28 research outputs found
Random, blocky and alternating ordering in supramolecular polymers of chemically bidisperse monomers
As a first step to understanding the role of molecular or chemical
polydispersity in self-assembly, we put forward a coarse-grained model that
describes the spontaneous formation of quasi-linear polymers in solutions
containing two self-assembling species. Our theoretical framework is based on a
two-component self-assembled Ising model in which the bidispersity is
parameterized in terms of the strengths of the binding free energies that
depend on the monomer species involved in the pairing interaction. Depending
upon the relative values of the binding free energies involved, different
morphologies of assemblies that include both components are formed, exhibiting
paramagnetic-, ferromagnetic- or anti ferromagnetic-like order,i.e., random,
blocky or alternating ordering of the two components in the assemblies.
Analyzing the model for the case of ferromagnetic ordering, which is of most
practical interest, we find that the transition from conditions of minimal
assembly to those characterized by strong polymerization can be described by a
critical concentration that depends on the concentration ratio of the two
species. Interestingly, the distribution of monomers in the assemblies is
different from that in the original distribution, i.e., the ratio of the
concentrations of the two components put into the system. The monomers with a
smaller binding free energy are more abundant in short assemblies and monomers
with a larger binding affinity are more abundant in longer assemblies. Under
certain conditions the two components congregate into separate supramolecular
polymeric species and in that sense phase separate. We find strong deviations
from the expected growth law for supramolecular polymers even for modest
amounts of a second component, provided it is chemically sufficiently distinct
from the main one.Comment: Submitted to Macromolecules, 6 figures. arXiv admin note: substantial
text overlap with arXiv:1111.176
K0SK0S and K0SK± femtoscopy in pp collisions at √s = 5.02 and 13 TeV
Femtoscopic correlations with the particle pair combinations (KSKS0)-K-0 and (KSK +/-)-K-0 are studied in pp collisions at root s= 5.02 and 13 TeV by the ALICE experiment. At both energies, boson source parameters are extracted for both pair combinations, by fitting models based on Gaussian size distributions of the sources, to the measured two-particle correlation functions. The interaction model used for the (KSKS0)-K-0 analysis includes quantum statistics and strong final-state interactions through the f(0) (980) and a(0) (980) resonances. The model used for the (KSK +/-)-K-0 analysis includes only the final-state interaction through the a(0) resonance. Source parameters extracted in the present work are compared with published values from pp collisions at root s = 7 TeV and the different pair combinations are found to be consistent. From the observation that the strength of the (KSKS0)-K-0 correlations is significantly greater than the strength of the (KSK +/-)-K-0 correlations, the new results are compatible with the a(0) resonance being a tetraquark state of the form (q(1), (q(2)) over bar, s, (s) over bar), where q(1) and q(2) are uor d quarks. (C) 2022 European Organization for Nuclear Research, ALICE. Published by Elsevier B.V
Tight junctions: from simple barriers to multifunctional molecular gates
Epithelia and endothelia separate different tissue compartments and protect multicellular organisms from the outside world. This requires the formation of tight junctions, selective gates that control paracellular diffusion of ions and solutes. Tight junctions also form the border between the apical and basolateral plasma-membrane domains and are linked to the machinery that controls apicobasal polarization. Additionally, signalling networks that guide diverse cell behaviours and functions are connected to tight junctions, transmitting information to and from the cytoskeleton, nucleus and different cell adhesion complexes. Recent advances have broadened our understanding of the molecular architecture and cellular functions of tight junctions
Spent fuel evolution under disposal conditions. Synthesis of the results from the Eu Spent Fuel Stability (SFS) project
vol. 04-09, Technical Report. Wettingen: Nagr