Extremality of Disordered Phase of λ-Model on Cayley Trees

In this paper, we consider the λ-model for an arbitrary-order Cayley tree that has a disordered phase. Such a phase corresponds to a splitting Gibbs measure with free boundary conditions. In communication theory, such a measure appears naturally, and its extremality is related to the solvability of the non-reconstruction problem. In general, the disordered phase is not extreme; hence, it is natural to find a condition for their extremality. In the present paper, we present certain conditions for the extremality of the disordered phase of the λ-model.

Delay-Induced Periodic Behaviour in Competitive Populations

We study a model of binary decisions in a fully connected network of interacting agents. Individual decisions are determined by social influence, coming from direct interactions with neighbours, and a group level pressure that accounts for social environment. In a competitive environment, the interplay of these two aspects results in the presence of a persistent disordered phase where no majority is formed. We show how the introduction of a delay mechanism in the agent’s detection of the global average choice may drastically change this scenario, giving rise to a coordinated self sustained periodic behaviour.

Anion reorientations and cation diffusion in a carbon-substituted sodium nido-borate Na-7,9-C2B9H12: 1H and 23Na NMR studies

Polyhydroborate-based salts of lithium and sodium have attracted much recent interest as promising solid-state electrolytes for energy-related applications. A member of this family, sodium dicarba-nido-undecahydroborate Na-7,9-C2B9H12 exhibits superionic conductivity above its order-disorder phase transition temperature, ∼360 K. To investigate the dynamics of the anions and cations in this compound at the microscopic level, we have measured the 1H and 23Na nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rates over the temperature range of 148–384 K. It has been found that the transition from the low-T ordered to the high-T disordered phase is accompanied by an abrupt, several-orders-of-magnitude acceleration of both the reorientational jump rate of the complex anions and the diffusive jump rate of Na+ cations. These results support the idea that reorientations of large [C2B9H12]− anions can facilitate cation diffusion and, thus, the ionic conductivity. The apparent activation energies for anion reorientations obtained from the 1H spin-lattice relaxation data are 314 meV for the ordered phase and 272 meV for the disordered phase. The activation energies for Na+ diffusive jumps derived from the 23Na spin-lattice relaxation data are 350 and 268 meV for the ordered and disordered phases, respectively.

The Fluidization Effect of a Bilayer Membrane on a Fatty Acid Vesicle by a Detergent

A bicelle, which is a bilayer molecular assembly, can be prepared by fluidizing a vesicle in the presence of a detergent. We investigated the effect of two different detergents, 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxypropane sulfonate (CHAPSO) and Triton X-100 (TX), on the formation of a bicelle from a vesicle containing oleic acid (OA) and the detergent molecules. The fluidization effect of the detergent was evaluated using the membrane packing density, which we measured using the fluorescent probe method with Laurdan, in conjunction with transmission electron microscopy to examine the morphology of the prepared bilayer molecular assemblies. As a result, it was discovered that the OA/CHAPSO system could form a heterogeneous phase with the highest packing density, implying that CHAPSO was the better detergent for a bicelle preparation, whereas the OA/TX system formed a disordered phase with the lowest packing density.

Parallel Simulation of Two-Dimensional Ising Models Using Probabilistic Cellular Automata

We study the numerical simulation of the shaken dynamics, a parallel Markovian dynamics for spin systems with local interaction and transition probabilities depending on the two parameters q and J that “tune” the geometry of the underlying lattice. The analysis of the mixing time of the Markov chain and the evaluation of the spin-spin correlations as functions of q and J, make it possible to determine in the (q, J) plane a phase transition curve separating the disordered phase from the ordered one. The relation between the equilibrium measure of the shaken dynamics and the Gibbs measure for the Ising model is also investigated. Finally two different coding approaches are considered for the implementation of the dynamics: a multicore CPU approach, coded in Julia, and a GPU approach coded with CUDA.

Hydrodynamic shear dissipation and transmission in lipid bilayers

Vital biological processes, such as trafficking, sensing, and motility, are facilitated by cellular lipid membranes, which interact mechanically with surrounding fluids. Such lipid membranes are only a few nanometers thick and composed of a liquid crystalline structure known as the lipid bilayer. Here, we introduce an active, noncontact, two-point microrheology technique combining multiple optical tweezers probes with planar freestanding lipid bilayers accessible on both sides. We use the method to quantify both fluid slip close to the bilayer surface and transmission of fluid flow across the structure, and we use numerical simulations to determine the monolayer viscosity and the intermonolayer friction. We find that these physical properties are highly dependent on the molecular structure of the lipids in the bilayer. We compare ordered-phase with liquid disordered-phase lipid bilayers, and we find the ordered-phase bilayers to be 10 to 100 times more viscous but with 100 times less intermonolayer friction. When a local shear is applied by the optical tweezers, the ultralow intermonolayer friction results in full slip of the two leaflets relative to each other and as a consequence, no shear transmission across the membrane. Our study sheds light on the physical principles governing the transfer of shear forces by and through lipid membranes, which underpin cell behavior and homeostasis.

Fe-X-B-Cu (X = Nb, NiZr) Alloys Produced by Mechanical Alloying: Influence of Milling Device

In this work, we analyze the influence of the milling device in the microstructural evolution of two Fe-X-B-Cu (X = Nb, NiZr) alloys produced by mechanical alloying (MA). The two milling devices are a planetary mil (P7) and a shaker mill (SPEX 8000). Microstructural analysis by X-ray diffraction detects the formation of a Fe rich solid solution. In the Fe-Nb-B-Cu alloy produced in the shaker mill also appears a Nb(B) minor phase, whereas in the Fe-NiZr-B-Cu alloy produced in the planetary mill, a minor disordered phase is formed. The comparative study regarding the energy transferred per unit of time in both devices determines that the shaker mill is more energetic. This fact explains that in the Fe-Nb-B-Cu alloy, Nb has not been introduced in the main Fe rich phase, whereas in the Fe-NiZr-B-Cu alloy milled in the shaker mill was formed the highly disordered phase. With regard to thermal analysis, the values of the apparent activation energies of the main crystallization process (above 200 kJ/mol) correspond to the crystalline growth of the nanocrystalline Fe rich phase.

Lipid phase dependent distinct emission behaviour of hydrophobic carbon dots: C-dots based membrane probe

We observe an unique distinct emission behaviour of hydrophobic carbon dots (H-CDs) embedded within the ordered and the disordered phase of the lipid membrane. The H-CDs exhibit the blue emission...