Analysis and simulations of multifrequency induction hardening

We study a model for induction hardening of steel. The related differential system consists of a time domain vector potential formulation of the Maxwell's equations coupled with an internal energy balance and an ODE for the volume fraction of {\sl austenite}, the high temperature phase in steel. We first solve the initial boundary value problem associated by means of a Schauder fixed point argument coupled with suitable a-priori estimates and regularity results. Moreover, we prove a stability estimate entailing, in particular, uniqueness of solutions for our Cauchy problem. We conclude with some finite element simulations for the coupled system

Exact Cosmological Solutions of Gravitational Theories

A global picture is drawn tying together most exact cosmological solutions of gravitational theories in four or more spacetime dimensions.Comment: 11 latex article style page

Vegetation Distributions along Lichen-Dominated Slopes of Opposing Aspect in the Eastern Canadian Subarctic

Detailed vegetation surveys along two opposing slopes in the boreal forest-tundra ecotone of Quebec-Labrador reveal distinct distributions and habitat preferences of prevalent lichen and shrub species. The presence or absence of a protective shrub layer was the main determinant of lichen distributions. Generally, there was an inverse relationship between the proportional surface coverages of vascular plants and lichens. At the most exposed site, nearest the ridge top, Cetraria nivalis (L.) Ach., Alectoria ochroleuca (Hoffm.) Massal. and Cetraria nigricans Nyl. were integrated well into the lichen mat and surrounded stoney earth circles. Increased shrub growth and protection quickly eliminated these lichens at lower elevations but allowed for more widespread growth of Cladina rangiferina (L.) Nyl. Cladina stellaris (Opiz) Brodo was the most pervasive lichen and appeared to be a generalist in habitat selection. Slope aspect influenced the distributions of three lichens of limited habitat range. The northerly facing slope provides preferable conditions for their growth farther downslope, thus extending their suitable habitat range. These results suggest the possibility of defining distinct lichen habitats based on exposure or, conversely, on protection provided by the presence of a shrub-tree canopy.Key words: lichens, vegetation gradient, subarctic, topography, tundra, eastern Canadian Subarctic Des relevés détaillés de la végétation sur deux pentes opposées dans l'écotone de la toundra-forêt boréale du Québec-Labrador, ont révélé des distributions distinctes et des préférences d'habitat pour des espèces de lichens et d'arbustes prédominants. La présence ou l'absence d'une couche protectrice d'arbustes était le facteur principal qui déterminait la distribution des plantes vasculaires et des lichens. Il y avait en général une relation inverse entre les proportions des surfaces couvertes par les plantes vasculaires et de celles couvertes par les lichens. Au site le plus exposé, près de la crête, les espèces Cetraria nivalis (L.) Ach., Alectoria ocholeuca (Hoffm) Massal. Et Cetraria Nigricans Nyl. Étaient intégrées profondément dans le tapis de lichens et entouraient des cercles de sol caillouteux. À des altitudes plus basses, la croissance et la protection accrues des arbustes éliminaient ces mêmes lichens tout en permettant une croissance plus répandue de Cladina rangiferina (L.) Nyl. L'espèce Cladina stellaris (Opiz) Brodo était le lichen le plus répandu et paraissait ne pas être spécifique dans le choix de son habitat.L'aspect de la pente avait une influence sur la distribution de trois lichens ayant une gamme d'habitat limitée. Les pentes orientées face au nord offraient les conditions les plus favorables à leur croissance plus bas sur la pente, ce qui augmentait la gamme d'habitat qui leur convenait. Ces résultats semblent indiquer qu'il est possible de définir des habitats distincts pour les lichens à partir de l'exposition, ou, à l'inverse, de la protection fournie par une couverture d'arbustes. Mots clés : lichens, gradient de végétation, zone subarctique, topographie, toundra, zone subarctique canadienne de l'es

Career conversations in coaching: the contribution that career theory can make to coaching practice

This paper responds to calls for an increased evidence base for coaching practice by exploring the contribution that career research and theory could make to this field. The paper summarises three small-scale studies focusing on career change undertaken by post-graduate students enrolled on an MSc in Career Coaching at a university in London. The studies explore the experiences of three groups of people who have recently changed career direction: female Black African entrepreneurs, academic research scientists moving to industry and people choosing a career in careers. The findings of the studies highlight the role of meaning and values, and the influence of others on career choice. The studies show too how the participants wrestle with subjective notions of career success, and that the impetus to make a career change comes from both a disenchantment with one situation and an attraction towards another. The paper concludes with some suggestions for coaching practice

Some exact non-vacuum Bianchi VI0 and VII0 instantons

We report some new exact instantons in general relativity. These solutions are K\"ahler and fall into the symmetry classes of Bianchi types VI0 and VII0, with matter content of a stiff fluid. The qualitative behaviour of the solutions is presented, and we compare it to the known results of the corresponding self-dual Bianchi solutions. We also give axisymmetric Bianchi VII0 solutions with an electromagnetic field.Comment: latex, 15 pages with 3 eps figure

Factors associated with mortality in HIV-infected people in rural and urban South Africa

PKBackground: Factors associated with mortality in HIV-infected people in sub-Saharan Africa are widely reported. However rural urban disparities and their association with all-cause mortality remain unclear. Furthermore, commonly used classical Cox regression ignores unmeasured variables and frailty. Objective: To incorporate frailty in assessing factors associated with mortality in HIV-infected people in rural and urban South Africa. Design: Using data from a prospective cohort following 6,690 HIV-infected participants from Soweto (urban) and Mpumalanga (rural) enrolled from 2003 to 2010; covariates of mortality were assessed by the integrated nested Laplace approximation method. Results: We enrolled 2,221 (33%) rural and 4,469 (67%) urban participants of whom 1,555 (70%) and 3,480 (78%) were females respectively. Median age (IQR) was 36.4 (31.0 44.1) in rural and 32.7 (28.2 38.1) in the urban participants. The mortality rate per 100 person-years was 11 (9.7 12.5) and 4 (3.6 4.5) in the rural and urban participants, respectively. Compared to those not on HAART, rural participants had a reduced risk of mortality if on HAART for 6 12 (HR: 0.20, 95% CI: 0.10 0.39) and 12 months (HR: 0.10, 95% CI: 0.05 0.18). Relative to those not on HAART, urban participants had a lower risk if on HAART 12 months (HR: 0.35, 95% CI: 0.27 0.46). The frailty variance was significant and 1 in rural participants indicating more heterogeneity. Similarly it was significant but B1 in the urban participants indicating less heterogeneity. Conclusion: The frailty model findings suggest an elevated risk of mortality in rural participants relative to the urban participants potentially due to unmeasured variables that could be biological, socio economic, or healthcare related. Use of robust methods that optimise data and account for unmeasured variables could be helpful in assessing the effect of unknown risk factors thus improving patient management and care in South Africa and elsewhere

Complexity reduction of astrochemical networks

We present a new computational scheme aimed at reducing the complexity of the chemical networks in astrophysical models, one which is shown to markedly improve their computational efficiency. It contains a flux-reduction scheme that permits to deal with both large and small systems. This procedure is shown to yield a large speed-up of the corresponding numerical codes and provides good accord with the full network results. We analyse and discuss two examples involving chemistry networks of the interstellar medium and show that the results from the present reduction technique reproduce very well the results from fuller calculations.Comment: 9 pages, 7 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journa

Non-Vacuum Bianchi Types I and V in f(R) Gravity

In a recent paper \cite{1}, we have studied the vacuum solutions of Bianchi types I and V spacetimes in the framework of metric f(R) gravity. Here we extend this work to perfect fluid solutions. For this purpose, we take stiff matter to find energy density and pressure of the universe. In particular, we find two exact solutions in each case which correspond to two models of the universe. The first solution gives a singular model while the second solution provides a non-singular model. The physical behavior of these models has been discussed using some physical quantities. Also, the function of the Ricci scalar is evaluated.Comment: 15 pages, accepted for publication in Gen. Realtiv. Gravi