Browsing by Subject "transport"

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    Eccentricity fluctuations in an integrated hybrid approach: Influence on elliptic flow
    (2010) Petersen, Hannah; Bleicher, Marcus
    The effects of initial state fluctuations on elliptic flow are investigated within a (3 + 1)-dimensional Boltzmann + hydrodynamics transport approach. The spatial eccentricity (epsilon(RP) and epsilon(part)) is calculated for initial conditions generated by a hadronic transport approach (ultrarelativistic quantum molecular dynamics). Elliptic flow results as a function of impact parameter, beam energy, and transverse momentum for two different equations of state and for averaged initial conditions or a full event-by-event setup are presented. These investigations allow the conclusion that in mid-central (b = 5-9 fm) heavy-ion collisions the final elliptic flow is independent of the initial state fluctuations and the equation of state. Furthermore, it is demonstrated that most of the v(2) is built up during the hydrodynamic stage of the evolution. Therefore, the use of averaged initial profiles does not contribute to the uncertainties of the extraction of transport properties of hot and dense QCD matter based on viscous hydrodynamic calculations.
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    Starch Binding Domain-containing Protein 1 Plays a Dominant Role in Glycogen Transport to Lysosomes in Liver.
    (J Biol Chem, 2016-08-05) Sun, Tao; Yi, Haiqing; Yang, Chunyu; Kishnani, Priya S; Sun, Baodong
    A small portion of cellular glycogen is transported to and degraded in lysosomes by acid α-glucosidase (GAA) in mammals, but it is unclear why and how glycogen is transported to the lysosomes. Stbd1 has recently been proposed to participate in glycogen trafficking to lysosomes. However, our previous study demonstrated that knockdown of Stbd1 in GAA knock-out mice did not alter lysosomal glycogen storage in skeletal muscles. To further determine whether Stbd1 participates in glycogen transport to lysosomes, we generated GAA/Stbd1 double knock-out mice. In fasted double knock-out mice, glycogen accumulation in skeletal and cardiac muscles was not affected, but glycogen content in liver was reduced by nearly 73% at 3 months of age and by 60% at 13 months as compared with GAA knock-out mice, indicating that the transport of glycogen to lysosomes was suppressed in liver by the loss of Stbd1. Exogenous expression of human Stbd1 in double knock-out mice restored the liver lysosomal glycogen content to the level of GAA knock-out mice, as did a mutant lacking the Atg8 family interacting motif (AIM) and another mutant that contains only the N-terminal 24 hydrophobic segment and the C-terminal starch binding domain (CBM20) interlinked by an HA tag. Our results demonstrate that Stbd1 plays a dominant role in glycogen transport to lysosomes in liver and that the N-terminal transmembrane region and the C-terminal CBM20 domain are critical for this function.
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    Transient anomalous diffusion of tracer particles in soft matter
    (2009) McKinley, Scott A; Yao, Lingxing; Forest, M Gregory
    This paper is motivated by experiments in which time series of tracer particles in viscoelastic liquids are recorded using advanced microscopy. The experiments seek to infer either viscoelastic properties of the sample [Mason and Weitz, Phys. Rev. Lett. 74, 1250-1253 (1995)] or diffusive properties of the specific tracer particle in the host medium [Suh et al., Adv. Drug Delivery Rev. 57, 63-78 (2005); Matsui et al., Proc. Natl. Acad. Sci. U. S. A. 103, 18131-18136 (2006); Lai et al., Proc. Natl. Acad. Sci. U. S. A. 104, 1482-1487 (2007); Fricks et al., SIAM J. Appl. Math. 69, 1277-1308 (2009)]. Our focus is the latter. Experimentalists often fit data to transient anomalous diffusion: a sub-diffusive power law scaling (t(v), with 0 < v < 1) of mean-squared displacement (MSD) over a finite time interval, with longtime viscous scaling (t(1)). The time scales of sub-diffusion and exponents v are observed to vary with particle size, particle surface chemistry, and viscoelastic properties of the host material. Until now, explicit models for transient sub-diffusive MSD scaling behavior [Doi and Edwards, The Theory of Polymer Physics (Oxford University Press, New York, 1986); Kremer and Grest, J. Chem. Phys. 92, 5057-5086 (1990); Rubinstein and Colby, Polymer Physics (Oxford University Press, New York, 2003)] are limited to precisely three exponents: monomer diffusion in Rouse chain melts (t(1/2)), in Zimm chain solutions (t(2/3)), and in reptating chains (t(1/4)). In this paper, we present an explicit parametrized family of stochastic processes (generalized Langevin equations with prescribed memory kernels) and derive their closed-form solutions which (1) span the complete range of transient sub-diffusive behavior and (2) possess the flexibility to tune both the time window of sub-diffusive scaling and the power law exponent v. These results establish a robust family of sub-diffusive models, for which the inverse problem of parameter inference from experimental data [Fricks et al., SIAM J. Appl. Math. 69, 1277-1308 (2009)] remains to be developed. (C) 2009 The Society of Rheology. [DOI: 10.1122/1.3238546]