Unitary Network Research Articles

Similarities and differences in the default mode network across rest, retrieval, and future imagining.

The default mode network (DMN) has been identified reliably during rest, as well as during the performance of tasks such as episodic retrieval and future imagining. It remains unclear why this network is engaged across these seemingly distinct conditions, though many hypotheses have been proposed to account for these effects. Prior to generating hypotheses explaining common DMN involvement, the degree of commonality in the DMN across these conditions, within individuals, must be statistically determined to test whether or not the DMN is truly a unitary network, equally engaged across rest, retrieval and future imagining. To provide such a test, we used comparable paradigms (self-directed, uninterrupted thought of equal duration) across the three conditions (rest, retrieval, and future imagining) in a within-participant design. We found lower than expected pattern similarity in DMN functional connectivity across the three conditions. Similarity in connectivity accounted for only 40-50% of the total variance. Partial Least Squares (PLS) analyses revealed the medial temporal regions of the DMN were preferentially coupled with one another during episodic retrieval and future imagining, whereas the non-medial temporal regions of the DMN (e.g., medial prefrontal cortex, lateral temporal cortex, and temporal pole) were preferentially coupled during rest. These results suggest that DMN connectivity may be more flexible than previously considered. Our findings are in line with emerging evidence that the DMN is not a static network engaged commonly across distinct cognitive processes, but is instead a dynamic system, topographically changing in relation to ongoing cognitive demands. Hum Brain Mapp 38:1155-1171, 2017. © 2016 Wiley Periodicals, Inc.

The hermeneutics of sport: limits and conditions of possibility of our understandings of sport

In this paper, linguistic-analytic philosophy has been identified as the dominant methodology in the philosophy of sport. The hermeneutics of sport is contrasted with linguistic-analytic philosophy by analyzing Heidegger’s view of Truth. In doing so, two views of philosophy are compared: ontology or description. Sport hermeneutics’ task has to do with description. Hermeneutical explanations of sport attempt to describe the facticity of sport. Such a facticity is formed by three moments: embodiment, capabilities, and tradition. They are not components of sport that can be identified as essential components but rather, they are identifiable only for analytic purposes. These three above-mentioned elements cannot be identified as elements, because they are intrinsically intertwined forming a unitary network of meaning. The task of sport hermeneutics is to describe the different relationships that compose such a network of meaning. In doing so, sport is a humane activity linked to the constitutive human task of making sense of reality by projecting meaning into it.

Spectral stability of unitary network models

We review various unitary network models used in quantum computing, spectral analysis or condensed matter physics and establish relationships between them. We show that symmetric one-dimensional quantum walks are universal, as are CMV matrices. We prove spectral stability and propagation properties for general asymptotically uniform models by means of unitary Mourre theory.

Tight bound on the trace distance between a realistic device with partially indistinguishable bosons and the ideal BosonSampling

We study the closeness of an experimental unitary bosonic network with only partially indistinguishable bosons in an arbitrary mixed input state, in particular an experimental realization of the BosonSampling, to the ideal bosonic network, where the measure of closeness of two networks is the trace distance between the output probability distributions. An upper bound on the trace distance to the ideal bosonic network is proven and also a bound on the difference between probabilities of an output configuration. Moreover, the upper bound on the trace distance is tight, provided that a physically transparent distinguishability conjecture is true. For a small distinguishability error, it is shown that a realistic device with $N$ bosons is at a constant trace distance to ideal BosonSampling under the $O({N}^{\ensuremath{-}1})$ scaling of the mismatch of internal states of bosons.

National targets, process transformation and local consequences in an NHS emergency department (ED): a qualitative study.

BackgroundIn the attempt to reduce waiting times in emergency departments, various national health services have used benchmarking and the optimisation of patient flows. The aim of this study was to examine staff attitudes and experience of providing emergency care following the introduction of a 4 hour wait target, focusing on clinical, organisational and spatial issues.MethodsA qualitative research design was used and semi-structured interviews were conducted with 28 clinical, managerial and administrative staff members working in an inner-city emergency department. A thematic analysis method was employed and NVivo 8 qualitative data analysis software was used to code and manage the emerging themes.ResultsThe wait target came to regulate the individual and collective timescales of healthcare work. It has compartmentalised the previous unitary network of emergency department clinicians and their workspace. It has also speeded up clinical performance and patient throughput. It has disturbed professional hierarchies and facilitated the development of new professional roles. A new clinical information system complemented these reconfigurations by supporting advanced patient tracking, better awareness of time, and continuous, real-time management of emergency department staff. The interviewees had concerns that this target-oriented way of working forces them to have a less personal relationship with their patients.ConclusionsThe imposition of a wait-target in response to a perceived “crisis” of patients’ dissatisfaction led to the development of a new and sophisticated way of working in the emergency department, but with deep and unintended consequences. We show that there is a dynamic interrelation of the social and the technical in the complex environment of the ED. While the 4 hour wait target raised the profile of the emergency department in the hospital, the added pressure on clinicians has caused some concerns over the future of their relationships with their patients and colleagues. To improve the sustainability of such sudden changes in policy direction, it is important to address clinicians’ experience and satisfaction.

Sufficient condition for the mode mismatch of single photons for scalability of the boson-sampling computer

The boson sampler proposed by Aaronson and Arkhipov is a nonuniversal quantum computer, which can serve as evidence against the extended Church-Turing thesis. It samples the probability distribution at the output of a linear unitary optical network with indistinguishable single photons at the input. Four experimental groups have already tested their small-scale prototypes with up to four photons. A boson sampler with a few dozens of single photons is believed to be hard to simulate on a classical computer. For scalability of a realistic boson sampler with current technology it is necessary to know the effect of the photon mode mismatch on its operation. Here a nondeterministic model of the boson sampler is analyzed, which employs partially indistinguishable single photons emitted by identical sources. A sufficient condition on the average mutual fidelity $\ensuremath{\langle}\mathcal{F}\ensuremath{\rangle}$ of the single photons is found, which guarantees that the realistic boson sampler outperforms the classical computer. Moreover, the boson-sampler computer with partially indistinguishable single photons is scalable and has more power than classical computers when the single-photon mode mismatch $1\ensuremath{-}\ensuremath{\langle}\mathcal{F}\ensuremath{\rangle}$ scales as $O({N}^{\ensuremath{-}3/2})$ with the total number of photons $N$.

Toward a self-consistent and unitary reaction network for big-bang nucleosynthesis

Author(s): Paris, MW; Brown, LS; Hale, GM; Hayes-Sterbenz, AC; Jungman, G; Kawano, T; Fuller, GM; Grohs, EB; Kunieda, S | Abstract: Unitarity, the mathematical expression of the conservation of probability in multichannel reactions, is an essential ingredient in the development of accurate nuclear reaction networks appropriate for nucleosynthesis in a variety of environments. We describe our ongoing program to develop a reaction for the big-bang nucleosynthesis environment and look at an example of the need and power of unitary parametrizations of nuclear scattering and reaction data. Recent attention has been focused on the possible role of the 9B compound nuclear system in the resonant destruction of 7Li during primordial nucleosynthesis. We have studied reactions in the 9B compound system with a multichannel, two-body unitary R-matrix code (EDA) using the known elastic and reaction data, in a four-channel treatment. The data include elastic 6Li(3He, 3He)6Li differential cross sections from 0.7 to 2.0 MeV, integrated reaction cross sections for energies from 0.7 to 5.0 MeV for 6Li(3He,p)8Be* and from 0.4 to 5.0 MeV for the 6Li(3He,d)7Be reaction. Capture data have been added to the previous analysis with integrated cross section measurements from 0.7 to 0.825 MeV for 6Li(3He,γ) 9B. The resulting resonance parameters are compared with tabulated values from TUNL Nuclear Data Group analyses. Previously unidentified resonances are noted and the relevance of this analysis and a unitary reaction network for big-bang nucleosynthesis are emphasized. © Owned by the authors, published by EDP Sciences, 2014.

ASYMPTOTIC EVALUATION OF BOSONIC PROBABILITY AMPLITUDES IN LINEAR UNITARY NETWORKS IN THE CASE OF LARGE NUMBER OF BOSONS

An asymptotic analytical approach is proposed for bosonic probability amplitudes in unitary linear networks, such as the optical multiport devices for photons. The asymptotic approach applies for large number of bosons N ≫ M in the M-mode network, where M is finite. The probability amplitudes of N bosons unitarily transformed from the input modes to the output modes of a unitary network are approximated by a multidimensional integral with the integrand containing a large parameter (N) in the exponent. The integral representation allows an asymptotic estimate of bosonic probability amplitudes up to a multiplicative error of order 1/N by the saddle point method. The estimate depends on solution of the scaling problem for the M × M-dimensional unitary network matrix: to find the left and right diagonal matrices which scale the unitary matrix to a matrix which has specified row and column sums (equal, respectively, to the distributions of bosons in the input and output modes). The scaled matrices give the saddle points of the integral. For simple saddle points, an explicit formula giving the asymptotic estimate of bosonic probability amplitudes is derived. Performance of the approximation and the scaling of the relative error with N are studied for two-mode network (the beam splitter), where the saddle-points are roots of a quadratic and an exact analytical formula for the probability amplitudes is available, and for three-mode network (the tritter).

The CDK Network: Linking Cycles of Cell Division and Gene Expression

Cyclin-dependent kinases (CDKs) play essential roles in cell proliferation and gene expression. Although distinct sets of CDKs work in cell division and transcription by RNA polymerase II (Pol II), they share a CDK-activating kinase (CAK), which is itself a CDK-Cdk7-in metazoans. Thus a unitary CDK network controls and may coordinate cycles of cell division and gene expression. Recent work reveals decisive roles for Cdk7 in both pathways. The CAK function of Cdk7 helps determine timing of activation and cyclin-binding preferences of different CDKs during the cell cycle. In the transcription cycle, Cdk7 is both an effector kinase, which phosphorylates Pol II and other proteins and helps establish promoter-proximal pausing; and a CAK for Cdk9 (P-TEFb), which releases Pol II from the pause. By governing the transition from initiation to elongation, Cdk7, Cdk9 and their substrates influence expression of genes important for developmental and cell-cycle decisions, and ensure co-transcriptional maturation of Pol II transcripts. Cdk7 engaged in transcription also appears to be regulated by phosphorylation within its own activation (T) loop. Here I review recent studies of CDK regulation in cell division and gene expression, and propose a model whereby mitogenic signals trigger a cascade of CDK T-loop phosphorylation that drives cells past the restriction (R) point, when continued cell-cycle progression becomes growth factor-independent. Because R-point control is frequently deregulated in cancer, the CAK-CDK pathway is an attractive target for chemical inhibition aimed at impeding the inappropriate commitment to cell division.

Variational Monte Carlo with the multiscale entanglement renormalization ansatz

Monte Carlo sampling techniques have been proposed as a strategy to reduce the computational cost of contractions in tensor network approaches to solving many-body systems. Here we put forward a variational Monte Carlo approach for the multi-scale entanglement renormalization ansatz (MERA), which is a unitary tensor network. Two major adjustments are required compared to previous proposals with non-unitary tensor networks. First, instead of sampling over configurations of the original lattice, made of L sites, we sample over configurations of an effective lattice, which is made of just log(L) sites. Second, the optimization of unitary tensors must account for their unitary character while being robust to statistical noise, which we accomplish with a modified steepest descent method within the set of unitary tensors. We demonstrate the performance of the variational Monte Carlo MERA approach in the relatively simple context of a finite quantum spin chain at criticality, and discuss future, more challenging applications, including two dimensional systems.

Meridian is a Three-Dimensional Network from Bio-Electromagnetic Radiation Interference: An Interference Hypothesis of Meridian

An electromagnetic radiation field within a biological organism is characterized by non-local interference. The interfering beams form a unitary tridimensional network with beams of varying intensity, also called striae, which are distributed on the organism surface. These striae are equivalent to semi-reflectors. The striae carry bio-information of corresponding organs and, thus, integrate all tissues, and organs of the organism. The longitudinal striae are classified as channels, while the transverse striae are collaterals. The acupoints are seen as the points where electromagnetic interfering striae intersect or converge. This hypothesis builds a foundation to understand the traditional Chinese medicine, including acupuncture, from the perspective of scientific knowledge.

Do distinct atypical cortical networks process biological motion information in adults with Autism Spectrum Disorders?

Whether people with Autism Spectrum Disorders (ASDs) have a specific deficit when processing biological motion has been a topic of much debate. We used psychophysical methods to determine individual behavioural thresholds in a point-light direction discrimination paradigm for a small but carefully matched groups of adults (N=10 per group) with and without ASDs. These thresholds were used to derive individual stimulus levels in an identical fMRI task, with the purpose of equalising task performance across all participants whilst inside the scanner. The results of this investigation show that despite comparable behavioural performance both inside and outside the scanner, the group with ASDs shows a different pattern of BOLD activation from the TD group in response to the same stimulus levels. Furthermore, connectivity analysis suggests that the main differences between the groups are that the TD group utilise a unitary network with information passing from temporal to parietal regions, whilst the ASD group utilise two distinct networks; one utilising motion sensitive areas and another utilising form selective areas. Furthermore, a temporal-parietal link that is present in the TD group is missing in the ASD group. We tentatively propose that these differences may occur due to early dysfunctional connectivity in the brains of people with ASDs, which to some extent is compensated for by rewiring in high functioning adults.

A dual physiological character for cerebral mechanisms of sexuality and cognition: common somatic peripheral afferents

The dual theory of sexuality is a work in progress that tries to put together all the significant physiological aspects described on this subject, the most recent published article discussing about the hormonal and pheromonal neuromodulation of somatic peripheral afferents. But sexuality and cognition shares common somatic peripheral afferents, so that a good understanding of sexual mechanisms supposes also a good knowledge of the essential psychological mechanisms/neuromodulators. Current psychological approaches could be limited to two general tendencies. Some authors consider that cerebral neuronal connexions generate a unitary network substrate that - increasing in its complexity - becomes compatible with our complex mental function. Others suggest that such a complex cerebral function correspond actually to a system based on subsystems, represented by distinct neuronal units (not necessarily complexes) that interact each other. Starting from basic somatic/sexual neurophysiological elements and general accepted psychological aspects, the discussion gave sense to the last point of view, namely that genesis of a new function is the result of cooperation between distinct structural and functional units. Contrary to the classical concepts, this paper sows the fact that mental perception corresponds actually (in term of touch/tangibility) to the internal representation of an external object while sensations realize an internal representation of the external characteristics of environmental object. As a conclusion, sexuality and cognition are two distinct autonomic/dual functions, interrelated at both cerebral and peripheral level. Peripheral interference implies intervention of some specific (mental and sexual) neuromodulators, making external information act as internal mental or internal sexual stimuli. Central cerebral interferences are also clinically and pharmacologically documented, specific neuromodulators being taken into account. Supplementary studies would be necessary to complete psychosexual dualism, presenting the association between image and perception for the genesis of visual perception or between image and sensation for the genesis of visual sensations, complex (mental or sexual) stimuli that suppose a synergic action between distinct neuromodulators. This central synergism supposes a peripheral synergism between left visual field and right nostril, aspects that will be discussed largely in a future article.

Statistical property of the effect of Au nanoparticle decoration on the carbon nanotube network

Statistical analysis of the change in electrical characteristic of single-walled carbon nanotube (swCNT) network after the decoration of Au nanoparticles (NPs) is presented. We have fabricated 100 unitary swCNT network devices on a single chip employing a concentric electrode array by swCNT dip-coating and thermal evaporation of Au. The experimental results show that the decoration of Au-NP on the swCNT network can decrease not only its resistance but also variation in the resistance distribution. Remarkably, we have found that the change in electrical characteristic is correlated with the resistance value of the bare swCNT network.

Merchant Fee Determination in Unitary Networks with Price Competition Among Merchants

This paper investigates the determination of the merchant usage fee of a monopolistic unitary payment card network based on characteristics of the downstream market. Merchants engage in Bertrand price competition that allows for an observation of heterogeneous products. We find that the payment card network extracts a part of the economic rent that merchants obtain. The higher this rent, the higher the corresponding merchant usage fee. The rent, and consequently the merchant usage fee, is increasing in the downstream market size but decreasing in the price elasticity of consumer demand, as well as in the substitutability of products, and, interestingly, in the fraction of consumers preferring card payments.

Ensembles of Neural Networks for Fault Diagnosis in Analog Circuits

A new neural network-based analog fault diagnosis strategy is introduced. Ensemble of neural networks is constructed and trained for efficient and accurate fault classification of the circuit under test (CUT). In the testing phase, the outputs of the individual ensemble members are combined to isolate the actual CUT fault. Prominent techniques for producing the ensemble are utilized, analyzed and compared. The created ensemble exhibit high classification accuracy even if the CUT has overlapping fault classes which cannot be isolated using a unitary neural network. Each neural classifier of the ensemble focuses on a particular region in the CUT measurement space. As a result, significantly better generalization performance is achieved by the ensemble as compared to any of its individual neural nets. Moreover, the selection of the proper architecture of the neural classifiers is simplified. Experimental results demonstrate the superior performance of the developed approach.

Standing Surety in Europe: Common Core or Tower of Babel?

This article analyses the treatment of non‐professional suretyship agreements across the EU in the context provided by Commission initiatives aimed firstly at creating a single market in financial services and secondly at improving the coherence of European private law. Predictably, given their polycontextual function, we are confronted with starkly divergent national approaches towards such agreements: a ‘Tower of Babel’ rather than a ‘common core’. The article proceeds to consider how we may see elements of commonality arising through the tension between the differing national approaches – seen in terms of a Unitary Network. In the course of this analysis the treble paradox of surety protection is described. The article finishes with a prediction of the relevance of a dual‐track strategy in this field: involving measures of sector‐specific, vertical harmonisation, and a programme of common‐law style, non‐legislative harmonisation through judicial convergence.

Quantum computing and hidden variables

This paper initiates the study of hidden variables from the discrete, abstract perspective of quantum computing. For us, a hidden-variable theory is simply a way to convert a unitary matrix that maps one quantum state to another, into a stochastic matrix that maps the initial probability distribution to the final one in some fixed basis. We list seven axioms that we might want such a theory to satisfy, and then investigate which of the axioms can be satisfied simultaneously. Toward this end, we construct a new hidden-variable theory that is both robust to small perturbations and indifferent to the identity operation, by exploiting an unexpected connection between unitary matrices and network flows. We also analyze previous hidden-variable theories of Dieks and Schrodinger in terms of our axioms. In a companion paper, we will show that actually sampling the history of a hidden variable under reasonable axioms is at least as hard as solving the Graph Isomorphism problem; and indeed is probably intractable even for quantum computers.

Enabling Italian e-government through a cooperative architecture

The Italian government is using the successes and failures of previous e-government networking projects to develop a unitary network that links all public administrations.

Stereophonic signal processor

A frequency-dependent linear audio signal processor takes source signals S in input signals and provide directionally spread directionally encoded output signals. The processor directionally encodes with constant gain magnitude frequency components of the source signal S to-and-fro across a predetermined directional stage P" as frequency increases such that at least three predetermined positions within the stage P", the directional encoding has substantially zero perceived phasiness. The processor may be a frequency-dependent rotation matrix for stereo input signal and may be a unitary network using a feedback path around parallel identical all-pass networks in series with a rotation matrix and a feedforward path bypassing the all-pass networks. Successive frequencies of positioning of source signal S at a predetermined position P within the stage P" are preferably spaced approximately uniformly on a logarithmic or Bark Frequency scale. Several sources S may have individually adjustable spreads while sharing common processor.