Chemotaxis When Bacteria Remember: Drift versus Diffusion

{\sl Escherichia coli} ({\sl E. coli}) bacteria govern their trajectories by switching between running and tumbling modes as a function of the nutrient concentration they experienced in the past. At short time one observes a drift of the bacterial population, while at long time one observes accumulation in high-nutrient regions. Recent work has viewed chemotaxis as a compromise between drift toward favorable regions and accumulation in favorable regions. A number of earlier studies assume that a bacterium resets its memory at tumbles -- a fact not borne out by experiment -- and make use of approximate coarse-grained descriptions. Here, we revisit the problem of chemotaxis without resorting to any memory resets. We find that when bacteria respond to the environment in a non-adaptive manner, chemotaxis is generally dominated by diffusion, whereas when bacteria respond in an adaptive manner, chemotaxis is dominated by a bias in the motion. In the adaptive case, favorable drift occurs together with favorable accumulation. We derive our results from detailed simulations and a variety of analytical arguments. In particular, we introduce a new coarse-grained description of chemotaxis as biased diffusion, and we discuss the way it departs from older coarse-grained descriptions.Comment: Revised version, journal reference adde

A time of flight method to measure the speed of sound using a stereo sound card

We present an inexpensive apparatus for measuring the speed of sound, with a time of flight method, using a computer with a stereo sound board. Students measure the speed of sound by timing the delay between the arrivals of a pulse to two microphones placed at different distances from the source. It can serve as a very effective demonstration, providing a quick measurement of the speed of sound in air; we have used it with great success in Open Days in our Department. It can also be used for a full fledged laboratory determination of the speed of sound in air.Comment: Accepted for publication in The Physics Teache

Kaehler Corrections for the Volume Modulus of Flux Compactifications

No-scale models arise in many compactifications of string theory and supergravity, the most prominent recent example being type IIB flux compactifications. Focussing on the case where the no-scale field is a single unstabilized volume modulus (radion), we analyse the general form of supergravity loop corrections that affect the no-scale structure of the Kaehler potential. These corrections contribute to the 4d scalar potential of the radion in a way that is similar to the Casimir effect. We discuss the interplay of this loop effect with string-theoretic alpha' corrections and its possible role in the stabilization of the radion.Comment: 8 pages, references adde

Hepatocyte Growth Factor Receptor c-Met Instructs T Cell Cardiotropism and Promotes T Cell Migration to the Heart via Autocrine Chemokine Release

© 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)This study was funded by the British Heart Foundation (RG/09/002/2642 to F.M.M.-B.) and the Medical Research Council of the UK (G0901084 to F.M.M.-B.). ImageStream X was funded by the Wellcome Trust (101604/Z/13/Z). This work forms part of the research themes contributing to the translational research portfolio of Barts and the London Cardiovascular Biomedical Research Unit, which is supported and funded by the National Institute of Health Research

Limited Effects of Pain Control Treatments on Behaviour and Weight Gain of Pure and Crossbred Nellore Heifer Calves When Subjected to Hot-Iron Branding

Simple Summary This study investigated the effects of pain relief treatments on behaviour and weight gain in 92 Nellore and crossbred (F1 Aberdeen Angus x Nellore) heifer calves (aged around 120 days) subjected to hot-iron branding on the cheek after vaccination against brucellosis. Four treatments were compared: Control (CO, no pain relief); local anaesthesia (LA, subcutaneous anaesthetic); analgesic (LT, intramuscular meloxicam); and local anaesthetic and analgesic (LL, both local anaesthesia and meloxicam). Calves in treatments CO and LT were subjected to face manipulation simulating application of local anaesthetic without introducing the needle. Facial and body expressions, flight speed, and body weight were recorded before, during, and five (5-d) and 60 days (60-d) after hot-iron branding. No effect of pain relief was observed for most calves studied. The only difference observed was higher tension ('tense') at 5-d in CO calves. All calves showed fear and stress responses during restraint and hot-iron branding, which probably masked pain responses. In conclusion, hot-iron facial branding impoverishes calf welfare and, due to the additional handling involved, adoption of a pain relief protocol is not an efficient way to minimise welfare impacts. Hot-iron branding is still commonly performed in cattle farming in tropical countries, and possibly has negative consequences for animal welfare and weight gain. This study examined the behavioural and weight gain responses of pure and crossbred Nellore heifer calves subjected to hot-iron branding on the cheek, without and with use of anaesthesia and analgesia. Ninety-two heifer calves, around 120 days old, were studied prospectively when subjected to hot-iron branding on the cheek (a statutory procedure in Brazil following brucellosis vaccination). Four randomly selected groups of calves were allocated to four treatments: no pain control (CO); subcutaneous anaesthetic local block (LA); intramuscular analgesia (meloxicam) (LT); and local anaesthesia plus meloxicam (LL). Behaviour, flight speed and body weight were evaluated before, during, and five (5-d) and 60 days (60-d) after branding. For these parameters, the only difference observed was higher tension in the CO group 5-d post-branding, suggesting a short-term negative effect of branding without pain control. The limited effects of the pain control treatments suggest interference in pain assessment by other factors, such as expression of fear and stress. Despite the lack of differences observed in behaviour and production parameters, facial hot-iron branding is an obvious welfare issue and, due to the additional handling involved, adoption of a simple pain relief protocol is not sufficient to minimise the welfare impact

CONSIDERAÇÕES SOBRE O DISCURSO DA ECOLOGIA HUMANA E SOCIAL

A ecopedagogia vem assumindo papel crítico na reorientação das pessoas envolvidas com o meio ambiente e com o cuidado com a casa comum. O objetivo desta resenha é analisar as propostas educacionais de três documentos fundadores da ecopedagogia social contemporânea: Carta da Terra, Ecologia, mundialização e espiritualidade e Laudato Si, com foco nas orientações para mudança de atitude e comportamento em relação à comunidade de vida do planeta. A tríade se justifica, por razões de convergência de ideias, de orientação filosófica e de metas. A partir da análise das orientações e princípios dos três documentos, formulamos propostas de intervenção. Fundamo-nos nas afirmações que são consensuais, alicerçadas em dados empíricos e em evidências robustas, sobre atitudes e práticas humanas, relativas à subsistência, ao lucro e ao descarte e legitimamos uma proposta de reorientação ecológica. No correr da análise, discutimos afirmações que parecem, à primeira vista, polêmicas ou inconsistentes e ressaltamos as mais produtivas

Análise de discursos de graduandos

The purpose of this study is to perform a discourse analysis of first semester students’ speeches and thereby to contribute to the development of qualified writers by guiding them to collect information from texts, interpret and recreate them, through their own texts. The methodology adopted is the pedagogic strategy of recontextualization, formulated by the educational sociolinguist Basil Bernstein, in which the teacher reformulates the texts in order to cooperate with the students' learning process so that they properly apprehend the proposed knowledge and produce new discourses. The theoretical framework is based on the educational concepts and proposals by the sociologists Pierre Bourdieu and Bruno Latour and by the linguist Norman Fairclough. To that proposal some contents were recontextualized: the film Finding Forrester, as well as journalistic and academic texts on contemporary themes, such as public policies in education, violence in educational environments, structural racism, and social representations of students about human rights. The analysis of the students' texts shows that they changed their discourse practices after the new context in which they acted.A proposta deste estudo é fazer análise de discursos de graduandos do primeiro semestre e contribuir para a formação de escritores competentes, guiando-os para recolher informações de textos, interpretá-las e recriá-las, por meio dos seus próprios textos.  A metodologia adota a estratégia de recontextualização pedagógica do sociolinguista educacional Basil Bernstein, na qual o professor reformula os textos de modo a cooperar com o processo de aprendizagem dos alunos, a fim de que apreendam com propriedade o conhecimento proposto e produzam novos discursos. O referencial teórico apoia-se nos conceitos e propostas educacionais dos sociólogos Pierre Bourdieu e Bruno Latour e do linguista Norman Fairclough.  Para este propósito, alguns conteúdos foram recontextualizados: o filme Encontrando Forrester e textos jornalísticos e acadêmicos sobre temas contemporâneos, como políticas públicas na educação, violência nos ambientes educacionais, racismo estrutural e representações sociais de estudantes sobre direitos humanos. A análise dos textos dos alunos mostra que eles mudaram suas práticas discursivas a partir do novo contexto em que atuaram

CAPITAL CULTURAL EM AVALIAÇÕES ENEM E ENADE

ENEM E ENADE são avaliações em larga escala que dizem sobre os estudantes e instituições do ensino médio e superior brasileiro. Este trabalho é um exercício de aplicação de dois princípios de Bourdieu: a teoria do capital cultural incorporado e a teoria da reprodução (Bourdieu e Passeron) a fim de verificar em que termos os conteúdos das duas provas contribuem para formação e avanço na carreira dos estudantes que fazem avaliação. A expectativa foi encontrar evidências de que as provas são constituídas por capital cultural da classe hegemônica e, por isso, podem dificultar o êxito dos estudantes das classes populares. Concluímos que os textos e as temáticas das provas são pouco inteligíveis para os estudantes das classes populares, que não possuem incorporadas as habilidades esperadas pelos elaboradores da prova