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The nonlinear absorption of nanoscale thin films of iron phthalocyanine, zinc phthalocyanine, and metal-free phthalocyanine fabricated via thermal evaporation at various deposition temperatures was studied using the open-aperture z-scan method with a continuous wave laser. A solution of tetra-tert-butyl-phthalocyanine in chloroform was also studied via z-scan. The thin films exhibit pronounced saturable absorption, with the degree of nonlinearity highly dependent on the type of metal complex. No significant correlation was found between deposition temperature and nonlinear absorption. The liquid sample exhibits a transition from saturable absorption to reverse saturable absorption at high irradiance. 

Abstract We use graph theory simulations and single molecule experiments to investigate percolation properties of kinetoplasts, the topologically linked mitochondrial DNA from trypanosome parasites. The edges of some kinetoplast networks contain a fiber of redundantly catenated DNA loops, but previous investigations of kinetoplast topology did not take this into account. Our graph simulations track the size of connected components in lattices as nodes are removed, analogous to the removal of minicircles from kinetoplasts. We find that when the edge loop is taken into account, the largest component after the network de‐percolates is a remnant of the edge loop, before it undergoes a second percolation transition and breaks apart. This implies that stochastically removing minicircles from kinetoplast DNA would isolate large polycatenanes, which is observed in experiments that use photonicking to stochastically destroy kinetoplasts fromCrithidia fasciculata. Our results imply kinetoplasts may be used as a source of linear polycatenanes for future experiments. 

We prove that the knots [Formula: see text] and [Formula: see text] both have stick number 10. These are the first non-torus prime knots with more than 9 crossings for which the exact stick number is known.