Computing NodeTrix Representations of Clustered Graphs

NodeTrix representations are a popular way to visualize clustered graphs; they represent clusters as adjacency matrices and inter-cluster edges as curves connecting the matrix boundaries. We study the complexity of constructing NodeTrix representations focusing on planarity testing problems, and we show several NP-completeness results and some polynomial-time algorithms. Building on such algorithms we develop a JavaScript library for NodeTrix representations aimed at reducing the crossings between edges incident to the same matrix.Comment: Appears in the Proceedings of the 24th International Symposium on Graph Drawing and Network Visualization (GD 2016

Identification of a Widespread Palmitoylethanolamide Contamination in Standard Laboratory Glassware.

Introduction: Fatty acid ethanolamides (FAEs) are a family of lipid mediators that participate in a host of biological functions. Procedures for the quantitative analysis of FAEs include organic solvent extraction from biological matrices (e.g., blood), followed by purification and subsequent quantitation by liquid chromatography-mass spectrometry (LC/MS) or gas chromatography-mass spectrometry. During the validation process of a new method for LC/MS analysis of FAEs in biological samples, we observed unusually high levels of the FAE, palmitoylethanolamide (PEA), in blank samples that did not contain any biological material. Materials and Methods: We investigated a possible source of this PEA artifact via liquid chromatography coupled to tandem mass spectrometry, as well as accurate mass analysis. Results: We found that high levels of a contaminant indistinguishable from PEA is present in new 5.75″ glass Pasteur pipettes, which are routinely used by laboratories to carry out lipid extractions. This artifact might account for discrepancies found in the literature regarding PEA levels in human blood serum and other tissues. Conclusions: It is recommended to take into account this pitfall by analyzing potential contamination of the disposable glassware during the validation process of any method used for analysis of FAEs

X-ray view of four high-luminosity Swift/BAT AGN: Unveiling obscuration and reflection with Suzaku

The Swift/BAT nine-month survey observed 153 AGN, all with ultra-hard X-ray BAT fluxes in excess of 10^-11 erg cm^-2 s^-1 and an average redshift of 0.03. Among them, four of the most luminous BAT AGN (44.73 < Log L(BAT) < 45.31) were selected as targets of Suzaku follow-up observations: J2246.0+3941 (3C 452), J0407.4+0339 (3C 105), J0318.7+6828, and J0918.5+0425. The column density, scattered/reflected emission, the properties of the Fe K line, and a possible variability are fully analyzed. For the latter, the spectral properties from Chandra, XMM-Newton and Swift/XRT public observations were compared with the present Suzaku analysis. Of our sample, 3C 452 is the only certain Compton-thick AGN candidate because of i) the high absorption and strong Compton reflection; ii) the lack of variability; iii) the "buried" nature, i.e. the low scattering fraction (<0.5%) and the extremely low relative [OIII] luminosity. In contrast 3C 105 is not reflection-dominated, despite the comparable column density, X-ray luminosity and radio morphology, but shows a strong long-term variability in flux and scattering fraction, consistent with the soft emission being scattered from a distant region (e.g., the narrow emission line region). The sample presents high (>100) X-to-[OIII] luminosity ratios, confirming the [OIII] luminosity to be affected by residual extinction in presence of mild absorption, especially for "buried" AGN such as 3C 452. Three of our targets are powerful FRII radio galaxies, making them the most luminous and absorbed AGN of the BAT Seyfert survey despite the inversely proportional N_H - L_X relation.Comment: A&A paper in press, 17 page

Hierarchical Partial Planarity

In this paper we consider graphs whose edges are associated with a degree of {\em importance}, which may depend on the type of connections they represent or on how recently they appeared in the scene, in a streaming setting. The goal is to construct layouts of these graphs in which the readability of an edge is proportional to its importance, that is, more important edges have fewer crossings. We formalize this problem and study the case in which there exist three different degrees of importance. We give a polynomial-time testing algorithm when the graph induced by the two most important sets of edges is biconnected. We also discuss interesting relationships with other constrained-planarity problems.Comment: Conference version appeared in WG201

High tide, low price? Flooding alerts and hotel prices in Venice

This research explores the effects of High Tide alerts on hotel prices in Venice, a city that is vulnerable to the impacts of extreme climate events due to its fragile ecosystem and a long history of floods in the city center. By analyzing and combining price data from Booking.com with publicly available information on tides and weather, this study uses regression discontinuity design to test for changes in hotel prices when tide levels reach a critical threshold. The results offer insights into the sensitivity of hotel prices to weather alerts and provide valuable information on the potential impact of climate change on Venice’s tourism-driven economy, with implications for the cost–benefit analysis of activating protective barriers for lagoon protection

Fast transmission of grapevine 'Pinot gris' virus (GPGV) in vineyard

Grapevine 'Pinot gris' virus (GPGV) is a newly emergent virus associated with the appearance of grapevine leaf mottling and deformation disease (GLMD). The worldwide spreading of this virus, and sometimes of the associated disease, that has occurred in the last years, requests further epidemiological studies to verify the progress of natural infection in the field. In the present paper, GPGV infection and spatiotemporal spreading of GLMD, investigated in two vineyards with high disease occurrence, confirmed an elevated presence of the virus in vineyards of Northeastern Italy, and revealed an increasing of symptomatic plants over the time. At the same time, the progress of natural infection was monitored after the placement of new grafted plants near the symptomatic grapevines in the infected vineyards. After three years, 76 % of the plantlets that were initially GPGV-free became GPGV-infected, giving an evidence of the fast transmission of GPGV in the field. Only 14 % of the plantlets, all collocated inside a patch with diseased plants, showed typical GLMD-symptoms. Interestingly, some plantlets, which were already GPGV-infected with the "asymptomatic" GPGV variant before planting in the field, did not become infected with the "symptomatic" viral wild variant after three years and never showed GLMD symptoms

Morphing Planar Graph Drawings Optimally

We provide an algorithm for computing a planar morph between any two planar straight-line drawings of any $n$-vertex plane graph in $O(n)$ morphing steps, thus improving upon the previously best known $O(n^2)$ upper bound. Further, we prove that our algorithm is optimal, that is, we show that there exist two planar straight-line drawings $\Gamma_s$ and $\Gamma_t$ of an $n$-vertex plane graph $G$ such that any planar morph between $\Gamma_s$ and $\Gamma_t$ requires $\Omega(n)$ morphing steps