Equipartition is a first principle in wave transport, based on the tendency of multiple scattering to homogenize phase space. We report observations of this principle for seismic waves created by earthquakes in Mexico. We find qualitative agreement with an equipartition model that accounts for mode conversions at the Earth's surface.

Using near-field optical microscopy, we investigate propagation and scattering of surface plasmon polaritons (SPP's) excited in the wavelength range of 780–820 nm at nanostructured gold-film surfaces with areas of 200-nm-wide scatterers arranged in a 400-nm-period triangular lattice containing line defects. We observe the SPP reflection by such an area and SPP guiding along line defects at 782 nm, as well as significant deterioration of these effects is 815 nm, thereby directly demonstrating the SPP band gap effect and showing first examples of SPP channel waveguides in surface band gap structures.

The Internet has a very complex connectivity recently modeled by the class of scale-free networks. This feature, which appears to be very efficient for a communications network, favors at the same time the spreading of computer viruses. We analyze real data from computer virus infections and find the average lifetime and persistence of viral strains on the Internet. We define a dynamical model for the spreading of infections on scale-free networks, finding the absence of an epidemic threshold and its associated critical behavior. This new epidemiological framework rationalizes data of computer viruses and could help in the understanding of other spreading phenomena on communication and social networks.

We consider inertial particles suspended in an incompressible turbulent flow. Because of particles' inertia their flow is compressible, which leads to fluctuations of concentration significant for heavy particles. We show that the statistics of these fluctuations is independent of details of the velocity statistics, which allows us to predict that the particles cluster on the viscous scale of turbulence and describe the probability distribution of concentration fluctuations. We discuss the possible role of the clustering in the physics of atmospheric aerosols, in particular, in cloud formation.

Composites with negative stiffness inclusions in a viscoelastic matrix are shown to have higher stiffness and mechanical damping $\tan \delta$ than that of either constituent and exceeding conventional bounds. The causal mechanism is a greater deformation in and near the inclusions than the composite as a whole. Though a block of negative stiffness is unstable, negative stiffness inclusions in a composite can be stabilized by the surrounding matrix. Such inclusions may be made from single domains of ferroelastic material below its phase transition temperature or from prebuckled lumped elements.

We describe in situ synthesis and characterization of single-walled BN nanotubes terminated by fullerenelike structures using electron-cyclotron resonance nitrogen and electron beam boron sources onto polycrystalline tungsten substrates. Detailed comparisons of experimental high-resolution electron microscopy images and simulations based upon molecular models show a dominance of kinks and bends involving fourfold and eightfold ring structures as against fivefold or sevenfold which have been found with carbon. Analysis of the structures as a function of film thickness indicates that they are growing by addition of atoms to the exposed ends of single sheets, not at the substrate-nanostructure interface.

We report on the first measurement of a hypernuclear $\gamma$-transition probability. $\gamma$ rays emitted in the $E2\mathrm{}(5/2^{+}\to 1/2^{+})$ transition of ${}_{\Lambda }^7\mathrm{Li}$ were detected by a large-acceptance germanium detector array (Hyperball), and the lifetime of the parent state ( $5/2^{+}$) was determined by the Doppler shift attenuation method. The obtained result, ${5.8}_{-0.7\mathrm{}}^{+0.9\mathrm{}}\pm 0.7\mathrm{ps}$, was then converted into the reduced transition probability [ $B\left(E2\mathrm{}\right)$] to be $B({E2;5/2\mathrm{}}^{+}\to {1/2}^{+})=3.6\mathrm{}\pm {0.5}_{-0.4\mathrm{}}^{+0.5\mathrm{}}{e}^2{\mathrm{fm}}^4$. Compared with the $B\left(E2\mathrm{}\right)$ of the corresponding $E2\mathrm{}(3^{+}\to 1^{+})$ transition in the ${}^6\mathrm{Li}$ nucleus, our result gives evidence that the size of the ${}^6\mathrm{Li}$ core in ${}_{\Lambda }^7\mathrm{Li}$ is smaller than the ${}^6\mathrm{Li}$ nucleus in the free space.

A principle for stereoscopic photographs that enables viewing three-dimensional atomic arrangements is proposed. The azimuthal shifts of forward-focusing peaks in the photoelectron diffraction pattern obtained by left and right helicity lights enables a stereoscopic image when the two images are, respectively, viewed by the left eye and the right eye simultaneously. By taking advantage of this phenomenon, a display-type spherical-mirror analyzer can obtain stereoscopic photographs directly on the screen without any computer-aided conversion process.

Motivated by higher-dimensional theories that predict new effects, we tested the gravitational $1/r^2$ law at separations ranging down to $218\mu \mathrm{m}$ using a 10-fold symmetric torsion pendulum and a rotating 10-fold symmetric attractor. We improved previous short-range constraints by up to a factor of 1000 and find no deviations from Newtonian physics.

We find that tracer material can be concentrated into invariant regions of flows due exclusively to transient effects, as are produced when tracers temporarily become more buoyant than the surrounding fluid. This can occur either as a single event, e.g., if the tracer is initially weakly buoyant, or under periodic forcing, e.g., when external effects (such as solar heating) change the tracer density periodically. We study both cases in experiments, in a model, and in direct numerical simulations of laminar flow in a stirred tank. Focusing occurs for very small tracer size and inertia in flows that are instantaneously strictly volume conserving.

A microscopic theory for the ubiquitous phenomenon of static friction is presented. Interactions between two surfaces are modeled by an energy penalty that increases exponentially with the degree of surface overlap. The resulting static friction is proportional to load, in accordance with Amontons's laws. However, the friction coefficient between bare surfaces vanishes as the area of individual contacts grows, except in the rare case of commensurate surfaces. An area independent friction coefficient is obtained for any surface geometry when an adsorbed layer of mobile atoms is introduced between the surfaces. The predictions from our simple analytic model are confirmed by detailed molecular dynamics simulations.

New sideband partners of the yrast bands built on the $\pi h_{11/2}\nu h_{11/2}$ configuration were identified in ${}_{55}\mathrm{Cs}$, ${}_{57}\mathrm{La}$, and ${}_{61}\mathrm{Pm}$ $N=75\mathrm{}$ isotones of ${}^{134}\mathrm{Pr}$. These bands form with ${}^{134}\mathrm{Pr}$ unique doublet-band systematics suggesting a common basis. Aplanar solutions of 3D tilted axis cranking calculations for triaxial shapes define left- and right-handed chiral systems out of the three angular momenta provided by the valence particles and the core rotation, which leads to spontaneous chiral symmetry breaking and the doublet bands. Small energy differences between the doublet bands suggest collective chiral vibrations.

An ultracold narrow atomic beam of metastable neon in the ${1s}_3\left[\right(2s{)}^{5}3p:{}_{}{}^1{}_{}{}^{}P_0^{}{}_{}{}^{}]$ state is used to study specular reflection of atoms from a solid surface at extremely slow incident velocity. The reflectivity on a silicon (1,0,0) surface and a BK7 glass surface is measured at the normal incident velocity between $1\mathrm{mm}/\mathrm{s}$ and $3\mathrm{cm}/\mathrm{s}$. The reflectivity above $30\%$ is observed at about $1\mathrm{mm}/\mathrm{s}$. The observed velocity dependence is explained semiquantitatively by the quantum reflection that is caused by the attractive Casimir–van der Waals potential of the atom-surface interaction.

We report the first observation of a striking history dependence of the structure function of vortex matter in the peak effect regime in a Nb single crystal by using small angle neutron scattering combined with in situ magnetic susceptibility measurements. Metastable phases of vortex matter, supercooled vortex liquid and superheated vortex solid, have been identified. We interpret our results as direct structural evidence for a first-order vortex solid-liquid transition at the peak effect.

Spatiotemporal magnetization reversal dynamics in a ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ microstructure is studied using ps time scale scanning Kerr microscopy. Time domain images reveal a striking change in the reversal associated with the reduction in switching time when a transverse bias field is applied. Magnetization oscillations subsequent to reversal are observed at two resonance frequencies, which sensitively depend on the bias field strength. The oscillation at $f=2\mathrm{}$ GHz is caused by the damped precession of $\mathbf{M}$, while the lower frequency $\sim 0.8$ GHz mode is interpreted in terms of domain wall oscillation.

We report conduction measurements on the clean, free surface of transparent insulating $\mathrm{BaTiO}{}_3$ single crystals in high vacuum. We find that the insulating $\mathrm{BaTiO}{}_3$ crystals exhibit surface conductance that is dependent on the spontaneous polarization, whereas no conduction perpendicular to the surface is observed. The surface conduction shows semimetallic temperature dependence and persists down to at least 100 K. The observations suggest a two-dimensional electron on a clean, free ferroelectric surface that may be regarded as a ferroelectric metal. The results have important implications for understandings of the fundamental properties of ferroelectrics, the size effect, and ferroelectric devices.

We study experimentally the jamming phenomenon of granular flow of monodisperse disks of $D=5\mathrm{}\mathrm{mm}$ diameter in a two-dimensional hopper with opening $R$. The jamming probability $J\left(d\right)$ is measured where $d\equiv R/D$. We found that $J\left(d\right)$ decreases from 1 to zero when $d$ increases from 2 to 5. From observing the disk configurations of the arch in the jamming events, the jamming probability can be explained quantitatively by treating the arch as the trajectory of a restricted random walker.

We propose a model for stochastic formation of opinion clusters, modeled by an evolving network, and herd behavior to account for the observed fat-tail distribution in returns of financial-price data. The only parameter of the model is $h$, the rate of information dispersion per trade, which is a measure of herding behavior. For $h$ below a critical $h^{*}$ the system displays a power-law distribution of the returns with exponential cutoff. However, for $h>\mathrm{}{h}^{*}$ an increase in the probability of large returns is found and may be associated with the occurrence of large crashes.

Electron microscope imaging for gadolinium metallofullerenes encapsulating in single-wall carbon nanotubes $\left[\right(\mathrm{Gd}@\mathrm{C}{}_{82}{)}_n@\mathrm{SWNTs}]$ identifies the single Gd atom encaged in each. The intermolecular distance between $\mathrm{Gd}@\mathrm{C}{}_{82}$ is extremely regular, regarding the chains of $\mathrm{Gd}@\mathrm{C}{}_{82}$ as novel one-dimensional crystals. Chemical state analysis of Gd atoms suggests evidence for charge transfer from Gd to either a fullerene cage or a nanotube. The slopes of the temperature dependence of electric resistance for the matlike films of $(\mathrm{Gd}@\mathrm{C}{}_{82}{)}_n@\mathrm{SWNTs}$ and $(\mathrm{C}{}_{60}{)}_n@\mathrm{SWNTs}$ are much steeper than that for empty SWNTs, suggesting the electron scattering due to the electrostatic potential from inside fullerenes playing an important role.

We calculate the shadow image in far field below a thin crystal when a coherent electron source is placed at micrometer distances above the specimen, and note that the presence of a planar fault results in very strong oscillatory contrast. We realize these predictions experimentally using a field-emission electron source in a microscope. With this technique, we determine displacement vectors at planar faults with an accuracy down to 1 pm in studies of the ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_8$ superconductor containing thin intercalated layers.