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Interface-roughening phase diagram of the three-dimensional Ising model for all interaction anisotropies from hard-spin mean-field theory
No full textThe roughening phase diagram of the d = 3 Ising model with uniaxially anisotropic interactions is calculated for the entire range of anisotropy, from decoupled planes to the isotropic model to the solid-on-solid model, using hard-spin mean-field theory. The phase diagram contains the line of ordering phase transitions and, at lower temperatures, the line of roughening phase transitions, where the interface between ordered domains roughens. Upon increasing the anisotropy, roughening transition temperatures settle after the isotropic case, whereas the ordering transition temperature increases to infinity. The calculation is repeated for the d = 2 Ising model for the full range of anisotropy, yielding no roughening transition
Quenched-vacancy induced spin-glass order
No full textThe ferromagnetic phase of an Ising model in d=3, with any amount of quenched antiferromagnetic bond randomness, is shown to undergo a transition to a spin-glass phase under sufficient quenched bond dilution. This result, demonstrated here with the numerically exact global renormalization-group solution of a d=3 hierarchical lattice, is expected to hold true generally, for the cubic lattice and for quenched site dilution. Conversely, in the ferromagnetic-spin-glass-antiferromagnetic phase diagram, the spin-glass phase expands under quenched dilution at the expense of the ferromagnetic and antiferromagnetic phases. In the ferromagnetic-spin-glass phase transition induced by quenched dilution, reentrance as a function of temperature is seen, as previously found in the ferromagnetic-spin-glass transition induced by increasing the antiferromagnetic bond concentration
Stepwise positional-orientational order and the multicritical-multistructural global phase diagram of the s=3/2 Ising model from renormalization-group theory
No full textThe spin-3/2 Ising model, with nearest-neighbor interactions only, is the prototypical system with two different ordering species, with concentrations regulated by a chemical potential. Its global phase diagram, obtained in d = 3 by renormalization-group theory in the Migdal-Kadanoff approximation or equivalently as an exact solution of a d = 3 hierarchical lattice, with flows subtended by 40 different fixed points, presents a very rich structure containing eight different ordered and disordered phases, with more than 14 different types of phase diagrams in temperature and chemical potential. It exhibits phases with orientational and/or positional order. It also exhibits quintuple phase transition reentrances. Universality of critical exponents is conserved across different renormalization-group flow basins via redundant fixed points. One of the phase diagrams contains a plastic crystal sequence, with positional and orientational ordering encountered consecutively as temperature is lowered. The global phase diagram also contains double critical points, first-order and critical lines between two ordered phases, critical end points, usual and unusual (inverted) bicritical points, tricritical points, multiple tetracritical points, and zero-temperature criticality and bicriticality. The four-state Potts permutation-symmetric subspace is contained in this model
Scale-free network hidden in a collapsing polymer
No full textWe show that the collapsed globular phase of a polymer accommodates a scale-free incompatibility graph of its contacts. The degree distribution of this network is found to decay with the exponent gamma=1/(2-c) up to a cutoff degree d(c)proportional to L2-c, where c is the loop exponent for dense polymers (c=11/8 in two dimensions) and L is the length of the polymer. Our results exemplify how a scale-free network can emerge from standard criticality
Effects of viscoelasticity on drop impact and spreading on a solid surface
No full textThe effects of viscoelasticity on drop impact and spreading on a flat solid surface are studied computationally using a finite-difference-front-tracking method. The finitely extensible nonlinear elastic-Chilcott-Rallison model is used to account for the fluid viscoelasticity. It is found that viscoelasticity favors advancement of contact line during the spreading phase, leading to a slight increase in the maximum spreading, in agreement with experimental observations [Huh, Jung, Seo, and Lee, Microfluid. Nanofluid. 18, 1221 (2015)]. However, in contrast with the well-known antirebound effects of polymeric additives, the viscoelasticity is found to enhance the tendency of the drop rebound in the receding phase. These results suggest that the antirebound effects are mainly due to the polymer-induced modification of wetting properties of the substrate rather than the change in the material properties of the drop fluid. A model is proposed to test this hypothesis. It is found that the model results in good qualitative agreement with the experimental observations and the antirebound behavior can be captured by the modification of surface wetting properties in the receding phase
Twist-writhe partitioning in a coarse-grained DNA minicircle model
No full textHere we present a systematic study of supercoil formation in DNA minicircles under varying linking number by using molecular-dynamics simulations of a two-bead coarse-grained model. Our model is designed with the purpose of simulating long chains without sacrificing the characteristic structural properties of the DNA molecule, such as its helicity, backbone directionality, and the presence of major and minor grooves. The model parameters are extracted directly from full-atomistic simulations of DNA oligomers via Boltzmann inversion; therefore, our results can be interpreted as an extrapolation of those simulations to presently inaccessible chain lengths and simulation times. Using this model, we measure the twist/writhe partitioning in DNA minicircles, in particular its dependence on the chain length and excess linking number. We observe an asymmetric supercoiling transition consistent with experiments. Our results suggest that the fraction of the linking number absorbed as twist and writhe is nontrivially dependent on chain length and excess linking number. Beyond the supercoiling transition, chains of the order of one persistence length carry equal amounts of twist and writhe. For longer chains, an increasing fraction of the linking number is absorbed by the writhe
Phase-space invariants as indicators of the critical behavior of nanoaggregates
No full textA phase-space approach is proposed for molecular dynamics simulations, which serve as a bridge between detailed descriptions of microscopic world and macroscopic properties of matter. The introduction-aside from the angular momentum of spatial rotations-of other "hyperangular" momenta (the overall grand angular momentum of a cluster of particles and those describing the deformation and rearrangement modes) permits one to analyze different degrees of freedom and to extract, from simulation data, a kinetic energy partition in terms of phase-space invariants. Model calculations illustrate how these provide specific signatures of critical behavior, such as energy thresholds for openings of chaotic pathways in small clusters and for phase transitions in nanoaggregates
Morphology and crystal structure control of alpha-Fe2O3 films by hydrothermal-electrochemical deposition in the presence of Ce3+ and/or acetate, F- ions
No full textHydrothermal-electrochemical growth of Hematite (alpha-Fe2O3) thin films in the presence of Ce3+ and/or CH3COO- and F- ions is reported. Primary attention is paid to understanding the synergistic effect of temperature and additive ions on the growth of Hematite particles. The literature describes the shape-controlled electrodeposition of iron oxide films, but these reports involve low-temperature depositions (<100 degrees C) that require a post-annealing step to obtain the Hematite phase. We studied size and shape control of Hematite crystals by introducing capping agents during hydrothermal-electrochemical deposition (HED) at 130 degrees C under autonomous pressure. When HED is used together with growth-modifying species such as CH3COO- and/or Ce3+, Hematite thin films with various structures including spherical, rhombohedral and platelet-like particles were obtained which were crystallized directly in the alpha-Fe2O3 phase without thermal annealing. In contrast, either Lepidocrocite or an amorphous phase forms with low-temperature electrodeposition under otherwise identical conditions. Addition of F- into the deposition solution induces formation of bundles that are composed of square planar Akaganeite particles even during HED. The aspect ratio of the Akaganeite particles is controlled with co-addition of Ce3+ ions. This variety of nanostructures gives us the opportunity to evaluate the photoelectrochemical performance of the alpha-Fe2O3 films based on particle size and shape. It was demonstrated that porous, square planar alpha-Fe2O3 with a high aspect ratio shows the highest performance
Silicon microspheres for mid infrared photonics - art. no. 64770C
No full textMicrospheres possess high quality factor morphology-dependent resonances, i.e., whispering gallery modes. These whispering gallery modes can be used in resonant cavity enhanced applications of optoelectronic devices such as, filters, detector, modulators and switches. Feasibility of silicon microsphere device at Mid-IR frequencies is studied. The high quality factor morphology dependent resonances have repetitive channel separations of 0.124 mu m in silicon microspheres with a radius of 50 mu m at wavelengths between 9.8 mu m and 10.6 mu m
Pearls and pitfalls in surgery for endometrioma
No full textEndometrioma surgery should be planned and executed very carefully as it is associated with risks that may hamper future reproductive potential. Symptoms, age, risk of malignancy, bilaterality, ovarian reserve, and desire to have children should all be taken into account prior to surgical intervention. Cyclic and noncyclic severe pain may be an indicator or deep infiltrating diseases. Laparoscopic surgery is the gold standard, however, the issue of resection versus ablation should be further studied