Fast and rewritable colloidal assembly via field synchronized particle swapping

We report a technique to realize reconfigurable colloidal crystals by using the controlled motion of particle defects above an externally modulated magnetic substrate. The transport of particles is induced by applying a uniform rotating magnetic field to a ferrite garnet film characterized by a periodic lattice of magnetic bubbles. For filling factor larger than one colloid per bubble domain, the particle current arises from propagating defects where particles synchronously exchange their position when passing from one occupied domain to the next. The amplitude of an applied alternating magnetic field can be used to displace the excess particles via a swapping mechanism, or to mobilize the entire colloidal system at a predefined speed

Evaluation of postsurgical crestal bone levels adjacent to non-submerged dental implants

In most of the studies on long-term radiographic evaluations of crestal bone levels adjacent to dental implants, no baseline radiographs taken immediately postsurgically had been obtained. The aim of this study was to test the reproducibility of a simple radiographic method for linear measurements of changes in bone levels and to evaluate changes in crestal bone levels adjacent to non-submerged ITI® implants 1 year following the surgical procedure. From 128 parents enrolled in a clinical and radiographic longitudinal study 40 patients also had radiographs taken immediately postsurgically. They were, however, not obtained as "identical" images. The radiographs were mounted onto slides and projected on a screen. Mesially and distally from 57 implants triplicate linear measurements of the distance implant shoulder to bone crest were taken, using known dimensions of the implants as internal reference distances. The median difference of 213 (out of 228 possible) duplicate measurements was 0.00 mm (ranging from -1.72 mm to +1.47 mm when comparing the second to the third reading). Some 81% of the double measurements were within ±0.5 mm and the precision was 0.30 mm. In the immediate postoperative radiographs the median mesial bone level was located at 2.07 mm (distally 2.19 mm) from the implant shoulder. A statistically significant amount of bone loss in the first year was observed mesially (median=-0.78 mm) and distally (-0.85 mm) (Wilcoxon matched pairs signed rank test P≤0.001). No statistically significant influence of the implant location, the implant length, type of the implant (screw; cylinder) was observed (Kruskal-Wallis P>0.05).The age of the patients was not correlated significantly to the amount of bone loss observed. In conclusion, methodological limitations existed when evaluating linear bone changes in non-identical radiographs using reference dimensions of the implants. The amount of postsurgical bone loss estimated in other studies was confirmed when using an immediate postoperative radiograph as a baseline. © Munksgaard 1998.link_to_subscribed_fulltex

Qualitative interpretation of MMS focussing data at low (panel a; cf. Fig 8A) and high (panel b; cf. Fig 8B) flow rates.

<p>The coloured maps are analogous to those shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0169919#pone.0169919.g003" target="_blank">Fig 3</a>. That is they represent the magnitude of the net lateral force acting on particles excluding the drag associated with the induced secondary flow. The latter is represented by arrows. The outwardly-directed magnetic field gradient is canted downwards by 25 degrees relative to the horizontal to reflect experimental conditions.</p

Schematic plan and (cross-sectional) side views of the array used to produce an octupolar magnetic field.

<p>Each 3.2 mm × 3.2 mm × 9.5 mm NdFeB magnet is magnetized parallel to its long axis. The distance between faces of opposing magnets is 17.7 mm and the diameter of the accessible bore is 16 mm. Curved arrows shown in the plan view indicate the qualitative sense of magnetic field lines. A thin annular ferromagnetic shield (green; side view only) between the array and the plane of the microfluidic spiral screens the magnetic field in the vicinity of the outlet ports and provides a field-free region for particle extraction. The distance of closest approach between the microfluidic spiral (represented by the dashed curve/line) and the plane of the shield is set by a microscope slide (not shown). See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0169919#pone.0169919.g006" target="_blank">Fig 6</a>.</p

Inertial focussing of particles in microfluidic channels (qualitative).

<p>The coloured maps represent (a) the downstream fluid speed U and (b and c) the magnitude of the net lift force F_NL; see Appendix A. The oriented texture superimposed on the latter is generated via line integral convolution [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0169919#pone.0169919.ref052" target="_blank">52</a>], and is thus tangential to F_NL. Particles (represented by yellow spheres) are driven away from the core of the flow toward regions of high stress, but are simultaneously kept away from the walls by asymmetric wake effects. In a straight rectangular channel (panels a and b), competition between these lift forces ultimately leads to particle aggregation along streamlines near the middle of the broad walls. In a curved channel (panel c), the induced secondary flow (indicated by arrows) contributes to the net lateral force and drives particles toward an apparent streamline near the midpoint of the inner wall of the turn. Here, and in all subsequent figures, the low end of the relevant scale (speed, force, etc) is mapped onto the colour blue.</p