Mathematical models of eye movements

This is the author accepted manuscript. The final version is available from [the Institute of Mathematics and its ApplicationsSupported by the BBSRC grant no 36/MMI09774

Observing the evaporation transition in vibro-fluidized granular matter

By shaking a sand box the grains on the top start to jump giving the picture of evaporating a sand bulk, and a gaseous transition starts at the surface granular matter (GM) bed. Moreover the mixture of the grains in the whole bed starts to move in a cooperative way which is far away from a Brownian description. In a previous work we have shown that the key element to describe the statistics of this behavior is the exclusion of volume principle, whereby the system obeys a Fermi configurational approach. Even though the experiment involves an archetypal non-equilibrium system, we succeeded in defining a global temperature, as the quantity associated to the Lagrange parameter in a maximum entropic statistical description. In fact in order to close our approach we had to generalize the equipartition theorem for dissipative systems. Therefore we postulated, found and measured a fundamental dissipative parameter, written in terms of pumping and gravitational energies, linking the configurational entropy to the collective response for the expansion of the centre of mass (c.m.) of the granular bed. Here we present a kinetic approach to describe the experimental velocity distribution function (VDF) of this non-Maxwellian gas of macroscopic Fermi-like particles (mFp). The evaporation transition occurs mainly by jumping balls governed by the excluded volume principle. Surprisingly in the whole range of low temperatures that we measured this description reveals a lattice-gas, leading to a packing factor, which is independent of the external parameters. In addition we measure the mean free path, as a function of the driving frequency, and corroborate our prediction from the present kinetic theory.Comment: 6 pages, 4 figures, submitted for publication September 1st, 200

"Importance didactique des conceptions des enseignants tunisiens sur l’éducation à la sexualité dans une perspective citoyenne"- 8th international congress on research in science teaching

L’objectif de cette étude est d’analyser les conceptions d'enseignants et futurs enseignants tunisiens et d'identifier les valeurs qu'expriment ces conceptions. Les nombreuses conceptions exprimées sont étudiées en tant qu’interactions entre les connaissances scientifiques, les valeurs et les pratiques d’enseignement, au moyen d’une analyse en composante principale (ACP). L'échantillon est formé de 753 enseignants et futurs enseignants du primaire et du secondaire, qui ont répondu à un questionnaire, dans un contexte strictement contrôlé

Soft singularity and the fundamental length

It is shown that some regular solutions in 5D Kaluza-Klein gravity may have interesting properties if one from the parameters is in the Planck region. In this case the Kretschman metric invariant runs up to a maximal reachable value in nature, i.e. practically the metric becomes singular. This observation allows us to suppose that in this situation the problems with such soft singularity will be much easier resolved in the future quantum gravity then by the situation with the ordinary hard singularity (Reissner-Nordstr\"om singularity, for example). It is supposed that the analogous consideration can be applied for the avoiding the hard singularities connected with the gauge charges.Comment: 5 page

Time-Symmetric Initial Data for Multi-Body Solutions in Three Dimensions

Time-symmetric initial data for two-body solutions in three dimensional anti-deSitter gravity are found. The spatial geometry has constant negative curvature and is constructed as a quotient of two-dimensional hyperbolic space. Apparent horizons correspond to closed geodesics. In an open universe, it is shown that two black holes cannot exist separately, but are necessarily enclosed by a third horizon. In a closed universe, two separate black holes can exist provided there is an additional image mass.Comment: 12 pages, harvmac macro, minor changes in wordin

Mental illness related discrimination:The role of self-devaluation and anticipated discrimination for decreased well-being

People with serious mental illness experience discrimination across many different contexts. Mental illness-related discrimination has, however, been an underresearched area until the last decade. This study aims is to expand understanding of the relationship between discrimination and well-being. Cross-sectional data on stigma, experiences of discrimination, and well-being were collected from adults in specialistmental health services in South London, United Kingdom as part of the MIRIAD study. Structural equation modeling supported the predictions that a higher degree of experienced discrimination would be associated with lower well-being via a pathway through higher internalized stigma and hopelessness. Higher anticipated discrimination also separately mediated the association between higher discrimination and lower wellbeing in the model. This suggests that discrimination is associated with lower wellbeing through both internalization of negative stereotypes and demoralization, as well as anticipation of further discrimination. In order to increase the well-being of people with severe mental illness, interventions may need to address the negative beliefs people hold about themselves (internalized stigma), as well as the sense of current and future threat that they experience (experienced and anticipated discrimination)

Killing Vector Fields in Three Dimensions: A Method to Solve Massive Gravity Field Equations

Killing vector fields in three dimensions play important role in the construction of the related spacetime geometry. In this work we show that when a three dimensional geometry admits a Killing vector field then the Ricci tensor of the geometry is determined in terms of the Killing vector field and its scalars. In this way we can generate all products and covariant derivatives at any order of the ricci tensor. Using this property we give ways of solving the field equations of Topologically Massive Gravity (TMG) and New Massive Gravity (NMG) introduced recently. In particular when the scalars of the Killing vector field (timelike, spacelike and null cases) are constants then all three dimensional symmetric tensors of the geometry, the ricci and einstein tensors, their covariant derivatives at all orders, their products of all orders are completely determined by the Killing vector field and the metric. Hence the corresponding three dimensional metrics are strong candidates of solving all higher derivative gravitational field equations in three dimensions.Comment: 25 pages, some changes made and some references added, to be published in Classical and Quantum Gravit

Maintenance Challenges of Multi-Owner Multi-Storey Residential Buildings in Lagos, Nigeria

It is noted that in Nigeria, buildings begin to demand for maintenance almost immediately after completion and handing over to users. As a single building belongs to several owners, corporate decision is required in maintaining it. The process of arriving at a workable decision remains a problem in the maintenance of such buildings due to protracted consultation and individual differences. This paper analytically investigates the frequency of maintenance of multi storey buildings compared with single owned building within the area Lagos, Nigeria. This paper examines these processes, the challenges and possible resolution for meeting point of ideas in order to sustain the commonwealth without jeopardizing the interest of any through a field survey. Structured questionnaire and non-participant case study were adopted in collecting quantitative and qualitative data. This study adopted quantitative analysis in form of tables to evaluate the attitude of respondents towards the maintenance of external surface of buildings vis-à-vis painting in the area. Three hundred and eighty four structured questionnaires were administered in six randomly selected Local Government Areas within the study area in April-May, 2012. The findings show that buildings that belong to single owners are better maintained than buildings that belong to multi-owners due to sense of ownership and ability to take decision on maintenance issues swiftly. Multi ownership system requires some level of enlightenment and thorough education in the area. The primary culture of the people in the selected area supports the compound system which multi ownership denies

Spherically symmetric Yang-Mills solutions in a (4+n)- dimensional space-time

We consider the Einstein-Yang-Mills Lagrangian in a (4+n)-dimensional space-time. Assuming the matter and metric fields to be independent of the n extra coordinates, a spherical symmetric Ansatz for the fields leads to a set of coupled ordinary differential equations. We find that for n > 1 only solutions with either one non-zero Higgs field or with all Higgs fields constant exist. We construct the analytic solutions which fulfill this conditions for arbitrary n, namely the Einstein-Maxwell-dilaton solutions. We also present generic solutions of the effective 4-dimensional Einstein-Yang-Mills-Higgs-dilaton model, which possesses n Higgs triplets coupled in a specific way to n independent dilaton fields. These solutions are the abelian Einstein-Maxwell- dilaton solutions and analytic non-abelian solutions, which have diverging Higgs fields. In addition, we construct numerically asymptotically flat and finite energy solutions for n=2.Comment: 15 Latex pages, 4 eps figures; v2: discussion of results revisite