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1

Directed network modules  

Microsoft Academic Search

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

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

2007-01-01

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

High performance directly modulated 10Gb\\/s DFB laser transmitters for low-cost, short distance optical communication network  

Microsoft Academic Search

The increasing demand on the capacity of the communication system is pushing the industry into more advanced development stage, especially true for SONET\\/SDH TDM 10Gb\\/s systems. In addition to the long haul network, there is a big interest in short distance, low cost system suitable for local ring architecture around Metropolitan area. In this talk, we investigate directly modulated 10Gb\\/s

Osamu Mizuhara; T. V. Nguyen; Roeland J. Nuyts; Liang D. Tzeng

1997-01-01

4

High performance directly modulated 10Gb/s DFB laser transmitters for low-cost, short distance optical communication network  

NASA Astrophysics Data System (ADS)

The increasing demand on the capacity of the communication system is pushing the industry into more advanced development stage, especially true for SONET/SDH TDM 10Gb/s systems. In addition to the long haul network, there is a big interest in short distance, low cost system suitable for local ring architecture around Metropolitan area. In this talk, we investigate directly modulated 10Gb/s DFB laser based transmitters. Both 1.3 micrometer and 1.55 micrometer DFB lasers are evaluated, including uncooled lasers. Since most of the installed fiber in the U.S. is conventional, non-dispersion shifted fiber, we also focus on chirp induced dispersion penalty using the 1.55 micrometer laser. Their performance is compared with some externally modulated transmitters, and experiments are conducted for transmitting over non-dispersion shifted fiber.

Mizuhara, Osamu; Nguyen, T. V.; Nuyts, Roeland J.; Tzeng, Liang D.

1997-04-01

5

Modulation of large-scale brain networks by transcranial direct current stimulation evidenced by resting-state functional MRI  

PubMed Central

Background Brain areas interact mutually to perform particular complex brain functions such as memory or language. Furthermore, under resting-state conditions several spatial patterns have been identified that resemble functional systems involved in cognitive functions. Among these, the default-mode network (DMN), which is consistently deactivated during task periods and is related to a variety of cognitive functions, has attracted most attention. In addition, in resting-state conditions some brain areas engaged in focused attention (such as the anticorrelated network, AN) show a strong negative correlation with DMN; as task demand increases, AN activity rises, and DMN activity falls. Objective We combined transcranial direct current stimulation (tDCS) with functional magnetic resonance imaging (fMRI) to investigate these brain network dynamics. Methods Ten healthy young volunteers underwent four blocks of resting-state fMRI (10-minutes), each of them immediately after 20 minutes of sham or active tDCS (2 mA), on two different days. On the first day the anodal electrode was placed over the left dorsolateral prefrontal cortex (DLPFC) (part of the AN) with the cathode over the contralateral supraorbital area, and on the second day, the electrode arrangement was reversed (anode right-DLPFC, cathode left-supraorbital). Results After active stimulation, functional network connectivity revealed increased synchrony within the AN components and reduced synchrony in the DMN components. Conclusions Our study reveals a reconfiguration of intrinsic brain activity networks after active tDCS. These effects may help to explain earlier reports of improvements in cognitive functions after anodal-tDCS, where increasing cortical excitability may have facilitated reconfiguration of functional brain networks to address upcoming cognitive demands. PMID:21962981

Peña-Gómez, Cleofé; Sala-Lonch, Roser; Junqué, Carme; Clemente, Immaculada C.; Vidal, Dídac; Bargalló, Núria; Falcón, Carles; Valls-Solé, Josep; Pascual-Leone, Álvaro; Bartrés-Faz, David

2013-01-01

6

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

7

A novel network module for medical devices  

Microsoft Academic Search

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

Ping-Yu Chen

2008-01-01

8

Explosive Percolation in Directed Networks  

E-print Network

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

Anlage, Steven

9

Epidemic threshold in directed networks.  

PubMed

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

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

2013-12-01

10

OM300 Direction Drilling Module  

SciTech Connect

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

MacGugan, Doug

2013-08-22

11

A direct density modulation cathode in magnetron  

SciTech Connect

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

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

2013-09-15

12

Potential Theory for Directed Networks  

PubMed Central

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

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

2013-01-01

13

Sampling properties of directed networks.  

PubMed

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

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

2012-10-01

14

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

15

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

16

Network models of frequency modulated sweep detection.  

PubMed

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

Skorheim, Steven; Razak, Khaleel; Bazhenov, Maxim

2014-01-01

17

Network Models of Frequency Modulated Sweep Detection  

PubMed Central

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

Skorheim, Steven; Razak, Khaleel; Bazhenov, Maxim

2014-01-01

18

Can developer-module networks predict failures?  

Microsoft Academic Search

Software teams should follow a well defined goal and keep their work focused. Work fragmentation is bad for efficiency and quality. In this paper we empirically investigate the relationship between the fragmentation of developer contributions and the number of post-release failures. Our approach is to represent developer contributions with a developer-module network that we call contribution network. We use network

Martin Pinzger; Nachiappan Nagappan; Brendan Murphy

2008-01-01

19

High performance directly modulated lasers: device physics  

NASA Astrophysics Data System (ADS)

Directly modulated lasers (DMLs) have two high performance applications: 1310 nm 10 Gb/s uncooled and 1550 2.5 Gs/s extended reach. Two key elements are gain coupled gratings and buried heterostructures. Gain coupled gratings simultaneously increase the DML's intrinsic relaxation oscillation frequency and damping, while the buried heterostructure reduces thermal chirp and parasitic capacitance. Large relaxation oscillation frequencies and reduced parasitic capacitance allow 85°C operation; large damping and reduced thermal chirp enable extended reach.

White, J. Kenton; Knight, Gordon; Das, Suhit; Finlay, Richard J.; Jones, Trevor; Blaauw, Cornelis; Fekecs, Andrew; Walters, Harry; Grevatt, Treena; Brooks, Nicholas; Firth, Paul; Nelson, Lee; Graham, Anthony; Woods, Ian; Hinzer, Karin; Goodchild, Darren; SpringThorpe, Anthony J.; Glew, Richard; Letal, Gregory J.

2003-07-01

20

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

21

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

22

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

23

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

24

Motor cortex feedback influences sensory processing by modulating network state  

PubMed Central

Summary Long range cortico-cortical communication may have important roles in context-dependent sensory processing, yet we know very little about how these pathways influence their target regions. We studied the influence of primary motor cortex activity on primary somatosensory cortex in the mouse whisker system. We show that primary motor and somatosensory cortices undergo coherent, context-dependent changes in network state. Moreover, we show that motor cortex activity can drive changes in somatosensory cortex network state. A series of experiments demonstrate the involvement of the direct cortico-cortical feedback pathway, providing temporally precise and spatially targeted modulation of network dynamics. Cortically-mediated changes in network state significantly impact sensory coding, with activated states increasing the reliability of responses to complex stimuli. By influencing network state, cortico-cortical communication from motor cortex may ensure that during active exploration the relevant sensory region is primed for enhanced sensory discrimination. PMID:23850595

Zagha, Edward; Casale, Amanda E.; Sachdev, Robert N. S.; McGinley, Matthew J.; McCormick, David A.

2013-01-01

25

CFinder: locating cliques and overlapping modules in biological networks  

Microsoft Academic Search

Summary:Mostcellulartasksareperformednotbyindividualproteins, but by groups of functionally associated proteins, often referred to as modules. In a protein assocation network modules appear as groups of densely interconnected nodes, also called communities or clusters. These modules often overlap with each other and form a network of their own, in which nodes (links) represent the modules (overlaps). We introduce CFinder, a fast program locating

Balazs Adamcsek; Gergely Palla; Illés J. Farkas; Imre Derenyi; Tamas Vicsek

2006-01-01

26

Directing Learning Activities for Instruction. Instructor Training Module #6.  

ERIC Educational Resources Information Center

Part of a series of instructor training modules on related subjects instruction for apprentices, this booklet deals with directing learning activities for instruction. The first chapter consists of an outline of the scope and content of the instructor training modules as well as a self-assessment pretest. Covered in the module are establishing a…

Rice, Eric; Spetz, Sally H.

27

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

28

Packaging issues related to network access modules  

NASA Astrophysics Data System (ADS)

WDM networks offer potentially increased bandwidth and functionality when compared to single wavelength ones, with applications ranging from straightforward capacity enhancement through to switched virtual dark fiber carrying disparate traffic to the customers' premises. However, to be implemented in the ground, these optical networks have to offer cost effective solutions to the users. This means that WDM equipment must be built small, rugged with low power consumption and high functional density. The NAM (network access module) developed by the ONTC, makes extensive use of array electronics, optoelectronics and optoelectronic integrated circuits (OEICs) and illustrates such system integration. But high level integration and high functional density bring new challenges in packaging together with the difficulty of managing crosstalk. In this paper we describe the network access module, detail some of the key packaging technologies and discuss alternative integration approaches which are explored as part of another collaboration project called Rozinante. To conclude, some applications using the NAM are proposed which show the key role of this network element in building reconfigurable optical networks.

Dreze, Cecile

1997-01-01

29

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

30

Transmission line directional protection using neural networks and filtering algorithms  

NASA Astrophysics Data System (ADS)

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

Sanaye-Pasand, Majid

2000-02-01

31

Cholinergic modulation of hippocampal network function  

PubMed Central

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

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

2013-01-01

32

On Functional Module Detection in Metabolic Networks  

PubMed Central

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

Koch, Ina; Ackermann, Jörg

2013-01-01

33

Direct Gaze Modulates Face Recognition in Young Infants  

ERIC Educational Resources Information Center

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

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

2007-01-01

34

Giant components in directed multiplex networks  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

35

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

36

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

37

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

38

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

39

Future directions in networked sensing  

Microsoft Academic Search

Started one decade ago as a wild academic idea, wireless sensor and actuator networks turned into a vibrant research area with a large R&D community dealing with a commercially highly relevant technology. The new paradigm in networked sensing has received significant attention because of the unprecedented benefits it promises in many areas.\\u000aSeamless integration of computing with the physical world

P. J. M. Havinga; Dijk van H. W; J. W. Maas; Schootbrugge van de G. A

2011-01-01

40

Nonconsensus opinion model on directed networks.  

PubMed

Dynamic social opinion models have been widely studied on undirected networks, and most of them are based on spin interaction models that produce a consensus. In reality, however, many networks such as Twitter and the World Wide Web are directed and are composed of both unidirectional and bidirectional links. Moreover, from choosing a coffee brand to deciding who to vote for in an election, two or more competing opinions often coexist. In response to this ubiquity of directed networks and the coexistence of two or more opinions in decision-making situations, we study a nonconsensus opinion model introduced by Shao et al. [Phys. Rev. Lett. 103, 018701 (2009)PRLTAO0031-900710.1103/PhysRevLett.103.018701] on directed networks. We define directionality ? as the percentage of unidirectional links in a network, and we use the linear correlation coefficient ? between the in-degree and out-degree of a node to quantify the relation between the in-degree and out-degree. We introduce two degree-preserving rewiring approaches which allow us to construct directed networks that can have a broad range of possible combinations of directionality ? and linear correlation coefficient ? and to study how ? and ? impact opinion competitions. We find that, as the directionality ? or the in-degree and out-degree correlation ? increases, the majority opinion becomes more dominant and the minority opinion's ability to survive is lowered. PMID:25493838

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

2014-11-01

41

Direct digital RF synthesis and modulation for MSAT mobile applications  

NASA Technical Reports Server (NTRS)

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

Crozier, Stewart; Datta, Ravi; Sydor, John

1993-01-01

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

Directly modulated lasers for high speed optical transmission  

NASA Astrophysics Data System (ADS)

Directly modulated lasers (DML) have been widely used in data rate at 2.5 Gb/s and below. The advantages of its simplicity and cost effectiveness have attracted considerable amount of effort in developing DMLs for higher data rate optical transmission systems, especially for short reach applications. The major issue is semiconductor laser's intrinsic modulation bandwidth and the amplitude modulation induced frequency chirp at high speed of 10 Gb/s and beyond. In this paper, we first briefly review the advancement of directly modulated lasers at 10 Gb/s and above. We then present our work on the investigation of using 10 Gb/s directly modulated laser in multiple amplified spans of a typical metro system. The experimental results show that 10 Gb/s DML may have potential to be a cost-effective option for a typical 100GHz spacing DWDM, 6x80km metro link over standard single-mode fiber. The DML performance will also be compared to conventional Mach-Zehnder modulator-based transmitter.

Du, Mei; Grüner-Nielsen, Lars

2007-11-01

44

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

Holubcová, Zuzana; Howard, Gillian; Schuh, Melina

2013-01-01

45

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

46

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

47

Directed diffusion for wireless sensor networking  

Microsoft Academic Search

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

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

2003-01-01

48

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

49

Analysis of linewidth and extinction ratio in directly modulated lasers for performance optimization in 10 Gbit/s CWDM systems  

NASA Astrophysics Data System (ADS)

Direct Modulation Lasers (DMLs) have attracted increased attention during the past few years because of their intrinsic simplicity and cost-effectiveness, especially when applied to WDM metro and access networks. However, the output power waveform from a directly modulated laser is not an exact replica of the modulation current and its instantaneous optical frequency varies with time depending on the changes in optical power and the extinction ratio (ER) (an effect also known as frequency chirp). In this work, using an Optical Communication System Design Software, we have studied a directly modulated WDM 10 Gb/s system which transmission performance depends strongly on DML characteristics; simulation results have provided supplementary details about the effects of DML type (adiabatic or transient chirp dominated) as well as the effects of the optical output power. These details can provide useful design guidelines for constructing a WDM metro network.

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

2010-08-01

50

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 scattering.

Vivian Britto; Joel Meyers

2014-09-09

51

Module Clustering to Minimize Delay in Digital Networks  

Microsoft Academic Search

An important aspect of the packaging of digital networks is the allocation of logic gates to modules such that a predetermined objective function is minimized. In order to develop techniques for this partitioning of a logic network we have considered the following problem: Given an acyclic combinational network composed of various primitive blocks such as NOR gates, assume that a

E. L. Lawler; K. N. Levitt; J. Turner

1969-01-01

52

Data reliability in complex directed networks  

NASA Astrophysics Data System (ADS)

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

Sanz, Joaquín; Cozzo, Emanuele; Moreno, Yamir

2013-12-01

53

A Novel Modulation Classification Approach Using Gabor Filter Network  

PubMed Central

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

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

2014-01-01

54

Characteristics of a code division multiplex configuration with direct modulation  

Microsoft Academic Search

Nature and optimal usage of signal multiplexing by direct modulation code division is described. The advantage of resulting spreading of the spectra of individual narrow band input signals over the whole frequency bandwidth of the transmission channel is pointed out. The coding and decoding signal processing is explained and signal distortion and crosstalk are discussed. It is shown that distortion

H. Huebner

1980-01-01

55

Identification of Biochemical Network Modules Based on Shortest Retroactive Distances  

PubMed Central

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

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

2011-01-01

56

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

57

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

58

Serotonin modulation of cortical neurons and networks  

PubMed Central

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

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

2013-01-01

59

Gaussian Networks for Direct Adaptive Control  

Microsoft Academic Search

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

Robert M. Sanner; Jean-Jacques E. Slotine

1991-01-01

60

NRC TLD direct radiation monitoring network  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

R. Struckmeyer; N. McNamara

1991-01-01

61

NRC TLD Direct Radiation Monitoring Network  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

R. Struckmeyer; N. McNamara

1992-01-01

62

High-performance directly modulated lasers: device physics  

NASA Astrophysics Data System (ADS)

Directly modulated lasers (DMLs) have two high performance applications: 1310 nm 10 Gb/s uncooled and 1550 2.5 Gb/s extended reach. Two key elements are gain coupled gratings and buried heterostructures. Gain coupled gratings simultaneously increase the DML's intrinsic relaxation oscillation frequency and damping, while the buried heterostructure reduces thermal chirp and parasitic capacitance. Large relaxation oscillation frequencies and reduced parasitic capacitance allow 85 °C operation; large damping and reduced thermal chirp enable extended reach.

White, J. Kenton

2004-12-01

63

Functional module identification in protein interaction networks by interaction patterns  

PubMed Central

Motivation: Identifying functional modules in protein–protein interaction (PPI) networks may shed light on cellular functional organization and thereafter underlying cellular mechanisms. Many existing module identification algorithms aim to detect densely connected groups of proteins as potential modules. However, based on this simple topological criterion of ‘higher than expected connectivity’, those algorithms may miss biologically meaningful modules of functional significance, in which proteins have similar interaction patterns to other proteins in networks but may not be densely connected to each other. A few blockmodel module identification algorithms have been proposed to address the problem but the lack of global optimum guarantee and the prohibitive computational complexity have been the bottleneck of their applications in real-world large-scale PPI networks. Results: In this article, we propose a novel optimization formulation LCP2 (low two-hop conductance sets) using the concept of Markov random walk on graphs, which enables simultaneous identification of both dense and sparse modules based on protein interaction patterns in given networks through searching for LCP2 by random walk. A spectral approximate algorithm SLCP2 is derived to identify non-overlapping functional modules. Based on a bottom-up greedy strategy, we further extend LCP2 to a new algorithm (greedy algorithm for LCP2) GLCP2 to identify overlapping functional modules. We compare SLCP2 and GLCP2 with a range of state-of-the-art algorithms on synthetic networks and real-world PPI networks. The performance evaluation based on several criteria with respect to protein complex prediction, high level Gene Ontology term prediction and especially sparse module detection, has demonstrated that our algorithms based on searching for LCP2 outperform all other compared algorithms. Availability and implementation: All data and code are available at http://www.cse.usf.edu/?xqian/fmi/slcp2hop/. Contact: yijie@mail.usf.edu or xqian@ece.tamu.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:24085567

Wang, Yijie; Qian, Xiaoning

2014-01-01

64

Identification and Evaluation of Functional Modules in Gene Coexpression Networks  

Microsoft Academic Search

Identifying gene functional modules is an im- portant step towards elucidating gene func- tions at a global scale. In this paper, we introduce a simple method to construct gene co-expression networks from microarray data, and then propose an efficient spectral clustering algorithm to identify natural com- munities, which are relatively densely con- nected sub-graphs, in the network. To as- sess

Jianhua Ruan; Weixiong Zhang

2006-01-01

65

NetWare Loadable Modules for CD-ROM Networking.  

ERIC Educational Resources Information Center

Provides an overview of CD-ROM technology and local area networking focusing on NetWare Loadable Modules (NLMs) which provide network access to CD-ROMs, using Novell's NetWare operating system. The characteristics and benefits of various products and concerns in choosing one are discussed, and comparative specifications and vendors are listed.…

Starr, Karen J.

1993-01-01

66

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

67

Direct QAM modulation of microwave subcarrier using electro-optically tunable microchip lasers  

E-print Network

Direct QAM modulation of microwave subcarrier using electro-optically tunable microchip lasers modulation of fiber radio signals is presented using direct vector modulation of electro- optically tunable a millimeter wave fiber radio link ­ an RF modulated optical carrier over an optical fiber. The communication

Herczfeld, Peter

68

Small-signal analysis of OOFDM signal transmission with directly modulated laser and direct detection.  

PubMed

This work presents a small-signal analysis for investigating the transmission performance of optical orthogonal frequency division multiplexing signals with a directly modulated DFB laser (DML). The analysis shows the positive chirp of DMLs can intensify power fading after transmission with positive dispersion and provide power gain instead with negative dispersion. The power of subcarrier-to-subcarrier intermixing interference after square-law direct detection, however, is independent on the sign of dispersion. PMID:21263483

Wei, Chia-Chien

2011-01-15

69

Smelling directions: Olfaction modulates ambiguous visual motion perception  

PubMed Central

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

Kuang, Shenbing; Zhang, Tao

2014-01-01

70

Enabling Technologies for Direct Detection Optical Phase Modulation Formats  

NASA Astrophysics Data System (ADS)

Phase modulation formats are believed to be one of the key enabling techniques for next generation high speed long haul fiber-optic communication systems due to the following main advantages: (1) with a balanced detection, a better receiver sensitivity over conventional intensity modulation formats, e.g., a ˜3-dB sensitivity improvement using differential phase shift keying (DPSK) and a ˜1.3-dB sensitivity improvement using differential quadrature phase shift keying (DQPSK); (2) excellent robustness against fiber nonlinearities; (3) high spectrum efficiency when using multilevel phase modulation formats, such as DQPSK. As the information is encoded in the phase of the optical field, the phase modulation formats are sensitive to the phase-related impairments and the deterioration induced in the phase-intensity conversion. This consequently creates new challenging issues. The research objective of this thesis is to depict some of the challenging issues and provide possible solutions. The first challenge is the cross-phase modulation (XPM) penalty for the phase modulated channels co-propagating with the intensity modulated channels. The penalty comes from the pattern dependent intensity fluctuations of the neighboring intensity modulated channels being converted into phase noise in the phase modulation channels. We propose a model to theoretically analyze the XPM penalty dependence on the walk off effect. From this model, we suggest that using fibers with large local dispersion or intentionally introducing some residual dispersion per span would help mitigate the XPM penalty. The second challenge is the polarization dependent frequency shift (PDf) induced penalty during the phase-intensity conversion. The direct detection DPSK is usually demodulated in a Mach-Zehnder delay interferometer (DI). The polarization dependence of DI introduces a PDf causing a frequency offset between the laser's frequency and the transmissivity peak of DI, degrading the demodulated DPSK signal. We found that PDf ratio, defined as PDf/FSR, plays a predominant role in determining the performance of the demodulator. We further investigate on the PDf induced penalty for a 40-GHz DPSK demodulator on a 40-Gb/s return-to-zero (RZ)-DPSK signal to study PDf incurred optical filtering effect and spectrum distortion. Degradation for the RZ signal has been found in the presence the PDf. The third challenge is fiber dispersion induced inter-symbol interference for the phase modulated signals. Traditionally the dispersion is compensated using dispersion compensation fibers (DCF). Recently emerged electronic dispersion compensation (EDC) not only avoids the attenuation that would be introduced by DCF, but also is capable of simultaneously compensating the chromatic dispersion (CD) and polarization mode dispersion (PMD). We investigate on EDC's CD and PMD compensation capabilities for the direct detection return-to-zero (NRZ)-DPSK signal. The simulation results show that around 300-ps/nm CD and 10-ps differential group delay (DGD) can be compensated by employing EDC. However, compared with the on-off keying (OOK) signal, the EDC is actually less effective with the DPSK signal. The investigation is extended to the RZ-DPSK signal and found out the decision feedback equalizer (DFE) exhibits better performance with the RZ-DPSK signal.

Xu, Xian

71

Motif-directed network component analysis for regulatory network inference  

PubMed Central

Background Network Component Analysis (NCA) has shown its effectiveness in discovering regulators and inferring transcription factor activities (TFAs) when both microarray data and ChIP-on-chip data are available. However, a NCA scheme is not applicable to many biological studies due to limited topology information available, such as lack of ChIP-on-chip data. We propose a new approach, motif-directed NCA (mNCA), to integrate motif information and gene expression data to infer regulatory networks. Results We develop motif-directed NCA (mNCA) to incorporate motif information into NCA for regulatory network inference. While motif information is readily available from knowledge databases, it is a "noisy" source of network topology information consisting of many false positives. To overcome this problem, we develop a stability analysis procedure embedded in mNCA to resolve the inconsistency between motif information and gene expression data, and to enable the identification of stable TFAs. The mNCA approach has been applied to a time course microarray data set of muscle regeneration. The experimental results show that the inferred TFAs are not only numerically stable but also biologically relevant to muscle differentiation process. In particular, several inferred TFAs like those of MyoD, myogenin and YY1 are well supported by biological experiments. Conclusion A novel computational approach, mNCA, has been developed to integrate motif information and gene expression data for regulatory network reconstruction. Specifically, motif analysis is used to obtain initial network topology, and stability analysis is developed and applied with mNCA to extract stable TFAs. Experimental results on muscle regeneration microarray data have demonstrated that mNCA is a practical and reliable computational method for regulatory network inference and pathway discovery. PMID:18315853

Wang, Chen; Xuan, Jianhua; Chen, Li; Zhao, Po; Wang, Yue; Clarke, Robert; Hoffman, Eric

2008-01-01

72

Directional ad hoc networking technology (DANTE) performance at sea  

Microsoft Academic Search

SPAWAR Systems Center Pacific has spent several years developing directional wireless networks. These networks harness the power of highly directive antennas (range extension, higher data rates, lower power consumption, etc.) and have software to deal with the additional beam-steering complexity. The directional networking technology, DANTE, is outlined first. Three Trident Warrior at-sea tests of DANTE are then described, with summaries

Christopher Meagher; Randall Olsen; Christopher Cirullo; Robert C. Ferro; Nathaniel Stevens; Joonyoung Yu

2011-01-01

73

The Direct Digital Modulation of Traveling Wave Tubes  

NASA Technical Reports Server (NTRS)

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

Radhamohan, Ranjan S.

2004-01-01

74

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

75

Direct evidence for diazepam modulation of GABAA receptor microscopic affinity.  

PubMed

Alteration of agonist affinity is a potential mechanism for pharmacological modulation of ligand-gated receptor channel function. The time course for receptor activation and current onset is determined by the combined rates for two kinetic transitions that underlie the protein confirmations for binding agonist and channel gating. Using ultrafast ligand exchange techniques, we distinguish between these previously difficult to separate events and demonstrate their independent pharmacological modulation. Diazepam, which increases apparent affinity of gamma-aminobutyric acid (GABA) to GABAA receptors, was used to examine its effects on GABA binding and ion channel gating of expressed alpha 2 beta 1 gamma 2 receptors from excised outside-out patches of acutely transfected HEK 293 cells. Diazepam increased rates of current onset evoked by low concentrations (< 1 mM) but not at saturating GABA concentrations. Furthermore, rates of current decay were not affected during brief applications of GABA, and thus, demonstrated a diazepam specific effect on ligand binding affinity and not channel gating kinetics. However, current decay during and following prolonged GABA applications were altered by diazepam in a fashion similar to that for higher concentrations of GABA which also increased receptor desensitization. These findings and analysis by computer modeling indicated that diazepam likely enhances GABA receptor currents primarily by accelerating GABA association to its receptor at the first agonist binding site. These results provide the first direct physiological evidence for pharmacological modulation of microscopic binding affinity of GABA receptors. PMID:9014155

Lavoie, A M; Twyman, R E

1996-01-01

76

Motif-directed network component analysis for regulatory network inference  

Microsoft Academic Search

BACKGROUND: Network Component Analysis (NCA) has shown its effectiveness in discovering regulators and inferring transcription factor activities (TFAs) when both microarray data and ChIP-on-chip data are available. However, a NCA scheme is not applicable to many biological studies due to limited topology information available, such as lack of ChIP-on-chip data. We propose a new approach, motif-directed NCA (mNCA), to integrate

Chen Wang; Jianhua Xuan; Li Chen; Po Zhao; Yue Wang; Robert Clarke; Eric P. Hoffman

2008-01-01

77

Coverage Optimizing and Node Scheduling in Directional Wireless Sensor Networks  

Microsoft Academic Search

Most of previous works on coverage problem are based on omni-directional sensing model. Due to different sensing capability in different direction, directional sensor networks require new solutions. We present two direction optimizing algorithms: greedy direction adjusting (GDA) algorithm and equitable direction optimizing (EDO) algorithm. GDA algorithm optimizes direction merely according to the amount of covered targets. EDO algorithm adjusts the

Jun Wen; Li Fang; Jie Jiang; Wenhua Dou

2008-01-01

78

Constructing module maps for integrated analysis of heterogeneous biological networks  

PubMed Central

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

Amar, David; Shamir, Ron

2014-01-01

79

Searching Similar Modules in Protein Interaction Networks  

Microsoft Academic Search

We developed a new method to search protein networks functionally similar to a given query signal transduction pathway within protein interaction networks. This method consists of two parts: 1) a backtracking search algorithm to find topologically identical subgraphs and 2) a measurement of similarity between proteins by using Gene Ontology (1). For validation of our method, we implemented a software

Hiroyuki Ok; Masanori Arit

80

Identification of hierarchical and overlapping functional modules in PPI networks.  

PubMed

Various evidences have demonstrated that functional modules are overlapping and hierarchically organized in protein-protein interaction (PPI) networks. Up to now, few methods are able to identify both overlapping and hierarchical functional modules in PPI networks. In this paper, a new hierarchical clustering algorithm, called OH-PIN, is proposed based on the overlapping M_clusters, ?-module, and a new concept of clustering coefficient between two clusters. By recursively merging two clusters with the maximum clustering coefficient, OH-PIN finally assembles all M_clusters into ? -modules. Since M_clusters are overlapping, ? -modules based on them are also overlapping. Thus, OH-PIN can detect a hierarchical organization of overlapping modules by tuning the value of ?. The hierarchical organization is similar to the hierarchical organization of GO annotations and that of the known complexes in MIPS. To compare the performance of OH-PIN and other existing competing algorithms, we apply them to the yeast PPI network. The experimental results show that OH-PIN outperforms the existing algorithms in terms of the functional enrichment and matching with known protein complexes. PMID:22955967

Wang, Jianxin; Ren, Jun; Li, Min; Wu, Fang-Xiang

2012-12-01

81

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

82

Direct ink writing of microvascular networks  

NASA Astrophysics Data System (ADS)

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

Wu, Willie

83

Multimedia Wireless Sensor Networks: Perspectives and Future Directions  

E-print Network

and treatment Assisted Technology for everyone 8 #12;Multimedia Wireless Sensor Network (MWSN) A networkMultimedia Wireless Sensor Networks: Perspectives and Future Directions S j l K D Perspectives://crewman.uta.edug p // [Funded by NSF, AFOSR, Texas ARP] #12;Outline Multimedia Wireless Sensor Networks (MWSNs

van Dyk, David

84

Name of Module Network Architectures Basics  

E-print Network

is principally designed to impart: Technical skills 50%, method skills 10%, system skills 30% , social skills 10. · Signaling · separation of control and data channel · soft state and hard state · using of randomization: good English language skills (Lecture will be held in English.) 6. Target Group of Module Master

Wichmann, Felix

85

[Modulation of cortical excitability by transcranial direct current stimulation].  

PubMed

Modulation of cerebral excitability is thought to be one mechanism underlying the pharmacological treatment of neuropsychiatric diseases such as epilepsy, depression, and dystonia. Repetitive transcranial magnetic stimulation (rTMS) has been tested for several years as a nonpharmacological, noninvasive method of directly influencing patients' cortical functions. We present an overview of the more easily performed transcranial direct current stimulation (tDCS) with weak current, which produces distinctly more pronounced changes in excitability than rTMS. The basic underlying mechanism is a shift in the resting membrane potential towards either hyper- or depolarisation, depending on stimulation polarity. This in turn leads to changes in the excitability of cortical neurons. Anodic stimulation increases cortical excitability, while cathodic stimulation decreases it. These changes persist after the end of stimulation if the stimulation lasts long enough, i.e., at least several minutes. The duration of this aftereffect can be controlled through the duration and intensity of the stimulation. Transcranial direct current stimulation essentially allows a focal, selective, reversible, pain-free, and noninvasive induction of changes in cortical excitability, the therapeutic potential of which must be evaluated in clinical studies, once possible risk factors have been assessed. PMID:12040980

Nitsche, M A; Liebetanz, D; Tergau, F; Paulus, W

2002-04-01

86

Goal-Directed Module Extraction for Explaining OWL DL Entailments  

Microsoft Academic Search

Module extraction methods have proved to be effective in improving the performance of some ontology reasoning tasks, including finding justifica- tions to explain why an entailment holds in an OWL DL ontology. However, the existing module extraction methods that compute a syntactic locality-based module for the sub-concept in a subsumption entailment, though ensuring the resulting module to preserve all justifications

Jianfeng Du; Guilin Qi; Qiu Ji

2009-01-01

87

Remote Synchronization Reveals Network Symmetries and Functional Modules  

NASA Astrophysics Data System (ADS)

We study a Kuramoto model in which the oscillators are associated with the nodes of a complex network and the interactions include a phase frustration, thus preventing full synchronization. The system organizes into a regime of remote synchronization where pairs of nodes with the same network symmetry are fully synchronized, despite their distance on the graph. We provide analytical arguments to explain this result, and we show how the frustration parameter affects the distribution of phases. An application to brain networks suggests that anatomical symmetry plays a role in neural synchronization by determining correlated functional modules across distant locations.

Nicosia, Vincenzo; Valencia, Miguel; Chavez, Mario; Díaz-Guilera, Albert; Latora, Vito

2013-04-01

88

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

89

Controllability and observability analysis for vertex domination centrality in directed networks  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

90

Oriented modulation for watermarking in direct binary search halftone images.  

PubMed

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

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

2012-09-01

91

Guide RNA functional modules direct Cas9 activity and orthogonality.  

PubMed

The RNA-guided Cas9 endonuclease specifically targets and cleaves DNA in a sequence-dependent manner and has been widely used for programmable genome editing. Cas9 activity is dependent on interactions with guide RNAs, and evolutionarily divergent Cas9 nucleases have been shown to work orthogonally. However, the molecular basis of selective Cas9:guide-RNA interactions is poorly understood. Here, we identify and characterize six conserved modules within native crRNA:tracrRNA duplexes and single guide RNAs (sgRNAs) that direct Cas9 endonuclease activity. We show the bulge and nexus are necessary for DNA cleavage and demonstrate that the nexus and hairpins are instrumental in defining orthogonality between systems. In contrast, the crRNA:tracrRNA complementary region can be modified or partially removed. Collectively, our results establish guide RNA features that drive DNA targeting by Cas9 and open new design and engineering avenues for CRISPR technologies. PMID:25373540

Briner, Alexandra E; Donohoue, Paul D; Gomaa, Ahmed A; Selle, Kurt; Slorach, Euan M; Nye, Christopher H; Haurwitz, Rachel E; Beisel, Chase L; May, Andrew P; Barrangou, Rodolphe

2014-10-23

92

Connected Coverage in Wireless Networks with Directional Antennas  

E-print Network

Connected Coverage in Wireless Networks with Directional Antennas Zuoming Yu, Jin Teng, Xiaole Bai are the optimal patterns to achieve connected coverage in wireless networks with directional antennas antennas are able to promote communication quality by focusing transmission energy in one direction

Xuan, Dong

93

Noradrenergic modulation of the respiratory neural network  

Microsoft Academic Search

Noradrenergic dysregulation has been reported in human pathologies affecting the control of breathing, such as sudden infant death syndrome, congenital central hypoventilation syndrome and Rett syndrome. Noradrenergic neurons, located predominantly in pontine nuclei, are among the earliest to arise within the hindbrain and play an essential role in the maturation of the respiratory network. Noradrenergic neurons also play a major

Jean-Charles Viemari

2008-01-01

94

Learning biological networks: from modules to dynamics  

Microsoft Academic Search

Learning regulatory networks from genomics data is an important problem with applications spanning all of biology and biomedicine. Functional genomics projects offer a cost-effective means of greatly expanding the completeness of our regulatory models, and for some prokaryotic organisms they offer a means of learning accurate models that incorporate the majority of the genome. There are, however, several reasons to

Richard Bonneau

2008-01-01

95

A Survey of Wormhole Routing Techniques in Direct Networks  

Microsoft Academic Search

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

Lionel M. Ni; Philip K. Mckinley

1993-01-01

96

Network Synchronization for Two-Way Multi-Hop Relay Networks with Block Modulation  

Microsoft Academic Search

This paper proposes novel time-efficient network synchronization schemes for TDD\\/TDMA based two-way multi-hop relay networks with block modulation. One of the proposed schemes is based on broadcast (BC) timing synchronization. Since this scheme causes network synchronization errors at each receiver, additional guard interval (GI) to compensate the error is introduced. The second proposed scheme is based on both of BC

Keiichi Mizutani; Kei Sakaguchi; Kiyomichi Araki

2010-01-01

97

Compression of Flow Can Reveal Overlapping-Module Organization in Networks  

NASA Astrophysics Data System (ADS)

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

Viamontes Esquivel, Alcides; Rosvall, Martin

2011-10-01

98

Network connectivity modulates power spectrum scale invariance.  

PubMed

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

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

2014-04-15

99

Directionality of real world networks as predicted by path length in directed and undirected graphs  

NASA Astrophysics Data System (ADS)

Many real world networks either support ordered processes, or are actually representations of such processes. However, the same networks contain large strong connectivity components and long circles, which hide a possible inherent order, since each vertex can be reached from each vertex in a directed path. Thus, the presence of an inherent directionality in networks may be hidden. We here discuss a possible definition of such a directionality and propose a method to detect it. Several common algorithms, such as the betweenness centrality or the degree, measure various aspects of centrality in networks. However, they do not address directly the issue of inherent directionality. The goal of the algorithm discussed here is the detection of global directionality in directed networks. Such an algorithm is essential to detangle complex networks into ordered process. We show that indeed the vast majority of measured real world networks have a clear directionality. Moreover, this directionality can be used to classify vertices in these networks from sources to sinks. Such an algorithm can be highly useful in order to extract a meaning from large interaction networks assembled in many domains.

Rosen, Yonatan; Louzoun, Yoram

2014-05-01

100

Search for Directed Networks by Different Random Walk Strategies  

NASA Astrophysics Data System (ADS)

A comparative study is carried out on the efficiency of five different random walk strategies searching on directed networks constructed based on several typical complex networks. Due to the difference in search efficiency of the strategies rooted in network clustering, the clustering coefficient in a random walker's eye on directed networks is defined and computed to be half of the corresponding undirected networks. The search processes are performed on the directed networks based on Erdös—Rényi model, Watts—Strogatz model, Barabási—Albert model and clustered scale-free network model. It is found that self-avoiding random walk strategy is the best search strategy for such directed networks. Compared to unrestricted random walk strategy, path-iteration-avoiding random walks can also make the search process much more efficient. However, no-triangle-loop and no-quadrangle-loop random walks do not improve the search efficiency as expected, which is different from those on undirected networks since the clustering coefficient of directed networks are smaller than that of undirected networks.

Zhu, Zi-Qi; Jin, Xiao-Ling; Huang, Zhi-Long

2012-03-01

101

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

Microsoft Academic Search

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

Rossano Pardini; Umberto Bruno; Roberto Izzo

2009-01-01

102

Adaptive Cluster Synchronization of Directed Complex Networks with Time Delays  

PubMed Central

This paper studied the cluster synchronization of directed complex networks with time delays. It is different from undirected networks, the coupling configuration matrix of directed networks cannot be assumed as symmetric or irreducible. In order to achieve cluster synchronization, this paper uses an adaptive controller on each node and an adaptive feedback strategy on the nodes which in-degree is zero. Numerical example is provided to show the effectiveness of main theory. This method is also effective when the number of clusters is unknown. Thus, it can be used in the community recognizing of directed complex networks. PMID:24763228

Liu, Heng; Wang, Xingyuan; Tan, Guozhen

2014-01-01

103

Exploring Security Improvement of Wireless Networks with Directional Antennas  

E-print Network

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

Wong, Raymond Chi-Wing

104

Energy Efficient Communications in Ad Hoc Networks Using Directional Antennas  

Microsoft Academic Search

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

Akis Spyropoulos; Cauligi S. Raghavendra

2002-01-01

105

Complete mathematical analysis of ripple current as a function of the modulation index for direct indirect and bus clamped space vector modulation techniques [motor drives  

Microsoft Academic Search

A detailed mathematical analysis was performed to estimate the current ripple as a function of modulation index for direct indirect and bus clamped methods of space vector modulation. The results, both experimental and simulated, show that for a modulation index above 0.45 the direct-indirect method progressively gives lesser current ripple and becomes almost half at around a modulation index of

S. Mazumder

1997-01-01

106

Detecting Blackholes and Volcanoes in Directed Networks  

E-print Network

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

Li, Zhongmou; Liu, Yanchi

2010-01-01

107

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

108

Identifying dynamical modules from genetic regulatory systems: applications to the segment polarity network  

PubMed Central

Background It is widely accepted that genetic regulatory systems are 'modular', in that the whole system is made up of smaller 'subsystems' corresponding to specific biological functions. Most attempts to identify modules in genetic regulatory systems have relied on the topology of the underlying network. However, it is the temporal activity (dynamics) of genes and proteins that corresponds to biological functions, and hence it is dynamics that we focus on here for identifying subsystems. Results Using Boolean network models as an exemplar, we present a new technique to identify subsystems, based on their dynamical properties. The main part of the method depends only on the stable dynamics (attractors) of the system, thus requiring no prior knowledge of the underlying network. However, knowledge of the logical relationships between the network components can be used to describe how each subsystem is regulated. To demonstrate its applicability to genetic regulatory systems, we apply the method to a model of the Drosophila segment polarity network, providing a detailed breakdown of the system. Conclusion We have designed a technique for decomposing any set of discrete-state, discrete-time attractors into subsystems. Having a suitable mathematical model also allows us to describe how each subsystem is regulated and how robust each subsystem is against perturbations. However, since the subsystems are found directly from the attractors, a mathematical model or underlying network topology is not necessarily required to identify them, potentially allowing the method to be applied directly to experimental expression data. PMID:17961242

Irons, David J; Monk, Nicholas AM

2007-01-01

109

RMaNI: Regulatory Module Network Inference framework  

PubMed Central

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

2013-01-01

110

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

111

Optical modulation of astrocyte network using ultrashort pulsed laser  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

112

Enabling Technologies for Direct Detection Optical Phase Modulation Formats  

Microsoft Academic Search

Phase modulation formats are believed to be one of the key enabling techniques for next generation high speed long haul fiber-optic communication systems due to the following main advantages: (1) with a balanced detection, a better receiver sensitivity over conventional intensity modulation formats, e.g., a ˜3-dB sensitivity improvement using differential phase shift keying (DPSK) and a ˜1.3-dB sensitivity improvement using

Xian Xu

2009-01-01

113

Resource Allocation in Wireless Networks Using Directional Antennas  

E-print Network

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

Wu, Jie

114

Resource Scheduling in Wireless Networks Using Directional Antennas  

E-print Network

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

Wu, Jie

115

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

116

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

PubMed

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

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

2012-12-10

117

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

NASA Astrophysics Data System (ADS)

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

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

1998-09-01

118

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

PubMed Central

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

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

2013-01-01

119

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

NASA Astrophysics Data System (ADS)

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

Bilgi, Mehmet; Yuksel, Murat

2010-04-01

120

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

121

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

122

Role of Directional Wireless Communication in Vehicular Networks  

E-print Network

Role of Directional Wireless Communication in Vehicular Networks Ashish Agarwal and Thomas D of an incident. Wireless radio communication has emerged as a key enabler for exchanging safety information safety communication. However, there are significant constraints to utilizing wireless radio

123

Asynchronous bi-directional relay-assisted communication networks.  

E-print Network

??We consider an asynchronous bi-directional relay network, consisting of two singleantenna transceivers and multiple single-antenna relays, where the transceiver-relay paths are subject to different relaying… (more)

Vahidnia, Reza

2014-01-01

124

On duality and fractionality of multicommodity flows in directed networks  

E-print Network

In this paper we address a topological approach to multiflow (multicommodity flow) problems in directed networks. Given a terminal weight $\\mu$, we define a metrized polyhedral complex, called the directed tight span $T_{\\mu}$, and prove that the dual of $\\mu$-weighted maximum multiflow problem reduces to a facility location problem on $T_{\\mu}$. Also, in case where the network is Eulerian, it further reduces to a facility location problem on the tropical polytope spanned by $\\mu$. By utilizing this duality, we establish the classifications of terminal weights admitting combinatorial min-max relation (i) for every network and (ii) for every Eulerian network. Our result includes Lomonosov-Frank theorem for directed free multiflows and Ibaraki-Karzanov-Nagamochi's directed multiflow locking theorem as special cases.

Hirai, Hiroshi

2010-01-01

125

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

PubMed

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

2014-01-01

126

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

2014-01-01

127

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

PubMed Central

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 we present a general method for inferring direct effects from an observed correlation matrix containing both direct and indirect effects. We formulate the problem as the inverse of network convolution, and introduce an algorithm that removes the combined effect of all indirect paths of arbitrary length in a closed-form solution by exploiting eigen-decomposition and infinite-series sums. We demonstrate the effectiveness of our approach in several network applications: distinguishing direct targets in gene expression regulatory networks; recognizing directly-interacting amino-acid residues for protein structure prediction from sequence alignments; and distinguishing strong collaborations in co-authorship social networks using connectivity information alone. PMID:23851448

Feizi, Soheil; Marbach, Daniel; Médard, Muriel; Kellis, Manolis

2013-01-01

128

Multiple-subcarrier modulation for non-directed wireless infrared communication  

Microsoft Academic Search

We examine multiple-subcarrier modulation (MSM) schemes for wireless infrared digital communication in the indoor environment. Intensity-modulation with direct-detection (IM\\/DD) as used, which results in equivalent baseband channels with a non-negativity constraint on the input. The power efficiencies of modulation schemes are compared at 30 Mb\\/s and 100 Mb\\/s over an ensemble of experimentally determined multipath channels. It is found that

Jeffrey B. Carruthers; Joseph M. Kahn

1994-01-01

129

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

130

Self-Organizing Directional Wireless Backbone Networks .  

E-print Network

??Directional wireless communications is emerging as a viable, cost-effective technology for rapidly deployable broadband wireless communication infrastructures. This technology provides extremely high data rates through… (more)

Llorca, Jaime

2008-01-01

131

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

E-print Network

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

Eisenstein, Gadi

132

Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex Modulates Repetition  

E-print Network

and learning of unfamiliar faces remains unclear. Transcranial direct current stimulation (tDCS) transiently excitability modulation by tDCS would cause polarity-dependent modulations of N170 RS during encoding of unfamiliar faces. tDCS-induced N170 RS enhancement would improve long- term recognition reaction time (RT

Gosselin, Frédéric

133

Direction-specific optokinetic modulation of monosynaptic hind limb reflexes in cats.  

PubMed

The excitability of hindlimb extensor and flexor motoneurons is tonically modulated by animal tilt and a large visual stimulus rotating about the animal's line of sight. This direction-specific modulation is opposite for extensor and flexor motoneurons and opposite for optokinetic and vestibular stimuli, thus combining to a functionally significant pattern of postural reflexes. PMID:304014

Thoden, U; Dichgans, J; Savidis, T

1977-10-24

134

Direction-specific optokinetic modulation of monosynaptic hind limb reflexes in cats  

Microsoft Academic Search

The excitability of hindlimb extensor and flexor motoneurons is tonically modulated by animal tilt and a large visual stimulus rotating about the animal's line of sight. This direction-specific modulation is opposite for extensor and flexor motoneurons and opposite for optokinetic and vestibular stimuli, thus combining to a functionally significant pattern of postural reflexes.

U. Thoden; J. Dichgans; Th. Savidis

1977-01-01

135

Low-dispersion penalty directly modulated 1.55-um DFB lasers with complex coupled gratings  

Microsoft Academic Search

Prior to the full maturation of electro-absorption modulated laser technology, directly modulated 1.55 micrometer distributed feedback lasers will continue to play a central role in long haul, high bit rate, optical communications systems. Maintaining a competitive advantage, however, requires that these devices be optimized for long fiber length transmission, high power, and low cost. In this talk we discuss the

Leonard J. Ketelsen; L. Eng; Ilyoung Kim; J. A. Grenko; D. Sutryn; T. Wessel; U. K. Chakrabarti; Debbie L. Coblentz; Robert L. Hartman

1996-01-01

136

System architecture directions for networked sensors  

Microsoft Academic Search

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

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

2000-01-01

137

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

NASA Technical Reports Server (NTRS)

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

Sun, Xiaoli; Abshire, James B.

2011-01-01

138

Optimal Opportunistic Scheduling and Adaptive Modulation Policies in Wireless Ad-Hoc Networks with Network Coding  

NASA Astrophysics Data System (ADS)

In this paper, we study an opportunistic scheduling and adaptive modulation scheme for a wireless network with an XOR network coding scheme, which results in a cross-layer problem for MAC and physical layers. A similar problem was studied in [2] which considered an idealized system with the Shannon capacity. They showed that it may not be optimal for a relay node to encode all possible native packets and there exists the optimal subset of native packets that depends on the channel condition at the receiver node of each native packet. In this paper, we consider a more realistic model than that of [2] with a practical modulation scheme such as M-PSK. We show that the optimal policy is to encode native as many native packets as possible in the network coding group into a coded packet regardless of the channel condition at the receiver node for each native packet, which is a different conclusion from that of [2]. However, we show that adaptive modulation, in which the constellation size of a coded packet is adjusted based on the channel condition of each receiver node, provides a higher throughput than fixed modulation, in which its constellation size is always fixed regardless of the channel condition at each receiver node.

Gong, Seong-Lyong; Kim, Byung-Gook; Lee, Jang-Won

139

Identification of important nodes in directed biological networks: a network motif approach.  

PubMed

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

Wang, Pei; Lü, Jinhu; Yu, Xinghuo

2014-01-01

140

On Designing MAC Protocols for Wireless Networks Using Directional Antennas  

E-print Network

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

Ramanathan, Ram

141

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

142

Nitrogen modulation on plant direct and indirect defenses  

Technology Transfer Automated Retrieval System (TEKTRAN)

Instead of being passively attacked by insect pests, plants possess a myriad of defense mechanisms to protect themselves. These mechanisms function broadly either by directly reducing herbivore fitness (direct plant defense), or by indirectly attracting natural enemies of the herbivores (indirect p...

143

Energy-Efficient Modulation Design for Reliable Communication in Wireless Networks  

E-print Network

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

Gursoy, Mustafa Cenk

144

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

PubMed Central

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

Banga, Ajay K.

2014-01-01

145

Heterogeneous Modulation for Trading-off Energy Balancing with Bandwidth Efficiency in Hierarchical Sensor Networks  

E-print Network

Heterogeneous Modulation for Trading-off Energy Balancing with Bandwidth Efficiency in Hierarchical modulation scheme and report its impact on the spatial distribution of energy dissipation and the resulting network lifetime. Moreover, we study how this heterogeneous modulation scheme affects the end-to-end delay

Pedram, Massoud

146

On redundancy in neural architecture: dynamics of a simple module-based neural network and initial-state independence  

Microsoft Academic Search

This article discusses the relationship between redundancy in neural architecture and activity (cell output or internal state) dynamics with a simple module-based neural network. In the network, a single neural cell with self-feedback is employed as a module sub-network, and all module sub-networks are connected via inter-module connections. In general, the activity dynamics of a single neural cell with positive

K. Tsutsumi

1999-01-01

147

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

148

CXCL14 is no direct modulator of CXCR4.  

PubMed

C-X-C motif chemokine 12/C-X-C chemokine receptor type 4 (CXCL12/CXCR4) signaling is involved in ontogenesis, hematopoiesis, immune function and cancer. Recently, the orphan chemokine CXCL14 was reported to inhibit CXCL12-induced chemotaxis - probably by allosteric modulation of CXCR4. We thus examined the effects of CXCL14 on CXCR4 regulation and function using CXCR4-transfected human embryonic kidney (HEK293) cells and Jurkat T cells. CXCL14 did not affect dose-response profiles of CXCL12-induced CXCR4 phosphorylation, G protein-mediated calcium mobilization, dynamic mass redistribution, kinetics of extracellular signal-regulated kinase 1 (ERK1) and ERK2 phosphorylation or CXCR4 internalization. Hence, essential CXCL12-operated functions of CXCR4 are insensitive to CXCL14, suggesting that interactions of CXCL12 and CXCL14 pathways depend on a yet to be identified CXCL14 receptor. PMID:25451233

Otte, Maik; Kliewer, Andrea; Schütz, Dagmar; Reimann, Christiane; Schulz, Stefan; Stumm, Ralf

2014-12-20

149

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

150

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

151

Integrin-directed modulation of macrophage responses to biomaterials.  

PubMed

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

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

2014-04-01

152

Direct Marketing Modeling Using Evolutionary Bayesian Network Learning Algorithm  

Microsoft Academic Search

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

Man Leung Wong

153

C-element: A New Clustering Algorithm to Find High Quality Functional Modules in PPI Networks  

PubMed Central

Graph clustering algorithms are widely used in the analysis of biological networks. Extracting functional modules in protein-protein interaction (PPI) networks is one such use. Most clustering algorithms whose focuses are on finding functional modules try either to find a clique like sub networks or to grow clusters starting from vertices with high degrees as seeds. These algorithms do not make any difference between a biological network and any other networks. In the current research, we present a new procedure to find functional modules in PPI networks. Our main idea is to model a biological concept and to use this concept for finding good functional modules in PPI networks. In order to evaluate the quality of the obtained clusters, we compared the results of our algorithm with those of some other widely used clustering algorithms on three high throughput PPI networks from Sacchromyces Cerevisiae, Homo sapiens and Caenorhabditis elegans as well as on some tissue specific networks. Gene Ontology (GO) analyses were used to compare the results of different algorithms. Each algorithm's result was then compared with GO-term derived functional modules. We also analyzed the effect of using tissue specific networks on the quality of the obtained clusters. The experimental results indicate that the new algorithm outperforms most of the others, and this improvement is more significant when tissue specific networks are used. PMID:24039752

Ghasemi, Mahdieh; Rahgozar, Maseud; Bidkhori, Gholamreza; Masoudi-Nejad, Ali

2013-01-01

154

Transcranial direct current stimulation over posterior parietal cortex modulates visuospatial localization  

E-print Network

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

Krekelberg, Bart

155

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

156

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

157

Wavelength tunable receiver for FSK modulated optical signals based on standard direct-detection circuitry  

NASA Astrophysics Data System (ADS)

A WDM system has been realized, intended for digital broadband (e.g. video) distribution in an optically splitted subscriber access network. Four standard 565 Mbit/s optical transmitter units have been equipped with wavelength-matched 1557 nm DFB laser diodes. The four transmitters are wavelength-locked to a temperature-stabilized fiber Fabry-Perot (FFP). The lasers are FSK modulated with a tone spacing of 6.7 GHz; the 565 Mbit/s input signals are 7B8B coded to avoid problems with the laser's non-linear FM response. Another tunable FFP precedes a standard direct-detection receiver for both wavelength channel selection and FSK demodulation. A wavelength control circuit (WCC) ensures locking of the FFP to the correct tone of the selected channel. The WCC continuously maximizes the average FFP output power, by determining the time-derivative of the mean photodiode current. The main advantage of this approach is the absence of a dithering signal, which interferes with the data signal. BER curves have been measured for each of the four channels and compared with theory, discrepancies are < 0.75 dB. A net system power budget of > 28 dB for each channel has been achieved, and no evidence for BER floors has been found down to a BER of 10-11.

van Eijk, P.; Jennen, J. G.; Koonen, Antonius A.

1995-02-01

158

High-Speed Transmission of Adaptively Modulated Optical OFDM Signals Over Multimode Fibers Using Directly Modulated DFBs  

NASA Astrophysics Data System (ADS)

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 300 m and 10 Gb/s over 900 m transmission of intensity modulation and direct detection (IMDD) AMOOFDM signals at 1550 nm is feasible in DML-based links using MMFs with 3-dB effective bandwidths of 200 MHz ...km. Apart from a higher signal capacity, AMOOFDM also has a greater spectral efficiency and is less susceptible to different launching conditions, modal dispersion, and fiber types, compared with all existing schemes. In addition, a large noise margin of about 15 dB is also observed. The bits of resolution of analog-to-digital converters (ADCs) and the cyclic prefix of AMOOFDM symbols are the main factors limiting the maximum achievable performance, on which the influence of DMLs is, however, negligible under the optimum operating condition.

Tang, J. M.; Lane, P. M.; Shore, K. Alan

2006-01-01

159

Secure Upgrade of Hardware Security Modules in Bank Networks  

NASA Astrophysics Data System (ADS)

We study the secure upgrade of critical components in wide networked systems, focussing on the case study of PIN processing Hardware Security Modules (HSMs). These tamper-resistant devices, used by banks to securely transmit and verify the PIN typed at the ATMs, have been shown to suffer from API level attacks that allow an insider to recover user PINs and, consequently, clone cards. Proposed fixes require to reduce and modify the HSM functionality by, e.g., sticking on a single format of the transmitted PIN or adding MACs for the integrity of user data. Upgrading HSMs worldwide is, of course, unaffordable. We thus propose strategies to incrementally upgrade the network so to obtain upgraded, secure subnets, while preserving the compatibility towards the legacy system. Our strategies aim at finding tradeoffs between the cost for special "guardian" HSMs used on the borderline between secure and insecure nodes, and the size of the team working in the upgrade process, representing the maximum number of nodes that can be simultaneously upgraded.

Focardi, Riccardo; Luccio, Flaminia L.

160

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

PubMed

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

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

2015-01-12

161

A direct AC\\/AC converter based on current-source converter modules  

Microsoft Academic Search

The research on direct AC\\/AC conversion in the past twenty years has been following two major directions: improving the performance of the original nine-bidirectional-switch matrix converter topology; and using converter topologies composed of unidirectional switches only. In this paper, a direct AC\\/AC converter topology based on current-source converter modules is proposed. It is shown, through analysis and simulation, that the

Mehrdad Kazerani

2003-01-01

162

Bandwidth Provisioning in Infrastructure-based Wireless Networks Employing Directional Antennas  

E-print Network

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

Urgaonkar, Bhuvan

163

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

PubMed Central

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

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

2013-01-01

164

Glycyrrhizin and glycyrrhetinic acid directly modulate rat cardiac performance.  

PubMed

Root extract of liquorice is traditionally used to treat several diseases. Liquorice-derived constituents present several biological actions. In particular, glycyrrhizin and its aglycone, glycyrrhetinic acid, exhibit well-known cardiovascular properties. The aim of this research was to explore the direct cardiac activity of glycyrrhizin and glycyrrhetinic acid. The effects of synthetic glycyrrhizin and glycyrrhetinic acid were evaluated on the isolated and Langendorff perfused rat heart. The intracellular signaling involved in the effects of the two substances was analyzed on isolated and perfused heart and by Western blotting on cardiac extracts. Under basal conditions, both glycyrrhizin and glycyrrhetinic acid influenced cardiac contractility and relaxation. Glycyrrhizin induced significant positive inotropic and lusitropic effects starting from very low concentrations, while both inotropism and lusitropism were negatively affected by glycyrrhetinic acid. Both substances significantly increased heart rate. Analysis of the signal transduction mechanisms suggested that glycyrrhizin acts through the endothelin receptor type A/phospholipase C axis while glycyrrhetinic acid acts through endothelin receptor type B/Akt/nitric oxide synthase/nitric oxide axis. To our knowledge, these data reveal, for the first time, that both glycyrrhizin and glycyrrhetinic acid directly affect cardiac performance. Additional information on the physiological significance of these substances and their cardiac molecular targets may provide indication on their biomedical application. PMID:21414764

Parisella, Maria L; Angelone, Tommaso; Gattuso, Alfonsina; Cerra, Maria C; Pellegrino, Daniela

2012-01-01

165

The Ndc80 kinetochore complex directly modulates microtubule dynamics  

PubMed Central

The conserved Ndc80 complex is an essential microtubule-binding component of the kinetochore. Recent findings suggest that the Ndc80 complex influences microtubule dynamics at kinetochores in vivo. However, it was unclear if the Ndc80 complex mediates these effects directly, or by affecting other factors localized at the kinetochore. Using a reconstituted system in vitro, we show that the human Ndc80 complex directly stabilizes the tips of disassembling microtubules and promotes rescue (the transition from microtubule shortening to growth). In vivo, an N-terminal domain in the Ndc80 complex is phosphorylated by the Aurora B kinase. Mutations that mimic phosphorylation of the Ndc80 complex prevent stable kinetochore-microtubule attachment, and mutations that block phosphorylation damp kinetochore oscillations. We find that the Ndc80 complex with Aurora B phosphomimetic mutations is defective at promoting microtubule rescue, even when robustly coupled to disassembling microtubule tips. This impaired ability to affect dynamics is not simply because of weakened microtubule binding, as an N-terminally truncated complex with similar binding affinity is able to promote rescue. Taken together, these results suggest that in addition to regulating attachment stability, Aurora B controls microtubule dynamics through phosphorylation of the Ndc80 complex. PMID:22908300

Umbreit, Neil T.; Gestaut, Daniel R.; Tien, Jerry F.; Vollmar, Breanna S.; Gonen, Tamir; Asbury, Charles L.; Davis, Trisha N.

2012-01-01

166

NRC TLD (thermoluminescent dosimeter) Direct Radiation Monitoring Network  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

R. Struckmeyer; N. McNamara

1990-01-01

167

Mobility Control for Joint Coverage-Connectivity Optimization in Directional Wireless Backbone Networks  

Microsoft Academic Search

The use of directional wireless communications to form flexible mesh backbone networks, which provide broadband connectivity to capacity-limited wireless networks or hosts, promises to circumvent the scalability limitations of traditional wireless networks. The main challenge in the design of directional wireless backbone (DWB) networks is to assure backbone network requirements such as coverage and connectivity in a dynamic wireless environment.

Jaime Llorca; Stuart D. Milner; Christopher C. Davis

2007-01-01

168

Direct Adaptive Aircraft Control Using Dynamic Cell Structure Neural Networks  

NASA Technical Reports Server (NTRS)

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

Jorgensen, Charles C.

1997-01-01

169

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

170

Dynamic modulation of the action observation network by movement familiarity.  

PubMed

When watching another person's actions, a network of sensorimotor brain regions, collectively termed the action observation network (AON), is engaged. Previous research suggests that the AON is more responsive when watching familiar compared with unfamiliar actions. However, most research into AON function is premised on comparisons of AON engagement during different types of task using univariate, magnitude-based approaches. To better understand the relationship between action familiarity and AON engagement, here we examine how observed movement familiarity modulates AON activity in humans using dynamic causal modeling, a type of effective connectivity analysis. Twenty-one subjects underwent fMRI scanning while viewing whole-body dance movements that varied in terms of their familiarity. Participants' task was to either predict the next posture the dancer's body would assume or to respond to a non-action-related attentional control question. To assess individuals' familiarity with each movement, participants rated each video on a measure of visual familiarity after being scanned. Parametric analyses showed more activity in left middle temporal gyrus, inferior parietal lobule, and inferior frontal gyrus as videos were rated as increasingly familiar. These clusters of activity formed the regions of interest for dynamic causal modeling analyses, which revealed attenuation of effective connectivity bidirectionally between parietal and temporal AON nodes when participants observed videos they rated as increasingly familiar. As such, the findings provide partial support for a predictive coding model of the AON, as well as illuminate how action familiarity manipulations can be used to explore simulation-based accounts of action understanding. PMID:25632133

Gardner, Tom; Goulden, Nia; Cross, Emily S

2015-01-28

171

Dynamic Modulation of the Action Observation Network by Movement Familiarity  

PubMed Central

When watching another person's actions, a network of sensorimotor brain regions, collectively termed the action observation network (AON), is engaged. Previous research suggests that the AON is more responsive when watching familiar compared with unfamiliar actions. However, most research into AON function is premised on comparisons of AON engagement during different types of task using univariate, magnitude-based approaches. To better understand the relationship between action familiarity and AON engagement, here we examine how observed movement familiarity modulates AON activity in humans using dynamic causal modeling, a type of effective connectivity analysis. Twenty-one subjects underwent fMRI scanning while viewing whole-body dance movements that varied in terms of their familiarity. Participants' task was to either predict the next posture the dancer's body would assume or to respond to a non–action-related attentional control question. To assess individuals' familiarity with each movement, participants rated each video on a measure of visual familiarity after being scanned. Parametric analyses showed more activity in left middle temporal gyrus, inferior parietal lobule, and inferior frontal gyrus as videos were rated as increasingly familiar. These clusters of activity formed the regions of interest for dynamic causal modeling analyses, which revealed attenuation of effective connectivity bidirectionally between parietal and temporal AON nodes when participants observed videos they rated as increasingly familiar. As such, the findings provide partial support for a predictive coding model of the AON, as well as illuminate how action familiarity manipulations can be used to explore simulation-based accounts of action understanding. PMID:25632133

Gardner, Tom; Goulden, Nia

2015-01-01

172

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

173

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

PubMed Central

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

Shribak, Michael

2013-01-01

174

Network oscillations modulate interictal epileptiform spike rate during human memory  

PubMed Central

Eleven patients being evaluated with intracranial electroencephalography for medically resistant temporal lobe epilepsy participated in a visual recognition memory task. Interictal epileptiform spikes were manually marked and their rate of occurrence compared between baseline and three 2 s periods spanning a 6 s viewing period. During successful, but not unsuccessful, encoding of the images there was a significant reduction in interictal epileptiform spike rate in the amygdala, hippocampus, and temporal cortex. During the earliest encoding period (0–2000 ms after image presentation) in these trials there was a widespread decrease in the power of theta, alpha and beta band local field potential oscillations that coincided with emergent focal gamma frequency activity. Interictal epileptiform spike rate correlated with spectral band power changes and broadband (4–150 Hz) desynchronization, which predicted significant reduction in interictal epileptiform spike rate. Spike-triggered averaging of the field potential power spectrum detected a burst of low frequency synchronization 200 ms before the interictal epileptiform spikes that arose during this period of encoding. We conclude that interictal epileptiform spikes are modulated by the patterns of network oscillatory activity that accompany human memory offering a new mechanistic insight into the interplay of cognitive processing, local field potential dynamics and interictal epileptiform spike generation. PMID:23803305

Matsumoto, Joseph Y.; Stead, Matt; Kucewicz, Michal T.; Matsumoto, Andrew J.; Peters, Pierce A.; Brinkmann, Benjamin H.; Danstrom, Jane C.; Goerss, Stephan J.; Marsh, W. Richard; Meyer, Fred B.

2013-01-01

175

Study of Transcriptional Regulatory Network Based on CIS Module Database  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

176

Self-oscillating modulators for direct energy conversion audio power amplifiers  

E-print Network

Self-oscillating modulators for direct energy conversion audio power amplifiers Petar Ljusev1 conversion audio power amplifier represents total integration of switching-mode power supply and Class D audio power amplifier into one compact stage, achieving high efficiency, high level of integration, low

177

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

178

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

Microsoft Academic Search

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

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

2001-01-01

179

Energy Efficient Wireless Transmitters: Polar and Direct-Digital Modulation Architectures  

E-print Network

Energy Efficient Wireless Transmitters: Polar and Direct-Digital Modulation Architectures Jason provided that copies are not made or distributed for profit or commercial advantage and that copies bear or to redistribute to lists, requires prior specific permission. #12;Energy Efficient Wireless Transmitters: Polar

Sanders, Seth

180

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

NASA Technical Reports Server (NTRS)

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

Levitt, B. K.

1980-01-01

181

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

Microsoft Academic Search

A W-band unamplified direct detection radiometer module is described that provides a wideband response and is scalable to large arrays. The radiometer design is intended to provide sufficient sensitivity for millimeter wave imaging applications with a goal of 2K noise equivalent temperature difference (NETD) at a 30 Hz frame rate. This effort leverages previously reported device scaling to increase sensitivity.

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

2008-01-01

182

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

183

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

Microsoft Academic Search

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

Takashi Hiyama; Ken Kitabayashi

1997-01-01

184

Module-based large-scale software evolution based on complex networks  

Microsoft Academic Search

Large-scale software systems usually consist of a huge number of modules, and have a series of releases along with these modules. This can be seen as software evolution. In recent years, researchers have put forward several models of software evolution by employing the theory of complex networks. In this paper, we put forward a refined model of software evolution based

Tao Chen; Qing Gu; Shusen Wang; Xiaoan Chen; Daoxu Chen

2008-01-01

185

Joint Voltage and Modulation Scaling for Energy Harvesting Sensor Networks Bo Zhang Robert Simon Hakan Aydin  

E-print Network

that combines energy harvesting with dynamic voltage scaling and dynamic modulation scaling. Our algorithmJoint Voltage and Modulation Scaling for Energy Harvesting Sensor Networks Bo Zhang Robert Simon, aydin}@cs.gmu.edu Abstract Energy harvesting is rapidly becoming a critical archi- tectural component

Aydin, Hakan

186

Building a neural network-based English-to-Arabic transfer module from an unrestricted domain  

Microsoft Academic Search

This paper presents a Transfer Module for an English-to-Arabic Machine Translation System (MTS) using an English-to-Arabic Bilingual Corpus. We propose an approach to build a transfer module by building a new transfer-based system for machine translation using Artificial Neural Networks (ANN). The idea is to allow the ANN-based transfer module to automatically learn correspondences between source and target language structures

Rasha Al Dam; Ahmed Guessoum

2010-01-01

187

Moving Target Tracking through Distributed Clustering in Directional Sensor Networks.  

PubMed

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

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

2014-01-01

188

Moving Target Tracking through Distributed Clustering in Directional Sensor Networks  

PubMed Central

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

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

2014-01-01

189

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

190

Learning modulates the ensemble representations for odors in primary olfactory networks  

E-print Network

in the AL are dynamic and related to olfactory memory consolidation. We furthermore provide evidenceLearning modulates the ensemble representations for odors in primary olfactory networks Kevin C shown in the vertebrate olfactory bulb. However, the specific network changes that occur in re- sponse

Daly, Kevin Charles

191

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

E-print Network

Multi-transceiver simulation modules for free-space optical mobile ad hoc networks Mehmet Bilgi-transceiver free-space-optical (FSO) mobile ad-hoc networks. We start with a physical propagation model for FSO. Keywords: Free-space-optics, wireless simulation, FSO propagation 1. INTRODUCTION AND MOTIVATION Wireless

Yuksel, Murat

192

Attentional modulation of SSVEP power depends on the network tagged by the flicker frequency  

PubMed Central

The modulation of steady-state visual evoked potential (SSVEP) by attention was studied in detail using 15 “tag” frequencies in the range of 2.5–20 Hz. The stimuli were two series of random disc search arrays superimposed on two concentric color-marked annuli respectively. Two series of arrays were updated independently; one updated at one fixed frequency (flicker) and the other updated randomly according to a white noise distribution (random broadband flicker, rbbf). On each trial, the subject was instructed to attend one annulus and to detect a target (a triangle) that occasionally appeared in a random disc array in the attended annulus. The SSVEP results show that the choice of flicker frequency selects which cortical network synchronizes to the flicker frequency; two distinct cortical networks showed different effects of attention. SSVEP power and the effects of attention on SSVEP power strongly depend on both flicker frequency and radial position of rbbf annulus. At flicker frequencies in the delta band (2–4 Hz), and in the upper alpha band (10–11 Hz), an occipital-frontal network appears to phase-lock to the flicker when attending to the flicker, increasing the magnitude of the SSVEP. At flicker frequencies in the lower alpha band (8–10 Hz), a global response to a peripheral flickering stimulus, that includes parietal cortex and posterior frontal cortex, has higher amplitude when attention is directed away from the flickering peripheral stimulus and towards a competing rbbf stimulus in the fovea. Increases in SSVEP power when attention is directed to peripheral flicker are always associated with increases in phase locking. By contrast, at frequencies in the lower alpha band, increases in SSVEP power when attention is directed away from the flicker and towards foveal stimuli are not associated with changes in phase-locking. Thus, whether attention to a flicker stimulus increases or decreases SSVEP amplitude and phase locking depends on which of two cortical networks is selected by the flicker frequency; different networks have distinct spatial and dynamic properties. PMID:16221931

Ding, Jian; Sperling, George; Srinivasan, Ramesh

2007-01-01

193

Modulation of cortical activity as a result of voluntary postural sway direction: an EEG study  

PubMed Central

There is increasing evidence demonstrating the role of the cerebral cortex in human postural control. Modulation of EEG both in voltage and frequency domains has been observed preceding and following self-paced postural movements and those induced by external perturbations. The current study set out to provide additional evidence regarding the role of cerebral cortex in human postural control by specifically examining modulation of EEG as a function of postural sway direction. Twelve neurologically normal subjects were instructed to produce self-paced voluntary postural sways in the anterior-posterior (AP) and medial-lateral (ML) directions. The center of pressure dynamics and EEG both in voltage and frequency domains were extracted by averaging and Morlet wavelet techniques, respectively. The amplitude of movement-related cortical potentials (MRCP) was significantly higher preceding ML sways. Also, time-frequency wavelet coefficients (TF) indicated differential modulation of EEG within alpha, beta and gamma bands as a function of voluntary postural sway direction. Thus, ML sway appear to be more difficult and energy demanding tasks than the AP sway as reflected in differential modulation of EEG. These results are discussed within the conceptual framework of differential patterns of brain activation as a result of postural task complexity. PMID:18639613

Slobounov, Semyon; Hallett, Mark; Cao, Cheng; Newell, Karl

2008-01-01

194

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

195

A Developmental Transcriptional Network for Maize Defines Coexpression Modules1[C][W][OA  

PubMed Central

Here, we present a genome-wide overview of transcriptional circuits in the agriculturally significant crop species maize (Zea mays). We examined transcript abundance data at 50 developmental stages, from embryogenesis to senescence, for 34,876 gene models and classified genes into 24 robust coexpression modules. Modules were strongly associated with tissue types and related biological processes. Sixteen of the 24 modules (67%) have preferential transcript abundance within specific tissues. One-third of modules had an absence of gene expression in specific tissues. Genes within a number of modules also correlated with the developmental age of tissues. Coexpression of genes is likely due to transcriptional control. For a number of modules, key genes involved in transcriptional control have expression profiles that mimic the expression profiles of module genes, although the expression of transcriptional control genes is not unusually representative of module gene expression. Known regulatory motifs are enriched in several modules. Finally, of the 13 network modules with more than 200 genes, three contain genes that are notably clustered (P < 0.05) within the genome. This work, based on a carefully selected set of major tissues representing diverse stages of maize development, demonstrates the remarkable power of transcript-level coexpression networks to identify underlying biological processes and their molecular components. PMID:23388120

Downs, Gregory S.; Bi, Yong-Mei; Colasanti, Joseph; Wu, Wenqing; Chen, Xi; Zhu, Tong; Rothstein, Steven J.; Lukens, Lewis N.

2013-01-01

196

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

197

Endogenous dopaminergic modulation of the lamprey spinal locomotor network.  

PubMed

The lamprey spinal cord contains three dopaminergic systems. The most extensive is the ventromedial plexus in which dopamine is co-localized with 5-HT and tachykinins. In this study we have investigated the effects of endogenously released dopamine on NMDA-induced spinal activity, and for comparison applied dopamine exogenously. The dopamine reuptake blocker bupropion increases the levels of extracellular dopamine in the spinal cord. Bath application of bupropion during ongoing NMDA-induced network activity (around 2 Hz) resulted in an initial increase of the burst rate followed by a transitional phase with the fast rhythm superimposed on a much slower ventral root burst activity (below 0.25 Hz). Finally only the slow rhythm was observed. The same response pattern with regard to the fast and slow rhythms was observed when dopamine was slowly perfused over the spinal cord, resulting in a gradual build-up of dopamine concentration. At low constant dopamine concentrations, however, an increased burst frequency was maintained, but at somewhat higher concentrations the fast burst rate instead was decreased. The degree of modulation of fictive locomotion by dopamine was also tested at low and high NMDA concentrations. Dopamine was found to exert stronger effects at low NMDA concentrations. With high NMDA concentrations dopamine did not induce the transition phase or the slow ventral root bursting. The slow alternating ventral root bursts, induced by bupropion, shifted to synchronized activity when glycinergic synaptic transmission was blocked with strychnine, testifying that the alternation depended on a crossed glycinergic action as previously shown for the fast rhythm. PMID:12706243

Svensson, Erik; Woolley, Joshua; Wikström, Martin; Grillner, Sten

2003-04-25

198

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

PubMed

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

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

2011-12-01

199

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

E-print Network

-Signal Direct Modulation of Extended Cavity Semiconductor Lasers with Dispersive Loss L. Ramunno and J. E. Sipe, the Ontario Graduate Scholarship Pro- gram for Science and Technology, and the Walter C. Sumner Foundation field resulting from the direct modulation of the bias current density across the diode J(t). (b

Sipe,J. E.

200

Power Allocation and Error Performance of Distributed Unitary Space–Time Modulation in Wireless Relay Networks  

Microsoft Academic Search

A wireless relay network allows relays to cooperate with each other, emulate a virtual array of transmit antennas, and perform distributed space-time modulation of the source signals. In this paper, two types of relay networks are considered-one with no channel state information (CSI) (i.e., the noncoherent networks) and one with only the information of the relay-to-destination channels (i.e., the partially

Duy H. N. Nguyen; Ha H. Nguyen; Hoang Duong Tuan

2009-01-01

201

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

PubMed

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

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

2014-11-26

202

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

203

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

PubMed

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

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

2014-01-10

204

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

PubMed

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

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

2014-10-01

205

Name of Module: Next Generation Network Project 1  

E-print Network

as a Service, virtualization, Machine-2-Machine, Evolved Packet Core and IP Multimedia Subsystem circuit-switched telecommunication networks, IP based Next Generation Networks (NGNs). Furthermore, Identity and Policy Management, Converged Instant Messaging, IP-TV, video streaming, Infrastructure

Wichmann, Felix

206

Name of Module: Next Generation Network Project 2  

E-print Network

as a Service, virtualization, Machine-2-Machine, Evolved Packet Core and IP Multimedia Subsystem circuit-switched telecommunication networks, IP based Next Generation Networks (NGNs). Furthermore, Identity and Policy Management, Converged Instant Messaging, IP-TV, video streaming, Infrastructure

Wichmann, Felix

207

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

PubMed Central

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

Klein, Alexander; Witzel, Oliver; Ebert, Volker

2014-01-01

208

Arabidopsis gene co-expression network and its functional modules  

Microsoft Academic Search

Background: Biological networks characterize the interactions of biomolecules at a systems-level. One important property of biological networks is the modular structure, in which nodes are densely connected with each other, but between which there are only sparse connections. In this report, we attempted to find the relationship between the network topology and formation of modular structure by comparing gene co-expression

Linyong Mao; John L. Van Hemert; Sudhansu Dash; Julie A. Dickerson

2009-01-01

209

Writing and erasing of temporal cavity solitons by direct phase modulation of the cavity driving field  

E-print Network

Temporal cavity solitons (CSs) are persisting pulses of light that can manifest themselves in continuously driven passive resonators, such as macroscopic fiber ring cavities and monolithic microresonators. Experiments so far have demonstrated two techniques for their excitation, yet both possess drawbacks in the form of system complexity or lack of control over soliton positioning. Here we experimentally demonstrate a new CS writing scheme that alleviates these deficiencies. Specifically, we show that temporal CSs can be excited at arbitrary positions through direct phase modulation of the cavity driving field, and that this technique also allows existing CSs to be selectively erased. Our results constitute the first experimental demonstration of temporal cavity soliton excitation via direct phase modulation, as well as their selective erasure (by any means). These advances reduce the complexity of CS excitation and could lead to controlled pulse generation in monolithic microresonators.

Jang, Jae K; Murdoch, Stuart G; Coen, Stephane

2015-01-01

210

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

SciTech Connect

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

None

2012-01-30

211

Transcriptionally Regulated Cell Adhesion Network Dictates Distal Tip Cell Directionality  

PubMed Central

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

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

2015-01-01

212

Scale and directional dependence of macrodispersivities in colonnade networks  

NASA Astrophysics Data System (ADS)

Macrodispersion in discrete colonnade network models is investigated using a series of Monte Carlo type numerical experiments. The numerical simulations consider fluid flow and advective transport through a square flow region of a two-dimensional network of hexagonal colonnades. Macrodispersivities are calculated as a function of the scale and orientation of the square flow region within the larger, parent geometry. Particle tracking, with flux-weighted tracer injection and monitoring, is used to generate experimental residence time distributions (RTDs). The method of moments is used to characterize the longitudinal tracer spreading. The simulated RTDs are utilized to examine the macrodispersive behavior in colonnade networks (column diameter, 1 m) with lognormally distributed fracture apertures (b, in millimeters). The network models are assumed to consist of open fractures with ?ln b = -1.945 and ?ln b = 0.896; this translates to an equivalent continuum log-conductivity variance (?ln K2) of 3.67. Based on an ensemble average of 100 realizations, the slope for spatial variance versus scale of observation ranges from 3.15 to 3.36 m for varying orientations of the hydraulic gradient. For ensemble-averaged data, the varying orientations appear to have little effect on the macrodispersive behavior. For single-realization experiments, the computed macrodispersivities are directionally dependent at a length scale as large as 30 times the column diameter (and probably much beyond). The computed asymptotic and preasymptotic macrodispersivities are compared with available stochastic solutions for two-dimensional isotropic heterogeneity in the horizontal plane. The ensemble-based numerical data are in excellent agreement with the solutions of Dagan (1984, 1988) and Gelhar and Axness (1983). However, for individual realizations, nonergodic behavior is clearly apparent in the near-source, evolving region of transport, and the numerical data are quite variable between realizations. The study provides important insight on applicability of stochastic continuum theories to discrete colonnade network models having ?ln K2 much greater than 1.

Khaleel, Raziuddin

1994-12-01

213

Substance P modulates NMDA responses and causes long-term protein synthesis-dependent modulation of the lamprey locomotor network.  

PubMed

Tachykinin immunoreactivity is found in a ventromedial spinal plexus in the lamprey. Neurons in this plexus project bilaterally and are thus in a position to modulate locomotor networks on both sides of the spinal cord. We have examined the effects of the tachykinin substance P on NMDA-evoked locomotor activity. Brief (10 min) application of tachykinin neuropeptides results in a prolonged concentration-dependent (>24 hr) modulation of locomotor activity, shown by the increased burst frequency and more regular burst activity. These effects are blocked by the tachykinin antagonist spantide II. There are at least two phases to the burst frequency modulation. An initial phase (approximately 2 hr) is associated with the protein kinase C-dependent potentiation of cellular responses to NMDA. The long-lasting phase (>2 hr) appears to be protein synthesis-dependent, with protein synthesis inhibitors causing the increased burst frequency to recover after washing for 2-3 hr. The modulation of the burst regularity is caused by a separate effect of tachykinins, because unlike the burst frequency modulation it does not require the modulation of NMDA receptors for its induction and is blocked by H8, an inhibitor of cAMP- and cGMP-dependent protein kinases. The effects of substance P were mimicked by the dopamine D2 receptor antagonist eticlopride. The effects of eticlopride were blocked by the tachykinin antagonist spantide II, suggesting that eticlopride may endogenously release tachykinins. Because locomotor activity in vitro corresponds to that during swimming in intact animals, we suggest that endogenously released tachykinins will result in prolonged modulation of locomotor behavior. PMID:9614253

Parker, D; Zhang, W; Grillner, S

1998-06-15

214

Delta Modulation for Multivariable Centralized Linear Networked Controlled Systems  

E-print Network

], adaptive delta modulation [6], and gain scheduling multi-bit coding [8]. Except for the trivial case, we provide an estimation of the stability attraction domain, and we give some simulation results

Paris-Sud XI, Université de

215

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

216

Superconducting Wire Network under Spatially Modulated Magnetic Field  

E-print Network

magnet system Sample solenoid coil Solenoid coil Split coil mK1~K3.1~min TT · Temperature Liq. 4He Modulation Checkerboard Pattern· SC/FM Hybrid System Stray field from FM dot field modulation Control ­ 120 �120 cells Co dots ­ 200 nm � 130 nm ­ 80 nm thick #12;Experiment ·Magnetic Field Cross coil

Katsumoto, Shingo

217

Advanced MCM-D micro-processor module for ATM wide-area network switching systems  

Microsoft Academic Search

This paper describes an advanced MCM-D microprocessor module and its high-performance cooling technologies for an ATM-WAN (wide area network) switching system. The MCM-D is fabricated on 2 Si-substrates using the stacking RAM technique to reduce module size. The MCM has 4-layer Si substrates, a microprocessor LSI, 4 ASIC-LSIs, 12 high-speed SRAMs, an FPGA and bus-driver ICs. By using the stacking

T. Kawamura; N. Yamanaka; K. Kaizu; A. Harada; Z. Yashiro

1998-01-01

218

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

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

219

Motion-Indicated Interest Dissemination With Directional Antennas for Wireless Sensor Networks With Mobile Sinks  

Microsoft Academic Search

Introducing mobile sinks into wireless sensor networks improves energy efficiency and prolongs network lifetime. Mobile sinks are also in demand in many sensor network applications. However, sink mobility causes frequent topology changes, resulting in high packet loss rate and poor energy efficiency. A directional-antenna-assisted reactive routing protocol, namely, interest dissemination with directional antennas (IDDA), is proposed to solve this problem.

Yiqun Wu; Lin Zhang; Yihong Wu; Zhisheng Niu

2009-01-01

220

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

221

Cartography of complex networks: modules and universal roles  

Microsoft Academic Search

Integrative approaches to the study of complex systems demand that one knows the manner in which the parts comprising the system are connected. The structure of the complex network defining the interactions provides insight into the function and evolution of the components of the system. Unfortunately, the large size and intricacy of these networks implies that such insight is usually

Roger Guimerà; Luís A Nunes Amaral

2005-01-01

222

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

223

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

224

Reach extension in 10Gb\\/s directly modulated transmission systems using asymmetric and narrowband optical filtering  

Microsoft Academic Search

Optical filtering has been used to extend the reach of directly modulated laser in 10Gb\\/s WDM systems via two separate mechanisms: narrowing the broadened spectrum, and converting frequency modulation into useful amplitude modulation. We investigate in detail, the impact of asymmetric and narrowband optical filtering at the transmitter or receiver. Experimental demonstrations for both shorter distance and long-haul like transmission

L.-S. Yan; Y. Wang; B. Zhang; C. Yu; J. McGeehan; L. Paraschis; A. E. Willner

2005-01-01

225

Directed Dynamic Small-World Network Model for Worm Epidemics in Mobile ad hoc Networks  

NASA Astrophysics Data System (ADS)

We investigate the worm spreading process in mobile ad hoc networks with a susceptible-infected-recovered model on a two-dimensional plane. A medium access control mechanism operates within it, inhibiting transmission and relaying a message by using other nodes inside the node's transmitting circle during speaking. We measure the rewiring probability p with the transmitting range r and the average relative velocity v¯ of the moving nodes, and map the problem into a directed dynamic small-world network. A new scaling relation for the recovered portion of the nodes reveals the effect caused by geometric distance, which has been ignored by previous models.

Zhu, Chen-Ping; Wang, Li; Liu, Xiao-Ting; Yan, Zhi-Jun

2012-01-01

226

Femtosecond pulse shaping directly in the mid-IR using acousto-optic modulation  

NASA Astrophysics Data System (ADS)

Pulse shaping directly in the mid-IR is accomplished by using a germanium acousto-optic modulator (Ge AOM) capable of programmable phase and amplitude modulation for IR light between 2 and 18 ?m. Shaped waveforms centered at 4.9 ?m are demonstrated in both the frequency and the time domains. With a 50% throughput efficiency, the Ge AOM can generate much more intense pulses with higher resolution than can indirect shaping methods. Furthermore, the phase stability of the shaped pulse proved sufficient for cross correlation with unshaped mid-IR pulses. Thus, phase- and amplitude-tailored pulses can now be readily incorporated into phase-sensitive experiments, such as heterodyned 2D IR spectroscopy.

Shim, Sang-Hee; Strasfeld, David B.; Fulmer, Eric C.; Zanni, Martin T.

2006-03-01

227

Femtosecond pulse shaping directly in the mid-IR using acousto-optic modulation.  

PubMed

Pulse shaping directly in the mid-IR is accomplished by using a germanium acousto-optic modulator (Ge AOM) capable of programmable phase and amplitude modulation for IR light between 2 and 18 microm. Shaped waveforms centered at 4.9 microm are demonstrated in both the frequency and the time domains. With a 50% throughput efficiency, the Ge AOM can generate much more intense pulses with higher resolution than can indirect shaping methods. Furthermore, the phase stability of the shaped pulse proved sufficient for cross correlation with unshaped mid-IR pulses. Thus, phase- and amplitude-tailored pulses can now be readily incorporated into phase-sensitive experiments, such as heterodyned 2D IR spectroscopy. PMID:16544641

Shim, Sang-Hee; Strasfeld, David B; Fulmer, Eric C; Zanni, Martin T

2006-03-15

228

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

E-print Network

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

Papp, Dávid

2013-01-01

229

Low-dispersion penalty directly modulated 1.55-um DFB lasers with complex coupled gratings  

NASA Astrophysics Data System (ADS)

Prior to the full maturation of electro-absorption modulated laser technology, directly modulated 1.55 micrometer distributed feedback lasers will continue to play a central role in long haul, high bit rate, optical communications systems. Maintaining a competitive advantage, however, requires that these devices be optimized for long fiber length transmission, high power, and low cost. In this talk we discuss the design elements needed to accomplish this. Focus is placed on factors leading to reduction of the linewidth enhancement factor, (alpha) . In particular, the role played by complex gratings is examined. We demonstrate typical cw (alpha) values of 1.65 can be achieved in a robust and manufacturable device. This device is shown to readily serve 2.5 Gb/s applications with span lengths of 200 km (approximately 3600 ps/nm).

Ketelsen, Leonard J. P.; Eng, L.; Kim, Il; Grenko, J. A.; Sutryn, D.; Wessel, Thomas; Chakrabarti, U. K.; Coblentz, Debbie L.; Hartman, Robert L.

1996-04-01

230

Performance evaluation of ePTFE and PVDF flat-sheet module direct contact membrane distillation.  

PubMed

This paper reports experiments using a flat-sheet module with 0.18 approximately 0.45 microm ePTFE (expanded polytetrafluoroethylene) and PVDF (polyvinylidene fluoride) membranes to show the effects of membrane properties, salt concentration and fluid hydrodynamics on the permeate flux and salt rejection of DCMD (direct contact membrane distillation). A theoretical prediction of the permeate flux was carried out, and was in close agreement with the experimental results. In addition, the energy integration of the process was also analyzed in order to evaluate module design to increase energy efficiency. According to the simulated results of the energy integration design, a combination of simultaneous cooling of the permeate stream and an additional heat exchanger to lower the temperature of the permeate stream not only enhances the MD flux, but also reduces energy consumption. PMID:20651439

Chuang, Ching-Jung; Tung, Kuo-Lun; Fan, Yang-Hsiang; Ho, Chii-Dong; Huang, James

2010-01-01

231

Hierarchical structure and modules in the Escherichia coli transcriptional regulatory network revealed by a new top-down approach  

Microsoft Academic Search

BACKGROUND: Cellular functions are coordinately carried out by groups of genes forming functional modules. Identifying such modules in the transcriptional regulatory network (TRN) of organisms is important for understanding the structure and function of these fundamental cellular networks and essential for the emerging modular biology. So far, the global connectivity structure of TRN has not been well studied and consequently

Hong-Wu Ma; Jan Buer; An-ping Zeng

2004-01-01

232

An in silico method for detecting overlapping functional modules from composite biological networks  

Microsoft Academic Search

BACKGROUND: The ever-increasing flow of gene expression and protein-protein interaction (PPI) data has assisted in understanding the dynamics of the cell. The detection of functional modules is the first step in deciphering the apparent modularity of biological networks. However, most network-partitioning algorithms consider only the topological aspects and ignore the underlying functional relationships. RESULTS: In the current study we integrate

Ioannis A Maraziotis; Konstantina Dimitrakopoulou; Anastasios Bezerianos

2008-01-01

233

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

Microsoft Academic Search

This paper presents realistic simulation modules to assess characteristics of multi-transceiver free-space-optical (FSO) mobile ad-hoc networks. We start with a physical propagation model for FSO communications in the context of mobile ad-hoc networks (MANETs). We specifically focus on the drop in power of the light beam and probability of error in the decoded signal due to a number of parameters

Mehmet Bilgi; Murat Yuksel

2010-01-01

234

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

SciTech Connect

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

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

2014-01-15

235

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

236

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

237

Superconducting Wire Network under Spatially Modulated Magnetic Field  

E-print Network

with a regular array of ferromagnetic Co dots. The network pattern consisted of 120 Ã? 120 unit cells, made of Al of the super/normal phase boundary Tc() for different values of . The magnetoresistance was measured

Iye, Yasuhiro

238

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

239

Physical Module Networks: an integrative approach for reconstructing transcription regulation  

E-print Network

Motivation: Deciphering the complex mechanisms by which regulatory networks control gene expression remains a major challenge. While some studies infer regulation from dependencies between the expression levels of putative ...

Regev, Aviv

240

An improved scheme for direct adaptive control of dynamical systems using backpropagation neural networks  

Microsoft Academic Search

This paper presents an improved direct control architecture for the on-line learning control of dynamical systems using backpropagation neural networks. The proposed architecture is compared with the other direct control schemes. In this scheme the neural network interconnection strengths are updated based on the output error of the dynamical system directly, rather than using a transformed version of the error

K. P. Venugopal; R. Sudhakar; A. S. Pandya

1995-01-01

241

Capacity analysis of wireless mesh networks with omni or directional antennas  

E-print Network

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

Jia, Xiaohua

242

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

E-print Network

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

Das, Samir R.

243

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

E-print Network

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

Gleeson, James P.

244

Unconditionally Reliable Message Transmission in Directed Neighbour Networks  

E-print Network

ring. Other examples include the Bluetooth or IEEE 802.11 network. Yet another motivation for the study-recipient networks arise frequently in practice; for instance, a local area network like an Ethernet bus or a token

245

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

246

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

NASA Astrophysics Data System (ADS)

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

Saito, Yuika; Fujita, Katsumasa

2015-01-01

247

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

248

Hofstadter butterflies in a modulated magnetic field: Superconducting wire network with magnetic decoration  

E-print Network

Hofstadter butterflies in a modulated magnetic field: Superconducting wire network with magnetic April 2004; published 29 October 2004) Hofstadter butterfly spectra of tight-binding electron systems butterfly, have since been calculated for a variety of lattices,3­5 and they have been discussed in various

Iye, Yasuhiro

249

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

250

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

SciTech Connect

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

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

2012-08-15

251

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

252

Neural Networks For Demodulation Of Phase-Modulated Signals  

NASA Technical Reports Server (NTRS)

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

Altes, Richard A.

1995-01-01

253

Modulating the Precision of Recurrent Bursts in Cultured Neural Networks  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

254

Impact of multivariate granger causality analyses with embedded dimension reduction on network modules.  

PubMed

High dimensional functional MRI data in combination with a low temporal resolution imposes computational limits on classical Granger Causality analyses with respect to a large-scale representations of functional interactions in the brain. To overcome these limitations and exploit information inherent in resulting brain connectivity networks at the large scale, we propose a multivariate Granger Causality approach with embedded dimension reduction. Using this approach, we computed binary connectivity networks from resting state fMRI images and analyzed them with respect to network module structure, which might be linked to distinct brain regions with an increased density of particular interaction patterns as compared to inter-module regions. As a proof of concept, we show that the modular structure of these large-scale connectivity networks can be recovered. These results are promising since further analysis of large-scale brain network partitions into modules might prove valuable for understanding and tracing changes in brain connectivity at a more detailed resolution level than before. PMID:25570572

Schmidt, Christoph; Pester, Britta; Nagarajan, Mahesh; Witte, Herbert; Leistritz, Lutz; Wismueller, Axel

2014-08-01

255

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

256

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

SciTech Connect

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

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

2003-08-01

257

In situ elasticity modulation with dynamic substrates to direct cell phenotype  

PubMed Central

Microenvironment elasticity influences critical cell functions such as differentiation, cytoskeletal organization, and process extension. Unfortunately, few materials allow elasticity modulation in real-time to probe its direct effect on these dynamic cellular processes. Here, a new approach is presented for the photochemical modulation of elasticity within the cell's microenvironment at any point in time. A photodegradable hydrogel was irradiated and degraded under cytocompatible conditions to generate a wide range of elastic moduli similar to soft tissues and characterized using rheometry and atomic force microscopy (AFM). The effect of the elastic modulus on valvular interstitial cell (VIC) activation into myofibroblasts was explored. In these studies, gradient samples were used to identify moduli that either promote or suppress VIC myofibroblastic activation. With this knowledge, VICs were cultured on a high modulus, activating hydrogel substrate, and uniquely, results show that decreasing the substrate modulus with irradiation reverses this activation, demonstrating that myofibroblasts can be de-activated solely by changing the modulus of the underlying substrate. This finding is important for the rational design of biomaterials for tissue regeneration and offers insight into fibrotic disease progression. These photodegradable hydrogels demonstrate the capability to both probe and direct cell function through dynamic changes in substrate elasticity. PMID:19788947

Kloxin, April M.; Benton, Julie A.; Anseth, Kristi S.

2009-01-01

258

Reverse engineering module networks by PSO-RNN hybrid modeling  

Microsoft Academic Search

BACKGROUND: Inferring a gene regulatory network (GRN) from high throughput biological data is often an under-determined problem and is a challenging task due to the following reasons: (1) thousands of genes are involved in one living cell; (2) complex dynamic and nonlinear relationships exist among genes; (3) a substantial amount of noise is involved in the data, and (4) the

Yuji Zhang; Jianhua Xuan; Benildo G de los Reyes; Robert Clarke; Habtom W Ressom

2009-01-01

259

RESEARCH Open Access Herb network construction and co-module  

E-print Network

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

Li, Shao

260

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

261

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

Microsoft Academic Search

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

M. Milanovic; Bojan Dobaj

2000-01-01

262

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

PubMed Central

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

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

2014-01-01

263

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

264

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

265

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

PubMed Central

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

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

2013-01-01

266

A testbed to emulate next-generation directional RF and free-space optical tactical networks  

Microsoft Academic Search

The tactical edge network emulation tool (TENET) hardware integration system (THIS) is designed to characterize higher layer responses to the dynamic physical layer topology of a tactical network utilizing directional communication links. THIS emulates the mobile, tactical, network environment using the hardware in a static infrastructure. MATLAB-based tools implement the TENET emulation to simulate mobility induced link fragility, and the

William M. Turner; Daniel J. Tebben; Jason R. Madsen; Anurag Dwivedi

2009-01-01

267

Expectancy constraints in degraded speech modulate the language comprehension network.  

PubMed

In speech comprehension, the processing of auditory information and linguistic context are mutually dependent. This functional magnetic resonance imaging study examines how semantic expectancy ("cloze probability") in variably intelligible sentences ("noise vocoding") modulates the brain bases of comprehension. First, intelligibility-modulated activation along the superior temporal sulci (STS) was extended anteriorly and posteriorly in low-cloze sentences (e.g., "she weighs the flour") but restricted to a mid-superior temporal gyrus/STS area in more predictable high-cloze sentences (e.g., "she sifts the flour"). Second, the degree of left inferior frontal gyrus (IFG) (Brodmann's area 44) involvement in processing low-cloze constructions was proportional to increasing intelligibility. Left inferior parietal cortex (IPC; angular gyrus) activation accompanied successful speech comprehension that derived either from increased signal quality or from semantic facilitation. The results show that successful decoding of speech in auditory cortex areas regulates language-specific computation (left IFG and IPC). In return, semantic expectancy can constrain these speech-decoding processes, with fewer neural resources being allocated to highly predictable sentences. These findings offer an important contribution toward the understanding of the functional neuroanatomy in speech comprehension. PMID:19561061

Obleser, Jonas; Kotz, Sonja A

2010-03-01

268

Ranking algorithms on directed configuration networks Ningyuan Chen  

E-print Network

Litvak University of Twente Mariana Olvera-Cravioto Columbia University October 12, 2014 Abstract network such as the Internet, the World Wide Web, and other social and biological networks, has been a hot

Olvera-Cravioto, Mariana

269

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

2015-01-01

270

Sex-specific modulation of gene expression networks in murine hypothalamus.  

PubMed

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

271

Current-mode implementation of processing modules in ART-based neural networks  

NASA Astrophysics Data System (ADS)

This paper describes implementation of neural network processing layers using basic current-mode operating modules. The research work has been focused on the implementation of neural networks based on the Adaptive Resonance Theory, developed by S. Grossberg and G.A. Carpenter. The ART-based neural network whose operating modules have been choosen for development is the one called MART, proposed by F. Delgado, because of its complex architecture, auto--adaptive self-learning process, able to discard unmeaningful cathegories. Our presentation starts introducing the behaviour of MART with an analysis of its structure. The development described by this research work is focused on the monochannel block included in the main signal processing part of the MART neural network. The description of the computing algorithm of the layers inside a monochannel block are also provided in order to show what operational current-mode modules are needed (multiplier, divider, square-rooter, adder, substractor, absolute value, maximum and minimum evaluator...). Descriptions at schematic and layout levels of all the processing layers are given. All of them have been designed using AMS 0.35 micron technology with a supply voltage of 3.3 volts. The modules are designed to deal with input currents in the range of 20 to 50 microamps, showing a lineal behaviour and an output error of less than 10%, which is good enough for neural signal processing systems. The maximum frecuency of operation is around 200 kHz. Simulation results are included to show that the operation performed by the hardware designed matches the behaviour described by the MART neural network. For testing purposes we show the design of a monochannel block hardware implementation restricted to five inputs and three cathegories.

Lopez-Alcantud, Jose-Alejandro; Hauer, Hans; Diaz-Madrid, Jose-Angel; Ruiz-Merino, Ramon

2003-04-01

272

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

273

Conservation laws for voter-like models on random directed networks  

E-print Network

Conservation laws for voter-like models on random directed networks M. ´Angeles Serrano1 quantity. The conservation laws obtained in the thermodynamic limit for a system that does not order. #12;Conservation laws for voter-like models on random directed networks 2 1. Introduction Conservation

Stadler, Peter F.

274

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

E-print Network

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

Kranakis, Evangelos

275

A distributed scheduler for airborne backbone networks with directional antennas  

Microsoft Academic Search

Airborne backbone networks are useful in tactical applications to interconnect sub-networks. A major challenge in such networks, normally comprising large numbers of highly mobile nodes, is the design of the medium access control (MAC) and routing protocols. We propose integration of MAC and routing functions, which use the attributes of a clustering scheme that addresses scalability. The reactive routing protocol

William Huba; Nicholas Martin; Yamin Al-Mousa; Chukwuchebem Orakwue; Nirmala Shenoy

2011-01-01

276

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

277

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

278

Angular MAC: a framework for directional antennas in wireless mesh networks  

Microsoft Academic Search

Capacity of wireless mesh networks can be enhanced through the use of smart directional antennas, which not only enable nodes\\u000a to have high quality links but also increase network throughput by allowing spatial reuse. This paper proposes a new MAC protocol\\u000a and framework, called Angular MAC (ANMAC) that enables directional antennas in wireless mesh networks. The protocols and algorithms\\u000a of

Erdem Ulukan; Özgür Gürbüz

2008-01-01

279

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

PubMed Central

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

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

2012-01-01

280

Guided-wave optoelectronic clock-distribution networks on multichip modules using MEMS fabrication techniques  

NASA Astrophysics Data System (ADS)

This paper addresses the design, fabrication, and packaging issues of optoelectronic clock distribution networks on multichip modules (MCM) by combining guided-wave optoelectronic interconnect, MCM packaging, and microelectromechanical system fabrication techniques. The proposed prototype employs the silica glass waveguide networks on silicon substrates and innovative I/O coupling method which utilizes the micromachined through-holes across MCM substrates and silicon mirror arrays. Microstructures for I/O coupling have been fabricated using KOH etchants at various processing conditions and the silica glass optical waveguide networks are fabricated using FHD and RIE processes. The four fanout optoelectronic clock distribution networks are prototyped and characterized by measuring the overall insertion losses and the power equalities at the fanout nodes.

Koh, Seungug; Suh, Sung-Dong; Wu, Danjin; Lantz, Mark

1998-05-01

281

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

282

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

PubMed

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

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

2014-11-01

283

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

PubMed

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

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

2014-07-01

284

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

285

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

286

Ultrawideband direct chaotic wireless communication systems and sensor networks  

Microsoft Academic Search

The ultrawideband communication facilities where chaotic radio pulses are used as an information carrier are considered. As perspective applications of such systems the wireless sensor networks are discussed.

A. S. Dmitriev; E. V. Efremova; A. V. Kletsov; L. V. Kuzmin; N. V. Rumyantsev

2010-01-01

287

CO2 directly modulates connexin 26 by formation of carbamate bridges between subunits  

PubMed Central

Homeostatic regulation of the partial pressure of CO2 (PCO2) is vital for life. Sensing of pH has been proposed as a sufficient proxy for determination of PCO2 and direct CO2-sensing largely discounted. Here we show that connexin 26 (Cx26) hemichannels, causally linked to respiratory chemosensitivity, are directly modulated by CO2. A ‘carbamylation motif’, present in CO2-sensitive connexins (Cx26, Cx30, Cx32) but absent from a CO2-insensitive connexin (Cx31), comprises Lys125 and four further amino acids that orient Lys125 towards Arg104 of the adjacent subunit of the connexin hexamer. Introducing the carbamylation motif into Cx31 created a mutant hemichannel (mCx31) that was opened by increases in PCO2. Mutation of the carbamylation motif in Cx26 and mCx31 destroyed CO2 sensitivity. Course-grained computational modelling of Cx26 demonstrated that the proposed carbamate bridge between Lys125 and Arg104 biases the hemichannel to the open state. Carbamylation of Cx26 introduces a new transduction principle for physiological sensing of CO2. DOI: http://dx.doi.org/10.7554/eLife.01213.001 PMID:24220509

Meigh, Louise; Greenhalgh, Sophie A; Rodgers, Thomas L; Cann, Martin J; Roper, David I; Dale, Nicholas

2013-01-01

288

Shape-Shifting 3D Protein Microstructures with Programmable Directionality via Quantitative Nanoscale Stiffness Modulation.  

PubMed

The ability to shape-shift in response to a stimulus increases an organism's survivability in nature. Similarly, man-made dynamic and responsive "smart" microtechnology is crucial for the advancement of human technology. Here, 10-30 ?m shape-changing 3D BSA protein hydrogel microstructures are fabricated with dynamic, quantitative, directional, and angle-resolved bending via two-photon photolithography. The controlled directional responsiveness is achieved by spatially controlling the cross-linking density of BSA at a nanometer lengthscale. Atomic force microscopy measurements of Young's moduli of structures indicate that increasing the laser writing distance at the z-axis from 100-500 nm decreases the modulus of the structure. Hence, through nanoscale modulation of the laser writing z-layer distance at the nanoscale, control over the cross-linking density is possible, allowing for the swelling extent of the microstructures to be quantified and controlled with high precision. This method of segmented moduli is applied within a single microstructure for the design of shape-shifting microstructures that exhibit stimulus-induced chirality, as well as for the fabrication of a free-standing 3D microtrap which is able to open and close in response to a pH change. PMID:25264141

Lee, Mian Rong; Phang, In Yee; Cui, Yan; Lee, Yih Hong; Ling, Xing Yi

2015-02-01

289

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

290

Differential Modulation of Synaptic Strength and Timing Regulate Synaptic Efficacy in a Motor Network  

PubMed Central

Neuromodulators modify network output by altering neuronal firing properties and synaptic strength at multiple sites; however, the functional importance of each site is often unclear. We determined the importance of monoamine modulation of a single synapse for regulation of network cycle frequency in the oscillatory pyloric network of the lobster. The pacemaker kernel of the pyloric network receives only one chemical synaptic feedback, an inhibitory synapse from the lateral pyloric (LP) neuron to the pyloric dilator (PD) neurons, which can limit cycle frequency. We measured the effects of dopamine (DA), octopamine (Oct), and serotonin (5HT) on the strength of the LP?PD synapse and the ability of the modified synapse to regulate pyloric cycle frequency. DA and Oct strengthened, whereas 5HT weakened, LP?PD inhibition. Surprisingly, the DA-strengthened LP?PD synapse lost its ability to slow the pyloric oscillations, whereas the 5HT-weakened LP?PD synapse gained a greater influence on the oscillations. These results are explained by monoamine modulation of factors that determine the firing phase of the LP neuron in each cycle. DA acts via multiple mechanisms to phase-advance the LP neuron into the pacemaker's refractory period, where the strengthened synapse has little effect. In contrast, 5HT phase-delays LP activity into a region of greater pacemaker sensitivity to LP synaptic input. Only Oct enhanced LP regulation of cycle period simply by enhancing LP?PD synaptic strength. These results show that modulation of the strength and timing of a synaptic input can differentially affect the synapse's efficacy in the network. PMID:21047938

Brown, Jessica M.; Kvarta, Mark D.; Lu, Jay Y. J.; Schneider, Lauren R.; Nadim, Farzan; Harris-Warrick, Ronald M.

2011-01-01

291

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

Microsoft Academic Search

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

H. Takesue; T. Sugie

2002-01-01

292

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

293

ABC and IFC: Modules Detection Method for PPI Network  

PubMed Central

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

Lei, Xiujuan; Tian, Jianfang

2014-01-01

294

Inherent directionality explains the lack of feedback loops in empirical networks  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

295

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

PubMed

We explore the hypothesis that the relative abundance of feedback loops in many empirical complex networks is severely reduced owing to the presence of an inherent global directionality. Aimed at quantifying this idea, we propose a simple probabilistic model in which a free parameter ? controls the degree of inherent directionality. Upon strengthening such directionality, the model predicts a drastic reduction in the fraction of loops which are also feedback loops. To test this prediction, we extensively enumerated loops and feedback loops in many empirical biological, ecological and socio-technological directed networks. We show that, in almost all cases, empirical networks have a much smaller fraction of feedback loops than network randomizations. Quite remarkably, this empirical finding is quantitatively reproduced, for all loop lengths, by our model by fitting its only parameter ?. Moreover, the fitted value of ? correlates quite well with another direct measurement of network directionality, performed by means of a novel algorithm. We conclude that the existence of an inherent network directionality provides a parsimonious quantitative explanation for the observed lack of feedback loops in empirical networks. PMID:25531727

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

2014-01-01

296

Inherent directionality explains the lack of feedback loops in empirical networks  

PubMed Central

We explore the hypothesis that the relative abundance of feedback loops in many empirical complex networks is severely reduced owing to the presence of an inherent global directionality. Aimed at quantifying this idea, we propose a simple probabilistic model in which a free parameter ? controls the degree of inherent directionality. Upon strengthening such directionality, the model predicts a drastic reduction in the fraction of loops which are also feedback loops. To test this prediction, we extensively enumerated loops and feedback loops in many empirical biological, ecological and socio-technological directed networks. We show that, in almost all cases, empirical networks have a much smaller fraction of feedback loops than network randomizations. Quite remarkably, this empirical finding is quantitatively reproduced, for all loop lengths, by our model by fitting its only parameter ?. Moreover, the fitted value of ? correlates quite well with another direct measurement of network directionality, performed by means of a novel algorithm. We conclude that the existence of an inherent network directionality provides a parsimonious quantitative explanation for the observed lack of feedback loops in empirical networks. PMID:25531727

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

2014-01-01

297

Direct frequency modulation of vapor phase transported distributed feedback semiconductor lasers  

SciTech Connect

The frequency modulation (FM) due to injection current modulation of vapor phase transported distributed feedback (VPT DFB) semiconductor lasers is measured as a function of modulation frequency from 10 kHz to 1 GHz. A large frequency modulation response of 350 MHz/mA is obtained for the modulation frequency range of 10 to 1000 MHz. Demodulation of optical frequency shift keying (FSK) at 560 Mb/s is demonstrated, indicating that frequency modulation due to thermal modulation does not pose a significant limitation at this bit rate or higher. The large FM response together with modulation bandwidths up to 8 GHz makes the VPT DFB laser an attractive source for high bit rate optical FSK transmission.

Vodhanel, R.S.; Cheung, N.K.; Koch, T.L.

1986-04-14

298

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

Microsoft Academic Search

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

Sriram Chellappan; Sanjay Kumar Madria

299

Performance evaluation of multiple access protocols for ad hoc networks using directional antennas  

Microsoft Academic Search

In this paper, we introduce a novel reservation based multiple access protocol for ad hoc networks using directional antennas. First, we investigate the limitations of the extreme reservation schemes, namely omni-directional and directional reservations. We highlight the trade-off between spatial reuse (favors directional reservation) and control\\/data packet collisions (favors omni-directional reservation). Next, we show that the so-called hybrid reservation schemes

Tamer ElBatt; Timothy Anderson; Bo Ryu

2003-01-01

300

Non-coplanar beam direction optimization for intensity-modulated radiotherapy  

NASA Astrophysics Data System (ADS)

An algorithm for the optimization of the direction of intensity-modulated beams is presented. Although the global optimum dose distribution cannot be predicted, usually a large number of equivalent beam configurations exists. This degeneracy facilitates beam direction optimization (BDO) through a number of possible approximations and because the target set of good beam configurations is very large. Usually, the target volume is accessible through a finite number of paths of little resistance, which are defined by the properties of the objective function and the global optimum dose distribution. Since these paths can be occupied by a finite number of beams, it is reasonable to assume that a minimum number of beams for a configuration that is degenerate to the global optimum exists. Efficiency of the BDO will be characterized by detecting this degeneracy threshold. Beam configurations are altered by adding and deleting beams. A fast exhaustive (up to 3500 non-coplanar orientations) search finds beam directions that improve a configuration. Redundant beams of a configuration can be identified by a fast criterion based on second-order derivative information of the objective function. This offers a fast means of iteratively substituting redundant beams from a configuration. Inferior stationary states can be evaded by adding more beams than the desired number to the current configuration, followed by the subsequent cancellation of superfluous beams. The significance of BDO is examined in a coplanar and a non-coplanar test case. The existence of a threshold number for the minimum configuration and its dependence on the complexity of the problem are shown. BDO outperforms manual configurations and equispaced coplanar beam arrangements in both example cases.

Meedt, G.; Alber, M.; Nüsslin, F.

2003-09-01

301

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

302

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

303

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

E-print Network

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

Gupta, Himanshu

304

Energy-efficient Differentiated Directed Diffusion (EDDD) in Wireless Sensor Networks  

E-print Network

the limitation of lacking application contexts for filtering or aggregation. To remedy this, Directed Diffusion1 Energy-efficient Differentiated Directed Diffusion (EDDD) in Wireless Sensor Networks Min Chen is dubbed energy-efficient differentiated directed diffusion (EDDD). Comprehensive simulation experiments

305

An Energy Efficient Power Control Protocol for Ad Hoc Networks Using Directional Antennas  

NASA Astrophysics Data System (ADS)

A wireless ad hoc network is a collection of mobile nodes that can communicate with each other. Typically, nodes employ omnidirectional antennas. The use of directional antennas can increase spatial reuse, reduce the number of hops to a destination, reduce interference, and increase the transmission range in a specific direction. This is because omnidirectional antennas radiate equally in all directions, limiting the transmission range.

Quiroz-Perez, Carlos; Gulliver, T. Aaron

306

2 Fast neighbor positioning and medium access in wireless networks 3 with directional antennas q  

E-print Network

Directional transmission through electronically steer- 46 able beams, sectorized antennas or adaptive antenna1 2 Fast neighbor positioning and medium access in wireless networks 3 with directional antennas q xxxx 11 Keywords: 12 WirelessQ4 access 13 Neighbor positioning 14 Directional antennas 15 Wireless

Koutsopoulos, Iordanis

307

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

PubMed Central

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

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

2014-01-01

308

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

309

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

PubMed

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

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

2014-01-01

310

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

E-print Network

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

Patel, Aniruddh D.

311

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

312

Insightful analysis of carrier PWM algorithms for direct AC-AC matrix converter based on voltage-source converter modules  

Microsoft Academic Search

This paper discusses the carrier PWM algorithms suitable for the direct AC-AC matrix converter composed of three three-phase voltage source converter modules. The relationship between the conjugated and nonconjugated terms from the dyadic matrix control theory and the harmonic performance of input current and output voltage are outlined through extended harmonic analysis. Furthermore, two algorithms that result in a larger

D. O. Neacsu; A. Alistar; M. Kazerani

2002-01-01

313

Direct Information Exchange in Wireless Networks: A Coding Perspective  

E-print Network

information exchange problems. First, algorithms are presented to increase the efficiency of cooperative communication in a network where the clients can communicate with each other through a broadcast channel. These algorithms are designed to minimize...

Ozgul, Damla

2011-10-21

314

Shaping Embodied Neural Networks for Adaptive Goal-directed Behavior  

PubMed Central

The acts of learning and memory are thought to emerge from the modifications of synaptic connections between neurons, as guided by sensory feedback during behavior. However, much is unknown about how such synaptic processes can sculpt and are sculpted by neuronal population dynamics and an interaction with the environment. Here, we embodied a simulated network, inspired by dissociated cortical neuronal cultures, with an artificial animal (an animat) through a sensory-motor loop consisting of structured stimuli, detailed activity metrics incorporating spatial information, and an adaptive training algorithm that takes advantage of spike timing dependent plasticity. By using our design, we demonstrated that the network was capable of learning associations between multiple sensory inputs and motor outputs, and the animat was able to adapt to a new sensory mapping to restore its goal behavior: move toward and stay within a user-defined area. We further showed that successful learning required proper selections of stimuli to encode sensory inputs and a variety of training stimuli with adaptive selection contingent on the animat's behavior. We also found that an individual network had the flexibility to achieve different multi-task goals, and the same goal behavior could be exhibited with different sets of network synaptic strengths. While lacking the characteristic layered structure of in vivo cortical tissue, the biologically inspired simulated networks could tune their activity in behaviorally relevant manners, demonstrating that leaky integrate-and-fire neural networks have an innate ability to process information. This closed-loop hybrid system is a useful tool to study the network properties intermediating synaptic plasticity and behavioral adaptation. The training algorithm provides a stepping stone towards designing future control systems, whether with artificial neural networks or biological animats themselves. PMID:18369432

Chao, Zenas C.; Bakkum, Douglas J.; Potter, Steve M.

2008-01-01

315

Directional MAC Approach for Wireless Body Area Networks  

PubMed Central

Wireless Body Area Networks (WBANs) designed for medical, sports, and entertainment applications, have drawn the attention of academia and industry alike. A WBAN is a special purpose network, designed to operate autonomously to connect various medical sensors and appliances, located inside and/or outside of a human body. This network enables physicians to remotely monitor vital signs of patients and provide real time feedback for medical diagnosis and consultations. The WBAN system can offer two significant advantages: patient mobility due to their use of portable monitoring devices and a location independent monitoring facility. With its appealing dimensions, it brings about a new set of challenges, which we do not normally consider in such small sensor networks. It requires a scalable network in terms of heterogeneous data traffic, low power consumption of sensor nodes, integration in and around the body networking and coexistence. This work presents a medium access control protocol for WBAN which tries to overcome the aforementioned challenges. We consider the use of multiple beam adaptive arrays (MBAA) at BAN Coordinator (BAN_C) node. When used as a BAN_C, an MBAA can successfully receive two or more overlapping packets at the same time. Each beam captures a different packet by automatically pointing its pattern toward one packet while annulling other contending packets. This paper describes how an MBAA can be integrated into a single hope star topology as a BAN_C. Simulation results show the performance of our proposed protocol. PMID:22346602

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

2011-01-01

316

Directional MAC approach for wireless body area networks.  

PubMed

Wireless Body Area Networks (WBANs) designed for medical, sports, and entertainment applications, have drawn the attention of academia and industry alike. A WBAN is a special purpose network, designed to operate autonomously to connect various medical sensors and appliances, located inside and/or outside of a human body. This network enables physicians to remotely monitor vital signs of patients and provide real time feedback for medical diagnosis and consultations. The WBAN system can offer two significant advantages: patient mobility due to their use of portable monitoring devices and a location independent monitoring facility. With its appealing dimensions, it brings about a new set of challenges, which we do not normally consider in such small sensor networks. It requires a scalable network in terms of heterogeneous data traffic, low power consumption of sensor nodes, integration in and around the body networking and coexistence. This work presents a medium access control protocol for WBAN which tries to overcome the aforementioned challenges. We consider the use of multiple beam adaptive arrays (MBAA) at BAN Coordinator (BAN_C) node. When used as a BAN_C, an MBAA can successfully receive two or more overlapping packets at the same time. Each beam captures a different packet by automatically pointing its pattern toward one packet while annulling other contending packets. This paper describes how an MBAA can be integrated into a single hope star topology as a BAN_C. Simulation results show the performance of our proposed protocol. PMID:22346602

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

2011-01-01

317

Modes of direct modulation by taurine of the glutamate NMDA receptor in rat cortex.  

PubMed

Taurine is an endogenous brain substance with robust neuromodulatory and possible neuroprotective properties. Though other mechanisms of action have been reported, its interaction with the NMDA (N-methyl-D-aspartic acid) receptor is undocumented. We investigated taurine's interaction with the NMDA receptor using electrophysiological and receptor binding approaches. The effects of taurine on field potential responses in layer-5 of prelimbic cortex in rat brain slices evoked by single-pulse electrical stimulation of ventral medial cortex were determined. Picrotoxin (80 µM) was present in all control and drug solutions to block the Cl(-) channels associated with the GABA-, taurine-, and strychnine sensitive glycine- receptors. A typical response consisted of an NBQX (2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo-[f]-quinoxaline-7-sulfonamide)-sensitive negative wave (N1) followed by a positive wave (P1) and a broad negativity (N2), both sensitive to dl-AP5 (dl-2-amino-5-phosphonopentanoic acid) inhibition. Taurine exerted a 41.5 ± 8.3% (n = 9) voltage reduction within the late phase of N2. This taurine action was prevented by 100 µM AP5, but not by 10 µM nifedipine, supporting a direct modulation of NMDA receptor function by taurine, without requiring the involvement of the L-type Ca(2+) channel. Taurine did not alter specific [(3)H] MK-801 binding to rat cortical membranes in the presence of glycine or glutamate; but inhibited spermine-potentiated specific [(3)H] MK-801 binding to NMDA receptors by 15-20% in the presence of glycine. In addition, taurine reduced the apparent affinity of the NMDA receptor for glycine (in the presence of spermine) by 10-fold. These results show that taurine interacts directly with the NMDA receptor by multiple mechanisms. PMID:24485893

Chan, Christopher Y; Sun, Herless S; Shah, Sanket M; Agovic, Mervan S; Friedman, Eitan; Banerjee, Shailesh P

2014-04-01

318

A neuronal-specific differentiation protein that directly modulates retinoid receptor transcriptional activation  

PubMed Central

Background The specificity of a nuclear receptor's ability to modulate gene expression resides in its ability to bind a specific lipophilic ligand, associate with specific dimerization partners and bind specific DNA sequences in the promoter regions of genes. This sequence of events appears to be the basis for targeting an additional regulatory complex composed of a variety of protein and RNA components that deliver signals for facilitation or inhibition of the RNA polymerase complex. Characterization of the tissue and cell-specific components of these coregulatory complexes appear to be integral to our understanding of nuclear receptor regulation of transcription. Results A novel yeast screen sensitive to retinoid-X receptor (RXR) transcriptional activation resulted in the isolation of the rat homologue of the mouse NPDC-1 gene. NPDC-1 has been shown to be involved in the control of neural cell proliferation and differentiation, possibly through interactions with the cell cycle promoting transcription factor E2F-1. Although the amino acid sequence of NPDC-1 is highly conserved between mouse, rat and human homologues, their tissue specific expression was seen to vary. A potential for direct protein:protein interaction between NPDC-1, RXR and retinoic acid receptor beta (RAR?) was observed in vitro and NPDC-1 facilitated RXR homodimer and RAR-RXR heterodimer DNA binding in vitro. Expression of NPDC-1 was also observed to repress transcription mediated by retinoid receptors as well as by several other nuclear receptor family members, although not in a universal manner. Conclusions These results suggest that NPDC-1, through direct interaction with retinoid receptors, functions to enhance the transcription complex formation and DNA binding function of retinoid receptors, but ultimately repress retinoid receptor-mediated gene expression. As with NPDC-1, retinoids and their receptors have been implicated in brain development and these data provide a point of convergence for NPDC-1 and retinoid mediation of neuronal differentiation. PMID:14567757

Henry II, Kenneth W; Spencer, Michael L; Theodosiou, Maria; Lou, Dingyuan; Noonan, Daniel J

2003-01-01

319

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

320

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

321

Transcranial direct current stimulation over posterior parietal cortex modulates visuospatial localization  

PubMed Central

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

Wright, Jessica M.; Krekelberg, Bart

2014-01-01

322

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

323

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

E-print Network

Disease-causing mutations usually change the interacting partners of mutant proteins. In this article, we propose that the biological consequences of mutation are directly related to the alteration of corresponding protein protein interaction networks (PPIN). Mutation of Huntingtin (HTT) which causes Huntington's disease (HD) and mutations to TP53 which is associated with different cancers are studied as two example cases. We construct the PPIN of wild type and mutant proteins separately and identify the structural modules of each of the networks. The functional role of these modules are then assessed by Gene Ontology (GO) enrichment analysis for biological processes (BPs). We find that a large number of significantly enriched (p<0.0001) GO terms in mutant PPIN were absent in the wild type PPIN indicating the gain of BPs due to mutation. Similarly some of the GO terms enriched in wild type PPIN cease to exist in the modules of mutant PPIN, representing the loss. GO terms common in modules of mutant and wil...

Basu, Mahashweta; Mohanty, Pradeep K

2013-01-01

324

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

325

Robotic localization of hostile networked radio sources with a directional antenna  

E-print Network

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

Hu, Qiang

2007-04-25

326

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

327

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

328

NRC TLD direct radiation monitoring network. Progress report, October 1997December 1997  

Microsoft Academic Search

This is the final report of the US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network, covering the fourth quarter of 1997. The Network was operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in

Struckmeyer

1998-01-01

329

Identifying progression related disease risk modules based on the human subcellular signaling networks.  

PubMed

Many studies have shown that the structure and dynamics of the human signaling network are disturbed in complex diseases such as coronary artery disease, and gene expression profiles can distinguish variations in diseases since they can accurately reflect the status of cells. Integration of subcellular localization and the human signaling network holds promise for providing insight into human diseases. In this study, we performed a novel algorithm to identify progression-related-disease-risk modules (PRDRMs) among patients of different disease states within eleven subcellular sub-networks from a human signaling network. The functional annotation and literature retrieval showed that the PRDRMs were strongly associated with disease pathogenesis. The results indicated that the PRDRM expression values as classification features had a good classification performance to distinguish patients of different disease states. Our approach compared with the method PageRank had a better classification performance. The identification of the PRDRMs in response to the dynamic gene expression change could facilitate our understanding of the pathological basis of complex diseases. Our strategy could provide new insights into the potential use of prognostic biomarkers and the effective guidance of clinical therapy from the human subcellular signaling network perspective. PMID:25315201

Xie, Ruiqiang; Huang, Hao; Li, Wan; Chen, Binbin; Jiang, Jing; He, Yuehan; Lv, Junjie; ma, Bo; Zhou, Yanyan; Feng, Chenchen; Chen, Lina; He, Weiming

2014-12-01

330

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

331

Precise Temporal Modulation in the Response of the SOS DNA Repair Network in Individual Bacteria  

PubMed Central

The SOS genetic network is responsible for the repair/bypass of DNA damage in bacterial cells. While the initial stages of the response have been well characterized, less is known about the dynamics of the response after induction and its shutoff. To address this, we followed the response of the SOS network in living individual Escherichia coli cells. The promoter activity (PA) of SOS genes was monitored using fluorescent protein-promoter fusions, with high temporal resolution, after ultraviolet irradiation activation. We find a temporal pattern of discrete activity peaks masked in studies of cell populations. The number of peaks increases, while their amplitude reaches saturation, as the damage level is increased. Peak timing is highly precise from cell to cell and is independent of the stage in the cell cycle at the time of damage. Evidence is presented for the involvement of the umuDC operon in maintaining the pattern of PA and its temporal precision, providing further evidence for the role UmuD cleavage plays in effecting a timed pause during the SOS response, as previously proposed. The modulations in PA we observe share many features in common with the oscillatory behavior recently observed in a mammalian DNA damage response. Our results, which reveal a hitherto unknown modulation of the SOS response, underscore the importance of carrying out dynamic measurements at the level of individual living cells in order to unravel how a natural genetic network operates at the systems level. PMID:15954802

2005-01-01

332

Precise temporal modulation in the response of the SOS DNA repair network in individual bacteria.  

PubMed

The SOS genetic network is responsible for the repair/bypass of DNA damage in bacterial cells. While the initial stages of the response have been well characterized, less is known about the dynamics of the response after induction and its shutoff. To address this, we followed the response of the SOS network in living individual Escherichia coli cells. The promoter activity (PA) of SOS genes was monitored using fluorescent protein-promoter fusions, with high temporal resolution, after ultraviolet irradiation activation. We find a temporal pattern of discrete activity peaks masked in studies of cell populations. The number of peaks increases, while their amplitude reaches saturation, as the damage level is increased. Peak timing is highly precise from cell to cell and is independent of the stage in the cell cycle at the time of damage. Evidence is presented for the involvement of the umuDC operon in maintaining the pattern of PA and its temporal precision, providing further evidence for the role UmuD cleavage plays in effecting a timed pause during the SOS response, as previously proposed. The modulations in PA we observe share many features in common with the oscillatory behavior recently observed in a mammalian DNA damage response. Our results, which reveal a hitherto unknown modulation of the SOS response, underscore the importance of carrying out dynamic measurements at the level of individual living cells in order to unravel how a natural genetic network operates at the systems level. PMID:15954802

Friedman, Nir; Vardi, Shuki; Ronen, Michal; Alon, Uri; Stavans, Joel

2005-07-01

333

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

334

The Dioxin receptor modulates Caveolin-1 mobilization during directional migration: role of cholesterol.  

PubMed

BackgroundAdhesion and migration are relevant physiological functions that must be regulated by the cell under both normal and pathological conditions. The dioxin receptor (AhR) has emerged as a transcription factor regulating both processes in mesenchymal, epithelial and endothelial cells. Indirect results suggest that AhR could cooperate not only with additional transcription factors but also with membrane-associated proteins to drive such processes.ResultsIn this study, we have used immortalized and primary dermal fibroblasts from wild type (AhR+/+) and AhR-null (AhR¿/¿) mice to show that AhR modulates membrane distribution and mobilization of caveolin-1 (Cav-1) during directional cell migration. AhR co-immunoprecipitated with Cav-1 and a fraction of both proteins co-localized to detergent-resistant membrane microdomains (DRM). Consistent with a role of AhR in the process, AhR¿/¿cells had a significant reduction in Cav-1 in DRMs. Moreover, high cell density reduced AhR nuclear levels and moved Cav-1 from DRMs to the soluble membrane in AhR+/+but not in AhR¿/¿cells. Tyrosine-14 phosphorylation had a complex role in the mechanism since its upregulation reduced Cav-1 in DRMs in both AhR+/+and AhR¿/¿cells, despite the lower basal levels of Y14-Cav-1 in the null cells. Fluorescence recovery after photobleaching revealed that AhR knock-down blocked Cav-1 transport to the plasma membrane, a deficit possibly influencing its depleted levels in DRMs. Membrane distribution of Cav-1 in AhR-null fibroblasts correlated with higher levels of cholesterol and with disrupted membrane microdomains, whereas addition of exogenous cholesterol changed the Cav-1 distribution of AhR+/+cells to the null phenotype. Consistently, higher cholesterol levels enhanced caveolae-dependent endocytosis in AhR-null cells.ConclusionsThese results suggest that AhR modulates Cav-1 distribution in migrating cells through the control of cholesterol-enriched membrane microdomains. Our study also supports the likely possibility of membrane-related, transcription factor independent, functions of AhR. PMID:25238970

Rey-Barroso, Javier; Alvarez-Barrientos, Alberto; Rico-Leo, Eva; Contador-Troca, María; Carvajal-Gonzalez, José M; Echarri, Asier; Del Pozo, Miguel A; Fernandez-Salguero, Pedro M

2014-09-21

335

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

336

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

337

Modulation of direct pathway striatal projection neurons by muscarinic M4-type receptors.  

PubMed

Models of basal ganglia (BG) function posit a dynamic balance between two classes of striatal projection neurons (SPNs): direct pathway neurons (dSPNs) that facilitate movements, and indirect pathway neurons (iSPNs) that repress movement execution. Two main modulatory transmitters regulate the output of these neurons: dopamine (DA) and acetylcholine (ACh). dSPNs express D1-type DA, M1-and M4-type ACh receptors, while iSPNs express D2-type DA and M1-type ACh receptors. Actions of M1-, D1-, and D2-receptors have been extensively reported, but we still ignore most actions of muscarinic M4-type receptors. Here, we used whole-cell recordings in acutely dissociated neurons, pharmacological tools such as mamba-toxins, and BAC D1or2-eGFP transgenic mice to show that activation of M4-type receptors with bath applied muscarine enhances Ca(2+)-currents through CaV1-channels in dSPNs and not in iSPNs. This action increases excitability of dSPNs after both direct current injection and synaptically driven stimulation. The increases in Ca(2+)-current and excitability were blocked specifically by mamba toxin-3, suggesting mediation via M4-type receptors. M4-receptor activation also increased network activity of dSPNs but not of iSPNs as seen with calcium-imaging techniques. Moreover, actions of D1-type and M4-type receptors may add to produce a larger enhancement of excitability of dSPNs or, paradoxically, oppose each other depending on the order of their activation. Possible implications of these findings are discussed. PMID:25290553

Hernández-Flores, Teresa; Hernández-González, Omar; Pérez-Ramírez, María B; Lara-González, Esther; Arias-García, Mario A; Duhne, Mariana; Pérez-Burgos, Azucena; Prieto, G Aleph; Figueroa, Alejandra; Galarraga, Elvira; Bargas, José

2015-02-01

338

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

PubMed Central

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

Wang, Xin; Castro, Mauro A.

2012-01-01

339

Improved transmission performance of adaptively modulated optical OFDM signals over directly modulated DFB laser-based IMDD links using adaptive cyclic prefix.  

PubMed

The impact of Adaptive Cyclic Prefix (ACP) on the transmission performance of Adaptively Modulated Optical OFDM (AMOOFDM) is explored thoroughly in directly modulated DFB laser-based, IMDD links involving Multimode Fibres (MMFs)/Single-Mode Fibres (SMFs). Three ACP mechanisms are identified, each of which can, depending upon the link properties, affect significantly the AMOOFDM transmission performance. In comparison with AMOOFDM having a fixed cyclic prefix duration of 25%, AMOOFDM with ACP can not only improve the transmission capacity by a factor of >2 (>1.3) for >1000 m MMFs (<80 km SMFs) with 1 dB link loss margin enhancement, but also relax considerably the requirement on the DFB bandwidth. PMID:18575513

Giacoumidis, E; Wei, J L; Jin, X Q; Tang, J M

2008-06-23

340

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

341

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

342

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

PubMed

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

Hong, Sang Wook

2015-01-01

343

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

344

Modulation of adult hippocampal neurogenesis during myelin-directed autoimmune neuroinflammation.  

PubMed

In chronic autoimmune diseases of the central nervous system (CNS) such as multiple sclerosis (MS) clinical signs of cognitive dysfunction have been associated with structural changes in the hippocampus. Moreover, experimental studies indicate that inflammatory responses within the CNS modulate the homeostasis of newborn cells in the adult dentate gyrus (DG). However, it remained open whether such changes happen regardless of the primary immunological target or whether a CNS antigen-directed T lymphocyte-mediated autoimmune response may exert a specific impact. We therefore induced experimental autoimmune encephalomyelitis (EAE), a common model of MS serving as a paradigm for a CNS-specific immune response, by immunizing C57BL/6 mice with encephalitogenic myelin oligodendrocyte glycoprotein (MOG) p35-55. In EAE animals, we found enhanced de novo generation and survival of doublecortin (DCX)-positive immature neurons when compared with controls immunized with CNS-irrelevant antigen (ovalbumine). However, despite activation of neurogenesis, we observed a reduced capacity of these cells to generate mature neurons. Moreover, the high number of newly born cells retained the expression of the glial marker GFAP. These effects were associated with downregulation of pro-neurogenic factors Neurogenin1 and Neurogenin2 and dysregulation of Notch, ?-catenin, Sonic Hedgehog (Shh) signaling as suggested by altered gene expression of effector molecules. Thus, a CNS antigen-specific immune response leads to an aberrant differentiation of neural precursors associated with dysbalance of signaling pathways relevant for adult hippocampal neurogenesis. These results may further extend our understanding of disturbed regeneration in the course of chronic inflammatory CNS diseases such as MS. PMID:20967885

Huehnchen, Petra; Prozorovski, Timour; Klaissle, Philipp; Lesemann, Anne; Ingwersen, Jens; Wolf, Susanne A; Kupsch, Andreas; Aktas, Orhan; Steiner, Barbara

2011-01-01

345

Molecular inspired models for prediction and control of directional FSO/RF wireless networks  

NASA Astrophysics Data System (ADS)

Directional wireless networks using FSO and RF transmissions provide wireless backbone support for mobile communications in dynamic environments. The heterogeneous and dynamic nature of such networks challenges their robustness and requires self-organization mechanisms to assure end-to-end broadband connectivity. We developed a framework based on the definition of a potential energy function to characterize robustness in communication networks and the study of first and second order variations of the potential energy to provide prediction and control strategies for network performance optimization. In this paper, we present non-convex molecular potentials such as the Morse Potential, used to describe the potential energy of bonds within molecules, for the characterization of communication links in the presence of physical constraints such as the power available at the network nodes. The inclusion of the Morse Potential translates into adaptive control strategies where forces on network nodes drive the release, retention or reconfiguration of communication links for network performance optimization. Simulation results show the effectiveness of our self-organized control mechanism, where the physical topology reorganizes to maximize the number of source to destination communicating pairs. Molecular Normal Mode Analysis (NMA) techniques for assessing network performance degradation in dynamic networks are also presented. Preliminary results show correlation between peaks in the eigenvalues of the Hessian of the network potential and network degradation.

Llorca, Jaime; Milner, Stuart D.; Davis, Christopher C.

2010-08-01

346

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

PubMed

Studies devoted to understanding locomotor control have mainly addressed the functioning of the neural circuits controlling leg movements and relatively little is known of the operation of networks that activate trunk muscles in coordination with limb movements. The aim of the present work was (1) to identify the exogenous neurotransmitter cocktail that most strongly activates postural thoracic circuitry; (2) to investigate how the biogenic amines serotonin (5-HT), dopamine (DA), and noradrenaline (NA) modulate the coordination between limb and axial motor networks. Experiments were carried out on in vitro isolated spinal cord preparations from newborn rats. We recorded from ventral roots to monitor hindlimb locomotor and axial postural network activity. Each combination of the three amines with excitatory amino acids (EAAs) elicited coordinated rhythmic motor activity at all segmental levels with specific characteristics. The variability in cycle period was similar with 5-HT and DA while it was significantly higher with NA. DA elicited motor bursts of smaller amplitude in thoracic segments compared to 5-HT and NA, while both DA and NA elicited motor bursts of higher amplitude than 5-HT in the lumbar and sacral segments. The amines modulated the phase relationships of bursts in various segments with respect to the reference lumbar segment. At the thoracic level there was a phase lag between all recorded segments in the presence of 5-HT, while DA and NA elicited synchronous bursting. At the sacral level, 5-HT and DA induced an intersegmental phase shift while relationships became phase-locked with NA. Various combinations of EAAs with two or even all three amines elicited rhythmic motor output that was more variable than with one amine alone. Our results provide new data on the coordinating processes between spinal cord networks, demonstrating that each amine has a characteristic "signature" regarding its specific effect on intersegmental phase relationships. PMID:25177275

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

2014-01-01

347

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

348

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

E-print Network

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

Li, Xiang-Yang

349

Medium Access Control Protocols Using Directional Antennas in Ad Hoc Networks  

E-print Network

Medium Access Control Protocols Using Directional Antennas in Ad Hoc Networks Young-Bae Ko Station, TX 77843-3112, USA youngbae,v0s5080,vaidya@cs.tamu.edu Abstract--Using directional antennas can- rectional antennas, a suitable Medium Access Control (MAC) protocolmust be designed. Current MAC protocols

Vaidya, Nitin

350

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

E-print Network

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

Hu, Y. Charlie

351

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

352

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

PubMed Central

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

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

2014-01-01

353

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

354

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

355

Directed Assembly of One-Dimensional Nanostructures into Functional Networks  

Microsoft Academic Search

One-dimensional nanostructures, such as nanowires and nanotubes, represent the smallest dimension for efficient transport of electrons and excitons and thus are ideal building blocks for hierarchical assembly of functional nanoscale electronic and photonic structures. We report an approach for the hierarchical assembly of one-dimensional nanostructures into well-defined functional networks. We show that nanowires can be assembled into parallel arrays with

Yu Huang; Xiangfeng Duan; Qingqiao Wei; Charles M. Lieber

2001-01-01

356

Mining Bayesian Networks from Direct Marketing Databases with Missing Values  

Microsoft Academic Search

Discovering knowledge from huge databases with missing values is a challenging problem in Data Mining. In this paper, a novel\\u000a hybrid algorithm for learning knowledge represented in Bayesian Networks is discussed. The new algorithm combines an evolutionary\\u000a algorithm with the Expectation-Maximization (EM) algorithm to overcome the problem of getting stuck in sub-optimal solutions\\u000a which occurs in most existing learning algorithms.

Yuan Yuan Guo; Man Leung Wong

357

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

PubMed

To investigate whether directionality in hyperbrain networks reflects different roles during interpersonal action coordination (IAC), we recorded EEG data from pairs of guitarists playing together as musical leaders versus followers. We used an asymmetric index of in-phase synchronization to analyze hyperbrain networks of directed functional connectivity in the alpha and beta frequency ranges for time segments around coordinated play onsets. After exploring the small-world characteristics of the networks at different thresholds, we examined the directed connection strengths within and between brains. As predicted, we found evidence suggesting that the musical roles of leader and follower are associated with different patterns of directed between-brain couplings. The functional significance of these differences for IAC requires further study. PMID:23761745

Sänger, Johanna; Müller, Viktor; Lindenberger, Ulman

2013-01-01

358

Frequency-modulation-selective Networks in Human Auditory Cortex Revealed Using fMRI and Multivariate Pattern Classification  

Microsoft Academic Search

Frequency modulation (FM) and amplitude modulation are the two building blocks of all complex sounds. Directional FM sweeps are especially pervasive in speech, music, animal vocalizations, and other natural sounds. Although the existence of FM-selective cells in the auditory cortex of animals has been documented, evidence in humans remains equivocal. Here we used multivariate pattern analysis to identify cortical selectivity

I-Hui Hsieh; Paul Fillmore; Feng Rong; Gregory Hickok; Kourosh Saberi

359

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

SciTech Connect

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.

Sun, Xiaoran, E-mail: sxr0806@gmail.com [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China) [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China); School of Mathematics and Statistics, The University of Western Australia, Crawley WA 6009 (Australia); Small, Michael, E-mail: michael.small@uwa.edu.au [School of Mathematics and Statistics, The University of Western Australia, Crawley WA 6009 (Australia)] [School of Mathematics and Statistics, The University of Western Australia, Crawley WA 6009 (Australia); Zhao, Yi [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China)] [Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China); Xue, Xiaoping [Department of Mathematics, Harbin Institute of Technology, Harbin 150025 (China)] [Department of Mathematics, Harbin Institute of Technology, Harbin 150025 (China)

2014-06-15

360

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

361

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

362

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

PubMed

Electrocortical and hemodynamic measures reliably identify enhanced activity in the ventral and dorsal visual cortices during the perception of emotionally arousing versus neutral images, an effect that may reflect directive feedback from the subcortical amygdala. However, other brain regions strongly modulate visual attention, such as frontal eye fields (FEF) and intraparietal sulcus (IPS). Here we employ rapid sampling of BOLD signal (4 Hz) in the amygdala, fusiform gyrus (FG), FEF and IPS in 42 human participants as they viewed a series of emotional and neutral natural scene photographs balanced for luminosity and complexity, to test whether emotional discrimination is evident in dorsal structures prior to such discrimination in the amygdala and FG. Granger causality analyses were used to assess directional connectivity within dorsal and ventral networks. Results demonstrate emotionally-enhanced peak BOLD signal in the amygdala, FG, FEF, and IPS, with the onset of BOLD signal discrimination occurring between 2 and 3s after stimulus onset in ventral structures, and between 4 and 5s in FEF and IPS. Granger causality estimates yield stronger directional connectivity from IPS to FEF than the reverse in this emotional picture paradigm. Consistent with a reentrant perspective of emotional scene perception, greater directional connectivity was found from the amygdala to FG compared to the reverse. These data support a perspective in which the registration of emotional scene content is orchestrated by the amygdala and rostral inferotemporal visual cortex. PMID:25018086

Sabatinelli, D; Frank, D W; Wanger, T J; Dhamala, M; Adhikari, B M; Li, X

2014-09-26

363

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

Microsoft Academic Search

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

Paulo S. Boggio; Soroush Zaghi; Felipe Fregni

2009-01-01

364

A wearable sensor module with a neural-network-based activity classification algorithm for daily energy expenditure estimation.  

PubMed

This paper presents a wearable module and neural-network-based activity classification algorithm for energy expenditure estimation. The purpose of our design is first to categorize physical activities with similar intensity levels, and then to construct energy expenditure regression (EER) models using neural networks in order to optimize the estimation performance. The classification of physical activities for EER model construction is based on the acceleration and ECG signal data collected by wearable sensor modules developed by our research lab. The proposed algorithm consists of procedures for data collection, data preprocessing, activity classification, feature selection, and construction of EER models using neural networks. In order to reduce the computational load and achieve satisfactory estimation performance, we employed sequential forward and backward search strategies for feature selection. Two representative neural networks, a radial basis function network (RBFN) and a generalized regression neural network (GRNN), were employed as EER models for performance comparisons. Our experimental results have successfully validated the effectiveness of our wearable sensor module and its neural-network-based activity classification algorithm for energy expenditure estimation. In addition, our results demonstrate the superior performance of GRNN as compared to RBFN. PMID:22875251

Lin, Che-Wei; Yang, Ya-Ting C; Wang, Jeen-Shing; Yang, Yi-Ching

2012-09-01

365

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

Microsoft Academic Search

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

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

2005-01-01

366

Module number of default mode network: Inter-subject variability and effects of sleep deprivation.  

PubMed

Sleep deprivation have shown its great influence on the default mode network (DMN). The DMN is a core system in resting state brain activity. Recent studies have focused on its subsystems and multiple functions. However, the individual specific organization of the DMN is rarely investigated. As the effects of sleep deprivation (SD) on mood are well documented, a more interesting question is whether changes in the processing of emotional information due to sleep deprivation are related to any specific topological properties of the DMN. In this study, we proposed an index, module number of DMN (mnDMN), to measure the specific modular structure of the DMN for each individual. Our results showed that the DMN was generally split into two modules after SD, and the decreased functional connectivity between the two modules was related to a worsening of the participants? self-reported emotional state. Furthermore, the mnDMN was correlated with participants' rating scores of high valence pictures in the SD session, indicating that the mnDMN might reflect mood valuation in the human brain. Overall, our research reveals the diversity of the DMN, and may contribute towards a better understanding of the properties and functions of the DMN. PMID:25446443

Wang, Yulin; Liu, Huan; Hitchman, Glenn; Lei, Xu

2015-01-30

367

A New Method to Measure Directional Modulation Transfer Function Using Sphere Phantoms in a Cone Beam Computed Tomography System.  

PubMed

We propose a new method to measure directional modulation transfer function (MTF) using sphere phantoms in a cone beam computed tomography (CBCT) system. To measure spatially varying three-dimensional (3D) MTFs, we model FDK reconstruction in local regions and calculate the plane integrals of an ideal sphere phantom and reconstructed sphere phantoms. Then, we modify the Richardson-Lucy (RL) deconvolution method to relax the non-negativity constraint in RL deconvolution and apply it to estimate the directional plane spread functions (PlSFs). Directional MTFs are calculated by taking the modulus of the Fourier transform of the estimated directional PlSFs. To validate the proposed method, we simulate ideal 3D MTFs and compare them with directional MTFs measured by simulation and experimental data along three major axes. For quantitative evaluation, we compare full width at half maximum (FWHM) and full width at tenth maximum (FWTM) of measured and ideal directional MTFs. The measured directional MTFs from simulation and experimental data show excellent agreement with the ideal directional MTFs, demonstrating the effectiveness of the proposed method to estimate directional MTFs in a CBCT system. PMID:25398176

Lee, Changwoo; Baek, Jongduk

2014-11-11

368

Direct aperture optimization as a means of reducing the complexity of Intensity Modulated Radiation Therapy plans.  

PubMed

Intensity Modulated Radiation Therapy (IMRT) is a means of delivering radiation therapy where the intensity of the beam is varied within the treatment field. This is done by dividing a large beam into many small beamlets. Dose constraints are assigned to both the target and sensitive structures and computerised inverse optimization is performed to find the individual weights of this large number of beamlets. The computer adjusts the intensities of these beamlets according to the required planning dose objectives. The optimized intensity patterns are then decomposed into a series of deliverable multi leaf collimator (MLC) shapes in the sequencing step. One of the main problems of IMRT, which becomes even more apparent as the complexity of the IMRT plan increases, is the dramatic increase in the number of Monitor Units (MU) required to deliver a fractionated treatment. The difficulty with this increase in MU is its association with increased treatment times and a greater leakage of radiation from the MLCs increasing the total body dose and the risk of secondary cancers in patients. Therefore one attempts to find ways of reducing these MU without compromising plan quality. The design of inverse planning systems where the beam is divided into small beamlets to produce the required intensity map automatically introduces complexity into IMRT treatment planning. Plan complexity is associated with many negative factors such as dosimetric uncertainty and delivery issues A large search space is required necessitating much computing power. However, the limitations of the delivery technology are not taken into consideration when designing the ideal intensity map therefore a further step termed the sequencing step is required to convert the ideal intensity map into a deliverable one. Many approaches have been taken to reduce the complexity. These include setting intensity limits, putting penalties on the cost function and using smoothing filters Direct Aperture optimization (DAO) incorporates the limitations of the delivery technology at the initial design of the intensity map thereby eliminating the sequencing step. It also gives control over the number of segments and hence control over the complexity of the plan although the design of the segments is independent of the person preparing the plan. PMID:19220906

Broderick, Maria; Leech, Michelle; Coffey, Mary

2009-01-01

369

Direct detection of RDX vapor using a conjugated polymer network.  

PubMed

1,3,5-Trinitroperhydro-1,3,5-triazine (RDX) is a principal component of plastic explosives used in acts of terrorism and within improvised explosive devices, among others. Approaches to detect RDX compatible with remote, "stand-off" sampling that do not require preconcentration strategies, such as the swabs commonly employed in airports, will benefit military and civilian security. Such detection remains a significant challenge because RDX is 10(3) less volatile than 1,3,5-trinitrotoluene (TNT), corresponding to a parts-per-trillion vapor pressure under ambient conditions. Therefore, while fluorescence quenching of conjugated polymers is sufficiently sensitive to detect TNT vapors, RDX vapor detection is undemonstrated. Here we report a cross-linked phenylene vinylene polymer network whose fluorescence is quenched by trace amounts of RDX introduced from solution or the vapor phase. Fluorescence quenching is reduced, but remains significant, when partially degraded RDX is employed, suggesting that the polymer responds to RDX itself. The polymer network also responds to TNT and PETN similarly introduced from solution or the vapor phase. Pure solvents, volatile amines, and the outgassed vapors from lipstick or sunscreen do not quench polymer fluorescence. The established success of TNT sensors based on fluorescence quenching makes this a material of interest for real-world explosive sensors and will motivate further interest in cross-linked polymers and framework materials for sensing applications. PMID:23641956

Gopalakrishnan, Deepti; Dichtel, William R

2013-06-01

370

Gene co-expression network and function modules in three types of glioma.  

PubMed

The aim of the present study was to identify the disease?associated genes and their functions involved in the development of three types of glioma (astrocytoma, glioblastoma and oligodendroglioma) with DNA microarray technology, and to analyze their differences and correlations. First, the gene expression profile GSE4290 was downloaded from the Gene Expression Omnibus database, then the probe?level data were pre?processed and the differentially expressed genes (DEGs) were identified with limma package in R language. Gene functions of the selected DEGs were further analyzed with the Database for Annotation, Visualization and Integrated Discovery. After the co?expression network of DEGs was constructed by Cytoscape, the functional modules were mined and enrichment analysis was performed, and then the similarities and differences between any two types of glioma were compared. A total of 1151 genes between normal and astrocytoma tissues, 684 genes between normal and malignant glioma tissues, and 551 genes between normal and oligodendroglioma tissues were filtered as DEGs, respectively. By constructing co?expression networks of DEGs, a total of 77232, 455 and 987 interactions were involved in the differentially co?expressed networks of astrocytoma, oligodendroglioma and glioblastoma, respectively. The functions of DEGs were consistent with the modules in astrocytoma, glioblastoma and oligodendroglioma, which were mainly enriched in neuron signal transmission, immune responses and synthesis of organic acids, respectively. Model functions of astrocytoma and glioblastoma were similar (mainly related with immune response), while the model functions of oligodendroglioma differed markedly from that of the other two types. The identification of the associations among these three types of glioma has potential clinical utility for improving the diagnosis of different types of glioma in the future. In addition, these results have marked significance in studying the underlying mechanisms, distinguishing between normal and cancer tissues, and examining novel therapeutic strategies for patients with glioma. PMID:25435164

Li, Gang; Pan, Weiran; Yang, Xiaoxiao; Miao, Jinming

2015-04-01

371

Second-Order Global Consensus in Multiagent Networks With Random Directional Link Failure.  

PubMed

In this paper, we consider the second-order globally nonlinear consensus in a multiagent network with general directed topology and random interconnection failure by characterizing the behavior of stochastic dynamical system with the corresponding time-averaged system. A criterion for the second-order consensus is derived by constructing a Lyapunov function for the time-averaged network. By associating the solution of random switching nonlinear system with the constructed Lyapunov function, a sufficient condition for second-order globally nonlinear consensus in a multiagent network with random directed interconnections is also established. It is required that the second-order consensus can be achieved in the time-averaged network and the Lyapunov function decreases along the solution of the random switching nonlinear system at an infinite subsequence of the switching moments. A numerical example is presented to justify the correctness of the theoretical results. PMID:25095263

Li, Huaqing; Liao, Xiaofeng; Huang, Tingwen; Zhu, Wei; Liu, Yanbing

2014-05-16

372

Parameter assignment for improved connectivity and security in randomly deployed wireless sensor networks via hybrid omni/uni-directional antennas  

E-print Network

,omni-directional antennas have been used for communication in wireless sensor net-works. In this thesis, a hybrid communication model is presented where-in, nodes ina network are capable of both omni-directional and uni-directional communication.The eect of such a model...

Shankar, Sonu

2009-05-15

373

Directed Diffusion for Wireless Sensor Networking Chalermek Intanagonwiwat, Ramesh Govindan, Deborah Estrin, John Heidemann, and Fabio Silva  

E-print Network

and processing data in-network (e.g., data aggregation). We explore and evaluate the use of directed diffusionDirected Diffusion for Wireless Sensor Networking Chalermek Intanagonwiwat, Ramesh Govindan explore the di- rected diffusion paradigm for such coordination. Directed diffusion is data- centric

Heidemann, John

374

Directed Diffusion for Wireless Sensor Networking Chalermek Intanagonwiwat, Ramesh Govindan, Deborah Estrin, John Heidemann, and Fabio Silva  

E-print Network

and processing data in­network (e.g., data aggregation). We explore and evaluate the use of directed diffusionDirected Diffusion for Wireless Sensor Networking Chalermek Intanagonwiwat, Ramesh Govindan explore the di­ rected diffusion paradigm for such coordination. Directed diffusion is data­ centric

Heidemann, John

375

Modulators of networks: molecular targets of arterial calcification identified in man and mice.  

PubMed

In recent years, mechanisms of arterial calcifications are beginning to be elucidated. Arterial calcification is now considered as an actively regulated process resembling osteogenesis within the arterial wall orchestrated by a number of systemic or constitutively expressed mediators. Genetic studies of rare monogenic human disorders and studies of naturally occurring or mutant mouse models have identified specific inductors and inhibitors of arterial calcification, which can be classified according to the networks they participate in. These networks include ATP and pyrophosphate metabolism, phosphate homeostasis and vitamin D receptor signaling. Furthermore, intracellular signaling molecules, including SMAD6 and a number of systemic circulatory inhibitors of arterial calcification, including fetuin, tumor necrosis factor receptor superfamily member 11b, matrix GLA protein, adiponectin and family with sequence similarity 20 member A have been identified by human and mouse genetics. Based on the in vivo evidence of their functional relevance, these proteins will serve as excellent targets for the prevention and treatment of arterial calcification. In this review we discuss the functional role of the identified modulators of arterial calcification and describe the networks they belong to. PMID:24533942

Nitschke, Yvonne; Rutsch, Frank

2014-01-01

376

Learning modulation of odor representations: new findings from Arc-indexed networks  

PubMed Central

We first review our understanding of odor representations in rodent olfactory bulb (OB) and anterior piriform cortex (APC). We then consider learning-induced representation changes. Finally we describe the perspective on network representations gained from examining Arc-indexed odor networks of awake rats. Arc-indexed networks are sparse and distributed, consistent with current views. However Arc provides representations of repeated odors. Arc-indexed repeated odor representations are quite variable. Sparse representations are assumed to be compact and reliable memory codes. Arc suggests this is not necessarily the case. The variability seen is consistent with electrophysiology in awake animals and may reflect top-down cortical modulation of context. Arc-indexing shows that distinct odors share larger than predicted neuron pools. These may be low-threshold neuronal subsets. Learning’s effect on Arc-indexed representations is to increase the stable or overlapping component of rewarded odor representations. This component can decrease for similar odors when their discrimination is rewarded. The learning effects seen are supported by electrophysiology, but mechanisms remain to be elucidated. PMID:25565958

Yuan, Qi; Harley, Carolyn W.

2014-01-01

377

Clustering and overlapping modules detection in PPI network based on IBFO.  

PubMed

As is known to all, traditional clustering algorithms do not work well due to the topological features of protein-protein interaction networks. An improved clustering method based on bacteria foraging optimization (BFO) mechanism and intuitionistic fuzzy set, short for improved BFO, is proposed in this paper, in which the trigonometric function is used to define the membership degrees and the indeterminacy degree is introduced to detect the overlapping modules. In chemotactic operation of BFO, the algorithm initializes a cluster center according to comprehensive network feature value of node and eliminates the isolated point in accordance with edge-clustering coefficient. In the reproduction operation of BFO, the nodes possessing high membership degrees are merged into the cluster that the cluster center belongs to and labeled as visited nodes. Meanwhile, the nodes that also have high indeterminacy degrees are visited again when generating another cluster. The procedure of elimination-dispersal operation is equivalent to the selection of the next cluster center. Finally, the algorithm merges the clusters having high similarity. The results show that the algorithm not only determines the cluster number automatically, improves the f-measure value of cluster results, but also identify the overlaps in protein-protein interaction network successfully. PMID:23229795

Lei, Xiujuan; Wu, Shuang; Ge, Liang; Zhang, Aidong

2013-01-01

378

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

379

Direct observation of domain wall evolution at a bifurcation in magnetic network structures  

NASA Astrophysics Data System (ADS)

We report on the magnetization dynamics at a bifurcation in a dual-branch magnetic network structure. When a transverse domain wall (DW) propagates through the network, interaction with an edge defect at the bifurcation leads to the transformation of the DW from transverse to vortex. The topological charge is conserved as the DW moves through the bifurcation, and this charge conservation is intrinsically linked to a ?1/2 topological defect in the system. Magnetic force microscopy (MFM) imaging enables the direct observation of defect displacement during DW transformation, which induces a selective switching in the branch of the network structure.

Murapaka, Chandrasekhar; Sethi, Pankaj; Goolaup, Sarjoosing; Maddu, Ramu; Chen, Yunjie; Leong, Siang Huei; Siang Lew, Wen

2014-11-01

380

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

381

Brain network dynamics characterization in epileptic seizures. Joint directed graph and pairwise synchronization measures  

NASA Astrophysics Data System (ADS)

Here we propose and evaluate a new approach to analyse multichannel mesial temporal lobe epilepsy EEG data from eight patients through complex network and synchronization theories. The method employs a Granger causality test to infer the directed connectivity graphs and a wavelet transform based phase synchronization measure whose characteristics allow studying dynamical transitions during epileptic seizures. We present a new combined graph measure that quantifies the level of network hub formation, called network hub out-degree, which closely reflects the level of synchronization observed during the ictus.

Rodrigues, A. C.; Machado, B. S.; Florence, G.; Hamad, A. P.; Sakamoto, A. C.; Fujita, A.; Baccalá, L. A.; Amaro, E.; Sameshima, K.

2014-12-01

382

An analysis of the sectorial influence of CSI300 stocks within the directed network  

NASA Astrophysics Data System (ADS)

This paper uses the Partial Correlation Planar maximally filtered Graph (PCPG) method to construct a directed network for the constituent stocks underlying the China Securities Index 300 (CSI300). We also analyse the impact of individual stocks. We find that the CSI300 market is a scale-free network with a relatively small power law exponent. The volatility of the stock prices has significant impact on other stocks. In the sectorial network, the industrial sector is the most influential one over other sectors, the financial sector only has a modest influence, while the telecommunication services sector’s influence is marginal. In addition, such inter-sector influence displays quarterly stability.

Mai, Yong; Chen, Huan; Meng, Lei

2014-02-01

383

A target coverage scheduling scheme based on genetic algorithms in directional sensor networks.  

PubMed

As a promising tool for monitoring the physical world, directional sensor networks (DSNs) consisting of a large number of directional sensors are attracting increasing attention. As directional sensors in DSNs have limited battery power and restricted angles of sensing range, maximizing the network lifetime while monitoring all the targets in a given area remains a challenge. A major technique to conserve the energy of directional sensors is to use a node wake-up scheduling protocol by which some sensors remain active to provide sensing services, while the others are inactive to conserve their energy. In this paper, we first address a Maximum Set Covers for DSNs (MSCD) problem, which is known to be NP-complete, and present a greedy algorithm-based target coverage scheduling scheme that can solve this problem by heuristics. This scheme is used as a baseline for comparison. We then propose a target coverage scheduling scheme based on a genetic algorithm that can find the optimal cover sets to extend the network lifetime while monitoring all targets by the evolutionary global search technique. To verify and evaluate these schemes, we conducted simulations and showed that the schemes can contribute to extending the network lifetime. Simulation results indicated that the genetic algorithm-based scheduling scheme had better performance than the greedy algorithm-based scheme in terms of maximizing network lifetime. PMID:22319387

Gil, Joon-Min; Han, Youn-Hee

2011-01-01

384

Direct2Experts: a pilot national network to demonstrate interoperability among research-networking platforms.  

PubMed

Research-networking tools use data-mining and social networking to enable expertise discovery, matchmaking and collaboration, which are important facets of team science and translational research. Several commercial and academic platforms have been built, and many institutions have deployed these products to help their investigators find local collaborators. Recent studies, though, have shown the growing importance of multiuniversity teams in science. Unfortunately, the lack of a standard data-exchange model and resistance of universities to share information about their faculty have presented barriers to forming an institutionally supported national network. This case report describes an initiative, which, in only 6 months, achieved interoperability among seven major research-networking products at 28 universities by taking an approach that focused on addressing institutional concerns and encouraging their participation. With this necessary groundwork in place, the second phase of this effort can begin, which will expand the network's functionality and focus on the end users. PMID:22037890

Weber, Griffin M; Barnett, William; Conlon, Mike; Eichmann, David; Kibbe, Warren; Falk-Krzesinski, Holly; Halaas, Michael; Johnson, Layne; Meeks, Eric; Mitchell, Donald; Schleyer, Titus; Stallings, Sarah; Warden, Michael; Kahlon, Maninder

2011-12-01

385

Direct2Experts: a pilot national network to demonstrate interoperability among research-networking platforms  

PubMed Central

Research-networking tools use data-mining and social networking to enable expertise discovery, matchmaking and collaboration, which are important facets of team science and translational research. Several commercial and academic platforms have been built, and many institutions have deployed these products to help their investigators find local collaborators. Recent studies, though, have shown the growing importance of multiuniversity teams in science. Unfortunately, the lack of a standard data-exchange model and resistance of universities to share information about their faculty have presented barriers to forming an institutionally supported national network. This case report describes an initiative, which, in only 6?months, achieved interoperability among seven major research-networking products at 28 universities by taking an approach that focused on addressing institutional concerns and encouraging their participation. With this necessary groundwork in place, the second phase of this effort can begin, which will expand the network's functionality and focus on the end users. PMID:22037890

Barnett, William; Conlon, Mike; Eichmann, David; Kibbe, Warren; Falk-Krzesinski, Holly; Halaas, Michael; Johnson, Layne; Meeks, Eric; Mitchell, Donald; Schleyer, Titus; Stallings, Sarah; Warden, Michael; Kahlon, Maninder

2011-01-01

386

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

E-print Network

University of New York, New York, USA December 3, 2014 Abstract Transcranial Direct Current Stimulation (tDCS hypothesis. Introduction The number of studies on transcranial direct current stimulation (tDCS) has rapidly

Parra, Lucas C.

387

Experimental demonstration of the efficacy of global versus direct beam use in performance prediction of flat plate photovoltaic modules  

SciTech Connect

Accuracy in prediction of module output in the installed configuration is critical to growth of the terrestrial photovoltaics market. Due to momentum from the space application, the United States has tended to retain reliance upon the better known reference spectrum, used in the prediction of photovoltaic output, from the direct beam component at Air Mass 1.5. However, flat plate modules view a hemispherical or global spectrum. Differences have resulted which require resolution. Experiments were performed which show the differences in reference cell calibration constant due solely to the difference in spectrum under which the calibrations were performed. Analysis and experiments demonstrate the ultimate effect of that difference upon I-V curve normalization and resulting power determination.

Whitaker, R.D.; Purnell, A.W.; Zerlaut, G.A.

1982-09-01

388

Mining susceptibility gene modules and disease risk genes from SNP data by combining network topological properties with support vector regression  

Microsoft Academic Search

Genome-wide association study is a powerful approach to identify disease risk loci. However, the molecular regulatory mechanisms for most complex diseases are still not well understood. Therefore, further investigating the interplay between genetic factors and biological networks is important for elucidating the molecular mechanisms of complex diseases. Here, we proposed a novel framework to identify susceptibility gene modules and disease

Lin Hua; Ping Zhou; Hong Liu; Lin Li; Zheng Yang; Zhi-cheng Liu

2011-01-01

389

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

390

A neural network model for the development of direction selectivity in the visual cortex.  

PubMed

A neural network model is proposed to explain the development of direction selectivity of cortical cells. The model is constructed under the following three hypotheses that are very plausible from recent neurophysiological findings. (1) Direction selectivity is developed by modifiable inhibitory synapses. (2) It results not from the direct convergence of many excitatory inputs from LGN cells but from cortical neural networks. (3) Direction-selective mechanism is independent of orientation-selective mechanism.--The model was simulated on a computer for a few kinds of inhibitory connections and initial conditions. The results were consistent with neurophysiological facts not only for normal cats but for cats reared in an abnormal visual environment. PMID:760831

Nagano, T; Fujiwara, M

1979-02-01

391

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

392

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

393

Demonstration of 48-Gb/s 16-QAM signal transmission using half cycle sub-carrier modulation in intensity modulation/direct detection system  

NASA Astrophysics Data System (ADS)

A simple spectral-efficiency intensity modulation/direct detection (IM/DD) system based on half cycle sub-carrier modulation (SCM) signal is proposed for short reach fiber communications in this paper. The signal impairment of frequency selective fading due to fiber chromatics dispersion (CD) is mathematically analyzed. To reduce the performance deterioration caused by the non-flat transfer function, digital pre- and post-equalization is applied in the system. The peak to average power ratio (PAPR) of the signal is also discussed in comparison with that of orthogonal frequency division multiplexing (OFDM). The transmission of 16-QAM half cycle SCM signal with a sub-carrier frequency of half the symbol rate and Nyquist pulse shaping is experimentally demonstrated. The bit-error rate (BER) of 48 Gb/s polarization multiplexing division (PDM) 16 QAM half cycle SCM signal is less than 7% forward-error-correction (FEC) threshold of 3.8 ×10-3 after transmission over 83 km standard single-mode fiber (SSMF).

Tang, Jin; He, Jing; Chen, Ming; Li, Danyu; Chen, Lin

2015-01-01

394

The role of GABAergic modulation in motor function related neuronal network activity.  

PubMed

At rest, the primary motor cortex (M1) exhibits spontaneous neuronal network oscillations in the beta (15-30 Hz) frequency range, mediated by inhibitory interneuron drive via GABA-A receptors. However, questions remain regarding the neuropharmacological basis of movement related oscillatory phenomena, such as movement related beta desynchronisation (MRBD), post-movement beta rebound (PMBR) and movement related gamma synchronisation (MRGS). To address this, we used magnetoencephalography (MEG) to study the movement related oscillatory changes in M1 cortex of eight healthy participants, following administration of the GABA-A modulator diazepam. Results demonstrate that, contrary to initial hypotheses, neither MRGS nor PMBR appear to be GABA-A dependent, whilst the MRBD is facilitated by increased GABAergic drive. These data demonstrate that while movement-related beta changes appear to be dependent upon spontaneous beta oscillations, they occur independently of one other. Crucially, MRBD is a GABA-A mediated process, offering a possible mechanism by which motor function may be modulated. However, in contrast, the transient increase in synchronous power observed in PMBR and MRGS appears to be generated by a non-GABA-A receptor mediated process; the elucidation of which may offer important insights into motor processes. PMID:21320607

Hall, S D; Stanford, I M; Yamawaki, N; McAllister, C J; Rönnqvist, K C; Woodhall, G L; Furlong, P L

2011-06-01

395

Propensity to imitate in autism is not modulated by the model's gaze direction: an eye-tracking study.  

PubMed

Individuals with Autism Spectrum Disorder (ASD) show a diminished propensity to imitate others' actions, as well as a diminished sensitivity and responsivity to others' communicative cues, such as a direct gaze. However, it is not known whether failure to appreciate the communicative value of a direct gaze is associated with imitation abnormalities in this population. In this eye-tracking study, we investigated how 25 preschoolers with ASD, compared with 25 developmental and chronological age-matched children, imitate actions that are associated with a model's direct gaze versus averted gaze. We found that the model's direct gaze immediately prior to the demonstration increased the attention to the model and the propensity to imitate the demonstrated action in children without ASD. In contrast, preschoolers with ASD showed a similar propensity to look at the model's face and to imitate the demonstrated actions across the direct gaze and the averted gaze conditions. These data indicate that atypical imitation in ASD might be linked to abnormal processing of the model's communicative signals (such as a direct gaze) that modulate imitative behaviours in individuals without ASD. Autism Res 2014, 7: 392-399. © 2014 International Society for Autism Research, Wiley Periodicals, Inc. PMID:24740914

Vivanti, Giacomo; Dissanayake, Cheryl

2014-06-01

396

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

397

Direct-modulated waveguide-coupled microspiral disk lasers with spatially selective injection for on-chip optical interconnects.  

PubMed

We investigate direct-modulated waveguide-coupled microspiral disk lasers for on-chip optical interconnects. Microspiral resonators, with a rotationally asymmetric shape and a waveguide directly gapless coupled to the notch, offer a compact unidirectional-emission on-chip laser source. We employ spatially selective injection by means of a ring-shaped p-contact on top of the microdisk rim region to selectively inject current to the whispering-gallery-like modes and thus enhance the laser performance. Here we report room-temperature continuous-wave electrically injected AlGaInAs/InP waveguide-coupled microspiral disk lasers with a disk radius of 30 and 40 ?m. For a 30 ?m microspiral disk laser gaplessly coupled with a 100 ?m-long passive waveguide that is directly connected to an on-chip AlGaInAs/InP photodiode, we estimate a laser output power of at least 200 ?W upon a 70 mA injection. We realize small-signal modulation with a 3dB bandwidth exceeding 10 GHz for the 30 ?m microspiral disk. We demonstrate an open eye diagram at 15 Gbit/s with a bias current of 90 mA at a stage temperature of 15 °C. PMID:24515042

Yang, Yue-De; Zhang, Yu; Huang, Yong-Zhen; Poon, Andrew W

2014-01-13

398

Direct measurement of local chromatin fluidity using optical trap modulation force spectroscopy.  

PubMed

Chromatin assembly is condensed by histone tail-tail interactions and other nuclear proteins into a highly compact structure. Using an optical trap modulation force spectroscopy, we probe the effect of tail interactions on local chromatin fluidity. Chromatin fibers, purified from mammalian cells, are tethered between a microscope coverslip and a glass micropipette. Mechanical unzipping of tail interactions, using the micropipette, lead to the enhancement of local fluidity. This is measured using an intensity-modulated optically trapped bead positioned as a force sensor on the chromatin fiber. Enzymatic digestion of the histone tail interactions of tethered chromatin fiber also leads to a similar increase in fluidity. Our experiments show that an initial increase in the local fluidity precedes chromatin decompaction, suggesting possible mechanisms by which chromatin-remodeling machines access regulatory sites. PMID:17012315

Roopa, T; Shivashankar, G V

2006-12-15

399

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

400

Directional selective neurons in the awake LGN: response properties and modulation by brain state.  

PubMed

Directionally selective (DS) neurons are found in the retina and lateral geniculate nucleus (LGN) of rabbits and rodents, and in rabbits, LGN DS cells project to primary visual cortex. Here, we compare visual response properties of LGN DS neurons with those of layer 4 simple cells, most of which show strong direction/orientation selectivity. These populations differed dramatically, suggesting that DS cells may not contribute significantly to the synthesis of simple receptive fields: 1) whereas the first harmonic component (F1)-to-mean firing rate (F0) ratios of LGN DS cells are strongly nonlinear, those of simple cells are strongly linear; 2) whereas LGN DS cells have overlapped ON/OFF subfields, simple cells have either a single ON or OFF subfield or two spatially separate subfields; and 3) whereas the preferred directions of LGN DS cells are closely tied to the four cardinal directions, the directional preferences of simple cells are more evenly distributed. We further show that directional selectivity in LGN DS neurons is strongly enhanced by alertness via two mechanisms, 1) an increase in responses to stimulation in the preferred direction, and 2) an enhanced suppression of responses to stimuli moving in the null direction. Finally, our simulations show that these two consequences of alertness could each serve, in a vector-based population code, to hasten the computation of stimulus direction when rabbits become alert. PMID:24790175

Hei, Xiaojuan; Stoelzel, Carl R; Zhuang, Jun; Bereshpolova, Yulia; Huff, Joseph M; Alonso, Jose-Manuel; Swadlow, Harvey A

2014-07-15

401

Evolution of ethnocentrism on undirected and directed Barab\\'asi-Albert networks  

E-print Network

Using Monte Carlo simulations, we study the evolution of contigent cooperation and ethnocentrism in the one-move game. Interactions and reproduction among computational agents are simulated on {\\it undirected} and {\\it directed} Barab\\'asi-Albert (BA) networks. We first replicate the Hammond-Axelrod model of in-group favoritism on a square lattice and then generalize this model on {\\it undirected} and {\\it directed} BA networks for both asexual and sexual reproduction cases. Our simulations demonstrate that irrespective of the mode of reproduction, ethnocentric strategy becomes common even though cooperation is individually costly and mechanisms such as reciprocity or conformity are absent. Moreover, our results indicate that the spread of favoritism toward similar others highly depends on the network topology and the associated heterogeneity of the studied population.

Lima, F W S; Stauffer, Dietrich

2009-01-01

402

Application of Controller Area Networks to Direct Load Control in Residential Areas  

Microsoft Academic Search

The objective of this paper is to describe and assess the application of Controller Area Networks to Direct Load Control programs, extending the CAN applications from industrial sector to residential automation. The proposed system allows the customers to monitor and control automatically their heating and cooling individual loads, maintaining minimum comfort levels and offering a flexible, low-cost and friendly tool-through

A. Molina-Garcia; R. Torres; J. L. Munoz; N. Encinas

2007-01-01

403

Multi-hop\\/Direct Forwarding (MDF) for Static Wireless Sensor Networks  

Microsoft Academic Search

The success of Wireless Sensor Networks (WSNs) depends largely on efficient information delivery from target areas toward data sinks. The problem of data forwarding is complicated by the severe energy constraints of sensors in WSNs. In this work, we propose and analyze a data forwarding scheme, termed Multi-hop\\/Direct Forwarding (MDF), for WSNs where sensor nodes forward data traffic toward a

JING DENG

2008-01-01

404

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

405

On Physical-Aware Directional MAC Protocol for Indoor Wireless Networks  

Microsoft Academic Search

Exploiting antenna directionality provides significant improvements in terms of spatial reuse, in comparison to omnidirectional antennas, leading to higher network capacity. However, this improvement is highly correlated to the presence of the hidden terminal and deafness problems. In this paper we propose to handle the sensed noise and the arrival of corrupted packets events in a way to address these

Yassine Hadjadj-Aoul; Farid Naït-abdesselam

2008-01-01

406

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

407

Novel direct and self-regulating approaches to determine optimum growing multi-experts network structure  

Microsoft Academic Search

This work presents two novel approaches to determine optimum growing multi-experts network (GMN) structure. The first method called direct method deals with expertise domain and levels in connection with local experts. The growing neural gas (GNG) algorithm is used to cluster the local experts. The concept of error distribution is used to apportion error among the local experts. After reaching

Chu Kiong Loo; Mandava Rajeswari; M. V. C. Rao

2004-01-01

408

NRC TLD direct radiation monitoring network: Progress report, July--September 1997. Volume 17, Number 3  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

Struckmeyer

1998-01-01

409

NRC TLD Direct Radiation Monitoring Network. Progress report, January--March 1994: Volume 14, Number 1  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels results from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

Struckmeyer

1994-01-01

410

NRC TLD (thermoluminescent dosimeters) Direct Radiation Monitoring Network: Progress report, July-September 1986  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

J. Jang; K. Rabatin; L. Cohen

1987-01-01

411

NRC TLD Direct Radiation Monitoring Network. Progress report, January--March 1992: Volume 12, No. 1  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

R. Struckmeyer; N. McNamara

1992-01-01

412

NRC TLD direct radiation monitoring network: Volume 15, No. 3. Progress report, July--September 1995  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

Struckmeyer

1995-01-01

413

NRC TLD (thermoluminescent dosimeter) Direct Radiation Monitoring Network: Progress report, July--September 1988  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

R. Struckmeyer; N. McNamara

1989-01-01

414

NRC TLD direct radiation monitoring network: Progress report, April--June 1996. Volume 16, Number 2  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

Struckmeyer

1996-01-01

415

NRC TLD (thermoluminescent dosimeter) Direct Radiation Monitoring Network: Progress report, January--March 1989  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

R. Struckmeyer; N. McNamara

1989-01-01

416

NRC TLD Direct Radiation Monitoring Network: Progress report, July--September 1996. Volume 16, Number 3  

Microsoft Academic Search

The US Nuclear Regulatory Commission (NRC) Direct Radiation Monitoring Network is operated by the NRC in cooperation with participating states to provide continuous measurement of the ambient radiation levels around licensed NRC facilities, primarily power reactors. Ambient radiation levels result from naturally occurring radionuclides present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution,

Struckmeyer

1997-01-01

417

Direct adaptive control of wind energy conversion systems using Gaussian networks  

Microsoft Academic Search

Grid connected wind energy conversion systems (WECS) present interesting control demands, due to the intrinsic nonlinear characteristics of windmills and electric generators. In this paper a direct adaptive control strategy for WECS control is proposed. It is based on the combination of two control actions: a radial basis function network-based adaptive controller, which drives the tracking error to zero with

Miguel Angel Mayosky; Gustavo I. E. Cancelo

1999-01-01

418

The photorefractive effect in directional coupler and Mach-Zehnder LiNbO3 optical modulators at a wavelength of 1.3 ?m  

Microsoft Academic Search

Previous work has shown that at a wavelength of 1.3 ?m and power levels on the order of a few milliwatts, directional coupler switches show negligible damage due to the photorefractive effect. The author's experiments at higher power levels (20 mW) show a significant reduction in performance for 1-cm-long directional coupler modulators with uniform electrodes. The reduction in modulation efficiency

G. T. Harvey

1988-01-01

419

Identifying influential nodes in large-scale directed networks: the role of clustering.  

PubMed

Identifying influential nodes in very large-scale directed networks is a big challenge relevant to disparate applications, such as accelerating information propagation, controlling rumors and diseases, designing search engines, and understanding hierarchical organization of social and biological networks. Known methods range from node centralities, such as degree, closeness and betweenness, to diffusion-based processes, like PageRank and LeaderRank. Some of these methods already take into account the influences of a node's neighbors but do not directly make use of the interactions among it's neighbors. Local clustering is known to have negative impacts on the information spreading. We further show empirically that it also plays a negative role in generating local connections. Inspired by these facts, we propose a local ranking algorithm named ClusterRank, which takes into account not only the number of neighbors and the neighbors' influences, but also the clustering coefficient. Subject to the susceptible-infected-recovered (SIR) spreading model with constant infectivity, experimental results on two directed networks, a social network extracted from delicious.com and a large-scale short-message communication network, demonstrate that the ClusterRank outperforms some benchmark algorithms such as PageRank and LeaderRank. Furthermore, ClusterRank can also be applied to undirected networks where the superiority of ClusterRank is significant compared with degree centrality and k-core decomposition. In addition, ClusterRank, only making use of local information, is much more efficient than global methods: It takes only 191 seconds for a network with about [Formula: see text] nodes, more than 15 times faster than PageRank. PMID:24204833

Chen, Duan-Bing; Gao, Hui; Lü, Linyuan; Zhou, Tao

2013-01-01

420

Identifying Influential Nodes in Large-Scale Directed Networks: The Role of Clustering  

PubMed Central

Identifying influential nodes in very large-scale directed networks is a big challenge relevant to disparate applications, such as accelerating information propagation, controlling rumors and diseases, designing search engines, and understanding hierarchical organization of social and biological networks. Known methods range from node centralities, such as degree, closeness and betweenness, to diffusion-based processes, like PageRank and LeaderRank. Some of these methods already take into account the influences of a node’s neighbors but do not directly make use of the interactions among it’s neighbors. Local clustering is known to have negative impacts on the information spreading. We further show empirically that it also plays a negative role in generating local connections. Inspired by these facts, we propose a local ranking algorithm named ClusterRank, which takes into account not only the number of neighbors and the neighbors’ influences, but also the clustering coefficient. Subject to the susceptible-infected-recovered (SIR) spreading model with constant infectivity, experimental results on two directed networks, a social network extracted from delicious.com and a large-scale short-message communication network, demonstrate that the ClusterRank outperforms some benchmark algorithms such as PageRank and LeaderRank. Furthermore, ClusterRank can also be applied to undirected networks where the superiority of ClusterRank is significant compared with degree centrality and k-core decomposition. In addition, ClusterRank, only making use of local information, is much more efficient than global methods: It takes only 191 seconds for a network with about nodes, more than 15 times faster than PageRank. PMID:24204833

Chen, Duan-Bing; Gao, Hui; Lü, Linyuan; Zhou, Tao

2013-01-01

421

Demonstration of monolithic optical injection locking for directly modulated RF photonic links  

NASA Astrophysics Data System (ADS)

Optical injection locking has been a known method for increasing the modulation performance of semiconductor lasers. Such benefits include increased modulation bandwidth, increased linearity, lower chirp and lower noise. For analog photonic applications the increased bandwidth and linearity are of main concern for the distribution of high frequency analog signals with maximum fidelity. Previous experiments involving optical injection locked lasers are typically done using a monolithic semiconductor laser as the slave and an external cavity semiconductor laser as the master. Such setups are ideal for laboratory use but often are impractical for real life implementation. Particularly, the external cavity laser is prone to vibration and the injection ration (coupling from the master laser into the slave) is limited by the coupling efficiency and polarization mismatch. Optical injection locking using a single monolithic distributed feedback (DFB) laser with two separate gain sections is demonstrated for the first time. With a relatively strong grating, each section can be made to operate independently and at different wavelengths. By varying the bias current, the two sections can be tuned closer to each other such that injection locking occurs. Since the master and slave laser share the same waveguide, very high injection ratios can be achieved. Under injection locked conditions the modulation bandwidth is increased from 12 GHz to 23 GHz. An increase of 20dB in linearity is also observed. The increase in modulation performance is on par with our experimental observations using an isolated master laser. This monolithic approach offers reduced size, weight and power consumption compared to external modulation schemes; making it ideal for analog photonic applications. A finite difference time domain model based on coupled traveling waves is developed to accurately model this dual section DFB laser. The model takes into account various optical modes and the spatial variations along the cavity length. The simulated performance is in good agreement with experimental results. Comparison to the classical lumped element laser rate equations is also done to highlight the benefits of using a distributed model.

Jung, Thomas

422

Treatment with Olanzapine is Associated with Modulation of the Default Mode Network in Patients with Schizophrenia  

PubMed Central

Earlier studies have shown widespread alterations of functional connectivity of various brain networks in schizophrenia, including the default mode network (DMN). The DMN has also an important role in the performance of cognitive tasks. Furthermore, treatment with second-generation antipsychotic drugs may ameliorate to some degree working memory (WM) deficits and related brain activity. The aim of this study was to evaluate the effects of treatment with olanzapine monotherapy on functional connectivity among brain regions of the DMN during WM. Seventeen patients underwent an 8-week prospective study and completed two functional magnetic resonance imaging (fMRI) scans at 4 and 8 weeks of treatment during the performance of the N-back WM task. To control for potential repetition effects, 19 healthy controls also underwent two fMRI scans at a similar time interval. We used spatial group-independent component analysis (ICA) to analyze fMRI data. Relative to controls, patients with schizophrenia had reduced connectivity strength within the DMN in posterior cingulate, whereas it was greater in precuneus and inferior parietal lobule. Treatment with olanzapine was associated with increases in DMN connectivity with ventromedial prefrontal cortex, but not in posterior regions of DMN. These results suggest that treatment with olanzapine is associated with the modulation of DMN connectivity in schizophrenia. In addition, our findings suggest critical functional differences in the regions of DMN. PMID:19956088

Sambataro, Fabio; Blasi, Giuseppe; Fazio, Leonardo; Caforio, Grazia; Taurisano, Paolo; Romano, Raffaella; Di Giorgio, Annabella; Gelao, Barbara; Lo Bianco, Luciana; Papazacharias, Apostolos; Popolizio, Teresa; Nardini, Marcello; Bertolino, Alessandro

2010-01-01

423

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

424

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

425

Estimating the 3D Pore Size Distribution of Biopolymer Networks from Directionally Biased Data  

PubMed Central

The pore size of biopolymer networks governs their mechanical properties and strongly impacts the behavior of embedded cells. Confocal reflection microscopy and second harmonic generation microscopy are widely used to image biopolymer networks; however, both techniques fail to resolve vertically oriented fibers. Here, we describe how such directionally biased data can be used to estimate the network pore size. We first determine the distribution of distances from random points in the fluid phase to the nearest fiber. This distribution follows a Rayleigh distribution, regardless of isotropy and data bias, and is fully described by a single parameter—the characteristic pore size of the network. The bias of the pore size estimate due to the missing fibers can be corrected by multiplication with the square root of the visible network fraction. We experimentally verify the validity of this approach by comparing our estimates with data obtained using confocal fluorescence microscopy, which represents the full structure of the network. As an important application, we investigate the pore size dependence of collagen and fibrin networks on protein concentration. We find that the pore size decreases with the square root of the concentration, consistent with a total fiber length that scales linearly with concentration. PMID:24209841

Lang, Nadine R.; Münster, Stefan; Metzner, Claus; Krauss, Patrick; Schürmann, Sebastian; Lange, Janina; Aifantis, Katerina E.; Friedrich, Oliver; Fabry, Ben

2013-01-01

426

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

427

Inference of directed climate networks: role of instability of causality estimation methods  

NASA Astrophysics Data System (ADS)

Climate data are increasingly analyzed by complex network analysis methods, including graph-theoretical approaches [1]. For such analysis, links between localized nodes of climate network are typically quantified by some statistical measures of dependence (connectivity) between measured variables of interest. To obtain information on the directionality of the interactions in the networks, a wide range of methods exists. These can be broadly divided into linear and nonlinear methods, with some of the latter having the theoretical advantage of being model-free, and principally a generalization of the former [2]. However, as a trade-off, this generality comes together with lower accuracy - in particular if the system was close to linear. In an overall stationary system, this may potentially lead to higher variability in the nonlinear network estimates. Therefore, with the same control of false alarms, this may lead to lower sensitivity for detection of real changes in the network structure. These problems are discussed on the example of daily SAT and SLP data from the NCEP/NCAR reanalysis dataset. We first reduce the dimensionality of data using PCA with VARIMAX rotation to detect several dozens of components that together explain most of the data variability. We further construct directed climate networks applying a selection of most widely used methods - variants of linear Granger causality and conditional mutual information. Finally, we assess the stability of the detected directed climate networks by computing them in sliding time windows. To understand the origin of the observed instabilities and their range, we also apply the same procedure to two types of surrogate data: either with non-stationarity in network structure removed, or imposed in a controlled way. In general, the linear methods show stable results in terms of overall similarity of directed climate networks inferred. For instance, for different decades of SAT data, the Spearman correlation of edge weights in the networks is ~ 0.6. The networks constructed using nonlinear measures were in general less stable both in real data and stationarized surrogates. Interestingly, when the nonlinear method parameters are optimized with respect to temporal stability of the networks, the networks seem to converge close to those detected by linear Granger causality. This provides further evidence for the hypothesis of overall sparsity and weakness of nonlinear coupling in climate networks on this spatial and temporal scale [3] and sufficient support for the use of linear methods in this context, unless specific clearly detectable nonlinear phenomena are targeted. Acknowledgement: This study is supported by the Czech Science Foundation, Project No. P103/11/J068. [1] Boccaletti, S.; Latora, V.; Moreno, Y.; Chavez, M. & Hwang, D. U.: Complex networks: Structure and dynamics, Physics Reports, 2006, 424, 175-308 [2] Barnett, L.; Barrett, A. B. & Seth, A. K.: Granger Causality and Transfer Entropy Are Equivalent for Gaussian Variables, Physical Review Letters, 2009, 103, 238701 [3] Hlinka, J.; Hartman, D.; Vejmelka, M.; Novotná, D.; Paluš, M.: Non-linear dependence and teleconnections in climate data: sources, relevance, nonstationarity, submitted preprint (http://arxiv.org/abs/1211.6688)

Hlinka, Jaroslav; Hartman, David; Vejmelka, Martin; Paluš, Milan

2013-04-01

428

Analysis of the large and small signal direct current modulation response up to 60GHz of metal-clad nano-lasers  

NASA Astrophysics Data System (ADS)

The response of metal clad nano-lasers to direct current modulation has been analysed in both the small signal and large signal regimes. Calculations have been performed using rate equations which include the Purcell cavity-enhanced spontaneous emission factor, F, and the spontaneous emission coupling factor ?. Calculations of both the small signal and large signal direct modulation response of nano-lasers indicate opportunities to achieve modulation bandwidth up to 60 GHz with peak responses at resonant frequencies of order 40 GHz and 30 GHz respectively.

Sattar, Z. A.; Shore, K. Alan

2014-09-01

429

Comparison Between Hybrid Direct Aperture Optimized Intensity-Modulated Radiotherapy and Forward Planning Intensity-Modulated Radiotherapy for Whole Breast Irradiation  

SciTech Connect

Purpose: To investigate the planning efficiency and dosimetric characteristics of hybrid direct aperture optimized (hDAO) intensity-modulated radiotherapy (IMRT) compared with forward planning (FP)-IMRT for whole breast irradiation with two tangential beams. Methods and Materials: A total of 15 patients with left-sided breast cancer, categorized with three different breast volumes, were selected for this study. All patients were treated with FP plans to 50 Gy in 25 fractions. The hDAO plans were created by combining two open fields with eight segments in two tangential beam directions and were inversely optimized. Results: The FP and hDAO plans achieved similar breast coverage and sparing of critical organs. The volume of breast receiving 105% of the prescription dose was significantly smaller in the hDAO than in the FP plans: 25% vs. 63% (p = .008) for small, 22% vs. 57% (p = .005) for medium, and 28% vs. 53% (p = .005) for large breasts. Furthermore, the tumor cavity coverage was slightly better in the hDAO plans (92.4% vs. 90.9%). Conclusion: Compared with FP-IMRT, hDAO-IMRT provided dosimetric advantages, significantly reducing the size of the hot spot and slightly improving the coverage of the tumor cavity. In addition, hDAO-IMRT required less planning time and was less dependent on the planner's ability.

Descovich, Martina; Fowble, Barbara; Bevan, Alison; Schechter, Naomi; Park, Catherine [Department of Radiation Oncology, University of California San Francisco, School of Medicine, San Francisco, CA (United States); Xia Ping, E-mail: pxia@radonc.ucsf.ed [Department of Radiation Oncology, University of California San Francisco, School of Medicine, San Francisco, CA (United States)

2010-01-15

430

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

431

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

432