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When a spilled drop of coffee dries on a solid surface, it leaves a dense, ring-like stain along the perimeter (Figure 1a). The coffee—initially dispersed over the entire drop—becomes concentrated into a tiny fraction of it. Such ring deposits are commonplace wherever drops containing dispersed solids evaporate on a surface. Thus ring deposits influence(More)
Thin cylindrical tethers are common lipid bilayer membrane structures, arising in situations ranging from micromanipulation experiments on artificial vesicles to the dynamic structure of the Golgi apparatus. We study the shape and formation of a tether in terms of the classical soap-film problem, which is applied to the case of a membrane disk under tension(More)
The residue left when coffee dries on the counter-top or at the bottom of a mug is typically darkest, and hence most concentrated, along the perimeter of the stain giving the deposit a ring-like appearance. Given that the coffee solute was uniformly distributed in the liquid prior to drying, its segregation to the edge is surprising. Ring-like stains are(More)
Studies of policy diffusion often focus on the horizontal spread of enactments from one state to another, paying little or no attention to the effects of local laws on state-level adoptions. For example, scholars have not tested whether local policy adoptions make state action more likely (through a snowball effect) or less likely (through a pressure valve(More)
The endoplasmic reticulum (ER) often forms stacked membrane sheets, an arrangement that is likely required to accommodate a maximum of membrane-bound polysomes for secretory protein synthesis. How sheets are stacked is unknown. Here, we used improved staining and automated ultrathin sectioning electron microscopy methods to analyze stacked ER sheets in(More)
When a helical bacterial flagellum, clamped at one end, is placed in an external flow, it has been observed that regions of the flagellum transform to the opposite chirality, and travel as pulses down the length of the filament, the process repeating periodically [H. Hotani, J. Mol. Biol. 156, 791 (1982)]]. We propose a theory for this phenomenon based on a(More)
Regulation of actin dynamics through the Nck/N-WASp (neural Wiskott-Aldrich syndrome protein)/Arp2/3 pathway is essential for organogenesis, cell invasiveness, and pathogen infection. Although many of the proteins involved in this pathway are known, the detailed mechanism by which it functions remains undetermined. To examine the signaling mechanism, we(More)
It has long been known that during the closed mitosis of many unicellular eukaryotes, including the fission yeast (Schizosaccharomyces pombe), the nuclear envelope remains intact while the nucleus undergoes a remarkable sequence of shape transformations driven by elongation of an intranuclear mitotic spindle whose ends are capped by spindle pole bodies(More)
Federalist democracies often hold concurrent elections for multiple offices. A potential consequence of simultaneously voting for multiple offices that vary with respect to scope and scale is that the personal appeal of candidates in a high-profile race may affect electoral outcomes in less salient races. In this paper I estimate the magnitude of such(More)