TY - JOUR AB - Creeping flow of polymeric fluid without inertia exhibits elastic instabilities and elastic turbulence accompanied by drag enhancement due to elastic stress produced by flow-stretched polymers. However, in inertia-dominated flow at high Re and low fluid elasticity El, a reduction in turbulent frictional drag is caused by an intricate competition between inertial and elastic stresses. Here we explore the effect of inertia on the stability of viscoelastic flow in a broad range of control parameters El and (Re,Wi). We present the stability diagram of observed flow regimes in Wi-Re coordinates and find that the instabilities' onsets show an unexpectedly nonmonotonic dependence on El. Further, three distinct regions in the diagram are identified based on El. Strikingly, for high-elasticity fluids we discover a complete relaminarization of flow at Reynolds number in the range of 1 to 10, different from a well-known turbulent drag reduction. These counterintuitive effects may be explained by a finite polymer extensibility and a suppression of vorticity at high Wi. Our results call for further theoretical and numerical development to uncover the role of inertial effect on elastic turbulence in a viscoelastic flow. AU - Varshney, Atul AU - Steinberg, Victor ID - 17 IS - 10 JF - Physical Review Fluids TI - Drag enhancement and drag reduction in viscoelastic flow VL - 3 ER - TY - JOUR AB - Although cells respond specifically to environments, how environmental identity is encoded intracellularly is not understood. Here, we study this organization of information in budding yeast by estimating the mutual information between environmental transitions and the dynamics of nuclear translocation for 10 transcription factors. Our method of estimation is general, scalable, and based on decoding from single cells. The dynamics of the transcription factors are necessary to encode the highest amounts of extracellular information, and we show that information is transduced through two channels: Generalists (Msn2/4, Tod6 and Dot6, Maf1, and Sfp1) can encode the nature of multiple stresses, but only if stress is high; specialists (Hog1, Yap1, and Mig1/2) encode one particular stress, but do so more quickly and for a wider range of magnitudes. In particular, Dot6 encodes almost as much information as Msn2, the master regulator of the environmental stress response. Each transcription factor reports differently, and it is only their collective behavior that distinguishes between multiple environmental states. Changes in the dynamics of the localization of transcription factors thus constitute a precise, distributed internal representation of extracellular change. We predict that such multidimensional representations are common in cellular decision-making. AU - Granados, Alejandro AU - Pietsch, Julian AU - Cepeda Humerez, Sarah A AU - Farquhar, Isebail AU - Tkacik, Gasper AU - Swain, Peter ID - 281 IS - 23 JF - PNAS TI - Distributed and dynamic intracellular organization of extracellular information VL - 115 ER - TY - JOUR AB - Clathrin-mediated endocytosis requires the coordinated assembly of various endocytic proteins and lipids at the plasma membrane. Accumulating evidence demonstrates a crucial role for phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) in endocytosis, but specific roles for PtdIns(4)P other than as the biosynthetic precursor of PtdIns(4,5)P2 have not been clarified. In this study we investigated the role of PtdIns(4)P or PtdIns(4,5)P2 in receptor-mediated endocytosis through the construction of temperature-sensitive (ts) mutants for the PI 4-kinases Stt4p and Pik1p and the PtdIns(4) 5-kinase Mss4p. Quantitative analyses of endocytosis revealed that both the stt4(ts)pik1(ts) and mss4(ts) mutants have a severe defect in endocytic internalization. Live-cell imaging of endocytic protein dynamics in stt4(ts)pik1(ts) and mss4(ts) mutants revealed that PtdIns(4)P is required for the recruitment of the alpha-factor receptor Ste2p to clathrin-coated pits whereas PtdIns(4,5)P2 is required for membrane internalization. We also found that the localization to endocytic sites of the ENTH/ANTH domain-bearing clathrin adaptors, Ent1p/Ent2p and Yap1801p/Yap1802p, is significantly impaired in the stt4(ts)pik1(ts) mutant, but not in the mss4(ts) mutant. These results suggest distinct roles in successive steps for PtdIns(4)P and PtdIns(4,5)P2 during receptor-mediated endocytosis. AU - Yamamoto, Wataru AU - Wada, Suguru AU - Nagano, Makoto AU - Aoshima, Kaito AU - Siekhaus, Daria E AU - Toshima, Junko AU - Toshima, Jiro ID - 620 IS - 1 JF - Journal of Cell Science TI - Distinct roles for plasma membrane PtdIns 4 P and PtdIns 4 5 P2 during yeast receptor mediated endocytosis VL - 131 ER - TY - CONF AB - We describe a new algorithm for the parametric identification problem for signal temporal logic (STL), stated as follows. Given a densetime real-valued signal w and a parameterized temporal logic formula φ, compute the subset of the parameter space that renders the formula satisfied by the signal. Unlike previous solutions, which were based on search in the parameter space or quantifier elimination, our procedure works recursively on φ and computes the evolution over time of the set of valid parameter assignments. This procedure is similar to that of monitoring or computing the robustness of φ relative to w. Our implementation and experiments demonstrate that this approach can work well in practice. AU - Bakhirkin, Alexey AU - Ferrere, Thomas AU - Maler, Oded ID - 182 SN - 978-1-4503-5642-8 T2 - Proceedings of the 21st International Conference on Hybrid Systems TI - Efficient parametric identification for STL ER - TY - CONF AB - Vector Addition Systems with States (VASS) provide a well-known and fundamental model for the analysis of concurrent processes, parameterized systems, and are also used as abstract models of programs in resource bound analysis. In this paper we study the problem of obtaining asymptotic bounds on the termination time of a given VASS. In particular, we focus on the practically important case of obtaining polynomial bounds on termination time. Our main contributions are as follows: First, we present a polynomial-time algorithm for deciding whether a given VASS has a linear asymptotic complexity. We also show that if the complexity of a VASS is not linear, it is at least quadratic. Second, we classify VASS according to quantitative properties of their cycles. We show that certain singularities in these properties are the key reason for non-polynomial asymptotic complexity of VASS. In absence of singularities, we show that the asymptotic complexity is always polynomial and of the form Θ(nk), for some integer k d, where d is the dimension of the VASS. We present a polynomial-time algorithm computing the optimal k. For general VASS, the same algorithm, which is based on a complete technique for the construction of ranking functions in VASS, produces a valid lower bound, i.e., a k such that the termination complexity is (nk). Our results are based on new insights into the geometry of VASS dynamics, which hold the potential for further applicability to VASS analysis. AU - Brázdil, Tomáš AU - Chatterjee, Krishnendu AU - Kučera, Antonín AU - Novotny, Petr AU - Velan, Dominik AU - Zuleger, Florian ID - 143 SN - 978-1-4503-5583-4 TI - Efficient algorithms for asymptotic bounds on termination time in VASS VL - F138033 ER -