Scaling in Late Stage Spinodal Decomposition with Quenched Disorder

We study the late stages of spinodal decomposition in a Ginzburg-Landau mean field model with quenched disorder. Random spatial dependence in the coupling constants is introduced to model the quenched disorder. The effect of the disorder on the scaling of the structure factor and on the domain growth is investigated in both the zero temperature limit and at finite temperature. In particular, we find that at zero temperature the domain size, $R(t)$, scales with the amplitude, $A$, of the quenched disorder as $R(t) = A^{-\beta} f(t/A^{-\gamma})$ with $\beta \simeq 1.0$ and $\gamma \simeq 3.0$ in two dimensions. We show that $\beta/\gamma = \alpha$, where $\alpha$ is the Lifshitz-Slyosov exponent. At finite temperature, this simple scaling is not observed and we suggest that the scaling also depends on temperature and $A$. We discuss these results in the context of Monte Carlo and cell dynamical models for phase separation in systems with quenched disorder, and propose that in a Monte Carlo simulation the concentration of impurities, $c$, is related to $A$ by $A \sim c^{1/d}$.Comment: RevTex manuscript 5 pages and 5 figures (obtained upon request via email [email protected]

The screens culture: impact on ADHD

Children’s use of electronic media, including Internet and video gaming, has increased dramatically to an average in the general population of roughly 3 h per day. Some children cannot control their Internet use leading to increasing research on “internet addiction.” The objective of this article is to review the research on ADHD as a risk factor for Internet addiction and gaming, its complications, and what research and methodological questions remain to be addressed. The literature search was done in PubMed and Psychinfo, as well as by hand. Previous research has demonstrated rates of Internet addiction as high as 25% in the population and that it is addiction more than time of use that is best correlated with psychopathology. Various studies confirm that psychiatric disorders, and ADHD in particular, are associated with overuse, with severity of ADHD specifically correlated with the amount of use. ADHD children may be vulnerable since these games operate in brief segments that are not attention demanding. In addition, they offer immediate rewards with a strong incentive to increase the reward by trying the next level. The time spent on these games may also exacerbate ADHD symptoms, if not directly then through the loss of time spent on more developmentally challenging tasks. While this is a major issue for many parents, there is no empirical research on effective treatment. Internet and off-line gaming overuse and addiction are serious concerns for ADHD youth. Research is limited by the lack of measures for youth or parents, studies of children at risk, and studies of impact and treatment

‘I gave that cue.’ Integrating dance studies, praxeology, and computational perspectives to model change in the case study of William Forsythe’s Duo

Choreographer William Forsythe calls the work Duo a ‘project’—reflecting the piece’s long history of vicissitudes from 1996 to the present. We attempt to visualize continuity and change over several iterations of Duo, spanning a period of 20 years. Our methods involved graphical and statistical approaches to performance video annotation, considering seven videos acquired from Forsythe’s private archive. Collaboration with Duo dancers was critical to develop this choreographic knowledge. The duet Duo was chosen to focus on annotation of partnering, choreographic structure, and interpretation; the case study furthermore enabled review of annotation methods from Forsythe’s Synchronous Objects for One Flat Thing, reproduced (Forsythe et al. 2009) and built upon prior research of entrainment in Duo (Waterhouse, Watts, and Bläsing 2014). Studying a choreography longitudinally, with close regard of the performers’ testimonies and digital traces, the problem required innovative methods. For this article, we focus on how annotation was used within this project. We outline our particular interdisciplinary approach, merging perspectives from dance studies, praxeology and creative coding. We present the language and concepts of annotation chosen, technical tools used for annotating, procedures of annotation analysis, and conclusions of the research. Thereby we present novel visualizations of choreographic process

Kinetics of Phase Separation in the Presence of Two Disparate Energy Scales

We develop a dynamical model for phase separation in a system with two disparate energy scales. Monte Carlo computer simulations of this model reveal a "pinning" of the structure factor during spinodal decomposition that obeys new scaling relations. We propose a mechanism for the pinning which allows us to predict The model contains monomers and solvent molecules on a lattice, with the key feature that nearest-neighbor monomers can interact with two different energies One probe in phase separation experiments is the dynamic structure factor, S(k, t), which contains information on the time evolution of the various length scales k . In ordinary spinodal decomposition, the characteristic wave vector moves to smaller values of k following a quench to the unstable region. One measure of this characteristic wave vector is the first moment of S(k), ki = Q"kS(k)/Q"S(k

Pinning in phase-separating systems.

We study a dynamical model of a system with two disparate energy scales, and focus on the kinetics of phase separation. In this model, nearest-neighbor monomers can interact with one of two quite distinct energies, thereby describing a system with, e. g., van der Waals and hydrogen bond interactions. While the model has been described by an efFective Ising model in equilibrium, the nonequilibrium dynamics of phase separation have never been explored. Here we use Monte Carlo computer simulations of spinodal decomposition to show that the model exhibits "pinning" of the structure factor, a behavior also seen in phase-separating polymer gels and binary alloys with impurities. The rate of strong bond formation depends on an entropic parameter 0, and we fInd both the pinned domain size and the crossover time between "normal" spinodal decomposition and the pinning scale with 0 as power laws with exponents that relate simply to the usual growth exponent. We propose a speci6c mechanism for pinning that permits the prediction of exact values for the pinning exponents. Finally, we discuss applications of the model to binary alloys with quenched disorder and polymer gels