Lusternik-Schnirelmann category of simplicial complexes and finite spaces

In this paper we establish a natural definition of Lusternik-Schnirelmann category for simplicial complexes via the well known notion of contiguity. This category has the property of being homotopy invariant under strong equivalences, and only depends on the simplicial structure rather than its geometric realization. In a similar way to the classical case, we also develop a notion of geometric category for simplicial complexes. We prove that the maximum value over the homotopy class of a given complex is attained in the core of the complex. Finally, by means of well known relations between simplicial complexes and posets, specific new results for the topological notion of category are obtained in the setting of finite topological spaces.Comment: 18 pages, 10 figures, this is a new version with some minor changes and a new exampl

A monolithic (Si) massively broadband non-reverberant monopole

Accepted versio

A Method to Determine the In-Air Spatial Spread of Clinical Electron Beams

We propose and analyze in detail a method to measure the in-air spatial spread parameter of clinical electron beams. Measurements are performed at the center of the beam and below the adjustable collimators sited in asymmetrical configuration in order to avoid the distortions due to the presence of the applicator. The main advantage of our procedure lies in the fact that the dose profiles are fitted by means of a function which includes, additionally to the Gaussian step usually considered, a background which takes care of the dose produced by different mechanisms that the Gaussian model does not account for. As a result, the spatial spread is obtained directly from the fitting procedure and the accuracy permits a good determination of the angular spread. The way the analysis is done is alternative to that followed by the usual methods based on the evaluation of the penumbra width. Besides, the spatial spread found shows the quadratic-cubic dependence with the distance to the source predicted by the Fermi-Eyges theory. However, the corresponding values obtained for the scattering power are differing from those quoted by ICRU nr. 35 by a factor ~2 or larger, what requires of a more detailed investigation.Comment: 11 pages, 5 Postscript figures, to be published in Medical Physic

Use of nanofiltration membrane technology for ceramic industry wastewater treatment

A study has been undertaken of an advanced wastewater treatment approach using polymer nanofiltration membranes, in an attempt to obtain water of sufficient quality to allow it to be reused in the same production process or, alternatively, to be discharged without any problems. The study has initially focused on the removal of organic matter (reduction of COD) and the most representative ions present in the wastewater, such as Na+ , Mg2+, Cl- , and SO4 2- . In a first part of the study, with a view to optimising the experimental phase, a simulation has been performed of the nanofiltration process using the NanoFlux software. Among other things, the simulation allows the most suitable membranes to be selected as a function of the permeate flow rate and desired level of retention in the substances to be removed. The subsequent experimentation was carried out in a laboratory tangential filtration system that works with flat membranes. It was found that retention values of about 90% were obtained for the studied substances, with a good permeate flow rate, using low operating pressures. These results demonstrate the feasibility of the studied technology and its potential as a treatment for improving ceramic industry wastewater qualit

Phase transitions on the surface of a carbon nanotube

A suspended carbon nanotube can act as a nanoscale resonator with remarkable electromechanical properties and the ability to detect adsorption on its surface at the level of single atoms. Understanding adsorption on nanotubes and other graphitic materials is key to many sensing and storage applications. Here we show that nanotube resonators offer a powerful new means of investigating fundamental aspects of adsorption on carbon, including the collective behaviour of adsorbed matter and its coupling to the substrate electrons. By monitoring the vibrational resonance frequency in the presence of noble gases, we observe the formation of monolayers on the cylindrical surface and phase transitions within these monolayers, and simultaneous modification of the electrical conductance. The monolayer observations also demonstrate the possibility of studying the fundamental behaviour of matter in cylindrical geometry.Comment: Unpublished; 7 pages with 4 figures plus 3 pages of supplementary materia

Hacia una armonización semántica de la Información Geográfica

La demanda de Información Geográfica (IG) se está convirtiendo en una necesidad de primer orden, consecuencia del potencial de los geodatos como instrumento para facilitar la toma de decisiones y la gestión de recursos en diversas áreas (catastro, recursos naturales, etc. ). Pero, consecuencia de la pobre estructuración y la heterogeneidad de vocabularios existentes, son muchos los problemas para conseguir búsquedas y recuperación de información exitosas, asegurar la continuidad entre informaciones semejantes de distintas fuentes, etc. Estos problemas surgen principalmente de una producción y uso de la cartografía tradicionalmente centrada en las necesidades específicas de cada cual, donde no era tan importante como ahora el disponer de modelos comunes de la realidad geográfica. Para satisfacer estas nuevas necesidades, las ontologías se pueden utilizar como un instrumento para definir los significados de los fenómenos y generar modelos coherentes de la realidad, proporcionando un entendimiento común y compartido que dará solución a estos problemas. La Ingeniería Ontológica está modificando muchos conceptos, ideas y estrategias aplicadas en los procesos de estructuración y gestión “clásica” de la IG

Variación anual de la concentración de aeropolen de Compositae en la atmósfera de Córdoba

La familia Composirae corwi tU)'C un grupo CU)'OS representantes son cntomófilas, por ello las concentraciones deted adas en la atmósfera han sido bajas. El muestreo se llevó a cabo en Córdoba durante los años 1982. 1983 y 1984 mediante un mucstrcador BURKARD sporc-trap colccado a unos 15m de altura. Se han reconocido un total de 7 tí pos morfológico!> de granos de polen pertenecientes a esta ramilia: tipo Aruflemis,Artemisia, Clutaurea, tipo fleliam! tuJ, Iipo Taraxawm, Srneáo yXa11lhium. Las mayorcscantidadm. tic granos de polen de· teClados pertenecen al tipo l!t !illntlzus, considerados como alergcnos por algunos autores. Sus altas conccnt.radoncs en el aire, en la época de. rccolc.cción del girasol, hace que posiblemente tenga alguna importanci<~ e~~ las polinosis cslivalu. Se han detectado granos de polen. de procedencia lejana, deArtemi.fia, planta con polen ahamenlc alcrgógcno, por tanto pueda ser causa de polioosis de verano en aquellas zonils de !a pro\'incia donde es abundanlcThc Composírae bclong 10 a broad systcmatic group allhough, duc to rhe cntomophylous charactcr of thc spccics, the pollcn conccnltations of lhc samplcs in thc atmosphcrc in thc city of Córdob3 were not beco vcry high. Sampling of poli en grains was e<1rricd out for thrcc ycars (1982, 1983 and 1984) by n1eans ola Burkard sporc- trap samplcr locatcd about t5 m abovc ground leve!. Scvcn morphologica1 typcs of rollen grain~ wcrc recognizcd: AnOzemir, Artemisia, Ccntaurcu typc, Helianrhus typ::, Toraxocum, Su:r:cio and Xanrhium rypc~. Thc largeSI annual amounts of poUeo glilins U::tcclcd wcrc of Hefiamlms typ:, considcrcd allcrgcnic by many authors. Thc higl1er lc-.·els in thc a.ir (ounU duriog tbc. harvcsling scason of sunflowcrs may be rc.spansible for summcr pollinoscs. Arlt misia pollcn g.rains dcvcloping far from thc sampling point wcrc dctcctc:d. Thcsc !.pccics are probably responsible for parl of summcr polli noses duc lo their higb aJlergenic polcntial, at lcast in thc arcas whcrc this plant is abundan!