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1

Directly Modulated Laser Intrinsic Parameters Optimization for WDM Systems  

Microsoft Academic Search

Direct modulation schemes have involved increased attention during the past few years because of their intrinsic simplicity and cost-effectiveness, especially when applied to WDM metro and access networks. However, the output power waveform from a directly modulated laser is not an exact replica of the current modulation and its instantaneous optical frequency varies with time depending on the changes in

Carmina del Río Campos; Paloma R. Horche

2008-01-01

2

Modularity of Directed Networks: Cycle Decomposition Approach  

E-print Network

The problem of decomposing networks into modules (or clusters) has gained much attention in recent years, as it can account for a coarse-grained description of complex systems, often revealing functional subunits of these systems. A variety of module detection algorithms have been proposed, mostly oriented towards finding hard partitionings of undirected networks. Despite the increasing number of fuzzy clustering methods for directed networks, many of these approaches tend to neglect important directional information. In this paper, we present a novel random walk based approach for finding fuzzy partitions of directed, weighted networks, where edge directions play a crucial role in defining how well nodes in a module are interconnected. We will show that cycle decomposition of a random walk process connects the notion of network modules and information transport in a network, leading to a new, symmetric measure of node communication. walk process, for which we will prove that although being time-reversible it inherits all necessary information about directions and modular structure of the original network. Finally, we will use this measure to introduce a communication graph, for which we will show that although being undirected it inherits all necessary information about modular structures from the original network.

Natasa Djurdjevac Conrad; Ralf Banisch; Christof Schütte

2014-07-31

3

Force directed module placement with pin consideration  

Microsoft Academic Search

This paper looks at developing a module placement algorithm by combining two well known force-directed graph drawing algorithms. It is in answer to the current gap of module placement tools within the electronic design automation community that this research is carried out. Whilst previous work has provided an introduction to the basis of the module placement flow followed by the

Meththa Samaranayake; Helen Ji

2010-01-01

4

OM300 Direction Drilling Module  

SciTech Connect

OM300 – Geothermal Direction Drilling Navigation Tool: Design and produce a prototype directional drilling navigation tool capable of high temperature operation in geothermal drilling Accuracies of 0.1° Inclination and Tool Face, 0.5° Azimuth Environmental Ruggedness typical of existing oil/gas drilling Multiple Selectable Sensor Ranges High accuracy for navigation, low bandwidth High G-range & bandwidth for Stick-Slip and Chirp detection Selectable serial data communications Reduce cost of drilling in high temperature Geothermal reservoirs Innovative aspects of project Honeywell MEMS* Vibrating Beam Accelerometers (VBA) APS Flux-gate Magnetometers Honeywell Silicon-On-Insulator (SOI) High-temperature electronics Rugged High-temperature capable package and assembly process

MacGugan, Doug

2013-08-22

5

Dopamine Directly Modulates GABAA Receptors.  

PubMed

Dopamine is a critical neuromodulator that activates GPCRs in mammals or ligand-gated ion channels in invertebrates. The present study demonstrates that dopamine (0.1-10 mm) exerts novel, opposing effects on different populations of mammalian (rat) GABAA receptors. Using whole-cell patch-clamp electrophysiology, we observed direct dopamine-mediated inhibition of tonic-level (1 ?m) GABA-evoked currents in untransfected striatal neurons that could be recapitulated in HEK293 cells containing ?1?3 or ?1?2?2 subunits. Surprisingly, direct activation by dopamine was seen in the absence of GABA with ?1?2?2, ?5?3?2, or ?1?3?2 transfections. This activity was also present in ?1?3?2 receptors containing a mutant ?3 subunit (H267A [(Z)?3]) insensitive to trace levels of inhibitory Zn(2+). Dopamine activation required ? and ? subunits but not ? subunits ((Z)?3?2 EC50 value, 660 ?m). Dopamine activity was fully blocked by picrotoxin but not GABAA competitive antagonists, and was strongly correlated with spontaneous receptor activity. We also report opposing effects of bicuculline and gabazine, such that bicuculline surprisingly activated non-?-containing (?3?2) GABAA receptors, whereas gabazine suppressed spontaneous activity in these receptors. Our results suggest that dopamine may directly inhibit GABAA receptors that are both immediately adjacent to dopamine release sites in the striatum and activated by tonic GABA. Furthermore, synaptic/phasic release of dopamine may directly enhance signaling at some spontaneously active noncanonical GABAA receptors that lack ? subunits. PMID:25716851

Hoerbelt, Paul; Lindsley, Tara A; Fleck, Mark W

2015-02-25

6

Adaptive multidimensional modulation and multiplexing for next generation optical networks  

NASA Astrophysics Data System (ADS)

The overall spectral efficiency in optical transmission systems needs to be enhanced by employment of advanced modulation, multiplexing, and coding schemes, as well as the advanced detection techniques. In parallel, novel networking concepts with the griddles and elastic bandwidth allocation are needed to increase the network dynamics and flexibility. In this paper we discuss multidimensional modulation, multiplexing, and coding schemes, which are enablers not only of the information capacity increase, but also for the next generation elastic high-speed optical networking and outline possible future directions and application scenario in different networking segments.

Cvijetic, Milorad

2015-01-01

7

Investigation of direct integrated optics modulators  

NASA Technical Reports Server (NTRS)

Direct optical modulation techniques applicable to integrated optical data preprocessors were studied. Emphasis was placed on the analysis and fabrication of a field effect type modulator. A series of computer modeling studies were performed to determine the effects of semiconductor cladding on the fields of propagating waves in planar dielectric waveguides. These studies predicted that changes in the propagation characteristics of waveguides clad with silicon and gallium arsenide could be made large enough to be useful in modulators. These effects are dependent on the complex permittivity and thickness of the cladding. Since the conductivity of the cladding can be changed by the photon generation of hole-electron pairs, incoherent light may be used as the input to modulate a coherent light beam. Waveguides were fabricated and silicon claddings were applied to verify the theoretical predictions.

Batchman, T. E.; Mcwright, G. M.

1981-01-01

8

Epidemic threshold in directed networks  

NASA Astrophysics Data System (ADS)

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 x1, 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.

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

2013-12-01

9

Potential Theory for Directed Networks  

PubMed Central

Uncovering factors underlying the network formation is a long-standing challenge for data mining and network analysis. In particular, the microscopic organizing principles of directed networks are less understood than those of undirected networks. This article proposes a hypothesis named potential theory, which assumes that every directed link corresponds to a decrease of a unit potential and subgraphs with definable potential values for all nodes are preferred. Combining the potential theory with the clustering and homophily mechanisms, it is deduced that the Bi-fan structure consisting of 4 nodes and 4 directed links is the most favored local structure in directed networks. Our hypothesis receives strongly positive supports from extensive experiments on 15 directed networks drawn from disparate fields, as indicated by the most accurate and robust performance of Bi-fan predictor within the link prediction framework. In summary, our main contribution is twofold: (i) We propose a new mechanism for the local organization of directed networks; (ii) We design the corresponding link prediction algorithm, which can not only testify our hypothesis, but also find out direct applications in missing link prediction and friendship recommendation. PMID:23408979

Zhang, Qian-Ming; Lü, Linyuan; Wang, Wen-Qiang; Zhou, Tao

2013-01-01

10

Notational usage modulates attention networks in binumerates  

PubMed Central

Multicultural environments require learning multiple number notations wherein some are encountered more frequently than others. This leads to differences in exposure and consequently differences in usage between notations. We find that differential notational usage imposes a significant neurocognitive load on number processing. Despite simultaneous acquisition, twenty four adult binumerates, familiar with two positional writing systems namely Hindu Nagari digits and Hindu Arabic digits, reported significantly lower preference and usage for Nagari as compared to Arabic. Twenty-four participants showed significantly increased reaction times and reduced accuracy while performing magnitude comparison tasks in Nagari with respect to Arabic. Functional magnetic resonance imaging revealed that processing Nagari elicited significantly greater activity in number processing and attention networks. A direct subtraction of networks for Nagari and Arabic notations revealed a neural circuit comprising of bilateral Intra-parietal Sulcus (IPS), Inferior and Mid Frontal Gyri, Fusiform Gyrus and the Anterior Cingulate Cortex (FDR p < 0.005). Additionally, whole brain correlation analysis showed that activity in the left inferior parietal region was modulated by task performance in Nagari. We attribute the increased activation in Nagari to increased task difficulty due to infrequent exposure and usage. Our results reiterate the role of left IPS in modulating performance in numeric tasks and highlight the role of the attention network for monitoring symbolic notation mode in binumerates. PMID:24904366

Koul, Atesh; Tyagi, Vaibhav; Singh, Nandini C.

2014-01-01

11

Sampling properties of directed networks  

NASA Astrophysics Data System (ADS)

For many real-world networks only a small “sampled” version of the original network may be investigated; those results are then used to draw conclusions about the actual system. Variants of breadth-first search (BFS) sampling, which are based on epidemic processes, are widely used. Although it is well established that BFS sampling fails, in most cases, to capture the IN component(s) of directed networks, a description of the effects of BFS sampling on other topological properties is all but absent from the literature. To systematically study the effects of sampling biases on directed networks, we compare BFS sampling to random sampling on complete large-scale directed networks. We present new results and a thorough analysis of the topological properties of seven complete directed networks (prior to sampling), including three versions of Wikipedia, three different sources of sampled World Wide Web data, and an Internet-based social network. We detail the differences that sampling method and coverage can make to the structural properties of sampled versions of these seven networks. Most notably, we find that sampling method and coverage affect both the bow-tie structure and the number and structure of strongly connected components in sampled networks. In addition, at a low sampling coverage (i.e., less than 40%), the values of average degree, variance of out-degree, degree autocorrelation, and link reciprocity are overestimated by 30% or more in BFS-sampled networks and only attain values within 10% of the corresponding values in the complete networks when sampling coverage is in excess of 65%. These results may cause us to rethink what we know about the structure, function, and evolution of real-world directed networks.

Son, S.-W.; Christensen, C.; Bizhani, G.; Foster, D. V.; Grassberger, P.; Paczuski, M.

2012-10-01

12

Sampling properties of directed networks.  

PubMed

For many real-world networks only a small "sampled" version of the original network may be investigated; those results are then used to draw conclusions about the actual system. Variants of breadth-first search (BFS) sampling, which are based on epidemic processes, are widely used. Although it is well established that BFS sampling fails, in most cases, to capture the IN component(s) of directed networks, a description of the effects of BFS sampling on other topological properties is all but absent from the literature. To systematically study the effects of sampling biases on directed networks, we compare BFS sampling to random sampling on complete large-scale directed networks. We present new results and a thorough analysis of the topological properties of seven complete directed networks (prior to sampling), including three versions of Wikipedia, three different sources of sampled World Wide Web data, and an Internet-based social network. We detail the differences that sampling method and coverage can make to the structural properties of sampled versions of these seven networks. Most notably, we find that sampling method and coverage affect both the bow-tie structure and the number and structure of strongly connected components in sampled networks. In addition, at a low sampling coverage (i.e., less than 40%), the values of average degree, variance of out-degree, degree autocorrelation, and link reciprocity are overestimated by 30% or more in BFS-sampled networks and only attain values within 10% of the corresponding values in the complete networks when sampling coverage is in excess of 65%. These results may cause us to rethink what we know about the structure, function, and evolution of real-world directed networks. PMID:23214649

Son, S-W; Christensen, C; Bizhani, G; Foster, D V; Grassberger, P; Paczuski, M

2012-10-01

13

Network Models of Frequency Modulated Sweep Detection  

PubMed Central

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

Skorheim, Steven; Razak, Khaleel; Bazhenov, Maxim

2014-01-01

14

Multifunction audio digitizer. [producing direct delta and pulse code modulation  

NASA Technical Reports Server (NTRS)

An illustrative embodiment of the invention includes apparatus which simultaneously produces both direct delta modulation and pulse code modulation. An input signal, after amplification, is supplied to a window comparator which supplies a polarity control signal to gate the output of a clock to the appropriate input of a binary up-down counter. The control signals provide direct delta modulation while the up-down counter output provides pulse code modulation.

Monford, L. G., Jr. (inventor)

1974-01-01

15

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

SciTech Connect

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.

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

16

Optimal design of reverse osmosis module networks  

SciTech Connect

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.

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

2000-05-01

17

Downhole drilling network using burst modulation techniques  

DOEpatents

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.

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

2007-04-03

18

Induction and Modulation of Neuroplasticity by Transcranial Direct Current Stimulation  

Microsoft Academic Search

Brain stimulation with weak direct current has recently been reintroduced as a method to elicit and modulate neuroplasticity of the human cerebral cortex. Transcranial direct current stimulation (tDCS) generates modulations of excitability during as well as up to an hour after the end of stimulation, depending on the duration of stimulation. While anodal stimulation increases excitability, cathodal stimulation reduces it.

M. Nitsche; A. Antal; D. Liebetanz; N. Lang; F. Tergau; W. Paulus

2007-01-01

19

Optical waveform generation using a directly modulated laser  

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

20

Caffeine Modulates Attention Network Function  

ERIC Educational Resources Information Center

The present work investigated the effects of caffeine (0 mg, 100 mg, 200 mg, 400 mg) on a flanker task designed to test Posner's three visual attention network functions: alerting, orienting, and executive control [Posner, M. I. (2004). "Cognitive neuroscience of attention". New York, NY: Guilford Press]. In a placebo-controlled, double-blind…

Brunye, Tad T.; Mahoney, Caroline R.; Lieberman, Harris R.; Taylor, Holly A.

2010-01-01

21

Direct Gaze Modulates Face Recognition in Young Infants  

ERIC Educational Resources Information Center

From birth, infants prefer to look at faces that engage them in direct eye contact. In adults, direct gaze is known to modulate the processing of faces, including the recognition of individuals. In the present study, we investigate whether direction of gaze has any effect on face recognition in four-month-old infants. Four-month infants were shown…

Farroni, Teresa; Massaccesi, Stefano; Menon, Enrica; Johnson, Mark H.

2007-01-01

22

Clustering and Community Detection in Directed Networks: A Survey  

E-print Network

Networks (or graphs) appear as dominant structures in diverse domains, including sociology, biology, neuroscience and computer science. In most of the aforementioned cases graphs are directed - in the sense that there is directionality on the edges, making the semantics of the edges non symmetric. An interesting feature that real networks present is the clustering or community structure property, under which the graph topology is organized into modules commonly called communities or clusters. The essence here is that nodes of the same community are highly similar while on the contrary, nodes across communities present low similarity. Revealing the underlying community structure of directed complex networks has become a crucial and interdisciplinary topic with a plethora of applications. Therefore, naturally there is a recent wealth of research production in the area of mining directed graphs - with clustering being the primary method and tool for community detection and evaluation. The goal of this paper is t...

Malliaros, Fragkiskos D

2013-01-01

23

On Functional Module Detection in Metabolic Networks  

PubMed Central

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

Koch, Ina; Ackermann, Jörg

2013-01-01

24

Inflation, modulation and baryogenesis with warm directions  

E-print Network

There are many flat directions in SUSY models, which may dissipate their energy and source the radiation background during inflation. However, the only possibility that has been studied in this direction is warm inflation, which uses "warm" (or "dissipative" if we consider more modest situation) direction as the inflaton. In this talk we discuss other significant possibilities of such directions which are dissipative and may or may not be "warm". Affleck-Dine (AD) mechanism and other cosmological scenarios are discussed in the light of "dissipative field", instead of using the conventional light field with mass protection. We sometimes consider Morikawa-Sasaki coefficient for the non-thermal background, which is important because the dissipation calculated for a naive thermal background with $T\\to 0$ is not enough to discuss the dissipation with the non-thermal background.

Tomohiro Matsuda

2010-01-26

25

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

26

Giant components in directed multiplex networks.  

PubMed

We describe the complex global structure of giant components in directed multiplex networks that generalizes the well-known bow-tie structure, generic for ordinary directed networks. By definition, a directed multiplex network contains vertices of one type and directed edges of m different types. In directed multiplex networks, we distinguish a set of different giant components based on the existence of directed paths of different types between their vertices such that for each type of edges, the paths run entirely through only edges of that type. If, in particular, m=2, we define a strongly viable component as a set of vertices in which for each type of edges each two vertices are interconnected by at least two directed paths in both directions, running through the edges of only this type. We show that in this case, a directed multiplex network contains in total nine different giant components including the strongly viable component. In general, the total number of giant components is 3^{m}. For uncorrelated directed multiplex networks, we obtain exactly the size and the emergence point of the strongly viable component and estimate the sizes of other giant components. PMID:25493836

Azimi-Tafreshi, N; Dorogovtsev, S N; Mendes, J F F

2014-11-01

27

Google matrix analysis of directed networks  

E-print Network

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 chain...

Ermann, Leonardo; Shepelyansky, Dima L

2014-01-01

28

Google matrix analysis of directed networks  

E-print Network

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.

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

2014-09-01

29

An effective method for network module extraction from microarray data  

PubMed Central

Background The development of high-throughput Microarray technologies has provided various opportunities to systematically characterize diverse types of computational biological networks. Co-expression network have become popular in the analysis of microarray data, such as for detecting functional gene modules. Results This paper presents a method to build a co-expression network (CEN) and to detect network modules from the built network. We use an effective gene expression similarity measure called NMRS (Normalized mean residue similarity) to construct the CEN. We have tested our method on five publicly available benchmark microarray datasets. The network modules extracted by our algorithm have been biologically validated in terms of Q value and p value. Conclusions Our results show that the technique is capable of detecting biologically significant network modules from the co-expression network. Biologist can use this technique to find groups of genes with similar functionality based on their expression information. PMID:23320896

2012-01-01

30

Edge direction and the structure of networks  

PubMed Central

Directed networks are ubiquitous and are necessary to represent complex systems with asymmetric interactions—from food webs to the World Wide Web. Despite the importance of edge direction for detecting local and community structure, it has been disregarded in studying a basic type of global diversity in networks: the tendency of nodes with similar numbers of edges to connect. This tendency, called assortativity, affects crucial structural and dynamic properties of real-world networks, such as error tolerance or epidemic spreading. Here we demonstrate that edge direction has profound effects on assortativity. We define a set of four directed assortativity measures and assign statistical significance by comparison to randomized networks. We apply these measures to three network classes—online/social networks, food webs, and word-adjacency networks. Our measures (i) reveal patterns common to each class, (ii) separate networks that have been previously classified together, and (iii) expose limitations of several existing theoretical models. We reject the standard classification of directed networks as purely assortative or disassortative. Many display a class-specific mixture, likely reflecting functional or historical constraints, contingencies, and forces guiding the system’s evolution. PMID:20505119

Foster, Jacob G.; Foster, David V.; Grassberger, Peter; Paczuski, Maya

2010-01-01

31

Direct frequency modulation in AlGaAs semiconductor lasers  

Microsoft Academic Search

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

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

1982-01-01

32

Modules in the metabolic network of E.coli with regulatory interactions  

E-print Network

We examine the modular structure of the metabolic network when combined with the regulatory network representing direct regulation of enzymes by small metabolites in E.coli. In order to identify the modular structure we introduce clustering algorithm based on a novel vertex similarity measure for bipartite graphs. We also apply a standard module identification method based on simulated annealing. Both methods identify the same modular core each of them with different resolution. We observe slight but still statistically significant increase of modularity after regulatory interactions addition. Enrichment of the metabolic network with the regulatory information leads to identification of new functional modules, which cannot be detected in the metabolic network only. Regulatory loops in the modules are the source of their self-control, i.e. autonomy, and allow to make hypothesis about module function. This study demonstrates that incorporation of regulatory information is important component in defining functio...

Geryk, Jan

2014-01-01

33

Inverter power module with distributed support for direct substrate cooling  

DOEpatents

Systems and/or methods are provided for an inverter power module with distributed support for direct substrate cooling. An inverter module comprises a power electronic substrate. A first support frame is adapted to house the power electronic substrate and has a first region adapted to allow direct cooling of the power electronic substrate. A gasket is interposed between the power electronic substrate and the first support frame. The gasket is configured to provide a seal between the first region and the power electronic substrate. A second support frame is adapted to house the power electronic substrate and joined to the first support frame to form the seal.

Miller, David Harold (San Pedro, CA); Korich, Mark D. (Chino Hills, CA); Ward, Terence G. (Redondo Beach, CA); Mann, Brooks S. (Redondo Beach, CA)

2012-08-21

34

Nonconsensus opinion model on directed networks  

NASA Astrophysics Data System (ADS)

Dynamic social opinion models have been widely studied on undirected networks, and most of them are based on spin interaction models that produce a consensus. In reality, however, many networks such as Twitter and the World Wide Web are directed and are composed of both unidirectional and bidirectional links. Moreover, from choosing a coffee brand to deciding who to vote for in an election, two or more competing opinions often coexist. In response to this ubiquity of directed networks and the coexistence of two or more opinions in decision-making situations, we study a nonconsensus opinion model introduced by Shao et al. [Phys. Rev. Lett. 103, 018701 (2009), 10.1103/PhysRevLett.103.018701] on directed networks. We define directionality ? as the percentage of unidirectional links in a network, and we use the linear correlation coefficient ? between the in-degree and out-degree of a node to quantify the relation between the in-degree and out-degree. We introduce two degree-preserving rewiring approaches which allow us to construct directed networks that can have a broad range of possible combinations of directionality ? and linear correlation coefficient ? and to study how ? and ? impact opinion competitions. We find that, as the directionality ? or the in-degree and out-degree correlation ? increases, the majority opinion becomes more dominant and the minority opinion's ability to survive is lowered.

Qu, Bo; Li, Qian; Havlin, Shlomo; Stanley, H. Eugene; Wang, Huijuan

2014-11-01

35

Low-cost adaptive directly modulated optical OFDM based on semiconductor optical amplifier  

NASA Astrophysics Data System (ADS)

Low cost optical OFDM has great potential for next generation optical access networks and PONs, due to its high flexibility in bandwidth manipulation, and high spectral efficiency. Here, a low cost optical OFDM is proposed, based on adaptive direct modulation semiconductor optical amplifier. Adaptive current loading techniques for PAPR (peak to average power ratio) reduction are proposed and analyzed. Simulations show that the proposed adaptive techniques enable significant BER improvement.

Kashany-Mizrahi, Inbal; Sadot, Dan

2013-10-01

36

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

Microsoft Academic Search

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

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

2003-01-01

37

Simulation of optical communication systems using direct and external modulation  

Microsoft Academic Search

In this work we present an analysis of the performance of optical communication systems using two types of modulation: direct and external. The analysis was based on mathematical models., which was implemented by using of PC SIMFO, a packet of simulation of optical systems developed by Photonic Technology Lab (LTF-UNICAMP). We used a nonlinear dispersive optical fiber and we optimized

M. I. B. de Maizman; L. C. Kakimoto; E. Moschim

2002-01-01

38

Dynamics-based centrality for directed networks  

NASA Astrophysics Data System (ADS)

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.

Masuda, Naoki; Kori, Hiroshi

2010-11-01

39

Random walks in directed modular networks  

NASA Astrophysics Data System (ADS)

Because diffusion typically involves symmetric interactions, scant attention has been focused on studying asymmetric cases. However, important networked systems underlain by diffusion (e.g. cortical networks and WWW) are inherently directed. In the case of undirected diffusion, it can be shown that the steady-state probability of the random walk dynamics is fully correlated with the degree, which no longer holds for directed networks. We investigate the relationship between such probability and the inward node degree, which we call efficiency, in modular networks. Our findings show that the efficiency of a given community depends mostly on the balance between its ingoing and outgoing connections. In addition, we derive analytical expressions to show that the internal degree of the nodes does not play a crucial role in their efficiency, when considering the Erd?s–Rényi and Barabási–Albert models. The results are illustrated with respect to the macaque cortical network, providing subsidies for improving transportation and communication systems.

Comin, Cesar H.; Viana, Mateus P.; Antiqueira, Lucas; Costa, Luciano da F.

2014-12-01

40

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

NASA Astrophysics Data System (ADS)

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.

Wang, Bingbo; Gao, Lin; Gao, Yong

2012-04-01

41

Targeting direct marketing campaigns by neural networks  

Microsoft Academic Search

Market-oriented companies increasingly aim at maximising the return of targeted direct marketing campaigns, rather than trying to reach customers and prospects indistinctly, according to a mass marketing approach. The profitability of direct marketing campaigns depends on a detailed definition of prospects and an accurate prediction of the response rate. This study shows how the use of Artificial Neural Networks (ANNs)

Gianluigi Guido; M. Irene Prete; Stefano Miraglia; Irma De Mare

2011-01-01

42

Mining directed social network from message board  

Microsoft Academic Search

In the paper, we present an approach to mining a directed social network from a message board on the Internet where vertices denote individuals and directed links denote the flow of influence. The influence is measured based on propagating terms among individuals via messages. The distance with respect to contextual similarity between individuals is acquired since the influence indicates the

Naohiro Matsumura; David E. Goldberg; Xavier Llorà

2005-01-01

43

Clustering and community detection in directed networks: A survey  

NASA Astrophysics Data System (ADS)

Networks (or graphs) appear as dominant structures in diverse domains, including sociology, biology, neuroscience and computer science. In most of the aforementioned cases graphs are directed - in the sense that there is directionality on the edges, making the semantics of the edges nonsymmetric as the source node transmits some property to the target one but not vice versa. An interesting feature that real networks present is the clustering or community structure property, under which the graph topology is organized into modules commonly called communities or clusters. The essence here is that nodes of the same community are highly similar while on the contrary, nodes across communities present low similarity. Revealing the underlying community structure of directed complex networks has become a crucial and interdisciplinary topic with a plethora of relevant application domains. Therefore, naturally there is a recent wealth of research production in the area of mining directed graphs - with clustering being the primary method sought and the primary tool for community detection and evaluation. The goal of this paper is to offer an in-depth comparative review of the methods presented so far for clustering directed networks along with the relevant necessary methodological background and also related applications. The survey commences by offering a concise review of the fundamental concepts and methodological base on which graph clustering algorithms capitalize on. Then we present the relevant work along two orthogonal classifications. The first one is mostly concerned with the methodological principles of the clustering algorithms, while the second one approaches the methods from the viewpoint regarding the properties of a good cluster in a directed network. Further, we present methods and metrics for evaluating graph clustering results, demonstrate interesting application domains and provide promising future research directions.

Malliaros, Fragkiskos D.; Vazirgiannis, Michalis

2013-12-01

44

Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex Modulates Repetition  

E-print Network

Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex Modulates Repetition and learning of unfamiliar faces remains unclear. Transcranial direct current stimulation (tDCS) transiently Direct Current Stimulation of the Dorsolateral Prefrontal Cortex Modulates Repetition Suppression

Gosselin, Frédéric

45

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

NASA Technical Reports Server (NTRS)

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.

Batchman, T. E.

1980-01-01

46

A Novel Modulation Classification Approach Using Gabor Filter Network  

PubMed Central

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

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

2014-01-01

47

Directed diffusion for wireless sensor networking  

Microsoft Academic Search

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

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

2003-01-01

48

Identify Dynamic Network Modules with Temporal and Spatial Constraints  

SciTech Connect

Despite the rapid accumulation of systems-level biological data, understanding the dynamic nature of cellular activity remains a difficult task. The reason is that most biological data are static, or only correspond to snapshots of cellular activity. In this study, we explicitly attempt to detangle the temporal complexity of biological networks by using compilations of time-series gene expression profiling data.We define a dynamic network module to be a set of proteins satisfying two conditions: (1) they form a connected component in the protein-protein interaction (PPI) network; and (2) their expression profiles form certain structures in the temporal domain. We develop the first efficient mining algorithm to discover dynamic modules in a temporal network, as well as frequently occurring dynamic modules across many temporal networks. Using yeast as a model system, we demonstrate that the majority of the identified dynamic modules are functionally homogeneous. Additionally, many of them provide insight into the sequential ordering of molecular events in cellular systems. We further demonstrate that identifying frequent dynamic network modules can significantly increase the signal to noise separation, despite the fact that most dynamic network modules are highly condition-specific. Finally, we note that the applicability of our algorithm is not limited to the study of PPI systems, instead it is generally applicable to the combination of any type of network and time-series data.

Jin, R; McCallen, S; Liu, C; Almaas, E; Zhou, X J

2007-09-24

49

Identification of biochemical network modules based on shortest retroactive distances.  

PubMed

Modularity analysis offers a route to better understand the organization of cellular biochemical networks as well as to derive practically useful, simplified models of these complex systems. While there is general agreement regarding the qualitative properties of a biochemical module, there is no clear consensus on the quantitative criteria that may be used to systematically derive these modules. In this work, we investigate cyclical interactions as the defining characteristic of a biochemical module. We utilize a round trip distance metric, termed Shortest Retroactive Distance (ShReD), to characterize the retroactive connectivity between any two reactions in a biochemical network and to group together network components that mutually influence each other. We evaluate the metric on two types of networks that feature feedback interactions: (i) epidermal growth factor receptor (EGFR) signaling and (ii) liver metabolism supporting drug transformation. For both networks, the ShReD partitions found hierarchically arranged modules that confirm biological intuition. In addition, the partitions also revealed modules that are less intuitive. In particular, ShReD-based partition of the metabolic network identified a 'redox' module that couples reactions of glucose, pyruvate, lipid and drug metabolism through shared production and consumption of NADPH. Our results suggest that retroactive interactions arising from feedback loops and metabolic cycles significantly contribute to the modularity of biochemical networks. For metabolic networks, cofactors play an important role as allosteric effectors that mediate the retroactive interactions. PMID:22102800

Sridharan, Gautham Vivek; Hassoun, Soha; Lee, Kyongbum

2011-11-01

50

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

PubMed

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

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

51

Data reliability in complex directed networks  

NASA Astrophysics Data System (ADS)

The availability of data from many different sources and fields of science has made it possible to map out an increasing number of networks of contacts and interactions. However, quantifying how reliable these data are remains an open problem. From Biology to Sociology and Economics, the identification of false and missing positives has become a problem that calls for a solution. In this work we extend one of the newest, best performing models—due to Guimerá and Sales-Pardo in 2009—to directed networks. The new methodology is able to identify missing and spurious directed interactions with more precision than previous approaches, which renders it particularly useful for analyzing data reliability in systems like trophic webs, gene regulatory networks, communication patterns and several social systems. We also show, using real-world networks, how the method can be employed to help search for new interactions in an efficient way.

Sanz, Joaquín; Cozzo, Emanuele; Moreno, Yamir

2013-12-01

52

Directional Dependence and Diurnal Modulation in Dark Matter Detectors  

E-print Network

In this paper we study the effect of the channeling of ions recoiling from collisions with weakly interacting massive particles (WIMPs) in single crystal detectors. In particular we investigate the possibility that channeling may give rise to diurnal modulations of the counting rate as the Earth rotates relative to the direction of the WIMP wind, and the effect that channeling has on the "quenching factor" of a detector.

Creswick, Richard J; Avignone, Frank T

2010-01-01

53

An iterative network partition algorithm for accurate identification of dense network modules  

PubMed Central

A key step in network analysis is to partition a complex network into dense modules. Currently, modularity is one of the most popular benefit functions used to partition network modules. However, recent studies suggested that it has an inherent limitation in detecting dense network modules. In this study, we observed that despite the limitation, modularity has the advantage of preserving the primary network structure of the undetected modules. Thus, we have developed a simple iterative Network Partition (iNP) algorithm to partition a network. The iNP algorithm provides a general framework in which any modularity-based algorithm can be implemented in the network partition step. Here, we tested iNP with three modularity-based algorithms: multi-step greedy (MSG), spectral clustering and Qcut. Compared with the original three methods, iNP achieved a significant improvement in the quality of network partition in a benchmark study with simulated networks, identified more modules with significantly better enrichment of functionally related genes in both yeast protein complex network and breast cancer gene co-expression network, and discovered more cancer-specific modules in the cancer gene co-expression network. As such, iNP should have a broad application as a general method to assist in the analysis of biological networks. PMID:22121225

Sun, Siqi; Dong, Xinran; Fu, Yao; Tian, Weidong

2012-01-01

54

Modulation of function and gated learning in a network memory  

SciTech Connect

Memory and learning are studied in a model neural network made from component cells with a variety of realistic intrinsic dynamic behaviors. Modulation of intrinsic cellular characteristics causes a network to switch between two entirely different modes of operation. In one mode the network acts as a selective, long-term associative memory, whereas in the other it is a nonselective, short-term latching memory. Such functional modulation can be used as a mechanism for initiating and terminating learning in a network associative memory.

Abbott, L.F. (Brandeis Univ., Waltham, MA (United States))

1990-12-01

55

Serotonin modulation of cortical neurons and networks  

PubMed Central

The serotonergic pathways originating in the dorsal and median raphe nuclei (DR and MnR, respectively) are critically involved in cortical function. Serotonin (5-HT), acting on postsynaptic and presynaptic receptors, is involved in cognition, mood, impulse control and motor functions by (1) modulating the activity of different neuronal types, and (2) varying the release of other neurotransmitters, such as glutamate, GABA, acetylcholine and dopamine. Also, 5-HT seems to play an important role in cortical development. Of all cortical regions, the frontal lobe is the area most enriched in serotonergic axons and 5-HT receptors. 5-HT and selective receptor agonists modulate the excitability of cortical neurons and their discharge rate through the activation of several receptor subtypes, of which the 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT3 subtypes play a major role. Little is known, however, on the role of other excitatory receptors moderately expressed in cortical areas, such as 5-HT2C, 5-HT4, 5-HT6, and 5-HT7. In vitro and in vivo studies suggest that 5-HT1A and 5-HT2A receptors are key players and exert opposite effects on the activity of pyramidal neurons in the medial prefrontal cortex (mPFC). The activation of 5-HT1A receptors in mPFC hyperpolarizes pyramidal neurons whereas that of 5-HT2A receptors results in neuronal depolarization, reduction of the afterhyperpolarization and increase of excitatory postsynaptic currents (EPSCs) and of discharge rate. 5-HT can also stimulate excitatory (5-HT2A and 5-HT3) and inhibitory (5-HT1A) receptors in GABA interneurons to modulate synaptic GABA inputs onto pyramidal neurons. Likewise, the pharmacological manipulation of various 5-HT receptors alters oscillatory activity in PFC, suggesting that 5-HT is also involved in the control of cortical network activity. A better understanding of the actions of 5-HT in PFC may help to develop treatments for mood and cognitive disorders associated with an abnormal function of the frontal lobe. PMID:23626526

Celada, Pau; Puig, M. Victoria; Artigas, Francesc

2013-01-01

56

Quantum secure direct communication network with hyperentanglement  

NASA Astrophysics Data System (ADS)

We propose a quantum secure direct communication protocol with entanglement swapping and hyperentanglement. Any two users, Alice and Bob, can communicate with each other in a quantum network, even though there is no direct quantum channel between them. The trust center, Trent, who provides a quantum channel to link them by performing entanglement swapping, cannot eavesdrop on their communication. This protocol provides a high channel capacity because it uses hyperentanglement, which can be generated using a beta barium borate crystal.

Chang, Ho Hong; Jino, Heo; Jong In, Lim; Hyung, Jin Yang

2014-09-01

57

Gaussian Networks for Direct Adaptive Control  

Microsoft Academic Search

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

Robert M. Sanner; Jean-Jacques E. Slotine

1991-01-01

58

Design of a directed molecular network  

PubMed Central

An ability to rationally design complex networks from the bottom up can offer valuable quantitative model systems for use in gaining a deeper appreciation for the principles governing the self-organization and functional characteristics of complex systems. We report herein the de novo design, graph prediction, experimental analysis, and characterization of simple self-organized, nonlinear molecular networks. Our approach makes use of the sequence-dependant auto- and cross-catalytic functional characteristics of template-directed peptide fragment condensation reactions in neutral aqueous solutions. Starting with an array of 81 sequence similar 32-residue coiled-coil peptides, we estimated the relative stability difference between all plausible A2B-type coiled-coil ensembles and used this information to predict the auto- and cross-catalysis pathways and the resulting plausible network motif and connectivities. Similar to most complex systems, the generated graph displays clustered nodes with an overall hierarchical architecture. To test the validity of the design principles used, nine nodes composing a main segment of the graph were experimentally analyzed for their capacity in establishing the predicted network connectivity. The resulting self-organized chemical network is shown to display 25 directed edges in good agreement with the graph analysis estimations. Moreover, we show that by varying the system parameters (presence or absence of certain substrates or templates), its operating network motif can be altered, even to the extremes of turning pathways on or off. We suggest that this approach can be expanded for the construction of large-scale networks, offering a means to study and to understand better the emergent, collective behaviors of networks. PMID:15256596

Ashkenasy, Gonen; Jagasia, Reshma; Yadav, Maneesh; Ghadiri, M. Reza

2004-01-01

59

Study of Orthogonal Modulation Schemes for Passive Optical Access Networks.  

E-print Network

as the most promising FTTH technology to meet the ever-increasing bandwidth demand, by using the minimal the adoption of orthogonal modulation techniques ­used in other types of networks- adapted adequately networks and the technologies used so far as well as the benefits of fiber optics in the access "part

Kouroupetroglou, Georgios

60

Module organization and variance in protein-protein interaction networks.  

PubMed

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

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

2015-01-01

61

Module organization and variance in protein-protein interaction networks  

PubMed Central

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

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

2015-01-01

62

The Direct Digital Modulation of Traveling Wave Tubes  

NASA Technical Reports Server (NTRS)

Traveling wave tube (TWT) technology, first described by Rudolf Kompfner in the early 1940s, has been a key component of space missions from the earliest communication satellites in the 1960s to the Cassini probe today. TWTs are essentially signal amplifiers that have the special capability of operating at microwave frequencies. The microwave frequency range, which spans from approximately 500 MHz to 300 GHz, is shared by many technologies including cellular phones, satellite television, space communication, and radar. TWT devices are superior in reliability, weight, and efficiency to solid-state amplifiers at the high power and frequency levels required for most space missions. TWTs have three main components -an electron gun, slow wave structure, and collector. The electron gun generates an electron beam that moves along the length of the tube axis, inside of the slow wave circuit. At the same time, the inputted signal is slowed by its travel through the coils of the helical slow wave circuit. The interaction of the electron beam and this slowed signal produces a transfer of kinetic energy to the signal, and in turn, amplification. At the end of its travel, the spent electron beam moves into the collector where its remaining energy is dissipated as heat or harnessed for reuse. TWTs can easily produce gains in the tens of decibels, numbers that are suitable for space missions. To date, however, TWTs have typically operated at fixed levels of gain. This gain is determined by various, unchanging, physical factors of the tube. Traditionally, to achieve varying gain, an input signal s amplitude has had to first be modulated by a separate device before being fed into the TWT. This is not always desirable, as significant distortion can occur in certain situations. My mentor, Mr. Dale Force, has proposed an innovative solution to this problem called direct digital modulation . The testing and implementation of this solution is the focus of my summer internship. The direct digital modulation of a TWT removes the need for a separate amplitude modulation device. Instead, different levels of gain are achieved by varying the electron beam current. The lower the current, the less kinetic energy is available to be transferred to the signal. To vary the current, a grid is placed in-between the electron gun and the slow wave circuit. By changing the voltage across the grid, the electron beam current can be controlled. Grid technology has mostly been used in pulse applications such as radar, where only two voltage states are necessary. For direct digital modulation, however, a continuous range of voltages is required.

Radhamohan, Ranjan S.

2004-01-01

63

eXamine: Exploring annotated modules in networks  

PubMed Central

Background Biological networks have a growing importance for the interpretation of high-throughput “omics” data. Integrative network analysis makes use of statistical and combinatorial methods to extract smaller subnetwork modules, and performs enrichment analysis to annotate the modules with ontology terms or other available knowledge. This process results in an annotated module, which retains the original network structure and includes enrichment information as a set system. A major bottleneck is a lack of tools that allow exploring both network structure of extracted modules and its annotations. Results This paper presents a visual analysis approach that targets small modules with many set-based annotations, and which displays the annotations as contours on top of a node-link diagram. We introduce an extension of self-organizing maps to lay out nodes, links, and contours in a unified way. An implementation of this approach is freely available as the Cytoscape app eXamine Conclusions eXamine accurately conveys small and annotated modules consisting of several dozens of proteins and annotations. We demonstrate that eXamine facilitates the interpretation of integrative network analysis results in a guided case study. This study has resulted in a novel biological insight regarding the virally-encoded G-protein coupled receptor US28. PMID:25002203

2014-01-01

64

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

Microsoft Academic Search

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

J. M. Tang; K. Alan Shore

2006-01-01

65

Protein Interaction Networks—More Than Mere Modules  

PubMed Central

It is widely believed that the modular organization of cellular function is reflected in a modular structure of molecular networks. A common view is that a “module” in a network is a cohesively linked group of nodes, densely connected internally and sparsely interacting with the rest of the network. Many algorithms try to identify functional modules in protein-interaction networks (PIN) by searching for such cohesive groups of proteins. Here, we present an alternative approach independent of any prior definition of what actually constitutes a “module”. In a self-consistent manner, proteins are grouped into “functional roles” if they interact in similar ways with other proteins according to their functional roles. Such grouping may well result in cohesive modules again, but only if the network structure actually supports this. We applied our method to the PIN from the Human Protein Reference Database (HPRD) and found that a representation of the network in terms of cohesive modules, at least on a global scale, does not optimally represent the network's structure because it focuses on finding independent groups of proteins. In contrast, a decomposition into functional roles is able to depict the structure much better as it also takes into account the interdependencies between roles and even allows groupings based on the absence of interactions between proteins in the same functional role. This, for example, is the case for transmembrane proteins, which could never be recognized as a cohesive group of nodes in a PIN. When mapping experimental methods onto the groups, we identified profound differences in the coverage suggesting that our method is able to capture experimental bias in the data, too. For example yeast-two-hybrid data were highly overrepresented in one particular group. Thus, there is more structure in protein-interaction networks than cohesive modules alone and we believe this finding can significantly improve automated function prediction algorithms. PMID:20126533

Pinkert, Stefan; Schultz, Jörg; Reichardt, Jörg

2010-01-01

66

Exploring the randomness of directed acyclic networks  

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

67

Chirped laser dispersion spectroscopy using a directly modulated quantum cascade laser  

NASA Astrophysics Data System (ADS)

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.

Hangauer, Andreas; Spinner, Georg; Nikodem, Michal; Wysocki, Gerard

2013-11-01

68

Biologically Realizable Reward-Modulated Hebbian Training for Spiking Neural Networks  

E-print Network

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

Ferrari, Silvia

69

Network modules help the identification of key transport routes, signaling pathways in cellular and other networks  

E-print Network

Complex systems are successfully reduced to interacting elements via the network concept. Transport plays a key role in the survival of networks. For example the specialized signaling cascades of cellular networks filter noise and efficiently adapt the network structure to new stimuli. However, our general understanding of transport mechanisms and signaling pathways in complex systems is yet limited. Here we summarize the key network structures involved in transport, list the solutions available to overloaded systems for relaxing their load and outline a possible method for the computational determination of signaling pathways. We highlight that in addition to hubs, bridges and the network skeleton, the overlapping modular structure is also essential in network transport. Moreover, by locating network elements in the space of overlapping network modules and evaluating their distance in this "module space", it may be possible to approximate signaling pathways computationally, which, in turn could serve the ide...

Palotai, Robin

2009-01-01

70

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

E-print Network

) systems. The modulation is carried out in a NFDAM system by means of a control unit that switches amongA Study of Near-Field Direct Antenna Modulation Systems Using Convex Optimization Javad Lavaei de- sign for a class of communication systems known as near-field direct antenna modulation (NFDAM

Hajimiri, Ali

71

Constructing module maps for integrated analysis of heterogeneous biological networks  

PubMed Central

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

Amar, David; Shamir, Ron

2014-01-01

72

Motion words selectively modulate direction discrimination sensitivity for threshold motion  

PubMed Central

Can speech selectively modulate the sensitivity of a sensory system so that, in the presence of a suitable linguistic context, the discrimination of certain perceptual features becomes more or less likely? In this study, participants heard upward or downward motion words followed by a single visual field of random dots moving upwards or downwards. The time interval between the onsets of the auditory and the visual stimuli was varied parametrically. Motion direction could be either discriminable (suprathreshold motion) or non-discriminable (threshold motion). Participants had to judge whether the dots were moving upward or downward. Results show a double dissociation between discrimination sensitivity (d?) and reaction times depending on whether vertical motion was above or at threshold. With suprathreshold motion, responses were faster for congruent directions of words and dots, but sensitivity was equal across conditions. With threshold motion, sensitivity was higher for congruent directions of words and dots, but responses were equally fast across conditions. The observed differences in sensitivity and response times were largest when the dots appeared 450 ms after word onset, that is, consistently with electrophysiology, at the time the up/down semantics of the word had become available. These data suggest that word meanings can alter the balance between signal and noise within the visual system and affect the perception of low-level sensory features. PMID:23596407

Pavan, Andrea; Skujevskis, M?ris; Baggio, Giosuè

2013-01-01

73

Excitability modulation of the motor system induced by transcranial direct current stimulation: a multimodal approach.  

PubMed

Anodal and cathodal transcranial direct current stimulations (tDCS) are both established techniques to induce cortical excitability changes. Typically, in the human motor system, such cortical modulations are inferred through changes in the amplitude of the motor evoked potentials (MEPs). However, it is now possible to directly evaluate tDCS-induced changes at the cortical level by recording the transcranial magnetic stimulation evoked potentials (TEPs) using electroencephalography (EEG). The present study investigated the modulation induced by the tDCS on the motor system. The study evaluates changes in the MEPs, in the amplitude and distribution of the TEPs, in resting state oscillatory brain activity and in behavioral performance in a simple manual response task. Both the short- and long-term tDCS effects were investigated by evaluating their time course at ~0 and 30min after tDCS. Anodal tDCS over the left primary motor cortex (M1) induced an enhancement of corticospinal excitability, whereas cathodal stimulation produced a reduction. These changes in excitability were indexed by changes in MEP amplitude. More interestingly, tDCS modulated the cortical reactivity, which is the neuronal activity evoked by TMS, in a polarity-dependent and site-specific manner. Cortical reactivity increased after anodal stimulation over the left M1, whereas it decreased with cathodal stimulation. These effects were partially present also at long term evaluation. No polarity-specific effect was found either on behavioral measures or on oscillatory brain activity. The latter showed a general increase in the power density of low frequency oscillations (theta and alpha) at both stimulation polarities. Our results suggest that tDCS is able to modulate motor cortical reactivity in a polarity-specific manner, inducing a complex pattern of direct and indirect cortical activations or inhibitions of the motor system-related network, which might be related to changes in synaptic efficacy of the motor cortex. PMID:23845429

Pellicciari, Maria Concetta; Brignani, Debora; Miniussi, Carlo

2013-12-01

74

Deciphering early development of complex diseases by progressive module network.  

PubMed

There is no effective cure nowadays for many complex diseases, and thus it is crucial to detect and further treat diseases in earlier stages. Generally, the development and progression of complex diseases include three stages: normal stage, pre-disease stage, and disease stage. For diagnosis and treatment, it is necessary to reveal dynamical organizations of molecular modules during the early development of the disease from the pre-disease stage to the disease stage. Thus, we develop a new framework, i.e. we identify the modules presenting at the pre-disease stage (pre-disease module) based on dynamical network biomarkers (DNBs), detect the modules observed at the advanced stage (disease-responsive module) by cross-tissue gene expression analysis, and finally find the modules related to early development (progressive module) by progressive module network (PMN). As an application example, we used this new method to analyze the gene expression data for NOD mouse model of Type 1 diabetes mellitus (T1DM). After the comprehensive comparison with the previously reported milestone molecules, we found by PMN: (1) the critical transition point was identified and confirmed by the tissue-specific modules or DNBs relevant to the pre-disease stage, which is considered as an earlier event during disease development and progression; (2) several key tissues-common modules related to the disease stage were significantly enriched on known T1DM associated genes with the rewired association networks, which are marks of later events during T1DM development and progression; (3) the tissue-specific modules associated with early development revealed several common essential progressive genes, and a few of pathways representing the effect of environmental factors during the early T1DM development. Totally, we developed a new method to detect the critical stage and the key modules during the disease occurrence and progression, and show that the pre-disease modules can serve as warning signals for the pre-disease state (e.g. T1DM early diagnosis) whereas the progressive modules can be used as the therapy targets for the disease state (e.g. advanced T1DM), which were also validated by experimental data. PMID:24561825

Zeng, Tao; Zhang, Chuan-chao; Zhang, Wanwei; Liu, Rui; Liu, Juan; Chen, Luonan

2014-06-01

75

Transcranial direct current stimulation modulates efficiency of reading processes  

PubMed Central

Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that offers promise as an investigative method for understanding complex cognitive operations such as reading. This study explores the ability of a single session of tDCS to modulate reading efficiency and phonological processing performance within a group of healthy adults. Half the group received anodal or cathodal stimulation, on two separate days, of the left temporo-parietal junction while the other half received anodal or cathodal stimulation of the right homologue area. Pre- and post-stimulation assessment of reading efficiency and phonological processing was carried out. A larger pre-post difference in reading efficiency was found for participants who received right anodal stimulation compared to participants who received left anodal stimulation. Further, there was a significant post-stimulation increase in phonological processing speed following right hemisphere anodal stimulation. Implications for models of reading and reading impairment are discussed. PMID:25852513

Thomson, Jennifer M.; Doruk, Deniz; Mascio, Bryan; Fregni, Felipe; Cerruti, Carlo

2015-01-01

76

Module-Based Association Analysis for Omics Data with Network Structure  

PubMed Central

Module-based analysis (MBA) aims to evaluate the effect of a group of biological elements sharing common features, such as SNPs in the same gene or metabolites in the same pathways, and has become an attractive alternative to traditional single bio-element approaches. Because bio-elements regulate and interact with each other as part of network, incorporating network structure information can more precisely model the biological effects, enhance the ability to detect true associations, and facilitate our understanding of the underlying biological mechanisms. How-ever, most MBA methods ignore the network structure information, which depicts the interaction and regulation relationship among basic functional units in biology system. We construct the con-nectivity kernel and the topology kernel to capture the relationship among bio-elements in a mod-ule, and use a kernel machine framework to evaluate the joint effect of bio-elements. Our proposed kernel machine approach directly incorporates network structure so to enhance the study effi-ciency; it can assess interactions among modules, account covariates, and is computational effi-cient. Through simulation studies and real data application, we demonstrate that the proposed network-based methods can have markedly better power than the approaches ignoring network information under a range of scenarios. PMID:25822417

Wang, Zhi; Maity, Arnab; Hsiao, Chuhsing Kate; Voora, Deepak; Kaddurah-Daouk, Rima; Tzeng, Jung-Ying

2015-01-01

77

Nicotinic modulation of intrinsic brain networks in schizophrenia  

PubMed Central

The nicotinic receptor is a promising drug target currently being investigated for the treatment of cognitive symptoms in schizophrenia. A key step in this process is the development of noninvasive functional neuroimaging biomarkers that can be used to determine if nicotinic agents are eliciting their targeted biological effect, ideally through modulation of a fundamental aspect of neuronal function. To that end, neuroimaging researchers are beginning to understand how nicotinic modulation affects “intrinsic” brain networks to elicit potentially therapeutic effects. An intrinsic network is a functionally and (often) structurally connected network of brain areas whose activity reflects a fundamental neurobiological organizational principle of the brain. This review summarizes findings of the effects of nicotinic drugs on three topics related to intrinsic brain network activity: (1) the default mode network, a group of brain areas for which activity is maximal at rest and reduced during cognitive tasks, (2) the salience network, which integrates incoming sensory data with prior internal representations to guide future actions and change predictive values, and (3) multi-scale complex network dynamics, which describe these brain’s ability to efficiency integrate information while preserving local functional specialization. These early findings can be used to inform future neuroimaging studies that examine the network effects of nicotinic agents. PMID:23796751

Smucny, Jason; Tregellas, Jason

2014-01-01

78

Default Network Modulation and Large-Scale Network Interactivity in Healthy Young and Old Adults  

PubMed Central

We investigated age-related changes in default, attention, and control network activity and their interactions in young and old adults. Brain activity during autobiographical and visuospatial planning was assessed using multivariate analysis and with intrinsic connectivity networks as regions of interest. In both groups, autobiographical planning engaged the default network while visuospatial planning engaged the attention network, consistent with a competition between the domains of internalized and externalized cognition. The control network was engaged for both planning tasks. In young subjects, the control network coupled with the default network during autobiographical planning and with the attention network during visuospatial planning. In old subjects, default-to-control network coupling was observed during both planning tasks, and old adults failed to deactivate the default network during visuospatial planning. This failure is not indicative of default network dysfunction per se, evidenced by default network engagement during autobiographical planning. Rather, a failure to modulate the default network in old adults is indicative of a lower degree of flexible network interactivity and reduced dynamic range of network modulation to changing task demands. PMID:22128194

Schacter, Daniel L.

2012-01-01

79

A directed network of Greek and Roman mythology  

NASA Astrophysics Data System (ADS)

We construct a directed network using a dictionary of Greek and Roman mythology in which the nodes represent the entries listed in the dictionary and we make directional links from an entry to other entries that appear in its explanatory part. We find that this network is clearly not a random network but a directed scale-free network in which the distributions of out-degree and in-degree follow a power-law with exponents ?out?3.0 and ?in?2.5, respectively. Also we measure several quantities which describe the topological properties of the network and compare it to that of other real networks.

Choi, Yeon-Mu; Kim, Hyun-Joo

2007-08-01

80

Transcranial direct current stimulation over posterior parietal cortex modulates visuospatial localization  

E-print Network

Transcranial direct current stimulation over posterior parietal cortex modulates visuospatial, our goal was to determine whether modulation of the PPC via transcranial direct current stimulation (t localization. We used transcranial direct current stimulation (tDCS) over the PPC of healthy human volunteers

Krekelberg, Bart

81

Spread of infectious diseases in directed and modular metapopulation networks.  

PubMed

We consider epidemics in metapopulations on different network topologies. Recent work on epidemics on networks has focused on epidemics of humans. In this work we present a model for epidemics on directed networks, which are found, for example, in the livestock trade. We show that the direction of edges and the modular structure of networks have an impact on the outbreak size and the time of the outbreak peak. In some circumstances, the outbreak size in directed networks can even be larger than in undirected systems. The results presented here could be useful for decision-making processes in directed modular systems. PMID:23005166

Lentz, Hartmut H K; Selhorst, Thomas; Sokolov, Igor M

2012-06-01

82

A direct adaptive neural-network control of nonlinear systems  

Microsoft Academic Search

A direct adaptive neural-network control strategy for a class of nonlinear system is presented. The system considered is described by an unknown NARMA model and a feedforward neural network is used to learn the system. Taking the neural network as a model of the system, control signals are directly obtained by minimizing either the instant difference or the cumulative differences

Niu Lin; Zhang Yunsheng

2000-01-01

83

Differential pulse code modulation image compression using artifical neural networks  

Microsoft Academic Search

Differential pulse code modulation (DPCM) is a widely used technique for both lossy and lossless compression of images. In this paper, the effect of using a nonlinear predictor based on artificial neural networks (ANN) for a DPCM encoder is investigated. The ANN predictor uses a 3-layer perceptron model with 3 input nodes, 30 hidden nodes, and 1 output node. The

Majid Rabbani; Soheil A. Dianat

1993-01-01

84

Controllability and observability analysis for vertex domination centrality in directed networks  

PubMed Central

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

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

2014-01-01

85

Controllability and observability analysis for vertex domination centrality in directed networks  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

86

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

PubMed

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

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

2014-01-01

87

Modulating cognition using transcranial direct current stimulation of the cerebellum.  

PubMed

Numerous studies have emerged recently that demonstrate the possibility of modulating, and in some cases enhancing, cognitive processes by exciting brain regions involved in working memory and attention using transcranial electrical brain stimulation. Some researchers now believe the cerebellum supports cognition, possibly via a remote neuromodulatory effect on the prefrontal cortex. This paper describes a procedure for investigating a role for the cerebellum in cognition using transcranial direct current stimulation (tDCS), and a selection of information-processing tasks of varying task difficulty, which have previously been shown to involve working memory, attention and cerebellar functioning. One task is called the Paced Auditory Serial Addition Task (PASAT) and the other a novel variant of this task called the Paced Auditory Serial Subtraction Task (PASST). A verb generation task and its two controls (noun and verb reading) were also investigated. All five tasks were performed by three separate groups of participants, before and after the modulation of cortico-cerebellar connectivity using anodal, cathodal or sham tDCS over the right cerebellar cortex. The procedure demonstrates how performance (accuracy, verbal response latency and variability) could be selectively improved after cathodal stimulation, but only during tasks that the participants rated as difficult, and not easy. Performance was unchanged by anodal or sham stimulation. These findings demonstrate a role for the cerebellum in cognition, whereby activity in the left prefrontal cortex is likely dis-inhibited by cathodal tDCS over the right cerebellar cortex. Transcranial brain stimulation is growing in popularity in various labs and clinics. However, the after-effects of tDCS are inconsistent between individuals and not always polarity-specific, and may even be task- or load-specific, all of which requires further study. Future efforts might also be guided towards neuro-enhancement in cerebellar patients presenting with cognitive impairment once a better understanding of brain stimulation mechanisms has emerged. PMID:25741744

Pope, Paul A

2015-01-01

88

Modulating Cognition Using Transcranial Direct Current Stimulation of the Cerebellum  

PubMed Central

Numerous studies have emerged recently that demonstrate the possibility of modulating, and in some cases enhancing, cognitive processes by exciting brain regions involved in working memory and attention using transcranial electrical brain stimulation. Some researchers now believe the cerebellum supports cognition, possibly via a remote neuromodulatory effect on the prefrontal cortex. This paper describes a procedure for investigating a role for the cerebellum in cognition using transcranial direct current stimulation (tDCS), and a selection of information-processing tasks of varying task difficulty, which have previously been shown to involve working memory, attention and cerebellar functioning. One task is called the Paced Auditory Serial Addition Task (PASAT) and the other a novel variant of this task called the Paced Auditory Serial Subtraction Task (PASST). A verb generation task and its two controls (noun and verb reading) were also investigated. All five tasks were performed by three separate groups of participants, before and after the modulation of cortico-cerebellar connectivity using anodal, cathodal or sham tDCS over the right cerebellar cortex. The procedure demonstrates how performance (accuracy, verbal response latency and variability) could be selectively improved after cathodal stimulation, but only during tasks that the participants rated as difficult, and not easy. Performance was unchanged by anodal or sham stimulation. These findings demonstrate a role for the cerebellum in cognition, whereby activity in the left prefrontal cortex is likely dis-inhibited by cathodal tDCS over the right cerebellar cortex. Transcranial brain stimulation is growing in popularity in various labs and clinics. However, the after-effects of tDCS are inconsistent between individuals and not always polarity-specific, and may even be task- or load-specific, all of which requires further study. Future efforts might also be guided towards neuro-enhancement in cerebellar patients presenting with cognitive impairment once a better understanding of brain stimulation mechanisms has emerged. PMID:25741744

Pope, Paul A.

2015-01-01

89

Concurrent Direct Network Access for Virtual Machine Monitors  

Microsoft Academic Search

This paper presents hardware and software mechanisms to enable concurrent direct network access (CDNA) by op- erating systems running within a virtual machine monitor. In a conventional virtual machine monitor, each operating system running within a virtual machine must access the network through a software-virtualized network interface . These virtual network interfaces are multiplexed in softwa re onto a physical

Jeffrey Shafer; David Carr; Aravind Menon; Scott Rixner; Alan L. Cox; Willy Zwaenepoel; Paul Willmann

2007-01-01

90

Direct ink writing of microvascular networks  

NASA Astrophysics Data System (ADS)

Nature is replete with examples of embedded microvascular systems that enable efficient fluid flow and distribution for autonomic healing, cooling, and energy harvesting. The ability to incorporate microvascular networks in functional materials systems is therefore both scientifically and technologically important. In this PhD thesis, the direct-write assembly of planar and 3D biomimetic microvascular networks within polymer and hydrogel matrices is demonstrated. In addition, the influence of network design of fluid transport efficiency is characterized. Planar microvascular networks composed of periodic lattices of uniformal microchannels and hierarchical, branching architectures are constructed by direct-write assembly of a fugitive organic ink. Several advancements are required to facilitate their patterning, including pressure valving, dual ink printing, and dynamic pressure variation to allow tunable control of ink deposition. The hydraulic conductance is measured using a high pressure flow meter as a function of network design. For a constant vascular volume and areal coverage, 2- and 4-generation branched architectures that obey Murray's Law exhibited the highest hydraulic conductivity. These experimental observations are in good agreement with predictions made by analytic models. 3D microvascular networks are fabricated by omnidirectional printing a fugitive organic ink into a photopolymerizable hydrogel matrix that is capped with fluid filler of nearly identical composition. Using this approach, 3D networks of arbitrary design can be patterned. After ink deposition is complete, the matrix and fluid filler are chemically cross-linked via UV irradiation, and the ink is removed by liquefication. Aqueous solutions composed of a triblock copolymer of polyethylene oxide (PEO)-polypropylene oxide (PPO)-PEO constitute the materials system of choice due to their thermal- and concentration-dependent phase behavior. Specifically, the fugitive ink consists of a 23 w/w% PEO-PPO-PEO (Pluronic F127) solution, while matrix (25 w/w%) and fluid filler (20 w/w%) are composed of an acrylate-modified form of the Pluronic F127 that can be subsequently photopolymerized. The ink and matrix concentrations exceed the critical micelle concentration (CMC) of 22 w/w% and thus reside in a physical gel state. At their respective concentrations, they possess an elastic plateau modulus G' > 104 Pa needed for ink filament formation, shape retention, and support during the printing process. By contrast, the fluid filler is formulated below the CMC to facilitate its flow into void spaces created as the nozzle translates through the matrix during printing. After printing is completed, photopolymerization is carried out to yield a chemically cross-linked matrix from which the fugitive ink is removed leaving behind the desired 3D microvascular network. Due to the potential application of 3D microvasularized hydrogels in tissue engineering, dye diffusion through the cured Pluronic F127-diacrylate matrix is investigated via fluorescent microscopy. Image analysis is used to extract diffusion profiles of the dye as a function of time. Extraction of the 1-D Gaussian fitting parameters is used to determine the spatial peak variance sigma2 and plotted as a function of time to determine the dye diffusivity.

Wu, Willie

91

Modulation of behavioral networks by selective interneuronal inactivation.  

PubMed

Gamma-aminobutyric acid (GABA)-ergic disturbances are hallmark features of schizophrenia and other neuropsychiatric disorders and encompass multiple interneuronal cell types. Using bacterial artificial chromosome-driven, miRNA silencing technology we generated transgenic mouse lines that suppress glutamic acid decarboxylase 1 (GAD1) in either cholecystokinin (CCK)- or neuropeptide Y (NPY)-expressing interneurons. In situ lipidomic and proteomic analyses on brain tissue sections revealed distinct, brain region-specific profiles in each transgenic line. Behavioral analyses revealed that suppression of GAD1 in CCK+ interneurons resulted in locomotor and olfactory sensory changes, whereas suppression in NPY+ interneurons affected anxiety-related behaviors and social interaction. Both transgenic mouse lines had altered sensitivity to amphetamine albeit in opposite directions. Together, these data argue that reduced GAD1 expression leads to altered molecular and behavioral profiles in a cell type-dependent manner, and that these subpopulations of interneurons are strong and opposing modulators of dopamine system function. Furthermore, our findings also support the hypothesis that neuronal networks are differentially controlled by diverse inhibitory subnetworks. PMID:24322205

Schmidt, M J; Horvath, S; Ebert, P; Norris, J L; Seeley, E H; Brown, J; Gellert, L; Everheart, M; Garbett, K A; Grice, T W; Caprioli, R M; Mirnics, K

2014-05-01

92

Identification of Modules in Protein-Protein Interaction Networks  

NASA Astrophysics Data System (ADS)

In biological systems, most processes are carried out through orchestration of multiple interacting molecules. These interactions are often abstracted using network models. A key feature of cellular networks is their modularity, which contributes significantly to the robustness, as well as adaptability of biological systems. Therefore, modularization of cellular networks is likely to be useful in obtaining insights into the working principles of cellular systems, as well as building tractable models of cellular organization and dynamics. A common, high-throughput source of data on molecular interactions is in the form of physical interactions between proteins, which are organized into protein-protein interaction (PPI) networks. This chapter provides an overview on identification and analysis of functional modules in PPI networks, which has been an active area of research in the last decade.

Erten, Sinan; Koyutürk, Mehmet

93

Efficient Broadcasting in Ad Hoc Networks Using Directional Antennas  

E-print Network

redundancy is not minimized. Wireless nodes with directional antenna can control their radiation patternEfficient Broadcasting in Ad Hoc Networks Using Directional Antennas Fei Dai and Jie Wu Department directional antennas to conserve bandwidth and energy con- sumption in ad hoc networks is becoming popular

Wu, Jie

94

Compression of Flow Can Reveal Overlapping-Module Organization in Networks  

NASA Astrophysics Data System (ADS)

To better understand the organization of overlapping modules in large networks with respect to flow, we introduce the map equation for overlapping modules. In this information-theoretic framework, we use the correspondence between compression and regularity detection. The generalized map equation measures how well we can compress a description of flow in the network when we partition it into modules with possible overlaps. When we minimize the generalized map equation over overlapping network partitions, we detect modules that capture flow and determine which nodes at the boundaries between modules should be classified in multiple modules and to what degree. With a novel greedy-search algorithm, we find that some networks, for example, the neural network of the nematode Caenorhabditis elegans, are best described by modules dominated by hard boundaries, but that others, for example, the sparse European-roads network, have an organization of highly overlapping modules.

Viamontes Esquivel, Alcides; Rosvall, Martin

2011-10-01

95

Functional connectivity of frontoparietal network predicts cognitive modulation of pain  

PubMed Central

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

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

96

Direct electrical-to-optical conversion and light modulation in micro whispering-gallery-mode resonators  

NASA Technical Reports Server (NTRS)

Techniques for directly converting an electrical signal into an optical signal by using a whispering gallery mode optical resonator formed of a dielectric material that allows for direct modulation of optical absorption by the electrical signal.

Maleki, Lute (Inventor); Levi, Anthony F. J. (Inventor)

2005-01-01

97

A Survey of Wormhole Routing Techniques in Direct Networks  

Microsoft Academic Search

Efficient routing of messages is critical to the performance of direct network systems.The popular wormhole routing technique faces several challenges - particularly flow control and deadlock avoidance

Lionel M. Ni; Philip K. Mckinley

1993-01-01

98

Modules of human micro-RNA co-target network  

NASA Astrophysics Data System (ADS)

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.

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

2011-05-01

99

Ocular Counterroll Modulates the Preferred Direction of Saccade-Related Pontine Burst Neurons in the Monkey  

E-print Network

Ocular Counterroll Modulates the Preferred Direction of Saccade- Related Pontine Burst Neurons Straumann, and Volker Henn. Ocular coun- terroll modulates the preferred direction of saccade to extraocular motoneurons for the generation of rapid eye movements. In the superior colliculus (SC), which

Scherberger, Hansjörg

100

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

Microsoft Academic Search

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

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

2010-01-01

101

Network connectivity modulates power spectrum scale invariance.  

PubMed

Measures of complexity are sensitive in detecting disease, which has made them attractive candidates for diagnostic biomarkers; one complexity measure that has shown promise in fMRI is power spectrum scale invariance (PSSI). Even if scale-free features of neuroimaging turn out to be diagnostically useful, however, their underlying neurobiological basis is poorly understood. Using modeling and simulations of a schematic prefrontal-limbic meso-circuit, with excitatory and inhibitory networks of nodes, we present here a framework for how network density within a control system can affect the complexity of signal outputs. Our model demonstrates that scale-free behavior, similar to that observed in fMRI PSSI data, can be obtained for sufficiently large networks in a context as simple as a linear stochastic system of differential equations, although the scale-free range improves when introducing more realistic, nonlinear behavior in the system. PSSI values (reflective of complexity) vary as a function of both input type (excitatory, inhibitory) and input density (mean number of long-range connections, or strength), independent of their node-specific geometric distribution. Signals show pink noise (1/f) behavior when excitatory and inhibitory influences are balanced. As excitatory inputs are increased and decreased, signals shift towards white and brown noise, respectively. As inhibitory inputs are increased and decreased, signals shift towards brown and white noise, respectively. The results hold qualitatively at the hemodynamic scale, which we modeled by introducing a neurovascular component. Comparing hemodynamic simulation results to fMRI PSSI results from 96 individuals across a wide spectrum of anxiety-levels, we show how our model can generate concrete and testable hypotheses for understanding how connectivity affects regulation of meso-circuits in the brain. PMID:24333393

R?dulescu, Anca; Mujica-Parodi, Lilianne R

2014-04-15

102

Nitric oxide-mediated modulation of the murine locomotor network  

PubMed Central

Spinal motor control networks are regulated by neuromodulatory systems to allow adaptability of movements. The present study aimed to elucidate the role of nitric oxide (NO) in the modulation of mammalian spinal locomotor networks. This was investigated with isolated spinal cord preparations from neonatal mice in which rhythmic locomotor-related activity was induced pharmacologically. Bath application of the NO donor diethylamine NONOate (DEA/NO) decreased the frequency and modulated the amplitude of locomotor-related activity recorded from ventral roots. Removal of endogenous NO with coapplication of a NO scavenger (PTIO) and a nitric oxide synthase (NOS) blocker [nitro-l-arginine methyl ester (l-NAME)] increased the frequency and decreased the amplitude of locomotor-related activity. This demonstrates that endogenously derived NO can modulate both the timing and intensity of locomotor-related activity. The effects of DEA/NO were mimicked by the cGMP analog 8-bromo-cGMP. In addition, the soluble guanylyl cyclase (sGC) inhibitor ODQ blocked the effects of DEA/NO on burst amplitude and frequency, although the frequency effect was only blocked at low concentrations of DEA/NO. This suggests that NO-mediated modulation involves cGMP-dependent pathways. Sources of NO were studied within the lumbar spinal cord during postnatal development (postnatal days 1–12) with NADPH-diaphorase staining. NOS-positive cells in the ventral horn exhibited a rostrocaudal gradient, with more cells in rostral segments. The number of NOS-positive cells was also found to increase during postnatal development. In summary, we have shown that NO, derived from sources within the mammalian spinal cord, modulates the output of spinal motor networks and is therefore likely to contribute to the fine-tuning of locomotor behavior. PMID:24259545

Foster, Joshua D.; Dunford, Catherine; Sillar, Keith T.

2013-01-01

103

Multiplexing Systems for Pulse-Code-Modulated Hierarchial Networks  

Microsoft Academic Search

Various synchronization systems which function to multiplex lower speed pulse-code-modulated (PCM) signals into a high-speed signal and to drop each lower signal from the highspeed PCM signal, are considered from a practical viewpoint for a useful PCM hierarchial network, and a suitable evaluation basis for such systems is introduced. Three new stuff-synchronization methods are proposed and designed. A severly reliable

N. Kuroyanagi; H. Saito; S. Kozuka; Y. Okamoto

1969-01-01

104

A Directionality based Location Discovery Scheme for Wireless Sensor Networks  

E-print Network

A Directionality based Location Discovery Scheme for Wireless Sensor Networks Asis Nasipuri and Kai is a large ad hoc network of densely dis- tributed sensors that are equipped with low power wireless number of such wireless sensors can be networked to coordinate amongst themselves and per- form the much

Ha, Dong S.

105

Multimedia Wireless Sensor Networks: Perspectives and Future Directions  

E-print Network

Multimedia Wireless Sensor Networks: Perspectives and Future Directions S j l K D Perspectives://crewman.uta.edug p // [Funded by NSF, AFOSR, Texas ARP] #12;Outline Multimedia Wireless Sensor Networks (MWSNs to understand, serve, and control #12;Wireless Sensor Networks (WSNs)( ) Communication (Wireless) Broadcast

van Dyk, David

106

Exploring Security Improvement of Wireless Networks with Directional Antennas  

E-print Network

Exploring Security Improvement of Wireless Networks with Directional Antennas Hong-Ning Dai--There are a number of studies on using directional antennas in wireless networks. Many of them concentrate on analyzing the theoretical capacity improvement by using direc- tional antennas. Other studies focus

Wong, Raymond Chi-Wing

107

Energy Efficient Communications in Ad Hoc Networks Using Directional Antennas  

Microsoft Academic Search

Directional antennas can be useful in significantly increasing node and network lifetime in wireless ad hoc networks. In order to utilize directional antennas, an algorithm is needed that will enable nodes to point their antennas to the right place at the right time. In this paper we present an energy-efficient routing and scheduling algorithm that coordinates transmissions in ad hoc

Akis Spyropoulos; Cauligi S. Raghavendra

2002-01-01

108

Google matrix analysis of directed networks Leonardo Ermann  

E-print Network

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

Shepelyansky, Dima

109

Parietal transcranial direct current stimulation modulates primary motor cortex excitability.  

PubMed

The posterior parietal cortex is part of the cortical network involved in motor learning and is structurally and functionally connected with the primary motor cortex (M1). Neuroplastic alterations of neuronal connectivity might be an important basis for learning processes. These have however not been explored for parieto-motor connections in humans by transcranial direct current stimulation (tDCS). Exploring tDCS effects on parieto-motor cortical connectivity might be functionally relevant, because tDCS has been shown to improve motor learning. We aimed to explore plastic alterations of parieto-motor cortical connections by tDCS in healthy humans. We measured neuroplastic changes of corticospinal excitability via motor evoked potentials (MEP) elicited by single-pulse transcranial magnetic stimulation (TMS) before and after tDCS over the left posterior parietal cortex (P3), and 3 cm posterior or lateral to P3, to explore the spatial specificity of the effects. Furthermore, short-interval intracortical inhibition/intracortical facilitation (SICI/ICF) over M1, and parieto-motor cortical connectivity were obtained before and after P3 tDCS. The results show polarity-dependent M1 excitability alterations primarily after P3 tDCS. Single-pulse TMS-elicited MEPs, M1 SICI/ICF at 5 and 7 ms and 10 and 15 ms interstimulus intervals (ISIs), and parieto-motor connectivity at 10 and 15 ms ISIs were all enhanced by anodal stimulation. Single pulse-TMS-elicited MEPs, and parieto-motor connectivity at 10 and 15 ms ISIs were reduced by cathodal tDCS. The respective corticospinal excitability alterations lasted for at least 120 min after stimulation. These results show an effect of remote stimulation of parietal areas on M1 excitability. The spatial specificity of the effects and the impact on parietal cortex-motor cortex connections suggest a relevant connectivity-driven effect. PMID:25645274

Rivera-Urbina, Guadalupe Nathzidy; Batsikadze, Giorgi; Molero-Chamizo, Andrés; Paulus, Walter; Kuo, Min-Fang; Nitsche, Michael A

2015-03-01

110

An experiential, social network-based approach to direct marketing  

Microsoft Academic Search

Purpose – Direct marketing faces challenges and opportunities associated with the emergence of social network media. Companies need to address target audiences both directly and also indirectly through social media. The purpose of this paper is to provide a review of the changing media landscape of direct marketing, and proposes a model of direct and indirect targeting of buyers. Design\\/methodology\\/approach

Adrian Palmer; Nicole Koenig-Lewis

2009-01-01

111

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

PubMed

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. PMID:21935134

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

2011-08-29

112

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

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

113

RMaNI: Regulatory Module Network Inference framework  

PubMed Central

Background Cell survival and development are orchestrated by complex interlocking programs of gene activation and repression. Understanding how this gene regulatory network (GRN) functions in normal states, and is altered in cancers subtypes, offers fundamental insight into oncogenesis and disease progression, and holds great promise for guiding clinical decisions. Inferring a GRN from empirical microarray gene expression data is a challenging task in cancer systems biology. In recent years, module-based approaches for GRN inference have been proposed to address this challenge. Despite the demonstrated success of module-based approaches in uncovering biologically meaningful regulatory interactions, their application remains limited a single condition, without supporting the comparison of multiple disease subtypes/conditions. Also, their use remains unnecessarily restricted to computational biologists, as accurate inference of modules and their regulators requires integration of diverse tools and heterogeneous data sources, which in turn requires scripting skills, data infrastructure and powerful computational facilities. New analytical frameworks are required to make module-based GRN inference approach more generally useful to the research community. Results We present the RMaNI (Regulatory Module Network Inference) framework, which supports cancer subtype-specific or condition specific GRN inference and differential network analysis. It combines both transcriptomic as well as genomic data sources, and integrates heterogeneous knowledge resources and a set of complementary bioinformatic methods for automated inference of modules, their condition specific regulators and facilitates downstream network analyses and data visualization. To demonstrate its utility, we applied RMaNI to a hepatocellular microarray data containing normal and three disease conditions. We demonstrate that how RMaNI can be employed to understand the genetic architecture underlying three disease conditions. RMaNI is freely available at http://inspect.braembl.org.au/bi/inspect/rmani Conclusion RMaNI makes available a workflow with comprehensive set of tools that would otherwise be challenging for non-expert users to install and apply. The framework presented in this paper is flexible and can be easily extended to analyse any dataset with multiple disease conditions. PMID:24564496

2013-01-01

114

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

PubMed

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

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

2012-05-21

115

Feasibility of synchronous pulse-density modulation arithmetic in integrated circuit implementations of artificial neural networks  

Microsoft Academic Search

The major goal is to find an effective method to implement artificial neural network structures on VLSI circuits. Pulse-density modulation (PDM) arithmetic offers a new interesting method to implement artificial neural network structures on silicon. The advantage is simple arithmetic structures leading to small area on silicon and thus larger networks on a single circuit. The pulse-density modulation technique in

Jouni Tomberg; Kimmo Kaski

1992-01-01

116

Detecting Blackholes and Volcanoes in Directed Networks  

E-print Network

In this paper, we formulate a novel problem for finding blackhole and volcano patterns in a large directed graph. Specifically, a blackhole pattern is a group which is made of a set of nodes in a way such that there are only inlinks to this group from the rest nodes in the graph. In contrast, a volcano pattern is a group which only has outlinks to the rest nodes in the graph. Both patterns can be observed in real world. For instance, in a trading network, a blackhole pattern may represent a group of traders who are manipulating the market. In the paper, we first prove that the blackhole mining problem is a dual problem of finding volcanoes. Therefore, we focus on finding the blackhole patterns. Along this line, we design two pruning schemes to guide the blackhole finding process. In the first pruning scheme, we strategically prune the search space based on a set of pattern-size-independent pruning rules and develop an iBlackhole algorithm. The second pruning scheme follows a divide-and-conquer strategy to fur...

Li, Zhongmou; Liu, Yanchi

2010-01-01

117

Link module for a downhole drilling network  

DOEpatents

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.

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

2007-05-29

118

FUMET: a fuzzy network module extraction technique for gene expression data.  

PubMed

Construction of co-expression network and extraction of network modules have been an appealing area of bioinformatics research. This article presents a co-expression network construction and a biologically relevant network module extraction technique based on fuzzy set theoretic approach. The technique is able to handle both positive and negative correlations among genes. The constructed network for some benchmark gene expression datasets have been validated using topological internal and external measures. The effectiveness of network module extraction technique has been established in terms of well-known p-value, Q-value and topological statistics. PMID:24845500

Mahanta, Priyakshi; Ahmed, Hasin Afzal; Bhattacharyya, Dhruba Kumar; Ghosh, Ashish

2014-06-01

119

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

PubMed Central

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

2015-01-01

120

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

PubMed Central

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

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

2013-01-01

121

Multi-transceiver simulation modules for free-space optical mobile ad hoc networks  

NASA Astrophysics Data System (ADS)

This paper presents realistic simulation modules to assess characteristics of multi-transceiver free-space-optical (FSO) mobile ad-hoc networks. We start with a physical propagation model for FSO communications in the context of mobile ad-hoc networks (MANETs). We specifically focus on the drop in power of the light beam and probability of error in the decoded signal due to a number of parameters (such as separation between transmitter and receiver and visibility in the propagation medium), comparing our results with well-known theoretical models. Then, we provide details on simulating multi-transceiver mobile wireless nodes in Network Simulator 2 (NS-2), realistic obstacles in the medium and communication between directional optical transceivers. We introduce new structures in the networking protocol stack at lower layers to deliver such functionality. At the end, we provide our findings resulted from detailed modeling and simulation of FSO-MANETs regarding effects of such directionality on higher layers in the networking stack.

Bilgi, Mehmet; Yuksel, Murat

2010-04-01

122

Lasting modulation of in-vitro oscillatory activity with weak direct current stimulation  

E-print Network

University of New York, New York, USA December 3, 2014 Abstract Transcranial Direct Current Stimulation (t hypothesis. Introduction The number of studies on transcranial direct current stimulation (tDCS) has rapidlyLasting modulation of in-vitro oscillatory activity with weak direct current stimulation Davide

Parra, Lucas C.

123

Characterizing Absorption Spectrum of Natural Rubidium by Using a Directly Modulated VCSEL  

E-print Network

Characterizing Absorption Spectrum of Natural Rubidium by Using a Directly Modulated VCSEL Ido Ben in the absorption profile of a medium containing system atoms. Moreover, the change leads to a very narrow spectra: the VCSEL output and the absorption. Two modulation side bands, separated by fhfs owe to coincide

Eisenstein, Gadi

124

A study of near-field direct antenna modulation systems using convex optimization  

Microsoft Academic Search

This paper studies the constellation diagram design for a class of communication systems known as near-field direct antenna modulation (NFDAM) systems. The modulation is carried out in a NFDAM system by means of a control unit that switches among a number of pre-designed passive controllers such that each controller generates a desired voltage signal at the far field. To find

Javad Lavaei; Aydin Babakhani; Ali Hajimiri; John C. Doyle

2010-01-01

125

Resource Scheduling in Wireless Networks Using Directional Antennas  

E-print Network

Resource Scheduling in Wireless Networks Using Directional Antennas Imad Jawhar, Member, IEEE, Jie. On the other hand, directional antenna technology provides the capability for considerable increases in spatialS routing in TDMA-based MWNs using directional antennas is presented. The routing algorithm allows a source

Wu, Jie

126

Resource Allocation in Wireless Networks Using Directional Antennas  

E-print Network

1 Resource Allocation in Wireless Networks Using Directional Antennas Imad Jawhar College multimedia and real-time applications. On the other hand, directional antenna technology provides. In this paper, a bandwidth reservation protocol for QoS routing in TDMA-based MANETs using directional antennas

Wu, Jie

127

Efficient Broadcasting in Ad Hoc Wireless Networks Using Directional Antennas  

E-print Network

be further improved. Wireless nodes with directional antenna can control their radiation pattern to reduceEfficient Broadcasting in Ad Hoc Wireless Networks Using Directional Antennas Fei Dai, Member, IEEE, and Jie Wu, Senior Member, IEEE Abstract--Using directional antennas to conserve bandwidth and energy

Wu, Jie

128

Capacity achieving modulation format for high-speed optical networks  

NASA Astrophysics Data System (ADS)

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.

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

2010-01-01

129

Signal to noise ratios of pulsed and sinewave modulated direct detection lidar for IPDA measurements  

Microsoft Academic Search

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.

Xiaoli Sun; James B. Abshire

2011-01-01

130

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

NASA Technical Reports Server (NTRS)

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

Sun, Xiaoli; Abshire, James B.

2011-01-01

131

Gelatinase A activity directly modulates melanoma cell adhesion and spreading.  

PubMed Central

Interaction of cells with the extracellular matrix (ECM) plays an important role in the regulation of cell behavior. Formation of adhesive contacts leads to transduction of signals into the cell and results in altered gene expression and modulation of the cellular phenotype. Specific adhesive interactions of the fibronectin and vitronectin receptors with their ligands in the matrix modulates expression of ECM-degrading metalloproteases. These proteases are involved in the acquisition of the invasive phenotype by a number of cell types. The activity of matrix metalloproteases (MMPs) is reduced by endogenous inhibitors referred to as tissue inhibitors of metalloproteases (TIMPs). Alterations in the balance between the activity of MMPs and TIMPs alters cellular invasion through effects on matrix degradation. In this study we demonstrate that inhibition of endogenous gelatinase A activity in A2058 human melanoma cells results in enhanced cellular adhesion. To further explore this phenomenon, we have used retroviral infection vectors to control the amount of the MMP inhibitor TIMP-2 in human melanoma A2058 cells. Altering the production of TIMP-2 modulates not only proteolysis of the extracellular matrix, but also the adhesive and spreading properties of the cells and results in altered cell morphology. These effects of TIMP-2 appear to be mediated by inhibition of gelatinase A activity. We conclude that gelatinase A, in addition to contributing to proteolysis of ECM components, also functions to proteolyse cell surface components that mediate attachment of A2058 cells to the ECM. Thus, gelatinase A may function to modulate cell attachment and facilitate cell migration and invasion. Images PMID:7534227

Ray, J M; Stetler-Stevenson, W G

1995-01-01

132

Deterministic graph-theoretic algorithm for detecting modules in biological interaction networks.  

PubMed

An approach for module identification, Modules of Networks (MoNet), introduced an intuitive module definition and clear detection method using edges ranked by the Girvan-Newman algorithm. Modules from a yeast network showed significant association with biological processes, indicating the method's utility; however, systematic bias leads to varied results across trials. MoNet modules also exclude some network regions. To address these shortcomings, we developed a deterministic version of the Girvan-Newman algorithm and a new agglomerative algorithm, Deterministic Modularization of Networks (dMoNet). dMoNet simultaneously processes structurally equivalent edges while preserving intuitive foundations of the MoNet algorithm and generates modules with full network coverage. PMID:20223734

Chang, Roger L; Luo, Feng; Johnson, Stuart; Scheuermann, Richard H

2010-01-01

133

Network Linkages and Location Choice in Foreign Direct Investment  

Microsoft Academic Search

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

Homin Chen; Tain-Jy Chen

1998-01-01

134

Neural Networks ( ) Contents lists available at ScienceDirect  

E-print Network

Neural Networks ( ) ­ Contents lists available at ScienceDirect Neural Networks journal homepage of a complex physical system for the purpose of control is a common problem in robotics. A typical system, this mapping can be inserted into the control loop of the robot, where appropriate motor commands are predicted

Schaal, Stefan

135

Effect of Modulated Alternating and Direct Current Iontophoresis on Transdermal Delivery of Lidocaine Hydrochloride  

PubMed Central

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

Banga, Ajay K.

2014-01-01

136

The theory of pattern formation on directed networks  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

137

Degree Correlations in Directed Scale-Free Networks  

PubMed Central

Scale-free networks, in which the distribution of the degrees obeys a power-law, are ubiquitous in the study of complex systems. One basic network property that relates to the structure of the links found is the degree assortativity, which is a measure of the correlation between the degrees of the nodes at the end of the links. Degree correlations are known to affect both the structure of a network and the dynamics of the processes supported thereon, including the resilience to damage, the spread of information and epidemics, and the efficiency of defence mechanisms. Nonetheless, while many studies focus on undirected scale-free networks, the interactions in real-world systems often have a directionality. Here, we investigate the dependence of the degree correlations on the power-law exponents in directed scale-free networks. To perform our study, we consider the problem of building directed networks with a prescribed degree distribution, providing a method for proper generation of power-law-distributed directed degree sequences. Applying this new method, we perform extensive numerical simulations, generating ensembles of directed scale-free networks with exponents between 2 and 3, and measuring ensemble averages of the Pearson correlation coefficients. Our results show that scale-free networks are on average uncorrelated across directed links for three of the four possible degree-degree correlations, namely in-degree to in-degree, in-degree to out-degree, and out-degree to out-degree. However, they exhibit anticorrelation between the number of outgoing connections and the number of incoming ones. The findings are consistent with an entropic origin for the observed disassortativity in biological and technological networks. PMID:25310101

Williams, Oliver; Del Genio, Charo I.

2014-01-01

138

Focused transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex modulates specific domains of self-regulation.  

PubMed

Recent neuroscience theories suggest that different kinds of self-regulation may share a common psychobiological mechanism. However, empirical evidence for a domain general self-regulation mechanism is scarce. The aim of this study was to investigate whether focused anodal transcranial direct current stimulation (tDCS), facilitating the activity of the dorsolateral prefrontal cortex (dlPFC), acts on a domain general self-regulation mechanism and thus modulates both affective and appetitive self-regulation. Twenty smokers participated in this within-subject sham controlled study. Effects of anodal left, anodal right and sham tDCS over the dlPFC on affective picture appraisal and nicotine craving-cue appraisal were assessed. Anodal right tDCS over the dlPFC reduced negative affect in emotion appraisal, but neither modulated regulation of positive emotion appraisal nor of craving appraisal. Anodal left stimulation did not induce any significant effects. The results of our study show that domain specific self-regulation networks are at work in the prefrontal cortex. Focused tDCS modulation of this specific self-regulation network could probably be used during the first phase of nicotine abstinence, during which negative affect might easily result in relapse. These findings have implications for neuroscience models of self-regulation and are of relevance for the development of brain stimulation based treatment methods for neuropsychiatric disorders associated with self-regulation deficits. PMID:25269861

Pripfl, Jürgen; Lamm, Claus

2015-02-01

139

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

E-print Network

Fast-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 is increased by 25 . © 2004 American Institute of Physics. DOI: 10.1063/1.1649816 Liquid crystal/polymer

Wu, Shin-Tson

140

Energy-Efficient Modulation Design for Reliable Communication in Wireless Networks  

E-print Network

Energy-Efficient Modulation Design for Reliable Communication in Wireless Networks Qing Chen transmit power scenarios. We have noted that variable power schemes can attain higher energy-efficiencies. The analysis of energy-efficient modulation design is also conducted in multi- hop linear networks

Gursoy, Mustafa Cenk

141

Integrin-directed modulation of macrophage responses to biomaterials.  

PubMed

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

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

2014-04-01

142

Integrin-Directed Modulation of Macrophage Responses to Biomaterials  

PubMed Central

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

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

2014-01-01

143

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

E-print Network

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

Thompson-Schill, Sharon

144

Infant-Directed Speech Is Modulated by Infant Feedback  

ERIC Educational Resources Information Center

When mothers engage in infant-directed (ID) speech, their voices change in a number of characteristic ways, including adopting a higher overall pitch. Studies have examined these acoustical cues and have tested infants' preferences for ID speech. However, little is known about how these cues change with maternal sensitivity to infant feedback in…

Smith, Nicholas A.; Trainor, Laurel J.

2008-01-01

145

System architecture directions for networked sensors  

Microsoft Academic Search

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

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

2000-01-01

146

Identification of Important Nodes in Directed Biological Networks: A Network Motif Approach  

PubMed Central

Identification of important nodes in complex networks has attracted an increasing attention over the last decade. Various measures have been proposed to characterize the importance of nodes in complex networks, such as the degree, betweenness and PageRank. Different measures consider different aspects of complex networks. Although there are numerous results reported on undirected complex networks, few results have been reported on directed biological networks. Based on network motifs and principal component analysis (PCA), this paper aims at introducing a new measure to characterize node importance in directed biological networks. Investigations on five real-world biological networks indicate that the proposed method can robustly identify actually important nodes in different networks, such as finding command interneurons, global regulators and non-hub but evolutionary conserved actually important nodes in biological networks. Receiver Operating Characteristic (ROC) curves for the five networks indicate remarkable prediction accuracy of the proposed measure. The proposed index provides an alternative complex network metric. Potential implications of the related investigations include identifying network control and regulation targets, biological networks modeling and analysis, as well as networked medicine. PMID:25170616

Wang, Pei; Lü, Jinhu; Yu, Xinghuo

2014-01-01

147

On Designing MAC Protocols for Wireless Networks Using Directional Antennas  

E-print Network

On Designing MAC Protocols for Wireless Networks Using Directional Antennas Romit Roy Choudhury, Senior Member, IEEE Abstract--We investigate the possibility of using directional antennas for medium the use of omnidirectional antennas at all nodes. With omnidirectional antennas, while two nodes

Ramanathan, Ram

148

Narrow linewidth 1.55?m directly modulated distributed-feedback laser  

NASA Astrophysics Data System (ADS)

We fabricated a narrow linewidth 1.55?m directly-modulated distributed-feedback (DFB) laser. The laser exhibits an output power of 14mW at 100mA, flat frequency response with -3 dB bandwidth of 18 GHz, the third-order intermodulation distortion (IMD3) with 39.8dBm, narrow optical linewidth with 181kHz, and RIN below -135.7dB/Hz in the 0.1-10GHz range along with the high side-mode suppression ratio (<52dB). We also experimentally verified the modulation bandwidth, linearity, and linewidth is related to the bias current. The characteristics of the laser, namely sufficient modulation bandwidth, high linearity, low relative intensity noise (RIN) and narrow linewidth, make it the perfect candidates for high dynamic directly modulated analog optical link.

Guo, Jin-Jin; Liu, Jianguo; Zhu, Ninghua; Chen, Wei; Sun, Wenhui; Huang, Ningbo; Wang, Qi

2014-11-01

149

Quetiapine modulates functional connectivity in brain aggression networks.  

PubMed

Aggressive behavior is associated with dysfunctions in an affective regulation network encompassing amygdala and prefrontal areas such as orbitofrontal (OFC), anterior cingulate (ACC), and dorsolateral prefrontal cortex (DLPFC). In particular, prefrontal regions have been postulated to control amygdala activity by inhibitory projections, and this process may be disrupted in aggressive individuals. The atypical antipsychotic quetiapine successfully attenuates aggressive behavior in various disorders; the underlying neural processes, however, are unknown. A strengthened functional coupling in the prefrontal-amygdala system may account for these anti-aggressive effects. An inhibition of this network has been reported for virtual aggression in violent video games as well. However, there have been so far no in-vivo observations of pharmacological influences on corticolimbic projections during human aggressive behavior. In a double-blind, placebo-controlled study, quetiapine and placebo were administered for three successive days prior to an fMRI experiment. In this experiment, functional brain connectivity was assessed during virtual aggressive behavior in a violent video game and an aggression-free control task in a non-violent modification. Quetiapine increased the functional connectivity of ACC and DLPFC with the amygdala during virtual aggression, whereas OFC-amygdala coupling was attenuated. These effects were observed neither for placebo nor for the non-violent control. These results demonstrate for the first time a pharmacological modification of aggression-related human brain networks in a naturalistic setting. The violence-specific modulation of prefrontal-amygdala networks appears to control aggressive behavior and provides a neurobiological model for the anti-aggressive effects of quetiapine. PMID:23501053

Klasen, Martin; Zvyagintsev, Mikhail; Schwenzer, Michael; Mathiak, Krystyna A; Sarkheil, Pegah; Weber, René; Mathiak, Klaus

2013-07-15

150

Fabricating fiber Bragg gratings using phase modulated direct UV writing  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

151

BPSK & QPSK modulated data communication for biomedical monitoring sensor network.  

PubMed

Data communication between body-mounted sensors is progressing towards wireless monitoring networks. In this work, digital data communication by galvanic coupling through the body is presented as a promising approach for wireless intra-body communication. The human body itself serves as the transmission medium of electrical current. Both binary and quadrature phase-shift-keying (BPSK and QPSK) modulated data transmissions are implemented and compared for galvanic coupled links between 2 differential electrode pairs. The adaptive system offers up to 1 mA maximum current amplitude between 10 kHz and 1MHz. Data communication at a rate of up to 64 kbit/s was realized with BER of 10(-4) corresponding to an SNR greater than 6 dB. The novel technology has shown its feasibility in clinical trials. Furthermore, such a low-current approach enables data communication that is more energy-saving than other wireless technologies. PMID:17946088

Wegmueller, Marc S; Fichtner, Wolfgang; Oberle, Michael; Kuster, Niels

2006-01-01

152

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

PubMed

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

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

2013-06-01

153

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

PubMed

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

Vukeli?, Mathias; Gharabaghi, Alireza

2015-05-01

154

Allosteric Modulators for the Treatment of Schizophrenia: Targeting Glutamatergic Networks  

PubMed Central

Schizophrenia is a highly debilitating mental disorder which afflicts approximately 1% of the global population. Cognitive and negative deficits account for the lifelong disability associated with schizophrenia, whose symptoms are not effectively addressed by current treatments. New medicines are needed to treat these aspects of the disease. Neurodevelopmental, neuropathological, genetic, and behavioral pharmacological data indicate that schizophrenia stems from a dysfunction of glutamate synaptic transmission, particularly in frontal cortical networks. A number of novel pre- and postsynaptic mechanisms affecting glutamatergic synaptic transmission have emerged as viable targets for schizophrenia. While developing orthosteric glutamatergic agents for these targets has proven extremely difficult, targeting allosteric sites of these targets has emerged as a promising alternative. From a medicinal chemistry perspective, allosteric sites provide an opportunity of finding agents with better drug-like properties and greater target specificity. Furthermore, allosteric modulators are better suited to maintaining the highly precise temporal and spatial aspects of glutamatergic synaptic transmission. Herein, we review neuropathological and genomic/genetic evidence underscoring the importance of glutamate synaptic dysfunction in the etiology of schizophrenia and make a case for allosteric targets for therapeutic intervention. We review progress in identifying allosteric modulators of AMPA receptors, NMDA receptors, and metabotropic glutamate receptors, all with the aim of restoring physiological glutamatergic synaptic transmission. Challenges remain given the complexity of schizophrenia and the difficulty in studying cognition in animals and humans. Nonetheless, important compounds have emerged from these efforts and promising preclinical and variable clinical validation has been achieved. PMID:23409764

Menniti, Frank S.; Lindsley, Craig W.; Conn, P. Jeffrey; Pandit, Jayvardhan; Zagouras, Panayiotis; Volkmann, Robert A.

2013-01-01

155

Glial-derived adenosine modulates spinal motor networks in mice  

PubMed Central

The activation of purinergic receptors modulates central pattern generators controlling rhythmic motor behaviors, including respiration in rodents and swimming in frog tadpoles. The present study aimed to determine whether purinergic signaling also modulates the mammalian locomotor central pattern generator. This was investigated by using isolated spinal cord preparations obtained from neonatal mice in which locomotor-related activity can be induced pharmacologically. The application of either ATP or adenosine led to a reduction in the frequency of locomotor activity recorded from ventral roots. ATP had no effect when applied in the presence of both the adenosine receptor antagonist theophylline and the ectonucleotidase inhibitor ARL67156, demonstrating that the effects of ATP application result from the breakdown of ATP to adenosine and subsequent activation of adenosine receptors. The application of theophylline or the A1-specific antagonist cyclopentyl dipropylxanthine, but not the A2A-receptor antagonist SCH58261, caused an increase in locomotor burst frequency, demonstrating that endogenously derived adenosine activates A1 receptors during locomotor network activity. Furthermore, theophylline had no effect in the presence of the ectonucleotidase inhibitor ARL67156 or the glial toxins methionine sulfoximine or ethyl fluoracetate, suggesting that endogenous adenosine is derived from ATP, which is released from glia. Finally, adenosine had no effect on slow rhythmic activity recorded upon blockade of all inhibitory transmission, suggesting that adenosine may act via the modulation of inhibitory transmission. Together, these data highlight endogenous purinergic gliotransmission, involving activation of A1 receptors, as an important intrinsic modulatory system controlling the frequency of activity generated by spinal locomotor circuitry in mammals. PMID:22205649

Witts, Emily C.; Panetta, Kara M.

2012-01-01

156

Glial-derived adenosine modulates spinal motor networks in mice.  

PubMed

The activation of purinergic receptors modulates central pattern generators controlling rhythmic motor behaviors, including respiration in rodents and swimming in frog tadpoles. The present study aimed to determine whether purinergic signaling also modulates the mammalian locomotor central pattern generator. This was investigated by using isolated spinal cord preparations obtained from neonatal mice in which locomotor-related activity can be induced pharmacologically. The application of either ATP or adenosine led to a reduction in the frequency of locomotor activity recorded from ventral roots. ATP had no effect when applied in the presence of both the adenosine receptor antagonist theophylline and the ectonucleotidase inhibitor ARL67156, demonstrating that the effects of ATP application result from the breakdown of ATP to adenosine and subsequent activation of adenosine receptors. The application of theophylline or the A(1)-specific antagonist cyclopentyl dipropylxanthine, but not the A(2A)-receptor antagonist SCH58261, caused an increase in locomotor burst frequency, demonstrating that endogenously derived adenosine activates A(1) receptors during locomotor network activity. Furthermore, theophylline had no effect in the presence of the ectonucleotidase inhibitor ARL67156 or the glial toxins methionine sulfoximine or ethyl fluoracetate, suggesting that endogenous adenosine is derived from ATP, which is released from glia. Finally, adenosine had no effect on slow rhythmic activity recorded upon blockade of all inhibitory transmission, suggesting that adenosine may act via the modulation of inhibitory transmission. Together, these data highlight endogenous purinergic gliotransmission, involving activation of A(1) receptors, as an important intrinsic modulatory system controlling the frequency of activity generated by spinal locomotor circuitry in mammals. PMID:22205649

Witts, Emily C; Panetta, Kara M; Miles, Gareth B

2012-04-01

157

Interarrival times of message propagation on directed networks  

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

158

Degree correlations in directed scale-free networks  

E-print Network

Scale-free networks, in which the distribution of the degrees obeys a power-law, are ubiquitous in the study of complex systems. One basic network property that relates to the structure of the links found is the degree assortativity, which is a measure of the correlation between the degrees of the nodes at the end of the links. Degree correlations are known to affect both the structure of a network and the dynamics of the processes supported thereon, including the resilience to damage, the spread of information and epidemics, and the efficiency of defence mechanisms. Nonetheless, while many studies focus on undirected scale-free networks, the interactions in real-world systems often have a directionality. Here, we investigate the dependence of the degree correlations on the power-law exponents in directed scale-free networks. To perform our study, we consider the problem of building directed networks with a prescribed degree distribution, providing a method for proper generation of power-law-distributed direc...

Williams, Oliver

2014-01-01

159

Baseline effects of transcranial direct current stimulation on glutamatergic neurotransmission and large-scale network connectivity.  

PubMed

Transcranial direct current stimulation (tDCS) modulates glutamatergic neurotransmission and can be utilized as a novel treatment intervention for a multitude of populations. However, the exact mechanism by which tDCS modulates the brain?s neural architecture, from the micro to macro scales, have yet to be investigated. Using a within-subjects design, resting-state functional magnetic resonance imaging (rs-fMRI) and proton magnetic resonance spectroscopy ((1)H MRS) were performed immediately before and after the administration of anodal tDCS over right parietal cortex. Group independent component analysis (ICA) was used to decompose fMRI scans into 75 brain networks, from which 12 resting-state networks were identified that had significant voxel-wise functional connectivity to anatomical regions of interest. (1)H MRS was used to obtain estimates of combined glutamate and glutamine (Glx) concentrations from bilateral intraparietal sulcus. Paired sample t-tests showed significantly increased Glx under the anodal electrode, but not in homologous regions of the contralateral hemisphere. Increases of within-network connectivity were observed within the superior parietal, inferior parietal, left frontal-parietal, salience and cerebellar intrinsic networks, and decreases in connectivity were observed in the anterior cingulate and the basal ganglia (p<0.05, FDR-corrected). Individual differences in Glx concentrations predicted network connectivity in most of these networks. The observed relationships between glutamatergic neurotransmission and network connectivity may be used to guide future tDCS protocols that aim to target and alter neuroplastic mechanisms in healthy individuals as well as those with psychiatric and neurologic disorders. PMID:25312829

Hunter, Michael A; Coffman, Brian A; Gasparovic, Charles; Calhoun, Vince D; Trumbo, Michael C; Clark, Vincent P

2015-01-12

160

Membrane Properties of Striatal Direct and Indirect Pathway Neurons in Mouse and Rat Slices and Their Modulation by Dopamine  

PubMed Central

D1 and D2 receptor expressing striatal medium spiny neurons (MSNs) are ascribed to striatonigral (“direct”) and striatopallidal (“indirect”) pathways, respectively, that are believed to function antagonistically in motor control. Glutamatergic synaptic transmission onto the two types is differentially affected by Dopamine (DA), however, less is known about the effects on MSN intrinsic electrical properties. Using patch clamp recordings, we comprehensively characterized the two pathways in rats and mice, and investigated their DA modulation. We identified the direct pathway by retrograde labeling in rats, and in mice we used transgenic animals in which EGFP is expressed in D1 MSNs. MSNs were subjected to a series of current injections to pinpoint differences between the populations, and in mice also following bath application of DA. In both animal models, most electrical properties were similar, however, membrane excitability as measured by step and ramp current injections consistently differed, with direct pathway MSNs being less excitable than their counterparts. DA had opposite effects on excitability of D1 and D2 MSNs, counteracting the initial differences. Pronounced changes in AP shape were seen in D2 MSNs. In direct pathway MSNs, excitability increased across experimental conditions and parameters, and also when applying DA or the D1 agonist SKF-81297 in presence of blockers of cholinergic, GABAergic, and glutamatergic receptors. Thus, DA induced changes in excitability were D1 R mediated and intrinsic to direct pathway MSNs, and not a secondary network effect of altered synaptic transmission. DAergic modulation of intrinsic properties therefore acts in a synergistic manner with previously reported effects of DA on afferent synaptic transmission and dendritic processing, supporting the antagonistic model for direct vs. indirect striatal pathway function. PMID:23469183

Planert, Henrike; Berger, Thomas K.; Silberberg, Gilad

2013-01-01

161

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

PubMed Central

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

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

2013-01-01

162

Bandwidth Provisioning in Infrastructure-based Wireless Networks Employing Directional Antennas  

E-print Network

1 Bandwidth Provisioning in Infrastructure-based Wireless Networks Employing Directional Antennas-- Motivated by the widespread proliferation of wire- less networks employing directional antennas, we study points possessing directional antennas, we formalize the problem of orienting these antennas in two

Urgaonkar, Bhuvan

163

Few-fJ/bit data transmissions using directly modulated lambda-scale embedded active region photonic-crystal lasers  

NASA Astrophysics Data System (ADS)

A low operating energy is needed for nanocavity lasers designed for on-chip photonic network applications. On-chip nanocavity lasers must be driven by current because they act as light sources driven by electronic circuits. Here, we report the high-speed direct modulation of a lambda-scale embedded active region photonic-crystal (LEAP) laser that holds three records for any type of laser operated at room temperature: a low threshold current of 4.8 µA, a modulation current efficiency of 2.0 GHz µA-0.5 and an operating energy of 4.4 fJ bit-1. Five major technologies make this performance possible: a compact buried heterostructure, a photonic-crystal nanocavity, a lateral p-n junction realized by ion implantation and thermal diffusion, an InAlAs sacrificial layer and current-blocking trenches. We believe that an output power of 2.17 µW and an operating energy of 4.4 fJ bit-1 will enable us to realize on-chip photonic networks in combination with the recently developed highly sensitive receivers.

Takeda, Koji; Sato, Tomonari; Shinya, Akihiko; Nozaki, Kengo; Kobayashi, Wataru; Taniyama, Hideaki; Notomi, Masaya; Hasebe, Koichi; Kakitsuka, Takaaki; Matsuo, Shinji

2013-07-01

164

Quantitative orientation-independent DIC microscope with fast switching shear direction and bias modulation  

PubMed Central

We describe quantitative orientation-independent differential interference contrast (OI-DIC) microscope, which allows the bias retardation to be modulated and shear directions to be switched rapidly without any mechanically moving. The shear direction is switched by regular liquid crystal cell sandwiched between two standard DIC prisms. Another liquid crystal cell modulates the bias. Techniques for measuring parameters of DIC prisms and calibrating the bias are shown. Two sets of raw DIC images with the orthogonal shear directions are captured within a second. Then the quantitative image of optical path gradient distribution within a thin optical section is computed. The gradient data are used to obtain quantitative distribution of optical path, which represents refractive index gradient or height distribution. Computing enhanced regular DIC images with any desired shear direction is also possible. PMID:23595339

Shribak, Michael

2013-01-01

165

Direct Cache Access for High Bandwidth Network I\\/O  

Microsoft Academic Search

Recent I\\/O technologies such as PCI-Express and 10Gb Ethernet enable unprecedented levels of I\\/O bandwidths in mainstream platforms. However, in traditional architectures, memory latency alone can limit processors from matching 10 Gb inbound network I\\/O traffic. We propose a platform-wide method called Direct Cache Access (DCA) to deliver inbound I\\/O data directly into processor caches. We demonstrate that DCA provides

Ram Huggahalli; Ravi R. Iyer; Scott Tetrick

2005-01-01

166

Impact of Modulator Bias on the OSNR Requirement of Direct-Detection Optical OFDM  

Microsoft Academic Search

In optical orthogonal frequency-division multiplexing (OFDM) with direct detection, modulator bias voltage has a significant impact on receiver sensitivity. It is a compromise between control of carrier power and nonlinear distortion of the OFDM signal. In this letter, sensitivity improvement due to reduction of carrier power is treated analytically. Its range of validity is examined by simulation. The impact of

Jochen Leibrich; Abdulamir Ali; Henning Paul; Werner Rosenkranz; Karl-Dirk Kammeyer

2009-01-01

167

Transcranial direct current stimulation modulates the spinal plasticity induced with patterned electrical stimulation  

Microsoft Academic Search

ObjectivePatterned sensory electrical stimulation (PES) has been shown to induce plasticity in spinal reciprocal Ia inhibition of the calf muscles. To study the cortical modulation of spinal plasticity, we examined the effects of giving transcranial direct current stimulation (tDCS) to the motor cortex before PES.

Toshiyuki Fujiwara; Tetsuya Tsuji; Kaoru Honaga; Kimitaka Hase; Junichi Ushiba; Meigen Liu

2011-01-01

168

Shear stress magnitude and directionality modulate growth factor gene expression in  

E-print Network

Shear stress magnitude and directionality modulate growth factor gene expression in preconditioned levels of 12 endothelial growth factor genes in response to alterations in wall shear stress (WSS) under by ECs in response to luminal wall shear stress (WSS)9-15 may contribute to the pathology of intimal

Passerini, Tony

169

Electrically-pumped directly-modulated tunable VCSEL for metro DWDM applications  

Microsoft Academic Search

We report the first electrically pumped tunable VCSELs with continuous tuning in 1530-1620 nm wavelength regime. The VCSELs are directly modulated at 2.5 Gbps (OC-48) rates and show error-free transmissions. Wavelength locking to ITU-grids are accomplished in 200 ?s

W. Yuen; G. S. Li; R. F. Nabiev; M. Jansen; D. Davis; C. J. Chang-Hasnain

2001-01-01

170

Effect of modulation format and jamming spectrum on performance of direct sequence spread spectrum systems  

NASA Technical Reports Server (NTRS)

The processing gain of a direct sequence spread spectrum system is approximately the ratio of the spreading code chip rate to the data rate. This paper provides a more accurate understanding of the performance of such systems as a function of the modulation scheme and jammer characteristics.

Levitt, B. K.

1980-01-01

171

Integrated Brain Circuits: Astrocytic Networks Modulate Neuronal Activity and Behavior  

PubMed Central

The past decade has seen an explosion of research on roles of neuron-astrocyte interactions in the control of brain function. We highlight recent studies performed on the tripartite synapse, the structure consisting of pre- and postsynaptic elements of the synapse and an associated astrocytic process. Astrocytes respond to neuronal activity and neuro-transmitters, through the activation of metabotropic receptors, and can release the gliotransmitters ATP, D-serine, and glutamate, which act on neurons. Astrocyte-derived ATP modulates synaptic transmission, either directly or through its metabolic product adenosine. D-serine modulates NMDA receptor function, whereas glia-derived glutamate can play important roles in relapse following withdrawal from drugs of abuse. Cell type–specific molecular genetics has allowed a new level of examination of the function of astrocytes in brain function and has revealed an important role of these glial cells that is mediated by adenosine accumulation in the control of sleep and in cognitive impairments that follow sleep deprivation. PMID:20148679

Halassa, Michael M.; Haydon, Philip G.

2011-01-01

172

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

PubMed Central

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

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

2013-01-01

173

Irreversible bimolecular chemical reactions on directed scale-free networks.  

PubMed

Kinetics of irreversible bimolecular chemical reactions A+A?0 and A+B?0 on directed scale-free networks with the in-degree distribution P(in)(k)?k(-?)(in) and the out-degree distribution P(out)(?)??(-?)(out) are investigated. Since the correlation between k and ? of each node generally exists in directed networks, we control the correlation (k?) with the probability r?[0,1] by two different algorithms for the construction of the directed networks, i.e., the so-called k and ? algorithms. For r=1, the k algorithm gives (k?)=(k(2)), whereas the ? algorithm gives (k?)=(?(2). For r=0, (k?)=(k)(?) for both algorithms. The kinetics of both reactions are analyzed using heterogeneous mean-field (HMF) theory and Monte Carlo simulations. The density of particles (?) algebraically decays in time t as ?(t)?t(-?). The kinetics of both reactions are determined by the same rate equation, d?/dt=a?(2)+b?(?-1), apart from coefficients. The exponent ? is determined by the algorithm: ?=?(in) for the k algorithm (r?0) and ?=?(min) for the ? algorithm (r>0), where ?(min) is the smaller exponent between ?(in) and ?(out). For ?>3, one observes the ordinary mean-field kinetics, ??1/t (?=1). In contrast, for ?<3, ?(t) anomalously decays with ?=1/(?-2). The HMF predictions are confirmed by the simulations on quenched directed networks. PMID:24229156

Kwon, Sungchul; Kim, Yup

2013-10-01

174

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

E-print Network

probability, with each DUBM configuration. The conditional distribution of a unit's stochastic state of a value and a certainty provides additional representational power in a unit. We present a proof for a network of stochastic directional units. This formulation is an extension of the Boltzmann machine

Williams, Chris

175

Direct Adaptive Aircraft Control Using Dynamic Cell Structure Neural Networks  

NASA Technical Reports Server (NTRS)

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.

Jorgensen, Charles C.

1997-01-01

176

DTN-based free-space optical and directional RF networks  

Microsoft Academic Search

With the growth in demand for capacity from users in wireless networks and the scarcity of available RF spectrum, directional networks are expected to provide effective solutions. Directional RF antennas offer increased capacity over omni-directional antenna networks and some emerging highly-directional networks like free-space optical communication (FSOC) systems will be an important part of future networking infrastructures. The ability to

Robert A. Nichols; A. Roger Hammons Jr

2008-01-01

177

RM-SORN: a reward-modulated self-organizing recurrent neural network  

PubMed Central

Neural plasticity plays an important role in learning and memory. Reward-modulation of plasticity offers an explanation for the ability of the brain to adapt its neural activity to achieve a rewarded goal. Here, we define a neural network model that learns through the interaction of Intrinsic Plasticity (IP) and reward-modulated Spike-Timing-Dependent Plasticity (STDP). IP enables the network to explore possible output sequences and STDP, modulated by reward, reinforces the creation of the rewarded output sequences. The model is tested on tasks for prediction, recall, non-linear computation, pattern recognition, and sequence generation. It achieves performance comparable to networks trained with supervised learning, while using simple, biologically motivated plasticity rules, and rewarding strategies. The results confirm the importance of investigating the interaction of several plasticity rules in the context of reward-modulated learning and whether reward-modulated self-organization can explain the amazing capabilities of the brain.

Aswolinskiy, Witali; Pipa, Gordon

2015-01-01

178

Acupuncture modulates resting state connectivity in default and sensorimotor brain networks  

E-print Network

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

Napadow, Vitaly

179

Artificial Neural Networks and Job-specific Modules to Assess Occupational Exposure  

Microsoft Academic Search

Job-specific modules (JSMs) were used to collect information for expert retrospective exposure assessment in a community-based non-Hodgkins Lymphoma study in New South Wales, Australia. Using exposure assessment by a hygienist, artificial neural networks were developed to predict overall and intermittent benzene exposure among the module of tanker drivers. Even with a small data set (189 drivers), neural networks could assess

JIM BLACK; GEZA BENKE; KATE SMITH; LIN FRITSCHI

2004-01-01

180

Networking genetic regulation and neural computation: directed network topology and its effect on the dynamics.  

PubMed

Two different types of directed networks are investigated, transcriptional regulation networks and neural networks. The directed network structure is studied and is also shown to reflect the different processes taking place on the networks. The distribution of influence, identified as the the number of downstream vertices, are used as a tool for investigating random vertex removal. In the transcriptional regulation networks we observe that only a small number of vertices have a large influence. The small influences of most vertices limit the effect of a random removal to, in most cases, only a small fraction of vertices in the network. The neural network has a rather different topology with respect to the influence, which are large for most vertices. To further investigate the effect of vertex removal we simulate the biological processes taking place on the networks. Opposed to the presumed large effect of random vertex removal in the neural network, the high density of edges in conjunction with the dynamics used makes the change in the state of the system to be highly localized around the removed vertex. PMID:15697403

Grönlund, Andreas

2004-12-01

181

Networking genetic regulation and neural computation: Directed network topology and its effect on the dynamics  

NASA Astrophysics Data System (ADS)

Two different types of directed networks are investigated, transcriptional regulation networks and neural networks. The directed network structure is studied and is also shown to reflect the different processes taking place on the networks. The distribution of influence, identified as the the number of downstream vertices, are used as a tool for investigating random vertex removal. In the transcriptional regulation networks we observe that only a small number of vertices have a large influence. The small influences of most vertices limit the effect of a random removal to, in most cases, only a small fraction of vertices in the network. The neural network has a rather different topology with respect to the influence, which are large for most vertices. To further investigate the effect of vertex removal we simulate the biological processes taking place on the networks. Opposed to the presumed large effect of random vertex removal in the neural network, the high density of edges in conjunction with the dynamics used makes the change in the state of the system to be highly localized around the removed vertex.

Grönlund, Andreas

2004-12-01

182

Moral enhancement via direct emotion modulation: a reply to John Harris.  

PubMed

Some argue that humans should enhance their moral capacities by adopting institutions that facilitate morally good motives and behaviour. I have defended a parallel claim: that we could permissibly use biomedical technologies to enhance our moral capacities, for example by attenuating certain counter-moral emotions. John Harris has recently responded to my argument by raising three concerns about the direct modulation of emotions as a means to moral enhancement. He argues (1) that such means will be relatively ineffective in bringing about moral improvements, (2) that direct modulation of emotions would invariably come at an unacceptable cost to our freedom, and (3) that we might end up modulating emotions in ways that actually lead to moral decline. In this article I outline some counter-intuitive potential implications of Harris' claims. I then respond individually to his three concerns, arguing that they license only the very weak conclusion that moral enhancement via direct emotion modulation is sometimes impermissible. However I acknowledge that his third concern might, with further argument, be developed into a more troubling objection to such enhancements. PMID:22092503

Douglas, Thomas

2013-03-01

183

MORAL ENHANCEMENT VIA DIRECT EMOTION MODULATION: A REPLY TO JOHN HARRIS  

PubMed Central

Some argue that humans should enhance their moral capacities by adopting institutions that facilitate morally good motives and behaviour. I have defended a parallel claim: that we could permissibly use biomedical technologies to enhance our moral capacities, for example by attenuating certain counter-moral emotions. John Harris has recently responded to my argument by raising three concerns about the direct modulation of emotions as a means to moral enhancement. He argues (1) that such means will be relatively ineffective in bringing about moral improvements, (2) that direct modulation of emotions would invariably come at an unacceptable cost to our freedom, and (3) that we might end up modulating emotions in ways that actually lead to moral decline. In this article I outline some counter-intuitive potential implications of Harris' claims. I then respond individually to his three concerns, arguing that they license only the very weak conclusion that moral enhancement via direct emotion modulation is sometimes impermissible. However I acknowledge that his third concern might, with further argument, be developed into a more troubling objection to such enhancements. PMID:22092503

Douglas, Thomas

2013-01-01

184

ModuleRole: A Tool for Modulization, Role Determination and Visualization in Protein-Protein Interaction Networks  

PubMed Central

Rapidly increasing amounts of (physical and genetic) protein-protein interaction (PPI) data are produced by various high-throughput techniques, and interpretation of these data remains a major challenge. In order to gain insight into the organization and structure of the resultant large complex networks formed by interacting molecules, using simulated annealing, a method based on the node connectivity, we developed ModuleRole, a user-friendly web server tool which finds modules in PPI network and defines the roles for every node, and produces files for visualization in Cytoscape and Pajek. For given proteins, it analyzes the PPI network from BioGRID database, finds and visualizes the modules these proteins form, and then defines the role every node plays in this network, based on two topological parameters Participation Coefficient and Z-score. This is the first program which provides interactive and very friendly interface for biologists to find and visualize modules and roles of proteins in PPI network. It can be tested online at the website http://www.bioinfo.org/modulerole/index.php, which is free and open to all users and there is no login requirement, with demo data provided by “User Guide” in the menu Help. Non-server application of this program is considered for high-throughput data with more than 200 nodes or user’s own interaction datasets. Users are able to bookmark the web link to the result page and access at a later time. As an interactive and highly customizable application, ModuleRole requires no expert knowledge in graph theory on the user side and can be used in both Linux and Windows system, thus a very useful tool for biologist to analyze and visualize PPI networks from databases such as BioGRID. Availability ModuleRole is implemented in Java and C, and is freely available at http://www.bioinfo.org/modulerole/index.php. Supplementary information (user guide, demo data) is also available at this website. API for ModuleRole used for this program can be obtained upon request. PMID:24788790

Li, GuiPeng; Li, Ming; Zhang, YiWei; Wang, Dong; Li, Rong; Guimerà, Roger; Gao, Juntao Tony; Zhang, Michael Q.

2014-01-01

185

Ion transport membrane module and vessel system with directed internal gas flow  

DOEpatents

An ion transport membrane system comprising (a) a pressure vessel having an interior, an inlet adapted to introduce gas into the interior of the vessel, an outlet adapted to withdraw gas from the interior of the vessel, and an axis; (b) a plurality of planar ion transport membrane modules disposed in the interior of the pressure vessel and arranged in series, each membrane module comprising mixed metal oxide ceramic material and having an interior region and an exterior region; and (c) one or more gas flow control partitions disposed in the interior of the pressure vessel and adapted to change a direction of gas flow within the vessel.

Holmes, Michael Jerome (Thompson, ND); Ohrn, Theodore R. (Alliance, OH); Chen, Christopher Ming-Poh (Allentown, PA)

2010-02-09

186

Study of Transcriptional Regulatory Network Based on CIS Module Database  

NASA Astrophysics Data System (ADS)

Microarray analysis is a high-throughput method for analyzing expression levels of multiple genes, therefore the microarray have been regarded by many investigators as a powerful method. Treating a huge amount of data and judgment of differentially expressed genes require appropriate statistical analysis. When the microarray analysis suggests there are co-expressed genes under a specific condition, there is high possibility that the common transcriptional factors (TFs) control them. It is also difficult to identify the TFs involved in co-expression through only biochemical experiments. In view of cis-element pattern related to co expressed genes might be one of the solutions to infer the gene expression mechanism clearly. So far, we have constructed Cis-Module database in order to specify cis-element location and distribution on genome. Using this database and rat microarray data, we have investigated the TFs network related to co-expression of genes. If we could also extract the human genes that are orthologous to co-expressed gene in rat, it will allow us to compare their cis-elements and TFs and to consider difference of gene expression profiles between rat and human. It will be very useful to find out attention to drug discovery targeting gene expression mechanism.

Akasaka, Shizu; Urushibara, Tomoko; Suzuki, Tomonori; Miyazaki, Satoru

2011-01-01

187

Creating a Universal Networking Language Module within an Advanced NLP System  

Microsoft Academic Search

A multifunctional NLP environment, ETAP-3, is presented. The environment has several NLP applications, including a machine translation system, a natural language interface to SQL type databases, synonymous paraphrasing of sentences, syntactic error correction module, and a computer-assisted language learning tool. Emphasis is laid on a new module of the processor responsible for the interface with the Universal Networking Language, a

Igor M. Boguslavsky; Nadezhda Frid; Leonid L. Iomdin; Leonid Kreidlin; Irina Sagalova; Victor G. Sizov

2000-01-01

188

Neural network based estimation of maximum power generation from PV module using environmental information  

Microsoft Academic Search

This paper presents an application of an artificial neural network for the estimation of maximum power generation from PV module. The output power from a PV module depends on environmental factors such as irradiation and cell temperature. For the operation planning of power systems, the prediction of the power generation is inevitable for PV systems. For this purpose, irradiation, temperature

Takashi Hiyama; Ken Kitabayashi

1997-01-01

189

Theory of interface: category theory, directed networks and evolution of biological networks.  

PubMed

Biological networks have two modes. The first mode is static: a network is a passage on which something flows. The second mode is dynamic: a network is a pattern constructed by gluing functions of entities constituting the network. In this paper, first we discuss that these two modes can be associated with the category theoretic duality (adjunction) and derive a natural network structure (a path notion) for each mode by appealing to the category theoretic universality. The path notion corresponding to the static mode is just the usual directed path. The path notion for the dynamic mode is called lateral path which is the alternating path considered on the set of arcs. Their general functionalities in a network are transport and coherence, respectively. Second, we introduce a betweenness centrality of arcs for each mode and see how the two modes are embedded in various real biological network data. We find that there is a trade-off relationship between the two centralities: if the value of one is large then the value of the other is small. This can be seen as a kind of division of labor in a network into transport on the network and coherence of the network. Finally, we propose an optimization model of networks based on a quality function involving intensities of the two modes in order to see how networks with the above trade-off relationship can emerge through evolution. We show that the trade-off relationship can be observed in the evolved networks only when the dynamic mode is dominant in the quality function by numerical simulations. We also show that the evolved networks have features qualitatively similar to real biological networks by standard complex network analysis. PMID:24012823

Haruna, Taichi

2013-11-01

190

Neural network approach for direction of arrival estimation  

NASA Astrophysics Data System (ADS)

The problem of Direction of Arrival (DOA) estimation of users in mobile communication systems using linear antenna arrays is addressed. Superresolution algorithms, such as Multiple Signal Classification (MUSIC), are used to locate desired as well as cochannel mobile users. However these algorithms require extensive computation and are difficult to implement in real-time. In this paper, the DOA problem is approached as a mapping problem which can be modeled using a suitable artificial neural network trained with input output pairs. A study of a three-layer Radial Basis Function Neural Network (RBFNN) which can learn multiple source direction finding with a six-element array is conducted. RBFNNs were used due to their ability for data interpolation in higher dimensions. The network weights are modified using the normalized cumulative delta rule. The performance of this network is compared to that of the MUSIC algorithm for both uncorrelated and corrected signals. It was found that networks implementing these functions were indeed successful in performing the required task and their performance approached that of the MUSIC algorithm. It is also shown that the RBFNN substantially reduced the CPU time for the DOA estimation computations.

El Zooghby, Ahmed H.; Christodoulou, Christos G.; Georgiopoulos, Michael

1997-04-01

191

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

PubMed

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

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

2011-12-01

192

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

E-print Network

Signal-to-noise ratio in direct-detection mid- infrared Random-Modulation Continuous-Wave lidar@ece.northwestern.edu, taflove@ece.northwestern.edu Abstract: We have derived the signal-to-noise ratio in direct-detection Random-Modulation Continuous-Wave (RM-CW) lidar in the presence of colored additive noise. In contrast

Taflove, Allen

193

Gene duplication models for directed networks with limits on growth  

NASA Astrophysics Data System (ADS)

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.

Enemark, Jakob; Sneppen, Kim

2007-11-01

194

Effect of gravitational focusing on annual modulation in dark-matter direct-detection experiments.  

PubMed

The scattering rate in dark-matter direct-detection experiments should modulate annually due to Earth's orbit around the Sun. The rate is typically thought to be extremized around June 1, when the relative velocity of Earth with respect to the dark-matter wind is maximal. We point out that gravitational focusing can alter this modulation phase. Unbound dark-matter particles are focused by the Sun's gravitational potential, affecting their phase-space density in the lab frame. Gravitational focusing can result in a significant overall shift in the annual-modulation phase, which is most relevant for dark matter with low scattering speeds. The induced phase shift for light O(10)??GeV dark matter may also be significant, depending on the threshold energy of the experiment. PMID:24483881

Lee, Samuel K; Lisanti, Mariangela; Peter, Annika H G; Safdi, Benjamin R

2014-01-10

195

Influence of self-steepening and intrapulse Raman scattering on modulation instability in oppositely directed coupler.  

PubMed

We investigate the modulation instability in oppositely directed coupler in the presence of higher-order effects. Using linear stability analysis, we obtain an expression for instability gain. Special attention is paid to find out the influence of self-steepening effect and intrapulse Raman scattering on modulation instability. The study shows that in normal dispersion, regime instability gain exists even if perturbation frequency (?) is zero. But the instability gain at ?=0 is zero, when the dispersion is anomalous. Moreover, self-steepening effect and intrapulse Raman scattering form new instability regions and, hence, provide a new way to generate solitons or ultrashort pulses. Further, efficient control of modulation instability by adjusting self-steepening effect and intrapulse Raman scattering also successfully demonstrated. PMID:25375570

Shafeeque Ali, A K; Porsezian, K; Uthayakumar, T

2014-10-01

196

Influence of self-steepening and intrapulse Raman scattering on modulation instability in oppositely directed coupler  

NASA Astrophysics Data System (ADS)

We investigate the modulation instability in oppositely directed coupler in the presence of higher-order effects. Using linear stability analysis, we obtain an expression for instability gain. Special attention is paid to find out the influence of self-steepening effect and intrapulse Raman scattering on modulation instability. The study shows that in normal dispersion, regime instability gain exists even if perturbation frequency (?) is zero. But the instability gain at ? =0 is zero, when the dispersion is anomalous. Moreover, self-steepening effect and intrapulse Raman scattering form new instability regions and, hence, provide a new way to generate solitons or ultrashort pulses. Further, efficient control of modulation instability by adjusting self-steepening effect and intrapulse Raman scattering also successfully demonstrated.

Shafeeque Ali, A. K.; Porsezian, K.; Uthayakumar, T.

2014-10-01

197

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

E-print Network

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

Tian, Jie

198

Simple models of small-world networks with directed links.  

PubMed

We investigate the effect of directed short- and long-range connections in a simple model of a small-world network. Our model is one in which we can determine many quantities of interest by an exact analytical method. We calculate the function V(T), defined as the number of sites affected up to time T when a naive spreading process starts in the network. As opposed to shortcuts, the presence of unfavorable bonds has a negative effect on this quantity. Hence, the spreading process may not be able to affect all of the network. We define and calculate a quantity identified as the average size of the accessible world in our model. The interplay of shortcuts and unfavorable bonds on the small world properties is studied. PMID:12366205

Ramezanpour, A; Karimipour, V

2002-09-01

199

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

PubMed Central

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

Klein, Alexander; Witzel, Oliver; Ebert, Volker

2014-01-01

200

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

PubMed

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

Klein, Alexander; Witzel, Oliver; Ebert, Volker

2014-01-01

201

Workshop Report: Future Directions in Network Architecture Steven Bauer, Xiaowei Yang  

E-print Network

Workshop Report: Future Directions in Network Architecture (FDNA-03) Steven Bauer, Xiaowei Yang {bauer,yxw}@mit.edu Introduction The Future Directions in Network Architecture (FDNA) Workshop, a one day

Yang, Xiaowei

202

A direct torque control scheme for permanent magnet synchronous motors based on space vector modulation  

NASA Astrophysics Data System (ADS)

In order to solve the problem of direct torque control (DTC) for permanent magnet synchronous motor (PMSM) related to the flux and the torque ripple and the uncertainty of switching frequency, A novel direct torque control system based on space vector modulation(SVM-DTC) for permanent magnet synchronous motor was proposed. In this method flux and torque are controlled through stator voltage components in stator flux linkage coordinate axes and space vector modulation is used to control inverters. Therefore, the errors of torque and flux linkage could be compensated accurately. The whole system has only one easily adjustable PI adjuster and needs no high for hardware and easy for realize. The simulation results verify the feasibility of this method, reduction of the flux and the torque ripple, and the good performance of DTC.

Su, Xiao-hui; Xu, Shu-Ping

2013-03-01

203

Goal Directed Relative Skyline Queries in Time Dependent Road Networks  

E-print Network

The Wireless GIS technology is progressing rapidly in the area of mobile communications. Location-based spatial queries are becoming an integral part of many new mobile applications. The Skyline queries are latest apps under Location-based services. In this paper we introduce Goal Directed Relative Skyline queries on Time dependent (GD-RST) road networks. The algorithm uses travel time as a metric in finding the data object by considering multiple query points (multi-source skyline) relative to user location and in the user direction of travelling. We design an efficient algorithm based on Filter phase, Heap phase and Refine Skyline phases. At the end, we propose a dynamic skyline caching (DSC) mechanism which helps to reduce the computation cost for future skyline queries. The experimental evaluation reflects the performance of GD-RST algorithm over the traditional branch and bound algorithm for skyline queries in real road networks.

Iyer, K B Priya

2012-01-01

204

Provider-sponsored networks. Physicians organize for direct contracting.  

PubMed

The Provider Service Network (PSN) concept is part of a wider movement by physicians to restructure for managed care to improve bargaining leverage for America's more than 600,000 active medical practitioners. Direct contracting has a simple appeal--no intermediaries. Imagine managed care contracts without the costs or hassles of an HMO or third-party intermediary. The PSN is a new form of managed care organization, but without the middleman. Savvy, self-insured employers, business coalitions, and government health programs are the potential "buyers." Doctors and hospitals are the "sellers," organizing provider networks on a regional and statewide basis. Up for grabs are over 225 million consumers whose health benefits are currently managed by insurance plans, HMOs, and third parties. This new marketplace of direct contracting may sound to doctors like the Garden of Eden, but there is plenty of opposition. PSNs will not become a national trend without a fight. PMID:10160042

Coile, R C

1996-08-01

205

On neighbor discovery in wireless networks with directional antennas  

Microsoft Academic Search

Abstract-We,consider,the,problem,of neighbor,discovery,in static wireless ad hoc,networks,with directional antennas. We propose several probabilistic algorithms,in which,nodes perform random, independent transmissions to discover their one-bop neighbors. Our neighbor,discovery algorithms,are classified hto two groups, viz. Direct-Discovery Algorithm in which nodes discover,their neighbors,only,upon,receiving a transmission from,their neighbors,and,Gossip-Based Algorithm in which nodes,gossip,about,their neighbors’ location,information,to enable faster discovery. We first consider the operation,of these algorithms in a

Sudarshan Vasudevan; James F. Kurose; Donald F. Towsley

2005-01-01

206

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

Microsoft Academic Search

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

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

207

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

Microsoft Academic Search

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,

Michael A. Nitsche; Walter Paulus; Jens Frahm

2001-01-01

208

Pinning down neutralino properties from a possible modulation signal in WIMP direct search  

E-print Network

We analyze the properties of neutralino under the hypothesis that some preliminary experimental results of the DAMA/NaI Collaboration may be indicative of a yearly modulation effect. We examine which supersymmetric configurations would be singled out by the DAMA/NaI data. We also discuss the possibility to investigate these configurations by means of experimental searches for relic neutralinos other than direct searches. We finally discuss the possibility to probe these configurations by accelerator searches.

Bottino, A; Fornengo, N; Scopel, S

1998-01-01

209

Pinning down neutralino properties from a possible modulation signal in WIMP direct search  

E-print Network

We analyze the properties of neutralino under the hypothesis that some preliminary experimental results of the DAMA/NaI Collaboration may be indicative of a yearly modulation effect. We examine which supersymmetric configurations would be singled out by the DAMA/NaI data. We also discuss the possibility to investigate these configurations by means of experimental searches for relic neutralinos other than direct searches. We finally discuss the possibility to probe these configurations by accelerator searches.

A. Bottino; F. Donato; N. Fornengo; S. Scopel

1997-09-09

210

A 1.9 GHz Si direct conversion receiver IC for QPSK modulation systems  

Microsoft Academic Search

This paper presents a possible BiCMOS solution for a direct conversion receiver (DCR) for QPSK communication systems such as personal handy-phone system (PHS). DCR chips reported are for constant-amplitude modulation systems such as FSK or GMSK. However, no DCR chip for QPSK systems has been reported yet,because a 2nd-order nonlinearity often strongly deteriorates a receiver sensitivity for QPSK systems. That

C. Takahashi; R. Fujimoto; S. Arai; T. Itakura; T. Ueno; H. Tsurumi; H. Tanimoto; S. Watanabe; K. Hirakawa

1995-01-01

211

Beam dithering: Acoustic feedback control using a modulated-directivity loudspeaker array  

Microsoft Academic Search

Acoustic feedback instability is a fundamental limitation in public address systems and hands-free full duplex teleconferencing systems; it occurs at the resonant peaks of the acoustic signal path. These resonances can be reduced by modulating the directivity of the loudspeaker or microphone, as in a digital beamforming loudspeaker array with time-varying shading coefficients. Beam dithering can be accomplished by time-stepping

Gary Elko; Michael M. Goodwin

1993-01-01

212

Application of direct pulsewidth modulation scheme to AC-DC converters: - a way to reduce ripple  

E-print Network

DC output voltage and unity power factor. This results in reducing voltage ripple and therefore contributes to overall improved performance. Among PWM schemes, The direct pulsewitch modulation(DPWM) technique was newly developed. In DPWM method... the pulse widths are determined by equating the incremental areas of the reference with the output pulse areas. DPWM is the simplest method for the microcomputer ? based converters. This thesis presents a new technique ? using DPWM scheme into AC ? DC con...

Zhang, Yuemin

1993-01-01

213

Rapid direct fabrication of active electro-optic modulators in GaAs  

Microsoft Academic Search

We have developed several direct-write laser processing techniques to masklessly fabricate prototypes of waveguiding devices in GaAs\\/AlGaAs substrates. This flexible technology allows the rapid, successive fabrication and testing of devices such as modulators. Previously, we had reported use of this technology to fabricate low-loss single-mode passive waveguiding structures and devices. In this paper, we report the fabrication of active electro-optic

Louay Eldada; Nongfan Zhu; Mark N. Ruberto; Miguel Levy; Robert Scarmozzino

1994-01-01

214

Network module detection: Affinity search technique with the multi-node topological overlap measure  

PubMed Central

Background Many clustering procedures only allow the user to input a pairwise dissimilarity or distance measure between objects. We propose a clustering method that can input a multi-point dissimilarity measure d(i1, i2, ..., iP) where the number of points P can be larger than 2. The work is motivated by gene network analysis where clusters correspond to modules of highly interconnected nodes. Here, we define modules as clusters of network nodes with high multi-node topological overlap. The topological overlap measure is a robust measure of interconnectedness which is based on shared network neighbors. In previous work, we have shown that the multi-node topological overlap measure yields biologically meaningful results when used as input of network neighborhood analysis. Findings We adapt network neighborhood analysis for the use of module detection. We propose the Module Affinity Search Technique (MAST), which is a generalized version of the Cluster Affinity Search Technique (CAST). MAST can accommodate a multi-node dissimilarity measure. Clusters grow around user-defined or automatically chosen seeds (e.g. hub nodes). We propose both local and global cluster growth stopping rules. We use several simulations and a gene co-expression network application to argue that the MAST approach leads to biologically meaningful results. We compare MAST with hierarchical clustering and partitioning around medoid clustering. Conclusion Our flexible module detection method is implemented in the MTOM software which can be downloaded from the following webpage: PMID:19619323

Li, Ai; Horvath, Steve

2009-01-01

215

ModuleBlast: identifying activated sub-networks within and across species  

PubMed Central

Identifying conserved and divergent response patterns in gene networks is becoming increasingly important. A common approach is integrating expression information with gene association networks in order to find groups of connected genes that are activated or repressed. In many cases, researchers are also interested in comparisons across species (or conditions). Finding an active sub-network is a hard problem and applying it across species requires further considerations (e.g. orthology information, expression data and networks from different sources). To address these challenges we devised ModuleBlast, which uses both expression and network topology to search for highly relevant sub-networks. We have applied ModuleBlast to expression and interaction data from mouse, macaque and human to study immune response and aging. The immune response analysis identified several relevant modules, consistent with recent findings on apoptosis and NF?B activation following infection. Temporal analysis of these data revealed cascades of modules that are dynamically activated within and across species. We have experimentally validated some of the novel hypotheses resulting from the analysis of the ModuleBlast results leading to new insights into the mechanisms used by a key mammalian aging protein. PMID:25428368

Zinman, Guy E.; Naiman, Shoshana; O'Dee, Dawn M.; Kumar, Nishant; Nau, Gerard J.; Cohen, Haim Y.; Bar-Joseph, Ziv

2015-01-01

216

ModuleBlast: identifying activated sub-networks within and across species.  

PubMed

Identifying conserved and divergent response patterns in gene networks is becoming increasingly important. A common approach is integrating expression information with gene association networks in order to find groups of connected genes that are activated or repressed. In many cases, researchers are also interested in comparisons across species (or conditions). Finding an active sub-network is a hard problem and applying it across species requires further considerations (e.g. orthology information, expression data and networks from different sources). To address these challenges we devised ModuleBlast, which uses both expression and network topology to search for highly relevant sub-networks. We have applied ModuleBlast to expression and interaction data from mouse, macaque and human to study immune response and aging. The immune response analysis identified several relevant modules, consistent with recent findings on apoptosis and NF?B activation following infection. Temporal analysis of these data revealed cascades of modules that are dynamically activated within and across species. We have experimentally validated some of the novel hypotheses resulting from the analysis of the ModuleBlast results leading to new insights into the mechanisms used by a key mammalian aging protein. PMID:25428368

Zinman, Guy E; Naiman, Shoshana; O'Dee, Dawn M; Kumar, Nishant; Nau, Gerard J; Cohen, Haim Y; Bar-Joseph, Ziv

2015-02-18

217

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

Microsoft Academic Search

A fast-response and scattering-free homogeneously aligned polymer network liquid crystal (PNLC) light modulator is demonstrated at lambda=1.55 mum wavelength. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. The strong polymer network anchoring assists LC to relax back quickly as the electric field is removed.

Yun-Hsing Fan; Yi-Hsin Lin; Hongwen Ren; Sebastian Gauza; Shin-Tson Wu

2004-01-01

218

Moving target tracking through distributed clustering in directional sensor networks.  

PubMed

The problem of moving target tracking in directional sensor networks (DSNs) introduces new research challenges, including optimal selection of sensing and communication sectors of the directional sensor nodes, determination of the precise location of the target and an energy-efficient data collection mechanism. Existing solutions allow individual sensor nodes to detect the target's location through collaboration among neighboring nodes, where most of the sensors are activated and communicate with the sink. Therefore, they incur much overhead, loss of energy and reduced target tracking accuracy. In this paper, we have proposed a clustering algorithm, where distributed cluster heads coordinate their member nodes in optimizing the active sensing and communication directions of the nodes, precisely determining the target location by aggregating reported sensing data from multiple nodes and transferring the resultant location information to the sink. Thus, the proposed target tracking mechanism minimizes the sensing redundancy and maximizes the number of sleeping nodes in the network. We have also investigated the dynamic approach of activating sleeping nodes on-demand so that the moving target tracking accuracy can be enhanced while maximizing the network lifetime. We have carried out our extensive simulations in ns-3, and the results show that the proposed mechanism achieves higher performance compared to the state-of-the-art works. PMID:25529205

Enayet, Asma; Razzaque, Md Abdur; Hassan, Mohammad Mehedi; Almogren, Ahmad; Alamri, Atif

2014-01-01

219

Moving Target Tracking through Distributed Clustering in Directional Sensor Networks  

PubMed Central

The problem of moving target tracking in directional sensor networks (DSNs) introduces new research challenges, including optimal selection of sensing and communication sectors of the directional sensor nodes, determination of the precise location of the target and an energy-efficient data collection mechanism. Existing solutions allow individual sensor nodes to detect the target's location through collaboration among neighboring nodes, where most of the sensors are activated and communicate with the sink. Therefore, they incur much overhead, loss of energy and reduced target tracking accuracy. In this paper, we have proposed a clustering algorithm, where distributed cluster heads coordinate their member nodes in optimizing the active sensing and communication directions of the nodes, precisely determining the target location by aggregating reported sensing data from multiple nodes and transferring the resultant location information to the sink. Thus, the proposed target tracking mechanism minimizes the sensing redundancy and maximizes the number of sleeping nodes in the network. We have also investigated the dynamic approach of activating sleeping nodes on-demand so that the moving target tracking accuracy can be enhanced while maximizing the network lifetime. We have carried out our extensive simulations in ns-3, and the results show that the proposed mechanism achieves higher performance compared to the state-of-the-art works. PMID:25529205

Enayet, Asma; Razzaque, Md. Abdur; Hassan, Mohammad Mehedi; Almogren, Ahmad; Alamri, Atif

2014-01-01

220

Extending the direct laser modulation bandwidth by exploiting the photon-photon resonance: modeling, simulations and experiments  

NASA Astrophysics Data System (ADS)

The direct laser modulation bandwidth can be extended substantially by introducing a supplementary photon-photon resonance (PPR) at a higher frequency than the carrier-photon resonance (CPR). The paper presents a modified rate equation model that takes into account the PPR by treating the longitudinal confinement factor as a dynamic variable. The conditions required for obtaining a strong PPR and an enhancement of the small-signal modulation bandwidth are analyzed and experimental results confirming the model are presented. Since the small-signal modulation bandwidth may not be indicative of the large-signal modulation capability, particularly in case of a small-signal modulation response with substantial variations across the bandwidth, we have also analyzed the influence of the PPR-enhanced small-signal modulation response shape on the large-signal modulation capability as well as the methods that can be employed to flatten the small-signal modulation transfer function between the CPR and PPR.

Dumitrescu, M.; Laakso, A.; Viheriala, J.; Kamp, M.; Bardella, P.; Eisenstein, G.

2013-03-01

221

Selective Attention to Semantic and Syntactic Features Modulates Sentence Processing Networks in Anterior Temporal Cortex  

PubMed Central

Numerous studies have identified an anterior temporal lobe (ATL) region that responds preferentially to sentence-level stimuli. It is unclear, however, whether this activity reflects a response to syntactic computations or some form of semantic integration. This distinction is difficult to investigate with the stimulus manipulations and anomaly detection paradigms traditionally implemented. The present functional magnetic resonance imaging study addresses this question via a selective attention paradigm. Subjects monitored for occasional semantic anomalies or occasional syntactic errors, thus directing their attention to semantic integration, or syntactic properties of the sentences. The hemodynamic response in the sentence-selective ATL region (defined with a localizer scan) was examined during anomaly/error-free sentences only, to avoid confounds due to error detection. The majority of the sentence-specific region of interest was equally modulated by attention to syntactic or compositional semantic features, whereas a smaller subregion was only modulated by the semantic task. We suggest that the sentence-specific ATL region is sensitive to both syntactic and integrative semantic functions during sentence processing, with a smaller portion of this area preferentially involved in the later. This study also suggests that selective attention paradigms may be effective tools to investigate the functional diversity of networks involved in sentence processing. PMID:18669589

Rogalsky, Corianne

2009-01-01

222

A MAC protocol for mobile ad hoc networks using directional antennas  

Microsoft Academic Search

We propose a medium access control (MAC) protocol for an ad hoc network of mobile wireless terminals that are equipped with multiple directional antennas. Use of directional antennas in ad hoc networks can largely reduce the radio interference, thereby improving the packet throughput. However, the main problem of using directional antennas in such networks is due to the dynamic nature

A. Nasipuri; S. Ye; J. You; R. E. Hiromoto

2000-01-01

223

Direction-dependent learning approach for radial basis function networks.  

PubMed

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

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

2007-01-01

224

Interest communities and flow roles in directed networks: the Twitter network of the UK riots.  

PubMed

Directionality is a crucial ingredient in many complex networks in which information, energy or influence are transmitted. In such directed networks, analysing flows (and not only the strength of connections) is crucial to reveal important features of the network that might go undetected if the orientation of connections is ignored. We showcase here a flow-based approach for community detection through the study of the network of the most influential Twitter users during the 2011 riots in England. Firstly, we use directed Markov Stability to extract descriptions of the network at different levels of coarseness in terms of interest communities, i.e. groups of nodes within which flows of information are contained and reinforced. Such interest communities reveal user groupings according to location, profession, employer and topic. The study of flows also allows us to generate an interest distance, which affords a personalized view of the attention in the network as viewed from the vantage point of any given user. Secondly, we analyse the profiles of incoming and outgoing long-range flows with a combined approach of role-based similarity and the novel relaxed minimum spanning tree algorithm to reveal that the users in the network can be classified into five roles. These flow roles go beyond the standard leader/follower dichotomy and differ from classifications based on regular/structural equivalence. We then show that the interest communities fall into distinct informational organigrams characterized by a different mix of user roles reflecting the quality of dialogue within them. Our generic framework can be used to provide insight into how flows are generated, distributed, preserved and consumed in directed networks. PMID:25297320

Beguerisse-Díaz, Mariano; Garduño-Hernández, Guillermo; Vangelov, Borislav; Yaliraki, Sophia N; Barahona, Mauricio

2014-12-01

225

Interest communities and flow roles in directed networks: the Twitter network of the UK riots  

PubMed Central

Directionality is a crucial ingredient in many complex networks in which information, energy or influence are transmitted. In such directed networks, analysing flows (and not only the strength of connections) is crucial to reveal important features of the network that might go undetected if the orientation of connections is ignored. We showcase here a flow-based approach for community detection through the study of the network of the most influential Twitter users during the 2011 riots in England. Firstly, we use directed Markov Stability to extract descriptions of the network at different levels of coarseness in terms of interest communities, i.e. groups of nodes within which flows of information are contained and reinforced. Such interest communities reveal user groupings according to location, profession, employer and topic. The study of flows also allows us to generate an interest distance, which affords a personalized view of the attention in the network as viewed from the vantage point of any given user. Secondly, we analyse the profiles of incoming and outgoing long-range flows with a combined approach of role-based similarity and the novel relaxed minimum spanning tree algorithm to reveal that the users in the network can be classified into five roles. These flow roles go beyond the standard leader/follower dichotomy and differ from classifications based on regular/structural equivalence. We then show that the interest communities fall into distinct informational organigrams characterized by a different mix of user roles reflecting the quality of dialogue within them. Our generic framework can be used to provide insight into how flows are generated, distributed, preserved and consumed in directed networks. PMID:25297320

Beguerisse-Díaz, Mariano; Garduño-Hernández, Guillermo; Vangelov, Borislav; Yaliraki, Sophia N.; Barahona, Mauricio

2014-01-01

226

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

PubMed Central

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

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

227

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

PubMed

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

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

228

A wideband radiometer module for an unamplified direct detection scalable W-band imaging array  

NASA Astrophysics Data System (ADS)

A W-band unamplified direct detection radiometer module is described that provides a wideband response and is scalable to large arrays. The radiometer design is intended to provide sufficient sensitivity for millimeter wave imaging applications with a goal of 2K noise equivalent temperature difference (NETD) at a 30 Hz frame rate. This effort leverages previously reported device scaling to increase sensitivity. We present a radiometer module designed for 60 GHz RF bandwidth that utilizes HRL's antimonide-based backward tunnel diode. An impedance matching circuit with on- and off-chip elements, as well as ridged waveguide, provides a wideband match to the detectors. Modules were designed with two different microwave substrates: 125 micron thick quartz and 100 micron thick alumina. flip-chip bonding of the detectors is amenable to automated pick-and-place for high volume manufacturing. The modular nature of the array approach allows large arrays to be manufactured in a straightforward manner. We present the design approach along with both electromagnetic simulations and measured performance of the modules. This work was supported by phase II of DARPA's MIATA program.

Schaffner, James H.; Lynch, Jonathan J.; Guinn, Keith V.; Schulman, Joel N.; Moyer, Harris P.; Bowen, Ross; Musni, Marcel

2008-04-01

229

Opinion formation of free speech on the directed social network  

NASA Astrophysics Data System (ADS)

A dynamical model with continuous opinion is proposed to study how the speech order and the topology of directed social network affect the opinion formation of free speech. In the model, agents express their opinions one by one with random order (RO) or probability order (PO), other agents paying attentions to the speaking agent, receive provider's opinion, update their opinions and then express their new opinions in their turns. It is proved that with the same agent j repeats its opinion more, other agents who pay their attentions to j and include j's opinion in their confidence level at initial time, will continue approaching j's opinion. Simulation results reveal that on directed scale-free network: (1) the model for PO forms fewer opinion clusters, larger maximum cluster (MC), smaller standard deviation (SD), and needs less waiting time to reach a middle level of consensus than RO; (2) as the parameter of scale-free degree distribution decreases or the confidence level increases, the results often get better for both speech orders; (3) the differences between PO and RO get smaller as the size of network decreases.

Su, Jiongming; Ma, Hongxu; Liu, Baohong; Li, Qi

2014-12-01

230

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

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

231

Dynamics of neuromodulatory feedback determines frequency modulation in a reduced respiratory network: A computational study  

PubMed Central

Neuromodulators, such as amines and neuropeptides, alter the activity of neurons and neuronal networks. In this work, we investigate how neuromodulators, which activate Gq-protein second messenger systems, can modulate the bursting frequency of neurons in a critical portion of the respiratory neural network, the pre-Bötzinger complex (preBötC). These neurons are a vital part of the ponto-medullary neuronal network, which generates a stable respiratory rhythm whose frequency is regulated by neuromodulator release from the nearby Raphe nucleus. Using a simulated 50-cell network of excitatory preBötC neurons with a heterogeneous distribution of persistent sodium conductance and Ca2+, we determined conditions for frequency modulation in such a network by simulating interaction between Raphe and preBötC nuclei. We found that the positive feedback between the Raphe excitability and preBötC activity induces frequency modulation in the preBötC neurons. In addition, the frequency of the respiratory rhythm can be regulated via phasic release of excitatory neuromodulators from the Raphe nucleus. We predict that the application of a Gq antagonist will eliminate this frequency modulation by the Raphe and keep the network frequency constant and low. In contrast, application of a Gq agonist will result in a high frequency for all levels of Raphe stimulation. Our modeling results also suggest that high [K+] requirement in respiratory brain slice experiments may serve as a compensatory mechanism for low neuromodulatory tone. PMID:23202052

Toporikova, Natalia; Butera, Robert J.

2013-01-01

232

Simple direct power control of three-phase PWM rectifier using space-vector modulation (DPC-SVM)  

Microsoft Academic Search

This paper proposes a novel and simple direct power control of three-phase pulsewidth-modulated (PWM) rectifiers with constant switching frequency using space-vector modulation (DPC-SVM). The active and reactive powers are used as the pulse width modulated (PWM) control variables instead of the three-phase line currents being used. Moreover, line voltage sensors are replaced by a virtual flux estimator. The theoretical principle

Mariusz Malinowski; M. Jasinski; M. P. Kazmierkowski

2004-01-01

233

Microwave sidebands for laser cooling by direct modulation of a tapered amplifier.  

PubMed

Laser cooling of atoms usually necessitates several laser frequencies. Alkaline atoms, for example, are cooled by two lasers with a frequency difference in the gigahertz range. This gap cannot be closed with simple shifting techniques. Here, we present a method of generating sidebands at 6.6 GHz by modulating the current of a tapered amplifier, which is seeded by an unmodulated master laser. The sidebands enable trapping of 1.1 × 10(9) (87)Rb atoms in a chip-based magneto-optical trap. Compared to the direct modulation of the master laser, this method allows for an easy implementation, a fast adjustment over a wide frequency range, and the simultaneous extraction of unmodulated light for manipulation and detection. The low power consumption, small size, and applicability for multiple frequencies benefit a wide range of applications reaching from atom-based mobile sensors to the laser cooling of molecules. PMID:23822336

Mahnke, J; Kulas, S; Geisel, I; Jöllenbeck, S; Ertmer, W; Klempt, C

2013-06-01

234

Microwave sidebands for laser cooling by direct modulation of a tapered amplifier  

NASA Astrophysics Data System (ADS)

Laser cooling of atoms usually necessitates several laser frequencies. Alkaline atoms, for example, are cooled by two lasers with a frequency difference in the gigahertz range. This gap cannot be closed with simple shifting techniques. Here, we present a method of generating sidebands at 6.6 GHz by modulating the current of a tapered amplifier, which is seeded by an unmodulated master laser. The sidebands enable trapping of 1.1 × 109 87Rb atoms in a chip-based magneto-optical trap. Compared to the direct modulation of the master laser, this method allows for an easy implementation, a fast adjustment over a wide frequency range, and the simultaneous extraction of unmodulated light for manipulation and detection. The low power consumption, small size, and applicability for multiple frequencies benefit a wide range of applications reaching from atom-based mobile sensors to the laser cooling of molecules.

Mahnke, J.; Kulas, S.; Geisel, I.; Jöllenbeck, S.; Ertmer, W.; Klempt, C.

2013-06-01

235

A Millimeter Wave Direct QPSK modulator MMIC Using PIN Technology And A Novel Approach to Self Error-Correction  

Microsoft Academic Search

In this paper we present two topologies of QPSK (Quadrature Phase Shift Keying) Modulator for direct carrier modulation at 29.5 GHz for satellite communications using PIN technology. Previously published designs use PHEMT technology. PIN diodes allow operation at high power level (several watts at Ka band) and yield better switching performance compared to PHEMT switches. Our designs exhibit wide bandwidth

Tsufit Magrisso; Asher Madjar

2002-01-01

236

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

237

Searching for Supersymmetric Dark Matter - The Directional Rate and the Modulation Effect Due to Caustic Rings  

E-print Network

The detection of the theoretically expected dark matter is central to particle physics and cosmology. Current fashionable supersymmetric models provide a natural dark matter candidate which is the lightest supersymmetric particle (LSP). The allowed parameter space of such models combined with fairly well understood physics (quark substructure of the nucleon and nuclear structure) permit the evaluation of the event rate for LSP-nucleus elastic scattering. The thus obtained event rates, which sensitively depend on the allowed parameter space parameters, are usually very low or even undetectable. So, for background reduction, one would like to exploit two nice features of the reaction, the directional rate, which depends on the sun's direction of motion and the modulation effect, i.e. the dependence of the event rate on the earth's annual motion. In the present paper we study these phenomena in a specific class of non isothermal models, which take into account the late in-fall of dark matter into our galaxy, producing flows of caustic rings. We find that the modulation effect arising from such models is smaller than that found previously with isothermal symmetric velocity distributions and much smaller compared to that obtained using a realistic asymmetric distribution with enhanced dispersion in the galactocentric direction.

J. D. Vergados

2001-01-02

238

Moral judgment modulation by disgust is bi-directionally moderated by individual sensitivity  

PubMed Central

Modern theories of moral judgment predict that both conscious reasoning and unconscious emotional influences affect the way people decide about right and wrong. In a series of experiments, we tested the effect of subliminal and conscious priming of disgust facial expressions on moral dilemmas. “Trolley-car”-type scenarios were used, with subjects rating how acceptable they found the utilitarian course of action to be. On average, subliminal priming of disgust facial expressions resulted in higher rates of utilitarian judgments compared to neutral facial expressions. Further, in replication, we found that individual change in moral acceptability ratings due to disgust priming was modulated by individual sensitivity to disgust, revealing a bi-directional function. Our second replication extended this result to show that the function held for both subliminally and consciously presented stimuli. Combined across these experiments, we show a reliable bi-directional function, with presentation of disgust expression primes to individuals with higher disgust sensitivity resulting in more utilitarian judgments (i.e., number-based) and presentations to individuals with lower sensitivity resulting in more deontological judgments (i.e., rules-based). Our results may reconcile previous conflicting reports of disgust modulation of moral judgment by modeling how individual sensitivity to disgust determines the direction and degree of this effect. PMID:24639665

Ong, How Hwee; Mullette-Gillman, O’Dhaniel A.; Kwok, Kenneth; Lim, Julian

2014-01-01

239

Module Discovery by Exhaustive Search for Densely Connected, Co-Expressed Regions in Biomolecular Interaction Networks  

Microsoft Academic Search

BackgroundComputational prediction of functionally related groups of genes (functional modules) from large-scale data is an important issue in computational biology. Gene expression experiments and interaction networks are well studied large-scale data sources, available for many not yet exhaustively annotated organisms. It has been well established, when analyzing these two data sources jointly, modules are often reflected by highly interconnected (dense)

Recep Colak; Flavia Moser; Jeffrey Shih-Chieh Chu; Alexander Schönhuth; Nansheng Chen; Martin Ester; Raya Khanin

2010-01-01

240

FPGA-based artificial neural network using CORDIC modules  

NASA Astrophysics Data System (ADS)

Artificial neural networks have been used in applications that require complex procedural algorithms and in systems which lack an analytical mathematic model. By designing a large network of computing nodes based on the artificial neuron model, new solutions can be developed for computational problems in fields such as image processing and speech recognition. Neural networks are inherently parallel since each neuron, or node, acts as an autonomous computational element. Artificial neural networks use a mathematical model for each node that processes information from other nodes in the same region. The information processing entails computing a weighted average computation followed by a nonlinear mathematical transformation. Some typical artificial neural network applications use the exponential function or trigonometric functions for the nonlinear transformation. Various simple artificial neural networks have been implemented using a processor to compute the output for each node sequentially. This approach uses sequential processing and does not take advantage of the parallelism of a complex artificial neural network. In this work a hardware-based approach is investigated for artificial neural network applications. A Field Programmable Gate Arrays (FPGAs) is used to implement an artificial neuron using hardware multipliers, adders and CORDIC functional units. In order to create a large scale artificial neural network, area efficient hardware units such as CORDIC units are needed. High performance and low cost bit serial CORDIC implementations are presented. Finally, the FPGA resources and the performance of a hardware-based artificial neuron are presented.

Liddicoat, Albert A.; Slivovsky, Lynne A.; McLenegan, Tim; Heyer, Don

2006-08-01

241

Integrative Multi-omics Module Network Inference with Lemon-Tree  

PubMed Central

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

Bonnet, Eric; Calzone, Laurence; Michoel, Tom

2015-01-01

242

Network analysis reveals that bacteria and fungi form modules that correlate independently with soil parameters.  

PubMed

Network and multivariate statistical analyses were performed to determine interactions between bacterial and fungal community terminal restriction length polymorphisms as well as soil properties in paired woodland and pasture sites. Canonical correspondence analysis (CCA) revealed that shifts in woodland community composition correlated with soil dissolved organic carbon, while changes in pasture community composition correlated with moisture, nitrogen and phosphorus. Weighted correlation network analysis detected two distinct microbial modules per land use. Bacterial and fungal ribotypes did not group separately, rather all modules comprised of both bacterial and fungal ribotypes. Woodland modules had a similar fungal?:?bacterial ribotype ratio, while in the pasture, one module was fungal dominated. There was no correspondence between pasture and woodland modules in their ribotype composition. The modules had different relationships to soil variables, and these contrasts were not detected without the use of network analysis. This study demonstrated that fungi and bacteria, components of the soil microbial communities usually treated as separate functional groups as in a CCA approach, were co-correlated and formed distinct associations in these adjacent habitats. Understanding these distinct modular associations may shed more light on their niche space in the soil environment, and allow a more realistic description of soil microbial ecology and function. PMID:25040229

de Menezes, Alexandre B; Prendergast-Miller, Miranda T; Richardson, Alan E; Toscas, Peter; Farrell, Mark; Macdonald, Lynne M; Baker, Geoff; Wark, Tim; Thrall, Peter H

2014-07-11

243

Inference and phase transitions in the detection of modules in sparse networks.  

PubMed

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. PMID:21902340

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

2011-08-01

244

Direct electron density modulation of surface plasmons with a scanning electron microscope  

NASA Astrophysics Data System (ADS)

The optical properties of localized surface plasmon resonance (LSPR) were modulated by direct electron injection using scanning electron microscopy (SEM). The predictions of electromagnetic theory for LSPR on charged metal nanoparticles were experimentally verified using a novel microscopic system. Extinction spectra were obtained for gold nanostructures that were under intense electron irradiation using an SEM system equipped with an optical microscope. High-frequency shifts of LSPR were observed for a single gold nanosphere, nanodimer, and nanorod, and the amount of the shifts was explained with respect to their symmetry.

Saito, Yuika; Fujita, Katsumasa

2015-01-01

245

The Limbic-Prefrontal Network Modulated by Electroacupuncture at CV4 and CV12  

PubMed Central

fMRI studies showed that acupuncture could induce hemodynamic changes in brain networks. Many of these studies focused on whether specific acupoints could activate specific brain regions and were often limited to manual acupuncture at acupoints on the limbs. In this fMRI study, we investigated acupuncture's modulation effects on brain functional networks by electroacupuncture (EA) at acupoints on the midline of abdomen. Acupoints Guanyuan (CV4) and Zhongwan (CV12) were stimulated in 21 healthy volunteers. The needling sensations, brain activation, and functional connectivity were studied. We found that the limbic-prefrontal functional network was deactivated by EA at CV4 and CV12. More importantly, the local functional connectivity was significantly changed during EA stimulation, and the change persisted during the period after the stimulation. Although minor differences existed, both acupoints similarly modulated the limbic-prefrontal functional network, which is overlapped with the functional circuits associated with emotional and cognitive regulation. PMID:22291848

Fang, Jiliang; Wang, Xiaoling; Liu, Hesheng; Wang, Yin; Zhou, Kehua; Hong, Yang; Liu, Jun; Wang, Lei; Xue, Chao; Song, Ming; Liu, Baoyan; Zhu, Bing

2012-01-01

246

A MAC Protocol for Mobile Ad Hoc Networks Using Directional Antennas  

Microsoft Academic Search

We propose a medium access control (MAC) pro- tocol for an ad hoc network of mobile wireless terminals that are equipped with multiple directional antennas. Use of direc- tional antennas in ad hoc networks can largely reduce the radio interference, thereby improving the packet throughput. How- ever, the main problem of using directional antennas in such networks is due to

A. Nasipuri; S. Ye; R. E. Hiromoto

247

Adaptive Cluster-Based Data Collection in Sensor Networks with Direct Sink Access  

Microsoft Academic Search

Recently wireless sensor networks featuring direct sink access have been studied as an efficient architecture to gather and process data for numerous applications. We focus on the joint effect of clustering and data correlation on the performance of such networks. We propose a novel cluster-based data collection scheme for sensor networks with direct sink access (CDC-DSA), and provide an analytical

Mahdi Lotfinezhad; Ben Liang; Elvino S. Sousa

2008-01-01

248

A direct adaptive neural-network control for unknown nonlinear systems and its application  

Microsoft Academic Search

In this paper a direct adaptive neural-network control strategy for unknown nonlinear systems is presented. The system considered is described by an unknown NARMA model, and a feedforward neural network is used to learn the system. Taking the neural network as a neural model of the system, control signals are directly obtained by minimizing either the instant difference or the

Jose R. Noriega; Hong Wang

1998-01-01

249

Myosin lever arm directs collective motion on cellular actin network  

PubMed Central

The molecular motor myosin teams up to drive muscle contraction, membrane traffic, and cell division in biological cells. Myosin function in cells emerges from the interaction of multiple motors tethered to a scaffold, with surrounding actin filaments organized into 3D networks. Despite the importance of myosin function, the influence of intermotor interactions on collective motion remains poorly understood. In this study, we used precisely engineered myosin assemblies to examine emergence in collective myosin movement. We report that tethering multiple myosin VI motors, but not myosin V motors, modifies their movement trajectories on keratocyte actin networks. Single myosin V and VI dimers display similar skewed trajectories, albeit in opposite directions, when traversing the keratocyte actin network. In contrast, tethering myosin VI motors, but not myosin V motors, progressively straightens the trajectories with increasing myosin number. Trajectory shape of multimotor scaffolds positively correlates with the stiffness of the myosin lever arm. Swapping the flexible myosin VI lever arm for the relatively rigid myosin V lever increases trajectory skewness, and vice versa. A simplified model of coupled motor movement demonstrates that the differences in flexural rigidity of the two myosin lever arms is sufficient to account for the differences in observed behavior of groups of myosin V and VI motors. In accordance with this model trajectory, shapes for scaffolds containing both myosin V and VI are dominated by the myosin with a stiffer lever arm. Our findings suggest that structural features unique to each myosin type may confer selective advantages in cellular functions. PMID:24591646

Hariadi, Rizal F.; Cale, Mario; Sivaramakrishnan, Sivaraj

2014-01-01

250

Heterogeneous Recovery Rates against SIS Epidemics in Directed Networks  

E-print Network

The nodes in communication networks are possibly and most likely equipped with different recovery resources, which allow them to recover from a virus with different rates. In this paper, we aim to understand know how to allocate the limited recovery resources to efficiently prevent the spreading of epidemics. We study the susceptible-infected-susceptible (SIS) epidemic model on directed scale-free networks. In the classic SIS model, a susceptible node can be infected by an infected neighbor with the infection rate $\\beta$ and an infected node can be recovered to be susceptible again with the recovery rate $\\delta$. In the steady state a fraction $y_\\infty$ of nodes are infected, which shows how severely the network is infected. We propose to allocate the recovery rate $\\delta_i$ for node $i$ according to its indegree and outdegree-$\\delta_i\\scriptsize{\\sim}k_{i,in}^{\\alpha_{in}}k_{i,out}^{\\alpha_{out}}$, given the finite average recovery rate $\\langle\\delta\\rangle$ representing the limited recovery resources ...

Qu, Bo; Wang, Huijuan

2014-01-01

251

Modulation of Visual Responses by Gaze Direction in Human Visual Cortex  

PubMed Central

To locate visual objects, the brain combines information about retinal location and direction of gaze. Studies in monkeys have demonstrated that eye position modulates the gain of visual signals with “gain fields,” so that single neurons represent both retinotopic location and eye position. We wished to know whether eye position and retinotopic stimulus location are both represented in human visual cortex. Using functional magnetic resonance imaging, we measured separately for each of several different gaze positions cortical responses to stimuli that varied periodically in retinal locus. Visually evoked responses were periodic following the periodic retinotopic stimulation. Only the response amplitudes depended on eye position; response phases were indistinguishable across eye positions. We used multivoxel pattern analysis to decode eye position from the spatial pattern of response amplitudes. The decoder reliably discriminated eye position in five of the early visual cortical areas by taking advantage of a spatially heterogeneous eye position-dependent modulation of cortical activity. We conclude that responses in retinotopically organized visual cortical areas are modulated by gain fields qualitatively similar to those previously observed neurophysiologically. PMID:23761883

Gardner, Justin L.; Movshon, J. Anthony; Heeger, David J.

2013-01-01

252

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

Microsoft Academic Search

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

Abbas Saberi Noghabi; Habib Rajabi Mashhadi; Javad Sadeh

2010-01-01

253

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

E-print Network

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

Spence, Harlan Ernest

254

Cortical spreading depression and central pain networks in trigeminal nuclei modulation: time for an integrated migraine pathogenesis perspective.  

PubMed

The role of the cortical spreading depression (CSD)-dependent trigeminovascular activation in migraine etiopathogenesis, long considered paradigmatic, has remained substantially unproven in humans. The parallel advancement of functional neuroimaging techniques promoted the extensive exploration of the brain networks involved in pain processing in search of a possible central migraine generator. However, despite initial enthusiasms, it has not been possible to clarify whether the functional central "markers" of pain observed in primary headaches could be considered as causative or just the neural correlates of the ongoing pain. Nonetheless, our knowledge on the complex interactions between CSD, neurogenic inflammation, peripheral trigeminovascular input, central cortico-trigeminal nuclei direct modulation and pain processing and limbic system networks has enormously grown, allowing the reconceptualisation of migraine from a neurovascular to a pure neurolimbic pain disorder, therefore relocating it in the much broader frame of the brain and whole organism homeostatic control. In this work, the available evidences currently supporting the relevance of CSD, of peripheral trigeminovascular input and of direct cortico-trigeminal nuclei modulation in migraine pathogenesis are reviewed in the light of a possible integrated migraine etiopathogenetic perspective. PMID:23695046

De Simone, R; Ranieri, A; Montella, S; Bonavita, V

2013-05-01

255

Characterization of submillisecond response optical addressing phase modulator based on low light scattering polymer network liquid crystal  

NASA Astrophysics Data System (ADS)

Optically addressed conventional nematic liquid crystal spatial light modulator has attracted wide research interests. But the slow response speed limited its further application. In this paper, polymer network liquid crystal (PNLC) was proposed to replace the conventional nematic liquid crystal to enhance the response time to the order of submillisecond. The maximum light scattering of the employed PNLC was suppressed to be less than 2% at 1.064 ?m by optimizing polymerization conditions and selecting large viscosity liquid crystal as solvent. The occurrence of phase ripple phenomenon due to electron diffusion and drift in photoconductor was found to deteriorate the phase modulation effect of the optical addressed PNLC phase modulator. The wavelength effect and AC voltage frequency effect on the on state dynamic response of phase change was investigated by experimental methods. These effects were interpreted by electron diffusion and drift theory based on the assumption that free electron was inhomogeneously distributed in accordance with the writing beam intensity distribution along the incident direction. The experimental results indicated that the phase ripple could be suppressed by optimizing the wavelength of the writing beam and the driving AC voltage frequency when varying the writing beam intensity to generate phase change in 2? range. The modulation transfer function was also measured.

Xiangjie, Zhao; Cangli, Liu; Jiazhu, Duan; Dayong, Zhang; Yongquan, Luo

2015-01-01

256

The anticonvulsant stiripentol acts directly on the GABAA receptor as a positive allosteric modulator  

PubMed Central

SUMMARY 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 anticonvulsant 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 GABAA 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 ?3-containing receptors and reduced potentiation when the ?1 or ? 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 ?3 subunit that reduced positive modulation by neurosteroids. The differential effect of STP on ?1- and ?2/?3-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 ?3-containing receptors as well as its activity at ?-containing receptors may provide a unique opportunity to target selected populations of GABARs. PMID:18585399

Fisher, Janet L.

2009-01-01

257

Directed deposition of inorganic oxide networks on patterned polymer templates  

NASA Astrophysics Data System (ADS)

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.

Ford, Thomas James Robert

258

Morphology effect on the light scattering and dynamic response of polymer network liquid crystal phase modulator.  

PubMed

Polymer network liquid crystal (PNLC) was one of the most potential liquid crystal for submillisecond response phase modulation, which was possible to be applied in submillisecond response phase only spatial light modulator. But until now the light scattering when liquid crystal director was reoriented by external electric field limited its phase modulation application. Dynamic response of phase change when high voltage was applied was also not elucidated. The mechanism that determines the light scattering was studied by analyzing the polymer network morphology by SEM method. Samples were prepared by varying the polymerization temperature, UV curing intensity and polymerization time. The morphology effect on the dynamic response of phase change was studied, in which high voltage was usually applied and electro-striction effect was often induced. The experimental results indicate that the polymer network morphology was mainly characterized by cross linked single fibrils, cross linked fibril bundles or even both. Although the formation of fibril bundle usually induced large light scattering, such a polymer network could endure higher voltage. In contrast, although the formation of cross linked single fibrils induced small light scattering, such a polymer network cannot endure higher voltage. There is a tradeoff between the light scattering and high voltage endurance. The electro-optical properties such as threshold voltage and response time were taken to verify our conclusion. For future application, the monomer molecular structure, the liquid crystal solvent and the polymerization conditions should be optimized to generate optimal polymer network morphology. PMID:24977571

Xiangjie, Zhao; Cangli, Liu; Jiazhu, Duan; Jiancheng, Zeng; Dayong, Zhang; Yongquan, Luo

2014-06-16

259

Modulation of Cortical Activity by Transcranial Direct Current Stimulation in Patients with Affective Disorder  

PubMed Central

Transcranial direct current stimulation (tDCS) has been shown to have antidepressant efficacy in patients experiencing a major depressive episode, but little is known about the underlying neurophysiology. The purpose of our study was to investigate the acute effects of tDCS on cortical activity using electroencephalography (EEG) in patients with an affective disorder. Eighteen patients diagnosed with an affective disorder and experiencing a depressive episode participated in a sham-controlled study of tDCS, each receiving a session of active (2 mA for 20 minutes) and sham tDCS to the left dorsolateral prefrontal cortex (DLPFC). The effects of tDCS on EEG activity were assessed after each session using event-related potentials (ERP) and measurement of spectral activity during a visual working memory (VWM) task. We observed task and intervention dependent effects on both ERPs and task-related alpha and theta activity, where active compared to sham stimulation resulted in a significant reduction in the N2 amplitude and reduced theta activity over frontal areas during memory retrieval. In summary a single session of anodal tDCS stimulation to the left DLPFC during a major depressive episode resulted in modulated brain activity evident in task-related EEG. Effects on the N2 and frontal theta activity likely reflect modulated activity in the medial frontal cortex and hence indicate that the after-effects of tDCS extend beyond the direct focal effects to the left DLPFC. PMID:24914953

Powell, Tamara Y.; Boonstra, Tjeerd W.; Martin, Donel M.; Loo, Colleen K.; Breakspear, Michael

2014-01-01

260

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

SciTech Connect

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.

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

261

Comparison of IPDA lidar receiver sensitivity for coherent detection and for direct detection using sine-wave and pulsed modulation.  

PubMed

We use theoretical models to compare the receiver signal to noise ratio (SNR) vs. average rate of detected signal photons for an integrated path differential absorption (IPDA) lidar using coherent detection with continuous wave (CW) lasers and direct detection with sine-wave and pulse modulations. The results show the coherent IPDA lidar has high receiver gain and narrow bandwidth to overcome the effects of detector circuit noise and background light, but the actual receiver performance can be limited by the coherent mixing efficiency, speckle and other factors. For direct detection, using sine-wave modulation allows the use of a low peak power laser transmitter and synchronous detection. The pulse modulation technique requires higher laser peak powers but is more efficient than sine-wave modulation in terms of average detected signal photon rate required to achieve a given receiver SNR. We also conducted experiments for the direct detection cases and the results agreed well with theory. PMID:23037252

Sun, Xiaoli; Abshire, James B

2012-09-10

262

Analysis of protein-protein interaction network and functional modules on primary osteoporosis  

PubMed Central

Background Primary osteoporosis is an age-related disease, and the main cause of this disease is the failure of bone homeostasis. Previous studies have shown that primary osteoporosis is associated with gene mutations. To explore the functional modules of the PPI (protein-protein interaction) network of differentially expressed genes (DEGs), and the related pathways participating in primary osteoporosis. Methods The gene expression profile of primary osteoporosis GSE35956 was downloaded from the GEO (Gene Expression Omnibus) database and included five MSC (mesenchymal stem cell) specimens of normal osseous tissue and five MSC specimens of osteoporosis. The DEGs between the two types of MSC specimens were identified by the samr package in R language. In addition, the functions and pathways of DEGs were enriched. Then the DEGs were mapped to String to acquire PPI pairs and the PPI network was constructed with by these PPI pairs. Topological properties of the network were calculated by Network Analyzer, and modules in the network were screened by Cluster ONE software. Subsequently, the fronting five modules whose P-value was less than 1.0e-05 were identified and function analysis was conducted. Results A total of 797 genes were filtered as DEGs from these ten specimens of GSE35956 with 660 up-regulated genes and 137 down-regulated genes. Meanwhile, up-regulated DEGs were mainly enriched in functions and pathways related to cell cycle and DNA replication. Furthermore, there were 4,135 PPI pairs and 377 nodes in the PPI network. Four modules were enriched in different pathways, including cell cycle and DNA replication pathway in module 2. Conclusions In this paper, we explored the genes and pathways involved in primary osteoporosis based on gene expression profiles, and the present findings have the potential to be used clinically for the future treatment of primary osteoporosis. PMID:24656062

2014-01-01

263

Substrate-Induced Modulation of Signal Transduction Networks  

E-print Network

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 ...

Del Vecchio, Domitilla

264

Network modulation following sham surgery in Parkinson’s disease  

PubMed Central

Patient responses to placebo and sham effects are a major obstacle to the development of therapies for brain disorders, including Parkinson’s disease (PD). Here, we used functional brain imaging and network analysis to study the circuitry underlying placebo effects in PD subjects randomized to sham surgery as part of a double-blind gene therapy trial. Metabolic imaging was performed prior to randomization, then again at 6 and 12 months after sham surgery. In this cohort, the sham response was associated with the expression of a distinct cerebello-limbic circuit. The expression of this network increased consistently in patients blinded to treatment and correlated with independent clinical ratings. Once patients were unblinded, network expression declined toward baseline levels. Analogous network alterations were not seen with open-label levodopa treatment or during disease progression. Furthermore, sham outcomes in blinded patients correlated with baseline network expression, suggesting the potential use of this quantitative measure to identify “sham-susceptible” subjects before randomization. Indeed, Monte Carlo simulations revealed that a priori exclusion of such individuals substantially lowers the number of randomized participants needed to demonstrate treatment efficacy. Individualized subject selection based on a predetermined network criterion may therefore limit the need for sham interventions in future clinical trials. PMID:25036712

Ko, Ji Hyun; Feigin, Andrew; Mattis, Paul J.; Tang, Chris C.; Ma, Yilong; Dhawan, Vijay; During, Matthew J.; Kaplitt, Michael G.; Eidelberg, David

2014-01-01

265

Network modulation following sham surgery in Parkinson's disease.  

PubMed

Patient responses to placebo and sham effects are a major obstacle to the development of therapies for brain disorders, including Parkinson's disease (PD). Here, we used functional brain imaging and network analysis to study the circuitry underlying placebo effects in PD subjects randomized to sham surgery as part of a double-blind gene therapy trial. Metabolic imaging was performed prior to randomization, then again at 6 and 12 months after sham surgery. In this cohort, the sham response was associated with the expression of a distinct cerebello-limbic circuit. The expression of this network increased consistently in patients blinded to treatment and correlated with independent clinical ratings. Once patients were unblinded, network expression declined toward baseline levels. Analogous network alterations were not seen with open-label levodopa treatment or during disease progression. Furthermore, sham outcomes in blinded patients correlated with baseline network expression, suggesting the potential use of this quantitative measure to identify "sham-susceptible" subjects before randomization. Indeed, Monte Carlo simulations revealed that a priori exclusion of such individuals substantially lowers the number of randomized participants needed to demonstrate treatment efficacy. Individualized subject selection based on a predetermined network criterion may therefore limit the need for sham interventions in future clinical trials. PMID:25036712

Ko, Ji Hyun; Feigin, Andrew; Mattis, Paul J; Tang, Chris C; Ma, Yilong; Dhawan, Vijay; During, Matthew J; Kaplitt, Michael G; Eidelberg, David

2014-08-01

266

A Topology Control Approach to Using Directional Antennas in Wireless Mesh Networks  

E-print Network

A Topology Control Approach to Using Directional Antennas in Wireless Mesh Networks Umesh Kumar Stony Brook, New York 11794-4400, U.S.A. Abstract-- Directional antennas in wireless mesh networks can directional antennas with legacy MAC layer protocols such as IEEE 802.11. The idea is to use multiple

Das, Samir R.

267

Capacity analysis of wireless mesh networks with omni or directional antennas  

E-print Network

Capacity analysis of wireless mesh networks with omni or directional antennas Jun Zhang Dept of wireless mesh networks that use omni or directional antennas. The capacity in our analysis is the end: 1) The capacity is O(1/N) for both omni and directional antennas, where N is number of nodes

Jia, Xiaohua

268

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

E-print Network

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

Gleeson, James P.

269

Optical Feedback-Tolerant Gain-Coupled DFB Lasers for Isolator-Free Modules in the Access Networks  

Microsoft Academic Search

Passive optical network topology has been widely adopted in access networks due to its low-cost and yet flexible network structure. To further promote the passive optical networks, the cost reduction of optical modules is critical. Relatively expensive combination of a conventional index-coupled distributed feedback laser diode (IC-DFB-LD) and an optical isolator is commonly used for passive optical networks with transmission

Koji Nakamura; Satoshi Miyamura; Hiroki Yaegashi

2010-01-01

270

Thematic Modules in an Asynchronous Learning Network: A Scandinavian Perspective on the Design of Introductory Courses  

Microsoft Academic Search

This paper discusses an educational philosophy and proposes a framework for structuring introductory courses in higher education. The philosophy is rooted in a Scandinavian tradition of social settings. Two elements are central in the philosophy: First, the notion of a thematic module (TM) which is a unit for studying a limited subject matter or topic. Second, asynchronous learning networks (ALN),

Urban Nulden

1999-01-01

271

Automatic Multi-Module Neural Network Evolution in an Artificial Brain  

Microsoft Academic Search

A major problem in artificial brain building is the au- tomatic construction and training of multi-module systems of neural networks. For example, consider a biological hu- man brain, which has millions of neural nets. If an artificial brain is to have similar complexity, it is unrealistic to re- quire that the training data set for each neural net must be

Jonathan Dinerstein; Nelson Dinerstein; Hugo De Garis

2003-01-01

272

Efficient Sensor Network Reprogramming through Compression of Executable Modules  

E-print Network

code modules. Code compression reduces the size of the software update, but the decompression consumption. We quantify the trade-offs in terms of dissemination time and energy, and decompression energy the fea- sibility of seven lossless data decompression algorithms, in- cluding the widely used GZIP

Dunkels, Adam

273

Multi-Objective Evolving Neural Network supporting SDR Modulations Management  

E-print Network

and transmission modulation schemes for fixed/mobile wireless nodes equipped with software defined radio abilities (Software Defined Radio) paradigm. The synergistic combination of controlled mobility and SDR in a totally with the software defined radio capabilities of such novel wireless devices can improve the performances of self

Paris-Sud XI, Université de

274

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

NASA Astrophysics Data System (ADS)

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.

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

2012-08-01

275

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

SciTech Connect

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.

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

276

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

PubMed

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

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

277

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

PubMed Central

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

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

2013-01-01

278

SENSE OF DIRECTION AND COMMUNICATION COMPLEXITY IN DISTRIBUTED NETWORKS  

E-print Network

in the case of complete networks. By exploiting the 'density' of the complete graph, in [KMZ1] it has been network. On the other hand, in [KMZ2], it has been shown that solving MST in a complete network might

Urrutia, Jorge

279

Normal aging modulates prefrontoparietal networks underlying multiple memory processes  

PubMed Central

Functional decline of brain regions underlying memory processing represents a hallmark of cognitive aging. Although a rich literature documents age-related differences in several memory domains, the effect of aging on networks that underlie multiple memory processes has been relatively unexplored. Here we used functional magnetic resonance imaging during working memory and incidental episodic encoding memory to investigate patterns of age-related differences in activity and functional covariance patterns common across multiple memory domains. Relative to younger subjects, older subjects showed increased activation in left dorso-lateral prefrontal cortex along with decreased deactivation in the posterior cingulate. Older subjects showed greater functional covariance during both memory tasks in a set of regions that included a positive prefronto-parietal-occipital networkas well as a negative network that spanned the default mode regions. These findings suggest that the memory process-invariant recruitment of brain regions within prefronto-parietal-occipital network increases with aging.Our results are in line with the dedifferentiation hypothesis of neurocognitive aging, thereby suggesting a decreased specialization of the brain networks supporting different memory networks. PMID:22909094

Sambataro, Fabio; Safrin, Martin; Lemaitre, Herve S.; Steele, Sonya U.; Das, Saumitra B.; Callicott, Joseph H; Weinberger, Daniel R.; Mattay, Venkata S.

2012-01-01

280

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

281

Modulating the Precision of Recurrent Bursts in Cultured Neural Networks  

NASA Astrophysics Data System (ADS)

Synchronized bursts are a very common feature in biological neural networks, and they play an important role in various brain functions and neurological diseases. This Letter investigates “recurrent synchronized bursts” induced by a single pulse stimulation in cultured networks of rat cortical neurons. We look at how the precision in their arrival times can be modified by a noble time-delayed stimulation protocol, which we term as “?t training.” The emergence of recurrent bursts and the change of the precision in their arrival times can be explained by the stochastic resonance of a damped, subthreshold, neural oscillation.

Choi, Joon Ho; Kim, June Hoan; Heo, Ryoun; Lee, Kyoung J.

2012-03-01

282

Design of physical layer management module of optical wireless local-area network  

NASA Astrophysics Data System (ADS)

As infrared transmission has the advantages of wide bandwidth, immunity to radio interference, high security and license-free, it is an attractive alternative to radio for wireless local area networks LAN. The design of an interface between the high-speed optical wireless transceiver (>20Mbps) and the optical wireless LAN is presented in this paper. We transplant the IEEE 802.11 medium access control (MAC) layer protocol to our system, define and implement a new physical (PHY) layer management module. This management module can also provide us an experimental platform to analyze the performance of the modulation schemes, such as L-PPM, PIM, DH-PIM, etc. Due to its characteristics of flexibility, simplicity and low cost, the management module is a good choice for the indoor optical wireless LANs.

Jiang, Feng; Zhang, Haitao; Gong, Mali; Yan, Ping; Yang, Xin; Zhang, Kai; Jin, Wei

2002-08-01

283

Janus particle microshuttle: 1D directional self-propulsion modulated by AC electrical field  

NASA Astrophysics Data System (ADS)

A catalytic Janus particle is capable of gaining energy from the surrounding fuel solution to drive itself to move continuously, which has an important impact in different fields, especially the field of micro-systems. However, the randomness of self-propulsion at the microscale restricts its use in practice. Achieving a directed self-propelled movement would greatly promote the application of the Janus particle. We proved experimentally that an AC electric field was an effective way to suppress Brownian motion and control the direction of self-propelled movement. The self-propulsion and dielectrophoretic response of a 2?m Janus particle were observed and the related basic data were collected. Interdigital electrodes, 20 ?m in width, were energized in pulsed style to modulate the self-propulsion, which resulted in a shuttle-style motion in which a single Janus particle moved to and fro inside the strip electrode. The change of direction depends on its unique position: the catalyst side is always pointed outward and the orientation angle relative to the electrode is about 60°. Numerical simulation also proved that this position is reasonable. The present study could be beneficial with regard to self-propulsion and AC electrokinetics of the Janus particle.

Chen, Jiliang; Zhang, Hongyan; Zheng, Xu; Cui, Haihang

2014-03-01

284

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

SciTech Connect

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.

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

285

Lasting modulation of in vitro oscillatory activity with weak direct current stimulation.  

PubMed

Transcranial direct current stimulation (tDCS) is emerging as a versatile tool to affect brain function. While the acute neurophysiological effects of stimulation are well understood, little is know about the long-term effects. One hypothesis is that stimulation modulates ongoing neural activity, which then translates into lasting effects via physiological plasticity. Here we used carbachol-induced gamma oscillations in hippocampal rat slices to establish whether prolonged constant current stimulation has a lasting effect on endogenous neural activity. During 10 min of stimulation, the power and frequency of gamma oscillations, as well as multiunit activity, were modulated in a polarity specific manner. Remarkably, the effects on power and multiunit activity persisted for more than 10 min after stimulation terminated. Using a computational model we propose that altered synaptic efficacy in excitatory and inhibitory pathways could be the source of these lasting effects. Future experimental studies using this novel in vitro preparation may be able to confirm or refute the proposed hypothesis. PMID:25505103

Reato, Davide; Bikson, Marom; Parra, Lucas C

2015-03-01

286

ADAPTATION OF MAMMALIAN PHOTORECEPTORS TO BACKGROUND LIGHT: PUTATIVE ROLE FOR DIRECT MODULATION OF PHOSPHODIESTERASE  

PubMed Central

All sensory receptors adapt. As the mean level of light or sound or odor is altered, the sensitivity of the receptor is adjusted to permit the cell to function over as wide a range of ambient stimulation as possible. In a rod photoreceptor, adaptation to maintained background light produces a decrease (or “sag) in the response to the prolonged illumination, as well as an acceleration in response decay time and a Weber-Fechner-like decrease in sensitivity. Earlier work on salamander indicated that adaptation is controlled by the intracellular concentration of Ca2+. Three Ca2+-dependent mechanisms were subsequently identified, namely regulation of guanylyl cyclase, modulation of activated rhodopsin lifetime, and alteration of channel opening probability, with the contribution of the cyclase thought to be the most important. Later experiments on mouse that exploit the powerful techniques of molecular genetics have shown that cyclase does indeed play a significant role in mammalian rods, but that much of adaptation remains even when regulation of cyclase and both of the other proposed pathways have been genetically deleted. The identity of the missing mechanism or mechanisms is unclear, but recent speculation has focused on direct modulation of spontaneous and light-activated phosphodiesterase. PMID:21922272

Fain, Gordon L

2011-01-01

287

Order-dependent Modulation of Directional Signals in the Supplementary and Pre-supplementary Motor Areas  

PubMed Central

To maximize reward and minimize effort, animals must often execute multiple movements in a timely and orderly manner. Such movement sequences must be usually discovered through experience, and during this process, signals related to the animal’s action, its ordinal position in the sequence, and subsequent reward need to be properly integrated. To investigate the role of the primate medial frontal cortex in planning and controlling multiple movements, monkeys were trained to produce a series of hand movements instructed by visual stimuli. We manipulated the number of movements in a sequence across trials, making it possible to dissociate the effects of the ordinal position of a given movement and the number of remaining movements necessary to obtain reward. Neurons in the supplementary and pre-supplementary motor areas modulated their activity according to the number of remaining movements, more often than in relation to the ordinal position, suggesting that they might encode signals related to the timing of reward or its temporally discounted value. In both cortical areas, signals related to the number of remaining movements and those related to movement direction were often combined multiplicatively, suggesting that the gain of the signals related to movements might be modulated by motivational factors. Finally, compared to the supplementary motor area, neurons in the pre-supplementary motor area were more likely to increase their activity when the number of remaining movements is large. These results suggest that these two areas might play complementary roles in controlling movement sequences. PMID:18077677

Sohn, Jeong-Woo; Lee, Daeyeol

2008-01-01

288

RESEARCH Open Access Herb network construction and co-module  

E-print Network

of China. 16-18 December 2010 Abstract Background: Traditional Chinese Medicine (TCM) is characterized the combination rule of traditional Chinese herbal formulae Shao Li* , Bo Zhang, Duo Jiang, Yingying Wei, Ningbo and demonstrate the potential of network biology approaches in the studies of TCM. Background Traditional Chinese

Li, Shao

289

Direct-detection optical communication with color coded pulse position modulation signaling  

NASA Technical Reports Server (NTRS)

The performance characteristics of a direct-detection optical communication system which is based on a laser transmitter which produces single light pulses at selected nonoverlapping optical center frequencies are discussed. The signal format, called color coded pulse position modulation (CCPPM), uses more of the total available response bandwidth characteristics of the photodetector than does ordinary PPM signaling. The advantages of CCPPM signaling are obtained at the expense of an increased optical bandwidth of the transmitted signal and a more complicated transmitter and receiver structure. When the signal format is used in conjunction with block length Reed-Solomon codes, high data rates and reliable high-speed optical communications under conditions of optimal energy efficiency are obtained.

Davidson, F.

1985-01-01

290

Laser output power stabilization for direct laser writing system by using an acousto-optic modulator.  

PubMed

We present experimental results on the output power stabilization of an Ar(+) laser for a direct laser writing system (LWS). Instability of the laser output power in the LWS cause resolution fluctuations of being fabricated diffractive optical elements or computer-generated holograms. For the purpose of reducing the power fluctuations, we have constituted a feedback loop with an acousto-optic modulator, a photodetector, and a servo controller. In this system, we have achieved the stability of +/-0.20% for 12 min and the relative intensity noise level of 2.1 x 10(-7) Hz(-12) at 100 Hz. In addition, we applied our system to a 2 mW internal mirror He-Ne laser. As a consequence, we achieved the output power stability of +/-0.12% for 25 min. PMID:17979409

Kim, Dong Ik; Rhee, Hyug-Gyo; Song, Jae-Bong; Lee, Yun-Woo

2007-10-01

291

Laser output power stabilization for direct laser writing system by using an acousto-optic modulator  

NASA Astrophysics Data System (ADS)

We present experimental results on the output power stabilization of an Ar+ laser for a direct laser writing system (LWS). Instability of the laser output power in the LWS cause resolution fluctuations of being fabricated diffractive optical elements or computer-generated holograms. For the purpose of reducing the power fluctuations, we have constituted a feedback loop with an acousto-optic modulator, a photodetector, and a servo controller. In this system, we have achieved the stability of ±0.20% for 12min and the relative intensity noise level of 2.1×10-7Hz-1/2 at 100Hz. In addition, we applied our system to a 2mW internal mirror He-Ne laser. As a consequence, we achieved the output power stability of ±0.12% for 25min.

Kim, Dong Ik; Rhee, Hyug-Gyo; Song, Jae-Bong; Lee, Yun-Woo

2007-10-01

292

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

PubMed Central

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

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

2013-01-01

293

Diffusible crosslinkers generate directed forces in microtubule networks.  

PubMed

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

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

2015-03-12

294

Glia contribute to the purinergic modulation of inspiratory rhythm-generating networks.  

PubMed

Glia modulate neuronal activity by releasing transmitters in a process called gliotransmission. The role of this process in controlling the activity of neuronal networks underlying motor behavior is unknown. ATP features prominently in gliotransmission; it also contributes to the homeostatic ventilatory response evoked by low oxygen through mechanisms that likely include excitation of preBötzinger complex (preBötC) neural networks, brainstem centers critical for breathing. We therefore inhibited glial function in rhythmically active inspiratory networks in vitro to determine whether glia contribute to preBötC ATP sensitivity. Glial toxins markedly reduced preBötC responses to ATP, but not other modulators. Furthermore, since preBötC glia responded to ATP with increased intracellular Ca(2+) and glutamate release, we conclude that glia contribute to the ATP sensitivity of preBötC networks, and possibly the hypoxic ventilatory response. Data reveal a role for glia in signal processing within brainstem motor networks that may be relevant to similar networks throughout the neuraxis. PMID:20237265

Huxtable, Adrianne G; Zwicker, Jennifer D; Alvares, Tucaauê S; Ruangkittisakul, Araya; Fang, Xin; Hahn, Leanne B; Posse de Chaves, Elena; Baker, Glen B; Ballanyi, Klaus; Funk, Gregory D

2010-03-17

295

Topologies for ad-hoc networks utilizing directional antennas with restricted fields of view  

E-print Network

ORCLE (Optical/RF Combined Link Experiment), is an airborne network in which aircraft have multiple directional antennas that are restricted in their pointing direction. A pair of aircraft in ORCLE can be linked if they ...

Anderson, Brian C. (Brian Curtis)

2006-01-01

296

Dopamine: a parallel pathway for the modulation of spinal locomotor networks  

PubMed Central

The spinal cord contains networks of neurons that can produce locomotor patterns. To readily respond to environmental conditions, these networks must be flexible yet at the same time robust. Neuromodulators play a key role in contributing to network flexibility in a variety of invertebrate and vertebrate networks. For example, neuromodulators contribute to altering intrinsic properties and synaptic weights that, in extreme cases, can lead to neurons switching between networks. Here we focus on the role of dopamine in the control of stepping networks in the spinal cord. We first review the role of dopamine in modulating rhythmic activity in the stomatogastric ganglion (STG) and the leech, since work from these preparations provides a foundation to understand its role in vertebrate systems. We then move to a discussion of dopamine’s role in modulation of swimming in aquatic species such as the larval xenopus, lamprey and zebrafish. The control of terrestrial walking in vertebrates by dopamine is less studied and we review current evidence in mammals with a focus on rodent species. We discuss data suggesting that the source of dopamine within the spinal cord is mainly from the A11 area of the diencephalon, and then turn to a discussion of dopamine’s role in modulating walking patterns from both in vivo and in vitro preparations. Similar to the descending serotonergic system, the dopaminergic system may serve as a potential target to promote recovery of locomotor function following spinal cord injury (SCI); evidence suggests that dopaminergic agonists can promote recovery of function following SCI. We discuss pharmacogenetic and optogenetic approaches that could be deployed in SCI and their potential tractability. Throughout the review we draw parallels with both noradrenergic and serotonergic modulatory effects on spinal cord networks. In all likelihood, a complementary monoaminergic enhancement strategy should be deployed following SCI. PMID:24982614

Sharples, Simon A.; Koblinger, Kathrin; Humphreys, Jennifer M.; Whelan, Patrick J.

2014-01-01

297

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

PubMed

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

Liu, Wei; Ye, Hua

2014-10-01

298

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

299

Identifying core gene modules in glioblastoma based on multilayer factor-mediated dysfunctional regulatory networks through integrating multi-dimensional genomic data  

PubMed Central

The driver genetic aberrations collectively regulate core cellular processes underlying cancer development. However, identifying the modules of driver genetic alterations and characterizing their functional mechanisms are still major challenges for cancer studies. Here, we developed an integrative multi-omics method CMDD to identify the driver modules and their affecting dysregulated genes through characterizing genetic alteration-induced dysregulated networks. Applied to glioblastoma (GBM), the CMDD identified a core gene module of 17 genes, including seven known GBM drivers, and their dysregulated genes. The module showed significant association with shorter survival of GBM. When classifying driver genes in the module into two gene sets according to their genetic alteration patterns, we found that one gene set directly participated in the glioma pathway, while the other indirectly regulated the glioma pathway, mostly, via their dysregulated genes. Both of the two gene sets were significant contributors to survival and helpful for classifying GBM subtypes, suggesting their critical roles in GBM pathogenesis. Also, by applying the CMDD to other six cancers, we identified some novel core modules associated with overall survival of patients. Together, these results demonstrate integrative multi-omics data can identify driver modules and uncover their dysregulated genes, which is useful for interpreting cancer genome. PMID:25653168

Ping, Yanyan; Deng, Yulan; Wang, Li; Zhang, Hongyi; Zhang, Yong; Xu, Chaohan; Zhao, Hongying; Fan, Huihui; Yu, Fulong; Xiao, Yun; Li, Xia

2015-01-01

300

Identifying core gene modules in glioblastoma based on multilayer factor-mediated dysfunctional regulatory networks through integrating multi-dimensional genomic data.  

PubMed

The driver genetic aberrations collectively regulate core cellular processes underlying cancer development. However, identifying the modules of driver genetic alterations and characterizing their functional mechanisms are still major challenges for cancer studies. Here, we developed an integrative multi-omics method CMDD to identify the driver modules and their affecting dysregulated genes through characterizing genetic alteration-induced dysregulated networks. Applied to glioblastoma (GBM), the CMDD identified a core gene module of 17 genes, including seven known GBM drivers, and their dysregulated genes. The module showed significant association with shorter survival of GBM. When classifying driver genes in the module into two gene sets according to their genetic alteration patterns, we found that one gene set directly participated in the glioma pathway, while the other indirectly regulated the glioma pathway, mostly, via their dysregulated genes. Both of the two gene sets were significant contributors to survival and helpful for classifying GBM subtypes, suggesting their critical roles in GBM pathogenesis. Also, by applying the CMDD to other six cancers, we identified some novel core modules associated with overall survival of patients. Together, these results demonstrate integrative multi-omics data can identify driver modules and uncover their dysregulated genes, which is useful for interpreting cancer genome. PMID:25653168

Ping, Yanyan; Deng, Yulan; Wang, Li; Zhang, Hongyi; Zhang, Yong; Xu, Chaohan; Zhao, Hongying; Fan, Huihui; Yu, Fulong; Xiao, Yun; Li, Xia

2015-02-27

301

Identification and validation of gene module associated with lung cancer through coexpression network analysis.  

PubMed

Lung cancer, a tumor with heterogeneous biology, is influenced by a complex network of gene interactions. Therefore, elucidating the relationships between genes and lung cancer is critical to attain further knowledge on tumor biology. In this study, we performed weighted gene coexpression network analysis to investigate the roles of gene networks in lung cancer regulation. Gene coexpression relationships were explored in 58 samples with tumorous and matched non-tumorous lungs, and six gene modules were identified on the basis of gene coexpression patterns. The overall expression of one module was significantly higher in the normal group than in the lung cancer group. This finding was validated across six datasets (all p values <0.01). The particular module was highly enriched for genes belonging to the biological Gene Ontology category "response to wounding" (adjusted p value=4.28×10(-10)). A lung cancer-specific hub network (LCHN) consisting of 15 genes was also derived from this module. A support vector machine based on classification model robustly separated lung cancer from adjacent normal tissues in the validation datasets (accuracy ranged from 91.7% to 98.5%) by using the LCHN gene signatures as predictors. Eight genes in the LCHN are associated with lung cancer. Overall, we identified a gene module associated with lung cancer, as well as an LCHN consisting of hub genes that may be candidate biomarkers and therapeutic targets for lung cancer. This integrated analysis of lung cancer transcriptome provides an alternative strategy for identification of potential oncogenic drivers. PMID:25752287

Liu, Rong; Cheng, Yu; Yu, Jing; Lv, Qiao-Li; Zhou, Hong-Hao

2015-05-25

302

Analysis of network based co-expression modules for Alzheimer's disease.  

PubMed

There has been an intensive research going on for Alzheimer's disease (AD) to understand its cause and progression through the past decade. However, the pathogenic factors that are responsible for these processes are still unclear. In this research we utilize the hippocampal gene expression data of 22 AD patients and present a framework for a comparative study to evaluate the two similarity measures, Mutual Information and Pearson Correlation Coefficient in developing gene coexpression networks. We hypothesize that Mutual Information based co-expression networks can capture more biologically significant dependencies as compared to Pearson Correlation Coefficient due to its ability to capture non-linear relationships. We utilize a parameter free module discovery algorithm to detect functional modules discovered by the two approaches. Further, to validate our approach, we compared the identified functional modules resulted by our experiments to the existing biological modules by computing the Jaccard index between them. Finally, we evaluated the discovered modules for their biological significance by performing biomedical literature search. We also investigated the drug interdiction pathways, which suggest potential targets for intervention. PMID:23921001

Dua, Prerna; Bais, Sonali; Lukiw, Walter J

2013-01-01

303

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

PubMed Central

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

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

304

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

PubMed Central

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

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

2015-01-01

305

Urban road network evolution mechanism based on the ‘direction preferred connection’ and ‘degree constraint’  

NASA Astrophysics Data System (ADS)

The urban road network is a complex system that exhibits the properties of self-organization and emergence. Recent theoretical and empirical studies have mainly focused on the structural properties of the urban road networks. This research concentrates on some important parameters such as degree, average degree, meshedness coefficient, betweeness, etc. These parameters of the real road network exhibit specific statistical properties. Some studies show that perhaps these specific statistical properties are caused by a compromise mechanism of the formation of a minimum spanning tree and the greedy triangulation. Inspired by these results, we propose a principle to construct the network (we call it a MG network in this paper) whose structure is located between the minimum spanning tree and the greedy triangulation at first. The structural properties of the MG network are analyzed. We find the formation mechanism of the MG network cannot explain the urban road network evolution well. Then, based on the formation mechanism of the MG network, we add the ‘direction preferred connection’ and ‘degree constraint’ principles to the urban road network evolution simulation process. The result of the simulation network turns out to be a planar network that is in accordance with reality. Compared with the real road network’s structural properties, we find the simulation results are so consistent with it. It indicates the validation of the model and also demonstrates perhaps the ‘direction preferred connection’ and ‘degree constraint’ principle can explain the urban road network evolution better.

Yuan, PengCheng; Juan, ZhiCai

2013-10-01

306

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

E-print Network

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

Fukai, Tomoki

307

Regulatory Snapshots: Integrative Mining of Regulatory Modules from Expression Time Series and Regulatory Networks  

PubMed Central

Explaining regulatory mechanisms is crucial to understand complex cellular responses leading to system perturbations. Some strategies reverse engineer regulatory interactions from experimental data, while others identify functional regulatory units (modules) under the assumption that biological systems yield a modular organization. Most modular studies focus on network structure and static properties, ignoring that gene regulation is largely driven by stimulus-response behavior. Expression time series are key to gain insight into dynamics, but have been insufficiently explored by current methods, which often (1) apply generic algorithms unsuited for expression analysis over time, due to inability to maintain the chronology of events or incorporate time dependency; (2) ignore local patterns, abundant in most interesting cases of transcriptional activity; (3) neglect physical binding or lack automatic association of regulators, focusing mainly on expression patterns; or (4) limit the discovery to a predefined number of modules. We propose Regulatory Snapshots, an integrative mining approach to identify regulatory modules over time by combining transcriptional control with response, while overcoming the above challenges. Temporal biclustering is first used to reveal transcriptional modules composed of genes showing coherent expression profiles over time. Personalized ranking is then applied to prioritize prominent regulators targeting the modules at each time point using a network of documented regulatory associations and the expression data. Custom graphics are finally depicted to expose the regulatory activity in a module at consecutive time points (snapshots). Regulatory Snapshots successfully unraveled modules underlying yeast response to heat shock and human epithelial-to-mesenchymal transition, based on regulations documented in the YEASTRACT and JASPAR databases, respectively, and available expression data. Regulatory players involved in functionally enriched processes related to these biological events were identified. Ranking scores further suggested ability to discern the primary role of a gene (target or regulator). Prototype is available at: http://kdbio.inesc-id.pt/software/regulatorysnapshots. PMID:22563474

Gonçalves, Joana P.; Aires, Ricardo S.; Francisco, Alexandre P.; Madeira, Sara C.

2012-01-01

308

Direct imaging of fluctuations in a cross-linked biopolymer network  

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

309

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

PubMed Central

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

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

2011-01-01

310

Spectral statistics in directed complex networks and universality of the Ginibre ensemble  

NASA Astrophysics Data System (ADS)

Spectra of the adjacency matrices of directed complex networks are analyzed by using non-Hermitian random matrix theory. Both the short-range and long-range correlations in the eigenvalues are calculated numerically for directed model complex networks and real-world networks. The results are compared with predictions of Ginibre’s ensemble. The spectral density ?(?), the nearest neighbor spacing distribution p(s) and the level-number variance ?2(L) show good agreement with Ginibre’s ensemble when the adjacency matrices of directed complex networks are in the strongly non-Hermitian regime.

Ye, Bin; Qiu, Liang; Wang, Xuesong; Guhr, Thomas

2015-03-01

311

Security-aware routing and localization for a directional mission critical network  

Microsoft Academic Search

There has been recent interest in the development of untethered sensor nodes that communicate directionally via free space optical communications for mission critical settings in which high-speed link guarantees in hostile environments are needed. Directional wireless optical sensor networks have the potential to provide gigabits per second speeds for relatively low power consumption enabling bursty traffic and longer network lifetimes.

Unoma Ndili Okorafor; Deepa Kundur

2010-01-01

312

Selective attention modulates high-frequency activity in the face-processing network.  

PubMed

Face processing depends on the orchestrated activity of a large-scale neuronal network. Its activity can be modulated by attention as a function of task demands. However, it remains largely unknown whether voluntary, endogenous attention and reflexive, exogenous attention to facial expressions equally affect all regions of the face-processing network, and whether such effects primarily modify the strength of the neuronal response, the latency, the duration, or the spectral characteristics. We exploited the good temporal and spatial resolution of intracranial electroencephalography (iEEG) and recorded from depth electrodes to uncover the fast dynamics of emotional face processing. We investigated frequency-specific responses and event-related potentials (ERP) in the ventral occipito-temporal cortex (VOTC), ventral temporal cortex (VTC), anterior insula, orbitofrontal cortex (OFC), and amygdala when facial expressions were task-relevant or task-irrelevant. All investigated regions of interest (ROI) were clearly modulated by task demands and exhibited stronger changes in stimulus-induced gamma band activity (50-150 Hz) when facial expressions were task-relevant. Observed latencies demonstrate that the activation is temporally coordinated across the network, rather than serially proceeding along a processing hierarchy. Early and sustained responses to task-relevant faces in VOTC and VTC corroborate their role for the core system of face processing, but they also occurred in the anterior insula. Strong attentional modulation in the OFC and amygdala (300 msec) suggests that the extended system of the face-processing network is only recruited if the task demands active face processing. Contrary to our expectation, we rarely observed differences between fearful and neutral faces. Our results demonstrate that activity in the face-processing network is susceptible to the deployment of selective attention. Moreover, we show that endogenous attention operates along the whole face-processing network, and that these effects are reflected in frequency-specific changes in the gamma band. PMID:25017647

Müsch, Kathrin; Hamamé, Carlos M; Perrone-Bertolotti, Marcela; Minotti, Lorella; Kahane, Philippe; Engel, Andreas K; Lachaux, Jean-Philippe; Schneider, Till R

2014-11-01

313

Asymmetric friction of nonmotor MAPs can lead to their directional motion in active microtubule networks.  

PubMed

Diverse cellular processes require microtubules to be organized into distinct structures, such as asters or bundles. Within these dynamic motifs, microtubule-associated proteins (MAPs) are frequently under load, but how force modulates these proteins' function is poorly understood. Here, we combine optical trapping with TIRF-based microscopy to measure the force dependence of microtubule interaction for three nonmotor MAPs (NuMA, PRC1, and EB1) required for cell division. We find that frictional forces increase nonlinearly with MAP velocity across microtubules and depend on filament polarity, with NuMA's friction being lower when moving toward minus ends, EB1's lower toward plus ends, and PRC1's exhibiting no directional preference. Mathematical models predict, and experiments confirm, that MAPs with asymmetric friction can move directionally within actively moving microtubule pairs they crosslink. Our findings reveal how nonmotor MAPs can generate frictional resistance in dynamic cytoskeletal networks via micromechanical adaptations whose anisotropy may be optimized for MAP localization and function within cellular structures. PMID:24725408

Forth, Scott; Hsia, Kuo-Chiang; Shimamoto, Yuta; Kapoor, Tarun M

2014-04-10

314

Unconditionally Reliable Message Transmission in Directed Neighbour Networks  

E-print Network

ring. Other examples include the Bluetooth or IEEE 802.11 network. Yet another motivation for the study, undirected graphs are not a suit- able model. For instance, in a sensor network where different nodes have

315

A metro-access integrated network with all-optical virtual private network function using DPSK/ASK modulation format  

NASA Astrophysics Data System (ADS)

All-optical virtual private network (VPN), which offers dedicated optical channels to connect users within a VPN group, is considered a promising approach to efficient internetworking with low latency and enhanced security implemented in the physical layer. On the other hand, time-division multiplexed (TDM) / wavelength-division multiplexed (WDM) network architecture based on a feeder-ring with access-tree topology, is considered a pragmatic migration scenario from current TDM-PONs to future WDM-PONs and a potential convergence scheme for access and metropolitan networks, due to its efficiently shared hardware and bandwidth resources. All-optical VPN internetworking in such a metro-access integrated structure is expected to cover a wider service area and therefore is highly desirable. In this paper, we present a TDM/WDM metro-access integrated network supporting all-optical VPN internetworking among ONUs in different sub- PONs based on orthogonal differential-phase-shift keying (DPSK) / amplitude-shift keying (ASK) modulation format. In each ONU, no laser but a single Mach-Zehnder modulator (MZM) is needed for the upstream and VPN signal generation, which is cost-effective. Experiments and simulations are performed to verify its feasibility as a potential solution to the future access service.

Tian, Yue; Leng, Lufeng; Su, Yikai

2008-11-01

316

A Comparison Between Cellular Encoding and Direct Encoding for Genetic Neural Networks  

Microsoft Academic Search

This paper compares the efficiency oftwo encoding schemes for Artificial NeuralNetworks optimized by evolutionaryalgorithms. Direct Encoding encodesthe weights for an a priori fixed neuralnetwork architecture. Cellular Encodingencodes both weights and the architectureof the neural network. In previousstudies, Direct Encoding and CellularEncoding have been used to createneural networks for balancing 1 and2 poles attached to a cart on a fixedtrack. The

Fr'ed'eric Gruau; Darrell Whitley; Larry Pyeatt

1996-01-01

317

Modulating parameters of excitability during and after transcranial direct current stimulation of the human motor cortex  

PubMed Central

Weak transcranial direct current stimulation (tDCS) of the human motor cortex results in excitability shifts which occur during and after stimulation. These excitability shifts are polarity-specific with anodal tDCS enhancing excitability, and cathodal reducing it. To explore the origin of this excitability modulation in more detail, we measured the input–output curve and motor thresholds as global parameters of cortico-spinal excitability, and determined intracortical inhibition and facilitation, as well as facilitatory indirect wave (I-wave) interactions. Measurements were performed during short-term tDCS, which elicits no after-effects, and during other tDCS protocols which do elicit short- and long-lasting after-effects. Resting and active motor thresholds remained stable during and after tDCS. The slope of the input–output curve was increased by anodal tDCS and decreased by cathodal tDCS. Anodal tDCS of the primary motor cortex reduced intracortical inhibition and enhanced facilitation after tDCS but not during tDCS. Cathodal tDCS reduced facilitation during, and additionally increased inhibition after its administration. During tDCS, I-wave facilitation was not influenced but, for the after-effects, anodal tDCS increased I-wave facilitation, while cathodal tDCS had only minor effects. These results suggest that the effect of tDCS on cortico-spinal excitability during a short period of stimulation (which does not induce after-effects) primarily depends on subthreshold resting membrane potential changes, which are able to modulate the input-output curve, but not motor thresholds. In contrast, the after-effects of tDCS are due to shifts in intracortical inhibition and facilitation, and at least partly also to facilitatory I-wave interaction, which is controlled by synaptic activity. PMID:16002441

Nitsche, Michael A; Seeber, Antje; Frommann, Kai; Klein, Cornelia Carmen; Rochford, Christian; Nitsche, Maren S; Fricke, Kristina; Liebetanz, David; Lang, Nicolas; Antal, Andrea; Paulus, Walter; Tergau, Frithjof

2005-01-01

318

Modulation of chest wall intermuscular coherence: effects of lung volume excursion and transcranial direct current stimulation.  

PubMed

Chest wall muscle recruitment varies as a function of the breathing task performed. However, the cortical control of the chest wall muscles during different breathing tasks is not known. We studied chest wall intermuscular coherence during various task-related lung volume excursions in 10 healthy adults (34 ± 15 yr; 2 men, 8 women) and determined if transcranial direct current stimulation (tDCS) could modulate chest wall intermuscular coherence during these tasks. Simultaneous assessment of regional intercostal and oblique electromyographic activity was measured while participants performed standardized tidal breathing, speech, maximum phonation, and vital capacity tasks. Lung volume and chest wall kinematics were determined using variable inductance plethysmography. We found that chest wall area of intermuscular coherence was greater during tidal and speech breathing compared with phonation and vital capacity (all P < 0.05) and between tidal breathing compared with speech breathing (P < 0.05). Anodal tDCS increased chest wall area of intermuscular coherence from 0.04 ± 0.09 prestimulation to 0.18 ± 0.19 poststimulation for vital capacity (P < 0.05). Sham tDCS and cathodal tDCS had no effect on coherence during lung volume excursions. Chest wall kinematics were not affected by tDCS. Our findings indicate that lung volume excursions about the midrange of vital capacity elicit a greater area of chest wall intermuscular coherence compared with lung volume excursions spanning the entire range of vital capacity in healthy adults. Our findings also demonstrate that brief tDCS may modulate the cortical control of the chest wall muscles in a stimulation- and lung volume excursion task-dependent manner but does not affect chest wall kinematics in healthy adults. PMID:23678011

Tomczak, Corey R; Greidanus, Krista R; Boliek, Carol A

2013-08-01

319

Two cascaded SOAs used as intensity modulators for adaptively modulated optical OFDM signals in optical access networks.  

PubMed

Detailed theoretical and numerical investigations of the transmission performance of adaptively modulated optical orthogonal frequency division multiplexed (AMOOFDM) signals are undertaken, for the first time, in optical amplification and chromatic dispersion (CD) compensation free single mode fiber (SMF) intensity-modulated and direct-detection (IMDD) systems using two cascaded semiconductor optical amplifiers in a counterpropagating configuration as an intensity modulator (TC-SOA-CC-IM). A theoretical model describing the characteristics of this configuration is developed. Extensive performance comparisons are also made between the TC-SOA-CC and the single SOA intensity modulators. It is shown that, the TC-SOA-CC reaches its strongly saturated region using a lower input optical power much faster than the single SOA resulting in significantly reduced effective carrier lifetime and thus wide TC-SOA-CC bandwidths. It is shown that at low input optical power, we can increase the signal line rate almost 115% which will be more than twice the transmission performance offered by single SOA. In addition, the TC-SOA-CC-IM is capable of supporting signal line rates higher than corresponding to the SOA-IM by using 10dB lower input optical powers. For long transmission distance, the TC-SOA-CC-IM has much stronger CD compensation capability compared to the SOA-IM. In addition the use of TC-SOA-CC-IM is more effective regarding the capability to benefit from the CD compensation for shorter distances starting at 60km SMF, whilst for the SOA-IM starting at 90km. PMID:24977835

Hamié, Ali; Hamzé, Mohamad; Taki, Haidar; Makouk, Layaly; Sharaiha, Ammar; Alaeddine, Ali; Al Housseini, Ali; Giacoumidis, Elias; Tang, J M

2014-06-30

320

A directionality based location discovery scheme for wireless sensor networks  

Microsoft Academic Search

A sensor network is a large ad hoc network of densely distributed sensors that are equipped with low power wireless transceivers. Such networks can be applied for cooperative signal detection, monitoring, and tracking, and are especially useful for applications in remote or hazardous locations. This paper addresses the problem of location discovery at the sensor nodes, which is one of

Asis Nasipuri; Kai Li

2002-01-01

321

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

E-print Network

. The PV modules have aluminum frames and were loaded uniformly. In agreement with the numerical analysis. The crystalline silicon PV modules have standard aluminum frames supporting the edges. Fig. 1 shows mechanical loads in order to develop crack-reducing module designs. In this paper we focus on the formation

322

Single Stage Inverter for a Direct AC Connection of a Photovoltaic Cell Module  

Microsoft Academic Search

There are several possibilities to transfer the energy taken from a photovoltaic cell to the grid. In the past, several cell modules used the same centralized inverter to transfer the energy to the grid. Nowadays, decentralized modules are preferred because of their versatility to harvest a larger amount of power, even when some of the modules of the total surface

A. Fernandez; J. Sebastian; M. M. Hernando; M. Arias; G. Perez

2006-01-01

323

Sequential interrogation of multiple FBG sensors using LPG modulation and an artificial neural network  

NASA Astrophysics Data System (ADS)

Interrogating multiple fiber Bragg gratings (FBG) requires highly sensitive spectrum scanning equipment such as optical spectrum analyzers, tunable filters, acousto-optic tunable filters etc, which are expensive, bulky and time consuming. In this paper, we present a new approach for multiple FBG sensor interrogation using long-period gratings and an artificial neural network. The reflection spectra of the multiplexed FBGs are modulated by two long period gratings separately and the modulated optical intensities were detected by two photodetectors. The outputs of the detectors are then used as input in a previously trained artificial neural network to interrogate the FBG sensors. Simulations have been performed to determine the strain and wavelength shift using two and four sensors. The interrogation system has also been demonstrated experimentally for two sensors using simply supported beams in the range of 0–350??strain. The proposed interrogation scheme has been found to identify the perturbed FBG, and to determine strain and wavelength shift with reasonable accuracy.

Basu, Mainak; Ghorai, S. K.

2015-04-01

324

Direction/location estimation and modulation detection for RF sources using steerable 3D IIR digital beam filters  

NASA Astrophysics Data System (ADS)

A planar antenna array based feature detection scheme is proposed to estimate the directional, location and modulation information pertaining to radio sources in a cognitive radio environment. The proposed system employs multiple direction estimation stations and a fusion station. Planar antenna arrays and three-dimensional (3-D) infinite impulse response (IIR) digital filters are employed to perform volume scanning of the radio environment, leading to a spatial power profile, which is subjected to peak detection in order to estimate the direction of arrival corresponding to each source. Cyclosationay feature detection is then performed along each direction to estimate the frequency and modulation information. Two simulation examples are provided to verify the feasibility of the proposed approach.

Udayanga, Nilan; Madanayake, Arjuna; Wijenayake, Chamith

2014-05-01

325

Estradiol interacts with an opioidergic network to achieve rapid modulation of a vocal pattern generator  

Microsoft Academic Search

Estrogens rapidly regulate neuronal activity within seconds-to-minutes, yet it is unclear how estrogens interact with neural\\u000a circuits to rapidly coordinate behavior. This study examines whether 17-beta-estradiol interacts with an opioidergic network\\u000a to achieve rapid modulation of a vocal control circuit. Adult plainfin midshipman fish emit vocalizations that mainly differ\\u000a in duration, and rhythmic activity of a hindbrain–spinal vocal pattern generator

Luke Remage-Healey; Andrew H. Bass

2010-01-01

326

A Spatial Domain Sigma-Delta Modulation via Discrete-Time Cellular Neural Networks  

Microsoft Academic Search

In this paper, a novel spatial domain sigma-delta modulation using two-layered discrete-time cellular neural networks (DT-CNNs) is proposed. Since the nature of CNN dynamics with the output function which has two saturation regions is to binarize the input image, the dynamics has a capabilities for a digital image halftoning. In the proposed architecture, the nonlinear interpolative dynamics is exploited to

Hisashi Aomori; Tsuyoshi Otake; Nobuaki Takahashi; Mamoru Tanaka

2007-01-01

327

Modulation of metabolic brain networks after subthalamic gene therapy for Parkinson's disease  

PubMed Central

Parkinson's disease (PD) is characterized by elevated expression of an abnormal metabolic brain network that is reduced by clinically effective treatment. We used fluorodeoxyglucose (FDG) positron emission tomography (PET) to determine the basis for motor improvement in 12 PD patients receiving unilateral subthalamic nucleus (STN) infusion of an adenoassociated virus vector expressing glutamic acid decarboxylase (AAV-GAD). After gene therapy, we observed significant reductions in thalamic metabolism on the operated side as well as concurrent metabolic increases in ipsilateral motor and premotor cortical regions. Abnormal elevations in the activity of metabolic networks associated with motor and cognitive functioning in PD patients were evident at baseline. The activity of the motor-related network declined after surgery and persisted at 1 year. These network changes correlated with improved clinical disability ratings. By contrast, the activity of the cognition-related network did not change after gene transfer. This suggests that modulation of abnormal network activity underlies the clinical outcome observed after unilateral STN AAV-GAD gene therapy. Network biomarkers may be used as physiological assays in early-phase trials of experimental therapies for PD and other neurodegenerative disease. PMID:18042721

Feigin, Andrew; Kaplitt, Michael G.; Tang, Chengke; Lin, Tanya; Mattis, Paul; Dhawan, Vijay; During, Matthew J.; Eidelberg, David

2007-01-01

328

EgoNet: identification of human disease ego-network modules  

PubMed Central

Background Mining novel biomarkers from gene expression profiles for accurate disease classification is challenging due to small sample size and high noise in gene expression measurements. Several studies have proposed integrated analyses of microarray data and protein-protein interaction (PPI) networks to find diagnostic subnetwork markers. However, the neighborhood relationship among network member genes has not been fully considered by those methods, leaving many potential gene markers unidentified. The main idea of this study is to take full advantage of the biological observation that genes associated with the same or similar diseases commonly reside in the same neighborhood of molecular networks. Results We present EgoNet, a novel method based on egocentric network-analysis techniques, to exhaustively search and prioritize disease subnetworks and gene markers from a large-scale biological network. When applied to a triple-negative breast cancer (TNBC) microarray dataset, the top selected modules contain both known gene markers in TNBC and novel candidates, such as RAD51 and DOK1, which play a central role in their respective ego-networks by connecting many differentially expressed genes. Conclusions Our results suggest that EgoNet, which is based on the ego network concept, allows the identification of novel biomarkers and provides a deeper understanding of their roles in complex diseases. PMID:24773628

2014-01-01

329

Intelligent stock trading system with price trend prediction and reversal recognition using dual-module neural networks  

Microsoft Academic Search

This article presents an intelligent stock trading system that can generate timely stock trading suggestions according to the prediction of short-term trends of price movement using dual-module neural networks(dual net). Retrospective technical indicators extracted from raw price and volume time series data gathered from the market are used as independent variables for neural modeling. Both neural network modules of thedual

Gia-shuh Jang; Feipei Lai; Bor-wei Jiang; Tai-ming Parng; Li-hua Chien

1993-01-01

330

Cancer core modules identification through genomic and transcriptomic changes correlation detection at network level  

PubMed Central

Background Identification of driver mutations among numerous genomic alternations remains a critical challenge to the elucidation of the underlying mechanisms of cancer. Because driver mutations by definition are associated with a greater number of cancer phenotypes compared to other mutations, we hypothesized that driver mutations could more easily be identified once the genotype-phenotype correlations are detected across tumor samples. Results In this study, we describe a novel network analysis to identify the driver mutation through integrating both cancer genomes and transcriptomes. Our method successfully identified a significant genotype-phenotype change correlation in all six solid tumor types and revealed core modules that contain both significantly enriched somatic mutations and aberrant expression changes specific to tumor development. Moreover, we found that the majority of these core modules contained well known cancer driver mutations, and that their mutated genes tended to occur at hub genes with central regulatory roles. In these mutated genes, the majority were cancer-type specific and exhibited a closer relationship within the same cancer type rather than across cancer types. The remaining mutated genes that exist in multiple cancer types led to two cancer type clusters, one cluster consisted of three neural derived or related cancer types, and the other cluster consisted of two adenoma cancer types. Conclusions Our approach can successfully identify the candidate drivers from the core modules. Comprehensive network analysis on the core modules potentially provides critical insights into convergent cancer development in different organs. PMID:22691569

2012-01-01

331

Identification of Functional Modules by Integration of Multiple Data Sources Using a Bayesian Network Classifier  

PubMed Central

Background Prediction of functional modules is indispensable for detecting protein deregulation in human complex diseases such as cancer. Bayesian network (BN) is one of the most commonly used models to integrate heterogeneous data from multiple sources such as protein domain, interactome, functional annotation, genome-wide gene expression, and the literature. Methods and Results In this paper, we present a BN classifier that is customized to: 1) increase the ability to integrate diverse information from different sources, 2) effectively predict protein-protein interactions, 3) infer aberrant networks with scale-free and small world properties, and 4) group molecules into functional modules or pathways based on the primary function and biological features. Application of this model on discovering protein biomarkers of hepatocelluar carcinoma (HCC) leads to the identification of functional modules that provide insights into the mechanism of the development and progression of HCC. These functional modules include cell cycle deregulation, increased angiogenesis (e.g., vascular endothelial growth factor, blood vessel morphogenesis), oxidative metabolic alterations, and aberrant activation of signaling pathways involved in cellular proliferation, survival, and differentiation. Conclusion The discoveries and conclusions derived from our customized BN classifier are consistent with previously published results. The proposed approach for determining BN structure facilitates the integration of heterogeneous data from multiple sources to elucidate the mechanisms of complex diseases. PMID:24736851

Wang, Jinlian; Zuo, Yiming; Liu, Lun; Man, Yangao; Tadesse, Mahlet G.; Ressom, Habtom W

2014-01-01

332

Efficient direct magneto-optical phase modulation of light waves in spun microstructured fibres  

SciTech Connect

We have proposed a phase modulator of optical radiation for an interferometric electric-current sensor. The modulator takes advantage of the Faraday effect in spun microstructured optical fibres. Such fibres enable small-diameter multiturn fibre coils to be produced, which is necessary for achieving a preset phase modulation amplitude at a moderate drive current. The principal characteristics of the modulator have been studied experimentally: frequency response, magneto-optical sensitivity and output signal contrast. The results demonstrate that the modulator ensures high efficiency, approaching the theoretical one, provided the modulation period exceeds the time it takes light to pass through the fibre. We have examined the influence of spun fibre parameters on the performance of the modulator.

Gubin, Vladimir P; Morshnev, Sergey K; Starostin, Nikolay I; Chamorovsky, Yury K; Sazonov, Aleksandr I; Przhiyalkovskii, Ya V; Boev, A I [V.A.Kotel'nikov Institute of Radio Engineering and Electronics, Fryazino Branch, Russian Academy of Sciences, Fryazino, Moscow Region (Russian Federation)

2011-09-30

333

The Journal of Neuroscience, May 1994, 14(5): 30193035 Muscarinic Modulation of a Pattern-Generating Network: Control of  

E-print Network

that under certain conditions of muscarinic modulation a new composite pacemaker could be created, composed, in a rhythmic "pattern-generating network," the pacemaker role may not be definitely attributed to a given, muscarinic modulation, oscillations, pacemaker] The generation of simple motor behaviors in both vertebrates

Bal, Thierry

334

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

Microsoft Academic Search

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.

H. Takesue; T. Sugie

2002-01-01

335

Modeling and simulation of digital recombination network for 2-1-1 cascaded doubled-sampled delta-sigma modulator  

Microsoft Academic Search

A mathematical model of the digital recombination network for 2-1-1 cascaded double-sampled (dS) delta-sigma (??) modulator, is presented. The model in the z-domain is used to evaluate the performance of the modulator, when the components mismatches are included. A 2-1-1 dS ?? modulator that operates from a single 2.5-V supply is designed in 0.6-?m CMOS technology. The clock frequency is

R. Salinas-Cruz; G. Espinosa-FIores-V

2004-01-01

336

8B10B line coding to mitigate the non-uniform FM laser response of direct modulated CPFSK transmitter.  

PubMed

We propose to employ 8B10B line coding as a simple technique to mitigate the impact of non-uniform laser diode FM response on the system performance of directly-modulated CPFSK. Experimental results show its effectiveness in decreasing signal distortion and penalty. PMID:18545433

Baroni, P; Miot, V; Carena, A; Poggiolini, P

2008-05-12

337

Direct Curriculum Development. Competency-Based Vocational Education Administrator Module Series. Leadership and Training Series No. 58B-7.  

ERIC Educational Resources Information Center

Designed to provide pre- and inservice vocational education administrators with the skills necessary to direct the curriculum development process, this competency-based module contains an introduction and three sequential learning experiences. Each learning experience consists of an overview, required and optional learning activities, a self-check…

Harrington, Lois G.; And Others

338

Direct Program Evaluation. Competency-Based Vocational Education Administrator Module Series. Leadership and Training Series No. 58B-10.  

ERIC Educational Resources Information Center

Designed to provide pre- and inservice vocational education administrators with background information and hands-on experiences for acquiring the skills necessary to direct a program evaluation, this competency-based learning module contains an introduction and four sequential learning experiences. Each learning experience consists of an overview,…

Harrington, Lois G.; And Others

339

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

PubMed Central

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

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

2015-01-01

340

General relationship of global topology, local dynamics, and directionality in large-scale brain networks.  

PubMed

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

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

2015-04-01

341

Potent and direct presynaptic modulation of glycinergic transmission in rat spinal neurons by atrial natriuretic peptide.  

PubMed

Atrial and brain natriuretic peptides (ANP and BNP) exist in the central nervous system and modulate neuronal function, although the locus of actions and physiological mechanisms are still unclear. In the present study we used rat spinal sacral dorsal commissural nucleus (SDCN) and hippocampal 'synaptic bouton' preparations, to record both spontaneous and evoked glycinergic inhibitory postsynaptic currents (sIPSCs and eIPSCs) in SDCN neurons, and the evoked excitatory postsynaptic currents (eEPSCs) in hippocampal CA3 neurons. ANP potently and significantly reduced the sIPSC frequency without affecting the amplitude. ANP also potently reduced the eIPSCs amplitude concurrently increasing the failure rate and the paired pulse ratio response. These ANP actions were blocked by anantin, a specific type A natriuretic peptide receptor (NPR-A) antagonist. The results clearly indicate that ANP acts directly on glycinergic presynaptic nerve terminals to inhibit glycine release via presynaptic NPR-A. The ANP effects were not blocked by the membrane permeable cGMP analog (8Br-cGMP) suggesting a transduction mechanisms not simply related to increasing cGMP levels in nerve terminals. BNP did not affect on glycinergic sIPSCs and eIPSCs. Moreover, both ANP and BNP had no effect on glutamatergic EPSCs in hippocampal CA3 neurons. The results indicate a potent and selective presynaptic inhibitory action of ANP on glycinergic transmission in spinal cord sensory circuits. PMID:24060848

Maeda, Megumi; Mizuno, Yuji; Wakita, Masahito; Yamaga, Toshitaka; Nonaka, Kiku; Shin, Min-Chul; Shoudai, Kiyomitsu; Akaike, Norio

2013-10-01

342

Transcranial direct current stimulation over posterior parietal cortex modulates visuospatial localization  

PubMed Central

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

Wright, Jessica M.; Krekelberg, Bart

2014-01-01

343

Community Structure Detection for Overlapping Modules through Mathematical Programming in Protein Interaction Networks  

PubMed Central

Community structure detection has proven to be important in revealing the underlying properties of complex networks. The standard problem, where a partition of disjoint communities is sought, has been continually adapted to offer more realistic models of interactions in these systems. Here, a two-step procedure is outlined for exploring the concept of overlapping communities. First, a hard partition is detected by employing existing methodologies. We then propose a novel mixed integer non linear programming (MINLP) model, known as OverMod, which transforms disjoint communities to overlapping. The procedure is evaluated through its application to protein-protein interaction (PPI) networks of the rat, E. coli, yeast and human organisms. Connector nodes of hard partitions exhibit topological and functional properties indicative of their suitability as candidates for multiple module membership. OverMod identifies two types of connector nodes, inter and intra-connector, each with their own particular characteristics pertaining to their topological and functional role in the organisation of the network. Inter-connector proteins are shown to be highly conserved proteins participating in pathways that control essential cellular processes, such as proliferation, differentiation and apoptosis and their differences with intra-connectors is highlighted. Many of these proteins are shown to possess multiple roles of distinct nature through their participation in different network modules, setting them apart from proteins that are simply ‘hubs’, i.e. proteins with many interaction partners but with a more specific biochemical role. PMID:25412367

Bennett, Laura; Kittas, Aristotelis; Liu, Songsong; Papageorgiou, Lazaros G.; Tsoka, Sophia

2014-01-01

344

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

PubMed Central

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

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

2014-01-01

345

ABC and IFC: Modules Detection Method for PPI Network  

PubMed Central

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

Lei, Xiujuan; Tian, Jianfang

2014-01-01

346

Acupuncture induce the different modulation patterns of the default mode network: an fMRI study  

NASA Astrophysics Data System (ADS)

According to Traditional Chinese Medicine (TCM) theory and certain clinical treatment reports, the sustained effects of acupuncture indeed exist, which may last several minutes or hours. Furthermore, increased attention has fallen on the sustained effects of acupuncture. Recently, it is reported that the sustained acupuncture effects may alter the default mode network (DMN). It raises interesting questions: whether the modulations of acupuncture effects to the DMN are still detected at other acupoints and whether the modulation patterns are different induced by different acupoints. In the present study, we wanted to investigate the questions. An experiment fMRI design was carried out on 36 subjects with the electroacupuncture stimulation (EAS) at the three acupoints: Guangming (GB37), Kunlun (BL60) and Jiaoxin (KI8) on the left leg. The data sets were analyzed by a data driven method named independent component analysis (ICA). The results indicated that the three acupoints stimulations may modulate the DMN. Moreover, the modulation patterns were distinct. We suggest the different modulation patterns on the DMN may attribute to the distinct functional effects of acupoints.

Liu, Peng; Qin, Wei; Tian, Jie; Zhang, Yi

2009-02-01

347

Inherent directionality explains the lack of feedback loops in empirical networks  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

348

Inherent directionality explains the lack of feedback loops in empirical networks  

PubMed Central

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. PMID:25531727

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

2014-01-01

349

Functional Modules Analysis Based on Coexpression Network in Pancreatic Ductal Adenocarcinoma.  

PubMed

Pancreatic ductal adenocarcinoma (PDAC) is the most common epithelial, exocrine pancreatic malignancy, accounting for more than 80 % of the malignant neoplasms of the pancreas. Although the molecular basis of pancreatic cancer is now better understood than ever before, there remains a long distance from being completely understood. In this study, we identified the differentially expressed genes (DEGs) in PDAC tissue compared with normal tissue and constructed a co-expression network by computing the pairwise correlation coefficient between the DEGs. We applied a statistical approach of MCODE to cluster genes in the coexpression network. Ten functional modules were identified in this network. Our results strongly suggest that dysregulations of immune response, homeostasis and cell adhesion may significantly contribute to the development and progression of PDAC. Results from this study will provide the groundwork for the understanding of PDAC. Future studies are needed to confirm some of the possible interactions suggested by this study. PMID:24185439

Shi, Baomin; Wang, Xiuyan; Han, Xujie; Liu, Pengfei; Wei, Weiwei; Li, Yan

2013-11-01

350

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

E-print Network

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

Patel, Aniruddh D.

351

Molecular Correlates of Cortical Network Modulation by Long-Term Sensory Experience in the Adult Rat Barrel Cortex  

ERIC Educational Resources Information Center

Modulation of cortical network connectivity is crucial for an adaptive response to experience. In the rat barrel cortex, long-term sensory stimulation induces cortical network modifications and neuronal response changes of which the molecular basis is unknown. Here, we show that long-term somatosensory stimulation by enriched environment…

Vallès, Astrid; Granic, Ivica; De Weerd, Peter; Martens, Gerard J. M.

2014-01-01

352

Delayed responses of analyte emission in a pulse-modulated direct-current argon arc at atmospheric pressure  

NASA Astrophysics Data System (ADS)

A pulse-modulated direct-current argon arc burning at atmospheric pressure has been investigated by analyzing temporally and spatially resolved analyte emission responses in a millisecond time domain. The arc current was a rectangular pulse modulated between 9 and 3.5 A with a modulation period of 250 ms and a low current interval of up to 50 ms. Both positive and negative step modulation in current strongly affected the analyte emission. Delayed responses of representative analytes with ionization energies ranging from 6.5 to 10 eV have been studied. Depending on the analyte ionization energy and the plasma zone observed, a sudden current change was in most cases followed by a line intensity increase. The magnitude of this increase is correlated with changes in the ionization-recombination balance, the extent of demixing and the gas dynamics processes invoked by a current modulation. For analytes with medium and low ionization energies a current drop is accompanied by a large increase in signal-to-background ratio, which opens up the possibility of the use of arc current modulation for sensitivity improvement.

Kuzmanovi?, M.; Savovi?, J.; Pavlovi?, M. S.; Stoiljkovi?, M.; Rankovi?, D.; Mom?ilovi?, M.

2010-12-01

353

Networks of genes modulating the pleiotropic drug response in Saccharomyces cerevisiae.  

PubMed

The pleiotropic drug response (PDR) or multidrug resistance (MDR) are cellular defence mechanisms present in all species to deal with potential toxicity from environmental small molecule toxins or bioactives. The rapid induction of MDR by xenobiotics in mammalian cells and PDR in budding yeast (S. cerevisiae) has been well studied but how pathway specificity is achieved across different structural classes of xenobiotics is not well understood. As a novel approach to this problem we investigated the genome-wide network of genes modulating the yeast PDR. Fluorescently-tagged ABC pumps Pdr5p-GFP and Yor1p-GFP were used as real-time reporters for the Pdr1p/Pdr3p controlled response. Using the yeast non-essential gene deletion set fifty-four gene deletions that suppressed up-regulation of reporter fluorescence to the cell surface in the presence of atorvastatin were identified by high content confocal automated microscopy. Secondary validation using spot dilution assays to known PDR substrates and Western blot assays of Pdr5p expression confirmed 26 genes able to modulate the PDR phenotype. By analysis of network connectivity, an additional 10 genes that fell below the primary screen cut-off were predicted to be involved in PDR and confirmed as above. The PDR modulating genes taken together were enriched in signalling (Rho-GTPase, MAPK), Mediator complexes, and chromatin modification (subunits of ADA and SAGA complexes). Many of the gene deletions cause extra sensitivity in ?pdr1?pdr3 strains strongly suggesting that there are alternative pathways to upregulate PDR, independently of Pdr1p/Pdr3p. We present here the first high-content microscopy screening for PDR modulators, and identify genes that are previously unsuspected regulators of PDR apparently contributing via network interactions. PMID:24201294

Yibmantasiri, Ploi; Bircham, Peter W; Maass, David R; Bellows, David S; Atkinson, Paul H

2014-01-01

354

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

PubMed

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. PMID:21935121

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

2011-08-29

355

A Topology Control Approach to Using Directional Antennas in Wireless Mesh Networks  

E-print Network

A Topology Control Approach to Using Directional Antennas in Wireless Mesh Networks Umesh Kumar Stony Brook, New York 11794-4400, U.S.A. Abstract-- Directional antennas in wireless mesh net- works can directional antennas with legacy MAC layer protocols such as IEEE 802.11. The idea is to use multiple

Gupta, Himanshu

356

Medium Access Control Protocols Using Directional Antennas in Ad Hoc Networks  

E-print Network

Medium Access Control Protocols Using Directional Antennas in Ad Hoc Networks Young-Bae Ko deliv- ery). To best utilize directional antennas, a suitable medium access control (MAC) protocol must Station, TX 77843-3112, USA youngbae,v0s5080,vaidya@cs.tamu.edu Abstract--Using directional antennas can

Vaidya, Nitin

357

SYN-DMAC: a directional MAC protocol for ad hoc networks with synchronization  

Microsoft Academic Search

Directional antenna has received intensive research interests in recent years due to its potential to increase communication efficiency and resilience to interference and jamming. In this paper, we provide a novel directional MAC protocol termed SYN-DMAC for ad hoc networks with synchronization. We demonstrate our proposed SYN-DMAC can efficiently address the major open problems in the directional MAC design such

Jianfeng Wang; Yuguang Fang; Dapeng Wu

2005-01-01

358

Networked Automotive Cyber Physical Systems: Applications, Challenges and Research Directions  

Microsoft Academic Search

Next-generation Automotive Cyber Physical Systems (CPS) are expected to be networked in the wireless domain. It is not un-reasonable to envisage thousands of automobiles with appropriate sensing, actuation and communication ability to network themselves wirelessly in the cyber world. A wide spectrum of applications are possible in this domain. In this article, we highlight three canonical applications, while illustrating their

Sriram Chellappan; Sanjay Kumar Madria

359

Direction finding in phased arrays with a neural network beamformer  

Microsoft Academic Search

Adaptive neural network processing of phased-array antenna received signals promises to decrease antenna manufacturing and maintenance costs while increasing mission uptime and performance between repair actions. We introduce one such neural network which performs aspects of digital beamforming with imperfectly manufactured, degraded, or failed antenna components. This paper presents measured results achieved with an adaptive radial basis function (ARBF) artificial

Hugh L. Southall; Jeffrey A. Simmers; T. H. O'Donnell

1995-01-01

360

Study of beam scan with variable linear polarization directions of antenna arrays using MMIC T/R modules  

NASA Astrophysics Data System (ADS)

The beam scan with variable linear polarization directions of antenna arrays using MMIC transmit-receive (T/R) modules is explored in this paper. It is shown that the beam scan and the polarizations of electric fields can be controlled simultaneously if the forms of module arrangement are chosen properly and the amplitudes and the phases of array excitation are determined by the method presented in this article. Moreover, the calculations of the amplitudes and the phases of array excitation are simplified greatly while using the bounded conditions properly, and the desired beam sweep rate is achieved.

Li, Zhen; Deng, Ciping

361

Gain modulation of synaptic inputs by network state in auditory cortex in vivo.  

PubMed

The cortical network recurrent circuitry generates spontaneous activity organized into Up (active) and Down (quiescent) states during slow-wave sleep or anesthesia. These different states of cortical activation gain modulate synaptic transmission. However, the reported modulation that Up states impose on synaptic inputs is disparate in the literature, including both increases and decreases of responsiveness. Here, we tested the hypothesis that such disparate observations may depend on the intensity of the stimulation. By means of intracellular recordings, we studied synaptic transmission during Up and Down states in rat auditory cortex in vivo. Synaptic potentials were evoked either by auditory or electrical (thalamocortical, intracortical) stimulation while randomly varying the intensity of the stimulus. Synaptic potentials evoked by the same stimulus intensity were compared in Up/Down states. Up states had a scaling effect on the stimulus-evoked synaptic responses: the amplitude of weaker responses was potentiated whereas that of larger responses was maintained or decreased with respect to the amplitude during Down states. We used a computational model to explore the potential mechanisms explaining this nontrivial stimulus-response relationship. During Up/Down states, there is different excitability in the network and the neuronal conductance varies. We demonstrate that the competition between presynaptic recruitment and the changing conductance might be the central mechanism explaining the experimentally observed stimulus-response relationships. We conclude that the effect that cortical network activation has on synaptic transmission is not constant but contingent on the strength of the stimulation, with a larger modulation for stimuli involving both thalamic and cortical networks. PMID:25673859

Reig, Ramon; Zerlaut, Yann; Vergara, Ramiro; Destexhe, Alain; Sanchez-Vives, Maria V

2015-02-11

362

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

363

Transcranial Direct Current Stimulation Modulates Human Color Discrimination in a Pathway-Specific Manner  

PubMed Central

Previous research showed that transcranial direct current stimulation (tDCS) can modulate visual cortex excitability. However, there is no experiment on the effects of tDCS on color perception to date. The present study aimed to investigate the effects of tDCS on color discrimination tasks. Fifteen healthy subjects (mean age of 25.6?±?4.4?years) were tested with Cambridge Color Test 2.0 (Trivector and ellipses protocols) and a Forced-choice Spatial Color Contrast Sensitivity task (vertical red-green sinusoidal grating) while receiving tDCS. Anodal, cathodal, and sham tDCS were delivered at Oz for 22?min using two square electrodes (25?cm2 with a current of 1.5?mA) in sessions separated by 7?days. Anodal tDCS significantly increased tritan sensitivity (p?

Costa, Thiago L.; Nagy, Balázs V.; Barboni, Mirella T. S.; Boggio, Paulo S.; Ventura, Dora F.

2012-01-01

364

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

PubMed

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

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

2006-11-01

365

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

PubMed Central

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

Trudell, James R.; Harris, R. Adron

2014-01-01

366

Low-cost and wideband frequency tunable optoelectronic oscillator based on a directly modulated distributed feedback semiconductor laser.  

PubMed

A novel scheme to realize a low-cost and wideband frequency tunable optoelectronic oscillator based on a directly modulated distributed feedback (DFB) semiconductor laser is proposed and experimentally demonstrated. In the proposed scheme, neither an external modulator nor an electrical filter is used, and no more than 25 dB of the electrical loop gain is required due to the high modulation efficiency of the relaxation oscillation frequency of the DFB laser. Microwave signals with frequency coarsely tuned from 3.77 to 8.75 GHz are generated by changing the bias current and operation temperature of the DFB laser. The single sideband phase noise of the generated 6.97 GHz microwave signal is measured to be -103.6 dBc/Hz at 10 kHz offset. PMID:24321940

Xiong, Jintian; Wang, Rong; Fang, Tao; Pu, Tao; Chen, Dalei; Lu, Lin; Xiang, Peng; Zheng, Jilin; Zhao, Jiyong

2013-10-15

367

Acupuncture Modulates Resting State Connectivity in Default and Sensorimotor Brain Networks  

PubMed Central

Previous studies have defined low-frequency, spatially consistent networks in resting fMRI data which may reflect functional connectivity. We sought to explore how a complex somatosensory stimulation, acupuncture, influences intrinsic connectivity in two of these networks: the default mode network (DMN) and sensorimotor network (SMN). We analyzed resting fMRI data taken before and after verum and sham acupuncture. Electrocardiography data was used to infer autonomic modulation through measures of heart rate variability (HRV). Probabilistic independent component analysis was used to separate resting fMRI data into DMN and SMN components. Following verum, but not sham, acupuncture there was increased DMN connectivity with pain (anterior cingulate cortex (ACC), periaqueductal gray), affective (amygdala, ACC), and memory (hippocampal formation, middle temporal gyrus) related brain regions. Furthermore, increased DMN connectivity with the hippocampal formation, a region known to support memory and interconnected with autonomic brain regions, was negatively correlated with acupuncture-induced increase in a sympathetic related HRV metric (LFu), and positively correlated with a parasympathetic related metric (HFu). Following verum, but not sham, acupuncture there was also increased SMN connectivity with pain related brain regions (ACC, cerebellum). We attribute differences between verum and sham acupuncture to more varied and stronger sensations evoked by verum acupuncture. Our results demonstrate for the first time that acupuncture can enhance the post-stimulation spatial extent of resting brain networks to include anti-nociceptive, memory, and affective brain regions. This modulation and sympathovagal response may relate to acupuncture analgesia and other potential therapeutic effects. PMID:18337009

Dhond, Rupali P.; Yeh, Calvin; Park, Kyungmo; Kettner, Norman; Napadow, Vitaly

2008-01-01

368

Making the Most Out of Direct-Access Network Attached Storage  

Microsoft Academic Search

The performance of high-speed network-attached stor- age applications is often limited by end-system over- head, caused primarily by memory copying and network protocol processing. In this paper, we examine alterna- tive strategies for reducing overhead in such systems. We consider optimizations to remote procedure call (RPC)-based data transfer using either remote direct memory access (RDMA) or network interface support for

Kostas Magoutis; Salimah Addetia; Alexandra Fedorova; Margo I. Seltzer

2003-01-01

369

NRC TLD direct radiation monitoring network: Progress report, October-December 1981. Technical report  

Microsoft Academic Search

The 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 facility sites throughout the country for the fourth quarter of 1981.

F. Costello; T. Thompson; L. Cohen

1982-01-01

370

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

PubMed Central

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

Tsanov, Marian; Chah, Ehsan; Noor, Muhammad S.; Egan, Catriona; Reilly, Richard B.; Aggleton, John P.; Erichsen, Jonathan T.; Vann, Seralynne D.

2014-01-01

371

On the Capacity of Multi-Channel Wireless Networks Using Directional Antennas  

E-print Network

of nodes, and traffic patterns can be optimally controlled. One approach to improve the network performanceOn the Capacity of Multi-Channel Wireless Networks Using Directional Antennas Hong-Ning Dai Kam consider that wireless nodes are equipped with only omnidirectional antennas, which cause high collisions

Wu, Dekai

372

Neural Networks 24 (2011) 99108 Contents lists available at ScienceDirect  

E-print Network

Neural Networks 24 (2011) 99­108 Contents lists available at ScienceDirect Neural Networks journal of a complex physical system for the purpose of control is a common problem in robotics. A typical system, this mapping can be inserted into the control loop of the robot, where appropriate motor commands are predicted

Schaal, Stefan

373

Direct Adaptive Control for Underactuated Mechatronic Systems using Fuzzy Systems and Neural Networks: A Pendubot Case  

Microsoft Academic Search

This paper describes the implementation of a direct adaptive control of a nonlinear underactuated mechatronics system known as the Pendubot robot using fuzzy systems and neural networks. A PD fuzzy controller is employed to control the two links motion from the free hanging position to the vertical position (the swing-up controller). Then, an intelligent adaptive fuzzy radial Gaussian neural networks

Murad Shibli

2006-01-01

374

Directional MAC approach for wireless body area networks.  

PubMed

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

Hussain, Md Asdaque; Alam, Md Nasre; Kwak, Kyung Sup

2011-01-01

375

Directional MAC Approach for Wireless Body Area Networks  

PubMed Central

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

Hussain, Md. Asdaque; Alam, Md. Nasre; Kwak, Kyung Sup

2011-01-01

376

Low voltage polymer network liquid crystal for infrared spatial light modulators.  

PubMed

We report a low-voltage and fast-response polymer network liquid crystal (PNLC) infrared phase modulator. To optimize device performance, we propose a physical model to understand the curing temperature effect on average domain size. Good agreement between model and experiment is obtained. By optimizing the UV curing temperature and employing a large dielectric anisotropy LC host, we have lowered the 2? phase change voltage to 22.8V at 1.55?m wavelength while keeping response time at about 1 ms. Widespread application of such a PNLC integrated into a high resolution liquid-crystal-on-silicon (LCoS) for infrared spatial light modulator is foreseeable. PMID:25836103

Peng, Fenglin; Xu, Daming; Chen, Haiwei; Wu, Shin-Tson

2015-02-01

377

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

PubMed

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

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

2012-02-22

378

Coherent site-directed transport in complex molecular networks: An effective Hamiltonian approach  

NASA Astrophysics Data System (ADS)

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.

Weissman, Shira; Peskin, Uri

2010-03-01

379

Novel Quantum Virtual Private Network Scheme for PON via Quantum Secure Direct Communication  

NASA Astrophysics Data System (ADS)

Two quantum secure direct communication (QSDC) protocols with quantum identification (QI) based on passive optical network (PON) architecture are proposed. One QSDC protocol can be implemented between two different optical network units just with simple configurations of PON by optical line terminal when they are in the same virtual private network after optical line terminal performing QI to the optical network units in the given PON architecture. The other QSDC protocol is also implemented between any two legitimated users in the virtual private network but with considerable reduction of workload of the optical line terminal. The security analysis shows that the proposed QSDC schemes with quantum identification are unconditionally secure and allow the legitimate users to exchange their secret information efficiently and to realize a quantum virtual private network in the PON networks ultimately.

Gong, Li-Hua; Liu, Ye; Zhou, Nan-Run

2013-09-01

380

Self-oscillating modulators for direct energy conversion audio power amplifiers  

E-print Network

to the loudspeaker output. It is therefore very interesting for the Active pulse modulated Transducer (AT) [5] intended for use in the new genera- tion of active loudspeaker systems and subwoofer units. This paper

381

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

Microsoft Academic Search

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

Paulo S. Boggio; Soroush Zaghi; Felipe Fregni

2009-01-01

382

A 1 Gbps 105.4 GHz Link with a Directly Modulated Photonic Integrated Dual Laser Source  

E-print Network

. 2009. [2] K. Ishigaki et al, “Direct Intensity Modulation and Wireless Data Transmission Characteristics of Terahertz-oscillating Resonant Tunnelling Diodes”, Electronics Letters, vol. 48, no. 10, p. 582, 2012. [3] P. H. Siegel, “Terahertz Technology... in the sub-terahertz range [1]. Such links will require compact and low-cost sub-THz transmitters operating at gigabits per second data rates. Furthermore, the carrier frequencies of the links should be widely tuneable if multi-channel communications...

Yang, Z.; Fice, M. J.; Balakier, K.; Wonfor, A.; Renaud, C.; Carpintero, G.; Kervella, G.; van Dijk, F.; Seeds, A. J.; Penty, R. V.; White, I. H.

2014-12-16

383

Rim1 modulates direct G-protein regulation of Cav2.2 channels Norbert Weiss1,2,  

E-print Network

1 Rim1 modulates direct G-protein regulation of Cav2.2 channels Norbert Weiss1,2,§ , Alejandro contributed equally to this work Key words: Calcium channel; Cav2.2 channel; N channel; beta subunit; Rim1; G-protein regulation of Cav2.2 channels. Activation of µ-opioid receptors expressed in HEK-293 cells along with Cav2

Paris-Sud XI, Université de

384

Common angiotensin receptor blockers may directly modulate the immune system via VDR, PPAR and CCR2b  

Microsoft Academic Search

BACKGROUND: There have been indications that common Angiotensin Receptor Blockers (ARBs) may be exerting anti-inflammatory actions by directly modulating the immune system. We decided to use molecular modelling to rapidly assess which of the potential targets might justify the expense of detailed laboratory validation. We first studied the VDR nuclear receptor, which is activated by the secosteroid hormone 1,25-dihydroxyvitamin-D. This

Trevor G Marshall; Robert E Lee; Frances E Marshall

2006-01-01

385

Variable Delay With Directly-Modulated R-SOA and Optical Filters for Adaptive Antenna Radio-Fiber Access  

Microsoft Academic Search

We present an all-optical adaptive-antenna radio over fiber transport system that uses proven, commercially-available components to effectively deliver standard-compliant optical signaling to adaptive multiantenna arrays for current and emerging radio technology implementations. The system is based on a directly-modulated reflective semiconductor amplifier (R-SOA) and exploits the interplay between transmission-line dispersion and tunable optical filtering to achieve flexible true time delay,

Kamau Prince; Marco Presi; Andrea Chiuchiarelli; Isabella Cerutti; Giampiero Contestabile; Idelfonso Tafur Monroy; Ernesto Ciaramella

2009-01-01

386

A 22 mW Bluetooth RF transceiver with direct RF modulation and on-chip IF filtering  

Microsoft Academic Search

A +2 dBm Bluetooth transceiver in 0.5 ?m SiGe BiCMOS consumes 22 mW at 2 V. The transmitter uses a ?? synthesizer and on-chip VCO to directly modulate the carrier and settles to 30 ppm within 180 ?s. The single low-IF I\\/O receiver uses a 7th-order complex IF filter with tuning, distributed AGC and digital PLL demodulation

N. Filiol; N. Birkett; J. Cherry; F. Balteanu; C. Gojocaru; A. Namdar; T. Pamir; K. Sheikh; G. Glandon; D. Payer; A. Swaminathan; R. Forbes; T. Riley; S. M. Alinoor; E. Macrobbie; M. Cloutier; S. Pipilos; T. Varelas

2001-01-01

387

60GHz direct-conversion gigabit modulator\\/demodulator on liquid-crystal polymer  

Microsoft Academic Search

In this paper, we demonstrate the first implementation of the integrated system-on-package (SOP) 60-GHz gigabit modulator and demodulator on liquid-crystal polymer (LCP). LCP provides an organic low-cost low dielectric-constant platform suitable for millimeter-wave passive design and packaging. Firstly, we demonstrate a 60-GHz planar bandpass filter and RF\\/baseband duplexer as the building blocks of the integrated module. Measurement results show ?3-dB

Saikat Sarkar; David A. Yeh; Stéphane Pinel; Joy Laskar

2006-01-01

388

FHT-based architectures for multicarrier modulation in direct detection and coherent optical systems  

Microsoft Academic Search

In this paper, flexible architectures based on the fast Hartley transform (FHT) for multicarrier modulation are presented. The analysis of performance using large size constellations shows that the proposed architectures furnish an alternative OFDM scheme for adaptive high-speed optical systems. Moreover, it is demonstrated that FHT modulation is suitable for cost-effective unamplified and ASE-dominated optical OFDM systems. Lowcomplexity PAPR reduction

Michela Svaluto Moreolo; Josep M. Fabrega; Laia Nadal; Gabriel Junyent

2011-01-01

389

Hybrid integrated bi-directional module using polymeric WDM filter based on multimode interference  

Microsoft Academic Search

We have presented a polymer wavelength division multiplexing (WDM) filter based on multimode interference and developed a hybrid integrated optical module for 1.31\\/1.55-mum bidirectional operation. The active devices were integrated on a silicon optical bench platform by flip-chip bonding technique. The polymer WDM filter chip using polymethylmethacrylate (PMMA) was fabricated by the hot embossing technique. This hybrid module exhibited a

Jung Woon Lim; Sung Hwan Hwang; Woo-Jin Lee; Tae Ho Lee; Myung Yong Jeong; Boo-Gyoun Kim; Byung Sup Rho

2009-01-01

390

Code sequence analysis of direct-sequence code-division multiple-access with M-ary FSK modulation  

NASA Astrophysics Data System (ADS)

This letter examines the correlation parameters of interest in a DS-CDMA communication network using M-ary FSK modulations. It is shown that the key multi-user interference parameters can be written in terms of cross-correlation functions with respect to a sinusoidal weighting function. Mean-squared interference is also studied and can be expressed in terms of the auto-correlation of the spreading sequences used. This is a generalization of a well-known result for binary DS-CDMA systems.

Miller, Scott L.

1994-02-01

391

Social Working Memory: Neurocognitive Networks and Directions for Future Research  

PubMed Central

Navigating the social world requires the ability to maintain and manipulate information about people’s beliefs, traits, and mental states. We characterize this capacity as social working memory (SWM). To date, very little research has explored this phenomenon, in part because of the assumption that general working memory systems would support working memory for social information. Various lines of research, however, suggest that social cognitive processing relies on a neurocognitive network (i.e., the “mentalizing network”) that is functionally distinct from, and considered antagonistic with, the canonical working memory network. Here, we review evidence suggesting that demanding social cognition requires SWM and that both the mentalizing and canonical working memory neurocognitive networks support SWM. The neural data run counter to the common finding of parametric decreases in mentalizing regions as a function of working memory demand and suggest that the mentalizing network can support demanding cognition, when it is demanding social cognition. Implications for individual differences in social cognition and pathologies of social cognition are discussed. PMID:23267340

Meyer, Meghan L.; Lieberman, Matthew D.

2012-01-01

392

A new method to measure directional modulation transfer function using sphere phantoms in a cone beam computed tomography system.  

PubMed

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

Lee, Changwoo; Baek, Jongduk

2015-04-01

393

Rapid decision threshold modulation by reward rate in a neural network  

PubMed Central

Optimal performance in two-alternative, free response decision making tasks can be achieved by the drift-diffusion model of decision making - which can be implemented in a neural network - as long as the threshold parameter of that model can be adapted to different task conditions. Evidence exists that people seek to maximize reward in such tasks by modulating response thresholds. However, few models have been proposed for threshold adaptation, and none have been implemented using neurally plausible mechanisms. Here we propose a neural network that adapts thresholds in order to maximize reward rate. The model makes predictions regarding optimal performance and provides a benchmark against which actual performance can be compared, as well as testable predictions about the way in which reward rate may be encoded by neural mechanisms. PMID:16987636

Simen, Patrick; Cohen, Jonathan D.; Holmes, Philip

2006-01-01

394

Wireless Multimedia Sensor Networks: Current Trends and Future Directions  

PubMed Central

Wireless Multimedia Sensor Networks (WMSNs) have emerged and shifted the focus from the typical scalar wireless sensor networks to networks with multimedia devices that are capable to retrieve video, audio, images, as well as scalar sensor data. WMSNs are able to deliver multimedia content due to the availability of inexpensive CMOS cameras and microphones coupled with the significant progress in distributed signal processing and multimedia source coding techniques. In this paper, we outline the design challenges of WMSNs, give a comprehensive discussion of the proposed architectures, algorithms and protocols for the different layers of the communication protocol stack for WMSNs, and evaluate the existing WMSN hardware and testbeds. The paper will give the reader a clear view of the state of the art at all aspects of this research area, and shed the light on its main current challenges and future trends. We also hope it will foster discussions and new research ideas among its researchers. PMID:22163571

Almalkawi, Islam T.; Zapata, Manel Guerrero; Al-Karaki, Jamal N.; Morillo-Pozo, Julian

2010-01-01

395

Wireless Multimedia Sensor Networks: current trends and future directions.  

PubMed

Wireless Multimedia Sensor Networks (WMSNs) have emerged and shifted the focus from the typical scalar wireless sensor networks to networks with multimedia devices that are capable to retrieve video, audio, images, as well as scalar sensor data. WMSNs are able to deliver multimedia content due to the availability of inexpensive CMOS cameras and microphones coupled with the significant progress in distributed signal processing and multimedia source coding techniques. In this paper, we outline the design challenges of WMSNs, give a comprehensive discussion of the proposed architectures, algorithms and protocols for the different layers of the communication protocol stack for WMSNs, and evaluate the existing WMSN hardware and testbeds. The paper will give the reader a clear view of the state of the art at all aspects of this research area, and shed the light on its main current challenges and future trends. We also hope it will foster discussions and new research ideas among its researchers. PMID:22163571

Almalkawi, Islam T; Zapata, Manel Guerrero; Al-Karaki, Jamal N; Morillo-Pozo, Julian

2010-01-01

396

Multiple monoaminergic modulation of posturo-locomotor network activity in the newborn rat spinal cord  

PubMed Central

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

Beliez, Lauriane; Barrière, Gregory; Bertrand, Sandrine S.; Cazalets, Jean-René

2014-01-01

397

Extrasynaptic Neurotransmission in the Modulation of Brain Function. Focus on the Striatal Neuronal–Glial Networks  

PubMed Central

Extrasynaptic neurotransmission is an important short distance form of volume transmission (VT) and describes the extracellular diffusion of transmitters and modulators after synaptic spillover or extrasynaptic release in the local circuit regions binding to and activating mainly extrasynaptic neuronal and glial receptors in the neuroglial networks of the brain. Receptor-receptor interactions in G protein-coupled receptor (GPCR) heteromers play a major role, on dendritic spines and nerve terminals including glutamate synapses, in the integrative processes of the extrasynaptic signaling. Heteromeric complexes between GPCR and ion-channel receptors play a special role in the integration of the synaptic and extrasynaptic signals. Changes in extracellular concentrations of the classical synaptic neurotransmitters glutamate and GABA found with microdialysis is likely an expression of the activity of the neuron-astrocyte unit of the brain and can be used as an index of VT-mediated actions of these two neurotransmitters in the brain. Thus, the activity of neurons may be functionally linked to the activity of astrocytes, which may release glutamate and GABA to the extracellular space where extrasynaptic glutamate and GABA receptors do exist. Wiring transmission (WT) and VT are fundamental properties of all neurons of the CNS but the balance between WT and VT varies from one nerve cell population to the other. The focus is on the striatal cellular networks, and the WT and VT and their integration via receptor heteromers are described in the GABA projection neurons, the glutamate, dopamine, 5-hydroxytryptamine (5-HT) and histamine striatal afferents, the cholinergic interneurons, and different types of GABA interneurons. In addition, the role in these networks of VT signaling of the energy-dependent modulator adenosine and of endocannabinoids mainly formed in the striatal projection neurons will be underlined to understand the communication in the striatal cellular networks. PMID:22675301

Fuxe, Kjell; Borroto-Escuela, Dasiel O.; Romero-Fernandez, Wilber; Diaz-Cabiale, Zaida; Rivera, Alicia; Ferraro, Luca; Tanganelli, Sergio; Tarakanov, Alexander O.; Garriga, Pere; Narváez, José Angel; Ciruela, Francisco; Guescini, Michele; Agnati, Luigi F.

2012-01-01

398

Criticality of forcing directions on the fragmentation and resilience of grid networks  

PubMed Central

A general framework for probing the dynamic evolution of spatial networks comprised of nodes applying force amongst each other is presented. Aside from the already reported magnitude of forces and elongation thresholds, we show that preservation of links in a network is also crucially dependent on how nodes are connected and how edges are directed. We demonstrate that the time it takes for the networks to reach its equilibrium network structure follows a robust power law relationship consistent with Basquin's law with an exponent that can be tuned by changing only the force directions. Further, we illustrate that networks with different connection structures, node positions and edge directions have different Basquin's exponent which can be used to distinguish spatial directed networks from each other. Using an extensive waiting time simulation that spans up to over 16 orders of magnitude, we establish that the presence of memory combined with the scale-free bursty dynamics of edge breaking at the micro level leads to the evident macroscopic power law distribution of network lifetime. PMID:25160061

Abundo, Cheryl; Monterola, Christopher; Legara, Erika Fille

2014-01-01

399

Criticality of forcing directions on the fragmentation and resilience of grid networks.  

PubMed

A general framework for probing the dynamic evolution of spatial networks comprised of nodes applying force amongst each other is presented. Aside from the already reported magnitude of forces and elongation thresholds, we show that preservation of links in a network is also crucially dependent on how nodes are connected and how edges are directed. We demonstrate that the time it takes for the networks to reach its equilibrium network structure follows a robust power law relationship consistent with Basquin's law with an exponent that can be tuned by changing only the force directions. Further, we illustrate that networks with different connection structures, node positions and edge directions have different Basquin's exponent which can be used to distinguish spatial directed networks from each other. Using an extensive waiting time simulation that spans up to over 16 orders of magnitude, we establish that the presence of memory combined with the scale-free bursty dynamics of edge breaking at the micro level leads to the evident macroscopic power law distribution of network lifetime. PMID:25160061

Abundo, Cheryl; Monterola, Christopher; Legara, Erika Fille

2014-01-01

400

Electro-acupuncture at different acupoints modulating the relative specific brain functional network  

NASA Astrophysics Data System (ADS)

Objective: The specific brain effects of acupoint are important scientific concern in acupuncture. However, previous acupuncture fMRI studies focused on acupoints in muscle layer on the limb. Therefore, researches on acupoints within connective tissue at trunk are warranted. Material and Methods: Brain effects of acupuncture on abdomen at acupoints Guanyuan (CV4) and Zhongwan (CV12) were tested using fMRI on 21 healthy volunteers. The data acquisition was performed at resting state, during needle retention, electroacupuncture (EA) and post-EA resting state. Needling sensations were rated after every electroacupuncture (EA) procedure. The needling sensations and the brain functional activity and connectivity were compared between CV4 and CV12 using SPSS, SPM2 and the local and remote connectivity maps. Results and conclusion: EA at CV4 and CV12 induced apparent deactivation effects in the limbic-paralimbic-neocortical network. The default mode of the brain was modified by needle retention and EA, respectively. The functional brain network was significantly changed post EA. However, the minor differences existed between these two acupoints. The results demonstrated similarity between functional brain network mode of acupuncture modulation and functional circuits of emotional and cognitive regulation. Acupuncture may produce analgesia, anti-anxiety and anti-depression via the limbic-paralimbic-neocortical network (LPNN).

Fang, Jiliang; Wang, Xiaoling; Wang, Yin; Liu, Hesheng; Hong, Yang; Liu, Jun; Zhou, Kehua; Wang, Lei; Xue, Chao; Song, Ming; Liu, Baoyan; Zhu, Bing

2010-11-01

401

Direct Information Exchange in Wireless Networks: A Coding Perspective  

E-print Network

The rise in the popularity of smartphones such as Blackberry and iPhone creates a strain on the world's mobile networks. The extensive use of these mobile devices leads to increasing congestion and higher rate of node failures. This increasing...

Ozgul, Damla

2011-10-21

402

Scalable, Absolute Position Recovery for OmniDirectional Image Networks  

Microsoft Academic Search

We describe a linear-time algorithm that recovers abso- lute camera positions for networks of thousands of terres- trial images spanning hundreds of meters, in outdoor urban scenes, under uncontrolled lighting. The algorithm requires no human input or interaction. For real data, it recovers camera pose globally consistent on average to roughly five centimeters, or about four pixels of epipolar alignment.

Matthew E. Antone; Seth J. Teller

2001-01-01

403

Scalable Extrinsic Calibration of OmniDirectional Image Networks  

Microsoft Academic Search

We describe a linear-time algorithm that recovers absolute camera orientations and positions, along with uncertainty estimates, for networks of terrestrial image nodes spanning hundreds of meters in outdoor urban scenes. The algorithm produces pose estimates globally consistent to roughly 0:1 (2 milliradians) and 5 centimeters on average, or about four pixels of epipolar alignment. We assume that adjacent nodes observe

Matthew E. Antone; Seth J. Teller

2002-01-01

404

All-optical virtual private network system in OFDM based long-reach PON using RSOA re-modulation technique  

NASA Astrophysics Data System (ADS)

We propose an all-optical virtual private network (VPN) system in an orthogonal frequency division multiplexing (OFDM) based long reach PON (LR-PON). In the optical access network field, technologies based on fundamental upstream (U/S) and downstream (D/S) have been actively researched to accommodate explosion of data capacity. However, data transmission among the end users which is arisen from cloud computing, file-sharing and interactive game takes a large weight inside of internet traffic. Moreover, this traffic is predicted to increase more if Internet of Things (IoT) services are activated. In a conventional PON, VPN data is transmitted through ONU-OLT-ONU via U/S and D/S carriers. It leads to waste of bandwidth and energy due to O-E-O conversion in the OLT and round-trip propagation between OLT and remote node (RN). Also, it causes inevitable load to the OLT for electrical buffer, scheduling and routing. The network inefficiency becomes more critical in a LR-PON which has been researched as an effort to reduce CAPEX and OPEX through metro-access consolidation. In the proposed system, the VPN data is separated from conventional U/S and re-modulated on the D/S carrier by using RSOA in the ONUs to avoid bandwidth consumption of U/S and D/S unlike in previously reported system. Moreover, the transmitted VPN data is re-directed to the ONUs by wavelength selective reflector device in the RN without passing through the OLT. Experimental demonstration for the VPN communication system in an OFDM based LR-PON has been verified.

Kim, Chang-Hun; Jung, Sang-Min; Kang, Su-Min; Han, Sang-Kook

2015-01-01

405

Wdpcp, a PCP Protein Required for Ciliogenesis, Regulates Directional Cell Migration and Cell Polarity by Direct Modulation of the Actin Cytoskeleton  

PubMed Central

Planar cell polarity (PCP) regulates cell alignment required for collective cell movement during embryonic development. This requires PCP/PCP effector proteins, some of which also play essential roles in ciliogenesis, highlighting the long-standing question of the role of the cilium in PCP. Wdpcp, a PCP effector, was recently shown to regulate both ciliogenesis and collective cell movement, but the underlying mechanism is unknown. Here we show Wdpcp can regulate PCP by direct modulation of the actin cytoskeleton. These studies were made possible by recovery of a Wdpcp mutant mouse model. Wdpcp-deficient mice exhibit phenotypes reminiscent of Bardet–Biedl/Meckel–Gruber ciliopathy syndromes, including cardiac outflow tract and cochlea defects associated with PCP perturbation. We observed Wdpcp is localized to the transition zone, and in Wdpcp-deficient cells, Sept2, Nphp1, and Mks1 were lost from the transition zone, indicating Wdpcp is required for recruitment of proteins essential for ciliogenesis. Wdpcp is also found in the cytoplasm, where it is localized in the actin cytoskeleton and in focal adhesions. Wdpcp interacts with Sept2 and is colocalized with Sept2 in actin filaments, but in Wdpcp-deficient cells, Sept2 was lost from the actin cytoskeleton, suggesting Wdpcp is required for Sept2 recruitment to actin filaments. Significantly, organization of the actin filaments and focal contacts were markedly changed in Wdpcp-deficient cells. This was associated with decreased membrane ruffling, failure to establish cell polarity, and loss of directional cell migration. These results suggest the PCP defects in Wdpcp mutants are not caused by loss of cilia, but by direct disruption of the actin cytoskeleton. Consistent with this, Wdpcp mutant cochlea has normal kinocilia and yet exhibits PCP defects. Together, these findings provide the first evidence, to our knowledge, that a PCP component required for ciliogenesis can directly modulate the actin cytoskeleton to regulate cell polarity and directional cell migration. PMID:24302887

Cui, Cheng; Chatterjee, Bishwanath; Lozito, Thomas P.; Zhang, Zhen; Francis, Richard J.; Yagi, Hisato; Swanhart, Lisa M.; Sanker, Subramaniam; Francis, Deanne; Yu, Qing; San Agustin, Jovenal T.; Puligilla, Chandrakala; Chatterjee, Tania; Tansey, Terry; Liu, Xiaoqin; Kelley, Matthew W.; Spiliotis, Elias T.; Kwiatkowski, Adam V.; Tuan, Rocky; Pazour, Gregory J.; Hukriede, Neil A.; Lo, Cecilia W.

2013-01-01

406

Optimizing Environmental Monitoring Networks with Direction-Dependent Distance Thresholds.  

ERIC Educational Resources Information Center

In the direction-dependent approach to location modeling developed herein, the distance within which a point of demand can find service from a facility depends on direction of measurement. The utility of the approach is illustrated through an application to groundwater remediation. (Author/MDH)

Hudak, Paul F.

1993-01-01

407

Early appraisal of the fixation probability in directed networks  

NASA Astrophysics Data System (ADS)

In evolutionary dynamics, the probability that a mutation spreads through the whole population, having arisen from a single individual, is known as the fixation probability. In general, it is not possible to find the fixation probability analytically given the mutant’s fitness and the topological constraints that govern the spread of the mutation, so one resorts to simulations instead. Depending on the topology in use, a great number of evolutionary steps may be needed in each of the simulation events, particularly in those that end with the population containing mutants only. We introduce two techniques to accelerate the determination of the fixation probability. The first one skips all evolutionary steps in which the number of mutants does not change and thereby reduces the number of steps per simulation event considerably. This technique is computationally advantageous for some of the so-called layered networks. The second technique, which is not restricted to layered networks, consists of aborting any simulation event in which the number of mutants has grown beyond a certain threshold value and counting that event as having led to a total spread of the mutation. For advantageous mutations in large populations and regardless of the network’s topology, we demonstrate, both analytically and by means of simulations, that using a threshold of about [N/(r-1)]1/4 mutants, where N is the number of simulation events and r is the ratio of the mutants’ fitness to that of the remainder of the population, leads to an estimate of the fixation probability that deviates in no significant way from that obtained from the full-fledged simulations. We have observed speedups of two orders of magnitude for layered networks with 10000 nodes.

Barbosa, Valmir C.; Donangelo, Raul; Souza, Sergio R.

2010-10-01

408

Exploration and Modulation of Brain Network Interactions with Noninvasive Brain Stimulation in Combination with Neuroimaging  

PubMed Central

Much recent work in systems neuroscience has focused on how dynamic interactions between different cortical regions underlie complex brain functions such as motor coordination, language, and emotional regulation. Various studies using neuroimaging and neurophysiologic techniques have suggested that in many neuropsychiatric disorders, these dynamic brain networks are dysregulated. Here we review the utility of combined noninvasive brain stimulation and neuroimaging approaches towards greater understanding of dynamic brain networks in health and disease. Brain stimulation techniques, such as transcranial magnetic stimulation and transcranial direct current stimulation, use electromagnetic principles to noninvasively alter brain activity, and induce focal but also network effects beyond the stimulation site. When combined with brain imaging techniques such as functional MRI, PET and EEG, these brain stimulation techniques enable a causal assessment of the interaction between different network components, and their respective functional roles. The same techniques can also be applied to explore hypotheses regarding the changes in functional connectivity that occur during task performance and in various disease states such as stroke, depression and schizophrenia. Finally, in diseases characterized by pathologic alterations in either the excitability within a single region or in the activity of distributed networks, such techniques provide a potential mechanism to alter cortical network function and architectures in a beneficial manner. PMID:22429242

Shafi, Mouhsin M.; Westover, M. Brandon; Fox, Michael D.; Pascual-Leone, Alvaro

2012-01-01

409

Double-ring network model of the head-direction system Xiaohui Xie,1,  

E-print Network

Double-ring network model of the head-direction system Xiaohui Xie,1, * Richard H. R. Hahnloser,1 2002; published 9 October 2002 In the head-direction system, the orientation of an animal's head in space is encoded internally by persistent activities of a pool of cells whose firing rates are tuned

Xie, Xiaohui Sunney

410

Medium Access Control Protocols using Directional Antennas in Ad Hoc Networks  

Microsoft Academic Search

Using directional antennas can be beneficial for wireless ad hoc networks consisting of a collection of wireless hosts. To best utilize di- rectional antennas, a suitable Medium Access Control (MAC) protocol must be designed. Current MAC protocols, such as the IEEE 802.11 standard, do not benefit when using directional antennas, because these protocols have been designed for omnidirectional antennas. In

Young-bae Ko; Vinaychandra Shankarkumar; Nitin H. Vaidya

2000-01-01

411

Minimum-Energy Broadcast Using Practical Directional Antennas in All-Wireless Networks  

E-print Network

Minimum-Energy Broadcast Using Practical Directional Antennas in All-Wireless Networks Sabyasachi transmission has been studied and shown to be NP-complete for omnidirectional antennas. In this paper, we investigate the minimum-energy broadcast problem under a wide spectrum of directional antenna models

Hu, Y. Charlie

412

Medium Access Control Protocols Using Directional Antennas in Ad Hoc Networks  

Microsoft Academic Search

Using directional antennas can be beneficial for wireless adhoc networks consisting of a collection of wireless hosts. To best utilize directionalantennas, a suitable Medium Access Control (MAC) protocol mustbe designed. Current MAC protocols, such as the IEEE 802.11 standard, donot benefit when using directional antennas, because these protocols havebeen designed for omnidirectional antennas. In this paper, we attempt todesign new

Young-bae Ko; Vinaychandra Shankarkumar

1999-01-01

413

Minimum-Energy Broadcast Using Practical Directional Antennas in All-Wireless Networks  

E-print Network

Minimum-Energy Broadcast Using Practical Directional Antennas in All-Wireless Networks Sabyasachi and shown to be NP-complete for omnidirectional antennas. In this paper, we investigate the minimum-energy broadcast problem under a wide spectrum of directional antenna models, including sectored antennas

Li, Xiang-Yang

414

Study on application of the asynchronous motor direct torque control based on neural network  

Microsoft Academic Search

A new improved direct torque control (DTC) method is proposed for an asynchronous motor direct torque control system, in this paper, after studying and analyzing model reference adaptive control (MRAC) and adaptive linear neural network motor speed identification. This method adopts an MRAC identification model with high-pass filter part and low-pass filter part. Based on this condition, we design a

Xiucheng Dong; Guijuan Wang; Jun Wang; Xiaoxiao Zhao

2005-01-01

415

Future Directions in Access Control for Online Social Networks Adnan Ahmad and Brian Whitworth  

E-print Network

Future Directions in Access Control for Online Social Networks Adnan Ahmad and Brian Whitworth research directions for access control models in the context of OSN. Keywords: Access control, Delegation Institute of Information and Mathematical Sciences Massey University, Auckland, New Zealand Abstract. Access

Whitworth, Brian

416

Detecting Blackhole and Volcano Patterns in Directed Networks Zhongmou Li1  

E-print Network

Detecting Blackhole and Volcano Patterns in Directed Networks Zhongmou Li1 , Hui Xiong1 , Yanchi and volcano patterns in a large directed graph. Specifically, a blackhole pattern is a group which is made. In contrast, a volcano pattern is a group which only has outlinks to the rest nodes in the graph. Both

Xiong, Hui

417

A Neural Network Model for Detecting the Direction of EgoMotion using  

E-print Network

A Neural Network Model for Detecting the Direction of Ego­Motion using Optical Flow and Extra in the optical flow field to perform this task. Previous research has ignored extra­ocular information which can optical flow field and extra­retinal information to detect the direction of ego­motion. My approach

Mirghafori, N. Nikki

418

Directed diffusion: a scalable and robust communication paradigm for sensor networks  

Microsoft Academic Search

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

Chalermek Intanagonwiwat; Ramesh Govindan; Deborah Estrin

2000-01-01

419

Energy Efficient Sleep Scheduling based on Moving Directions in Target Tracking Sensor Network  

E-print Network

Energy Efficient Sleep Scheduling based on Moving Directions in Target Tracking Sensor Network Bo presents a target direction-based sleep scheduling algorithm (TDSS) to enhance the energy efficiency and the sleep scheduling, achieves the energy efficiency but suffers little performance loss. For the sleep

Ravindran, Binoy

420

UpConversion of IQ Modulated Subcarriers with Dispersive Fiber for 60 GHz Radio-Over-Fiber Networks  

Microsoft Academic Search

An optical microwave mixing technique based on optical phase modulation and fiber chromatic dispersion is investigated for up-conversion of IQ modulated microwave subcarriers. Experiments with analog signals have validated up-conversion theory. Error Vector Magnitude measurements have shown low penalty induced by optical microwave up-conversion process on QAM signals within the 10 GHz band. For future radio-over-fiber networks, optical microwave up-conversion

Y. Le Guennec; Ghislaine Maury; Beatrice Cabon; J. Yao

2006-01-01

421

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

E-print Network

communications technologies, and the software for pervasive or ubiquitous computing systems. Case study, and of modular approaches to the rapid prototyping of hardware and software for such systems. * Use professional? No Module Credits: 10 Module Management Information Module Leader Name Haitao Ye Email Address h

Neirotti, Juan Pablo

422

Directionality in hyperbrain networks discriminates between leaders and followers in guitar duets.  

PubMed

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

Sänger, Johanna; Müller, Viktor; Lindenberger, Ulman

2013-01-01

423

Directionality in hyperbrain networks discriminates between leaders and followers in guitar duets  

PubMed Central

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

Sänger, Johanna; Müller, Viktor; Lindenberger, Ulman

2013-01-01

424

Phospho-?Np63?/microRNA network modulates epigenetic regulatory enzymes in squamous cell carcinomas  

PubMed Central

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

Ratovitski, Edward A

2014-01-01

425

Biological network module-based model for the analysis of differential expression in shotgun proteomics.  

PubMed

Protein differential expression analysis plays an important role in the understanding of molecular mechanisms as well as the pathogenesis of complex diseases. With the rapid development of mass spectrometry, shotgun proteomics using spectral counts has become a prevailing method for the quantitative analysis of complex protein mixtures. Existing methods in differential proteomics expression typically carry out analysis at the single-protein level. However, it is well-known that proteins interact with each other when they function in biological processes. In this study, focusing on biological network modules, we proposed a negative binomial generalized linear model for differential expression analysis of spectral count data in shotgun proteomics. In order to show the efficacy of the model in protein expression analysis at the level of protein modules, we conducted two simulation studies using synthetic data sets generated from theoretical distribution of count data and a real data set with shuffled counts. Then, we applied our method to a colorectal cancer data set and a nonsmall cell lung cancer data set. When compared with single-protein analysis methods, the results showed that module-based statistical model which takes account of the interactions among proteins led to more effective identification of subtle but coordinated changes at the systems level. PMID:25327611

Xu, Jia; Wang, Lily; Li, Jing

2014-12-01

426

The timing and directional connectivity of human frontoparietal and ventral visual attention networks in emotional scene perception.  

PubMed

Electrocortical and hemodynamic measures reliably identify enhanced activity in the ventral and dorsal visual cortices during the perception of emotionally arousing versus neutral images, an effect that may reflect direc