1,721,237 research outputs found
Urinary Nucleic Acid in Tumor: Bioinformatics Approaches
No full textApplication of next generation sequencing techniques in the field of liquid biopsy, in particular urine, requires specific bioinformatics methods in order to deal with its peculiarity. Many aspects of cancer can be explored starting from nucleic acids, especially from cell-free DNA and circulating tumor DNA in order to characterize cancer. It is possible to detect small mutations, as single nucleotide variants, small insertions and deletions, copy-number alterations, and epigenetic profiles. Due to the low fraction of circulating tumor DNA over the whole cell-free DNA, some methods have been exploited. One of them is the application of unique barcodes to each DNA fragment in order to lower the limit of detection of cancer-related variants. Some bioinformatics workflows and tools are the same of a classic analysis of tumor tissue, but there are some steps in which specific algorithms have to be introduced
On consensus protocols allowing joint-agent interactions
Full text linkIn this note we consider consensus protocols where an agent would not be influenced by any of his neighbours singularly taken, but might be sensitive to the simultaneous and coherent influence of two or more of them. This may resemble several common behaviours in social, economic and opinion networks (i.e. conformity, risk aversion, social inertia, herding). We derive novel graph-theoretical concepts to describe and analyze the ability of general networks with joint-agent interactions to converge towards consensus. Interestingly, and for the first time, we borrow to this end the language of Petri Nets as a convenient way to describe bipartite directed graphs, showing how the notion of siphon is helpful in characterizing the flow of information across the network and its ability to induce attainment of consensus among agents in the considered set-up
Necessary and Sufficient Conditions for Consensus in Nonlinear Monotone Networks with Unilateral Interactions
Full text linkThis paper deals with an extended framework of the distributed asymptotic agreement problem by allowing the presence of unilateral interactions (optimistic or pessimistic) in place of bilateral ones, for a large class of nonlinear monotone time-varying networks. In this original setup we firstly introduce notions of unilateral optimistic and/or pessimistic interaction, of associated bicolored edge in the interaction graph and a suitable graph-theoretical connectedness property. Secondly, we formulate a new assumption of integral connectivity and show that it is sufficient to guarantee exponential convergence towards the agreement subspace. Finally, we show that the proposed conditions are also necessary for consensuability and discuss how the new notions of bicolored graph and related connectivity concepts encompass the usual criteria in the standard case of bilateral interactions. Theoretical advances are emphasized through illustrative examples given both to support the discussion and to highlight how the proposed framework extends all existing conditions for consensus of monotone networks
A fast algorithm for Direct Numerical Simulation of turbulent convection with immersed boundaries
No full textA parallel algorithm is presented for the Direct Numerical Simulation of convection flows in open or partially confined periodic domains, containing immersed cylindrical bodies of arbitrary cross-section. The governing equations are discretized by means of the Finite Volume method on Cartesian grids. The method presented includes a triperiodic Poisson solver employed irrespective of the actual boundary shape and a second order accuracy for the computational domain, including the near wall regions, when walls are defined as immersed boundaries. The numerical solution of the set of linear equations resulting from discretization is carried out by means of efficient and highly parallel direct solvers. Verification and validation of the numerical procedure is reported in the paper, for laminar and turbulent pipe flow, and for the case of flow around an array of heated cylindrical rods arranged in a triangular lattice. The formal accuracy of the method is demonstrated in laminar flow conditions, and DNS results in turbulent conditions are compared to available literature data, thus confirming the favorable qualities of the method
Two-phase flow characterization through recurrence quantification analysis of the dominant features of experimental dynamics
No full textThis paper describes a novel approach to the analysis of the experimental void fraction time series detected in air–water upward two-phase flows within a vertical channel. Singular Value Decomposition (SVD) is applied to the experimental void fraction time series in order to assess a novel state space spanned by the principal components of the flow dynamics; in fact, this was demonstrated in a previous study to be effective in separating the dominant features from noise-like dynamics and, above all, in evidencing the existence of recurrent behaviours. As recurrence is a typical and fundamental signature of low-order deterministic nonlinear dynamics, the present study aims at reaching a detailed insight on the recurrent structures that characterize the experimental void fraction time series, which were measured during an experimental campaign encompassing the entire spectrum of patterns in vertical air–water upward flows. The main novelty of the present study is the adoption of the tools collectively known as Recurrence Quantification Analysis not directly to the experimental time series, as it is increasingly proposed in the analysis of two-phase flows, but to their most important principal components. The goal is to obtain a more reliable characterization of two-phase flow patterns, which is based only on the relevant features and, hence, is unbiased by noisy high-order dynamics. Reported results show that the present approach indeed provides a powerful tool for the characterisation of the variety of complex dynamics exhibited by two-phase flows, as well as for flow pattern classification
Towards a new Liquid Argon Imaging Chamber for the MODULAr project
No full textThe MODULAr project foresees the exploitation of a new liquid Argon imaging de- tector, of at least 20 kt fiducial mass, to be operated in a shallow depth location under the Gran Sasso Mountain. It will be devoted to study neutrino oscillations with an optimized off-axis CNGS neutrino beam. Cosmic neutrinos as well as proton decay will also be addressed. The MODULAr detector will vastly inherit from the technology developed for ICARUS-T600. However, such an increase in the volume over the current ICARUS-T600 needs to be carefully considered. It is con- cluded that a single, huge volume is an inoperable and uneconomical solution for many reasons. A very large mass is best realized with a modular set of many identical, independent units, each of about 5 kt, “cloning” the basic technology of the ICARUS-T600. Several of such modular units will be assembled to reach at least 20 kt as initial sensitive volume. The increase of the active volume of about one order of magnitude with respect to the ICARUS-T600 detector requires some specific R&D activity, which will be implemented in a ∼ 360 ton prototype unit (SLICE) of reduced length
On adversary robust consensus protocols through joint-agent interactions
No full textA generalized family of adversary robust consensus protocols is proposed and analyzed. These are distributed algorithms for multiagent systems seeking to agree on a common value of a shared variable, even in the presence of faulty or malicious agents, which are updating their local state according to the protocol rules. In particular, we adopt monotone joint-agent interactions, a very general mechanism for processing locally available information and allowing cross-comparisons between state-values of multiple agents simultaneously. The salient features of the proposed class of algorithms are abstracted as a Petri net and convergence criteria for the resulting time evolutions formulated by employing structural invariants of the net
Buoyancy-driven turbulent convection in a bundle of vertical heated cylinders
No full textBuoyant, turbulent convective heat transfer around cylindrical rods arranged in bundles is a technically relevant heat transfer configuration which finds application in steam generators, cooling of reactor core fuel assemblies and heat exchangers in general. Most of the research performed so far considered forced convection conditions on vertical rod bundles, corresponding for example to the configuration of a nuclear reactor primary loop. Fewer works have focused on the effect of buoyancy, with or without an external source of momentum. This paper reports a Direct Numerical Simulation study of the fully developed, mixed convection in a bundle of vertical, heated cylinders, where each cylinder releases an equal, uniform heat flux distribution, and a Boussinesq approximation is introduced to represent buoyancy effects. Simulations are performed for Gr = 10^7 , Reτ = 180 and Pr = 0.1. As experimental velocity and temperature profiles are not available in the literature, a preliminary validation of the method employed is performed by the comparison of the global quantities like f and Nu. The time averaged velocity and temperature fields are reported in the paper, together with first order and higher-order statistics. In addition the main turbulent flow features are described through coherent structure eduction methods
Buoyancy-driven turbulent convection in a bundle of vertical heated cylinders
No full textBackground Buoyant, turbulent convective heat transfer around cylindrical rods arranged in bundles is a technically relevant heat transfer configuration which finds application in steam generators, cooling of reactor core fuel assemblies and heat exchangers in general. Most of the research performed so far considered forced convection conditions on vertical rod bundles, corresponding for example to the configuration of a nuclear reactor primary loop. Fewer works have focused on the effect of buoyancy, with or without an external source of momentum. In their experimental investigation, Hallinan and Viskanta [4] employed a thermosyphon loop to determine the average heat transfer coefficients for water under natural circulation conditions in a tube bundle containing twenty-one tubes; their work is mainly focused on the favorable effect of grid spacers on heat transfer enhancement. El Genk et al. performed experiments of upflow- and downflow-forced turbulent and laminar convection, natural convection and buoyancy-assisted combined convection of water in a uniformly heated square lattice of seven [2] and nine [3] rod bundles with variable pitch-to-diameter ratio, Reynolds and Rayleigh number. They proposed heat transfer correlations and concluded that the rod arrangement only negligibly affects the overall Nusselt number in both forced and natural convection regimes. Concerning the numerical modeling of this class of flows, only very recent works resort to the Large Eddy Simulation [5], and even less frequently, to the Direct Numerical Simulation [7]. This is largely due to the geometric complexity of the flow domain and the difficulties related to the adoption of numerical techniques allowing for sufficiently accurate results
Consensus-based algorithm for distributed estimation of the maximum of a field
Full text linkThis paper deals with the problem of distributed estimation of the maximum of a continuous scalar field by combining exhaustive ergodic search with multi-agent consensus protocols. In this original set-up, the presence of unilateral interactions and exogenous signals is considered, the latter representing the measures sampled by the agents and an algorithm is devised to estimate the maximum of the field over the domain spanned by the agents. Necessary and sufficient conditions are given to guarantee convergence to the maximum field value. Illustrative examples are presented to show the effectiveness of the proposed framework and conditions
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