16 research outputs found
Stability of Triple Star Systems with Highly Inclined Orbits
It is well established that certain detached eclipsing binary stars exhibit
apsidal motions whose value is in disagreement with with calculated deviations
from Keplerian motion based on tidal effects and the general theory of
relativity. Although many theoretical senarios have been demonstrated to bring
calculations into line with observations, all have seemed unlikely for various
reasons. In particular, it has been established that the hypothesis of a third
star in an orbit almost perpendicular to the orbital plane of the close binary
system can explain the anomalous motion in at least some cases. The stability
of triple star systems with highly inclined orbits has been in doubt, however.
We have found conditions which allow the long term stability of such systems
so that the third body hypothesis now seems a likely resolution of the apsidal
motion problem. We apply our stability criteria to the cases of AS Cam and DI
Her and recommend observations at the new Keck interferometer which should be
able to directly observe the third bodies in these systems.Comment: edited to match published versio
Implementation and effectiveness of 'care navigation', coordinated management for people with complex chronic illness: rationale and methods of a randomised controlled trial
Single-Cell Control of Initial Spatial Structure in Biofilm Development Using Laser Trapping
Biofilms are sessile communities of microbes that are spatially structured by an embedding matrix. Biofilm infections are notoriously intractable. This arises, in part, from changes in the bacterial phenotype that result from spatial structure. Understanding these interactions requires methods to control the spatial structure of biofilms. We present a method for growing biofilms from initiating cells whose positions are controlled with single-cell precision using laser trapping. The native growth, motility, and surface adhesion of positioned microbes are preserved, as we show for model organisms Pseudomonas aeruginosa and Staphylococcus aureus. We demonstrate that laser-trapping and placing bacteria on surfaces can reveal the effects of spatial structure on bacterial growth in early biofilm development