Article
Physics, Nuclear
P. Alexa, M. Abolghasem, G. Thiamova, D. Bonatsos, T. R. Rodriguez, P-G Reinhard
Summary: The study investigates the spherical-to-deformed phase transition in cerium isotopes using macroscopic algebraic collective model and two microscopic approaches. The results suggest the presence of octupole softness and shape coexistence in 146Ce and 148Ce.
Article
Physics, Nuclear
H. G. Ganev
Summary: This study applies a recently proposed microscopic version of the Bohr-Mottelson collective model to describe the low-lying collective excitations in Ru-104 and Os-192. The results show a good overall description of the excitation energies and quadrupole collectivity in these transitional nuclei.
EUROPEAN PHYSICAL JOURNAL A
(2022)
Article
Physics, Nuclear
H. G. Ganev
Summary: This article discusses the theoretical basis of the Bohr-Mottelson collective model at the algebraic level. It shows how the irrotational-flow dynamics of Bohr-Mottelson type can be interpreted at the microscopic level using the proton-neutron shell-model theory within the framework of the proton-neutron symplectic model. The theory is illustrated with simple examples of Cd-110 and Ru-110 nuclei, which exhibit such irrotational-flow dynamics, and the ground state quadrupole irrotational-flow collectivity in these nuclei is well described without the need for an effective charge.
EUROPEAN PHYSICAL JOURNAL A
(2023)
Article
Physics, Multidisciplinary
Mathieu Jeannin, Mathieu Jeannin, Jean-Michel Manceau, Jean-Michel Manceau, Raffaele Colombelli
Summary: This research proposes a unified description of intersubband absorption saturation for quantum wells in a resonator, demonstrating how absorption saturation can be engineered and how it varies with doping concentration in weak and strong light-matter coupling regimes. The study reveals that saturation intensity increases linearly with doping in strong coupling, but remains doping independent in weak coupling. The research opens up possibilities for ultrafast midinfrared semiconductor saturable absorption mirrors and bistable systems.
PHYSICAL REVIEW LETTERS
(2021)
Article
Astronomy & Astrophysics
Simon Birrer
Summary: This work presents a formalism for describing gravitational lensing distortion effects resulting in curved extended arcs based on the eigenvectors and eigenvalues of the local lensing Jacobian. The methodology allows for accurate extraction of lensing information without the need for an explicit global deflector model, and can break degeneracies based on assumptions about the local lensing nature and intrinsic source shape. The formalism is applicable across different lensing regimes and provides a model-independent way to quantify extracted lensing information.
ASTROPHYSICAL JOURNAL
(2021)
Article
Polymer Science
Aristotelis P. Sgouros, Constantinos J. Revelas, Apostolos T. Lakkas, Doros N. Theodorou
Summary: The study uses self-consistent field theory to investigate the contact of single or opposing silica plates with bare or grafted surfaces in vacuum or melt phases. Non-bonded interactions are described using Hamaker potential and free energy densities, with a focus on wetting conditions and the potential of mean force between plates. The research also examines the impact of asymmetries, grafting density, and chain length of grafted molecules on steric stabilization.
Article
Biochemical Research Methods
Grigorios Megariotis, Nikolaos Romanos, Aggelos Avramopoulos, Georgios Mikaelian, Doros N. Theodorou
Summary: This article presents atomistic molecular dynamics and umbrella sampling simulations of levodopa in hydrated cholesterol-free DPPC and cholesterol-containing POPC bilayers at various concentrations. The study focuses on understanding how levodopa behaves in different hydrated lipid membranes and reveals aspects of its permeation mechanism through them. Special attention is paid to the calculation of mass density profiles, order parameters, and self-diffusion coefficients, showing that levodopa zwitterions are preferentially located at the water/lipid interface and in the aqueous phase surrounding the membranes.
JOURNAL OF MOLECULAR GRAPHICS & MODELLING
(2021)
Article
Chemistry, Physical
A. P. Sgouros, D. S. Tsagkalakis, D. N. Theodorou
Summary: This study investigates the impact of surface nanopatterning on slip behavior of polymer melt flow, revealing that nanopatterns can perturb chain ordering and affect slip. In some cases, nanopatterns can minimize slip. Applying symmetric or asymmetric nanopattern configurations generates different flow effects.
JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Polymer Science
Fotis Venetsanos, Stefanos D. Anogiannakis, Doros N. Theodorou
Summary: In this study, a full thermodynamic analysis is conducted on polyethylene oxide/polyethylene oligomeric blends using a methodology introduced by Petris et al. The Kirkwood-Buff theory is applied, and a composition-dependent estimation of the Flory-Huggins interaction parameter is obtained. The results are compared with experimental measurements and previous simulations, showing a good agreement, which validates the proposed methodology.
Article
Chemistry, Physical
Aristotelis P. Sgouros, Constantinos J. Revelas, Apostolos T. Lakkas, Doros N. Theodorou
Summary: Predicting the distribution of a chemical species in different phases is crucial for environmental protection, pharmaceuticals, and high added-value chemicals. This study develops a theoretical framework to determine the solvation free energy of grafted particles in a molten polymer matrix, which can be used to estimate their partition coefficients in polymer melts.
JOURNAL OF PHYSICAL CHEMISTRY B
(2022)
Article
Biochemical Research Methods
Grigorios Megariotis, Georgios Mikaelian, Aggelos Avramopoulos, Nikolaos Romanos, Doros N. Theodorou
Summary: Fluoxetine's behavior in cholesterol-free and cholesterol-containing lipid bilayers was studied using molecular dynamics simulations. The drug was found to prefer to reside in the lipid phase, and important thermodynamic properties were calculated. In addition, the interaction between fluoxetine and beta-cyclodextrin in aqueous solutions was also investigated, and a noncovalent complex was observed.
JOURNAL OF MOLECULAR GRAPHICS & MODELLING
(2022)
Article
Polymer Science
Constantinos J. Revelas, Aristotelis P. Sgouros, Apostolos T. Lakkas, Doros N. Theodorou
Summary: We have developed a three-dimensional self-consistent field-theoretic approach (3D-SCFT) to study polymer matrix nano composites with different geometries. By using the finite element method (FEM), we discretized Edwards's diffusion equation in space and time. The accuracy of the smearing approximation (SA), which treats grafting points as delocalized across a spherical shell, was assessed by comparing it with the 3D-SCFT. The SA is able to reproduce important structural and thermodynamic properties of the nano composites, but deviations are observed in the mushroom regime. The 3D-SCFT, which fixes grafting points in space, provides a more accurate description of chain stretching and offers detailed visualization of the brush transition.
Article
Mathematics, Interdisciplinary Applications
Aristotelis P. Sgouros, Doros N. Theodorou
Summary: Mesoscopic simulations are commonly used to study long polymer chains and soft matter systems and understand their relaxation processes. However, coarse-grained chains may experience unphysical intercrossing due to their softness. This issue is addressed by introducing slip-springs to restore topological constraints. The fixed image convention (FIC) is proposed as a more stable and efficient method for determining the separation vectors of overextended bonds compared to the commonly used minimum image convention (MIC).
Article
Chemistry, Physical
Georgios G. Vogiatzis, Lambert C. A. van Breemen, Markus Huetter, Doros N. Theodorou
Summary: An out-of-equilibrium simulation method is presented for tracking the time evolution of glassy systems. The method uses graph theory and complexity concepts to provide a unified framework for dealing with non-ergodic systems. The probability balance equation is analytically solved without assuming an equilibrium distribution among states and the relaxation mechanisms of the system are studied by analyzing the probability flux. The proposed approach is applied to the energy landscape of an atomistically detailed glassy specimen and accurately probes the relaxation mechanisms and time-scales.
MOLECULAR SYSTEMS DESIGN & ENGINEERING
(2023)
Article
Chemistry, Physical
Nikolaos Sigalas, Stefanos D. Anogiannakis, Doros N. Theodorou, Alexey Lyulin
Summary: This paper develops a new coarse-grained model based on the MARTINI force field to reproduce the helical behavior of isotactic polypropylene, with predicted properties compared to previous simulation results and experimental data. The development of the new coarse-grained force field utilized an efficient single unperturbed chain Monte Carlo algorithm.
Article
Chemistry, Physical
Aristotelis P. Sgouros, Stefan Knippenberg, Maxime Guillaume, Doros N. Theodorou
Summary: The mesoscopic dissipative particle dynamics (DPD) model is an important tool for studying the structural and thermodynamic properties of zwitterionic polymers, its development requires multiscale simulation strategies.
Article
Mathematics, Interdisciplinary Applications
Constantinos J. Revelas, Aristotelis P. Sgouros, Apostolos T. Lakkas, Doros N. Theodorou
Summary: This article introduces the one-dimensional version of the in-house code RuSseL, which can be used for a wide variety of systems involving polymeric interfaces. It includes a range of functional potentials and detailed descriptions of equation solutions.
Article
Chemistry, Physical
Apostolos T. Lakkas, Aristotelis P. Sgouros, Constantinos J. Revelas, Doros N. Theodorou
Summary: Polymer/matrix nanocomposites have exceptional properties and promising applications in key industrial sectors. To ensure the best dispersion, nanoparticles are often stabilized by grafting polymer chains on their surface of the same chemical constitution as the matrix. A model is proposed to predict key structural and thermodynamic properties, exploring various regimes and extracting important quantities related to the distribution and configuration of polymer chains.