The structure of thin accretion discs around magnetised stars

Aims: We determine the steady-state of an axisymmetric thin accretion disc with an internal dynamo around a magnetised star. Methods: Starting from the vertically integrated equations of magnetohydrodynamics we derive a single ordinary differential equation for a thin accretion disc around a massive magnetic dipole and integrate this equation numerically from the outside inwards. Results: Our numerical solution shows that the torque between the star and the accretion disc is dominated by the contribution from the dynamo in the disc. The location of the inner edge of the accretion disc varies between $R_{\rm A}$ and $10R_{\rm A}$ depending mainly on the strength and direction of the magnetic field generated by the dynamo in the discComment: 9 pages, 10 figures. The paper is accepted for publication in Astronomy & Astrophysic

Addressing gender gaps in agricultural productivity in Africa: comparative case studies from Tanzania, Malawi and Uganda+

This article examines why, in most African countries, women farmers achieve lower productivity in agriculture than men. It contributes to this debate by interrogating whether or not addressing gender gaps in agricultural production significantly contributes to socio-economic well-being (resilience) of women as well as the gross domestic product (GDP). The Living Standards Measurement Studies-Integrated Survey for Agriculture projects was adopted to produce estimates for three countries in Sub-Saharan Africa (Malawi, Tanzania and Uganda). The article draws from a research report and collaborative study by UN Women with UNEP and World Bank. The result shows that although female farmers individually manage slightly more than 25 per cent of all plots in Malawi and Uganda and about 20 per cent of all plots in Tanzania, Malawi shows the largest difference in mean productivity where women’s plots are, on average, 28 per cent less productive than men’s while Tanzania and Uganda reported 16 per cent and 13 per cent gender gaps, respectively. This result implies that the importance of other productive resources other than access to land may be key – for instance, the need to tackle constraints related to women’s access to “household male labour” and policies that help women farmers to access labour-saving technologies.Keywords: Keywords: Land Access, Gender, Agricultural Productivity, Malawi, Tanzania, Uganda

Djurägarens upplevelser i samband med avlivning av hund

Att avliva sitt djur är ett beslut som många djurägare en dag kommer att behöva ta, hur ont det än gör. Med anledning av denna svåra stund är det av största vikt att det görs på rätt sätt samt att hänsyn tas till djurägarens önskningar för att göra upplevelsen, trots ändamålet, så bra som möjligt. För att möjliggöra detta krävs kunskap kring de upplevelser djurägare har från avlivningar de närvarat vid. Detta kandidatabete gjordes med anledning av den bristande kunskap som finns gällande djurägares upplevelser i samband med avlivning av hund. Syftet avsåg att skapa en bild av dessa upplevelser och känslor, och på vilket sätt man som djurhälsopersonal kan påverka dessa. Studien består av en litteraturstudie och en enkätstudie, vilken skickades ut i 30 hundgrupper på sociala medier. De enkäter som var ofullständiga, rörde sig om andra djurslag än hund samt de enkäter där djurägaren inte närvarat vid avlivning exkluderades, vilket resulterade i 977 användbara enkäter. Frågorna utformades för att bilda en uppfattning om hur djurägare upplevt hela processen från bokning av avlivning till omhändertagande av kroppen efteråt, samt hur stor roll personalen hade i dessa upplevelser. Med förväntningarna att majoriteten utav enkäterna skulle redogöra för specifika negativa händelser, pekar studiens resultat på att majoriteten av respondenterna har, förutom sorgen från förlusten av sin hund, överhängande positiva upplevelser från hela processen. Upplevelserna i samband med avlivningstillfället varierade mellan respondenterna, där sorg, tomhet och förtvivlan var de mest förekommande. Något som uppmärksammade författarna var att 83 % av respondenterna inte blev erbjudna någon form av stöd/kontakt efter avlivningen vilket studien antyder att det finns ett behov av. Av de negativa upplevelserna som uppdagas i enkäterna visar många av dem på ett samband med bristande kommunikation. Eftersom kommunikation och interaktion med djurägaren är en grundläggande aspekt inom djurhälsovården, kan en förbättring av detta resultera i en förbättring av vården som tillfredsställer alla parter.To let a beloved animal go is a decision that a lot of pet owners one day will have to make, no matter how bad it hurts. Due to this difficult time, it is of the utmost importance that it is done in the right way and that the pet owner's wishes are taken into account in order to make the experience, despite the purpose, as good as possible. To make this possible, knowledge is required about the experiences pet owners actually carry from the euthanasia they have attended. This bachelor thesis was done due to the lack of knowledge that exists regarding pet owner´s experiences in connection with euthanasia of a dog. The aim was to create an image of these experiences and feelings, and in what way you as an animal health professional can influence these. The study consists of a literature study and a survey which was sent out in 30 dog groups on social media. Incomplete survey responses, surveys concerned animals other than dogs and surveys where the pet owner was not present during the euthanasia were excluded, which resulted in 977 useful surveys. The questions were formulated in such a way as to find out how pet owners experienced the entire process from booking the euthanasia to how the body was taken care of afterwards, and how much the animal health professionals affected these experiences. With the expectation that the majority of the surveys would report on specific negative situations, the results of the study indicate that the majority of the respondents have, in addition to the grief from the loss of their dog, imminent positive experiences from the entire process. The experienced emotions in connection with the euthanasia varied among the owners, with grief, emptiness and despair being the most common. Something that drew the authors´ attention was that a total of 83 % of the respondents hadn´t been offered any form of support/contact following the euthanasia, which the present study also suggest is a need. Of the negative experiences discovered in the surveys, many of them show a connection with a lack of communication. Since communication and interaction with the pet owner is a fundamental aspect of animal health care, improved communication skills can with good opportunities result in an improvement of the animal health care that satisfies all parts

Magnetohydrodynamic turbulence in warped accretion discs

Warped, precessing accretion discs appear in a range of astrophysical systems, for instance the X-ray binary Her X-1 and in the active nucleus of NGC4258. In a warped accretion disc there are horizontal pressure gradients that drive an epicyclic motion. We have studied the interaction of this epicyclic motion with the magnetohydrodynamic turbulence in numerical simulations. We find that the turbulent stress acting on the epicyclic motion is comparable in size to the stress that drives the accretion, however an important ingredient in the damping of the epicyclic motion is its parametric decay into inertial waves.Comment: to appear in the proceedings of the 20th Texas Symposium on Relativistic Astrophysics, J. C. Wheeler & H. Martel (eds.

The response of a turbulent accretion disc to an imposed epicyclic shearing motion

We excite an epicyclic motion, whose amplitude depends on the vertical position, $z$, in a simulation of a turbulent accretion disc. An epicyclic motion of this kind may be caused by a warping of the disc. By studying how the epicyclic motion decays we can obtain information about the interaction between the warp and the disc turbulence. A high amplitude epicyclic motion decays first by exciting inertial waves through a parametric instability, but its subsequent exponential damping may be reproduced by a turbulent viscosity. We estimate the effective viscosity parameter, $\alpha_{\rm v}$, pertaining to such a vertical shear. We also gain new information on the properties of the disc turbulence in general, and measure the usual viscosity parameter, $\alpha_{\rm h}$, pertaining to a horizontal (Keplerian) shear. We find that, as is often assumed in theoretical studies, $\alpha_{\rm v}$ is approximately equal to $\alpha_{\rm h}$ and both are much less than unity, for the field strengths achieved in our local box calculations of turbulence. In view of the smallness ($\sim 0.01$) of $\alpha_{\rm v}$ and $\alpha_{\rm h}$ we conclude that for $\beta = p_{\rm gas}/p_{\rm mag} \sim 10$ the timescale for diffusion or damping of a warp is much shorter than the usual viscous timescale. Finally, we review the astrophysical implications.Comment: 12 pages, 18 figures, MNRAS accepte

The effects of vertical outflows on disk dynamos

We consider the effect of vertical outflows on the mean-field dynamo in a thin disk. These outflows could be due to winds or magnetic buoyancy. We analyse both two-dimensional finite-difference numerical solutions of the axisymmetric dynamo equations and a free-decay mode expansion using the thin-disk approximation. Contrary to expectations, a vertical velocity can enhance dynamo action, provided it is not too strong. In the nonlinear regime this can lead to super-exponential growth of the magnetic field.Comment: 14 pages, final version after referee comments, accepted in A&