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A qualitative model that relates the period of the surface roughness to the vertical and spherical growth rates of glancing angle deposited (GLAD) nanorods suggests that rod self-shadowing is responsible for the previously reported temperature dependence in the rod width. Atomic shadowing interactions between neighboring rods as well as surface islands on the rod growth fronts control the morphological evolution which is quantified by the growth exponent p that relates the rod width w (=Ahp) to their height h. An analytical formalism predicts linear dependences of p and A on the average island separation and provides an explanation for reported anomalous p values. Experimental validation using new and previously published GLAD data for Al, Cr, Nb, and Ta shows quantitative agreement for all metallic systems under consideration and confirms the predicted dependences. In addition, a discontinuity in the p versus homologous deposition temperature θ suggests a critical value θc=0.24±0.02 for a transition from two-dimensional to three-dimensional island growth, which is independently confirmed by a discontinuity in the measured island width. [ABSTRACT FROM AUTHOR]

Polymers are naturally polydisperse. Polydispersity may have a large effect on the phase behavior of polymer solutions, in particular, on the liquid-liquid phase equilibria. In this paper, we determine the cloud and shadow curves bounded by lower critical solution temperatures for a number of polymer+solvent systems where the polymer is polydisperse in terms of molecular weight (chain length). The moment method [P. Sollich, P. B. Warren, and M. E. Cates, Adv. Chem. Phys. 116, 265 (2001)] is applied with the SAFT approach to determine cloud and shadow curves with continuous Schulz-Flory distributions. It is seen that chain length polydispersity always enhances the extent of liquid-liquid phase equilibria. The predicted cloud curves obtained for continuous distributions are very similar to those obtained for simple ternary mixtures with the same polydispersity index, while the corresponding shadow curves can be very different depending on the composition of the parent distribution. The ternary phase behavior can be used to provide an understanding of the shape of the cloud and shadow curves. Regions of phase equilibria between three liquid phases are found for ternary systems when the chain length distribution is very asymmetrical; such regions are not observed for Schulz-Flory distributions even in the case of a large degree of polydispersity. [ABSTRACT FROM AUTHOR]

We present a variational implementation of the Verlet algorithm for molecular dynamics which is both conceptually and computationally attractive. Given an approximate path, this variational Verlet algorithm computes an actual trajectory close to the path. Instead of initial conditions, we specify end-point conditions, which makes it possible to compute trajectories with fixed end points as well as trajectories that are exactly periodic (nonlinear modes of vibration). With a simple sign change, the method yields approximate reaction pathways. We present several applications which illustrate how this alternative approach to dynamics can yield unusual trajectories that are difficult to attain by conventional means. In our first model system, a simple double well, we examine the seemingly paradoxical shadowing lemma of classical mechanics which claims that, in spite of the cumulative numerical errors which cause rapid deviation from the correct path, a calculated trajectory can still be close to some true trajectory of the system over a relatively long time period. We explicitly calculate such so-called shadowing trajectories. We also study isomerization events in which trajectories cross from one potential well to another, obtaining guesses from simple line segments and from dynamics on a perturbed version of the double-well potential. A closed loop of briefly recurrent motion in a trajectory can serve as an initial guess in the computation of a large-amplitude nonlinear mode of vibration. Finally, we use a model AB+C reaction in rare-gas solution to demonstrate the feasibility of calculations on molecular systems with many degrees of freedom. A gas-phase reactive trajectory of the A, B, and C atoms is, with the variational Verlet algorithm, transformed into a similar solution-phase trajectory and vice versa. This calculation suggests that rare events, such as reactions in solution, may be obtained through refining initial paths of perturbed or decoupled systems... [ABSTRACT FROM AUTHOR]

We explore connections among the regional proximal relation, the asymptotic relation, and the distal relation for a topological dynamical system with the shadowing property and show that if a Devaney chaotic system has the shadowing property then it is distributionally chaotic. [ABSTRACT FROM AUTHOR]

Flow of magnetized plasma past an obstacle creates a traditional wake, but also a forewake region arising from shadowing of electrons. The electron forewakes resulting from supersonic flows past insulating and floating-potential obstacles are explored with 2D electrostatic particle-in-cell simulations, using a physical ion to electron mass ratio. Drift-energization is discovered to give rise to modifications to the electron velocity-distribution, including a slope-reversal, providing a novel drive of forewake instability. The slope-reversal is present at certain locations in all the simulations, and appears to be quite robustly generated. Wings of enhanced electron density are observed in some of the simulations, also associated with drift-energization. In the simulations with a floating-potential obstacle, the specific potential structure behind that obstacle allows fast electrons to cross the wake, giving rise to a more traditional shadowing-driven two-stream instability. Fluctuations associated with such instability are observed in the simulations, but this instabilitymechanism is expected to be more sensitive to the plasma parameters than that associated with the slope-reversal. [ABSTRACT FROM AUTHOR]

Arrays of Ta nanorods were grown by glancing angle deposition (GLAD)onto honeycomb Cr nanodot patterns that were evaporated onto Si substrates through a self-assembled monolayer of SiO2 nanospheres. Statistical size analyses from arrays of rods with variable average length l and width w, with 210 nm≤1≤650 nm and 109 nm≤w≤304 nm, show that the distribution in w broadens with increasing l and decreasing w, but remains approximately constant with a fixed l/w ratio. This is attributed to an intercolumnar growth competition that exacerbates nanorod size fluctuations but scales with rod size. These results suggest that the overall nanostructure shapes during low-temperature GLAD are independent of material-specific length scales and are, therefore, completely controlled by the geometric shadowing [ABSTRACT FROM AUTHOR]

We have worked out the details of a single camera, single exposure method to perform three-dimensional imaging of a finite particle cluster. The procedure is based on the plenoptic imaging principle and utilizes a commercial Lytro light field still camera. We demonstrate the capabilities of our technique on a single layer particle cluster in a dusty plasma, where the camera is aligned and inclined at a small angle to the particle layer. The reconstruction of the third coordinate (depth) is found to be accurate and even shadowing particles can be identified. [ABSTRACT FROM AUTHOR]