On the complexity of computing the kk-restricted edge-connectivity of a graph

The \emph{$k$-restricted edge-connectivity} of a graph $G$, denoted by $\lambda_k(G)$, is defined as the minimum size of an edge set whose removal leaves exactly two connected components each containing at least $k$ vertices. This graph invariant, which can be seen as a generalization of a minimum edge-cut, has been extensively studied from a combinatorial point of view. However, very little is known about the complexity of computing $\lambda_k(G)$. Very recently, in the parameterized complexity community the notion of \emph{good edge separation} of a graph has been defined, which happens to be essentially the same as the $k$-restricted edge-connectivity. Motivated by the relevance of this invariant from both combinatorial and algorithmic points of view, in this article we initiate a systematic study of its computational complexity, with special emphasis on its parameterized complexity for several choices of the parameters. We provide a number of NP-hardness and W[1]-hardness results, as well as FPT-algorithms.Comment: 16 pages, 4 figure

Assessment of natural radioactivity levels and radiation exposure in new building materials in Spain

Novel building materials were manufactured and analyzed for 226Ra, 232Th and 40K using an HPGe gamma-ray spectrometer. The results show that the highest value of 40K was 4530 Bq per kg which was measured in a sample containing fly ashes from olive stones. The highest values of 226Ra and 232Th activities were 181 and 185 Bq per kg, which were measured in a sample with fly ashes from the co-combustion of coal and coke, respectively. On the other hand, the lowest values of 40K, 226Ra and 232Th activities were obtained for samples incorporating mussel shells. The radiological health hazard parameters, such as radium equivalent activity (Raeq), activity concentration index (I), absorbed and effective dose rates, associated with these radionuclides were evaluated. These values are within the EU recommended limits in building materials, except for samples of concrete containing fly ashes from olive stones, coal and coke. This study has contributed to the inclusion of industrial wastes that have not been collected previously in the Naturally Occurring Radioactive Material (NORM) databases on radioactivity of building materials

Optical inspection of liquid crystal variable retarder inhomogeneities

Liquid crystal variable retarders (LCVRs) are starting to be widely used in optical systems because of their capacity to provide a controlled variable optical retardance between two orthogonal components of incident polarized light or to introduce a known phase shifting (PS) between coherent waves, both by means of an applied voltage. Typically, the retardance or PS introduced by an LCVR is not homogeneous across the aperture. On the one hand, the LCVR glass substrates present a global bend that causes an overall variation of the retardance or PS. On the other hand, in the manufacturing process of an LCVR, there sometimes appears a set of micro-air bubbles that causes local retardance or PS inhomogeneities. In this work, we present an interferometric technique based on a Mach-Zehnder interferometer that is insensitive to vibrations and capable of inspecting and characterizing the LCVR's retardance or PS inhomogeneities. The feasibility of the proposed method is demonstrated in the experimental results, where the LCVR retardance is measured with an error of about 0:2 rad. The thickness of possible micro-air bubbles is obtained with a resolution of about 50 nm

Disentangling the determinants of symbiotic species richness in native and invasive gammarids (Crustacea, Amphipoda) of the Baltic region

Dispersal of alien species is a global problem threatening native biodiversity. Co-introduction of nonnative parasites and pathogens adds to the severity of this threat, but this indirect impact has received less attention. To shed light on the key factors determining the richness of microorganisms in native and invasive host species, we compared symbiotic (parasitic and epibiotic) communities of gammarids across different habitats and localities along the Baltic coast of Poland. Seven gammarid species, two native and five invasive, were sampled from 16 freshwater and brackish localities. Sixty symbiotic species of microorganisms of nine phyla were identified. This taxonomically diverse species assemblage of symbionts allowed us to assess the effect of host translocation and regional ecological determinants driving assembly richness in the gammarid hosts. Our results revealed that (i) the current assemblages of symbionts of gammarid hosts in the Baltic region are formed by native and co-introduced species; (ii) species richness of the symbiotic community was higher in the native Gammarus pulex than in the invasive hosts, probably reflecting a process of species loss by invasive gammarids in the new area and the distinct habitat conditions occupied by G. pulex and invasive hosts; (iii) both host species and locality were key drivers shaping assembly composition of symbionts, whereas habitat condition (freshwater versus brackish) was a stronger determinant of communities than geographic distance; (iv) the dispersion patterns of the individual species richness of symbiotic communities were best described by Poisson distributions; in the case of an invasive host, the dispersion of the rich species diversity may switch to a right-skewed negative binomial distribution, suggesting a host-mediated regulation process. We believe this is the first analysis of the symbiotic species richness in native and invasive gammarid hosts in European waters based on original field data and a broad range of taxonomic groups including Microsporidia, Choanozoa, Ciliophora, Apicomplexa, Platyhelminthes, Nematoda, Nematomorha, Acanthocephala and Rotifera, to document the patterns of species composition and distributio

Efectos de la suplementación proteica invernal sobre parámetros productivos de vaquillas de reposición

Con el objetivo de evaluar la respuesta animal a diferentes niveles de expeller de algodón (EA) durante el invierno, se utilizaron cuarenta vaquillas cruza cebú, agrupadas por tipo (predominio cebú o británico) y asignadas en número de 10 animales para cada uno de los cuatro tratamientos: control (ningún suplemento), bajo (0,4), medio (0,8) y alto (1,2) por ciento del peso vivo. La suplementación fue realizada de mayo a octubre (150 días) y las vaquillas fueron mantenidas en cuatro potreros pastoreando Dichantium caricosum, rotándose semanalmente a efectos de minimizar el efecto potrero. Cada 28 días se realizaron pesajes, mediciones de altura de cadera y perímetro torácico, así como determinación de condición corporal (escala 1 a 9). La oferta de forraje inicial fue de 2 toneladas de materia seca por vaquilla. Considerando a los animales como unidades experimentales, las fuentes de variación fueron: tratamiento, tipo de animal e interacción. La ganancia de peso vivo (vacío y lleno) y el perímetro torácico fueron afectados de manera cuadrática. La condición corporal mostró interacción de tratamiento por tipo de animal; en cambio para altura de cadera no se observó efecto alguno. La ganancia de peso vivo vacío fue de 223, 379, 459 y 460 g/día (p = cuadrático) mientras que los incrementos de perímetro torácico fueron 7,7 - 16,0 - 18,0 - 17,5 cm (p = cuadrático) para los tratamientos control, bajo, medio y alto respectivamente. La eficiencia aparente de la utilización del suplemento fue de 4,18 - 5,85 y 8,78 kg de suplemento por kg de ganancia adicional en cada animal. Los resultados indican que el EA debería ser usado al 0,4% del peso vivo para una buena utilización de pasturas tropicales durante el invierno

Developing an Energy Effective Autonomous USV for Undertaking Missions at the Highlands of Peru

This paper describes a novel multi-task allocation method for the autonomous navigation to improve the efficiency for executing mission considering an Unmanned Surface Vehicle (USV) developed by the Pontificia Universidad Catolica del Peru (PUCP). The new method is developed based upon the self-organizing map (SOM) algorithm, with the consideration of the priorities of the sample stations that USV need to visit, as well as the lattice distances from the sample stations to the start point. Using this new method, an optimized order of visiting sequence can be calculated according to the battery energy limit of the USV. The new multi-task allocation method has been verified in simulation environments with results proving the effectiveness and capabilities of the system

Efectos del tráfico del tractor sobre la distribución de la compactación del suelo y los rendimientos de trigo en España

395-403The general objective of this paper was to quantify the changes in the physical properties of an Aridisol soil and the effect on wheat yield due to agricultural tractors traffic in the Vélez Blanco District, Almería Spain. Parameters measured were cone index (CI) in the 0-600 mm depth profile, bulk density (BD) and rut depth; the variable wheat yields (WY) was measured too. The traffic treatments applied were: 0 (control plot), 1, 3, 5, and 7 tractor passes in the same tracks. Each experimental plot was trafficked with two tractors, one light (60 kN) and one heavy (80 kN). In topsoil (0-200 mm), up to five passes of the heavy (HT) and light tractors (LT), as in one and three passes, the BD and CI values responded to the ground pressure being higher in absolute value for LT. For the 200 to 400 mm depth range HT caused higher CI (1,570 to 2,200 kPa) and BD (1.38 to 1.68 Mg m-3) values than LT. Eight months later, WY was evaluated in tractor's track areas and decreases in the range of 18-38 percent, were measured. For seven passes the applications of total loads of 80 and 60 kN increased BD up to 1.5 Mg m-3 at depths of 200-600 mm. Although soil had high bulk density prior to traffic treatments, a significant increment of subsoil compaction still occurred due to the high traffic intensities applied

Spirodela polyrhiza (L.) Schleid. (Lemnaceae): primera cita para Galicia (NO de la Península Ibérica)

La familia Lemnaceae Martinov incluye monocotiledóneas propias de aguas continentales que viven flotando libremente o sumergidas. Se trata de un grupo de plantas que, debido a su reducido tamaño y particular morfología, presentan una compleja taxonomía lo que dificulta su identificación. Esta familia comprende 6 géneros de los que tres −Lemna L., Spirodela Schleid. y Wolffia Horkel ex Schleid− han sido citados para la Península Ibérica (Galán de Mera & Castroviejo, 2007). En Galicia, hasta el momento, sólo viven dos especies de Lemna: L. minor L., en las cuatro provincias gallegas y L. giba L., esta última únicamente en Lugo y Ourense

Collecting high-order interactions in an effective pairwise intermolecular potential using the hydrated ion concept: The hydration of Cf3+

This work proposes a new methodology to build interaction potentials between a highly charged metal cation and water molecules. These potentials, which can be used in classical computer simu- lations, have been fitted to reproduce quantum mechanical interaction energies (MP2 and BP86) for a wide range of [M(H2O)n]m+(H2O)l clusters (n going from 6 to 10 and l from 0 to 18). A flexible and polarizable water shell model (Mobile Charge Density of Harmonic Oscillator) has been coupled to the cation-water potential. The simultaneous consideration of poly-hydrated clusters and the polarizability of the interacting particles allows the inclusion of the most important many-body effects in the new polarizable potential. Applications have been centered on the californium, Cf(III) the heaviest actinoid experimentally studied in solution. Two different strategies to select a set of about 2000 structures which are used for the potential building were checked. Monte Carlo simulations of Cf(III)+500 H2O for three of the intermolecular potentials predict an aquaion structure with coordination number close to 8 and average RCf–O in the range 2.43–2.48 Å, whereas the fourth one is closer to 9 with RCf–O = 2.54 Å. Simulated EXAFS spectra derived from the structural Monte Carlo distribution compares fairly well with the available experimental spectrum for the simulations bearing 8 water molecules. An angular distribution similar to that of a square antiprism is found for the octa-coordination.Ministerio de Ciencia e Innovación CTQ2011-2593