Classical Consensus Research Articles

Consensus model for multi-criteria large-group emergency decision making considering non-cooperative behaviors and minority opinions

Emergency situations often demand high-quality decision-making results because a wrong decision may cause incalculable losses. Therefore, in such cases, the views of all decision makers should be fully considered, especially minority opinions, and the interests of all parties should be well balanced. Additionally, an emergency decision often has to be made within a short period of time, which may require the rational treatment of non-cooperative behaviors. Classical consensus models mainly focus on group decision-making problems where a small number of decision makers participate. However, an emergency decision often involves many stakeholders, and thus requires the participation of larger number of decision makers. In this paper, an improved consensus model is proposed for large-group emergency decision making, and an approach to managing minority opinions and non-cooperative behaviors is described. By simulating the consensus reaching process, a method is presented to determine two important parameters: the minimum group consensus threshold and the maximum number of iterations. Finally, an illustrative example proves that the proposed consensus model is feasible and effective, and a detailed discussion highlights the advantages of this model for managing large-group emergency decision-making problems.

Egalitarianism in the rank aggregation problem: a new dimension for democracy

Winner selection by majority, in an election between two candidates, is the only rule compatible with democratic principles. Instead, when the candidates are three or more and the voters rank candidates in order of preference, there are no univocal criteria for the selection of the winning (consensus) ranking and the outcome is known to depend sensibly on the adopted rule. Building upon XVIII century Condorcet theory, whose idea was to maximize total voter satisfaction, we propose here the addition of a new basic principle (dimension) to guide the selection: satisfaction should be distributed among voters as equally as possible. With this new criterion we identify an optimal set of rankings. They range from the Condorcet solution to the one which is the most egalitarian with respect to the voters. We show that highly egalitarian rankings have the important property to be more stable with respect to fluctuations and that classical consensus rankings (Copeland, Tideman, Schulze) often turn out to be non optimal. The new dimension we have introduced provides, when used together with that of Condorcet, a clear classification of all the possible rankings. By increasing awareness in selecting a consensus ranking our method may lead to social choices which are more egalitarian compared to those achieved by presently available voting systems.

Reaching a Quantum Consensus: Master Equations that Generate Symmetrization and Synchronization

In this paper, we propose and study a master-equation based approach to drive a quantum network with n qubits to a consensus (symmetric) state introduced by Mazzarella et al. The state evolution of the quantum network is described by a Lindblad master equation with the Lindblad terms generated by continuous-time swapping operators, which also introduce an underlying interaction graph. We establish a graphical method that bridges the proposed quantum consensus scheme and classical consensus dynamics by studying an induced graph (with 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2n</sup> nodes) of the quantum interaction graph (with n qubits). A fundamental connection is then shown that quantum consensus over the quantum graph is equivalent to componentwise classical consensus over the induced graph, which allows various existing works on classical consensus to be applicable to the quantum setting. Some basic scaling and structural properties of the quantum induced graph are established via combinatorial analysis. Necessary and sufficient conditions for exponential and asymptotic quantum consensus are obtained, respectively, for switching quantum interaction graphs. As a quantum analogue of classical synchronization of coupled oscillators, quantum synchronization conditions are also presented, in which the reduced states of all qubits tend to a common trajectory.

A nonlinear model of opinion formation on the sphere

In this paper we present a model for opinion dynamics on the $d$-dimensional sphere based on classical consensus algorithms.The choice of the model is motivated by the analysis of the comprehensive literature on the subject, both from the mathematical and the sociological point of views. The resulting dynamics is highly nonlinear and therefore presents a rich structure. Equilibria and asymptotic behavior are then analysed and sufficient condition for consensus are established. Finally we address global stabilization and controllability.

Average consensus via max consensus

Since intuition states that it is simple and fast to compute maxima over networks, we aim at understanding the limits of computing averages over networks through computing maxima. We thus build on top of max-consensus based networks’ cardinality estimation protocols a novel estimation strategy that infers averages through computing maxima of opportunely and locally generated random initial conditions. We motivate the max-consensus strategy explaining why it satisfies practical requirements, we characterize completely its statistical properties, and we analyze when and under which conditions it performs favorably against classical linear consensus strategies in static Cayley graphs.

Consensus for Quantum Networks: Symmetry From Gossip Interactions

This paper extends the consensus framework, widely studied in the literature on distributed computing and control algorithms, to networks of quantum systems. We define consensus situations on the basis of invariance and symmetry properties, finding four different generalizations of classical consensus states. This new viewpoint can be directly used to study consensus for probability distributions, as these can be seen as a particular case of quantum statistical states: in this light, our analysis is also relevant for classical problems. We then extend the gossip consensus algorithm to the quantum setting and prove it converges to symmetric states while preserving the expectation of permutation-invariant global observables. Applications of the framework and the algorithms to estimation and control problems on quantum networks are discussed.

Weighted average consensus problem in networks of agents with diverse time-delays

This paper studies the weighted average consensus problem for networks of agents with fixed directed asymmetric unbalance information exchange topology. We suppose that the classical distributed consensus protocol is destroyed by diverse time-delays which include communication time-delay and self time-delay. Based on the generalized Nyquist stability criterion and the Gerschgorin disk theorem, some sufficient conditions for the consensus of multi-agent systems are obtained. And we give the expression of the weighted average consensus value for our consensus protocol. Finally, numerical examples are presented to illustrate the theoretical results.

A recursive Byzantine-resilient protocol

To solve the consensus problem, the classical consensus protocols require t+1 rounds of message exchange to tolerate t faulty processors, where t=⌊(n−1)/3⌋ and n is the total number of processors in the network. With advancement of software and hardware technologies in recent years, the “actual number of faulty processors” (fact) in a network is usually smaller than t, and fact≪t. However, the classical consensus protocols still need to execute t+1 rounds of message exchange even if there are no faulty processors in the network. To address this issue, we propose a new consensus protocol called Recursive Byzantine-Resilient protocol (RBR protocol). We integrate the concepts of parallel computing, grouping, hierarchy and recursion into this protocol to reduce its time and space complexity. Specifically, the RBR protocol can solve the consensus problem in the presence of 2h(⌊((n/4h)−1)/3⌋+1)−1 Byzantine faulty processors, where h=⌊(lg(n)−2)/2⌋. The time complexity and space complexity of RBR protocol are O(lg(n)) and O(nklg(n)) respectively. The results reveal that RBR protocol outperforms previous protocols in terms of time complexity and in terms of space complexity. In this paper, we also discuss how to enhance the fault-tolerance capability of RBR protocol in achieving consensus through repetitive execution of the protocol when the number of Byzantine faulty processors is greater than 2h(⌊((n/4h)−1)/3⌋+1)−1.

The $$k$$ k -Set consensus problem with weight consideration

In the cloud computing environment, files are duplicated into several copies for storage at different locations to increase their access efficiency and fault tolerance. However, there may exist malicious processors in the cloud computing environment. How to ensure that fault-free processors coordinate to find appropriate locations to store these duplicated files without influence from malicious processors is an important issue. In this paper, we propose a consensus algorithm to assist fault-free processors in reaching a consensus on where to store the duplicated files in the presence of malicious processors. In this paper, we will extend the classical consensus problem to a new type of consensus problem called the $$k$$k-Set consensus problem with weight consideration ($$k$$k-SetW problem). This problem is integrated with the concepts of weight and $$k$$k-Set. In other words, each processor in this problem is allowed to have multiple initial values (i.e., the expected locations for the duplicated files) and set the weight for each initial value. The weighted value shows the processor's preference for an initial value. Regarding the consensus, this problem does not require agreement among all fault-free processors on a single consensus value. It allows coexistence of multiple consensus values as long as the number of consensus values is not greater than $$k$$k (i.e., the maximum number of duplicated files). By solving the $$k$$k-SetW problem, we can help fault-free processors determine the locations for storing the duplicates of at most $$k$$k copies based on their preferences in the presence of malicious processors.

Regulation of the human ABCB10 gene by E2F transcription factors

Here, we report for the first time a functional study of transcriptional regulation of the human ABCB10 gene. We cloned a functional promoter sequence, and then showed that E2F2, E2F3 and E2F4 can activate transcription from the ABCB10 promoter. We identified sites responsible for this activation and confirmed direct binding of E2F4 to these sites in EMSA and ChIP assays. Finally, by silencing the expression of E2F factors we demonstrated their importance in maintenance of the basal ABCB10 expression. This study provides important atypical examples of E2F4 being a transcriptional activator rather than repressor as well as directly binding to a promoter and regulating it through an alternative and classical DNA consensus response element sequences. It also provides a mechanistic link between E2F4 and ABCB10, both of which are involved in the same physiological phenomena: erythroid lineage differentiation and maturation as well as protection against cardiomyocyte cell death.

An Unbiased Proteomic Screen Reveals Caspase Cleavage Is Positively and Negatively Regulated by Substrate Phosphorylation

Post-translational modifications of proteins regulate diverse cellular functions, with mounting evidence suggesting that hierarchical cross-talk between distinct modifications may fine-tune cellular responses. For example, in apoptosis, caspases promote cell death via cleavage of key structural and enzymatic proteins that in some instances is inhibited by phosphorylation near the scissile bond. In this study, we systematically investigated how protein phosphorylation affects susceptibility to caspase cleavage using an N-terminomic strategy, namely, a modified terminal amino isotopic labeling of substrates (TAILS) workflow, to identify proteins for which caspase-catalyzed cleavage is modulated by phosphatase treatment. We validated the effects of phosphorylation on three of the identified proteins and found that Yap1 and Golgin-160 exhibit decreased cleavage when phosphorylated, whereas cleavage of MST3 was promoted by phosphorylation. Furthermore, using synthetic peptides we systematically examined the influence of phosphoserine throughout the entirety of caspase-3, -7, and -8 recognition motifs and observed a general inhibitory effect of phosphorylation even at residues considered outside the classical consensus motif. Overall, our work demonstrates a role for phosphorylation in controlling caspase-mediated cleavage and shows that N-terminomic strategies can be tailored to study cross-talk between phosphorylation and proteolysis.

Consensus for black-box nonlinear agents using optimistic optimization

An important problem in multiagent systems is consensus, which requires the agents to agree on certain controlled variables of interest. We focus on the challenge of dealing in a generic way with nonlinear agent dynamics, represented as a black box with unknown mathematical form. Our approach designs a reference behavior with a classical consensus method. The main novelty is using optimistic optimization (OO) to find controls that closely follow the reference behavior. The first advantage of OO is that it only needs to sample the black-box model of the agent, and so achieves our goal of handling unknown nonlinearities. Secondly, a tight relationship is guaranteed between computation invested and closeness to the reference behavior. Our main results exploit these properties to prove practical consensus. An analysis of representative examples builds additional insight and shows that in some nontrivial problems the optimization is easy to solve by OO. Simulations on these examples accompany the analysis.

Characterization of EstB, a novel cold-active and organic solvent-tolerant esterase from marine microorganism Alcanivorax dieselolei B-5(T)

A novel esterase gene, estB, was cloned from the marine microorganism Alcanivorax dieselolei B-5(T) and overexpressed in E. coli DE3 (BL21). The expressed protein EstB with a predicted molecular weight of 45.1 kDa had a distinct catalytic triad (Ser(211)-Trp(353)-Gln(385)) and the classical consensus motif conserved in most lipases and esterases Gly(209)-X-Ser(211)-X-Gly(213). EstB showed very low similarity to any known proteins and displayed the highest similarity to the hypothetical protein (46%) from Rhodococcus jostii RHA1. EstB showed the optimal activity around pH 8.5 and 20 °C and was identified to be extremely cold-adaptative retaining more than 95% activity between 0 and 10 °C. The values of kinetic parameters on p-NP caproate (K m, K cat and K cat/K m) were 0.15 mM, 0.54 × 10(3) s(-1) and 3.6 × 10(3) s(-1) mM(-1), respectively. In addition, EstB showed remarkable stability in several studied organic solvents and detergents of high concentrations with the retention of more than 70% activity after treatment for 30 min. The cold activity and its tolerance towards organic solvents made it a promising biocatalyst for industrial applications under extreme conditions.

Plant-Derived Food Ingredients for Stimulation of Energy Expenditure

The development of obesity is related to the regulation of energy intake, energy expenditure, and energy storage in the body. Increasing energy expenditure by inducing lipolysis followed by fat oxidation is one of the alternatives which could help to reverse this increasingly widespread condition. Currently, there is no approved drug targeting on stimulation of energy expenditure available. The use of herbal medicines has become a preferred alternative, supported by the classical consensus on the innocuity of herbal medicine vs synthetic drugs, something that often lacks a scientific basis (ban on Ephedra, for example). The inclusion of functional food in the daily diet has also been promoted although its efficacy requires further investigation. This review summarizes the results of recent work focused on the investigation of edible plant materials targeted at various important pathways related to stimulation of energy expenditure. The aim is to evaluate a number of plants that may be of interest for further studies because of their potential to provide novel lead compounds or functional foods which may be used to combat obesity, but require further studies to evaluate their antiobesity activity in humans.

Accurate Registration Using Adaptive Block Processing for Multispectral Images

Image registration is a challenging task, with applications in surveillance, motion estimation, and fusion systems. Due to the diversity of sensors, local distortions and large image size, satellite images are often difficult to accurately register. In the literature, local descriptor-based processing techniques, such as scale-invariant feature transforms (SIAdaptive Block ProcessingFTs), have been applied to register satellite images, which provide robust features. However, these techniques suffer from a high-computational cost, lack of features, and low-distribution quality, which affect the registration accuracy. In this paper, we develop an algorithm to register satellite images based on adaptive block processing to increase the number of features and to improve the distribution quality. In addition, outlier removal using statistical masks are associated with classical random sample consensus (RANSAC); a subsequent comparative analysis demonstrates the accuracy of the proposed method. Typically, a classical SIFT prevents its wide application in recent remote sensing, although this is no longer the case with the proposed adaptive block processing method.

Robustness to noise in synchronization of complex networks

In this report, we investigate dynamical robustness of a complex network to noise injected through one of its nodes. We focus on synchronization of coupled nonlinear systems and, as a special instance, we address the classical consensus protocol for linear integrators. We establish an exact closed-form expression of the synchronization error for the consensus protocol and an approximate result for chaotic units. While structural robustness is known to be significantly affected by attacks targeted to network hubs, our results posit that dynamical robustness is controlled by both the topology of the network and the dynamics of the units. We provide examples where hubs perform better or worse than isolated nodes.

The transcription factor activating enhancer‐binding protein epsilon (AP–2ε) regulates the core promoter of type II collagen (COL2A1)

The transcription factor activating enhancer-binding protein epsilon (AP-2ε) was recently shown to be expressed during late chondrocyte differentiation, especially in hypertrophic chondrocytes. In this study, we were able to reveal that the promoter of the type II collagen (COL2A1) gene, encoding the extracellular matrix protein type II collagen, is specifically regulated by AP-2ε. Expression of COL2A1 is downregulated at the transition of chondroblasts into hypertrophic chondrocytes and our data provide evidence that AP-2ε is involved in this process. In reporter gene assays, overexpression of AP-2ε in cartilaginous cell lines resulted in a significant reduction in COL2A1 core promoter activity of ~ 45%. Furthermore, we found that this process is dose-dependent and highly specific for the epsilon isoform. Computational analysis offered only a single putative AP-2-binding motif within the chosen promoter fragment but site-directed mutagenesis revealed this motif to be regulatory inactive. After expanding our screening to motifs containing minor differences from the classical AP-2 consensus sequence (5'-GCCN3 GGC-3'), we determined the sequence 5'-GCCCAGGC-3' ranging from position -128 to -135 bp as an important regulatory site and responsible for COL2A1 downregulation through AP-2ε. Interaction of AP-2ε with the COL2A1 promoter at this site was confirmed by chromatin immunoprecipitation and electromobility shift assay. Further, our experiments suggest that at least one additional factor is involved in this process. This is the first study to prove regulation of COL2A1 by AP-2ε highlighting the role of the transcription factor as a modulator of cartilage development.

Specificity of linear motifs that bind to a common mitogen-activated protein kinase docking groove.

Mitogen-activated protein kinases (MAPKs) have a docking groove that interacts with linear "docking" motifs in binding partners. To determine the structural basis of binding specificity between MAPKs and docking motifs, we quantitatively analyzed the ability of 15 docking motifs from diverse MAPK partners to bind to c-Jun amino-terminal kinase 1 (JNK1), p38α, and extracellular signal-regulated kinase 2 (ERK2). Classical docking motifs mediated highly specific binding only to JNK1, and only those motifs with a sequence pattern distinct from the classical MAPK binding docking motif consensus differentiated between the topographically similar docking grooves of ERK and p38α. Crystal structures of four complexes of MAPKs with docking peptides, representing JNK-specific, ERK-specific, or ERK- and p38-selective binding modes, revealed that the regions located between consensus positions in the docking motifs showed conformational diversity. Although the consensus positions in the docking motifs served as anchor points that bound to common MAPK surface features and mostly contributed to docking in a nondiscriminatory fashion, the conformation of the intervening region between the anchor points mostly determined specificity. We designed peptides with tailored MAPK binding profiles by rationally changing the length and amino acid composition of intervening regions located between anchor points. These results suggest a coherent structural model for MAPK docking specificity that reveals how short linear motifs binding to a common kinase docking groove can mediate diverse interaction patterns and contribute to correct MAPK partner selection in signaling networks.

Design of a class of nonlinear consensus protocols for multi‐agent systems

SUMMARYThis paper investigates the consensus problem for multi‐agent systems and presents a class of nonlinear consensus protocols. First, we reveal some structure property of the corresponding Laplacian matrix by decomposing the interaction graph into strongly connected components. Then, by means of the input‐to‐state stability and algebraic graph theory, we propose a framework to prove consensus for multi‐agent systems with nonlinear protocols. In particular, we prove that consensus can be always reached in systems of single‐integrator agents with a directed communication topology containing a spanning tree, provided the nonlinear protocol is an odd and increasing function. The nonlinear consensus protocols proposed in this paper include the classical linear consensus protocol as a special case, and may have a wide range of applications, including consensus with faster convergence rates and with bounded control inputs. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Final report on force key comparison CCM.F-K4.a and CCM.F-K4.b for 4 MN and 2 MN forces

This report gives the results for the Comité International des Poids et Mesures (CIPM) key comparisons in force, designated by comparison numbers CCM.F-K4.a and CCM.F-K4.b, for the maximum force values of 4 MN and 2 MN, respectively. Eight National Metrology Institutes, employing nine national force standard machines, participated in these comparisons. The National Institute of Standards and Technology (NIST) served as the pilot institute for these comparisons. Four transducers were employed in two star circulations, with one pair circulated among the participants of CCM.F-K4.a and the other pair circulated for CCM.F-K4.b. The transducers exhibited only minor drift over the circulation time periods; however, the results for one of the transducers circulated for CCM.F-K4.a were limited by excessive sensitivity to orientation about the axis of force application.Two analysis approaches for calculating Key Comparison Reference Values (KCRV) are presented, one employing a classical consensus mean analysis and the other based on weighted mean calculations. Reasonable correlation in the conclusions for individual transducers is seen between the two approaches. The weighted mean approach is extended to yield a KCRV for each of the two force values from the combined data from all of the associated transducers. One of the seven participants at 4 MN, and two of the nine participants at 2 MN, have expanded uncertainty intervals that lie outside of the expanded uncertainty bands for the corresponding weighted mean KCRVs.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).