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1

Directed network modules  

NASA Astrophysics Data System (ADS)

A search technique locating network modules, i.e. internally densely connected groups of nodes in directed networks is introduced by extending the clique percolation method originally proposed for undirected networks. After giving a suitable definition for directed modules we investigate their percolation transition in the Erdos Rényi graph both analytically and numerically. We also analyse four real-world directed networks, including Google's own web-pages, an email network, a word association graph and the transcriptional regulatory network of the yeast Saccharomyces cerevisiae. The obtained directed modules are validated by additional information available for the nodes. We find that directed modules of real-world graphs inherently overlap and the investigated networks can be classified into two major groups in terms of the overlaps between the modules. Accordingly, in the word-association network and Google's web-pages, overlaps are likely to contain in-hubs, whereas the modules in the email and transcriptional regulatory network tend to overlap via out-hubs.

Palla, Gergely; Farkas, Illés J.; Pollner, Péter; Derényi, Imre; Vicsek, Tamás

2007-06-01

2

Influence of current pulse shape on directly modulated system performance in metro area optical networks  

NASA Astrophysics Data System (ADS)

Due to the fact that a metro network market is very cost sensitive, direct modulated schemes appear attractive. In this paper a CWDM (Coarse Wavelength Division Multiplexing) system is studied in detail by means of an Optical Communication System Design Software; a detailed study of the modulated current shape (exponential, sine and gaussian) for 2.5 Gb/s CWDM Metropolitan Area Networks is performed to evaluate its tolerance to linear impairments such as signal-to-noise-ratio degradation and dispersion. Point-to-point links are investigated and optimum design parameters are obtained. Through extensive sets of simulation results, it is shown that some of these shape pulses are more tolerant to dispersion when compared with conventional gaussian shape pulses. In order to achieve a low Bit Error Rate (BER), different types of optical transmitters are considered including strongly adiabatic and transient chirp dominated Directly Modulated Lasers (DMLs). We have used fibers with different dispersion characteristics, showing that the system performance depends, strongly, on the chosen DML-fiber couple.

Campos, Carmina del Rio; Horche, Paloma R.; Martin-Minguez, Alfredo

2011-03-01

3

Module bay with directed flow  

DOEpatents

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

Torczynski, John R. (Albuquerque, NM)

2001-02-27

4

Weighted network modules  

NASA Astrophysics Data System (ADS)

The inclusion of link weights into the analysis of network properties allows a deeper insight into the (often overlapping) modular structure of real-world webs. We introduce a clustering algorithm clique percolation method with weights (CPMw) for weighted networks based on the concept of percolating k-cliques with high enough intensity. The algorithm allows overlaps between the modules. First, we give detailed analytical and numerical results about the critical point of weighted k-clique percolation on (weighted) Erdos Rényi graphs. Then, for a scientist collaboration web and a stock correlation graph we compute three-link weight correlations and with the CPMw the weighted modules. After reshuffling link weights in both networks and computing the same quantities for the randomized control graphs as well, we show that groups of three or more strong links prefer to cluster together in both original graphs.

Farkas, Illés; Ábel, Dániel; Palla, Gergely; Vicsek, Tamás

2007-06-01

5

Flux modules in metabolic networks.  

PubMed

The huge number of elementary flux modes in genome-scale metabolic networks makes analysis based on elementary flux modes intrinsically difficult. However, it has been shown that the elementary flux modes with optimal yield often contain highly redundant information. The set of optimal-yield elementary flux modes can be compressed using modules. Up to now, this compression was only possible by first enumerating the whole set of all optimal-yield elementary flux modes. We present a direct method for computing modules of the thermodynamically constrained optimal flux space of a metabolic network. This method can be used to decompose the set of optimal-yield elementary flux modes in a modular way and to speed up their computation. In addition, it provides a new form of coupling information that is not obtained by classical flux coupling analysis. We illustrate our approach on a set of model organisms. PMID:24141488

Müller, Arne C; Bockmayr, Alexander

2014-11-01

6

NDBC's digital directional wave module  

Microsoft Academic Search

The National Data Buoy Center (NDBC) has developed a compact, low power, directional wave measurement system called the Digital Directional Wave Module (DDWM). It represents the latest advance in NDBC's 30-year history of producing wave measurement systems. The DDWM consists of embedded electronics; a commercial off-the-shelf (COTS) motion sensor; custom, embedded software and hardware; and a mounting plate. The COTS

Chung-Chu Teng; Richard Bouchard; Rodney Riley; Theodore Mettlach; Richard Dinoso; Joel Chaffin

2009-01-01

7

2.5 Gbps Direct Modulation of Reflective Semiconductor Optical Amplifier for Wavelength Division Multiplexing Passive Optical Network Colourless Sources  

NASA Astrophysics Data System (ADS)

We present fabrication results of a planar-buried-heterostructure (PBH)-type reflective semiconductor optical amplifier (R-SOA). Active and passive waveguides forming R-SOA were integrated by butt-coupling. The optical gain and 3 dB amplified spontaneous emission (ASE) bandwidth were about 25 dB and 35 nm, respectively. The polarization-dependent gain (PDG) was about 0.8 dB. We could obtain a clearly opened eye diagram under 2.5 Gbps direct modulation. In a bit-error-rate (BER) test, the receiver sensitivity and power penalty after 20 km transmission were about -27 dBm and 2 dB, respectively.

Kim, Dong Churl; Choi, Byung-Seok; Kim, Hyun-Soo; Kim, Ki Soo; Yoon, Ki-Hong; Kwon, O-Kyun; Oh, Dae-Kon

2009-12-01

8

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

2014-07-30

9

Module identification in bipartite and directed networks Roger Guimer, Marta Sales-Pardo, and Lus A. Nunes Amaral  

E-print Network

Plant-animal mutualistic networks 21,22 , one set represents animal species and the other set represents plant species. Links indicate mutualistic relationships between ani- mals and plants for example

Fienberg, Stephen E.

10

Dynamic behaviors in directed networks  

SciTech Connect

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

Park, Sung Min [Center of Complex Systems, Samsung Economic Research Institute, Seoul 140-702 (Korea, Republic of); Kim, Beom Jun [Department of Physics, BK21 Physics Research Division, and Institute of Basic Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

2006-08-15

11

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

12

Is My Network Module Preserved and Reproducible?  

Microsoft Academic Search

In many applications, one is interested in determining which of the properties of a network module change across conditions. For example, to validate the existence of a module, it is desirable to show that it is reproducible (or preserved) in an independent test network. Here we study several types of network preservation statistics that do not require a module assignment

Peter Langfelder; Rui Luo; Michael C. Oldham; Steve Horvath; Philip E. Bourne

2011-01-01

13

A mean field neural network for hierarchical module placement  

NASA Technical Reports Server (NTRS)

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

Unaltuna, M. Kemal; Pitchumani, Vijay

1992-01-01

14

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; Lu, Linyuan; Wang, Wen-Qiang; Zhou, Tao

2013-01-01

15

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

16

Is My Network Module Preserved and Reproducible?  

PubMed Central

In many applications, one is interested in determining which of the properties of a network module change across conditions. For example, to validate the existence of a module, it is desirable to show that it is reproducible (or preserved) in an independent test network. Here we study several types of network preservation statistics that do not require a module assignment in the test network. We distinguish network preservation statistics by the type of the underlying network. Some preservation statistics are defined for a general network (defined by an adjacency matrix) while others are only defined for a correlation network (constructed on the basis of pairwise correlations between numeric variables). Our applications show that the correlation structure facilitates the definition of particularly powerful module preservation statistics. We illustrate that evaluating module preservation is in general different from evaluating cluster preservation. We find that it is advantageous to aggregate multiple preservation statistics into summary preservation statistics. We illustrate the use of these methods in six gene co-expression network applications including 1) preservation of cholesterol biosynthesis pathway in mouse tissues, 2) comparison of human and chimpanzee brain networks, 3) preservation of selected KEGG pathways between human and chimpanzee brain networks, 4) sex differences in human cortical networks, 5) sex differences in mouse liver networks. While we find no evidence for sex specific modules in human cortical networks, we find that several human cortical modules are less preserved in chimpanzees. In particular, apoptosis genes are differentially co-expressed between humans and chimpanzees. Our simulation studies and applications show that module preservation statistics are useful for studying differences between the modular structure of networks. Data, R software and accompanying tutorials can be downloaded from the following webpage: http://www.genetics.ucla.edu/labs/horvath/CoexpressionNetwork/ModulePreservation. PMID:21283776

Langfelder, Peter; Luo, Rui; Oldham, Michael C.; Horvath, Steve

2011-01-01

17

Direct Current Series Circuits: An Educational Module.  

ERIC Educational Resources Information Center

This module was developed as remedial material for physics students who have difficulty understanding concepts of circuits and calculating resistances, and voltage drops and currents. Lists of prerequisite skills and instructional objectives are followed by a pretest (with answers). Students are directed to the subject matter in the module based…

Sturgess, Keith

18

Notational usage modulates attention networks in binumerates.  

PubMed

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

19

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

20

Real time network modulation for intractable epilepsy Behnaam Aazhang  

E-print Network

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

Aazhang, Behnaam

21

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

Doug MacGugan

2013-08-22

22

Modulation for emergent networks: serotonin and dopamine.  

PubMed

In autonomous learning, value-sensitive experiences can improve the efficiency of learning. A learning network needs be motivated so that the limited computational resources and the limited lifetime are devoted to events that are of high value for the agent to compete in its environment. The neuromodulatory system of the brain is mainly responsible for developing such a motivation system. Although reinforcement learning has been extensively studied, many existing models are symbolic whose internal nodes or modules have preset meanings. Neural networks have been used to automatically generate internal emergent representations. However, modeling an emergent motivational system for neural networks is still a great challenge. By emergent, we mean that the internal representations emerge autonomously through interactions with the external environments. This work proposes a generic emergent modulatory system for emergent networks, which includes two subsystems - the serotonin system and the dopamine system. The former signals a large class of stimuli that are intrinsically aversive (e.g., stress or pain). The latter signals a large class of stimuli that are intrinsically appetitive (e.g., pleasure or sweet). We experimented with this motivational system for two settings. The first is a visual recognition setting to investigate how such a system can learn through interactions with a teacher, who does not directly give answers, but only punishments and rewards. The second is a setting for wandering in the presence of a friend and a foe. PMID:23294763

Weng, Juyang; Paslaski, Stephen; Daly, James; VanDam, Courtland; Brown, Jacob

2013-05-01

23

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

24

Dense module enumeration in biological networks.  

PubMed

Automatic discovery of functional complexes from protein interaction data is a rewarding but challenging problem. While previous approaches use approximations to extract dense modules, our approach exactly solves the problem of dense module enumeration. Furthermore, constraints from additional information sources such as gene expression and phenotype data can be integrated, so we can systematically detect dense modules with interesting profiles. Given a weighted protein interaction network, our method discovers all protein sets that satisfy a user-defined minimum density threshold. We employ a reverse search strategy, which allows us to exploit the density criterion in an efficient way. PMID:23192536

Tsuda, Koji; Georgii, Elisabeth

2013-01-01

25

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

26

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

27

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

PubMed

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. PMID:25381548

Krishnan, J; Mois, Kristina; Suwanmajo, Thapanar

2014-11-01

28

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

NASA Astrophysics Data System (ADS)

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.; Mois, Kristina; Suwanmajo, Thapanar

2014-11-01

29

Network management, status and directions  

SciTech Connect

It has been said that the network is the system''. This implies providing levels of service, reliability, predictability and availability that are commensurate with or better than those that individual computers provide today. To provide this requires integrated network management for interconnected networks of heterogeneous devices covering both the local campus and across the world and spanning many administrative domains. This talk will review the status of existing tools to address management for networks. It draws on experience from both within and outside the HEP community.

Cottrell, R.L.A.; Streater, T.C.

1992-09-01

30

Network management, status and directions  

SciTech Connect

It has been said that the ``network is the system``. This implies providing levels of service, reliability, predictability and availability that are commensurate with or better than those that individual computers provide today. To provide this requires integrated network management for interconnected networks of heterogeneous devices covering both the local campus and across the world and spanning many administrative domains. This talk will review the status of existing tools to address management for networks. It draws on experience from both within and outside the HEP community.

Cottrell, R.L.A.; Streater, T.C.

1992-09-01

31

Weakly explosive percolation in directed networks  

NASA Astrophysics Data System (ADS)

Percolation, the formation of a macroscopic connected component, is a key feature in the description of complex networks. The dynamical properties of a variety of systems can be understood in terms of percolation, including the robustness of power grids and information networks, the spreading of epidemics and forest fires, and the stability of gene regulatory networks. Recent studies have shown that if network edges are added “competitively” in undirected networks, the onset of percolation is abrupt or “explosive.” The unusual qualitative features of this phase transition have been the subject of much recent attention. Here we generalize this previously studied network growth process from undirected networks to directed networks and use finite-size scaling theory to find several scaling exponents. We find that this process is also characterized by a very rapid growth in the giant component, but that this growth is not as sudden as in undirected networks.

Squires, Shane; Sytwu, Katherine; Alcala, Diego; Antonsen, Thomas M.; Ott, Edward; Girvan, Michelle

2013-05-01

32

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

33

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

34

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

35

Core organization of directed complex networks  

E-print Network

The recursive removal of leaves (dead end vertices) and their neighbors from an undirected network results, when this pruning algorithm stops, in a so-called core of the network. This specific subgraph should be distinguished from $k$-cores, which are principally different subgraphs in networks. If the vertex mean degree of a network is sufficiently large, the core is a giant cluster containing a finite fraction of vertices. We find that generalization of this pruning algorithm to directed networks provides a significantly more complex picture of cores. By implementing a rate equation approach to this pruning procedure for directed uncorrelated networks, we identify a set of cores progressively embedded into each other in a network and describe their birth points and structure.

Azimi-Tafreshi, N; Mendes, J F F

2012-01-01

36

Direct characterization of linear-optical networks  

E-print Network

We introduce an efficient method for fully characterizing multimode linear-optical networks. Our approach requires only a standard laser source and intensity measurements to directly and uniquely determine all moduli and non-trivial phases of the matrix describing a network. We experimentally demonstrate the characterization of a $6{\\times}6$ fiber-optic network and independently verify the results via nonclassical two-photon interference.

Saleh Rahimi-Keshari; Matthew A. Broome; Robert Fickler; Alessandro Fedrizzi; Timothy C. Ralph; Andrew G. White

2012-10-24

37

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

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

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

E-print Network

Finding communities in directed networks by PageRank random walk induced network embedding Darong proposed method uses PageRank random walk induced network embedding to transform a directed network in directed networks. PACS: 89.75.Hc Keywords: directed network; community; random walk; network embedding

Nardini, Christine

40

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

41

Constructing module maps for integrated analysis of heterogeneous biological networks  

E-print Network

for integrated analysis of heterogeneous large-scale omic data are direly needed. Here, we take a networkConstructing module maps for integrated analysis of heterogeneous biological networks David Amar. Our study demonstrates that module maps are a powerful tool for deeper analysis of heterogeneous high

Shamir, Ron

42

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

PubMed

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

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

1993-06-01

43

Differential pulse code modulation image compression using artifical neural networks  

NASA Astrophysics Data System (ADS)

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 back-propagation learning algorithm is used for the training of the network. Simulation results are presented to compare the performance of the proposed ANN-based nonlinear predictor with that of a global linear predictor as well as an optimized minimum-mean-squared-error (MMSE) linear predictor. Preliminary computer simulations demonstrate that for a typical test image, the zeroth-order entropy of the differential (error) image can be reduced by more than 15% compared to the case where optimum linear predictors are employed. Some future research directions are also discussed.

Rabbani, Majid; Dianat, Soheil A.

1993-04-01

44

Modulating the default mode network using hypnosis.  

PubMed

Debate regarding the neural basis of the hypnotic state continues, but a recent hypothesis suggests that it may produce alterations in the default mode network (DMN). DMN describes a network of brain regions more active during low-demand compared to high-demand task conditions and has been linked to processes such as task-independent thinking, episodic memory, semantic processing, and self-awareness. However, the experiential and cognitive correlates of DMN remain difficult to investigate directly. Using hypnosis as a means of altering the resting ("default") state in conjunction with subjective measures and brain imaging, the authors found that the state of attentional absorption following a hypnotic induction was associated with reduced activity in DMN and increased activity in prefrontal attentional systems, under invariant conditions of passive visual stimulation. The findings that hypnosis and spontaneous conceptual thought at rest were subjectively and neurally distinctive are also relevant to understanding hypnosis itself. PMID:22443526

Deeley, Quinton; Oakley, David A; Toone, Brian; Giampietro, Vincent; Brammer, Michael J; Williams, Steven C R; Halligan, Peter W

2012-01-01

45

Mechanism of gain modulation at single neuron and network levels  

E-print Network

online: 23 January 2008 # Springer Science + Business Media, LLC 2007 Abstract Gain modulation, in which a nonlinear additive form of gain modulation through learning-driven adjustment of synaptic weights. We useMechanism of gain modulation at single neuron and network levels M. Brozovi & L. F. Abbott & R. A

Columbia University

46

Vesicles modulate an actin network for asymmetric spindle positioning  

PubMed Central

Actin networks drive many essential cellular processes, including cell migration, cytokinesis and tissue morphogenesis. But how cells organize and regulate dynamic actin networks that consist of long, unbranched actin filaments is only poorly understood. This study in mouse oocytes reveals that cells can use vesicles as adaptable, motorized network nodes to regulate the dynamics and density of intracellular actin networks. In particular, Rab11a-positive vesicles drive the network dynamics in a myosin-Vb-dependent manner, and modulate the network density by sequestering and clustering the network’s actin nucleators. We also report a simple way by which networks of different densities can be generated, namely by adjusting the number and volume of vesicles in the cell. This vesicle-based mechanism of actin network modulation is essential for asymmetric positioning of the meiotic spindle in mouse oocytes, a vital step in the development of a fertilizable egg in mammals. PMID:23873150

Holubcova, Zuzana; Howard, Gillian; Schuh, Melina

2013-01-01

47

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

48

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

49

A Measurement Framework for Directed Networks  

E-print Network

Partially-observed network data collected by link-tracing based sampling methods is often being studied to obtain the characteristics of a large complex network. However, little attention has been paid to sampling from directed networks such as WWW and Peer-to-Peer networks. In this paper, we propose a novel two-step (sampling/estimation) framework to measure nodal characteristics which can be defined by an average target function in an arbitrary directed network. To this end, we propose a personalized PageRank-based algorithm to visit and sample nodes. This algorithm only uses already visited nodes as local information without any prior knowledge about the latent structure of the network. Moreover, we introduce a new estimator based on the approximate importance sampling to estimate average target functions. The proposed estimator utilizes calculated PageRank value of each sampled node as an approximation for the exact visiting probability. To the best of our knowledge, this is the first study on correcting ...

Salehi, Mostafa

2014-01-01

50

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

51

Point process modeling for directed interaction networks  

Microsoft Academic Search

Network data often take the form of repeated interactions between senders and receivers tabulated over time. A primary question to ask of such data is which traits and behaviors are predictive of interaction. To answer this question, a model is introduced for treating directed interactions as a multivariate point process: a Cox multiplicative intensity model using covariates that depend on

Patrick O. Perry; Patrick J. Wolfe

2010-01-01

52

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

53

?-Secretase modulators: current status and future directions.  

PubMed

This chapter reviews the current status of ?-secretase modulators, highlighting key compounds by each company involved in the area. The review focuses on the three main chemotypes: acids, imidazoles and related derivatives and natural products. A section on chemical biology and ligand-binding site elucidation studies is also included. The primary source of information is drawn from peer reviewed literature as this permits analysis of PK-PD relationships and subsequent comment. Discussion of the patent literature is included for completeness. From this analysis, the key issues and challenges in the area are highlighted. The review concludes with a summary of the clinical development status and comment on future prospects of the field. PMID:24418609

Hall, Adrian; Patel, Toshal R

2014-01-01

54

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

55

Heterogeneous Transparent Optical Networking Based on Coded OAM Modulation  

E-print Network

-modulation. 1. Introduction The invention of the Internet has fundamentally changed the underlying information optical networks should allow the interoperability of radio frequency (RF), fiber-optic, and free

Djordjevic, Ivan B.

56

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

57

Point process modeling for directed interaction networks  

Microsoft Academic Search

Network data often take the form of repeated interactions between senders and\\u000areceivers tabulated over time. Rather than reducing these data to binary ties,\\u000aa model is introduced for treating directed interactions as a multivariate\\u000apoint process: a Cox multiplicative intensity model using covariates that\\u000adepend on the history of the process. Consistency and asymptotic normality are\\u000aproved for the

Patrick O. Perry; Patrick J. Wolfe

2010-01-01

58

Index modulation type waveguides written by laser direct writing technology  

NASA Astrophysics Data System (ADS)

In this paper, we describe the cost-effective and simplified fabrication of an index modulation type buried waveguide using laser direct writing. Our studies have a potential of manufacturing waveguides on an uneven surface and a large area because there is no need for photo-mask, etching and development processes. We used organic-inorganic hybrid materials (HYBRIMER) for the fabrication of the waveguides, which have a high transparency from a visible region to an infrared region. We exposed the core layer (HYBRIMER) to a focused laser beam after a one-step spin coating process on a buffer layer. The silicon oxide was used as a buffer layer. The refractive index of the HYBRIMER film is increased by exposure from a laser beam. Therefore, the refractive index of the exposed region is higher than that of the unexposed region, which forms the index modulation type waveguide without an etching process. The fabricated waveguide channels were baked at 120°C during 3hrs for stabilization of the organic and inorganic networks. The laser direct writing apparatus was used to produce the pattern of waveguide channels. This system consists of a He-Cd laser radiating 325nm beam, high-resolution computer-controlled translation stages and a video camera that images the sample onto a monitor. The pattern of the waveguide channel was written using various writing speeds to optimize the writing condition. The core section of optimized waveguides was a rectangular shape and the core dimension was 7?m wide and 8?m high. The refractive index is increased from 1.495 to 1.5 after exposure. The difference of the refractive index between the core and cladding was approximately 0.33%. The insertion loss of the waveguides was measured by cut-back method using a single-mode fiber as an input tip, a multimode fiber (50 ?m GI) as an output tip, and a 1310nm wavelength laser light source. The insertion loss shows a linear relationship with the length of the waveguide. The propagation loss of the buried waveguide was approximately 0.3dB/cm at a wavelength of 1310nm.

Lee, Woo-Jin; Cho, In-Kui; Han, Sang-Pil; Kim, Woo-Soo; Bae, Byeong-Soo; Ahn, Seoung-Ho

2006-09-01

59

Exploring the randomness of Directed Acyclic Networks  

E-print Network

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

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

2010-06-11

60

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

61

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

62

Monthly Modulation in Dark Matter Direct-Detection Experiments  

E-print Network

The count rate in dark matter direct-detection experiments should exhibit modulation signatures due to the Earth's motion with respect to the Galactic dark matter halo. The annual and daily modulations, due to the Earth's revolution about the Sun and rotation about its own axis, have been explored previously. Monthly modulation is another such feature present in rate counts, and provides a nearly model-independent method of distinguishing dark matter signal events from background. We study here monthly modulations in detail, examining both the effect of the motion of the Earth about the Earth-Moon barycenter and the gravitational focusing due to the Moon. We show that the former is the dominant source of monthly modulation, and that the amplitude of the monthly modulation varies on an annual cycle. The expected amplitude of monthly modulation is quite small which makes its detection challenging; any such detection however, would provide very strong evidence that candidate events are due to dark matter scatter...

Britto, Vivian

2014-01-01

63

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

64

Identifying protein complexes and functional modules--from static PPI networks to dynamic PPI networks.  

PubMed

Cellular processes are typically carried out by protein complexes and functional modules. Identifying them plays an important role for our attempt to reveal principles of cellular organizations and functions. In this article, we review computational algorithms for identifying protein complexes and/or functional modules from protein-protein interaction (PPI) networks. We first describe issues and pitfalls when interpreting PPI networks. Then based on types of data used and main ideas involved, we briefly describe protein complex and/or functional module identification algorithms in four categories: (i) those based on topological structures of unweighted PPI networks; (ii) those based on characters of weighted PPI networks; (iii) those based on multiple data integrations; and (iv) those based on dynamic PPI networks. The PPI networks are modelled increasingly precise when integrating more types of data, and the study of protein complexes would benefit by shifting from static to dynamic PPI networks. PMID:23780996

Chen, Bolin; Fan, Weiwei; Liu, Juan; Wu, Fang-Xiang

2014-03-01

65

Design considerations for an electrooptic directional coupler modulator  

Microsoft Academic Search

A rigorous numerical model is presented for an electrooptic directional coupler (DC) modulator. It was observed that it is possible for such a device to be optimized by the variation of a number of fabrication parameters. The applied field, the induced refractive index changes, and hence the change in the waveguide optical field due to the antisymmetric refractive index change

N. Anwar; C. Themistos; B. M. Azizur Rahman; Kenneth T. V. Grattan

1999-01-01

66

Network-dependent modulation of brain activity during sleep.  

PubMed

Brain activity dynamically changes even during sleep. A line of neuroimaging studies has reported changes in functional connectivity and regional activity across different sleep stages such as slow-wave sleep (SWS) and rapid-eye-movement (REM) sleep. However, it remains unclear whether and how the large-scale network activity of human brains changes within a given sleep stage. Here, we investigated modulation of network activity within sleep stages by applying the pairwise maximum entropy model to brain activity obtained by functional magnetic resonance imaging from sleeping healthy subjects. We found that the brain activity of individual brain regions and functional interactions between pairs of regions significantly increased in the default-mode network during SWS and decreased during REM sleep. In contrast, the network activity of the fronto-parietal and sensory-motor networks showed the opposite pattern. Furthermore, in the three networks, the amount of the activity changes throughout REM sleep was negatively correlated with that throughout SWS. The present findings suggest that the brain activity is dynamically modulated even in a sleep stage and that the pattern of modulation depends on the type of the large-scale brain networks. PMID:24814208

Watanabe, Takamitsu; Kan, Shigeyuki; Koike, Takahiko; Misaki, Masaya; Konishi, Seiki; Miyauchi, Satoru; Miyahsita, Yasushi; Masuda, Naoki

2014-09-01

67

Constructing module maps for integrated analysis of heterogeneous biological networks.  

PubMed

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

2014-04-01

68

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

69

Direct quadrature phase shift keying modulator using six-port technology  

E-print Network

Direct quadrature phase shift keying modulator using six-port technology Y. Zhao, C. Viereck, J.F. Frigon, R.G. Bosisio and K. Wu A direct quadrature phase shift keying modulator based on six terminations. Using this modulator, direct phase shift keying modulation was achieved. Six-port technol- ogy

Frigon, Jean-François

70

NeMo: Network Module identification in Cytoscape  

PubMed Central

Background As the size of the known human interactome grows, biologists increasingly rely on computational tools to identify patterns that represent protein complexes and pathways. Previous studies have shown that densely connected network components frequently correspond to community structure and functionally related modules. In this work, we present a novel method to identify densely connected and bipartite network modules based on a log odds score for shared neighbours. Results To evaluate the performance of our method (NeMo), we compare it to other widely used tools for community detection including kMetis, MCODE, and spectral clustering. We test these methods on a collection of synthetically constructed networks and the set of MIPS human complexes. We apply our method to the CXC chemokine pathway and find a high scoring functional module of 12 disconnected phospholipase isoforms. Conclusion We present a novel method that combines a unique neighbour-sharing score with hierarchical agglomerative clustering to identify diverse network communities. The approach is unique in that we identify both dense network and dense bipartite network structures in a single approach. Our results suggest that the performance of NeMo is better than or competitive with leading approaches on both real and synthetic datasets. We minimize model complexity and generalization error in the Bayesian spirit by integrating out nuisance parameters. An implementation of our method is freely available for download as a plugin to Cytoscape through our website and through Cytoscape itself. PMID:20122237

2010-01-01

71

Name of Module: Communication Network Security  

E-print Network

skills 5% social skills 15% 2. Content Introduction (Attacks, Services, Mechanisms) Classical Encryption Reading, Lecture Notes Lecture notes available in paper form? yes X no Lecture notes in paper form and solutions for communications networks. Lecture supported by the project will enable students to analyse

Wichmann, Felix

72

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

73

Direct Information Exchange in Wireless Networks: A Coding Perspective  

E-print Network

the problem and reduce the stress on the wireless networks. One strategy to reduce the strain on the wireless networks is to utilize cooperative communication. The purpose of this thesis is to provide more efficient and reliable solutions for direct...

Ozgul, Damla

2011-10-21

74

Deploying Directional Sensor Networks with Guaranteed Connectivity and Coverage  

Microsoft Academic Search

In contrast to existing work on the connected cov- erage problem in wireless sensor networks which assumes omni- directional sensors with disk-like sensing range, this pap er inves- tigates a suite of novel problems related to connected coverage in directional sensor networks where sensors only sense directionally and have a sector-like sensing range. We first consider the problems of deploying

Xiaofeng Han; Xiang Cao; Errol L. Lloyd; Chien-chung Shen

2008-01-01

75

Modulation of behavioral networks by selective interneuronal inactivation  

PubMed Central

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, MJ; Horvath, S; Ebert, P; Norris, JL; Seeley, EH; Brown, J; Gellert, L; Everheart, M; Garbett, KA; Grice, TW; Caprioli, RM; Mirnics, K

2014-01-01

76

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

77

Sigma-delta cellular neural network for 2D modulation.  

PubMed

Although sigma-delta modulation is widely used for analog-to-digital (A/D) converters, sigma-delta concepts are only for 1D signals. Signal processing in the digital domain is extremely useful for 2D signals such as used in image processing, medical imaging, ultrasound imaging, and so on. The intricate task that provides true 2D sigma-delta modulation is feasible in the spatial domain sigma-delta modulation using the discrete-time cellular neural network (DT-CNN) with a C-template. In the proposed architecture, the A-template is used for a digital-to-analog converter (DAC), the C-template works as an integrator, and the nonlinear output function is used for the bilevel output. In addition, due to the cellular neural network (CNN) characteristics, each pixel of an image corresponds to a cell of a CNN, and each cell is connected spatially by the A-template. Therefore, the proposed system can be thought of as a very large-scale and super-parallel sigma-delta modulator. Moreover, the spatio-temporal dynamics is designed to obtain an optimal reconstruction signal. The experimental results show the excellent reconstruction performance and capabilities of the CNN as a sigma-delta modulator. PMID:18215502

Aomori, Hisashi; Otake, Tsuyoshi; Takahashi, Nobuaki; Tanaka, Mamoru

2008-01-01

78

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

79

DHCVIM: A direct heating containment vessel interactions module  

SciTech Connect

Models for prediction of direct containment heating phenomena as implemented in the DHCVIM computer module are described. The models were designed to treat thermal, chemical and hydrodynamic processes in the three regions of the Sandia National Laboratory Surtsey DCH test facility: the melt generator, cavity and vessel. The fundamental balance equations, along with constitutive relations are described. A combination of Eulerian treatment for the gas phase and Lagrangian treatment for the droplet phase is used in the modeling. Comparisons of calculations and DCH-1 test results are presented. Reasonable agreement is demonstrated for the vessel pressure rise, melt generator pressure decay and particle size distribution.

Ginsberg, T.; Tutu, N.K.

1987-01-01

80

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

81

Ad hoc networking with directional antennas: a complete system solution  

Microsoft Academic Search

Directional antennas offer tremendous potential for improving the performance of ad hoc networks. Harnessing this potential, however, requires new mechanisms at the medium access and network layers for intelligently and adaptively exploiting the antenna system. While recent years have seen a surge of research into such mechanisms, the problem of developing a complete ad hoc networking system, including the unique

Ram Ramanathan; Jason Redi; Cesar Santivanez; David Wiggins; Stephen Polit

2005-01-01

82

Connectivity guarantees for wireless networks with directional antennas  

Microsoft Academic Search

We study a combinatorial geometric problem related to the design of wireless networks with directional antennas. Specifically, we are interested in necessary and sufficient conditions on such antennas that enable one to build a connected communication network, and in efficient algorithms for building such networks when possible.We formulate the problem by a set P of n points in the plane,

Paz Carmi; Matthew J. Katz; Zvi Lotker; Adi Rosén

2011-01-01

83

Distributed Broadcasting and Mapping Protocols in Directed Anonymous Networks  

E-print Network

Distributed Broadcasting and Mapping Protocols in Directed Anonymous Networks Michael Langberg of their incoming and outgoing edges, have no unique identity, and have no knowledge of the network topology or even. These two protocols enable a complete mapping of the network and can serve as key building blocks in more

Bruck, Jehoshua (Shuki)

84

Investigation on high speed directly modulated microcircular lasers  

NASA Astrophysics Data System (ADS)

High speed modulation characteristics are investigated for microcircular lasers connected with an output waveguide theoretically and experimentally. The injection current profile and carrier spatial hole-burning and diffusion are accounted in the rate equation model by radially dividing the microcircular resonator into two regions under the approximation of uniform carrier densities. The numerical results indicate that wide mode field pattern in radial direction has merit for high speed modulation, which is expected for coupled modes in circular microlasers connected with an output waveguide. Small signal response curves and large signal modulation responses are investigated for a 15-?mradius microlaser connected with a 2 ?m wide output waveguide. The highest resonance frequencies of 7.2, 5.9 and 3.9 GHz are obtained at the temperatures of 287, 298 and 312 K from the small signal response curves, and clear eye diagrams at 12.5Gbit/s with an extinction ratio of 6.1 dB are observed for the microlaser at biasing current of 38 mA and the temperature of 287 K.

Huang, Yong-Zhen; Lv, Xiao-Meng; Zou, Ling-Xiu; Long, Heng; Xiao, Jin-Long; Yang, Yue-De; Du, Yun

2014-03-01

85

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

86

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

87

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

88

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

89

5 Gbit/s direct optical DPSK modulation of a 1530-nm DFB laser  

SciTech Connect

In this paper 5 Gbit/s direct optical differential-phase-shift-keying (DPSK) modulation of a 1530-nm distributed feedback laser is demonstrated using injection current modulation with a bipolar signal format. There was no degradation of the optical DPSK signal due to thermal frequency modulation of the laser. This direct DPSK modulation technique avoids the insertion loss and systems complexity of external DPSK modulators.

Vodhanel, R.S. (Bellcore, Red Bank, NJ (US))

1989-08-01

90

Network deconvolution as a general method to distinguish direct dependencies in networks  

E-print Network

Recognizing direct relationships between variables connected in a network is a pervasive problem in biological, social and information sciences as correlation-based networks contain numerous indirect relationships. Here ...

Feizi, Soheil

91

Chirped laser dispersion spectroscopy using a directly modulated quantum cascade laser  

SciTech Connect

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

2013-11-04

92

Research Directions for Network Intrusion Recovery  

Microsoft Academic Search

One of the most significant unsolved problems for network managers and system administrators is how to repair a net- work infrastructure after discovering evidence of an exten- sive compromise. The technical issues are compounded by a breathtaking variety of human factors. We highlight lessons learned from three real, significant, and recent intrusion in- cidents. We do so as a way

Michael E. Locasto; Matthew Burnside; Darrell Bethea

2008-01-01

93

Serotonin targets inhibitory synapses to induce modulation of network functions  

PubMed Central

The cellular effects of serotonin (5-HT), a neuromodulator with widespread influences in the central nervous system, have been investigated. Despite detailed knowledge about the molecular biology of cellular signalling, it is not possible to anticipate the responses of neuronal networks to a global action of 5-HT. Heterogeneous expression of various subtypes of serotonin receptors (5-HTR) in a variety of neurons differently equipped with cell-specific transmitter receptors and ion channel assemblies can provoke diverse cellular reactions resulting in various forms of network adjustment and, hence, motor behaviour. Using the respiratory network as a model for reciprocal synaptic inhibition, we demonstrate that 5-HT1AR modulation primarily affects inhibition through glycinergic synapses. Potentiation of glycinergic inhibition of both excitatory and inhibitory neurons induces a functional reorganization of the network leading to a characteristic change of motor output. The changes in network operation are robust and help to overcome opiate-induced respiratory depression. Hence, 5-HT1AR activation stabilizes the rhythmicity of breathing during opiate medication of pain. PMID:19651659

Manzke, Till; Dutschmann, Mathias; Schlaf, Gerald; Morschel, Michael; Koch, Uwe R.; Ponimaskin, Evgeni; Bidon, Olivier; Lalley, Peter M.; Richter, Diethelm W.

2009-01-01

94

Space station common module network topology and hardware development  

NASA Technical Reports Server (NTRS)

Conceptual space station common module power management and distribution (SSM/PMAD) network layouts and detailed network evaluations were developed. Individual pieces of hardware to be developed for the SSM/PMAD test bed were identified. A technology assessment was developed to identify pieces of equipment requiring development effort. Equipment lists were developed from the previously selected network schematics. Additionally, functional requirements for the network equipment as well as other requirements which affected the suitability of specific items for use on the Space Station Program were identified. Assembly requirements were derived based on the SSM/PMAD developed requirements and on the selected SSM/PMAD network concepts. Basic requirements and simplified design block diagrams are included. DC remote power controllers were successfully integrated into the DC Marshall Space Flight Center breadboard. Two DC remote power controller (RPC) boards experienced mechanical failure of UES 706 stud-mounted diodes during mechanical installation of the boards into the system. These broken diodes caused input to output shorting of the RPC's. The UES 706 diodes were replaced on these RPC's which eliminated the problem. The DC RPC's as existing in the present breadboard configuration do not provide ground fault protection because the RPC was designed to only switch the hot side current. If ground fault protection were to be implemented, it would be necessary to design the system so the RPC switched both the hot and the return sides of power.

Anderson, P.; Braunagel, L.; Chwirka, S.; Fishman, M.; Freeman, K.; Eason, D.; Landis, D.; Lech, L.; Martin, J.; Mccorkle, J.

1990-01-01

95

Default Network Modulation and Large-Scale Network Interactivity in Healthy Young and R. Nathan Spreng and Daniel L. Schacter  

E-print Network

Default Network Modulation and Large-Scale Network Interactivity in Healthy Young and Old Adults R-related changes in default, attention, and control network activity and their interactions in young and old adults analysis and with intrinsic connectivity networks as regions of interest. In both groups, autobiographical

Schacter, Daniel

96

How familiarization and repetition modulate the picture naming network.  

PubMed

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

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

2014-06-01

97

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

98

The theory of pattern formation on directed networks.  

PubMed

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. PMID:25077521

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

2014-01-01

99

Inter-arrival times of message propagation on directed networks  

E-print Network

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

Mihaljev, Tamara; Herrmann, Hans J

2010-01-01

100

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

101

Modulated Scale-free Network in the Euclidean Space  

E-print Network

A random network is grown by introducing at unit rate randomly selected nodes on the Euclidean space. A node is randomly connected to its $i$-th predecessor of degree $k_i$ with a directed link of length $\\ell$ using a probability proportional to $k_i \\ell^{\\alpha}$. Our numerical study indicates that the network is Scale-free for all values of $\\alpha > \\alpha_c $ and the degree distribution decays stretched exponentially for the other values of $\\alpha$. The link length distribution follows a power law: $D(\\ell) \\sim \\ell^{\\delta}$ where $\\delta$ is calculated exactly for the whole range of values of $\\alpha$.

S. S. Manna; Parongama Sen

2002-03-10

102

Directed progression brain networks in Alzheimer's disease: properties and classification.  

PubMed

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

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

2014-06-01

103

Revealing the Hidden Relationship by Sparse Modules in Complex Networks with a Large-Scale Analysis  

PubMed Central

One of the remarkable features of networks is module that can provide useful insights into not only network organizations but also functional behaviors between their components. Comprehensive efforts have been devoted to investigating cohesive modules in the past decade. However, it is still not clear whether there are important structural characteristics of the nodes that do not belong to any cohesive module. In order to answer this question, we performed a large-scale analysis on 25 complex networks with different types and scales using our recently developed BTS (bintree seeking) algorithm, which is able to detect both cohesive and sparse modules in the network. Our results reveal that the sparse modules composed by the cohesively isolated nodes widely co-exist with the cohesive modules. Detailed analysis shows that both types of modules provide better characterization for the division of a network into functional units than merely cohesive modules, because the sparse modules possibly re-organize the nodes in the so-called cohesive modules, which lack obvious modular significance, into meaningful groups. Compared with cohesive modules, the sizes of sparse ones are generally smaller. Sparse modules are also found to have preferences in social and biological networks than others. PMID:23762457

Jiao, Qing-Ju; Huang, Yan; Liu, Wei; Wang, Xiao-Fan; Chen, Xiao-Shuang; Shen, Hong-Bin

2013-01-01

104

Adaptive MAC Protocol for UAV Communication Networks Using Directional Antennas  

E-print Network

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

Dong, Liang

105

Identifying Functional Modules Using MST-Based Weighted Gene CoExpression Networks  

Microsoft Academic Search

This paper proposes an effective method for identifying functional modules of the weighted gene co-expression network using a minimum spanning tree (MST) approach coupled with network neighborhood connectivity. The MST-based gene co-expression network was reconstructed to serve as the backbone of gene co-expression network. Highly connected hub genes were identified based on the connectivity of the backbone network. All sub-networks

Atthawut Chanthaphan; Santitham Prom-on; Asawin Meechai; Jonathan Hoyin Chan

2009-01-01

106

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

PubMed Central

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

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

2014-01-01

107

Interarrival times of message propagation on directed networks.  

PubMed

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

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

2011-08-01

108

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

109

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

110

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

111

Low-frequency analog signal distribution on digital photonic networks by optical delta-sigma modulation  

NASA Astrophysics Data System (ADS)

We propose a delta-sigma modulation scheme for low- and medium-frequency signal transmission in a digital photonic network system. A 10-Gb/s-class optical transceiver with a delta-sigma modulator utilized as a high-speed analog-to-digital converter (ADC) provides a binary optical signal. On the signal reception side, a low-cost and slow-speed photonic receiver directly converts the binary signal into an analog signal at frequencies from several hundreds of kilohertz several tens of megahertz. Further, by using a clock and data recovery circuit at the receiver to reduce jitters, the single-sideband phase noise of the generated signals can be significantly reduced.

Kanno, Atsushi; Kawanishi, Tetsuya

2013-12-01

112

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

113

Heterogeneous optical networking using orthogonal OAM multimode modulation  

NASA Astrophysics Data System (ADS)

In order to solve capacity and energy-efficiency problems of future Internet technologies simultaneously, in this paper, we propose the use of energy-efficient N-dimensional (ND) orbital angular momentum (OAM) coded-modulation. The energy-efficient signal constellation is obtained by employing the energy-efficient signal constellation design algorithm. This scheme can achieve beyond 100 Gb/s transmission while employing the state-of-the-art 10 Gb/s technology. The proposed scheme significantly outperforms conventional M-ary PAM. The proposed scheme represents a promising candidate for indoor optical wireless communication, terrestrial free-space optical (FSO) communication, data center applications and can be used as enabling technology for heterogeneous optical networking, thanks to its transparency to both free-space optical and few-mode/multimode fiber links.

Djordjevic, Ivan B.; Anguita, Jaime

2012-10-01

114

Metastability and Inter-Band Frequency Modulation in Networks of Oscillating Spiking Neuron Populations  

PubMed Central

Groups of neurons firing synchronously are hypothesized to underlie many cognitive functions such as attention, associative learning, memory, and sensory selection. Recent theories suggest that transient periods of synchronization and desynchronization provide a mechanism for dynamically integrating and forming coalitions of functionally related neural areas, and that at these times conditions are optimal for information transfer. Oscillating neural populations display a great amount of spectral complexity, with several rhythms temporally coexisting in different structures and interacting with each other. This paper explores inter-band frequency modulation between neural oscillators using models of quadratic integrate-and-fire neurons and Hodgkin-Huxley neurons. We vary the structural connectivity in a network of neural oscillators, assess the spectral complexity, and correlate the inter-band frequency modulation. We contrast this correlation against measures of metastable coalition entropy and synchrony. Our results show that oscillations in different neural populations modulate each other so as to change frequency, and that the interaction of these fluctuating frequencies in the network as a whole is able to drive different neural populations towards episodes of synchrony. Further to this, we locate an area in the connectivity space in which the system directs itself in this way so as to explore a large repertoire of synchronous coalitions. We suggest that such dynamics facilitate versatile exploration, integration, and communication between functionally related neural areas, and thereby supports sophisticated cognitive processing in the brain. PMID:23614040

Bhowmik, David; Shanahan, Murray

2013-01-01

115

Direct modulation of lasers by dispersive threshold switching  

SciTech Connect

For the first time it is demonstrated, that a laser can be switched electrically on and off at a fixed net gain by a dispersive threshold switching. Switching with 30 dB contrast is achieved by 0.5 mA phase current variation. Short optical pulses were generated by 1 GHz sinus modulation of the phase current. Low chirp was observed at 5 GHz modulation.

Sartorius, B.; Moehrle, M. [Heinrich-Hertz-Inst. fuer Nachrichtentechnik Berlin GmbH (Germany)

1996-12-31

116

The prefrontal–limbic network in depression: Modulation by hypothalamus, basal ganglia and midbrain  

Microsoft Academic Search

The anterior cingulate cortex, amygdala and hippocampus form part of an interconnected prefrontal neocortical and limbic archicortical network that is dysregulated in major depressive disorders (MDD). Modulation of this prefrontal–limbic network (PLN) is principally through the hypothalamus, basal ganglia and midbrain. Here the likely mechanisms by which these modulations are affected are described and the implications of their failure for

M. R. Bennett

2011-01-01

117

Eigengene networks for studying the relationships between co-expression modules  

Microsoft Academic Search

BACKGROUND: There is evidence that genes and their protein products are organized into functional modules according to cellular processes and pathways. Gene co-expression networks have been used to describe the relationships between gene transcripts. Ample literature exists on how to detect biologically meaningful modules in networks but there is a need for methods that allow one to study the relationships

Peter Langfelder; Steve Horvath

2007-01-01

118

Directed percolation effects emerging from superadditivity of quantum networks  

NASA Astrophysics Data System (ADS)

Entanglement-induced nonadditivity of classical communication capacity in networks consisting of quantum channels is considered. Communication lattices consisting of butterfly-type entanglement-breaking channels augmented, with some probability, by identity channels are analyzed. The capacity superadditivity in the network is manifested in directed correlated bond percolation which we consider in two flavors: simply directed and randomly oriented. The obtained percolation properties show that high-capacity information transfer sets in much faster in the regime of superadditive communication capacity than otherwise possible. As a by-product, this sheds light on a type of entanglement-based quantum capacity percolation phenomenon.

Czekaj, L.; Chhajlany, R. W.; Horodecki, P.

2012-03-01

119

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

120

Communities, roles, and informational organigrams in directed networks: the Twitter network of the UK riots  

E-print Network

Directionality is a crucial ingredient in many complex networks, in which information, energy or influence are transmitted. We showcase a framework for flow-based analysis for directed networks through the study of a network of influential Twitter users during the 2011 riots in England. Our analysis extracts nuanced descriptions of the network in terms of a multiresolution structure of interest communities within which flows of information are contained and reinforced. Such communities identify groups according to location, profession, employer, and topic, and are largely undetected if edge directionality is ignored. The flow structure also allows us to generate an interest distance, affording a personalised view of the network from any given user. A complementary flow-based analysis leads to a classification of users into five roles beyond the standard leader-follower dichotomy. Integrating both viewpoints, we find that interest communities fall into distinct informational organigrams, which reflect their mi...

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

2013-01-01

121

A Rule-based Detection of Functional Modules in Protein-Protein Interaction Networks  

Microsoft Academic Search

In the protein-protein interaction (PPI) network there are many functional modules, each involving several protein interactions to perform discrete functions. Pathways and protein complexes are the examples of the functional modules. In this paper, we propose a rule-based method for detecting the modules. The rule is expressed in terms of triples and operators between the triples. The former represents conceptual

Jongmin Park; Jaehun Choi; Jaedong Yang; Soo-Jun Park

2006-01-01

122

The Southern California Integrated GPS Network Education Module  

NSDL National Science Digital Library

This educational module was designed to allow students to interactively explore the use of SCIGN (Southern California Integrated GPS Network) and its data in earthquake studies. It is divided into four major sections: Plate Tectonics, Earthquakes, GPS (Global Positioning System), and Space Technology at Work. All of the sections include background material and activities; the first three sections focus primarily on introducing satellite technology and tectonic phenomena, and the final section serves to integrate knowledge learned in the first three by allowing students to use real SCIGN data in their investigations into plate tectonics, earthquakes, and GPS. Primary concepts include: Forces in the Earth cause its surface to change over time, earthquakes release stress causing permanent change in the Earth's crust, GPS is a satellite technology used as a tool to measure crustal change, and SCIGN is a network of GPS stations used to study tectonics and earthquakes in Southern California. The activities include: How many earthquakes does it take to build a mountain?, Are GPS measurements accurate or precise? What is a rate? How far away are satellites? How fast is the Jet Propulsion Laboratory's station moving? How long will it take for Los Angeles and San Francisco to meet?

Glasscoe, Maggi; Mikolajcik, Anne; Donnellan, Andrea; Watkins, Michael; Smith, Mark

123

The Southern California Integrated GPS Network Education Module  

NSDL National Science Digital Library

This educational module was designed to allow students to interactively explore the use of SCIGN (Southern California Integrated GPS Network) and its data in earthquake studies. It is divided into four major sections: Plate Tectonics, Earthquakes, GPS (Global Positioning System), and Space Technology at Work. All of the sections include background material and activities; the first three sections focus primarily on introducing satellite technology and tectonic phenomena, and the final section serves to integrate knowledge learned in the first three by allowing students to use real SCIGN data in their investigations into plate tectonics, earthquakes, and GPS. Primary concepts include: Forces in the Earth cause its surface to change over time, earthquakes release stress causing permanent change in the Earth\\'s crust, GPS is a satellite technology used as a tool to measure crustal change, and SCIGN is a network of GPS stations used to study tectonics and earthquakes in Southern California. The activities include: How many earthquakes does it take to build a mountain?, Are GPS measurements accurate or precise? What is a rate? How far away are satellites? How fast is the Jet Propulsion Laboratory\\'s station moving? How long will it take for Los Angeles and San Francisco to meet?

Donnellan, Andrea; Glasscoe, Maggi; Mikolajcik, Anne; Smith, Mark; Watkins, Michael

2006-12-21

124

Identification of direction in gene networks from expression and methylation  

PubMed Central

Background Reverse-engineering gene regulatory networks from expression data is difficult, especially without temporal measurements or interventional experiments. In particular, the causal direction of an edge is generally not statistically identifiable, i.e., cannot be inferred as a statistical parameter, even from an unlimited amount of non-time series observational mRNA expression data. Some additional evidence is required and high-throughput methylation data can viewed as a natural multifactorial gene perturbation experiment. Results We introduce IDEM (Identifying Direction from Expression and Methylation), a method for identifying the causal direction of edges by combining DNA methylation and mRNA transcription data. We describe the circumstances under which edge directions become identifiable and experiments with both real and synthetic data demonstrate that the accuracy of IDEM for inferring both edge placement and edge direction in gene regulatory networks is significantly improved relative to other methods. Conclusion Reverse-engineering directed gene regulatory networks from static observational data becomes feasible by exploiting the context provided by high-throughput DNA methylation data. An implementation of the algorithm described is available at http://code.google.com/p/idem/. PMID:24182195

2013-01-01

125

Noradrenergic modulation of electrical coupling in GABAergic networks of the hippocampus.  

PubMed

Noradrenergic modulation of cortical circuits is involved in information processing, regulation of higher functions, and prevention of epileptic activity. Here, we studied the effects of noradrenaline on the functional connectivity of GABAergic networks of the hippocampus and show that electrical synapses between interneurons are a novel target of noradrenergic modulation in vitro. Application of noradrenaline or of the selective beta-adrenergic agonist isoproterenol decreased gap junction-based coupling in paired recordings from stratum lacunosum-moleculare interneurons by approximately 40%. Similar results were obtained after pharmacological stimulation of the adenylyl cyclase with forskolin. In contrast, the adenylyl cyclase antagonist MDL12330A [cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine] or the specific protein kinase A (PKA) inhibitor H89 (N-[2-(p-bromocinnamyl-amino)ethyl]-5-isoquinolinesulfonamide dihydrochloride) enhanced the basal strength of coupling by approximately 30%. In addition, PKA-mediated phosphorylation was critical for both isoproterenol- and forskolin-dependent regulation of coupling, because inclusion of the PKA antagonist KT5720 [(9S,10R,12R)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylicacid hexyl ester] in the recording pipettes prevented modulation. Lastly, we studied the effects of beta-adrenergic modulation on mixed polysynaptic transmission within the GABAergic network. Isoproterenol depressed propagation of GABA(A) receptor-mediated synaptic currents, but did not change significantly direct GABAergic input, indicating that regulation of electrical coupling adds flexibility to the information flow generated by chemical synapses. In conclusion, activation of beta-adrenergic receptors in stratum lacunosum-moleculare GABAergic networks reduces electrical synaptic transmission via a cAMP/PKA signaling cascade, and affects the degree of synaptic divergence within the circuit. We propose that this dynamic modulation and interplay between electrical and chemical synaptic transmission in GABAergic networks contributes to the tuning of memory processes in vivo, and prevents hypersynchronous activity. PMID:18287497

Zsiros, Veronika; Maccaferri, Gianmaria

2008-02-20

126

Maintain the structural controllability under malicious attacks on directed networks  

NASA Astrophysics Data System (ADS)

The directedness of the links in a network plays a critical role in determining many dynamical processes among which the controllability has received much recent attention. The control robustness of a network against malicious attack and random failure also becomes a significant issue. In this paper, we propose a novel control robustness index motivated by recent studies on the global connectivity and controllability. In its general form, the problem of optimizing the control robustness index is computationally infeasible for large-scale networks. By analysing the influences of several directed topological factors on the dynamical control process, we transform the control robustness problem into the problem of transitivity maximization for control routes, and propose an efficient greedy algorithm to make control routes transitive. A series of experiments on real-world and synthetic networks show that the global connectivity and controllability can be improved simultaneously and we can mitigate the destruction of malicious attack through backing up the control routes.

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

2013-03-01

127

Hamilton circuits in the directed wrapped Butter y network1  

E-print Network

Hamilton circuits in the directed wrapped Butter y network1 J-C. Bermonda , E. Darrota , O. Delmasa Antipolis Cedex (France)2 Abstract In this paper, we prove that the wrapped Butter y digraph ~WBF divisible by a number q, with 4 q 12000. Key words: Butter y digraph, graph theory, Hamilton decomposition

Bermond, Jean-Claude

128

Measuring the Statistical Significance of Local Connections in Directed Networks  

E-print Network

of p-values derived from a directed configuration null model. We derive the asymptotic distribution of the number of edges between a vertex and a community under the null model and show how to calculate p Introduction Networks arise in the modeling and understanding of a host of complex systems, ranging from

Pratt, Vaughan

129

Irreversible bimolecular chemical reactions on directed scale-free networks  

NASA Astrophysics Data System (ADS)

Kinetics of irreversible bimolecular chemical reactions A+A?0 and A+B?0 on directed scale-free networks with the in-degree distribution Pin(k)˜k-?in and the out-degree distribution Pout(?)˜?-?out are investigated. Since the correlation between k and ? of each node generally exists in directed networks, we control the correlation 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 =, whereas the ? algorithm gives =. For r=0, = 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.

Kwon, Sungchul; Kim, Yup

2013-10-01

130

Standard Chinese: A Modular Approach. Student Workbook. Module 3: Money; Module 4: Directions.  

ERIC Educational Resources Information Center

Texts in spoken Standard Chinese were developed to improve and update Chinese materials and to reflect current usage in Beijing and Taipei. The focus is on communicating in Chinese in practical situations. The overall course is organized into 10 situational modules, student workbooks, and resource modules. This workbook covers the money and…

Defense Language Inst., Monterey, CA.

131

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

E-print Network

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

Orchard, Jeffery J.

132

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

133

Low chirp observed in directly modulated quantum dot lasers  

Microsoft Academic Search

We have examined the dynamic properties of high-aspect-ratio InAs-quantum-dot (QD) lasers at room temperature. A novel characteristic of low chirp in the lasing wavelength under 1-GHz current modulation was found in the quantum dot lasers. This is more than one order of magnitude less than the typical chirp (0.2-nm) found in a conventional quantum well laser that we used as

Hideaki Saito; Kenichi Nishi; Akio Kamei; Shigeo Sugou

2000-01-01

134

Network statistics of genetically-driven gene co-expression modules in mouse crosses  

PubMed Central

In biology, networks are used in different contexts as ways to represent relationships between entities, such as for instance interactions between genes, proteins or metabolites. Despite progress in the analysis of such networks and their potential to better understand the collective impact of genes on complex traits, one remaining challenge is to establish the biologic validity of gene co-expression networks and to determine what governs their organization. We used WGCNA to construct and analyze seven gene expression datasets from several tissues of mouse recombinant inbred strains (RIS). For six out of the 7 networks, we found that linkage to “module QTLs” (mQTLs) could be established for 29.3% of gene co-expression modules detected in the several mouse RIS. For about 74.6% of such genetically-linked modules, the mQTL was on the same chromosome as the one contributing most genes to the module, with genes originating from that chromosome showing higher connectivity than other genes in the modules. Such modules (that we considered as “genetically-driven”) had network statistic properties (density and centralization) that set them apart from other modules in the network. Altogether, a sizeable portion of gene co-expression modules detected in mouse RIS panels had genetic determinants as their main organizing principle. In addition to providing a biologic interpretation validation for these modules, these genetic determinants imparted on them particular properties that set them apart from other modules in the network, to the point that they can be predicted to a large extent on the basis of their network statistics. PMID:24421784

Scott-Boyer, Marie-Pier; Haibe-Kains, Benjamin; Deschepper, Christian F.

2013-01-01

135

Network statistics of genetically-driven gene co-expression modules in mouse crosses.  

PubMed

In biology, networks are used in different contexts as ways to represent relationships between entities, such as for instance interactions between genes, proteins or metabolites. Despite progress in the analysis of such networks and their potential to better understand the collective impact of genes on complex traits, one remaining challenge is to establish the biologic validity of gene co-expression networks and to determine what governs their organization. We used WGCNA to construct and analyze seven gene expression datasets from several tissues of mouse recombinant inbred strains (RIS). For six out of the 7 networks, we found that linkage to "module QTLs" (mQTLs) could be established for 29.3% of gene co-expression modules detected in the several mouse RIS. For about 74.6% of such genetically-linked modules, the mQTL was on the same chromosome as the one contributing most genes to the module, with genes originating from that chromosome showing higher connectivity than other genes in the modules. Such modules (that we considered as "genetically-driven") had network statistic properties (density and centralization) that set them apart from other modules in the network. Altogether, a sizeable portion of gene co-expression modules detected in mouse RIS panels had genetic determinants as their main organizing principle. In addition to providing a biologic interpretation validation for these modules, these genetic determinants imparted on them particular properties that set them apart from other modules in the network, to the point that they can be predicted to a large extent on the basis of their network statistics. PMID:24421784

Scott-Boyer, Marie-Pier; Haibe-Kains, Benjamin; Deschepper, Christian F

2013-01-01

136

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

137

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

138

Comment on "Dynamics and Directionality in Complex Networks"  

E-print Network

Authors of Phys. Rev. Lett. 103, 228702 (2009) claim that "The residual degree gradient (RDG) method can enhance thesynchronizability of networks by simply changing the direction of the links". In this paper, we argue that in some case the RDG method will lead to the failure of synchronization ($R=\\lambda^{r}_{2}/\\lambda^{r}_{N}=0$). Additionally, we also propose a so-called residual betweenness gradient (RBG) method to solve this problem.

An Zeng; Ying Fan; Zengru Di

2010-06-28

139

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

140

Different types of laughter modulate connectivity within distinct parts of the laughter perception network.  

PubMed

Laughter is an ancient signal of social communication among humans and non-human primates. Laughter types with complex social functions (e.g., taunt and joy) presumably evolved from the unequivocal and reflex-like social bonding signal of tickling laughter already present in non-human primates. Here, we investigated the modulations of cerebral connectivity associated with different laughter types as well as the effects of attention shifts between implicit and explicit processing of social information conveyed by laughter using functional magnetic resonance imaging (fMRI). Complex social laughter types and tickling laughter were found to modulate connectivity in two distinguishable but partially overlapping parts of the laughter perception network irrespective of task instructions. Connectivity changes, presumably related to the higher acoustic complexity of tickling laughter, occurred between areas in the prefrontal cortex and the auditory association cortex, potentially reflecting higher demands on acoustic analysis associated with increased information load on auditory attention, working memory, evaluation and response selection processes. In contrast, the higher degree of socio-relational information in complex social laughter types was linked to increases of connectivity between auditory association cortices, the right dorsolateral prefrontal cortex and brain areas associated with mentalizing as well as areas in the visual associative cortex. These modulations might reflect automatic analysis of acoustic features, attention direction to informative aspects of the laughter signal and the retention of those in working memory during evaluation processes. These processes may be associated with visual imagery supporting the formation of inferences on the intentions of our social counterparts. Here, the right dorsolateral precentral cortex appears as a network node potentially linking the functions of auditory and visual associative sensory cortices with those of the mentalizing-associated anterior mediofrontal cortex during the decoding of social information in laughter. PMID:23667619

Wildgruber, Dirk; Szameitat, Diana P; Ethofer, Thomas; Brück, Carolin; Alter, Kai; Grodd, Wolfgang; Kreifelts, Benjamin

2013-01-01

141

Direct torque control of induction machines using space vector modulation  

Microsoft Academic Search

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

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

1992-01-01

142

The tetraspanin network modulates MT1-MMP cell surface trafficking.  

PubMed

The membrane-type 1 matrix metalloproteinase (MT1-MMP) drives fundamental physiological and pathophysiological processes. Among other substrates, MT1-MMP cleaves components of the extracellular matrix and activates other matrix-cleaving proteases such as MMP-2. Trafficking is a highly effective means to modulate MT1-MMP cell surface expression, and hence regulate its function. Here, we describe the complex interaction of MT1-MMP with tetraspanins, their effects on MT1-MMP intracellular trafficking and proteolytic function. Tetraspanins are credited as membrane organizers that form a network within the membrane to regulate the trafficking of associated proteins. In short, we found MT1-MMP to interact with the tetraspanin-associated EWI-2 protein by a yeast two-hybrid screen. Immunoprecipitation analysis confirmed this interaction and further revealed that MT1-MMP also stably interacts with distinct tetraspanins (CD9, CD37, CD53, CD63, CD81, and CD82) and the tetraspanin-like MAL protein. By using different MT1-MMP truncation constructs and mutants, we observed that all tetraspanins and MAL associated with the hemopexin domain of MT1-MMP. Moreover, this interaction was independent of O-glycosylation of MT1-MMP and exclusively occurred in the endoplasmic reticulum. Here, the respective subcellular compartment was identified by fitting the MT1-MMP interaction pattern to a model for post-translational processing of MT1-MMP. In addition, tetraspanins differentially affected the cell surface localization of MT1-MMP, its capacity to activate pro-MMP-2, and the collagen invasion capacity. Interestingly, the degree of tetraspanin-MT1-MMP association did not correlate with its impact on MT1-MMP function. Tetraspanins thus distinctly affect MT1-MMP subcellular localization and function, and may constitute an effective mechanism to control MT1-MMP-dependent proteolysis at the cell surface. PMID:23500527

Schröder, H M; Hoffmann, S C; Hecker, M; Korff, T; Ludwig, T

2013-06-01

143

A controllable phase coherent modulated RF signal for use with microwave network analyzer measurements  

Microsoft Academic Search

A method is proposed to build a phase coherent modulated RF signal, that can be used as excitation signal for microwave network analyzer measurements. A software feedback technique is used to correct the amplitude and phase distortions introduced in the signal path to the input port of the device under test (DUT). This technique allows one to create a modulated

Philip VAEL; Y. Rolain

1999-01-01

144

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

145

Modulation of cortical-subcortical networks in Parkinson's disease by applied field effects  

PubMed Central

Studies suggest that endogenous field effects may play a role in neuronal oscillations and communication. Non-invasive transcranial electrical stimulation with low-intensity currents can also have direct effects on the underlying cortex as well as distant network effects. While Parkinson’s disease (PD) is amenable to invasive neuromodulation in the basal ganglia by deep brain stimulation (DBS), techniques of non-invasive neuromodulation like transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS) are being investigated as possible therapies. tDCS and tACS have the potential to influence the abnormal cortical-subcortical network activity that occurs in PD through sub-threshold changes in cortical excitability or through entrainment or disruption of ongoing rhythmic cortical activity. This may allow for the targeting of specific features of the disease involving abnormal oscillatory activity, as well as the enhancement of potential cortical compensation for basal ganglia dysfunction and modulation of cortical plasticity in neurorehabilitation. However, little is currently known about how cortical stimulation will affect subcortical structures, the size of any effect, and the factors of stimulation that will influence these effects. PMID:24062667

Hess, Christopher W.

2013-01-01

146

Index modulation Bragg gratings directly imprinted on sol gel layers  

NASA Astrophysics Data System (ADS)

Among the fabrication techniques of integrated optical devices, the sol-gel chemistry is now performant enough to make thin films of transparent materials with controlled purity and composition, at low temperature. Semi-mineral semi-organic solutions allow dip coating followed by low temperature baking to deposit vitreous films up to eight micrometers thick which are free from cracks. A local polymerization process through UV exposure enables hybrid components compatible with electronic planar silicon or III- V components. This UV imprinting method is used here to make index modulation gratings with use of a holographic equipment as an alternative to the use of a costly phase mask. Gratings have been imprinted on various sol-gel films; single layer, with a protective coating, and/or with an isolating buffer layer from the substrate, which is silicon and glass. Diffraction magnitude is measured in the various cases, as well as analysis and computer simulations are performed. Wavelength filters are experimented and studied. This shows the potential of this low cost technology in integrated optics, for application in telecommunications.

Moreau, Yves; Arguel, Philippe; Coudray, Paul; Porque, Jerome; Etienne, Pascal

1998-01-01

147

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

148

Network based elucidation of drug response: from modulators to targets  

PubMed Central

Network-based drug discovery aims at harnessing the power of networks to investigate the mechanism of action of existing drugs, or new molecules, in order to identify innovative therapeutic treatments. In this review, we describe some of the most recent advances in the field of network pharmacology, starting with approaches relying on computational models of transcriptional networks, then moving to protein and signaling network models and concluding with “drug networks”. These networks are derived from different sources of experimental data, or literature-based analysis, and provide a complementary view of drug mode of action. Molecular and drug networks are powerful integrated computational and experimental approaches that will likely speed up and improve the drug discovery process, once fully integrated into the academic and industrial drug discovery pipeline. PMID:24330611

2013-01-01

149

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

150

Direct intensity modulation of a rectangular ring laser with bidirectional lasing characteristics  

NASA Astrophysics Data System (ADS)

The direct intensity modulation of a three-guide coupled rectangular ring laser having bidirectional lasing characteristics is reported for the first time. The rectangular laser cavity consists of four low loss total internal reflection mirrors and an output coupler made out of three passive coupled waveguides. The laser is fabricated using a total cavity length of 580 ?m with active section lengths of 250 ?m. For both the clockwise and counterclockwise circulating directions, a lasing threshold of around 38 mA is obtained at room temperature under continuous wave operation. A maximum 3-dB modulation bandwidth of approximately 3.2 GHz is observed in both circulating directions.

Kim, Doo Gun; Oh, Geum-Yoon; Lee, Tae-Kyeong; Kim, Seon Hoon; Ki, Hyun Chul; Lim, Jung Woon; Kim, Hwe Jong; Kim, Boo-Gyoun; Dagli, Nadir; Choi, Young-Wan

2011-09-01

151

Cellular and Synaptic Modulation Underlying Substance P-Mediated Plasticity of the Lamprey Locomotor Network  

Microsoft Academic Search

The tachykinin substance P modulates the lamprey locomotor network by increasing the frequency of NMDA-evoked ventral root bursts and by making the burst activity more regular. These effects can last in excess of 24 hr. In this paper, the effects of substance P on the synaptic and cellular properties of motor neurons and identified network interneurons have been examined. Substance

David Parker; Sten Grillner

1998-01-01

152

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

153

Cross-Layer Scheduling and Power Control Combined With Adaptive Modulation for Wireless Ad Hoc Networks  

Microsoft Academic Search

Efficient resource management is a major challenge in the operation of wireless systems, especially energy-constrained ad hoc networks. In this paper, we propose a cross-layer optimization framework to jointly design the scheduling and power control in wireless ad hoc networks. We study the system performance by combining scheduling, power control, and adaptive modulation. Specifically, the transmitted power and constellation size

Wei Lan Huang; Khaled Ben Letaief

2007-01-01

154

Directional Antenna at Sink (DAaS) to prolong network lifetime in Wireless Sensor Networks  

E-print Network

extension. Previous studies on wireless sensor networks have assumed only an omni-directional antenna model scheduling algorithm, which coordi- nates MAC layer wakeup/sleep schedules of the sink and the neighbor nodes the duty-cycle and hence saves more energy of the sink's neighbor nodes. Through extensive simulation

155

Lighting direction and visual field modulate perceived intensity of illumination  

PubMed Central

When interpreting object shape from shading the visual system exhibits a strong bias that illumination comes from above and slightly from the left. We asked whether such biases in the perceived direction of illumination might also influence its perceived intensity. Arrays of nine cubes were stereoscopically rendered where individual cubes varied in their 3D pose, but possessed identical triplets of visible faces. Arrays were virtually illuminated from one of four directions: Above-Left, Above-Right, Below-Left, and Below-Right (±24.4° azimuth; ±90° elevation). Illumination intensity possessed 15 levels, resulting in mean cube array luminances ranging from 1.31–3.45 cd/m2. A “reference” array was consistently illuminated from Above-Left at mid-intensity (mean array luminance = 2.38 cd/m2). The reference array's illumination was compared to that of matching arrays which were illuminated from all four directions at all intensities. Reference and matching arrays appeared in the left and right visual field, respectively, or vice versa. Subjects judged which cube array appeared to be under more intense illumination. Using the method of constant stimuli we determined the illumination level of matching arrays required to establish subjective equality with the reference array as a function of matching cube visual field, illumination elevation, and illumination azimuth. Cube arrays appeared significantly more intensely illuminated when they were situated in the left visual field (p = 0.017), and when they were illuminated from below (p = 0.001), and from the left (p = 0.001). An interaction of modest strength was that the effect of illumination azimuth was greater for matching arrays situated in the left visual field (p = 0.042). We propose that objects lit from below appear more intensely illuminated than identical objects lit from above due to long-term adaptation to downward lighting. The amplification of perceived intensity of illumination for stimuli situated in the left visual field and lit from the left is best explained by tonic egocentric and allocentric leftward attentional biases, respectively. PMID:24399990

McCourt, Mark E.; Blakeslee, Barbara; Padmanabhan, Ganesh

2013-01-01

156

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

157

A 50kW module power station of directly solar-pumped iodine laser  

Microsoft Academic Search

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 (>25 kW) electric power requirements. Integration of multiple modules would provide an amount of power that exceeds the power of a single

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

1997-01-01

158

Advanced Glycation End Products Are Direct Modulators of ?-Cell Function  

PubMed Central

OBJECTIVE Excess accumulation of advanced glycation end products (AGEs) contributes to aging and chronic diseases. We aimed to obtain evidence that exposure to AGEs plays a role in the development of type 1 diabetes (T1D). RESEARCH DESIGN AND METHODS The effect of AGEs was examined on insulin secretion by MIN6N8 cells and mouse islets and in vivo in three separate rodent models: AGE-injected or high AGE–fed Sprague-Dawley rats and nonobese diabetic (NODLt) mice. Rodents were also treated with the AGE-lowering agent alagebrium. RESULTS ?-Cells exposed to AGEs displayed acute glucose-stimulated insulin secretory defects, mitochondrial abnormalities including excess superoxide generation, a decline in ATP content, loss of MnSOD activity, reduced calcium flux, and increased glucose uptake, all of which were improved with alagebrium treatment or with MnSOD adenoviral overexpression. Isolated mouse islets exposed to AGEs had decreased glucose-stimulated insulin secretion, increased mitochondrial superoxide production, and depletion of ATP content, which were improved with alagebrium or with MnTBAP, an SOD mimetic. In rats, transient or chronic exposure to AGEs caused progressive insulin secretory defects, superoxide generation, and ?-cell death, ameliorated with alagebrium. NODLt mice had increased circulating AGEs in association with an increase in islet mitochondrial superoxide generation, which was prevented by alagebrium, which also reduced the incidence of autoimmune diabetes. Finally, at-risk children who progressed to T1D had higher AGE concentrations than matched nonprogressors. CONCLUSIONS These findings demonstrate that AGEs directly cause insulin secretory defects, most likely by impairing mitochondrial function, which may contribute to the development of T1D. PMID:21911745

Coughlan, Melinda T.; Yap, Felicia Y.T.; Tong, David C.K.; Andrikopoulos, Sofianos; Gasser, Anna; Thallas-Bonke, Vicki; Webster, Diane E.; Miyazaki, Jun-ichi; Kay, Thomas W.; Slattery, Robyn M.; Kaye, David M.; Drew, Brian G.; Kingwell, Bronwyn A.; Fourlanos, Spiros; Groop, Per-Henrik; Harrison, Leonard C.; Knip, Mikael; Forbes, Josephine M.

2011-01-01

159

Myosin lever arm directs collective motion on cellular actin network.  

PubMed

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

2014-03-18

160

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

161

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

162

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

163

Photonic microwave generation and transmission using direct modulation of stably injection-locked semiconductor lasers  

NASA Astrophysics Data System (ADS)

Direct modulation of a semiconductor laser subject to stable injection locking is capable of generating microwave subcarriers that are broadly frequency-tunable, more than 4 times its free-running relaxation resonance frequency, and are highly sideband-asymmetric, more than 22 dB. The latter characteristic makes the laser system particularly attractive for radio-over-fiber applications. Therefore, such modulation sideband asymmetry, its underlying mechanism, and its effect on chromatic dispersion-induced microwave power variation are extensively studied, in particular, over a broad range of injection conditions. Mappings showing integrated and global understandings of the modulation sideband asymmetry together with the modulation frequency enhancement are obtained accordingly. Interestingly, it is found that the microwave frequency can be tuned over a broad range while keeping a similar level of modulation sideband asymmetry and vice versa, either of which is achieved by simply changing the injection condition. This, therefore, considerably adds the flexibility and re-configurability to the laser system. The cavity resonance shift due to injection locking is responsible for not only the enhanced modulation frequency but also the modulation sideband asymmetry, where a modification in its previous interpretation is obtained for explanation. The modified modulation characteristics are strong functions of the linewidth enhancement factor, making it possible to choose lasers with proper values of the factor for different photonic microwave characteristics.

Hwang, Sheng-Kwang; Chan, Sze-Chun; Hsieh, Shie-Chin; Li, Cheng-Yu

2011-07-01

164

Direct intensity modulation of three-guide coupled rectangular ring laser having bidirectional lasing characteristics  

NASA Astrophysics Data System (ADS)

We investigate the modulation properties of a three-guide coupled rectangular ring laser having bidirectional lasing characteristics. Two different rectangular lasers having active section lengths of 250 and 350 ?m and total cavity lengths of 580 and 780 ?m are fabricated. The rectangular laser cavity consists of four low loss total internal reflection mirrors and an output coupler made out of three passive coupled waveguides. For both the clockwise and counterclockwise circulating directions, the lasing threshold currents of around 38 mA are obtained at room temperature under continuous wave operation. A 3-dB modulation bandwidth over 3 GHz is observed in both circulating directions for two different lasers.

Kim, Doo Gun; Kim, Seon Hoon; Ki, Hyun Chul; Jang, Won-Gun; Lee, Dong-Kil; Kim, Hyo Jin; Kim, Hwe Jong; Oh, Geum-Yoon; Choi, Young-Wan; Dagli, Nadir

2012-03-01

165

Communities, modules and large-scale structure in networks  

NASA Astrophysics Data System (ADS)

Networks, also called graphs by mathematicians, provide a useful abstraction of the structure of many complex systems, ranging from social systems and computer networks to biological networks and the state spaces of physical systems. In the past decade there have been significant advances in experiments to determine the topological structure of networked systems, but there remain substantial challenges in extracting scientific understanding from the large quantities of data produced by the experiments. A variety of basic measures and metrics are available that can tell us about small-scale structure in networks, such as correlations, connections and recurrent patterns, but it is considerably more difficult to quantify structure on medium and large scales, to understand the `big picture'. Important progress has been made, however, within the past few years, a selection of which is reviewed here.

Newman, M. E. J.

2012-01-01

166

Spatially resolved non-invasive chemical stimulation for modulation of signalling in reconstructed neuronal networks.  

PubMed

Functional coupling of reconstructed neuronal networks with microelectronic circuits has potential for the development of bioelectronic devices, pharmacological assays and medical engineering. Modulation of the signal processing properties of on-chip reconstructed neuronal networks is an important aspect in such applications. It may be achieved by controlling the biochemical environment, preferably with cellular resolution. In this work, we attempt to design cell-cell and cell-medium interactions in confined geometries with the aim to manipulate non-invasively the activity pattern of an individual neuron in neuronal networks for long-term modulation. Therefore, we have developed a biohybrid system in which neuronal networks are reconstructed on microstructured silicon chips and interfaced to a microfluidic system. A high degree of geometrical control over the network architecture and alignment of the network with the substrate features has been achieved by means of aligned microcontact printing. Localized non-invasive on-chip chemical stimulation of micropatterned rat cortical neurons within a network has been demonstrated with an excitatory neurotransmitter glutamate. Our system will be useful for the investigation of the influence of localized chemical gradients on network formation and long-term modulation. PMID:16849242

Mourzina, Yulia; Steffen, Alfred; Kaliaguine, Dmitri; Wolfrum, Bernhard; Schulte, Petra; Böcker-Meffert, Simone; Offenhäusser, Andreas

2006-04-22

167

An integrated approach to identify causal network modules of complex diseases with application to colorectal cancer  

PubMed Central

Background Many methods have been developed to identify disease genes and further module biomarkers of complex diseases based on gene expression data. It is generally difficult to distinguish whether the variations in gene expression are causative or merely the effect of a disease. The limitation of relying on gene expression data alone highlights the need to develop new approaches that can explore various data to reflect the casual relationship between network modules and disease traits. Methods In this work, we developed a novel network-based approach to identify putative causal module biomarkers of complex diseases by integrating heterogeneous information, for example, epigenomic data, gene expression data, and protein–protein interaction network. We first formulated the identification of modules as a mathematical programming problem, which can be solved efficiently and effectively in an accurate manner. Then, we applied our approach to colorectal cancer (CRC) and identified several network modules that can serve as potential module biomarkers for characterizing CRC. Further validations using three additional gene expression datasets verified their candidate biomarker properties and the effectiveness of the method. Functional enrichment analysis also revealed that the identified modules are strongly related to hallmarks of cancer, and the enriched functions, such as inflammatory response, receptor and signaling pathways, are specific to CRC. Results Through constructing a transcription factor (TF)-module network, we found that aberrant DNA methylation of genes encoding TF considerably contributes to the activity change of some genes, which may function as causal genes of CRC, and that can also be exploited to develop efficient therapies or effective drugs. Conclusion Our method can potentially be extended to the study of other complex diseases and the multiclassification problem. PMID:22967703

Wen, Zhenshu; Liu, Zhi-Ping; Liu, Zhengrong; Zhang, Yan; Chen, Luonan

2013-01-01

168

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

169

Social network modulation of reward-related signals  

PubMed Central

Everyday goals and experiences are often shared with others who may hold different places within our social networks. We investigated whether the experience of sharing a reward differs with respect to social network. Twenty human participants played a card guessing game for shared monetary outcomes with three partners: a computer, a confederate (out-of-network), and a friend (in-network). Participants subjectively rated the experience of sharing a reward more positively with their friend than the other partners. Neuroimaging results support participants’ subjective reports, as ventral striatal BOLD responses were more robust when sharing monetary gains with a friend, as compared to with the confederate or computer, suggesting a higher value for sharing with an in-network partner. Interestingly, ratings of social closeness co-varied with this activity, resulting in a significant partner × closeness interaction: exploratory analysis showed that only participants reporting higher levels of closeness demonstrated partner-related differences in striatal BOLD response. These results suggest that reward valuation in social contexts is sensitive to distinctions of social network, such that sharing positive experiences with in-network others may carry higher value. PMID:22745503

Fareri, Dominic S.; Niznikiewicz, Michael A.; Lee, Victoria K.; Delgado, Mauricio R.

2012-01-01

170

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

171

Development of high-speed directly modulated DFB and DBR lasers with surface gratings  

NASA Astrophysics Data System (ADS)

The conventional distributed feedback and distributed Bragg reflector edge-emitting lasers employ buried gratings, which require two or more epitaxial growth steps. By using lateral corrugations of the ridge-waveguide as surface gratings the epitaxial overgrowth is avoided, reducing the fabrication complexity, increasing the yield and reducing the fabrication cost. The surface gratings are applicable to different materials, including Al-containing ones and can be easily integrated in complex device structures and photonic circuits. Single-contact and multiple contact edge-emitting lasers with laterally-corrugated ridge waveguide gratings have been developed both on GaAs and InP substrates with the aim to exploit the photon-photon resonance in order to extend their direct modulation bandwidth. The paper reports on the characteristics of such surface-grating-based lasers emitting both at 1.3 and 1.55 ?m and presents the photon-photon resonance extended small-signal modulation bandwidth (> 20 GHz) achieved with a 1.6 mm long single-contact device under direct modulation. Similarly structured devices, with shorter lengths are expected to exceed 40 GHz small-signal modulation bandwidth under direct modulation.

Dumitrescu, M.; Telkkälä, J.; Karinen, J.; Viheriälä, J.; Laakso, A.; Afzal, S.; Reithmaier, J.-P.; Kamp, M.; Melanen, P.; Uusimaa, P.; Bardella, P.; Vallone, M.; Montrosset, I.; Parillaud, O.; Krakowski, M.; Gready, D.; Eisenstein, G.; Sek, G.

2011-02-01

172

Simulation-based comparison of noise effects in wavelength modulation spectroscopy and direct absorption TDLAS  

NASA Astrophysics Data System (ADS)

A simulative investigation of noise effects in wavelength modulation spectroscopy (WMS) and direct absorption diode laser absorption spectroscopy is presented. Special attention is paid to the impact of quantization noise of the analog-to-digital conversion (ADC) of the photodetector signal in the two detection schemes with the goal of estimating the necessary ADC resolution for each technique. With laser relative intensity noise (RIN), photodetector shot noise and thermal amplifier noise included, the strategies used for noise reduction in direct and wavelength modulation spectroscopy are compared by simulating two respective systems. Results show that because of the combined effects of dithering by RIN and signal averaging, the resolutions required for the direct absorption setup are only slightly higher than for the WMS setup. Only for small contributions of RIN an increase in resolution will significantly improve signal quality in the direct scheme.

Lins, B.; Zinn, P.; Engelbrecht, R.; Schmauss, B.

2010-08-01

173

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

174

A digital receiver module with direct data acquisition for magnetic resonance imaging systems.  

PubMed

A digital receiver module for magnetic resonance imaging (MRI) with detailed hardware implementations is presented. The module is based on a direct sampling scheme using the latest mixed-signal circuit design techniques. A single field-programmable gate array chip is employed to perform software-based digital down conversion for radio frequency signals. The modular architecture of the receiver allows multiple acquisition channels to be implemented on a highly integrated printed circuit board. To maintain the phase coherence of the receiver and the exciter in the context of direct sampling, an effective phase synchronization method was proposed to achieve a phase deviation as small as 0.09°. The performance of the described receiver module was verified in the experiments for both low- and high-field (0.5 T and 1.5 T) MRI scanners and was compared to a modern commercial MRI receiver system. PMID:23126784

Tang, Weinan; Sun, Hongyu; Wang, Weimin

2012-10-01

175

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

176

Direct observation of atomic network migration in glass  

NASA Astrophysics Data System (ADS)

Many physical properties of glasses are still far from being understood at the atomic level. The lack of experimental methods capable of studying glassy dynamics at this scale has impeded the development of a complete model for atomic transport processes. Here we apply the new technique of atomic-scale x-ray photon correlation spectroscopy to directly observe single atomic motion in lead silicate glass. We show that dynamics change significantly depending on the glass composition, from single jump processes between inhomogeneous regions to multiple jump processes along network paths and through voids. Up until now, such measurements were far out of reach for temperatures below the glass transition. Our findings suggest that the method and the model introduced here will also help understanding atomic diffusion in a wide range of other glass systems.

Ross, Manuel; Stana, Markus; Leitner, Michael; Sepiol, Bogdan

2014-09-01

177

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

178

Picosecond optical pulse generation at gigahertz rates by direct modulation of a semiconductor laser  

NASA Technical Reports Server (NTRS)

We report the generation of picosecond pulses by the direct modulation of a buried heterostructure GaAlAs diode laser. Pulse width of 28 ps is achieved at a repetition frequency of 2.5 GHz. Pulse width dependence on the experimental parameters is described.

Auyeung, J.

1981-01-01

179

CORTICAL KYNURENIC ACID BI-DIRECTIONALLY MODULATES PREFRONTAL GLUTAMATE LEVELS AS ASSESSED BY  

E-print Network

CORTICAL KYNURENIC ACID BI-DIRECTIONALLY MODULATES PREFRONTAL GLUTAMATE LEVELS AS ASSESSED glutamate levels by endogenously produced kynurenic acid (KYNA) in the prefrontal cortex (PFC) of awake rats elevated extracellular KYNA and reduced extracellular glutamate (nadir after 50 mg/kg kynurenine: 60

Bruno, John P.

180

Modeling and simulation of a direct space vector modulated Matrix Converter using different switching strategies  

Microsoft Academic Search

This paper presents a MATLAB\\/Simulink simulation model for a direct space vector modulated matrix converter (MC). The power circuit model, consisting of an input filter, a matrix of bidirectional switches and an RL load, is completely implemented using the power library in Simulink, contributing to the simplicity and clearness of the whole model. Two switching strategies are modeled, simulated and

J. Vadillo; J. M. Echeverria; L. Fontan; M. Martinez-Iturralde; I. Elosegui

2008-01-01

181

Effect of Electrode Loss on the Dynamic Range of Linearized Directional Coupler Modulators.  

National Technical Information Service (NTIS)

Numerical simulations were used to study the effect of electrode loss on the two-tone spur-free dynamic range (SFDR) of analog photonic links with linearized directional coupler modulators. Radio-frequency loss in the traveling wave electrode significantl...

G. A. Brost, R. Michalak, P. Payson, K. Magde

2006-01-01

182

Self-oscillating modulators for direct energy conversion audio power amplifiers  

E-print Network

of the improved efficiency of the power supplies and power amplifiers that use switching approach instead will introduce a new control approach for SICAMs, that utilizes self-oscillating principle to im- proveSelf-oscillating modulators for direct energy conversion audio power amplifiers Petar Ljusev1

183

Neural Networks 23 (2010) 1415 Contents lists available at ScienceDirect  

E-print Network

Neural Networks 23 (2010) 14­15 Contents lists available at ScienceDirect Neural Networks journal homepage: www.elsevier.com/locate/neunet Neural networks letter Minimal neuroanatomy for a conscious brain: Homing in on the networks constituting consciousness Ezequiel Morsellaa,b, , Stephen C. Kriegerc , John A

Bargh, John A.

184

Superconducting Wire Network under Spatially Modulated Magnetic Field  

E-print Network

, Shingo Katsumoto, Yasuhiro Iye #12;Overview · Previous studies ­ Critical temperature Little Split coil #12;Little-Parks Oscillation ( ) -= 2 max 0 4 arccos )0( 1 l TBT cc Hofstadter butterfly under checkerboard modulation B. Pannetier et al., Phys. Rev. Lett. 53, 1845 #12;Result

Katsumoto, Shingo

185

The segment polarity network is a robust developmental module  

NASA Astrophysics Data System (ADS)

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

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

2000-07-01

186

Topological interactive analysis of power system and its communication module: A complex network approach  

NASA Astrophysics Data System (ADS)

Power system and its communication system, which can be called a cyber-physical system, are interconnected and interdependent on each other. This paper considers the interaction problem between power system and its communication module from the perspective of the topological structure. Firstly, some structural properties and centrality measures of complex networks are briefly reviewed. Furthermore, novel interactive measures are proposed to describe the interactive system in terms of topologies. Finally, based on these metrics, the statistical properties and the interactive relationships of the main power system and its communication module (abstracted as two complex heterogeneous networks) of one province in China are investigated.

Hu, Jianqiang; Yu, Jie; Cao, Jinde; Ni, Ming; Yu, Wenjie

2014-12-01

187

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

188

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

PubMed

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

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

2014-02-15

189

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

190

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

191

Superconducting Wire Network under Spatially Modulated Magnetic Field  

E-print Network

· Previous studies ­ Critical temperature Little-Parks oscillation ­ I-V Characteristics The nature of phase by rotating magnetization (B//=const.) #12;Sample Al network ­ 70 nm wide ­ 35 nm thick ­ Period = 500 nm + RP #12;Little-Parks Oscillation W. A. Little et al., Phys. Rev. Lett. 14, 2239 (1976). 215 0 Tm10072

Katsumoto, Shingo

192

Parallel microfluidic networks for studying cellular response to chemical modulation  

Microsoft Academic Search

A microfluidic chip featuring parallel gradient-generating networks etched on glass plate was designed and fabricated. The dam and weir structures were fabricated to facilitate cell positioning and seeding, respectively. The microchip contains five gradient generators and 30 cell chambers where the resulted concentration gradients of drugs are delivered to stimulate the on-chip cultured cells. This microfluidics exploits the advantage of

Dayu Liu; Lihui Wang; Runtao Zhong; Bowei Li; Nannan Ye; Xin Liu; Bingcheng Lin

2007-01-01

193

A MAC protocol for full exploitation of directional antennas in ad-hoc wireless networks  

Microsoft Academic Search

Directional antennas in ad hoc networks offer many benefits compared with classical omnidirectional antennas. The most important include significant increase of spatial reuse, coverage range and subsequently network capacity as a whole. On the other hand, the use of directional antennas requires new approach in the design of a MAC protocol to fully exploit these benefits. Unfortunately, directional transmissions increase

Thanasis Korakis; Gentian Jakllari; Leandros Tassiulas

2003-01-01

194

Clustering signatures classify directed networks S. E. Ahnert1  

E-print Network

-dimensional quantity consists of a recent gener- alization [11] of the undirected clustering coefficient [7- ent roles played by the nodes in these networks. For undirected networks the clustering coefficient

Halligan, Daniel

195

Effect of Gravitational Focusing on Annual Modulation in Dark-Matter Direct-Detection Experiments  

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

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

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

E-print Network

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

Tian, Jie

198

Modulation of spontaneous alpha brain rhythms using low-intensity transcranial direct-current stimulation  

PubMed Central

Transcranial direct-current stimulation (tDCS) is a form of neurostimulation in which a constant, low current is delivered directly to the brain area of interest by small electrodes. The overall aim of this study was to examine and monitor the modulation of brain activity by electroencephalogram (EEG) in the frequency domain during tDCS in the resting state. To this end, we considered the modulation of spontaneous EEG to be a marker of the perturbation that was induced through the direct current (1.5 mA for 15 min). In all conditions (anodal, cathodal, and sham), an active electrode was placed over the right posterior parietal cortex, and a reference electrode was placed on the ipsilateral deltoid muscle. The EEG was recorded using a 64-channel system. The effect of tDCS was limited to the alpha rhythm, and the anodal stimulation significantly affected the alpha rhythm, whereas the cathodal stimulation did not elicit any modifications. Further, we observed modulation of alpha activity in areas that were stimulated directly through tDCS and in anterior noncontiguous areas. Finally, the anodal effect peaked 7.5 min after stimulation and decreased gradually over time. Our study demonstrates that in the resting brain, monocephalic anodal tDCS over posterior parietal areas alters ongoing brain activity, specifically in the alpha band rhythm. Our data can be used to fine-tune tDCS protocols in neurorehabilitation settings. PMID:24027517

Spitoni, Grazia F.; Cimmino, Rocco L.; Bozzacchi, Chiara; Pizzamiglio, Luigi; Di Russo, Francesco

2013-01-01

199

Integration of turbo-generator modules in digital transient network analyzer  

SciTech Connect

The behavior of a small power system consisting of two interconnected generators is simulated in real-time by a prototype Digital Transient Network Analyzer (TNA). The prototype Digital TNA consists of two Computational Modules and one I/O Module. The Modules communicate with each other through ribbon cables. Each Computational Module simulates one Turbo-Generator, its Transformer, its Governor, Exciter, and Power System Stabilizer Systems. The numerical integration is shared by two TMS320C30 DSPs at a step-size of 100 microseconds in real-time. The I/O module post-processes the state variables and presents selected information for analog display. The paper presents oscillograms from a test program which includes symmetry checks and behavioral checks against well known waveforms of hunting oscillations, synchronization out-of-phase torques, and subsynchronous resonance phenomena. The success of the Digital TNA depends on: (a) the theoretical method of Decoupled Partitioning so that different portions of the power system can be allocated to different DSP-modules, (b) the architecture of the DSP-modules which can communicate the numerical integration results of one module to its contiguous neighbors with minimum delay.

Guo, Y.; Ooi, B.T.; Lee, H.C. (McGill Univ., Montreal, Quebec (Canada). Dept. of Electrical Engineering)

1994-05-01

200

Discrimination of Direction in Fast Frequency-Modulated Tones by Rats  

PubMed Central

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

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

2006-01-01

201

Directly phase-modulation-mode-locked doubly-resonant optical parametric oscillator.  

PubMed

We present results on direct mode-locking of a doubly-resonant optical parametric oscillator (DRO) using an electro-optic phase modulator with low resonant frequency of 80 MHz as the single mode-locking element. Pumped by a cw laser at 532 nm and based on MgO:sPPLT as the nonlinear material, the DRO generates 533 ps pulses at 80 MHz and 471 ps pulses at 160 MHz. Stable train of mode-locked pulses is obtained at a modulation depth of 1.83 radians when the modulation frequency is precisely tuned and the cavity length is carefully adjusted. The effects of frequency detuning, modulation depth, input laser pump power, crystal temperature and position of modulator inside the cavity, on pulse duration and repetition rate have been studied. Operating at degeneracy, under mode-locked condition, the signal-idler spectrum exhibits a bandwidth of ~31 nm, and the spectrum has been investigated for different phase-matching temperatures. Mode-locked operation has been confirmed by second-harmonic-generation of the DRO output in a ?-BaB?O? crystal, where a 4 times enhancement in green power is observed compared to cw operation. PMID:24104250

Devi, Kavita; Kumar, S Chaitanya; Ebrahim-Zadeh, M

2013-10-01

202

Improved performance of traveling wave directional coupler modulator based on electro-optic polymer  

E-print Network

Polymer based electro-optic modulators have shown great potentials in high frequency analog optical links. Existing commercial LiNibO3 Mach-Zehnder modulators have intrinsic drawbacks in linearity to provide high fidelity communication. In this paper, we present the design, fabrication and characterization of a traveling wave directional coupler modulator based on electro-optic polymer, which is able to provide high linearity, high speed, and low optical insertion loss. A silver ground electrode is used to reduce waveguide sidewall roughness due to the scattering of UV light in photolithography process in addition to suppressing the RF loss. A 1-to-2 multi-mode interference 3dB-splitter, a photobleached refractive index taper and a quasi-vertical taper are used to reduce the optical insertion loss of the device. The symmetric waveguide structure of the MMI-fed directional coupler is intrinsically bias-free, and the modulation is obtained at the 3-dB point regardless of the ambient temperature. By achieving lo...

Zhang, Xingyu; Lin, Che-yun; Wang, Alan X; Hosseini, Amir; Lin, Xiaohui; Chen, Ray T

2014-01-01

203

Temperature-modulated direct thermoelectric gas sensors: thermal modeling and results for fast hydrocarbon sensors  

NASA Astrophysics Data System (ADS)

Direct thermoelectric gas sensors are a promising alternative to conductometric gas sensors. For accurate results, a temperature modulation technique in combination with a regression analysis is advantageous. However, the thermal time constant of screen-printed sensors is quite large. As a result, up to now the temperature modulation frequency (20 mHz) has been too low and the corresponding principle-related response time (50 s) has been too high for many applications. With a special design, respecting the physical properties of thermal waves and the use of signal processing similar to a lock-in-amplifier, it is possible to achieve response times of about 1 s. As a result, direct thermoelectric gas sensors with SnO2 as a gas-sensitive material respond fast and are reproducible to the propane concentration in the ambient atmosphere. Due to the path-independent behavior of the thermovoltage and the temperature, the measured thermopower of two sensors is almost identical.

Rettig, Frank; Moos, Ralf

2009-06-01

204

Social status modulates neural activity in the mentalizing network  

PubMed Central

The current research explored the neural mechanisms linking social status to perceptions of the social world. Two fMRI studies provide converging evidence that individuals lower in social status are more likely to engage neural circuitry often involved in ‘mentalizing’ or thinking about others' thoughts and feelings. Study 1 found that college students' perception of their social status in the university community was related to neural activity in the mentalizing network (e.g., DMPFC, MPFC, precuneus/PCC) while encoding social information, with lower social status predicting greater neural activity in this network. Study 2 demonstrated that socioeconomic status, an objective indicator of global standing, predicted adolescents' neural activity during the processing of threatening faces, with individuals lower in social status displaying greater activity in the DMPFC, previously associated with mentalizing, and the amygdala, previously associated with emotion/salience processing. These studies demonstrate that social status is fundamentally and neurocognitively linked to how people process and navigate their social worlds. PMID:22289808

Muscatell, Keely A.; Morelli, Sylvia A.; Falk, Emily B.; Way, Baldwin M.; Pfeifer, Jennifer H.; Galinsky, Adam D.; Lieberman, Matthew D.; Dapretto, Mirella; Eisenberger, Naomi I.

2013-01-01

205

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

206

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

207

Dynamics and Directionality in Complex Networks Seung-Woo Son,1  

E-print Network

Dynamics and Directionality in Complex Networks Seung-Woo Son,1 Beom Jun Kim,2 Hyunsuk Hong,3 November 2009) We investigate how we can improve the synchronizability of complex networks simply, 05.45.Xt, 89.75.Fb For the last decade, complex network theory has suc- ceeded in describing diverse

Jeong, Hawoong

208

Transcriptional override: a regulatory network model of indirect responses to modulations in microRNA expression  

PubMed Central

Background Documented changes in levels of microRNAs (miRNA) in a variety of diseases including cancer are leading to their development as early indicators of disease, and as a potential new class of therapeutic agents. A significant hurdle to the rational application of miRNAs as therapeutics is our current inability to reliably predict the range of molecular and cellular consequences of perturbations in the levels of specific miRNAs on targeted cells. While the direct gene (mRNA) targets of individual miRNAs can be computationally predicted with reasonable degrees of accuracy, reliable predictions of the indirect molecular effects of perturbations in miRNA levels remain a major challenge in molecular systems biology. Results Changes in gene (mRNA) and miRNA expression levels between normal precursor and ovarian cancer cells isolated from patient tissue samples were measured by microarray. Expression of 31 miRNAs was significantly elevated in the cancer samples. Consistent with previous reports, the expected decrease in expression of the mRNA targets of upregulated miRNAs was observed in only 20-30% of the cancer samples. We present and provide experimental support for a network model (The Transcriptional Override Model; TOM) to account for the unexpected regulatory consequences of modulations in the expression of miRNAs on expression levels of their target mRNAs in ovarian cancer. Conclusions The direct and indirect regulatory effects of changes in miRNA expression levels in vivo are interactive and complex but amenable to systems level modeling. Although TOM has been developed and validated within the context of ovarian cancer, it may be applicable in other biological contexts as well, including of potential future use in the rational design of miRNA-based strategies for the treatment of cancers and other diseases. PMID:24666724

2014-01-01

209

Global analysis of the human pathophenotypic similarity gene network merges disease module components.  

PubMed

The molecular complexity of genetic diseases requires novel approaches to break it down into coherent biological modules. For this purpose, many disease network models have been created and analyzed. We highlight two of them, "the human diseases networks" (HDN) and "the orphan disease networks" (ODN). However, in these models, each single node represents one disease or an ambiguous group of diseases. In these cases, the notion of diseases as unique entities reduces the usefulness of network-based methods. We hypothesize that using the clinical features (pathophenotypes) to define pathophenotypic connections between disease-causing genes improve our understanding of the molecular events originated by genetic disturbances. For this, we have built a pathophenotypic similarity gene network (PSGN) and compared it with the unipartite projections (based on gene-to-gene edges) similar to those used in previous network models (HDN and ODN). Unlike these disease network models, the PSGN uses semantic similarities. This pathophenotypic similarity has been calculated by comparing pathophenotypic annotations of genes (human abnormalities of HPO terms) in the "Human Phenotype Ontology". The resulting network contains 1075 genes (nodes) and 26197 significant pathophenotypic similarities (edges). A global analysis of this network reveals: unnoticed pairs of genes showing significant pathophenotypic similarity, a biological meaningful re-arrangement of the pathological relationships between genes, correlations of biochemical interactions with higher similarity scores and functional biases in metabolic and essential genes toward the pathophenotypic specificity and the pleiotropy, respectively. Additionally, pathophenotypic similarities and metabolic interactions of genes associated with maple syrup urine disease (MSUD) have been used to merge into a coherent pathological module.Our results indicate that pathophenotypes contribute to identify underlying co-dependencies among disease-causing genes that are useful to describe disease modularity. PMID:23437198

Reyes-Palomares, Armando; Rodríguez-López, Rocío; Ranea, Juan A G; Sánchez Jiménez, Francisca; Medina, Miguel Angel

2013-01-01

210

Global Analysis of the Human Pathophenotypic Similarity Gene Network Merges Disease Module Components  

PubMed Central

The molecular complexity of genetic diseases requires novel approaches to break it down into coherent biological modules. For this purpose, many disease network models have been created and analyzed. We highlight two of them, “the human diseases networks” (HDN) and “the orphan disease networks” (ODN). However, in these models, each single node represents one disease or an ambiguous group of diseases. In these cases, the notion of diseases as unique entities reduces the usefulness of network-based methods. We hypothesize that using the clinical features (pathophenotypes) to define pathophenotypic connections between disease-causing genes improve our understanding of the molecular events originated by genetic disturbances. For this, we have built a pathophenotypic similarity gene network (PSGN) and compared it with the unipartite projections (based on gene-to-gene edges) similar to those used in previous network models (HDN and ODN). Unlike these disease network models, the PSGN uses semantic similarities. This pathophenotypic similarity has been calculated by comparing pathophenotypic annotations of genes (human abnormalities of HPO terms) in the “Human Phenotype Ontology”. The resulting network contains 1075 genes (nodes) and 26197 significant pathophenotypic similarities (edges). A global analysis of this network reveals: unnoticed pairs of genes showing significant pathophenotypic similarity, a biological meaningful re-arrangement of the pathological relationships between genes, correlations of biochemical interactions with higher similarity scores and functional biases in metabolic and essential genes toward the pathophenotypic specificity and the pleiotropy, respectively. Additionally, pathophenotypic similarities and metabolic interactions of genes associated with maple syrup urine disease (MSUD) have been used to merge into a coherent pathological module. Our results indicate that pathophenotypes contribute to identify underlying co-dependencies among disease-causing genes that are useful to describe disease modularity. PMID:23437198

Reyes-Palomares, Armando; Rodriguez-Lopez, Rocio; Ranea, Juan A. G.; Jimenez, Francisca Sanchez; Medina, Miguel Angel

2013-01-01

211

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

212

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

PubMed

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

2015-02-01

213

A Property-Based Optimization of Direct Recycle Networks and Wastewater  

E-print Network

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

Grossmann, Ignacio E.

214

Sex-Specific Modulation of Gene Expression Networks in Murine Hypothalamus  

PubMed Central

The hypothalamus contains nuclei and cell populations that are critical in reproduction and that differ significantly between the sexes in structure and function. To examine the molecular and genetic basis for these differences, we quantified gene expression in the hypothalamus of 39 pairs of adult male and female mice belonging to the BXD strains. This experimental design enabled us to define hypothalamic gene coexpression networks and provided robust estimates of absolute expression differences. As expected, sex has the strongest effect on the expression of genes on the X and Y chromosomes (e.g., Uty, Xist, Kdm6a). Transcripts associated with the endocrine system and neuropeptide signaling also differ significantly. Sex-differentiated transcripts often have well delimited expression within specific hypothalamic nuclei that have roles in reproduction. For instance, the estrogen receptor (Esr1) and neurokinin B (Tac2) genes have intense expression in the medial preoptic and arcuate nuclei and comparatively high expression in females. Despite the strong effect of sex on single transcripts, the global pattern of covariance among transcripts is well preserved, and consequently, males and females have well matched coexpression modules. However, there are sex-specific hub genes in functionally equivalent modules. For example, only in males is the Y-linked gene, Uty, a highly connected transcript in a network that regulates chromatin modification and gene transcription. In females, the X chromosome paralog, Kdm6a, takes the place of Uty in the same network. We also find significant effect of sex on genetic regulation and the same network in males and females can be associated with markedly different regulatory loci. With the exception of a few sex-specific modules, our analysis reveals a system in which sets of functionally related transcripts are organized into stable sex-independent networks that are controlled at a higher level by sex-specific modulators. PMID:22593731

Mozhui, Khyobeni; Lu, Lu; Armstrong, William E.; Williams, Robert W.

2012-01-01

215

Improved Connectivity using Hybrid Uni/Omni-Directional Antennas in Sensor Networks  

E-print Network

the capability of networks to be able to report sensed information. The ability of member nodes to communicate with each other and collectively report data largely depends on connectivity. Density of node deployment, the transmission radius of the antenna... and the communication paradigm employed has a significant effect on connectivity. A network deployment is said to be connected when every node within the network is capable of communicating, either via multi-hops or direct links to every other node in the network...

Kwon, Ji Heon

2008-05-27

216

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

217

ABC and IFC: modules detection method for PPI network.  

PubMed

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; Wu, Fang-Xiang; Tian, Jianfang; Zhao, Jie

2014-01-01

218

A 50-kW module power station of directly solar-pumped iodine laser  

SciTech Connect

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 (>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. [NASA Langley Research Center, Hampton, VA (United States)

1997-11-01

219

A Scheduling Algorithm for Connected Target Coverage in Rotatable Directional Sensor Networks  

NASA Astrophysics Data System (ADS)

A key challenge in developing energy-efficient sensor networks is to extend network lifetime in resource-limited environments. As sensors are often densely distributed, they can be scheduled on alternative duty cycles to conserve energy while satisfying the system requirements. Directional sensor networks composed of a large number of directional sensors equipped with a limited battery and with a limited angle of sensing have recently attracted attention. Many types of directional sensors can rotate to face a given direction. Maximizing network lifetime while covering all of the targets in a given area and forwarding sensor data to the sink is a challenge in developing such rotatable directional sensor networks. In this paper, we address the maximum directional cover tree (MDCT) problem of organizing directional sensors into a group of non-disjoint subsets to extend network lifetime. One subset, in which the directional sensors cover all of the targets and forward the data to the sink, is activated at a time, while the others sleep to conserve energy. For the MDCT problem, we first present an energy-consumption model that mainly takes into account the energy expenditure for sensor rotation as well as for the sensing and relaying of data. We also develop a heuristic scheduling algorithm called directional coverage and connectivity (DCC)-greedy to solve the MDCT problem. To verify and evaluate the algorithm, we conduct extensive simulations and show that it extends network lifetime to a reasonable degree.

Han, Youn-Hee; Kim, Chan-Myung; Gil, Joon-Min

220

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

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

2012-01-01

221

Towards a direction-sensitive optical module for neutrino telescopes based on a hybrid photon detector  

NASA Astrophysics Data System (ADS)

The optical modules of all currently operating neutrino telescopes contain one standard PMT with a large hemispherical photo-cathode. The maximum spatial resolution of this detection principle is thus limited to the photo-cathode area and no information is obtained on the direction of the incoming photons. We propose a new direction-sensitive design featuring a fisheye lens and a hybrid photon detector. The lens system maps incoming photons from one direction on a well-defined point on the photo-cathode of the hybrid photon detector. The photo-electrons are accelerated in a cross-focussed optics and detected using a pixelated anode, which allows for very high spatial resolution. As a candidate chip for the photo-electron detection we propose the Timepix detector of the Medipix family. We have successfully shown its capability to detect photo-electrons in the experiment and evaluated the time resolution by simulation and measurement.

Rügheimer, Tilman K.; Gebert, Ulrike; Michel, Thilo; Anton, Gisela; Séguinot, Jacques; Joram, Christian

2009-12-01

222

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

NASA Astrophysics Data System (ADS)

We report a field sensor, which senses the external field by detecting the change of frequency component in the modulated GMR output. The proposed sensor works in a closed-loop mode with negative feedback and the free-layer magnetization is modulated by an alternative field Hac (2.3 Oe). The sensor output (Vout) is proportional to the applied external field (Hex) in the range from -1.5 to +1.5 Oe. Vout is determined only by the feedback current, and has no direct relationship with the magnetoresistance ratio or the gains of the amplifiers. The proposed sensor exhibits a much lower temperature drift (about 1/50) compared with a typical magnetization rotation-type sensor and a further reduction in the drift can be achieved by improving the signal acquisition circuit; thus it can be used for high-precision dc field detection without any additional temperature compensation.

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

2011-06-01

223

A method for evaluating dynamic functional network connectivity and task-modulation: application to schizophrenia  

Microsoft Academic Search

Objective  In this paper, we develop a dynamic functional network connectivity (FNC) analysis approach using correlations between windowed\\u000a time-courses of different brain networks (components) estimated via spatial independent component analysis (sICA). We apply\\u000a the developed method to fMRI data to evaluate it and to study task-modulation of functional connections.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and methods  We study the theoretical basis of the approach, perform a

Ünal Sako?lu; Godfrey D. Pearlson; Kent A. Kiehl; Y. Michelle Wang; Andrew M. Michael; Vince D. Calhoun

2010-01-01

224

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

225

Acupuncture modulates temporal neural responses in wide brain networks: evidence from fMRI study  

Microsoft Academic Search

BACKGROUND: Accumulating neuroimaging studies in humans have shown that acupuncture can modulate a widely distributed brain network, large portions of which are overlapped with the pain-related areas. Recently, a striking feature of acupuncture-induced analgesia is found to be associated with its long-last effect, which has a delayed onset and gradually reaches a peak even after acupuncture needling being terminated. Identifying

Lijun Bai; Jie Tian; Chongguang Zhong; Ting Xue; Youbo you; Zhenyu Liu; Peng Chen; Qiyong Gong; Lin Ai; Wei Qin; Jianping Dai; Yijun Liu

2010-01-01

226

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

Microsoft Academic Search

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

Ai Li; Steve Horvath

2009-01-01

227

Identifying missing and spurious connections via the bi-directional diffusion on bipartite networks  

NASA Astrophysics Data System (ADS)

Link prediction and spurious link detection in complex networks have attracted increasing attention from both physical and computer science communities, due to their wide applications in many real systems. Related previous works mainly focus on monopartite networks while these problems in bipartite networks are not yet systematically addressed. Containing two different kinds of nodes, bipartite networks are essentially different from monopartite networks, especially in node similarity calculation: the similarity between nodes of different kinds (called inter-similarity) is not well defined. In this letter, we employ the local diffusion processes to measure the inter-similarity in bipartite networks. We find that the inter-similarity is asymmetric if the diffusion is applied in different directions. Accordingly, we propose a bi-directional hybrid diffusion method which is shown to achieve higher accuracy than the existing diffusion methods in identifying missing and spurious links in bipartite networks.

Zhang, Peng; Zeng, An; Fan, Ying

2014-06-01

228

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

PubMed

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

229

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

230

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

SciTech Connect

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

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

2012-11-15

231

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

232

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

233

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

234

Performance comparison of frequency-hop spread-spectrum multiple-access networks using different modulation orders  

Microsoft Academic Search

The main concern of this paper is to estimate the symbol error probability of asynchronous FHSS multiple-access networks through Monte Carlo simulations and use this estimate to compare more accurately the performance of FHSS multiple-access networks with different modulation orders M. The author concentrates on systems transmitting one M-ary (M⩾2) orthogonal FSK modulated symbol per hop with noncoherent demodulation. The

KYUNGWHOON CHEUN

1993-01-01

235

Modulation of synchronization dynamics in a network of self-sustained systems  

NASA Astrophysics Data System (ADS)

This paper addresses the combined modulatory effects of non-nearest neighbor oscillators and local injection on synchronized states dynamics with their corresponding stability boundaries in a network of self-sustained systems. The Whittaker method and Floquet theory are used to predict analytically the stability of these states for identical and non-identical coupling parameters. Charts revealing the modulation of synchronized states and their stability boundaries at the second order of interaction in the cases of identical and non-identical coupling parameters are constructed with and without an external signal locally injected in the network. Numerical simulations validate and complement the results of analytical surveys. The limits of the stability regions are numerically explored when a small amount of Gaussian white noise is also injected in the network.

Enjieu Kadji, H. G.; Chabi Orou, J. B.; Sanjuán, M. A. F.

2014-03-01

236

Agreement Problems in Networks with Directed Graphs and Switching Topology  

E-print Network

vehicles (UAVs), flocking of birds, schooling for underwater ve- hicles, distributed sensor networks problems have a long history in the field of computer science, particularly in automata theory to the motion of the individual agents. As a result, it is important to address agreement problems in their gen

Murray, Richard M.

237

Implementing direct, spatially isolated problems on transputer networks  

NASA Technical Reports Server (NTRS)

Parametric studies were performed on transputer networks of up to 40 processors to determine how to implement and maximize the performance of the solution of problems where no processor-to-processor data transfer is required for the problem solution (spatially isolated). Two types of problems are investigated a computationally intensive problem where the solution required the transmission of 160 bytes of data through the parallel network, and a communication intensive example that required the transmission of 3 Mbytes of data through the network. This data consists of solutions being sent back to the host processor and not intermediate results for another processor to work on. Studies were performed on both integer and floating-point transputers. The latter features an on-chip floating-point math unit and offers approximately an order of magnitude performance increase over the integer transputer on real valued computations. The results indicate that a minimum amount of work is required on each node per communication to achieve high network speedups (efficiencies). The floating-point processor requires approximately an order of magnitude more work per communication than the integer processor because of the floating-point unit's increased computing capacity.

Ellis, Graham K.

1988-01-01

238

Impedance is modulated to meet accuracy demands during goal-directed arm movements.  

PubMed

The neuromuscular system is inherently noisy and joint impedance may serve to filter this noise. In the present experiment, we investigated whether individuals modulate joint impedance to meet spatial accuracy demands. Twelve subjects were instructed to make rapid, time constrained, elbow extensions to three differently sized targets. Some trials (20 out of 140 for each target, randomly assigned) were perturbed mechanically at 75% of movement amplitude. Inertia, damping and stiffness were estimated from the torque and angle deviation signal using a forward simulation and optimization routine. Increases in endpoint accuracy were not always reflected in a decrease in trajectory variability. Only in the final quarter of the trajectory the variability decreased as target width decreased. Stiffness estimates increased significantly with accuracy constraints. Damping estimates only increased for perturbations that were initially directed against the movement direction. We concluded that joint impedance modulation is one of the strategies used by the neuromuscular system to generate accurate movements, at least during the final part of the movement. PMID:16372169

Selen, Luc P J; Beek, Peter J; van Dieën, Jaap H

2006-06-01

239

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

240

Modulation of cortical activity by transcranial direct current stimulation in patients with affective disorder.  

PubMed

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

241

Performance of motor imagery brain-computer interface based on anodal transcranial direct current stimulation modulation.  

PubMed

Voluntarily modulating neural activity plays a key role in brain-computer interface (BCI). In general, the self-regulated neural activation patterns are used in the current BCI systems involving the repetitive trainings with feedback for an attempt to achieve a high-quality control performance. With the limitation posed by the training procedure in most BCI studies, the present work aims to investigate whether directly modulating the neural activity by using an external method could facilitate the BCI control. We designed an experimental paradigm that combines anodal transcranial direct current stimulation (tDCS) with a motor imagery (MI)-based feedback EEG BCI system. Thirty-two young and healthy human subjects were randomly assigned to the real and sham stimulation groups to evaluate the effect of tDCS-induced EEG pattern changes on BCI classification accuracy. Results showed that the anodal tDCS obviously induces sensorimotor rhythm (SMR)-related event-related desynchronization (ERD) pattern changes in the upper-mu (10-14 Hz) and beta (14-26 Hz) rhythm components. Both the online and offline BCI classification results demonstrate that the enhancing ERD patterns could conditionally improve BCI performance. This pilot study suggests that the tDCS is a promising method to help the users to develop reliable BCI control strategy in a relatively short time. PMID:23475381

Wei, Pengfei; He, Wei; Zhou, Yi; Wang, Liping

2013-05-01

242

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

243

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

244

The Myth of Spatial Reuse with Directional Antennas in Indoor Wireless Networks  

NASA Astrophysics Data System (ADS)

Interference among co-channel users is a fundamental problem in wireless networks, which prevents nearby links from operating concurrently. Directional antennas allow the radiation patterns of wireless transmitters to be shaped to form directed beams. Conventionally, such beams are assumed to improve the spatial reuse (i.e. concurrency) in indoor wireless networks. In this paper, we use experiments in an indoor office setting of Wifi Access points equipped with directional antennas, to study their potential for interference mitigation and spatial reuse. In contrast to conventional wisdom, we observe that the interference mitigation benefits of directional antennas are minimal. On analyzing our experimental traces we observe that directional links do not reduce interference to nearby links due to the lack of signal confinement due to indoor multipath fading. We then use the insights derived from our study to develop an alternative approach that provides better interference reduction in indoor networks compared to directional links.

Lakshmanan, Sriram; Sundaresan, Karthikeyan; Rangarajan, Sampath; Sivakumar, Raghupathy

245

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

246

The Myth of Spatial Reuse with Directional Antennas in Indoor Wireless Networks  

E-print Network

wireless networks. In this paper, we use experiments in an indoor office setting of Wifi Access points antennas are minimal. On analyzing our experimental traces we observe that directional links do not reduce

Sivakumar, Raghupathy

247

Neural Networks 22 (2009) 425449 Contents lists available at ScienceDirect  

E-print Network

Neural Networks 22 (2009) 425­449 Contents lists available at ScienceDirect Neural Networks journal for Perceptual Dynamics, RIKEN (Institute for Physical and Chemical Research) Brain Science Institute, 2 x, y y} Symbols x, y denote variables on different spatial axes. The value of S0(x, y) depends

248

Neural Networks 22 (2009) 781790 Contents lists available at ScienceDirect  

E-print Network

to reconstruct kinematic trajectories with the purpose of bypass- ing spinal cord lesions (Brockwell, RojasNeural Networks 22 (2009) 781­790 Contents lists available at ScienceDirect Neural Networks journal, Donoghue, & Black, 2006). While an animal performs 3D food-reaching tasks or 2D target-tracking tasks

Slatton, Clint

249

Performance of the Direct Binary n-Cube Network for Multiprocessors  

Microsoft Academic Search

A mathematical model for predicting the performance of the direct binary n-cube interconnection scheme is presented. These predictions are checked against simulations of a comparable system. The results for the network are compared to known results for indirect interconnection schemes like the crossbar and indirect n-cube networks. Special operation conditions such as broadcasts and hot spots are considered. The following

Seth Abraham; Krishnan Padmanabhan

1989-01-01

250

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

251

Modulation of cholinergic transmission in the neuronal network of the gill and siphon withdrawal reflex in Aplysia  

Microsoft Academic Search

Inhibitory interneurons are important elements of the network underlying the gill and siphon withdrawal reflex in Aplysia, and a large component of this inhibition is cholinergic. In this study, we investigated one key identified cholinergic inhibitory interneuron of the network, neuron L16, and studied some properties of its synaptic transmission and its modulation. We found that a slow inhibitory postsynaptic

M Storozhuk; V. F Castellucci

1999-01-01

252

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

253

Modulation of cerebellar excitability by polarity-specific non-invasive direct current stimulation  

PubMed Central

The cerebellum is a crucial structure involved in movement control and cognitive processing. Non-invasive stimulation of the cerebellum results in neurophysiological and behavioral changes, an effect that has been attributed to modulation of cerebello–brain connectivity. At rest, the cerebellum exerts an overall inhibitory tone over the primary motor cortex (M1), cerebello-brain inhibition (CBI), likely through dentate-thalamo-cortical connections. The level of excitability of this pathway before and after stimulation of the cerebellum, however, has not been directly investigated. In this study we used transcranial magnetic stimulation (TMS) to determine changes in M1, brainstem and CBI before and after 25 minutes of anodal, cathodal or sham transcranial direct current stimulation (tDCS) applied over the right cerebellar cortex. We hypothesized that anodal tDCS would result in an enhancement of CBI and cathodal would decrease it, relative to sham stimulation. We found that cathodal tDCS resulted in a clear decrease of CBI, whereas anodal tDCS increased it, in the absence of changes after sham stimulation. These effects were specific to the cerebello-cortical connections with no changes in other M1 or brainstem excitability measures. The cathodal effect on CBI was found to be dependent on stimulation intensity and lasted up to 30 minutes after the cessation of tDCS. These results suggest that tDCS can modulate in a focal and polarity-specific manner cerebellar excitability, likely through changes in Purkinje cell activity. Therefore, direct current stimulation of the cerebellum may have significant potential implications for patients with cerebellar dysfunction as well as to motor control studies. PMID:19605648

Galea, Joseph M.; Jayaram, Gowri; Ajagbe, Loni; Celnik, Pablo

2009-01-01

254

Dopaminergic modulation of tracer coupling in a ganglion-amacrine cell network  

PubMed Central

Many retinal ganglion cells are coupled via gap junctions with neighboring amacrine cells and ganglion cells. We investigated the extent and dynamics of coupling in one such network, the OFF ? ganglion cell of rabbit retina and its associated amacrine cells. We also observed the relative spread of Neurobiotin injected into a ganglion cell in the presence of modulators of gap junctional permeability. We found that gap junctions between amacrine cells were closed via stimulation of a D1 dopamine receptor, while the gap junctions between ganglion cells were closed via stimulation of a D2 dopamine receptor. The pairs of hemichannels making up the heterologous gap junctions between the ganglion and amacrine cells were modulated independently, so that elevations of cAMP in the ganglion cell open the ganglion cell hemichannels, while elevations of cAMP in the amacrine cell close its hemichannels. We also measured endogenous dopamine release from an eyecup preparation and found a basal release from the dark-adapted retina of approximately 2 pmol/min during the day. Maximal stimulation with light increased the rate of dopamine release from rabbit retina by 66%. The results suggest that coupling between members of the OFF ? ganglion cell/amacrine cell network is differentially modulated with changing levels of dopamine. PMID:17711603

MILLS, STEPHEN L.; XIA, XIAO-BO; HOSHI, HIDEO; FIRTH, SALLY I.; RICE, MARGARET E.; FRISHMAN, LAURA J.; MARSHAK, DAVID W.

2008-01-01

255

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

256

Energy Efficient Broadcast Routing in Ad Hoc Sensor Networks with Directional Antennas  

Microsoft Academic Search

Different from omni-directional antennas, directional antennas model allows that each sensor can adjust the beam-width from\\u000a ?\\u000a \\u000a min\\u000a to 360° and steer the antenna orientation to any desired direction [1], [2]. In this paper, we discuss the energy efficient\\u000a broadcast problem with the directional antenna model in ad hoc sensor networks. The problem of our concern is: given n nodes

Deying Li; Zheng Li; Lin Liu

2008-01-01

257

An Experimental Wireless Mesh Network Node Based on AVR ATmega16 Microcontroller and RFM12B Radio Module  

NASA Astrophysics Data System (ADS)

The paper describes a simple node designed to act as part of an experimental wireless mesh network. The node is based on Atmel AVR ATmega16 microcontroller and Hope Microelectronics RFM12B radio module. Along with technical details of the node, the network layer (addressing scheme and routing algorithms) is presented. Fundamental principles on wireless mesh networks are also presented. Experimental results summarize the paper and prove limited usability of the project.

Olejnik, Remigiusz

258

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

259

Transcranial direct-current stimulation modulates synaptic mechanisms involved in associative learning in behaving rabbits  

PubMed Central

Transcranial direct-current stimulation (tDCS) is a noninvasive brain stimulation technique that has been successfully applied for modulation of cortical excitability. tDCS is capable of inducing changes in neuronal membrane potentials in a polarity-dependent manner. When tDCS is of sufficient length, synaptically driven after-effects are induced. The mechanisms underlying these after-effects are largely unknown, and there is a compelling need for animal models to test the immediate effects and after-effects induced by tDCS in different cortical areas and evaluate the implications in complex cerebral processes. Here we show in behaving rabbits that tDCS applied over the somatosensory cortex modulates cortical processes consequent to localized stimulation of the whisker pad or of the corresponding area of the ventroposterior medial (VPM) thalamic nucleus. With longer stimulation periods, poststimulation effects were observed in the somatosensory cortex only after cathodal tDCS. Consistent with the polarity-specific effects, the acquisition of classical eyeblink conditioning was potentiated or depressed by the simultaneous application of anodal or cathodal tDCS, respectively, when stimulation of the whisker pad was used as conditioned stimulus, suggesting that tDCS modulates the sensory perception process necessary for associative learning. We also studied the putative mechanisms underlying immediate effects and after-effects of tDCS observed in the somatosensory cortex. Results when pairs of pulses applied to the thalamic VPM nucleus (mediating sensory input) during anodal and cathodal tDCS suggest that tDCS modifies thalamocortical synapses at presynaptic sites. Finally, we show that blocking the activation of adenosine A1 receptors prevents the long-term depression (LTD) evoked in the somatosensory cortex after cathodal tDCS. PMID:22493252

Marquez-Ruiz, Javier; Leal-Campanario, Rocio; Sanchez-Campusano, Raudel; Molaee-Ardekani, Behnam; Wendling, Fabrice; Miranda, Pedro C.; Ruffini, Giulio; Gruart, Agnes; Delgado-Garcia, Jose Maria

2012-01-01

260

Task-related concurrent but opposite modulations of overlapping functional networks as revealed by spatial ICA  

PubMed Central

Animal studies indicate that different functional networks (FNs), each with a unique timecourse, may overlap at common brain regions. For understanding how different FNs overlap in the human brain and how the timecourses of overlapping FNs are modulated by cognitive tasks, we applied spatial independent component analysis (sICA) to functional magnetic resonance imaging (fMRI) data. These data were acquired from healthy participants while they performed a visual task with parametric loads of attention and working memory. SICA identified a total of 14 FNs, and they showed different extents of overlap at a majority of brain regions exhibiting any functional activity. More FNs overlapped at the higher-order association cortex including the anterior and posterior cingulate, precuneus, insula, and lateral and medial frontoparietal cortex (FPC) than at the primary sensorimotor cortex. Furthermore, overlapping FNs exhibited concurrent but different task-related modulations of timecourses. FNs showing task-related up- vs. down-modulation of timecourses overlapped at both the lateral and medial FPC and subcortical structures including the thalamus, striatum, and midbrain ventral tegmental area (VTA). Such task-related, concurrent, but opposite changes in timecourses in the same brain regions may not be detected by current analyses based on General-Linear-Model (GLM). The present findings indicate that multiple cognitive processes may associate with common brain regions and exhibit simultaneous but different modulations in timecourses during cognitive tasks. PMID:23611864

Xu, Jiansong; Zhang, Sheng; Calhoun, Vince D.; Monterosso, John; Li, Chiang-Shan R.; Worhunsky, Patrick D.; Stevens, Michael; Pearlson, Godfrey D.; Potenza, Marc N.

2013-01-01

261

Towards the identification of protein complexes and functional modules by integrating PPI network and gene expression data  

PubMed Central

Background Identification of protein complexes and functional modules from protein-protein interaction (PPI) networks is crucial to understanding the principles of cellular organization and predicting protein functions. In the past few years, many computational methods have been proposed. However, most of them considered the PPI networks as static graphs and overlooked the dynamics inherent within these networks. Moreover, few of them can distinguish between protein complexes and functional modules. Results In this paper, a new framework is proposed to distinguish between protein complexes and functional modules by integrating gene expression data into protein-protein interaction (PPI) data. A series of time-sequenced subnetworks (TSNs) is constructed according to the time that the interactions were activated. The algorithm TSN-PCD was then developed to identify protein complexes from these TSNs. As protein complexes are significantly related to functional modules, a new algorithm DFM-CIN is proposed to discover functional modules based on the identified complexes. The experimental results show that the combination of temporal gene expression data with PPI data contributes to identifying protein complexes more precisely. A quantitative comparison based on f-measure reveals that our algorithm TSN-PCD outperforms the other previous protein complex discovery algorithms. Furthermore, we evaluate the identified functional modules by using “Biological Process” annotated in GO (Gene Ontology). The validation shows that the identified functional modules are statistically significant in terms of “Biological Process”. More importantly, the relationship between protein complexes and functional modules are studied. Conclusions The proposed framework based on the integration of PPI data and gene expression data makes it possible to identify protein complexes and functional modules more effectively. Moveover, the proposed new framework and algorithms can distinguish between protein complexes and functional modules. Our findings suggest that functional modules are closely related to protein complexes and a functional module may consist of one or multiple protein complexes. The program is available at http://netlab.csu.edu.cn/bioinfomatics/limin/DFM-CIN/index.html. PMID:22621308

2012-01-01

262

Modulation of the directional attention deficit in visual neglect by hemispatial factors.  

PubMed

Using a visuo-spatial cuing paradigm, Posner and collaborators (Posner, Cohen, & Rafal, 1982; Posner, Walker, Friedrich, & Rafal, 1984) reported that subjects with a parietal lobe lesion have difficulty in disengaging their visual attention from an invalidly precued location in the ipsilesional hemifield when the target they have to respond to is presented in the contralesional field. Later, these authors (Posner, Walker, Friedrich, & Rafal, 1987) proposed that this disengagement deficit is one involving spatial shifts of attention in a contralesional direction, irrespective of the visual hemifield in which the target is presented. This proposal of a directional disengagement deficit along the horizontal axis, present in either hemifield, contrasts with a report by Baynes, Holtzman, & Volpe (1986) showing, in right parietal subjects, a disengagement deficit for shifts of attention along the vertical axis that is only manifest in the contralesional hemifield. In the present report, we assessed the disengagement deficit of a neglect subject along the horizontal and vertical axes. Results show a disengagement deficit restricted to shifts of attention in the contralesional direction (horizontal axis), which is significant only in the contralesional visual hemifield. However, there is a clear trend for a directional disengagement deficit in the ipsilateral field. These observations indicate that the attention deficit present in neglect is directional and is modulated either by hemispatial factors or by the lateral target location in the visual field. On the basis of the present results, it is proposed that the deficit of parietal subjects may best be conceptualized as one of attentional capture for stimuli located on the contralesional side of the current focus of attention rather than one of disengagement. PMID:8373569

Arguin, M; Bub, D

1993-07-01

263

Identification of a gene module associated with BMD through the integration of network analysis and genome-wide association data.  

PubMed

Bone mineral density (BMD) is influenced by a complex network of gene interactions; therefore, elucidating the relationships between genes and how those genes, in turn, influence BMD is critical for developing a comprehensive understanding of osteoporosis. To investigate the role of transcriptional networks in the regulation of BMD, we performed a weighted gene coexpression network analysis (WGCNA) using microarray expression data on monocytes from young individuals with low or high BMD. WGCNA groups genes into modules based on patterns of gene coexpression. and our analysis identified 11 gene modules. We observed that the overall expression of one module (referred to as module 9) was significantly higher in the low-BMD group (p =?.03). Module 9 was highly enriched for genes belonging to the immune system-related gene ontology (GO) category "response to virus" (p = 7.6 × 10(-11)). Using publically available genome-wide association study data, we independently validated the importance of module 9 by demonstrating that highly connected module 9 hubs were more likely, relative to less highly connected genes, to be genetically associated with BMD. This study highlights the advantages of systems-level analyses to uncover coexpression modules associated with bone mass and suggests that particular monocyte expression patterns may mediate differences in BMD. PMID:20499364

Farber, Charles R

2010-11-01

264

CINCINNATA in Antirrhinum majus directly modulates genes involved in cytokinin and auxin signaling.  

PubMed

Mutations in the CINCINNATA (CIN) gene in Antirrhinum majus and its orthologs in Arabidopsis result in crinkly leaves as a result of excess growth towards the leaf margin. CIN homologs code for TCP (TEOSINTE-BRANCHED 1, CYCLOIDEA, PROLIFERATING CELL FACTOR 1 AND 2) transcription factors and are expressed in a broad zone in a growing leaf distal to the proliferation zone where they accelerate cell maturation. Although a few TCP targets are known, the functional basis of CIN-mediated leaf morphogenesis remains unclear. We compared the global transcription profiles of wild-type and the cin mutant of A. majus to identify the targets of CIN. We cloned and studied the direct targets using RNA in situ hybridization, DNA-protein interaction, chromatin immunoprecipitation and reporter gene analysis. Many of the genes involved in the auxin and cytokinin signaling pathways showed altered expression in the cin mutant. Further, we showed that CIN binds to genomic regions and directly promotes the transcription of a cytokinin receptor homolog HISTIDINE KINASE 4 (AmHK4) and an IAA3/SHY2 (INDOLE-3-ACETIC ACID INDUCIBLE 3/SHORT HYPOCOTYL 2) homolog in A. majus. Our results suggest that CIN limits excess cell proliferation and maintains the flatness of the leaf surface by directly modulating the hormone pathways involved in patterning cell proliferation and differentiation during leaf growth. PMID:25109749

Das Gupta, Mainak; Aggarwal, Pooja; Nath, Utpal

2014-12-01

265

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

266

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

267

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

268

Direct modulation and mode locking of 1.3 ?m quantum dot lasers  

NASA Astrophysics Data System (ADS)

We report 7 GHz cut-off frequency, 2.5 and 5 Gb s-1 eye pattern measurements upon direct modulation of 1.3 ?m quantum dot lasers grown without incorporating phosphorus in the layers. Passive mode-locking is achieved from very low frequencies up to 50 GHz and hybrid mode-locking is achieved up to 20 GHz. The minimum pulse width of the Fourier-limited pulses at 50 GHz is 3 ps, with an uncorrelated timing jitter below 1 ps. The lasers are optimized for high frequency operation by a ridge waveguide design that includes etching through the active layer and ridge widths down to 1 ?m. The far-field shape for 1 ?m is close to circular with a remaining asymmetry of 1.2.

Kuntz, M.; Fiol, G.; Lämmlin, M.; Bimberg, D.; Thompson, M. G.; Tan, K. T.; Marinelli, C.; Wonfor, A.; Sellin, R.; Penty, R. V.; White, I. H.; Ustinov, V. M.; Zhukov, A. E.; Shernyakov, Yu M.; Kovsh, A. R.; Ledentsov, N. N.; Schubert, C.; Marembert, V.

2004-11-01

269

Directional Bias and Pheromone for Discovery and Coverage on Networks  

SciTech Connect

Natural multi-agent systems often rely on “correlated random walks” (random walks that are biased toward a current heading) to distribute their agents over a space (e.g., for foraging, search, etc.). Our contribution involves creation of a new movement and pheromone model that applies the concept of heading bias in random walks to a multi-agent, digital-ants system designed for cyber-security monitoring. We examine the relative performance effects of both pheromone and heading bias on speed of discovery of a target and search-area coverage in a two-dimensional network layout. We found that heading bias was unexpectedly helpful in reducing search time and that it was more influential than pheromone for improving coverage. We conclude that while pheromone is very important for rapid discovery, heading bias can also greatly improve both performance metrics.

Fink, Glenn A.; Berenhaut, Kenneth S.; Oehmen, Christopher S.

2012-09-11

270

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

271

Direct torque controlled space vector modulated induction motor fed by a Z-source inverter for electric vehicles  

Microsoft Academic Search

This paper proposes a new closed loop speed control of an induction motor fed by a high performance Z-source inverter (ZSI), the speed control is based on direct torque control space vector modulation (DTC-SVM) control strategy. The modified space vector modulation (MSVM) is used to insert the shoot-through state within the switching signals for the ZSI. A dual loop controller

Omar Ellabban; Joeri Van Mierlo; Philippe Lataire

2011-01-01

272

Chirp reduction of directly modulated semiconductor lasers at 10 Gb\\/s by strong CW light injection  

Microsoft Academic Search

The influence of strong light injection on the reduction of the dynamical linewidth broadening of directly current-modulated semiconductor lasers at high bit rates is theoretically investigated and experimentally verified for 10 Gb\\/s NRZ pseudorandom modulation with a large current swing of 40 mA pp. Significant chirp reduction and single-mode operation are observed for bulk DFB, quantum well DFB lasers at

Stefan Mohrdiek; Herbert Burkhard; Herbert Walter

1994-01-01

273

Direct solutions of sparse network equations by optimally ordered triangular factorization  

Microsoft Academic Search

Matrix inversion is very inefficient for computing direct solutions of the large sparse systems of linear equations that arise in many network problems. Optimally ordered triangular factorization of sparse matrices is more efficient and offers other important computational advantages in some applications. With this method, direct solutions are computed from sparse matrix factors instead of from a full inverse matrix,

W. F. Tinney; J. W. Walker

1967-01-01

274

Link search algorithms for a spread-spectrum mobile communication network with directive\\/adaptive antennas  

Microsoft Academic Search

A non-centralized fully distributed mobile communication network with directive or adaptive antennas is proposed. Every node uses directive or adaptive antennas for transmitting and receiving communication signals. The spatial and temporal synchronization of the transmitting and receiving antenna beams is accomplished by employing the Global Positioning System (GPS) information and a double-ended spatial search algorithm. This research focuses on the

Tien-Yow Liu; Robert A. Scholtz

1998-01-01

275

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

276

Directed Cycles in Bayesian Belief Networks: Probabilistic Semantics and Consistency Checking Complexity  

Microsoft Academic Search

Although undirected cycles in directed graphs of Bayesian belief networks have been thoroughly studied, little attention has so far been given to a systematic analysis of directed (feedback) cycles. In this paper we propose a way of looking at those cycles; namely, we suggest that a feedback cycle represents a family of probabilistic distributions rather than a single distribution (as

Alexander L. Tulupyev; Sergey I. Nikolenko

2005-01-01

277

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

278

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

279

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

Sanger, Johanna; Muller, Viktor; Lindenberger, Ulman

2013-01-01

280

Characterizing system dynamics with a weighted and directed network constructed from time series data.  

PubMed

In this work, we propose a novel method to transform a time series into a weighted and directed network. For a given time series, we first generate a set of segments via a sliding window, and then use a doubly symbolic scheme to characterize every windowed segment by combining absolute amplitude information with an ordinal pattern characterization. Based on this construction, a network can be directly constructed from the given time series: segments corresponding to different symbol-pairs are mapped to network nodes and the temporal succession between nodes is represented by directed links. With this conversion, dynamics underlying the time series has been encoded into the network structure. We illustrate the potential of our networks with a well-studied dynamical model as a benchmark example. Results show that network measures for characterizing global properties can detect the dynamical transitions in the underlying system. Moreover, we employ a random walk algorithm to sample loops in our networks, and find that time series with different dynamics exhibits distinct cycle structure. That is, the relative prevalence of loops with different lengths can be used to identify the underlying dynamics. PMID:24985456

Sun, Xiaoran; Small, Michael; Zhao, Yi; Xue, Xiaoping

2014-06-01

281

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

PubMed

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

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

2011-09-21

282

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

283

Neural networks, field theory, directed percolation, and critical branching  

NASA Astrophysics Data System (ADS)

We describe the dynamics of neural activity using field-theoretic methods for non-equilibrium statistical processes. Using a Markov assumption, we introduce the "spike model". The spike model permits a characterization of both neural fluctuations and response, presenting a tractable way to extend the mean field (Wilson-Cowan) equations used in much of theoretical and computational neuroscience. We also demonstrate the formalism's application to the Cowan models, one of which is equivalent to the forest fire model with immune trees. We argue that neural activity under mild conditions exhibits a dynamical phase transition which is in the universality class of directed percolation (DP). Owing to the spatial extent of neural interactions, there is a region in which the critical behavior is that of a branching process before crossing over into the DP region, consistent with measurements in cortical slice preparations. From the perspective of theoretical neuroscience, a principal contribution of this work is the connection of the problem of non-linear, non-Gaussian systems with the problem of dealing with infrared singularities in field theory. This work suggests a general characterization of epilepsy as a manifestation of a directed percolation phase transition.

Buice, Michael A.

284

Physician directed networks: the new generation of managed care.  

PubMed

The external pressure to reduce cost while maintaining quality and services is moving the whole industry into a rapid mode of integration. Hospitals, vendors, MCOs, and now, physicians, are faced with the difficult decisions concerning how their operations will be integrated into the larger health care delivery system. These pressures have forced physicians to consolidate, build leverage, and create efficiencies to become more productive; thereby better positioning themselves to respond to the challenges and the opportunities that lie before them. This initial phase of consolidation has given many physicians the momentum to begin to wrestle back the control of health care and the courage to design the next generation of managed care: Physician Directed Managed Care. What will be the next phase? Perhaps, the next step will be fully-integrated specialty and multi-specialty groups leading to alternate delivery sites. "Everyone thinks of changing the world, but no one thinks of changing himself." - Leo Tolstoy PMID:8772322

Bennett, T; O'Sullivan, D

1996-07-01

285

Node-weighted measures for complex networks with directed and weighted edges for studying continental moisture recycling  

NASA Astrophysics Data System (ADS)

In many real-world networks nodes represent agents or objects of different sizes or importance. However, the size of the nodes is rarely taken into account in network analysis, possibly inducing bias in network measures and confusion in their interpretation. Recently, a new axiomatic scheme of node-weighted network measures has been suggested for networks with undirected and unweighted edges. However, many real-world systems are best represented by complex networks which have directed and/or weighted edges. Here, we extend this approach and suggest new versions of the degree and the clustering coefficient associated to network motifs for networks with directed and/or weighted edges and weighted nodes. We apply these measures to a spatially embedded network model and a real-world moisture recycling network. We show that these measures improve the representation of the underlying systems' structure and are of general use for studying any type of complex network.

Zemp, D. C.; Wiedermann, M.; Kurths, J.; Rammig, A.; Donges, J. F.

2014-09-01

286

Direct Correlation between Nonrandom Ion Hopping and Network Structure in Ion-Conducting Borophosphate Glasses  

NASA Astrophysics Data System (ADS)

We present temperature-dependent conductivity spectra of sodium borophosphate glasses with a varying borate/phosphate ratio but a constant sodium oxide content which can be mapped into time-dependent mean square displacements. For the first time, we show that characteristic lengths of ion transport derived thereof are directly linked to features of network structure, viz., the number of boron oxide tetrahedra. Our results also shed light on the mixed network former effect.

Zielniok, D.; Eckert, H.; Cramer, C.

2008-01-01

287

Direct correlation between nonrandom ion hopping and network structure in ion-conducting borophosphate glasses.  

PubMed

We present temperature-dependent conductivity spectra of sodium borophosphate glasses with a varying borate/phosphate ratio but a constant sodium oxide content which can be mapped into time-dependent mean square displacements. For the first time, we show that characteristic lengths of ion transport derived thereof are directly linked to features of network structure, viz., the number of boron oxide tetrahedra. Our results also shed light on the mixed network former effect. PMID:18233003

Zielniok, D; Eckert, H; Cramer, C

2008-01-25

288

Reduced-order modelling of biochemical networks: application to the GTPase-cycle signalling module  

PubMed Central

Biochemical systems embed complex networks and hence development and analysis of their detailed models pose a challenge for computation. Coarse-grained biochemical models, called reduced-order models (ROMs), consisting of essential biochemical mechanisms are more useful for computational analysis and for studying important features of a biochemical network. The authors present a novel method to model-reduction by identifying potentially important parameters using multidimensional sensitivity analysis. A ROM is generated for the GTPase-cycle module of m1 muscarinic acetylcholine receptor, Gq, and regulator of G-protein signalling 4 (a GTPase-activating protein or GAP) starting from a detailed model of 48 reactions. The resulting ROM has only 17 reactions. The ROM suggested that complexes of G-protein coupled receptor (GPCR) and GAP – which were proposed in the detailed model as a hypothesis – are required to fit the experimental data. Models previously published in the literature are also simulated and compared with the ROM. Through this comparison, a minimal ROM, that also requires complexes of GPCR and GAP, with just 15 parameters is generated. The proposed reduced-order modelling methodology is scalable to larger networks and provides a general framework for the reduction of models of biochemical systems. PMID:16986265

Maurya, M.R.; Bornheimer, S.J.; Venkatasubramanian, V.; Subramaniam, S.

2011-01-01

289

Spontaneous formation of InGaN nanowall network directly on Si  

SciTech Connect

We present the study on epitaxial growth of an InGaN nanowall network directly on Si by plasma-assisted molecular beam epitaxy. Scanning electron microscopy, high-resolution X-ray diffraction, and transmission electron microscopy together with energy-dispersive X-ray analysis infer the crystalline nature of the InGaN nanowall network, oriented along the C-axis, with In composition ranging from pure GaN to 40%. Room temperature photoluminescence is observed, indicating good optical quality. The nanowall network is highly in-plane electrically conductive.

Soto Rodriguez, P. E. D.; Kumar, Praveen; Gomez, V. J.; Alvi, N. H.; Calleja, E.; Noetzel, R. [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)] [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Manuel, J. M.; Morales, F. M.; Jimenez, J. J.; Garcia, R. [Dep. Ciencia de los Materiales e IM y QI., F. Ciencias, Universidad de Cadiz, 11510-Puerto Real, Cadiz (Spain)] [Dep. Ciencia de los Materiales e IM y QI., F. Ciencias, Universidad de Cadiz, 11510-Puerto Real, Cadiz (Spain)

2013-04-29

290

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

291

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

PubMed Central

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

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

2013-01-01

292

Electronic polarization-division demultiplexing based on digital signal processing in intensity-modulation direct-detection optical communication systems.  

PubMed

We propose a novel configuration of optical receivers for intensity-modulation direct-detection (IM · DD) systems, which can cope with dual-polarization (DP) optical signals electrically. Using a Stokes analyzer and a newly-developed digital signal-processing (DSP) algorithm, we can achieve polarization tracking and demultiplexing in the digital domain after direct detection. Simulation results show that the power penalty stemming from digital polarization manipulations is negligibly small. PMID:24515206

Kikuchi, Kazuro

2014-01-27

293

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

PubMed

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

294

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

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

295

Direct modulation of calmodulin targets by the neuronal calcium sensor NCS-1.  

PubMed Central

Ca2+ and its ubiquitous intracellular receptor calmodulin (CaM) are required in the nervous system, among a host of cellular responses, for the modulation of several important enzymes and ion channels involved in synaptic efficacy and neuronal plasticity. Here, we report that CaM can be replaced by the neuronal calcium sensor NCS-1 both in vitro and in vivo. NCS-1 is a calcium binding protein with two Ca(2+)-binding domains that shares only 21% of homology with CaM. We observe that NCS-1 directly activates two Ca2+/CaM-dependent enzymes (3':5'-cyclic nucleotide phosphodiesterase and protein phosphatase calcineurin). Co-activation of nitric oxide synthase by NCS-1 and CaM results in a higher activity than with CaM alone. Moreover, NCS-1 is coexpressed with calcineurin and nitric oxide synthase in several neuron populations. Finally, injections of NCS-1 into calmodulin-defective cam1 Paramecium partially restore wildtype behavioral responses. With this highly purified preparation of NCS-1, we have obtained crystals suitable for crystallographic structure studies. NCS-1, despite its very different structure, distribution, and Ca(2+)-binding affinity as compared with CaM, can substitute for or potentiate CaM functions. Therefore, NCS-1 represents a novel protein capable of mediating multiple Ca(2+)-signaling pathways in the nervous system. Images Fig. 3 Fig. 4 Fig. 5 PMID:8799187

Schaad, N C; De Castro, E; Nef, S; Hegi, S; Hinrichsen, R; Martone, M E; Ellisman, M H; Sikkink, R; Rusnak, F; Sygush, J; Nef, P

1996-01-01

296

Secure Network Coding for Wireless Mesh Networks: Threats, Challenges, and Directions  

E-print Network

intermediate nodes to mix packets before forwarding them. Recently, several real-world systems have been coding are well understood, a real-world system needs to solve a plethora of practical aspects before, real-world systems need to solve a plethora of practical aspects before network coding meets its

Curtmola, Reza

297

IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 40, NO. 5, MAY 2004 445 Shaping Current Waveforms for Direct Modulation  

E-print Network

is maintained in a con- stant light-emitting state, and some sort of external "shutter," typically a Mach and there is a considerable memory effect [9]. This effect is called Manuscript received January 9, 2004. This work, commu- nication using high-speed direct modulation is limited by tran- sient oscillations, known

Illing, Lucas

298

IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. 49, NO. 6, JUNE 2003 1385 Optical Intensity-Modulated Direct Detection  

E-print Network

-Modulated Direct Detection Channels: Signal Space and Lattice Codes Steve Hranilovic, Student Member, IEEE are with the Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON M5S 3G4 Canada (e-mail: steve@comm.utoronto.ca; frank@comm.utoronto.ca). Communicated by R. Urbanke

Hranilovic, Steve

299

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

300

Node-weighted measures for complex networks with directed and weighted edges for studying atmospheric moisture recycling  

NASA Astrophysics Data System (ADS)

In many real-world networks, nodes represents agents of different sizes or importance. However, the sizes of the node are rarely taken into account in networks analysis, inducing bias in network measures and confusion in their interpretation. Recently, a new axiomatic scheme of node-weighted network measures have been suggested for networks with undirected and unweighted edges. However, many real-world systems are best represented by complex networks which have directed and/or weighted edges. Here, we extend this approach and suggest node-centrality measures for the networks with directed and/or weighted edges and weighted nodes. We apply these measures on a artificial spatially embedded network and a real-world moisture recycling network. We show that these measures improve the representation of the underlying physical systems and can be used for any types of complex networks.

Zemp, Delphine; Wiedermann, Marc; Donges, Jonathan; Schleussner, Carl-Friedrich; Rammig, Anja

2014-05-01

301

Astrocytes Modulate Neural Network Activity by Ca2+-Dependent Uptake of Extracellular K+  

PubMed Central

Astrocytes are electrically nonexcitable cells that display increases in cytosolic calcium ion (Ca2+) in response to various neurotransmitters and neuromodulators. However, the physiological role of astrocytic Ca2+ signaling remains controversial. We show here that astrocytic Ca2+ signaling ex vivo and in vivo stimulated the Na+,K+-ATPase (Na+- and K+-dependent adenosine triphosphatase), leading to a transient decrease in the extracellular potassium ion (K+) concentration. This in turn led to neuronal hyperpolarization and suppressed baseline excitatory synaptic activity, detected as a reduced frequency of excitatory postsynaptic currents. Synaptic failures decreased in parallel, leading to an increase in synaptic fidelity. The net result was that astrocytes, through active uptake of K+, improved the signal-to-noise ratio of synaptic transmission. Active control of the extracellular K+ concentration thus provides astrocytes with a simple yet powerful mechanism to rapidly modulate network activity. PMID:22472648

Wang, Fushun; Smith, Nathan A.; Xu, Qiwu; Fujita, Takumi; Baba, Akemichi; Matsuda, Toshio; Takano, Takahiro; Bekar, Lane; Nedergaard, Maiken

2012-01-01

302

Acupuncture Modulates the Functional Connectivity of the Default Mode Network in Stroke Patients  

PubMed Central

Abundant evidence from previous fMRI studies on acupuncture has revealed significant modulatory effects at widespread brain regions. However, few reports on the modulation to the default mode network (DMN) of stroke patients have been investigated in the field of acupuncture. To study the modulatory effects of acupuncture on the DMN of stroke patients, eight right hemispheric infarction and stable ischemic stroke patients and ten healthy subjects were recruited to undergo resting state fMRI scanning before and after acupuncture stimulation. Functional connectivity analysis was applied with the bilateral posterior cingulate cortices chosen as the seed regions. The main finding demonstrated that the interregional interactions between the ACC and PCC especially enhanced after acupuncture at GB34 in stroke patients, compared with healthy controls. The results indicated that the possible mechanisms of the modulatory effects of acupuncture on the DMN of stroke patients could be interpreted in terms of cognitive ability and motor function recovery. PMID:24734113

Zhang, Yong; Li, Kuangshi; Ren, Yi; Cui, Fangyuan; Xie, Zijing; Shin, Jae-Young; Tan, Zhongjian; Tang, Lixin; Bai, Lijun; Zou, Yihuai

2014-01-01

303

A network module-based method for identifying cancer prognostic signatures  

PubMed Central

Discovering robust prognostic gene signatures as biomarkers using genomics data can be challenging. We have developed a simple but efficient method for discovering prognostic biomarkers in cancer gene expression data sets using modules derived from a highly reliable gene functional interaction network. When applied to breast cancer, we discover a novel 31-gene signature associated with patient survival. The signature replicates across 5 independent gene expression studies, and outperforms 48 published gene signatures. When applied to ovarian cancer, the algorithm identifies a 75-gene signature associated with patient survival. A Cytoscape plugin implementation of the signature discovery method is available at http://wiki.reactome.org/index.php/Reactome_FI_Cytoscape_Plugin PMID:23228031

2012-01-01

304

Bandwidth provisioning in infrastructure-based wireless networks employing directional antennas  

SciTech Connect

Motivated by the widespread proliferation of wireless networks employing directional antennas, we study the problem of provisioning bandwidth in such networks. Given a set of subscribers and one or more access points possessing directional antennas, we formalize the problem of orienting these antennas in two fundamental settings: (1) subscriber-centric, where the objective is to fairly allocate bandwidth among the subscribers and (2) provider-centric, where the objective is to maximize the revenue generated by satisfying the bandwidth requirements of subscribers. For both the problems, we first design algorithms for a network with only one access point working under the assumption that the number of antennas does not exceed the number of noninterfering channels. Using the well-regarded lexicographic max-min fair allocation as the objective for a subscriber-centric network, we present an optimum dynamic programming algorithm. For a provider-centric network, the allocation problem turns out to be NP-hard. We present a greedy heuristic based algorithm that guarantees almost half of the optimum revenue. We later enhance both these algorithms to operate in more general networks with multiple access points and no restrictions on the relative numbers of antennas and channels. A simulation-based evaluation using OPNET demonstrates the efficacy of our approaches and provides us further in insights into these problems.

Hasiviswanthan, Shiva [Los Alamos National Laboratory; Zhao, Bo [PENN STATE UNIV.; Vasudevan, Sudarshan [UNIV OF MASS AMHERST; Yrgaonkar, Bhuvan [PENN STATE UNIV.

2009-01-01

305

A Model of Consistent Node Types in Signed Directed Social Networks  

E-print Network

Signed directed social networks, in which the relationships between users can be either positive (indicating relations such as trust) or negative (indicating relations such as distrust), are increasingly common. Thus the interplay between positive and negative relationships in such networks has become an important research topic. Most recent investigations focus upon edge sign inference using structural balance theory or social status theory. Neither of these two theories, however, can explain an observed edge sign well when the two nodes connected by this edge do not share a common neighbor (e.g., common friend). In this paper we develop a novel approach to handle this situation by applying a new model for node types. Initially, we analyze the local node structure in a fully observed signed directed network, inferring underlying node types. The sign of an edge between two nodes must be consistent with their types; this explains edge signs well even when there are no common neighbors. We show, moreover, that ...

Song, Dongjin

2014-01-01

306

High-Speed Non-Directional Infrared Communication for Wireless Local-Area Networks  

E-print Network

radio are the availabil- ity of a virtually unlimited, unregulated spectrum, and the fact that infrared- diodes, the wavelength band near 800 nm is probably the best choice for diffuse infrared communicationsHigh-Speed Non-Directional Infrared Communication for Wireless Local-Area Networks J. M. Kahn, J. R

Carruthers, Jeffrey

307

NRC TLD Direct Radiation Monitoring Network. Progress report, October--December 1996  

SciTech Connect

This report presents the results of the NRC Direct Radiation Monitoring Network for the fourth quarter of 1996. It provides the ambient radiation levels measured in the vicinity of 74 sites throughout the United States. In addition, it describes the equipment used, monitoring station selection criteria, characterization of the dosimeter response, calibration procedures, statistical methods, intercomparison, and quality assurance program. 3 figs., 4 tabs.

Struckmeyer, R.

1997-03-01

308

NRC TLD Direct Radiation Monitoring Network progress report, October--December 1994. Volume 14, No. 4  

SciTech Connect

This report presents the results of the NRC Direct Radiation Monitoring Network for the fourth quarter of 1994. It provides the ambient radiation levels measured in the vicinity of 75 sites throughout the United States. In addition, it describes the equipment used, monitoring station selection criteria, characterization of the dosimeter response, calibration procedures, statistical methods, intercomparison, and quality assurance program.

Struckmeyer, R.

1995-03-01

309

PHYSICAL REVIEW E 84, 046107 (2011) Spectral properties of directed random networks with modular structure  

E-print Network

PHYSICAL REVIEW E 84, 046107 (2011) Spectral properties of directed random networks with modular that the details of the physical systems are less important for many statistical properties of interest. Often that respect the same symmetries as the physical system [3]. Recent investigations of statistical properties

Li, Baowen

310

Selective Encryption of Multimedia Content in Distribution Networks: Challenges and New Directions  

E-print Network

Science Brooklyn College of the City University of New York 2900 Bedford Avenue, Brooklyn, NY 11210, USA1 Selective Encryption of Multimedia Content in Distribution Networks: Challenges and New Directions Xiliang Liu The Graduate Center The City University of New York 365 Fifth Avenue, New York, NY

Liu, Xiliang

311

Stability and Flexibility in Preschoolers' Social Networks: A Dynamic Analysis of Socially Directed Behavior Allocation  

Microsoft Academic Search

The author studied preschoolers' social networks by investigating the allocation of children's social investment within and across time in a classroom of a French nursery school during an academic year. Observations of children's social exchanges during free play revealed that social behaviors were directed toward particular group members. After an important turnover in the peer group at the beginning of

Stéphanie Barbu

2003-01-01

312

Power-Efficient Direct-Voting Assurance for Data Fusion in Wireless Sensor Networks  

E-print Network

Power-Efficient Direct-Voting Assurance for Data Fusion in Wireless Sensor Networks Hung-Ta Pai data. In this approach, the base station receives the fusion data and "votes" on the data from a randomly chosen sensor node. The vote comes from other sensor nodes, called "witnesses," to confirm

Pai, Hung-Ta

313

Face detection directly from h.264 compressed video with convolutional neural network  

Microsoft Academic Search

Human faces provide a useful cue in indexing video content. In this paper, we propose a novel face detection algorithm based on a convolutional neural network architecture that can rapidly detect human face regions in video sequences encoded by H.264\\/AVC. By detecting faces directly in the compressed domain, we use the discrete cosine transform (DCT) coefficients in H.264 intra coding

Shin-Shan Zhuang; Shang-Hong Lai

2009-01-01

314

Switching the H-bonding network of a foldamer by modulating the backbone chirality and constitutional ratio of amino acids.  

PubMed

This communication describes the folding propensity of a heterofoldamer motif featuring proline (Pro) and anthranilic acid (Ant) residues in a 1:2:1 (?:?:?) constitutional ratio. Structural investigations unequivocally suggest that the hydrogen-bonding network of this foldamer motif can be switched between 9-membered and 6-membered by modulating the backbone chirality and constitutional ratio of the amino acid residues. PMID:24057152

Ramesh, Veera V E; Vijayadas, Kuruppanthara N; Dhokale, Snehal; Gonnade, Rajesh G; Rajamohanan, Pattuparambil R; Sanjayan, Gangadhar J

2013-11-01

315

Measurement of cross-phase modulation in optical materials through the direct measurement of the optical phase change  

SciTech Connect

We measure the cross-phase modulation (XPM) nonlinear indices of optical materials resulting from the interaction of an ultrashort pump pulse at 800nm with a weak ultrashort probe pulse at 400nm through the direct measurement of the optical phase change, using frequency-resolved optical gating. The materials studied include fused silica (SiO{sub 2} ) , borosilicate glass (BK-7), {beta}-BBO , and KD{sup *}P . This method results in a XPM nonlinear index that is in agreement with calculations based on nonlinear indices from previous self-phase modulation measurements. {copyright} {ital 1998} {ital Optical Society of America}

Rodriguez, G.; Taylor, A.J. [Material Science and Technology Division, Los Alamos National Laboratory, MS D429, Los Alamos, New Mexico 87545 (United States)

1998-06-01

316

Modulation of EEG Functional Connectivity Networks in Subjects Undergoing Repetitive Transcranial Magnetic Stimulation  

PubMed Central

Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation technique that utilizes magnetic fluxes to alter cortical activity. Continuous theta-burst repetitive TMS (cTBS) results in long-lasting decreases in indices of cortical excitability, and alterations in performance of behavioral tasks. We investigated the effects of cTBS on cortical function via functional connectivity and graph theoretical analysis of EEG data. Thirty-one channel resting-state EEG recordings were obtained before and after 40 s of cTBS stimulation to the left primary motor cortex. Functional connectivity between nodes was assessed in multiple frequency bands using lagged max-covariance, and subsequently thresholded to construct undirected graphs. After cTBS, we find widespread decreases in functional connectivity in the alpha band. There are also simultaneous increases in functional connectivity in the high-beta bands, especially amongst anterior and interhemispheric connections. The analysis of the undirected graphs reveals that interhemispheric and interregional connections are more likely to be modulated after cTBS than local connections. There is also a shift in the topology of network connectivity, with an increase in the clustering coefficient after cTBS in the beta bands, and a decrease in clustering and increase in path length in the alpha band, with the alpha-band connectivity primarily decreased near the site of stimulation. cTBS produces widespread alterations in cortical functional connectivity, with resulting shifts in cortical network topology. PMID:23471637

Shafi, Mouhsin M.; Westover, M. Brandon; Oberman, Lindsay; Cash, Sydney S.; Pascual-Leone, Alvaro

2014-01-01

317

Emotional reactivity to threat modulates activity in mentalizing network during aggression.  

PubMed

Aggression is a common response to provocation, albeit with considerable interindividual differences. In this fMRI study, we investigated emotional reactivity to threat as possible link between provocation and aggression, as well as the neural correlates of this relationship. We hypothesized that emotional reactivity, measured as fear potentiation (FP) of the startle response, would be negatively associated with aggressive behavior and would modulate neural activity during an aggressive interaction. In 30 healthy female participants, FP was measured as the difference between blink amplitudes while watching threatening vs neutral pictures. Participants subsequently engaged in a variant of the Taylor Aggression Paradigm (TAP), while being scanned. During the TAP, participants selected a punishment level for either a highly provoking or a nonprovoking opponent. There was no difference in aggressive behavior between participants high and low in FP. However, we found a negative correlation between FP and the neural provocation effect in several regions of a network previously associated with mentalizing including the medial prefrontal cortex, precuneus and the temporo-parietal junction. Independently of the FP variability, aggressive behavior correlated with the provocation effect on activity in the caudate nucleus. Our results indicate that during a provocative confrontation, high emotional reactivity to threat suppresses recruitment of the mentalizing network. PMID:23986265

Beyer, Frederike; Münte, Thomas F; Erdmann, Christian; Krämer, Ulrike M

2014-10-01

318

Arachidonic Acid: An Evolutionarily Conserved Signaling Molecule Modulates Plant Stress Signaling Networks[C][W  

PubMed Central

Fatty acid structure affects cellular activities through changes in membrane lipid composition and the generation of a diversity of bioactive derivatives. Eicosapolyenoic acids are released into plants upon infection by oomycete pathogens, suggesting they may elicit plant defenses. We exploited transgenic Arabidopsis thaliana plants (designated EP) producing eicosadienoic, eicosatrienoic, and arachidonic acid (AA), aimed at mimicking pathogen release of these compounds. We also examined their effect on biotic stress resistance by challenging EP plants with fungal, oomycete, and bacterial pathogens and an insect pest. EP plants exhibited enhanced resistance to all biotic challenges, except they were more susceptible to bacteria than the wild type. Levels of jasmonic acid (JA) were elevated and levels of salicylic acid (SA) were reduced in EP plants. Altered expression of JA and SA pathway genes in EP plants shows that eicosapolyenoic acids effectively modulate stress-responsive transcriptional networks. Exogenous application of various fatty acids to wild-type and JA-deficient mutants confirmed AA as the signaling molecule. Moreover, AA treatment elicited heightened expression of general stress-responsive genes. Importantly, tomato (Solanum lycopersicum) leaves treated with AA exhibited reduced susceptibility to Botrytis cinerea infection, confirming AA signaling in other plants. These studies support the role of AA, an ancient metazoan signaling molecule, in eliciting plant stress and defense signaling networks. PMID:20935246

Savchenko, Tatyana; Walley, Justin W.; Chehab, E. Wassim; Xiao, Yanmei; Kaspi, Roy; Pye, Matthew F.; Mohamed, Maged E.; Lazarus, Colin M.; Bostock, Richard M.; Dehesh, Katayoon

2010-01-01

319

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

PubMed

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; O'Mara, Shane M

2014-11-01

320

Single-wavelength-pump bi-directional hybrid fiber amplifier for bi-directional local area network application  

NASA Astrophysics Data System (ADS)

This paper proposes a novel bi-directional hybrid fiber amplifier using a single-wavelength pump laser diode (LD) at 1495 nm. The hybrid amplifier is theoretically applied in a 50 km bi-directional local area network (LAN) with 26 ch × 10 Gb/s for bi-directional transmission. Thirteen C-band channels serve as downlink signals while the other 13 L-band channels are employed as uplink signals. Without loss of generality, four channels (two from each band) are experimentally analyzed. Erbium doped fiber (EDF) provides amplification for the C-band channels and Raman amplification amplifies the L-band channels. The pump efficiency is improved by employing a double-pass scheme for both the Erbium doped fiber amplifier (EDFA) and Raman fiber amplifier (RFA). The chromatic dispersion incurred by all the channels is precisely compensated for by inserting a fiber Bragg grating (FBG) array in appropriate locations along the dispersion compensating fiber (DCF) segments. Moreover, gain equalization of all the channels is achieved by adjusting the FBG reflectivity. Both the simulation results and experimental measurements confirm the proposed device feasibility and potential application in a bi-directional LAN.

Guo, Mars Ning; Liaw, Shien-Kuei; Shum, Perry Ping; Chen, Nan-Kuang; Hung, Hsin-Kai; Lin, Chinlon

2011-01-01

321

Modulation of attention network activation under antidepressant agents in healthy subjects.  

PubMed

While antidepressants are supposed to exert similar effects on mood and drive via various mechanisms of action, diverging effects are observed regarding side-effects and accordingly on neural correlates of motivation, emotion, reward and salient stimuli processing as a function of the drugs impact on neurotransmission. In the context of erotic stimulation, a unidirectional modulation of attentional functioning despite opposite effects on sexual arousal has been suggested for the selective serotonin reuptake-inhibitor (SSRI) paroxetine and the selective dopamine and noradrenaline reuptake-inhibitor (SDNRI) bupropion. To further elucidate the effects of antidepressant-related alterations of neural attention networks, we investigated 18 healthy males under subchronic administration (7 d) of paroxetine (20 mg), bupropion (150 mg) and placebo within a randomized placebo-controlled cross-over double-blind functional magnetic resonance imaging (fMRI) design during an established preceding attention task. Neuropsychological effects beyond the fMRI-paradigm were assessed by measuring alertness and divided attention. Comparing preceding attention periods of salient vs. neutral pictures, we revealed congruent effects of both drugs vs. placebo within the anterior midcingulate cortex, dorsolateral prefrontal cortex, anterior prefrontal cortex, superior temporal gyrus, anterior insula and the thalamus. Relatively decreased activation in this network was paralleled by slower reaction times in the divided attention task in both verum conditions compared to placebo. Our results suggest similar effects of antidepressant treatments on behavioural and neural attentional functioning by diverging neurochemical pathways. Concurrent alterations of brain regions within a fronto-parietal and cingulo-opercular attention network for top-down control could point to basic neural mechanisms of antidepressant action irrespective of receptor profiles. PMID:23200084

Graf, Heiko; Abler, Birgit; Hartmann, Antonie; Metzger, Coraline D; Walter, Martin

2013-07-01

322

Modulations of the executive control network by stimulus onset asynchrony in a Stroop task  

PubMed Central

Background Manipulating task difficulty is a useful way of elucidating the functional recruitment of the brain’s executive control network. In a Stroop task, pre-exposing the irrelevant word using varying stimulus onset asynchronies (‘negative’ SOAs) modulates the amount of behavioural interference and facilitation, suggesting disparate mechanisms of cognitive processing in each SOA. The current study employed a Stroop task with three SOAs (?400, -200, 0 ms), using functional magnetic resonance imaging to investigate for the first time the neural effects of SOA manipulation. Of specific interest were 1) how SOA affects the neural representation of interference and facilitation; 2) response priming effects in negative SOAs; and 3) attentional effects of blocked SOA presentation. Results The results revealed three regions of the executive control network that were sensitive to SOA during Stroop interference; the 0 ms SOA elicited the greatest activation of these areas but experienced relatively smaller behavioural interference, suggesting that the enhanced recruitment led to more efficient conflict processing. Response priming effects were localized to the right inferior frontal gyrus, which is consistent with the idea that this region performed response inhibition in incongruent conditions to overcome the incorrectly-primed response, as well as more general action updating and response preparation. Finally, the right superior parietal lobe was sensitive to blocked SOA presentation and was most active for the 0 ms SOA, suggesting that this region is involved in attentional control. Conclusions SOA exerted both trial-specific and block-wide effects on executive processing, providing a unique paradigm for functional investigations of the cognitive control network. PMID:23902451

2013-01-01

323

Acupuncture modulates temporal neural responses in wide brain networks: evidence from fMRI study  

PubMed Central

Background Accumulating neuroimaging studies in humans have shown that acupuncture can modulate a widely distributed brain network, large portions of which are overlapped with the pain-related areas. Recently, a striking feature of acupuncture-induced analgesia is found to be associated with its long-last effect, which has a delayed onset and gradually reaches a peak even after acupuncture needling being terminated. Identifying temporal neural responses in these areas that occur at particular time -- both acute and sustained effects during acupuncture processes -- may therefore shed lights on how such peripheral inputs are conducted and mediated through the CNS. In the present study, we adopted a non-repeated event-related (NRER) fMRI paradigm and control theory based approach namely change-point analysis in order to capture the detailed temporal profile of neural responses induced by acupuncture. Results Our findings demonstrated that neural activities at the different stages of acupuncture presented distinct temporal patterns, in which consistently positive neural responses were found during the period of acupuncture needling while much more complex and dynamic activities found during a post-acupuncture period. These brain responses had a significant time-dependent effect which showed different onset time and duration of neural activities. The amygdala and perigenual anterior cingulate cortex (pACC), exhibited increased activities during the needling phase while decreased gradually to reach a peak below the baseline. The periaqueductal gray (PAG) and hypothalamus presented saliently intermittent activations across the whole fMRI session. Apart from the time-dependent responses, relatively persistent activities were also identified in the anterior insula and prefrontal cortices. The overall findings indicate that acupuncture may engage differential temporal neural responses as a function of time in a wide range of brain networks. Conclusions Our study has provided evidence supporting a view that acupuncture intervention involves complex modulations of temporal neural response, and its effect can gradually resolve as a function of time. The functional specificity of acupuncture at ST36 may involve multiple levels of differential activities of a wide range of brain networks, which are gradually enhanced even after acupuncture needle being terminated. PMID:21044291

2010-01-01

324

Double-Directional Information Azimuth Spectrum and Relay Network Tomography for a Decentralized Wireless Relay Network  

Microsoft Academic Search

A novel channel representation for a two-hop decentralized wireless relay\\u000anetwork (DWRN) is proposed, where the relays operate in a completely\\u000adistributive fashion. The modeling paradigm applies an analogous approach to\\u000athe description method for a double-directional multipath propagation channel,\\u000aand takes into account the finite system spatial resolution and the extended\\u000arelay listening\\/transmitting time. Specifically, the double-directional\\u000ainformation azimuth

Yifan Chen; Chau Yuen; Yong Huat Chew

2010-01-01

325

New directions for diffusion-based network prediction of protein function: incorporating pathways with confidence  

PubMed Central

Motivation: It has long been hypothesized that incorporating models of network noise as well as edge directions and known pathway information into the representation of protein–protein interaction (PPI) networks might improve their utility for functional inference. However, a simple way to do this has not been obvious. We find that diffusion state distance (DSD), our recent diffusion-based metric for measuring dissimilarity in PPI networks, has natural extensions that incorporate confidence, directions and can even express coherent pathways by calculating DSD on an augmented graph. Results: We define three incremental versions of DSD which we term cDSD, caDSD and capDSD, where the capDSD matrix incorporates confidence, known directed edges, and pathways into the measure of how similar each pair of nodes is according to the structure of the PPI network. We test four popular function prediction methods (majority vote, weighted majority vote, multi-way cut and functional flow) using these different matrices on the Baker’s yeast PPI network in cross-validation. The best performing method is weighted majority vote using capDSD. We then test the performance of our augmented DSD methods on an integrated heterogeneous set of protein association edges from the STRING database. The superior performance of capDSD in this context confirms that treating the pathways as probabilistic units is more powerful than simply incorporating pathway edges independently into the network. Availability: All source code for calculating the confidences, for extracting pathway information from KEGG XML files, and for calculating the cDSD, caDSD and capDSD matrices are available from http://dsd.cs.tufts.edu/capdsd Contact: lenore.cowen@tufts.edu or benjamin.hescott@tufts.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:24931987

Cowen, Lenore J.; Hescott, Benjamin J.

2014-01-01

326

Allosteric modulation of Ras positions Q61 for a direct role in catalysis  

SciTech Connect

Ras and its effector Raf are key mediators of the Ras/Raf/MEK/ERK signal transduction pathway. Mutants of residue Q61 impair the GTPase activity of Ras and are found prominently in human cancers. Yet the mechanism through which Q61 contributes to catalysis has been elusive. It is thought to position the catalytic water molecule for nucleophilic attack on the {gamma}-phosphate of GTP. However, we previously solved the structure of Ras from crystals with symmetry of the space group R32 in which switch II is disordered and found that the catalytic water molecule is present. Here we present a structure of wild-type Ras with calcium acetate from the crystallization mother liquor bound at a site remote from the active site and likely near the membrane. This results in a shift in helix 3/loop 7 and a network of H-bonding interactions that propagates across the molecule, culminating in the ordering of switch II and placement of Q61 in the active site in a previously unobserved conformation. This structure suggests a direct catalytic role for Q61 where it interacts with a water molecule that bridges one of the {gamma}-phosphate oxygen atoms to the hydroxyl group of Y32 to stabilize the transition state of the hydrolysis reaction. We propose that Raf together with the binding of Ca{sup 2+} and a negatively charged group mimicked in our structure by the acetate molecule induces the ordering of switch I and switch II to complete the active site of Ras.

Buhrman, Greg; Holzapfel, Genevieve; Fetics, Susan; Mattos, Carla (NCSU)

2010-11-03

327

Extracting directed information flow networks: an application to genetics and semantics.  

PubMed

We introduce a general method to infer the directional information flow between populations whose elements are described by n-dimensional vectors of symbolic attributes. The method is based on the Jensen-Shannon divergence and on the Shannon entropy and has a wide range of application. We show here the results of two applications: first we extract the network of genetic flow between meadows of the seagrass Poseidonia oceanica, where the meadow elements are specified by sets of microsatellite markers, and then we extract the semantic flow network from a set of Wikipedia pages, showing the semantic channels between different areas of knowledge. PMID:21405885

Masucci, A P; Kalampokis, A; Eguíluz, V M; Hernández-García, E

2011-02-01

328

A Polygon Model for Wireless Sensor Network Deployment with Directional Sensing Areas  

PubMed Central

The modeling of the sensing area of a sensor node is essential for the deployment algorithm of wireless sensor networks (WSNs). In this paper, a polygon model is proposed for the sensor node with directional sensing area. In addition, a WSN deployment algorithm is presented with topology control and scoring mechanisms to maintain network connectivity and improve sensing coverage rate. To evaluate the proposed polygon model and WSN deployment algorithm, a simulation is conducted. The simulation results show that the proposed polygon model outperforms the existed disk model and circular sector model in terms of the maximum sensing coverage rate. PMID:22303159

Wu, Chun-Hsien; Chung, Yeh-Ching

2009-01-01

329

Prediction of direct runoff hydrographs utilizing stochastic network models: a case study in South Korea  

NASA Astrophysics Data System (ADS)

In this study, we combine stochastic network models that reproduce the actual width function and the width function based instantaneous unit hydrograph (WFIUH) that directly makes use of a width function and converts it into runoff hydrographs. We evaluated the stochastic network models in terms of reproducing the actual width function and also the robustness of the semi-distributed model (WFIUH) in application to a test watershed in South Korea. The stochastic network model has an advantage that it replicates width functions of actual river networks, whereas the WFIUH has an advantage that the parameter values are physically determined, which can be potentially advantageous in prediction of ungauged basins. This study demonstrates that the combination of the Gibbsian model and the WFIUH is able to reproduce runoff hydrographs not just for the case of uniform rainfall over the test catchment but also for moving storms. Therefore, results of this study indicate that the impact of spatial and temporal rainfall variation on runoff hydrographs can be evaluated by the suggested approach in ungauged basins even without detailed knowledge of river networks. Once the regional similarity in river network configuration is identified, the proposed approach can be potentially utilized to estimate the runoff hydrographs for ungauged basins.

Seo, Y.; Park, S.-Y.

2014-10-01

330

Stitching together Multiple Data Dimensions Reveals Interacting Metabolomic and Transcriptomic Networks That Modulate Cell Regulation  

PubMed Central

Cells employ multiple levels of regulation, including transcriptional and translational regulation, that drive core biological processes and enable cells to respond to genetic and environmental changes. Small-molecule metabolites are one category of critical cellular intermediates that can influence as well as be a target of cellular regulations. Because metabolites represent the direct output of protein-mediated cellular processes, endogenous metabolite concentrations can closely reflect cellular physiological states, especially when integrated with other molecular-profiling data. Here we develop and apply a network reconstruction approach that simultaneously integrates six different types of data: endogenous metabolite concentration, RNA expression, DNA variation, DNA–protein binding, protein–metabolite interaction, and protein–protein interaction data, to construct probabilistic causal networks that elucidate the complexity of cell regulation in a segregating yeast population. Because many of the metabolites are found to be under strong genetic control, we were able to employ a causal regulator detection algorithm to identify causal regulators of the resulting network that elucidated the mechanisms by which variations in their sequence affect gene expression and metabolite concentrations. We examined all four expression quantitative trait loci (eQTL) hot spots with colocalized metabolite QTLs, two of which recapitulated known biological processes, while the other two elucidated novel putative biological mechanisms for the eQTL hot spots. PMID:22509135

Dombek, Kenneth M.; Xu, Ethan Y.; Vu, Heather; Tu, Zhidong; Brem, Rachel B.; Bumgarner, Roger E.; Schadt, Eric E.

2012-01-01

331

Positive allosteric activation of GABAA receptors bi-directionally modulates hippocampal glutamate plasticity and behaviour.  

PubMed

Long-term BZ (benzodiazepine) anxiolytic therapy increases the risk of physical dependence manifested as withdrawal anxiety. BZ-induced potentiation of GABA(A)R (gamma-aminobutyric acid type-A receptor) function by 1-week oral administration of FZP (flurazepam) bi-directionally modulates excitatory glutamatergic synaptic transmission in hippocampal CA1 neurons during drug withdrawal. Previous electrophysiological studies on acutely isolated and intact CA1 neurons, as well as immunofluorescence and post-embedding immunogold electron microscopy studies, suggest increased synaptic insertion of GluR (glutamate receptor) 2-lacking AMPARs (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors) in 2-day FZP-withdrawn rats. Preliminary studies indicated a similar increase in GluR1, then phospho-Ser(831)-GluR1, as well as CaMKIIalpha (Ca(2+)/calmodulin-dependent protein kinase IIalpha), but not phospho-Thr(286)-CaMKII levels at the same time point. In our studies, whole-cell recordings in hippocampal slices revealed that AMPAR mEPSC [miniature EPSC (excitatory postsynaptic current)] amplitude was increased in 1-day FZP-withdrawn rats followed by an increase in estimated single-channel conductance in 2-day-FZP-withdrawn rats. Enhanced conductance was no longer observed in slices pre-incubated for 2 h in the CaMKII inhibitor KN-93, but not the inactive analogue KN-92. To evaluate whether CaMKII-mediated AMPA potentiation could occlude LTP (long-term potentiation), LTP was induced by TBS (theta burst stimulation) and recorded using whole-cell and extracellular techniques. LTP was induced in both groups, but only maintained for <15 min in 2-day FZP-withdrawn rats. LTP was fully restored after 7-day withdrawal. Despite the lack of LTP maintenance, impairment of object recognition, place and context was not observed in 2-day-FZP-withdrawn rats. Since L-VGCC (L-type voltage-gated calcium channel) current density was doubled on drug withdrawal and up to 2 days, Ca(2+) entry through L-VGCCs and perhaps subsequently through Ca(2+)-permeable AMPARs are proposed to be responsible for enhanced CaMKIIalpha levels and AMPAR potentiation. Mechanisms associated with several different models of activity-dependent plasticity may underlie BZ physical dependence. PMID:19909283

Shen, Guofu; Mohamed, Mahmoud S; Das, Paromita; Tietz, Elizabeth I

2009-12-01

332

Submillisecond-response IR spatial light modulators with polymer network liquid crystal  

NASA Astrophysics Data System (ADS)

Polymer network liquid crystal (PNLC) is attractive for many photonic applications because of its fast response time and large phase modulation. However, the voltage-on state light scattering caused by multi-domains of LC molecules hinders its applications in the visible and near infrared regions. To reduce domain sizes and eliminate scattering for ?=1.06 ?m and 1.55 ?m, we studied the effect of LC viscosity on domain sizes. PNLCs based on five different LC hosts were prepared. The LC host was first mixed with 6% reactive mesogen and then filled into a 12-?m cell with homogeneous alignment. After UV curing, we measured the on-state transmission spectra of these five PNLCs. By fitting the transmission spectra with Rayleigh-Gans-Debye model, we can estimate the average domain sizes. We found that the domain sizes of PNLC are inversely proportional to the rotational viscosity of the LC host. This finding can be explained by the Stokes-Einstein equation. As a result, PNLC with a slower diffusion rate would cause smaller domain sizes, which in turn lead to faster response time. To achieve a slower diffusion rate, we cured the PNLC samples at a lower temperature. By selecting a high viscosity and high ?? LC host, we demonstrate a scattering-free (<3%) 2? phase modulator at ?=1.06 ?m and ?=1.55 ?m. Temperature affects the PNLC performance significantly. As the operation temperature increases from 25oC to 70oC, the response time drops from 220 ?s to 30 ?s. 2? operating voltage for ?=1.06 ?m slightly increases from 65V to 85V. Meanwhile, hysteresis decreases from 7.7% to 2%. For ?=1.55?m, operating voltage is 100V. If reflective mode is employed, operating voltage can be reduced to 55V.

Sun, Jie; Chen, Yuan; Wu, Shin-Tson

2013-03-01

333

Functional network reorganization in motor cortex can be explained by reward-modulated Hebbian learning  

PubMed Central

The control of neuroprosthetic devices from the activity of motor cortex neurons benefits from learning effects where the function of these neurons is adapted to the control task. It was recently shown that tuning properties of neurons in monkey motor cortex are adapted selectively in order to compensate for an erroneous interpretation of their activity. In particular, it was shown that the tuning curves of those neurons whose preferred directions had been misinterpreted changed more than those of other neurons. In this article, we show that the experimentally observed self-tuning properties of the system can be explained on the basis of a simple learning rule. This learning rule utilizes neuronal noise for exploration and performs Hebbian weight updates that are modulated by a global reward signal. In contrast to most previously proposed reward-modulated Hebbian learning rules, this rule does not require extraneous knowledge about what is noise and what is signal. The learning rule is able to optimize the performance of the model system within biologically realistic periods of time and under high noise levels. When the neuronal noise is fitted to experimental data, the model produces learning effects similar to those found in monkey experiments.

Legenstein, Robert; Chase, Steven M.; Schwartz, Andrew B.; Maass, Wolfgang

2011-01-01

334

Network Offoaded Hierarchical Collectives Using ConnectX-2's CORE-Direct Capabilities  

SciTech Connect

As the scale of High Performance Computing (HPC) systems continues to increase, demanding that we extract even more parallelism from applications, the need to move communication management away from the Central Processing Unit (CPU) becomes even greater. Moving this management to the network, frees up CPU cycles for computation, making it possible to overlap computation and communication. In this paper we continue to investigate how to best use the new CORE-Direct support added in the ConnectX-2 Host Channel Adapter (HCA) for creating high performance, asynchronous collective operations that are managed by the HCA. Specifically we consider the network topology, creating a two-level communication hierarchy, reducing the MPI Barrier completion time by 45%, from 26.59 microseconds, when not considering network topology, to 14.72 microseconds, with the CPU based collective barrier operation completing in 19.04 microseconds. The nonblocking barrier algorithm has similar performance, with about 50% of that time available for computation.

Rabinovitz, Ishai [Mellanox Technologies, Inc.] [Mellanox Technologies, Inc.; Shamis, Pavel [ORNL] [ORNL; Graham, Richard L [ORNL] [ORNL; Bloch, Noam [Mellanox Technologies, Inc.] [Mellanox Technologies, Inc.; Shainer, Gilad [Mellanox Technologies, Inc.] [Mellanox Technologies, Inc.

2010-01-01

335

Chemokine signaling directs trunk lymphatic network formation along the preexisting blood vasculature  

PubMed Central

SUMMARY The lymphatic system is crucial for fluid homeostasis, immune responses, and numerous pathological processes. However, the molecular mechanisms responsible for establishing the anatomical form of the lymphatic vascular network remain largely unknown. Here, we show that chemokine signaling provides critical guidance cues directing early trunk lymphatic network assembly and patterning. The chemokine receptors Cxcr4a and Cxcr4b are expressed in lymphatic endothelium, while chemokine ligands Cxcl12a and Cxcl12b are expressed in adjacent tissues along which the developing lymphatics align. Loss- and gain- of function studies in the zebrafish demonstrate that chemokine signaling orchestrates the stepwise assembly of the trunk lymphatic network. In addition to providing evidence for a lymphatic vascular guidance mechanism, these results also suggest a molecular basis for the anatomical co-alignment of lymphatic and blood vessels. PMID:22516200

Cha, Young Ryun; Fujita, Misato; Butler, Matthew; Isogai, Sumio; Kochhan, Eva; Siekmann, Arndt F.; Weinstein, Brant M.

2014-01-01

336

An accelerated direct demodulation method for image reconstruction using spherical data from the hard X-ray modulation telescope  

NASA Astrophysics Data System (ADS)

The hard X-ray modulation telescope (HXMT) mission is mainly devoted to performing an all-sky survey at 1 - 250 keV with both high sensitivity and high spatial resolution. The observed data reduction as well as the image reconstruction for HXMT can be achieved by using the direct demodulation method (DDM). However the original DDM is too computationally expensive for multi-dimensional data with high resolution to be employed for HXMT data. We propose an accelerated direct demodulation method especially adapted for data from HXMT. Simulations are also presented to demonstrate this method.

Huo, Zhuo-Xi; Zhou, Jian-Feng

2013-08-01

337

Direct evidence for the modulation of the activity of the Erwinia chrysanthemi quorum-sensing regulator ExpR by acylhomoserine lactone pheromone.  

PubMed

In Erwinia chrysanthemi production of pectic enzymes is controlled by a complex network involving several regulators. Among them is ExpR, the quorum-sensing regulatory protein. ExpR is a member of the LuxR family of transcriptional regulators, the activity of which is modulated by the binding of diffusible N-acylhomoserine lactone pheromones to the N-terminal receptor site of the proteins. Previous in vitro DNA-ExpR binding studies suggested that ExpR might activate pectic enzyme production and repress its cognate gene expression. This report presents genetic evidence that ExpR represses its own gene expression in the absence of pheromone and that the addition of pheromone promotes concentration-dependent de-repression. In vitro experiments show that (i) ExpR binds target DNA in the absence of pheromone and that the pheromone dissociates ExpR-DNA complexes, (ii) ExpR binds target DNA in a non-cooperative fashion, and (iii) two molecules of pheromone are bound per molecule of ExpR dimer. In the absence of N-(3-oxo-hexanoyl)-homoserine lactone, ExpR prevents RNA polymerase access to the expR promoter, thereby directly repressing transcription initiation. The presence of pheromone renders the expR promoter accessible to RNA polymerase and results in the de-repression of transcription initiation. Overall we have established that there is a direct modulation of the repressive activity of a LuxR family regulator by a pheromone. Furthermore, site-directed mutagenesis experiments strongly suggest that the ExpR residues Leu-19, Tyr-31, and Ser-125 are involved in the transduction of conformational changes induced by ligand binding, and this provides new insights into the structure-function relationship of this bacterial regulator family. PMID:16831870

Castang, Sandra; Reverchon, Sylvie; Gouet, Patrice; Nasser, William

2006-10-01

338

Identification of the direction of the neural network activation with a cellular resolution by fast two-photon imaging  

NASA Astrophysics Data System (ADS)

Spatiotemporal activity patterns in local neural networks are fundamental to understanding how information is processed and stored in brain microcircuits. Currently, imaging techniques are able to map the directional activation of macronetworks across brain areas; however, these strategies still fail to resolve the activation direction for fine microcircuits with cellular spatial resolution. Here, we show the capability to identify the activation direction of a multicell network with a cellular resolution and millisecond precision by using fast two-photon microscopy and cross correlation procedures. As an example, we characterized a directional neuronal network in an epilepsy brain slice to provide different initiation delay among multiple neurons defined at a millisecond scale.

Liu, Xiuli; Quan, Tingwei; Zeng, Shaoqun; Lv, Xiaohua

2011-08-01

339

Wdpcp, a PCP protein required for ciliogenesis, regulates directional cell migration and cell polarity by direct modulation of the actin cytoskeleton.  

PubMed

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

2013-11-01

340

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

341

Direct Correlation between Nonrandom Ion Hopping and Network Structure in Ion-Conducting Borophosphate Glasses  

Microsoft Academic Search

We present temperature-dependent conductivity spectra of sodium borophosphate glasses with a varying borate\\/phosphate ratio but a constant sodium oxide content which can be mapped into time-dependent mean square displacements. For the first time, we show that characteristic lengths of ion transport derived thereof are directly linked to features of network structure, viz., the number of boron oxide tetrahedra. Our results

D. Zielniok; H. Eckert; C. Cramer

2008-01-01

342

Nonlinear control for MIMO magnetic levitation system using direct decentralized neural networks  

Microsoft Academic Search

A direct modified Elman neural networks (MENNs)-based decentralized controller is proposed to control the magnets of a nonlinear and unstable multi-input multi-output (MIMO) levitation system for the tracking of reference trajectory. First, the operating principles of a magnetic levitation system with two moving magnets are introduced. Then, due to the exact dynamic model of the MIMO magnetic levitation system is

Syuan-Yi Chen; Faa-Jeng Lin

2009-01-01

343

Hypoxia-Ischemia Disrupts Directed Interactions within Neonatal Prefrontal-Hippocampal Networks  

PubMed Central

Due to improved survival rates and outcome of human infants experiencing a hypoxic-ischemic episode, cognitive dysfunctions have become prominent. They might result from abnormal communication within prefrontal-hippocampal networks, as synchrony and directed interactions between the prefrontal cortex and hippocampus account for mnemonic and executive performance. Here, we elucidate the structural and functional impact of hypoxic-ischemic events on developing prefrontal-hippocampal networks in an immature rat model of injury. The magnitude of infarction, cell loss and astrogliosis revealed that an early hypoxic-ischemic episode had either a severe or a mild/moderate outcome. Without affecting the gross morphology, hypoxia-ischemia with mild/moderate outcome diminished prefrontal neuronal firing and gamma network entrainment. This dysfunction resulted from decreased coupling synchrony within prefrontal-hippocampal networks and disruption of hippocampal theta drive. Thus, early hypoxia-ischemia may alter the functional maturation of neuronal networks involved in cognitive processing by disturbing the communication between the neonatal prefrontal cortex and hippocampus. PMID:24376636

Brockmann, Marco D.; Kukovic, Maja; Schonfeld, Michael; Sedlacik, Jan; Hanganu-Opatz, Ileana L.

2013-01-01

344

Optical Access Architecture Designs Based on WDM-Direct toward New Generation Networks  

NASA Astrophysics Data System (ADS)

We present our proposed designs of optical access architecture based on WDM technology toward new-generation networks for two types of topologies: Single-star (SS) and passive-double-star (PDS). We adopt the concept of WDM-direct which links multiple wavelengths to each optical network unit (ONU). Our proposed architecture based on WDM-direct can achieve more than 10Gbps access per ONU. Moreover, our architecture can provide not only conventional bandwidth-shared services but also bandwidth-guaranteed services requiring more than 10Gbps bandwidth by establishing end-to-end lightpaths directly to each ONU, and thus meet high requirements of QoS in new-generation networks. Firstly, we show our proposed designs of SS-type architecture, and experimentally demonstrate the system. We confirm that the optical line terminal (OLT) successfully switches between packet/lightpath data transmissions for each ONU. In addition, we measure and evaluate optical power loss in upstream/downstream transmissions between the OLT and ONUs. Secondly, we show our proposed designs of PDS-type architecture, and theoretically analyze and evaluate the bit-rate capacity of the system.

Miyazawa, Takaya; Harai, Hiroaki

345

Modulation of cultured neural networks using neurotrophin release from hydrogel-coated microelectrode arrays  

PubMed Central

Polyacrylamide and poly(ethylene glycol) diacrylate hydrogels were synthesized and characterized for use as drug-release and substrates for neuron cell culture. Protein release kinetics was determined by incorporating bovine serum albumin (BSA) into hydrogels during polymerization. To determine if hydrogel incorporation and release affects bioactivity, alkaline phosphatase was incorporated into hydrogels and released enzyme activity determined using the fluorescence-based ELF-97 assay. Hydrogels were then used to deliver brain derived neurotrophic factor (BDNF) from hydrogels polymerized over planar microelectrode arrays (MEA). Primary hippocampal neurons were cultured on both control and neurotrophin-containing hydrogel-coated MEAs. The effect of released BDNF on neurite length and process arborization was investigated using automated image analysis. Increased spontaneous activity as a response to released BDNF was recorded from the neurons cultured on top of hydrogel layers. These results demonstrate that proteins of biological interest can be incorporated into hydrogels to modulate development and function of cultured neural networks. These results also set the stage for development of hydrogel-coated neural prosthetic devices for local delivery of various biologically active molecules. PMID:18477815

Jun, Sang Beom; Hynd, Matthew R.; Dowell-Mesfin, Natalie M.; Al-Kofahi, Yousef; Roysam, Badrinath; Shain, William; Kim, Sung June

2009-01-01

346

Flexible establishment of functional brain networks supports attentional modulation of unconscious cognition.  

PubMed

In classical theories of attention, unconscious automatic processes are thought to be independent of higher-level attentional influences. Here, we propose that unconscious processing depends on attentional enhancement of task-congruent processing pathways implemented by a dynamic modulation of the functional communication between brain regions. Using functional magnetic resonance imaging, we tested our model with a subliminally primed lexical decision task preceded by an induction task preparing either a semantic or a perceptual task set. Subliminal semantic priming was significantly greater after semantic compared to perceptual induction in ventral occipito-temporal (vOT) and inferior frontal cortex, brain areas known to be involved in semantic processing. The functional connectivity pattern of vOT varied depending on the induction task and successfully predicted the magnitude of behavioral and neural priming. Together, these findings support the proposal that dynamic establishment of functional networks by task sets is an important mechanism in the attentional control of unconscious processing. Hum Brain Mapp 35:5500-5516, 2014. © 2014 Wiley Periodicals, Inc. PMID:24954512

Ulrich, Martin; Adams, Sarah C; Kiefer, Markus

2014-11-01

347

Estimating the RAR modulation transfer function directly from SAR ocean wave image spectra  

Microsoft Academic Search

A new method for estimating the phase and amplitude of the real aperture radar (RAR) modulation transfer function (MTF) is proposed. Conventionally, in situ measurements of the seastate have been used in connection with SAR estimation of the RAR MTF. However, investigations using synthetic data reveal that the SAR image spectrum for realistic seastates is shaped by the unknown transfer

K. A. Hogda; S. Jacobsen

1993-01-01

348

Performance evaluation for on-demand routing protocols based on OPNET modules in wireless mesh networks  

Microsoft Academic Search

In wireless networks, users expect to get access to the network securely and seamlessly to share the data flow of access points anytime and anywhere. However, either point-to-point or point-to-multipoint methods in traditional wireless networks make the network bandwidth decrease rapidly, which cannot meet the requirements of users. Recently, a new wireless broadband access network, wireless mesh networks (WMNs), has

Lei Guo; Yuhuai Peng; Xingwei Wang; Dingde Jiang; Yinpeng Yu

2011-01-01

349

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

NASA Astrophysics Data System (ADS)

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 distance more than 30km. Although gain-coupled DFB-LDs (GC-DFB-LD) have been widely investigated in the hope of eliminating the isolator in optical modules, their limited output power keeps them from practical use in passive optical networks. In this paper, we describe the development of 1.31µm and 1.49µm GC-DFB-LDs with high output power and optical feed back tolerance for isolator-free optical modules in access networks. The relative intensity noise (RIN) degradation was well suppressed below -120dB/Hz at -8dB optical feedback in the temperatures range from 0°C to 85°C from both 1.31µm and 1.49µm GC-DFB-LDs. Optical feedback tolerance of 1.31µm and 1.49µm GC-DFB-LDs were improved by more than 6dB and 4dB as compared with conventional IC-DFB-LDs. Dispersion power penalty after over 30km transmission at 1.25Gbps were achieved less than 0.3dB and 0.7dB under -15dB optical feedback conditions. The proposed 1.31µm GC-DFB-LD prototypes experimentally demonstrated 14mW output power with over 5, 000-hour operation at 85°C. Our devices are found to fully complying IEEE 802.3ah standard and seem to be promising for the low-cost optical modules in long-reach access network applications. The details of the device structure as well as transmission experiments are also reported.

Nakamura, Koji; Miyamura, Satoshi; Yaegashi, Hiroki

350

Direct and complete calibration of phase modulation depth of LCOS by using double exposure digital holography  

NASA Astrophysics Data System (ADS)

The digital holographic method is used to characterize the phase modulation depth of phase-only LCOS. Compared with the conventional ways, the digital holographic method could obtain the information around the whole field of view. Besides, the digital holographic method is a non-contact, lossless, high-fidelity way to achieve the phase distribution. In this paper, the lensless Fourier transform digital holography is employed, due to its simple setup and reconstruction process. In LCOS the phase modulation is controlled by displaying the gray level images on its active area. Usually for the phase modulation characterization, the total of all 255 gray level images are displayed in a step change of 10, for each recording. That is why it takes time for the complete calibration. In this method a mask with the entire range of gray-level i.e. from 0-255 is displayed on the LCOS active area and the hologram is recorded, which on reconstruction gives the depth of phase modulation of LCOS for the entire range of gray level. In order to avoid the aberration a double exposure method is used in which two holograms are recorded, one with the 0-255 and other with the zero gray level masks. Also, the sorting by reliability, following a non-continuous path (SNRCP) phase unwrapping algorithm is used for unwrapping the final result. The main advantages of this method are the less number of required recording holograms, the easy and real time calibration. Results are then compared with the conventional method that is young double slit method, which is widely proposed to obtain the phase modulation depth of the LCOS and they are in good agreement with each other. The efficiency of our method is verified by comparison.

Panezai, Spozmai; Wang, Dayong; Zhao, Jie; Wang, Yunxin; Ma, Sijin; Rong, Lu

2013-12-01

351

A yeast phenomic model for the gene interaction network modulating CFTR-?F508 protein biogenesis  

PubMed Central

Background The overall influence of gene interaction in human disease is unknown. In cystic fibrosis (CF) a single allele of the cystic fibrosis transmembrane conductance regulator (CFTR-?F508) accounts for most of the disease. In cell models, CFTR-?F508 exhibits defective protein biogenesis and degradation rather than proper trafficking to the plasma membrane where CFTR normally functions. Numerous genes function in the biogenesis of CFTR and influence the fate of CFTR-?F508. However it is not known whether genetic variation in such genes contributes to disease severity in patients. Nor is there an easy way to study how numerous gene interactions involving CFTR-?F would manifest phenotypically. Methods To gain insight into the function and evolutionary conservation of a gene interaction network that regulates biogenesis of a misfolded ABC transporter, we employed yeast genetics to develop a 'phenomic' model, in which the CFTR-?F508-equivalent residue of a yeast homolog is mutated (Yor1-?F670), and where the genome is scanned quantitatively for interaction. We first confirmed that Yor1-?F undergoes protein misfolding and has reduced half-life, analogous to CFTR-?F. Gene interaction was then assessed quantitatively by growth curves for approximately 5,000 double mutants, based on alteration in the dose response to growth inhibition by oligomycin, a toxin extruded from the cell at the plasma membrane by Yor1. Results From a comparative genomic perspective, yeast gene interactions influencing Yor1-?F biogenesis were representative of human homologs previously found to modulate processing of CFTR-?F in mammalian cells. Additional evolutionarily conserved pathways were implicated by the study, and a ?F-specific pro-biogenesis function of the recently discovered ER membrane complex (EMC) was evident from the yeast screen. This novel function was validated biochemically by siRNA of an EMC ortholog in a human cell line expressing CFTR-?F508. The precision and accuracy of quantitative high throughput cell array phenotyping (Q-HTCP), which captures tens of thousands of growth curves simultaneously, provided powerful resolution to measure gene interaction on a phenomic scale, based on discrete cell proliferation parameters. Conclusion We propose phenomic analysis of Yor1-?F as a model for investigating gene interaction networks that can modulate cystic fibrosis disease severity. Although the clinical relevance of the Yor1-?F gene interaction network for cystic fibrosis remains to be defined, the model appears to be informative with respect to human cell models of CFTR-?F. Moreover, the general strategy of yeast phenomics can be employed in a systematic manner to model gene interaction for other diseases relating to pathologies that result from protein misfolding or potentially any disease involving evolutionarily conserved genetic pathways. PMID:23270647

2012-01-01

352

Modulation of motion after-e¡ect by transcranial direct current stimulation over MT + \\/V5 in humans  

Microsoft Academic Search

While there is strong evidence for the central role of the human MT + \\/V5 in motion processing, its involvement in motion adapta- tion is still the subject of debate. We used transcranial direct cur- rent stimulation (tDCS) to test whether MT + \\/V5 is part of the neural network involved in the long-term adaptation-induced mo- tion after-e¡ect in humans.

Andrea Antal; Edina T. Varga; Michael A. Nitsche; Zoltan Chadaide; Gyula Kovacs

353

Silicon microring modulator for 40 Gb/s NRZ-OOK metro networks in O-band.  

PubMed

A microring-based silicon modulator operating at 40 Gb/s near 1310 nm is demonstrated for the first time to our knowledge. NRZ-OOK signals at 40 Gb/s with 6.2 dB extinction ratio are observed by applying a 4.8 Vpp driving voltage and biasing the modulator at 7 dB insertion loss point. The energy efficiency is 115 fJ/bit. The transmission performance of 40 Gb/s NRZ-OOK through 40 km of standard single mode fiber without dispersion compensation is also investigated. We show that the link suffers negligible dispersion penalty. This makes the modulator a potential candidate for metro network applications. PMID:25402070

Xuan, Zhe; Ma, Yangjin; Liu, Yang; Ding, Ran; Li, Yunchu; Ophir, Noam; Lim, Andy Eu-Jin; Lo, Guo-Qiang; Magill, Peter; Bergman, Keren; Baehr-Jones, Tom; Hochberg, Michael

2014-11-17

354

Identifying Grade/Stage-Related Active Modules in Human Co-regulatory Networks: A Case Study for Breast Cancer  

PubMed Central

Abstract The histological grade/stage of tumor is widely acknowledged as an important clinical prognostic factor for cancer progression. Recent experimental studies have explored the following two topics at the molecular level: (1) whether or not gene expression levels vary by different degrees among different tumor grades/stages, and (2) whether some well-defined modules could distinguish one grade/stage from another. In this article, using breast cancer as an example, we investigated this topic and identified grade/stage-related active modules under the framework of a weighted network integrated from a human protein interaction network and a transcriptional regulatory network. Our results enabled us to draw the conclusion that the gene expression profile could provide more clues about tumor grade, but reveals less evidence about tumor stage. In addition, we found that our modular biomarker method had additional advantages in identifying some tumor grade/stage-related genes with slightly altered expression. According to our case study, the framework we introduced could be used for other cancers to identify their modules during grading or staging. PMID:23215806

Feng, Chenchen; Li, Wan; Wang, Hong; Zhang, Liangcai; Jia, Xu; Miao, Zhengqiang; Qu, Xiaoli; Li, Weiguo; He, Weiming

2012-01-01

355

The study of optical FSK modulation for 40-Gb/s WDM-PON network with centralized lightwave source  

NASA Astrophysics Data System (ADS)

This paper proposes and numerically investigated a novel high-speed wavelength-division-multiplexed passive optical network (WDM-PON) architecture with colorless user terminals based on the use of a different modulation scheme for downstream and upstream transmission. In the central office (CO), based on the carrier suppressing functionality of Mach-Zehnder modulator (MZM) and differential-phase-shift-keying to amplitude-shift-keying conversion using Mach-Zehnder delay interferometer, 40-Gb/s optical frequency shift keying (FSK) is generated and employed for transmitting the downstream data. In the remote node (RN) or optical network unit (ONU), the upstream data is re-modulated at 2.5-Gb/s by an intensity modulator and sent back to CO with the same fiber. Since only one light source is needed for each WDM channel, and the MZM to generate carrier suppressed signal can be shared by all the channels, a centralized 40-Gb/s WDM-PON access system with low-cost configuration is realized. Error free transmission over 20-km SMF can be observed for both downstream and upstream signals in our simulation.

Li, Minghao; Hong, Wei; Zhang, Xinliang; Li, Wei; Huang, Dexiu

2008-11-01

356

Network analysis of genomic alteration profiles reveals co-altered functional modules and driver genes for glioblastoma.  

PubMed

The heterogeneity of genetic alterations in human cancer genomes presents a major challenge to advancing our understanding of cancer mechanisms and identifying cancer driver genes. To tackle this heterogeneity problem, many approaches have been proposed to investigate genetic alterations and predict driver genes at the individual pathway level. However, most of these approaches ignore the correlation of alteration events between pathways and miss many genes with rare alterations collectively contributing to carcinogenesis. Here, we devise a network-based approach to capture the cooperative functional modules hidden in genome-wide somatic mutation and copy number alteration profiles of glioblastoma (GBM) from The Cancer Genome Atlas (TCGA), where a module is a set of altered genes with dense interactions in the protein interaction network. We identify 7 pairs of significantly co-altered modules that involve the main pathways known to be altered in GBM (TP53, RB and RTK signaling pathways) and highlight the striking co-occurring alterations among these GBM pathways. By taking into account the non-random correlation of gene alterations, the property of co-alteration could distinguish oncogenic modules that contain driver genes involved in the progression of GBM. The collaboration among cancer pathways suggests that the redundant models and aggravating models could shed new light on the potential mechanisms during carcinogenesis and provide new indications for the design of cancer therapeutic strategies. PMID:23344900

Gu, Yunyan; Wang, Hongwei; Qin, Yao; Zhang, Yujing; Zhao, Wenyuan; Qi, Lishuang; Zhang, Yuannv; Wang, Chenguang; Guo, Zheng

2013-03-01

357

Latent Modulation: A Basis for Non-Disruptive Promotion of Two Incompatible Behaviors by a Single Network State  

PubMed Central

Behavioral states often preferentially enhance specific classes of behavior and suppress incompatible behaviors. In the nervous system, this may involve upregulation of the efficacy of neural modules that mediate responses to one stimulus and suppression of modules that generate antagonistic or incompatible responses to another stimulus. In Aplysia, prestimulation of egestive inputs [esophageal nerve (EN)] facilitates subsequent EN-elicited egestive responses and weakens ingestive responses to ingestive inputs [Cerebral-Buccal Interneuron (CBI-2)]. However, a single state can also promote incompatible behaviors in response to different stimuli. This is the case in Aplysia, where prestimulation of CBI-2 inputs not only enhances subsequent CBI-2-elicited ingestive responses, but also strengthens EN-elicited egestive responses. We used the modularly organized feeding network of Aplysia to characterize the organizational principles that allow a single network state to promote two opposing behaviors, ingestion and egestion, without the two interfering with each other. We found that the CBI-2 prestimulation-induced state upregulates the excitability of neuron B65 which, as a member of the egestive module, increases the strength of egestive responses. Furthermore,we found that this upregulation is likely mediated by the actions of the neuropeptides FCAP (Feeding Circuit Activating Peptide) and CP2 (Cerebral Peptide 2). This increased excitability is mediated by a form of modulation that we refer to as “latent modulation” because it is established during stimulation of CBI-2, which does not activate B65. However, when B65 is recruited into EN-elicited egestive responses, the effects of the latent modulation are expressed as a higher B65 firing rate and a resultant strengthening of the egestive response. PMID:23447591

Dacks, Andrew M.; Weiss, Klaudiusz R.

2013-01-01

358

Latent modulation: a basis for non-disruptive promotion of two incompatible behaviors by a single network state.  

PubMed

Behavioral states often preferentially enhance specific classes of behavior and suppress incompatible behaviors. In the nervous system, this may involve upregulation of the efficacy of neural modules that mediate responses to one stimulus and suppression of modules that generate antagonistic or incompatible responses to another stimulus. In Aplysia, prestimulation of egestive inputs [esophageal nerve (EN)] facilitates subsequent EN-elicited egestive responses and weakens ingestive responses to ingestive inputs [Cerebral-Buccal Interneuron (CBI-2)]. However, a single state can also promote incompatible behaviors in response to different stimuli. This is the case in Aplysia, where prestimulation of CBI-2 inputs not only enhances subsequent CBI-2-elicited ingestive responses, but also strengthens EN-elicited egestive responses. We used the modularly organized feeding network of Aplysia to characterize the organizational principles that allow a single network state to promote two opposing behaviors, ingestion and egestion, without the two interfering with each other. We found that the CBI-2 prestimulation-induced state upregulates the excitability of neuron B65 which, as a member of the egestive module, increases the strength of egestive responses. Furthermore, we found that this upregulation is likely mediated by the actions of the neuropeptides FCAP (Feeding Circuit Activating Peptide) and CP2 (Cerebral Peptide 2). This increased excitability is mediated by a form of modulation that we refer to as "latent modulation" because it is established during stimulation of CBI-2, which does not activate B65. However, when B65 is recruited into EN-elicited egestive responses, the effects of the latent modulation are expressed as a higher B65 firing rate and a resultant strengthening of the egestive response. PMID:23447591

Dacks, Andrew M; Weiss, Klaudiusz R

2013-02-27

359

A Nonisolated ZVS Asymmetrical Buck Voltage Regulator Module With Direct Energy Transfer  

Microsoft Academic Search

This paper presents a new nonisolated asymmetrical buck voltage regulator module. A transformer is used to extend the extremely low duty cycle of a conventional buck converter. Turn-off losses can be significantly reduced due to the extension of duty cycle, and there are no turn-on losses owing to the zero-voltage turn-on condition. At the same time, the voltage stress over

Zhiliang Zhang; Wilson Eberle; Yan-Fei Liu; Paresh C. Sen

2009-01-01

360

Suppressing the relaxation oscillation noise of injection-locked WRC-FPLD for directly modulated OFDM transmission.  

PubMed

By up-shifting the relaxation oscillation peak and suppressing its relative intensity noise in a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) under intense injection-locking, the directly modulated transmission of optical 16 quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) data-stream is demonstrated. The total bit rate of up to 20 Gbit/s within 5-GHz bandwidth is achieved by using the OFDM subcarrier pre-leveling technique. With increasing the injection-locking power from -12 to -3 dBm, the effective reduction on threshold current of the WRC-FPLD significantly shifts its relaxation oscillation frequency from 5 to 7.5 GHz. This concurrently induces an up-shift of the peak relative intensity noise (RIN) of the WRC-FPLD, and effectively suppresses the background RIN level to -104 dBc/Hz within the OFDM band between 3 and 6 GHz. The enhanced signal-to-noise ratio from 16 to 20 dB leads to a significant reduction of bit-error-rate (BER) of the back-to-back transmitted 16-QAM-OFDM data from 1.3 × 10(-3) to 5 × 10(-5), which slightly degrades to 1.1 × 10(-4) after 25-km single-mode fiber (SMF) transmission. However, the enlarged injection-locking power from -12 to -3 dBm inevitably declines the modulation throughput and increases its negative throughput slope from -0.8 to -1.9 dBm/GHz. After pre-leveling the peak amplitude of the OFDM subcarriers to compensate the throughput degradation of the directly modulated WRC-FPLD, the BER under 25-km SMF transmission can be further improved to 3 × 10(-5) under a receiving power of -3 dBm. PMID:24977832

Cheng, Min-Chi; Chi, Yu-Chieh; Li, Yi-Cheng; Tsai, Cheng-Ting; Lin, Gong-Ru

2014-06-30

361

30-gb\\/s signal transmission over 40-km directly modulated DFB-laser-based single-mode-fiber links without optical amplification and dispersion compensation  

Microsoft Academic Search

Based on a recently proposed novel optical-signal-modulation technique of adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM), numerical simulations of the transmission performance of AMOOFDM signals are undertaken in directly modulated DFB laser (DML)-based single-mode-fiber (SMF) links without optical amplification and dispersion compensation. It is shown that a 30-Gb\\/s transmission over a 40-km SMF with a loss margin of greater than

J. M. Tang; K. Alan Shore

2006-01-01

362

Supramolecular Fullerene Polymers and Networks Directed by Molecular Recognition between Calix[5]arene and C60.  

PubMed

A biscalix[5]arene-C60 supramolecular structure was utilized for the development of supramolecular fullerene polymers. Di- and tritopic hosts were developed to generate the linear and network supramolecular polymers through the complexation of a dumbbell-shaped fullerene. The molecular association between the hosts and the fullerene were carefully studied by using (1) H?NMR, UV/Vis absorption, and fluorescence spectroscopy. The formation of the supramolecular fullerene polymers and networks was confirmed by diffusion-ordered (1) H?NMR spectroscopy (DOSY) and solution viscometry. Upon concentrating the mixtures of di- or tritopic hosts and dumbbell-shaped fullerene in the range of 1.0-10?mmol?L(-1) , the diffusion coefficients of the complexes decreased, and the solution viscosities increased, suggesting that large polymeric assemblies were formed in solution. Scanning electron microscopy (SEM) was used to image the supramolecular fullerene polymers and networks. Atomic force microscopy (AFM) provided insight into the morphology of the supramolecular polymers. A mixture of the homoditopic host and the fullerene resulted in fibers with a height of (1.4±0.1)?nm and a width of (5.0±0.8)?nm. Interdigitation of the alkyl side chains provided secondary interchain interactions that facilitated supramolecular organization. The homotritopic host generated the supramolecular networks with the dumbbell-shaped fullerene. Honeycomb sheet-like structures with many voids were found. The growth of the supramolecular polymers is evidently governed by the shape, dimension, and directionality of the monomers. PMID:25302995

Hirao, Takehiro; Tosaka, Masatoshi; Yamago, Shigeru; Haino, Takeharu

2014-12-01

363

Does Gaze Direction Modulate Facial Expression Processing in Children with Autism Spectrum Disorder?  

ERIC Educational Resources Information Center

Two experiments investigated whether children with autism spectrum disorder (ASD) integrate relevant communicative signals, such as gaze direction, when decoding a facial expression. In Experiment 1, typically developing children (9-14 years old; n = 14) were faster at detecting a facial expression accompanying a gaze direction with a congruent…

Akechi, Hironori; Senju, Atsushi; Kikuchi, Yukiko; Tojo, Yoshikuni; Osanai, Hiroo; Hasegawa, Toshikazu

2009-01-01

364

Kisspeptin neurons do not directly signal to RFRP-3 neurons but RFRP-3 may directly modulate a subset of hypothalamic kisspeptin cells in mice  

PubMed Central

The neuropeptides kisspeptin (encoded by Kiss1) and RFamide-related peptide-3 (also known as GnIH; encoded by Rfrp) are potent stimulators and inhibitors, respectively, of reproduction. Whether kisspeptin or RFRP-3 might act directly on each other’s neuronal populations to indirectly modulate reproductive status is unknown. To examine possible interconnectivity of the kisspeptin and RFRP-3 systems, we performed double label in-situ hybridization (ISH) for RFRP-3’s receptors, Gpr147 and Gpr74, in hypothalamic Kiss1 neurons of adult male and female mice, as well as double-label ISH for kisspeptin’s receptor, Kiss1r, in Rfrp-expressing neurons of the hypothalamic dorsal-medial nucleus (DMN). Only a very small proportion (5–10%) of Kiss1 neurons of the anteroventral periventricular region expressed Gpr147 or Gpr74 in either sex, whereas higher co-expression (~25%) existed in Kiss1 neurons in the arcuate nucleus. Thus, RFRP-3 could signal to a small, primarily arcuate, subset of Kiss1 neurons, a conclusion supported by the finding of ~35% of arcuate kisspeptin cells receiving RFRP-3--immunoreactive fibre contacts. In contrast to the former situation, no Rfrp neurons co-expressed Kiss1r in either sex, and Tacr3, the receptor for neurokinin B (NKB; a neuropeptide co-expressed with arcuate kisspeptin neurons) was found in <10% of Rfrp neurons. Moreover, kisspeptin-immunoreactive fibres did not readily appose RFRP-3 cells in either sex, further excluding the likelihood that kisspeptin neurons directly communicate to RFRP-3 neurons. Lastly, despite abundant NKB in the DMN region where RFRP-3 soma reside, NKB was not co-expressed in the majority of Rfrp neurons. Our results suggest that RFRP-3 may modulate a small proportion of kisspeptin-producing neurons in mice, particularly in the arcuate nucleus, whereas kisspeptin neurons are unlikely to have any direct reciprocal actions on RFRP-3 neurons. PMID:23927071

Poling, Matthew C.; Quennell, Janette H.; Anderson, Greg M.; Kauffman, Alexander S.

2013-01-01

365

Reconstruction of an integrated genome-scale co-expression network reveals key modules involved in lung adenocarcinoma.  

PubMed

Our goal of this study was to reconstruct a "genome-scale co-expression network" and find important modules in lung adenocarcinoma so that we could identify the genes involved in lung adenocarcinoma. We integrated gene mutation, GWAS, CGH, array-CGH and SNP array data in order to identify important genes and loci in genome-scale. Afterwards, on the basis of the identified genes a co-expression network was reconstructed from the co-expression data. The reconstructed network was named "genome-scale co-expression network". As the next step, 23 key modules were disclosed through clustering. In this study a number of genes have been identified for the first time to be implicated in lung adenocarcinoma by analyzing the modules. The genes EGFR, PIK3CA, TAF15, XIAP, VAPB, Appl1, Rab5a, ARF4, CLPTM1L, SP4, ZNF124, LPP, FOXP1, SOX18, MSX2, NFE2L2, SMARCC1, TRA2B, CBX3, PRPF6, ATP6V1C1, MYBBP1A, MACF1, GRM2, TBXA2R, PRKAR2A, PTK2, PGF and MYO10 are among the genes that belong to modules 1 and 22. All these genes, being implicated in at least one of the phenomena, namely cell survival, proliferation and metastasis, have an over-expression pattern similar to that of EGFR. In few modules, the genes such as CCNA2 (Cyclin A2), CCNB2 (Cyclin B2), CDK1, CDK5, CDC27, CDCA5, CDCA8, ASPM, BUB1, KIF15, KIF2C, NEK2, NUSAP1, PRC1, SMC4, SYCE2, TFDP1, CDC42 and ARHGEF9 are present that play a crucial role in cell cycle progression. In addition to the mentioned genes, there are some other genes (i.e. DLGAP5, BIRC5, PSMD2, Src, TTK, SENP2, PSMD2, DOK2, FUS and etc.) in the modules. PMID:23874428

Bidkhori, Gholamreza; Narimani, Zahra; Hosseini Ashtiani, Saman; Moeini, Ali; Nowzari-Dalini, Abbas; Masoudi-Nejad, Ali

2013-01-01

366

Herb network construction and co-module analysis for uncovering the combination rule of traditional Chinese herbal formulae  

PubMed Central

Background Traditional Chinese Medicine (TCM) is characterized by the wide use of herbal formulae, which are capable of systematically treating diseases determined by interactions among various herbs. However, the combination rule of TCM herbal formulae remains a mystery due to the lack of appropriate methods. Methods From a network perspective, we established a method called Distance-based Mutual Information Model (DMIM) to identify useful relationships among herbs in numerous herbal formulae. DMIM combines mutual information entropy and “between-herb-distance” to score herb interactions and construct herb network. To evaluate the efficacy of the DMIM-extracted herb network, we conducted in vitro assays to measure the activities of strongly connected herbs and herb pairs. Moreover, using the networked Liu-wei-di-huang (LWDH) formula as an example, we proposed a novel concept of “co-module” across herb-biomolecule-disease multilayer networks to explore the potential combination mechanism of herbal formulae. Results DMIM, when used for retrieving herb pairs, achieves a good balance among the herb’s frequency, independence, and distance in herbal formulae. A herb network constructed by DMIM from 3865 Collaterals-related herbal formulae can not only nicely recover traditionally-defined herb pairs and formulae, but also generate novel anti-angiogenic herb ingredients (e.g. Vitexicarpin with IC50=3.2 ?M, and Timosaponin A-III with IC50=3.4 ?M) as well as herb pairs with synergistic or antagonistic effects. Based on gene and phenotype information associated with both LWDH herbs and LWDH-treated diseases, we found that LWDH-treated diseases show high phenotype similarity and identified certain “co-modules” enriched in cancer pathways and neuro-endocrine-immune pathways, which may be responsible for the action of treating different diseases by the same LWDH formula. Conclusions DMIM is a powerful method to identify the combination rule of herbal formulae and lead to new discoveries. We also provide the first evidence that the co-module across multilayer networks may underlie the combination mechanism of herbal formulae and demonstrate the potential of network biology approaches in the studies of TCM. PMID:21172056

2010-01-01

367

Direct activation of EXPANSIN14 by LBD18 in the gene regulatory network of lateral root formation in Arabidopsis.  

PubMed

Root system architecture is important for plants to adapt to a changing environment. The major determinant of the root system is lateral roots originating from the primary root. The developmental process of lateral root formation can be divided into priming, initiation, primordium development and the emergence of lateral roots, and is well characterized in Arabidopsis. The hormone auxin plays a critical role in lateral root development, and several auxin response modules involving AUXIN RESPONSE FACTORS (ARFs), transcriptional regulators of auxin-regulated genes and Aux/IAA, negative regulators of ARFs, regulate lateral root formation. The LATERAL ORGAN BOUNDARIES DOMAIN/ASYMMETRIC LEAVES2-LIKE (LBD/ASL) gene family encodes a unique class of transcription factors harbouring a conserved plant-specific lateral organ boundary domain and plays a role in lateral organ development of plants including lateral root formation. In our previous study, we showed that LBD18 stimulates lateral root formation in combination with LBD16 downstream of ARF7 and ARF19 during the auxin response. We have recently demonstrated that LBD18 activates expression of EXP14, a gene encoding the cell-wall loosening factor, by directly binding to the EXP14 promoter to promote lateral root emergence. Here we present the molecular function of LBD18 and its gene regulatory network during lateral root formation. PMID:23299420

Kim, Jungmook; Lee, Han Woo

2013-02-01

368

Direct activation of EXPANSIN14 by LBD18 in the gene regulatory network of lateral root formation in Arabidopsis  

PubMed Central

Root system architecture is important for plants to adapt to a changing environment. The major determinant of the root system is lateral roots originating from the primary root. The developmental process of lateral root formation can be divided into priming, initiation, primordium development and the emergence of lateral roots, and is well characterized in Arabidopsis. The hormone auxin plays a critical role in lateral root development, and several auxin response modules involving AUXIN RESPONSE FACTORS (ARFs), transcriptional regulators of auxin-regulated genes and Aux/IAA, negative regulators of ARFs, regulate lateral root formation. The LATERAL ORGAN BOUNDARIES DOMAIN/ASYMMETRIC LEAVES2-LIKE (LBD/ASL) gene family encodes a unique class of transcription factors harbouring a conserved plant-specific lateral organ boundary domain and plays a role in lateral organ development of plants including lateral root formation. In our previous study, we showed that LBD18 stimulates lateral root formation in combination with LBD16 downstream of ARF7 and ARF19 during the auxin response. We have recently demonstrated that LBD18 activates expression of EXP14, a gene encoding the cell-wall loosening factor, by directly binding to the EXP14 promoter to promote lateral root emergence. Here we present the molecular function of LBD18 and its gene regulatory network during lateral root formation. PMID:23299420

Kim, Jungmook; Lee, Han Woo

2013-01-01

369

Spectral properties of the Google matrix of the World Wide Web and other directed networks Bertrand Georgeot, Olivier Giraud,* and Dima L. Shepelyansky  

E-print Network

Spectral properties of the Google matrix of the World Wide Web and other directed networks Bertrand of the Google matrix of various examples of directed networks such as vocabulary networks of dictionaries eigenvalue for Google damping parameter equal to unity. The vocabulary networks have relatively homogeneous

Shepelyansky, Dima

370

Stability and flexibility in preschoolers' social networks: a dynamic analysis of socially directed behavior allocation.  

PubMed

The author studied preschoolers' social networks by investigating the allocation of children's social investment within and across time in a classroom of a French nursery school during an academic year. Observations of children's social exchanges during free play revealed that social behaviors were directed toward particular group members. After an important turnover in the peer group at the beginning of the school year, the social network became more structured. Children's strong associations were mostly same sex and small sized. Even if the stability of children's connections remained low, it increased over time. High-frequency partners as well as same-sex partners were more likely to be maintained over time. These findings as well as conceptual and methodological issues are discussed from a developmental perspective. PMID:14717645

Barbu, Stephanie

2003-12-01

371

Differential Modulation of Spontaneous and Evoked Thalamocortical Network Activity by Acetylcholine Level In Vitro  

PubMed Central

Different levels of cholinergic neuromodulatory tone have been hypothesized to set the state of cortical circuits either to one dominated by local cortical recurrent activity (low ACh) or to one dependent on thalamic input (high ACh). High ACh levels depress intracortical but facilitate thalamocortical synapses, whereas low levels potentiate intracortical synapses. Furthermore, recent work has implicated the thalamus in controlling cortical network state during waking and attention, when ACh levels are highest. To test this hypothesis, we used rat thalamocortical slices maintained in medium to generate spontaneous up- and down-states and applied different ACh concentrations to slices in which thalamocortical connections were either maintained or severed. The effects on spontaneous and evoked up-states were measured using voltage-sensitive dye imaging, intracellular recordings, local field potentials, and single/multiunit activity. We found that high ACh can increase the frequency of spontaneous up-states, but reduces their duration in slices with intact thalamocortical connections. Strikingly, when thalamic connections are severed, high ACh instead greatly reduces or abolishes spontaneous up-states. Furthermore, high ACh reduces the spatial propagation, velocity, and depolarization amplitude of evoked up-states. In contrast, low ACh dramatically increases up-state frequency regardless of the presence or absence of intact thalamocortical connections and does not reduce the duration, spatial propagation, or velocity of evoked up-states. Therefore, our data support the hypothesis that strong cholinergic modulation increases the influence, and thus the signal-to-noise ratio, of afferent input over local cortical activity and that lower cholinergic tone enhances recurrent cortical activity regardless of thalamic input. PMID:24198382

Wester, Jason C.

2013-01-01

372

Social network analysis shows direct evidence for social transmission of tool use in wild chimpanzees.  

PubMed

Social network analysis methods have made it possible to test whether novel behaviors in animals spread through individual or social learning. To date, however, social network analysis of wild populations has been limited to static models that cannot precisely reflect the dynamics of learning, for instance, the impact of multiple observations across time. Here, we present a novel dynamic version of network analysis that is capable of capturing temporal aspects of acquisition--that is, how successive observations by an individual influence its acquisition of the novel behavior. We apply this model to studying the spread of two novel tool-use variants, "moss-sponging" and "leaf-sponge re-use," in the Sonso chimpanzee community of Budongo Forest, Uganda. Chimpanzees are widely considered the most "cultural" of all animal species, with 39 behaviors suspected as socially acquired, most of them in the domain of tool-use. The cultural hypothesis is supported by experimental data from captive chimpanzees and a range of observational data. However, for wild groups, there is still no direct experimental evidence for social learning, nor has there been any direct observation of social diffusion of behavioral innovations. Here, we tested both a static and a dynamic network model and found strong evidence that diffusion patterns of moss-sponging, but not leaf-sponge re-use, were significantly better explained by social than individual learning. The most conservative estimate of social transmission accounted for 85% of observed events, with an estimated 15-fold increase in learning rate for each time a novice observed an informed individual moss-sponging. We conclude that group-specific behavioral variants in wild chimpanzees can be socially learned, adding to the evidence that this prerequisite for culture originated in a common ancestor of great apes and humans, long before the advent of modern humans. PMID:25268798

Hobaiter, Catherine; Poisot, Timothée; Zuberbühler, Klaus; Hoppitt, William; Gruber, Thibaud

2014-09-01

373

Social Network Analysis Shows Direct Evidence for Social Transmission of Tool Use in Wild Chimpanzees  

PubMed Central

Social network analysis methods have made it possible to test whether novel behaviors in animals spread through individual or social learning. To date, however, social network analysis of wild populations has been limited to static models that cannot precisely reflect the dynamics of learning, for instance, the impact of multiple observations across time. Here, we present a novel dynamic version of network analysis that is capable of capturing temporal aspects of acquisition—that is, how successive observations by an individual influence its acquisition of the novel behavior. We apply this model to studying the spread of two novel tool-use variants, “moss-sponging” and “leaf-sponge re-use,” in the Sonso chimpanzee community of Budongo Forest, Uganda. Chimpanzees are widely considered the most “cultural” of all animal species, with 39 behaviors suspected as socially acquired, most of them in the domain of tool-use. The cultural hypothesis is supported by experimental data from captive chimpanzees and a range of observational data. However, for wild groups, there is still no direct experimental evidence for social learning, nor has there been any direct observation of social diffusion of behavioral innovations. Here, we tested both a static and a dynamic network model and found strong evidence that diffusion patterns of moss-sponging, but not leaf-sponge re-use, were significantly better explained by social than individual learning. The most conservative estimate of social transmission accounted for 85% of observed events, with an estimated 15-fold increase in learning rate for each time a novice observed an informed individual moss-sponging. We conclude that group-specific behavioral variants in wild chimpanzees can be socially learned, adding to the evidence that this prerequisite for culture originated in a common ancestor of great apes and humans, long before the advent of modern humans. PMID:25268798

Hobaiter, Catherine; Poisot, Timothee; Zuberbuhler, Klaus; Hoppitt, William; Gruber, Thibaud

2014-01-01

374

Direct Observation of Cross-Phase-Modulation-Induced Nonlinear Phase Noise  

NASA Astrophysics Data System (ADS)

This paper reports a quantitative investigation of the nonlinear phase noise (NLPN) in dispersion-shifted and single-mode optical fibers, which is induced by amplified spontaneous emission (ASE) noise through cross-phase modulation. The phase noise power spectral density (PN-PSD) of a probe light, which is transmitted through the fibers and is affected by the copropagating ASE, is precisely measured with the delayed self-heterodyne method. The observed PN-PSDs agree well with the theory that takes account of the group velocity dispersion of the fiber and the polarization states of the propagating lights.

Tsuchida, Hidemi

2013-06-01

375

SC-FDE for MMF short reach optical interconnects using directly modulated 850 nm VCSELs.  

PubMed

We propose the use of single-carrier frequency-domain equalization (SC-FDE) for the compensation of modal dispersion in short distance optical links using multimode fibers and 850 nm VCSELs. By post-processing of experimental data, we demonstrate, at 7.9% overhead, the error-free transmission (over a 4 Mbit sequence) of OOK-modulated 5 Gbps over 2443 meters of OM3 fiber (with a nominal 3300 MHz×km bandwidth). The proposed solution may be applied as a low cost alternative for data center and supercomputer interconnects. PMID:23187354

Teichmann, Victor S C; Barreto, Andre N; Pham, Tien-Thang; Rodes, Roberto; Monroy, Idelfonso T; Mello, Darli A A

2012-11-01

376

Long-Lasting, Kin-Directed Female Interactions in a Spatially Structured Wild Boar Social Network  

PubMed Central

Individuals can increase inclusive fitness benefits through a complex network of social interactions directed towards kin. Preferential relationships with relatives lead to the emergence of kin structures in the social system. Cohesive social groups of related individuals and female philopatry of wild boar create conditions for cooperation through kin selection and make the species a good biological model for studying kin structures. Yet, the role of kinship in shaping the social structure of wild boar populations is still poorly understood. In the present study, we investigated spatio-temporal patterns of associations and the social network structure of the wild boar Sus scrofa population in Bia?owie?a National Park, Poland, which offered a unique opportunity to understand wild boar social interactions away from anthropogenic factors. We used a combination of telemetry data and genetic information to examine the impact of kinship on network cohesion and the strength of social bonds. Relatedness and spatial proximity between individuals were positively related to the strength of social bond. Consequently, the social network was spatially and genetically structured with well-defined and cohesive social units. However, spatial proximity between individuals could not entirely explain the association patterns and network structure. Genuine, kin-targeted, and temporarily stable relationships of females extended beyond spatial proximity between individuals while males interactions were short-lived and not shaped by relatedness. The findings of this study confirm the matrilineal nature of wild boar social structure and show how social preferences of individuals translate into an emergent socio-genetic population structure. PMID:24919178

Podgorski, Tomasz; Lusseau, David; Scandura, Massimo; Sonnichsen, Leif; Jedrzejewska, Bogumila

2014-01-01

377

Adaline neural networks for online extracting the direct, inverse and homopolar voltage components from a composite voltage  

Microsoft Academic Search

This work describes an improved Adaline neural networks method for online extracting the direct, inverse and homopolar voltage components from a composite voltage. A new voltage decomposition is thus proposed and developed. These skills are transferred to four Adalines by fixing their inputs. Adaline neural networks are used with a LMS learning process to compute the weights biases and thus

Djaffar Ould Abdeslam; Damien Flieller; Patrice Wira; Jean Mercklé

2005-01-01

378

Walking Drosophila align with the e-vector of linearly polarized light through directed modulation of angular acceleration.  

PubMed

Understanding the mechanisms that link sensory stimuli to animal behavior is a central challenge in neuroscience. The quantitative description of behavioral responses to defined stimuli has led to a rich understanding of different behavioral strategies in many species. One important navigational cue perceived by many vertebrates and insects is the e-vector orientation of linearly polarized light. Drosophila manifests an innate orientation response to this cue ('polarotaxis'), aligning its body axis with the e-vector field. We have established a population-based behavioral paradigm for the genetic dissection of neural circuits guiding polarotaxis to both celestial as well as reflected polarized stimuli. However, the behavioral mechanisms by which flies align with a linearly polarized stimulus remain unknown. Here, we present a detailed quantitative description of Drosophila polarotaxis, systematically measuring behavioral parameters that are modulated by the stimulus. We show that angular acceleration is modulated during alignment, and this single parameter may be sufficient for alignment. Furthermore, using monocular deprivation, we show that each eye is necessary for modulating turns in the ipsilateral direction. This analysis lays the foundation for understanding how neural circuits guide these important visual behaviors. PMID:24810784

Velez, Mariel M; Wernet, Mathias F; Clark, Damon A; Clandinin, Thomas R

2014-06-01

379

Quantum dot based photonic devices at 1.3 ?m: Direct modulation, mode-locking, SOAs and VCSELs  

NASA Astrophysics Data System (ADS)

We present results on directly modulated lasers with high-reflectivity coating, mode-locked lasers with a gain and absorber section, and semiconductor optical amplifiers (SOA) with anti-reflection coating, all based on InGaAs/GaAs quantum dot (QD) material emitting at 1.3 ?m. Error free 8 and 10 Gb/s data modulation is presented. 80 GHz passive mode-locking of two-section QD lasers is reported. Hybrid mode-locking was achieved at 40 GHz. The minimum pulse width at 80 GHz was 1.5 ps, with a time-bandwidth product of 1.7. QD SOAs are shown to have a chip gain larger than 26 dB. Modeling of the gain characteristics of these devices predicts 40 dB amplification under ideal biasing and input power. QD-VCSEL with 17 p-modulation doped QD layers placed in 5 field intensity antinodes and fully doped GaAs/AlGaAs DBRs show a peak multimode RT cw output power of 1.8 mW and differential efficiency of 20%. The maximum -3dB bandwidth is 3 GHz.

Laemmlin, M.; Fiol, G.; Kuntz, M.; Hopfer, F.; Mutig, A.; Ledentsov, N. N.; Kovsh, A. R.; Schubert, C.; Jacob, A.; Umbach, A.; Bimberg, D.

2006-03-01

380

Transcranial direct current stimulation of the prefrontal cortex modulates working memory performance: combined behavioural and electrophysiological evidence  

PubMed Central

Background Transcranial direct current stimulation (tDCS) is a technique that can systematically modify behaviour by inducing changes in the underlying brain function. In order to better understand the neuromodulatory effect of tDCS, the present study examined the impact of tDCS on performance in a working memory (WM) task and its underlying neural activity. In two experimental sessions, participants performed a letter two-back WM task after sham and either anodal or cathodal tDCS over the left dorsolateral prefrontal cortex (DLPFC). Results Results showed that tDCS modulated WM performance by altering the underlying oscillatory brain activity in a polarity-specific way. We observed an increase in WM performance and amplified oscillatory power in the theta and alpha bands after anodal tDCS whereas cathodal tDCS interfered with WM performance and decreased oscillatory power in the theta and alpha bands under posterior electrode sides. Conclusions The present study demonstrates that tDCS can alter WM performance by modulating the underlying neural oscillations. This result can be considered an important step towards a better understanding of the mechanisms involved in tDCS-induced modulations of WM performance, which is of particular importance, given the proposal to use electrical brain stimulation for the therapeutic treatment of memory deficits in clinical settings. PMID:21211016

2011-01-01

381

UTILITY OF MECHANISTIC MODELS FOR DIRECTING ADVANCED SEPARATIONS RESEARCH & DEVELOPMENT ACTIVITIES: Electrochemically Modulated Separation Example  

SciTech Connect

The objective for this work was to demonstrate the utility of mechanistic computer models designed to simulate actinide behavior for use in efficiently and effectively directing advanced laboratory R&D activities associated with developing advanced separations methods.

Schwantes, Jon M.

2009-06-01

382

Dislocation luminescence and electrical properties of dislocation network produced by silicon direct wafer bonding  

NASA Astrophysics Data System (ADS)

Cathodoluminescent (CL) and electrical properties of the dislocation network (DN) produced by direct silicon wafer bonding were investigated. A strong impact of the electric field on the spectrum shape and the intensity of dislocation related CL of the DN built into space charge region (SCR) of Schottky-diode was found. Correlations between the characteristic features of the dependences of CL, dark current, electron beam induced current (EBIC) and capacitance on the applied bias were established. The energy diagram explaining obtained results is proposed.

Bondarenko, Anton; Vyvenko, Oleg; Bazlov, Nikolay; Kononchuk, Oleg

2009-12-01

383

(BCI), which allowed us to directly specify which co-modulation patterns we would like the subject to show. We implanted a monkey with a 96-channel electrode array in the primary motor cortex. The subject modulated his  

E-print Network

activity by the spinal cord and other subcortical structures? Or does motor cortex produce muscle activity from readily generating co-modulation patterns outside the IM. This work provides a novel network with the possibility that spinal dynamics may provide filter- ing. However, such studies have not applied standard

Shenoy, Krishna V.

384

Stimulated Raman crosstalk in bi-directional pumped distributed Raman amplifier for DPSK and OOK modulation format  

NASA Astrophysics Data System (ADS)

Novel closed form formulae are derived to study crosstalk degradation due to stimulated Raman scattering (SRS) in WDM systems employing bi-directional pumped distributed Raman amplifier (DRA). They are applied to evaluate the crosstalk performance of different modulation formats, especially differential phase-shift keying (DPSK) and ON-OFF keying (OOK), which are widely used in optical communication. Further, SRS crosstalk is evaluated for different data rates and pulse shapes prevalent in optical data transmission. Next, crosstalk is calculated for different pumping schemes as special cases of bi-directional pumped DRA. The study shows that minimum SRS crosstalk can be achieved for 40 Gb/s RZ-DPSK signal with 33.3% duty cycle in WDM system employing backward pumped DRA.

Anamika; Priye, Vishnu

2013-03-01

385

Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex Modulates Repetition Suppression to Unfamiliar Faces: An ERP Study  

PubMed Central

Repeated visual processing of an unfamiliar face suppresses neural activity in face-specific areas of the occipito-temporal cortex. This "repetition suppression" (RS) is a primitive mechanism involved in learning of unfamiliar faces, which can be detected through amplitude reduction of the N170 event-related potential (ERP). The dorsolateral prefrontal cortex (DLPFC) exerts top-down influence on early visual processing. However, its contribution to N170 RS and learning of unfamiliar faces remains unclear. Transcranial direct current stimulation (tDCS) transiently increases or decreases cortical excitability, as a function of polarity. We hypothesized that DLPFC excitability modulation by tDCS would cause polarity-dependent modulations of N170 RS during encoding of unfamiliar faces. tDCS-induced N170 RS enhancement would improve long-term recognition reaction time (RT) and/or accuracy rates, whereas N170 RS impairment would compromise recognition ability. Participants underwent three tDCS conditions in random order at ?72 hour intervals: right anodal/left cathodal, right cathodal/left anodal and sham. Immediately following tDCS conditions, an EEG was recorded during encoding of unfamiliar faces for assessment of P100 and N170 visual ERPs. The P3a component was analyzed to detect prefrontal function modulation. Recognition tasks were administered ?72 hours following encoding. Results indicate the right anodal/left cathodal condition facilitated N170 RS and induced larger P3a amplitudes, leading to faster recognition RT. Conversely, the right cathodal/left anodal condition caused N170 amplitude and RTs to increase, and a delay in P3a latency. These data demonstrate that DLPFC excitability modulation can influence early visual encoding of unfamiliar faces, highlighting the importance of DLPFC in basic learning mechanisms. PMID:24324721

Lafontaine, Marc Philippe; Theoret, Hugo; Gosselin, Frederic; Lippe, Sarah

2013-01-01

386

Design algorithms for multihop packet radio networks with multiple directional antennas stations  

NASA Astrophysics Data System (ADS)

A new protocol called the simple tone sense (STS) protocol is designed for multihop packet radio networks (PRN's) with multiple directional antennas stations. The protocol can minimize transmission interference by using a group of tones to identify the active neighbors. A variation of the STS protocol called the variable power tone sense (VPTS) protocol is also designed to further reduce interference. Algorithms for assigning tones and for determining the orientation and broadcasting angles of the directional antennas are designed. Design examples are given. Simulation result shows that the STS protocol gives better throughput-delay performance than the BTMA protocol, especially when the traffic is heavy. The VPTS protocol gives still better throughput-delay performance than the STS protocol.

Yum, Tak-Shing; Hung, Kwok-Wah

1992-11-01

387

Direct observation of frequency modulated transcription in single cells using light activation  

PubMed Central

Single-cell analysis has revealed that transcription is dynamic and stochastic, but tools are lacking that can determine the mechanism operating at a single gene. Here we utilize single-molecule observations of RNA in fixed and living cells to develop a single-cell model of steroid-receptor mediated gene activation. We determine that steroids drive mRNA synthesis by frequency modulation of transcription. This digital behavior in single cells gives rise to the well-known analog dose response across the population. To test this model, we developed a light-activation technology to turn on a single steroid-responsive gene and follow dynamic synthesis of RNA from the activated locus. DOI: http://dx.doi.org/10.7554/eLife.00750.001 PMID:24069527

Larson, Daniel R; Fritzsch, Christoph; Sun, Liang; Meng, Xiuhau; Lawrence, David S; Singer, Robert H

2013-01-01

388

Autophagy is modulated in human neuroblastoma cells through direct exposition to low frequency electromagnetic fields.  

PubMed

In neurogenerative diseases, comprising Alzheimer's (AD), functional alteration in autophagy is considered one of the pathological hallmarks and a promising therapeutic target. Epidemiological investigations on the possible causes undergoing these diseases have suggested that electromagnetic fields (EMF) exposition can contribute to their etiology. On the other hand, EMF have therapeutic implications in reactivating neuronal functionality. To partly clarify this dualism, the effect of low-frequency EMF (LF-EMF) on the modulation of autophagy was investigated in human neuroblastoma SH-SY5Y cells, which were also subsequently exposed to A? peptides, key players in AD. The results primarily point that LF-EMF induce a significant reduction of microRNA 30a (miR-30a) expression with a concomitant increase of Beclin1 transcript (BECN1) and its corresponding protein. Furthermore, LF-EMF counteract the induced miR-30a up-regulation in the same cells transfected with miR-30a mimic precursor molecules and, on the other side, rescue Beclin1 expression after BECN1 siRNA treatment. The expression of autophagy-related markers (ATG7 and LC3B-II) as well as the dynamics of autophagosome formation were also visualized after LF-EMF exposition. Finally, different protocols of repeated LF-EMF treatments were assayed to contrast the effects of A? peptides in vitro administration. Overall, this research demonstrates, for the first time, that specific LF-EMF treatments can modulate in vitro the expression of a microRNA sequence, which in turn affects autophagy via Beclin1 expression. Taking into account the pivotal role of autophagy in the clearance of protein aggregates within the cells, our results indicate a potential cytoprotective effect exerted by LF-EMF in neurodegenerative diseases such as AD. J. Cell. Physiol. 229: 1776-1786, 2014. © 2014 Wiley Periodicals, Inc. PMID:24676932

Marchesi, Nicoletta; Osera, Cecilia; Fassina, Lorenzo; Amadio, Marialaura; Angeletti, Francesca; Morini, Martina; Magenes, Giovanni; Venturini, Letizia; Biggiogera, Marco; Ricevuti, Giovanni; Govoni, Stefano; Caorsi, Salvatore; Pascale, Alessia; Comincini, Sergio

2014-11-01

389

Gel-expanded to gel-condensed transition in neurofilament networks revealed by direct force measurements  

NASA Astrophysics Data System (ADS)

Neurofilaments (NF)-the principal cytoskeletal constituent of myelinated axons in vertebrates-consist of three molecular-weight subunit proteins NF-L (low), NF-M (medium) and NF-H (high), assembled to form mature filaments with protruding unstructured C-terminus side arms. Liquid-crystal gel networks of side-arm-mediated neurofilament assemblies have a key role in the mechanical stability of neuronal processes. Disruptions of the neurofilament network, owing to neurofilament over-accumulation or incorrect side-arm interactions, are a hallmark of motor-neuron diseases including amyotrophic lateral sclerosis. Using synchrotron X-ray scattering, we report on a direct measurement of forces in reconstituted neurofilament gels under osmotic pressure (P). With increasing pressure near physiological salt and average phosphorylation conditions, NF-LMH, comprising the three subunits near in vivo composition, or NF-LH gels, undergo for P>Pc~10kPa, an abrupt non-reversible gel-expanded to gel-condensed transition. The transition indicates side-arm-mediated attractions between neurofilaments consistent with an electrostatic model of interpenetrating chains. In contrast, NF-LM gels remain in a collapsed state for PPc. These findings, which delineate the distinct roles of NF-M and NF-H in regulating neurofilament interactions, shed light on possible mechanisms for disruptions of optimal mechanical network properties.

Beck, Roy; Deek, Joanna; Jones, Jayna B.; Safinya, Cyrus R.

2010-01-01

390

Research 2.0: social networking and direct-to-consumer (DTC) genomics.  

PubMed

The convergence of increasingly efficient high throughput sequencing technology and ubiquitous Internet use by the public has fueled the proliferation of companies that provide personal genetic information (PGI) direct-to-consumers. Companies such as 23andme (Mountain View, CA) and Navigenics (Foster City, CA) are emblematic of a growing market for PGI that some argue represents a paradigm shift in how the public values this information and incorporates it into how they behave and plan for their futures. This new class of social networking business ventures that market the science of the personal genome illustrates the new trend in collaborative science. In addition to fostering a consumer empowerment movement, it promotes the trend of democratizing information--openly sharing of data with all interested parties, not just the biomedical researcher--for the purposes of pooling data (increasing statistical power) and escalating the innovation process. This target article discusses the need for new approaches to studying DTC genomics using social network analysis to identify the impact of obtaining, sharing, and using PGI. As a locus of biosociality, DTC personal genomics forges social relationships based on beliefs of common genetic susceptibility that links risk, disease, and group identity. Ethical issues related to the reframing of DTC personal genomic consumers as advocates and research subjects and the creation of new social formations around health research may be identified through social network analysis. PMID:19998112

Lee, Sandra Soo-Jin; Crawley, LaVera

2009-01-01

391

The co-evolutionary dynamics of directed network of spin market agents  

NASA Astrophysics Data System (ADS)

The spin market model [S. Bornholdt, Int. J. Mod. Phys. C 12 (2001) 667] is generalized by employing co-evolutionary principles, where strategies of the interacting and competitive traders are represented by local and global couplings between the nodes of dynamic directed stochastic network. The co-evolutionary principles are applied in the frame of Bak-Sneppen self-organized dynamics [P. Bak, K. Sneppen, Phys. Rev. Lett. 71 (1993) 4083] that includes the processes of selection and extinction actuated by the local (node) fitness. The local fitness is related to orientation of spin agent with respect to the instant magnetization. The stationary regime is formed due to the interplay of self-organization and adaptivity effects. The fat tailed distributions of log-price returns are identified numerically. The non-trivial model consequence is the evidence of the long time market memory indicated by the power-law range of the autocorrelation function of volatility with exponent smaller than one. The simulations yield network topology with broad-scale node degree distribution characterized by the range of exponents 1.3networks.

Horváth, Denis; Kuscsik, Zoltán; Gmitra, Martin

2006-09-01

392

Destination-directed, packet-switched architecture for a geostationary communications satellite network  

NASA Technical Reports Server (NTRS)

A major goal of the Digital Systems Technology Branch at the NASA Lewis Research Center is to identify and develop critical digital components and technologies that either enable new commercial missions or significantly enhance the performance, cost efficiency, and/or reliability of existing and planned space communications systems. NASA envisions a need for low-data-rate, interactive, direct-to-the-user communications services for data, voice, facsimile, and video conferencing. The network would provide enhanced very-small-aperture terminal (VSAT) communications services and be capable of handling data rates of 64 kbps through 2.048 Mbps in 64-kbps increments. Efforts have concentrated heavily on the space segment; however, the ground segment has been considered concurrently to ensure cost efficiency and realistic operational constraints. The focus of current space segment developments is a flexible, high-throughput, fault-tolerant onboard information-switching processor (ISP) for a geostationary satellite communications network. The Digital Systems Technology Branch is investigating both circuit and packet architectures for the ISP. Destination-directed, packet-switched architectures for geostationary communications satellites are addressed.

Ivancic, William D.; Shalkhauser, Mary JO; Bobinsky, Eric A.; Soni, Nitin J.; Quintana, Jorge A.; Kim, Heechul; Wager, Paul; Vanderaar, Mark

1993-01-01

393

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

E-print Network

Sarah Kajari-Schröder, Iris Kunze, Ulrich Eitner and Marc Köntges Institute for Solar Energy Research are prone to the formation of cracks in the solar cells when subjected to mechanical loads. In extreme cases more often than less critical cracks in other directions. Furthermore, we present a statistical

394

Design of bi-directional and multi-channel miniaturized telemetry module for wireless endoscopy  

Microsoft Academic Search

A bi-directional and multi-channel wireless telemetry capsule, 11 mm in diameter, is presented that can transmit video images from inside the human body and receive a control signal from an external control unit. The proposed telemetry capsule includes transmitting and receiving antennas, a demodulator, decoder, four LEDs, and CMOS image sensor, along with their driving circuits. The receiver demodulates the

H. J. Park; H. W. Nam; B. S. Song; J. L. Choi; H. C. Choi; J. C. Park; M. N. Kim; J. T. Lee; J. H. Cho

2002-01-01

395

Contextual Modulation of Reading Rate for Direct versus Indirect Speech Quotations  

ERIC Educational Resources Information Center

In human communication, direct speech (e.g., "Mary said: "I'm hungry"") is perceived to be more vivid than indirect speech (e.g., "Mary said [that] she was hungry"). However, the processing consequences of this distinction are largely unclear. In two experiments, participants were asked to either orally (Experiment 1) or silently (Experiment 2,…

Yao, Bo; Scheepers, Christoph

2011-01-01

396

A dual selection module for directed evolution of genetic YOHEI YOKOBAYASHI  

E-print Network

and specificities of molecular interactions, and the effects of temperature and host genotype, most of which genetic circuit by directing its evolution inside the host cells, by screening randomly- Natural Computing to the survival or death of the host bacteria. In this way, we can use bacterial growth under appropriate

Arnold, Frances H.

397

Neural-network-directed alignment of optical systems using the laser-beam spatial filter as an example  

NASA Technical Reports Server (NTRS)

This report describes an effort at NASA Lewis Research Center to use artificial neural networks to automate the alignment and control of optical measurement systems. Specifically, it addresses the use of commercially available neural network software and hardware to direct alignments of the common laser-beam-smoothing spatial filter. The report presents a general approach for designing alignment records and combining these into training sets to teach optical alignment functions to neural networks and discusses the use of these training sets to train several types of neural networks. Neural network configurations used include the adaptive resonance network, the back-propagation-trained network, and the counter-propagation network. This work shows that neural networks can be used to produce robust sequencers. These sequencers can learn by example to execute the step-by-step procedures of optical alignment and also can learn adaptively to correct for environmentally induced misalignment. The long-range objective is to use neural networks to automate the alignment and operation of optical measurement systems in remote, harsh, or dangerous aerospace environments. This work also shows that when neural networks are trained by a human operator, training sets should be recorded, training should be executed, and testing should be done in a manner that does not depend on intellectual judgments of the human operator.

Decker, Arthur J.; Krasowski, Michael J.; Weiland, Kenneth E.

1993-01-01

398

Fast algorithms for detecting overlapping functional modules in protein-protein interaction networks  

Microsoft Academic Search

Accumulating evidence suggests that biological systems are composed of interacting, separable, functional modules which is that groups of vertices within which connections are dense but between which they are sparse. Identifying these modules is likely to capture the biologically meaningful interactions. In recent years, many algorithms have been developed for detecting such structures. These algorithms however are computationally demanding, which

Peng-Gang Sun; Lin Gao

2009-01-01

399

The Local Structure of Globalization. The Network Dynamics of Foreign Direct Investments in the International Electricity Industry  

NASA Astrophysics Data System (ADS)

We study the evolution of the network of foreign direct investment (FDI) in the international electricity industry during the period 1994-2003. We assume that the ties in the network of investment relations between countries are created and deleted in continuous time, according to a conditional Gibbs distribution. This assumption allows us to take simultaneously into account the aggregate predictions of the well-established gravity model of international trade as well as local dependencies between network ties connecting the countries in our sample. According to the modified version of the gravity model that we specify, the probability of observing an investment tie between two countries depends on the mass of the economies involved, their physical distance, and the tendency of the network to self-organize into local configurations of network ties. While the limiting distribution of the data generating process is an exponential random graph model, we do not assume the system to be in equilibrium. We find evidence of the effects of the standard gravity model of international trade on evolution of the global FDI network. However, we also provide evidence of significant dyadic and extra-dyadic dependencies between investment ties that are typically ignored in available research. We show that local dependencies between national electricity industries are sufficient for explaining global properties of the network of foreign direct investments. We also show, however, that network dependencies vary significantly over time giving rise to a time-heterogeneous localized process of network evolution.

Koskinen, Johan; Lomi, Alessandro

2013-05-01

400

Demand and Modality of Directed Attention Modulate "Pre-attentive" Sensory Processes in Schizophrenia Patients and Nonpsychiatric Controls  

PubMed Central

Background Mismatch negativity (MNN) and P3a are event related potential (ERP) measures of early sensory information processing. These components are usually conceptualized as being “pre-attentive” and therefore immune to changes with variations in attentional functioning. This study aimed to determine whether manipulations of attention influence the amplitudes and latencies of MMN and P3a and, if so, the extent to which these early sensory processes govern concurrent behavioral vigilance performance in schizophrenia patients and normal subjects. Methods Schizophrenia patients (SZ; n=20) and Nonpsychiatric Control Subjects (NCS; n=20) underwent auditory ERP testing to assess MMN and P3a across 4 EEG recording sessions in which attentional demand (low vs. high) and sensory modality of directed attention (visual vs. auditory) were experimentally varied. Results Across conditions, SZ patients exhibited deficits in MMN and P3a amplitudes. Significant amplitude and latency modulation were observed in both SZ and NCS but there were no group-by- condition interactions. The amount of MMN amplitude attenuation from low- to-high-demand tasks was significantly associated with increased vigilance performance in both SZ and NCS groups (r=-0.67 and r=-0.60). Conclusions Attentional demand and modality of directed attention significantly influence the amplitude and latencies of “pre-attentive” ERP components in both SZ and NCS. Deficits in MMN and P3a were not “normalized” when attention was directed to the auditory stimuli in schizophrenia patients. The adaptive modulation of early sensory information processing appears to govern concurrent attentional task performance. MMN and P3a may serve as a gateway to some higher order cognitive operations necessary for psychosocial functioning. PMID:23490760

Rissling, Anthony J.; Park, Sung-Hyouk; Young, Jared W.; Rissling, Michelle B.; Sugar, Catherine A.; Sprock, Joyce; Mathias, Daniel J.; Pela, Marlena; Sharp, Richard F.; Braff, David L.; Light, Gregory A.

2013-01-01

401

Temperature regulates limb length in homeotherms by directly modulating cartilage growth  

PubMed Central

Allen's Rule documents a century-old biological observation that strong positive correlations exist among latitude, ambient temperature, and limb length in mammals. Although genetic selection for thermoregulatory adaptation is frequently presumed to be the primary basis of this phenomenon, important but frequently overlooked research has shown that appendage outgrowth is also markedly influenced by environmental temperature. Alteration of limb blood flow via vasoconstriction/vasodilation is the current default hypothesis for this growth plasticity, but here we show that tissue perfusion does not fully account for differences in extremity elongation in mice. We show that peripheral tissue temperature closely reflects housing temperature in vivo, and we demonstrate that chondrocyte proliferation and extracellular matrix volume strongly correlate with tissue temperature in metatarsals cultured without vasculature in vitro. Taken together, these data suggest that vasomotor changes likely modulate extremity growth indirectly, via their effects on appendage temperature, rather than vascular nutrient delivery. When combined with classic evolutionary theory, especially genetic assimilation, these results provide a potentially comprehensive explanation of Allen's Rule, and may substantially impact our understanding of phenotypic variation in living and extinct mammals, including humans. PMID:19047632

Serrat, Maria A.; King, Donna; Lovejoy, C. Owen

2008-01-01

402

Eye Remember You Two: Gaze Direction Modulates Face Recognition in a Developmental Study  

ERIC Educational Resources Information Center

The effects of gaze direction on memory for faces were studied in children from three different age groups (6-7, 8-9, and 10-11 years old) using a computerized version of a task devised by Hood, Macrae, Cole-Davies and Dias (2003). Participants were presented with a sequence of faces in an encoding phase, and were then required to judge which…

Smith, Alastair D.; Hood, Bruce M.; Hector, Karen

2006-01-01

403

Directional invariance during loading-related modulations of muscle activity: evidence for motor equivalence  

Microsoft Academic Search

.   In the present study, we investigated the influence of external force manipulations on movements in different directions,\\u000a while keeping the amplitude invariant. Subjects (n=10) performed a series of cyclical anteroposterior, mediolateral, and oblique line-drawing movements (star drawing task)\\u000a with their dominant limb in the horizontal plane. To dissociate kinematics from the underlying patterns of muscle activation,\\u000a spring loading was

Oron Levin; Nicole Wenderoth; Maarten Steyvers; Stephan P. Swinnen

2003-01-01

404

Opposite Modulation of Brain Functional Networks Implicated at Low vs. High Demand of Attention and Working Memory  

PubMed Central

Background Functional magnetic resonance imaging (fMRI) studies indicate that the brain organizes its activity into multiple functional networks (FNs) during either resting condition or task-performance. However, the functions of these FNs are not fully understood yet. Methodology/Principal Findings To investigate the operation of these FNs, spatial independent component analysis (sICA) was used to extract FNs from fMRI data acquired from healthy participants performing a visual task with two levels of attention and working memory load. The task-related modulations of extracted FNs were assessed. A group of FNs showed increased activity at low-load conditions and reduced activity at high-load conditions. These FNs together involve the left lateral frontoparietal cortex, insula, and ventromedial prefrontal cortex. A second group of FNs showed increased activity at high-load conditions and reduced activity at low-load conditions. These FNs together involve the intraparietal sulcus, frontal eye field, lateral frontoparietal cortex, insula, and dorsal anterior cingulate, bilaterally. Though the two groups of FNs showed opposite task-related modulations, they overlapped extensively at both the lateral and medial frontoparietal cortex and insula. Such an overlap of FNs would not likely be revealed using standard general-linear-model-based analyses. Conclusions By assessing task-related modulations, this study differentiated the functional roles of overlapping FNs. Several FNs including the left frontoparietal network are implicated in task conditions of low attentional load, while another set of FNs including the dorsal attentional network is implicated in task conditions involving high attentional demands. PMID:24498021

Xu, Jiansong; Calhoun, Vince D.; Pearlson, Godfrey D.; Potenza, Marc N.

2014-01-01

405

Respiration drives network activity and modulates synaptic and circuit processing of lateral inhibition in the olfactory bulb  

PubMed Central

Respiration produces rhythmic activity in the entire olfactory system, driving neurons in the olfactory epithelium, bulb (OB) and cortex. The rhythmic nature of this activity is believed to be a critical component of sensory processing. OB projection neurons, mitral and tufted cells, exhibit both spiking and subthreshold membrane potential oscillations rhythmically coupled to respiration. Yet, the network and synaptic mechanisms that produce respiration-coupled activity, and the effects of respiration on lateral inhibition, a major component of sensory processing in OB circuits, are not known. Is respiration-coupled activity in mitral and tufted cells produced by sensory synaptic inputs from nasal airflow alone, cortico-bulbar feedback, or intrinsic membrane properties of the projection neurons? Does respiration facilitate or modulate the activity of inhibitory lateral circuits in the OB? Here, in vivo intracellular recordings from identified mitral and tufted cells in anesthetized rats demonstrate that nasal airflow provides excitatory synaptic inputs to both cell types and drives respiration-coupled spiking. Lateral inhibition, inhibitory post-synaptic potentials evoked by intrabulbar microstimulation, was modulated by respiration. In individual mitral and tufted cells inhibition was larger at specific respiratory phases. However, lateral inhibition was not uniformly larger during a particular respiratory phase in either cell type. Removing nasal airflow abolished respiration-coupled spiking in both cell types and nearly eliminated spiking in mitral, but not tufted cells. In the absence of nasal airflow, lateral inhibition was weaker in mitral cells and less modulated in tufted cells. Thus, respiration drives distinct network activities that functionally modulate sensory processing in the OB. PMID:22219272

Phillips, Matthew E.; Sachdev, Robert N. S.; Willhite, David C.; Shepherd, Gordon M.

2012-01-01

406

Integration of Metabolic and Gene Regulatory Networks Modulates The C. elegans Dietary Response  

PubMed Central

SUMMARY Expression profiles are tailored according to dietary input. However, the networks that control dietary responses remain largely uncharacterized. Here, we combine forward and reverse genetic screens to delineate a network of 184 genes that affect the C. elegans dietary response to Comamonas DA1877 bacteria. We find that perturbation of a mitochondrial network comprised of enzymes involved in amino acid metabolism and the TCA cycle affects the dietary response. In humans, mutations in the corresponding genes cause inborn diseases of amino acid metabolism, most of which are treated by dietary intervention. We identify several transcription factors (TFs) that mediate the changes in gene expression upon metabolic network perturbations. Altogether, our findings unveil a transcriptional response system that is poised to sense dietary cues and metabolic imbalances, illustrating extensive communication between metabolic networks in the mitochondria and gene regulatory networks in the nucleus. PMID:23540702

Arda, H. Efsun; Zhu, Lihua Julie; Walhout, Albertha J.M.

2013-01-01

407

Neural network models for spatial data mining, map production, and cortical direction selectivity  

NASA Astrophysics Data System (ADS)

A family of ARTMAP neural networks for incremental supervised learning has been developed over the last decade. The Sensor Exploitation Group of MIT Lincoln Laboratory (LL) has incorporated an early version of this network as the recognition engine of a hierarchical system for fusion and data mining of multiple registered geospatial images. The LL system has been successfully fielded, but it is limited to target vs. non-target identifications and does not produce whole maps. This dissertation expands the capabilities of the LL system so that it learns to identify arbitrarily many target classes at once and can thus produce a whole map. This new spatial data mining system is designed particularly to cope with the highly skewed class distributions of typical mapping problems. Specification of a consistent procedure and a benchmark testbed has permitted the evaluation of candidate recognition networks as well as pre- and post-processing and feature extraction options. The resulting default ARTMAP network and mapping methodology set a standard for a variety of related mapping problems and application domains. The second part of the dissertation investigates the development of cortical direction selectivity. The possible role of visual experience and oculomotor behavior in the maturation of cells in the primary visual cortex is studied. The responses of neurons in the thalamus and cortex of the cat are modeled when natural scenes are scanned by several types of eye movements. Inspired by the Hebbian-like synaptic plasticity, which is based upon correlations between cell activations, the second-order statistical structure of thalamo-cortical activity is examined. In the simulations, patterns of neural activity that lead to a correct refinement of cell responses are observed during visual fixation, when small ocular movements occur, but are not observed in the presence of large saccades. Simulations also replicate experiments in which kittens are reared under stroboscopic illumination. The abnormal fixational eye movements of these cats may account for the puzzling finding of a specific loss of cortical direction selectivity but preservation of orientation selectivity. This work indicates that the oculomotor behavior of visual fixation may play an important role in the refinement of cell response selectivity.

Parsons, Olga

408

RanBP9 Modulates AICD Localization and Transcriptional Activity via Direct Interaction with Tip60.  

PubMed

Proteolytic processing of the amyloid-? protein precursor (A?PP) occurs via alternative pathways, culminating with the production of the A?PP intracellular domain (AICD). AICD can translocate to the nucleus and regulate transcription, but its activity is modulated by interactions with other proteins. In the nucleus, AICD, FE65, and Tip60 associate into AFT complexes, which are targeted to nuclear spots which correspond to transcription factories. Here we report that RanBP9 interacts with the cytoplasmic domain of A?PP, through the NPXY internalization motif. Moreover, RanBP9 interaction with Tip60 is also described. The RanBP9-Tip60 interaction dramatically relocated RanBP9 from a widespread cellular distribution to nuclear speckles. A?PP processing is a central aspect in determining the protein's function and that of its resulting proteolytic fragments, among them AICD. The latter results from the amyloidogenic pathway and is the peptidic species predominantly involved in nuclear signaling. Of note RanBP9 transfection was previously demonstrated to increase amyloid-? generation. Here we show that RanBP9 relocates AICD to the Tip60-enriched nuclear speckles, and prevented the formation of nuclear spots formation, having therefore a negative effect on AICD mediated nuclear signaling and consequently AFT complex formation. Furthermore, by transfecting cells with increasing amounts of RanBP9, the expression of AICD-regulated genes, including A?PP itself, was reduced. Given the data presented, one can deduce that RanBP9 has an inhibitory regulatory effect on AICD-mediated transcription and the effect is mediated by relocating AICD away from transcription factories. PMID:25024339

Domingues, Sara C; Konietzko, Uwe; Henriques, Ana Gabriela; Rebelo, Sandra; Fardilha, Margarida; Nishitani, Hideo; Nitsch, Roger M; da Cruz E Silva, Edgar F; da Cruz E Silva, Odete A B

2014-01-01

409

Connexin43 Modulates Cell Polarity and Directional Cell Migration by Regulating Microtubule Dynamics  

PubMed Central

Knockout mice deficient in the gap junction gene connexin43 exhibit developmental anomalies associated with abnormal neural crest, primordial germ cell, and proepicardial cell migration. These migration defects are due to a loss of directional cell movement, and are associated with abnormal actin stress fiber organization and a loss of polarized cell morphology. To elucidate the mechanism by which Cx43 regulates cell polarity, we used a wound closure assays with mouse embryonic fibroblasts (MEFs) to examine polarized cell morphology and directional cell movement. Studies using embryonic fibroblasts from Cx43 knockout (Cx43KO) mice showed Cx43 deficiency caused cell polarity defects as characterized by a failure of the Golgi apparatus and the microtubule organizing center to reorient with the direction of wound closure. Actin stress fibers at the wound edge also failed to appropriately align, and stabilized microtubule (Glu-tubulin) levels were markedly reduced. Forced expression of Cx43 with deletion of its tubulin-binding domain (Cx43dT) in both wildtype MEFs and neural crest cell explants recapitulated the cell migration defects seen in Cx43KO cells. However, forced expression of Cx43 with point mutation causing gap junction channel closure had no effect on cell motility. TIRF imaging revealed increased microtubule instability in Cx43KO cells, and microtubule targeting of membrane localized Cx43 was reduced with expression of Cx43dT construct in wildtype cells. Together, these findings suggest the essential role of Cx43 gap junctions in development is mediated by regulation of the tubulin cytoskeleton and cell polarity by Cx43 via a nonchannel function. PMID:22022608

Francis, Richard; Xu, Xin; Park, Hyunsoo; Wei, Chin-Jen; Chang, Stephen; Chatterjee, Bishwanath; Lo, Cecilia

2011-01-01

410