Can we predict diffusion behavior of molecules in confinement by looking at the match between the molecule and the structure of the confinement? This question has proven difficult to answer for many decades. As a case study, we use methane and a simple model of ellipsoids to arrive at a molecular picture that allows us to make a classification of pore topologies and to explain their diffusion behavior as a function of loading. Our model is surprisingly simple: regarding a structure as consisting of interconnected ellipsoids is enough to understand the full loading dependence.

The classical experiments on turbulent friction in rough pipes were performed by Nikuradse in the 1930s. Seventy years later, they continue to defy theory. Here we model Nikuradse’s experiments using the phenomenological theory of Kolmogórov, a theory that is widely thought to be applicable only to highly idealized flows. Our results include both the empirical scalings of Blasius and Strickler and are otherwise in minute qualitative agreement with the experiments; they suggest that the phenomenological theory may be relevant to other flows of practical interest; and they unveil the existence of close ties between two milestones of experimental and theoretical turbulence.

I present empirical evidence that turbulent flows are closely analogous to critical phenomena, from a reanalysis of friction factor measurements in rough pipes. The data collapse found here corresponds to Widom scaling near critical points, and implies that a full understanding of turbulence requires explicit accounting for boundary roughness.

We present a method to reduce the ${\mathbb{R}}^N$ dynamics of coupled map lattices (CMLs) of $N$ invertibly coupled unimodal maps to a sequence of $N$-bit symbols. We claim that the symbolic description is complete and provides for the identification of all fixed points, periodic orbits, and dense orbits as well as an efficient representation for studying pattern formation in CMLs. We give our results for CMLs in terms of symbolic dynamical concepts well known for one-dimensional chaotic maps, including generating partitions, Gray orderings, and kneading sequences. An example utilizing coupled quadratic maps is given.

A unique, new stand-alone acoustic inertial confinement nuclear fusion test device was successfully tested. Experiments using four different liquid types were conducted in which bubbles were self-nucleated without the use of external neutrons. Four independent detection systems were used (i.e., a neutron track plastic detector to provide unambiguous visible records for fast neutrons, a ${\mathrm{BF}}_3$ detector, a NE-113-type liquid scintillation detector, and a NaI $\gamma$ ray detector). Statistically significant nuclear emissions were observed for deuterated benzene and acetone mixtures but not for heavy water. The measured neutron energy was $\le 2.45\mathrm{MeV}$, which is indicative of deuterium-deuterium (D-D) fusion. Neutron emission rates were in the range $\sim 5\times {10}^3\mathrm{n}/\mathrm{s}$ to $\sim {10}^4\mathrm{n}/\mathrm{s}$ and followed the inverse law dependence with distance. Control experiments did not result in statistically significant neutron or $\gamma$ ray emissions.

We perform numerical experiments to calculate the kinematic $\alpha$ effect for a family of maximally helical, chaotic flows with a range of correlation times. We find that the value of $\alpha$ depends on the structure of the flow, on its correlation time and on the magnetic Reynolds number in a nontrivial way. Furthermore, it seems that there is no clear relation between $\alpha$ and the helicity of the flow, contrary to what is often assumed for the parametrization of mean-field dynamo models.

In zero gravity, liquid does not drip from a tube but hangs from it for all time as a pendant drop. It is shown that a drop can be made to fall off a tube by heating the contact line (CL), which causes a temperature gradient between the drop’s CL and its tip. Simulations show that whether a drop detaches from or remains attached to the tube is set by the competition between the Marangoni stress that causes flow away from its CL, where the surface tension $\sigma$ is low, toward its tip, where $\sigma$ is high, and the capillary pressure that causes flow from the tip back toward the CL. The method can be used to make microscopic (nanoscopic) drops by dripping in ordinary gravity, which had heretofore been unattainable.

We investigate the interaction dynamics of an existing stable microbubble $B_1$ and another laser induced nearby expanding microbubble $B_2$ in a thin ink sheet between two glass slices. The fast expanding $B_2$ causes anistropic compression of $B_1$ with a forward penetrating jet. In the subsequent expansion stage of $B_1$, the gas associated with jet protrusion to the opposite edge of $B_1$ and the nonuniform surrounding flow field induce necking with transverse inward jetting from the side lobes, which further interact with the axial jet and lead to the final fragmentation into smaller bubbles. At small interbubble distance, the backward interaction from $B_1$ first leads to the pointed pole of the expanding $B_2$ and then a backward jetting during its collapsing. The strong interaction can merge the two bubbles with complicated asymmetric intermediated patterns.

We show that a saddle point Van Hove singularity in a band adjacent to a photonic crystal band gap can lead to situations which defy the conventional wisdom that the strongest band-gap confinement is found at frequencies near the midgap. As an example, we present a two-dimensional square photonic crystal waveguide where the strongest confinement is close to the band edge. The underlying mechanism can also apply to any system that is described by a band structure with a gap. In general, the saddle point favors the appearance of a very flat band, which in turn results in an enhanced confinement at band-gap frequencies immediately above or below the flat band.

We experimentally demonstrate that the near-field patterns of conical second harmonic generation of a laser in random domain structures can be used to explore the spatial structure of two-dimensional disordered wave functions with weak localization. The statistics of the experimental near-field patterns agree very well with the theoretical distributions. In addition to the short-range correlation, the localization effects are found to contribute a nearly constant value to the long-range correlation. The result of this Letter also confirms the possibility of using conical second harmonic generation as a diagnostic tool for topographical characterization of crystals.

The effects of disorder in external forces on the dynamical behavior of coupled nonlinear oscillator networks are studied. When driven synchronously, i.e., all driving forces have the same phase, the networks display chaotic dynamics. We show that random phases in the driving forces result in regular, periodic network behavior. Intermediate phase disorder can produce network synchrony. Specifically, there is an optimal amount of phase disorder, which can induce the highest level of synchrony. These results demonstrate that the spatiotemporal structure of external influences can control chaos and lead to synchronization in nonlinear systems.

Nonlinear interactions between the baroclinic Rossby waves trapped in the equatorial waveguide and the barotropic Rossby waves freely propagating across the equator are studied within the two-layer model of the atmosphere, or the ocean. It is shown that a barotropic wave can resonantly excite a pair of baroclinic waves with amplitudes much greater than its proper amplitude. The envelopes of the baroclinic waves obey Ginzburg-Landau-type equations and exhibit nonlinear saturation and formation of characteristic “domain-wall” and “dark-soliton” defects.

In this Letter, we experimentally show that the amplitude and arrival time of the terahertz optical transmission through dense ensembles of subwavelength-size ferromagnetic particles is strongly dependent on the orientation of an externally applied magnetic field. The attenuation and delay have the same magnetic field orientation dependence as the electrical anisotropic magnetoresistance inherent to bulk ferromagnetic metals. We envision the application of this magnetic effect in terahertz photonic devices.

We present experimental observations of polarization vector fields from a highly isotropic microchip laser with a large Fresnel number. The experimental polarization vector field leads to complex entanglement of spatial structures and polarization states. We theoretically derive the representation of generalized coherent states to reconstruct the experimental polarization-resolved patterns. The analytical and precise reconstruction enables the vector singularities to be clearly visualized.

Lasing was achieved in a new type of random laser: the planar random microcavity laser. The laser consists of a planar microcavity with a random gain layer. Optical confinement by the two-dimensional random cavity and the one-dimensional planar microcavity drastically reduces the number of resonant modes. As a result, the laser output is highly directional (the divergence angle is 1.68°) with an extremely narrow-linewidth and ultralow threshold. All these phenomena are explained in terms of the coupling of random cavity modes and planar microcavity modes. The results demonstrate an important step towards applications of random lasers.

Realistic networks display not only a complex topological structure, but also a heterogeneous distribution of weights in the connection strengths. Here we study synchronization in weighted complex networks and show that the synchronizability of random networks with a large minimum degree is determined by two leading parameters: the mean degree and the heterogeneity of the distribution of node’s intensity, where the intensity of a node, defined as the total strength of input connections, is a natural combination of topology and weights. Our results provide a possibility for the control of synchronization in complex networks by the manipulation of a few parameters.

A method for stabilizing periodic orbits and steady states of chaotic systems is presented using specifically filtered feedback signals. The efficiency of this control technique is illustrated with simulations (Rössler system, laser model) and a successful experimental application for stabilizing intensity fluctuations of an intracavity frequency-doubled $\mathrm{Nd}:\mathrm{YAG}$ laser.

The behavior of topological solitons in a parallel array of a Josephson junction is studied experimentally. We observe the fusion of two relativistic $2\pi$ solitons of the same polarity into a single $4\pi$ soliton. The $4\pi$ soliton carries two quanta of magnetic flux and, most strikingly, travels 18% faster than an ordinary $2\pi$ soliton under the same driving force. We also find a variety of bunched states composed of $2\pi$ solitons of the same polarity, moving with fixed separation.

In our experiment, an interface between a viscous liquid and air is deformed by a sink flow of constant flow rate to form a sharp tip. Using a microscope, the interface shape is recorded down to a tip size of $1\mu \mathrm{m}$. The curvature at the tip is controlled by the distance $h$ between the tip and the sink. As a critical distance $h^{*}$ is approached, the curvature diverges like $1/(h-h^{*}{)}^3$ and the tip becomes cone shaped. As the distance to the sink is decreased further, the opening angle of the cone vanishes like $h^2$. No evidence for air entrainment was found, except when the tip was inside the orifice.

Three different types of chaotic behavior and instabilities (homoclinic chaos, hyperbolic resonance, and parabolic resonance) in Hamiltonian perturbations of the nonlinear Schrödinger (NLS) equation are described. The analysis is performed on a truncated model using a novel framework in which a hierarchy of bifurcations is constructed. It is demonstrated numerically that the forced NLS equation exhibits analogous types of chaotic phenomena. Thus, by adjusting the forcing frequency, the behavior near the plane wave solution may be set to any one of the three different types of chaos for any periodic box length.