Estimating the trace of matrix functions with application to complex networks

The approximation of trace(f(Ω)), where f is a function of a symmetric matrix Ω, can be challenging when Ω is exceedingly large. In such a case even the partial Lanczos decomposition of Ω is computationally demanding and the stochastic method investigated by Bai et al. (J. Comput. Appl. Math. 74:71–89, 1996) is preferred. Moreover, in the last years, a partial global Lanczos method has been shown to reduce CPU time with respect to partial Lanczos decomposition. In this paper we review these techniques, treating them under the unifying theory of measure theory and Gaussian integration. This allows generalizing the stochastic approach, proposing a block version that collects a set of random vectors in a rectangular matrix, in a similar fashion to the partial global Lanczos method. We show that the results of this technique converge quickly to the same approximation provided by Bai et al. (J. Comput. Appl. Math. 74:71–89, 1996), while the block approach can leverage the same computational advantages as the partial global Lanczos. Numerical results for the computation of the Von Neumann entropy of complex networks prove the robustness and efficiency of the proposed block stochastic method

Matrices associated to two conservative discretizations of Riesz fractional operators and related multigrid solvers

In this article, we focus on a two-dimensional conservative steady-state Riesz fractional diffusion problem. As is typical for problems in conservative form, we adopt a finite volume (FV)-based discretization approach. Precisely, we use both classical FVs and the so-called finite volume elements (FVEs). While FVEs have already been applied in the context of fractional diffusion equations, classical FVs have only been applied in first-order discretizations. By exploiting the Toeplitz-like structure of the resulting coefficient matrices, we perform a qualitative study of their spectrum and conditioning through their symbol, leading to the design of a second-order FV discretization. This same information is leveraged to discuss parameter-free symbol-based multigrid methods for both discretizations. Tests on the approximation error and the performances of the considered solvers are given as well

Abstract Meaning Representation for Human-Robot Dialogue

In this research, we begin to tackle the challenge of natural language understanding (NLU) in the context of the development of a robot dialogue system. We explore the adequacy of Abstract Meaning Representation (AMR) as a conduit for NLU. First, we consider the feasibility of using existing AMR parsers for automatically creating meaning representations for robot-directed transcribed speech data. We evaluate the quality of output of two parsers on this data against a manually annotated gold-standard data set. Second, we evaluate the semantic coverage and distinctions made in AMR overall: how well does it capture the meaning and distinctions needed in our collaborative human-robot dialogue domain? We find that AMR has gaps that align with linguistic information critical for effective human-robot collaboration in search and navigation tasks, and we present task-specific modifications to AMR to address the deficiencies

Endoscopic management of gastrointestinal leaks and fistulae: What option do we have?

Gastrointestinal leaks and fistulae are serious, potentially life threatening conditions that may occur with a wide variety of clinical presentations. Leaks are mostly related to post-operative anastomotic defects and are responsible for an important share of surgical morbidity and mortality. Chronic leaks and long standing post-operative collections may evolve in a fistula between two epithelialized structures. Endoscopy has earned a pivotal role in the management of gastrointestinal defects both as first line and as rescue treatment. Endotherapy is a minimally invasive, effective approach with lower morbidity and mortality compared to revisional surgery. Clips and luminal stents are the pioneer of gastrointestinal (GI) defect endotherapy, whereas innovative endoscopic closure devices and techniques, such as endoscopic internal drainage, suturing system and vacuum therapy, has broadened the indications of endoscopy for the management of GI wall defect. Although several endoscopic options are currently used, a standardized evidence-based algorithm for management of GI defect is not available. Successful management of gastrointestinal leaks and fistulae requires a tailored and multidisciplinary approach based on clinical presentation, defect features (size, location and onset time), local expertise and the availability of devices. In this review, we analyze different endoscopic approaches, which we selected on the basis of the available literature and our own experience. Then, we evaluate the overall efficacy and procedural-specific strengths and weaknesses of each approach

Chimera: a Bioconductor package for secondary analysis of fusion products

Chimera is a Bioconductor package that organizes, annotates, analyses and validates fusions reported by different fusion detection tools; current implementation can deal with output from bellerophontes, chimeraScan, deFuse, fusionCatcher, FusionFinder, FusionHunter, FusionMap, mapSplice, Rsubread, tophat-fusion and STAR. The core of Chimera is a fusion data structure that can store fusion events detected with any of the aforementioned tools. Fusions are then easily manipulated with standard R functions or through the set of functionalities specifically developed in Chimera with the aim of supporting the user in managing fusions and discriminating falsepositive results

Cardiopulmonary-bypass induces hyperglycemia only in preoperative insulin resistant patients

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THE EFFECT OF THE THERMODYNAMIC MODELS ON THE THERMOECONOMIC RESULTS FOR COST ALLOCATION IN A GAS TURBINE COGENERATION SYSTEM

The thermoeconomics combines economics and thermodynamics to provide information not available from conventional energy and economic analysis. For thermoeconomics modeling one of the keys points is the thermodynamic model that should be adopted. Different thermodynamic models can be used in the modeling of a gas turbine system depending on the accuracy required. A detailed study of the performance of gas turbine would take into account many features. These would include the combustion process, the change of composition of working fluid during combustion, the effects of irreversibilities associated with friction and with pressure and temperature gradients and heat transfer between the gases and walls. Owing to these and others complexities, the accurate modeling of gas turbine normally involves computer simulation. To conduct elementary thermodynamic analyses, considerable simplifications are required. Thus, there are simplified models that lead to different results in thermoeconomics. At this point, three questions arise: How different can the results be? Are these simplifications reasonable? Is it worth using such a complex model? In order to answer these questions, this paper compares three thermodynamic models in a gas turbine cogeneration system from thermoeconomic point of view: cold air-standard model, CGAM model and complete combustion with excess air

Modelling shifts in agroclimate and crop cultivar response under climate change

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