Two QLS seminars this week - 21 and 23 June

[Quantitative Life Sciences]

Dear All,

This week, the QLS Section will hold two seminars:


On Wednesday, 21 June  2023 at 11:00 CET,  Elena Rufeil Fiori (CONICET 
Facultad de Matemática, Astronomía, Física y Computación, Universidad 
Nacional de Córdoba, Argentina) will give a seminar titled:
*
Dipolar density inter-domain interaction in lipid monolayers *

Abstract:
A challenging problem in the biophysics of cell membranes is the 
characterization of the lateral organization of their domains. These 
domains are made up of lipids in an ordered phase and are dispersed in a 
more disordered continuous lipid phase. A widely used experimental model 
to study these systems are the lipid monolayers at the water-air 
interface. Based on these experiments and using Brownian simulations, we 
study how the dipolar interaction between domains affects the structure 
of monolayers with phase coexistence. We present a new way to estimate 
the dipole repulsion directly from the experimental results. Besides, we 
also study an analytical approach to this system based on the 
Ornstein-Zernike integral equation theories (OZ-IETs). When the pair 
correlation function serves as the measure, we found that the closures 
that outperform better are the Modified Hypernetted Chain (MHNC) and the 
Variational Modified Hypernetted Chain (VMHNC), with a reference system 
based on an extension of the hard spheres parametrization. On the other 
hand, when the structure factor is used as a measure, the reference 
system that performs better depends on the particular region of the 
phase diagram.
___
__The seminar will take place in the Fibonacci room, Galileo guest 
house__, via Beirut, 7

_Indico webpage: https://indico.ictp.it/event/10406


***************************************************************************************************************************************

On Friday, 23 June  2023 at 11:00 CET, Farzan Vafa (Harvard Center of 
Mathematical Sciences and Applications) will give a seminar titled:

*    Dynamics of active nematic defects on cones*

Abstract:
In the first part of the talk, we investigate the ground-state 
configurations of two-dimensional liquid crystals with p-fold rotational 
symmetry (p-atics) on cones. The cone apex develops an effective 
topological charge, which in analogy to electrostatics, leads to defect 
absorption and emission at the cone apex as the deficit angle of the 
cone is varied. We find three types of ground-state configurations as a 
function of cone angle, which is determined by charged defects screening 
the effective apex charge: (i) for sharp cones, all of the +1/p defects 
are absorbed by the apex; (ii) at intermediate cone angles, some of the 
+1/p defects are absorbed by the apex and the rest lie equally spaced 
along a concentric ring on the flank; and (iii) for nearly flat cones, 
all of the +1/p defects lie equally spaced along a concentric ring on 
the flank. We check these results with numerical simulations for a set 
of commensurate cone angles and find excellent agreement. In the second 
part of the talk, we investigate the dynamics of an active nematic on a 
cone, and via simulations find long-time circular orbits of either one 
or two flank defects, with transitions between these states mediated by 
the apex via defect absorption, emission, or defect pair creation.

_The seminar will take place in the Fibonacci room, Galileo guest 
house__, via Beirut, 7

_Indico webpage: https://indico.ictp.it/event/10389/


You are all most welcome to attend!

Best regards,
Erica

-- 
Erica Sarnataro
Group Secretary
Quantitative Life Sciences
The Abdus Salam International Centre for Theoretical Physics (ICTP)
Trieste,  Italy
Tel. +39-040-2240623
www.ictp.it/research/qls.aspx
e-mail:qls at ictp.it