Cell viability within oral biofilms

Bacteria are not distributed homogenously throughout an oral biofilm. This is primarily due to regions of differing environmental conditions, themselves a manifestation of nutrient, gaseous and ionic concentration gradients within the biofilm. Confocal laser scanning microscopy in conjunction with fluorescent staining techniques and image analysis can both visualise and quantify the distribution of viable and nonviable bacteria within the three-dimensional volume of the biofilm

The inability of a bacteriophage to infect Staphylococcus aureus does not prevent it from specifically delivering a photosensitizer to the bacterium enabling its lethal photosensitization

Objectives: It has been demonstrated that the efficiency of lethal photosensitization can be improved by covalently binding photosensitizing agents to bacteriophage. In this study we have investigated whether a bacteriophage requires the capacity to infect the bacterium to enhance lethal photosensitization when linked to a photosensitizer.Methods: Tin (IV) chlorin e6 (SnCe6) was conjugated to bacteriophage Phi 11, a transducing phage that can infect Staphylococcus aureus NCTC 8325-4, but not epidemic methicillin-resistant S. aureus (EMRSA)-16. The conjugate and appropriate controls were incubated with these bacteria and either exposed to laser light at 632.8 nm or kept in the dark.Results: The SnCe6/Phi 11 conjugate achieved a statistically significant reduction in the number of viable bacteria of both 8325-4 and EMRSA-16 strains by 2.31 log(10) and 2.63 log(10), respectively. The conjugate could not however instigate lethal photosensitization of Escherichia coli. None of the other combinations of controls, such as an equivalent concentration of SnCe6 only, an equivalent titre of bacteriophage only or experiments conducted without laser light, yielded significant reductions in the number of viable bacteria recovered.Conclusions: The inability of a bacteriophage to infect S. aureus does not prevent it from specifically delivering a photosensitizer to a bacterium enabling its lethal photosensitization

Reactive Momentum Transfer Contributes to the Self-Propulsion of Janus Particles

We report simulations of a spherical Janus particle undergoing exothermic surface reactions around one pole only. Our model excludes self-phoretic transport by design. Nevertheless, net motion occurs from direct momentum transfer between solvent and colloid, with speed scaling as the square root of the energy released during the reaction. We find that such propulsion is dominated by the system’s short-time response, when neither the time dependence of the flow around the colloid nor the solvent compressibility can be ignored. Our simulations agree reasonably well with previous experiments.Horizon 2020 FET Ope

Media And Information Literacy Curriculum For Teachers

Fulltext in: http://unesdoc.unesco.org/images/0019/001929/192971e.pd

The Darlington and Northallerton Long Term Asthma Study: pulmonary function

BACKGROUND: The Darlington and Northallerton Asthma Study is an observational cohort study started in 1983. At that time little was published about long term outcome in asthma and the contribution of change in reversible disease or airway remodelling to any excess deterioration in function. The study design included regular review of overall and fixed function lung. We report the trends over fifteen years. METHODS: All asthmatics attending secondary care in 1983, 1988 and 1993 were recruited. Pulmonary function was recorded at attendance and potential best function estimated according to protocol. Rate of decline was calculated over each 5-year period and by linear regression analysis in those seen every time. The influence of potential explanatory variables on this decline was explored. RESULTS: 1724 satisfactory 5-year measurements were obtained in 912 subjects and in 200 subjects on all occasions. Overall rate of decline (ml/year (95%CI)) calculated from 5-year periods was FEV1 ♂41.0 (34.7–47.3), ♀28.9 (23.2–34.6) and best FVC ♂63.1 (55.1–71.2)ml/year, ♀45.8 (40.0–51.6).The principal association was with age. A dominant cubic factor suggested fluctuations in the rate of change in middle life with less rapid decline in youth and more rapid decline in the elderly. Rapid decline was possibly associated with short duration. Treatment step did not predict rate of deterioration. CONCLUSIONS: Function declined non-linearly and more rapidly than predicted from normal subjects. It reports for the first time a cubic relationship between age and pulmonary function. This should be taken into account when interpreting other articles reporting change in function over time

Hydrodynamic and Contact Contributions to Continuous Shear Thickening in Colloidal Suspensions.

Shear thickening is a widespread phenomenon in suspension flow that, despite sustained study, is still the subject of much debate. The longstanding view that shear thickening is due to hydrodynamic clusters has been challenged by recent theory and simulations suggesting that contact forces dominate, not only in discontinuous, but also in continuous shear thickening. Here, we settle this dispute using shear reversal experiments on micron-sized silica and latex particles to measure directly the hydrodynamic and contact force contributions to shear thickening. We find that contact forces dominate even continuous shear thickening. Computer simulations show that these forces most likely arise from frictional interactions