Metachronal waves in a chain of rowers with hydrodynamic interactions

Filaments on the surface of a microorganism such as Paramecium or Ophalina beat highly synchronized and form so-called metachronal waves that travel along the surfaces. In order to study under what principal conditions these waves form, we introduce a chain of beads, called rowers, each periodically driven by an external force on a straight line segment. To implement hydrodynamic interactions between the beads, they are considered point-like. Two beads synchronize in antiphase or in phase depending on the positive or negative curvature of their driving-force potential. Concentrating on in-phase synchronizing rowers, we find that they display only transient synchronization in a bulk fluid. On the other hand, metachronal waves with wavelengths of 7-10 rower distances emerge, when we restrict the range of hydrodynamic interactions either artificially to nearest neighbors or by the presence of a bounding surface as in any relevant biological system.Comment: 9 pages, 10 figure

Doing Agroecology : democratic practice and social learning in civic food organizations

Localization of food networks has been heralded as a way of creating a more just and sustainable food system. This study explores the potential of civic food networks to serve as sites for “really existing” food democracy, providing opportunities for participation and capacity building for democratic organization and learning about food and the food system. Through interviews with participants in a food cooperative and a Transition Towns initiative in the city of Oslo, analysed through a combination of participatory democratic theory and social learning theory, the study shows how civic food initiatives acts as a frame for new civic relationships, and as “practical experiments” in food democracy.M-A

Rural mobilites and urban norms

This article deals with everyday life in sparsely populated parts of northern Sweden. It investigates the relationship between local practice and political discourses. The discussion is based on fieldwork carried out in two northern municipalities. Empirical themes include everyday life mobilities and means of transport. The theoretical concepts of everyday life, community, place, and policy shape the analysis of processes pertaining to space and movement. In particular, the article discusses sustainable development as policy and argues for alternative understandings of social sustainability in relation torural settings. Keywords: everyday life mobilities, means of transport, sparsely populated parts of northernSweden, place, policy, sustainable development, social sustainability   Key words: everyday life mobilities, means of transport, sparsely populated parts of Northern Sweden, place, policy, sustainable development, social sustainabilit

Homing geographies : sexuality and community among homeless youth in Los Angeles

Scholarly literature on sexuality and homeless youth has focused almost exclusively on young people nested within a culture of risk on the streets. This study broadens the body of work on this population by exploring how homeless and runaway youth in Los Angeles make meaning of their sexualities. While these individuals are extremely vulnerable and fragile, they also display remarkable resilience. Researchers conducted two sets of in person, semi-structured interviews with six homeless youth at a homeless service agency in Los Angeles as part of an HIV peer intervention project. The interviews focused on sex education and messages about sexuality, as well as the youths\u27 participation in the project. Five additional interviews were conducted in which the youth interviewed one another, which took the form of testimonial videos about their sexual experiences. Sexual identity, sexual activity, family norms about sexuality, STI and HIV prevention, and substance abuse were salient themes in the sexual lives of many youth. The youth discussed issues of homophobia, family abuse, and situations of extreme risk, but they also focused on supportive peer relationships, processing and understanding sexuality, and the importance of using protection when engaging in sexual behaviors. Nuanced descriptions of sexuality among homeless youth is crucial in order to help social workers and other professionals understand the complex and difficult realities weathered by this population on a regular basis

Apparent correlation of palaeomagnetic intensity and climatic records in deep-sea sediments

Most reports of a correlation between Pleistocene climate and geomagnetic field intensity rely strongly on the assumption that sediment natural remanent magnetic (NRM) intensity provides a record of geomagnetic field strength and is not sensitive to local changes in properties of the sediment. Critical assessment of relevant data presented here and elsewhere from deep-sea sediment cores shows that a pronounced dependence of NRM intensity on sediment composition can occur which implies that this assumption is unlikely to be generally valid. As sediment composition often reflects varying depositional conditions induced by climatic change, the significance of correlations proposed between Pleistocene palaeomagnetism and climatic indicators in deep-sea sediments may be less dramatic than sometimes supposed

Bistånd för förändring

Den här uppsatsen undersöker hur svenskt bistånd påverkar lokala förhållanden i Rwanda. Genom att analysera hur en NGO verksam i Rwanda, Vi-skogen, påverkas av de riktlinjer som satts upp av Sida, Sveriges biståndsorgan, så visar den hur en instrumentell inställning i bistånd kan vara etiskt problematiskt, samt ett hot mot själva genomförandet. Först fokuserar analysen på Vi-skogen Rwandas inbördes relationer och hur dessa påverkas av den instrumentella målsättningen, för att sedan vidgas till att diskutera hur deras arbete i Rwanda påverkas, och hur detta påverkar de bönder de arbetar med. Studien bygger på empiriskt material insamlat under ett tre månaders besök till Rwanda och Vi-skogen. Analysen använder sig främst av Jürgen Habermas teorier kring systemets kolonialisering av livsvärlden, samt Erving Goffmans teorier om individers självpresentation i samhället. Återkommande i uppsatsen är förhållandet mellan en instrumentell rationalitet och de förståelseprocesser som människor är beroende av för att skapa tillit i interaktioner.This essay examines how Swedish aid affects local conditions in Rwanda. By analyzing how an NGO operating in Rwanda, Vi-Agroforestry, is affected by the guidelines set by Sida, the Swedish development agency, it shows how an instrumental orientation in aid may be ethically problematic, as well as a threat to its implementation. First the analysis focuses on Vi-Agroforestry Rwanda´s internal relations and how these are affected by the instrumental rationality, and then expands to discuss how their work in Rwanda is affected, and how this affects the farmers they are working with. The study is based on empirical material collected during a three-month visit to Rwanda and Vi-Agroforestry. The analysis primarily makes use of Jürgen Habermas theories of the systems colonization of the lifeworld, and Erving Goffman's theories on individuals' self-presentation in society. Recurring throughout the paper is the relationship between an instrumental rationality and the processes of understanding that people rely on to create trust in interactions