Extra Connections Research Articles

Single Stage Extra Cardiac Conduit Total Cavopulmonary Connection in Atrial Situs Inversus and Levocardia

10-year female child was presented with complex congenital heart defect—atrial situs inversus, levocardia, discordant atrioventricular connections, double outlet right ventricle, ventricular septal defect, pulmonic stenosis and straddling of atrio-ventricular valves along with bilateral superior vena cava and large patent ductus arteriosus. We describe here the strategy adopted to perform single stage fenestrated extra cardiac conduit total cavo-pulmonary connections in this patient especially concerning cardiac malposition of atrial situs inversus and levocardia.

Modeling of retrofitted steel transmission towers

To meet the increased design loads from upgraded wind load standards and higher power demands, existing aging transmission towers are often in need of retrofitting. One effective way to increase the load carrying capacity of a tower structure is to reinforce its critical leg members through attaching additional elements with bolted cruciform connections. The effectiveness of the leg retrofitted method has been verified experimentally in both leg segments and tower systems. In this paper, a new modeling method for lattice transmission towers with retrofitted leg members was developed in STRAND 7 through the use of truss-beam elements to represent tower members, and spring elements to simulate bolted connections. Numerical results based on the new modeling method agreed well with those from previous experimental retrofitted tower tests. A parametric study showed that: (a) the cruciform connections have a high load-transfer performance in retrofitted steel lattice towers and thus are effective in enhancing the strength of the whole structure, (b) pre-loading in tower members delays the occurrence of the peak load-sharing rate and excessive pre-loading causes a significant reduction of structural strength, and (c) extra mid-panel connections, cruciform connections with higher slip-resistance and increased retrofitting member size can significantly enhance the structural load carrying capacity.

Exploring the Enantioselective Mechanism of Halohydrin Dehalogenase from Agrobacterium radiobacter AD1 by Iterative Saturation Mutagenesis

Halohydrin dehalogenase from Agrobacterium radiobacter AD1 (HheC) shows great potential in producing valuable chiral epoxides and β-substituted alcohols. The wild-type (WT) enzyme displays a high R-enantiopreference toward most aromatic substrates, whereas no S-selective HheC has been reported to date. To obtain more enantioselective enzymes, seven noncatalytic active-site residues were subjected to iterative saturation mutagenesis (ISM). After two rounds of screening aspects of both activity and enantioselectivity (E), three outstanding mutants (Thr134Val/Leu142Met, Leu142Phe/Asn176His, and Pro84Val/Phe86Pro/Thr134Ala/Asn176Ala mutants) with divergent enantioselectivity were obtained. The two double mutants displayed approximately 2-fold improvement in R-enantioselectivity toward 2-chloro-1-phenylethanol (2-CPE) without a significant loss of enzyme activity compared with the WT enzyme. Strikingly, the Pro84Val/Phe86Pro/Thr134Ala/Asn176Ala mutant showed an inverted enantioselectivity (from an ER of 65 [WT] to an ES of 101) and approximately 100-fold-enhanced catalytic efficiency toward (S)-2-CPE. Molecular dynamic simulation and docking analysis revealed that the phenyl side chain of (S)-2-CPE bound at a different location than that of its R-counterpart; those mutations generated extra connections for the binding of the favored enantiomer, while the eliminated connections reduced binding of the nonfavored enantiomer, all of which could contribute to the observed inverted enantiopreference.

Efficiency and robustness of ant colony transportation networks

Efficient and robust transportation networks are key to the effectiveness of many natural systems. In polydomous ant colonies, which consist of two or more spatially separated but socially connected nests, resources must be transported between nests. In this study, we analyse the network structure of the inter-nest trails formed by natural polydomous ant colonies. In contrast to previous laboratory studies, the natural colonies in our study do not form minimum spanning tree networks. Instead the networks contain extra connections, suggesting that in natural colonies, robustness may be an important factor in network construction. Spatial analysis shows that nests are randomly distributed within the colony boundary and we find nests are most likely to connect to their nearest neighbours. However, the network structure is not entirely determined by spatial associations. By showing that the networks do not minimise total trail length and are not determined only by spatial associations, the results suggest that the inter-nest networks produced by ant colonies are influenced by previously unconsidered factors. We show that the transportation networks of polydomous ant colonies balance trail costs with the construction of networks that enable efficient transportation of resources. These networks therefore provide excellent examples of effective biological transport networks which may provide insight into the design and management of transportation systems.

Limited Comp Handover Algorithm For LTE-Advanced

Coordinated multipoint (CoMP) transmission and reception is the key technique in LTE-Advanced to improve the cell-edge throughput and/or system throughput. Joint processing (JP) in CoMP technology provides multiple data transmission points for each user among multiple cooperated radio base stations. Hard handover mechanism is adopted to be used in LTE-Advanced. Standard hard handover algorithm could not satisfy the concept of JP in CoMP in LTE-A due to the constraint of single connection for each user at any time. While the radio resources in the system are fixed, the more multiple data connections a user has, the more radio resources are used for the extra data connections, thus the lower capacity a system becomes. Therefore a new handover algorithm that not only supports JP in CoMP but also takes system capacity into consideration in LTE-A system is necessary. This paper proposes a new handover algorithm known as Limited CoMP Handover Algorithm to support JP in CoMP and overcome the system capacity issue. System performance of Limited CoMP Handover Algorithm is evaluated and compared with open literature handover algorithm via simulation in this paper. The simulation results show that Limited CoMP Handover Algorithm outperforms open literature handover algorithm by having shorter system delay and less system load whilst maintaining a higher system throughput in a high congested network.

An MEG neuroimaging study on the developmental changes of face processing in pre-school aged children

Event Abstract Back to Event An MEG neuroimaging study on the developmental changes of face processing in pre-school aged children Wei He1*, Jon Brock1 and Blake W. Johnson1 1 Macquarie University, Department of Cognitive Science, Australia Introduction: An important research question in developmental neuroscience concerns how the underlying neural mechanisms of face perception develop in early childhood. Magnetoencephalography (MEG) holds great promise for examining this question, because it measures a well-known face sensitive brain response, termed the M170, from young children in an entirely passive manner. The M170 and its electrical equivalent N170 discriminate faces from other non-face objects based on larger amplitudes to face stimuli around 170 ms from stimulus onsets in adults (Rossion & Jacques, 2011). The current study measured the M170 from pre-schoolers using a unique child custom-sized magnetoencephalography (MEG) system (Johnson et al., 2010). Furthermore, we evaluated the effective connectivity of cortical networks underlying the M170 using dynamic causal modelling (DCM); and compared the connectivity patterns in children to those of adults. Methods: Brain responses were measured from 15 young children (aged 4.46 ± 0.93 years) and 15 adults (aged 27.6 ± 6.46 years) during flashing pictures of faces, cars, as well as their phase-scrambled counterparts (Kuefner et al, 2010). There were 64 channels in the child MEG system and 160 channels in the adult MEG system. Surface waveforms were analysed by averaging the strongest response across occipital and temporal sensors separately on each hemisphere based on the time window determined by visual checking on individual data. DCM analyses assumed that the M170 was mediated by sources in the occipital face area (OFA), fusiform face area (FFA), and superior temporal sulcus (STS). Using Bayesian model selection, we evaluated three models of the interconnections between these regions based on previous studies using DCM (Fairhall & Ishai, 2007; Chen, et al., 2009; David et al., 2006). Results: In the surface waveform analysis, the child M170 was slower than the adult M170, but it already showed an adult function pattern (i.e., faster and stronger to faces than cars). Analyses of DCM models showed that the first and simplest model with only forward intra-hemispheric connections from OFA to FFA and STS had the largest model evidence in adults, while in children, the second model with extra inter-hemispheric connections between OFA and contralateral FFA showed the largest model evidence. Conclusions: Early face sensitive brain responses indexed by the M170 are present and functioning in the adult pattern in children as young as 4 years old. However, the functional neural mechanism underlying the M170 undergoes further development and fine-tuning before it reaches adult capacities. Acknowledgements This work was supported by Australian Research Council Linkage Infrastructure Equipment and Facilities Grant LEO668421, Australian Research Council Linkage Project Grant LP0669471, and the Australian Research Council Centre of Excellence for Cognition and its Disorders (CE110001021), http://www.ccd.edu.au. The authors thank Romina Polermo and Douglas Cheyne for helpful comments during the design of the experiment and Bruno Russion for providing the picture stimuli.

QUANTUM TRANSPORT THROUGH FULLY CONNECTED BETHE LATTICES

We introduce a variant of the Bethe lattice, the fully connected Bethe lattice (FCBL); with every site in each shell of the Bethe lattice connected to every other site in the shell. A recently introduced decimation renormalization group (RG) method is utilized to obtain the quantum transmission through the Bethe lattice and FCBL. Although classically the extra intra-shell connections would not change the transmission, they have a large effect on the quantum transport and the wave functions.

Stimulus Artifact Suppression Using the Stimulation Synchronous Adaptive Impulse Correlated Filter for Surface EMG Application

The voluntary EMG (vEMG) signal from electrically stimulated muscle is very useful for feedback control in functional electrical stimulation. However, the recorded EMG signal from surface electrodes has unwanted stimulation artifact and M-wave as well as vEMG. Here, we propose an event-synchronous adaptive digital filter for the suppression of stimulation artifact and M-wave in this application. The proposed method requires a simple experimental setup that does not require extra hardware connections to obtain the reference signals of adaptive digital filter. For evaluating the efficiency of this proposed method, the filter was tested and compared with a least square (LS) algorithm using previously measured data. We conclude that the cancellation of both primary and residual stimulation artifacts is enhanced with an event-synchronous adaptive digital filter and shows promise for clinical application to rehabilitate paretic limbs. Moreover because this algorithm is far simpler than the LS algorithm, it is portable and ready for real-time application.

Dynamical properties of the repressilator model

Oscillatory regulatory networks have been discovered in many regulatory pathways. Due to their enormous complexity, it is necessary to study their dynamics by means of highly simplified models. These models have received particular value because artificial regulatory networks can be engineered experimentally. In this paper, we study dynamical properties of an artificial regulatory oscillator called repressilator. We have shown that oscillations arise from the existence of an absorbing toruslike region in the phase space of the model. This geometric structure requires monotonic repression at all promoters and the absence of any regulatory connections apart from a cyclic repression loop. We show that oscillations collapse as only weak extra connections are introduced if there is imbalance between the attended concentrations and those sufficient for saturation of the promoters. We found that a pair of diffusively coupled repressilators displays synchronization properties similar to those of relaxation oscillators if the regulatory connections in the cyclic repression loop are strong. Thus, the role of strengthening these connections can be viewed as introducing time scale separation among variables. This may explain controversial synchronization properties reported for repressilators in earlier studies.

Influence of feedback in wave based chaotic networks

The effective connectivity between input and output channels in complex coupled networks based on the transfer of electro-magnetic waves (RF, microwave or optical) plays an important role in many fields. The transfer of the waves between connected nodes in complex coupled networks is strongly influenced by the presence of non-reciprocal feedback channels with uni-directional amplification. The introduction of such non-reciprocal channels breaks the time reversal invariance of the connectivity matrix between the input and the output channels of the network. The feedback channels are intrinsically changing the spectral properties of the connectivity matrix and hence the associated static and dynamic transfer properties of the ingoing and outgoing ports of the network. Here we use a random matrix model to represent the complex and fully chaotic network without feedback. Extra feedback connections are introduced that change the reciprocity and time reversal invariance of the reference network and hence the connectivity. Exploiting a modern electrical engineering description of multi-port complex circuits in terms of the S-matrix of internal multi-port sections, we show by computer simulations the influence of feedback for increasing network complexity. The results are interpreted using a random matrix approach for the multi-port connectivity matrix. The effect of amplifying bi-directional or uni-directional connecting loop on the properties of the resulting S-matrix are computed for increasing network size. The signal transfer capacity of a multi channel the network based on the Smatrix shows for smaller networks a strong influence of the extra connected loop. In particular for the uni-directional amplifying feedback loop.

Blasting Off on an Actin Comet Tail

Blasting Off on an Actin Comet Tail

New Cardiac MRI Gating Method Using Event-Synchronous Adaptive Digital Filter

When imaging the heart using MRI, an artefact-free electrocardiograph (ECG) signal is not only important for monitoring the patient's heart activity but also essential for cardiac gating to reduce noise in MR images induced by moving organs. The fundamental problem in conventional ECG is the distortion induced by electromagnetic interference. Here, we propose an adaptive algorithm for the suppression of MR gradient artefacts (MRGAs) in ECG leads of a cardiac MRI gating system. We have modeled MRGAs by assuming a source of strong pulses used for dephasing the MR signal. The modeled MRGAs are rectangular pulse-like signals. We used an event-synchronous adaptive digital filter whose reference signal is synchronous to the gradient peaks of MRI. The event detection processor for the event-synchronous adaptive digital filter was implemented using the phase space method-a sort of topology mapping method-and least-squares acceleration filter. For evaluating the efficiency of the proposed method, the filter was tested using simulation and actual data. The proposed method requires a simple experimental setup that does not require extra hardware connections to obtain the reference signals of adaptive digital filter. The proposed algorithm was more effective than the multichannel approach.

On final evolutions in the restricted planar parabolic three-body problem

In this paper, we prove the existence of special type of motions in the restricted planar parabolic three-body problem, of the type exchange, emission—capture, and emission—escape with close passages to collinear and equilateral triangle configuration, among others. The proof is based on a gradient-like property of the Jacobian function when equations of motion are written in a rotating-pulsating reference frame, and the extended phase space is compactified in the time direction. Thus a phase space diffeomorphic to [−π/2, π/2] × ℂ−μ1,μ2 × ℂ -coordinates (θ, ζ, ζ′) is obtained with the boundary manifolds θ = ±π/2 corresponding to escapes of the binaries when time tends to±∞. It is shown there exists exactly five critical points on each boundary, corresponding to classic homographic solutions. The connections of the invariant manifolds associated to the collinear configurations, and stable/unstable sets associated to binary collision on the boundary manifolds, are obtained for arbitrary masses of the primaries. For equal masses extra connections are obtained, which include equilateral configurations. Based on the gradient-like property, a geometric criterion for capture is proposed and is compared with a criterion introduced by Merman (1953b) in the fifties, and an example studied numerically by Kocina (1954).

Regularization of dynamics in an ensemble of nondiffusively coupled chaotic elements

We investigate the dynamics in an ensemble of chaotic elements with nondiffusive coupling. First, we analyze the case of global coupling. The type of coupling we consider leads to the suppression of oscillations in the whole ensemble at a high coupling strength. A distinct feature of this transition from high-dimensional chaos at a low coupling strength to the stationary state is that there is no partially ordered phase characterized by a large number of coexisting synchronized clusters. A two-cluster mode emerges abruptly, replacing the asynchronous mode. We focus on the influence of connectivity on the dynamics in the two-cluster modes and their domains of existence. We introduce a parameter that characterizes the connectivity: the range of coupling. Our computational and analytical results indicate that the most significant changes in the dynamics occur in the case of local coupling, when extra connections are added. By contrast, if the range of coupling is high, even substantial changes in this range have a small influence on the dynamics.

Fault prediction/diagnosis and sensor validation technique for a steam power plant

An intelligent sensor validation and fault prediction/diagnosis technique for a typical steam power plant is proposed and studied. An auto-associative Artificial Neural Network (ANN) is trained to examine the consistency of the overall simulated data and allocate a confidence level to each signal.The same set is used to replace the missing or faulty data with a close approximation. For fault prediction and diagnostic system a feed-forward ANN with extra linear connections is trained to recognise faulty and healthy behaviour of the steam cycle for a wide range of operating conditions. Both ANNs are tested with unseen data sets, including combined scenarios of the partially failed system to assess fault prediction capability of the proposed ANN. It is concluded that a significantly more reliable sensor reading and a highly accurate fault prediction/diagnosis system is achieved.

Crossover behavior in a communication network.

We address the problem of message transfer in a communication network. The network consists of nodes and links, with the nodes lying on a two-dimensional lattice. Each node has connections with its nearest neighbors, whereas some special nodes, which are designated as hubs, have connections to all the sites within a certain area of influence. The degree distribution for this network is bimodal in nature and has finite variance. The distribution of travel times between two sites situated at a fixed distance on this lattice shows fat-fractal behavior as a function of hub density. If extra assortative connections are now introduced between the hubs so that each hub is connected to two or three other hubs, the distribution crosses over to power-law behavior. Crossover behavior is also seen if end-to-end short cuts are introduced between hubs whose areas of influence overlap, but this is much milder in nature. In yet another information transmission process, namely, the spread of infection on the network with assortative connections, we again observed crossover behavior of another type, viz., from one power law to another for the threshold values of disease transmission probability. Our results are relevant for the understanding of the role of network topology in information spread processes.

Extracting diffusion length using the single contact electron beam induced current technique

The single contact electron beam induced current (SC-EBIC) technique has been shown to be more effective than conventional EBIC in the imaging of complex VLSI circuitry. This configuration allows large areas of integrated circuits to be imaged. It is proposed in this paper that the application of SC-EBIC can be extended to extracting the diffusion length of semiconductor materials. The accuracy of the diffusion length obtained with this configuration was found to be approximately the same as those obtained using conventional EBIC techniques. However, the SC-EBIC configuration requires only a single connection to the specimen and no extra connections even for multi-junction devices.

Fault-tolerant processor arrays using additional bypass linking allocated by Graph-Node coloring

An advanced spare-connection scheme for k-out-of-n redundancy called generalized additional bypass linking is proposed for constructing fault-tolerant massively parallel computers with series-connected, mesh-connected, or tree-connected processing element (PE) arrays. This scheme uses bypass links with wired OR connections to selectively connect the primary PEs to a spare PE in parallel. These bypass links are allocated to the primary PEs by node-coloring of a graph with a minimum inter-node distance of three in order to minimize the number of bypass links (i.e., the chromatic number). The main advantage of this scheme is that it can be used for constructing various k-out-of-n configurations capable of enhanced PE-to-PE communication and broadcast while still achieving strong fault tolerance for these PEs and links. In particular, it enables the construction of optimal r-strongly-fault-tolerant configurations capable of direct k-out-of-n selections by providing r spare PEs and r extra connections per PE for any kind of array when node-coloring with a distance of three is used. This simple spare-circuit structure enhances fault tolerance more than conventional schemes do. The node-coloring patterns were constructed using new node-coloring algorithms and the chromatic numbers were evaluated theoretically. Enhanced PE-to-PE communication and broadcast were achieved by using new fault-tolerant routing algorithms based on the properties of the node-coloring patterns with four or five message transmission steps being optimal configurations with any size array.

Learning from instructional text: Test of an individual-differences model.

An individual-differences model of learning from instructional text was tested on 211 Air Force recruits. The results strongly supported the model, with a high level of fit for a structural equation modeling analysis using LISREL 8 (K. Joreskog & D. Sorbom, 1993). According to the model, learning from text is determined by making connections among ideas, including ideas from the text and from prior knowledge. Making the connections depends in part on 4 variables that differ among individuals: metacognition, specifically the ability to sense that one's mental representation is not coherent and consequently needs extra connections; inference-making ability, which spreads activation among the elements within working memory, which provides the arena in which the connections are made; and domain knowledge, which provides prior knowledge elements for use by the inference-making process to make connections.

Smaller diameters in hypercube-variant networks

A number of hypercube-variant networks attempt to improve the hypercube by adding extra connections and thus reducing the diameter of the constructed network. We briefly outline a model which describes these variant networks. Further, we show that by restricting this model, we can describe hypercube variants with exactly the same number of edges as the hypercube. We mention several such networks which all have diameter about n/2. We describe a new network within this class that has diameter about 2n/5, thus improving the best known previous bound by a constant factor. We show that within a limited construction paradigm our network is best possible.