Relevance of Negative Links in Graph Partitioning: A Case Study Using Votes From the European Parliament

In this paper, we want to study the informative value of negative links in signed complex networks. For this purpose, we extract and analyze a collection of signed networks representing voting sessions of the European Parliament (EP). We first process some data collected by the VoteWatch Europe Website for the whole 7 th term (2009-2014), by considering voting similarities between Members of the EP to define weighted signed links. We then apply a selection of community detection algorithms, designed to process only positive links, to these data. We also apply Parallel Iterative Local Search (Parallel ILS), an algorithm recently proposed to identify balanced partitions in signed networks. Our results show that, contrary to the conclusions of a previous study focusing on other data, the partitions detected by ignoring or considering the negative links are indeed remarkably different for these networks. The relevance of negative links for graph partitioning therefore is an open question which should be further explored.Comment: in 2nd European Network Intelligence Conference (ENIC), Sep 2015, Karlskrona, Swede

Exploring the capabilities of the Anti-Coincidence Shield of the INTEGRAL spectrometer to study solar flares

INTEGRAL is a hard X-ray/gamma-ray observatory for astrophysics (ESA) covering photon energies from 15 keV to 10 MeV. It was launched in 2002 and since then the BGO detectors of the Anti-Coincidence shield (ACS) of the SPI spectrometer have detected many hard X-ray (HXR) bursts from the Sun, producing lightcurves at photon energies above ~ 100 keV. The spacecraft has a highly elliptical orbit, providing a long uninterrupted observing time (about 90% of the orbital period) with nearly constant background due to the reduction of the crossing time of the Earth's radiation belts. However, due to technical constraints, INTEGRAL cannot point to the Sun and high-energy solar photons are always detected in non-standard observation conditions. To make the data useful for solar studies, we have undertaken a major effort to specify the observing conditions through Monte-Carlo simulations of the response of ACS for several selected flares. We check the performance of the model employed for the Monte-Carlo simulations using RHESSI observations for the same sample of solar flares. We conclude that, despite the fact that INTEGRAL was not designed to perform solar observations, ACS is a useful instrument in solar flare research. In particular, its relatively large effective area allows the determination of good-quality HXR/gamma-ray lightcurves for X- and M-class solar flares and, in some cases, probably also for C-class flares.Comment: 18 pages, 6 figures; Solar Physics 201

Multiple Partitioning of Multiplex Signed Networks: Application to European Parliament Votes

For more than a decade, graphs have been used to model the voting behavior taking place in parliaments. However, the methods described in the literature suffer from several limitations. The two main ones are that 1) they rely on some temporal integration of the raw data, which causes some information loss, and/or 2) they identify groups of antagonistic voters, but not the context associated to their occurrence. In this article, we propose a novel method taking advantage of multiplex signed graphs to solve both these issues. It consists in first partitioning separately each layer, before grouping these partitions by similarity. We show the interest of our approach by applying it to a European Parliament dataset.Comment: Social Networks, 2020, 60, 83 - 10

Efficient Enumeration of the Optimal Solutions to the Correlation Clustering problem

According to the structural balance theory, a signed graph is considered structurally balanced when it can be partitioned into a number of modules such that positive and negative edges are respectively located inside and between the modules. In practice, real-world networks are rarely structurally balanced, though. In this case, one may want to measure the magnitude of their imbalance, and to identify the set of edges causing this imbalance. The correlation clustering (CC) problem precisely consists in looking for the signed graph partition having the least imbalance. Recently, it has been shown that the space of the optimal solutions of the CC problem can be constituted of numerous and diverse optimal solutions. Yet, this space is difficult to explore, as the CC problem is NP-hard, and exact approaches do not scale well even when looking for a single optimal solution. To alleviate this issue, in this work we propose an efficient enumeration method allowing to retrieve the complete space of optimal solutions of the CC problem. It combines an exhaustive enumeration strategy with neighborhoods of varying sizes, to achieve computational effectiveness. Results obtained for middle-sized networks confirm the usefulness of our method

Miniature standoff Raman probe for neurosurgical applications

Removal of intrinsic brain tumors is a delicate process, where a high degree of specificity is required to remove all of the tumor tissue without damaging healthy brain. The accuracy of this process can be greatly enhanced by intraoperative guidance. Optical biopsies using Raman spectroscopy are a minimally invasive and lower-cost alternative to current guidance methods. A miniature Raman probe for performing optical biopsies of human brain tissue is presented. The probe allows sampling inside a conventional stereotactic brain biopsy system: a needle of length 200 mm and inner diameter of 1.8 mm. By employing a miniature stand-off Raman design, the probe removes the need for any additional components to be inserted into the brain. Additionally, the probe achieves a very low internal silica background while maintaining good collection of Raman signal. To illustrate this, the probe is compared with a Raman probe that uses a pair of optical fibers for collection. The miniature stand-off Raman probe is shown to collect a comparable number of Raman scattered photons, but the Raman signal to background ratio is improved by a factor of five at Raman shifts below ∼500  cm−1. The probe’s suitability for use on tissue is demonstrated by discriminating between different types of healthy porcine brain tissue

Surface topography of hydroxyapatite affects ROS17/2.8 cells response

Hydroxyapatite (HA) has been used in orthopedic, dental, and maxillofacial surgery as a bone substitute. The aim of this investigation was to study the effect of surface topography produced by the presence of microporosity on cell response, evaluating: cell attachment, cell morphology, cell proliferation, total protein content, and alkaline phosphatase (ALP) activity. HA discs with different percentages of microporosity (< 5%, 15%, and 30%) were confected by means of the combination of uniaxial powder pressing and different sintering conditions. ROS17/2.8 cells were cultured on HA discs. For the evaluation of attachment, cells were cultured for two hours. Cell morphology was evaluated after seven days. After seven and fourteen days, cell proliferation, total protein content, and ALP activity were measured. Data were compared by means of ANOVA and Duncan’s multiple range test, when appropriate. Cell attachment (p = 0.11) and total protein content (p = 0.31) were not affected by surface topography. Proliferation after 7 and 14 days (p = 0.0007 and p = 0.003, respectively), and ALP activity (p = 0.0007) were both significantly decreased by the most irregular surface (HA30). These results suggest that initial cell events were not affected by surface topography, while surfaces with more regular topography, as those present in HA with 15% or less of microporosity, favored intermediary and final events such as cell proliferation and ALP activity

Análisis del comportamiento de las exportaciones de ecuador a Venezuela durante los años 2008 hasta el 2013, como resultado de la aplicación del sistema único de compensación regional (sucre)

A lo largo de la historia, América Latina ha buscado consolidarse como un bloque económico con la finalidad de tener poder de negociación a nivel internacional y; de esta manera, promover el desarrollo de los países latinoamericanos. Aunque se han realizado varios intentos, no se ha tenido mayor éxito por la desigualdad económica que existe entre los países de la región mencionada, lo que ha impedido que se logre una verdadera integración económica, limitándose a la creación de áreas comerciales entre países en los cuales se promueve el intercambio de bienes con algunos beneficios arancelarios. Uno de los intentos con mayor éxito en la región es el desarrollado por los países del ALBA, el cual lleva por nombre SUCRE, consiste en un sistema unitario de compensación para el comercio entre los países participantes (Venezuela, Ecuador, Bolivia, Nicaragua y Cuba), este sistema iniciado en el año 2010 ha demostrado tener éxito y se ha venido apoyando; principalmente, en Venezuela y Ecuador. Por lo cual, el objetivo de esta investigación es evaluar el comportamiento de las exportaciones de Ecuador a Venezuela tras la aplicación del Sistema Unitario de Compensación Regional de Pagos SUCRE. Se pudo conocer que Venezuela realiza el 98% de sus transacciones por medio del SUCRE con Ecuador, siendo en su mayoría importaciones, lo que ha traído muchas ventajas y beneficios para Ecuador, entre los que se encuentran un saldo superavitario en la balanza comercial con la República Bolivariana, aumentar las exportaciones de atún, vehículos, aceite de palma, cocinas, neveras, conservas de pescado, polipropileno, neumáticos, harina de pescado o alimento para animales (camarones, etc.) y mejorar la agilidad en el proceso de cobro de las exportaciones y de los pagos, entre otros.Throughout history, Latin America has sought to establish itself as an economic bloc in order to have bargaining power at the international level; thus promoting the development of Latin American countries. Although there have been several attempts, it has not been more successful by economic inequality between countries in the region mentioned, which prevented a true economic integration is achieved, merely creating commercial areas between countries which the exchange of goods with some tariff benefits promoted. One of the most successful attempts in the region is developed by the ALBA countries, which is called SUCRE, is a unitary system of compensation for trade between the participating countries (Venezuela, Ecuador, Bolivia, Nicaragua and Cuba), this system started in 2010 has proved successful and has supported; mainly in Venezuela and Ecuador. Therefore, the objective of this research is to evaluate the behavior of exports from Ecuador to Venezuela after application of the Unitary System Regional Payments SUCRE. It was learned that Venezuela takes 98% of your transactions through SUCRE with Ecuador, being mostly imports, which has brought many advantages and benefits for Ecuador, including a surplus are in the trade balance with the Bolivarian Republic, increase exports of tuna, vegetables, palm oil, stoves, refrigerators, canned fish, polypropylene, tires, fishmeal or feed (shrimp, etc.) and improve agility in the collection process exports and payments, among others