High order amplitude equation for steps on creep curve

We consider a model proposed by one of the authors for a type of plastic instability found in creep experiments which reproduces a number of experimentally observed features. The model consists of three coupled non-linear differential equations describing the evolution of three types of dislocations. The transition to the instability has been shown to be via Hopf bifurcation leading to limit cycle solutions with respect to physically relevant drive parameters. Here we use reductive perturbative method to extract an amplitude equation of up to seventh order to obtain an approximate analytic expression for the order parameter. The analysis also enables us to obtain the bifurcation (phase) diagram of the instability. We find that while supercritical bifurcation dominates the major part of the instability region, subcritical bifurcation gradually takes over at one end of the region. These results are compared with the known experimental results. Approximate analytic expressions for the limit cycles for different types of bifurcations are shown to agree with their corresponding numerical solutions of the equations describing the model. The analysis also shows that high order nonlinearities are important in the problem. This approach further allows us to map the theoretical parameters to the experimentally observed macroscopic quantities.Comment: LaTex file and eps figures; Communicated to Phys. Rev.

Syntectonic mobility of supergene nickel ores of New Caledonia (Southwest Pacific). Evidence from faulted regolith and garnierite veins.

International audienceSupergene nickel deposits of New Caledonia that have been formed in the Neogene by weathering of obducted ultramafic rocks are tightly controlled by fracture development. The relationship of tropical weathering and tectonic structures, faults and tension gashes, have been investigated in order to determine whether fractures have play a passive role only, as previously thought; or alternatively, if brittle tectonics was acting together with alteration. From the observation of time-relationship, textures, and mineralogy of various fracture fills and fault gouges, it may be unambiguously established that active faulting has play a prominent role not only in facilitating drainage and providing room for synkinematic crystallisation of supergene nickel silicate, but also in mobilising already formed sparse nickel ore, giving birth to the very high grade ore nicknamed "green gold"

Exclusion and reappropriation: Experiences of contemporary enclosure among children in three East Anglian schools

Transformations of the landscapes which children inhabit have significant impacts on their lives; yet, due to the limited economic visibility of children’s relationships with place, they have little stake in those transformations. Their experience, therefore, illustrates in an acute way the experience of contemporary enclosure as a mode of subordination. Following fieldwork in three primary schools in South Cambridgeshire, UK, we offer an ethnographic account of children’s experiences of socio-spatial exclusion. Yet, we suggest that such exclusion is by no means an end-point in children’s relationships with place. Challenging assumptions that children are disconnected from nature, we argue that through play and imaginative exploration of their environments, children find ways to rebuild relationships with places from which they find themselves excluded. This is the author accepted manuscript. The final version is available from SAGE via http://dx.doi.org/10.1177/026377581664194

Algunes reflexions entorn de la conceptualització de la infància i adolescència en risc social a l'Estat espanyol

L'article realitza una aproximació a les interpretacions del concepte de risc social de la infancia per part de diversos autors d'àmbit estatal, tenint també en compte els marcs legals català i espanyol. Pretén aclarir quins són els criteris valoratius emprats, tant des de l'àmbit acadèmic com del professional, per interpretar les categoritzacions de la infància i l'adolescència en processos de dificultat i precarietat social. Des d'aquesta perspectiva, s'hi analitza l'estreta relació entre factors de risc, desemparament i marginació. S'hi rebutgen les interpretacions que responsabilitzen el propi menor de la desadaptació, i s'hi defensa la hipótesi de la necessitat d'una intervenció socioeducativa que treballi per una disminució dels factors de risc en el propi medi, mantenint el seu protagonisme en aquest procés.This article is an approach to the different acceptances of the concept social risk as well as the terms neglect and maladjustment, based on the reflections made by different authors and both statal and autonomous legal framework. It intends to clarify which are the criteria of values used in academic and professional ambits in order to understand the categoriesfound in the fields of childhood and adolescence in difficult and precarious conditions. The strong relation between risk factors, neglect and margination has been analysed from this point of view. In the same way the interpretations that hold the minor himself responsible for his maladjustment are rejected and the author defends the necessity of a socio-educational intervention, which reduces the risk factors in the child's environment, and the need of paying close attention to the child's main role in this process.El artículo realiza una aproximación a las interpretaciones del concepto de riesgo social de la infancia por parte de diversos autores de ámbito estatal, teniendo también en cuenta los marcos legales catalán y español. Pretende aclarar cuáles son los criterios valorativos utilizados, tanto desde el ámbito academico como profesional, para interpretar las categorizaciones de la infancia en procesos de dificultad y precariedad. Desde esta perspectiva, se analiza la estrecha relación entre factores de riesgo, desamparamiento y marginación. Se rechazan las interpretaciones que responsabilizan al propio menor de la desadaptación y se defiende la hipótesis de la necesidad de una intervención socioeducativa que trabaje para una disminución de los factores de riesgo en el propio medio, manteniendo su protagonismo en este proceso

Some factors influencing populations of the European corn borer, Ostrinia nubilalis (Hubner) in the north central states: Resistance of corn, time of planting and weather conditions Part II, 1958-1962

A cooperative project was conducted by the agricultural experiment stations of Iowa, Minnesota and Ohio and the U. S. Department of Agriculture to study the effects of weather, planting date and resistant hybrids as factors influencing populations of the European com borer, Ostrinia nubilalis (Hübner). Identical studies were carried out at Ankeny, Iowa; Waseca, Minnesota; and Wooster, Ohio, during a 10-year period, 1953-1962. The first 4 years of the study (1953-56) were reported by Everett et al. (1958). The work reported herein is a companion bulletin to the Everett et al. (1958) publication and deals with the results of experiments conducted during 1958-1962. The experimental design was a randomized block, split plot with five replications. The whole plot treatments were four hybrid-planting date combinations consisting of early- or late-planting dates and susceptible or resistant hybrids. The subplot treatments consisted of a factorial arrangement of all possible combinations of three levels of infestation (zero, natural and natural + 3 egg masses) by first brood and the same three levels of infestation by second-brood borers. Temperature and rainfall records were kept at each of the three stations. Borer population and injury to the plant were recorded at the end of the first brood and in the fall. Yield data were collected