Electromagnetic quasinormal modes of five-dimensional topological black holes

We calculate exactly the QNF of the vector type and scalar type electromagnetic fields propagating on a family of five-dimensional topological black holes. To get a discrete spectrum of quasinormal frequencies for the scalar type electromagnetic field we find that it is necessary to change the boundary condition usually imposed at the asymptotic region. Furthermore for the vector type electromagnetic field we impose the usual boundary condition at the asymptotic region and we discuss the existence of unstable quasinormal modes in the five-dimensional topological black holes.Comment: 16 pages. Already published in Revista Mexicana de Fisic

Fixed-term Contracts, Transitions and Wage Growth: Evidence from Spain

Employment instability is considered one of the main problems of the Spanish labour market. Thus, the proportion of temporary workers in Spain is around 30 per cent that is the highest rate of the European Union countries. The persistence of this situation could increase the risk of labour market segmentation. This paper presents new evidence of the factors affecting workers' transition from temporary work to permanent one and analyses whether this transition has a positive effect on wage growth. The former objective is obtained by estimating discrete choice models and the latter by estimating a wage growth equation correcting for selectivity bias through the two-step method developed by Trost and Lee (1984). The data are obtained from the second and third waves of the Spanish Household Panel Survey (INE 1996) conducted over the period 1995–1996. The main results are, on the one hand, that personal and job characteristics have a significant influence on the probability of becoming a permanent worker and, on the other hand, that this transition has an important positive effect on wage growth.labour force transitions, temporary and permanent workers, wage growth

Towards a navigational logic for graphical structures

One of the main advantages of the Logic of Nested Conditions, defined by Habel and Pennemann, for reasoning about graphs, is its generality: this logic can be used in the framework of many classes of graphs and graphical structures. It is enough that the category of these structures satisfies certain basic conditions. In a previous paper [14], we extended this logic to be able to deal with graph properties including paths, but this extension was only defined for the category of untyped directed graphs. In addition it seemed difficult to talk about paths abstractly, that is, independently of the given category of graphical structures. In this paper we approach this problem. In particular, given an arbitrary category of graphical structures, we assume that for every object of this category there is an associated edge relation that can be used to define a path relation. Moreover, we consider that edges have some kind of labels and paths can be specified by associating them to a set of label sequences. Then, after the presentation of that general framework, we show how it can be applied to several classes of graphs. Moreover, we present a set of sound inference rules for reasoning in the logic.Peer ReviewedPostprint (author's final draft

A logic of graph conditions extended with paths

In this paper we tackle the problem of extending the logic of nested graph conditions with paths. This means, for instance, that we may state properties about the existence of paths between some given nodes. As a main contribution, a sound and complete tableau method is defined for reasoning about this kind of properties.Peer ReviewedPostprint (published version

Kindergarten Diagnostic Toolkit

This project was used for multiple purposes. The first was the identification of supplemental intervention activities in attempt to treat reading difficulties. The second was the creation of a Kindergarten Diagnostic Toolkit (KDT) as a means for early detection of learning deficits. Upon completion of beginning of the year assessments and use of the KDT checklist, instructional suggestions for remediation were made with a focus on explicit/systematic alphabetic, phonemic, and decoding skills. The need for such specific diagnostic assessment of early reading skills is further required with such high stakes testing requirements. Strategies specific to early literacy skills are connected to Dynamic Indicators of Basic Early Literacy Skills (DIBELS) probes and Consortium on Reading Excellence (CORE) assessment areas, as a means for instruction. Teachers and Intervention Specialists may use this toolkit to help form and modify small group instructional decisions. Research supporting the need for early reading intervention was utilized to supply instructional suggestions

The effect of rippling on the mechanical properties of graphene

Graphene is the stiffest material known so far but, due to its one-atom thickness, it is also very bendable. Consequently, free-standing graphene exhibit ripples that has major effects on its elastic properties. Here we will summarize three experiments where the influence of rippling is essential to address the results. Firstly, we observed that atomic vacancies lessen the negative thermal expansion coefficient of free-standing graphene. We also observed an increase of the Young's modulus with global applied strain and with the introduction of small density defects that we attributed to the decrease of rippling. Here, we will focus on a surprising feature observed in the data: the experiments consistently indicate that only the rippling with wavelengths between 5-10nm influences the mechanics of graphene. The rippling responsible of the negative TEC and anomalous elasticity is thought to be dynamic, i.e. flexural phonons. However, flexural phonons with these wavelengths should have minor effects on the mechanics of graphene, therefore other mechanisms must be considered to address our observations. We propose static ripples as one of the key elements to correctly understand the thermomechanics of graphene and suggest that rippling arises naturally due to a competition of symmetry breaking and anharmonic fluctuations

Revisión sobre el estado del arte del análisis de ciclo de vida para tableros derivados de la madera

El presente trabajo tiene por objeto realizar una revisión del „estado del arte‟ sobre los estudios del análisis de ciclo de vida de la madera, más concretamente el caso de los tableros derivados, ya que conforman el eslabón que permite su reutilización en fases sucesivas, asumiéndose de forma intrínseca el concepto de reciclado dentro de la cadena de transformación de esta industria. Todo ello sumado a las ventajas medioambientales de la madera caracterizadas por el efecto sumidero del CO2, así como la reducción del consumo de energía en el proceso de fabricación. En la etapa de recopilación de la documentación durante la búsqueda, se han tratado de recoger y resaltar aquellas experiencias, más interesantes e innovadoras, llevadas a cabo en los últimos años en el tema mencionado, tratando de extraer aquellos casos que permitan obtener una visión tanto de las tendencias en el ámbito internacional como del nacional, e incluso local. De la información aquí recogida sobre el análisis del ciclo de vida de los productos derivados de la madera, se busca constatar las ventajas resultantes de su empleo, respecto de otros materiales

Concrete in high-rise buildings: practical experiences in Madrid

The use of concrete in high-rise buildings has increased significantly in the last 20 years mainly owing to improvement in all of the technologies associated with this material: admixtures, pumping, transportation and elevation methods, etc. These enhanced possibilities are illustrated by means of four high-rise buildings that were built recently in Madrid, each about 250 m high. The main structural elements of these buildings are presented focusing on the advantages offered by concrete compared to other materials that are commonly used in high-rise construction. The types of concrete considered are high-resistance concrete up to C80, self-compacting concrete, precast and in situ concrete, reinforced or prestressed concrete, as well as normal weight or lightweight concrete. These examples clearly show that, even in structures where the role of self weight is determinant, concrete can be the best solution if all of the different factors involved in the success of a construction site are considered: geometry, ease of construction, means of elevation, prefabrication at factory, repetitiveness, material costs, control requirements, and so o