2,615 research outputs found
Shape characteristics of the aggregates formed by amphiphilic stars in water: dissipative particle dynamics study
We study the effect of the molecular architecture of amphiphilic star
polymers on the shape of aggregates they form in water. Both solute and solvent
are considered at a coarse-grained level by means of dissipative particle
dynamics simulations. Four different molecular architectures are considered:
the miktoarm star, two different diblock stars and a group of linear diblock
copolymers, all of the same composition and molecular weight. Aggregation is
started from a closely packed bunch of molecules immersed into
water. In most cases, a single aggregate is observed as a result of
equilibration, and its shape characteristics are studied depending on the
aggregation number . Four types of aggregate shape are observed:
spherical, rod-like and disc-like micelle and a spherical vesicle. We estimate
"phase boundaries" between these shapes depending on the molecular
architecture. Sharp transitions between aspherical micelle and a vesicle are
found in most cases. The pretransition region shows large amplitude
oscillations of the shape characteristics with the oscillation frequency
strongly dependent on the molecular architecture.Comment: 10 pages, 7 figure
Public transportation in UK viewed as a complex network
In this paper we investigate the topological and spatial features of public
transport networks (PTN) within the UK. Networks investigated include London,
Manchester, West Midlands, Bristol, national rail and coach networks during
2011. Using methods in complex network theory and statistical physics we are
able to discriminate PTNs with respect to their stability; which is the first
of this kind for national networks. Moreover, taking advantage of various
fractal properties we gain useful insights into the serviceable area of
stations. These features can be employed as key performance indicators in aid
of further developing efficient and stable PTNs.Comment: 23 pages, 9 figure
A role for the cleaved cytoplasmic domain of E-cadherin in the nucleus
Cell-cell contacts play a vital role in intracellular signaling, although the molecular mechanisms of these signaling pathways are not fully understood. E-cadherin, an important mediator of cell-cell adhesions, has been shown to be cleaved by γ-secretase. This cleavage releases a fragment of E-cadherin, E-cadherin C-terminal fragment 2 (E-cad/CTF2), into the cytosol. Here, we study the fate and function of this fragment. First, we show that coexpression of the cadherin-binding protein, p120 catenin (p120), enhances the nuclear translocation of E-cad/CTF2. By knocking down p120 with short interfering RNA, we also demonstrate that p120 is necessary for the nuclear localization of E-cad/CTF2. Furthermore, p120 enhances and is required for the specific binding of E-cad/CTF2 to DNA. Finally, we show that E-cad/CTF2 can regulate the p120-Kaiso-mediated signaling pathway in the nucleus. These data indicate a novel role for cleaved E-cadherin in the nucleus
Dynamical Scaling Behavior of Percolation Clusters in Scale-free Networks
In this work we investigate the spectra of Laplacian matrices that determine
many dynamic properties of scale-free networks below and at the percolation
threshold. We use a replica formalism to develop analytically, based on an
integral equation, a systematic way to determine the ensemble averaged
eigenvalue spectrum for a general type of tree-like networks. Close to the
percolation threshold we find characteristic scaling functions for the density
of states rho(lambda) of scale-free networks. rho(lambda) shows characteristic
power laws rho(lambda) ~ lambda^alpha_1 or rho(lambda) ~ lambda^alpha_2 for
small lambda, where alpha_1 holds below and alpha_2 at the percolation
threshold. In the range where the spectra are accessible from a numerical
diagonalization procedure the two methods lead to very similar results.Comment: 9 pages, 6 figure
Lower bounds for the first eigenvalue of the magnetic Laplacian
We consider a Riemannian cylinder endowed with a closed potential 1-form A
and study the magnetic Laplacian with magnetic Neumann boundary conditions
associated with those data. We establish a sharp lower bound for the first
eigenvalue and show that the equality characterizes the situation where the
metric is a product. We then look at the case of a planar domain bounded by two
closed curves and obtain an explicit lower bound in terms of the geometry of
the domain. We finally discuss sharpness of this last estimate.Comment: Replaces in part arXiv:1611.0193
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