A Tool for Integer Homology Computation: Lambda-At Model

In this paper, we formalize the notion of lambda-AT-model (where $\lambda$ is a non-null integer) for a given chain complex, which allows the computation of homological information in the integer domain avoiding using the Smith Normal Form of the boundary matrices. We present an algorithm for computing such a model, obtaining Betti numbers, the prime numbers p involved in the invariant factors of the torsion subgroup of homology, the amount of invariant factors that are a power of p and a set of representative cycles of generators of homology mod p, for each p. Moreover, we establish the minimum valid lambda for such a construction, what cuts down the computational costs related to the torsion subgroup. The tools described here are useful to determine topological information of nD structured objects such as simplicial, cubical or simploidal complexes and are applicable to extract such an information from digital pictures.Comment: Journal Image and Vision Computing, Volume 27 Issue 7, June, 200

Enquitreidos (Annelida, Oligochaeta) en un robledal del valle de Ulzama, Navarra

Estudiado un robledal del Valle de Ulzama (Navarra), se han hallado cuatro especies de Enquitreidos: Buchholzia fallax Michaelsen 1887, Cognettia sp., Fridericia perrieri (Vejdovsky, 1877), y F. ratzeli (Eisen, 1872)

Environmental and social consequences of the increase in the demand for superfoods world-wide

1.The search for healthy diets has led to a surge in the demand for functional foods or ‘superfoods’, which have now become popular among the middle- and high- income fractions of the society in developed regions of the world. ‘Superfoods’ are predominantly consumed far from their centres of origin and out of their cul- tural context with different environmental and social effects. 2. Here, we present a series of case studies to provide an overview of the different environmental impacts driven by superfood expansion. 3. We show that if these crops are to follow the path of other global commodities, then strong environmental impacts and large carbon footprints are expected in terms of land clearing, use of agrochemicals and transportation during times of high prices (boom) and social problems as farmers have to abandon their liveli- hoods when prices sink below the cost of production (bust). 4. We also showcase how a combination of management practices, consumer choices and policy changes could help in alleviating the ecological footprint of these crops.Both A.M. and M.J.S. are funded through Ikerbasque, the Basque Foundation for Science. Research was also supported by the Spanish State Research Agency through María de Maeztu Excellence Unit accreditation (MDM‐2017‐0714) and the Basque Government BERC Programme

An update of the UK’s test reference year: The implications of a revised climate on building design

Copyright © 2015 SAGE PublicationsAverage weather years have been used around the world for testing buildings to ascertain their likely energy use using thermal modelling software. In the UK, the Test Reference Years which are in current use were released in 2006 but generally consisted of data from 1983 to 2004. In this work, revised test reference years will be proposed which are based on a new climatic period from 1984 to 2013. The differences between the two years will be highlighted and the implications for building design will be discussed.Engineering and Physical Sciences Research Council (EPSRC)CIBS

Resonant Raman scattering off neutral quantum dots

Resonant inelastic (Raman) light scattering off neutral GaAs quantum dots which contain a mean number, N=42, of electron-hole pairs is computed. We find Raman amplitudes corresponding to strongly collective final states (charge-density excitations) of similar magnitude as the amplitudes related to weakly collective or single-particle excitations. As a function of the incident laser frequency or the magnetic field, they are rapidly varying amplitudes. It is argued that strong Raman peaks should come out in the spin-density channels, not related to valence-band mixing effects in the intermediate states.Comment: Accepted in Physical Review

Economics: An Emerging Small World?

This paper examines the small world hypothesis. The first part of the paper presents empirical evidence on the evolution of a particular world: the world of journal publishing economists during the period 1970-2000. We find that in the 1970's the world of economics was a collection of islands. Two decades later, in the 1990's the world of economics was much more integrated, with the largest island covering close to half of the population. At the same time, the distance between individuals on the largest island had fallen significantly. Thus we believe that economics is an emerging small world. An exploration of the micro aspects of the network yields three findings: one, the average number of co-authors is very small but increasing; two, the distribution of co-authors is very unequal; and three, there exist a number of `stars', individuals who have a large number of co-authors. Thus the economics world is a set of inter-connected stars. We take the view that individuals decide on whether to work alone or with others; this means that individual incentives should help us understand why the economics world has the structure it does. The second part of the paper develops a simple theoretical model of co-authorship. The main finding of the model is that in the presence of productivity differentials and a shortage of high productivity individuals, inter-connected stars will arise naturally in equilibrium

Patterns of phytoplankton size structure and productivity in contrasting open-ocean environments

A total of 94 vertical profiles of size-fractionated chlorophyll a concentration and primary production rate were obtained along a meridional transect from the United Kingdom to the Falkland Islands (50°N to 50°S) during 4 cruises carried out in April and October 1996 and in April and October 1997. This data set allowed us to characterize the patterns of phytoplankton size-structure and productivity in temperate, oligotrophic, upwelling and equatorial regions. On average, picophytoplankton (0.2 to 2 µm) accounted for 56 and 71% of the total integrated carbon (C) fixation and autotrophic biomass, respectively. Enhanced biomass and productivity contributions by nano- and microplankton took place in the temperate regions and in the upwelling area off Mauritania. Small (<2 µm in diameter) phytoplankton cells should not be regarded as a background, relatively invariant component of the microbial community, given that most of the latitudinal variability in total photoautotrophic biomass and production was driven by changes in the picophytoplankton. In temperate regions and in the upwelling area off Mauritania, small (<2 µm) and large (>2 µm) phytoplankton accounted for a proportion of total biomass that was similar to their shares of productivity. In the oligotrophic and equatorial regions, in contrast, large phytoplankton tended to account for a fraction of the total production that was significantly higher than their share of the biomass. We found that the equatorial upwelling causes an increase in phytoplankton biomass and productivity without altering the typical size structure found in less productive regions such as the subtropical gyres. In the oligotrophic ocean, significant changes in C fixation rates take place without accompanying variations in the magnitude of the phytoplankton standing stocks or the size structure of the microbial community

Upholding the unified model for Active Galactic Nuclei: VLT/FORS2 spectropolarimetry of Seyfert 2 galaxies

The origin of the unification model for Active Galactic Nuclei (AGN) was the detection of broad hydrogen recombination lines in the optical polarized spectrum of the Seyfert 2 galaxy (Sy2) NGC 1068. Since then, a search for the hidden broad-line region (HBLR) of nearby Sy2s started, but polarized broad lines have only been detected in ?30–40% of the nearby Sy2s observed to date. Here we present new VLT/FORS2 optical spectropolarimetry of a sample of 15 Sy2s, including Compton-thin and Compton-thick sources. The sample includes six galaxies without previously published spectropolarimetry, some of them normally treated as non-hidden BLR (NHBLR) objects in the literature, four classified as NHBLR, and five as HBLR based on previous data. We report ?4? detections of a HBLR in 11 of these galaxies (73% of the sample) and a tentative detection in NGC 5793, which is Compton-thick according to the analysis of X-ray data performed here. Our results confirm that at least some NHBLRs are misclassified, bringing previous publications reporting differences between HBLR and NHBLR objects into question. We detect broad H? and H? components in polarized light for 10 targets, and just broad H? for NGC 5793 and NGC 6300, with line widths ranging between 2100 and 9600 km s?1. High bolometric luminosities and low column densities are associated with higher polarization degrees, but not necessarily with the detection of the scattered broad components

Factores con mayor influencia sobre la elección de alimentos en la población española

Fundamentos: Encuesta poblacional dirigida a conocer los factores que influyen en la elección de los alimentos de la población española. Métodos: Análisis de una muestra de todo el territorio español compuesta por 1009 individuos y seleccionada por un procedimiento aleatorio multietápico. Este estudio corresponde a la participación española en un estudio europeo sobre las actitudes de la población frente a la alimentación, nutrición y salud dirigido por el Instituto Europeo de Estudios Nutricionales de Dublín. Se determinó el porcentaje de individuos que situó a alguno de los cinco factores mencionados con más frecuencia (calidad, precio, dieta sana, condicionantes españoles, sabor) entre las tres primeras influencias en la elección de alimentos. Se ajustó un modelo multivariante para identificar los factores asociados a la elección de una dieta sana como una de las tres primeras influencias en la alimentación.Resultados: El precio influía más en los individuos de mayor edad, en niveles socioeconómicos más bajos y en individuos con menor nivel educativo. Fue mayor el impacto del precio en las mujeres de la zona Norte, Noreste y Noroeste. El sexo, la distribución geográfica, la edad y el nivel educativo presentaron un efecto independiente y significativo sobre la importancia concedida por la población a la elección de una dieta sana. Conclusiones: Los resultados sugieren la necesidad de una mayor educación sobre dieta y salud especialmente en hombre jóvenes, personas con menor nivel educativo y mujeres del Noroeste del país

Flexible Power Modeling of LTE Base Stations

With the explosion of wireless communications in number of users and data rates, the reduction of network power consumption becomes more and more critical. This is especially true for base stations which represent a dominant share of the total power in cellular networks. In order to study power reduction techniques, a convenient power model is required, providing estimates of the power consumption in different scenarios. This paper proposes such a model, accurate but simple to use. It evaluates the base station power consumption for different types of cells supporting the 3GPP LTE standard. It is flexible enough to enable comparisons between state-of-the-art and advanced configurations, and an easy adaptation to various scenarios. The model is based on a combination of base station components and sub-components as well as power scaling rules as functions of the main system parameters