Aggregation of frictional particles due to capillary attraction

Capillary attraction between identical millimeter sized spheres floating at a liquid-air interface and the resulting aggregation is investigated at low Reynolds number. We show that the measured capillary forces between two spheres as a function of distance can be described by expressions obtained using the Nicolson approximation at low Bond numbers for far greater particle sizes than previously assumed. We find that viscous hydrodynamics interactions between the spheres needs to be included to describe the dynamics close to contact. We then consider the aggregates formed when a third sphere is added after the initial two spheres are already in contact. In this case, we find that linear superposition of capillary forces describes the observed approach qualitatively but not quantitatively. Further, we observe an angular dependence of the structure due to a rapid decrease of capillary force with distance of separation which has a tendency to align the particles before contact. When the three particles come in contact, they may preserve their shape or rearrange to form an equilateral triangle cluster - the lowest energy state - depending on the competition between attraction between particles and friction. Using these observations, we demonstrate that a linear particle chain can be built from frictional particles with capillary attraction.Comment: accepted for Physical Review

Development of a conductive photoresist with a mixture of SU-8 and HCL doped polyaniline

A novel electrically conductive photoresist has been formulated to fabricate microcomponents. The developed conductive photoresist is based upon SU-8 photopolymer, an insulating negative-tone epoxy, in which protonically doped polyaniline (PANI) nanoparticles have been dispersed to enhance the electrical properties. The characteristics of this new conductive photoresist have been studied via electrical measurements. The process for preparing the conductive films from the combination of EB (Emeraldine base) PANI, SU-8 and NMP (N-methyl-2-pyrrolidinone) will be presented. Different weight percentages (wt%) of SU-8 in the above combination have been prepared and spin coated to form thin-films which have been protonated with HCl. The conductivities of the thin- films were measured using a four point probe. The highest conductivity achieved was approximately 1.6 S/cm for the mixture of 10 wt% of SU-8 25 with EB-PANI mixed with NMP. The morphology of the thin-films was studied using a scanning electron microscopy (SEM)

Biological Effects of a De Novo Designed Myxoma Virus Peptide Analogue: Evaluation of Cytotoxicity on Tumor Cells

Not availabl

‘The International Teacher Leadership project,’ a case of international action research.

Copyright CARNThe paper arises from the International Teacher Leadership project, a research and development project involving researchers and practitioners in 14 European countries. The paper provides a conceptual exploration of the idea of teacher leadership and its role in educational reform, central to which is the idea that teachers, regardless of their level of power and organisational position, can engage in the leadership of enquiry-based development activity aimed at influencing their colleagues and embedding improved practices in their schools. The paper provides an outline of the project’s methodology which builds on that used in the Carpe Vitam Leadership for Learning project (Frost, 2008a). It is a form of collaborative action research which is highly developmental and discursive. It seeks to identify principles, strategies and tools that can be applied in a range of cultural settings. The paper includes a thematic analysis of the cultural contexts and policy environments of the participating countries in order to identify the obstacles to teacher leadership and to inform the nature of the support strategies employed

Gebitstoestand en mondgezondheid van basisschoolkinderen

De laatste decennia is er veel aandacht besteed aan het verbeteren van de gebitstoestand van basisschoolkinderen. Om een indruk te krijgen van de huidige stand van zaken met betrekking tot de gebitstoestand en de mondgezondheid is in de provincie Drenthe een onderzoek gedaan onder 1.147 kinderen van groep 2 en groep 8. Van de kinderen heeft 33% een niet-gaaf gebit en 13% heeft last van gingivitis. Het hoogste percentage niet-gave gebitten is te vinden onder kinderen uit de lage sociaaleconomische klasse en kinderen uit het speciaal onderwijs. Het blijkt dat deze kinderen minder vaak poetsen, later naar de tandarts gaan en vaker snoepen. De gebitstoestand van kinderen die een poetsinstructie hebben gehad is niet beter dan die van kinderen die geen poetsinstructie hebben gehad. Ook van de kinderen van wie de ouders voorlichting over mondgezondheid hebben gehad, is de gebitstoestand niet beter dan die van kinderen van wie de ouders geen voorlichting hebben gehad. Versch. in: Ned Tijdschr Tandheelkd 2005; 112: 358-362

Late-Onset Sepsis Mortality among Preterm Infants: Beyond Time to First Antibiotics

Objective: To investigate the impact of timing, in vitro activity and appropriateness of empirical antimicrobials on the outcome of late-onset sepsis among preterm very low birth weight infants that are at high risk of developing meningitis. Study design: This retrospective study included 83 LOS episodes in 73 very low birth weight infants born at ≤32 weeks’ gestation with positive blood and/or cerebrospinal fluid culture or polymerase chain reaction at >72 h of age. To define the appropriateness of empirical antimicrobials we considered both their in vitro activity and their ideal delivery through the blood-brain barrier when meningitis was confirmed or not ruled out through a lumbar puncture. The primary outcome was sepsis-related mortality. The secondary outcome was the development of brain lesions. Timing, in vitro activity and appropriateness of empirical antimicrobials, were compared between fatal and non-fatal episodes. Uni- and multi-variable analyses were carried out for the primary outcome. Results: Time to antibiotics and in vitro activity of empirical antimicrobials were similar between fatal and non-fatal cases. By contrast, empirical antimicrobials were appropriate in a lower proportion of fatal episodes of late-onset sepsis (4/17, 24%) compared to non-fatal episodes (39/66, 59%). After adjusting for Gram-negative vs. Gram-positive pathogen and for other supportive measures (time to volume administration), inappropriate empirical antimicrobials remained associated with mortality (aOR, 10.3; 95% CI, 1.4–76.8, p = 0.023), while timing to first antibiotics was not (aOR 0.9; 95% CI, 0.7–1.2, p = 0.408; AUC = 0.88). The association between appropriate antimicrobials and brain sequelae was also significant (p = 0.024). Conclusions: The risk of sepsis-related mortality and brain sequelae in preterm very low birth weight infants is significantly associated with the appropriateness (rather than the timing and the in vitro activity) of empirical antimicrobials. Until meningitis is ruled out through lumbar puncture, septic very low birth weight infants at high risk of mortality should receive empiric antimicrobials with high delivery through the blood-brain barrier