Effective Rheology of Bubbles Moving in a Capillary Tube

We calculate the average volumetric flux versus pressure drop of bubbles moving in a single capillary tube with varying diameter, finding a square-root relation from mapping the flow equations onto that of a driven overdamped pendulum. The calculation is based on a derivation of the equation of motion of a bubble train from considering the capillary forces and the entropy production associated with the viscous flow. We also calculate the configurational probability of the positions of the bubbles.Comment: 4 pages, 1 figur

Infected Dendritic Cells Facilitate Systemic Dissemination and Transplacental Passage of the Obligate Intracellular Parasite Neospora caninum in Mice

The obligate intracellular parasite Neospora caninum disseminates across the placenta and the blood-brain barrier, to reach sites where it causes severe pathology or establishes chronic persistent infections. The mechanisms used by N. caninum to breach restrictive biological barriers remain elusive. To examine the cellular basis of these processes, migration of different N. caninum isolates (Nc-1, Nc-Liverpool, Nc-SweB1 and the Spanish isolates: Nc-Spain 3H, Nc-Spain 4H, Nc-Spain 6, Nc-Spain 7 and Nc-Spain 9) was studied in an in vitro model based on a placental trophoblast-derived BeWo cell line. Here, we describe that infection of dendritic cells (DC) by N. caninum tachyzoites potentiated translocation of parasites across polarized cellular monolayers. In addition, powered by the parasite's own gliding motility, extracellular N. caninum tachyzoites were able to transmigrate across cellular monolayers. Altogether, the presented data provides evidence of two putative complementary pathways utilized by N. caninum, in an isolate-specific fashion, for passage of restrictive cellular barriers. Interestingly, adoptive transfer of tachyzoite-infected DC in mice resulted in increased parasitic loads in various organs, e.g. the central nervous system, compared to infections with free parasites. Inoculation of pregnant mice with infected DC resulted in an accentuated vertical transmission to the offspring with increased parasitic loads and neonatal mortality. These findings reveal that N. caninum exploits the natural cell trafficking pathways in the host to cross cellular barriers and disseminate to deep tissues. The findings are indicative of conserved dissemination strategies among coccidian apicomplexan parasites

Alignment of the ALICE Inner Tracking System with cosmic-ray tracks

37 pages, 15 figures, revised version, accepted by JINSTALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 micron in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10^5 charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.Peer reviewe

Adolescent´s perceptions and expectations of parental action on children´s smoking and snus use : national cross sectional data from three decades

Background: Parents play a vital role as children develop tobacco behaviours. Many parents feel unsure about their possibility to influence their teenager's lifestyle. Knowledge about young people's acceptance for parental intervention could increase parental involvement. The overall objective of this study was to explore adolescents' perceptions and expectations of parental action regarding children's smoking and snus use, and whether they have changed over time. To see if there were differences whether the adolescent was a tobacco user or not the adolescents' tobacco use was followed; and described to put the findings on their perceptions and expectations of parental action in a context. Methods: The study used a repeated cross-sectional design, reporting Swedish national data from three decades. Data were collected in 1987, 1994 and 2003 by a questionnaire mailed to homes, in total to 13500 persons. The annual samples, which were random and national representative, consisted of 4500 young people aged 13, 15 and 17 yr, 1500 individuals per age group. The sampling and data collection procedures were done the same way during each survey. Chi2- tests were used to evaluate differences in distributions. Results: Adolescents in all age groups became more positive toward parental action over time. In 2003, more then 86% of the adolescents, including both smokers and non-smokers, strongly supported parental action on their children's smoking by trying to persuade them not to smoke (94%), by not smoking themselves (87%) and by not allowing their children to smoke at home (86%). Both non-smokers and smokers supported the idea of parental action in a similar way. Reduced pocket money had a weak support (42%), especially from girls. Eighty-nine percent of the adolescents expected their parents to act against smoking and 85% against snus use. Smoking was stable at 8% in 1987 and 1994 but decreased to 4% in 2003. In 1987 the snus use prevalence was 4% and in 2003 it was 3%. Snus users were mostly boys while few girls had done more than tried snus. More young people in all age groups had never tried smoking compared to the previous studies. In 2003 57% stated that they had never tried smoking. Conclusion: Adolescent smoking in Sweden has decreased and the proportion who never tried smoking has increased. The results of this study show that a growing majority of adolescents support strong parental intervention to help them refrain from tobacco, but preferably not in a punitive manner. This finding dismisses the notion that adolescents ignore or even disdain parental practices concerning tobacco. Prevention strategies and interventions addressing adolescent tobacco use that involve parents can be improved by using these findings to encourage parents to intervene against their children's tobacco use.Funding from Vasterbotten County Council, Umea, Sweden and the Swedish National Public Health Institute, Stockholm, Sweden, supported research for this article.</p