Magnetization plateaux and jumps in a class of frustrated ladders: A simple route to a complex behaviour

We study the occurrence of plateaux and jumps in the magnetization curves of a class of frustrated ladders for which the Hamiltonian can be written in terms of the total spin of a rung. We argue on the basis of exact diagonalization of finite clusters that the ground state energy as a function of magnetization can be obtained as the minimum - with Maxwell constructions if necessary - of the energies of a small set of spin chains with mixed spins. This allows us to predict with very elementary methods the existence of plateaux and jumps in the magnetization curves in a large parameter range, and to provide very accurate estimates of these magnetization curves from exact or DMRG results for the relevant spin chains.Comment: 14 pages REVTeX, 7 PostScript figures included using psfig.sty; this is the final version to appear in Eur. Phys. J B; some references added and a few other minor change

Rule-based Modelling and Tunable Resolution

We investigate the use of an extension of rule-based modelling for cellular signalling to create a structured space of model variants. This enables the incremental development of rule sets that start from simple mechanisms and which, by a gradual increase in agent and rule resolution, evolve into more detailed descriptions

Digraph Complexity Measures and Applications in Formal Language Theory

We investigate structural complexity measures on digraphs, in particular the cycle rank. This concept is intimately related to a classical topic in formal language theory, namely the star height of regular languages. We explore this connection, and obtain several new algorithmic insights regarding both cycle rank and star height. Among other results, we show that computing the cycle rank is NP-complete, even for sparse digraphs of maximum outdegree 2. Notwithstanding, we provide both a polynomial-time approximation algorithm and an exponential-time exact algorithm for this problem. The former algorithm yields an O((log n)^(3/2))- approximation in polynomial time, whereas the latter yields the optimum solution, and runs in time and space O*(1.9129^n) on digraphs of maximum outdegree at most two. Regarding the star height problem, we identify a subclass of the regular languages for which we can precisely determine the computational complexity of the star height problem. Namely, the star height problem for bideterministic languages is NP-complete, and this holds already for binary alphabets. Then we translate the algorithmic results concerning cycle rank to the bideterministic star height problem, thus giving a polynomial-time approximation as well as a reasonably fast exact exponential algorithm for bideterministic star height.Comment: 19 pages, 1 figur

Design and Development of Software Tools for Bio-PEPA

This paper surveys the design of software tools for the Bio-PEPA process algebra. Bio-PEPA is a high-level language for modelling biological systems such as metabolic pathways and other biochemical reaction networks. Through providing tools for this modelling language we hope to allow easier use of a range of simulators and model-checkers thereby freeing the modeller from the responsibility of developing a custom simulator for the problem of interest. Further, by providing mappings to a range of different analysis tools the Bio-PEPA language allows modellers to compare analysis results which have been computed using independent numerical analysers, which enhances the reliability and robustness of the results computed.

The Knowledge Production Function for University Patenting

We estimate a knowledge production function for university patenting using an individual effects negative binomial model. We control for R&D expenditures, research field and the presence of a TTO office. We distinguish between three kinds of researchers who staff labs: faculty, postdoctoral students and PhD students. We also examine whether PhDs and postdoctoral scholars contribute equally to patent activity or whether there is a differential effect depending upon visa status. We find patent counts relate positively and significantly to the number of faculty, number of PhD students and number of postdocs. Our results also suggest that not all graduate students and postdocs contribute equally to patenting but that contribution is mediated by visa status. Working Paper 07-0

A descriptive review and classification of organizational information security awareness research

Information security awareness (ISA) is a vital component of information security in organizations. The purpose of this research is to descriptively review and classify the current body of knowledge on ISA. A sample of 59 peer-reviewed academic journal articles, which were published over the last decade from 2008 to 2018, were analyzed. Articles were classified using coding techniques from the grounded theory literature-review method. The results show that ISA research is evolving with behavioral research studies still being explored. Quantitative empirical research is the dominant methodology and the top three theories used are general deterrence theory, theory of planned behavior, and protection motivation theory. Future research could focus on qualitative approaches to provide greater depth of ISA understanding

Same-Sex Couples and Immigration in the United States

This report uses Census Bureau data to provide a portrait of same-sex couples affected by United States immigration policy. Using data from the American Community Survey (ACS) it presents demographic profiles of three different types of same-sex couples: binational couples in which one partner is a U.S. citizen and one is not; dual non-citizen couples; and couples that include a naturalized U.S. citizen. Binational couples and non-citizen couples in which only one partner is a permanent resident would gain protections and rights if U.S. immigration law were changed to treat same-sex couples as their different-sex counterparts are treated. As of 2010, nearly 79,200 same-sex couples living in the United States include at least one partner who is currently not a U.S citizen or was naturalized as a citizen. Of the nearly 650,000 same-sex couples in the US: 4.4% or 28,574 are binational couples (one partner is a U.S. citizen and one is not)1.8% or 11,442 are dual non-citizen couples6.1% or 39,176 are dual citizen couples with at least one naturalized partne

Metáforas para profesor y estudiante de pedagogía en un grupo de estudiantes de pedagogía chilenos

En este artículo se presentan los resultados de una investigación de tipo cualitativo, cuyo objetivo general es identificar los conceptos metafóricos los estudiantes de pedagogía acerca de cómo ellos creen que el profesor es representado por la sociedad, y como representan ellos a sí mismos. El marco de referencia lo constituyen la cognición docente y la metáfora conceptual. Para la elicitación de metáforas se aplicó un cuestionario a un grupo de 70 estudiantes de Pedagogía de la Universidad de Concepción, Chile. Se realizó un análisis de contenido que abarcó las siguientes etapas: etiquetado, clasificación, categorización y juicio de externos. Para las metáforas sobre cómo es representado el profesor por la sociedad, a través del análisis, se identificaron las siguientes categorías: Metáforas centradas en el profesor, Metáforas centradas en el estudiante, Metáforas centradas en la valoración social. Para las metáforas sobre cómo es representado el estudiante de pedagogía se identificaron las siguientes categorías: Metáforas centradas en el proceso de formación profesional, Metáforas centradas en el proceso de enseñanza aprendizaje, Metáforas centradas en la valoración social. Finalmente, se comentan los alcances y proyecciones del estudio, y se discute la pertinencia de algunas categorías en el contexto de la formación de profesores. This article provides the results of a qualitative study, whose main objective is to identify the metaphorical concepts through which teacher candidates believe how teachers are represented by society, and how they represent themselves. The referential framework of this study is given by teacher cognition and conceptual metaphor. A questionnaire was applied to elicit metaphors from 70 teacher candidates at the University of Concepción, Chile. Content analysis was used, following these stages: coding, classification, categorization and scholar review. For the metaphors on how teachers are represented by society through the analysis, the following categories are identified: teacher-centered, student-centered and socially laden. For the metaphors on how student-teachers are represented, the identified categories are: professional formation metaphors, teaching and learning metaphors and social value metaphors. Future work is commented and the relevance of some categories for teacher education is also discussed