Errors and Artefacts in Agent-Based Modelling

The objectives of this paper are to define and classify different types of errors and artefacts that can appear in the process of developing an agent-based model, and to propose activities aimed at avoiding them during the model construction and testing phases. To do this in a structured way, we review the main concepts of the process of developing such a model – establishing a general framework that summarises the process of designing, implementing, and using agent-based models. Within this framework we identify the various stages where different types of errors and artefacts may appear. Finally we propose activities that could be used to detect (and hence eliminate) each type of error or artefact.Verification, Replication, Artefact, Error, Agent-Based Modelling, Modelling Roles

On domain walls in a Ginzburg-Landau non-linear S^2-sigma model

The domain wall solutions of a Ginzburg-Landau non-linear $S^2$-sigma hybrid model are unveiled. There are three types of basic topological walls and two types of degenerate families of composite - one topological, the other non-topological- walls. The domain wall solutions are identified as the finite action trajectories (in infinite time) of a related mechanical system that is Hamilton-Jacobi separable in sphero-conical coordinates. The physical and mathematical features of these domain walls are thoroughly discussed.Comment: 26 pages, 18 figure

The Moduli Space of BPS Domain Walls

N=2 SQED with several flavors admits multiple, static BPS domain wall solutions. We determine the explicit two-kink metric and examine the dynamics of colliding domain walls. The multi-kink metric has a toric Kahler structure and we reduce the Kahler potential to quadrature. In the second part of this paper, we consider semi-local vortices compactified on circle. We argue that, in the presence of a suitable Wilson line, the vortices separate into domain wall constituents. These play the role of fractional instantons in two-dimensional gauge theories and sigma-models.Comment: 16 pages, LaTex, 2 figures; factors of zeta corrected, meaning of cross-terms elucidated, further clarifying comments; (more) references adde

Changes in serotypes causing invasive pneumococcal disease (2005–2007 vs. 1997–1999) in children under 2 years of age in a population with intermediate coverage of the 7-valent pneumococcal conjugated vaccine

AbstractSerotypes causing invasive pneumococcal disease (IPD) in children aged <2 years in Catalonia (Spain) before and after licensing of the 7-valent pneumococcal conjugated vaccine (7vPCV) were assessed, using samples taken during 1997–1999 and 2005–2007 respectively. The distribution of serotypes causing IPD within these groups was obtained by serotyping strains sent by 22 Catalan hospitals to the Carlos III Health Institute, Madrid. Between 1997–99 and 2005–2007, the proportion of vaccine serotypes causing IPD in Catalonia fell from 70.54% to 31.67% (p <0.0001). The proportion of vaccine-related serotypes, mainly serotype 19A, increased from 9.82% to 32.50% (p <0.0001). The proportion of non-vaccine, non-related serotypes (serotypes not related to vaccine serotypes) rose from 19.64% to 35.83% (p <0.05). Within this group, the proportions of serotype 24F increased significantly. There has been a change in the distribution of serotypes isolated from cases of IPD in children <2 years old in Catalonia, comprising a reduction in the proportion of 7-valent vaccine serotypes, a rise in vaccine-related serotypes, especially 19A, and a smaller rise in non-vaccine, non-related serotypes, especially serotype 24F. A new 13-valent vaccine will cover 77.91% of the serotypes causing IPD in children <2 years old in Catalonia from 2005 to 2007

Supersymmetric black holes in 2D dilaton supergravity: baldness and extremality

We present a systematic discussion of supersymmetric solutions of 2D dilaton supergravity. In particular those solutions which retain at least half of the supersymmetries are ground states with respect to the bosonic Casimir function (essentially the ADM mass). Nevertheless, by tuning the prepotential appropriately, black hole solutions may emerge with an arbitrary number of Killing horizons. The absence of dilatino and gravitino hair is proven. Moreover, the impossibility of supersymmetric dS ground states and of nonextremal black holes is confirmed, even in the presence of a dilaton. In these derivations the knowledge of the general analytic solution of 2D dilaton supergravity plays an important role. The latter result is addressed in the more general context of gPSMs which have no supergravity interpretation. Finally it is demonstrated that the inclusion of non-minimally coupled matter, a step which is already nontrivial by itself, does not change these features in an essential way.Comment: 30 pages, LaTeX, v2: mayor revision (rearranged title, shortened abstract, revised introduction, inserted section from appendix to main text, added subsection with new material on non-SUGRA gPSMs, added clarifying remarks at some places, updated references); v3: corrected minor misprints, added note with a new referenc

Analysis of platelets from a diet-induced obesity rat model: elucidating platelet dysfunction in obesity

Obesity is one of the main health problems in industrialized countries. The contribution of multiple factors developed in obesity can hardly be modeled in vitro. In this context, the development of animal models mimicking human obesity could be essential. The aim of the present study was to compare platelets from a diet-induced obesity (DIO) rat model with their lean control group in order to elucidate platelet dysfunction mechanisms in obesity and correlate the results with previous data from morbid obese patients. In parallel, we also established a blood collection and platelet isolation methodology to study the DIO rat model at biochemical and functional level. Optimal blood collection was obtained from vena cava and platelet isolation was based on a serial of centrifugations avoiding platelet activation. Our results show that the DIO rat model simulate obesity pathologically since weight gain, fasting glucose and platelet counts are increased in obese rats. Interestingly, platelet levels of the active form of Src (pTyr(419)) showed a tendency to increase in DIO rats pointing towards a potential dysfunction in Src family kinases-related signalling pathways in obesity. Moreover, platelets from DIO rats adhere more to collagen compared with the control group, pointing towards Glycoprotein VI (GPVI) as one of the dysregulated receptors in obesity, in agreement with our recent studies in humans. These results confirm that obesity, in line with human studies, present a platelet dysregulation, and highlight the relevance of considering novel antithrombotic drug targets in these patients, such as GPVI

Quantum cosmic models and thermodynamics

The current accelerating phase of the evolution of the universe is considered by constructing most economical cosmic models that use just general relativity and some dominating quantum effects associated with the probabilistic description of quantum physics. Two of such models are explicitly analyzed. They are based on the existence of a sub-quantum potential and correspond to a generalization of the spatially flat exponential model of de Sitter space. The thermodynamics of these two cosmic solutions is discussed, using the second principle as a guide to choose which among the two is more feasible. The paper also discusses the relativistic physics on which the models are based, their holographic description, some implications from the classical energy conditions, and an interpretation of dark energy in terms of the entangled energy of the universe.Comment: 15 pages, 1 figure, accepted for publication in Class. Quantum Gra

All electron and pseudopotential study of the spin polarization of the V (001) surface: LDA versus GGA

The spin-polarization at the V(001) surface has been studied by using different local (LSDA) and semilocal (GGA) approximations to the exchange-correlation potential of DFT within two ab initio methods: the all-electron TB-LMTO-ASA and the pseudopotential LCAO code SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms). A comparative analysis is performed first for the bulk and then for a N-layer V(001) film (7 < N < 15). The LSDA approximation leads to a non magnetic V(001) surface with both theoretical models in agreement (disagreement) with magneto-optical Kerr (electron-capture spectroscopy) experiments. The GGA within the pseudopotential method needs thicker slabs than the LSDA to yield zero moment at the central layer, giving a high surface magnetization (1.70 Bohr magnetons), in contrast with the non magnetic solution obtained by means of the all-electron code.Comment: 12 pages, 1 figure. Latex gzipped tar fil

Supergravity interacting with bosonic p-branes and local supersymmetry

We study the coupling of supergravity with a purely bosonic brane source (bosonic p-brane). The interaction, described by the sum of their respective actions, is self-consistent if the bosonic p-brane is the pure bosonic limit of a super-p-brane. In that case the dynamical system preserves 1/2 of the local supersymmetry characteristic of the `free' supergravity.Comment: 11 pages, RevTe