Large grains are well known to rise to the top of granular beds. In this Letter, we report to the contrary on a shaking regime in which large, heavy grains rise, but equally large, light grains sink in a granular bed. This behavior occurs in deep beds with high amplitude vibrations—precisely the regime encountered during transportation of industrial solids mixtures. We examine a simple one-dimensional model that captures some aspects of this effect. The central observation underlying this model is that inertia causes heavy objects to lift off the bed, permitting smaller particles to infiltrate beneath; the motion of light objects, by contrast, can fluctuate wildly, preventing this infiltration.

Charge symmetry for parton distributions can be tested by comparing structure functions from neutrino and charged lepton deep inelastic scattering. New experiments provide rather tight upper limits on parton charge symmetry violation (CSV) for intermediate $x$, but suggest CSV effects at small $x$. Careful study of several corrections fails to remove this low- $x$ discrepancy. We are thus forced to consider surprisingly large CSV effects in nucleon sea distributions.

It is quantitatively explained why incoherent transmission electron microscope imaging is extremely robust to the effects of chromatic aberration, which usually limits the resolution in the conventional coherent mode of imaging. Combining this robustness with using underfocus to counter the effects of spherical aberration, we demonstrate subangstrom lattice resolution and information transfer to 0.078 nm.

We report observation of Bose-Einstein condensation (BEC) of a trapped, dilute gas of atomic hydrogen. The condensate and normal gas are studied by two-photon spectroscopy of the $1S$- $2S$ transition. Interactions among the atoms produce a shift of the resonance frequency proportional to density. The condensate is clearly distinguished by its large frequency shift. The peak condensate density is $4.8\pm 1.1\times {10}^{15}{\mathrm{cm}}^{-3\mathrm{}}$, corresponding to a condensate population of ${10}^9$ atoms. The BEC transition occurs at about $T=50\mathrm{}\mu \mathrm{K}$ and $n=1.8\mathrm{}\times {10}^{14}{\mathrm{cm}}^{-3\mathrm{}}$.

A thin solid, burning against an oxidizing wind, develops a fingering instability. The effect is observed in a narrow gap geometry, where free convection is suppressed. Focusing on the developed nonlinear state, we find that two length scales coexist. The spacing between fingers is determined by the Péclet number, and the finger width is determined by heat losses. Dense fingers develop by tip splitting. A phenomenological model accurately predicts the fingers' spacing, and is generally applicable to diffusion limited systems. We suggest that the effect is a new, accurately controllable, version of the thermal-diffusive instability.

Through use of quantum coherence in an atomic system, we demonstrate that an optical field can be used to completely control the polarization state of another field. Theoretical and experimental results show that by applying a field with a frequency tuned near one transition, an initially isotropic atomic vapor can be made to behave as a linearly or circularly birefringent material for fields tuned near an adjoining transition.

The conductance of carbon-atom chains is found from first-principles calculations to vary in an oscillatory manner as the number of carbon atoms is increased, with odd-numbered chains having a lower resistance than even-numbered chains. This finding is explained in terms of the electronic structure of the free chains and its modification by interaction with the metal electrodes: the critical factor is the density of states at the Fermi level of the combined electrode–atomic-wire system. Stronger electrode–atomic-wire coupling, i.e., shorter metal-carbon distance, does not necessarily imply a higher conductance.

A working free-space quantum key distribution system has been developed and tested over an outdoor optical path of $\sim 1\mathrm{km}$ at Los Alamos National Laboratory under nighttime conditions. Results show that free-space quantum key distribution can provide secure real-time key distribution between parties who have a need to communicate secretly. Finally, we examine the feasibility of surface to satellite quantum key distribution.

We have combined electron heating experiments and noise thermometry to perform quantitative measurements of the thermopower in mesoscopic samples. This new measuring technique allows us to detect finite size effects in the thermopower of narrow AuFe wires with an Fe concentration ranging from 50 to 3000 ppm. The size effects emerge when reducing the width of the wires below $\simeq 300\mathrm{nm}$ and may be related to a spin-orbit induced magnetic anisotropy close to the wire surface.

In this paper we present results of experimental and theoretical studies of both elastic and inelastic scattering of fast electrons on the fullerene ${\mathrm{C}}_{60}$ in the gas phase. We report the first experimental observation of the electron diffraction on ${\mathrm{C}}_{60}$, manifesting itself in both elastic and inelastic scattering processes. Diffraction patterns of the cross sections carry important information about the characteristics of the target fullerene, such as its size, distribution of the charge density near the cluster surface, frequencies of plasmon resonance excitations, etc.

$(2+1)$-dimensional anti–de Sitter (AdS) gravity is quantized in the presence of an external scalar field. We find that the coupling between the scalar field and gravity is equivalently described by a perturbed conformal field theory at the boundary of ${\mathrm{AdS}}_3$. This allows us to perform a microscopic computation of the transition rates between black hole states due to absorption and induced emission of the scalar field. Detailed thermodynamic balance then yields Hawking radiation as spontaneous emission, and we find agreement with the semiclassical result, including greybody factors. This result also has application to four and five-dimensional black holes in supergravity.

Photonic molecules have been fabricated by coupling pairs of micrometer-sized semiconductor cavities via a narrow channel. The optical modes in these structures have been studied spectroscopically as a function of the coupling and the mode energies are compared to detailed calculations. These results provide a rich picture of photonic modes in these molecules.

We study several scale-independent measures of cardiac interbeat interval dynamics defined through the application of the wavelet transform. We test their performance in detecting heart disease using a database consisting of records of interbeat intervals for a group of healthy individuals and subjects with congestive heart failure. We find that scale-independent measures effectively distinguish healthy from pathologic behavior and propose a new two-variable scale-independent measure that could be clinically useful. We compare the performance of a recently proposed scale-dependent measure and find that the results depend on the database analyzed and on the analyzing wavelet.

Candidates for epitaxially stabilized structures of Fe, Co, and Ni silicides are searched by ab initio calculations. We find that the pseudomorphic phases of ${\mathrm{FeSi}}_2$ in the $C1\mathrm{}$ structure and CoSi and NiSi in the $B2\mathrm{}$ structure soften dramatically under compressive biaxial strain induced by epitaxy on a (100) substrate. This supersoft effect is reflected by zero strain energy, constant volume, and constant bond energies.

We present an analysis of atmospheric neutrino data from a 33.0 kton yr (535-day) exposure of the Super-Kamiokande detector. The data exhibit a zenith angle dependent deficit of muon neutrinos which is inconsistent with expectations based on calculations of the atmospheric neutrino flux. Experimental biases and uncertainties in the prediction of neutrino fluxes and cross sections are unable to explain our observation. The data are consistent, however, with two-flavor ${\nu }_{\mu }\leftrightarrow {\nu }_{\tau }$ oscillations with ${sin}^{2}2\theta >0.82\mathrm{}$ and $5\times {10}^{-4\mathrm{}}<\Delta m^2<6\mathrm{}\times 10^{-3\mathrm{}}\mathrm{eV}{}^2$ at 90% confidence level.

We observe the effects of noise and dissipation on dynamical localization. Our system consists of cold cesium atoms in a pulsed standing wave of light, and is an experimental realization of the $\delta$-kicked rotor. We compare the effects of amplitude noise with those of spontaneous scattering. The experimental signature in both cases is an increased growth in energy, with qualitatively similar momentum distributions.

We have discovered that the dc mass current through a superfluid ${}^3\mathrm{He}$ weak link is substantially increased when the Josephson frequency matches the resonant frequency of a coupled mechanical oscillator. The phenomenon is the result of homodyne mixing between the Josephson oscillations and the oscillating pressure field associated with the resonant system. The measured sizes of the current enhancements are in excellent agreement with calculations based on this homodyne model. Similar observations in superconducting junctions, in which microwave radiation changes the dc electronic current, were used for the first confirmation of the dynamics of the superconducting Josephson effect.

By charging a thin wire we realize a pure attractive $1/r^2$ potential of variable strength for cold neutral atoms. Scattering experiments are performed where the charged wire is placed inside a confined gas of cold lithium atoms. We observe the “falling” of atoms into the $1/r^2$ singularity which so far has been only theoretically discussed in textbooks.

We extend previous proofs that violations of the null energy condition are a generic and universal feature of traversable wormholes to completely nonsymmetric time-dependent wormholes. We show that the analysis can be phrased purely in terms of local geometry at and near the wormhole throat, and we do not have to make any technical assumptions about asymptotic flatness or other global properties. A key aspect of the analysis is the demonstration that time-dependent wormholes have two throats, one for each direction through the wormhole, and that the two throats coalesce only for the case of a static wormhole.

The structure factor $S\left(Q\right)$ and the pair distribution function $g\left(r\right)$ has been measured for liquid boron in the temperature range 2600–2000 K, extending over both the normal and supercooled liquid states. The bond length and coordination number of the first coordination shell are similar to those reported for the crystalline and amorphous solid forms, but the second and third coordination shells are broader and shifted to higher distances. The insulator-metal transition that takes place in boron upon melting is associated with a relatively small change in both volume and short-range order.