Using particle shape to induce tilted and bistable liquid crystal anchoring

We use Monte Carlo simulations of hard Gaussian overlap (HGO) particles symmetrically confined in slab geometry to investigate the role of particle-substrate interactions on liquid crystalline anchoring. Despite the restriction here to purely steric interactions and smooth substrates, a range of behaviours are captured, including tilted anchoring and homeotropic-planar bistability. These macroscopic behaviours are all achieved through appropriate tuning of the microscopics of the HGO-substrate interaction, based upon non-additive descriptions for the HGO-substrate shape parameter.</p

Free Fermionic Heterotic Model Building and Root Systems

We consider an alternative derivation of the GSO Projection in the free fermionic construction of the weakly coupled heterotic string in terms of root systems, as well as the interpretation of the GSO Projection in this picture. We then present an algorithm to systematically and efficiently generate input sets (i.e. basis vectors) in order to study Landscape statistics with minimal computational cost. For example, the improvement at order 6 is approximately 10^{-13} over a traditional brute force approach, and improvement increases with order. We then consider an example of statistics on a relatively simple class of models.Comment: Standard Latex, 12 page

Évaluation de l’utilisation et de la présentation des résultats d’analyses factorielles et d’analyses en composantes principales en éducation

Nous évaluons l’utilisation et la présentation des résultats d’analyses factorielles et d’analyses en composantes principales dans six périodiques canadiens en éducation publiés entre 1995 et 2005. À partir de 1089 articles, nous avons relevé 61 utilisations de ces analyses. En ayant recours à une grille de lecture, nous avons recueilli des informations sur le but de l’utilisation de l’analyse, la taille de l’échantillon, les variables, la méthode d’extraction, le critère de dimensionnalité, la méthode de rotation des axes et les résultats présentés. Nous avons identifié des lacunes, tant au niveau des pratiques que de la présentation des résultats. Enfin, nous formulons quelques recommandations quant à l’utilisation rigoureuse de ces types d’analyses.This paper presents an evaluation of the use and presentation of results of factor analysis and principal component analysis as published between 1995 and 2005 in six Canadian educational periodicals. From a corpus of 1089 articles, the authors noted 61 uses of these analyses. Using a reading grid, they noted information on the objective of the analysis, the sample size, the variables, the extraction method, the dimensionality criteria, the method for axes rotation, and the results presented. They identified deficiencies both at the level of practices and in the result presentation. Finally, the authors formulate several recommendations regarding a more rigorous use of these types of analyses.Evaluamos la utilización y la presentación de los resultados de análisis factoriales y de análisis en componentes principales dentro de seis publicaciones periódicas canadienses en educación publicadas entre 1995 et 2005. En 1089 artículos, notamos 61 utilizaciones de estos análisis. Mediante una matriz de lectura, recolectamos informaciones en cuanto al objetivo de la utilización de análisis, el tamaño de la muestra, las variables, el método de extracción, el criterio de dimensionalidad, el método de rotación de los ejes y los resultados presentados. Identificamos unas lagunas, tanto a nivel de las prácticas como de la presentación de los resultados. Por terminar, formulamos algunas recomendaciones en cuanto a la utilización rigorosa de estos tipos de análisis

Computer simulation of bistable switching in a nematic device containing pear-shaped particles

We study the microscopic basis of bistable switching of a confined liquid crystal via Monte Carlo simulations of hard pear-shaped particles. Using both dielectric and dipolar field couplings to this intrinsically flexoelectric fluid, it is shown that pulsed fields of opposing polarity can be used to switch between the vertical and hybrid aligned states. Further, it is shown that the field-susceptibility of the surface polarisation, rather than the bulk flexoelectricity, is the main driver of this switching behaviour.</p

Between supply and demand: the limits to participatory development in South Africa

Much of the focus in the literature on participatory development has been on the demand side and on the extent to which citizens succeed in pressuring the state to deliver basic services. Less attention has been focused on the supply side of participatory development, namely on how state institutions give effect to development policies. Post-Apartheid South Africa is replete with policies and legislation supporting participatory processes and yet in practice this has seldom lived up to the ideals espoused. This article examines the delivery of public housing in poor communities in three municipalities in South Africa and argues that there is a mismatch between how the formulators of policy understand participation and how it is interpreted by beneficiary communities and local officials. It concludes that considerably more attention needs to be focused on why officials fail to translate national policies into action if participatory democracy is to attain any legitimacy in the population at large.Web of Scienc

Initial Systematic Investigations of the Landscape of Low Layer NAHE Extensions

The discovery that the number of physically consistent string vacua is on the order of 10^500 has prompted several statistical studies of string phenomenology. Contained here is one such study that focuses on the Weakly Coupled Free Fermionic Heterotic String (WCFFHS) formalism. Presented are systematic extensions of the well-known NAHE (Nanopoulos, Antoniadis, Hagelin, Ellis) set of basis vectors, which have been shown to produce phenomenologically realistic models. Statistics related to the number of U(1)'s, gauge group factors, non-Abelian singlets, ST SUSYs, as well as the gauge groups themselve are discussed for the full range of models produced as well as models containing GUT groups only. Prior results of other large-scale investigations are compared with these regarding the aforementioned quantities. Statistical coupling between the gauge groups and the number of ST SUSYs is also discussed, and it was found that for order-3 extensions there are more models with enhanced ST SUSY when there is an exceptional group present. Also discussed are some three-generation GUT models found in the data sets. These models are unique because they come from basis vectors which still have a geometric interpretation -- there are no "rank-cuts" in these models.Comment: 65 Pages, 31 Tables, 31 Figure

Entropy-driven formation of the gyroid cubic phase

We show, by computer simulation, that tapered or pear-shaped particles, interacting through purely repulsive interactions, can freely self-assemble to form the three-dimensionally periodic, gyroid cubic phase. The Ia3d gyroid cubic phase is formed by these particles both on compression of an isotropic configuration and on expansion of a smectic A bilayer arrangement. For the latter case, it is possible identify the steps by which the topological transformation from non-intersecting planes to fully interpenetrating, periodic networks takes place</p

Indications for an Extra Neutral Gauge Boson in Electroweak Precision Data

A new analysis of the hadronic peak cross section at LEP 1 implies a small amount of missing invisible width in Z decays, while the effective weak charge in atomic parity violation has been determined recently to 0.6% accuracy, indicating a significantly negative S parameter. As a consequence of these two deviations, the data are described well if the presence of an additional Z' boson, such as predicted in Grand Unified Theories, is assumed. Moreover, the data are now rich enough to study an arbitrary extra Z' boson and to determine its couplings in a model independent way. An excellent best fit to the data is obtained in this case, suggesting the possibility of a family non-universal Z' with properties similar to ones predicted in a class of superstring theories.Comment: 5 pages of ReVTeX, 2 figure

Understanding process, power, and meaning in adaptive governance: A critical institutional reading

Adaptive governance continues to attract considerable interest in academic and policy circles. This is with good reason, given its increasing relevance in a globalized and changing world. At the same time, adaptive governance is the subject of a growing body of critical literature concerned with the ways in which it theorizes the social world. In this paper, we respond to these critiques, which we see as broadly concerning the process, power, and meaning dimensions of environmental and natural resource governance. We argue that adaptive governance theory would benefit from engaging constructively with critical institutionalism, a school of thought that, like adaptive governance, has one foot in commons scholarship. Critical institutionalism conceives of institutional change as a process of bricolage, where those involved piece together new arrangements from the resources to hand. This approach highlights the interplay of structure and agency, and illuminates how new governance arrangements form and come to be seen as natural in dynamic relation to the wider social and cultural landscape. We consider how these arrangements tend to reflect dominant power relations, whilst the plural nature of social life also provides scope for adaptation and transformative change