inference in large networks.

    PubMed

    Peixoto, Tiago P

    2013-04-01

    We investigate the detectability of modules in large networks when the number of modules is not known in advance. We employ the minimum description length principle which seeks to minimize the total amount of information required to describe the network, and avoid overfitting. According to this criterion, we obtain general bounds on the detectability of any prescribed block structure, given the number of nodes and edges in the sampled network. We also obtain that the maximum number of detectable blocks scales as sqrt[N], where N is the number of nodes in the network, for a fixed average degree ?k?. We also show that the simplicity of the minimum description length approach yields an efficient multilevel Monte Carlo inference algorithm with a complexity of O(?NlogN), if the number of blocks is unknown, and O(?N) if it is known, where ? is the mixing time of the Markov chain. We illustrate the application of the method on a large network of actors and films with over 10(6) edges, and a dissortative, bipartite block structure. PMID:25167049

  9. Parsimonious Module Inference in Large Networks

    NASA Astrophysics Data System (ADS)

    Peixoto, Tiago P.

    2013-04-01

    We investigate the detectability of modules in large networks when the number of modules is not known in advance. We employ the minimum description length principle which seeks to minimize the total amount of information required to describe the network, and avoid overfitting. According to this criterion, we obtain general bounds on the detectability of any prescribed block structure, given the number of nodes and edges in the sampled network. We also obtain that the maximum number of detectable blocks scales as N, where N is the number of nodes in the network, for a fixed average degree ?k?. We also show that the simplicity of the minimum description length approach yields an efficient multilevel Monte Carlo inference algorithm with a complexity of O(?Nlog?N), if the number of blocks is unknown, and O(?N) if it is known, where ? is the mixing time of the Markov chain. We illustrate the application of the method on a large network of actors and films with over 106 edges, and a dissortative, bipartite block structure.

  10. Distributed pulse forming network for magnetic modulator

    NASA Astrophysics Data System (ADS)

    Weiner, M.; Carter, J. L.; Youmans, R. J.

    1984-05-01

    A pulse forming network with distributed inductance and capacitance is disclosed for use in a magnetic modulator. The magnetic modulator has a magnetic core with a primary winding and a secondary winding around it. The pulse forming network includes an inner winding of flattened wire around the magnetic core and connected to one end of the secondary winding for receiving an induced voltage. The pulse forming network also includes a metal foil shield around the inner winding, so that the induced voltage may be stored capacitively between the inner winding and the shield. When the magnetic core saturates, the impedance of the secondary winding drops, so that the pulse forming network discharges through a load. The shape of the pulse through the load is determined by the inductance of the inner winding and the capacitance between the inner winding and the shield. The number of turns per unit length of the inner winding, the spacing between the inner winding and the shield, and the dielectric constant of an insulating layer of material between the inner winding and the shield may all be modified to obtain a pulse forming network forming a desired pulse shape.

  11. Cholinergic modulation of hippocampal network function

    PubMed Central

    Teles-Grilo Ruivo, Leonor M.; Mellor, Jack R.

    2013-01-01

    Cholinergic septohippocampal projections from the medial septal area to the hippocampus are proposed to have important roles in cognition by modulating properties of the hippocampal network. However, the precise spatial and temporal profile of acetylcholine release in the hippocampus remains unclear making it difficult to define specific roles for cholinergic transmission in hippocampal dependent behaviors. This is partly due to a lack of tools enabling specific intervention in, and recording of, cholinergic transmission. Here, we review the organization of septohippocampal cholinergic projections and hippocampal acetylcholine receptors as well as the role of cholinergic transmission in modulating cellular excitability, synaptic plasticity, and rhythmic network oscillations. We point to a number of open questions that remain unanswered and discuss the potential for recently developed techniques to provide a radical reappraisal of the function of cholinergic inputs to the hippocampus. PMID:23908628

  12. Main resonances in directly modulated semiconductor lasers: effect of spontaneous

    E-print Network

    Toral, Raúl

    Main resonances in directly modulated semiconductor lasers: effect of spontaneous emission and gain saddle-node bifurcations related to the main resonances in pump-modulated laser diodes are obtained via] and of the spontaneous emission terms [lo] have already been considered, but little attention has been given to main

  13. Synthesis of optical directional coupler modulators with linear response

    Microsoft Academic Search

    Jaesang Oh; R. T. Schermer; Kang-Hyun Baek; Anand Gopinath

    2004-01-01

    The variable coupling directional coupler modulator is of interest for analog RF\\/microwave links because it can be synthesized to give linear electrical to optical conversion. The synthesis methods are still relatively undeveloped, however. This paper introduces an improvement to the preferred synthesis technique, the iterative Newton's method, which allows a closer match to the desired modulator response. A variable coupling

  14. On functional module detection in metabolic networks.

    PubMed

    Koch, Ina; Ackermann, Jörg

    2013-01-01

    Functional modules of metabolic networks are essential for understanding the metabolism of an organism as a whole. With the vast amount of experimental data and the construction of complex and large-scale, often genome-wide, models, the computer-aided identification of functional modules becomes more and more important. Since steady states play a key role in biology, many methods have been developed in that context, for example, elementary flux modes, extreme pathways, transition invariants and place invariants. Metabolic networks can be studied also from the point of view of graph theory, and algorithms for graph decomposition have been applied for the identification of functional modules. A prominent and currently intensively discussed field of methods in graph theory addresses the Q-modularity. In this paper, we recall known concepts of module detection based on the steady-state assumption, focusing on transition-invariants (elementary modes) and their computation as minimal solutions of systems of Diophantine equations. We present the Fourier-Motzkin algorithm in detail. Afterwards, we introduce the Q-modularity as an example for a useful non-steady-state method and its application to metabolic networks. To illustrate and discuss the concepts of invariants and Q-modularity, we apply a part of the central carbon metabolism in potato tubers (Solanum tuberosum) as running example. The intention of the paper is to give a compact presentation of known steady-state concepts from a graph-theoretical viewpoint in the context of network decomposition and reduction and to introduce the application of Q-modularity to metabolic Petri net models. PMID:24958145

  15. Inspiring Climate Education Excellence (ICEE): Developing self-directed professional development modules for secondary science teachers

    NASA Astrophysics Data System (ADS)

    Buhr, S. M.; Lynds, S. E.; McCaffrey, M. S.; Morton, E.

    2010-12-01

    Inspiring Climate Education Excellence (ICEE) is a NASA-funded project to develop online course modules and self-directed learning resources aligned with the Essential Principles of Climate Science. Following a national needs assessment survey and a face to face workshop to pilot test topics, a suite of online modules is being developed suitable for self-directed learning by secondary science teachers. Modules are designed around concepts and topics in which teachers express the most interest and need for instruction. Module design also includes attention to effective teaching strategies, such as awareness of student misconceptions, strategies for forestalling controversy and advice from master teachers on implementation and curriculum development. The resources are being developed in partnership with GLOBE, and the National Science Digital Library (NSDL) and is informed by the work of the Climate Literacy and Energy Awareness Network (CLEAN) project. ICEE will help to meet the professional development needs of teachers, including those participating in the GLOBE Student Climate Research Campaign. Modules and self-directed learning resources will be developed and disseminated in partnership with the National Science Digital Library (NSDL). This presentation introduces the needs assessment and pilot workshop data upon which the modules are based, and describes the modules that are available and in development.

  16. Joint scaling of battery discharge and modulation scheme in wireless sensor networks

    Microsoft Academic Search

    Tang Qiuling; Liang Ye; Qin Yongming; Wen Huan

    2010-01-01

    In wireless sensor networks (WSNs), battery lifetime directly impacts the network lifetime. One of the key considerations in the design of energy consumption modules of a sensor node should be to maximize the energy delivered by the battery; and hence the battery lifetime. In view of the main duty of a sensor node being data collection and transmission and most

  17. Direct digital RF synthesis and modulation for MSAT mobile applications

    NASA Technical Reports Server (NTRS)

    Crozier, Stewart; Datta, Ravi; Sydor, John

    1993-01-01

    A practical method of performing direct digital RF synthesis using the Hilbert transform single sideband (SSB) technique is described. It is also shown that amplitude and phase modulation can be achieved directly at L-band with frequency stability and spurii performance exceeding stringent MSAT system requirements.

  18. About direct summands of projective modules over Laurent polynomial rings

    E-print Network

    Mandal, Satyagopal

    1991-08-01

    and R = A[X, X-1] is a Laurent polynomial ring. We prove that for projective Ä-modules P and Q with rank Q < rank P , if Q, is a direct summand of Pf for a doubly monic poly- nomial / then Q is also a direct summand of P . We also prove the analogue... of the Horrock's theorem for Laurent polynomials rings. 1. Introduction In [R] Roy proved that if R = A[X] is a polynomial ring over a local ring A and if P and Q are two projective .R-modules with rankß < rankP, then Qj is a direct summand of P, for some monic...

  19. Directionality of contact networks suppresses selection pressure in evolutionary dynamics

    E-print Network

    Masuda, Naoki

    2008-01-01

    Individuals of different types, may it be genetic, cultural, or else, with different levels of fitness often compete for reproduction and survival. A fitter type generally has higher chances of disseminating their copies to other individuals. The fixation probability of a single mutant type introduced in a population of wild-type individuals quantifies how likely the mutant type spreads. How much the excess fitness of the mutant type increases its fixation probability, namely, the selection pressure, is important in assessing the impact of the introduced mutant. Previous studies mostly based on undirected and unweighted contact networks of individuals showed that the selection pressure depends on the structure of networks and the rule of reproduction. Real networks underlying ecological and social interactions are usually directed or weighted. Here we examine how the selection pressure is modulated by directionality of interactions under several update rules. Our conclusions are twofold. First, directionality...

  20. Relative direction determination in mobile computing networks

    Microsoft Academic Search

    Antonis Kalis; Theodore AntonakopouloS

    2001-01-01

    A novel relative direction determination method is presented for stations of mobile computing networks. The method uses a switched beam array for determining the direction of arrival (DOA) of the incident electromagnetic field in a time efficient way, in order to confront the strict timing requirements of packet switching networks. Additionally, the method associates certain MAC layer functions with different

  1. Direct frequency modulation in AlGaAs semiconductor lasers

    Microsoft Academic Search

    S. Kobayashi; Y. Yamamoto; T. Kimura; M. Ito

    1982-01-01

    A theoretical and experimental study is presented of direct FM characteristics in three AlGaAs lasers: (1) a channeled-substrate planar (CSP) laser; (2) a buried-heterostructure laser; and (3) a transverse-junction-stripe (TJS) laser. It is determined that, while FM response in the low-modulation frequency region from zero to 10 MHz gradually decreases with modulation frequency due to thermal effects, FM response in

  2. Google matrix analysis of directed networks

    E-print Network

    Leonardo Ermann; Klaus M. Frahm; Dima L. Shepelyansky

    2015-06-19

    In past ten years, modern societies developed enormous communication and social networks. Their classification and information retrieval processing become a formidable task for the society. Due to the rapid growth of World Wide Web, social and communication networks, new mathematical methods have been invented to characterize the properties of these networks on a more detailed and precise level. Various search engines are essentially using such methods. It is highly important to develop new tools to classify and rank enormous amount of network information in a way adapted to internal network structures and characteristics. This review describes the Google matrix analysis of directed complex networks demonstrating its efficiency on various examples including World Wide Web, Wikipedia, software architecture, world trade, social and citation networks, brain neural networks, DNA sequences and Ulam networks. The analytical and numerical matrix methods used in this analysis originate from the fields of Markov chains, quantum chaos and Random Matrix theory.

  3. Self-organized Collaboration Network Model Based on Module Emerging

    NASA Astrophysics Data System (ADS)

    Yang, Hongyong; Lu, Lan; Liu, Qiming

    Recently, the studies of the complex network have gone deep into many scientific fields, such as computer science, physics, mathematics, sociology, etc. These researches enrich the realization for complex network, and increase understands for the new characteristic of complex network. Based on the evolvement characteristic of the author collaboration in the scientific thesis, a self-organized network model of the scientific cooperation network is presented by module emerging. By applying the theoretical analysis, it is shown that this network model is a scale-free network, and the strength degree distribution and the module degree distribution of the network nodes have the same power law. In order to make sure the validity of the theoretical analysis for the network model, we create the computer simulation and demonstration collaboration network. By analyzing the data of the network, the results of the demonstration network and the computer simulation are consistent with that of the theoretical analysis of the model.

  4. A generalized maximum neural network for the module orientation problem

    Microsoft Academic Search

    KUO CHUN LEE; YOSHIYASU TAKEFUJI

    1992-01-01

    Several neuron models and artificial neural networks have been intensively studied since McCulloch and Pitts proposed the simplified neuron model in 1943. In this paper a generalized maximum neural network for parallel computing is introduced to solve the module orientation problem which belongs to the class of NP-complete problems. The goal of the module orientation problem in VLSI circuits or

  5. Module networks: identifying regulatory modules and their condition-specific regulators from gene expression data

    Microsoft Academic Search

    Michael Shapira; Aviv Regev; Dana Pe'er; David Botstein; Nir Friedman; Eran Segal; Daphne Koller

    2003-01-01

    Much of a cell's activity is organized as a network of interacting modules: sets of genes coregulated to respond to different conditions. We present a probabilistic method for identifying regulatory modules from gene expression data. Our procedure identifies modules of coregulated genes, their regulators and the conditions under which regulation occurs, generating testable hypotheses in the form 'regulator X regulates

  6. A high-gain directly modulated L-band microwave optical link

    Microsoft Academic Search

    E. Ackerman; D. Kasemset; S. Wanuga; D. Hogue; J. Komiak

    1990-01-01

    A directly modulated microwave optical data link has yielded high gain. An efficient lossless impedance matching approach was used to maximize the transducer gains in the laser and detector matching networks. The free-space optical link operates at 900 MHz with a peak gain of 3.7 dB over a 3-dB bandwidth of 90 MHz. The link also exhibits a wide dynamic

  7. Coherent network oscillations by olfactory interneurons: modulation by endogenous amines.

    PubMed

    Gelperin, A; Rhines, L D; Flores, J; Tank, D W

    1993-06-01

    1. The procerebral (PC) lobe of the terrestrial mollusk Limax maximus contains a highly interconnected network of local olfactory interneurons that receives direct axonal projections from the two pairs of noses. This olfactory processing network generates a 0.7-Hz oscillation in its local field potential (LFP) that is coherent throughout the network. The oscillating LFP is modulated by natural odorants applied to the neuroepithelium of the superior nose. 2. Two amines known to be present in the PC lobe, dopamine and serotonin, increase the frequency of the PC lobe oscillation and alter its waveform. 3. Glutamate, another putative neurotransmitter known to be present in the lobe, suppresses the PC lobe oscillation by a quisqualate-type receptor and appears to be used by one of the two classes of neurons in the PC lobe to generate the basic LFP oscillation. 4. The known activation of second messengers in Limax PC lobe by dopamine and serotonin together with their effects on the oscillatory rhythm suggest the hypothesis that these amines augment mechanisms mediating synaptic plasticity in the olfactory network, similar to hypothesized effects of amines in vertebrate olfactory systems. 5. The use of a distributed network of interneurons showing coherent oscillations may relate to the highly developed odor recognition and odor learning ability of Limax. PMID:8102394

  8. Organization of signal flow in directed networks

    NASA Astrophysics Data System (ADS)

    Bányai, M.; Négyessy, L.; Bazsó, F.

    2011-06-01

    Confining an answer to the question of whether and how the coherent operation of network elements is determined by the network structure is the topic of our work. We map the structure of signal flow in directed networks by analysing the degree of edge convergence and the overlap between the in- and output sets of an edge. Definitions of convergence degree and overlap are based on the shortest paths, thus they encapsulate global network properties. Using the defining notions of convergence degree and overlapping set we clarify the meaning of network causality and demonstrate the crucial role of chordless circles. In real-world networks the flow representation distinguishes nodes according to their signal transmitting, processing and control properties. The analysis of real-world networks in terms of flow representation was in accordance with the known functional properties of the network nodes. It is shown that nodes with different signal processing, transmitting and control properties are randomly connected at the global scale, while local connectivity patterns depart from randomness. The grouping of network nodes according to their signal flow properties was unrelated to the network's community structure. We present evidence that the signal flow properties of small-world-like, real-world networks cannot be reconstructed by algorithms used to generate small-world networks. Convergence degree values were calculated for regular oriented trees, and the probability density function for networks grown with the preferential attachment mechanism. For Erdos-Rényi graphs we calculated the probability density function of both convergence degrees and overlaps.

  9. Approved Module Information for EE3NPD, 2014/5 Module Title/Name: Networked Product Development Module Code: EE3NPD

    E-print Network

    Neirotti, Juan Pablo

    Approved Module Information for EE3NPD, 2014/5 Module Title/Name: Networked Product Development? No Module Credits: 10 Module Management Information Module Leader Name Haitao Ye Email Address h products and their design. To investigate a range of networked products, from simple smart cards and RFID

  10. Federal Statutes & Directives Regarding National Origin Students. Technical Assistance Module.

    ERIC Educational Resources Information Center

    Gonzales, Frank

    Federal statutes and directives regarding national origin students is the subject of this technical assistance module. It is a guide for trainers who seek to familiarize education personnel with the legal aspects of providing services to limited English proficient (LEP) students. Nine activities are described and materials, including 17…

  11. Automatic modulation format recognition for the next generation optical communication networks using artificial neural networks

    NASA Astrophysics Data System (ADS)

    Guesmi, Latifa; Hraghi, Abir; Menif, Mourad

    2015-03-01

    A new technique for Automatic Modulation Format Recognition (AMFR) in next generation optical communication networks is presented. This technique uses the Artificial Neural Network (ANN) in conjunction with the features of Linear Optical Sampling (LOS) of the detected signal at high bit rates using direct detection or coherent detection. The use of LOS method for this purpose mainly driven by the increase of bit rates which enables the measurement of eye diagrams. The efficiency of this technique is demonstrated under different transmission impairments such as chromatic dispersion (CD) in the range of -500 to 500 ps/nm, differential group delay (DGD) in the range of 0-15 ps and the optical signal tonoise ratio (OSNR) in the range of 10-30 dB. The results of numerical simulation for various modulation formats demonstrate successful recognition from a known bit rates with a higher estimation accuracy, which exceeds 99.8%.

  12. Approved Module Information for EE4016, 2014/5 Module Title/Name: Mobile Data Networks Module Code: EE4016

    E-print Network

    Neirotti, Juan Pablo

    : Network planning. Cell fundamentals. Mobility management. Radio resources and power management. Security technology. Mobile data networks. Mobile application protocols. Local Broadband and Ad Hoc Networks: Wireless Modules/ Exempt from Anonymous Marking Details Assessment Weight February to June Exam Closed Book 2:00hrs

  13. Investigation of direct integrated optics modulators. [applicable to data preprocessors

    NASA Technical Reports Server (NTRS)

    Batchman, T. E.

    1980-01-01

    Direct modulation techniques applicable to integrated optics data preprocessors were investigated. Several methods of modulating a coherent optical beam by interaction with an incoherent beam were studied. It was decided to investigate photon induced conductivity changes in thin semiconductor cladding layers on optical waveguides. Preliminary calculations indicate significant changes can be produced in the phase shift in a propagating wave when the conductivity is changed by ten percent or more. Experimental devices to verify these predicted phase changes and experiments designed to prove the concept are described.

  14. A Novel Modulation Classification Approach Using Gabor Filter Network

    PubMed Central

    Ghauri, Sajjad Ahmed; Qureshi, Ijaz Mansoor; Cheema, Tanveer Ahmed; Malik, Aqdas Naveed

    2014-01-01

    A Gabor filter network based approach is used for feature extraction and classification of digital modulated signals by adaptively tuning the parameters of Gabor filter network. Modulation classification of digitally modulated signals is done under the influence of additive white Gaussian noise (AWGN). The modulations considered for the classification purpose are PSK 2 to 64, FSK 2 to 64, and QAM 4 to 64. The Gabor filter network uses the network structure of two layers; the first layer which is input layer constitutes the adaptive feature extraction part and the second layer constitutes the signal classification part. The Gabor atom parameters are tuned using Delta rule and updating of weights of Gabor filter using least mean square (LMS) algorithm. The simulation results show that proposed novel modulation classification algorithm has high classification accuracy at low signal to noise ratio (SNR) on AWGN channel. PMID:25126603

  15. Dynamics-based centrality for directed networks

    NASA Astrophysics Data System (ADS)

    Masuda, Naoki; Kori, Hiroshi

    2010-11-01

    Determining the relative importance of nodes in directed networks is important in, for example, ranking websites, publications, and sports teams, and for understanding signal flows in systems biology. A prevailing centrality measure in this respect is the PageRank. In this work, we focus on another class of centrality derived from the Laplacian of the network. We extend the Laplacian-based centrality, which has mainly been applied to strongly connected networks, to the case of general directed networks such that we can quantitatively compare arbitrary nodes. Toward this end, we adopt the idea used in the PageRank to introduce global connectivity between all the pairs of nodes with a certain strength. Numerical simulations are carried out on some networks. We also offer interpretations of the Laplacian-based centrality for general directed networks in terms of various dynamical and structural properties of networks. Importantly, the Laplacian-based centrality defined as the stationary density of the continuous-time random walk with random jumps is shown to be equivalent to the absorption probability of the random walk with sinks at each node but without random jumps. Similarly, the proposed centrality represents the importance of nodes in dynamics on the original network supplied with sinks but not with random jumps.

  16. Control range: a controllability-based index for node significance in directed networks

    NASA Astrophysics Data System (ADS)

    Wang, Bingbo; Gao, Lin; Gao, Yong

    2012-04-01

    While a large number of methods for module detection have been developed for undirected networks, it is difficult to adapt them to handle directed networks due to the lack of consensus criteria for measuring the node significance in a directed network. In this paper, we propose a novel structural index, the control range, motivated by recent studies on the structural controllability of large-scale directed networks. The control range of a node quantifies the size of the subnetwork that the node can effectively control. A related index, called the control range similarity, is also introduced to measure the structural similarity between two nodes. When applying the index of control range to several real-world and synthetic directed networks, it is observed that the control range of the nodes is mainly influenced by the network's degree distribution and that nodes with a low degree may have a high control range. We use the index of control range similarity to detect and analyze functional modules in glossary networks and the enzyme-centric network of homo sapiens. Our results, as compared with other approaches to module detection such as modularity optimization algorithm, dynamic algorithm and clique percolation method, indicate that the proposed indices are effective and practical in depicting structural and modular characteristics of sparse directed networks.

  17. Response maxima in time-modulated turbulence: Direct numerical simulations

    NASA Astrophysics Data System (ADS)

    Kuczaj, A. K.; Geurts, B. J.; Lohse, D.

    2006-03-01

    The response of turbulent flow to time-modulated forcing is studied by direct numerical simulations of the Navier-Stokes equations. The large-scale forcing is modulated via periodic energy input variations at frequency ?. The response is maximal for frequencies in the range of the inverse of the large eddy turnover time, confirming the mean-field predictions of von der Heydt, Grossmann and Lohse (Phys. Rev. E, 67 (2003) 046308). In accordance with the theory the response maximum shows only a small dependence on the Reynolds number. At sufficiently high frequencies the amplitude of the kinetic energy response decreases as 1/?. For frequencies beyond the range of maximal response, a significant change in the phase-shift relative to the time-modulated forcing is observed. For large ? the phase shift approaches roughly 90° for the total energy and 180° for the energy dissipation rate.

  18. Directed diffusion for wireless sensor networking

    Microsoft Academic Search

    Chalermek Intanagonwiwat; Ramesh Govindan; Deborah Estrin; John S. Heidemann; Fabio Silva

    2003-01-01

    Advances in processor, memory, and radio technology will enable small and cheap nodes capable of sensing, communication, and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed-diffusion paradigm for such coordination. Directed diffusion is data-centric in that all communication is for named data. All nodes in a directed-diffusion-based

  19. On-chip microwave photonic beamformer circuits operating with phase modulation and direct detection.

    PubMed

    Zhuang, Leimeng; Hoekman, Marcel; Taddei, Caterina; Leinse, Arne; Heideman, René G; Hulzinga, Adriaan; Verpoorte, Jaco; Oldenbeuving, Ruud M; van Dijk, Paulus W L; Boller, Klaus-J; Roeloffzen, Chris G H

    2014-07-14

    We propose and experimentally demonstrate the working principles of two novel microwave photonic (MWP) beamformer circuits operating with phase modulation (PM) and direct detection (DD). The proposed circuits incorporate two major signal processing functionalities, namely a broadband beamforming network employing ring resonator-based delay lines and an optical sideband manipulator that renders the circuit outputs equivalent to those of intensity-modulated MWP beamformers. These functionalities allow the system to employ low-circuit-complexity modulators and detectors, which brings significant benefits on the system construction cost and operation stability. The functionalities of the proposed MWP beamformer circuits were verified in experimental demonstrations performed on two sample circuits realized in Si(3)N(4)/SiO(2) waveguide technology. The measurements exhibit a 2 × 1 beamforming effect for an instantaneous RF transmission band of 3?7 GHz, which is, to our best knowledge, the first verification of on-chip MWP beamformer circuits operating with PM and DD. PMID:25090522

  20. Core Module Biomarker Identification with Network Exploration for Breast Cancer Metastasis

    E-print Network

    Petzold, Linda R.

    - 1 - Core Module Biomarker Identification with Network Exploration for Breast Cancer Metastasis "disease module". Results We have developed COMBINER: COre Module Biomarker Identification with Network biomarkers. We applied COMBINER to three benchmark breast cancer datasets for identifying prognostic

  1. Spatiotemporal positioning of multipotent modules in diverse biological networks.

    PubMed

    Chen, Yinying; Wang, Zhong; Wang, Yongyan

    2014-07-01

    A biological network exhibits a modular organization. The modular structure dependent on functional module is of great significance in understanding the organization and dynamics of network functions. A huge variety of module identification methods as well as approaches to analyze modularity and dynamics of the inter- and intra-module interactions have emerged recently, but they are facing unexpected challenges in further practical applications. Here, we discuss recent progress in understanding how such a modular network can be deconstructed spatiotemporally. We focus particularly on elucidating how various deciphering mechanisms operate to ensure precise module identification and assembly. In this case, a system-level understanding of the entire mechanism of module construction is within reach, with important implications for reasonable perspectives in both constructing a modular analysis framework and deconstructing different modular hierarchical structures. PMID:24413666

  2. On the annual modulation signal in dark matter direct detection

    SciTech Connect

    Herrero-Garcia, Juan; Schwetz, Thomas [Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg (Germany); Zupan, Jure, E-mail: juan.a.herrero@uv.es, E-mail: schwetz@mpi-hd.mpg.de, E-mail: jure.zupan@cern.ch [Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221 (United States)

    2012-03-01

    We derive constraints on the annual modulation signal in Dark Matter (DM) direct detection experiments in terms of the unmodulated event rate. A general bound independent of the details of the DM distribution follows from the assumption that the motion of the earth around the sun is the only source of time variation. The bound is valid for a very general class of particle physics models and also holds in the presence of an unknown unmodulated background. More stringent bounds are obtained, if modest assumptions on symmetry properties of the DM halo are adopted. We illustrate the bounds by applying them to the annual modulation signals reported by the DAMA and CoGeNT experiments in the framework of spin-independent elastic scattering. While the DAMA signal satisfies our bounds, severe restrictions on the DM mass can be set for CoGeNT.

  3. Smelling directions: Olfaction modulates ambiguous visual motion perception

    PubMed Central

    Kuang, Shenbing; Zhang, Tao

    2014-01-01

    Senses of smells are often accompanied by simultaneous visual sensations. Previous studies have documented enhanced olfactory performance with concurrent presence of congruent color- or shape- related visual cues, and facilitated visual object perception when congruent smells are simultaneously present. These visual object-olfaction interactions suggest the existences of couplings between the olfactory pathway and the visual ventral processing stream. However, it is not known if olfaction can modulate visual motion perception, a function that is related to the visual dorsal stream. We tested this possibility by examining the influence of olfactory cues on the perceptions of ambiguous visual motion signals. We showed that, after introducing an association between motion directions and olfactory cues, olfaction could indeed bias ambiguous visual motion perceptions. Our result that olfaction modulates visual motion processing adds to the current knowledge of cross-modal interactions and implies a possible functional linkage between the olfactory system and the visual dorsal pathway. PMID:25052162

  4. Module organization and variance in protein-protein interaction networks

    PubMed Central

    Lin, Chun-Yu; Lee, Tsai-Ling; Chiu, Yi-Yuan; Lin, Yi-Wei; Lo, Yu-Shu; Lin, Chih-Ta; Yang, Jinn-Moon

    2015-01-01

    A module is a group of closely related proteins that act in concert to perform specific biological functions through protein–protein interactions (PPIs) that occur in time and space. However, the underlying module organization and variance remain unclear. In this study, we collected module templates to infer respective module families, including 58,041 homologous modules in 1,678 species, and PPI families using searches of complete genomic database. We then derived PPI evolution scores and interface evolution scores to describe the module elements, including core and ring components. Functions of core components were highly correlated with those of essential genes. In comparison with ring components, core proteins/PPIs were conserved across multiple species. Subsequently, protein/module variance of PPI networks confirmed that core components form dynamic network hubs and play key roles in various biological functions. Based on the analyses of gene essentiality, module variance, and gene co-expression, we summarize the observations of module organization and variance as follows: 1) a module consists of core and ring components; 2) core components perform major biological functions and collaborate with ring components to execute certain functions in some cases; 3) core components are more conserved and essential during organizational changes in different biological states or conditions. PMID:25797237

  5. Module organization and variance in protein-protein interaction networks

    NASA Astrophysics Data System (ADS)

    Lin, Chun-Yu; Lee, Tsai-Ling; Chiu, Yi-Yuan; Lin, Yi-Wei; Lo, Yu-Shu; Lin, Chih-Ta; Yang, Jinn-Moon

    2015-03-01

    A module is a group of closely related proteins that act in concert to perform specific biological functions through protein-protein interactions (PPIs) that occur in time and space. However, the underlying module organization and variance remain unclear. In this study, we collected module templates to infer respective module families, including 58,041 homologous modules in 1,678 species, and PPI families using searches of complete genomic database. We then derived PPI evolution scores and interface evolution scores to describe the module elements, including core and ring components. Functions of core components were highly correlated with those of essential genes. In comparison with ring components, core proteins/PPIs were conserved across multiple species. Subsequently, protein/module variance of PPI networks confirmed that core components form dynamic network hubs and play key roles in various biological functions. Based on the analyses of gene essentiality, module variance, and gene co-expression, we summarize the observations of module organization and variance as follows: 1) a module consists of core and ring components; 2) core components perform major biological functions and collaborate with ring components to execute certain functions in some cases; 3) core components are more conserved and essential during organizational changes in different biological states or conditions.

  6. A Study of Near-Field Direct Antenna Modulation Systems Using Convex Optimization

    E-print Network

    Hajimiri, Ali

    de- sign for a class of communication systems known as near-field direct antenna modulation (NFDAMA Study of Near-Field Direct Antenna Modulation Systems Using Convex Optimization Javad Lavaei systems, referred to as near-field direct antenna modulation (NFDAM) systems. The objective is to propose a s

  7. Gaussian Networks for Direct Adaptive Control

    Microsoft Academic Search

    Robert M. Sanner; Jean-Jacques E. Slotine

    1991-01-01

    A direct adaptive tracking control architecture is proposed and evaluated for a class of continuous-time nonlinear dynamic systems for which an explicit linear parameterization of the uncertainty in the dynamics is either unknown or impossible. The architecture employs a network of gausian radial basis functions to adaptively compensate for the plant nonlinearities. Under mild assumptions about the degree of smoothness

  8. High-speed transmission of adaptively modulated optical OFDM signals over multimode fibers using directly Modulated DFBs

    Microsoft Academic Search

    J. M. Tang; K. Alan Shore

    2006-01-01

    A novel optical signal modulation concept of adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM) is proposed, and a comprehensive theoretical model of AMOOFDM modems is developed. Numerical simulations of the transmission performance of the AMOOFDM signals are undertaken in unamplified multimode fiber (MMF)-based links using directly modulated distributed feedback (DFB) lasers (DMLs). It is shown that 28 Gb\\/s over

  9. Complex networks vulnerability to module-based attacks

    E-print Network

    da Cunha, Bruno Requião; Gonçalves, Sebastián

    2015-01-01

    In the multidisciplinary field of Network Science, optimization of procedures for efficiently breaking complex networks is attracting much attention from practical points of view. In this contribution we present a module-based method to efficiently break complex networks. The procedure first identifies the communities in which the network can be represented, then it deletes the nodes (edges) that connect different modules by its order in the betweenness centrality ranking list. We illustrate the method by applying it to various well known examples of social, infrastructure, and biological networks. We show that the proposed method always outperforms vertex (edge) attacks which are based on the ranking of node (edge) degree or centrality, with a huge gain in efficiency for some examples. Remarkably, for the US power grid, the present method breaks the original network of 4941 nodes to many fragments smaller than 197 nodes (4% of the original size) by removing mere 164 nodes (~3%) identified by the procedure. B...

  10. System characteristics of direct modulated and externally modulated RF fiber-optic links

    Microsoft Academic Search

    W. E. Stephens; T. R. Joseph

    1987-01-01

    RF fiber-optic links have numerous applications to microwave systems. To fully exploit their usefulness, and RF system designer must understand their properties in terms of the performance parameters that are used to describe the terminal properties of other RF components such as loss, signal-to-noise, linearity, and dynamics. This review paper details the performance of direct and external modulation fiber-optic links

  11. Differential network analysis reveals genetic effects on catalepsy modules.

    PubMed

    Iancu, Ovidiu D; Oberbeck, Denesa; Darakjian, Priscila; Kawane, Sunita; Erk, Jason; McWeeney, Shannon; Hitzemann, Robert

    2013-01-01

    We performed short-term bi-directional selective breeding for haloperidol-induced catalepsy, starting from three mouse populations of increasingly complex genetic structure: an F2 intercross, a heterogeneous stock (HS) formed by crossing four inbred strains (HS4) and a heterogeneous stock (HS-CC) formed from the inbred strain founders of the Collaborative Cross (CC). All three selections were successful, with large differences in haloperidol response emerging within three generations. Using a custom differential network analysis procedure, we found that gene coexpression patterns changed significantly; importantly, a number of these changes were concordant across genetic backgrounds. In contrast, absolute gene-expression changes were modest and not concordant across genetic backgrounds, in spite of the large and similar phenotypic differences. By inferring strain contributions from the parental lines, we are able to identify significant differences in allelic content between the selected lines concurrent with large changes in transcript connectivity. Importantly, this observation implies that genetic polymorphisms can affect transcript and module connectivity without large changes in absolute expression levels. We conclude that, in this case, selective breeding acts at the subnetwork level, with the same modules but not the same transcripts affected across the three selections. PMID:23555609

  12. Development of an optical neural network module

    Microsoft Academic Search

    Toyohiko Yatagai

    1994-01-01

    The main features of artificial neural networks are the large number of nonlinear processing elements and the massively parallel interconnections among them. Many researchers have studied the hardware required for artificial neural networks and the software for such highly parallel co mputations. In terms of the hardware, two different ap- proaches have been proposed: VLSI-based neural networks and optical neural

  13. Cartography of complex networks: modules and universal roles

    NASA Astrophysics Data System (ADS)

    Guimerà, Roger; Nunes Amaral, Luís A.

    2005-02-01

    Integrative approaches to the study of complex systems demand that one knows the manner in which the parts comprising the system are connected. The structure of the complex network defining the interactions provides insight into the function and evolution of the components of the system. Unfortunately, the large size and intricacy of these networks implies that such insight is usually difficult to extract. Here, we propose a method that allows one to systematically extract and display information contained in complex networks. Specifically, we demonstrate that one can (i) find modules in complex networks and (ii) classify nodes into universal roles according to their pattern of within- and between-module connections. The method thus yields a 'cartographic representation' of complex networks.

  14. Chirped laser dispersion spectroscopy using a directly modulated quantum cascade laser

    SciTech Connect

    Hangauer, Andreas, E-mail: hangauer@princeton.edu; Nikodem, Michal; Wysocki, Gerard, E-mail: gwysocki@princeton.edu [Electrical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States)] [Electrical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States); Spinner, Georg [Electrical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States) [Electrical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States); Institute for Quantum Electronics, ETH Zurich, 8093 Zurich (Switzerland)

    2013-11-04

    Chirped laser dispersion spectroscopy (CLaDS) utilizing direct modulation of a quantum cascade laser (QCL) is presented. By controlling the laser bias nearly single- and dual-sideband CLaDS operation can be realized in an extremely simplified optical setup with no external optical modulators. Capability of direct single-sideband modulation is a unique feature of QCLs that exhibit a low linewidth enhancement factor. The developed analytical model shows excellent agreement with the experimental, directly modulated CLaDS spectra. This method overcomes major technical limitations of mid-infrared CLaDS systems by allowing significantly higher modulation frequencies and eliminating optical fringes introduced by external modulators.

  15. Exploring the randomness of directed acyclic networks

    NASA Astrophysics Data System (ADS)

    Goñi, Joaquín; Corominas-Murtra, Bernat; Solé, Ricard V.; Rodríguez-Caso, Carlos

    2010-12-01

    The feed-forward relationship naturally observed in time-dependent processes and in a diverse number of real systems—such as some food webs and electronic and neural wiring—can be described in terms of the so-called directed acyclic graphs (DAGs). An important ingredient of the analysis of such networks is a proper comparison of their observed architecture against an ensemble of randomized graphs, thereby quantifying the randomness of the real systems with respect to suitable null models. This approximation is particularly relevant when the finite size and/or large connectivity of real systems make inadequate a comparison with the predictions obtained from the so-called configuration model. In this paper we analyze two methods of DAG randomization as defined by the desired combination of two topological invariants (directed degree sequence and component distributions) aimed to be preserved. A highly ordered DAG, called snake graph, and an Erdös-Rényi DAG were used to validate the performance of the algorithms. Finally, three real case studies, namely, the C. elegans cell lineage network, a Ph.D. student-supervisor network, and the Milgram’s citation network, were analyzed using each randomization method. Results show how the interpretation of degree-degree relations in DAGs with respect to their randomized ensembles depends on the topological invariants imposed.

  16. Noradrenergic modulation of cortical networks engaged in visuomotor processing.

    PubMed

    Grefkes, Christian; Wang, Ling E; Eickhoff, Simon B; Fink, Gereon R

    2010-04-01

    Both animal and human data suggest that stimulation of the noradrenergic system may influence neuronal excitability in regions engaged in sensory processing and visuospatial attention. We tested the hypothesis that the neural mechanisms subserving motor performance in tasks relying on the visuomotor control of goal-directed hand movements might be modulated by noradrenergic influences. Healthy subjects were stimulated using the selective noradrenaline reuptake inhibitor reboxetine (RBX) in a placebo-controlled crossover design. Functional magnetic resonance imaging and dynamic causal modeling (DCM) were used to assess drug-related changes in blood oxygen level-dependent activity and interregional connectivity while subjects performed a joystick task requiring goal-directed movements. Improved task performance under RBX was associated with increased activity in right visual, intraparietal and superior frontal cortex (premotor/frontal eye field). DCM revealed that the neuronal coupling among these regions was significantly enhanced when subjects were stimulated with RBX. Concurrently, right intraparietal cortex and right superior frontal cortex exerted a stronger driving influence on visuomotor areas of the left hemisphere, including SMA and M1. These effects were independent from task difficulty. The data suggest that stimulating noradrenergic mechanisms may rearrange the functional network architecture within and across the hemispheres, for example, by synaptic gating, thereby optimizing motor behavior. PMID:19687293

  17. Seed selection strategy in global network alignment without destroying the entire structures of functional modules

    PubMed Central

    2012-01-01

    Background Network alignment is one of the most common biological network comparison methods. Aligning protein-protein interaction (PPI) networks of different species is of great important to detect evolutionary conserved pathways or protein complexes across species through the identification of conserved interactions, and to improve our insight into biological systems. Global network alignment (GNA) problem is NP-complete, for which only heuristic methods have been proposed so far. Generally, the current GNA methods fall into global heuristic seed-and-extend approaches. These methods can not get the best overall consistent alignment between networks for the opinionated local seed. Furthermore These methods are lost in maximizing the number of aligned edges between two networks without considering the original structures of functional modules. Methods We present a novel seed selection strategy for global network alignment by constructing the pairs of hub nodes of networks to be aligned into multiple seeds. Beginning from every hub seed and using the membership similarity of nodes to quantify to what extent the nodes can participate in functional modules associated with current seed topologically we align the networks by modules. By this way we can maintain the functional modules are not damaged during the heuristic alignment process. And our method is efficient in resolving the fatal problem of most conventional algorithms that the initialization selected seeds have a direct influence on the alignment result. The similarity measures between network nodes (e.g., proteins) include sequence similarity, centrality similarity, and dynamic membership similarity and our algorithm can be called Multiple Hubs-based Alignment (MHA). Results When applying our seed selection strategy to several pairs of real PPI networks, it is observed that our method is working to strike a balance, extending the conserved interactions while maintaining the functional modules unchanged. In the case study, we assess the effectiveness of MHA on the alignment of the yeast and fly PPI networks. Our method outperforms state-of-the-art algorithms at detecting conserved functional modules and retrieves in particular 86% more conserved interactions than IsoRank. Conclusions We believe that our seed selection strategy will lead us to obtain more topologically and biologically similar alignment result. And it can be used as the reference and complement of other heuristic methods to seek more meaningful alignment results. PMID:22759574

  18. Biologically Realizable Reward-Modulated Hebbian Training for Spiking Neural Networks

    E-print Network

    Ferrari, Silvia

    Biologically Realizable Reward-Modulated Hebbian Training for Spiking Neural Networks Silvia neural networks have been shown capable of simulating sigmoidal artificial neural networks providing promising evidence that they too are universal function ap- proximators. Spiking neural networks offer

  19. Modulation and Sleeping Strategies for Wireless Sensor Networks

    Microsoft Academic Search

    F. F. Digham; G. B. Giannakis

    2006-01-01

    Motivated by the recent and rapidly increasing interest in energy-saving schemes, this paper presents a novel PHY\\/MAC layer design for wireless sensor networks (WSNs). Capitalizing on the observed rare-event feature of most WSNs, we first design an energy-efficient ternary modulation scheme wherein the modulated symbols can classify (or color) the state of the underlying phenomenon as green, yellow or red.

  20. UWB radio module design for wireless sensor networks

    Microsoft Academic Search

    Meigen Shen; Tero Koivisto; Teemu Peltonen; Li-Rong Zheng; Esa Tjukanoff; H. Tenhunerf

    2005-01-01

    In this paper, we have designed an impulse-based ultra wideband (UWB) radio module for wireless sensor networks (WSN) applications. The UWB radio module includes transceiver block, baseband process unit and power management block. The transceiver block includes Gaussian pulse generator, wideband low noise amplifier (LNA), multiplier, integrator and timing circuits, which use 0.18?m, 1P6M CMOS technology. The wideband LNA has

  1. Genetic programming: building nanobrains with genetically programmed neural network modules

    Microsoft Academic Search

    Hugo de Garis

    1990-01-01

    The author extends ideas concerning the programming methodology called genetic programming, which is the application of the genetic algorithm to the evolution of the signs and weights of fully (self-) connected neural network modules which perform some time-(in)dependent function (e.g. walking, oscillating, etc.) in an optimal manner. Genetically programmed neural net (GenNet) modules are of two types, functional and control.

  2. Protein complexes and functional modules in molecular networks

    NASA Astrophysics Data System (ADS)

    Spirin, Victor; Mirny, Leonid A.

    2003-10-01

    Proteins, nucleic acids, and small molecules form a dense network of molecular interactions in a cell. Molecules are nodes of this network, and the interactions between them are edges. The architecture of molecular networks can reveal important principles of cellular organization and function, similarly to the way that protein structure tells us about the function and organization of a protein. Computational analysis of molecular networks has been primarily concerned with node degree [Wagner, A. & Fell, D. A. (2001) Proc. R. Soc. London Ser. B 268, 1803-1810; Jeong, H., Tombor, B., Albert, R., Oltvai, Z. N. & Barabasi, A. L. (2000) Nature 407, 651-654] or degree correlation [Maslov, S. & Sneppen, K. (2002) Science 296, 910-913], and hence focused on single/two-body properties of these networks. Here, by analyzing the multibody structure of the network of protein-protein interactions, we discovered molecular modules that are densely connected within themselves but sparsely connected with the rest of the network. Comparison with experimental data and functional annotation of genes showed two types of modules: (i) protein complexes (splicing machinery, transcription factors, etc.) and (ii) dynamic functional units (signaling cascades, cell-cycle regulation, etc.). Discovered modules are highly statistically significant, as is evident from comparison with random graphs, and are robust to noise in the data. Our results provide strong support for the network modularity principle introduced by Hartwell et al. [Hartwell, L. H., Hopfield, J. J., Leibler, S. & Murray, A. W. (1999) Nature 402, C47-C52], suggesting that found modules constitute the "building blocks" of molecular networks.

  3. Constructing module maps for integrated analysis of heterogeneous biological networks

    PubMed Central

    Amar, David; Shamir, Ron

    2014-01-01

    Improved methods for integrated analysis of heterogeneous large-scale omic data are direly needed. Here, we take a network-based approach to this challenge. Given two networks, representing different types of gene interactions, we construct a map of linked modules, where modules are genes strongly connected in the first network and links represent strong inter-module connections in the second. We develop novel algorithms that considerably outperform prior art on simulated and real data from three distinct domains. First, by analyzing protein–protein interactions and negative genetic interactions in yeast, we discover epistatic relations among protein complexes. Second, we analyze protein–protein interactions and DNA damage-specific positive genetic interactions in yeast and reveal functional rewiring among protein complexes, suggesting novel mechanisms of DNA damage response. Finally, using transcriptomes of non–small-cell lung cancer patients, we analyze networks of global co-expression and disease-dependent differential co-expression and identify a sharp drop in correlation between two modules of immune activation processes, with possible microRNA control. Our study demonstrates that module maps are a powerful tool for deeper analysis of heterogeneous high-throughput omic data. PMID:24497192

  4. Distributed Broadcasting and Mapping Protocols in Directed Anonymous Networks

    E-print Network

    Bruck, Jehoshua (Shuki)

    Distributed Broadcasting and Mapping Protocols in Directed Anonymous Networks Michael Langberg anonymous networks that are not neces- sarily strongly connected. In such networks, nodes are aware only bounds on its parame- ters, like the number of nodes or the network diameter. Anonymous networks

  5. Ku-band microwave optical emitter based on a directly modulated DFB laser

    Microsoft Academic Search

    F. Van Djik; Reynald BOULA-PICARD; O. Parillaud; A. Enard; J.-P. Plaze; C. Fourdin; N. Vodjdani

    2004-01-01

    We have fabricated a high speed emitting module associating a 19 GHz-band DFB laser and an amplifier with a 5? output impedance for microwave direct modulation. The bandwidth of the emitter was measured to be 17 GHz.

  6. Exploring the randomness of Directed Acyclic Networks

    E-print Network

    Joaquín Goñi; Bernat Corominas-Murtra; Ricard V. Solé; Carlos Rodríguez-Caso

    2010-06-11

    The feed-forward relationship naturally observed in time-dependent processes and in a diverse number of real systems -such as some food-webs and electronic and neural wiring- can be described in terms of so-called directed acyclic graphs (DAGs). An important ingredient of the analysis of such networks is a proper comparison of their observed architecture against an ensemble of randomized graphs, thereby quantifying the {\\em randomness} of the real systems with respect to suitable null models. This approximation is particularly relevant when the finite size and/or large connectivity of real systems make inadequate a comparison with the predictions obtained from the so-called {\\em configuration model}. In this paper we analyze four methods of DAG randomization as defined by the desired combination of topological invariants (directed and undirected degree sequence and component distributions) aimed to be preserved. A highly ordered DAG, called \\textit{snake}-graph and a Erd\\:os-R\\'enyi DAG were used to validate the performance of the algorithms. Finally, three real case studies, namely, the \\textit{C. elegans} cell lineage network, a PhD student-advisor network and the Milgram's citation network were analyzed using each randomization method. Results show how the interpretation of degree-degree relations in DAGs respect to their randomized ensembles depend on the topological invariants imposed. In general, real DAGs provide disordered values, lower than the expected by chance when the directedness of the links is not preserved in the randomization process. Conversely, if the direction of the links is conserved throughout the randomization process, disorder indicators are close to the obtained from the null-model ensemble, although some deviations are observed.

  7. Oriented modulation for watermarking in direct binary search halftone images.

    PubMed

    Guo, Jing-Ming; Su, Chang-Cheng; Liu, Yun-Fu; Lee, Hua; Lee, Jiann-Der

    2012-09-01

    In this paper, a halftoning-based watermarking method is presented. This method enables high pixel-depth watermark embedding, while maintaining high image quality. This technique is capable of embedding watermarks with pixel depths up to 3 bits without causing prominent degradation to the image quality. To achieve high image quality, the parallel oriented high-efficient direct binary search (DBS) halftoning is selected to be integrated with the proposed orientation modulation (OM) method. The OM method utilizes different halftone texture orientations to carry different watermark data. In the decoder, the least-mean-square-trained filters are applied for feature extraction from watermarked images in the frequency domain, and the naïve Bayes classifier is used to analyze the extracted features and ultimately to decode the watermark data. Experimental results show that the DBS-based OM encoding method maintains a high degree of image quality and realizes the processing efficiency and robustness to be adapted in printing applications. PMID:22581134

  8. Comparison of an in-line asymmetric directional coupler modulator with distributed optical loss to other linearized electrooptic modulators

    Microsoft Academic Search

    Scott A. Hamilton; Diego R. Yankelevich; Andr ´ e Knoesen; Robert T. Weverka; Richard A. Hill

    1999-01-01

    The transfer function of an external modulator is the critical factor that determines the spurious free dynamic range, signal power gain, and noise figure of a wide-band analog RF-photonic link. We present an in-line asymmetric directional coupler modulator with distributed optical loss capable of providing a transfer function linearized to the fourth order for multioctave bandwidths. This modulator compares favorably

  9. Compensating the island network voltage unsymmetricity with DTC-modulation-based power conditioning system

    Microsoft Academic Search

    Antti Tarkiainen; Riku Pöllänen; Markku Niemelä; Juha Pyrhönen; Mikko Vertanen

    2004-01-01

    An algorithm for compensating island network voltage unsymmetricity with a direct torque control modulation-based scalar-controlled power conditioning system is introduced and experimentally verified. The proposed method consists of two separate stages where at first the unsymmetricity is detected and then a compensating negative-sequence system is calculated. Experimental results show that the proposed method fully compensates the voltage unsymmetricity resulting from

  10. Distributed Target Tracking with Directional Binary Sensor Networks

    E-print Network

    Varela, Carlos

    Distributed Target Tracking with Directional Binary Sensor Networks Zijian Wang, Eyuphan Bulut--One of the most common and important applications of wireless sensor networks is target tracking. We study. A novel, real-time and distributed target tracking algorithm with directional binary sensor networks

  11. Controllability and observability analysis for vertex domination centrality in directed networks.

    PubMed

    Wang, Bingbo; Gao, Lin; Gao, Yong; Deng, Yue; Wang, Yu

    2014-01-01

    Topological centrality is a significant measure for characterising the relative importance of a node in a complex network. For directed networks that model dynamic processes, however, it is of more practical importance to quantify a vertex's ability to dominate (control or observe) the state of other vertices. In this paper, based on the determination of controllable and observable subspaces under the global minimum-cost condition, we introduce a novel direction-specific index, domination centrality, to assess the intervention capabilities of vertices in a directed network. Statistical studies demonstrate that the domination centrality is, to a great extent, encoded by the underlying network's degree distribution and that most network positions through which one can intervene in a system are vertices with high domination centrality rather than network hubs. To analyse the interaction and functional dependence between vertices when they are used to dominate a network, we define the domination similarity and detect significant functional modules in glossary and metabolic networks through clustering analysis. The experimental results provide strong evidence that our indices are effective and practical in accurately depicting the structure of directed networks. PMID:24954137

  12. SPATIAL AND DIRECTIONAL DISTRIBUTION OF CRACKS IN SILICON PV MODULES AFTER UNIFORM MECHANICAL LOADS

    E-print Network

    to mechanical stresses within the PV module depending on the process temperatures [1,2]. Additionally of position-dependent cracking directions in terms of a principal strain analysis. Cracks parallel an electroluminescence (EL) image of a PV module after such a mechanical load test. Modules subjected to this kind

  13. Characterization of a fiber-optic direct modulation analog link with chirp radar signals

    Microsoft Academic Search

    Rossano Pardini; Umberto Bruno; Roberto Izzo

    2009-01-01

    This paper describes the experimental investigations carried out to evaluate the behaviour of a fiber-optic direct modulation analog link as a substitute of traditional transmission means, like coaxial cables or waveguides, for X-band chirp modulated radar signals. First of all, the link has been completely characterized, and the spurious frequency modulation has been measured in presence of pulsed signals. Afterwards,

  14. Probability Bounds for Goal Directed Queries in Bayesian Networks

    Microsoft Academic Search

    Michael V. Mannino; Vijay S. Mookerjee

    2002-01-01

    We derive bounds on the probability of a goal node given a set of acquired input nodes. The bounds apply to decomposable networks, a class of Bayesian Networks encompassing causal trees and causal polytrees. The difficulty of computing the bounds depends on the characteristics of the decomposable network. For directly connected networks with binary goal nodes, tight bounds can be

  15. Mechanical compaction directly modulates the dynamics of bile canaliculi formation.

    PubMed

    Wang, Yan; Toh, Yi-Chin; Li, Qiushi; Nugraha, Bramasta; Zheng, Baixue; Lu, Thong Beng; Gao, Yi; Ng, Mary Mah Lee; Yu, Hanry

    2013-02-01

    Homeostatic pressure-driven compaction is a ubiquitous mechanical force in multicellular organisms and is proposed to be important in the maintenance of multicellular tissue integrity and function. Previous cell-free biochemical models have demonstrated that there are cross-talks between compaction forces and tissue structural functions, such as cell-cell adhesion. However, its involvement in physiological tissue function has yet to be directly demonstrated. Here, we use the bile canaliculus (BC) as a physiological example of a multicellular functional structure in the liver, and employ a novel 3D microfluidic hepatocyte culture system to provide an unprecedented opportunity to experimentally modulate the compaction states of primary hepatocyte aggregates in a 3D physiological-mimicking environment. Mechanical compaction alters the physical attributes of the hepatocyte aggregates, including cell shape, cell packing density and cell-cell contact area, but does not impair the hepatocytes' remodeling and functional capabilities. Characterization of structural and functional polarity shows that BC formation in compact hepatocyte aggregates is accelerated to as early as 12 hours post-seeding; whereas non-compact control requires 48 hours for functional BC formation. Further dynamic immunofluorescence imaging and gene expression profiling reveal that compaction accelerated BC formation is accompanied by changes in actin cytoskeleton remodeling dynamics and transcriptional levels of hepatic nuclear factor 4? and Annexin A2. Our report not only provides a novel strategy of modeling BC formation for in vitro hepatology research, but also shows a first instance that homeostatic pressure-driven compaction force is directly coupled to the higher-order multicellular functions. PMID:23233209

  16. Functional connectivity of frontoparietal network predicts cognitive modulation of pain

    PubMed Central

    Kong, Jian; Jensen, Karin; Loiotile, Rita; Cheetham, Alexandra; Wey, Hsiao-Ying; Tan, Ying; Rosen, Bruce; Smoller, Jordan W.; Kaptchuk, Ted J.; Gollub, Randy L.

    2013-01-01

    The experience of pain can be significantly influenced by expectancy (predictive cues). This ability to modulate pain has the potential to affect therapeutic analgesia substantially and constitutes a foundation for non-pharmacological pain relief. In this study, we investigated 1) brain regions involved in visual cue modulation of pain during anticipation of pain, pain administration, and pain rating; and 2) the association between pre-test resting-state functional connectivity and the magnitude of cue effects on pain ratings. We found that after cue conditioning, visual cues can significantly modulate subjective pain ratings. fMRI results suggested that brain regions pertaining to the frontoparietal network (prefrontal and parietal cortex) and a pain/emotion modulatory region (rostral anterior cingulate cortex, rACC) are involved in cue modulation during both pain anticipation and administration stage. Most interestingly, we found that pre-test resting state functional connectivity between the frontoparietal network (as identified by independent component analysis) and the rACC/MPFC was positively associated with cue effects on pain rating changes. We believe that these finding will shed new light on our understanding of variable cue/expectancy effects across individuals and how the intrinsic connectivity of the brain may influence expectancy induced modulation of pain. PMID:23352757

  17. An analytic and experimental comparison of direct and external modulation in analog fiber-optic links

    Microsoft Academic Search

    G. E. Betts; L. M. Johnson

    1990-01-01

    Analytic lumped-element small-signal models of directly and externally modulated analog fiber-optic links are derived. Incremental modulation efficiency is defined and used to compare the performances of these modulation techniques. In experiments to optimize link RF-to-RF gain and noise figure, the measurements obtained agreed with calculations to within ≈1 dB. The externally modulated link was operated with two different impedance matching

  18. Direct quadrature phase shift keying modulator using six-port technology

    E-print Network

    Frigon, Jean-François

    for microwave measurements [1] and direct conversion receivers of quadrature phase shift keying (QPSK) signals heterodyne architecture, which requires IF mixers, in-phase and quadrature carriers and an RF upconversion section. Compared with a heterodyne modulator, this direct QPSK modulator eliminates the need

  19. Optimization of fiber amplifier SCM lightwave video systems using direct and external modulation

    Microsoft Academic Search

    Kamal E. Alameh; Robert A. Minasian

    1993-01-01

    An analysis of the design factors involved in optimizing laser transmitters for SCM video distribution networks is presented. This includes optimization of the erbium-doped amplifier, linearized external modulation, and laser overmodulation to increase the optical loss budget. A full nonlinear distortion spectral analysis is employed to determine the dependence of the optimum optical modulation index on the allowable postamplifier loss.

  20. Modules of human micro-RNA co-target network

    NASA Astrophysics Data System (ADS)

    Basu, Mahashweta; Bhattacharyya, Nitai P.; Mohanty, P. K.

    2011-05-01

    Human micro RNAs (miRNAs) target about 90% of the coding genes and form a complex regulatory network. We study the community structure of the miRNA co-target network considering miRNAs as the nodes which are connected by weighted links. The weight of link that connects a pair of miRNAs denote the total number of common transcripts targeted by that pair. We argue that the network consists of about 74 modules, quite similar to the components (or clusters) obtained earlier [Online J Bioinformatics, 10,280], indicating that the components of the miRNA co-target network are self organized in a way to maximize the modularity.

  1. UWB radio module design for wireless sensor networks

    Microsoft Academic Search

    Majid Baghaei Nejad; Meigen Shen; Tero Koivisto; Teemu Peltonen; Esa Tjukanoff; Hannu Tenhunen; Li-Rong Zheng

    2007-01-01

    In this paper, we describe an impulse-based ultra wideband (UWB) radio system for wireless sensor network (WSN) applications.\\u000a Different architectures have been studied for base station and sensor nodes. The base station node uses coherent UWB architecture\\u000a because of the high performance and good sensitivity requirements. However, to meet complexity, power and cost constraints,\\u000a the sensor module uses a novel

  2. Exploring the randomness of Directed Acyclic Networks

    E-print Network

    Goñi, Joaquín; Solé, Ricard V; Rodríguez-Caso, Carlos

    2010-01-01

    The feed-forward relationship naturally observed in time-dependent processes and in a diverse number of real systems -such as some food-webs and electronic and neural wiring- can be described in terms of so-called directed acyclic graphs (DAGs). An important ingredient of the analysis of such networks is a proper comparison of their observed architecture against an ensemble of randomized graphs, thereby quantifying the {\\em randomness} of the real systems with respect to suitable null models. This approximation is particularly relevant when the finite size and/or large connectivity of real systems make inadequate a comparison with the predictions obtained from the so-called {\\em configuration model}. In this paper we analyze four methods of DAG randomization as defined by the desired combination of topological invariants (directed and undirected degree sequence and component distributions) aimed to be preserved. A highly ordered DAG, called \\textit{snake}-graph and a Erd\\:os-R\\'enyi DAG were used to validate ...

  3. Nonlinear distortion reduction in directly modulated semiconductor laser using feedforward linearisation

    E-print Network

    Haddadi, Hamed

    modulated semiconductor laser diode for Wireless Local Area Network (WLAN) operating in the Industrial networks which are capable of delivering broadband signals to remote areas "over the air" [1]. Due to high frequencies requires the radio base stations to be closely spaced in distance and use micro cellular

  4. 40-Gb/s directly-modulated photonic crystal lasers under optical injection-locking

    NASA Astrophysics Data System (ADS)

    Chen, Chin-Hui; Takeda, Koji; Shinya, Akihiko; Nozaki, Kengo; Sato, Tomonari; Kawaguchi, Yoshihiro; Notomi, Masaya; Matsuo, Shinji

    2011-08-01

    CMOS integrated circuits (IC) usually requires high data bandwidth for off-chip input/output (I/O) data transport with sufficiently low power consumption in order to overcome pin-count limitation. In order to meet future requirements of photonic network interconnect, we propose an optical output device based on an optical injection-locked photonic crystal (PhC) laser to realize low-power and high-speed off-chip interconnects. This device enables ultralow-power operation and is suitable for highly integrated photonic circuits because of its strong light-matter interaction in the PhC nanocavity and ultra-compact size. High-speed operation is achieved by using the optical injection-locking (OIL) technique, which has been shown as an effective means to enhance modulation bandwidth beyond the relaxation resonance frequency limit. In this paper, we report experimental results of the OIL-PhC laser under various injection conditions and also demonstrate 40-Gb/s large-signal direct modulation with an ultralow energy consumption of 6.6 fJ/bit.

  5. Modulation format identification in heterogeneous fiber-optic networks using artificial neural networks.

    PubMed

    Khan, Faisal Nadeem; Zhou, Yudi; Lau, Alan Pak Tao; Lu, Chao

    2012-05-21

    We propose a simple and cost-effective technique for modulation format identification (MFI) in next-generation heterogeneous fiber-optic networks using an artificial neural network (ANN) trained with the features extracted from the asynchronous amplitude histograms (AAHs). Results of numerical simulations conducted for six different widely-used modulation formats at various data rates demonstrate that the proposed technique can effectively classify all these modulation formats with an overall estimation accuracy of 99.6% and also in the presence of various link impairments. The proposed technique employs extremely simple hardware and digital signal processing (DSP) to enable MFI and can also be applied for the identification of other modulation formats at different data rates without necessitating hardware changes. PMID:22714229

  6. Tractable model for heterogeneous cellular networks with directional antennas

    Microsoft Academic Search

    He Wang; Mark C. Reed

    2012-01-01

    Heterogeneous cellular networks consisting of microcell, picocell, femtocell, distributed antennas and relays codeployed in space and frequency with carefully planned tower-mounted base stations, increase the complexity of the cellular network structure, which makes a tractable analysis model difficult to obtain. In this paper, we extend the original tractable model for downlink heterogeneous cellular network to the scenario with directional antennas,

  7. Direct DPSK modulation of chirp-managed laser as cost-effective downstream transmitter for symmetrical 10-Gbit/s WDM PONs.

    PubMed

    Le, Quang Trung; Emsia, Ali; Briggmann, Dieter; Küppers, Franko

    2012-12-10

    This paper proposes the use of chirp-managed lasers (CML) as cost-effective downstream (DS) transmitters for next generation access networks. As the laser bandwidth is as high as 10 GHz, the CML could be directly modulated at 10 Gbit/s for downstream transmission in future wavelength division multiplexing passive optical networks (WDM PON). The laser adiabatic chirp, which is the main drawback limiting the transmission performance of directly modulated lasers, is now utilized to generate phase-shift keying (PSK) modulation format by direct modulation. At the user premise, the wavelength reuse technique based on reflective colorless upstream transmitter is applied. The optical network unit (ONU) reflects and orthogonally remodulates the received light with upstream data. A full-duplex transmission with symmetrical 10-Gbit/s bandwidth is demonstrated. Bit-error-rate measurement showed that optical power budgets of 29 dB at BER of 10(-9) or of 36 dB at BER of 10(-3) could be obtained with direct phase-shift-keying modulation of CML which proves that the proposed solution is a viable candidate for future WDM-PONs. PMID:23262890

  8. Optical modulation of astrocyte network using ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Yoon, Jonghee; Ku, Taeyun; Chong, Kyuha; Ryu, Seung-Wook; Choi, Chulhee

    2012-03-01

    Astrocyte, the most abundant cell type in the central nervous system, has been one of major topics in neuroscience. Even though many tools have been developed for the analysis of astrocyte function, there has been no adequate tool that can modulates astrocyte network without pharmaceutical or genetic interventions. Here we found that ultrashort pulsed laser stimulation can induce label-free activation of astrocytes as well as apoptotic-like cell death in a dose-dependent manner. Upon irradiation with high intensity pulsed lasers, the irradiated cells with short exposure time showed very rapid mitochondria fragmentation, membrane blebbing and cytoskeletal retraction. We applied this technique to investigate in vivo function of astrocyte network in the CNS: in the aspect of neurovascular coupling and blood-brain barrier. We propose that this noninvasive technique can be widely applied for in vivo study of complex cellular network.

  9. Link module for a downhole drilling network

    DOEpatents

    Hall, David R. (Provo, UT); Fox, Joe (Provo, UT)

    2007-05-29

    A repeater is disclosed in one embodiment of the present invention as including a cylindrical housing, characterized by a proximal end and a distal end, and having a substantially cylindrical wall, the cylindrical wall defining a central bore passing therethrough. The cylindrical housing is formed to define at least one recess in the cylindrical wall, into which a repeater is inserted. The cylindrical housing also includes an annular recess formed into at least one of the proximal end and the distal end. An annular transmission element, operably connected to the repeater, is located in the annular recess. In selected embodiments, the annular transmission element inductively converts electrical energy to magnetic energy. In other embodiments, the annular transmission element includes an electrical contact to transmit electrical energy directly to another contact.

  10. Google matrix analysis of directed networks Leonardo Ermann

    E-print Network

    Shepelyansky, Dima

    Google matrix analysis of directed networks Leonardo Ermann Departamento de F´isica Te´orica, GIy network structures and characteristics. This review describes the Google matrix analysis of directed III. Construction of Google matrix and its properties 3 A. Construction rules 3 B. Markov chains

  11. An AWG-based 10 Gbit/s colorless WDM-PON system using a chirp-managed directly modulated laser

    NASA Astrophysics Data System (ADS)

    Latif, Abdul; Yu, Chong-xiu; Xin, Xiang-jun; Husain, Aftab; Hussain, Ashiq; Munir, Abid; Khan, Yousaf

    2012-09-01

    We propose an arrayed waveguide grating (AWG)-based 10 Gbit/s per channel full duplex wavelength division multiplexing passive optical network (WDM-PON). A chirp managed directly modulated laser with return-to-zero (RZ) differential phase shift keying (DPSK) modulation technique is utilized for downlink (DL) direction, and then the downlink signal is re-modulated for the uplink (UL) direction using intensity modulation technique with the data rate of 10 Gbit/s per channel. A successful WDM-PON transmission operation with the data rate of 10 Gbit/s per channel over a distance of 25 km without any optical amplification or dispersion compensation is demonstrated with low power penalty.

  12. MOfinder: A Novel Algorithm for Detecting Overlapping Modules from Protein-Protein Interaction Network

    PubMed Central

    Yu, Qi; Li, Gong-Hua; Huang, Jing-Fei

    2012-01-01

    Since organism development and many critical cell biology processes are organized in modular patterns, many algorithms have been proposed to detect modules. In this study, a new method, MOfinder, was developed to detect overlapping modules in a protein-protein interaction (PPI) network. We demonstrate that our method is more accurate than other 5 methods. Then, we applied MOfinder to yeast and human PPI network and explored the overlapping information. Using the overlapping modules of human PPI network, we constructed the module-module communication network. Functional annotation showed that the immune-related and cancer-related proteins were always together and present in the same modules, which offer some clues for immune therapy for cancer. Our study around overlapping modules suggests a new perspective on the analysis of PPI network and improves our understanding of disease. PMID:22500072

  13. IIIDB: a database for isoform-isoform interactions and isoform network modules

    PubMed Central

    2015-01-01

    Background Protein-protein interactions (PPIs) are key to understanding diverse cellular processes and disease mechanisms. However, current PPI databases only provide low-resolution knowledge of PPIs, in the sense that "proteins" of currently known PPIs generally refer to "genes." It is known that alternative splicing often impacts PPI by either directly affecting protein interacting domains, or by indirectly impacting other domains, which, in turn, impacts the PPI binding. Thus, proteins translated from different isoforms of the same gene can have different interaction partners. Results Due to the limitations of current experimental capacities, little data is available for PPIs at the resolution of isoforms, although such high-resolution data is crucial to map pathways and to understand protein functions. In fact, alternative splicing can often change the internal structure of a pathway by rearranging specific PPIs. To fill the gap, we systematically predicted genome-wide isoform-isoform interactions (IIIs) using RNA-seq datasets, domain-domain interaction and PPIs. Furthermore, we constructed an III database (IIIDB) that is a resource for studying PPIs at isoform resolution. To discover functional modules in the III network, we performed III network clustering, and then obtained 1025 isoform modules. To evaluate the module functionality, we performed the GO/pathway enrichment analysis for each isoform module. Conclusions The IIIDB provides predictions of human protein-protein interactions at the high resolution of transcript isoforms that can facilitate detailed understanding of protein functions and biological pathways. The web interface allows users to search for IIIs or III network modules. The IIIDB is freely available at http://syslab.nchu.edu.tw/IIIDB. PMID:25707505

  14. Formation and dynamics of modules in a dual-tasking multilayer feed-forward neural network

    NASA Astrophysics Data System (ADS)

    Lam, Chi-Hang; Shin, F. G.

    1998-09-01

    We study a feed-forward neural network for two independent function approximation tasks. Upon training, two modules are automatically formed in the hidden layers, each handling one of the tasks predominantly. We demonstrate that the sizes of the modules can be dynamically driven by varying the complexities of the tasks. The network serves as a simple example of an artificial neural network with an adaptable modular structure. This study was motivated by related dynamical nature of modules in animal brains.

  15. RO module RTD analyses based on directly processing conductivity signals

    Microsoft Academic Search

    Qingfeng Yang; Alexander Drak; David Hasson; Raphael Semiat

    2007-01-01

    Residence time distribution (RTD) techniques can be used to diagnose the flow characteristics in spiral wound reverse osmosis (RO) modules. However, the methods of processing tracer response conductivity signals and mathematically modeling of RTD curves often involve complicated steps including conductivity-concentration transformation, baseline selection and the use of exit age distribution function of Et, or dimensionless exit age distribution function

  16. The middleware architecture supports heterogeneous network systems for module-based personal robot system

    NASA Astrophysics Data System (ADS)

    Choo, Seongho; Li, Vitaly; Choi, Dong Hee; Jung, Gi Deck; Park, Hong Seong; Ryuh, Youngsun

    2005-12-01

    On developing the personal robot system presently, the internal architecture is every module those occupy separated functions are connected through heterogeneous network system. This module-based architecture supports specialization and division of labor at not only designing but also implementation, as an effect of this architecture, it can reduce developing times and costs for modules. Furthermore, because every module is connected among other modules through network systems, we can get easy integrations and synergy effect to apply advanced mutual functions by co-working some modules. In this architecture, one of the most important technologies is the network middleware that takes charge communications among each modules connected through heterogeneous networks systems. The network middleware acts as the human nerve system inside of personal robot system; it relays, transmits, and translates information appropriately between modules that are similar to human organizations. The network middleware supports various hardware platform, heterogeneous network systems (Ethernet, Wireless LAN, USB, IEEE 1394, CAN, CDMA-SMS, RS-232C). This paper discussed some mechanisms about our network middleware to intercommunication and routing among modules, methods for real-time data communication and fault-tolerant network service. There have designed and implemented a layered network middleware scheme, distributed routing management, network monitoring/notification technology on heterogeneous networks for these goals. The main theme is how to make routing information in our network middleware. Additionally, with this routing information table, we appended some features. Now we are designing, making a new version network middleware (we call 'OO M/W') that can support object-oriented operation, also are updating program sources itself for object-oriented architecture. It is lighter, faster, and can support more operation systems and heterogeneous network systems, but other general purposed middlewares like CORBA, UPnP, etc. can support only one network protocol or operating system.

  17. Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex Modulates Repetition

    E-print Network

    Gosselin, Frédéric

    and learning of unfamiliar faces remains unclear. Transcranial direct current stimulation (tDCS) transiently excitability modulation by tDCS would cause polarity-dependent modulations of N170 RS during encoding underwent three tDCS conditions in random order at ,72 hour intervals: right anodal/left cathodal, right

  18. Directional collision avoidance in ad hoc networks

    Microsoft Academic Search

    Yu Wang; Jose Joaquin Garcia-luna-aceves

    2004-01-01

    This paper analyzes the performance of directional collision avoidance schemes, in which antenna systems are used to direct the transmission and reception of control and data packets in channel access protocols based on four-way handshakes to try to avoid collisions. The first analytical model to consider directional reception and the possible difference in gain between omni-directional and directional transmissions is

  19. Beyond Modules & Hubs: the potential of gene coexpression networks for investigating molecular mechanisms of complex brain disorders

    PubMed Central

    Gaiteri, Chris; Ding, Ying; French, Beverly; Tseng, George C.; Sibille, Etienne

    2013-01-01

    In a research environment dominated by reductionist approaches to brain disease mechanisms, gene network analysis provides a complementary framework in which to tackle the complex dysregulations that occur in neuropsychiatric and other neurological disorders. Gene-gene expression correlations are a common source of molecular networks because they can be extracted from high-dimensional disease data and encapsulate the activity of multiple regulatory systems. However, the analysis of gene coexpression patterns is often treated as a mechanistic black box, in which looming “hub genes” direct cellular networks, and where other features are obscured. By examining the biophysical bases of coexpression and gene regulatory changes that occur in disease, recent studies suggest it is possible to use coexpression networks as a multi-omic screening procedure to generate novel hypotheses for disease mechanisms. Because technical processing steps can affect the outcome and interpretation of coexpression networks, we examine the assumptions and alternatives to common patterns of coexpression analysis and discuss additional topics such as acceptable datasets for coexpression analysis, the robust identification of modules, disease-related prioritization of genes and molecular systems and network meta-analysis. To accelerate coexpression research beyond modules and hubs, we highlight some emerging directions for coexpression network research that are especially relevant to complex brain disease, including the centrality-lethality relationship, integration with machine learning approaches and network pharmacology. PMID:24320616

  20. How familiarization and repetition modulate the picture naming network

    PubMed Central

    Llorens, Anaïs; Trébuchon, Agnès; Riès, Stéphanie; Liégeois-Chauvel, Catherine; Alario, F.-Xavier

    2014-01-01

    A common strategy to reveal the components of the speech production network is to use psycholinguistic manipulations previously tested in behavioral protocols. This often disregards how implementation aspects that are nonessential for interpreting behavior may affect the neural response. We compared the electrophysiological (EEG) signature of two popular picture naming protocols involving either unfamiliar pictures without repetitions or repeated familiar pictures. We observed significant semantic interference effects in behavior but not in the EEG, contrary to some previous findings. Remarkably, the two protocols elicited clearly distinct EEG responses. These were not due to naming latency differences nor did they reflect a homogeneous modulation of amplitude over the trial time-window. The effect of protocol is attributed to the familiarization induced by the first encounter with the materials. Picture naming processes can be substantially modulated by specific protocol requirements controlled by familiarity and, to a much lesser degree, the repetition of materials. PMID:24785306

  1. How familiarization and repetition modulate the picture naming network.

    PubMed

    Llorens, Anaïs; Trébuchon, Agnès; Riès, Stéphanie; Liégeois-Chauvel, Catherine; Alario, F-Xavier

    2014-06-01

    A common strategy to reveal the components of the speech production network is to use psycholinguistic manipulations previously tested in behavioral protocols. This often disregards how implementation aspects that are nonessential for interpreting behavior may affect the neural response. We compared the electrophysiological (EEG) signature of two popular picture naming protocols involving either unfamiliar pictures without repetitions or repeated familiar pictures. We observed significant semantic interference effects in behavior but not in the EEG, contrary to some previous findings. Remarkably, the two protocols elicited clearly distinct EEG responses. These were not due to naming latency differences nor did they reflect a homogeneous modulation of amplitude over the trial time-window. The effect of protocol is attributed to the familiarization induced by the first encounter with the materials. Picture naming processes can be substantially modulated by specific protocol requirements controlled by familiarity and, to a much lesser degree, the repetition of materials. PMID:24785306

  2. Capacity achieving modulation format for high-speed optical networks

    NASA Astrophysics Data System (ADS)

    Batshon, Hussam G.; Djordjevic, Ivan B.; Xu, Lei; Wang, Ting

    2010-01-01

    In recent years, we have witnessed an increased demand on optical-networks transmission-capacities due to the growing popularity of the Internet and multimedia in everyday life. According to industry expert estimates, 1Tb/s-Ethernet should be standardized by the year 2012-2013. To this end, we propose a non-uniform modulation format that achieves the channel capacity for SNRs of up to 25dB. The proposed modulation format is optimized for ASE-noise-dominated channels and can achieve 400Gb/s data rate per polarization utilizing the currently-available components operating at 50-GSymbols/s. One major benefit of the current scheme is that it is an affordable upgrade to the current systems.

  3. Signal to Noise Ratios of Pulsed and Sinewave Modulated Direct Detection Lidar for IPDA Measurements

    NASA Technical Reports Server (NTRS)

    Sun, Xiaoli; Abshire, James B.

    2011-01-01

    The signal-to-noise ratios have been derived for IPDA lidar using a direct detection receiver for both pulsed and sinewave laser modulation techniques, and the results and laboratory measurements are presented

  4. Matrix mechanical properties modulate ECFC vascular network formation

    Microsoft Academic Search

    Paul John Critser

    2011-01-01

    Development of a functional vascular network is a major problem limiting current tissue engineering strategies targeting repair and regeneration of damaged or diseased tissue. Recently endothelial colony forming cells (ECFCs) have been shown to vascularize a type I collagen scaffold in vivo. ECFCs are the only cells that have been shown to possess direct in vivo vessel forming ability upon

  5. Physiological modules for generating discrete and rhythmic movements: action identification by a dynamic recurrent neural network.

    PubMed

    Bengoetxea, Ana; Leurs, Françoise; Hoellinger, Thomas; Cebolla, Ana M; Dan, Bernard; McIntyre, Joseph; Cheron, Guy

    2014-01-01

    In this study we employed a dynamic recurrent neural network (DRNN) in a novel fashion to reveal characteristics of control modules underlying the generation of muscle activations when drawing figures with the outstretched arm. We asked healthy human subjects to perform four different figure-eight movements in each of two workspaces (frontal plane and sagittal plane). We then trained a DRNN to predict the movement of the wrist from information in the EMG signals from seven different muscles. We trained different instances of the same network on a single movement direction, on all four movement directions in a single movement plane, or on all eight possible movement patterns and looked at the ability of the DRNN to generalize and predict movements for trials that were not included in the training set. Within a single movement plane, a DRNN trained on one movement direction was not able to predict movements of the hand for trials in the other three directions, but a DRNN trained simultaneously on all four movement directions could generalize across movement directions within the same plane. Similarly, the DRNN was able to reproduce the kinematics of the hand for both movement planes, but only if it was trained on examples performed in each one. As we will discuss, these results indicate that there are important dynamical constraints on the mapping of EMG to hand movement that depend on both the time sequence of the movement and on the anatomical constraints of the musculoskeletal system. In a second step, we injected EMG signals constructed from different synergies derived by the PCA in order to identify the mechanical significance of each of these components. From these results, one can surmise that discrete-rhythmic movements may be constructed from three different fundamental modules, one regulating the co-activation of all muscles over the time span of the movement and two others elliciting patterns of reciprocal activation operating in orthogonal directions. PMID:25278868

  6. Physiological modules for generating discrete and rhythmic movements: action identification by a dynamic recurrent neural network

    PubMed Central

    Bengoetxea, Ana; Leurs, Françoise; Hoellinger, Thomas; Cebolla, Ana M.; Dan, Bernard; McIntyre, Joseph; Cheron, Guy

    2014-01-01

    In this study we employed a dynamic recurrent neural network (DRNN) in a novel fashion to reveal characteristics of control modules underlying the generation of muscle activations when drawing figures with the outstretched arm. We asked healthy human subjects to perform four different figure-eight movements in each of two workspaces (frontal plane and sagittal plane). We then trained a DRNN to predict the movement of the wrist from information in the EMG signals from seven different muscles. We trained different instances of the same network on a single movement direction, on all four movement directions in a single movement plane, or on all eight possible movement patterns and looked at the ability of the DRNN to generalize and predict movements for trials that were not included in the training set. Within a single movement plane, a DRNN trained on one movement direction was not able to predict movements of the hand for trials in the other three directions, but a DRNN trained simultaneously on all four movement directions could generalize across movement directions within the same plane. Similarly, the DRNN was able to reproduce the kinematics of the hand for both movement planes, but only if it was trained on examples performed in each one. As we will discuss, these results indicate that there are important dynamical constraints on the mapping of EMG to hand movement that depend on both the time sequence of the movement and on the anatomical constraints of the musculoskeletal system. In a second step, we injected EMG signals constructed from different synergies derived by the PCA in order to identify the mechanical significance of each of these components. From these results, one can surmise that discrete-rhythmic movements may be constructed from three different fundamental modules, one regulating the co-activation of all muscles over the time span of the movement and two others elliciting patterns of reciprocal activation operating in orthogonal directions. PMID:25278868

  7. Anodal transcranial direct current stimulation of the motor cortex induces opposite modulation of reciprocal inhibition in wrist extensor and flexor.

    PubMed

    Lackmy-Vallée, Alexandra; Klomjai, Wanalee; Bussel, Bernard; Katz, Rose; Roche, Nicolas

    2014-09-15

    Transcranial direct current stimulation (tDCS) is used as a noninvasive tool to modulate brain excitability in humans. Recently, several studies have demonstrated that tDCS applied over the motor cortex also modulates spinal neural network excitability and therefore can be used to explore the corticospinal control acting on spinal neurons. Previously, we showed that reciprocal inhibition directed to wrist flexor motoneurons is enhanced during contralateral anodal tDCS, but it is likely that the corticospinal control acting on spinal networks controlling wrist flexors and extensors is not similar. The primary aim of the study was to explore the effects of anodal tDCS on reciprocal inhibition directed to wrist extensor motoneurons. To further examine the supraspinal control acting on the reciprocal inhibition between wrist flexors and extensors, we also explored the effects of the tDCS applied to the ipsilateral hand motor area. In healthy volunteers, we tested the effects induced by sham and anodal tDCS on reciprocal inhibition pathways innervating wrist muscles. Reciprocal inhibition directed from flexor to extensor muscles and the reverse situation, i.e., reciprocal inhibition, directed from extensors to flexors were studied in parallel with the H reflex technique. Our main finding was that contralateral anodal tDCS induces opposing effects on reciprocal inhibition: it decreases reciprocal inhibition directed from flexors to extensors, but it increases reciprocal inhibition directed from extensors to flexors. The functional result of these opposite effects on reciprocal inhibition seems to favor wrist extension excitability, suggesting an asymmetric descending control onto the interneurons that mediate reciprocal inhibition. PMID:24920031

  8. Directions in Packet Classification for Network Processors

    Microsoft Academic Search

    Michael E. Kounavis; Alok Kumar; Harrick Vin; Raj Yavatkar; Andrew T. Campbell

    To classify a packet as belonging to a flow often requires network systems—such as routers and firewalls—to maintain large data structures and perform several memory accesses. Network processors, on the other hand, are generally configured with only a small amount of memory with limited access bandwidth. Hence, a key challenge is to design packet classification algorithms that can be implemented

  9. Corticofugal modulation of directional sensitivity in the midbrain of the big brown bat, Eptesicus fuscus.

    PubMed

    Zhou, Xiaoming; Jen, Philip H-S

    2005-05-01

    In our recent study of corticofugal modulation of collicular amplitude sensitivity of the big brown bat, Eptesicus fuscus, we suggested that the corticofugal modulation is based upon the best frequency (BF) differences and the relative amplitude sensitivity difference between collicular (IC) and cortical (AC) neurons but not the absolute amplitude sensitivity of IC and AC neurons. To show that corticofugal modulation is systematic and multiparametric, we studied corticofugal modulation of directional sensitivity in 89 corticofugally inhibited IC neurons in the same bat species under free field stimulation conditions. A neuron's directional sensitivity was expressed with the azimuthal range (AR) at 50% below the maximum of each directional sensitivity curve and the best azimuth (BAZ) at which the neuron discharged maximally. Cortical electrical stimulation did not affect the directional sensitivity of 40 (45%) neurons with BF(IC-AC) differences of 7.3+/-4.4kHz but sharpened the directional sensitivity of other 49 (55%) neurons with BF(IC-AC) differences of 2.3+/-1.8kHz. Corticofugal modulation sharpened directional sensitivity curves of IC neurons by decreasing the AR and shifting collicular BAZ toward cortical BAZ. The decrease in AR and the shift in BAZ increased significantly with AR(IC-AC) and BAZ(IC-AC) differences but not with absolute AR and BAZ of IC and AC neurons or BF(IC-AC) differences. Corticofual modulation also shifted collicular BF toward cortical BF. The shift in BF increased significantly with BF(IC-AC) differences but not with the BF of IC and AC neurons or BAZ shift. Consonant with our previous study, these data indicate that corticofugal modulation of collicular directional sensitivity is based on topographic projections between the IC and the AC and the difference in directional sensitivity but not the absolute directional sensitivity of IC or AC neurons. PMID:15855045

  10. Network modulation in the treatment of Parkinson's disease

    PubMed Central

    Asanuma, Kotaro; Tang, Chengke; Ma, Yilong; Dhawan, Vijay; Mattis, Paul; Edwards, Christine; Kaplitt, Michael G.; Feigin, Andrew; Eidelberg, David

    2015-01-01

    It has been proposed that deep brain stimulation (DBS) of the subthalamic nucleus (STN DBS) and dopaminergic therapy ameliorate the symptoms of Parkinson's disease through similar functional mechanisms. We examined this notion using PET to compare the metabolic effects of these treatment approaches. Nine Parkinson's disease patients (age 61.7 ± 11.1 years) were scanned ON and OFF STN stimulation and nine others (age 60.0 ± 9.3 years) were scanned ON and OFF an individual titrated intravenous levodopa infusion. The two treatment groups were matched for baseline disease severity as well as clinical response to therapy. Similarities and differences in the effects of treatment on regional metabolism were assessed using statistical parametric mapping (SPM). In addition, we used network analysis to assess the effect of therapy on the expression of an abnormal Parkinson's disease-related spatial covariance pattern (PDRP). We found that both STN DBS and levodopa therapy were associated with significant (P < 0.001) metabolic reductions in the putamen/globus pallidus, sensorimotor cortex and cerebellar vermis, as well as increases in the precuneus (BA 7). The metabolic effects of the two interventions differed in the STN and medial prefrontal cortex, with relative increases with stimulation in the former structure and decreases in the latter. Network quantification disclosed reductions in PDRP activity with both interventions, which correlated with clinical improvement (P < 0.05). The degree of network modulation by therapy did not differ significantly for the two treatment approaches (P > 0.6). These findings support the results of previous imaging studies indicating that effective symptomatic therapies for Parkinson's disease involve a common mechanism. The modulation of pathological brain networks is a critical feature of the treatment response in parkinsonism. PMID:16844713

  11. Direct torque control of induction machines using space vector modulation

    Microsoft Academic Search

    T. G. Habetler; F. Profumo; M. Pastorelli; L. M. Tolbert

    1991-01-01

    A control scheme for direct torque and flux control of induction machines based on the stator flux field orientation method is proposed. With the proposed predictive control scheme, an inverter duty cycle is directly based on the torque and flux errors, the transient reactance of the machine, and an estimated value of the voltage behind the transient reactance. A method

  12. Effect of modulated alternating and direct current iontophoresis on transdermal delivery of lidocaine hydrochloride.

    PubMed

    Bhatia, Gaurav; Banga, Ajay K

    2014-01-01

    The objective of this study was to investigate the iontophoretic delivery of lidocaine hydrochloride through porcine skin and to compare the effects of modulated alternating and direct current iontophoresis. Continuous and modulated iontophoresis was applied for one hour and two hours (0-1 h and 4-5th h) using a 1% w/v solution of lidocaine hydrochloride. Tape stripping was done to quantify the amount of drug permeated into stratum corneum and skin extraction studies were performed to determine the amount of drug in stripped skin. Receptor was sampled and analyzed over predefined time periods. The amount of lidocaine delivered across porcine skin after modulated direct current iontophoresis for 2 h was 1069.87 ± 120.03 ? g/sq · cm compared to 744.81 ± 125.41 ? g/sq · cm after modulated alternating current iontophoresis for 2 h. Modulated direct current iontophoresis also enhanced lidocaine delivery by twelvefold compared to passive delivery as 91.27 ± 18.71 ? g/sq · cm of lidocaine was delivered after passive delivery. Modulated iontophoresis enhanced the delivery of lidocaine hydrochloride across porcine skin compared to the passive delivery. Modulated alternating current iontophoresis for duration of 2 h at frequency of 1 kHz was found to be comparable to the continuous direct current iontophoresis for 1 h. PMID:24959580

  13. Network-based survival-associated module biomarker and its crosstalk with cell death genes in ovarian cancer

    PubMed Central

    Jin, Nana; Wu, Hao; Miao, Zhengqiang; Huang, Yan; Hu, Yongfei; Bi, Xiaoman; Wu, Deng; Qian, Kun; Wang, Liqiang; Wang, Changliang; Wang, Hongwei; Li, Kongning; Li, Xia; Wang, Dong

    2015-01-01

    Ovarian cancer remains a dismal disease with diagnosing in the late, metastatic stages, therefore, there is a growing realization of the critical need to develop effective biomarkers for understanding underlying mechanisms. Although existing evidences demonstrate the important role of the single genetic abnormality in pathogenesis, the perturbations of interactors in the complex network are often ignored. Moreover, ovarian cancer diagnosis and treatment still exist a large gap that need to be bridged. In this work, we adopted a network-based survival-associated approach to capture a 12-gene network module based on differential co-expression PPI network in the advanced-stage, high-grade ovarian serous cystadenocarcinoma. Then, regulatory genes (protein-coding genes and non-coding genes) direct interacting with the module were found to be significantly overlapped with cell death genes. More importantly, these overlapping genes tightly clustered together pointing to the module, deciphering the crosstalk between network-based survival-associated module and cell death in ovarian cancer. PMID:26099452

  14. Multicast tree construction in directed networks

    Microsoft Academic Search

    J. Eric Klinker

    1996-01-01

    Significant interest exists within the military in moving towards an integrated services environment where traditional network services such as ftp, telnet, and e-mail can co-exist with real-time services such as voice, video, and satellite imagery. Multicast routing is an effective means of providing the efficient utilization of network resources required to realize such an environment. Traditional multicast routing algorithms assume

  15. Network Linkages and Location Choice in Foreign Direct Investment

    Microsoft Academic Search

    Homin Chen; Tain-Jy Chen

    1998-01-01

    This paper shows that network linkage is an important determinant of location choice in foreign direct investment (FDI). Network linkages are divided into internal (intra-firm) and external (inter-firm) linkages. External linkages are further separated into strategic and relational linkages. We found that Taiwanese firms are keen on making external linkages, but are indifferent to, or incapable of, making internal linkages

  16. Fast-response and scattering-free polymer network liquid crystals for infrared light modulators

    E-print Network

    Wu, Shin-Tson

    - ever, the associated light scattering is quite strong in the visible region. As the polymerFast-response and scattering-free polymer network liquid crystals for infrared light modulators Yun-response and scattering-free homogeneously aligned polymer network liquid crystal PNLC light modulator is demonstrated

  17. Physical-layer Network Coding using FSK Modulation under Frequency Offset

    E-print Network

    Valenti, Matthew C.

    Physical-layer Network Coding using FSK Modulation under Frequency Offset Terry Ferrett, Hideki of the network-coded information using a specific modulation scheme, binary frequency-shift keying (binary FSK throughput over conventional relaying in the two- way relay channel, but is sensitive to phase and frequency

  18. Regular and irregular modulation of frequencies in limit cycle oscillator networks

    E-print Network

    Masashi Tachikawa

    2009-02-02

    Frequency modulation by perturbation is the essential trait that differentiates limit cycle oscillators from phase oscillators. We studied networks of identical limit cycle oscillators whose frequencies are modulated sensitively by the change of their amplitudes, and demonstrated that the frequencies sustainably take distributed values. We observed two complex phenomena in the networks: stationarily distributed frequencies at a regular interval, and continuous irregular modulation of frequencies. In the analysis we reveal the mechanisms by which the frequencies are distributed, and show how the sensitive modulation of frequencies produces these complex phenomena. We also illustrate the topology of networks regulating the behaviors of the systems.

  19. The theory of pattern formation on directed networks

    NASA Astrophysics Data System (ADS)

    Asllani, Malbor; Challenger, Joseph D.; Pavone, Francesco Saverio; Sacconi, Leonardo; Fanelli, Duccio

    2014-07-01

    Dynamical processes on networks have generated widespread interest in recent years. The theory of pattern formation in reaction-diffusion systems defined on symmetric networks has often been investigated, due to its applications in a wide range of disciplines. Here we extend the theory to the case of directed networks, which are found in a number of different fields, such as neuroscience, computer networks and traffic systems. Owing to the structure of the network Laplacian, the dispersion relation has both real and imaginary parts, at variance with the case for a symmetric, undirected network. The homogeneous fixed point can become unstable due to the topology of the network, resulting in a new class of instabilities, which cannot be induced on undirected graphs. Results from a linear stability analysis allow the instability region to be analytically traced. Numerical simulations show travelling waves, or quasi-stationary patterns, depending on the characteristics of the underlying graph.

  20. Inter-arrival times of message propagation on directed networks

    E-print Network

    Mihaljev, Tamara; Herrmann, Hans J

    2010-01-01

    One of the challenges in fighting cybercrime is to understand the dynamics of message propagation on botnets, networks of infected computers used to send viruses, unsolicited commercial emails (SPAM) or denial of service attacks. We map this problem to the propagation of multiple random walkers on directed networks and we evaluate the inter-arrival time distribution between successive walkers arriving at a target. We show that the temporal organization of this process, which models information propagation on unstructured peer to peer networks, has the same features as SPAM arriving to a single user. We study the behavior of the message inter-arrival time distribution on three different network topologies using two different rules for sending messages. In all networks the propagation is not a pure Poisson process. It shows universal features on Poissonian networks and a more complex behavior on scale free networks. Results open the possibility to indirectly learn about the process of sending messages on networ...

  1. Transcranial direct current stimulation over posterior parietal cortex modulates visuospatial localization

    E-print Network

    Krekelberg, Bart

    , our goal was to determine whether modulation of the PPC via transcranial direct current stimulation (tDCS the left PPC (dual tDCS) and varied the polarity of the stimulation. We found that this manipulation localization. We used transcranial direct current stimulation (tDCS) over the PPC of healthy human volunteers

  2. Categorization is modulated by transcranial direct current stimulation over left prefrontal cortex

    E-print Network

    Thompson-Schill, Sharon

    Categorization is modulated by transcranial direct current stimulation over left prefrontal cortex transcranial direct current stimulation alters performance of healthy subjects on a simple categoriza- tion of multiple catego- ries. A given object, such as a pillow may be--depending on current task demands

  3. Experimental Results of Single Carrier Digital Modulation for Underwater Sensor Networks

    Microsoft Academic Search

    Se-Young Kim; Jeong-woo Han; Ki-Man Kim; Sang-hoon Baek; Hyung-chul Kim; Chang-hwa Kim

    2010-01-01

    This paper presents the experimental results of single carrier digital modulation schemes for underwater sensor networks. To obtain a real sea data of acoustic communications, an experiment was performed at the shallow water environments. ASK and FSK were used as non-coherent modulation scheme and QPSK and 16-QAM are used as coherent modulation scheme. Except for 16 QAM, the experimental results

  4. Integrin-directed modulation of macrophage responses to biomaterials.

    PubMed

    Zaveri, Toral D; Lewis, Jamal S; Dolgova, Natalia V; Clare-Salzler, Michael J; Keselowsky, Benjamin G

    2014-04-01

    Macrophages are the primary mediator of chronic inflammatory responses to implanted biomaterials, in cases when the material is either in particulate or bulk form. Chronic inflammation limits the performance and functional life of numerous implanted medical devices, and modulating macrophage interactions with biomaterials to mitigate this response would be beneficial. The integrin family of cell surface receptors mediates cell adhesion through binding to adhesive proteins nonspecifically adsorbed onto biomaterial surfaces. In this work, the roles of integrin Mac-1 (?M?2) and RGD-binding integrins were investigated using model systems for both particulate and bulk biomaterials. Specifically, the macrophage functions of phagocytosis and inflammatory cytokine secretion in response to a model particulate material, polystyrene microparticles were investigated. Opsonizing proteins modulated microparticle uptake, and integrin Mac-1 and RGD-binding integrins were found to control microparticle uptake in an opsonin-dependent manner. The presence of adsorbed endotoxin did not affect microparticle uptake levels, but was required for the production of inflammatory cytokines in response to microparticles. Furthermore, it was demonstrated that integrin Mac-1 and RGD-binding integrins influence the in vivo foreign body response to a bulk biomaterial, subcutaneously implanted polyethylene terephthalate. A thinner foreign body capsule was formed when integrin Mac-1 was absent (~30% thinner) or when RGD-binding integrins were blocked by controlled release of a blocking peptide (~45% thinner). These findings indicate integrin Mac-1 and RGD-binding integrins are involved and may serve as therapeutic targets to mitigate macrophage inflammatory responses to both particulate and bulk biomaterials. PMID:24462356

  5. Integrin-Directed Modulation of Macrophage Responses to Biomaterials

    PubMed Central

    Zaveri, Toral D.; Lewis, Jamal S.; Dolgova, Natalia V.; Clare-Salzler, Michael J.; Keselowsky, Benjamin G.

    2014-01-01

    Macrophages are the primary mediator of chronic inflammatory responses to implanted biomaterials, in cases when the material is either in particulate or bulk form. Chronic inflammation limits the performance and functional life of numerous implanted medical devices, and modulating macrophage interactions with biomaterials to mitigate this response would be beneficial. The integrin family of cell surface receptors mediates cell adhesion through binding to adhesive proteins nonspecifically adsorbed onto biomaterial surfaces. In this work, the roles of integrin Mac-1 (?M?2) and RGD-binding integrins were investigated using model systems for both particulate and bulk biomaterials. Specifically, the macrophage functions of phagocytosis and inflammatory cytokine secretion in response to a model particulate material, polystyrene microparticles were investigated. Opsonizing proteins modulated microparticle uptake, and integrin Mac-1 and RGD-binding integrins were found to control microparticle uptake in an opsonin-dependent manner. The presence of adsorbed endotoxin did not affect microparticle uptake levels, but was required for the production of inflammatory cytokines in response to microparticles. Furthermore, it was demonstrated that integrin Mac-1 and RGD-binding integrins influence the in vivo foreign body response to a bulk biomaterial, subcutaneously implanted polyethylene terephthalate. A thinner foreign body capsule was formed when integrin Mac-1 was absent (~30% thinner) or when RGD-binding integrins were blocked by controlled release of a blocking peptide (~45% thinner). These findings indicate integrin Mac-1 and RGD-binding integrins are involved and may serve as therapeutic targets to mitigate macrophage inflammatory responses to both particulate and bulk biomaterials. PMID:24462356

  6. Direct torque control of induction machines using space vector modulation

    Microsoft Academic Search

    Thomas G. Habetler; Francesco Profumo; Michele Pastorelli; Leon M. Tolbert

    1992-01-01

    A direct induction machine torque control method based on predictive, deadbeat control of the torque and flux is presented. By estimating the synchronous speed and the voltage behind the transient reactance, the change in torque and flux over the switching period is calculated. The stator voltage required to cause the torque and flux to be equal to their respective reference

  7. Directed Progression Brain Networks in Alzheimer's Disease: Properties and Classification

    PubMed Central

    Young, Karl; Asif, Danial; Jutla, Inderjit; Liang, Michael; Wilson, Scott; Landsberg, Adam S.; Schuff, Norbert

    2014-01-01

    Abstract This article introduces a new approach in brain connectomics aimed at characterizing the temporal spread in the brain of pathologies like Alzheimer's disease (AD). The main instrument is the development of “directed progression networks” (DPNets), wherein one constructs directed edges between nodes based on (weakly) inferred directions of the temporal spreading of the pathology. This stands in contrast to many previously studied brain networks where edges represent correlations, physical connections, or functional progressions. In addition, this is one of a few studies showing the value of using directed networks in the study of AD. This article focuses on the construction of DPNets for AD using longitudinal cortical thickness measurements from magnetic resonance imaging data. The network properties are then characterized, providing new insights into AD progression, as well as novel markers for differentiating normal cognition (NC) and AD at the group level. It also demonstrates the important role of nodal variations for network classification (i.e., the significance of standard deviations, not just mean values of nodal properties). Finally, the DPNets are utilized to classify subjects based on their global network measures using a variety of data-mining methodologies. In contrast to most brain networks, these DPNets do not show high clustering and small-world properties. PMID:24901258

  8. System architecture directions for networked sensors

    Microsoft Academic Search

    Jason L. Hill; Robert Szewczyk; Alec Woo; Seth Hollar; David E. Culler; Kristofer S. J. Pister

    2000-01-01

    Technological progress in integrated, low-power, CMOS communication devices and sensors makes a rich design space of networked sensors viable. They can be deeply embedded in the physical world and spread throughout our environment like smart dust. The missing elements are an overall system architecture and a methodology for systematic advance. To this end, we identify key requirements, develop a small

  9. Enhancing complex network controllability by minimum link direction reversal

    NASA Astrophysics Data System (ADS)

    Hou, Lvlin; Lao, Songyang; Small, Michael; Xiao, Yandong

    2015-07-01

    Controllability of complex networks has recently become one of the most popular research fields, but the importance of link direction for controllability has not been systematically considered. We propose a method to enhance controllability of a directed network by changing the direction of a small fraction of links while keeping the total number of links unchanged. The main idea of the method is to find candidate links based on the matching path. Extensive numerical simulation on many modeled networks demonstrates that this method is effective. Furthermore, we find that the nodes linked to candidate links have a distinct character, which provide us with a strategy to improve the controllability based on the local structure. Since the whole topology of many real networks is not visible and we only get some local structure information, this strategy is potentially more practical compared to those that demand complete topology information.

  10. AN EXTERNAL CORROSION DIRECT ASSESSMENT MODULE FOR A PIPELINE INTEGRITY MANAGEMENT SYSTEM

    Microsoft Academic Search

    Menno T. van Os; Piet van Mastrigt; Andrew Francis

    2006-01-01

    A significant part of the high pressure gas transport system of Gasunie cannot be examined by in-line inspection techniques. To ensure safe operation of these pipelines, an External Corrosion Direct Assessment (ECDA) module for PIMSLIDER (a pipeline integrity management system) is currently under development. The functional specifications of this module are based on NACE RP0502-2002, a recommended practice for ECDA.

  11. Directional medium access control for ad hoc networks

    Microsoft Academic Search

    Jianfeng Wang; Hongqiang Zhai; Pan Li; Yuguang Fang; Dapeng Wu

    2009-01-01

    Using directional antennas in ad hoc networks may introduce the well-known deafness problem, exacer- bate the hidden terminal problem and the exposed terminal problem, add difficulty on mobile communication, and distort the operation of existing routing and TCP protocols. Although a lot of studies have been undertaken on the directional MAC protocols, most of them focus only on one or

  12. Lending Direction to Neural Networks \\Lambda Richard S. Zemel

    E-print Network

    Williams, Chris

    for a network of stochastic directional units. This formulation is an extension of the Boltzmann machine in which the units are not binary, but take on values on a cyclic range, between 0 and 2ß radians, days of the week, phases of the moon. The state of each unit in a Directional­Unit Boltzmann Machine

  13. Adaptive MAC Protocol for UAV Communication Networks Using Directional Antennas

    E-print Network

    Dong, Liang

    Adaptive MAC Protocol for UAV Communication Networks Using Directional Antennas Abdel Ilah Alshbatat and Liang Dong, Senior Member, IEEE Abstract-- Unmanned aerial vehicle (UAV) has been used inspection and range extension. Moreover, UAVs are suited for situations that are too dangerous for direct

  14. Study on PID neural-network-based inverter space-vector pulse width modulation strategy

    Microsoft Academic Search

    Bo You; Fengjing Zhang

    2008-01-01

    A PID neural-network-based space-vector pulse width modulation (SVPWM) for a three-level inverter is proposed in this paper. A three-level inverter has lots of switching states about the vectors, and the implementation of modulation algorithm is considerably complex. In the proposed design, fast implementation of SVPWM algorithm is realized based on PID neural network instead of conventional neural network. A three-layer

  15. The cascading vulnerability of the directed and weighted network

    NASA Astrophysics Data System (ADS)

    Jin, Wei-Xin; Song, Ping; Liu, Guo-Zhu; Stanley, H. Eugene

    2015-06-01

    The cascading failure can bring a huge loss for most real-world networks; but, we cannot uncover fully the mechanism and law of the cascading events occurrence. Most networks in which the cascading failure occurred are based on the various 'flows', such as power, oils, and information; moreover, the same link degree of the different nodes likely contain the different meanings, where some are large pivotal nodes and some are mini switching centers. Thus, these networks must be described by the directed and weighted network model. Besides, the 'over-loading' cascading failures were more analyzed and studied; but the cascading failures caused by 'short-loading' were less studied relatively. However, for some directed networks, such as power grids, oil pipe nets, gas pipe nets and information networks, the large-scale failures of network nodes substantially could be induced by 'short-loading' in a such similar way as 'over-loading'. Based on the above reasons, in this paper, we first built the 'load-capacity' model of the directed and weighted network. Afterwards the 'over-loading' cascading failure model and the 'short-loading' cascading failure model based on the directed and weighted network were built. Meanwhile, applying the models to two typical real networks-Poisson distribution network and power law distribution network-intensive study and numerical analysis were carried out. Lastly, two classical networks simulation experiment results are provided. After the numerical and simulation analyses, we gained the following conclusions. For the power law network, the power exponent ? of 'load-capacity' function should be taken value (0, 1) for a good robustness, and the minimum in-degree and out-degree should be increased respectively, meanwhile, the weight and the scaling exponents of the in-degree and the out-degree distributions should be increased synchronously in the interval (2, 3) for enhancing the resistibility of 'over-loading' and 'short-loading' failures. For the Poisson network, the power exponent ? of loading function should be taken value (0, 3) for a good robustness, and the average weight and the average in-degree should be increased respectively restricting 2 < ? < 3 for enhancing the resistibility of 'over-loading' and 'short-loading' failures.

  16. Fabricating fiber Bragg gratings using phase modulated direct UV writing

    NASA Astrophysics Data System (ADS)

    Holmes, C.; Sima, C.; Mennea, P. L.; Carpenter, L. G.; Gates, J. C.; Smith, P. G. R.

    2014-03-01

    The authors present a direct UV writing approach to fabricate fiber Bragg gratings (FBGs) and gratings in photolithographic waveguides. The technique uses two coherent UV beams, which are focused to a small spot (~7?m diameter) at the point at which they overlap. The resulting interference pattern at the foci consists of fringes which are used to define several grating planes per exposure, giving greater design flexibility and a significantly larger accessible spectral range compared to traditional approaches. The typical index contrast during grating fabrication is observed to be 4.7×10-3, at writing speeds of 8 mm/min.

  17. Finding communities in directed networks by PageRank random walk induced network embedding

    E-print Network

    Nardini, Christine

    , many networks of interest are directed, including the World Wide Web, food webs and many other literature ignores edges directions and applies methods designed for community finding in undirected networks, and it is important in many aspects. Communities in worldwide web usually correspond to sets of web pages with common

  18. Modulation of hippocampal rhythms by subthreshold electric fields and network topology.

    PubMed

    Berzhanskaya, Julia; Chernyy, Nick; Gluckman, Bruce J; Schiff, Steven J; Ascoli, Giorgio A

    2013-06-01

    Theta (4-12 Hz) and gamma (30-80 Hz) rhythms are considered important for cortical and hippocampal function. Although several neuron types are implicated in rhythmogenesis, the exact cellular mechanisms remain unknown. Subthreshold electric fields provide a flexible, area-specific tool to modulate neural activity and directly test functional hypotheses. Here we present experimental and computational evidence of the interplay among hippocampal synaptic circuitry, neuronal morphology, external electric fields, and network activity. Electrophysiological data are used to constrain and validate an anatomically and biophysically realistic model of area CA1 containing pyramidal cells and two interneuron types: dendritic- and perisomatic-targeting. We report two lines of results: addressing the network structure capable of generating theta-modulated gamma rhythms, and demonstrating electric field effects on those rhythms. First, theta-modulated gamma rhythms require specific inhibitory connectivity. In one configuration, GABAergic axo-dendritic feedback on pyramidal cells is only effective in proximal but not distal layers. An alternative configuration requires two distinct perisomatic interneuron classes, one exclusively receiving excitatory contacts, the other additionally targeted by inhibition. These observations suggest novel roles for particular classes of oriens and basket cells. The second major finding is that subthreshold electric fields robustly alter the balance between different rhythms. Independent of network configuration, positive electric fields decrease, while negative fields increase the theta/gamma ratio. Moreover, electric fields differentially affect average theta frequency depending on specific synaptic connectivity. These results support the testable prediction that subthreshold electric fields can alter hippocampal rhythms, suggesting new approaches to explore their cognitive functions and underlying circuitry. PMID:23053863

  19. Modulation of hippocampal rhythms by subthreshold electric fields and network topology

    PubMed Central

    Berzhanskaya, Julia; Chernyy, Nick; Gluckman, Bruce J.; Schiff, Steven J.; Ascoli, Giorgio A.

    2012-01-01

    Theta (4–12 Hz) and gamma (30–80 Hz) rhythms are considered important for cortical and hippocampal function. Although several neuron types are implicated in rhythmogenesis, the exact cellular mechanisms remain unknown. Subthreshold electric fields provide a flexible, area-specific tool to modulate neural activity and directly test functional hypotheses. Here we present experimental and computational evidence of the interplay among hippocampal synaptic circuitry, neuronal morphology, external electric fields, and network activity. Electrophysiological data are used to constrain and validate an anatomically and biophysically realistic model of area CA1 containing pyramidal cells and two interneuron types: dendritic- and perisomatic-targeting. We report two lines of results: addressing the network structure capable of generating theta-modulated gamma rhythms, and demonstrating electric field effects on those rhythms. First, theta-modulated gamma rhythms require specific inhibitory connectivity. In one configuration, GABAergic axo-dendritic feedback on pyramidal cells is only effective in proximal but not distal layers. An alternative configuration requires two distinct perisomatic interneuron classes, one exclusively receiving excitatory contacts, the other additionally targeted by inhibition. These observations suggest novel roles for particular classes of oriens and basket cells. The second major finding is that subthreshold electric fields robustly alter the balance between different rhythms. Independent of network configuration, positive electric fields decrease, while negative fields increase the theta/gamma ratio. Moreover, electric fields differentially affect average theta frequency depending on specific synaptic connectivity. These results support the testable prediction that subthreshold electric fields can alter hippocampal rhythms, suggesting new approaches to explore their cognitive functions and underlying circuitry. PMID:23053863

  20. Oscillatory entrainment of the motor cortical network during motor imagery is modulated by the feedback modality.

    PubMed

    Vukeli?, Mathias; Gharabaghi, Alireza

    2015-05-01

    Neurofeedback of self-regulated brain activity in circumscribed cortical regions is used as a novel strategy to facilitate functional restoration following stroke. Basic knowledge about its impact on motor system oscillations and functional connectivity is however scarce. Specifically, a direct comparison between different feedback modalities and their neural signatures is missing. We assessed a neurofeedback training intervention of modulating ?-activity in circumscribed sensorimotor regions by kinesthetic motor imagery (MI). Right-handed healthy participants received two different feedback modalities contingent to their MI-associated brain activity in a cross-over design: (I) visual feedback with a brain-computer interface (BCI) and (II) proprioceptive feedback with a brain-robot interface (BRI) orthosis attached to the right hand. High-density electroencephalography was used to examine the reactivity of the cortical motor system during the training session of each task by studying both local oscillatory power entrainment and distributed functional connectivity. Both feedback modalities activated a distributed functional connectivity network of coherent oscillations. A significantly higher skill and lower variability of self-controlled sensorimotor ?-band modulation could, however, be achieved in the BRI condition. This gain in controlling regional motor oscillations was accompanied by functional coupling of remote ?-band and ?-band activity in bilateral fronto-central regions and left parieto-occipital regions, respectively. The functional coupling of coherent ?-band oscillations correlated moreover with the skill of regional ?-modulation thus revealing a motor learning related network. Our findings indicate that proprioceptive feedback is more suitable than visual feedback to entrain the motor network architecture during the interplay between motor imagery and feedback processing thus resulting in better volitional control of regional brain activity. PMID:25665968

  1. A phase-modulated direct-detection fiber optical CATV transport system

    NASA Astrophysics Data System (ADS)

    Chen, Chia-Yi; Lu, Hai-Han; Lin, Chun-Yu; Wu, Kuan-Hung; Jhang, Tai-Wei; Ying, Cheng-Ling

    2014-05-01

    A fiber optical CATV transport system based on phase modulation (PM) and direct-detection schemes to reduce noise and distortion induced by systems is proposed and experimentally demonstrated. The architecture of the proposed systems is simplified by the fiber-dispersion-induced PM-to-intensity modulation (IM) conversion technique. As a result, the optical signal is detected directly by a photodiode (PD), without using the sophisticated and expensive delay interferometer (DI). Impressive performances of carrier-to-noise ratio (CNR), composite second-order (CSO), and composite triple beat (CTB) were obtained in our proposed systems over a 100-km single-mode fiber (SMF) transport.

  2. How biologically relevant are interaction-based modules in protein networks?

    Microsoft Academic Search

    Juan F Poyatos; Laurence D Hurst

    2004-01-01

    By applying a graph-based algorithm to yeast protein-interaction networks we have extracted modular structures and show that they can be validated using information from the phylogenetic conservation of the network components. We show that the module cores, the parts with the highest intramodular connectivity, are biologically relevant components of the networks. These constituents correlate only weakly with other levels of

  3. Mammalian-like visual learning by spatially modulating learning rate in deep belief networks

    E-print Network

    Orchard, Jeffery J.

    Mammalian-like visual learning by spatially modulating learning rate in deep belief networks of visual learning in a deep belief network show that this simple learning variant successfully produces in V1. However, unsupervised training of deep belief networks has failed to generate all

  4. Implementation of neural network based Space Vector Pulse Width Modulation inverter induction motor drive system

    Microsoft Academic Search

    Syed Abdul Rahman Kashif; Muhammad Asghar Saqib; Saba Zia; Ayesha Kaleem

    2009-01-01

    This paper presents a voltage source inverter which is controlled with space vector pulse width modulation (SPWM) designed using three layers feed forward back propagation based artificial neural network (ANN). The input output samples were obtained using simulations in Matlab Simulink; which were used for extensive training of network. With calculated weights and biases, the neural network was implemented using

  5. Community landscapes: an integrative approach to determine overlapping network module hierarchy, identify key nodes and predict network dynamics

    Microsoft Academic Search

    Istvan A. Kovacs; Robin Palotai; Mate S. Szalay; Peter Csermely

    2009-01-01

    Background: Network communities help the functional organization and\\u000aevolution of complex networks. However, the development of a method, which is\\u000aboth fast and accurate, provides modular overlaps and partitions of a\\u000aheterogeneous network, has proven to be rather difficult. Methodology\\/Principal\\u000aFindings: Here we introduce the novel concept of ModuLand, an integrative\\u000amethod family determining overlapping network modules as hills of

  6. Goal certainty modulates infants' goal-directed gaze shifts.

    PubMed

    Henrichs, Ivanina; Elsner, Claudia; Elsner, Birgit; Wilkinson, Nick; Gredebäck, Gustaf

    2014-01-01

    We investigated whether 12-month-old infants rely on information about the certainty of goal selection in order to predict observed reaching actions. Infants' goal-directed gaze shifts were recorded as they observed action sequences in a multiple-goals design. We found that 12-month-old infants exhibited gaze shifts significantly earlier when the observed hand reached for the same goal object in all trials (frequent condition) compared with when the observed hand reached for different goal objects across trials (nonfrequent condition). Infants in the frequent condition were significantly more accurate at predicting the action goal than infants in the nonfrequent condition. In addition, findings revealed rapid learning in the case of certainty and no learning in the case of uncertainty of goal selection over the course of trials. Together, our data indicate that by the end of their first year of life, infants rely on information about the certainty of goal selection to make inferences about others' action goals. PMID:23586939

  7. Serotonergic modulation of spatial working memory: predictions from a computational network model

    PubMed Central

    Cano-Colino, Maria; Almeida, Rita; Compte, Albert

    2013-01-01

    Serotonin (5-HT) receptors of types 1A and 2A are strongly expressed in prefrontal cortex (PFC) neurons, an area associated with cognitive function. Hence, 5-HT could be effective in modulating prefrontal-dependent cognitive functions, such as spatial working memory (SWM). However, a direct association between 5-HT and SWM has proved elusive in psycho-pharmacological studies. Recently, a computational network model of the PFC microcircuit was used to explore the relationship between 5-HT and SWM (Cano-Colino et al., 2013). This study found that both excessive and insufficient 5-HT levels lead to impaired SWM performance in the network, and it concluded that analyzing behavioral responses based on confidence reports could facilitate the experimental identification of SWM behavioral effects of 5-HT neuromodulation. Such analyses may have confounds based on our limited understanding of metacognitive processes. Here, we extend these results by deriving three additional predictions from the model that do not rely on confidence reports. Firstly, only excessive levels of 5-HT should result in SWM deficits that increase with delay duration. Secondly, excessive 5-HT baseline concentration makes the network vulnerable to distractors at distances that were robust to distraction in control conditions, while the network still ignores distractors efficiently for low 5-HT levels that impair SWM. Finally, 5-HT modulates neuronal memory fields in neurophysiological experiments: Neurons should be better tuned to the cued stimulus than to the behavioral report for excessive 5-HT levels, while the reverse should happen for low 5-HT concentrations. In all our simulations agonists of 5-HT1A receptors and antagonists of 5-HT2A receptors produced behavioral and physiological effects in line with global 5-HT level increases. Our model makes specific predictions to be tested experimentally and advance our understanding of the neural basis of SWM and its neuromodulation by 5-HT receptors. PMID:24133418

  8. Transcutaneous spinal direct current stimulation modulates human corticospinal system excitability.

    PubMed

    Bocci, Tommaso; Marceglia, Sara; Vergari, Maurizio; Cognetto, Valeria; Cogiamanian, Filippo; Sartucci, Ferdinando; Priori, Alberto

    2015-07-01

    This study aimed to assess the effects of thoracic anodal and cathodal transcutaneous spinal direct current stimulation (tsDCS) on upper and lower limb corticospinal excitability. Although there have been studies assessing how thoracic tsDCS influences the spinal ascending tract and reflexes, none has assessed the effects of this technique over upper and lower limb corticomotor neuronal connections. In 14 healthy subjects we recorded motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) from abductor hallucis (AH) and hand abductor digiti minimi (ADM) muscles before (baseline) and at different time points (0 and 30 min) after anodal or cathodal tsDCS (2.5 mA, 20 min, T9-T11 level). In 8 of the 14 subjects we also tested the soleus H reflex and the F waves from AH and ADM before and after tsDCS. Both anodal and cathodal tsDCS left the upper limb MEPs and F wave unchanged. Conversely, while leaving lower limb H reflex unchanged, they oppositely affected lower limb MEPs: whereas anodal tsDCS increased resting motor threshold [(mean ± SE) 107.33 ± 3.3% increase immediately after tsDCS and 108.37 ± 3.2% increase 30 min after tsDCS compared with baseline] and had no effects on MEP area and latency, cathodal tsDCS increased MEP area (139.71 ± 12.9% increase immediately after tsDCS and 132.74 ± 22.0% increase 30 min after tsDCS compared with baseline) without affecting resting motor threshold and MEP latency. Our results show that tsDCS induces polarity-specific changes in corticospinal excitability that last for >30 min after tsDCS offset and selectively affect responses in lower limb muscles innervated by lumbar and sacral motor neurons. PMID:25925328

  9. Direct Marketing Modeling Using Evolutionary Bayesian Network Learning Algorithm

    Microsoft Academic Search

    Man Leung Wong

    \\u000a Direct marketing modeling identifies effective models for improving managerial decision making in marketing. This paper proposes\\u000a a novel system for discovering models represented as Bayesian networks from incomplete databases in the presence of missing\\u000a values. It combines an evolutionary algorithm with the traditional Expectation-Maximization(EM) algorithm to find better network structures in each iteration round. A data completing method is also

  10. Interarrival times of message propagation on directed networks.

    PubMed

    Mihaljev, Tamara; de Arcangelis, Lucilla; Herrmann, Hans J

    2011-08-01

    One of the challenges in fighting cybercrime is to understand the dynamics of message propagation on botnets, networks of infected computers used to send viruses, unsolicited commercial emails (SPAM) or denial of service attacks. We map this problem to the propagation of multiple random walkers on directed networks and we evaluate the interarrival time distribution between successive walkers arriving at a target. We show that the temporal organization of this process, which models information propagation on unstructured peer to peer networks, has the same features as SPAM reaching a single user. We study the behavior of the message interarrival time distribution on three different network topologies using two different rules for sending messages. In all networks the propagation is not a pure Poisson process. It shows universal features on Poissonian networks and a more complex behavior on scale free networks. Results open the possibility to indirectly learn about the process of sending messages on networks with unknown topologies, by studying interarrival times at any node of the network. PMID:21929069

  11. Interarrival times of message propagation on directed networks

    NASA Astrophysics Data System (ADS)

    Mihaljev, Tamara; de Arcangelis, Lucilla; Herrmann, Hans J.

    2011-08-01

    One of the challenges in fighting cybercrime is to understand the dynamics of message propagation on botnets, networks of infected computers used to send viruses, unsolicited commercial emails (SPAM) or denial of service attacks. We map this problem to the propagation of multiple random walkers on directed networks and we evaluate the interarrival time distribution between successive walkers arriving at a target. We show that the temporal organization of this process, which models information propagation on unstructured peer to peer networks, has the same features as SPAM reaching a single user. We study the behavior of the message interarrival time distribution on three different network topologies using two different rules for sending messages. In all networks the propagation is not a pure Poisson process. It shows universal features on Poissonian networks and a more complex behavior on scale free networks. Results open the possibility to indirectly learn about the process of sending messages on networks with unknown topologies, by studying interarrival times at any node of the network.

  12. Predicting Fault Prone Modules by the Dempster-Shafer Belief Networks

    PubMed Central

    Guo, Lan; Cukic, Bojan; Singh, Harshinder

    2015-01-01

    This paper describes a novel methodology for predicting fault prone modules. The methodology is based on Dempster-Shafer (D-S) belief networks. Our approach consists of three steps: First, building the Dempster-Shafer network by the induction algorithm; Second, selecting the predictors (attributes) by the logistic procedure; Third, feeding the predictors describing the modules of the current project into the inducted Dempster-Shafer network and identifying fault prone modules. We applied this methodology to a NASA dataset. The prediction accuracy of our methodology is higher than that achieved by logistic regression or discriminant analysis on the same dataset.

  13. Controlling the likelihood of rogue waves in an optically injected semiconductor laser via direct current modulation

    NASA Astrophysics Data System (ADS)

    Perrone, S.; Vilaseca, R.; Zamora-Munt, J.; Masoller, C.

    2014-03-01

    Extreme and rare events are nowadays the object of intensive research. Rogue waves are extreme waves that appear suddenly in many natural systems, even in apparently calm situations. Here we study numerically the rogue wave dynamics in an optically injected semiconductor laser with external periodic forcing that is implemented via direct modulation of the laser pump current. In the region of optical injection parameters where the laser intensity is chaotic and occasional ultrahigh pulses occur, our aim is to control the system by applying a weak modulation. We find that for an adequate range of frequency and amplitude parameters, the modulation can completely suppress the extreme pulses. We also show that the interplay between modulation and an external source of noise can significantly modify their probability of occurrence. These results can motivate a range of experimental and theoretical investigations in other natural systems.

  14. Economical Quantum Secure Direct Communication Network with Single Photons

    E-print Network

    Fu-Guo Deng; Xi-Han Li; Chun-Yan Li; Ping Zhou; Hong-Yu Zhou

    2007-12-13

    A scheme for quantum secure direct communication (QSDC) network is proposed with a sequence of polarized single photons. The single photons are prepared originally in the same state |0> by the servers on the network, which will reduce the difficulty for the legitimate users to check eavesdropping largely. The users code the information on the single photons with two unitary operations which do not change their measuring bases. Some decoy photons, which are produced by operating the sample photons with a Hadamard, are used for preventing a potentially dishonest server from eavesdropping the quantum lines freely. This scheme is an economical one as it is the easiest way for QSDC network communication securely.

  15. Convective stability in the Rayleigh-Benard and directional solidification problems - High-frequency gravity modulation

    NASA Technical Reports Server (NTRS)

    Wheeler, A. A.; Mcfadden, G. B.; Murray, B. T.; Coriell, S. R.

    1991-01-01

    The effect of vertical, sinusoidal, time-dependent gravitational acceleration on the onset of solutal convection during directional solidification is analyzed in the limit of large modulation frequency. When the unmodulated state is unstable, the modulation amplitude required to stabilize the system is determined by the method of averaging. When the unmodulated state is stable, resonant modes of instability occur at large modulation amplitude. These are analyzed using matched asymptotic expansions to elucidate the boundary-layer structure for both the Rayleigh-Benard and directional solidification configurations. Based on these analyses, a thorough examination of the dependence of the stability criteria on the unmodulated Rayleigh number, Schmidt number, and distribution coefficient, is carried out.

  16. Direct Antenna Modulation scheme for enhanced capacity performance of near-field communication link

    Microsoft Academic Search

    Umar Azad; Yuanxun Ethan Wang

    2012-01-01

    Shannon theorem suggests that power coupled through and bandwidth of an inductively coupled near field communication (NFC) link must be traded off for optimal capacity. Direct Antenna Modulation (DAM) is a possible scheme to break this dilemma. With DAM technology utilized in NFC link, the power and bandwidth product limit in a high Q system can be circumvented because of

  17. Shear stress magnitude and directionality modulate growth factor gene expression in

    E-print Network

    Passerini, Tony

    Shear stress magnitude and directionality modulate growth factor gene expression in preconditioned ( 15) dynes/cm2 or low magnitude WSS reversal ( 2.5 dynes/cm2 ) for 6 hours. A focused complementary increase in WSS ( 10) or to WSS reversal. Low magnitude retrograde WSS evoked significant (P

  18. Effective Transceiver Selection for Mobile Multi-Directional Free-Space-Optical Modules

    E-print Network

    Yuksel, Murat

    money and upgrading their infrastructure from 3G to 4G. However, it is expected that the demandEffective Transceiver Selection for Mobile Multi-Directional Free-Space-Optical Modules Abdullah and complementary technologies in wireless communication. Free-space-optical (FSO) communication has the potential

  19. Calling for help is independently modulated by brain systems underlying goal-directed behavior and

    E-print Network

    Calling for help is independently modulated by brain systems underlying goal-directed behavior for review December 17, 2004) In primates, during times of need, calling for help is a universal experience. Calling for help recruits social support and promotes survival. However, calling for help also can attract

  20. Toward Structural Dynamics: Protein Motions Viewed by Chemical Shift Modulations and Direct Detection of CN

    E-print Network

    Toward Structural Dynamics: Protein Motions Viewed by Chemical Shift Modulations and Direct of anti-correlated fluctuations) in R-helices. This extends the prospects of structure- dynamics, several groups have proposed to investigate the existence of structure-dynamics relationships. We like

  1. Observation of a time modulated muon flux in the direction of Cygnus X-3

    Microsoft Academic Search

    G. Battistoni; E. Bellotti; C. Bloise; G. Bologna; P. Campana; C. Castagnoli; A. Castellina; V. Chiarella; A. Ciocio; Donald C Cundy; B. D'Ettorre-Piazzoli; Ettore Fiorini; P. Galeotti; Enzo Iarocci; C. Liguori; G. Mannocchi; G P Murtas; P. Negri; G. Nicoletti; P. Picchi; M. Price; Antonio Pullia; S. Ragazzi; M. Rollier; O. Saavedra; L. Satta; P. Serri; S. Vernetto; L. Zanotti

    1985-01-01

    The analysis of angular and phase distribution is reported for high energy muons recorded in the NUSEX nucleon decay detector, located in the Mont Blanc tunnel at a depth of about 5000 hg of standard rock. Evidence is found for a signal correlated to the direction and time modulation of Cygnus X-3.

  2. Light intensity modulation direct overwrite MO disks with magnetically induced super resolution readout function

    Microsoft Academic Search

    T. Tokunaga; Y. Fujii; K. Yamada

    1997-01-01

    We have previously proposed LIMDOW-MO (laser intensity modulation direct overwrite magneto-optical) disks with MSR (magnetically induced super resolution) by FAD (front aperture detection) system. In this study, we improve recording characteristics of LIMDOW-MSR disks using RAD (rear aperture detection) without any initializing magnet for the MSR layer. This enables high density recording as a result of low crosstalk

  3. A space vector modulation direct torque control for permanent magnet synchronous motor drive systems

    Microsoft Academic Search

    D. Sun; J. G. Zhu; Y. K. He

    2003-01-01

    To minimize the ripples of the electro-magnetic torque and flux linkage and to fix the variable switching frequency produced in the conventional direct torque control (DTC) system for permanent magnet synchronous motors, this paper proposes a space vector modulation (SVM) DTC concept. Both simulation and experimental results show that the proposed SVM DTC can dramatically improve the steady state performance

  4. Integrated Module and Gene-Specific Regulatory Inference Implicates Upstream Signaling Networks

    PubMed Central

    Roy, Sushmita; Lagree, Stephen; Hou, Zhonggang; Thomson, James A.; Stewart, Ron; Gasch, Audrey P.

    2013-01-01

    Regulatory networks that control gene expression are important in diverse biological contexts including stress response and development. Each gene's regulatory program is determined by module-level regulation (e.g. co-regulation via the same signaling system), as well as gene-specific determinants that can fine-tune expression. We present a novel approach, Modular regulatory network learning with per gene information (MERLIN), that infers regulatory programs for individual genes while probabilistically constraining these programs to reveal module-level organization of regulatory networks. Using edge-, regulator- and module-based comparisons of simulated networks of known ground truth, we find MERLIN reconstructs regulatory programs of individual genes as well or better than existing approaches of network reconstruction, while additionally identifying modular organization of the regulatory networks. We use MERLIN to dissect global transcriptional behavior in two biological contexts: yeast stress response and human embryonic stem cell differentiation. Regulatory modules inferred by MERLIN capture co-regulatory relationships between signaling proteins and downstream transcription factors thereby revealing the upstream signaling systems controlling transcriptional responses. The inferred networks are enriched for regulators with genetic or physical interactions, supporting the inference, and identify modules of functionally related genes bound by the same transcriptional regulators. Our method combines the strengths of per-gene and per-module methods to reveal new insights into transcriptional regulation in stress and development. PMID:24146602

  5. Direction finding in IEEE802.11 wireless networks

    Microsoft Academic Search

    Antonis Kalis; Theodore Antonakopoulos

    2002-01-01

    A novel direction-finding method for stations of IEEE802.11 wireless local area networks is presented in this paper. The method uses a switched beam array for determining the direction of arrival of the incident electromagnetic field in a time efficient way and associates certain medium access control (MAC) layer functions with different radiation patterns of the switched antenna array, in order

  6. Acupuncture modulates resting state connectivity in default and sensorimotor brain networks

    E-print Network

    Napadow, Vitaly

    Acupuncture modulates resting state connectivity in default and sensorimotor brain networks Rupali to explore how a complex somatosensory stimulation, acupuncture, influences intrinsic connectivity in two taken before and after verum and sham acupuncture. Electrocardiography data were used to infer autonomic

  7. Urban Wireless Mesh Network Planning: The Case of Directional Antennas

    Microsoft Academic Search

    Chun-cheng Chen; Chandra Chekuri

    2007-01-01

    As more and more cities plan to deploy municipal wireless mesh networks to provide publicly-accessible infrastruc- ture, it becomes critical to come up with a deployment plan that provides sufficient accessibility with financial and technological constraints. In this paper, we consider deploying the mesh routers that are equipped with directional antennas to form the mesh backbone. We propose GPSR, an

  8. Poisson Geometry of Directed Networks in a Disk

    Microsoft Academic Search

    Michael Gekhtman; Michael Shapiro; Alek Vainshtein

    2008-01-01

    We investigate Poisson properties of Postnikov's map from the space of edge weights of a planar directed network into the Grassmannian. We show that this map is Poisson if the space of edge weights is equipped with a representative of a 6-parameter family of universal quadratic Poisson brackets and the Grasmannian is viewed as a Poisson homogeneous space of the

  9. On the design of optimal adaptive routers for direct networks

    Microsoft Academic Search

    A. Lagman; Walid A. Najjar

    1994-01-01

    Adaptive routing systems for direct networks can make use of the multiple paths that exist between pairs of nodes, and thus have the potential to deliver low latency communication. The performance of such systems, however, is dependent on the choice of the message buffering scheme as well as on the routing algorithm used. In this paper, we describe a general

  10. Majority-vote on directed Barabasi-Albert networks

    E-print Network

    Lima, F W S

    2005-01-01

    On directed Barabasi-Albert networks with two and seven neighbours selected by each added site, the Ising model was seen not to show a spontaneous magnetisation. Instead, the decay time for flipping of the magnetisation followed an Arrhenius law for Metropolis and Glauber algorithms, but for Wolff cluster flipping the magnetisation decayed exponentially with time. On these networks the Majority-vote model with noise is now studied through Monte Carlo simulations. However, in this model, the order-disorder phase transition of the order parameter is well defined in this system. We calculate the value of the critical noise parameter q_c for several values of connectivity z of the directed Barabasi-Albert network. The critical exponents beta/nu., gamma/nu and 1/nu were calculated for several values of z.

  11. Direct experimental observation of periodic intensity modulation along a straight hollow-core optical waveguide

    SciTech Connect

    Pfeifer, T.; Downer, M. C. [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

    2007-05-15

    We report the direct observation of periodic intensity modulation of a laser pulse propagating in a hollow-core waveguide. A series of equally spaced plasma sparks along the gas-filled capillary is produced. This effect can be explained by the beating of different fiber modes, which are excited by controlling the size of the focal spot at the capillary entrance. As compared with an artificial modulated waveguide structure, our presented approach represents an easier and more flexible quasi-phase-matching scheme for nonlinear-optical frequency conversion.

  12. A novel functional module detection algorithm for protein-protein interaction networks

    Microsoft Academic Search

    Woochang Hwang; Young-rae Cho; Aidong Zhang; Murali Ramanathan

    2006-01-01

    BACKGROUND: The sparse connectivity of protein-protein interaction data sets makes identification of functional modules challenging. The purpose of this study is to critically evaluate a novel clustering technique for clustering and detecting functional modules in protein-protein interaction networks, termed STM. RESULTS: STM selects representative proteins for each cluster and iteratively refines clusters based on a combination of the signal transduced

  13. Direct Adaptive Aircraft Control Using Dynamic Cell Structure Neural Networks

    NASA Technical Reports Server (NTRS)

    Jorgensen, Charles C.

    1997-01-01

    A Dynamic Cell Structure (DCS) Neural Network was developed which learns topology representing networks (TRNS) of F-15 aircraft aerodynamic stability and control derivatives. The network is integrated into a direct adaptive tracking controller. The combination produces a robust adaptive architecture capable of handling multiple accident and off- nominal flight scenarios. This paper describes the DCS network and modifications to the parameter estimation procedure. The work represents one step towards an integrated real-time reconfiguration control architecture for rapid prototyping of new aircraft designs. Performance was evaluated using three off-line benchmarks and on-line nonlinear Virtual Reality simulation. Flight control was evaluated under scenarios including differential stabilator lock, soft sensor failure, control and stability derivative variations, and air turbulence.

  14. Dopaminergic modulation of motor network dynamics in Parkinson's disease.

    PubMed

    Michely, Jochen; Volz, Lukas J; Barbe, Michael T; Hoffstaedter, Felix; Viswanathan, Shivakumar; Timmermann, Lars; Eickhoff, Simon B; Fink, Gereon R; Grefkes, Christian

    2015-03-01

    Although characteristic motor symptoms of Parkinson's disease such as bradykinesia typically improve under dopaminergic medication, deficits in higher motor control are less responsive. We here investigated the dopaminergic modulation of network dynamics underlying basic motor performance, i.e. finger tapping, and higher motor control, i.e. internally and externally cued movement preparation and selection. Twelve patients, assessed ON and OFF medication, and 12 age-matched healthy subjects underwent functional magnetic resonance imaging. Dynamic causal modelling was used to assess effective connectivity in a motor network comprising cortical and subcortical regions. In particular, we investigated whether impairments in basic and higher motor control, and the effects induced by dopaminergic treatment are due to connectivity changes in (i) the mesial premotor loop comprising the supplementary motor area; (ii) the lateral premotor loop comprising lateral premotor cortex; and (iii) cortico-subcortical interactions. At the behavioural level, we observed a marked slowing of movement preparation and selection when patients were internally as opposed to externally cued. Preserved performance during external cueing was associated with enhanced connectivity between prefrontal cortex and lateral premotor cortex OFF medication, compatible with a context-dependent compensatory role of the lateral premotor loop in the hypodopaminergic state. Dopaminergic medication significantly improved finger tapping speed in patients, which correlated with a drug-induced coupling increase of prefrontal cortex with the supplementary motor area, i.e. the mesial premotor loop. In addition, only in the finger tapping condition, patients ON medication showed enhanced excitatory influences exerted by cortical premotor regions and the thalamus upon the putamen. In conclusion, the amelioration of bradykinesia by dopaminergic medication seems to be driven by enhanced connectivity within the mesial premotor loop and cortico-striatal interactions. In contrast, medication did not improve internal motor control deficits concurrent to missing effects at the connectivity level. This differential effect of dopaminergic medication on the network dynamics underlying motor control provides new insights into the clinical finding that in Parkinson's disease dopaminergic drugs especially impact on bradykinesia but less on executive functions. PMID:25567321

  15. Feature-based attention modulates direction-selective hemodynamic activity within human MT.

    PubMed

    Stoppel, Christian Michael; Boehler, Carsten Nicolas; Strumpf, Hendrik; Heinze, Hans-Jochen; Noesselt, Toemme; Hopf, Jens-Max; Schoenfeld, Mircea Ariel

    2011-12-01

    Attending to the spatial location or to nonspatial features of a stimulus modulates neural activity in cortical areas that process its perceptual attributes. The feature-based attentional selection of the direction of a moving stimulus is associated with increased firing of individual neurons tuned to the direction of the movement in area V5/MT, while responses of neurons tuned to opposite directions are suppressed. However, it is not known how these multiplicatively scaled responses of individual neurons tuned to different motion-directions are integrated at the population level, in order to facilitate the processing of stimuli that match the perceptual goals. Using functional magnetic resonance imaging (fMRI) the present study revealed that attending to the movement direction of a dot field enhances the response in a number of areas including the human MT region (hMT) as a function of the coherence of the stimulus. Attending the opposite direction, however, lead to a suppressed response in hMT that was inversely correlated with stimulus-coherence. These findings demonstrate that the multiplicative scaling of single-neuron responses by feature-based attention results in an enhanced direction-selective population response within those cortical modules that processes the physical attributes of the attended stimuli. Our results provide strong support for the validity of the "feature similarity gain model" on the integrated population response as quantified by parametric fMRI in humans. PMID:21305663

  16. Protein kinase A directly phosphorylates metabotropic glutamate receptor 5 to modulate its function.

    PubMed

    Uematsu, Ken; Heiman, Myriam; Zelenina, Marina; Padovan, Júlio; Chait, Brian T; Aperia, Anita; Nishi, Akinori; Greengard, Paul

    2015-03-01

    Metabotropic glutamate receptor 5 (mGluR5) regulates excitatory post-synaptic signaling in the central nervous system (CNS) and is implicated in various CNS disorders. Protein kinase A (PKA) signaling is known to play a critical role in neuropsychiatric disorders such as Parkinson's disease, schizophrenia, and addiction. Dopamine signaling is known to modulate the properties of mGluR5 in a cAMP- and PKA-dependent manner, suggesting that mGluR5 may be a direct target for PKA. Our study identifies mGluR5 at Ser870 as a direct substrate for PKA phosphorylation and demonstrates that this phosphorylation plays a critical role in the PKA-mediated modulation of mGluR5 functions such as extracellular signal-regulated kinase phosphorylation and intracellular Ca(2+) oscillations. The identification of the molecular mechanism by which PKA signaling modulates mGluR5-mediated cellular responses contributes to the understanding of the interaction between dopaminergic and glutamatergic neuronal signaling. We identified serine residue 870 (S870) in metabotropic glutamate receptor 5 (mGluR5) as a direct substrate for protein kinase A (PKA). The phosphorylation of this site regulates the ability of mGluR5 to induce extracellular signal-regulated kinase (ERK) phosphorylation and intracellular Ca(2+) oscillations. This study provides a direct molecular mechanism by which PKA signaling interacts with glutamate neurotransmission. PMID:25639954

  17. Discrimination of Direction in Fast Frequency-Modulated Tones by Rats

    PubMed Central

    King, Isabella; Felsheim, Christian; Ostwald, Joachim; von der Behrens, Wolfger

    2006-01-01

    Fast frequency modulations (FM) are an essential part of species-specific auditory signals in animals as well as in human speech. Major parameters characterizing non-periodic frequency modulations are the direction of frequency change in the FM sweep (upward/downward) and the sweep speed, i.e., the speed of frequency change. While it is well established that both parameters are represented in the mammalian central auditory pathway, their importance at the perceptual level in animals is unclear. We determined the ability of rats to discriminate between upward and downward modulated FM-tones as a function of sweep speed in a two-alternative-forced-choice-paradigm. Directional discrimination in logarithmic FM-sweeps was reduced with increasing sweep speed between 20 and 1,000 octaves/s following a psychometric function. Average threshold sweep speed for FM directional discrimination was 96 octaves/s. This upper limit of perceptual FM discrimination fits well the upper limit of preferred sweep speeds in auditory neurons and the upper limit of neuronal direction selectivity in the rat auditory cortex and midbrain, as it is found in the literature. Influences of additional stimulus parameters on FM discrimination were determined using an adaptive testing-procedure for efficient threshold estimation based on a maximum likelihood approach. Directional discrimination improved with extended FM sweep range between two and five octaves. Discrimination performance declined with increasing lower frequency boundary of FM sweeps, showing an especially strong deterioration when the boundary was raised from 2 to 4 kHz. This deterioration corresponds to a frequency-dependent decline in direction selectivity of FM-encoding neurons in the rat auditory cortex, as described in the literature. Taken together, by investigating directional discrimination of FM sweeps in the rat we found characteristics at the perceptual level that can be related to several aspects of FM encoding in the central auditory pathway. PMID:16411160

  18. Rapid, Time-Division Multiplexed, Direct Absorption- and Wavelength Modulation-Spectroscopy

    PubMed Central

    Klein, Alexander; Witzel, Oliver; Ebert, Volker

    2014-01-01

    We present a tunable diode laser spectrometer with a novel, rapid time multiplexed direct absorption- and wavelength modulation-spectroscopy operation mode. The new technique allows enhancing the precision and dynamic range of a tunable diode laser absorption spectrometer without sacrificing accuracy. The spectroscopic technique combines the benefits of absolute concentration measurements using calibration-free direct tunable diode laser absorption spectroscopy (dTDLAS) with the enhanced noise rejection of wavelength modulation spectroscopy (WMS). In this work we demonstrate for the first time a 125 Hz time division multiplexed (TDM-dTDLAS-WMS) spectroscopic scheme by alternating the modulation of a DFB-laser between a triangle-ramp (dTDLAS) and an additional 20 kHz sinusoidal modulation (WMS). The absolute concentration measurement via the dTDLAS-technique allows one to simultaneously calibrate the normalized 2f/1f-signal of the WMS-technique. A dTDLAS/WMS-spectrometer at 1.37 ?m for H2O detection was built for experimental validation of the multiplexing scheme over a concentration range from 50 to 3000 ppmV (0.1 MPa, 293 K). A precision of 190 ppbV was achieved with an absorption length of 12.7 cm and an averaging time of two seconds. Our results show a five-fold improvement in precision over the entire concentration range and a significantly decreased averaging time of the spectrometer. PMID:25405508

  19. Rapid, time-division multiplexed, direct absorption- and wavelength modulation-spectroscopy.

    PubMed

    Klein, Alexander; Witzel, Oliver; Ebert, Volker

    2014-01-01

    We present a tunable diode laser spectrometer with a novel, rapid time multiplexed direct absorption- and wavelength modulation-spectroscopy operation mode. The new technique allows enhancing the precision and dynamic range of a tunable diode laser absorption spectrometer without sacrificing accuracy. The spectroscopic technique combines the benefits of absolute concentration measurements using calibration-free direct tunable diode laser absorption spectroscopy (dTDLAS) with the enhanced noise rejection of wavelength modulation spectroscopy (WMS). In this work we demonstrate for the first time a 125 Hz time division multiplexed (TDM-dTDLAS-WMS) spectroscopic scheme by alternating the modulation of a DFB-laser between a triangle-ramp (dTDLAS) and an additional 20 kHz sinusoidal modulation (WMS). The absolute concentration measurement via the dTDLAS-technique allows one to simultaneously calibrate the normalized 2f/1f-signal of the WMS-technique. A dTDLAS/WMS-spectrometer at 1.37 µm for H2O detection was built for experimental validation of the multiplexing scheme over a concentration range from 50 to 3000 ppmV (0.1 MPa, 293 K). A precision of 190 ppbV was achieved with an absorption length of 12.7 cm and an averaging time of two seconds. Our results show a five-fold improvement in precision over the entire concentration range and a significantly decreased averaging time of the spectrometer. PMID:25405508

  20. Detection of dynamic brain networks modulated by acupuncture using a graph theory model

    E-print Network

    Tian, Jie

    Detection of dynamic brain networks modulated by acupuncture using a graph theory model Lijun Bai acupuncture manipulation have already demonstrated significant modulatory effects on wide limbic of acupuncture, however, knowledge on the organization of such large-scale cortical networks behind the active

  1. Network module design based on photonic-EthetCAT for robot drive

    Microsoft Academic Search

    Yongseon Moon; Nak Yong Ko; Eunju Kim; Youngchul Bae

    2008-01-01

    In this paper, we design and implement an optical cable interface module of 100 BaseFx for physical layer of network based on EtherCAT, industrial Ethernet protocol. We propose the suitability as control network of the intelligent service robot after optical cable interface applied in sensor\\/actuator of control system.

  2. Target dependence of the annual modulation in direct dark matter searches

    NASA Astrophysics Data System (ADS)

    Del Nobile, Eugenio; Gelmini, Graciela B.; Witte, Samuel J.

    2015-06-01

    Due to Earth's revolution around the Sun, the expected scattering rate in direct dark matter searches is annually modulated. This modulation is expected to differ between experiments when given as a function of recoil energy ER, e.g. due to the gravitational focusing effect of the Sun. A better variable to compare results among experiments employing different targets is the minimum speed vmin a dark matter particle must have to impart a recoil energy ER to a target nucleus. It is widely believed that the modulation expressed as a function of vmin is common to all experiments, irrespective of the dark matter distribution. We point out that the annual modulation as a function of vmin, and in particular the times at which the rate is maximum and minimum, could be very different depending on the detector material. This would be an indication of a scattering cross section with nonfactorizable velocity and target material dependence. Observing an annual modulation with at least two different target elements would be necessary to identify this type of cross section.

  3. Gene duplication models for directed networks with limits on growth

    NASA Astrophysics Data System (ADS)

    Enemark, Jakob; Sneppen, Kim

    2007-11-01

    Background: Duplication of genes is important for evolution of molecular networks. Many authors have therefore considered gene duplication as a driving force in shaping the topology of molecular networks. In particular it has been noted that growth via duplication would act as an implicit means of preferential attachment, and thereby provide the observed broad degree distributions of molecular networks. Results: We extend current models of gene duplication and rewiring by including directions and the fact that molecular networks are not a result of unidirectional growth. We introduce upstream sites and downstream shapes to quantify potential links during duplication and rewiring. We find that this in itself generates the observed scaling of transcription factors for genome sites in prokaryotes. The dynamical model can generate a scale-free degree distribution, p(k)\\propto 1/k^{\\gamma } , with exponent ? = 1 in the non-growing case, and with ?>1 when the network is growing. Conclusions: We find that duplication of genes followed by substantial recombination of upstream regions could generate features of genetic regulatory networks. Our steady state degree distribution is however too broad to be consistent with data, thereby suggesting that selective pruning acts as a main additional constraint on duplicated genes. Our analysis shows that gene duplication can only be a main cause for the observed broad degree distributions if there are also substantial recombinations between upstream regions of genes.

  4. Tunable photonic microwave generation by directly modulating a dual-wavelength amplified feedback laser

    NASA Astrophysics Data System (ADS)

    Yu, Liqiang; Lu, Dan; Sun, Yu; Zhao, Lingjuan

    2015-06-01

    A compact and simple approach to realizing tunable high-frequency photonic microwave using a directly-modulated dual-wavelength amplified feedback laser (AFL) diode is demonstrated. By directly modulating the AFL at the 1/2 sub-harmonic frequency of its fundamental mode spacing, frequency-doubled microwave is generated. At a low RF driven power of 2.8 dBm, tunable microwave outputs ranging from 15 GHz to 33 GHz are obtained with 2-GHz locking range. The phase noise and frequency stability of the generated microwave signal are also investigated. The proposed scheme requires much lower RF driven power and can be a viable choice for situations where high power and high frequency RF signal is not available.

  5. Lightweight PV Inverters: Dual Bi-Directional IGBTs Modules Enables Breakthrough PV Inverter Using Current Modulation Topology

    SciTech Connect

    None

    2012-01-30

    Solar ADEPT Project: PV inverters convert DC power generated by modules into usable AC power. IPC’s initial 30kW 94lb. PV inverter reduces the weight of comparable 30kW PV inverters by 90%—reducing the cost of materials, manufacturing, shipping, and installation. With ARPA-E support, new bi-directional silicon power switches will be developed, commercialized, and utilized in IPC’s next-generation PV inverter. With these components, IPC will produce 100kW inverters that weight less than 100lb., reducing the weight of conventional 3,000lb. 100kW inverters by more than 95%. The new power switches will cut IPC’s $/W manufacturing cost in half, as well as further reduce indirect shipping and installation costs.

  6. Direct-Sequence Spread Spectrum with DPSK Modulation and Diversity for Indoor Wireless Communications

    Microsoft Academic Search

    MOHSEN KAVEHRAD; BHASKAR RAMAMURTHI

    1987-01-01

    Direct-sequence spread spectrum with differential phase shift-keying (DPSK) modulation and code-division multiple-access is a promising approach for wireless communications in an indoor environment, which is characterized in this paper by a Rayleigh-fading multipath channel. In this study, we consider two specific channel models having different path-delay distributions and average path power profiles. A star configuration, in which each user exercises

  7. The performance of direct-sequence spread spectrum with complex processing and quaternary data modulation

    Microsoft Academic Search

    Thomas G. Macdonald; Michael B. Pursley

    2000-01-01

    The receiver processing that is often employed for direct-sequence spread spectrum with quaternary data modulation operates separately on in-phase and quadrature components of the spread-spectrum signal. Previous results on complex quaternary sequences, which are also referred to as four-phase sequences, provide a strong motivation to employ alternative processing methods that permit the receiver to benefit from the correlation properties of

  8. Transcranial direct current stimulation of the prefrontal cortex modulates the desire for specific foods

    Microsoft Academic Search

    Felipe Fregni; Fernanda Orsati; Waldelle Pedrosa; Shirley Fecteau; Fatima A. M. Tome; Michael A. Nitsche; Tatiana Mecca; Elizeu C. Macedo; Alvaro Pascual-Leone; Paulo S. Boggio

    2008-01-01

    We aimed to assess whether modulation of the dorsolateral prefrontal cortex (DLFPC) with noninvasive brain stimulation, namely transcranial direct current stimulation (tDCS), modifies food craving in healthy subjects. We performed a randomized sham-controlled cross-over study in which 23 subjects received sham and active tDCS (anode left\\/cathode right and anode right\\/cathode left) of the DLPFC. Subjects were exposed to food and

  9. Regional modulation of BOLD MRI responses to human sensorimotor activation by transcranial direct current stimulation

    Microsoft Academic Search

    Michael A. Nitsche; Walter Paulus; Jens Frahm

    2001-01-01

    Blood oxygenation level dependent (BOLD) MRI was used to monitor modulations of human sensorimotor activity by prior transcranial direct current stimulation (tDCS). Activation maps for a right hand sequential finger opposition task were obtained for six subjects before as well as 0 -5 min and 15-20 min after a 5-min period of 1 mA cathodal and, in a separate session,

  10. Direct AC-AC matrix converter based on three-phase voltage-source converter modules

    Microsoft Academic Search

    Mehrdad Kazerani; B. T. Ooi

    1993-01-01

    The original direct AC-AC matrix power converter employs bi-lateral switches. In this paper, a new topology, based on three-phase voltage-source power converter modules, is proposed. The total number of valves and diodes used is the same as in the original topology of nine bilateral switches. However, thanks to better knowledge of the voltage-source converter, it is possible to ensure safe

  11. Distribution of IR-UWB Signals With PAM Modulation in Long-Reach FTTH Networks

    Microsoft Academic Search

    T. Valente; A. V. T. Cartaxo

    2010-01-01

    Fiber-to-the-home (FTTH) networks have been proposed as a means to extend the application of ultrawideband (UWB) radio signals in future wireless personal area networks to the delivery of high-definition content. In this paper, we analyze, using numerical simulation, the feasibility of the distribution of impulse-radio UWB signals with pulse amplitude modulation in long-reach FTTH networks. The simulation results show a

  12. An ELMO2-RhoG-ILK network modulates microtubule dynamics.

    PubMed

    Jackson, Bradley C; Ivanova, Iordanka A; Dagnino, Lina

    2015-07-15

    ELMO2 belongs to a family of scaffold proteins involved in phagocytosis and cell motility. ELMO2 can simultaneously bind integrin-linked kinase (ILK) and RhoG, forming tripartite ERI complexes. These complexes are involved in promoting ?1 integrin-dependent directional migration in undifferentiated epidermal keratinocytes. ELMO2 and ILK have also separately been implicated in microtubule regulation at integrin-containing focal adhesions. During differentiation, epidermal keratinocytes cease to express integrins, but ERI complexes persist. Here we show an integrin-independent role of ERI complexes in modulation of microtubule dynamics in differentiated keratinocytes. Depletion of ERI complexes by inactivating the Ilk gene in these cells reduces microtubule growth and increases the frequency of catastrophe. Reciprocally, exogenous expression of ELMO2 or RhoG stabilizes microtubules, but only if ILK is also present. Mechanistically, activation of Rac1 downstream from ERI complexes mediates their effects on microtubule stability. In this pathway, Rac1 serves as a hub to modulate microtubule dynamics through two different routes: 1) phosphorylation and inactivation of the microtubule-destabilizing protein stathmin and 2) phosphorylation and inactivation of GSK-3?, which leads to the activation of CRMP2, promoting microtubule growth. At the cellular level, the absence of ERI species impairs Ca(2+)-mediated formation of adherens junctions, critical to maintaining mechanical integrity in the epidermis. Our findings support a key role for ERI species in integrin-independent stabilization of the microtubule network in differentiated keratinocytes. PMID:25995380

  13. Identification of functional modules using network topology and high-throughput data

    PubMed Central

    Ulitsky, Igor; Shamir, Ron

    2007-01-01

    Background With the advent of systems biology, biological knowledge is often represented today by networks. These include regulatory and metabolic networks, protein-protein interaction networks, and many others. At the same time, high-throughput genomics and proteomics techniques generate very large data sets, which require sophisticated computational analysis. Usually, separate and different analysis methodologies are applied to each of the two data types. An integrated investigation of network and high-throughput information together can improve the quality of the analysis by accounting simultaneously for topological network properties alongside intrinsic features of the high-throughput data. Results We describe a novel algorithmic framework for this challenge. We first transform the high-throughput data into similarity values, (e.g., by computing pairwise similarity of gene expression patterns from microarray data). Then, given a network of genes or proteins and similarity values between some of them, we seek connected sub-networks (or modules) that manifest high similarity. We develop algorithms for this problem and evaluate their performance on the osmotic shock response network in S. cerevisiae and on the human cell cycle network. We demonstrate that focused, biologically meaningful and relevant functional modules are obtained. In comparison with extant algorithms, our approach has higher sensitivity and higher specificity. Conclusion We have demonstrated that our method can accurately identify functional modules. Hence, it carries the promise to be highly useful in analysis of high throughput data. PMID:17408515

  14. Poisson geometry of directed networks in a disk

    Microsoft Academic Search

    Michael Gekhtman; Michael Shapiro; Alek Vainshtein

    2009-01-01

    .  We investigate Poisson properties of Postnikov’s map from the space of edge weights of a planar directed network into the\\u000a Grassmannian. We show that this map is Poisson if the space of edge weights is equipped with a representative of a 6-parameter\\u000a family of universal quadratic Poisson brackets and the Grassmannian is viewed as a Poisson homogeneous space of the

  15. The Psychedelic State Induced by Ayahuasca Modulates the Activity and Connectivity of the Default Mode Network

    PubMed Central

    Palhano-Fontes, Fernanda; Andrade, Katia C.; Tofoli, Luis F.; Santos, Antonio C.; Crippa, Jose Alexandre S.; Hallak, Jaime E. C.; Ribeiro, Sidarta; de Araujo, Draulio B.

    2015-01-01

    The experiences induced by psychedelics share a wide variety of subjective features, related to the complex changes in perception and cognition induced by this class of drugs. A remarkable increase in introspection is at the core of these altered states of consciousness. Self-oriented mental activity has been consistently linked to the Default Mode Network (DMN), a set of brain regions more active during rest than during the execution of a goal-directed task. Here we used fMRI technique to inspect the DMN during the psychedelic state induced by Ayahuasca in ten experienced subjects. Ayahuasca is a potion traditionally used by Amazonian Amerindians composed by a mixture of compounds that increase monoaminergic transmission. In particular, we examined whether Ayahuasca changes the activity and connectivity of the DMN and the connection between the DMN and the task-positive network (TPN). Ayahuasca caused a significant decrease in activity through most parts of the DMN, including its most consistent hubs: the Posterior Cingulate Cortex (PCC)/Precuneus and the medial Prefrontal Cortex (mPFC). Functional connectivity within the PCC/Precuneus decreased after Ayahuasca intake. No significant change was observed in the DMN-TPN orthogonality. Altogether, our results support the notion that the altered state of consciousness induced by Ayahuasca, like those induced by psilocybin (another serotonergic psychedelic), meditation and sleep, is linked to the modulation of the activity and the connectivity of the DMN. PMID:25693169

  16. The psychedelic state induced by ayahuasca modulates the activity and connectivity of the default mode network.

    PubMed

    Palhano-Fontes, Fernanda; Andrade, Katia C; Tofoli, Luis F; Santos, Antonio C; Crippa, Jose Alexandre S; Hallak, Jaime E C; Ribeiro, Sidarta; de Araujo, Draulio B

    2015-01-01

    The experiences induced by psychedelics share a wide variety of subjective features, related to the complex changes in perception and cognition induced by this class of drugs. A remarkable increase in introspection is at the core of these altered states of consciousness. Self-oriented mental activity has been consistently linked to the Default Mode Network (DMN), a set of brain regions more active during rest than during the execution of a goal-directed task. Here we used fMRI technique to inspect the DMN during the psychedelic state induced by Ayahuasca in ten experienced subjects. Ayahuasca is a potion traditionally used by Amazonian Amerindians composed by a mixture of compounds that increase monoaminergic transmission. In particular, we examined whether Ayahuasca changes the activity and connectivity of the DMN and the connection between the DMN and the task-positive network (TPN). Ayahuasca caused a significant decrease in activity through most parts of the DMN, including its most consistent hubs: the Posterior Cingulate Cortex (PCC)/Precuneus and the medial Prefrontal Cortex (mPFC). Functional connectivity within the PCC/Precuneus decreased after Ayahuasca intake. No significant change was observed in the DMN-TPN orthogonality. Altogether, our results support the notion that the altered state of consciousness induced by Ayahuasca, like those induced by psilocybin (another serotonergic psychedelic), meditation and sleep, is linked to the modulation of the activity and the connectivity of the DMN. PMID:25693169

  17. Different Current Intensities of Anodal Transcranial Direct Current Stimulation Do Not Differentially Modulate Motor Cortex Plasticity

    PubMed Central

    Kidgell, Dawson J.; Daly, Robin M.; Young, Kayleigh; Lum, Jarrod; Tooley, Gregory; Jaberzadeh, Shapour; Zoghi, Maryam; Pearce, Alan J.

    2013-01-01

    Transcranial direct current stimulation (tDCS) is a noninvasive technique that modulates the excitability of neurons within the motor cortex (M1). Although the aftereffects of anodal tDCS on modulating cortical excitability have been described, there is limited data describing the outcomes of different tDCS intensities on intracortical circuits. To further elucidate the mechanisms underlying the aftereffects of M1 excitability following anodal tDCS, we used transcranial magnetic stimulation (TMS) to examine the effect of different intensities on cortical excitability and short-interval intracortical inhibition (SICI). Using a randomized, counterbalanced, crossover design, with a one-week wash-out period, 14 participants (6 females and 8 males, 22–45 years) were exposed to 10 minutes of anodal tDCS at 0.8, 1.0, and 1.2?mA. TMS was used to measure M1 excitability and SICI of the contralateral wrist extensor muscle at baseline, immediately after and 15 and 30 minutes following cessation of anodal tDCS. Cortical excitability increased, whilst SICI was reduced at all time points following anodal tDCS. Interestingly, there were no differences between the three intensities of anodal tDCS on modulating cortical excitability or SICI. These results suggest that the aftereffect of anodal tDCS on facilitating cortical excitability is due to the modulation of synaptic mechanisms associated with long-term potentiation and is not influenced by different tDCS intensities. PMID:23577272

  18. Gaze direction modulates auditory spatial deficits in stroke patients with neglect.

    PubMed

    Pavani, Francesco; Làdavas, Elisabetta; Driver, Jon

    2005-04-01

    We investigated the effects of eye position on auditory spatial deficits in four patients with left neglect and right-hemisphere damage, using three blocked gaze directions (35 degrees to the right, central, or 35 degrees to the left), while preventing any head-movement to ensure that initial auditory inputs remained constant regardless of eye-in-orbit position. The auditory task required speeded discrimination of sound elevation, with patients moving a central lever up or down according to the vertical position of a peripheral target sound, regardless of its side (left or right). Replicating previous auditory research, the patients' vertical discrimination performance was worse for auditory targets on the contralesional (left) versus the ipsilesional side, indicating neglect-related auditory deficits on this task. Critically, while this worse performance for left than right auditory targets was present (for both reaction times and errors) when gaze was directed centrally or rightwards, it was considerably reduced when gaze was directed leftwards. These results demonstrate that lateral gaze-direction can modulate neglect-related auditory spatial deficits, even though eye-position did not alter the initial auditory inputs. This outcome may relate to audio-visual links in spatial orienting and potentially some retinocentric influences on perceived sound location, although the latter alone could not explain all our results. Such findings might involve multisensory brain structures in which responses to sounds are modulated by eye-in-orbit position. PMID:15714900

  19. A 50-kW Module Power Station of Directly Solar-Pumped Iodine Laser

    NASA Technical Reports Server (NTRS)

    Choi, S. H.; Lee, J. H.; Meador, W. E.; Conway, E. J.

    1997-01-01

    The conceptual design of a 50 kW Directly Solar-Pumped Iodine Laser (DSPIL) module was developed for a space-based power station which transmits its coherent-beam power to users such as the moon, Martian rovers, or other satellites with large (greater than 25 kW) electric power requirements. Integration of multiple modules would provide an amount of power that exceeds the power of a single module by combining and directing the coherent beams to the user's receiver. The model developed for the DSPIL system conservatively predicts the laser output power (50 kW) that appears much less than the laser output (93 kW) obtained from the gain volume ratio extrapolation of experimental data. The difference in laser outputs may be attributed to reflector configurations adopted in both design and experiment. Even though the photon absorption by multiple reflections in experimental cavity setup was more efficient, the maximum secondary absorption amounts to be only 24.7 percent of the primary. However, the gain volume ratio shows 86 percent more power output than theoretical estimation that is roughly 60 percent more than the contribution by the secondary absorption. Such a difference indicates that the theoretical model adopted in the study underestimates the overall performance of the DSPIL. This fact may tolerate more flexible and radical selection of design parameters than used in this design study. The design achieves an overall specific power of approximately 5 W/kg and total mass of 10 metric tons.

  20. Direction-dependent learning approach for radial basis function networks.

    PubMed

    Singla, Puneet; Subbarao, Kamesh; Junkins, John L

    2007-01-01

    Direction-dependent scaling, shaping, and rotation of Gaussian basis functions are introduced for maximal trend sensing with minimal parameter representations for input output approximation. It is shown that shaping and rotation of the radial basis functions helps in reducing the total number of function units required to approximate any given input-output data, while improving accuracy. Several alternate formulations that enforce minimal parameterization of the most general radial basis functions are presented. A novel "directed graph" based algorithm is introduced to facilitate intelligent direction based learning and adaptation of the parameters appearing in the radial basis function network. Further, a parameter estimation algorithm is incorporated to establish starting estimates for the model parameters using multiple windows of the input-output data. The efficacy of direction-dependent shaping and rotation in function approximation is evaluated by modifying the minimal resource allocating network and considering different test examples. The examples are drawn from recent literature to benchmark the new algorithm versus existing methods. PMID:17278473

  1. A new kind of node centrality in directed weighted networks based on the demands of network clients

    NASA Astrophysics Data System (ADS)

    Ma, Lili; Jiang, Xin; Zhang, Zhanli; Tang, Shaoting; Zheng, Zhiming

    2011-08-01

    To reveal the correlation between the demands of network clients and the safety and robustness of real-world networks, we propose client demand centrality (CDC) in order to quantify the contributions of nodes in the transportation processes in directed weighted networks. CDC is defined by incorporating not only the topology and dynamics of the network but also the demands of network clients. The centrality measures node potential to ensure acceptable and successful transportation for clients and does quite well in distinguishing the roles of different nodes in the network. Simulation results show that node CDC has Gaussian distributions in directed networks with different link weight distributions, and the expected value of the Gaussian distribution increases from negative to positive with a decrease of the client demand. In particular, for directed scale-free networks with the scale-free link weight distribution, the network CDC is only correlated with the degree structure of the network when the client demand is large.

  2. Wireless audio and burst communication link with directly modulated THz photoconductive antenna.

    PubMed

    Liu, Tze-An; Lin, Gong-Ru; Chang, Yung-Cheng; Pan, Ci-Ling

    2005-12-12

    We demonstrate transmission of audio and burst signals through a prototype THz analog communication link employing laser-gated low-temperature-grown GaAs dipole antenna as THz emitter and receiver. The transmission distance is about 100 cm. By using a direct voltage modulation format, we successfully demodulated a burst signal with a rising time of 41 micros. The corresponding modulating bandwidth achieved was 23 kHz in this first experiment. Noise analysis reveals a 10% power fluctuation in the received signal with on-off extinction ratio of greater than 1000. The transmission of a six-channel analog and burst audio signal with least distortion is also demonstrated. We further demonstrate the fidelity of the transmission of a melody through the THz link with and without any amplification. PMID:19503256

  3. Direct leaf trajectory optimization for volumetric modulated arc therapy planning with sliding window delivery

    E-print Network

    Papp, Dávid

    2013-01-01

    We propose a novel optimization model for volumetric modulated arc therapy (VMAT) planning that directly optimizes deliverable leaf trajectories in the treatment plan optimization problem, and eliminates the need for a separate arc-sequencing step. In this model, a 360-degree arc is divided into a given number of arc segments in which the leaves move unidirectionally. This facilitates an algorithm that determines the optimal piecewise linear leaf trajectories for each arc segment, which are deliverable in a given treatment time. Multi-leaf collimator (MLC) constraints, including maximum leaf speed and interdigitation, are accounted for explicitly. The algorithm is customized to allow for VMAT delivery using constant gantry speed and dose rate, however, the algorithm generalizes to variable gantry speed if beneficial. We demonstrate the method for three different tumor sites: a head-and-neck case, a prostate case, and a paraspinal case. For that purpose, we first obtain a reference plan for intensity modulated...

  4. Performance of delay and add direct sequence spread spectrum modulation scheme with fast frequency hopping in frequency selective Rayleigh channels

    Microsoft Academic Search

    Vincent Le Nir; Bart Scheers

    2011-01-01

    The coherent direct-sequence spread spectrum (DSSS) modulation is a very attractive modulation technique for military communication systems, mainly due to its resistance to interference and low probability of detection (LPD). However, the synchronisation to the spreading code phase in the receiver takes time, which makes this technique less interesting for sending very short messages or to combine this technique with

  5. Direct leaf trajectory optimization for volumetric modulated arc therapy planning with sliding window delivery

    SciTech Connect

    Papp, Dávid, E-mail: Papp.David@mgh.harvard.edu; Unkelbach, Jan [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 30 Fruit Street, Boston, Massachusetts 02114 (United States)] [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 30 Fruit Street, Boston, Massachusetts 02114 (United States)

    2014-01-15

    Purpose: The authors propose a novel optimization model for volumetric modulated arc therapy (VMAT) planning that directly optimizes deliverable leaf trajectories in the treatment plan optimization problem, and eliminates the need for a separate arc-sequencing step. Methods: In this model, a 360° arc is divided into a given number of arc segments in which the leaves move unidirectionally. This facilitates an algorithm that determines the optimal piecewise linear leaf trajectories for each arc segment, which are deliverable in a given treatment time. Multileaf collimator constraints, including maximum leaf speed and interdigitation, are accounted for explicitly. The algorithm is customized to allow for VMAT delivery using constant gantry speed and dose rate, however, the algorithm generalizes to variable gantry speed if beneficial. Results: The authors demonstrate the method for three different tumor sites: a head-and-neck case, a prostate case, and a paraspinal case. The authors first obtain a reference plan for intensity modulated radiotherapy (IMRT) using fluence map optimization and 20 intensity-modulated fields in equally spaced beam directions, which is beyond the standard of care. Modeling the typical clinical setup for the treatment sites considered, IMRT plans using seven or nine beams are also computed. Subsequently, VMAT plans are optimized by dividing the 360° arc into 20 corresponding arc segments. Assuming typical machine parameters (a dose rate of 600 MU/min, and a maximum leaf speed of 3 cm/s), it is demonstrated that the optimized VMAT plans with 2–3 min delivery time are of noticeably better quality than the 7–9 beam IMRT plans. The VMAT plan quality approaches the quality of the 20-beam IMRT benchmark plan for delivery times between 3 and 4 min. Conclusions: The results indicate that high quality treatments can be delivered in a single arc with 20 arc segments if sufficient time is allowed for modulation in each segment.

  6. Broadband millimeter-wave electro-optic modulator using multi-patch antennas for pico-cell radar networks

    NASA Astrophysics Data System (ADS)

    Wijayanto, Yusuf Nur; Kanno, Atsushi; Kawanishi, Tetsuya

    2015-01-01

    An electro-optic (EO) modulator using multi patch antennas is proposed for broadband millimeter-wave bands in pico-cell radar networks. The proposed device is composed of multi patch antennas with a gap fabricated on a LiNbO3 crystal bonded with a low-k dielectric material. Multiple millimeter-wave operational frequencies can be received by the multi patch antennas and converting directly to lightwave signals through the Pockel effects of the LiNbO3 crystal. By adjusting the metal patch size for receiving with relatively close millimeter-wave frequencies, the bandwidth of the EO modulator can be enlarged. Based on that, bandwidth of over 30% in millimeter-wave bands can be achieved using the proposed device.

  7. Direct white-light and a dual-channel barcode module from Pr(iii)-MOF crystals.

    PubMed

    Du, Bin-Bin; Zhu, Yi-Xuan; Pan, Mei; Yue, Mei-Qin; Hou, Ya-Jun; Wu, Kai; Zhang, Lu-Yin; Chen, Ling; Yin, Shao-Yun; Fan, Ya-Nan; Su, Cheng-Yong

    2015-07-23

    Direct white-light emission and further a dual-channel readable barcode module in both visible and NIR region was established by single-component homo-metallic Pr(iii)-MOF crystals for the first time. PMID:26152399

  8. How slaves affect a master module in gene transcription networks

    E-print Network

    Gyorgy, Andras

    One of the major challenges in systems and synthetic biology is the lack of modular composition. Modules change their behavior once connected, due to retroactivity. In this paper, we build upon our earlier results and ...

  9. Integrative Multi-omics Module Network Inference with Lemon-Tree

    PubMed Central

    Bonnet, Eric; Calzone, Laurence; Michoel, Tom

    2015-01-01

    Module network inference is an established statistical method to reconstruct co-expression modules and their upstream regulatory programs from integrated multi-omics datasets measuring the activity levels of various cellular components across different individuals, experimental conditions or time points of a dynamic process. We have developed Lemon-Tree, an open-source, platform-independent, modular, extensible software package implementing state-of-the-art ensemble methods for module network inference. We benchmarked Lemon-Tree using large-scale tumor datasets and showed that Lemon-Tree algorithms compare favorably with state-of-the-art module network inference software. We also analyzed a large dataset of somatic copy-number alterations and gene expression levels measured in glioblastoma samples from The Cancer Genome Atlas and found that Lemon-Tree correctly identifies known glioblastoma oncogenes and tumor suppressors as master regulators in the inferred module network. Novel candidate driver genes predicted by Lemon-Tree were validated using tumor pathway and survival analyses. Lemon-Tree is available from http://lemon-tree.googlecode.com under the GNU General Public License version 2.0. PMID:25679508

  10. Identification of Modules in Protein-Protein Interaction Networks

    Microsoft Academic Search

    Sinan Erten; Mehmet Koyutürk

    2011-01-01

    \\u000a In biological systems, most processes are carried out through orchestration of multiple interacting molecules. These interactions\\u000a are often abstracted using network models. A key feature of cellular networks is their modularity, which contributes significantly\\u000a to the robustness, as well as adaptability of biological systems. Therefore, modularization of cellular networks is likely\\u000a to be useful in obtaining insights into the working

  11. Transcriptionally Regulated Cell Adhesion Network Dictates Distal Tip Cell Directionality

    PubMed Central

    Wong, Ming-Ching; Kennedy, William P.; Schwarzbauer, Jean E.

    2015-01-01

    Background The mechanisms that govern directional changes in cell migration are poorly understood. The migratory paths of two distal tip cells (DTC) determine the U-shape of the C. elegans hermaphroditic gonad. The morphogenesis of this organ provides a model system to identify genes necessary for the DTCs to execute two stereotyped turns. Results Using candidate genes for RNAi knockdown in a DTC-specific strain, we identified two transcriptional regulators required for DTC turning: cbp-1, the CBP/p300 transcriptional coactivator homologue, and let-607, a CREBH transcription factor homologue. Further screening of potential target genes uncovered a network of integrin adhesion-related genes that have roles in turning and are dependent on cbp-1 and let-607 for expression. These genes include src-1/Src kinase, tln-1/talin, pat-2/? integrin and nmy-2, a nonmuscle myosin heavy chain. Conclusions Transcriptional regulation by means of cbp-1 and let-607 is crucial for determining directional changes during DTC migration. These regulators coordinate a gene network that is necessary for integrin-mediated adhesion. Overall, these results suggest that directional changes in cell migration rely on the precise gene regulation of adhesion. PMID:24811939

  12. Inference and Phase Transitions in the Detection of Modules in Sparse Networks

    NASA Astrophysics Data System (ADS)

    Decelle, Aurelien; Krzakala, Florent; Moore, Cristopher; Zdeborová, Lenka

    2011-08-01

    We present an asymptotically exact analysis of the problem of detecting communities in sparse random networks generated by stochastic block models. Using the cavity method of statistical physics and its relationship to belief propagation, we unveil a phase transition from a regime where we can infer the correct group assignments of the nodes to one where these groups are undetectable. Our approach yields an optimal inference algorithm for detecting modules, including both assortative and disassortative functional modules, assessing their significance, and learning the parameters of the underlying block model. Our algorithm is scalable and applicable to real-world networks, as long as they are well described by the block model.

  13. Annual Modulation Signature for the Direct Detection of Milky Way Wimps and Supergravity Models

    E-print Network

    R. Arnowitt; Pran Nath

    1999-02-03

    An analysis is given of the annual modulation signal for the direct detection of relic neutralinos within the framework of supergravity unified models. It is shown that both the minimal and the non-minimal SUGRA models can generate neutralino-proton cross-sections at the level compatible with the signals reported in the DAMA experiment at the Gran Sasso National Laboratory. Effects of proton stability on the analysis of the DAMA data in the minimal and the non-minimal SUGRA models are also discussed.

  14. Steganography in clustered-dot halftones using orientation modulation and modification of direct binary search

    NASA Astrophysics Data System (ADS)

    Chen, Yung-Yao; Hong, Sheng-Yi; Chen, Kai-Wen

    2015-03-01

    This paper proposes a novel message-embedded halftoning scheme that is based on orientation modulation (OM) encoding. To achieve high image quality, we employ a human visual system (HVS)-based error metric between the continuous-tone image and a data-embedded halftone, and integrate a modified direct binary search (DBS) framework into the proposed message-embedded halftoning method. The modified DBS framework ensures that the resulting data-embedded halftones have optimal image quality from the viewpoint of the HVS.

  15. Test particle simulation of direct laser acceleration in a density-modulated plasma waveguide

    SciTech Connect

    Lin, M.-W.; Jovanovic, I. [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2012-11-15

    Direct laser acceleration (DLA) of electrons by the use of the intense axial electric field of an ultrafast radially polarized laser pulse is a promising technique for future compact accelerators. Density-modulated plasma waveguides can be implemented for guiding the propagation of the laser pulse to extend the acceleration distance and for the quasi-phase-matching between the accelerated electrons and the laser pulse. A test particle model is developed to study the optimal axial density modulation structure of plasma waveguides for laser pulses to efficiently accelerate co-propagating electrons. A simple analytical approach is also presented, which can be used to estimate the energy gain in DLA. The analytical model is validated by the test particle simulation. The effect of injection phase and acceleration of electrons injected at various radial positions are studied. The results indicate that a positively chirped density modulation of the waveguide structure is required to accelerate electron with low initial energies, and can be effectively optimized. A wider tolerance on the injection phase and radial distance from the waveguide axis exists for electrons injected with a higher initial energy.

  16. Design and characterization of analog VLSI neural network modules

    SciTech Connect

    Gowda, S.M.; Sheu, B.J.; Choi, Joongho (Univ. of Southern California, Los Angeles (United States)); Hwang, Changgyu (Samsung Electronics Co., Kiheung-Eup (Korea, Republic of)); Cable, J.S. (TRW Inc., Redondo Beach, CA (United States))

    1993-03-01

    High-speed computational capabilities of artificial neural networks can be used to solve many complex pattern recognition and image processing problems in science and engineering applications. These networks are implemented in VLSI technologies as regular arrays of analog or digital circuit cells. Although neural networks inherently contain some degree of fault tolerance, a significant percentage of possible processing defects can result in failure of the network. In order to assure the quality and reliability of neural networks, a systematic method to test large arrays of analog, digital, or mixed-signal circuit components that constitute these networks is necessary. A detailed testing procedure for such networks, consisting of a parametric test and a behavioral test, is described. Characteristics of the input neuron, synapse, and output neuron circuits are used to distinguish between faulty and useful chips. Stochastic analysis of the parametric test results can be used to predict chip yield information. Several measurement results from two analog neural network processor designs that are fabricated in 2-[mu]m double-polysilicon CMOS technologies are presented to demonstrate the testing procedure.

  17. Assessing the functional coherence of modules found in multiple-evidence networks from Arabidopsis

    PubMed Central

    2011-01-01

    Background Combining multiple evidence-types from different information sources has the potential to reveal new relationships in biological systems. The integrated information can be represented as a relationship network, and clustering the network can suggest possible functional modules. The value of such modules for gaining insight into the underlying biological processes depends on their functional coherence. The challenges that we wish to address are to define and quantify the functional coherence of modules in relationship networks, so that they can be used to infer function of as yet unannotated proteins, to discover previously unknown roles of proteins in diseases as well as for better understanding of the regulation and interrelationship between different elements of complex biological systems. Results We have defined the functional coherence of modules with respect to the Gene Ontology (GO) by considering two complementary aspects: (i) the fragmentation of the GO functional categories into the different modules and (ii) the most representative functions of the modules. We have proposed a set of metrics to evaluate these two aspects and demonstrated their utility in Arabidopsis thaliana. We selected 2355 proteins for which experimentally established protein-protein interaction (PPI) data were available. From these we have constructed five relationship networks, four based on single types of data: PPI, co-expression, co-occurrence of protein names in scientific literature abstracts and sequence similarity and a fifth one combining these four evidence types. The ability of these networks to suggest biologically meaningful grouping of proteins was explored by applying Markov clustering and then by measuring the functional coherence of the clusters. Conclusions Relationship networks integrating multiple evidence-types are biologically informative and allow more proteins to be assigned to a putative functional module. Using additional evidence types concentrates the functional annotations in a smaller number of modules without unduly compromising their consistency. These results indicate that integration of more data sources improves the ability to uncover functional association between proteins, both by allowing more proteins to be linked and producing a network where modular structure more closely reflects the hierarchy in the gene ontology. PMID:21612636

  18. 25 Gbit/s differential phase-shift-keying signal generation using directly modulated quantum-dot semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Zeghuzi, A.; Schmeckebier, H.; Stubenrauch, M.; Meuer, C.; Schubert, C.; Bunge, C.-A.; Bimberg, D.

    2015-05-01

    Error-free generation of 25-Gbit/s differential phase-shift keying (DPSK) signals via direct modulation of InAs quantum-dot (QD) based semiconductor optical amplifiers (SOAs) is experimentally demonstrated with an input power level of -5 dBm. The QD SOAs emit in the 1.3-?m wavelength range and provide a small-signal fiber-to-fiber gain of 8 dB. Furthermore, error-free DPSK modulation is achieved for constant optical input power levels from 3 dBm down to only -11 dBm for a bit rate of 20 Gbit/s. Direct phase modulation of QD SOAs via current changes is thus demonstrated to be much faster than direct gain modulation.

  19. A 4-channel coil array interconnection by analog direct modulation optical link for 1.5-T MRI.

    PubMed

    Yuan, Jing; Wei, Juan; Shen, Gary X

    2008-10-01

    Optical glass fiber shows great advantages over coaxial cables in terms of electromagnetic interference, thus, it should be considered a potential alternative for magnetic resonance imaging (MRI) receive coil interconnection, especially for a large number coil array at high field. In this paper, we propose a 4-channel analog direct modulation optical link for a 1.5-T MRI coil array interconnection. First, a general direct modulated optical link is compared to an external modulated optical link. And then the link performances of the proposed direct modulated optical link, including power gain, frequency response, and dynamic range, are analyzed and measured. Phantom and in vivo head images obtained using this optical link are demonstrated for comparison with those obtained by cable connections. The signal-to-noise (SNR) analysis shows that the optical link achieves 6%-8% SNR a improvement over coaxial cables by elimination of electrical interference between cables during MR signal transmission. PMID:18815095

  20. Lateralized alpha-band cortical networks regulate volitional modulation of beta-band sensorimotor oscillations.

    PubMed

    Vukeli?, Mathias; Bauer, Robert; Naros, Georgios; Naros, Ilias; Braun, Christoph; Gharabaghi, Alireza

    2014-02-15

    Sensorimotor rhythms (SMRs) are oscillatory brain activities in the ?- and ?-bands across the sensorimotor regions of the brain. Each frequency band has its own specific function. The ?-band oscillations are closely related to intrinsic cortical networks, whereas oscillations in the ?-band are relevant for the information transfer between the cortex and periphery, as well as for visual and proprioceptive feedback. This study aimed to investigate the interaction between these two frequency bands, under the premise that the regional modulation of ?-band power is linked to a cortical network in the ?-band. We therefore designed a procedure to maximize the modulation of ?-band activity over the sensorimotor cortex by combining kinesthetic motor-imagery with closed-loop haptic feedback. The cortical network activity during this procedure was estimated via the phase slope index in electroencephalographic recordings. Analysis of effective connectivity within the ?-band network revealed an information flow between the precentral (premotor and primary motor), postcentral (primary somatosensory) and parietal cortical areas. The range of ?-modulation was connected to a reduction of an ipsilateral sensorimotor and parietal ?-network and, consequently, to a lateralization of this network to the contralateral side. These results showed that regional sensorimotor oscillatory activity in the ?-band was regulated by cortical coupling of distant areas in the ?-band. PMID:24121086

  1. RadSensor: Xray Detection by Direct Modulation of an Optical Probe Beam

    SciTech Connect

    Lowry, M E; Bennett, C V; Vernon, S P; Bond, T; Welty, R; Behymer, E; Petersen, H; Krey, A; Stewart, R; Kobayashi, N P; Sperry, V; Stephan, P; Reinhardt, C; Simpson, S; Stratton, P; Bionta, R; McKernan, M; Ables, E; Ott, L; Bond, S; Ayers, J.; Landen, O L; Bell, P M

    2003-08-01

    We present a new x-ray detection technique based on optical measurement of the effects of x-ray absorption and electron hole pair creation in a direct band-gap semiconductor. The electron-hole pairs create a frequency dependent shift in optical refractive index and absorption. This is sensed by simultaneously directing an optical carrier beam through the same volume of semiconducting medium that has experienced an xray induced modulation in the electron-hole population. If the operating wavelength of the optical carrier beam is chosen to be close to the semiconductor band-edge, the optical carrier will be modulated significantly in phase and amplitude. This approach should be simultaneously capable of very high sensitivity and excellent temporal response, even in the difficult high-energy xray regime. At xray photon energies near 10 keV and higher, we believe that sub-picosecond temporal responses are possible with near single xray photon sensitivity. The approach also allows for the convenient and EMI robust transport of high-bandwidth information via fiber optics. Furthermore, the technology can be scaled to imaging applications. The basic physics of the detector, implementation considerations, and preliminary experimental data are presented and discussed.

  2. Directed assembly of three-dimensional microvascular networks

    NASA Astrophysics Data System (ADS)

    Therriault, Daniel

    Three-dimensional (3-D) microvascular networks with pervasive, interconnected channels less than 300 mum in diameter may find widespread application in microfluidic devices, biotechnology, sensors, and autonomic healing materials. Although microchannel arrays are readily constructed in two-dimensions by photolithographic or soft lithographic techniques, their construction in three-dimensions remains a challenging problem. The development of a microfabrication method to build 3-D microvascular networks based on direct-write assembly is described is this thesis. The method is based on the robotic deposition of a fugitive organic ink to form a free-standing scaffold structure. Secondary infiltration of a structural resin followed by setting of the matrix and removal of the scaffold yields an embedded pervasive network of smooth cylindrical channels (˜10--500 mum) with defined connectivity. Rheological and other material properties studies of fugitive organic ink were performed in order to identify the critical characteristics required for successful deposition of 3-D scaffolds by direct-write assembly. Guided by the results of these studies, several new ink formulations were screened for improved deposition performance. The most successful of these inks (40wt% microcrystalline wax, 60wt% petroleum jelly) showed excellent deposition and had an equilibrium modulus at room temperature (G 'eq ˜ 7.70 kPa 1 Hz) nearly two orders of magnitude higher than the original ink. The optimized ink was used to successfully build thick (i.e., ˜100 layers) scaffold structures at room temperature with negligible time-dependent deformation post-deposition. Secondary infiltration of the resin was accomplished at room temperature while maintaining the scaffold architecture. The optimized ink was also successfully extruded through small micronozzles (1 mum). The construction of 3-D microvascular networks enables microfluidic devices with unparallel geometric complexity. In one example, a 3-D microfluidic mixing device was demonstrated with square-spiral mixing towers isolated within the vascular network by a secondary photopatterning process. These vertical towers give rise to chaotic advection of the fluid streams and dramatic improvements in mixing relative to simple straight (1-D) and square-wave (2-D) channels while significantly reducing the device planar footprint.

  3. Influences of impedance matching network on pulse-modulated radio frequency atmospheric pressure glow discharges

    NASA Astrophysics Data System (ADS)

    Huo, W. G.; Xu, K.; Sun, B.; Ding, Z. F.

    2012-08-01

    Pulse-modulated RF atmospheric pressure glow discharges (APDGs) were investigated in recent years to reduce the thermal accumulation and extend the operation region of the stable alpha glow mode. Different pulse-modulated voltage and current waveforms were acquired in previous experiments, but no attention was paid to the interpretation. We investigated this issue and associated phenomenon via positive and negative feedback effects derived from varying the series capacitor in the inversely L-shaped matching network used in our pulse-modulated RF APGD source. The evolutions of pulse-modulated RF waveforms were found to be associated with the feedback region and the pulsed plasma absorbed RF power. In the positive feedback region, pulse-modulated RF APGDs are relatively stable. In the negative feedback region, wide spikes as well as undershoots occur in RF voltage and current waveforms and the plasma absorbed RF power. In case of a high RF power discharge with a low modulation frequency, the pulse-modulated RF APGD is extinguished and re-ignited due to the enhanced undershoot during the initial pulse phase. The pulse-modulated RF APGD can transit from positive to negative feedback region in a range of series capacitance. Experimental results are discussed by the aid of equivalent circuit, negative and positive feedback effects.

  4. Influences of impedance matching network on pulse-modulated radio frequency atmospheric pressure glow discharges

    SciTech Connect

    Huo, W. G. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116023 (China); School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029 (China); Xu, K.; Sun, B.; Ding, Z. F. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116023 (China)

    2012-08-15

    Pulse-modulated RF atmospheric pressure glow discharges (APDGs) were investigated in recent years to reduce the thermal accumulation and extend the operation region of the stable alpha glow mode. Different pulse-modulated voltage and current waveforms were acquired in previous experiments, but no attention was paid to the interpretation. We investigated this issue and associated phenomenon via positive and negative feedback effects derived from varying the series capacitor in the inversely L-shaped matching network used in our pulse-modulated RF APGD source. The evolutions of pulse-modulated RF waveforms were found to be associated with the feedback region and the pulsed plasma absorbed RF power. In the positive feedback region, pulse-modulated RF APGDs are relatively stable. In the negative feedback region, wide spikes as well as undershoots occur in RF voltage and current waveforms and the plasma absorbed RF power. In case of a high RF power discharge with a low modulation frequency, the pulse-modulated RF APGD is extinguished and re-ignited due to the enhanced undershoot during the initial pulse phase. The pulse-modulated RF APGD can transit from positive to negative feedback region in a range of series capacitance. Experimental results are discussed by the aid of equivalent circuit, negative and positive feedback effects.

  5. Anesthesia differentially modulates spontaneous network dynamics by cortical area and layer.

    PubMed

    Sellers, Kristin K; Bennett, Davis V; Hutt, Axel; Fröhlich, Flavio

    2013-12-01

    Anesthesia is widely used in medicine and research to achieve altered states of consciousness and cognition. Whereas changes to macroscopic cortical activity patterns by anesthesia measured at the spatial resolution of electroencephalography have been widely studied, modulation of mesoscopic and microscopic network dynamics by anesthesia remain poorly understood. To address this gap in knowledge, we recorded spontaneous mesoscopic (local field potential) and microscopic (multiunit activity) network dynamics in primary visual cortex (V1) and prefrontal cortex (PFC) of awake and isoflurane anesthetized ferrets (Mustela putoris furo). This approach allowed for examination of activity as a function of cortical area, cortical layer, and anesthetic depth with much higher spatial and temporal resolution than in previous studies. We hypothesized that a primary sensory area and an association cortical area would exhibit different patterns of network modulation by anesthesia due to their different functional roles. Indeed, we found effects specific to cortical area and cortical layer. V1 exhibited minimal changes in rhythmic structure with anesthesia but differential modulation of input layer IV. In contrast, anesthesia profoundly altered spectral power in PFC, with more uniform modulation across cortical layers. Our results demonstrate that anesthesia modulates spontaneous cortical activity in an area- and layer-specific manner. These finding provide the basis for 1) refining anesthesia monitoring algorithms, 2) reevaluating the large number of systems neuroscience studies performed in anesthetized animals, and 3) increasing our understanding of differential dynamics across cortical layers and areas. PMID:24047911

  6. Substrate-Induced Modulation of Signal Transduction Networks

    E-print Network

    Del Vecchio, Domitilla

    Biological signal transduction networks are commonly viewed as circuits that pass along information—in the process amplifying signals, enhancing sensitivity, or performing other signal-processing tasks—to transcriptional ...

  7. The segment polarity network is a robust developmental module

    NASA Astrophysics Data System (ADS)

    von Dassow, George; Meir, Eli; Munro, Edwin M.; Odell, Garrett M.

    2000-07-01

    All insects possess homologous segments, but segment specification differs radically among insect orders. In Drosophila, maternal morphogens control the patterned activation of gap genes, which encode transcriptional regulators that shape the patterned expression of pair-rule genes. This patterning cascade takes place before cellularization. Pair-rule gene products subsequently `imprint' segment polarity genes with reiterated patterns, thus defining the primordial segments. This mechanism must be greatly modified in insect groups in which many segments emerge only after cellularization. In beetles and parasitic wasps, for instance, pair-rule homologues are expressed in patterns consistent with roles during segmentation, but these patterns emerge within cellular fields. In contrast, although in locusts pair-rule homologues may not control segmentation, some segment polarity genes and their interactions are conserved. Perhaps segmentation is modular, with each module autonomously expressing a characteristic intrinsic behaviour in response to transient stimuli. If so, evolution could rearrange inputs to modules without changing their intrinsic behaviours. Here we suggest, using computer simulations, that the Drosophila segment polarity genes constitute such a module, and that this module is resistant to variations in the kinetic constants that govern its behaviour.

  8. Optimal Coordination of Directional Overcurrent Relays Considering Different Network Topologies Using Interval Linear Programming

    Microsoft Academic Search

    Abbas Saberi Noghabi; Habib Rajabi Mashhadi; Javad Sadeh

    2010-01-01

    In real power systems, the network topology is subjected to uncertainty due to single-line outage contingencies, maintenance activities, and network reconfigurations. These changes in the network topology may lead to miscoordination of directional overcurrent relays (DOCRs). To overcome this drawback, corresponding to each primary\\/backup relay pair, a set of inequality coordination constraints which is related to different network topologies should

  9. Neural Networks 23 (2010) 11351138 Contents lists available at ScienceDirect

    E-print Network

    Spence, Harlan Ernest

    2010-01-01

    Neural Networks 23 (2010) 1135­1138 Contents lists available at ScienceDirect Neural Networks journal homepage: www.elsevier.com/locate/neunet Editorial Towards building a neural networks community December 31, 2010 is my last day as the founding editor-in- chief of Neural Networks and also my 71st

  10. Neural Networks 23 (2010) 667668 Contents lists available at ScienceDirect

    E-print Network

    Fukai, Tomoki

    2010-01-01

    Neural Networks 23 (2010) 667­668 Contents lists available at ScienceDirect Neural Networks journal of large-scale neural network simulations poses the same challenge as experimental data does. This special massively parallel neural recordings and large-scale neural network simulations; (b) Frameworks

  11. Energy-Limited Wireless Networking with Directional Antennas: The Case of Session-Based Multicasting

    Microsoft Academic Search

    Jeffrey E. Wieselthier; Gam D. Nguyen; Anthony Ephremides

    2002-01-01

    We consider ad hoc wireless networks that use directional antennas and have limited energy resources. The performance objectives of such networks depend largely on the application. However, a robust performance measure is the total traffic volume that the network can deliver when all nodes are equipped with a finite and non-renewable amount of energy. We show that the network's lifetime

  12. Directed deposition of inorganic oxide networks on patterned polymer templates

    NASA Astrophysics Data System (ADS)

    Ford, Thomas James Robert

    Inspired by nature, we have successfully directed the deposition of inorganic oxide materials on polymer templates via a combination of top-down and bottom-up fabrication methods. We have functionally mimicked the hierarchical silica exoskeletons of diatoms, where specialized proteins chaperone the condensation of silicic acid into nanoscale silica networks confined by microscopic vesicle walls. We replaced the proteins with functionally analogous polyamines and vesicles with lithographically defined polymer templates. We grafted the polyamines either to the surface or throughout the template by changing the template chemistry and altering our grafting strategy. Exposure to an inorganic oxide precursor solution led to electrostatic aggregation at the polyamine chains, catalyzing hydrolysis and condensation to form long-range inorganic oxide nanoparticle networks. Grafted to epoxy surfaces, swelling effects and the hyperbranched brush morphology lead to the formation of nanofruit features that generated thin, conformal inorganic coatings. When the polyamines were grafted throughout hydrogel templates, we obtained composite networks that yielded faithful inorganic replicas of the original patterns. By varying the polyamine chain length and combustion parameters, we controlled the nanoparticle size, morphology, and crystalline phase. The polyamine morphology affected the resulting inorganic network in both fabrication schemes and we could control the depostion over multiple length scales. Because our methods were compatible with a variety of lithographic methods, we were able to generate inorganic replicas of 1D, 2D, and 3D polymer structures. These may be used for a wide range of applications, including sensing, catalysis, photonic, phononic, photovoltaic, and others that require well-defined inorganic structures.

  13. Optimal Adaptive Modulation Policy For QoS Constrained Wireless Networks With

    E-print Network

    Jagannatham, Aditya K.

    the battery and hence performance of mobile nodes. The random charging nature of such renewable sources calls1 Optimal Adaptive Modulation Policy For QoS Constrained Wireless Networks With Renewable Energy to minimize the average number of dropped packets for a delay constrained wireless node with a renewable

  14. Optimal Adaptive Modulation For QoS Constrained Wireless Networks With

    E-print Network

    Jagannatham, Aditya K.

    etc.) can be utilized to enhance the battery and hence performance of mobile nodes. The random1 Optimal Adaptive Modulation For QoS Constrained Wireless Networks With Renewable Energy Sources the average number of dropped packets for a delay constrained wireless node with a renewable energy source

  15. Investigation of the large-scale functional brain networks modulated by acupuncture

    E-print Network

    Tian, Jie

    Investigation of the large-scale functional brain networks modulated by acupuncture Yuanyuan Fenga effects of acupuncture. Considering that acupuncture can induce long-lasting effects, several researchers have begun to pay attention to the sustained effects of acupuncture on the resting brain. Most

  16. Age-related sensitivity to task-related modulation of language-processing networks

    E-print Network

    Zernicka-Goetz, Magdalena

    Age-related sensitivity to task-related modulation of language-processing networks Simon W. Davis n on the relationship between changing patterns of PFC activity and behavioural performance (Davis, Dennis, Daselaar cognitive functions (Dennis & Cabeza, 2008; Eyler, Sherzai, Kaup, & Jeste, 2011). The functional relevance

  17. Unified active and reactive power modulation of HVDC transmission systems

    Microsoft Academic Search

    C. E. Grund; R. V. Pohl

    1981-01-01

    The power modulation of a high voltage direct current (HVDC) system for stabilization of an ac\\/dc network was investigated. It was found that simultaneous modulation of both dc current and voltage was more effective than just current modulation by itself, since the dc voltage modulation could be used to minimize the reactive power changes resulting from a change of the

  18. Unity input displacement factor correction principle for direct AC to AC matrix converters based on modulation strategy

    Microsoft Academic Search

    M. Milanovic; Bojan Dobaj

    2000-01-01

    Modulation strategies for a matrix structured direct AC to AC converter are developed. In principle, for a given set of input three-phase voltages, any desired set of output voltages can be synthesized by suitable toggling matrix switches. Mathematical proof that the direct AC to AC matrix converter can operate with unity displacement factor is provided by analyses based on the

  19. Attentional load modulates large-scale functional brain connectivity beyond the core attention networks.

    PubMed

    Alnæs, Dag; Kaufmann, Tobias; Richard, Geneviève; Duff, Eugene P; Sneve, Markus H; Endestad, Tor; Nordvik, Jan Egil; Andreassen, Ole A; Smith, Stephen M; Westlye, Lars T

    2015-04-01

    In line with the notion of a continuously active and dynamic brain, functional networks identified during rest correspond with those revealed by task-fMRI. Characterizing the dynamic cross-talk between these network nodes is key to understanding the successful implementation of effortful cognitive processing in healthy individuals and its breakdown in a variety of conditions involving aberrant brain biology and cognitive dysfunction. We employed advanced network modeling on fMRI data collected during a task involving sustained attentive tracking of objects at two load levels and during rest. Using multivariate techniques, we demonstrate that attentional load levels can be significantly discriminated, and from a resting-state condition, the accuracy approaches 100%, by means of estimates of between-node functional connectivity. Several network edges were modulated during task engagement: The dorsal attention network increased connectivity with a visual node, while decreasing connectivity with motor and sensory nodes. Also, we observed a decoupling between left and right hemisphere dorsal visual streams. These results support the notion of dynamic network reconfigurations based on attentional effort. No simple correspondence between node signal amplitude change and node connectivity modulations was found, thus network modeling provides novel information beyond what is revealed by conventional task-fMRI analysis. The current decoding of attentional states confirms that edge connectivity contains highly predictive information about the mental state of the individual, and the approach shows promise for the utilization in clinical contexts. PMID:25595500

  20. Single-chip fully integrated direct-modulation CMOS RF transmitters for short-range wireless applications.

    PubMed

    El-Desouki, Munir M; Qasim, Syed Manzoor; BenSaleh, Mohammed; Deen, M Jamal

    2013-01-01

    Ultra-low power radio frequency (RF) transceivers used in short-range application such as wireless sensor networks (WSNs) require efficient, reliable and fully integrated transmitter architectures with minimal building blocks. This paper presents the design, implementation and performance evaluation of single-chip, fully integrated 2.4 GHz and 433 MHz RF transmitters using direct-modulation power voltage-controlled oscillators (PVCOs) in addition to a 2.0 GHz phase-locked loop (PLL) based transmitter. All three RF transmitters have been fabricated in a standard mixed-signal CMOS 0.18 µm technology. Measurement results of the 2.4 GHz transmitter show an improvement in drain efficiency from 27% to 36%. The 2.4 GHz and 433 MHz transmitters deliver an output power of 8 dBm with a phase noise of -122 dBc/Hz at 1 MHz offset, while drawing 15.4 mA of current and an output power of 6.5 dBm with a phase noise of -120 dBc/Hz at 1 MHz offset, while drawing 20.8 mA of current from 1.5 V power supplies, respectively. The PLL transmitter delivers an output power of 9 mW with a locking range of 128 MHz and consumes 26 mA from 1.8 V power supply. The experimental results demonstrate that the RF transmitters can be efficiently used in low power WSN applications. PMID:23917260

  1. Single-Chip Fully Integrated Direct-Modulation CMOS RF Transmitters for Short-Range Wireless Applications

    PubMed Central

    El-Desouki, Munir M.; Qasim, Syed Manzoor; BenSaleh, Mohammed; Deen, M. Jamal

    2013-01-01

    Ultra-low power radio frequency (RF) transceivers used in short-range application such as wireless sensor networks (WSNs) require efficient, reliable and fully integrated transmitter architectures with minimal building blocks. This paper presents the design, implementation and performance evaluation of single-chip, fully integrated 2.4 GHz and 433 MHz RF transmitters using direct-modulation power voltage-controlled oscillators (PVCOs) in addition to a 2.0 GHz phase-locked loop (PLL) based transmitter. All three RF transmitters have been fabricated in a standard mixed-signal CMOS 0.18 ?m technology. Measurement results of the 2.4 GHz transmitter show an improvement in drain efficiency from 27% to 36%. The 2.4 GHz and 433 MHz transmitters deliver an output power of 8 dBm with a phase noise of ?122 dBc/Hz at 1 MHz offset, while drawing 15.4 mA of current and an output power of 6.5 dBm with a phase noise of ?120 dBc/Hz at 1 MHz offset, while drawing 20.8 mA of current from 1.5 V power supplies, respectively. The PLL transmitter delivers an output power of 9 mW with a locking range of 128 MHz and consumes 26 mA from 1.8 V power supply. The experimental results demonstrate that the RF transmitters can be efficiently used in low power WSN applications. PMID:23917260

  2. Mean size of avalanches on directed random networks with arbitrary degree distributions James P. Gleeson

    E-print Network

    Gleeson, James P.

    Mean size of avalanches on directed random networks with arbitrary degree distributions James P avalanches on infinite directed random networks may be determined using the damage propagation function.057101 PACS number s : 89.75.Da, 02.50.Ey, 02.10.Ox, 05.50. q Unordered binary avalanches UBAs on directed net

  3. Alterations in physical cross-linking modulate mechanical properties of two-phase protein polymer networks.

    PubMed

    Wu, Xiaoyi; Sallach, Rory; Haller, Carolyn A; Caves, Jeffrey A; Nagapudi, Karthik; Conticello, Vincent P; Levenston, Marc E; Chaikof, Elliot L

    2005-01-01

    Physically cross-linked protein-based materials possess a number of advantages over their chemically cross-linked counterparts, including ease of processing and the ability to avoid the addition or removal of chemical reagents or unreacted intermediates. The investigations reported herein sought to examine the nature of physical cross-links within two-phase elastin-mimetic protein triblock copolymer networks through an analysis of macroscopic viscoelastic properties. Given the capacity of solution processing conditions, including solvent type and temperature to modulate the microstructure of two-phase protein polymer networks, viscoelastic properties were examined under conditions in which interphase block mixing had been either accentuated or diminished during network formation. Protein networks exhibited strikingly different properties in terms of elastic modulus, hysteresis, residual deformability, and viscosity in response to interdomain mixing. Thus, two-phase protein polymer networks exhibit tunable responses that extend the range of application of these materials to a variety of tissue engineering applications. PMID:16283724

  4. Near\\/far effects on packet radio networks with direct-sequence spread-spectrum signaling

    Microsoft Academic Search

    Yu-Dong Yao; A. U. H. Sheikh; Shi-Xin Cheng

    1989-01-01

    The near\\/far effect on a direct-sequence spread-spectrum packet radio network is investigated. It is found that the maximum throughput of the network is decreased in the presence of near\\/far problems. Under high traffic conditions, however, the network with near\\/far problems provides higher throughput than the one without near\\/far problems. This suggests that the direct-sequence spread-spectrum packet radio network with near\\/far

  5. Modulation of amplitude and latency of motor evoked potential by direction of transcranial magnetic stimulation

    NASA Astrophysics Data System (ADS)

    Sato, Aya; Torii, Tetsuya; Iwahashi, Masakuni; Itoh, Yuji; Iramina, Keiji

    2014-05-01

    The present study analyzed the effects of monophasic magnetic stimulation to the motor cortex. The effects of magnetic stimulation were evaluated by analyzing the motor evoked potentials (MEPs). The amplitude and latency of MEPs on the abductor pollicis brevis muscle were used to evaluate the effects of repetitive magnetic stimulation. A figure eight-shaped flat coil was used to stimulate the region over the primary motor cortex. The intensity of magnetic stimulation was 120% of the resting motor threshold, and the frequency of magnetic stimulation was 0.1 Hz. In addition, the direction of the current in the brain was posterior-anterior (PA) or anterior-posterior (AP). The latency of MEP was compared with PA and AP on initial magnetic stimulation. The results demonstrated that a stimulus in the AP direction increased the latency of the MEP by approximately 2.5 ms. MEP amplitude was also compared with PA and AP during 60 magnetic stimulations. The results showed that a stimulus in the PA direction gradually increased the amplitude of the MEP. However, a stimulus in the AP direction did not modulate the MEP amplitude. The average MEP amplitude induced from every 10 magnetic pulses was normalized by the average amplitude of the first 10 stimuli. These results demonstrated that the normalized MEP amplitude increased up to approximately 150%. In terms of pyramidal neuron indirect waves (I waves), magnetic stimulation inducing current flowing backward to the anterior preferentially elicited an I1 wave, and current flowing forward to the posterior elicited an I3 wave. It has been reported that the latency of the I3 wave is approximately 2.5 ms longer than the I1 wave elicitation, so the resulting difference in latency may be caused by this phenomenon. It has also been reported that there is no alteration of MEP amplitude at a frequency of 0.1 Hz. However, this study suggested that the modulation of MEP amplitude depends on stimulation strength and stimulation direction.

  6. Transcranial direct current stimulation of the posterior parietal cortex modulates arithmetic learning.

    PubMed

    Grabner, Roland H; Rütsche, Bruno; Ruff, Christian C; Hauser, Tobias U

    2015-07-01

    The successful acquisition of arithmetic skills is an essential step in the development of mathematical competencies and has been associated with neural activity in the left posterior parietal cortex (PPC). It is unclear, however, whether this brain region plays a causal role in arithmetic skill acquisition and whether arithmetic learning can be modulated by means of non-invasive brain stimulation of this key region. In the present study we addressed these questions by applying transcranial direct current stimulation (tDCS) over the left PPC during a short-term training that simulates the typical path of arithmetic skill acquisition (specifically the transition from effortful procedural to memory-based problem-solving strategies). Sixty participants received either anodal, cathodal or sham tDCS while practising complex multiplication and subtraction problems. The stability of the stimulation-induced learning effects was assessed in a follow-up test 24 h after the training. Learning progress was modulated by tDCS. Cathodal tDCS (compared with sham) decreased learning rates during training and resulted in poorer performance which lasted over 24 h after stimulation. Anodal tDCS showed an operation-specific improvement for subtraction learning. Our findings extend previous studies by demonstrating that the left PPC is causally involved in arithmetic learning (and not only in arithmetic performance) and that even a short-term tDCS application can modulate the success of arithmetic knowledge acquisition. Moreover, our finding of operation-specific anodal stimulation effects suggests that the enhancing effects of tDCS on learning can selectively affect just one of several cognitive processes mediated by the stimulated area. PMID:25970697

  7. Neural Networks For Demodulation Of Phase-Modulated Signals

    NASA Technical Reports Server (NTRS)

    Altes, Richard A.

    1995-01-01

    Hopfield neural networks proposed for demodulating quadrature phase-shift-keyed (QPSK) signals carrying digital information. Networks solve nonlinear integral equations prior demodulation circuits cannot solve. Consists of set of N operational amplifiers connected in parallel, with weighted feedback from output terminal of each amplifier to input terminals of other amplifiers. Used to solve signal processing problems. Implemented as analog very-large-scale integrated circuit that achieves rapid convergence. Alternatively, implemented as digital simulation of such circuit. Also used to improve phase estimation performance over that of phase-locked loop.

  8. ?FosB differentially modulates nucleus accumbens direct and indirect pathway function.

    PubMed

    Grueter, Brad A; Robison, Alfred J; Neve, Rachael L; Nestler, Eric J; Malenka, Robert C

    2013-01-29

    Synaptic modifications in nucleus accumbens (NAc) medium spiny neurons (MSNs) play a key role in adaptive and pathological reward-dependent learning, including maladaptive responses involved in drug addiction. NAc MSNs participate in two parallel circuits, direct and indirect pathways that subserve distinct behavioral functions. Modification of NAc MSN synapses may occur in part via changes in the transcriptional potential of certain genes in a cell type–specific manner. The transcription factor ?FosB is one of the key proteins implicated in the gene expression changes in NAc caused by drugs of abuse, yet its effects on synaptic function in NAc MSNs are unknown. Here, we demonstrate that overexpression of ?FosB decreased excitatory synaptic strength and likely increased silent synapses onto D1 dopamine receptor–expressing direct pathway MSNs in both the NAc shell and core. In contrast, ?FosB likely decreased silent synapses onto NAc shell, but not core, D2 dopamine receptor–expressing indirect pathway MSNs. Analysis of NAc MSN dendritic spine morphology revealed that ?FosB increased the density of immature spines in D1 direct but not D2 indirect pathway MSNs. To determine the behavioral consequences of cell type-specific actions of ?FosB, we selectively overexpressed ?FosB in D1 direct or D2 indirect MSNs in NAc in vivo and found that direct (but not indirect) pathway MSN expression enhances behavioral responses to cocaine. These results reveal that ?FosB in NAc differentially modulates synaptic properties and reward-related behaviors in a cell type- and subregion-specific fashion. PMID:23319622

  9. Direct acceleration of electrons by a circular polarized laser pulse with phase modulation

    SciTech Connect

    Zhu, Lun-Wu [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China) [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Department of Science, Zhejiang University of Science and Technology, Hangzhou 310023 (China); Sheng, Zheng-Mao; Yu, M. Y. [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)] [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)

    2013-11-15

    Electron acceleration by transversely echelon phase-modulated (EPM) circularly polarized (CP) intense laser pulse is investigated. Solution of the relativistic electron equations of motion shows that the CP EPM light wave structure can disrupt the harmonic response of a trapped electron not only in the transverse direction but also in the direction of laser propagation. In each laser cycle, there can be a net gain in the electron's transverse momentum, which is promptly converted into the forward direction by the Lorentz force. As a result, the electron can be trapped and accelerated in the favorable phase of the laser for a rather long time. Its momentum gain then accumulates and can eventually reach high levels. It is also found that with the CP EPM laser, the net acceleration of the electron is not sensitive to its initial position and velocity relative to the phase of the laser fields, so that such a laser can also be useful for accelerating thermal electron bunches to high energies.

  10. Transcranial direct current stimulation of the prefrontal cortex: a means to modulate fear memories.

    PubMed

    Mungee, Aditya; Kazzer, Philipp; Feeser, Melanie; Nitsche, Michael A; Schiller, Daniela; Bajbouj, Malek

    2014-05-01

    Targeting memory processes by noninvasive interventions is a potential gateway to modulate fear memories as shown by animal and human studies in recent years. Modulation of fear memories by noninvasive brain stimulation techniques might be an attractive approach, which, however, has not been examined so far. We investigated the effect of transcranial direct current stimulation (tDCS) applied to the right dorsolateral prefrontal cortex and left supraorbital region on fear memories in humans. Seventy-four young, healthy individuals were assigned randomly to two groups, which underwent fear conditioning with mild electric stimuli paired with a visual stimulus. Twenty-four hours later, both groups were shown a reminder of the conditioned fearful stimulus. Shortly thereafter, they received either tDCS (right prefrontal--anodal, left supraorbital--cathodal) for 20 min at 1 mA current intensity or sham stimulation. A day later, fear responses of both groups were compared by monitoring skin conductance. On day 3, during fear response assessment, the tDCS group had a significantly (P<0.05) higher mean skin conductance in comparison with the sham group. These results suggest that tDCS (right prefrontal--anodal, left supraorbital--cathodal) enhanced fear memories, possibly by influencing the prefrontal cortex-amygdala circuit underlying the memory for fear. PMID:24384505

  11. Parallel direct laser writing of micro-optical and photonic structures using spatial light modulator

    NASA Astrophysics Data System (ADS)

    Yang, Liang; El-Tamer, Ayman; Hinze, Ulf; Li, Jiawen; Hu, Yanlei; Huang, Wenhao; Chu, Jiaru; Chichkov, Boris N.

    2015-07-01

    Two-photon polymerization (2PP) is a powerful tool for direct laser writing of micro-optical and photonic structures due to its flexibility in 3D structuring and sub-micrometer resolution. However, it can be time consuming to fabricate arrays of micro-optical devices and complex photonic structures. In this study, we propose to use predefined patterns (PPs) for parallel 2PP processing. A PP contains a multiple focal spot pattern optimized for the fabrication of certain microstructures. PP can be created by holographic laser beam modulation with a spatial light modulator (SLM). The quantity and position of the multiple foci can be flexibly and precisely controlled by predesigned computer generated holograms (CGHs). With these specially designed PPs, parallel fabrication of arbitrary distributed microlens arrays and 3D photonic structures is demonstrated. This method significantly improves throughput and flexibility of the 2PP technique and can be used for mass production of functional devices in micro-optics and photonics.

  12. Analytical formulation of directly modulated OOFDM signals transmitted over an IM/DD dispersive link.

    PubMed

    Sánchez, C; Ortega, B; Wei, J L; Tang, J; Capmany, J

    2013-03-25

    We provide an analytical study on the propagation effects of a directly modulated OOFDM signal through a dispersive fiber and subsequent photo-detection. The analysis includes the effects of the laser operation point and the interplay between chromatic dispersion and laser chirp. The final expression allows to understand the physics behind the transmission of a multi-carrier signal in the presence of residual frequency modulation and the description of the induced intermodulation distortion gives us a detailed insight into the diferent intermodulation products which impair the recovered signal at the receiver-end side. Numerical comparisons between transmission simulations results and those provided by evaluating the expression obtained are carried out for different laser operation points. Results obtained by changing the fiber length, laser parameters and using single mode fiber with negative and positive dispersion are calculated in order to demonstrate the validity and versatility of the theory provided in this paper. Therefore, a novel analytical formulation is presented as a versatile tool for the description and study of IM/DD OOFDM systems with variable design parameters. PMID:23546148

  13. Robust criticality of an Ising model on rewired directed networks

    NASA Astrophysics Data System (ADS)

    Lipowski, Adam; Gontarek, Krzysztof; Lipowska, Dorota

    2015-06-01

    We show that preferential rewiring, which is supposed to mimic the behavior of financial agents, changes a directed-network Ising ferromagnet with a single critical point into a model with robust critical behavior. For the nonrewired random graph version, due to a constant number of out-links for each site, we write a simple mean-field-like equation describing the behavior of magnetization; we argue that it is exact and support the claim with extensive Monte Carlo simulations. For the rewired version, this equation is obeyed only at low temperatures. At higher temperatures, rewiring leads to strong heterogeneities, which apparently invalidates mean-field arguments and induces large fluctuations and divergent susceptibility. Such behavior is traced back to the formation of a relatively small core of agents that influence the entire system.

  14. Modulation and Coding Techniques for Infrared Wireless Local Area Networks

    Microsoft Academic Search

    T. A. Gulliver

    2006-01-01

    Because of low-cost optical devices and virtually unlimited bandwidth, optical wireless communications (OWC) for indoor wireless local area networks (WLANs) has become an attractive alternative to radio frequency systems. Since optical signals cannot penetrate through walls or other opaque barriers, the security of infrared WLANs is very high and there is no interference between rooms. This makes cell planning easier,

  15. Comparison of Modules of Wild Type and Mutant Huntingtin and TP53 Protein Interaction Networks: Implications in Biological Processes and Functions

    PubMed Central

    Basu, Mahashweta; Bhattacharyya, Nitai P.; Mohanty, Pradeep K.

    2013-01-01

    Disease-causing mutations usually change the interacting partners of mutant proteins. In this article, we propose that the biological consequences of mutation are directly related to the alteration of corresponding protein protein interaction networks (PPIN). Mutation of Huntingtin (HTT) which causes Huntington's disease (HD) and mutations to TP53 which is associated with different cancers are studied as two example cases. We construct the PPIN of wild type and mutant proteins separately and identify the structural modules of each of the networks. The functional role of these modules are then assessed by Gene Ontology (GO) enrichment analysis for biological processes (BPs). We find that a large number of significantly enriched () GO terms in mutant PPIN were absent in the wild type PPIN indicating the gain of BPs due to mutation. Similarly some of the GO terms enriched in wild type PPIN cease to exist in the modules of mutant PPIN, representing the loss. GO terms common in modules of mutant and wild type networks indicate both loss and gain of BPs. We further assign relevant biological function(s) to each module by classifying the enriched GO terms associated with it. It turns out that most of these biological functions in HTT networks are already known to be altered in HD and those of TP53 networks are altered in cancers. We argue that gain of BPs, and the corresponding biological functions, are due to new interacting partners acquired by mutant proteins. The methodology we adopt here could be applied to genetic diseases where mutations alter the ability of the protein to interact with other proteins. PMID:23741403

  16. Additive functions in boolean models of gene regulatory network modules.

    PubMed

    Darabos, Christian; Di Cunto, Ferdinando; Tomassini, Marco; Moore, Jason H; Provero, Paolo; Giacobini, Mario

    2011-01-01

    Gene-on-gene regulations are key components of every living organism. Dynamical abstract models of genetic regulatory networks help explain the genome's evolvability and robustness. These properties can be attributed to the structural topology of the graph formed by genes, as vertices, and regulatory interactions, as edges. Moreover, the actual gene interaction of each gene is believed to play a key role in the stability of the structure. With advances in biology, some effort was deployed to develop update functions in boolean models that include recent knowledge. We combine real-life gene interaction networks with novel update functions in a boolean model. We use two sub-networks of biological organisms, the yeast cell-cycle and the mouse embryonic stem cell, as topological support for our system. On these structures, we substitute the original random update functions by a novel threshold-based dynamic function in which the promoting and repressing effect of each interaction is considered. We use a third real-life regulatory network, along with its inferred boolean update functions to validate the proposed update function. Results of this validation hint to increased biological plausibility of the threshold-based function. To investigate the dynamical behavior of this new model, we visualized the phase transition between order and chaos into the critical regime using Derrida plots. We complement the qualitative nature of Derrida plots with an alternative measure, the criticality distance, that also allows to discriminate between regimes in a quantitative way. Simulation on both real-life genetic regulatory networks show that there exists a set of parameters that allows the systems to operate in the critical region. This new model includes experimentally derived biological information and recent discoveries, which makes it potentially useful to guide experimental research. The update function confers additional realism to the model, while reducing the complexity and solution space, thus making it easier to investigate. PMID:22132067

  17. Co-expression network analysis identifies transcriptional modules in the mouse liver.

    PubMed

    Liu, Wei; Ye, Hua

    2014-10-01

    The mouse liver transcriptome has been extensively studied but little is known about the global hepatic gene network of the mouse under normal physiological conditions. Understanding this will help reveal the transcriptional organization of the liver and elucidate its functional complexity. Here, weighted gene co-expression network analysis (WGCNA) was carried out to explore gene co-expression networks using large-scale microarray data from normal mouse livers. A total of 7,203 genes were parsed into 16 gene modules associated with protein catabolism, RNA processing, muscle contraction, transcriptional regulation, oxidation reduction, sterol biosynthesis, translation, fatty acid metabolism, immune response and others. The modules were organized into higher order co-expression groups. Hub genes in each module were found to be critical for module function. In sum, the analyses revealed the gene modular map of the mouse liver under normal physiological condition. These results provide a systems-level framework to help understand the complexity of the mouse liver at the molecular level, and should be beneficial in annotating uncharacterized genes. PMID:24816893

  18. Electrophysiological properties of rostral ventrolateral medulla presympathetic neurons modulated by the respiratory network in rats.

    PubMed

    Moraes, Davi J A; da Silva, Melina P; Bonagamba, Leni G H; Mecawi, André S; Zoccal, Daniel B; Antunes-Rodrigues, José; Varanda, Wamberto A; Machado, Benedito H

    2013-12-01

    The respiratory pattern generator modulates the sympathetic outflow, the strength of which is enhanced by challenges produced by hypoxia. This coupling is due to the respiratory-modulated presympathetic neurons in the rostral ventrolateral medulla (RVLM), but the underlining electrophysiological mechanisms remain unclear. For a better understanding of the neural substrates responsible for generation of this respiratory-sympathetic coupling, we combined immunofluorescence, single cell qRT-pCR, and electrophysiological recordings of the RVLM presympathetic neurons in in situ preparations from normal rats and rats submitted to a metabolic challenge produced by chronic intermittent hypoxia (CIH). Our results show that the spinally projected cathecholaminergic C1 and non-C1 respiratory-modulated RVLM presympathetic neurons constitute a heterogeneous neuronal population regarding the intrinsic electrophysiological properties, respiratory synaptic inputs, and expression of ionic currents, albeit all neurons presented persistent sodium current-dependent intrinsic pacemaker properties after synaptic blockade. A specific subpopulation of non-C1 respiratory-modulated RVLM presympathetic neurons presented enhanced excitatory synaptic inputs from the respiratory network after CIH. This phenomenon may contribute to the increased sympathetic activity observed in CIH rats. We conclude that the different respiratory-modulated RVLM presympathetic neurons contribute to the central generation of respiratory-sympathetic coupling as part of a complex neuronal network, which in response to the challenges produced by CIH contribute to respiratory-related increase in the sympathetic activity. PMID:24305818

  19. Finding pathway-modulating genes from a novel Ontology Fingerprint-derived gene network

    PubMed Central

    Qin, Tingting; Matmati, Nabil; Tsoi, Lam C.; Mohanty, Bidyut K.; Gao, Nan; Tang, Jijun; Lawson, Andrew B.; Hannun, Yusuf A.; Zheng, W. Jim

    2014-01-01

    To enhance our knowledge regarding biological pathway regulation, we took an integrated approach, using the biomedical literature, ontologies, network analyses and experimental investigation to infer novel genes that could modulate biological pathways. We first constructed a novel gene network via a pairwise comparison of all yeast genes’ Ontology Fingerprints—a set of Gene Ontology terms overrepresented in the PubMed abstracts linked to a gene along with those terms’ corresponding enrichment P-values. The network was further refined using a Bayesian hierarchical model to identify novel genes that could potentially influence the pathway activities. We applied this method to the sphingolipid pathway in yeast and found that many top-ranked genes indeed displayed altered sphingolipid pathway functions, initially measured by their sensitivity to myriocin, an inhibitor of de novo sphingolipid biosynthesis. Further experiments confirmed the modulation of the sphingolipid pathway by one of these genes, PFA4, encoding a palmitoyl transferase. Comparative analysis showed that few of these novel genes could be discovered by other existing methods. Our novel gene network provides a unique and comprehensive resource to study pathway modulations and systems biology in general. PMID:25063300

  20. CAN-DOO: The Climate Action Network through Direct Observations and Outreach

    NASA Astrophysics Data System (ADS)

    Taubman, B.; Sherman, J. P.; Perry, L. B.; Markham, J.; Kelly, G.

    2011-12-01

    The urgency of climate change demands a greater understanding of our climate system, not only by the leaders of today, but by the scientists, policy makers, and citizens of tomorrow. Unfortunately, a large segment of the population currently possesses inadequate knowledge of climate science. In direct response to a need for greater scientific literacy with respect to climate science, researchers from Appalachian State University's Appalachian Atmospheric Interdisciplinary Research (AppalAIR) group, with support from NASA, have developed CAN-DOO: the Climate Action Network through Direct Observations and Outreach. CAN-DOO addresses climate science literacy by 1) Developing the infrastructure for sustaining and expanding public outreach through long-term climate measurements capable of complementing existing NASA measurements, 2) Enhancing public awareness of climate science and NASA's role in advancing our understanding of the Earth System, and 3) Introducing Science, Technology, Engineering, and Mathematics principles to homeschooled, public school, and Appalachian State University students through applied climate science activities. Project partners include the Grandfather Mountain Stewardship Foundation, Pisgah Astronomical Research Institute, and local elementary schools. In partnership with Grandfather Mountain, climate science awareness is promoted through citizen science activities, interactive public displays, and staff training. CAN-DOO engages students by involving them in the entire scientific investigative process as applied to climate science. We introduce local elementary and middle school students, homeschooled students throughout North Carolina, and undergraduate students in a new Global Climate Change course and select other courses at Appalachian State University to instrument assembly, measurement techniques, data collection, hypothesis testing, and drawing conclusions. Results are placed in the proper context via comparisons with other student data products, local research-grade measurements, and NASA measurements. Several educational modules have been developed that address specific topics in climate science. The modules are scalable and have been successfully implemented at levels ranging from 2nd grade through first-year graduate as well as with citizen science groups. They also can be applied in user-desired segments to a variety of Earth Science units. In this paper, we will introduce the project activities and present results from the first year of observations and outreach, with a special emphasis on two of the developed modules, the surface energy balance and aerosol optical depth module.

  1. Synergy of direct and indirect cholinergic septo-hippocampal pathways coordinates firing in hippocampal networks.

    PubMed

    Dannenberg, Holger; Pabst, Milan; Braganza, Oliver; Schoch, Susanne; Niediek, Johannes; Bayraktar, Melike; Mormann, Florian; Beck, Heinz

    2015-06-01

    The medial septum/diagonal band of Broca complex (MSDB) is a key structure that modulates hippocampal rhythmogenesis. Cholinergic neurons of the MSDB play a central role in generating and pacing theta-band oscillations in the hippocampal formation during exploration, novelty detection, and memory encoding. How precisely cholinergic neurons affect hippocampal network dynamics in vivo, however, has remained elusive. In this study, we show that stimulation of cholinergic MSDB neurons in urethane-anesthetized mice acts on hippocampal networks via two distinct pathways. A direct septo-hippocampal cholinergic projection causes increased firing of hippocampal inhibitory interneurons with concomitantly decreased firing of principal cells. In addition, cholinergic neurons recruit noncholinergic neurons within the MSDB. This indirect pathway is required for hippocampal theta synchronization. Activation of both pathways causes a reduction in pyramidal neuron firing and a more precise coupling to the theta oscillatory phase. These two anatomically and functionally distinct pathways are likely relevant for cholinergic control of encoding versus retrieval modes in the hippocampus. PMID:26041909

  2. Temperature monitoring in wireless sensor network using Zigbee transceiver module

    Microsoft Academic Search

    Rajesh Singh; Shailesh Mishra

    2010-01-01

    In this paper, we are using the features and technology of wireless sensor networks such as distributed and self-organization to build temperature monitoring system, which can monitor the temperature of bus bar junction in real time to prevent fire and other accidents. This system applies ZigBee communication protocol and uses the IC-CC2500, 2.4GHz(ISM) as RF transceiver. It has the characteristics

  3. Diffusible crosslinkers generate directed forces in microtubule networks.

    PubMed

    Lansky, Zdenek; Braun, Marcus; Lüdecke, Annemarie; Schlierf, Michael; ten Wolde, Pieter Rein; Janson, Marcel E; Diez, Stefan

    2015-03-12

    Cytoskeletal remodeling is essential to eukaryotic cell division and morphogenesis. The mechanical forces driving the restructuring are attributed to the action of molecular motors and the dynamics of cytoskeletal filaments, which both consume chemical energy. By contrast, non-enzymatic filament crosslinkers are regarded as mere friction-generating entities. Here, we experimentally demonstrate that diffusible microtubule crosslinkers of the Ase1/PRC1/Map65 family generate directed microtubule sliding when confined between partially overlapping microtubules. The Ase1-generated forces, directly measured by optical tweezers to be in the piconewton-range, were sufficient to antagonize motor-protein driven microtubule sliding. Force generation is quantitatively explained by the entropic expansion of confined Ase1 molecules diffusing within the microtubule overlaps. The thermal motion of crosslinkers is thus harnessed to generate mechanical work analogous to compressed gas propelling a piston in a cylinder. As confinement of diffusible proteins is ubiquitous in cells, the associated entropic forces are likely of importance for cellular mechanics beyond cytoskeletal networks. PMID:25748652

  4. Interferon ?-1b directly modulates human neural stem/progenitor cell fate.

    PubMed

    Arscott, W Tristram; Soltys, John; Knight, Julia; Mao-Draayer, Yang

    2011-09-21

    Interferon beta (IFN-?) is a mainline treatment for multiple sclerosis (MS); however its exact mechanism of action is not completely understood. IFN-? is known as an immunomodulator; although recent evidence suggests that IFN-? may also act directly on neural stem/progenitor cells (NPCs) in the central nervous system (CNS). NPCs can differentiate into all neural lineage cells, which could contribute to the remyelination and repair of MS lesions. Understanding how IFN-? influences NPC physiology is critical to develop more specific therapies that can better assist this repair process. In this study, we investigated the effects of IFN ?-1b (Betaseron®) on human NPCs in vitro (hNPCs). Our data demonstrate a dose-dependent response of hNPCs to IFN ?-1b treatment via sustained proliferation and differentiation. Furthermore, we offer insight into the signaling pathways involved in these mechanisms. Overall, this study shows a direct effect of IFN ?-1b on hNPCs and highlights the need to further understand how current MS treatments can modulate endogenous NPC populations within the CNS. PMID:21855056

  5. DIRECT MODULATION OF THE PROTEIN KINASE A CATALYTIC SUBUNIT ? BY GROWTH FACTOR RECEPTOR TYROSINE KINASES

    PubMed Central

    Caldwell, George B.; Howe, Alan K.; Nickl, Christian K.; Dostmann, Wolfgang R.; Ballif, Bryan A.; Deming, Paula B.

    2011-01-01

    The cyclic-AMP-dependent protein kinase A (PKA) regulates processes such as cell proliferation and migration following activation of growth factor receptor tyrosine kinases (RTKs), yet the signaling mechanisms that link PKA with growth factor receptors remain largely undefined. Here we report that RTKs can directly modulate the function of the catalytic subunit of PKA (PKA-C) through post-translational modification. In vitro kinase assays revealed that both the epidermal growth factor and platelet derived growth factor receptors (EGFR and PDGFR, respectively) tyrosine phosphorylate PKA-C. Mass spectrometry identified tyrosine 330 (Y330) as a receptor-mediated phosphorylation site and mutation of Y330 to phenylalanine (Y330F) all but abolished the RTK-mediated phosphorylation of PKA-C in vitro. Y330 resides within a conserved region at the C-terminal tail of PKA-C that allosterically regulates enzymatic activity. Therefore, the effect of phosphorylation at Y330 on the activity of PKA-C was investigated. The Km for a peptide substrate was markedly decreased when PKA-C subunits were tyrosine phosphorylated by the receptors as compared to un-phosphorylated controls. Importantly, tyrosine-phosphorylated PKA-C subunits were detected in cells stimulated with EGF, PDGF and FGF2 and in fibroblasts undergoing PDGF-mediated chemotaxis. These results demonstrate a direct, functional interaction between RTKs and PKA-C and identify tyrosine phosphorylation as a novel mechansim for regulating PKA activity. PMID:21866565

  6. Modulating Bone Resorption and Bone Formation in Opposite Directions in the Treatment of Postmenopausal Osteoporosis.

    PubMed

    Appelman-Dijkstra, Natasha M; Papapoulos, Socrates E

    2015-07-01

    Bone remodeling, the fundamental process for bone renewal, is targeted by treatments of osteoporosis to correct the imbalance between bone resorption and bone formation and reduce the risk of fractures and associated clinical consequences. Currently available therapeutics affect bone resorption and bone formation in the same direction and either decrease (inhibitors of bone resorption) or increase (parathyroid hormone [PTH] peptides) bone remodeling. Studies of patients with rare bone diseases and genetically modified animal models demonstrated that bone resorption and bone formation may not necessarily be coupled, leading to identification of molecular targets in bone cells for the development of novel agents for the treatment of osteoporosis. Application of such agents to the treatment of women with low bone mass confirmed that bone resorption and bone formation can be modulated in different directions and so far two new classes of therapeutics for osteoporosis have been defined with distinct mechanisms of action. Such treatments, if combined with a favorable safety profile, will offer new therapeutic options and will improve the management of patients with osteoporosis. PMID:26056029

  7. Functional module search in protein networks based on semantic similarity improves the analysis of proteomics data.

    PubMed

    Boyanova, Desislava; Nilla, Santosh; Klau, Gunnar W; Dandekar, Thomas; Müller, Tobias; Dittrich, Marcus

    2014-07-01

    The continuously evolving field of proteomics produces increasing amounts of data while improving the quality of protein identifications. Albeit quantitative measurements are becoming more popular, many proteomic studies are still based on non-quantitative methods for protein identification. These studies result in potentially large sets of identified proteins, where the biological interpretation of proteins can be challenging. Systems biology develops innovative network-based methods, which allow an integrated analysis of these data. Here we present a novel approach, which combines prior knowledge of protein-protein interactions (PPI) with proteomics data using functional similarity measurements of interacting proteins. This integrated network analysis exactly identifies network modules with a maximal consistent functional similarity reflecting biological processes of the investigated cells. We validated our approach on small (H9N2 virus-infected gastric cells) and large (blood constituents) proteomic data sets. Using this novel algorithm, we identified characteristic functional modules in virus-infected cells, comprising key signaling proteins (e.g. the stress-related kinase RAF1) and demonstrate that this method allows a module-based functional characterization of cell types. Analysis of a large proteome data set of blood constituents resulted in clear separation of blood cells according to their developmental origin. A detailed investigation of the T-cell proteome further illustrates how the algorithm partitions large networks into functional subnetworks each representing specific cellular functions. These results demonstrate that the integrated network approach not only allows a detailed analysis of proteome networks but also yields a functional decomposition of complex proteomic data sets and thereby provides deeper insights into the underlying cellular processes of the investigated system. PMID:24807868

  8. Directed Network Motifs in Alzheimer’s Disease and Mild Cognitive Impairment

    PubMed Central

    Friedman, Eric J.; Young, Karl; Tremper, Graham; Liang, Jason; Landsberg, Adam S.; Schuff, Norbert

    2015-01-01

    Directed network motifs are the building blocks of complex networks, such as human brain networks, and capture deep connectivity information that is not contained in standard network measures. In this paper we present the first application of directed network motifs in vivo to human brain networks, utilizing recently developed directed progression networks which are built upon rates of cortical thickness changes between brain regions. This is in contrast to previous studies which have relied on simulations and in vitro analysis of non-human brains. We show that frequencies of specific directed network motifs can be used to distinguish between patients with Alzheimer’s disease (AD) and normal control (NC) subjects. Especially interesting from a clinical standpoint, these motif frequencies can also distinguish between subjects with mild cognitive impairment who remained stable over three years (MCI) and those who converted to AD (CONV). Furthermore, we find that the entropy of the distribution of directed network motifs increased from MCI to CONV to AD, implying that the distribution of pathology is more structured in MCI but becomes less so as it progresses to CONV and further to AD. Thus, directed network motifs frequencies and distributional properties provide new insights into the progression of Alzheimer’s disease as well as new imaging markers for distinguishing between normal controls, stable mild cognitive impairment, MCI converters and Alzheimer’s disease. PMID:25879535

  9. Soft-Input Soft-Output Modules for the Construction and Distributed Iterative Decoding of Code Networks

    NASA Technical Reports Server (NTRS)

    Benedetto, S.; Divsalar, D.; Montorsi, G.; Pollara, F.

    1998-01-01

    Soft-input soft-output building blocks (modules) are presented to construct and iteratively decode in a distributed fashion code networks, a new concept that includes, and generalizes, various forms of concatenated coding schemes.

  10. Spatial and directional distribution of cracks in silicon PV modules after uniform mechanical loads

    Microsoft Academic Search

    Sarah Kajari-Schroder; Iris Kunze; Ulrich Eitner; Marc Kontges

    2011-01-01

    Crystalline silicon photovoltaic (PV) modules are prone to the formation of cracks in the solar cells when subjected to mechanical loads. In extreme cases these cracks lead to an electrical separation of cell parts, thus reducing the power output of the module. We present the analysis of crack distributions in PV modules after being subjected to a uniform mechanical load.

  11. Predicting testability of program modules using a neural network

    Microsoft Academic Search

    T. M. Khoshgoftaar; E. B. Allen; Z. Xu

    2000-01-01

    J.M. Voas (1992) defines testability as the probability that a test case will fail if the program has a fault. It is defined in the context of an oracle for the test, and a distribution of test cases, usually emulating operations. Because testability is a dynamic attribute of software, it is very computation-intensive to measure directly. The paper presents a

  12. Long Distance Wireless Disaster Information Network by Automatic Directional Antenna Control Method

    Microsoft Academic Search

    Daisuke Asahizawa; Goshi Sato; Toshihiro Suzuki; Yoshitaka Shibata

    2010-01-01

    It is proved that wireless network is suitable for disaster information infrastructure because of its robustness, mobility and flexibility. However current conventional wireless networks have limit in communication distance because of low electro-magnetic power density, non-directional antenna. This is quite fatal as emergency network particularly in mountain areas like Japan. In order to solve those problems, in this paper, we

  13. Modification of a neuronal network direction using stepwise photo-thermal etching of an agarose architecture

    Microsoft Academic Search

    Ikurou Suzuki; Yoshihiro Sugio; Hiroyuki Moriguchi; Yasuhiko Jimbo; Kenji Yasuda

    2004-01-01

    Control over spatial distribution of individual neurons and the pattern of neural network provides an important tool for studying information processing pathways during neural network formation. Moreover, the knowledge of the direction of synaptic connections between cells in each neural network can provide detailed information on the relationship between the forward and feedback signaling. We have developed a method for

  14. Neural Networks 24 (2011) 950960 Contents lists available at SciVerse ScienceDirect

    E-print Network

    Fukai, Tomoki

    2011-01-01

    Neural Networks 24 (2011) 950­960 Contents lists available at SciVerse ScienceDirect Neural of a spiking neural network model of the basal ganglia circuitry using general purpose computing on graphics neural networks Real-time simulation GPGPUs Basal ganglia High-performance computing a b s t r a c t Real

  15. Magnetoencephalographic evidence for the modulation of cortical swallowing processing by transcranial direct current stimulation.

    PubMed

    Suntrup, Sonja; Teismann, Inga; Wollbrink, Andreas; Winkels, Martin; Warnecke, Tobias; Flöel, Agnes; Pantev, Christo; Dziewas, Rainer

    2013-12-01

    Swallowing is a complex neuromuscular task that is processed within multiple regions of the human brain. Rehabilitative treatment options for dysphagia due to neurological diseases are limited. Because the potential for adaptive cortical changes in compensation of disturbed swallowing is recognized, neuromodulation techniques like transcranial direct current stimulation (tDCS) are currently considered as a treatment option. Here we evaluate the effect of tDCS on cortical swallowing network activity and behavior. In a double-blind crossover study, anodal tDCS (20 min, 1 mA) or sham stimulation was administered over the left or right swallowing motor cortex in 21 healthy subjects in separate sessions. Cortical activation was measured using magnetoencephalography (MEG) before and after tDCS during cued "simple", "fast" and "challenged" swallow tasks with increasing levels of difficulty. Swallowing response times and accuracy were measured. Significant bilateral enhancement of cortical swallowing network activation was found in the theta frequency range after left tDCS in the fast swallow task (p=0.006) and following right tDCS in the challenged swallow task (p=0.007), but not after sham stimulation. No relevant behavioral effects were observed on swallow response time, but swallow precision improved after left tDCS (p<0.05). Anodal tDCS applied over the swallowing motor cortex of either hemisphere was able to increase bilateral swallow-related cortical network activation in a frequency specific manner. These neuroplastic effects were associated with subtle behavioral gains during complex swallow tasks in healthy individuals suggesting that tDCS deserves further evaluation as a treatment tool for dysphagia. PMID:23800793

  16. Direct imaging of fluctuations in a cross-linked biopolymer network

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Jiang, Lingxiang; Tsang, Boyce; Granick, Steve; Steve Granick Team

    2013-03-01

    Cross-linked networks are ubiquitous in synthetic and biological polymer systems, such as rubbers and cytoskeletons. To model cross-linked networks, several theories have been developed on the basis of different assumptions as to fluctuations in the networks. Here we put these theories to direct test. This talk will describe direct single-molecule imaging of the dynamic fluctuations of junction points in a cross-linked semiflexible polymer (F-actin) network. The actin filaments are cross linked by biotin/avidin. The junction points are selectively labeled to allow nm spatial imaging resolution. The surprising results point to limitations of the prevailing network models.

  17. Quantum secure direct communication network with Einstein-Podolsky-Rosen pairs

    E-print Network

    Fu-Guo Deng; Xi-Han Li; Chun-Yan Li; Ping Zhou; Hong-Yu Zhou

    2006-10-16

    We discuss the four requirements for a real point-to-point quantum secure direct communication (QSDC) first, and then present two efficient QSDC network schemes with an N ordered Einstein-Podolsky-Rosen pairs. Any one of the authorized users can communicate another one on the network securely and directly.

  18. Sensor Network Connectivity with Multiple Directional Antennae of a Given Angular Sum

    E-print Network

    Kranakis, Evangelos

    , ESPAR (Electronically Steerable Passive Array Radiator) antennae consisting of a steerable centralSensor Network Connectivity with Multiple Directional Antennae of a Given Angular Sum Binay into strongly connected networks of sensors using multiple directional antennae. Consider a set S of n points

  19. A Property-Based Optimization of Direct Recycle Networks and Wastewater

    E-print Network

    Grossmann, Ignacio E.

    A Property-Based Optimization of Direct Recycle Networks and Wastewater Treatment Processes Jose a mathematical programming approach to optimize direct recycle-reuse networks together with wastewater treatment of wastewater treatment units. In addition to composition-based constraints, the formulation also incorporates

  20. Soft-input soft-output modules for the construction and distributed iterative decoding of code networks

    Microsoft Academic Search

    Sergio Benedetto; Guido Montorsi; Dariush Divsalar; Fabrizio Pollara

    1998-01-01

    Soft-input soft-output building blocks #modules# are presented to construct and iteratively decode in a distributed fashion code networks, a new concept that includes, and generalizes, various forms of concatenated coding schemes. Among the modules, a central role is played by the SISO module #and the underlying algorithm#: it consists of a four-port device performing a processing of the sequences of

  1. Data Rewrite of Wavelength Channel Using Saturated SOA Modulator for WDM Metro\\/Access Networks with Centralized Light Sources

    Microsoft Academic Search

    H. Takesue; T. Sugie

    2002-01-01

    We propose a simple wavelength reuse technique for WDM metro\\/access networks with centralized light sources. Using a deeply saturated SOA modulator located in a remote node, we erase the data on a low-extinction-ratio downstream signal and modulate it with new data to generate an upstream signal.

  2. DSP based direct torque control of permanent magnet synchronous motor (PMSM) using space vector modulation (DTC-SVM)

    Microsoft Academic Search

    D. Swierczynski; M. P. Kazmierkowski; F. Blaabjerg

    2002-01-01

    This paper presents digital signal processor (DSP) based direct torque control scheme using space vector modulation (DTC-SVM) for permanent magnet synchronous motor (PMSM) drives. The analysis of PMSM shows that the increase of electromagnetic torque is proportional to the increase of the angle between the stator and rotor flux linkages and therefore fast torque response can be obtained by increasing

  3. Direct torque control of permanent magnet synchronous motor (PMSM) using space vector modulation (DTC-SVM)-simulation and experimental results

    Microsoft Academic Search

    D. Swierczynski; M. P. Kazmierkowski

    2002-01-01

    This paper presents digital signal processor (DSP) based direct torque control scheme using space vector modulation (DTC-SVM) for permanent magnet synchronous motor (PMSM) drives. The analysis of PMSM shows that the increase of electromagnetic torque is proportional to the increase of the angle between the stator and rotor flux linkages and therefore fast torque response can be obtained by increasing

  4. Signal-to-noise ratio in direct-detection mid-infrared Random-Modulation Continuous-Wave

    E-print Network

    Taflove, Allen

    Signal-to-noise ratio in direct-detection mid- infrared Random-Modulation Continuous-Wave lidar conditions in the near-infrared, our result is applicable mainly at longer, mid-infrared wavelengths. Unlike lidar. A need for balanced sequences ­ particularly in the mid-infrared ­ is explained, although

  5. IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 36, NO. 11, NOVEMBER 2000 1299 Theory of Large-Signal Direct Modulation of

    E-print Network

    Sipe,J. E.

    , particularly for application to op- tical communications. The fiber grating laser (FGL) [1]­[7] is an example fiber cavity. The cavity length is on the order of centimeters, and one mirror of the laser cavity-Signal Direct Modulation of Extended Cavity Semiconductor Lasers with Dispersive Loss L. Ramunno and J. E. Sipe

  6. Building Robust Nomadic Wireless Mesh Networks Using Directional Antennas

    Microsoft Academic Search

    Qunfeng Dong; Yigal Bejerano

    2008-01-01

    Recently, wireless mesh technology has been used for military applications and fast recovery networks, referred to as nomadic wireless mesh networks (NWMNs). In such systems, wireless routers, termed nodes, are mounted on top of vehicles or vessels, which may change their location according to application needs; and the nodes are required to establish a reliable wireless mesh network. For improving

  7. Je pense donc je fais: transcranial direct current stimulation modulates brain oscillations associated with motor imagery and movement observation

    PubMed Central

    Lapenta, Olivia M.; Minati, Ludovico; Fregni, Felipe; Boggio, Paulo S.

    2013-01-01

    Motor system neural networks are activated during movement imagery, observation and execution, with a neural signature characterized by suppression of the Mu rhythm. In order to investigate the origin of this neurophysiological marker, we tested whether transcranial direct current stimulation (tDCS) modifies Mu rhythm oscillations during tasks involving observation and imagery of biological and non-biological movements. We applied tDCS (anodal, cathodal, and sham) in 21 male participants (mean age 23.8 ± 3.06), over the left M1 with a current of 2 mA for 20 min. Following this, we recorded the EEG at C3, C4, and Cz and surrounding C3 and C4 electrodes. Analyses of C3 and C4 showed significant effects for biological vs. non-biological movement (p = 0.005), and differential hemisphere effects according to the type of stimulation (p = 0.04) and type of movement (p = 0.02). Analyses of surrounding electrodes revealed significant interaction effects considering type of stimulation and imagery or observation of biological or non-biological movement (p = 0.03). The main findings of this study were (1) Mu desynchronization during biological movement of the hand region in the contralateral hemisphere after sham tDCS; (2) polarity-dependent modulation effects of tDCS on the Mu rhythm, i.e., anodal tDCS led to Mu synchronization while cathodal tDCS led to Mu desynchronization during movement observation and imagery (3) specific focal and opposite inter-hemispheric effects, i.e., contrary effects for the surrounding electrodes during imagery condition and also for inter-hemispheric electrodes (C3 vs. C4). These findings provide insights into the cortical oscillations during movement observation and imagery. Furthermore, it shows that tDCS can be highly focal when guided by a behavioral task. PMID:23761755

  8. A high power high voltage short pulse width pulse generator using direct drive method in application of modulating-cathode tubes drive

    Microsoft Academic Search

    A. Hasanzadeh; S. M. R. Sadriyeh; A. Mohammadi; B. Maghsoudlou; H. Mokhtari; H. R. Alizadeh; S. M. Shams Mousavi

    2009-01-01

    The power supply of microwave tubes has high voltage and the possibility of produce high power pulse, which called in modulator. In this work, the results of design, construction and characterization of a direct drive pulse modulator for driving high power short pulse-width magnetron are reported. The sub-assemblies of modulator are; a primary high voltage supply, a switch bank with

  9. Subthalamic stimulation modulates cortical motor network activity and synchronization in Parkinson's disease.

    PubMed

    Weiss, Daniel; Klotz, Rosa; Govindan, Rathinaswamy B; Scholten, Marlieke; Naros, Georgios; Ramos-Murguialday, Ander; Bunjes, Friedemann; Meisner, Christoph; Plewnia, Christian; Krüger, Rejko; Gharabaghi, Alireza

    2015-03-01

    Dynamic modulations of large-scale network activity and synchronization are inherent to a broad spectrum of cognitive processes and are disturbed in neuropsychiatric conditions including Parkinson's disease. Here, we set out to address the motor network activity and synchronization in Parkinson's disease and its modulation with subthalamic stimulation. To this end, 20 patients with idiopathic Parkinson's disease with subthalamic nucleus stimulation were analysed on externally cued right hand finger movements with 1.5-s interstimulus interval. Simultaneous recordings were obtained from electromyography on antagonistic muscles (right flexor digitorum and extensor digitorum) together with 64-channel electroencephalography. Time-frequency event-related spectral perturbations were assessed to determine cortical and muscular activity. Next, cross-spectra in the time-frequency domain were analysed to explore the cortico-cortical synchronization. The time-frequency modulations enabled us to select a time-frequency range relevant for motor processing. On these time-frequency windows, we developed an extension of the phase synchronization index to quantify the global cortico-cortical synchronization and to obtain topographic differentiations of distinct electrode sites with respect to their contributions to the global phase synchronization index. The spectral measures were used to predict clinical and reaction time outcome using regression analysis. We found that movement-related desynchronization of cortical activity in the upper alpha and beta range was significantly facilitated with 'stimulation on' compared to 'stimulation off' on electrodes over the bilateral parietal, sensorimotor, premotor, supplementary-motor, and prefrontal areas, including the bilateral inferior prefrontal areas. These spectral modulations enabled us to predict both clinical and reaction time improvement from subthalamic stimulation. With 'stimulation on', interhemispheric cortico-cortical coherence in the beta band was significantly attenuated over the bilateral sensorimotor areas. Similarly, the global cortico-cortical phase synchronization was attenuated, and the topographic differentiation revealed stronger desynchronization over the (ipsilateral) right-hemispheric prefrontal, premotor and sensorimotor areas compared to 'stimulation off'. We further demonstrated that the cortico-cortical phase synchronization was largely dominated by genuine neuronal coupling. The clinical improvement with 'stimulation on' compared to 'stimulation off' could be predicted from this cortical decoupling with multiple regressions, and the reduction of synchronization over the right prefrontal area showed a linear univariate correlation with clinical improvement. Our study demonstrates wide-spread activity and synchronization modulations of the cortical motor network, and highlights subthalamic stimulation as a network-modulating therapy. Accordingly, subthalamic stimulation may release bilateral cortical computational resources by facilitating movement-related desynchronization. Moreover, the subthalamic nucleus is critical to balance inhibitory and facilitatory cortical players within the motor program. PMID:25558877

  10. A role for direct interactions in the modulation of rhodopsin by -3 polyunsaturated lipids

    NASA Astrophysics Data System (ADS)

    Grossfield, Alan; Feller, Scott E.; Pitman, Michael C.

    2006-03-01

    Rhodopsin, the G protein-coupled receptor primarily responsible for sensing light, is found in an environment rich in polyunsaturated lipid chains and cholesterol. Biophysical experiments have shown that lipid unsaturation and cholesterol both have significant effects on rhodopsin's stability and function; -3 polyunsaturated chains, such as docosahexaenoic acid (DHA), destabilize rhodopsin and enhance the kinetics of the photocycle, whereas cholesterol has the opposite effect. Here, we use molecular dynamics simulations to investigate the possibility that polyunsaturated chains modulate rhodopsin stability and kinetics via specific direct interactions. By analyzing the results of 26 independent 100-ns simulations of dark-adapted rhodopsin, we found that DHA routinely forms tight associations with the protein in a small number of specific locations qualitatively different from the nonspecific interactions made by saturated chains and cholesterol. Furthermore, the presence of tightly packed DHA molecules tends to weaken the interhelical packing. These results are consistent with recent NMR work, which proposes that rhodopsin binds DHA, and they suggest a molecular rationale for DHA's effects on rhodopsin stability and kinetics. cholesterol | molecular dynamics | fatty acid | protein-lipid interactions

  11. Transcranial direct current stimulation over posterior parietal cortex modulates visuospatial localization

    PubMed Central

    Wright, Jessica M.; Krekelberg, Bart

    2014-01-01

    Visual localization is based on the complex interplay of bottom-up and top-down processing. Based on previous work, the posterior parietal cortex (PPC) is assumed to play an essential role in this interplay. In this study, we investigated the causal role of the PPC in visual localization. Specifically, our goal was to determine whether modulation of the PPC via transcranial direct current stimulation (tDCS) could induce visual mislocalization similar to that induced by an exogenous attentional cue (Wright, Morris, & Krekelberg, 2011). We placed one stimulation electrode over the right PPC and the other over the left PPC (dual tDCS) and varied the polarity of the stimulation. We found that this manipulation altered visual localization; this supports the causal involvement of the PPC in visual localization. Notably, mislocalization was more rightward when the cathode was placed over the right PPC than when the anode was placed over the right PPC. This mislocalization was found within a few minutes of stimulation onset, it dissipated during stimulation, but then resurfaced after stimulation offset and lasted for another 10–15 min. On the assumption that excitability is reduced beneath the cathode and increased beneath the anode, these findings support the view that each hemisphere biases processing to the contralateral hemifield and that the balance of activation between the hemispheres contributes to position perception (Kinsbourne, 1977; Szczepanski, Konen, & Kastner, 2010). PMID:25104830

  12. Modulating the pain network--neurostimulation for central poststroke pain.

    PubMed

    Hosomi, Koichi; Seymour, Ben; Saitoh, Youichi

    2015-05-01

    Central poststroke pain (CPSP) is one of the most under-recognized consequences of stroke, occurring in up to 10% of patients, and is also one of the most difficult to treat. The condition characteristically develops after selective lesions to the spinothalamic system, most often to the ventral posterior thalamus. Here, we suggest that CPSP is best characterized as a disorder of brain network reorganization, and that this characterization offers insight into the inadequacy of most current pharmacological treatments. Accordingly, we review the progress in identification of nonpharmacological treatments, which could ultimately lead to mechanism-based therapeutics. Of the invasive neurostimulation treatments available, electrical motor cortex stimulation seems to be superior to deep brain stimulation of the thalamus or brainstem, but enthusiasm for clinical use of the procedure is limited by its invasiveness. The current preference is for noninvasive transcranial magnetic stimulation, which, though effective, requires repeated application, causing logistical difficulties. Although CPSP is often severe and remains difficult to treat, future characterization of the precise underlying neurophysiological mechanisms, together with technological innovation, should allow new treatments to evolve. PMID:25896085

  13. ABC and IFC: Modules Detection Method for PPI Network

    PubMed Central

    Lei, Xiujuan; Tian, Jianfang

    2014-01-01

    Many clustering algorithms are unable to solve the clustering problem of protein-protein interaction (PPI) networks effectively. A novel clustering model which combines the optimization mechanism of artificial bee colony (ABC) with the fuzzy membership matrix is proposed in this paper. The proposed ABC-IFC clustering model contains two parts: searching for the optimum cluster centers using ABC mechanism and forming clusters using intuitionistic fuzzy clustering (IFC) method. Firstly, the cluster centers are set randomly and the initial clustering results are obtained by using fuzzy membership matrix. Then the cluster centers are updated through different functions of bees in ABC algorithm; then the clustering result is obtained through IFC method based on the new optimized cluster center. To illustrate its performance, the ABC-IFC method is compared with the traditional fuzzy C-means clustering and IFC method. The experimental results on MIPS dataset show that the proposed ABC-IFC method not only gets improved in terms of several commonly used evaluation criteria such as precision, recall, and P value, but also obtains a better clustering result. PMID:24991575

  14. Unilateral deafness in children affects development of multi-modal modulation and default mode networks

    PubMed Central

    Schmithorst, Vincent J.; Plante, Elena; Holland, Scott

    2014-01-01

    Monaural auditory input due to congenital or acquired unilateral hearing loss (UHL) may have neurobiological effects on the developing brain. Using functional magnetic resonance imaging (fMRI), we investigated the effect of UHL on the development of functional brain networks used for cross-modal processing. Children ages 7–12 with moderate or greater unilateral hearing loss of sensorineural origin (UHL-SN; N = 21) and normal-hearing controls (N = 23) performed an fMRI-compatible adaptation of the Token Test involving listening to a sentence such as “touched the small green circle and the large blue square” and simultaneously viewing an arrow touching colored shapes on a video. Children with right or severe-to-profound UHL-SN displayed smaller activation in a region encompassing the right inferior temporal, middle temporal, and middle occipital gyrus (BA 19/37/39), evidencing differences due to monaural hearing in cross-modal modulation of the visual processing pathway. Children with UHL-SN displayed increased activation in the left posterior superior temporal gyrus, likely the result either of more effortful low-level processing of auditory stimuli or differences in cross-modal modulation of the auditory processing pathway. Additionally, children with UHL-SN displayed reduced deactivation of anterior and posterior regions of the default mode network. Results suggest that monaural hearing affects the development of brain networks related to cross-modal sensory processing and the regulation of the default network during processing of spoken language. PMID:24723873

  15. W-band RoF transmission based on optical multi-carrier generation by cascading one directly-modulated DFB laser and one phase modulator

    NASA Astrophysics Data System (ADS)

    Li, Xinying; Yu, Jianjun

    2015-06-01

    We experimentally demonstrate that, adopting an optical multi-carrier source based on cascaded directly-modulated distributed-feedback laser (DML) and phase modulator (PM), any pair of subcarriers spaced by 100 GHz selected from the generated optical subcarriers can be used to generate 100-GHz millimeter-wave (mm-wave) frequency based on remote heterodyning technique, and thus realize 3.125-Gb/s on-off-keying (OOK) signal transmission over a radio-over-fiber (RoF) system at W-band. After 20-km large-effective-area fiber (LEAF) transmission and 2-m wireless delivery, the bit-error ratio (BER) of 1×10-9 can be attained when the two selected subcarriers spaced by 100 GHz are simultaneously modulated before remote heterodyning. 1.5-dB power penalty at the BER of 1×10-9 is caused by 2-m wireless delivery while almost no penalty is caused by 20-km LEAF transmission. However, because of different path lengths and the quite wide linewidth of the DML, the 3.125-Gb/s OOK signal after the same RoF transmission cannot be recovered when the two selected subcarriers are separated into two different optical paths and only one of them is modulated before remote heterodyning.

  16. Performance of Directional Collision Avoidance in Multihop Wireless Networks

    Microsoft Academic Search

    J. J. Garcia-Luna-Aceves; Yu Wang

    This chapter analyzes the performance of directional collision avoidance schemes, in which antenna systems are used to direct the transmission and reception of control and data packets in channel access protocols based on four-way handshakes to try to avoid collisions. The rst analytical model to consider directional reception and the possible difference in gain between omni-directional and directional trans- missions

  17. 2 IEEE/ACMTRANSACTIONS ON NETWORKING, VOL. l 1, NO. 1, FEBRUARY2003 Directed Diffusion for Wireless Sensor Networking

    E-print Network

    Heidemann, John

    2 IEEE/ACMTRANSACTIONS ON NETWORKING, VOL. l 1, NO. 1, FEBRUARY2003 Directed Diffusion for Wireless Sensor Networking Chalermek Intanagonwiwat, Ramesh Govindan, Deborah Estfin, John Heidemann, Member, IEEE 90089 USA. He is now with Chulalongkorn University, Bangkok 10330, Thailand (intanago@yahoo.com). R

  18. 2 IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 11, NO. 1, FEBRUARY 2003 Directed Diffusion for Wireless Sensor Networking

    E-print Network

    Scheuermann, Peter

    @yahoo.com). R. Govindan is with the Department of Computer Science, University of Southern California, Los2 IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 11, NO. 1, FEBRUARY 2003 Directed Diffusion for Wireless Sensor Networking Chalermek Intanagonwiwat, Ramesh Govindan, Deborah Estrin, John Heidemann

  19. Evolutionary developmental transcriptomics reveals a gene network module regulating interspecific diversity in plant leaf shape

    PubMed Central

    Ichihashi, Yasunori; Aguilar-Martínez, José Antonio; Farhi, Moran; Chitwood, Daniel H.; Kumar, Ravi; Millon, Lee V.; Peng, Jie; Maloof, Julin N.; Sinha, Neelima R.

    2014-01-01

    Despite a long-standing interest in the genetic basis of morphological diversity, the molecular mechanisms that give rise to developmental variation are incompletely understood. Here, we use comparative transcriptomics coupled with the construction of gene coexpression networks to predict a gene regulatory network (GRN) for leaf development in tomato and two related wild species with strikingly different leaf morphologies. The core network in the leaf developmental GRN contains regulators of leaf morphology that function in global cell proliferation with peripheral gene network modules (GNMs). The BLADE-ON-PETIOLE (BOP) transcription factor in one GNM controls the core network by altering effective concentration of the KNOTTED-like HOMEOBOX gene product. Comparative network analysis and experimental perturbations of BOP levels suggest that variation in BOP expression could explain the diversity in leaf complexity among these species through dynamic rewiring of interactions in the GRN. The peripheral location of the BOP-containing GNM in the leaf developmental GRN and the phenotypic mimics of evolutionary diversity caused by alteration in BOP levels identify a key role for this GNM in canalizing the leaf morphospace by modifying the maturation schedule of leaves to create morphological diversity. PMID:24927584

  20. Caffeine modulates attention network function Tad T. Bruny a,b,*, Caroline R. Mahoney a,b

    E-print Network

    Patel, Aniruddh D.

    Caffeine modulates attention network function Tad T. Brunyé a,b,*, Caroline R. Mahoney a,b , Harris 2009 Available online 5 September 2009 Keywords: Caffeine Arousal Attention networks Visuospatial attention a b s t r a c t The present work investigated the effects of caffeine (0 mg, 100 mg, 200 mg, 400

  1. General Relationship of Global Topology, Local Dynamics, and Directionality in Large-Scale Brain Networks

    PubMed Central

    Moon, Joon-Young; Lee, UnCheol; Blain-Moraes, Stefanie; Mashour, George A.

    2015-01-01

    The balance of global integration and functional specialization is a critical feature of efficient brain networks, but the relationship of global topology, local node dynamics and information flow across networks has yet to be identified. One critical step in elucidating this relationship is the identification of governing principles underlying the directionality of interactions between nodes. Here, we demonstrate such principles through analytical solutions based on the phase lead/lag relationships of general oscillator models in networks. We confirm analytical results with computational simulations using general model networks and anatomical brain networks, as well as high-density electroencephalography collected from humans in the conscious and anesthetized states. Analytical, computational, and empirical results demonstrate that network nodes with more connections (i.e., higher degrees) have larger amplitudes and are directional targets (phase lag) rather than sources (phase lead). The relationship of node degree and directionality therefore appears to be a fundamental property of networks, with direct applicability to brain function. These results provide a foundation for a principled understanding of information transfer across networks and also demonstrate that changes in directionality patterns across states of human consciousness are driven by alterations of brain network topology. PMID:25874700

  2. Cost-effective 33-Gbps intensity modulation direct detection multi-band OFDM LR-PON system employing a 10-GHz-based transceiver

    NASA Astrophysics Data System (ADS)

    Hsu, Dar-Zu; Wei, Chia-Chien; Chen, Hsing-Yu; Li, Wei-Yuan; Chen, Jyehong

    2011-08-01

    We develop a dynamic multi-band OFDM subcarrier allocation scheme to fully utilize the available bandwidth under the restriction of dispersion- and chirp-related power fading. The experimental results successfully demonstrate an intensity-modulation-direct-detection 34.78-Gbps OFDM signal transmissions over 100-km long-reach (LR) passive-optical networks (PONs) based on a cost-effective 10-GHz EAM and a 10-GHz PIN. Considering 0--100-km transmission bandwidth of a 10-GHz EAM, the narrowest bandwidth is theoretically evaluated to occur at ~40 km, instead of 100 km. Consequently, the performances of 20--100-km PONs are experimentally investigated, and at least 33-Gbps capacity is achieved to support LR-PONs of all possible 20--100-km radii.

  3. Inherent directionality explains the lack of feedback loops in empirical networks

    NASA Astrophysics Data System (ADS)

    Domínguez-García, Virginia; Pigolotti, Simone; Muñoz, Miguel A.

    2014-12-01

    We explore the hypothesis that the relative abundance of feedback loops in many empirical complex networks is severely reduced owing to the presence of an inherent global directionality. Aimed at quantifying this idea, we propose a simple probabilistic model in which a free parameter ? controls the degree of inherent directionality. Upon strengthening such directionality, the model predicts a drastic reduction in the fraction of loops which are also feedback loops. To test this prediction, we extensively enumerated loops and feedback loops in many empirical biological, ecological and socio-technological directed networks. We show that, in almost all cases, empirical networks have a much smaller fraction of feedback loops than network randomizations. Quite remarkably, this empirical finding is quantitatively reproduced, for all loop lengths, by our model by fitting its only parameter ?. Moreover, the fitted value of ? correlates quite well with another direct measurement of network directionality, performed by means of a novel algorithm. We conclude that the existence of an inherent network directionality provides a parsimonious quantitative explanation for the observed lack of feedback loops in empirical networks.

  4. Neural Networks 54 (2014) 1116 Contents lists available at ScienceDirect

    E-print Network

    Neumann, Heiko

    2014-01-01

    or gist information with the sensory data (Bullier, 2006). These feedforward and recurrent signals of such signal fusion, namely the combination of driv- ing and modulating input signals, might focus on different network circuit that replicates physiological data. This functionality can be successfully described

  5. Radial bias for orientation and direction of motion modulates access to visual awareness during continuous flash suppression.

    PubMed

    Hong, Sang Wook

    2015-01-01

    Two types of radial bias have been demonstrated in the primate visual cortex: for orientation and for direction of motion. Considering that a visual neuron's directional selectivity is generally perpendicular to its preferred orientation, it is counterintuitive that radial biases for orientation and direction of motion coexist in retinotopic cortex including primary visual cortex. The current study measured the influence of radial bias for orientation and direction of motion on the access to visual awareness during continuous flash suppression. Strength of static and moving target stimuli, inferred by time to breakup of suppression, was modulated by the orientation and motion direction of the suppressed target stimulus according to its spatial location, indicating radial biases for both orientation and motion direction. However, orientation dominated over direction of motion when they were perpendicular to each other. These results indicate that, first, orientation-specific neural responses may be stronger than direction-specific neural responses at the stage of visual processing where interocular suppression is resolved. Second, the preferential processing of both orientation and direction of motion may result from anisotropic distribution of orientation- and direction-selective cells. Third, the neural substrate of the radial direction bias may reflect an orientation-specific neural response induced by fast-moving random dot patterns. PMID:25572349

  6. Directed diffusion light: low overhead data dissemination in wireless sensor networks

    Microsoft Academic Search

    Alessia Marcucci; Michele Nati; Chiara Petrioli; Andrea Vitaletti

    2005-01-01

    In this paper we introduce directed diffusion light, a variant of the well-known protocol directed diffusion (DD), which results in significant savings in terms of exchanged control messages and energy consumption, and improvements in network lifetime. Directed diffusion light defines local rules to generate a sparse logical topology over which DD can be run. This decreases the costs associated to

  7. Seeking Structural Specificity: Direct Modulation of Pentameric Ligand-Gated Ion Channels by Alcohols and General Anesthetics

    PubMed Central

    Trudell, James R.; Harris, R. Adron

    2014-01-01

    Alcohols and other anesthetic agents dramatically alter neurologic function in a wide range of organisms, yet their molecular sites of action remain poorly characterized. Pentameric ligand-gated ion channels, long implicated in important direct effects of alcohol and anesthetic binding, have recently been illuminated in renewed detail thanks to the determination of atomic-resolution structures of several family members from lower organisms. These structures provide valuable models for understanding and developing anesthetic agents and for allosteric modulation in general. This review surveys progress in this field from function to structure and back again, outlining early evidence for relevant modulation of pentameric ligand-gated ion channels and the development of early structural models for ion channel function and modulation. We highlight insights and challenges provided by recent crystal structures and resulting simulations, as well as opportunities for translation of these newly detailed models back to behavior and therapy. PMID:24515646

  8. Direct search for global minimum in neural network

    NASA Astrophysics Data System (ADS)

    Toguchi, Katsuo; Shimizu, Toshihiro

    2000-06-01

    A new model of neural network is proposed and applied to the traveling salesman problem with 10 cities. It is shown that the network can find the shortest path in the ratio of 100% without being trapped in any local minima. The mechanism is investigated. .

  9. Direct Sequence Spread Spectrum Access to Local Area Networks

    Microsoft Academic Search

    C. T. Spracklen; C. Smythe

    1987-01-01

    The Electronics Research Groups of Aberdeen and Surrey Universities have for several years been involved in the development of local area networks (LAN's) specifically oriented towards the military communications environment.[l, 2, 3, 4]. In particular they have been responsible for development of the ASWE Serial Highway a token passing bus local area network currently employed in the Command and Control

  10. Goal-Directed Modulation of Neural Memory Patterns: Implications for fMRI-Based Memory Detection.

    PubMed

    Uncapher, Melina R; Boyd-Meredith, J Tyler; Chow, Tiffany E; Rissman, Jesse; Wagner, Anthony D

    2015-06-01

    Remembering a past event elicits distributed neural patterns that can be distinguished from patterns elicited when encountering novel information. These differing patterns can be decoded with relatively high diagnostic accuracy for individual memories using multivoxel pattern analysis (MVPA) of fMRI data. Brain-based memory detection-if valid and reliable-would have clear utility beyond the domain of cognitive neuroscience, in the realm of law, marketing, and beyond. However, a significant boundary condition on memory decoding validity may be the deployment of "countermeasures": strategies used to mask memory signals. Here we tested the vulnerability of fMRI-based memory detection to countermeasures, using a paradigm that bears resemblance to eyewitness identification. Participants were scanned while performing two tasks on previously studied and novel faces: (1) a standard recognition memory task; and (2) a task wherein they attempted to conceal their true memory state. Univariate analyses revealed that participants were able to strategically modulate neural responses, averaged across trials, in regions implicated in memory retrieval, including the hippocampus and angular gyrus. Moreover, regions associated with goal-directed shifts of attention and thought substitution supported memory concealment, and those associated with memory generation supported novelty concealment. Critically, whereas MVPA enabled reliable classification of memory states when participants reported memory truthfully, the ability to decode memory on individual trials was compromised, even reversing, during attempts to conceal memory. Together, these findings demonstrate that strategic goal states can be deployed to mask memory-related neural patterns and foil memory decoding technology, placing a significant boundary condition on their real-world utility. PMID:26041920

  11. Direct extraction of curvature-based metric shape from stereo by view-modulated receptive fields.

    PubMed

    Noest, A J; van Ee, R; van den Berg, A V

    2006-11-01

    Any computation of metric surface structure from horizontal disparities depends on the viewing geometry, and analysing this dependence allows us to narrow down the choice of viable schemes. For example, all depth-based or slant-based schemes (i.e. nearly all existing models) are found to be unrealistically sensitive to natural errors in vergence. Curvature-based schemes avoid these problems and require only moderate, more robust view-dependent corrections to yield local object shape, without any depth coding. This fits the fact that humans are strikingly insensitive to global depth but accurate in discriminating surface curvature. The latter also excludes coding only affine structure. In view of new adaptation results, our goal becomes to directly extract retinotopic fields of metric surface curvatures (i.e. avoiding intermediate disparity curvature). To find a robust neural realisation, we combine new exact analysis with basic neural and psychophysical constraints. Systematic, step-by-step 'design' leads to neural operators which employ a novel family of 'dynamic' receptive fields (RFs), tuned to specific (bi-)local disparity structure. The required RF family is dictated by the non-Euclidean geometry that we identify as inherent in cyclopean vision. The dynamic RF-subfield patterns are controlled via gain modulation by binocular vergence and version, and parameterised by a cell-specific tuning to slant. Our full characterisation of the neural operators invites a range of new neurophysiological tests. Regarding shape perception, the model inverts widely accepted interpretations: It predicts the various types of errors that have often been mistaken for evidence against metric shape extraction. PMID:16955316

  12. The 22-Year Hale Cycle in Cosmic Ray Flux - Evidence for Direct Heliospheric Modulation

    NASA Astrophysics Data System (ADS)

    Thomas, S. R.; Owens, M. J.; Lockwood, M.

    2014-01-01

    The ability to predict times of greater galactic cosmic ray (GCR) fluxes is important for reducing the hazards caused by these particles to satellite communications, aviation, or astronauts. The 11-year solar-cycle variation in cosmic rays is highly correlated with the strength of the heliospheric magnetic field. Differences in GCR flux during alternate solar cycles yield a 22-year cycle, known as the Hale Cycle, which is thought to be due to different particle drift patterns when the northern solar pole has predominantly positive (denoted as qA>0 cycle) or negative ( qA<0) polarities. This results in the onset of the peak cosmic-ray flux at Earth occurring earlier during qA>0 cycles than for qA<0 cycles, which in turn causes the peak to be more dome-shaped for qA>0 and more sharply peaked for qA<0. In this study, we demonstrate that properties of the large-scale heliospheric magnetic field are different during the declining phase of the qA<0 and qA>0 solar cycles, when the difference in GCR flux is most apparent. This suggests that particle drifts may not be the sole mechanism responsible for the Hale Cycle in GCR flux at Earth. However, we also demonstrate that these polarity-dependent heliospheric differences are evident during the space-age but are much less clear in earlier data: using geomagnetic reconstructions, we show that for the period of 1905 - 1965, alternate polarities do not give as significant a difference during the declining phase of the solar cycle. Thus we suggest that the 22-year cycle in cosmic-ray flux is at least partly the result of direct modulation by the heliospheric magnetic field and that this effect may be primarily limited to the grand solar maximum of the space-age.

  13. Multi-Dimensional Prioritization of Dental Caries Candidate Genes and Its Enriched Dense Network Modules

    PubMed Central

    Wang, Quan; Jia, Peilin; Cuenco, Karen T.; Feingold, Eleanor; Marazita, Mary L.; Wang, Lily; Zhao, Zhongming

    2013-01-01

    A number of genetic studies have suggested numerous susceptibility genes for dental caries over the past decade with few definite conclusions. The rapid accumulation of relevant information, along with the complex architecture of the disease, provides a challenging but also unique opportunity to review and integrate the heterogeneous data for follow-up validation and exploration. In this study, we collected and curated candidate genes from four major categories: association studies, linkage scans, gene expression analyses, and literature mining. Candidate genes were prioritized according to the magnitude of evidence related to dental caries. We then searched for dense modules enriched with the prioritized candidate genes through their protein-protein interactions (PPIs). We identified 23 modules comprising of 53 genes. Functional analyses of these 53 genes revealed three major clusters: cytokine network relevant genes, matrix metalloproteinases (MMPs) family, and transforming growth factor-beta (TGF-?) family, all of which have been previously implicated to play important roles in tooth development and carious lesions. Through our extensive data collection and an integrative application of gene prioritization and PPI network analyses, we built a dental caries-specific sub-network for the first time. Our study provided insights into the molecular mechanisms underlying dental caries. The framework we proposed in this work can be applied to other complex diseases. PMID:24146904

  14. Network modulation by the subthalamic nucleus in the treatment of Parkinson’s disease

    PubMed Central

    Trošt, Maja; Su, Sherwin; Su, Philip; Yen, Ruoh-Fang; Tseng, Ham-Min; Barnes, Anna; Ma, Yilong; Eidelberg, David

    2015-01-01

    Deep brain stimulation of the subthalamic nucleus (STN DBS) has become an accepted tool for the treatment of Parkinson’s disease (PD). Although the precise mechanism of action of this intervention is unknown, its effectiveness has been attributed to the modulation of pathological network activity. We examined this notion using positron emission tomography (PET) to quantify stimulation-induced changes in the expression of a PD-related covariance pattern (PDRP) of regional metabolism. These metabolic changes were also compared with those observed in a similar cohort of patients undergoing STN lesioning. We found that PDRP activity declined significantly (P < 0.02) with STN stimulation. The degree of network modulation with DBS did not differ from that measured following lesioning (P = 0.58). Statistical parametric mapping (SPM) revealed that metabolic reductions in the internal globus pallidus (GPi) and caudal midbrain were common to both STN interventions (P < 0.01), although declines in GPi were more pronounced with lesion. By contrast, elevations in posterior parietal metabolism were common to the two procedures, albeit more pronounced with stimulation. These findings indicate that suppression of abnormal network activity is a feature of both STN stimulation and lesioning. Nonetheless, these two interventions may differ metabolically at a regional level. PMID:16466936

  15. Comparison of Gene Coexpression Profiles and Construction of Conserved Gene Networks to Find Functional Modules

    PubMed Central

    Okamura, Yasunobu; Obayashi, Takeshi; Kinoshita, Kengo

    2015-01-01

    Background Computational approaches toward gene annotation are a formidable challenge, now that many genome sequences have been determined. Each gene has its own function, but complicated cellular functions are achieved by sets of genes. Therefore, sets of genes with strong functional relationships must be identified. For this purpose, the similarities of gene expression patterns and gene sequences have been separately utilized, although the combined information will provide a better solution. Result & Discussion We propose a new method to find functional modules, by comparing gene coexpression profiles among species. A coexpression pattern is represented as a list of coexpressed genes with each guide gene. We compared two coexpression lists, one from a human guide gene and the other from a homologous mouse gene, and defined a measure to evaluate the similarity between the lists. Based on this coexpression similarity, we detected the highly conserved genes, and constructed human gene networks with conserved coexpression between human and mouse. Some of the tightly coupled genes (modules) showed clear functional enrichment, such as immune system and cell cycle, indicating that our method could identify functionally related genes without any prior knowledge. We also found a few functional modules without any annotations, which may be good candidates for novel functional modules. All of the comparisons are available at the http://v1.coxsimdb.info web database. PMID:26147120

  16. Plastic modulation of PTSD resting-state networks by EEG neurofeedback

    PubMed Central

    Kluetsch, Rosemarie C.; Ros, Tomas; Théberge, Jean; Frewen, Paul A.; Calhoun, Vince D.; Schmahl, Christian; Jetly, Rakesh; Lanius, Ruth A.

    2015-01-01

    Objective Electroencephalographic (EEG) neurofeedback training has been shown to produce plastic modulations in salience network and default mode network functional connectivity in healthy individuals. In this study, we investigated whether a single session of neurofeedback training aimed at the voluntary reduction of alpha rhythm (8–12 Hz) amplitude would be related to differences in EEG network oscillations, functional MRI (fMRI) connectivity, and subjective measures of state anxiety and arousal in a group of individuals with PTSD. Method 21 individuals with PTSD related to childhood abuse underwent 30 minutes of EEG neurofeedback training preceded and followed by a resting-state fMRI scan. Results Alpha desynchronizing neurofeedback was associated with decreased alpha amplitude during training, followed by a significant increase (‘rebound’) in resting-state alpha synchronization. This rebound was linked to increased calmness, greater salience network connectivity with the right insula, and enhanced default mode network connectivity with bilateral posterior cingulate, right middle frontal gyrus, and left medial prefrontal cortex. Conclusion Our study represents a first step in elucidating the potential neurobehavioral mechanisms mediating the effects of neurofeedback treatment on regulatory systems in PTSD. Moreover, it documents for the first time a spontaneous EEG ‘rebound’ after neurofeedback, pointing to homeostatic/compensatory mechanisms operating in the brain. PMID:24266644

  17. Serotonin in the modulation of neural plasticity and networks: implications for neurodevelopmental disorders.

    PubMed

    Lesch, Klaus-Peter; Waider, Jonas

    2012-10-01

    Serotonin (5-HT) shapes brain networks during development and modulates a wide spectrum of essential neuronal functions ranging from perception and cognitive appraisal to emotional responses in the mature brain. Deficits in 5-HT-moderated synaptic signaling fundamentally impact the pathophysiology and long-term outcome of neurodevelopmental disorders. Our understanding of how 5-HT-dependent modulation of circuit configuration influences social cognition and emotional learning has been enhanced by recent insight into the molecular and cellular mechanisms of synapse formation and plasticity. In this review, we discuss emerging concepts as to how defects in synaptic plasticity impact our biosocial brain and how recent findings regarding 5-HT's role in brain development and function provide insight into the cellular and physiological basis of neurodevelopmental disorders. PMID:23040814

  18. The irregular firing properties of thalamic head direction cells mediate turn-specific modulation of the directional tuning curve.

    PubMed

    Tsanov, Marian; Chah, Ehsan; Noor, Muhammad S; Egan, Catriona; Reilly, Richard B; Aggleton, John P; Erichsen, Jonathan T; Vann, Seralynne D; O'Mara, Shane M

    2014-11-01

    Head direction cells encode an animal's heading in the horizontal plane. However, it is not clear why the directionality of a cell's mean firing rate differs for clockwise, compared with counterclockwise, head turns (this difference is known as the "separation angle") in anterior thalamus. Here we investigated in freely behaving rats whether intrinsic neuronal firing properties are linked to this phenomenon. We found a positive correlation between the separation angle and the spiking variability of thalamic head direction cells. To test whether this link is driven by hyperpolarization-inducing currents, we investigated the effect of thalamic reticular inhibition during high-voltage spindles on directional spiking. While the selective directional firing of thalamic neurons was preserved, we found no evidence for entrainment of thalamic head direction cells by high-voltage spindle oscillations. We then examined the role of depolarization-inducing currents in the formation of separation angle. Using a single-compartment Hodgkin-Huxley model, we show that modeled neurons fire with higher frequencies during the ascending phase of sinusoidal current injection (mimicking the head direction tuning curve) when simulated with higher high-threshold calcium channel conductance. These findings demonstrate that the turn-specific encoding of directional signal strongly depends on the ability of thalamic neurons to fire irregularly in response to sinusoidal excitatory activation. Another crucial factor for inducing phase lead to sinusoidal current injection was the presence of spike-frequency adaptation current in the modeled neurons. Our data support a model in which intrinsic biophysical properties of thalamic neurons mediate the physiological encoding of directional information. PMID:25122712

  19. A novel prediction methodology for detecting failures and instabilities in directional wireless networks

    NASA Astrophysics Data System (ADS)

    Coleman, David M.; Milner, Stuart D.; Davis, Christopher C.

    2012-10-01

    Even though advances in wireless technology have yielded lower power consumption, higher data rates, and numerous other improvements, the ability to develop a proactive strategy towards handling degradations and failures in directional wireless networks has evaded the research community. In this paper, we introduce a methodology using an analogy to molecular systems in which a directional wireless network utilizing free space optical (FSO) or RF links is modeled as a molecule whose links can grow/retract similarly to bonds. A normal mode analysis (NMA) is performed to identify link instabilities (degradations and failures) and an N-dimensional potential energy surface (PES) is derived with respect to network and environmental parameters to aide in the detection of when a new topology is available ahead of the topology computation stage. Together, the NMA and PES form a basis for a proactive network methodology aimed at improving performance in directional wireless networks.

  20. Posterior Association Networks and Functional Modules Inferred from Rich Phenotypes of Gene Perturbations

    PubMed Central

    Wang, Xin; Castro, Mauro A.

    2012-01-01

    Combinatorial gene perturbations provide rich information for a systematic exploration of genetic interactions. Despite successful applications to bacteria and yeast, the scalability of this approach remains a major challenge for higher organisms such as humans. Here, we report a novel experimental and computational framework to efficiently address this challenge by limiting the ‘search space’ for important genetic interactions. We propose to integrate rich phenotypes of multiple single gene perturbations to robustly predict functional modules, which can subsequently be subjected to further experimental investigations such as combinatorial gene silencing. We present posterior association networks (PANs) to predict functional interactions between genes estimated using a Bayesian mixture modelling approach. The major advantage of this approach over conventional hypothesis tests is that prior knowledge can be incorporated to enhance predictive power. We demonstrate in a simulation study and on biological data, that integrating complementary information greatly improves prediction accuracy. To search for significant modules, we perform hierarchical clustering with multiscale bootstrap resampling. We demonstrate the power of the proposed methodologies in applications to Ewing's sarcoma and human adult stem cells using publicly available and custom generated data, respectively. In the former application, we identify a gene module including many confirmed and highly promising therapeutic targets. Genes in the module are also significantly overrepresented in signalling pathways that are known to be critical for proliferation of Ewing's sarcoma cells. In the latter application, we predict a functional network of chromatin factors controlling epidermal stem cell fate. Further examinations using ChIP-seq, ChIP-qPCR and RT-qPCR reveal that the basis of their genetic interactions may arise from transcriptional cross regulation. A Bioconductor package implementing PAN is freely available online at http://bioconductor.org/packages/release/bioc/html/PANR.html. PMID:22761558

  1. Improved sequence learning with subthalamic nucleus deep brain stimulation: evidence for treatment-specific network modulation.

    PubMed

    Mure, Hideo; Tang, Chris C; Argyelan, Miklos; Ghilardi, Maria-Felice; Kaplitt, Michael G; Dhawan, Vijay; Eidelberg, David

    2012-02-22

    We used a network approach to study the effects of anti-parkinsonian treatment on motor sequence learning in humans. Eight Parkinson's disease (PD) patients with bilateral subthalamic nucleus (STN) deep brain stimulation underwent H(2)(15)O positron emission tomography (PET) imaging to measure regional cerebral blood flow (rCBF) while they performed kinematically matched sequence learning and movement tasks at baseline and during stimulation. Network analysis revealed a significant learning-related spatial covariance pattern characterized by consistent increases in subject expression during stimulation (p = 0.008, permutation test). The network was associated with increased activity in the lateral cerebellum, dorsal premotor cortex, and parahippocampal gyrus, with covarying reductions in the supplementary motor area (SMA) and orbitofrontal cortex. Stimulation-mediated increases in network activity correlated with concurrent improvement in learning performance (p < 0.02). To determine whether similar changes occurred during dopaminergic pharmacotherapy, we studied the subjects during an intravenous levodopa infusion titrated to achieve a motor response equivalent to stimulation. Despite consistent improvement in motor ratings during infusion, levodopa did not alter learning performance or network activity. Analysis of learning-related rCBF in network regions revealed improvement in baseline abnormalities with STN stimulation but not levodopa. These effects were most pronounced in the SMA. In this region, a consistent rCBF response to stimulation was observed across subjects and trials (p = 0.01), although the levodopa response was not significant. These findings link the cognitive treatment response in PD to changes in the activity of a specific cerebello-premotor cortical network. Selective modulation of overactive SMA-STN projection pathways may underlie the improvement in learning found with stimulation. PMID:22357863

  2. Nyquist-shaped dispersion-precompensated subcarrier modulation with direct detection for spectrally-efficient WDM transmission.

    PubMed

    Erk?l?nç, M S; Kilmurray, S; Maher, R; Paskov, M; Bouziane, R; Pachnicke, S; Griesser, H; Thomsen, B C; Bayvel, P; Killey, R I

    2014-04-21

    The use of single-sideband subcarrier modulation (SCM) with Nyquist (N) pulse shaping for cost-effective spectrally-efficient wavelength division multiplexed transmission with direct detection is described. Transmission of digitally pre-compensated 7 × 11 GHz-spaced QPSK SCM channels at 14 Gb/s per channel is experimentally demonstrated over distances of up to 800 km of uncompensated standard single-mode fiber (SSMF) (13440 ps/nm chromatic dispersion). PMID:24787831

  3. Modulation of emotions associated with images of human pain using anodal transcranial direct current stimulation (tDCS)

    Microsoft Academic Search

    Paulo S. Boggio; Soroush Zaghi; Felipe Fregni

    2009-01-01

    Viewing images of other humans in pain elicits a variety of responses including distress, anxiety, and a sensation that is similar to pain. We aimed to evaluate whether transcranial direct current stimulation (tDCS) could be effective in modulating the emotional aspects of pain as to further explore mechanisms of tDCS in pain relief. Twenty-three healthy subjects rated images with respect

  4. Returnability in complex directed networks (digraphs) Ernesto Estrada1*

    E-print Network

    Mottram, Nigel

    are unidirectional [6-8]. In ecological food webs, some species predate others in a unidirectional way [9.E.) to account for the participation of a node in all subgraphs of the network, giving higher weights

  5. Robotic localization of hostile networked radio sources with a directional antenna 

    E-print Network

    Hu, Qiang

    2007-04-25

    propose a scheme to localize hostile networked radio sources based on the radio signal strength and communication protocol pattern analysis using a mobile robot with a directional antenna. We integrate a Particle Filter algorithm with a new sensing model...

  6. NRC TLD Direct Radiation Monitoring Network. Progress report, July--September 1993: Volume 13, No. 3

    SciTech Connect

    Struckmeyer, R.

    1993-11-01

    This report provides the status and results of the NRC Thermoluminescent Dosimeter (TLD) Direct Radiation Monitoring Network. It presents the radiation levels measured in the vicinity of NRC licensed facilities throughout the country for the third quarter of 1993.

  7. Direct comparison of Neural Network, Fuzzy Logic and Model Prediction Variable Structure vortex flow controllers

    E-print Network

    Joshi, Praveen Sudhakar

    1999-01-01

    given quadratic performance index. This performance index allows the designer to specify appropriate weights for states and control effectors to satisfy given specifications. The Neural Network Controller is directly compared to previously designed Model...

  8. Joint Routing and Scheduling in Multi-hop Wireless Networks with Directional Antennas

    Microsoft Academic Search

    Partha Dutta; Vivek Mhatre; Debmalya Panigrahi; Rajeev Rastogi

    2010-01-01

    Abstract—Long-distance multi-hop wireless networks have been used in recent years to provide connectivity to rural areas. The salient features of such networks include TDMA channel access, nodes with multiple radios, and point-to-point long- distance wireless links established using high-gain directional antennas mounted on high towers. It has been demonstrated previously that in such network architectures, nodes can transmit concurrently on

  9. Throughput enhancement of direct-sequence spread-spectrum packet radio networks by adaptive power control

    Microsoft Academic Search

    Asrar Sheikh; Yu-Dong Yao; Shixin Clneng

    1994-01-01

    Investigates the performance of direct-sequence spread-spectrum packet radio networks in the presence of the near\\/far problem. It is found that the maximum throughput of the network suffers degradation due to the near\\/far problem. However, analysis also shows that, under high traffic conditions, a network with the near\\/far problem delivers higher throughput than another without the near\\/far problem. This suggests that

  10. Wideband direct conversion hybrid LCP millimeter-wave 4× subharmonic mixer for gigabit wireless module

    Microsoft Academic Search

    S. Sarkar; D. Yeh; S. Pinel; J. Laskar

    2005-01-01

    In this paper, we describe the realization of highly integrated system-on-package (SOP) millimeter wave module on liquid crystal polymer (LCP). LCP provides an organic, low-cost, low dielectric constant platform suitable for mm-wave passive design and packaging. Here we firstly demonstrate 40GHz planar bandpass filter and RF\\/baseband duplexer as building blocks of the integrated module. ?3dB insertion loss and >6GHz RF

  11. Low-drift giant magnetoresistive field sensor using modulation of free-layer magnetization direction

    Microsoft Academic Search

    G. A. Wang; S. Arai; T. Kato; S. Iwata

    2011-01-01

    We report a field sensor, which senses the external field by detecting the change of frequency component in the modulated GMR output. The proposed sensor works in a closed-loop mode with negative feedback and the free-layer magnetization is modulated by an alternative field Hac (2.3 Oe). The sensor output (Vout) is proportional to the applied external field (Hex) in the

  12. Directional MAC approach for wireless body area networks.

    PubMed

    Hussain, Md Asdaque; Alam, Md Nasre; Kwak, Kyung Sup

    2011-01-01

    Wireless Body Area Networks (WBANs) designed for medical, sports, and entertainment applications, have drawn the attention of academia and industry alike. A WBAN is a special purpose network, designed to operate autonomously to connect various medical sensors and appliances, located inside and/or outside of a human body. This network enables physicians to remotely monitor vital signs of patients and provide real time feedback for medical diagnosis and consultations. The WBAN system can offer two significant advantages: patient mobility due to their use of portable monitoring devices and a location independent monitoring facility. With its appealing dimensions, it brings about a new set of challenges, which we do not normally consider in such small sensor networks. It requires a scalable network in terms of heterogeneous data traffic, low power consumption of sensor nodes, integration in and around the body networking and coexistence. This work presents a medium access control protocol for WBAN which tries to overcome the aforementioned challenges. We consider the use of multiple beam adaptive arrays (MBAA) at BAN Coordinator (BAN_C) node. When used as a BAN_C, an MBAA can successfully receive two or more overlapping packets at the same time. Each beam captures a different packet by automatically pointing its pattern toward one packet while annulling other contending packets. This paper describes how an MBAA can be integrated into a single hope star topology as a BAN_C. Simulation results show the performance of our proposed protocol. PMID:22346602

  13. On the Planning Problem of Wireless Local Area Networks with Directional Antennas

    Microsoft Academic Search

    Marc-olivier Ouellet; Steven Chamberland; Philippe Galinier

    2008-01-01

    Wireless local area networks (WLANs) are more deployed today than ever before. However, this rapid growth led to uncoordinated deployment and planning tools are rarely used. In this paper, we first propose a mathematical model to solve the WLAN planning problem considering directional antennas. The problem consists of selecting the location of the access points in the network and selecting

  14. Interference-Aware Routing in Multihop Wireless Networks using Directional Antennas

    E-print Network

    Tang, Jian "Neil"

    Interference-Aware Routing in Multihop Wireless Networks using Directional Antennas Jian Tang-- Recent research has shown that interference can make a significant impact on the performance of multihop wireless networks. Researchers have studied interference-aware topology control recently [1]. In this paper

  15. Interference modeling in a direct-sequence spread-spectrum packet radio network

    Microsoft Academic Search

    Elvino S. Sousa

    1990-01-01

    A technique for characterizing multiuser interference and background noise in a direct-sequence spread-spectrum network is introduced, and packet error probabilities are calculated. The multiuser interference over a packet in the network is modeled as a compound Gaussian multivariate random variable for moderate to large values of the processing gain. The conditional variance is dependent on the number of users and

  16. An Efficient Localization Based on Directional Antenna for Wireless Sensor Networks (WSN's)

    Microsoft Academic Search

    Dileep Kumar; Shirshu Varma

    2009-01-01

    In this paper we have introduced an algorithm for localization in wireless sensor network (WSN) with the help of directional antenna. Location of each node in a wireless sensor network play an important role after tracing or event detection on a particular node. Manually configuration of location about each node in wireless sensor environment is not feasible at the time

  17. Performance of the Direct Binary n-Cube Network for Multiprocessors

    Microsoft Academic Search

    Seth Abraham; Krishnan Padmanabhan

    1989-01-01

    A mathematical model for predicting the performance of the direct binary n-cube interconnection scheme is presented. These predictions are checked against simulations of a comparable system. The results for the network are compared to known results for indirect interconnection schemes like the crossbar and indirect n-cube networks. Special operation conditions such as broadcasts and hot spots are considered. The following

  18. A new method to measure directional modulation transfer function using sphere phantoms in a cone beam computed tomography system.

    PubMed

    Lee, Changwoo; Baek, Jongduk

    2015-04-01

    We propose a new method to measure directional modulation transfer function (MTF) using sphere phantoms in a cone beam computed tomography (CBCT) system. To measure spatially varying 3-D MTFs, we model FDK reconstruction in local regions and calculate the plane integrals of an ideal sphere phantom and reconstructed sphere phantoms. Then, we modify the Richardson-Lucy (RL) deconvolution method to relax the non-negativity constraint in RL deconvolution and apply it to estimate the directional plane spread functions (PlSFs). Directional MTFs are calculated by taking the modulus of the Fourier transform of the estimated directional PlSFs. To validate the proposed method, we simulate ideal 3-D MTFs and compare them with directional MTFs measured by simulation and experimental data along three major axes. For quantitative evaluation, we compare full-width at half-maximum (FWHM) and full-width at tenth-maximum (FWTM) of measured and ideal directional MTFs. The measured directional MTFs from simulation and experimental data show excellent agreement with the ideal directional MTFs, demonstrating the effectiveness of the proposed method to estimate directional MTFs in a CBCT system. PMID:25398176

  19. Rapid and Continuous Modulation of Hippocampal Network State during Exploration of New Places

    PubMed Central

    Karlsson, Mattias P.; Frank, Loren M.

    2013-01-01

    Hippocampal information processing is often described as two-state, with a place cell state during movement and a reactivation state during stillness. Relatively little is known about how the network transitions between these different patterns of activity during exploration. Here we show that hippocampal network changes quickly and continuously as animals explore and become familiar with initially novel places. We measured the relationship between moment-by-moment changes in behavior and information flow through hippocampal output area CA1 in rats. We examined local field potential (LFP) patterns, evoked potentials and ensemble spiking and found evidence suggestive of a smooth transition from strong CA3 drive of CA1 activity at low speeds to entorhinal cortical drive of CA1 activity at higher speeds. These changes occurred with changes in behavior on a timescale of less than a second, suggesting a continuous modulation of information processing in the hippocampal circuit as a function of behavioral state. PMID:24023818

  20. Allosteric modulation of Ras positions Q61 for a direct role in catalysis

    SciTech Connect

    Buhrman, Greg; Holzapfel, Genevieve; Fetics, Susan; Mattos, Carla (NCSU)

    2010-11-03

    Ras and its effector Raf are key mediators of the Ras/Raf/MEK/ERK signal transduction pathway. Mutants of residue Q61 impair the GTPase activity of Ras and are found prominently in human cancers. Yet the mechanism through which Q61 contributes to catalysis has been elusive. It is thought to position the catalytic water molecule for nucleophilic attack on the {gamma}-phosphate of GTP. However, we previously solved the structure of Ras from crystals with symmetry of the space group R32 in which switch II is disordered and found that the catalytic water molecule is present. Here we present a structure of wild-type Ras with calcium acetate from the crystallization mother liquor bound at a site remote from the active site and likely near the membrane. This results in a shift in helix 3/loop 7 and a network of H-bonding interactions that propagates across the molecule, culminating in the ordering of switch II and placement of Q61 in the active site in a previously unobserved conformation. This structure suggests a direct catalytic role for Q61 where it interacts with a water molecule that bridges one of the {gamma}-phosphate oxygen atoms to the hydroxyl group of Y32 to stabilize the transition state of the hydrolysis reaction. We propose that Raf together with the binding of Ca{sup 2+} and a negatively charged group mimicked in our structure by the acetate molecule induces the ordering of switch I and switch II to complete the active site of Ras.

  1. Eye'm talking to you: speakers' gaze direction modulates co-speech gesture processing in the right MTG.

    PubMed

    Holler, Judith; Kokal, Idil; Toni, Ivan; Hagoort, Peter; Kelly, Spencer D; Özyürek, Asl?

    2015-02-01

    Recipients process information from speech and co-speech gestures, but it is currently unknown how this processing is influenced by the presence of other important social cues, especially gaze direction, a marker of communicative intent. Such cues may modulate neural activity in regions associated either with the processing of ostensive cues, such as eye gaze, or with the processing of semantic information, provided by speech and gesture. Participants were scanned (fMRI) while taking part in triadic communication involving two recipients and a speaker. The speaker uttered sentences that were and were not accompanied by complementary iconic gestures. Crucially, the speaker alternated her gaze direction, thus creating two recipient roles: addressed (direct gaze) vs unaddressed (averted gaze) recipient. The comprehension of Speech&Gesture relative to SpeechOnly utterances recruited middle occipital, middle temporal and inferior frontal gyri, bilaterally. The calcarine sulcus and posterior cingulate cortex were sensitive to differences between direct and averted gaze. Most importantly, Speech&Gesture utterances, but not SpeechOnly utterances, produced additional activity in the right middle temporal gyrus when participants were addressed. Marking communicative intent with gaze direction modulates the processing of speech-gesture utterances in cerebral areas typically associated with the semantic processing of multi-modal communicative acts. PMID:24652857

  2. Multiple monoaminergic modulation of posturo-locomotor network activity in the newborn rat spinal cord

    PubMed Central

    Beliez, Lauriane; Barrière, Gregory; Bertrand, Sandrine S.; Cazalets, Jean-René

    2014-01-01

    Studies devoted to understanding locomotor control have mainly addressed the functioning of the neural circuits controlling leg movements and relatively little is known of the operation of networks that activate trunk muscles in coordination with limb movements. The aim of the present work was (1) to identify the exogenous neurotransmitter cocktail that most strongly activates postural thoracic circuitry; (2) to investigate how the biogenic amines serotonin (5-HT), dopamine (DA), and noradrenaline (NA) modulate the coordination between limb and axial motor networks. Experiments were carried out on in vitro isolated spinal cord preparations from newborn rats. We recorded from ventral roots to monitor hindlimb locomotor and axial postural network activity. Each combination of the three amines with excitatory amino acids (EAAs) elicited coordinated rhythmic motor activity at all segmental levels with specific characteristics. The variability in cycle period was similar with 5-HT and DA while it was significantly higher with NA. DA elicited motor bursts of smaller amplitude in thoracic segments compared to 5-HT and NA, while both DA and NA elicited motor bursts of higher amplitude than 5-HT in the lumbar and sacral segments. The amines modulated the phase relationships of bursts in various segments with respect to the reference lumbar segment. At the thoracic level there was a phase lag between all recorded segments in the presence of 5-HT, while DA and NA elicited synchronous bursting. At the sacral level, 5-HT and DA induced an intersegmental phase shift while relationships became phase-locked with NA. Various combinations of EAAs with two or even all three amines elicited rhythmic motor output that was more variable than with one amine alone. Our results provide new data on the coordinating processes between spinal cord networks, demonstrating that each amine has a characteristic “signature” regarding its specific effect on intersegmental phase relationships. PMID:25177275

  3. Coherent site-directed transport in complex molecular networks: An effective Hamiltonian approach

    NASA Astrophysics Data System (ADS)

    Weissman, Shira; Peskin, Uri

    2010-03-01

    Defining the conditions for coherent site-directed transport from an electron donor to a specific acceptor through tunneling barriers in a network of multiple donor/acceptors sites is an important step toward controlling electronic processes in molecular networks. The required analysis is most challenging since the entire network in essentially involved in coherent transport. In this work we introduce an efficient approach for formulating an effective donor/acceptor coupling in terms of the entire network parameters. The approach is based on implementation of Feshbach projection operators to map the entire network Hamiltonian onto a subspace defined by two specific donor and acceptor sites. This nonperturbative approach enables to define regimes of network parameters in which the effective donor-acceptor coupling is optimal. This is demonstrated numerically for simple models of molecular networks.

  4. Pre-stimulus BOLD-network activation modulates EEG spectral activity during working memory retention

    PubMed Central

    Kottlow, Mara; Schlaepfer, Anthony; Baenninger, Anja; Michels, Lars; Brandeis, Daniel; Koenig, Thomas

    2015-01-01

    Working memory (WM) processes depend on our momentary mental state and therefore exhibit considerable fluctuations. Here, we investigate the interplay of task-preparatory and task-related brain activity as represented by pre-stimulus BOLD-fluctuations and spectral EEG from the retention periods of a visual WM task. Visual WM is used to maintain sensory information in the brain enabling the performance of cognitive operations and is associated with mental health. We tested 22 subjects simultaneously with EEG and fMRI while performing a visuo-verbal Sternberg task with two different loads, allowing for the temporal separation of preparation, encoding, retention and retrieval periods. Four temporally coherent networks (TCNs)—the default mode network (DMN), the dorsal attention, the right and the left WM network—were extracted from the continuous BOLD data by means of a group ICA. Subsequently, the modulatory effect of these networks' pre-stimulus activation upon retention-related EEG activity in the theta, alpha, and beta frequencies was analyzed. The obtained results are informative in the context of state-dependent information processing. We were able to replicate two well-known load-dependent effects: the frontal-midline theta increase during the task and the decrease of pre-stimulus DMN activity. As our main finding, these two measures seem to depend on each other as the significant negative correlations at frontal-midline channels suggested. Thus, suppressed pre-stimulus DMN levels facilitated later task related frontal midline theta increases. In general, based on previous findings that neuronal coupling in different frequency bands may underlie distinct functions in WM retention, our results suggest that processes reflected by spectral oscillations during retention seem not only to be “online” synchronized with activity in different attention-related networks but are also modulated by activity in these networks during preparation intervals. PMID:25999828

  5. Directed clustering coefficient as a measure of systemic risk in complex banking networks

    NASA Astrophysics Data System (ADS)

    Tabak, Benjamin M.; Takami, Marcelo; Rocha, Jadson M. C.; Cajueiro, Daniel O.; Souza, Sergio R. S.

    2014-01-01

    Recent literature has focused on the study of systemic risk in complex networks. It is clear now, after the crisis of 2008, that the aggregate behavior of the interaction among agents is not straightforward and it is very difficult to predict. Contributing to this debate, this paper shows that the directed clustering coefficient may be used as a measure of systemic risk in complex networks. Furthermore, using data from the Brazilian interbank network, we show that the directed clustering coefficient is negatively correlated with domestic interest rates.

  6. Phospho-?Np63?/microRNA network modulates epigenetic regulatory enzymes in squamous cell carcinomas

    PubMed Central

    Ratovitski, Edward A

    2014-01-01

    The tumor protein (TP) p63/microRNAs functional network may play a key role in supporting the response of squamous cell carcinomas (SCC) to chemotherapy. We show that the cisplatin exposure of SCC-11 cells led to upregulation of miR-297, miR-92b-3p, and miR-485-5p through a phosphorylated ?Np63?-dependent mechanism that subsequently modulated the expression of the protein targets implicated in DNA methylation (DNMT3A), histone deacetylation (HDAC9), and demethylation (KDM4C). Further studies showed that mimics for miR-297, miR-92b-3p, or miR-485-5p, along with siRNA against and inhibitors of DNMT3A, HDAC9, and KDM4C modulated the expression of DAPK1, SMARCA2, and MDM2 genes assessed by the quantitative PCR, promoter luciferase reporter, and chromatin immunoprecipitation assays. Finally, the above-mentioned treatments affecting epigenetic enzymes also modulated the response of SCC cells to chemotherapeutic drugs, rendering the resistant SCC cells more sensitive to cisplatin exposure, thereby providing the groundwork for novel chemotherapeutic venues in treating patients with SCC. PMID:24394434

  7. Intensity-modulated radiation therapy in gynecologic malignancies: current status and future directions.

    PubMed

    Kochanski, Joel D; Mell, Loren K; Roeske, John C; Mundt, Arno J

    2006-05-01

    Radiation therapy is used as either definitive or adjuvant therapy following surgery in many gynecologic malignancies. Though effective, radiation therapy is limited by the adverse sequelae that result from normal tissues receiving external-beam radiation. A novel approach, intensity-modulated radiation therapy, can overcome these limitations by sparing the tissue surrounding the malignancy through conforming the dose to the shape of the target in three dimensions. This review provides an overview of current use, published research, and ongoing studies of intensity-modulated radiation therapy. PMID:16728946

  8. Implementing direct, spatially isolated problems on transputer networks

    NASA Technical Reports Server (NTRS)

    Ellis, Graham K.

    1988-01-01

    Parametric studies were performed on transputer networks of up to 40 processors to determine how to implement and maximize the performance of the solution of problems where no processor-to-processor data transfer is required for the problem solution (spatially isolated). Two types of problems are investigated a computationally intensive problem where the solution required the transmission of 160 bytes of data through the parallel network, and a communication intensive example that required the transmission of 3 Mbytes of data through the network. This data consists of solutions being sent back to the host processor and not intermediate results for another processor to work on. Studies were performed on both integer and floating-point transputers. The latter features an on-chip floating-point math unit and offers approximately an order of magnitude performance increase over the integer transputer on real valued computations. The results indicate that a minimum amount of work is required on each node per communication to achieve high network speedups (efficiencies). The floating-point processor requires approximately an order of magnitude more work per communication than the integer processor because of the floating-point unit's increased computing capacity.

  9. Proximal Interactions: A Direct Manipulation Technique for Wireless Networking

    Microsoft Academic Search

    Jun Rekimoto; Yuji Ayatsuka; Michimune Kohno; Haruo Oba

    2003-01-01

    As a number of networked digital devices are ubiquitously used, control of inter-device communications becomes a complicated task. People can no longer keep track of all the devices' addresses and name. Some devices (such as wireless headsets) have very limited information display capability, making it difficult to use normal GUI techniques (such as menu selection). This paper proposes a solution

  10. Combating persistent adversaries in wireless sensor networks using directional antennas

    Microsoft Academic Search

    Eliana Stavrou; Andreas Pitsillides

    2011-01-01

    Security is an important property in applications offering services in mission-critical areas, such as in healthcare, military, transportation, etc. Wireless sensor networks (WSN) support the mission of these applications by monitoring the environment and reporting observations to appropriate authorities that are responsible for decision-making. Often, their operation can be at risk by adversaries that launch attacks against the WSN with

  11. Computing with Snakes in Directed Networks of Automata

    Microsoft Academic Search

    Shimon Even; Ami Litman; Peter Winkler

    1997-01-01

    ABSTRACT We consider unidirectional, strongly connected networks of identical finite - state automata, of bounded in - and out - degree but unknown topology and unbounded size n Protocols which are quadratic or linear in n are provided which accomplish the following tasks: wake - up and report when done; construct spanning trees out from the root and in to

  12. Building rural wireless networks: lessons learnt and future directions

    Microsoft Academic Search

    David Lloyd Johnson; Kobus Roux

    2008-01-01

    Providing connectivity to rural areas comes with a unique set of challenges and are currently under-serviced due to the high cost of installing equipment, lack of reliable power, skill shortages and high cost of providing Internet connectivity which is mostly satellite based. The recent emergence of low- cost commodity wireless 802.11 devices and the use of mesh networking as a

  13. Molecular inspired models for prediction and control of directional FSO/RF wireless networks

    NASA Astrophysics Data System (ADS)

    Llorca, Jaime; Milner, Stuart D.; Davis, Christopher C.

    2010-08-01

    Directional wireless networks using FSO and RF transmissions provide wireless backbone support for mobile communications in dynamic environments. The heterogeneous and dynamic nature of such networks challenges their robustness and requires self-organization mechanisms to assure end-to-end broadband connectivity. We developed a framework based on the definition of a potential energy function to characterize robustness in communication networks and the study of first and second order variations of the potential energy to provide prediction and control strategies for network performance optimization. In this paper, we present non-convex molecular potentials such as the Morse Potential, used to describe the potential energy of bonds within molecules, for the characterization of communication links in the presence of physical constraints such as the power available at the network nodes. The inclusion of the Morse Potential translates into adaptive control strategies where forces on network nodes drive the release, retention or reconfiguration of communication links for network performance optimization. Simulation results show the effectiveness of our self-organized control mechanism, where the physical topology reorganizes to maximize the number of source to destination communicating pairs. Molecular Normal Mode Analysis (NMA) techniques for assessing network performance degradation in dynamic networks are also presented. Preliminary results show correlation between peaks in the eigenvalues of the Hessian of the network potential and network degradation.

  14. Fault Diagnosis of Steam Generator Using Signed Directed Graph and Artificial Neural Networks

    Microsoft Academic Search

    Mohamed N. Aly; Hesham N. Hegazy

    2006-01-01

    Diagnosis is a very complex and important task for finding the root cause of faults in nuclear power plants. The objective of this paper is to investigate the feasibility of using the combination of signed directed graph (SDG) and artificial neural networks for fault diagnosis in nuclear power plants especially in U-Tube steam generator. Signed directed graph has been the

  15. Directed diffusion: a scalable and robust communication paradigm for sensor networks

    Microsoft Academic Search

    Chalermek Intanagonwiwat; Ramesh Govindan; Deborah Estrin

    2000-01-01

    Advances in processor, memory and radio technology will enable small and cheap nodes capable of sensing, communication and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed diffusion paradigm for such coordination. Directed diffusion is datacentric in that all communication is for named data. All nodes in a

  16. Distributed Load Balancing over Directed Network Topologies Alejandro Gonzalez-Ruiz and Yasamin Mostofi

    E-print Network

    Mostofi, Yasamin

    Distributed Load Balancing over Directed Network Topologies Alejandro Gonzalez-Ruiz and Yasamin the problem of dis- tributed load balancing over a directed graph that is not fully connected. We study Informed Load Balancing (I-LB), an approach in which the nodes first reach an agreement over the balanced

  17. Machine Learning for Direct Marketing Response Models: Bayesian Networks with Evolutionary Programming

    Microsoft Academic Search

    Geng Cui; Man Leung Wong; Hon-Kwong Lui

    2006-01-01

    Machine learning methods are powerful tools for data mining with large noisy databases and give researchers the opportunity to gain new insights into consumer behavior and to improve the performance of marketing operations. To model consumer responses to direct marketing, this study proposes Bayesian networks learned by evolutionary programming. Using a large direct marketing data set, we tested the endogeneity

  18. Optimization methods for locating lightning flashes using magnetic direction finding networks

    NASA Technical Reports Server (NTRS)

    Goodman, Steven J.

    1989-01-01

    Techniques for producing best point estimates of target position using direction finder bearing information are reviewed. The use of an algorithm that calculates the cloud-to-ground flash location given multiple bearings is illustrated and the position errors are described. This algorithm can be used to analyze direction finder network performance.

  19. Minimum energy broadcast in multi-channel wireless sensor network with directional antennas

    Microsoft Academic Search

    Ailian Jiang; Keming Xie

    2010-01-01

    We studied the Minimum Energy Broadcast problem in wireless sensor network that were subjected to hard constraints on available energy and equipped with directional multibeam antennas by formulating and solving the corresponding optimization problem. Multibeam is the combination of two technologies of multi-channel and directional antennas. It was used to save energy further, improve the throughput and reduce the interference

  20. Simultaneous classification and ranging of direct fire weapons using an asynchronous acoustic sensor network

    Microsoft Academic Search

    Kam W. Lo; Brian G. Ferguson

    2011-01-01

    A direct fire weapon produces two impulsive sounds, namely, a muzzle blast and a ballistic shock wave, when firing a supersonic bullet. A ballistic model-based method which uses both the muzzle blast and shock wave received at each node of an asynchronous acoustic sensor network for simultaneous classification and ranging (SCR) of direct fire weapons is described. The initial speed

  1. Lasting modulation of in-vitro oscillatory activity with weak direct current stimulation

    E-print Network

    Parra, Lucas C.

    University of New York, New York, USA December 3, 2014 Abstract Transcranial Direct Current Stimulation (tDCS hypothesis. Introduction The number of studies on transcranial direct current stimulation (tDCS) has rapidly

  2. Direct Evidence For Diazepam Modulation of GABA A Receptor Microscopic Affinity

    Microsoft Academic Search

    A. M LAVOIE; R. E TWYMAN

    1996-01-01

    Alteration of agonist affinity is a potential mechanism for pharmacological modulation of ligandgated receptor channel function. The time course for receptor activation and current onset is determined by the combined rates for two kinetic transitions that underlie the protein conformations for binding agonist and channel gating. Using ultrafast ligand exchange techniques, we distinguish between these previously difficult to separate events

  3. Arabidopsis Phytochrome A Directly Targets Numerous Promoters for Individualized Modulation of Genes in a

    E-print Network

    Deng, Xing-Wang

    widely affects gene promoters involved in multiple FR-modulated aspects of plant growth. Furthermore, we under FR. Our study provides new insight into how plants rapidly fine-tune their growth strategy upon,d Mingqiu Dai,e Xiarong Shi,f and Xing Wang Denga,b,2 a Peking-Yale Joint Center for Plant Molecular

  4. Forming conditions and neural network control of continuously directional microstructure in directional solidification continuous casting process

    Microsoft Academic Search

    Li-ming Peng; Xie-min Mao; Kuang-di Xu

    1999-01-01

    Directional solidification continuous casting (DSCC) process is a new manufacturing technology for metallic materials which\\u000a combines advantages of both directional solidification technology and continuous casting technology. Unlimited long shaped\\u000a metal with directionally solidifying microstructure can be produced by this process. It is experimentally shown that controlling\\u000a condition of stable and continuous growth of single crystal structure means the precise control

  5. Fast-response IR spatial light modulators with a polymer network liquid crystal

    NASA Astrophysics Data System (ADS)

    Peng, Fenglin; Chen, Haiwei; Tripathi, Suvagata; Twieg, Robert J.; Wu, Shin-Tson

    2015-03-01

    Liquid crystals (LC) have widespread applications for amplitude modulation (e.g. flat panel displays) and phase modulation (e.g. beam steering). For phase modulation, a 2? phase modulo is required. To extend the electro-optic application into infrared region (MWIR and LWIR), several key technical challenges have to be overcome: 1. low absorption loss, 2. high birefringence, 3. low operation voltage, and 4. fast response time. After three decades of extensive development, an increasing number of IR devices adopting LC technology have been demonstrated, such as liquid crystal waveguide, laser beam steering at 1.55?m and 10.6 ?m, spatial light modulator in the MWIR (3~5?m) band, dynamic scene projectors for infrared seekers in the LWIR (8~12?m) band. However, several fundamental molecular vibration bands and overtones exist in the MWIR and LWIR regions, which contribute to high absorption coefficient and hinder its widespread application. Therefore, the inherent absorption loss becomes a major concern for IR devices. To suppress IR absorption, several approaches have been investigated: 1) Employing thin cell gap by choosing a high birefringence liquid crystal mixture; 2) Shifting the absorption bands outside the spectral region of interest by deuteration, fluorination and chlorination; 3) Reducing the overlap vibration bands by using shorter alkyl chain compounds. In this paper, we report some chlorinated LC compounds and mixtures with a low absorption loss in the near infrared and MWIR regions. To achieve fast response time, we have demonstrated a polymer network liquid crystal with 2? phase change at MWIR and response time less than 5 ms.

  6. Inspiring Climate Education Excellence (ICEE): Towards a suite of online modules and self-directed learning resources for secondary science teachers

    Microsoft Academic Search

    S. M. Buhr; S. Lynds; M. S. McCaffrey; S. van Gundy; S. B. Wise

    2009-01-01

    Inspiring Climate Education Excellence (ICEE) is a NASA-funded project to develop online course modules and self-directed learning resources aligned with the Essential Principles of Climate Science. Focusing on changes in Arctic ice and sea level rise, the modules will use NASA resources for professional development around key guiding questions, and build content knowledge and pedagogical skills for how to teach

  7. Directionality in hyperbrain networks discriminates between leaders and followers in guitar duets

    PubMed Central

    Sänger, Johanna; Müller, Viktor; Lindenberger, Ulman

    2013-01-01

    To investigate whether directionality in hyperbrain networks reflects different roles during interpersonal action coordination (IAC), we recorded EEG data from pairs of guitarists playing together as musical leaders versus followers. We used an asymmetric index of in-phase synchronization to analyze hyperbrain networks of directed functional connectivity in the alpha and beta frequency ranges for time segments around coordinated play onsets. After exploring the small-world characteristics of the networks at different thresholds, we examined the directed connection strengths within and between brains. As predicted, we found evidence suggesting that the musical roles of leader and follower are associated with different patterns of directed between-brain couplings. The functional significance of these differences for IAC requires further study. PMID:23761745

  8. Directionality in hyperbrain networks discriminates between leaders and followers in guitar duets.

    PubMed

    Sänger, Johanna; Müller, Viktor; Lindenberger, Ulman

    2013-01-01

    To investigate whether directionality in hyperbrain networks reflects different roles during interpersonal action coordination (IAC), we recorded EEG data from pairs of guitarists playing together as musical leaders versus followers. We used an asymmetric index of in-phase synchronization to analyze hyperbrain networks of directed functional connectivity in the alpha and beta frequency ranges for time segments around coordinated play onsets. After exploring the small-world characteristics of the networks at different thresholds, we examined the directed connection strengths within and between brains. As predicted, we found evidence suggesting that the musical roles of leader and follower are associated with different patterns of directed between-brain couplings. The functional significance of these differences for IAC requires further study. PMID:23761745

  9. Estimating the Performance of Direct-Detection DPSK in Optical Networking Environments Using Eigenfunction Expansion Techniques

    Microsoft Academic Search

    João J. O. Pires; Luís G. C. Cancela

    2010-01-01

    In-band crosstalk, due to multiple interferers, has been identified as one of the most severe impairments in optical transparent networks, especially in the ones with a large number of nodes and a high wavelength density. Due to its robustness to in-band crosstalk differential phase-shift keying (DPSK) emerges as an attractive modulation scheme to be used in such environments. This paper

  10. Suppressing the relaxation oscillation noise of injection-locked WRC-FPLD for directly modulated OFDM transmission.

    PubMed

    Cheng, Min-Chi; Chi, Yu-Chieh; Li, Yi-Cheng; Tsai, Cheng-Ting; Lin, Gong-Ru

    2014-06-30

    By up-shifting the relaxation oscillation peak and suppressing its relative intensity noise in a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) under intense injection-locking, the directly modulated transmission of optical 16 quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) data-stream is demonstrated. The total bit rate of up to 20 Gbit/s within 5-GHz bandwidth is achieved by using the OFDM subcarrier pre-leveling technique. With increasing the injection-locking power from -12 to -3 dBm, the effective reduction on threshold current of the WRC-FPLD significantly shifts its relaxation oscillation frequency from 5 to 7.5 GHz. This concurrently induces an up-shift of the peak relative intensity noise (RIN) of the WRC-FPLD, and effectively suppresses the background RIN level to -104 dBc/Hz within the OFDM band between 3 and 6 GHz. The enhanced signal-to-noise ratio from 16 to 20 dB leads to a significant reduction of bit-error-rate (BER) of the back-to-back transmitted 16-QAM-OFDM data from 1.3 × 10(-3) to 5 × 10(-5), which slightly degrades to 1.1 × 10(-4) after 25-km single-mode fiber (SMF) transmission. However, the enlarged injection-locking power from -12 to -3 dBm inevitably declines the modulation throughput and increases its negative throughput slope from -0.8 to -1.9 dBm/GHz. After pre-leveling the peak amplitude of the OFDM subcarriers to compensate the throughput degradation of the directly modulated WRC-FPLD, the BER under 25-km SMF transmission can be further improved to 3 × 10(-5) under a receiving power of -3 dBm. PMID:24977832

  11. Site-directed mutagenesis of serine 158 demonstrates its role in spinach leaf sucrose-phosphate synthase modulation

    NASA Technical Reports Server (NTRS)

    Toroser, D.; McMichael, R. Jr; Krause, K. P.; Kurreck, J.; Sonnewald, U.; Stitt, M.; Huber, S. C.; Davies, E. (Principal Investigator)

    1999-01-01

    Site-directed mutagenesis of spinach sucrose-phosphate synthase (SPS) was performed to investigate the role of Ser158 in the modulation of spinach leaf SPS. Tobacco plants expressing the spinach wild-type (WT), S158A, S158T and S157F/S158E SPS transgenes were produced. Expression of transgenes appeared not to reduce expression of the tobacco host SPS. SPS activity in the WT and the S158T SPS transgenics showed light/dark modulation, whereas the S158A and S157F/S158E mutants were not similarly light/dark modulated: the S158A mutant enzyme was not inactivated in the dark, and the S157F/S158E was not activated in the light. The inability to modulate the activity of the S158A mutant enzyme by protein phosphorylation was demonstrated in vitro. The WT spinach enzyme immunopurified from dark transgenic tobacco leaves had a low initial activation state, and could be activated by PP2A and subsequently inactivated by SPS-kinase plus ATP. Rapid purification of the S158A mutant enzyme from dark leaves of transgenic plants using spinach-specific monoclonal antibodies yielded enzyme that had a high initial activation state, and pre-incubation with leaf PP2A or ATP plus SPS-kinase (the PKIII enzyme) caused little modulation of activity. The results demonstrate the regulatory significance of Ser158 as the major site responsible for dark inactivation of spinach SPS in vivo, and indicate that the significance of phosphorylation is the introduction of a negative charge at the Ser158 position.

  12. Mining Bayesian Networks from Direct Marketing Databases with Missing Values

    Microsoft Academic Search

    Yuan Yuan Guo; Man Leung Wong

    Discovering knowledge from huge databases with missing values is a challenging problem in Data Mining. In this paper, a novel\\u000a hybrid algorithm for learning knowledge represented in Bayesian Networks is discussed. The new algorithm combines an evolutionary\\u000a algorithm with the Expectation-Maximization (EM) algorithm to overcome the problem of getting stuck in sub-optimal solutions\\u000a which occurs in most existing learning algorithms.

  13. Collision Avoidance in Single-Channel Ad Hoc Networks Using Directional Antennas

    Microsoft Academic Search

    Yu Wang; J. J. Garcia-luna-aceves

    2003-01-01

    Three collision-avoidance protocols are analyzed that use omni-directional packet reception together with omni- directional transmissions, directional transmissions, o r a combination of both. A simple model is introduced to an- alyze the performance of these collision avoidance proto- cols in multi-hop networks with arbitrary topologies. The numerical results of this analysis show that collision avoi d- ance using a narrow

  14. Networked telepresence system using web browsers and omni-directional video streams

    Microsoft Academic Search

    Tomoya Ishikawa; Kazumasa Yamazawa; Tomokazu Sato; Sei Ikeda; Yutaka Nakamura; Kazutoshi Fujikawa; Hideki Sunahara; Naokazu Yokoya

    2005-01-01

    In this paper, we describe a new telepresence system which enables a user to look around a virtualized real world easily in network environments. The proposed system includes omni-directional video viewers on web browsers and allows the user to look around the omni-directional video contents on the web browsers. The omni-directional video viewer is implemented as an Active-X program so

  15. Reduced-order modelling of biochemical networks: application to the GTPase-cycle signalling module

    PubMed Central

    Maurya, M.R.; Bornheimer, S.J.; Venkatasubramanian, V.; Subramaniam, S.

    2011-01-01

    Biochemical systems embed complex networks and hence development and analysis of their detailed models pose a challenge for computation. Coarse-grained biochemical models, called reduced-order models (ROMs), consisting of essential biochemical mechanisms are more useful for computational analysis and for studying important features of a biochemical network. The authors present a novel method to model-reduction by identifying potentially important parameters using multidimensional sensitivity analysis. A ROM is generated for the GTPase-cycle module of m1 muscarinic acetylcholine receptor, Gq, and regulator of G-protein signalling 4 (a GTPase-activating protein or GAP) starting from a detailed model of 48 reactions. The resulting ROM has only 17 reactions. The ROM suggested that complexes of G-protein coupled receptor (GPCR) and GAP – which were proposed in the detailed model as a hypothesis – are required to fit the experimental data. Models previously published in the literature are also simulated and compared with the ROM. Through this comparison, a minimal ROM, that also requires complexes of GPCR and GAP, with just 15 parameters is generated. The proposed reduced-order modelling methodology is scalable to larger networks and provides a general framework for the reduction of models of biochemical systems. PMID:16986265

  16. Characterizing system dynamics with a weighted and directed network constructed from time series data

    SciTech Connect

    Sun, Xiaoran, E-mail: sxr0806@gmail.com [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China) [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China); School of Mathematics and Statistics, The University of Western Australia, Crawley WA 6009 (Australia); Small, Michael, E-mail: michael.small@uwa.edu.au [School of Mathematics and Statistics, The University of Western Australia, Crawley WA 6009 (Australia)] [School of Mathematics and Statistics, The University of Western Australia, Crawley WA 6009 (Australia); Zhao, Yi [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China)] [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China); Xue, Xiaoping [Department of Mathematics, Harbin Institute of Technology, Harbin 150025 (China)] [Department of Mathematics, Harbin Institute of Technology, Harbin 150025 (China)

    2014-06-15

    In this work, we propose a novel method to transform a time series into a weighted and directed network. For a given time series, we first generate a set of segments via a sliding window, and then use a doubly symbolic scheme to characterize every windowed segment by combining absolute amplitude information with an ordinal pattern characterization. Based on this construction, a network can be directly constructed from the given time series: segments corresponding to different symbol-pairs are mapped to network nodes and the temporal succession between nodes is represented by directed links. With this conversion, dynamics underlying the time series has been encoded into the network structure. We illustrate the potential of our networks with a well-studied dynamical model as a benchmark example. Results show that network measures for characterizing global properties can detect the dynamical transitions in the underlying system. Moreover, we employ a random walk algorithm to sample loops in our networks, and find that time series with different dynamics exhibits distinct cycle structure. That is, the relative prevalence of loops with different lengths can be used to identify the underlying dynamics.

  17. Building wireless mesh networks in forests: antenna direction, transmit power, and vegetation effects on network performance

    Microsoft Academic Search

    Kuang-ching Wang; Gayatri Venkatesh; Sajindra Pradhananga; Sandeep Lokala; Shari Carter; Jason Isenhower; James Vaughn

    2008-01-01

    Wireless mesh networks have become an effective solution for extending Internet connectivity to large areas without an existing communication infrastructure. Building a mesh network in areas with heavy vegetation, however, is challenging due to their severe radio attenuating effects. At Clemson, a wireless mesh network testbed is being built in deep forests to connect watershed monitoring sensors to Internet. This

  18. Gene network coherence based on prior knowledge using direct and indirect relationships.

    PubMed

    Gómez-Vela, Francisco; Lagares, José Antonio; Díaz-Díaz, Norberto

    2015-06-01

    Gene networks (GNs) have become one of the most important approaches for modeling biological processes. They are very useful to understand the different complex biological processes that may occur in living organisms. Currently, one of the biggest challenge in any study related with GN is to assure the quality of these GNs. In this sense, recent works use artificial data sets or a direct comparison with prior biological knowledge. However, these approaches are not entirely accurate as they only take into account direct gene-gene interactions for validation, leaving aside the weak (indirect) relationships. We propose a new measure, named gene network coherence (GNC), to rate the coherence of an input network according to different biological databases. In this sense, the measure considers not only the direct gene-gene relationships but also the indirect ones to perform a complete and fairer evaluation of the input network. Hence, our approach is able to use the whole information stored in the networks. A GNC JAVA-based implementation is available at: http://fgomezvela.github.io/GNC/. The results achieved in this work show that GNC outperforms the classical approaches for assessing GNs by means of three different experiments using different biological databases and input networks. According to the results, we can conclude that the proposed measure, which considers the inherent information stored in the direct and indirect gene-gene relationships, offers a new robust solution to the problem of GNs biological validation. PMID:25935118

  19. Periodic and aperiodic liquid crystal-polymer composite structures realized via spatial light modulator direct holography.

    PubMed

    Infusino, M; De Luca, A; Barna, V; Caputo, R; Umeton, C

    2012-10-01

    In this work we present the first realization and characterization of two-dimensional periodic and aperiodic POLICRYPS (Polymer Liquid Crystal Polymer Slices) structures, obtained by means of a single-beam holographic technique exploiting a high resolution spatial light modulator (SLM). A first investigation shows that the gratings, operating in the Raman Nath regime, exhibit a morphology and a electro-optical behavior that are typical of the POLICRYPS gratings realized by two-beam interference holography. PMID:23188278

  20. Selective glucocorticoid receptor modulation: New directions with non-steroidal scaffolds.

    PubMed

    Sundahl, Nora; Bridelance, Jolien; Libert, Claude; De Bosscher, Karolien; Beck, Ilse M

    2015-08-01

    Glucocorticoids remain the frontline treatment for inflammatory disorders, yet represent a double-edged sword with beneficial therapeutic actions alongside adverse effects, mainly in metabolic regulation. Considerable efforts were made to improve this balance by attempting to amplify therapeutic beneficial anti-inflammatory actions and to minimize adverse metabolic actions. Most attention has focused on the development of novel compounds favoring the transrepressing actions of the glucocorticoid receptor, assumed to be important for anti-inflammatory actions, over the transactivating actions, assumed to underpin the undesirable actions. These compounds are classified as selective glucocorticoid receptor agonists (SEGRAs) or selective glucocorticoid receptor modulators (SEGRMs). The latter class is able to modulate the activity of a GR agonist and/or may not classically bind the glucocorticoid receptor ligand-binding pocket. SEGRAs and SEGRMs are collectively denominated SEGRAMs (selective glucocorticoid receptor agonists and modulators). Although this transrepression vs transactivation concept proved to be too simplistic, the developed SEGRAMs were helpful in elucidating various molecular actions of the glucocorticoid receptor, but have also raised many novel questions. We discuss lessons learned from recent mechanistic studies of selective glucocorticoid receptor modulators. This is approached by analyzing recent experimental insights in comparison with knowledge obtained using mutant GR research, thus clarifying the current view on the SEGRAM field. These insights also contribute to our understanding of the processes controlling glucocorticoid-mediated side effects as well as glucocorticoid resistance. Our perspective on non-steroidal SEGRAs and SEGRMs considers remaining opportunities to address research gaps in order to harness the potential for more safe and effective glucocorticoid receptor therapies. PMID:25958032

  1. Parameter assignment for improved connectivity and security in randomly deployed wireless sensor networks via hybrid omni/uni-directional antennas 

    E-print Network

    Shankar, Sonu

    2009-05-15

    ,omni-directional antennas have been used for communication in wireless sensor net-works. In this thesis, a hybrid communication model is presented where-in, nodes ina network are capable of both omni-directional and uni-directional communication.The eect of such a model...

  2. Direction-Dependent Learning Approach for Radial Basis Function Networks

    Microsoft Academic Search

    Puneet Singla; Kamesh Subbarao; John L. Junkins

    2007-01-01

    Direction-dependent scaling, shaping, and rotation of Gaussian basis functions are introduced for maximal trend sensing with minimal parameter representations for input output approximation. It is shown that shaping and rotation of the radial basis functions helps in reducing the total number of function units required to approximate any given input-output data, while improving accuracy. Several alternate formulations that enforce minimal

  3. Direct detection of RDX vapor using a conjugated polymer network.

    PubMed

    Gopalakrishnan, Deepti; Dichtel, William R

    2013-06-01

    1,3,5-Trinitroperhydro-1,3,5-triazine (RDX) is a principal component of plastic explosives used in acts of terrorism and within improvised explosive devices, among others. Approaches to detect RDX compatible with remote, "stand-off" sampling that do not require preconcentration strategies, such as the swabs commonly employed in airports, will benefit military and civilian security. Such detection remains a significant challenge because RDX is 10(3) less volatile than 1,3,5-trinitrotoluene (TNT), corresponding to a parts-per-trillion vapor pressure under ambient conditions. Therefore, while fluorescence quenching of conjugated polymers is sufficiently sensitive to detect TNT vapors, RDX vapor detection is undemonstrated. Here we report a cross-linked phenylene vinylene polymer network whose fluorescence is quenched by trace amounts of RDX introduced from solution or the vapor phase. Fluorescence quenching is reduced, but remains significant, when partially degraded RDX is employed, suggesting that the polymer responds to RDX itself. The polymer network also responds to TNT and PETN similarly introduced from solution or the vapor phase. Pure solvents, volatile amines, and the outgassed vapors from lipstick or sunscreen do not quench polymer fluorescence. The established success of TNT sensors based on fluorescence quenching makes this a material of interest for real-world explosive sensors and will motivate further interest in cross-linked polymers and framework materials for sensing applications. PMID:23641956

  4. Walking Drosophila align with the e-vector of linearly polarized light through directed modulation of angular acceleration.

    PubMed

    Velez, Mariel M; Wernet, Mathias F; Clark, Damon A; Clandinin, Thomas R

    2014-06-01

    Understanding the mechanisms that link sensory stimuli to animal behavior is a central challenge in neuroscience. The quantitative description of behavioral responses to defined stimuli has led to a rich understanding of different behavioral strategies in many species. One important navigational cue perceived by many vertebrates and insects is the e-vector orientation of linearly polarized light. Drosophila manifests an innate orientation response to this cue ('polarotaxis'), aligning its body axis with the e-vector field. We have established a population-based behavioral paradigm for the genetic dissection of neural circuits guiding polarotaxis to both celestial as well as reflected polarized stimuli. However, the behavioral mechanisms by which flies align with a linearly polarized stimulus remain unknown. Here, we present a detailed quantitative description of Drosophila polarotaxis, systematically measuring behavioral parameters that are modulated by the stimulus. We show that angular acceleration is modulated during alignment, and this single parameter may be sufficient for alignment. Furthermore, using monocular deprivation, we show that each eye is necessary for modulating turns in the ipsilateral direction. This analysis lays the foundation for understanding how neural circuits guide these important visual behaviors. PMID:24810784

  5. Walking Drosophila align with the e-vector of linearly polarized light through directed modulation of angular acceleration

    PubMed Central

    Velez, Mariel M.; Wernet, Mathias F.; Clark, Damon A.

    2014-01-01

    Understanding the mechanisms that link sensory stimuli to animal behavior is a central challenge in neuroscience. The quantitative description of behavioral responses to defined stimuli has led to a rich understanding of different behavioral strategies in many species. One important navigational cue perceived by many vertebrates and insects is the e-vector orientation of linearly polarized light. Drosophila manifests an innate orientation response to this cue (‘polarotaxis’), aligning its body axis with the e-vector field. We have established a population-based behavioral paradigm for the genetic dissection of neural circuits guiding polarotaxis to both celestial as well as reflected polarized stimuli. However, the behavioral mechanisms by which flies align with a linearly polarized stimulus remain unknown. Here, we present a detailed quantitative description of Drosophila polarotaxis, systematically measuring behavioral parameters that are modulated by the stimulus. We show that angular acceleration is modulated during alignment, and this single parameter may be sufficient for alignment. Furthermore, using monocular deprivation, we show that each eye is necessary for modulating turns in the ipsilateral direction. This analysis lays the foundation for understanding how neural circuits guide these important visual behaviors. PMID:24810784

  6. Optimum Transmission Ranges in a Direct-Sequence Spread-Spectrum Multihop Packet Radio Network

    Microsoft Academic Search

    Elvino S. Sousa; John A. Silvester

    1990-01-01

    The authors obtain the optimum transmission ranges to maximize throughput for a direct-sequence spread-spectrum multihop packet radio network. In the analysis, they model the network self-interference as a random variable which is equal to the sum of the interference power of all other terminals plus background noise. The model is applicable to other spread-spectrum schemes where the interference of one

  7. Improved Connectivity using Hybrid Uni/Omni-Directional Antennas in Sensor Networks

    E-print Network

    Kwon, Ji Heon

    2008-05-27

    . This is a very strict connectivity requirement called 100% connectivity. This work deals with analyzing connectivity in various randomly deployed sensor network deployments iii and comparing metrics between omni and hybrid uni/omni-directional sensor... is not connected to the rest of the network, the activity detected by the node 3 will not be reported to the sink. 5 Figure 2 Example emphasizing on the importance of connectivity in WSNs There are two existing paradigms for antennas in wireless sensor...

  8. A network module-based method for identifying cancer prognostic signatures.

    PubMed

    Wu, Guanming; Stein, Lincoln

    2012-01-01

    Discovering robust prognostic gene signatures as biomarkers using genomics data can be challenging. We have developed a simple but efficient method for discovering prognostic biomarkers in cancer gene expression data sets using modules derived from a highly reliable gene functional interaction network. When applied to breast cancer, we discover a novel 31-gene signature associated with patient survival. The signature replicates across 5 independent gene expression studies, and outperforms 48 published gene signatures. When applied to ovarian cancer, the algorithm identifies a 75-gene signature associated with patient survival. A Cytoscape plugin implementation of the signature discovery method is available at http://wiki.reactome.org/index.php/Reactome_FI_Cytoscape_Plugin. PMID:23228031

  9. Astrocytes Modulate Neural Network Activity by Ca2+-Dependent Uptake of Extracellular K+

    PubMed Central

    Wang, Fushun; Smith, Nathan A.; Xu, Qiwu; Fujita, Takumi; Baba, Akemichi; Matsuda, Toshio; Takano, Takahiro; Bekar, Lane; Nedergaard, Maiken

    2012-01-01

    Astrocytes are electrically nonexcitable cells that display increases in cytosolic calcium ion (Ca2+) in response to various neurotransmitters and neuromodulators. However, the physiological role of astrocytic Ca2+ signaling remains controversial. We show here that astrocytic Ca2+ signaling ex vivo and in vivo stimulated the Na+,K+-ATPase (Na+- and K+-dependent adenosine triphosphatase), leading to a transient decrease in the extracellular potassium ion (K+) concentration. This in turn led to neuronal hyperpolarization and suppressed baseline excitatory synaptic activity, detected as a reduced frequency of excitatory postsynaptic currents. Synaptic failures decreased in parallel, leading to an increase in synaptic fidelity. The net result was that astrocytes, through active uptake of K+, improved the signal-to-noise ratio of synaptic transmission. Active control of the extracellular K+ concentration thus provides astrocytes with a simple yet powerful mechanism to rapidly modulate network activity. PMID:22472648

  10. INFORMAS (International Network for Food and Obesity/non-communicable diseases Research, Monitoring and Action Support): summary and future directions.

    PubMed

    Kumanyika, S

    2013-10-01

    This supplement presents the foundational elements for INFORMAS (International Network for Food and Obesity/non-communicable diseases Research, Monitoring and Action Support). As explained in the overview article by Swinburn and colleagues, INFORMAS has a compelling rationale and has set forth clear objectives, outcomes, principles and frameworks for monitoring and benchmarking key aspects of food environments and the policies and actions that influence the healthiness of food environments. This summary highlights the proposed monitoring approaches for the 10 interrelated INFORMAS modules: public and private sector policies and actions; key aspects of food environments (food composition, labelling, promotion, provision, retail, prices, and trade and investment) and population outcomes (diet quality). This ambitious effort should be feasible when approached in a step-wise manner, taking into account existing monitoring efforts, data sources, country contexts and capacity, and when adequately resourced. After protocol development and pilot testing of the modules, INFORMAS aims to be a sustainable, low-cost monitoring framework. Future directions relate to institutionalization, implementation and, ultimately, to leveraging INFORMAS data in ways that will bring key drivers of food environments into alignment with public health goals. PMID:24074219

  11. The anti-convulsant stiripentol acts directly on the GABA(A) receptor as a positive allosteric modulator.

    PubMed

    Fisher, Janet L

    2009-01-01

    Stiripentol (STP) has been used as co-therapy for treatment of epilepsy for many years. Its mechanism of action has long been considered to be indirect, as it inhibits the enzymes responsible for metabolism of other anti-convulsant agents. However, a recent report suggested that STP might also act at the neuronal level, increasing inhibitory GABAergic neurotransmission. We examined the effect of STP on the functional properties of recombinant GABA(A) receptors (GABARs) and found that it was a positive allosteric modulator of these ion channels. Its activity showed some dependence on subunit composition, with greater potentiation of alpha3-containing receptors and reduced potentiation when the beta1 or epsilon subunits were present. STP caused a leftward shift in the GABA concentration-response relationship, but did not increase the peak response of the receptors to a maximal GABA concentration. Although STP shares some functional characteristics with the neurosteroids, its activity was not inhibited by a neurosteroid site antagonist and was unaffected by a mutation in the alpha3 subunit that reduced positive modulation by neurosteroids. The differential effect of STP on beta1- and beta2/beta3-containing receptors was not altered by mutations within the second transmembrane domain that affect modulation by loreclezole. These findings suggest that STP acts as a direct allosteric modulator of the GABAR at a site distinct from many commonly used anti-convulsant, sedative and anxiolytic drugs. Its higher activity at alpha3-containing receptors as well as its activity at delta-containing receptors may provide a unique opportunity to target selected populations of GABARs. PMID:18585399

  12. Accurate optical vector network analyzer based on optical single-sideband modulation and balanced photodetection.

    PubMed

    Xue, Min; Pan, Shilong; Zhao, Yongjiu

    2015-02-15

    A novel optical vector network analyzer (OVNA) based on optical single-sideband (OSSB) modulation and balanced photodetection is proposed and experimentally demonstrated, which can eliminate the measurement error induced by the high-order sidebands in the OSSB signal. According to the analytical model of the conventional OSSB-based OVNA, if the optical carrier in the OSSB signal is fully suppressed, the measurement result is exactly the high-order-sideband-induced measurement error. By splitting the OSSB signal after the optical device-under-test (ODUT) into two paths, removing the optical carrier in one path, and then detecting the two signals in the two paths using a balanced photodetector (BPD), high-order-sideband-induced measurement error can be ideally eliminated. As a result, accurate responses of the ODUT can be achieved without complex post-signal processing. A proof-of-concept experiment is carried out. The magnitude and phase responses of a fiber Bragg grating (FBG) measured by the proposed OVNA with different modulation indices are superimposed, showing that the high-order-sideband-induced measurement error is effectively removed. PMID:25680152

  13. Directional Bias and Pheromone for Discovery and Coverage on Networks

    SciTech Connect

    Fink, Glenn A.; Berenhaut, Kenneth S.; Oehmen, Christopher S.

    2012-09-11

    Natural multi-agent systems often rely on “correlated random walks” (random walks that are biased toward a current heading) to distribute their agents over a space (e.g., for foraging, search, etc.). Our contribution involves creation of a new movement and pheromone model that applies the concept of heading bias in random walks to a multi-agent, digital-ants system designed for cyber-security monitoring. We examine the relative performance effects of both pheromone and heading bias on speed of discovery of a target and search-area coverage in a two-dimensional network layout. We found that heading bias was unexpectedly helpful in reducing search time and that it was more influential than pheromone for improving coverage. We conclude that while pheromone is very important for rapid discovery, heading bias can also greatly improve both performance metrics.

  14. Brain network dynamics characterization in epileptic seizures. Joint directed graph and pairwise synchronization measures

    NASA Astrophysics Data System (ADS)

    Rodrigues, A. C.; Machado, B. S.; Florence, G.; Hamad, A. P.; Sakamoto, A. C.; Fujita, A.; Baccalá, L. A.; Amaro, E.; Sameshima, K.

    2014-12-01

    Here we propose and evaluate a new approach to analyse multichannel mesial temporal lobe epilepsy EEG data from eight patients through complex network and synchronization theories. The method employs a Granger causality test to infer the directed connectivity graphs and a wavelet transform based phase synchronization measure whose characteristics allow studying dynamical transitions during epileptic seizures. We present a new combined graph measure that quantifies the level of network hub formation, called network hub out-degree, which closely reflects the level of synchronization observed during the ictus.

  15. Spontaneous formation of InGaN nanowall network directly on Si

    SciTech Connect

    Soto Rodriguez, P. E. D.; Kumar, Praveen; Gomez, V. J.; Alvi, N. H.; Calleja, E.; Noetzel, R. [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)] [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Manuel, J. M.; Morales, F. M.; Jimenez, J. J.; Garcia, R. [Dep. Ciencia de los Materiales e IM y QI., F. Ciencias, Universidad de Cadiz, 11510-Puerto Real, Cadiz (Spain)] [Dep. Ciencia de los Materiales e IM y QI., F. Ciencias, Universidad de Cadiz, 11510-Puerto Real, Cadiz (Spain)

    2013-04-29

    We present the study on epitaxial growth of an InGaN nanowall network directly on Si by plasma-assisted molecular beam epitaxy. Scanning electron microscopy, high-resolution X-ray diffraction, and transmission electron microscopy together with energy-dispersive X-ray analysis infer the crystalline nature of the InGaN nanowall network, oriented along the C-axis, with In composition ranging from pure GaN to 40%. Room temperature photoluminescence is observed, indicating good optical quality. The nanowall network is highly in-plane electrically conductive.

  16. Design and development of micro-strip stacked module prototypes to measure flying particle directions

    NASA Astrophysics Data System (ADS)

    Bernardini, J.; Bosi, F.; Dell'Orso, R.; Fiori, F.; Messineo, A.; Palla, F.; Profeti, A.; Verdini, P. G.

    2011-06-01

    Experience at high luminosity hadron collider experiments shows that tracking information enhances the trigger rejection capabilities while retaining high efficiency for interesting physics events [F. Palla and G. Parrini, Tracking in the trigger: from the CDF experience to CMS upgrade, 2007. Published in PoS VER-TEX2007:034, 2007]. The design of a tracking based trigger for Super LHC (S-LHC), the already envisaged high luminosity upgrade of the LHC collider, is an extremely challenging task, and requires the identification of high-momentum particle tracks as a part of the Level 1 Trigger. Simulation studies show that this can be achieved by correlating hits on two closely spaced silicon strip sensors. This work focuses on the design and development of micro-strip stacked prototype modules and will also discuss the technical challenges in the construction and the final detector performance. Studies of possible sensor geometries and wire-bonding techniques will be also presented. The prototypes have been built with the silicon sensors and electronics used to equip the present CMS Tracker [CMS Collaboration, The CMS experiment at the CERN LHC, JINST 3:S08004:26-89, 2008]. Correlation of signals collected from sensors are processed off detector. We will present the results of tests performed on the prototype modules in terms of the noise performance of the proposed stack geometry. Preliminary results in terms of signal over noise and tracking performance with cosmic rays will also be shown.

  17. Bilateral transcranial direct current stimulation modulates activation-induced regional blood flow changes during voluntary movement

    Microsoft Academic Search

    Caroline Paquette; Michael Sidel; Basia A Radinska; Jean-Paul Soucy; Alexander Thiel

    2011-01-01

    Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that induces changes in cortical excitability: anodal stimulation increases while cathodal stimulation reduces excitability. Imaging studies performed after unilateral stimulation have shown conflicting results regarding the effects of tDCS on surrogate markers of neuronal activity. The aim of this study was to directly measure these effects on activation-induced changes

  18. Engineering a Blood Vessel Network Module for Body-on-a-Chip Applications.

    PubMed

    Ryu, Hyunryul; Oh, Soojung; Lee, Hyun Jae; Lee, Jin Young; Lee, Hae Kwang; Jeon, Noo Li

    2015-06-01

    The blood circulatory system links all organs from one to another to support and maintain each organ's functions consistently. Therefore, blood vessels have been considered as a vital unit. Engineering perfusable functional blood vessels in vitro has been challenging due to difficulties in designing the connection between rigid macroscale tubes and fragile microscale ones. Here, we propose a generalizable method to engineer a "long" perfusable blood vessel network. To form millimeter-scale vessels, fibroblasts were co-cultured with human umbilical vein endothelial cells (HUVECs) in close proximity. In contrast to previous works, in which all cells were permanently placed within the device, we developed a novel method to culture paracrine factor secreting fibroblasts on an O-ring-shaped guide that can be transferred in and out. This approach affords flexibility in co-culture, where the effects of secreted factors can be decoupled. Using this, blood vessels with length up to 2 mm were successfully produced in a reproducible manner (>90%). Because the vessels form a perfusable network within the channel, simple links to inlets and outlets of the device allowed connections to the outside world. The robust and reproducible formation of in vitro engineered vessels can be used as a module to link various organ components as parts of future body-on-a-chip applications. PMID:25532526

  19. Arachidonic Acid: An Evolutionarily Conserved Signaling Molecule Modulates Plant Stress Signaling Networks[C][W

    PubMed Central

    Savchenko, Tatyana; Walley, Justin W.; Chehab, E. Wassim; Xiao, Yanmei; Kaspi, Roy; Pye, Matthew F.; Mohamed, Maged E.; Lazarus, Colin M.; Bostock, Richard M.; Dehesh, Katayoon

    2010-01-01

    Fatty acid structure affects cellular activities through changes in membrane lipid composition and the generation of a diversity of bioactive derivatives. Eicosapolyenoic acids are released into plants upon infection by oomycete pathogens, suggesting they may elicit plant defenses. We exploited transgenic Arabidopsis thaliana plants (designated EP) producing eicosadienoic, eicosatrienoic, and arachidonic acid (AA), aimed at mimicking pathogen release of these compounds. We also examined their effect on biotic stress resistance by challenging EP plants with fungal, oomycete, and bacterial pathogens and an insect pest. EP plants exhibited enhanced resistance to all biotic challenges, except they were more susceptible to bacteria than the wild type. Levels of jasmonic acid (JA) were elevated and levels of salicylic acid (SA) were reduced in EP plants. Altered expression of JA and SA pathway genes in EP plants shows that eicosapolyenoic acids effectively modulate stress-responsive transcriptional networks. Exogenous application of various fatty acids to wild-type and JA-deficient mutants confirmed AA as the signaling molecule. Moreover, AA treatment elicited heightened expression of general stress-responsive genes. Importantly, tomato (Solanum lycopersicum) leaves treated with AA exhibited reduced susceptibility to Botrytis cinerea infection, confirming AA signaling in other plants. These studies support the role of AA, an ancient metazoan signaling molecule, in eliciting plant stress and defense signaling networks. PMID:20935246

  20. Direct2Experts: a pilot national network to demonstrate interoperability among research-networking platforms

    PubMed Central

    Barnett, William; Conlon, Mike; Eichmann, David; Kibbe, Warren; Falk-Krzesinski, Holly; Halaas, Michael; Johnson, Layne; Meeks, Eric; Mitchell, Donald; Schleyer, Titus; Stallings, Sarah; Warden, Michael; Kahlon, Maninder

    2011-01-01

    Research-networking tools use data-mining and social networking to enable expertise discovery, matchmaking and collaboration, which are important facets of team science and translational research. Several commercial and academic platforms have been built, and many institutions have deployed these products to help their investigators find local collaborators. Recent studies, though, have shown the growing importance of multiuniversity teams in science. Unfortunately, the lack of a standard data-exchange model and resistance of universities to share information about their faculty have presented barriers to forming an institutionally supported national network. This case report describes an initiative, which, in only 6?months, achieved interoperability among seven major research-networking products at 28 universities by taking an approach that focused on addressing institutional concerns and encouraging their participation. With this necessary groundwork in place, the second phase of this effort can begin, which will expand the network's functionality and focus on the end users. PMID:22037890

  1. Modulations of the executive control network by stimulus onset asynchrony in a Stroop task

    PubMed Central

    2013-01-01

    Background Manipulating task difficulty is a useful way of elucidating the functional recruitment of the brain’s executive control network. In a Stroop task, pre-exposing the irrelevant word using varying stimulus onset asynchronies (‘negative’ SOAs) modulates the amount of behavioural interference and facilitation, suggesting disparate mechanisms of cognitive processing in each SOA. The current study employed a Stroop task with three SOAs (?400, -200, 0 ms), using functional magnetic resonance imaging to investigate for the first time the neural effects of SOA manipulation. Of specific interest were 1) how SOA affects the neural representation of interference and facilitation; 2) response priming effects in negative SOAs; and 3) attentional effects of blocked SOA presentation. Results The results revealed three regions of the executive control network that were sensitive to SOA during Stroop interference; the 0 ms SOA elicited the greatest activation of these areas but experienced relatively smaller behavioural interference, suggesting that the enhanced recruitment led to more efficient conflict processing. Response priming effects were localized to the right inferior frontal gyrus, which is consistent with the idea that this region performed response inhibition in incongruent conditions to overcome the incorrectly-primed response, as well as more general action updating and response preparation. Finally, the right superior parietal lobe was sensitive to blocked SOA presentation and was most active for the 0 ms SOA, suggesting that this region is involved in attentional control. Conclusions SOA exerted both trial-specific and block-wide effects on executive processing, providing a unique paradigm for functional investigations of the cognitive control network. PMID:23902451

  2. Sweep direction and efficiency of the swept-frequency two pulse phase modulated scheme for heteronuclear dipolar-decoupling in solid-state NMR

    NASA Astrophysics Data System (ADS)

    Paul, Subhradip; Vinod Chandran, C.; Bräuniger, T.; Madhu, P. K.

    2011-04-01

    We present here a bimodal Floquet theoretical and experimental investigation of the direction of sweep in the swept-frequency two pulse phase modulated (SW f-TPPM) scheme used for heteronuclear dipolar decoupling in solid-state NMR. The efficiency of the decoupling turns out to be independent of the sweep direction.

  3. Direct observation of frequency modulated transcription in single cells using light activation

    PubMed Central

    Larson, Daniel R; Fritzsch, Christoph; Sun, Liang; Meng, Xiuhau; Lawrence, David S; Singer, Robert H

    2013-01-01

    Single-cell analysis has revealed that transcription is dynamic and stochastic, but tools are lacking that can determine the mechanism operating at a single gene. Here we utilize single-molecule observations of RNA in fixed and living cells to develop a single-cell model of steroid-receptor mediated gene activation. We determine that steroids drive mRNA synthesis by frequency modulation of transcription. This digital behavior in single cells gives rise to the well-known analog dose response across the population. To test this model, we developed a light-activation technology to turn on a single steroid-responsive gene and follow dynamic synthesis of RNA from the activated locus. DOI: http://dx.doi.org/10.7554/eLife.00750.001 PMID:24069527

  4. Receiver Signal to Noise Ratios for IPDA Lidars Using Sine-wave and Pulsed Laser Modulation and Direct Detections

    NASA Technical Reports Server (NTRS)

    Sun, Xiaoli; Abshire, James B.

    2011-01-01

    Integrated path differential absorption (IPDA) lidar can be used to remotely measure the column density of gases in the path to a scattering target [1]. The total column gas molecular density can be derived from the ratio of the laser echo signal power with the laser wavelength on the gas absorption line (on-line) to that off the line (off-line). 80th coherent detection and direct detection IPDA lidar have been used successfully in the past in horizontal path and airborne remote sensing measurements. However, for space based measurements, the signal propagation losses are often orders of magnitude higher and it is important to use the most efficient laser modulation and detection technique to minimize the average laser power and the electrical power from the spacecraft. This paper gives an analysis the receiver signal to noise ratio (SNR) of several laser modulation and detection techniques versus the average received laser power under similar operation environments. Coherent detection [2] can give the best receiver performance when the local oscillator laser is relatively strong and the heterodyne mixing losses are negligible. Coherent detection has a high signal gain and a very narrow bandwidth for the background light and detector dark noise. However, coherent detection must maintain a high degree of coherence between the local oscillator laser and the received signal in both temporal and spatial modes. This often results in a high system complexity and low overall measurement efficiency. For measurements through atmosphere the coherence diameter of the received signal also limits the useful size of the receiver telescope. Direct detection IPDA lidars are simpler to build and have fewer constraints on the transmitter and receiver components. They can use much larger size 'photon-bucket' type telescopes to reduce the demands on the laser transmitter. Here we consider the two most widely used direct detection IPDA lidar techniques. The first technique uses two CW seeder lasers, one on-line and one offline that are intensity modulated by two different frequency sine-waves signals before being amplified by a common laser amplifier. The receiver uses narrowband amplitude demodulation, or lock-in, Signal processing at the given laser modulation frequencies [3,4]. The laser transmitter operates in a quasi CW mode with the peak power equal to twice the average power. The on-line and off-line lasers can be transmitted at the same time without interference. Another direct detection technique uses a low duty cycle pulsed laser modulation [5,6] with the laser wavelengths alternating between on-line and off-line on successive pulses. The receiver uses time resolved detection and can also provide simultaneous target range measurement. With a lower laser duty cycle it requires a much higher peak laser power for the same average power.

  5. Modulation of spatial propagation dynamics in a three-core linear directional coupler

    NASA Astrophysics Data System (ADS)

    Bayal, Indranil; Dutta, Bibhas Kumar; Panchadhyayee, Pradipta; Mahapatra, Prasanta Kumar

    2013-05-01

    A new class of three-core linear directional coupler is demonstrated, in which the centers of the cross-section of the waveguides (WGs) form the vertices of a triangle. Gaussian-type interaction is assumed to couple each WG directly to other WGs. By employing coupled mode equations under slowly varying envelope approximation, we numerically analyze the optical field dynamics in the three transmission channels. Under different parameter conditions, the coupler exhibits wide-ranging characteristics including nonadiabatic to adiabatic evolution of light transfer in versatile manners.

  6. Dynamic routing and frequency slot allocation in elastic optical path network using adaptive modulations with consideration of both spectrum availability and distance

    NASA Astrophysics Data System (ADS)

    Ding, Hui; Zhang, Min; Xie, Jiuyu; Wang, Ying; Ye, Fei; Zhang, Lifang; Chen, Xue

    2011-12-01

    We proposed a dynamic routing and frequency slots allocation scheme which adopted the adaptive modulation for a novel Spectrum-sLICed Elastic optical path network (SLICE). In our dynamic routing scheme, both spectrum resource availability (SRA) and distance (hop number) are considered at the modulation format selection phase for adaptive modulation. We then conducted numerical simulation to compare our Spectrum Resource Adaptive and Distance Adaptive (SRA-DA) mechanism with previous DA in both small network topology and 7×7 mesh topology. Results shown that SRA-DA mechanism achieved lower blocking rate and higher slots utilization compared to DA in bigger networks.

  7. Random and directed walk-based top-  queries in wireless sensor networks.

    PubMed

    Fu, Jun-Song; Liu, Yun

    2015-01-01

    In wireless sensor networks, filter-based top-  query approaches are the state-of-the-art solutions and have been extensively researched in the literature, however, they are very sensitive to the network parameters, including the size of the network, dynamics of the sensors' readings and declines in the overall range of all the readings. In this work, a random walk-based top-  query approach called RWTQ and a directed walk-based top-  query approach called DWTQ are proposed. At the beginning of a top-  query, one or several tokens are sent to the specific node(s) in the network by the base station. Then, each token walks in the network independently to record and process the readings in a random or directed way. A strategy of choosing the "right" way in DWTQ is carefully designed for the token(s) to arrive at the high-value regions as soon as possible. When designing the walking strategy for DWTQ, the spatial correlations of the readings are also considered. Theoretical analysis and simulation results indicate that RWTQ and DWTQ both are very robust against these parameters discussed previously. In addition, DWTQ outperforms TAG, FILA and EXTOK in transmission cost, energy consumption and network lifetime. PMID:26016914

  8. Goal Certainty Modulates Infants' Goal-Directed Gaze Shifts

    ERIC Educational Resources Information Center

    Henrichs, Ivanina; Elsner, Claudia; Elsner, Birgit; Wilkinson, Nick; Gredebäck, Gustaf

    2014-01-01

    We investigated whether 12-month-old infants rely on information about the certainty of goal selection in order to predict observed reaching actions. Infants' goal-directed gaze shifts were recorded as they observed action sequences in a multiple-goals design. We found that 12-month-old infants exhibited gaze shifts significantly earlier when…

  9. Multi-Disciplinary Challenges and Directions in Networked Cyber-Physical Systems

    E-print Network

    Liberatore, Vincenzo

    plants (e.g., robots, infrastructure). New Metrics. Cyber-physical research should be evaluated alongMulti-Disciplinary Challenges and Directions in Networked Cyber-Physical Systems Michael S. Branicky M. Cenk C¸avu¸soglu Vincenzo Liberatore Introduction. Cyber-physical research is an inherently

  10. Conservation laws for voter-like models on random directed networks

    E-print Network

    Stadler, Peter F.

    Conservation laws for voter-like models on random directed networks M. ´Angeles Serrano1 that conserved quantities as weighted linear superpositions of spin states exist for all three processes and of the relative densities that decay exponentially to a homogeneous stationary value given by the conserved

  11. Neural network speed controller of induction motor drive based on direct MRAC method

    Microsoft Academic Search

    Xianglong Jiang; Jin Zhao; Hui Luo; Shanmei Cheng; Shuyun Wan

    2003-01-01

    A novel neural network speed controller (NNSC) of induction motor drive is presented, which is on-line trained by a dynamic BP algorithm based on direct model reference adaptive control (MRAC) method. In particular, a new error function is used for the dynamic BP algorithm, which can adjust the parameters of NNSC and minimize the error between motor speed and the

  12. Computing with Snakes in Directed Networks of Automata Shimon Even*, Ami Litman* and Peter Winkler*

    E-print Network

    Winkler, Peter

    ­­ ­­ Computing with Snakes in Directed Networks of Automata Shimon Even*, Ami Litman* and Peter, Lucent Technologies, 700 Mountain Ave., Murray Hill, NJ. E­address: even@cs.technion.ac.il Ami litman­ address: litman@cs.technion.ac.il Peter Winkler is with Bell Laboratories, Lucent Technologies, 700

  13. Global epidemic invasion thresholds in directed cattle subpopulation networks having source, sink, and transit nodes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Through the characterization of a metapopulation cattle disease model on a directed network having source, transit, and sink nodes, we derive two global epidemic invasion thresholds. The first threshold defines the conditions necessary for an epidemic to successfully spread at the global scale. The ...

  14. NRC TLD Direct Radiation Monitoring Network progress report, October--December 1994. Volume 14, No. 4

    SciTech Connect

    Struckmeyer, R.

    1995-03-01

    This report presents the results of the NRC Direct Radiation Monitoring Network for the fourth quarter of 1994. It provides the ambient radiation levels measured in the vicinity of 75 sites throughout the United States. In addition, it describes the equipment used, monitoring station selection criteria, characterization of the dosimeter response, calibration procedures, statistical methods, intercomparison, and quality assurance program.

  15. Direct Frequency-Information Processing Using Neural Networks Akira Hirose1 and Rolf Eckmiller

    E-print Network

    Behnke, Sven

    is applicable not only to frequency-signal processing but also to future optical neural computing and quantum carrier we use. This fact suggests that the future neural device should treat quantum aspectsDirect Frequency-Information Processing Using Neural Networks Akira Hirose1 and Rolf Eckmiller

  16. Quantum secure direct communication network with superdense coding and decoy photons

    E-print Network

    Fu-Guo Deng; Xi-Han Li; Chun-Yan Li; Ping Zhou; Hong-Yu Zhou

    2007-06-15

    A quantum secure direct communication network scheme is proposed with quantum superdense coding and decoy photons. The servers on a passive optical network prepare and measure the quantum signal, i.e., a sequence of the $d$-dimensional Bell states. After confirming the security of the photons received from the receiver, the sender codes his secret message on them directly. For preventing a dishonest server from eavesdropping, some decoy photons prepared by measuring one photon in the Bell states are used to replace some original photons. One of the users on the network can communicate any other one. This scheme has the advantage of high capacity, and it is more convenient than others as only a sequence of photons is transmitted in quantum line.

  17. Identifying influential nodes in large-scale directed networks: the role of clustering.

    PubMed

    Chen, Duan-Bing; Gao, Hui; Lü, Linyuan; Zhou, Tao

    2013-01-01

    Identifying influential nodes in very large-scale directed networks is a big challenge relevant to disparate applications, such as accelerating information propagation, controlling rumors and diseases, designing search engines, and understanding hierarchical organization of social and biological networks. Known methods range from node centralities, such as degree, closeness and betweenness, to diffusion-based processes, like PageRank and LeaderRank. Some of these methods already take into account the influences of a node's neighbors but do not directly make use of the interactions among it's neighbors. Local clustering is known to have negative impacts on the information spreading. We further show empirically that it also plays a negative role in generating local connections. Inspired by these facts, we propose a local ranking algorithm named ClusterRank, which takes into account not only the number of neighbors and the neighbors' influences, but also the clustering coefficient. Subject to the susceptible-infected-recovered (SIR) spreading model with constant infectivity, experimental results on two directed networks, a social network extracted from delicious.com and a large-scale short-message communication network, demonstrate that the ClusterRank outperforms some benchmark algorithms such as PageRank and LeaderRank. Furthermore, ClusterRank can also be applied to undirected networks where the superiority of ClusterRank is significant compared with degree centrality and k-core decomposition. In addition, ClusterRank, only making use of local information, is much more efficient than global methods: It takes only 191 seconds for a network with about [Formula: see text] nodes, more than 15 times faster than PageRank. PMID:24204833

  18. Functional network reorganization in motor cortex can be explained by reward-modulated Hebbian learning.

    PubMed

    Legenstein, Robert; Chase, Steven M; Schwartz, Andrew B; Maass, Wolfgang

    2009-01-01

    The control of neuroprosthetic devices from the activity of motor cortex neurons benefits from learning effects where the function of these neurons is adapted to the control task. It was recently shown that tuning properties of neurons in monkey motor cortex are adapted selectively in order to compensate for an erroneous interpretation of their activity. In particular, it was shown that the tuning curves of those neurons whose preferred directions had been misinterpreted changed more than those of other neurons. In this article, we show that the experimentally observed self-tuning properties of the system can be explained on the basis of a simple learning rule. This learning rule utilizes neuronal noise for exploration and performs Hebbian weight updates that are modulated by a global reward signal. In contrast to most previously proposed reward-modulated Hebbian learning rules, this rule does not require extraneous knowledge about what is noise and what is signal. The learning rule is able to optimize the performance of the model system within biologically realistic periods of time and under high noise levels. When the neuronal noise is fitted to experimental data, the model produces learning effects similar to those found in monkey experiments. PMID:25284966

  19. GABAergic and glycinergic inputs modulate rhythmogenic mechanisms in the lamprey respiratory network

    PubMed Central

    Cinelli, Elenia; Mutolo, Donatella; Robertson, Brita; Grillner, Sten; Contini, Massimo; Pantaleo, Tito; Bongianni, Fulvia

    2014-01-01

    We have previously shown that GABA and glycine modulate respiratory activity in the in vitro brainstem preparations of the lamprey and that blockade of GABAA and glycine receptors restores the respiratory rhythm during apnoea caused by blockade of ionotropic glutamate receptors. However, the neural substrates involved in these effects are unknown. To address this issue, the role of GABAA, GABAB and glycine receptors within the paratrigeminal respiratory group (pTRG), the proposed respiratory central pattern generator, and the vagal motoneuron region was investigated both during apnoea induced by blockade of glutamatergic transmission and under basal conditions through microinjections of specific antagonists. The removal of GABAergic, but not glycinergic transmission within the pTRG, causes the resumption of rhythmic respiratory activity during apnoea, and reveals the presence of a modulatory control of the pTRG under basal conditions. A blockade of GABAA and glycine receptors within the vagal region strongly increases the respiratory frequency through disinhibition of neurons projecting to the pTRG from the vagal region. These neurons were retrogradely labelled (neurobiotin) from the pTRG. Intense GABA immunoreactivity is observed both within the pTRG and the vagal area, which corroborates present findings. The results confirm the pTRG as a primary site of respiratory rhythm generation, and suggest that inhibition modulates the activity of rhythm-generating neurons, without any direct role in burst formation and termination mechanisms. PMID:24492840

  20. Estimating the 3D Pore Size Distribution of Biopolymer Networks from Directionally Biased Data

    PubMed Central

    Lang, Nadine R.; Münster, Stefan; Metzner, Claus; Krauss, Patrick; Schürmann, Sebastian; Lange, Janina; Aifantis, Katerina E.; Friedrich, Oliver; Fabry, Ben

    2013-01-01

    The pore size of biopolymer networks governs their mechanical properties and strongly impacts the behavior of embedded cells. Confocal reflection microscopy and second harmonic generation microscopy are widely used to image biopolymer networks; however, both techniques fail to resolve vertically oriented fibers. Here, we describe how such directionally biased data can be used to estimate the network pore size. We first determine the distribution of distances from random points in the fluid phase to the nearest fiber. This distribution follows a Rayleigh distribution, regardless of isotropy and data bias, and is fully described by a single parameter—the characteristic pore size of the network. The bias of the pore size estimate due to the missing fibers can be corrected by multiplication with the square root of the visible network fraction. We experimentally verify the validity of this approach by comparing our estimates with data obtained using confocal fluorescence microscopy, which represents the full structure of the network. As an important application, we investigate the pore size dependence of collagen and fibrin networks on protein concentration. We find that the pore size decreases with the square root of the concentration, consistent with a total fiber length that scales linearly with concentration. PMID:24209841

  1. Opinion formation driven by PageRank node influence on directed networks

    E-print Network

    Eom, Young-Ho

    2015-01-01

    We study a two states opinion formation model driven by PageRank node influence and report an extensive numerical study on how PageRank affects collective opinion formations in large-scale empirical directed networks. In our model the opinion of a node can be updated by the sum of its neighbor nodes' opinions weighted by the node influence of the neighbor nodes at each step. We consider PageRank probability and its sublinear power as node influence measures and investigate evolution of opinion under various conditions. First, we observe that all networks reach steady state opinion after a certain relaxation time. This time scale is decreasing with the heterogeneity of node influence in the networks. Second, we find that our model shows consensus and non-consensus behavior in steady state depending on types of networks: Web graph, citation network of physics articles, and LiveJournal social network show non-consensus behavior while Wikipedia article network shows consensus behavior. Third, we find that a more ...

  2. Multifunctional carbon nanotube/bioceramics modulate the directional growth and activity of osteoblastic cells.

    PubMed

    Mata, D; Oliveira, F J; Ferro, M; Gomes, P S; Fernandes, M H; Lopes, M A; Silval, R F

    2014-05-01

    Biomaterials can still be reinvented to become simple and universal bone regeneration solutions. Following this roadmap, a bone graft of carbon nanotube (CNT)/glass/hydroxyapatite (HA) with controlled CNT agglomeration state was designed with multifunctionalities able to stimulate the bone cell phenotype. The preparation route, the mechanical and electrical behavior and the in vitro profiles of degradation and osteocompatibility were described. A non-destructive dynamic route was found to have a higher influence than the Diels-Alder functionalization one on controlling the CNT agglomerate state in the ceramic-matrix composite. Biologically safe CNT agglomerates, with diameter sizes below 3 microm homogenously distributed, were obtained in non-functionalized and functionalized composites. Yet, the lowest CNT damage and the highest mechanical and electrical properties were found for the non-functionalized materials. Even though that these composites present higher degradation rate at pH:3 than the ceramic matrix, the CNT agglomerates are released with safe diameter sizes. Also, non-functionalized composites allowed cellular adhesion and modulated the orientation of the cell growth, with a proliferation/differentiation relationship favoring osteoblastic functional activity. Findings offer further contributions for bone tissue engineering by showing that multifunctional bone grafts with high electroconductivity, and integrating CNT agglomerates with maximized interfacing area, allow the in situ control of bone cell functions. PMID:24734525

  3. Temperature regulates limb length in homeotherms by directly modulating cartilage growth.

    PubMed

    Serrat, Maria A; King, Donna; Lovejoy, C Owen

    2008-12-01

    Allen's Rule documents a century-old biological observation that strong positive correlations exist among latitude, ambient temperature, and limb length in mammals. Although genetic selection for thermoregulatory adaptation is frequently presumed to be the primary basis of this phenomenon, important but frequently overlooked research has shown that appendage outgrowth is also markedly influenced by environmental temperature. Alteration of limb blood flow via vasoconstriction/vasodilation is the current default hypothesis for this growth plasticity, but here we show that tissue perfusion does not fully account for differences in extremity elongation in mice. We show that peripheral tissue temperature closely reflects housing temperature in vivo, and we demonstrate that chondrocyte proliferation and extracellular matrix volume strongly correlate with tissue temperature in metatarsals cultured without vasculature in vitro. Taken together, these data suggest that vasomotor changes likely modulate extremity growth indirectly, via their effects on appendage temperature, rather than vascular nutrient delivery. When combined with classic evolutionary theory, especially genetic assimilation, these results provide a potentially comprehensive explanation of Allen's Rule, and may substantially impact our understanding of phenotypic variation in living and extinct mammals, including humans. PMID:19047632

  4. Bilateral dorsolateral prefrontal cortex modulation for tinnitus by transcranial direct current stimulation: a preliminary clinical study

    Microsoft Academic Search

    Sven Vanneste; Mark Plazier; Jan Ost; Elsa van der Loo; Paul Van de Heyning; Dirk De Ridder

    2010-01-01

    Tinnitus is considered as an auditory phantom percept. Preliminary evidence indicates that transcranial direct current stimulation\\u000a (tDCS) of the temporo-parietal area might reduce tinnitus. tDCS studies of the prefrontal cortex have been successful in reducing\\u000a depression, impulsiveness and pain. Recently, it was shown that the prefrontal cortex is important for the integration of\\u000a sensory and emotional aspects of tinnitus. As

  5. Multiplexed dual first-dimension comprehensive two-dimensional gas chromatography-mass spectrometry with contra-directional thermal modulation.

    PubMed

    Savareear, Benjamin; Jacobs, Matthew R; Shellie, Robert A

    2014-10-24

    A multiplexed dual-primary column comprehensive two-dimensional gas chromatography-mass spectrometry approach (2GC×GC-MS) is introduced. The approach splits injected samples into two first-dimension columns with different stationary phases, and recombines the two streams into one second-dimension column that terminates at a single detector. The approach produces two two-dimensional chromatograms for each injection, and is made possible by using a dual-stage modulator operated in contra-directional modulation mode. The dual two-dimensional chromatograms produced by this single detector system provide complementary information due to selectivity differences between the three separation columns used in the column ensemble. An aged Australian tea tree (Melaleuca alternifolia) essential oil was analyzed to demonstrate the 2GC×GC-MS approach. The number of compounds separated by each of the GC×GC separations in the 2GC×GC experiment is comparable to conventional GC×GC experiments with matching column configurations. Robust peak assignment was possible for this sample based on the combination of MS library matches and multiple linear retention index searching. Forty-nine components (22 unique) were identified using a non-polar×mid-polar column combination and 34 components (7 unique) were positively identified using a polar×mid-polar column combination. Twenty-seven peak assignments were corroborated by positive identification in both of the multiplexed separations. PMID:25249490

  6. Recent developments of InP-based quantum dashes for directly modulated lasers and semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Lelarge, F.; Brenot, R.; Rousseau, B.; Martin, F.; Patriarche, G.; Poingt, F.; LeGouezigou, L.; Le Gouezigou, O.; Dernazaretian, C.; Derouin, E.; Drisse, O.; Pommereau, F.; Accard, A.; Caligaro, M.; Make, D.; Provost, J.-G.; Resneau, P.; Dagens, B.; van-Dijk, F.; Krakowski, M.; Duan, G. H.

    2008-02-01

    We report on the recent advances in InP-based Quantum Dashes (Qdashes) material for 1.55?m optoelectronic devices. We achieve highly uniform, reproducible and wavelength-controlled Qdashes, with a length ranging from 50nm to 500nm depending on the growth conditions. These Qdashes lead either to high modal gain distributed feedback (DFB) lasers or low chirp semiconductor optical amplifier (SOA). Moreover, we demonstrate that Qdashes are compatible with buried ridge stripe and shallow ridge technology and lead to very reliable lasers. Directly modulated lasers with 10GHz bandwidth are demonstrated in continuous wave mode operation. 10Gb/s transmission over 25km in semi-cooled operation is achieved using DFB buried lasers. Qdashes optimization leads to SOA with internal gain of 10 dB and a -3dB optical bandwidth of 120 nm at 50°C, paving the way for semi-cooled CWDM optical sources. Furthermore, low chirp Qdashes SOA are evaluated as optical boosters after a modulated source. Although we still observe overshoots on the amplified signal, the chirp, even in their saturation regime, is low enough to allow for 50 km of transmission at 10Gb/s.

  7. Spike coherence and synchronization on Newman-Watts small-world neuronal networks modulated by spike-timing-dependent plasticity

    NASA Astrophysics Data System (ADS)

    Yu, Haitao; Guo, Xinmeng; Wang, Jiang; Deng, Bin; Wei, Xile

    2015-02-01

    The effects of spike-timing-dependent plasticity (STDP) and noise intensity on the temporal and spatial dynamics of Newman-Watts small-world neuronal networks are studied. Numerical results show that, an intermediate intensity of additive noise can optimize the dynamical response of the neural system, where the noise-induced coherence resonance and spiking synchronization occur. The adaptive coupling modulated by STDP can largely depress the temporal coherence and spatial synchrony induced by external noise and random shortcuts. In particular, as the adjusting rate increases, lower noise intensity is needed to maximize the networked synchronization, and more connections are introduced to achieve coherence resonance. Moreover, the small-world topology can significantly affect the dynamics of excitable neuronal networks. It is found that the temporal coherence of neuronal activity reaches peaks for an appropriate number of random shortcuts, while the spiking synchronization is always enhanced as more shortcuts are added into the network.

  8. Generation of linear frequency modulation signal with reduced round-off error using pulse-output direct digital synthesis technique

    NASA Astrophysics Data System (ADS)

    Peng, Cheng Y.; Ma, Xiao C.; Yan, She F.; Yang, Li.

    2014-02-01

    The pulse-output Direct Digital Synthesis (DDS), in which the overflow signal of the phase accumulator is used for the pulse output, can be easily implemented due to its simple hardware architecture and low algorithm complexity. This paper introduces the fundamentals for generating Linear Frequency Modulation (LFM) pulse using pulse-output DDS technique. Error introducing mechanisms that affect the accuracy of signal's duration, initial phase, and frequency are studied. Extensive analysis of round-off error is given. A modified hardware architecture for LFM pulse generation with reduced round-off error is proposed. Experiment results are given, which shows that the proposed generator is promising in applications such as sonar transmitters.

  9. Transcranial direct current stimulation of SMA modulates anticipatory postural adjustments without affecting the primary movement.

    PubMed

    Bolzoni, Francesco; Bruttini, Carlo; Esposti, Roberto; Castellani, Carlotta; Cavallari, Paolo

    2015-09-15

    Recent works provide evidences that anticipatory postural adjustments (APAs) are programmed with the prime mover recruitment as a shared posturo-focal command. However the ability of the CNS to adjust APAs to changes in the postural context implies that the postural and voluntary components should take different pathways before reaching the representation of single muscles in the primary motor cortex. Here we test if such bifurcation takes place at the level of the supplementary motor area (SMA). TDCS was applied over the SMA in 14 subjects, who produced a brisk index-finger flexion. This activity is preceded by inhibitory APAs, carved in the tonic activity of Biceps Brachii and Anterior Deltoid, and by an excitatory APA in Triceps Brachii. Subjects performed a series of 30 flexions before, during and after 20min of tDCS in CATHODAL, ANODAL or SHAM configuration. The inhibitory APA in Biceps and the excitatory APA in Triceps were both greater in ANODAL than in SHAM and CATHODAL configurations, while no difference was found among the latter two (ANODAL vs. SHAM: biceps +26.5%, triceps +66%; ANODAL vs. CATHODAL: biceps +20.5%, triceps: +63.4%; for both muscles, ANOVA p<0.02, Tukey p<0.05). Instead, the APA in anterior deltoid was unchanged in all configurations. No changes were observed in prime mover recruitment and index-finger kinematics. Results show that the SMA is involved in modulating APAs amplitude. Moreover, the differential effect of tDCS observed on postural and voluntary commands suggests that these two components of the motor program are already separated before entering SMA. PMID:26055201

  10. Mesoporous silica nanoparticle-based substrates for cell directed delivery of Notch signalling modulators to control myoblast differentiation

    NASA Astrophysics Data System (ADS)

    Böcking, Dominique; Wiltschka, Oliver; Niinimäki, Jenni; Shokry, Hussein; Brenner, Rolf; Lindén, Mika; Sahlgren, Cecilia

    2014-01-01

    Biochemical cues are critical to control stem cell function and can be utilized to develop smart biomaterials for stem cell engineering. The challenge is to deliver these cues in a restricted manner with spatial and temporal control. Here we have developed bilayer films of mesoporous silica nanoparticles for delayed cellular delivery of Notch modulators to promote muscle stem cell differentiation. We demonstrate that drug-loaded particles are internalized from the particle-covered surface, which allows for direct delivery of the drug into the cell and a delayed and confined drug release. Substrates of particles loaded with ?-secretase-inhibitors, which block the Notch signalling pathway, promoted efficient differentiation of myoblasts. The particle substrates were fully biocompatible and did not interfere with the inherent differentiation process. We further demonstrate that impregnating commercially available, biocompatible polymer scaffolds with MSNs allows for a free standing substrate for cell directed drug delivery.Biochemical cues are critical to control stem cell function and can be utilized to develop smart biomaterials for stem cell engineering. The challenge is to deliver these cues in a restricted manner with spatial and temporal control. Here we have developed bilayer films of mesoporous silica nanoparticles for delayed cellular delivery of Notch modulators to promote muscle stem cell differentiation. We demonstrate that drug-loaded particles are internalized from the particle-covered surface, which allows for direct delivery of the drug into the cell and a delayed and confined drug release. Substrates of particles loaded with ?-secretase-inhibitors, which block the Notch signalling pathway, promoted efficient differentiation of myoblasts. The particle substrates were fully biocompatible and did not interfere with the inherent differentiation process. We further demonstrate that impregnating commercially available, biocompatible polymer scaffolds with MSNs allows for a free standing substrate for cell directed drug delivery. Electronic supplementary information (ESI) available: (1) Particle characterization. (2) Immunohistochemistry and SEM analyses of C2C12 cells grown on films for 3, 6, 24 and 72 h. Light microscopy and WST1 analyses of cells grown on cover slips and films for 6, 24 and 72 h (3) Quantification of protein levels of C2C12 cells differentiating on cover slips versus MSN films. (4) Stability of MSN films in biological solution and the influence on cell viability. (5) Cell internalization of particles from MSN films and intracellular drug release at 12 and 24 h (6) Cell internalization and intracellular DiI release of MSNs from (3Dtro®) fiber scaffolds impregnated with MSNs. See DOI: 10.1039/c3nr04022d

  11. A radio-aware routing algorithm for reliable directed diffusion in lossy wireless sensor networks.

    PubMed

    Kim, Yong-Pyo; Jung, Euihyun; Park, Yong-Jin

    2009-01-01

    In Wireless Sensor Networks (WSNs), transmission errors occur frequently due to node failure, battery discharge, contention or interference by objects. Although Directed Diffusion has been considered as a prominent data-centric routing algorithm, it has some weaknesses due to unexpected network errors. In order to address these problems, we proposed a radio-aware routing algorithm to improve the reliability of Directed Diffusion in lossy WSNs. The proposed algorithm is aware of the network status based on the radio information from MAC and PHY layers using a cross-layer design. The cross-layer design can be used to get detailed information about current status of wireless network such as a link quality or transmission errors of communication links. The radio information indicating variant network conditions and link quality was used to determine an alternative route that provides reliable data transmission under lossy WSNs. According to the simulation result, the radio-aware reliable routing algorithm showed better performance in both grid and random topologies with various error rates. The proposed solution suggested the possibility of providing a reliable transmission method for QoS requests in lossy WSNs based on the radio-awareness. The energy and mobility issues will be addressed in the future work. PMID:22408493

  12. Attitudes towards Social Networking and Sharing Behaviors among Consumers of Direct-to-Consumer Personal Genomics

    PubMed Central

    Lee, Sandra Soo-Jin; Vernez, Simone L.; Ormond, K.E.; Granovetter, Mark

    2013-01-01

    Little is known about how consumers of direct-to-consumer personal genetic services share personal genetic risk information. In an age of ubiquitous online networking and rapid development of social networking tools, understanding how consumers share personal genetic risk assessments is critical in the development of appropriate and effective policies. This exploratory study investigates how consumers share personal genetic information and attitudes towards social networking behaviors. Methods: Adult participants aged 23 to 72 years old who purchased direct-to-consumer genetic testing from a personal genomics company were administered a web-based survey regarding their sharing activities and social networking behaviors related to their personal genetic test results. Results: 80 participants completed the survey; of those, 45% shared results on Facebook and 50.9% reported meeting or reconnecting with more than 10 other individuals through the sharing of their personal genetic information. For help interpreting test results, 70.4% turned to Internet websites and online sources, compared to 22.7% who consulted their healthcare providers. Amongst participants, 51.8% reported that they believe the privacy of their personal genetic information would be breached in the future. Conclusion: Consumers actively utilize online social networking tools to help them share and interpret their personal genetic information. These findings suggest a need for careful consideration of policy recommendations in light of the current ambiguity of regulation and oversight of consumer initiated sharing activities. PMID:25562728

  13. miR-25 modulates NSCLC cell radio-sensitivity through directly inhibiting BTG2 expression.

    PubMed

    He, Zhiwei; Liu, Yi; Xiao, Bing; Qian, Xiaosen

    2015-02-13

    A large proportion of the NSCLC patients were insensitive to radiotherapy, but the exact mechanism is still unclear. This study explored the role of miR-25 in regulating sensitivity of NSCLC cells to ionizing radiation (IR) and its downstream targets. Based on measurement in tumor samples from NSCLC patients, this study found that miR-25 expression is upregulated in both NSCLC and radio-resistant NSCLC patients compared the healthy and radio-sensitive controls. In addition, BTG expression was found negatively correlated with miR-25a expression in the both tissues and cells. By applying luciferase reporter assay, we verified two putative binding sites between miR-25 and BTG2. Therefore, BTG2 is a directly target of miR-25 in NSCLC cancer. By applying loss-and-gain function analysis in NSCLC cell lines, we demonstrated that miR-25-BTG2 axis could directly regulated BTG2 expression and affect radiotherapy sensitivity of NSCLC cells. PMID:25576360

  14. Study Modules for Calculus-Based General Physics. [Includes Modules 27-30: Direct-Current Circuits; Magnetic Forces; Ampere's Law; and Faraday's Law].

    ERIC Educational Resources Information Center

    Fuller, Robert G., Ed.; And Others

    This is part of a series of 42 Calculus Based Physics (CBP) modules totaling about 1,000 pages. The modules indlude study guides, practice tests, and mastery tests for a full-year individualized course in calculus-based physics based on the Personalized System of Instruction (PSI). The units are not intended to be used without outside materials;…

  15. Silicon microring modulator for 40 Gb/s NRZ-OOK metro networks in O-band.

    PubMed

    Xuan, Zhe; Ma, Yangjin; Liu, Yang; Ding, Ran; Li, Yunchu; Ophir, Noam; Lim, Andy Eu-Jin; Lo, Guo-Qiang; Magill, Peter; Bergman, Keren; Baehr-Jones, Tom; Hochberg, Michael

    2014-11-17

    A microring-based silicon modulator operating at 40 Gb/s near 1310 nm is demonstrated for the first time to our knowledge. NRZ-OOK signals at 40 Gb/s with 6.2 dB extinction ratio are observed by applying a 4.8 Vpp driving voltage and biasing the modulator at 7 dB insertion loss point. The energy efficiency is 115 fJ/bit. The transmission performance of 40 Gb/s NRZ-OOK through 40 km of standard single mode fiber without dispersion compensation is also investigated. We show that the link suffers negligible dispersion penalty. This makes the modulator a potential candidate for metro network applications. PMID:25402070

  16. Noise-Induced Modulation of the Relaxation Kinetics around a Non-Equilibrium Steady State of Non-Linear Chemical Reaction Networks

    Microsoft Academic Search

    Rajesh Ramaswamy; Ivo F. Sbalzarini; Nélido González-Segredo

    2011-01-01

    Stochastic effects from correlated noise non-trivially modulate the kinetics of non-linear chemical reaction networks. This is especially important in systems where reactions are confined to small volumes and reactants are delivered in bursts. We characterise how the two noise sources confinement and burst modulate the relaxation kinetics of a non-linear reaction network around a non-equilibrium steady state. We find that

  17. Latent Modulation: A Basis for Non-Disruptive Promotion of Two Incompatible Behaviors by a Single Network State

    PubMed Central

    Dacks, Andrew M.; Weiss, Klaudiusz R.

    2013-01-01

    Behavioral states often preferentially enhance specific classes of behavior and suppress incompatible behaviors. In the nervous system, this may involve upregulation of the efficacy of neural modules that mediate responses to one stimulus and suppression of modules that generate antagonistic or incompatible responses to another stimulus. In Aplysia, prestimulation of egestive inputs [esophageal nerve (EN)] facilitates subsequent EN-elicited egestive responses and weakens ingestive responses to ingestive inputs [Cerebral-Buccal Interneuron (CBI-2)]. However, a single state can also promote incompatible behaviors in response to different stimuli. This is the case in Aplysia, where prestimulation of CBI-2 inputs not only enhances subsequent CBI-2-elicited ingestive responses, but also strengthens EN-elicited egestive responses. We used the modularly organized feeding network of Aplysia to characterize the organizational principles that allow a single network state to promote two opposing behaviors, ingestion and egestion, without the two interfering with each other. We found that the CBI-2 prestimulation-induced state upregulates the excitability of neuron B65 which, as a member of the egestive module, increases the strength of egestive responses. Furthermore,we found that this upregulation is likely mediated by the actions of the neuropeptides FCAP (Feeding Circuit Activating Peptide) and CP2 (Cerebral Peptide 2). This increased excitability is mediated by a form of modulation that we refer to as “latent modulation” because it is established during stimulation of CBI-2, which does not activate B65. However, when B65 is recruited into EN-elicited egestive responses, the effects of the latent modulation are expressed as a higher B65 firing rate and a resultant strengthening of the egestive response. PMID:23447591

  18. Social networks and future direction for obesity research: A scoping review.

    PubMed

    Nam, Soohyun; Redeker, Nancy; Whittemore, Robin

    2015-01-01

    Despite significant efforts to decrease obesity rates, the prevalence of obesity continues to increase in the United States. Obesity risk behaviors including physical inactivity, unhealthy eating, and sleep deprivation are intertwined during daily life and are difficult to improve in the current social environment. Studies show that social networks-the thick webs of social relations and interactions-influence various health outcomes, such as HIV risk behaviors, alcohol consumption, smoking, depression, and cardiovascular mortality; however, there is limited information on the influences of social networks on obesity and obesity risk behaviors. Given the complexities of the biobehavioral pathology of obesity and the lack of clear evidence of effectiveness and sustainability of existing interventions that are usually focused on an individual approach, targeting change in an individual's health behaviors or attitude may not take sociocontextual factors into account; there is a pressing need for a new perspective on this problem. In this review, we evaluate the literature on social networks as a potential approach for obesity prevention and treatment (i.e., how social networks affect various health outcomes), present two major social network data analyses (i.e., egocentric and sociometric analysis), and discuss implications and the future direction for obesity research using social networks. PMID:25982770

  19. Modulation of cultured neural networks using neurotrophin release from hydrogel-coated microelectrode arrays

    PubMed Central

    Jun, Sang Beom; Hynd, Matthew R.; Dowell-Mesfin, Natalie M.; Al-Kofahi, Yousef; Roysam, Badrinath; Shain, William; Kim, Sung June

    2009-01-01

    Polyacrylamide and poly(ethylene glycol) diacrylate hydrogels were synthesized and characterized for use as drug-release and substrates for neuron cell culture. Protein release kinetics was determined by incorporating bovine serum albumin (BSA) into hydrogels during polymerization. To determine if hydrogel incorporation and release affects bioactivity, alkaline phosphatase was incorporated into hydrogels and released enzyme activity determined using the fluorescence-based ELF-97 assay. Hydrogels were then used to deliver brain derived neurotrophic factor (BDNF) from hydrogels polymerized over planar microelectrode arrays (MEA). Primary hippocampal neurons were cultured on both control and neurotrophin-containing hydrogel-coated MEAs. The effect of released BDNF on neurite length and process arborization was investigated using automated image analysis. Increased spontaneous activity as a response to released BDNF was recorded from the neurons cultured on top of hydrogel layers. These results demonstrate that proteins of biological interest can be incorporated into hydrogels to modulate development and function of cultured neural networks. These results also set the stage for development of hydrogel-coated neural prosthetic devices for local delivery of various biologically active molecules. PMID:18477815

  20. Virus-induced gene complementation reveals a transcription factor network in modulation of tomato fruit ripening

    PubMed Central

    Zhou, Tao; Zhang, Hang; Lai, Tongfei; Qin, Cheng; Shi, Nongnong; Wang, Huizhong; Jin, Mingfei; Zhong, Silin; Fan, Zaifeng; Liu, Yule; Wu, Zirong; Jackson, Stephen; Giovannoni, James J.; Rolin, Dominique; Gallusci, Philippe; Hong, Yiguo

    2012-01-01

    Plant virus technology, in particular virus-induced gene silencing, is a widely used reverse- and forward-genetics tool in plant functional genomics. However the potential of virus technology to express genes to induce phenotypes or to complement mutants in order to understand the function of plant genes is not well documented. Here we exploit Potato virus X as a tool for virus-induced gene complementation (VIGC). Using VIGC in tomato, we demonstrated that ectopic viral expression of LeMADS-RIN, which encodes a MADS-box transcription factor (TF), resulted in functional complementation of the non-ripening rin mutant phenotype and caused fruits to ripen. Comparative gene expression analysis indicated that LeMADS-RIN up-regulated expression of the SBP-box (SQUAMOSA promoter binding protein-like) gene LeSPL-CNR, but down-regulated the expression of LeHB-1, an HD-Zip homeobox TF gene. Our data support the hypothesis that a transcriptional network may exist among key TFs in the modulation of fruit ripening in tomato. PMID:23150786

  1. Virus-induced gene complementation reveals a transcription factor network in modulation of tomato fruit ripening.

    PubMed

    Zhou, Tao; Zhang, Hang; Lai, Tongfei; Qin, Cheng; Shi, Nongnong; Wang, Huizhong; Jin, Mingfei; Zhong, Silin; Fan, Zaifeng; Liu, Yule; Wu, Zirong; Jackson, Stephen; Giovannoni, James J; Rolin, Dominique; Gallusci, Philippe; Hong, Yiguo

    2012-01-01

    Plant virus technology, in particular virus-induced gene silencing, is a widely used reverse- and forward-genetics tool in plant functional genomics. However the potential of virus technology to express genes to induce phenotypes or to complement mutants in order to understand the function of plant genes is not well documented. Here we exploit Potato virus X as a tool for virus-induced gene complementation (VIGC). Using VIGC in tomato, we demonstrated that ectopic viral expression of LeMADS-RIN, which encodes a MADS-box transcription factor (TF), resulted in functional complementation of the non-ripening rin mutant phenotype and caused fruits to ripen. Comparative gene expression analysis indicated that LeMADS-RIN up-regulated expression of the SBP-box (SQUAMOSA promoter binding protein-like) gene LeSPL-CNR, but down-regulated the expression of LeHB-1, an HD-Zip homeobox TF gene. Our data support the hypothesis that a transcriptional network may exist among key TFs in the modulation of fruit ripening in tomato. PMID:23150786

  2. Evaluation of the new ESR network software for the retrieval of direct sun products from CIMEL CE318 and PREDE POM01 sun-sky radiometers

    NASA Astrophysics Data System (ADS)

    Estellés, V.; Campanelli, M.; Smyth, T. J.; Utrillas, M. P.; Martínez-Lozano, J. A.

    2012-12-01

    The European Skynet Radiometers network (EuroSkyRad or ESR) has been recently established as a research network of European PREDE sun-sky radiometers. Moreover, ESR is federated with SKYNET, an international network of PREDE sun-sky radiometers mostly present in East Asia. In contrast to SKYNET, the European network also integrates users of the CIMEL CE318 sky-sun photometer. Keeping instrumental duality in mind, a set of open source algorithms has been developed consisting of two modules for (1) the retrieval of direct sun products (aerosol optical depth, wavelength exponent and water vapor) from the sun extinction measurements; and (2) the inversion of the sky radiance to derive other aerosol optical properties such as size distribution, single scattering albedo or refractive index. In this study we evaluate the ESR direct sun products in comparison with the AERosol RObotic NETwork (AERONET) products. Specifically, we have applied the ESR algorithm to a CIMEL CE318 and PREDE POM simultaneously for a 4-yr database measured at the Burjassot site (Valencia, Spain), and compared the resultant products with the AERONET direct sun measurements obtained with the same CIMEL CE318 sky-sun photometer. The comparison shows that aerosol optical depth differences are mostly within the nominal uncertainty of 0.003 for a standard calibration instrument, and fall within the nominal AERONET uncertainty of 0.01-0.02 for a field instrument in the spectral range 340 to 1020 nm. In the cases of the Ångström exponent and the columnar water vapor, the differences are lower than 0.02 and 0.15 cm, respectively. Therefore, we present an open source code program that can be used with both CIMEL and PREDE sky radiometers and whose results are equivalent to AERONET and SKYNET retrievals.

  3. Spinal direct current stimulation modulates the activity of gracile nucleus and primary somatosensory cortex in anaesthetized rats

    PubMed Central

    Aguilar, J; Pulecchi, F; Dilena, R; Oliviero, A; Priori, A; Foffani, G

    2011-01-01

    Abstract Afferent somatosensory activity from the spinal cord has a profound impact on the activity of the brain. Here we investigated the effects of spinal stimulation using direct current, delivered at the thoracic level, on the spontaneous activity and on the somatosensory evoked potentials of the gracile nucleus, which is the main entry point for hindpaw somatosensory signals reaching the brain from the dorsal columns, and of the primary somatosensory cortex in anaesthetized rats. Anodal spinal direct current stimulation (sDCS) increased the spontaneous activity and decreased the amplitude of evoked responses in the gracile nucleus, whereas cathodal sDCS produced the opposite effects. At the level of the primary somatosensory cortex, the changes in spontaneous activity induced by sDCS were consistent with the effects observed in the gracile nucleus, but the changes in cortical evoked responses were more variable and state dependent. Therefore, sDCS can modulate in a polarity-specific manner the supraspinal activity of the somatosensory system, offering a versatile bottom-up neuromodulation technique that could potentially be useful in a number of clinical applications. PMID:21825031

  4. A yeast phenomic model for the gene interaction network modulating CFTR-?F508 protein biogenesis

    PubMed Central

    2012-01-01

    Background The overall influence of gene interaction in human disease is unknown. In cystic fibrosis (CF) a single allele of the cystic fibrosis transmembrane conductance regulator (CFTR-?F508) accounts for most of the disease. In cell models, CFTR-?F508 exhibits defective protein biogenesis and degradation rather than proper trafficking to the plasma membrane where CFTR normally functions. Numerous genes function in the biogenesis of CFTR and influence the fate of CFTR-?F508. However it is not known whether genetic variation in such genes contributes to disease severity in patients. Nor is there an easy way to study how numerous gene interactions involving CFTR-?F would manifest phenotypically. Methods To gain insight into the function and evolutionary conservation of a gene interaction network that regulates biogenesis of a misfolded ABC transporter, we employed yeast genetics to develop a 'phenomic' model, in which the CFTR-?F508-equivalent residue of a yeast homolog is mutated (Yor1-?F670), and where the genome is scanned quantitatively for interaction. We first confirmed that Yor1-?F undergoes protein misfolding and has reduced half-life, analogous to CFTR-?F. Gene interaction was then assessed quantitatively by growth curves for approximately 5,000 double mutants, based on alteration in the dose response to growth inhibition by oligomycin, a toxin extruded from the cell at the plasma membrane by Yor1. Results From a comparative genomic perspective, yeast gene interactions influencing Yor1-?F biogenesis were representative of human homologs previously found to modulate processing of CFTR-?F in mammalian cells. Additional evolutionarily conserved pathways were implicated by the study, and a ?F-specific pro-biogenesis function of the recently discovered ER membrane complex (EMC) was evident from the yeast screen. This novel function was validated biochemically by siRNA of an EMC ortholog in a human cell line expressing CFTR-?F508. The precision and accuracy of quantitative high throughput cell array phenotyping (Q-HTCP), which captures tens of thousands of growth curves simultaneously, provided powerful resolution to measure gene interaction on a phenomic scale, based on discrete cell proliferation parameters. Conclusion We propose phenomic analysis of Yor1-?F as a model for investigating gene interaction networks that can modulate cystic fibrosis disease severity. Although the clinical relevance of the Yor1-?F gene interaction network for cystic fibrosis remains to be defined, the model appears to be informative with respect to human cell models of CFTR-?F. Moreover, the general strategy of yeast phenomics can be employed in a systematic manner to model gene interaction for other diseases relating to pathologies that result from protein misfolding or potentially any disease involving evolutionarily conserved genetic pathways. PMID:23270647

  5. Modulation of direct electron transfer of cytochrome c by use of a molecularly imprinted thin film.

    PubMed

    Bosserdt, Maria; Gajovic-Eichelman, Nenad; Scheller, Frieder W

    2013-08-01

    We describe the preparation of a molecularly imprinted polymer film (MIP) on top of a self-assembled monolayer (SAM) of mercaptoundecanoic acid (MUA) on gold, where the template cytochrome c (cyt c) participates in direct electron transfer (DET) with the underlying electrode. To enable DET, a non-conductive polymer film is electrodeposited from an aqueous solution of scopoletin and cyt c on to the surface of a gold electrode previously modified with MUA. The electroactive surface concentration of cyt c was 0.5 pmol cm(-2). In the absence of the MUA layer, no cyt c DET was observed and the pseudo-peroxidatic activity of the scopoletin-entrapped protein, assessed via oxidation of Ampliflu red in the presence of hydrogen peroxide, was only 30% of that for the MIP on MUA. This result indicates that electrostatic adsorption of cyt c by the MUA-SAM substantially increases the surface concentration of cyt c during the electrodeposition step, and is a prerequisite for the productive orientation required for DET. After template removal by treatment with sulfuric acid, rebinding of cyt c to the MUA-MIP-modified electrode occurred with an affinity constant of 100,000 mol(-1) L, a value three times higher than that determined by use of fluorescence titration for the interaction between scopoletin and cyt c in solution. The DET of cyt c in the presence of myoglobin, lysozyme, and bovine serum albumin (BSA) reveals that the MIP layer suppresses the effect of competing proteins. PMID:23660694

  6. Cytosolic extensions directly regulate a rhomboid protease by modulating substrate gating.

    PubMed

    Baker, Rosanna P; Urban, Siniša

    2015-07-01

    Intramembrane proteases catalyse the signal-generating step of various cell signalling pathways, and continue to be implicated in diseases ranging from malaria infection to Parkinsonian neurodegeneration. Despite playing such decisive roles, it remains unclear whether or how these membrane-immersed enzymes might be regulated directly. To address this limitation, here we focus on intramembrane proteases containing domains known to exert regulatory functions in other contexts, and characterize a rhomboid protease that harbours calcium-binding EF-hands. We find calcium potently stimulates proteolysis by endogenous rhomboid-4 in Drosophila cells, and, remarkably, when rhomboid-4 is purified and reconstituted in liposomes. Interestingly, deleting the amino-terminal EF-hands activates proteolysis prematurely, while residues in cytoplasmic loops connecting distal transmembrane segments mediate calcium stimulation. Rhomboid regulation is not orchestrated by either dimerization or substrate interactions. Instead, calcium increases catalytic rate by promoting substrate gating. Substrates with cleavage sites outside the membrane can be cleaved but lose the capacity to be regulated. These observations indicate substrate gating is not an essential step in catalysis, but instead evolved as a mechanism for regulating proteolysis inside the membrane. Moreover, these insights provide new approaches for studying rhomboid functions by investigating upstream inputs that trigger proteolysis. PMID:25970241

  7. Transforming Growth Factor ? Controls the Directional Migration of Hepatocyte Cohorts by Modulating Their Adhesion to Fibronectin

    PubMed Central

    Binamé, Fabien; Lassus, Patrice

    2008-01-01

    Transforming growth factor ? (TGF-?) has a strong impact on liver development and physiopathology, exercised through its pleiotropic effects on growth, differentiation, survival, and migration. When exposed to TGF-?, the mhAT3F cells, immortalized, highly differentiated hepatocytes, maintained their epithelial morphology and underwent dramatic alterations of adhesion, leading to partial or complete detachment from a culture plate, followed by readhesion and spreading. These alterations of adhesive behavior were caused by sequential changes in expression of the ?5?1 integrin and of its ligand, the fibronectin. The altered specificity of anchorage to the extracellular matrix gave rise to changes in cells' collective motility: cohorts adhering to fibronectin maintained a persistent, directional motility, with ezrin-rich pathfinder cells protruding from the tips of the cohorts. The absence of adhesion to fibronectin prevented the appearance of polarized pathfinders and lead to random, oscillatory motility. Our data suggest a novel role for TGF-? in the control of collective migration of epithelial cohorts. PMID:18094041

  8. Checkpoint modulation - A new way to direct the immune system against renal cell carcinoma.

    PubMed

    Bedke, Jens; Kruck, Stephan; Gakis, Georgios; Stenzl, Arnulf; Goebell, Peter J

    2015-05-01

    The introduction of targeted therapies like the tyrosine kinase (TKI) and mammalian target of rapamycin (mTOR) inhibitors has improved patients´ survival in general. Nevertheless the prognosis remains limited. Therapies with a new mode of action are urgently warranted, especially those who would provoke long-term responders or long-lasting complete remissions as observed with unspecific immunotherapy with the cytokines interleukin-2 and interferon-?. In the recent years a deeper understanding of the underlying immunology of T cell activation led to the development of checkpoint inhibitors, which are mainly monocloncal antibodies and which enhances the presence of the co-stimulatory signals needed for T cell activation or priming. This review discusses the clinical data and ongoing studies available for the inhibition of the PD-1 (CD279) and CTLA-4 (CD152) axis in mRCC. In addition, potential future immunological targets are discussed. This approach of T-cell activation or re-activation by immunological checkpoint inhibition holds the inherent promise to directly affect the tumor cell and thereby to potentially cure a subset of patients with mRCC. PMID:25912622

  9. Selective attention modulates the direction of audio-visual temporal recalibration.

    PubMed

    Ikumi, Nara; Soto-Faraco, Salvador

    2014-01-01

    Temporal recalibration of cross-modal synchrony has been proposed as a mechanism to compensate for timing differences between sensory modalities. However, far from the rich complexity of everyday life sensory environments, most studies to date have examined recalibration on isolated cross-modal pairings. Here, we hypothesize that selective attention might provide an effective filter to help resolve which stimuli are selected when multiple events compete for recalibration. We addressed this question by testing audio-visual recalibration following an adaptation phase where two opposing audio-visual asynchronies were present. The direction of voluntary visual attention, and therefore to one of the two possible asynchronies (flash leading or flash lagging), was manipulated using colour as a selection criterion. We found a shift in the point of subjective audio-visual simultaneity as a function of whether the observer had focused attention to audio-then-flash or to flash-then-audio groupings during the adaptation phase. A baseline adaptation condition revealed that this effect of endogenous attention was only effective toward the lagging flash. This hints at the role of exogenous capture and/or additional endogenous effects producing an asymmetry toward the leading flash. We conclude that selective attention helps promote selected audio-visual pairings to be combined and subsequently adjusted in time but, stimulus organization exerts a strong impact on recalibration. We tentatively hypothesize that the resolution of recalibration in complex scenarios involves the orchestration of top-down selection mechanisms and stimulus-driven processes. PMID:25004132

  10. Categorization is modulated by transcranical direct current stimulation over left prefrontal cortex

    PubMed Central

    Lupyan, Gary; Mirman, Daniel; Hamilton, Roy; Thompson-Schill, Sharon L.

    2013-01-01

    Humans have an unparalleled ability to represent objects as members of multiple categories. A given object, such as a pillow may be—depending on current task demands—represented as an instance of something that is soft, as something that contains feathers, as something that is found in bedrooms, or something that is larger than a toaster. This type of processing requires the individual to dynamically highlight task-relevant properties and abstract over or suppress object properties that, although salient, are not relevant to the task at hand. Neuroimaging and neuropsychological evidence suggests that this ability may depend on cognitive control processes associated with the left inferior prefrontal gyrus. Here, we show that stimulating the left inferior frontal cortex using transcranial direct current stimulation alters performance of healthy subjects on a simple categorization task. Our task required subjects to select pictures matching a description, e.g., “click on all the round things.“ Cathodal stimulation led to poorer performance on classification trials requiring attention to specific dimensions such as color or shape as opposed to trials that required selecting items belonging to a more thematic category such as objects that hold water. A polarity reversal (anodal stimulation) lowered the threshold for selecting items that were more weakly associated with the target category. These results illustrate the role of frontally-mediated control processes in categorization and suggest potential interactions between categorization, cognitive control, and language. PMID:22578885

  11. Transcranial direct current stimulation modulates ERP-indexed inhibitory control and reduces food consumption.

    PubMed

    Lapenta, Olivia Morgan; Sierve, Karina Di; de Macedo, Elizeu Coutinho; Fregni, Felipe; Boggio, Paulo Sérgio

    2014-12-01

    Food craving can be defined as the "urge to eat a specific food". Previous findings suggest impairment of inhibitory control, specifically a regulatory deficit in the lateral prefrontal circuitry that is associated with a compulsion for food. As demonstrated by three previous studies, bilateral transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC) (anode right/cathode left) reduces food craving and caloric intake. We designed the present study to evaluate the neural mechanisms that underlie these effects. We replicated the design of one of these previous studies but included electroencephalographic assessments to register evoked potentials in a Go/No-go task that contained pictures of food and furniture (a control visual stimulus). We collected data from nine women (mean age?=?23.4?±?2 years) in a crossover experiment. We observed that active DLPFC tDCS (anode right/cathode left), compared with sham stimulation, reduced the frontal N2 component and enhanced the P3a component of responses to No-go stimuli, regardless of the stimulus condition (food or furniture). Active tDCS was also associated with a reduction in caloric intake. We discuss our findings in the context of cortico-subcortical processing of craving and tDCS effects on inhibitory control neural circuitry. PMID:25128836

  12. Açaí (Euterpe oleracea Mart.) Modulates Oxidative Stress Resistance in Caenorhabditis elegans by Direct and Indirect Mechanisms

    PubMed Central

    Bonomo, Larissa de Freitas; Silva, David Nunes; Boasquivis, Patrícia Ferreira; Paiva, Franciny Aparecida; Guerra, Joyce Ferreira da Costa; Martins, Talita Alves Faria; de Jesus Torres, Álvaro Gustavo; de Paula, Igor Thadeu Borges Raposo; Caneschi, Washington Luiz; Jacolot, Philippe; Grossin, Nicolas; Tessier, Frederic J.; Boulanger, Eric; Silva, Marcelo Eustáquio; Pedrosa, Maria Lúcia; de Paula Oliveira, Riva

    2014-01-01

    Açaí (Euterpe oleracea Mart.) has recently emerged as a promising source of natural antioxidants. Despite its claimed pharmacological and nutraceutical value, studies regarding the effects of açaí in vivo are limited. In this study, we use the Caenorhabditis elegans model to evaluate the in vivo antioxidant properties of açaí on an organismal level and to examine its mechanism of action. Supplementation with açaí aqueous extract (AAE) increased both oxidative and osmotic stress resistance independently of any effect on reproduction and development. AAE suppressed bacterial growth, but this antimicrobial property did not influence stress resistance. AAE-increased stress resistance was correlated with reduced ROS production, the prevention of sulfhydryl (SH) level reduction and gcs-1 activation under oxidative stress conditions. Our mechanistic studies indicated that AAE promotes oxidative stress resistance by acting through DAF-16 and the osmotic stress response pathway OSR-1/UNC-43/SEK-1. Finally, AAE increased polyglutamine protein aggregation and decreased proteasome activity. Our findings suggest that natural compounds available in AAE can improve the antioxidant status of a whole organism under certain conditions by direct and indirect mechanisms. PMID:24594796

  13. Poster Abstract: Message Position Modulation for Power Saving and Increased Bandwidth in Sensor Networks

    E-print Network

    Poster Abstract: Message Position Modulation for Power Saving and Increased Bandwidth in Sensor@tik.ee.ethz.ch Abstract We use a form of pulse-position modulation, i.e. message- position modulation (MPM), to reduce power sensor net- works. For many applications information, e.g. measured data, reaches the base station

  14. Characteristic optimization of 1.3-?m InGaAsP MQW lasers for direct modulation applications

    NASA Astrophysics Data System (ADS)

    Guo, Fei; Zhang, Ruikang; Lu, Dan; Wang, We; Ji, Chen

    2014-10-01

    We have investigated 1.3-?m InGaAsP strained multi-quantum-well (MQW) lasers on InP substrate for direct modulation applications using the commercial laser simulator PIC3D. The physical mechanisms affecting the laser dynamic characteristics such as nonradiative recombination losses and vertical electron leakage effect are considered in our simulation. The number of wells is optimized because increasing the number of QWs can decrease the nonradiative recombination losses and increase the modal differential gain, nevertheless, the carrier distribution between wells become more non-uniform with too many QWs numbers resulting in uneven simulated recombination rate and increasing Auger recombination. The influence of barrier height is analyzed and a tradeoff has to be determined because too high barriers results in more nonuniform carrier distribution in the active regions, increasing the Auger recombination rate severely while the vertical current leakage outside the QWs will increase dramatically at lower barrier height. The 1.3-?m FP laser with the MQWs of 6 wells, 1.15 Q barriers bandgap and 8 wells, 1.1 Q barrier bandgaps is fabricated and characterized. The FP laser with MQWs structures composed of 8 compressive strain quantum wells and 9 barriers with the optimized bandgap 1.1 Q shows better properties. The threshold current is around 19 mA and the resonance frequency of 9.5 GHz and 3-dB bandwidth in excess of 13.3 GHz at 120 mA injection current. This modulation frequency is suitable for 10 Gbits/s optical data transmission.

  15. Design a linear irregular Fresnel lens to thin an LED-based direct-type backlight module and improve the illuminance and uniformity of LCD panel

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Gong

    2011-05-01

    We propose a Linear Irregular Fresnel Lens (denoted as LIFL) to replace the diffusion sheet and prism sheet in a rectangular LED-based Direct-type Backlight Module. The aim is to improve the illuminance and uniformity of LCD panel, as well as to reduce the cost of Backlight Module and make the Module thin. Here "Linear" means the grooves of a Fresnel lens are arranged linearly and "irregular" means that the sequence of all groove angles is not increasing or decreasing. To let the designed LIFL possess good effects of light ray guiding, two layers of LIFLs are needed. The first layer LIFL consists of x-axis grooves, whereas the second layer LIFL consists of y-axis grooves to guide all light rays guided by the first layer LIFL. The groove angles of the designed LIFL are evolved by a Genetic Algorithm which is developed in terms of the performance requirement on illuminance and uniformity of LCD panel in a rectangular LED-based Direct-type Backlight Module. In this paper, we will simulate a simple fifteen-LED Direct-type Backlight Module to demonstrate the performances on illuminance and uniformity of the designed LIFL.

  16. Modulation of Enhancer Looping and Differential Gene Targeting by Epstein-Barr Virus Transcription Factors Directs Cellular Reprogramming

    PubMed Central

    McClellan, Michael J.; Wood, C. David; Ojeniyi, Opeoluwa; Cooper, Tim J.; Kanhere, Aditi; Arvey, Aaron; Webb, Helen M.; Palermo, Richard D.; Harth-Hertle, Marie L.; Kempkes, Bettina; Jenner, Richard G.; West, Michelle J.

    2013-01-01

    Epstein-Barr virus (EBV) epigenetically reprogrammes B-lymphocytes to drive immortalization and facilitate viral persistence. Host-cell transcription is perturbed principally through the actions of EBV EBNA 2, 3A, 3B and 3C, with cellular genes deregulated by specific combinations of these EBNAs through unknown mechanisms. Comparing human genome binding by these viral transcription factors, we discovered that 25% of binding sites were shared by EBNA 2 and the EBNA 3s and were located predominantly in enhancers. Moreover, 80% of potential EBNA 3A, 3B or 3C target genes were also targeted by EBNA 2, implicating extensive interplay between EBNA 2 and 3 proteins in cellular reprogramming. Investigating shared enhancer sites neighbouring two new targets (WEE1 and CTBP2) we discovered that EBNA 3 proteins repress transcription by modulating enhancer-promoter loop formation to establish repressive chromatin hubs or prevent assembly of active hubs. Re-ChIP analysis revealed that EBNA 2 and 3 proteins do not bind simultaneously at shared sites but compete for binding thereby modulating enhancer-promoter interactions. At an EBNA 3-only intergenic enhancer site between ADAM28 and ADAMDEC1 EBNA 3C was also able to independently direct epigenetic repression of both genes through enhancer-promoter looping. Significantly, studying shared or unique EBNA 3 binding sites at WEE1, CTBP2, ITGAL (LFA-1 alpha chain), BCL2L11 (Bim) and the ADAMs, we also discovered that different sets of EBNA 3 proteins bind regulatory elements in a gene and cell-type specific manner. Binding profiles correlated with the effects of individual EBNA 3 proteins on the expression of these genes, providing a molecular basis for the targeting of different sets of cellular genes by the EBNA 3s. Our results therefore highlight the influence of the genomic and cellular context in determining the specificity of gene deregulation by EBV and provide a paradigm for host-cell reprogramming through modulation of enhancer-promoter interactions by viral transcription factors. PMID:24068937

  17. A multi-chip directly mounted 512-MEMS-mirror array module with a hermetically sealed package for large optical cross-connects

    NASA Astrophysics Data System (ADS)

    Mi, Xiaoyu; Soneda, Hiromitsu; Okuda, Hisao; Tsuboi, Osamu; Kouma, Norinao; Mizuno, Yoshihiro; Ueda, Satoshi; Sawaki, Ippei

    2006-07-01

    This paper describes the design, fabrication and performance of a 512-MEMS-mirror array module with a hermetically sealed package for large optical cross-connects. This configuration enables a ± 5° rotation of the two-axis stationary operation under a drive voltage of 160 V, with a high resonant frequency of 2 kHz. The 512-MEMS-mirror array module was constructed using newly developed multi-chip direct mounting (MCDM) technology, which allowed us to use small scale mirror array chips and greatly simplifies the fabrication process. The MCDM technology was demonstrated to be especially well suited to building large port count mirror array modules without the size limitation involved with handling wafers. The 512-MEMS-mirror array module measures a compact 122 mm × 60 mm.

  18. Localized Minimum-Energy Broadcasting for Wireless Multihop Networks with Directional Antennas

    Microsoft Academic Search

    Julien Iguchi-cartigny; Pedro M. Ruiz; David Simplot-ryl; Ivan Stojmenovic; Carmen M. Yago

    2009-01-01

    We propose several localized algorithms to achieve energy-efficient broadcasting in wireless multihop networks using directional antennas. Each node needs to know only geographic position of itself and its neighbors. Our first protocol is called DRBOP and it follows the one-to-one communication model to reach to all nodes in the relative neighborhood graph (RNG). Each node that receives a message for

  19. Spectral properties of the Google matrix of the World Wide Web and other directed networks Bertrand Georgeot, Olivier Giraud,* and Dima L. Shepelyansky

    E-print Network

    Shepelyansky, Dima

    Spectral properties of the Google matrix of the World Wide Web and other directed networks Bertrand of the Google matrix of various examples of directed networks such as vocabulary networks of dictionaries eigenvalue for Google damping parameter equal to unity. The vocabulary networks have relatively homogeneous

  20. Formation of microvascular networks: role of stromal interactions directing angiogenic growth.

    PubMed

    Hoying, James B; Utzinger, Urs; Weiss, Jeffrey A

    2014-05-01

    In the adult, angiogenesis leads to an expanded microvascular network as new vessel segments are added to an existing microcirculation. Necessarily, growing neovessels must navigate through tissue stroma as they locate and grow toward other vessel elements. We have a growing body of evidence demonstrating that angiogenic neovessels reciprocally interact with the interstitial matrix of the stroma resulting in directed neovascular growth during angiogenesis. Given the compliance and the viscoelastic properties of collagen, neovessel guidance by the stroma is likely due to compressive strain transverse to the direction of primary tensile forces present during active tissue deformation. Similar stromal strains control the final network topology of the new microcirculation, including the distribution of arterioles, capillaries, and venules. In this case, stromal-derived stimuli must be present during the post-angiogenesis remodeling and maturation phases of neovascularization to have this effect. Interestingly, the preexisting organization of vessels prior to the start of angiogenesis has no lasting influence on the final, new network architecture. Combined, the evidence describes interplay between angiogenic neovessels and stroma that is important in directed neovessel growth and invasion. This dynamic is also likely a mechanism by which global tissue forces influence vascular form and function. PMID:24447042

  1. Hypoxia-Ischemia Disrupts Directed Interactions within Neonatal Prefrontal-Hippocampal Networks

    PubMed Central

    Brockmann, Marco D.; Kukovic, Maja; Schönfeld, Michael; Sedlacik, Jan; Hanganu-Opatz, Ileana L.

    2013-01-01

    Due to improved survival rates and outcome of human infants experiencing a hypoxic-ischemic episode, cognitive dysfunctions have become prominent. They might result from abnormal communication within prefrontal-hippocampal networks, as synchrony and directed interactions between the prefrontal cortex and hippocampus account for mnemonic and executive performance. Here, we elucidate the structural and functional impact of hypoxic-ischemic events on developing prefrontal-hippocampal networks in an immature rat model of injury. The magnitude of infarction, cell loss and astrogliosis revealed that an early hypoxic-ischemic episode had either a severe or a mild/moderate outcome. Without affecting the gross morphology, hypoxia-ischemia with mild/moderate outcome diminished prefrontal neuronal firing and gamma network entrainment. This dysfunction resulted from decreased coupling synchrony within prefrontal-hippocampal networks and disruption of hippocampal theta drive. Thus, early hypoxia-ischemia may alter the functional maturation of neuronal networks involved in cognitive processing by disturbing the communication between the neonatal prefrontal cortex and hippocampus. PMID:24376636

  2. Integration of offshore wind farms through high voltage direct current networks

    NASA Astrophysics Data System (ADS)

    Livermore, Luke

    The integration of offshore wind farms through Multi Terminal DC (MTDC) networks into the GB network was investigated. The ability of Voltage Source Converter (VSC) High Voltage Direct Current (HVDC) to damp Subsynchronous Resonance (SSR) and ride through onshore AC faults was studied. Due to increased levels of wind generation in Scotland, substantial onshore and offshore reinforcements to the GB transmission network are proposed. Possible inland reinforcements include the use of series compensation through fixed capacitors. This potentially can lead to SSR. Offshore reinforcements are proposed by two HVDC links. In addition to its primary functions of bulk power transmission, a HVDC link can be used to provide damping against SSR, and this function has been modelled. Simulation studies have been carried out in PSCAD. In addition, a real-time hardware-in-the-loop HVDC test rig has been used to implement and validate the proposed damping scheme on an experimental platform. When faults occur within AC onshore networks, offshore MTDC networks are vulnerable to DC overvoltages, potentially damaging the DC plant and cables. Power reduction and power dissipation control systems were investigated to ride through onshore AC faults. These methods do not require dedicated fast communication systems. Simulations and laboratory experiments are carried out to evaluate the control systems, with the results from the two platforms compared..

  3. Energy-Aware Wireless Networking with Directional Antennas: The Case of Session-Based Broadcasting and Multicasting

    Microsoft Academic Search

    Jeffrey E. Wieselthier; Gam D. Nguyen; Anthony Ephremides

    2002-01-01

    We consider ad hoc wireless networks that use directional antennas and have limited energy resources. To explore quantitatively the advantage offered by the use of directional antennas over the case of omnidirectional antennas, we consider the case of connection-oriented multicast traffic. Building upon our prior work on multicasting algorithms, we introduce two protocols that exploit the use of directional antennas

  4. Functional and Transcriptional Coherency of Modules in the Human Protein Interaction Network

    Microsoft Academic Search

    Matthias E. Futschik; Gautam Chaurasia; Anna Tschaut; Jenny Russ; M. Madan Babu; Hanspeter Herzel

    2007-01-01

    Summary Modularity is a major design principle in interaction networks. Various studies have shown that protein interaction networks in prokaryotes and eukaryotes display a modular structure. A majority of the studies have been performed for the yeast interaction network, for which data have become abundant. The systematic examination of the human protein interaction network, however, is still in an early

  5. Nswap: A Network Swapping Module for Linux Tia Newhall, Sean Finney, Kuzman Ganchev, Michael Spiegel

    E-print Network

    Newhall, Tia

    network speeds and disk speeds continues to grow, network swapping will be faster than traditional swapping to local disk. We present Nswap, a network swapping system for heterogeneous Linux clusters to between 1.3 and 4.6 times slower than disk for most workloads. We show that with faster networking technol

  6. Distributed Network Size Estimation and Average Degree Estimation and Control in Networks Isomorphic to Directed Graphs

    E-print Network

    Hadjicostis, Christoforos

    Isomorphic to Directed Graphs Iman Shames, Themistoklis Charalambous, Christoforos N. Hadjicostis and Mikael purely on local measurements. Particularly, we are Iman Shames was formerly with the Automatic Control Engineering, University of Melbourne. E-mail: iman.shames@unimelb.edu.au. Themistoklis Charalambous and Mikael

  7. Phosphorus and magnesium interactively modulate the elongation and directional growth of primary roots in Arabidopsis thaliana (L.) Heynh.

    PubMed

    Niu, Yaofang; Jin, Gulei; Li, Xin; Tang, Caixian; Zhang, Yongsong; Liang, Yongchao; Yu, Jingquan

    2015-07-01

    A balanced supply of essential nutrients is an important factor influencing root architecture in many plants, yet data related to the interactive effects of two nutrients on root growth are limited. Here, we investigated the interactive effect between phosphorus (P) and magnesium (Mg) on root growth of Arabidopsis grown in pH-buffered agar medium at different P and Mg levels. The results showed that elongation and deviation of primary roots were directly correlated with the amount of P added to the medium but could be modified by the Mg level, which was related to the root meristem activity and stem-cell division. High P enhanced while low P decreased the tip-focused fluorescence signal of auxin biosynthesis, transport, and redistribution during elongation of primary roots; these effects were greater under low Mg than under high Mg. The altered root growth in response to P and Mg supply was correlated with AUX1, PIN2, and PIN3 mRNA abundance and expression and the accumulation of the protein. Application of either auxin influx inhibitor or efflux inhibitor inhibited the elongation and increased the deviation angle of primary roots, and decreased auxin level in root tips. Furthermore, the auxin-transport mutants aux1-22 and eir1-1 displayed reduced root growth and increased the deviation angle. Our data suggest a profound effect of the combined supply of P and Mg on the development of root morphology in Arabidopsis through auxin signals that modulate the elongation and directional growth of primary root and the expression of root differentiation and development genes. PMID:25922494

  8. Phosphorus and magnesium interactively modulate the elongation and directional growth of primary roots in Arabidopsis thaliana (L.) Heynh

    PubMed Central

    Niu, Yaofang; Jin, Gulei; Li, Xin; Tang, Caixian; Zhang, Yongsong; Liang, Yongchao; Yu, Jingquan

    2015-01-01

    A balanced supply of essential nutrients is an important factor influencing root architecture in many plants, yet data related to the interactive effects of two nutrients on root growth are limited. Here, we investigated the interactive effect between phosphorus (P) and magnesium (Mg) on root growth of Arabidopsis grown in pH-buffered agar medium at different P and Mg levels. The results showed that elongation and deviation of primary roots were directly correlated with the amount of P added to the medium but could be modified by the Mg level, which was related to the root meristem activity and stem-cell division. High P enhanced while low P decreased the tip-focused fluorescence signal of auxin biosynthesis, transport, and redistribution during elongation of primary roots; these effects were greater under low Mg than under high Mg. The altered root growth in response to P and Mg supply was correlated with AUX1, PIN2, and PIN3 mRNA abundance and expression and the accumulation of the protein. Application of either auxin influx inhibitor or efflux inhibitor inhibited the elongation and increased the deviation angle of primary roots, and decreased auxin level in root tips. Furthermore, the auxin-transport mutants aux1-22 and eir1-1 displayed reduced root growth and increased the deviation angle. Our data suggest a profound effect of the combined supply of P and Mg on the development of root morphology in Arabidopsis through auxin signals that modulate the elongation and directional growth of primary root and the expression of root differentiation and development genes. PMID:25922494

  9. A single module type I polyketide synthase directs de novo macrolactone biogenesis during galbonolide biosynthesis in Streptomyces galbus.

    PubMed

    Kim, Hyun-Ju; Karki, Suman; Kwon, So-Yeon; Park, Si-Hyung; Nahm, Baek-Hie; Kim, Yeon-Ki; Kwon, Hyung-Jin

    2014-12-12

    Galbonolide (GAL) A and B are antifungal macrolactone polyketides produced by Streptomyces galbus. During their polyketide chain assembly, GAL-A and -B incorporate methoxymalonate and methylmalonate, respectively, in the fourth chain extension step. The methoxymalonyl-acyl carrier protein biosynthesis locus (galG to K) is specifically involved in GAL-A biosynthesis, and this locus is neighbored by a gene cluster composed of galA-E. GalA-C constitute a single module, highly reducing type I polyketide synthase (PKS). GalD and GalE are cytochrome P450 and Rieske domain protein, respectively. Gene knock-out experiments verified that galB, -C, and -D are essential for GAL biosynthesis. A galD mutant accumulated a GAL-C that lacked two hydroxyl groups and a double bond when compared with GAL-B. A [U-(13)C]propionate feeding experiment indicated that no rare precursor other than methoxymalonate was incorporated during GAL biogenesis. A search of the S. galbus genome for a modular type I PKS system, the type that was expected to direct GAL biosynthesis, resulted in the identification of only one modular type I PKS gene cluster. Homology analysis indicated that this PKS gene cluster is the locus for vicenistatin biosynthesis. This cluster was previously reported in Streptomyces halstedii. A gene deletion of the vinP2 ortholog clearly demonstrated that this modular type I PKS system is not involved in GAL biosynthesis. Therefore, we propose that GalA-C direct macrolactone polyketide formation for GAL. Our studies provide a glimpse into a novel biochemical strategy used for polyketide synthesis; that is, the iterative assembly of propionates with highly programmed ?-keto group modifications. PMID:25336658

  10. Intensity-modulated radiation therapy in advanced head and neck patients treated with intensive chemoradiotherapy: preliminary experience and future directions.

    PubMed

    Milano, Michael T; Vokes, Everett E; Kao, Johnny; Jackson, Wells; List, Marcy A; Stenson, Kerstin M; Witt, Mary Ellyn; Dekker, Allison; MacCracken, Ellen; Garofalo, Michael C; Chmura, Steven J; Weichselbaum, Ralph R; Haraf, Daniel J

    2006-05-01

    We review our recent experience with intensity-modulated radiation therapy (IMRT) and conventional three-dimensional radiation therapy (C3DRT) in advanced head and neck cancer. Sixty-nine patients with Stage IV head and neck cancer (and stage III base of tongue and hypopharynx) enrolled in a Phase II study of definitive chemoradiation; 20 received all or part of their radiation with IMRT. Image-guided set-up, using video subtraction techniques, was used in all patients. Six weekly doses of induction carboplatin (AUC=2) and paclitaxel (135 mg/m2) were followed by alternating weekly chemoradiation to 75 Gy with 1.5 Gy BID fractions, concurrent with paclitaxel (100 mg/m2/week), 5-fluorouracil (600 mg/m2/d) and hydroxyurea (500 mg PO BID). Two consecutive cohorts enrolled, differing in radiation scheme: 75 Gy to gross disease in both, 60 or 54 Gy to first echelon lymphatics and 45 or 39 Gy to second echelon lymphatics. With a median follow-up of 47 months, 3-year overall survival is 68.5% and 3-year locoregional control is 94.0%, with no significant differences between those treated with C3DRT versus IMRT, nor between the two radiation dosing schemes. Actuarial overall survival without tracheostomy or laryngectomy, or without a gastrostomy tube was also similar. Acute mucositis, dermatitis and pain were similar with C3DRT and IMRT. Preliminary data suggests IMRT is well tolerated, and does not compromise locoregional control, indicating that IMRT adequately covers the clinical volume at risk. Building on the present clinical experience, future directions include more directed efforts at reducing toxicity, with better planning software and planning techniques. PMID:16596230

  11. Thin-Layer Chemical Modulations by a Combined Selective Proton Pump and pH Probe for Direct Alkalinity Detection.

    PubMed

    Afshar, Majid Ghahraman; Crespo, Gastón A; Bakker, Eric

    2015-07-01

    We report a general concept based on a selective electrochemical ion pump used for creating concentration perturbations in thin layer samples (?40??L). As a first example, hydrogen ions are released from a selective polymeric membrane (proton pump) and the resulting pH is assessed potentiometrically with a second membrane placed directly opposite. By applying a constant potential modulation for 30?s, an induced proton concentration of up to 350?mM may be realized. This concept may become an attractive tool for in?situ titrations without the need for sampling, because the thin layer eventually re-equilibrates with the contacting bulk sample. Acid-base titrations of NaOH and Na2 CO3 are demonstrated. The determination of total alkalinity in a river water sample is carried out, giving levels (23.1?mM) comparable to that obtained by standard methods (23.6?mM). The concept may be easily extended to other ions (cations, anions, polyions) and may become attractive for environmental and clinical applications. PMID:26014101

  12. Huntingtin modulates transcription, occupies gene promoters in vivo and binds directly to DNA in a polyglutamine-dependent manner

    PubMed Central

    Benn, Caroline L.; Sun, Tingting; Sadri-Vakili, Ghazaleh; McFarland, Karen N.; DiRocco, Derek P.; Yohrling, George J.; Clark, Timothy W.; Bouzou, Bérengère; Cha, Jang-Ho J.

    2008-01-01

    Transcriptional dysregulation is a central pathogenic mechanism in Huntington’s disease, a fatal neurodegenerative disorder associated with polyglutamine (polyQ) expansion in the huntingtin (Htt) protein. In this study, we show that mutant Htt alters the normal expression of specific mRNA species at least partly by disrupting the binding activities of many transcription factors which govern the expression of the dysregulated mRNA species. Chromatin immunoprecipitation (ChIP) demonstrates Htt occupation of gene promoters in vivo in a polyQ-dependent manner and furthermore, ChIP-on-chip and ChIP subcloning reveal that wild-type and mutant Htt exhibit differential genomic distributions. Exon 1 Htt binds DNA directly in the absence of other proteins and alters DNA conformation. PolyQ expansion increases Htt-DNA interactions, with binding to recognition elements of transcription factors whose function is altered in HD. Taken together; these findings suggest mutant Htt modulates gene expression through abnormal interactions with genomic DNA, altering DNA conformation and transcription factor binding. PMID:18923047

  13. Airborne pollutant ROFA enhances the allergic airway inflammation through direct modulation of dendritic cells in an uptake-dependent mechanism.

    PubMed

    Arantes-Costa, Fernanda Magalhaes; Grund, Lidiane Zito; Martins, Milton Arruda; Lima, Carla

    2014-09-01

    Studies suggest that airborne pollutants are important cofactors in the exacerbation of lung diseases. The role of DC on the exacerbation of lung inflammation induced by particulate matter pollutants is unclear. We evaluated the effects of residual oil fly ash (ROFA) on the phenotype and function of bone marrow-derived dendritic cells (BMDCs) in vitro and lung dendritic cells (DCs) in vivo, and the subsequent T-cell response. In a model of asthma, exposure to ROFA exacerbated pulmonary inflammation, which was attributed to the increase of eosinophils, IL-5- and IFN-?-producing T cells, and goblet cells as well as decreased number of Treg and pDC. However, the ROFA showed no ability to modulate the production of anaphylactic IgE. In vitro studies showed that ROFA directly induced the maturation of DCs up-regulating the expression of co-stimulatory molecules and cytokines and MMP production in an uptake-dependent and oxidative stress-dependent manner. Furthermore, ROFA-pulsed BMDC transferred to allergic mice exacerbated eosinophilic inflammation as well as promoted increased epithelial and goblet cells changes. Thus, pollutants may constitute an important and risk factor in the exacerbation of asthma with inhibition of the negative regulatory signals in the lung, with enhanced mDC activation that sustains the recruitment of effector T lymphocytes and eosinophil. PMID:24975839

  14. Unified active and reactive power modulation of HVDC transmission systems. Final report

    Microsoft Academic Search

    C. E. Grund; R. V. Pohl

    1981-01-01

    In a study conducted by the General Electric Company for EPRI, the power modulation of a high-voltage direct-current (HVDC) system for stabilization of an ac\\/dc network was investigated. The use of both active and reactive power modulation (as opposed to only active modulation techniques) was studied. It was found that simultaneous modulation of both dc current and voltage was more

  15. Design, implementation and testing of an artificial neural network based fault direction discriminator for protecting transmission lines

    Microsoft Academic Search

    T. S. Sidhu; H. Singh; M. S. Sachdev

    1995-01-01

    This paper describes a fault direction discriminator that uses an Artificial Neural Network (ANN) for protecting transmission lines. The discriminator uses various attributes to reach a decision and tends to emulate the conventional pattern classification problem. An equation of the boundary describing the classification is embedded in the Multilayer Feedforward Neural Network (MFNN) by training through the use of an

  16. Sector Tests of a Low-NO(sub x), Lean, Direct- Injection, Multipoint Integrated Module Combustor Concept Conducted

    NASA Technical Reports Server (NTRS)

    Tacina, Robert R.; Wey, Chang-Lie; Laing, Peter; Mansour, Adel

    2002-01-01

    The low-emissions combustor development described is directed toward advanced high pressure aircraft gas-turbine applications. The emphasis of this research is to reduce nitrogen oxides (NOx) at high-power conditions and to maintain carbon monoxide and unburned hydrocarbons at their current low levels at low power conditions. Low-NOx combustors can be classified into rich-burn and lean-burn concepts. Lean-burn combustors can be further classified into lean-premixed-prevaporized (LPP) and lean direct injection (LDI) concepts. In both concepts, all the combustor air, except for liner cooling flow, enters through the combustor dome so that the combustion occurs at the lowest possible flame temperature. The LPP concept has been shown to have the lowest NOx emissions, but for advanced high-pressure-ratio engines, the possibility of autoignition or flashback precludes its use. LDI differs from LPP in that the fuel is injected directly into the flame zone, and thus, it does not have the potential for autoignition or flashback and should have greater stability. However, since it is not premixed and prevaporized, good atomization is necessary and the fuel must be mixed quickly and uniformly so that flame temperatures are low and NOx formation levels are comparable to those of LPP. The LDI concept described is a multipoint fuel injection/multiburning zone concept. Each of the multiple fuel injectors has an air swirler associated with it to provide quick mixing and a small recirculation zone for burning. The multipoint fuel injection provides quick, uniform mixing and the small multiburning zones provide for reduced burning residence time, resulting in low NOx formation. An integrated-module approach was used for the construction where chemically etched laminates, diffusion bonded together, combine the fuel injectors, air swirlers, and fuel manifold into a single element. The multipoint concept combustor was demonstrated in a 15 sector test. The configuration tested had 36 fuel injectors and fuel-air mixers that replaced two fuel injectors in a conventional dual-annular combustor. During tests, inlet temperatures were up to 870 K and inlet pressures were up to 5400 kPa. A correlation was developed that related the NOx emissions with the inlet temperature, inlet pressure, fuel-air ratio, and pressure drop. At low-power conditions, fuel staging was used so that high combustion efficiency was obtained with only one-fourth of the fuel injectors flowing. The test facility had optical access, and visual images showed the flame to be very short, approximately 25 mm long.

  17. An efficient approximation for minimum energy broadcast in multi-channel multi-hop wireless network with directional antennas

    Microsoft Academic Search

    Xianyue Li; Shan Shan; Hongjie Du; Ailian Jiang; Weili Wu

    In this paper, We discuss the minimum energy broadcast problem (MEB) in multi-channel multi-hop wireless networks with directional antennas (MEB-MB). This problem is NP-hard since its special version, MEB in single-channel network with directional antennas (MEB-SB) is proved to be NP-hard. We design an efficient approximation for MEB-MB problem, analyze its approximation ratio, and evaluate its performance via\\u000a numerical experiments.

  18. NRC TLD direct radiation monitoring network. Progress report, October 1997--December 1997

    SciTech Connect

    Struckmeyer, R.

    1998-03-01

    This is the final report of the US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network, covering the fourth quarter of 1997. The Network was operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution, if any, from the monitored facilities and other man-made sources. The Network was intended to measure radiation levels during routine facility operations and to establish background radiation levels used to assess the radiological impact of an unusual condition, such as an accident. This report presents the radiation levels measured around all facilities in the Network for the fourth quarter of 1997. A complete listing of the site facilities monitored is included. In some instances, two power reactor facilities are monitored by the same set of dosimeters (e.g., Kewaunee and Point Beach).

  19. Respiration drives network activity and modulates synaptic and circuit processing of lateral inhibition in the olfactory bulb

    PubMed Central

    Phillips, Matthew E.; Sachdev, Robert N. S.; Willhite, David C.; Shepherd, Gordon M.

    2012-01-01

    Respiration produces rhythmic activity in the entire olfactory system, driving neurons in the olfactory epithelium, bulb (OB) and cortex. The rhythmic nature of this activity is believed to be a critical component of sensory processing. OB projection neurons, mitral and tufted cells, exhibit both spiking and subthreshold membrane potential oscillations rhythmically coupled to respiration. Yet, the network and synaptic mechanisms that produce respiration-coupled activity, and the effects of respiration on lateral inhibition, a major component of sensory processing in OB circuits, are not known. Is respiration-coupled activity in mitral and tufted cells produced by sensory synaptic inputs from nasal airflow alone, cortico-bulbar feedback, or intrinsic membrane properties of the projection neurons? Does respiration facilitate or modulate the activity of inhibitory lateral circuits in the OB? Here, in vivo intracellular recordings from identified mitral and tufted cells in anesthetized rats demonstrate that nasal airflow provides excitatory synaptic inputs to both cell types and drives respiration-coupled spiking. Lateral inhibition, inhibitory post-synaptic potentials evoked by intrabulbar microstimulation, was modulated by respiration. In individual mitral and tufted cells inhibition was larger at specific respiratory phases. However, lateral inhibition was not uniformly larger during a particular respiratory phase in either cell type. Removing nasal airflow abolished respiration-coupled spiking in both cell types and nearly eliminated spiking in mitral, but not tufted cells. In the absence of nasal airflow, lateral inhibition was weaker in mitral cells and less modulated in tufted cells. Thus, respiration drives distinct network activities that functionally modulate sensory processing in the OB. PMID:22219272

  20. Identification and analysis of evolutionarily cohesive functional modules in protein networks

    Microsoft Academic Search

    Mónica Campillos; Christian von Mering; Lars Juhl Jensen; Peer Bork

    2006-01-01

    The increasing number of sequenced genomes makes it possible to infer the evolutionary history of functional modules, i.e., groups of proteins that contribute jointly to the same cellular function in a given species. Here we identify and analyze those prokaryotic functional modules, whose composition remains largely unchanged during evolution, and study their properties. Such \\