A new bound for the connectivity of cages

AbstractAn (r,g)-cage is an r-regular graph of girth g of minimum order. We prove that all (r,g)-cages are at least ⌈r/2⌉-connected for every odd girth g≥7 by means of a matrix technique which allows us to construct graphs without short cycles. This lower bound on the vertex connectivity of cages is a new advance in proving the conjecture of Fu, Huang and Rodger which states that all (r,g)-cages are r-connected

Use of Steel Industry Wastes for the Preparation of Self-Cleaning Mortars

An important problem, which must be solved, is the accumulation of industrial waste in landfills. Science has an obligation to transform this waste into new products and, if possible, with high added value. In this sense, we propose the valorization of the waste which is generated in the steel lamination process (HSL) through its conversion into a new material with photocatalytic activity which is suitable for use as an additive to obtain a self-cleaning construction material. The valorization of steel husk lamination waste is achieved through a grinding process, which allows the sample to be homogenized, in size, without altering its phase composition, and a thermal treatment that turns it into iron oxide, which acts as a photocatalyst. These residues, before and after treatment, were characterized by different techniques such as PXRD (Powder X-Ray Diffraction), TGA (Thermogravimetric Analysis), SBET (Specific surface area, Brunauer-Emmett-Teller), SEM (Scanning Electron Microscopy) and Diffuse reflectance (DR). MB and RhB tests show that this material is capable of self-cleaning, both of the material itself and when it is incorporated into a construction material (mortar). In addition, the NOx gas elimination test shows that it is also capable of acting on greenhouse gases such as NOx

Preparación de nuevos materiales fotocatalizadores para la descontaminación de gases NOx

El desarrollo del presente trabajo de investigación ha permitido alcanzar las siguientes conclusiones generales. a) En lo que respecta al diseño de nuevos materiales fotocatalizadores avanzados: - Se demuestra la capacidad de la fase hematita del óxido de hierro, -Fe2O3, como fotocatalizador eficiente para la degradación de gases NOx. - Se ha confirmado que el mecanismo fotocatalítico De-NOx conlleva el siguiente proceso de foto-oxidación: NO NO2 NO3 - No obstante, y a pesar de su tamaño nanométrico, la eficiencia fotocatalítica de la hematita resulta ser pobre. - La eficiencia fotocatalítica de la fase hematita se mejora al incrementar su superficie específica. En este sentido, estructuras unidimensionales constituidas por nanohilos nanocristalinos muestran una mejorada actividad De-NOX. - La fase α-Fe2O3 se puede preparar por la técnica CVD con un control efectivo de su nano-organización estructural. De igual modo se pueden preparar depósitos de α-Fe2O3/TiO2 nanoestructurados. La fase α-Fe2O3 actúa en sinergia con la fase anatasa del TiO2 obteniendo unas láminas delgadas muy eficientes en el proceso De-NOX. - Se demuestra que la actividad De-NOX de la fase TiO2 anatasa puede ser mejorada. La preparación de una estructura mesoporosa nanoparticulada conlleva a la obtención de un óxido TiO2 no sólo activo a la luz UV sino también en el Visible, además de una sobresaliente mejora en la selectividad del proceso fotoquímico. b) Por otra parte, en relación al estudio de nuevos materiales fotocatalíticos obtenidos a partir de residuos sólidos procedentes de otras industrias: - Se ha demostrado que se pueden realizar transformaciones adecuadas de los residuos industriales que les aporten un nuevo valor añadido y propiedades para la mejora de la calidad medioambiental. - Se ha optimizado el proceso de transformado de un residuo industrial en agente fotocatalizador. - Los residuos ricos en hierro son utilizados eficazmente como aditivos fotocatalizadores en materiales de construcción para aplicaciones de auto-limpieza y descontaminación de gases NOx. - En los materiales de construcción que además de incorporar los residuos transformados también incorporan TiO2, se observa una acción sinérgica de ambos aditivos fotocatalizadores que conduce a una clara mejora de la eficiencia fotocatalítica última del material. - Se ha demostrado que las cenizas de procedentes de la combustión de la cascarilla de arroz sirven de soporte útil de material fotocatalizador. - El proceso térmico de preparación de composites Fe2O3/SiO2 condiciona la morfología de la fase hematita soportada, así como su superficie específica. - Los composites Fe2O3/SiO2 presentan actividad De-NOX mejorada respecto a la observada para la muestra de hematite nanocristalina en polvo. Todas las conclusiones anteriores evidencian que se pueden preparar nuevos materiales con propiedades fotocatalíticas mejoradas en lo que respecta a la eliminación de gases NOX en atmósferas contaminadas, objetivo principal planteado al iniciar esta Tesis Doctoral

ZnO on rice husk: a sustainable photocatalyst for urban air purification

A cost-effective and sustainable De-NOx photocatalyst is prepared usingzinc acetate and rice husk. ZnO@SiO2samples are obtained from the calcination of a homogenised precursor mixture at 600 C. ZnO nanoparticles (70 –180 nm) grow aggregated in spheres and well dispersed (40 –53 m2g-1surface area) covering the silicon skeleton. The corresponding band gap for ZnO@SiO2photocatalysts was estimated at3.1 –3.2 eV. When the samples are irradiated by sunlight in anitrogen oxide atmosphere the NO HNO2NO2NO3-photochemical oxidation takes place. In comparison to unsupported ZnO and TiO2-P25, ZnO@SiO2samples exhibit high NOXremoval values (70 %) and outstanding selectivity (> 90%), the latter related to the sensitivity of zinc oxide towards NO2gas. This new photocatalyst is easily recyclable and reusabl

Effect of cascade overlap and C15 clusters on the damage evolution in Fe : An OKMC study

In order to investigate the long-term evolution of radiation-induced defects in the fission- and fusion-relevant material iron, we introduce cascade overlap effects into Object Kinetic Monte Carlo simulations. In addition to cascade overlap, we study the effect of introducing discrete C15 Laves phase clusters into the simulations. By applying either, none, or both of these effects we identify how they influence the evolution of the system. We find that both cascade overlap and C15 clusters affect the evolution of the radiation damage in different ways and on different time scales. Cascade overlap is found to reduce the number of Frenkel pairs. On the other hand, the explicit consideration of C15 Laves phase clusters increases the accumulation of defects at low dose. The results are compared to Molecular Dynamics simulation results under similar conditions.Peer reviewe

Rainbow connectivity of Moore cages of girth 6

Let be an edge-colored graph. A path of is said to be rainbow if no two edges of have the same color. An edge-coloring of is a rainbow-coloring if for any two distinct vertices and of there are at least internally vertex-disjoint rainbow -paths. The rainbow-connectivity of a graph is the minimum integer such that there exists a rainbow -coloring using colors. A -cage is a -regular graph of girth and minimum number of vertices denoted . In this paper we focus on . It is known that and when the -cage is called a Moore cage. In this paper we prove that the rainbow -connectivity of a Moore -cage satisfies that . It is also proved that the rainbow 3-connectivity of the Heawood graph is 6 or 7.Peer ReviewedPostprint (author's final draft

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