Pursuit-evasion predator-prey waves in two spatial dimensions

We consider a spatially distributed population dynamics model with excitable predator-prey dynamics, where species propagate in space due to their taxis with respect to each other's gradient in addition to, or instead of, their diffusive spread. Earlier, we have described new phenomena in this model in one spatial dimension, not found in analogous systems without taxis: reflecting and self-splitting waves. Here we identify new phenomena in two spatial dimensions: unusual patterns of meander of spirals, partial reflection of waves, swelling wavetips, attachment of free wave ends to wave backs, and as a result, a novel mechanism of self-supporting complicated spatio-temporal activity, unknown in reaction-diffusion population models.Comment: 15 pages, 15 figures, submitted to Chao

Experiences of Education for Democratic Citizenship in Italian Schools in Recent Years: Research Lines. In: INVALSI–CIDREE. Building Democracy in Europe Through Citizenship: EducationEuropean Year of Citizenship Through Education: General Assembly 2005 CIDREE, Frascati 17th November 2005

The research assumes the definition of Education for Citizenship proposed by the Council of Europe: “is a set of practices and principles that aim to make young people and adults better equipped to participate actively in democratic life by assuming and exercising their rights and responsibilities in society” . The main questions of the research are borrowed from the area ‘Curriculum Teaching and Learning’ of the ‘Tool for quality assurance of EDC in schools’ : - Is there evidence of an adequate place for EDC in the school’s goals, policies and curriculum plans? - Is there evidence of students and teachers acquiring understanding of EDC and applying EDC principles to their everyday practice in schools and classrooms? - Are the design and practice of assessment within the school consonant with EDC? The information/data-base is –mainly- the on-line documentation of schools (good) practices, collected by National Institute for the Documentation of Innovation and Research in Education and by other organizations. Evidences. In italian schools, according to the examinated documents, EDC seems to be - an educational principle firmly sustained - a teaching content relevant in specific educational activities - carried on already from nursery schools; developed by the whole school within compulsory education; mainly an initiative of one or few teachers in secondary school, added to social studies classes - developed thanks to the “meeting and melting” of different interests: - from inside (specific problems or care) - from external institutions (ministerial or international, mainly european) - from external organizations and groups (local authorities, non-profit organizations, lobbies) - focused on the development of an active, participate, overnational citizenship that leads to a social and political status more than a legal one - crosscurricolar and interdisciplinary activity in nursery and primary schools; while in secondary schools it often moves from one specific subject to the others (pluridisciplinary approach) - carried on by active teachers working together and with experts and militants from outside the school too. - Developed through active teaching/learning strategies including discussions, teamworks, workshops, researchs and scientific, literary and artistic productions (monographs, exhibitions, shows, multimedia), simulations and fieldworks - aimed to the dissemination, implementation and sharing of values and awareness, information and knowledge of citizenship; the practice of skills and competences is focused on specific activities or on daily life - evaluated more by qualitative appreciations on the experience, its contents and values, than using structured and formal instruments - concluding, it’s more a teaching/learning topic than a daily school practice Suggestions. The report suggests that EDC is a complex, multilevel and integrated action strategy within the school and in interaction with society. So, starting from daily school practice and rules, EDC should be developed throught crosscurricolar activity and as social and civics studies subject and with specific projects, together. Concluding, the author proposes a plan of action-researches aimed to develop EDC practice in italian schools, using the strategy and methodology suggested by the Council of Europe in the quoted ‘Tool for quality assurance of EDC in schools’. That is a bottom-up approach and not only a top-down one

Automatic drainage pattern recognition in river networks

In both geographic information system and terrain analysis, drainage systems are important components. Owing to local topography and subsurface geology, a drainage system achieves a particular drainage pattern based on the form and texture of its network of stream channels and tributaries. Although research has been done on the description of drainage patterns in geography and hydrology, automatic drainage pattern recognition in river networks is not well developed. This article introduces a new method for automatic classification of drainage systems in different patterns. The method applies to river networks, and the terrain model is not required in the process. A series of geometric indicators describing each pattern are introduced. Network classification is based on fuzzy set theory. For each pattern, the level of membership of the network is given by the different indicator values. The method was implemented, and the experimental results are presented and discussed

Suspended redistribution: ‘green economy’ and water inequality in the Waterberg, South Africa

In this article I show how ideas and practices of ‘green economy’ can reproduce and even naturalise inequality in water access for local users. Evidence to support my argument is drawn from the Waterberg region in the Limpopo Province of South Africa. Following the demise of apartheid and the appeal of the green economy, the Waterberg has been ‘reinvented’ as a wildlife destination. Whereas game farms enjoy secure water supply, the rural poor relocated to the small town of Vaalwater suffer severe water shortages. The article questions the mainstream view according to which game farms have no relationship to the water problems in town. Rather, I suggest that by conceiving and managing water as a private commodity deriving from land ownership and largely unregulated by the state, green economy initiatives contribute both materially and discursively to hampering more equality in water redistribution

Superconducting NbN microstrip detectors

Superconducting NbN strip transmission line counters and coupling circuits were processed on silicon wafers using thin film techniques, and they were characterized with several methods to verify the design principles. The stripline circuits, designed using microwave design rules, were simulated using a circuit design tool enhanced to include modelling of the superconducting lines. The strips, etched out of the 282 nm thick top NbN film with resistivity 284 µ?cm at 20 K, have critical temperatures in the range 12 to 13 K and a critical current density approximately Jc(0) = 3.3·105 A/cm2. The linearized heat transfer coefficient between the strip and the substrate is approximately 1.1·105 W/(m2K) and the healing length is about 1.6 µm between 3 and 5 K temperatures. Traversing 5 MeV a-particles caused the strips to quench. No events due to electrons could be detected in agreement with the predicted signal amplitude which is below the noise threshold of our wideband circuitry. The strip bias current and hence the signal amplitude were limited due to a microbridge at the isolator step of the impedance transformer

Mesoscale circulation in the Black Sea : a study combining numerical modelling and observations

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Experimental study of stratified turbulence forced with columnar dipoles

International audienceWe present a novel experimental setup aimed at producing a forced strongly stratified turbulent flow. The flow is forced by an arena of 12 vortex pair generators in a large tank. The continuous interactions of the randomly produced vortex pairs give rise to a statistically stationary disordered flow in contrast to previous experiments where the stratified turbulence is decaying. The buoyancy frequency N is set to its highest value N = 1.7 rad/s using salt as stratifying agent so that the horizontal Froude number F h = Ω/N is low, while the buoyancy Reynolds number R=ReFh2 , where Re = Ωa 2/ν is the classical Reynolds number, is as high as possible given the experimental constraints (Ω is the maximum angular velocity of the vortices, a their radius and ν the viscosity). PIV measurements show that the flow is not homogeneous in the horizontal plane and is organised into horizontal layers along the vertical. When R is increased, we observe a progressive evolution from the viscosity dominated regime with smooth layers to a regime with small scales superimposed on the layers and for which the vertical Froude number is of order one. The latter regime resembles the strongly stratified turbulent regime with a downscale cascade that has been predicted for large R . However, horizontal second order structure functions do not exhibit a clear inertial range for the largest R achieved R=310 . In addition, the corresponding turbulent buoyancy Reynolds number Rt=P/(νN2) based on an estimation of the injection rate of energy P is only of order unity Rt≃0.4 indicating that only the edge of the strongly stratified turbulent regime has been reached. However, these results suggest that sufficiently large turbulent buoyancy Reynolds numbers, Rt≃10 , could be achieved experimentally by scaling up five times this novel set-up