A bacterial ratchet motor

Self-propelling bacteria are a dream of nano-technology. These unicellular organisms are not just capable of living and reproducing, but they can swim very efficiently, sense the environment and look for food, all packaged in a body measuring a few microns. Before such perfect machines could be artificially assembled, researchers are beginning to explore new ways to harness bacteria as propelling units for micro-devices. Proposed strategies require the careful task of aligning and binding bacterial cells on synthetic surfaces in order to have them work cooperatively. Here we show that asymmetric micro-gears can spontaneously rotate when immersed in an active bacterial bath. The propulsion mechanism is provided by the self assembly of motile Escherichia coli cells along the saw-toothed boundaries of a nano-fabricated rotor. Our results highlight the technological implications of active matter's ability to overcome the restrictions imposed by the second law of thermodynamics on equilibrium passive fluids.Comment: 4 pages, 3 figure

The Coming of Age of the Global Trademark: The Effect of TRIPS on the Well-Known Marks Exception to the Principle of Territoriality

Article published in the Michigan State International Law Review

Hydrodynamic attraction of swimming microorganisms by surfaces

Cells swimming in confined environments are attracted by surfaces. We measure the steady-state distribution of smooth-swimming bacteria (Escherichia coli) between two glass plates. In agreement with earlier studies, we find a strong increase of the cell concentration at the boundaries. We demonstrate theoretically that hydrodynamic interactions of the swimming cells with solid surfaces lead to their re-orientation in the direction parallel to the surfaces, as well as their attraction by the closest wall. A model is derived for the steady-state distribution of swimming cells, which compares favorably with our measurements. We exploit our data to estimate the flagellar propulsive force in swimming E. coli

Generic flow profiles induced by a beating cilium

We describe a multipole expansion for the low Reynolds number fluid flows generated by a localized source embedded in a plane with a no-slip boundary condition. It contains 3 independent terms that fall quadratically with the distance and 6 terms that fall with the third power. Within this framework we discuss the flows induced by a beating cilium described in different ways: a small particle circling on an elliptical trajectory, a thin rod and a general ciliary beating pattern. We identify the flow modes present based on the symmetry properties of the ciliary beat.Comment: 12 pages, 6 figures, to appear in EPJ

Yours ever (well, maybe): Studies and signposts in letter writing

Electronic mail and other digital communications technologies seemingly threaten to end the era of handwritten and typed letters, now affectionately seen as part of snail mail. In this essay, I analyze a group of popular and scholarly studies about letter writing-including examples of pundits critiquing the use of e-mail, etiquette manuals advising why the handwritten letter still possesses value, historians and literary scholars studying the role of letters in the past and what it tells us about our present attitudes about digital communications technologies, and futurists predicting how we will function as personal archivists maintaining every document including e-mail. These are useful guideposts for archivists, providing both a sense of the present and the past in the role, value and nature of letters and their successors. They also provide insights into how such documents should be studied, expanding our gaze beyond the particular letters, to the tools used to create them and the traditions dictating their form and function. We also can discern a role for archivists, both for contributing to the literature about documents and in using these studies and commentaries, suggesting not a new disciplinary realm but opportunities for new interdisciplinary work. Examining a documentary form makes us more sensitive to both the innovations and traditions as it shifts from the analog to the digital; we can learn not to be caught up in hysteria or nostalgia about one form over another and archivists can learn about what they might expect in their labors to document society and its institutions. At one time, paper was part of an innovative technology, with roles very similar to the Internet and e-mail today. It may be that the shifts are far less revolutionary than is often assumed. Reading such works also suggests, finally, that archivists ought to rethink how they view their own knowledge and how it is constructed and used. © 2010 Springer Science+Business Media B.V

Laughing at lunacy: othering and comic ambiguity in popular humour about mental distress

Jokes and humour about mental distress are said by anti-stigma campaigners to be no laughing matter. The article takes issue with this viewpoint arguing that this is clearly not the case since popular culture past and present has laughed at the antics of those perceived as ‘mad’. Drawing on past and present examples of the othering of insanity in jokes and humour the article incorporates a historical perspective on continuity and change in humour about madness/mental distress, which enables us to recognise that psychiatry is a funny-peculiar enterprise and its therapeutic practices in past times are deserving of funny ha-ha mockery and mirth in the present. By doing so, the article also argues that humour and mental distress illuminate how psychiatric definitions and popular representations conflict and that some psychiatric service users employ comic ambiguity to reflexively puncture their public image as ‘nuts’

Book Review: Christopher Darnton. Rivalry and Alliance Politics in Cold War Latin America

This document includes Dr. Field\u27s review of Christopher Darnton\u27s Rivalry and Alliance Politics in Cold War Latin America. Baltimore: Johns Hopkins University Press, 2014. ISBN: 9781421413617 (paperback, $44.95). It is part of H-Diplo | ISSF, Roundtable, Volume VIII, No. 8 (2016)

Conclusions and recommendations of a who expert consultation meeting on iron supplementation for infants and young children in malaria endemic areas [Conclusions et recommandations à l\u27issue de la consultation de l\u27oms sur la lutte contre la carence martiale chez le nourrisson et le jeune enfant dans les pays d\u27endémie palustre]

This article presents the results of an expert consultation meeting aimed at evaluating the safety and public health implications of administering supplemental iron to infants and young children in malaria-endemic areas. Participants at this meeting that took place in Lyon, France on June 12-14, 2006 reached consensus on several important issues related to iron supplementation for infants and young children in malaria-endemic areas. The conclusions in this report apply specifically to regions where malaria is endemic

Cell morphology governs directional control in swimming bacteria

The ability to rapidly detect and track nutrient gradients is key to the ecological success of motile bacteria in aquatic systems. Consequently, bacteria have evolved a number of chemotactic strategies that consist of sequences of straight runs and reorientations. Theoretically, both phases are affected by fluid drag and Brownian motion, which are themselves governed by cell geometry. Here, we experimentally explore the effect of cell length on control of swimming direction. We subjected Escherichia coli to an antibiotic to obtain motile cells of different lengths, and characterized their swimming patterns in a homogeneous medium. As cells elongated, angles between runs became smaller, forcing a change from a run-and-tumble to a run-and-stop/reverse pattern. Our results show that changes in the motility pattern of microorganisms can be induced by simple morphological variation, and raise the possibility that changes in swimming pattern may be triggered by both morphological plasticity and selection on morphology

Entusiastas da cultura: O universo do livro e suas representações nas cartas do Centro Cultural Euclides da Cunha

Este artigo é uma breve tentativa de se pensar algumas das muitas ideias e representações construídas no passado sobre o universo do livro. A pesquisa que o originou partiu exclusivamente do exame das correspondências recebidas e acumuladas pelo extinto Centro Cultural Euclides da Cunha, uma agremiação de intelectuais que funcionou de 1948 a 1985 na cidade de Ponta Grossa, no Paraná. Em termos estruturais, o estudo aqui conduzido busca comentar inicialmente alguns aspectos pontuais da referida instituição, procurando enfatizar em seguida o enorme entusiasmo que ali gravitava em torno das lides literárias. Para finalizar, são então examinados os traços maiores do inusitado sistema de representações em que tal entusiasmo se apoiava, tentando integrar seus elementos num sentido um pouco mais amplo. Em linhas gerais, o objetivo do artigo é delinear e compreender algumas das possíveis relações que, na metade do século passado, ainda se estabeleceriam entre cultura, livro e intelectualidade.This article is a brief attempt to think about the many ideas and representations built in the past about the book universe. The research which originated it was exclusively done by examining the mail received and kept by the former Centro Cultural Euclides da Cunha, in Ponta Grossa, Paraná, Brazil. In structural terms, this study seeks to comment, initially, some punctual aspects of the referred institution, emphasizing, in sequence, the enormous enthusiasm which gravitated around the literary battle. To conclude, the larger traces of the unusual representation system on which such enthusiasm was based are, then, examined, trying to integrate the elements in a little broader sense. In general terms, the aim of the article is to outline and understand some of the possible relations which, in the middle of the last century, would be still established between culture, books and intelligentsia