Microgel particles with a soft repulsive interaction potential are investigated with particle tracking methods to study the phase behavior of soft-sphere systems. The use of poly(N-isopropylacrylamide) particles allows the effective volume fraction of a sample to be tuned via thermal modulation without altering the particle number density. This allows for investigation of the phase behavior of ...

Maximally random jammed (MRJ) particle packings can be viewed as prototypical glasses in that they are maximally disordered while simultaneously being mechanically rigid. The prediction of the MRJ packing density ϕMRJ, among other packing properties of frictionless particles, still poses many theoretical challenges, even for congruent spheres or disks. Using the geometric-structure approach, we...

We say that a graph G has a perfect H-packing if there exists a set of vertex-disjoint copies of H which cover all the vertices in G. We consider various problems concerning perfect Hpackings: Given n, r,D ∈ N, we characterise the edge density threshold that ensures a perfect Kr-packing in any graph G on n vertices and with minimum degree δ(G) ≥ D. We also give two conjectures concerning degree...

We have used amperometric measurements in a model system consisting of two liposomes connected with a membrane nanotube to monitor catechol release during artificial exocytosis and thereby to elucidate the effect of small-chain alcohols on this dynamic membrane process. To determine the rate of membrane shape change, catechol release during membrane distention was monitored amperometrically, an...

We have used an adaptive-optics scanning laser ophthalmoscope to image the cone photoreceptor mosaic throughout the central 10 degrees -12 degrees of the retina for four normal subjects. We then constructed montages of the images and processed the montages to determine cone locations. Cone densities range from approximately 10,000 cones/mm2 at 7 degrees to 40,000 cones/mm2 at 1 degrees . The sm...

We address the problem of covering R with congruent balls, while minimizing the number of balls that contain an average point. Considering the 1-parameter family of lattices defined by stretching or compressing the integer grid in diagonal direction, we give a closed formula for the covering density that depends on the distortion parameter. We observe that our family contains the thinnest latti...

PURPOSE To investigate the distribution of cone density and spacing as well as the preferred packing arrangement of the cone mosaic as a function of retinal eccentricity. METHODS An adaptive optics retinal camera (rtx1, www.imagine-eyes.com) was used to obtain images of the parafoveal cone mosaic in nineteen healthy volunteers. Cone density and spacing were estimated for each subject (both ey...

Tetrahedra are special among the platonic solids. They are the simplest polyhedra and the ones most unlike spheres. Surprisingly, much of our knowledge about the packing properties of tetrahedra is very recent: the past year has witnessed a sudden proliferation of novel, and often surprising, findings. Using Monte Carlo simulations, Haji-Akbari et al.[1] found that, upon compression, systems of...

MOTIVATION There is no consensus in the literature about how the deepest portions of protein structures are packed. Using an improved Voronoi procedure, we calculate reference packing densities for different regions in the protein interior. Furthermore, we want to clarify where cavities are located. RESULTS Sets of reference packing densities are provided for regions in proteins that differ i...

We study the dependence on the packing fraction of the pair-correlation function g(r) and particle mobility in a dense three-dimensional packing of soft colloids made of poly N-isopropyl acrylamide (pNIPAM), a thermosensitive gel. We find that g(r) for our samples is qualitatively like that of a liquid at all packing fractions. There is a peak in g(1), the height of the first peak of g(r), as a...