Resumen multidocumento utilizando teorías semántico-discursivas

El resumen automático tiene por objetivo reducir el tamaño de los textos, preservando el contenido más importante. En este trabajo, proponemos algunos métodos de resumen basados en dos teorías semántico-discursivas: Teoría de la Estructura Retórica (Rhetorical Structure Theory, RST) y Teoría de la Estructura Inter-Documento (Cross-document Structure Theory, CST). Han sido elegidas ambas teorías con el fin de abordar de un modo más relevante de un texto, los fenómenos relacionales de inter-documentos y la distribución de subtopicos en los textos. Los resultados muestran que el uso de informaciones semánticas y discursivas para la selección de contenidos mejora la capacidad informativa de los resúmenes automáticos.Automatic multi-document summarization aims at reducing the size of texts while preserving the important content. In this paper, we propose some methods for automatic summarization based on two semantic discourse models: Rhetorical Structure Theory (RST) and Cross-document Structure Theory (CST). These models are chosen in order to properly address the relevance of information, multi-document phenomena and subtopical distribution in the source texts. The results show that using semantic discourse knowledge for content selection improve the informativeness of automatic summaries

Removal of polycyclic aromatic hydrocarbons by biosorbents

Introduction: - Polycyclic aromatic hydrocarbons (PAHs) are a group of environmental carcinogens. They are formed during the incomplete combustion of organic matter. Humans are exposed to PAHs by various sources, including occupational environments, cigarette smoke, vehicle exhaust, and dietary sources as grilled and flame-broiled food. - In vivo studies in animals proved that PAHs are associated to cancer, and epidemiologic studies with exposed workers, especially in coke ovens and aluminium smelters, have shown clear excess of lung cancer and highly suggestive excesses of bladder cancer. - These compounds can enter in drinking water sources by precipitation and runoff on the earth’s surface. - Portuguese legislation for water for human consumption (DL 306/2007) proposes the determination of five PAHs; limits of the maximum concentration are 0.10 µg/L for total BghiP, BbF, BkF, IcdP, and 0.010 µg/L for BaP.This work was financial suported by the COMPETE program, under the Watercork project (nº. 2009/552).N/

Graviton emission from a higher-dimensional black hole

We discuss the graviton absorption probability (greybody factor) and the cross-section of a higher-dimensional Schwarzschild black hole (BH). We are motivated by the suggestion that a great many BHs may be produced at the LHC and bearing this fact in mind, for simplicity, we shall investigate the intermediate energy regime for a static Schwarzschild BH. That is, for $(2M)^{1/(n-1)}\omega\sim 1$, where $M$ is the mass of the black hole and $\omega$ is the energy of the emitted gravitons in $(2+n)$-dimensions. To find easily tractable solutions we work in the limit $l \gg 1$, where $l$ is the angular momentum quantum number of the graviton.Comment: 10 pages, 8 figures, references added, typos corrected. Graviton degeneracy factor included; main results remain unchange

Spinless bosons embedded in a vector Duffin-Kemmer-Petiau oscillator

Some properties of minimal and nonminimal vector interactions in the Duffin-Kemmer-Petiau (DKP) formalism are discussed. The conservation of the total angular momentum for spherically symmetric nonminimal potentials is derived from its commutation properties with each term of the DKP equation and the proper boundary conditions on the spinors are imposed. It is shown that the space component of the nonminimal vector potential plays a crucial role for the confinement of bosons. The exact solutions for the vector DKP oscillator (nonminimal vector coupling with a linear potential which exhibits an equally spaced energy spectrum in the weak-coupling limit) for spin-0 bosons are presented in a closed form and it is shown that the spectrum exhibits an accidental degeneracy

Inconsistencies of a purported probability current in the Duffin-Kemmer-Petiau theory

The Duffin-Kemmer-Petiau (DKP) equation with a square step potential is used in a simple way with polymorphic purposes. It proves adequate to refuse a proposed new current that is currently interpreted as a probability current,to show that the Klein paradox does exist in the DKP theory and to revise other minor misconceptions diffused in the literature.Comment: 11 page

Halogenated polycyclic aromatic hydrocarbons associated with drinking water disinfection

Introduction: Disinfection by-products (DBPs) have been identified in chlorinated water. This fact justifies the growing concern about the potential health effects of emerging unregulated DBPs, some of which appear to be more genotoxic than the regulated DBPs[1]. Polycyclic aromatic hydrocarbons (PAHs) are among the most persistent contaminants detected in environmental samples such as river sediments and tap water. A few studies have already proven that water disinfection can lead to the formation of halogenated derivatives of PAHs, such as chlorinated and brominated PAHs[2] . The available toxicological studies have shown that these compounds possess, in general, greater mutagenicity than the corresponding parent PAHs. Our research group has also shown that exposure of HepG2 cells to a dose-range of 6-Cl-benzo[a]pyrene (6-ClBaP) and BaP resulted in cytotoxicity above 50 µM and that, at the equimolar doses of 100 and 125 µM, 6-ClBaP was able to induce a significantly higher level of DNA damage than BaP[3] . The present study had two main objectives: 1) identification of the major chlorinated and brominated derivatives of benzo[a]anthracene (BaA) and pyrene (Pyr) formed as disinfection by-products and 2) evaluation of their potential hazard to humans, through the characterization of their potential cytotoxic and genotoxic effects in a human cell line.The authors wish to thank Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa for financial support by the grant BRJ-DSA/2012- Doenças Oncológica

Drinking water contaminants: toxicity of halogenated polycyclic aromatic hydrocarbons

Food may be contaminated with polycyclic aromatic hydrocarbons (PAHs) in the process of smoking or heating. These contaminants or their derivatives can also be present in drinking water when raw water contacts with discharges of untreated industrial/waste water effluents, forest fires or by solubilisation of organic material from contaminated soils. A few studies have shown that water disinfection can lead to halogenated derivatives of PAHs (HPAHs) as chlorinated and brominated derivatives, and there are evidences that these compounds may have greater mutagenicity than the parent PAHs. In this study the cytotoxic and genotoxic effects of chlorinated/brominated derivatives of pyrene (Pyr) and benzo[a]anthracene (BaA), 1-ClPyr, 1-BrPyr and 7-ClBaA, which can be formed as water disinfection by-products, were studied in HepG2 cells to assess their potential hazard to human health. The formation of 1-ClPyr, 1-BrPyr and 7-ClBaA under aqueous disinfection conditions in waters contaminated with Pyr and BaA, was confirmed with an optimized gas chromatography method. Cells exposed (24h) to several concentrations of BaA and 7-ClBaA (1 to 200μM) displayed a dose-related and significant increase of cytotoxicity (neutral red assay) with IC50 values of 3.37 and 12.63µM respectively. For Pyr, 1-ClPyr and 1-BrPyr (10 to 200μM), a lower but significant dose-related cytotoxicity was observed. At non-cytotoxic concentrations (10 and 15µM), 7-ClBaA was able to induce a significantly higher level of oxidative DNA damage in HepG2 cells than its parent compound, as assessed by the FPG-modified comet assay. Under these conditions neither Pyr nor its derivatives were genotoxic. In conclusion, the disinfection process may give rise to genotoxic HPAHs with potential impact on human health and it should be performed in raw waters with minimal content of total organic carbon. In real conditions, humans may be exposed to a mixture of these organic compounds and thus their combined toxic effects should be further evaluated

Water retention and characteristic curves representing tropical clay soils from Africa

Soil water retention curves (SWRCs) form an essential component of frameworks coupling the hydromechanical behaviour of unsaturated soils. The curves describe how suction changes with variables such as degree of saturation, void ratio and volumetric/gravimetric water content. SWRCs can be determined from incrementally drying initially saturated reconstituted samples to a final residual state, thus developing the primary drying curve (PDC). The primary wetting curve (PWC) is established from subsequent incremental wetting from residual state and is hysteretic compared with the PDC. SWRCs for reconstituted, high-plasticity, tropical clays from Africa (Sudan, Tanzania and South Africa) will be produced using suction measuring instruments, a tensiometer, filter paper and a dew point potentiometer. The development of SWRCs under various subsequent cycles of drying will be presented and discussed along with details concerning volumetric changes and cracking during drying. In order to investigate the uniqueness of the PDC and PWC and the effect of initial void ratio, SWRCs will be determined for samples formed by reconstituted from slurry under different applied energy levels.</jats:p